Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRON-EMITTING DEVICE, ELECTRON SOURCE SUBSTRATE,
ELECTRON SOURCE, DISPLAY PANEL AND IMAGE-FORMING
APPARATUS, AND PRODUCTION METHOD THEREOF
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an
electron-emitting device, and also to an electron
source substrate, an electron source, a display panel
and an image-forming apparatus, using the
electron=emitting device. The present invention also
relates to methods of producing these devices and
apparatus.
Related Background Art
In the art of electron-emitting devices, two
types are known, one is a thermionic emission source
and the other is a cold-cathode emission source.
Cold-cathode emission source types include a field
emission type (hereafter referred to as an FE type),
metal/insulator/metal type (hereafter referred to as an
MIM type), and a surface conduction type
electron-emitting device.
Examples of FE types are disclosed for example
in "Field Emission" (W. P. Dyke and W. W. Dolan,
Advance in Blectron Physics. 8, 89(1956)) and "Physical
Properties of Thin-Film Field Emission Cathodes with
Molybdenum Cones" (C. A. Spindt, J. Appl. Phys., 47,
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5248(1976)).
An example of an MIM type has been reported by
C. M. Mead (J. Appl. Phys., 32,646 (1961)).
An example of a surface conduction type
electron-emitting device has been reported by M. I.
Elinson (Radio Eng. Electron Phys.,l0 (1965)).
Surface conduction type electron-emitting
devices use a phenomenon that electron emission occurs
when a current is passed through a thin film with a
small area formed on a substrate in a direction
parallel to the film surface. Various types of surface
conduction electron-emitting devices are known. They
include a device using a thin SnOz film proposed by
Elinson et. al., a device using a thin Au film (G.
Dittmer, Thin Solid Films, 9, 317 (1972)), a device
using a thin Inz03/SnOz film ( M. Hartwell and C. G.
Fonstad, IEEE Trans. ED Conf., 519 (1975)), and a
device using a thin carbon film (Araki et. al., Vacuum,
26(1), 22 (1983)).
The device proposed by Hartwell is taken here
as a representative example of a surface conduction
type electron-emitting device, wherein its structure is
shown in Figure 39. In this figure, reference numeral
1 denotes a substrate. Reference numeral 4 denotes an
electrically-conductive thin film which is formed of a
metal oxide in an H pattern by means of sputtering.
The electrically-conductive thin film 4 is subjected to
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a process called energization forming (hereafter
referred to simply as a forming process), which will be
described in greater detail later, so that an electron
emission region 5 is formed in the
electrically-conductive thin film 4. The distance L
between electrodes is set to a value in the range from
0.5 mm to 1 mm and the width W' is set to 0.1 mm. The
detailed position and shape of the electron emission
region 5 are not described in the above reference, and
thus Figure 39 is a rough sketch of the structure.
In conventional surface conduction type
electron-emitting devices, before using the devices to
emit electrons, the electrically-conductive thin film 4
is subjected to an energization forming process thereby
forming an electron emission region 5. In this
energization forming, a DC voltage or a voltage which
rises at a very slow rate for example 1 V/min is
applied across the electrically-conductive thin film 4
so that the electrically-conductive thin film is
locally broken, deformed, or changed in quality,
thereby forming an electron emission region 5 having a
high electric resistance. In the electron emission
region 5, cracks are partially formed in the
electrically-conductive thin film 4 and electrons are
emitted via the cracks or via regions near the cracks.
After completion of the forming process, a voltage is
applied across the electrically-conductive thin film 4
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so that a current flows through the
electrically-conductive thin film 4 thereby emitting an
electron from the electron emission region 5.
The electron-emitting device of the surface
conduction type has a simple structure and thus can be
easily produced. Therefore, it is possible to dispose
a great number of similar devices over a large area.
To take such advantages in practical applications such
as an electron beam source, a display device or an
image display device, etc., extensive research and
development is being done.
The inventors of the present invention have
investigated the electron-emitting device of the
surface conduction type and have proposed a new method
of producing an electron-emitting device in Japanese
Patent Application Laid-Open No. 2-56822 (1990).
Figure 38 shows the device disclosed in this patent.
In this figure, reference numeral 1 denotes a
substrate, reference numerals 2 and 3 denote a device
electrode, reference numeral 4 denote an
electrically-conductive thin film, and reference
numeral 5 denotes an electron emission region. This
electron-emitting device can be produced as follows.
First, device electrodes 2 and 3 are formed on a
substrate 1 using a common technique such as vacuum
evaporation and photolithography. Then an electrically
conductive material is coated on the substrate by means
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of for example dispersive coating and then is patterned
so as to form an electrically-conductive thin film 4.
A forming process is then performed by applying a
voltage across the device electrodes 2 and 3 thereby
forming an electron emission region 5.
However, in the conventional production method
described above, it is based on the semiconductor
process and thus it is difficult to form a large number
of electron-emitting devices over a large area.
Besides, this technique needs a special and expensive
production apparatus. Furthermore, the above
patterning process requires a plurality of long steps.
At present, therefore, high cost is required to form a
great number of electron-emitting devices over a large
area of a substrate. Thus there is a need for a
simplified patterning technique.
SUMMARY OF THE INVENTION
It is an object of the present invention to
solve the above problems. More particularly, it is an
object of ~fhe present invention to provide a method of
producing an electron-emitting device, capable of
forming a large number of electron-emitting devices on
a substrate at a low cost. It is another object of the
present invention to provide an electron source
substrate, an electron source, a display panel, and an
image-forming apparatus using such an electron-emitting
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device.
It is still another object of the present
invention to provide a method of producing an
electron-emitting device, in which patterning is
performed with a simplified process.
It is a further object of the present invention
to provide a method of producing an electron-emitting
device, capable of supplying a desired amount of
conductive material at a desired location on a
substrate, using a simplified production process.
It is still another object of the present
invention to provide an electron source substrate, an
electron source, a display panel, and an image-forming
apparatus using such an electron-emitting device.
The above objects are achieved by the present
invention having various aspects and features as
described below.
In a first aspect of the present invention,
there is provided a method of producing an
electron-emitting device including the steps of:
forming a pair of electrodes and an
electrically-conductive thin film on a substrate in
such a manner that the pair of electrodes are in
contact with the electrically-conductive thin film; and
forming an electron emission region using the
electrically-conductive thin film, the method being
characterized in that a solution containing a metal
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element is supplied in a droplet form onto the
substrate thereby forming the electrically-conductive
thin film.
In a second aspect of the present invention,
there is provided a method of producing an
electron-emitting device having a thin film forming an
electron emission region between a pair of (each pair
of) electrodes located at opposing positions on a
substrate, the method including the steps of: supplying
one or more droplets of solution onto the substrate,
the solution including a material constituting the
electrically-conductive thin film; detecting the state
of the supplied droplets; supplying one or more
droplets again on the basis of the obtained information
of the state of the supplied droplets.
In a third aspect of the present invention,
there is provided a method of producing an
electron-emitting device, including the steps of:
forming an electrically-conductive thin film by
supplying a plurality of droplets so that the
center-to-center distance between adjacent dots formed
by the droplets is less than the diameter of the dot;
and passing a current through the
electrically-conductive thin film so that an electron
emission region is formed in each
electrically-conductive thin film.
In a fourth aspect of the present invention,
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there is provided a method of producing an
electron-emitting device, including the steps of:
treating the surface of the substrate so that the
surface of the substrate becomes hydrophobic; and then
supplying a solution in a droplet form containing a
material constituting an electrically-conductive thin
film to a location between a pair of electrodes thereby
forming an electrically-conductive thin film, the above
solution being hydrophilic.
In a fifth aspect of the present invention,
there is provided a method of producing an
electron-emitting device, including the steps of:
supplying at least one droplet of solution onto a
substrate, the solution including a material
constituting an electrically-conductive thin film,
thereby forming an electrically-conductive thin film in
a dot shape; and then forming a pair of device
electrodes in such a manner that the device electrodes
are in contact with the electrically-conductive thin
film.
It should be understood that an
electron-emitting device produced according to the
production method of the invention is also included in
the scope of the invention.
The present invention also provides an electron
source substrate characterized in that a plurality of
electron-emitting devices according to the present
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invention are disposed on a substrate.
The present invention also provides an electron
source characterized in that a plurality of
electron-emitting devices on the electron source
substrate of the invention are connected.
Furthermore, the present invention provides a
display panel comprising: a rear plate provided with
the electron source of the invention; and a face plate
provided with a fluorescent film, the rear plate and
the face plate being located at opposing positions,
whereby the fluorescent film is irradiated by an
electron emitted by the electron source thereby
displaying an image.
The present invention also provides an
image-forming apparatus including the display panel of
the invention and further at least a driving circuit
connected to the display panel.
The present invention also provides an
apparatus for producing an electron-emitting device.
In one aspect of the invention, there is
provided an apparatus for producing an
electron-emitting device, the apparatus comprising:
droplet supplying means for ejecting a droplet
containing a metal element toward a substrate thereby
supplying the droplet on the substrate; detection means
for detecting the state of the supplied droplet; and
control means for controlling the ejecting condition of
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the droplet supplying means on the basis of the
information obtained via the detection means.
In another aspect of the invention, there is
provided a method of producing an electron source
substrate, including the steps of: forming a plurality
of pairs of device electrodes on a substrate; and
supplying one or more droplets of a solution containing
a metal element onto a location between each pair of
device electrodes thereby forming an
electrically-conductive thin film at that location and
thus forming a plurality of electron-emitting devices.
In still another aspect of the invention, there
is provided a method of producing an electron source,
including the steps of: forming a plurality of pairs of
device electrodes on a substrate; supplying one or more
droplets of a solution containing a metal element onto
a location between each pair of device electrodes
thereby forming an electrically-conductive thin film at
that location and thus forming a plurality of
electron-emitting devices; and connecting the
electron-emitting devices via interconnections.
In a further aspect of the invention, there is
provided a method of producing a display panel,
including the steps of: forming a plurality of pairs of
device electrodes on a substrate; supplying one or more
droplets of a solution containing a metal element onto
a location between each pair of device electrodes
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thereby forming an electrically-conductive thin film at
that location and thus forming a plurality of
electron-emitting devices; connecting the
electron-emitting devices via interconnections; and
connecting a rear plate, having the substrate on which
electron-emitting devices are formed, to a face plate
provided with a fluorescent film via a supporting frame
so that both plates are located at opposing positions.
In still another aspect of the invention, there
is provided a method of producing an image-forming
apparatus, including the steps of: forming a plurality
of pairs of device electrodes on a substrate; supplying
one or more droplets of a solution containing a metal
element onto a location between each pair of device
electrodes thereby forming an electrically-conductive
thin film at that location and thus forming a plurality
of electron-emitting devices; connecting the
electron-emitting devices via interconnections;
connecting a rear plate, having the substrate on which
electron-emitting devices are formed, to a face plate
provided with a fluorescent film via a supporting frame
so that both plates are located at opposing positions
thereby forming a display panel; and connecting a
driving circuit to the display panel.
In the method of producing an electron-emitting
device according to the present invention, since a
solution containing a metal element is supplied in a
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droplet form onto a substrate thereby forming an
electrically-conductive thin film which constitutes an
electron emission region, it is possible to supply a
desired amount of solution at a desired location.
Thus, it is possible to greatly simplify the process of
producing an electron-emitting device.
Furthermore, in the second aspect of the
invention regarding the method of producing an
electron-emitting device, information of the sate of a
supplied droplet is detected, then the ejecting
conditions and the ejecting position are corrected on
the basis of the obtained information, and finally a
droplet is supplied again under the corrected
conditions. Therefore, it is possible to produce a
thin film having a very small number of defects.
Furthermore, it is possible to achieve a great
improvement in uniformity of device characteristics,
and thus it is possible to solve the problem of the
production yield which becomes serious with the
increase in the size of the substrate.
Furthermore, it is possible to produce a
high-quality electron source substrate, electron
source, display panel, and image-forming apparatus,
using the electron-emitting device of the invention.
In the third aspect of the present invention
regarding the method of producing an electron-emitting
device, a plurality of droplets of a solution in which
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a metal material which constitutes an electron emission
region is dissolved or dispersed are supplied onto a
substrate so that the center-to-center distance between
adjacent dots formed by the droplets is less than the
diameter of the dot. Thus, it is possible to form the
electrically-conductive film constituting the electron
emission region with very high accuracy.
In the fourth aspect of the present invention
concerning the method of producing an electron-emitting
device, the surface of the substrate is treated so that
the surface of the substrate becomes hydrophobic, and
then a hydrophilic solution in a droplet form is
supplied onto a substrate. Thus, it is possible to
produce an electrically-conductive thin film with good
reproducibility. This means that it is possible to
produce a great number of surface conduction
electron-emitting devices having uniform
characteristics over a large area.
Furthermore, in the fifth aspect of the
invention regarding the method of producing an
electron-emitting device, device electrodes are formed
after forming an electrically-conductive thin film.
This allows the present invention to be used in a wider
range of applications.
Furthermore, in the production of an electron
source, an electron source substrate, a display panel,
an image-forming apparatus, and an electron-emitting
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device according to the present invention, an
electrically-conductive thin film can be disposed
precisely at a desired location, and thus it is
possible to achieve uniform and excellent
characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
Figures lA to 1D are schematic diagrams
illustrating a method of producing an electron-emitting
device according to the present invention;
Figures 2A and 2B are schematic diagrams
illustrating a surface conduction electron-emitting
device according to the present invention;
Figure 3 is a plan view of another surface
conduction electron-emitting device according to the
present invention;
Figures 4A and 4B illustrate voltage waveforms
used in an energization forming process which is
performed during the process of producing an
electron-emitting device according to the invention,
wherein Figure 4A illustrates a waveform having a
constant pulse height, and Figure 4B illustrates a
waveform with an increasing pulse height;
Figure 5 is a schematic diagram of a system for
measuring electron emission characteristics;
Figure 6 is a plan view partially illustrating
an electron source in a simple matrix.form according to
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the present invention;
Figure 7 is a schematic diagram of an
image-forming apparatus according to the present
invention;
Figures 8A and 8H are schematic diagrams
partially illustrating a fluorescent film wherein
Figure 8A illustrates a type having black stripes, and
Figure 8B illustrates a type having a black matrix;
Figure 9 is a block diagram of a driving
circuit for driving an image-forming apparatus so as to
display an image thereon in response to an NTSC TV
signal, according to the present invention;
Figure 10 is a schematic diagram of a
ladder-type electron source;
Figure 11 is a perspective view, partially cut
away, of an image display device according to the
present invention;
Figure 12 is a schematic diagram of a substrate
on which device electrodes are formed in a matrix
fashion;
Figure 13 is a schematic diagram of a substrate
on which device electrodes are formed in a ladder
fashion;
Figure 14 is a schematic representation of an
example of a process of supplying a droplet according
to the present invention;
Figure 15 is a flow chart associated with a
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production method according to the present invention;
Figure 16 is a schematic representation of
another example of a process of supplying a droplet
according to the present invention;
Figure 17 is a schematic representation of
still another example of a process of supplying a
droplet according to the present invention;
Figures 18A to 18C are schematic diagrams
illustrating the structure of an optical detecting
system/ejection nozzle used in a production apparatus
according to the present invention, wherein Figure 18A
illustrates a vertical reflection type, Figure 18B
illustrates an oblique reflection type, and Figure 18C
illustrates a vertical transmission type;
Figures 19A and 19B are schematic
representations of the operation of the optical
detecting system/ejection nozzle of the vertical
reflection type used in the production apparatus
according to the present invention, wherein Figure 19A
illustrates a droplet information detecting operation,
and Figure 19B illustrates an ejecting operation;
Figures 20A and 20B are schematic
representations of the operation of the optical
detecting system/ejection nozzle of the vertical
transmission type used in the production apparatus
according to the present invention, wherein Figure 20A
illustrates a droplet information detecting operation,
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and Figure 20B illustrates an ejecting operation;
Figure 21 is a perspective view of an example
of an electron beam generation apparatus provided with
a device produced according to the production method of
the present invention;
Figure 22 is a schematic diagram illustrating
an example of an electron source substrate on which
electron-emitting devices are formed by means of an
ink-jet technique on a substrate having a simple 10 x
10 matrix-shaped interconnection;
Figure 23 is a block diagram illustrating an
example of an ejecting operation control system used in
a production apparatus according to the present
invention;
Figure 24 is a schematic diagram illustrating
an example of an optical detecting system of the
vertical reflection type used in a production apparatus
according to the present invention;
Figure 25 is a block diagram illustrating an
example of an ejecting operation control system used in
a production apparatus according to the present
invention;
Figure 26 is a block diagram illustrating
another example of an ejecting operation control system
used in a production apparatus according to the present
invention;
Figure 27 is a block diagram illustrating still
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another example of an ejecting operation control system
used in a production apparatus according to the present
invention;
Figures 28A and 28B are schematic
representations of a process of correcting an abnormal
cell with a removal nozzle used in a production
apparatus according to the present invention;
Figure 29 is a block diagram illustrating
another example of an ejecting operation control system
used in a production apparatus according to the present
invention;
Figure 30 is a schematic representation of a
process of correcting an abnormal cell with a complex
system including a displacement correction/ejecting
control system;
Figures 31A to 31C illustrate possible
variations of the device structure of a surface
conduction electron-emitting device produced by a
production method using an ink-jet technique according
to the present invention;
Figures 32A and 32B are schematic diagrams
illustrating a basic pattern of a pad and dots wherein
Figure 32A illustrates the distance between adjacent
dots, and Figure 32B illustrates a pad formed between
device electrodes;
Figures 33A to 33D are schematic diagrams
illustrating examples of pad patterns used in a
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production method according to the present invention;
Figure 34 is a plan view illustrating an
example of a surface conduction electron-emitting
device produced according to a production method of the
present invention;
Figures 35A1 to 35C2 are schematic
representations of a production flow associated with a
surface conduction electron-emitting device according
to the present invention;
Figure 36 is a schematic diagram illustrating
an example of an electron source substrate having a
matrix-shaped interconnection according to the present
invention;
Figure 37 is a schematic diagram illustrating
an example of an electron source substrate having a
ladder-shaped interconnection according to the present
invention;
Figure 38 is a schematic diagram illustrating
an example of a conventional surface conduction
electron-emitting device; and
Figure 39 is a schematic diagram illustrating
an example of a conventional surface conduction
electron-emitting device.
Figures 40A and 40B are schematic diagrams
illustrating an example of a preparing process of an
electron-emitting device 4f the present invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in
detail with reference to the accompanying drawings.
Figures lA to 1D are schematic diagrams
illustrating a method of producing an electron-emitting
device according to the present invention, and Figures
2A to 3 are schematic diagrams illustrating a surface
conduction type electron-emitting device produced
according to the method of the present invention.
In Figures lA to 1D, 2A and 2B, and 3,
reference numeral 1 denotes a substrate, reference
numerals 2 and 3 denote a device electrode, reference
numeral 4 denotes an electrically-conductive thin film,
reference numeral 5 denotes an electron emission
region, reference numeral 6 denotes a droplet supplying
mechanism, and reference numeral 7 denotes a droplet.
First, in this embodiment, device electrodes 2
and 3 are formed on the substrate 1 so that the device
electrodes 2 and 3 are apart by a distance of L1
(Figure lA). Then, a droplet 7 consisting of a
solution containing a metal element is ejected from the
droplet supplying device (ink-jet printing apparatus) 6
(Figure 1B), thereby forming an electrically-conductive
thin film 4 so that the electrically-conductive thin
film 4 is formed in contact with the device electrodes
2 and 3 (Figure 1C). Cracks are then produced in the
electrically-conductive thin film by means of for
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example a forming process, which will be described
later, thereby forming an electron emission region 5.
In the above-described technique of supplying
droplets, a small droplet of solution can be
selectively deposited only at a desired location
without uselessly consuming the material for forming
devices. Furthermore, neither a vacuum process using
an expensive apparatus nor a photolithographic
patterning process including a large number of steps is
required, and thus it is possible to greatly reduce the
production cost.
As for the droplet supplying device 6, any
apparatus can be employed as long as it can produce a
droplet in a desired form. However, it is preferable
to use an apparatus based on an ink-jet technique
capable of easily producing a very small droplet in the
range from 10 ng to a few ten ng and capable of control
the amount of the droplet in that range.
The ink-jet type apparatus include an ink-jet
ejecting apparatus using a piezo-electric device and an
ink-jet ejecting apparatus based on a technique of
forming a bubble in liquid by means of thermal energy
thereby ejecting the liquid in the form of a droplet
(hereafter referred to as a bubble jet technique).
As for the electrically-conductive thin film 4,
it is preferable to employ a particle film formed of
particles so as to achieve good performance in electron
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emission. The film thickness is set to a proper value
taking into account various conditions such as step
coverage over the device electrode 2 and 3, resistance
between the device electrodes 2 and 3, and energization
forming conditions, which will be described later,
while it is preferably in the range from a few ~ to a
few thousand ~1, and more preferably in the range from
~ to 500 ~1. The sheet resistance is preferably in
the range from 103 to 10' S2/square.
10 Materials which can be employed to form the
electrically-conductive thin film 4 include metal such
as Pd, Pt, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta,
W, or Pb, oxides such as PdO, SnOZ, Inz03, PbO, or Sbz03,
borides such as HfBZ, ZrB2, LaBb, CeB6, YB4, or GdB4,
carbides such as TiC, ZrC, HfC, TaC, SiC, or WC,
nitrides such as TiN, ZrN, or HfN, semiconductors such
as Si, or Ge, or carbon.
The term "particle film" is used herein to
refer to a film composed of a plurality of particles,
wherein the particles may be dispersed in the film, or
otherwise the particles may be disposed so that they
are adjacent to each other or they overlap each other
(or may be disposed in the form of islands). The
particle diameter is preferably in the range from a few
~ to a few thousand ~, and more preferably from 10 ~ to
200 ~.
As for the solution for creating a droplet 7,
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it is possible to employ a solution such as water or a
solvent in which a material for forming the
electrically-conductive thin film is dissolved, or an
organometallic solution, wherein it is required that
the solution should have a viscosity high enough to
produce a droplet.
It is preferable that the solution should be
supplied between the device electrodes so that the
amount of the solution does not exceed the volume of a
recessed portion formed with a substrate and a pair of
device electrode, as shown in the following equation.
Volume of the recessed portion =
Thickness of the device electrode (d)
x Width (W1) of the device electrode
x The distance (L1) between the device
electrodes (1)
As for the substrate 1, quartz glass, glass with low
contents of impurities such as Na, a plate glass, glass
substrate coated with Si02, ceramic substrate such as
aluminum oxide, etc., may be employed.
As for the material for the device electrodes 2
and 3, it is possible to employ a common
electrically-conductive material for example metal or
an alloy such as Ni, Cr, Au, Mo, W, Pt, Ti, A1, Cu, or
Pd, a printed conductor composed of glass and a metal
or a metal oxide such as Pd, Ag, Au, Ru02, Pd-Ag, a
transparent conductor such as In203 or Sn02, or a
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semiconductor material such as polysilicon.
The distance L between the device electrodes is
preferably in the range from a few hundred ~1 to a few
hundred um. It is desirable that the voltage applied
between the device electrodes be as low as posible, and
thus it is required to form device electrodes
precisely. From this point of view, the distance
between the device electrode is preferably in the range
from a few um to a few ten um.
The length W' of the device electrode is set to
a value in the range from a few um to a few hundred um
to satisfy the requirements of the resistance of the
electrode and the requirements of electron emission
characteristics. The film thickness of the device
electrodes 2 and 3 is preferably in the range from a
few hundred ~ to a few um.
The electron emission region 5 includes cracks
formed in a part of the electrically-conductive thin
film 4 wherein the cracks are formed by means of for
example energization forming. In the cracks, there may
be electrically-conductive particles with a particle
size of a few ~ to a few hundred ~. The
electrically-conductive particle contains at least a
part of elements constituting the material of the
electrically-conductive thin film 4. The electron
emission region 5 and the electrically-conductive thin
film 4 adjacent to it may include carbon or a carbon
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compound.
The electron emission region 5 is created by
performing an energization forming process in which a
current is passed through a device including the
electrically-conductive thin film 4 and the device
electrodes 2 and 3. In the energization forming, a
voltage from a power supply (not shown) is applied
between the device electrodes 2 and 3 so that the
electrically-conductive thin film 4 is locally broken,
deformed, or changed in quality, thereby creating a
portion having a structure different from the other
portions. Such the portion whose structure is locally
changed is herein referred to as the electron emission
region 5. Figures 4A and 4B illustrate examples of a
voltage waveform used in the energization forming.
As for the voltage waveform, it is preferable
to employ a pulse. A series of voltage pulses having a
constant peak value may be applied (Figure 4A) or
otherwise voltage pulses having an increasing peak
value may be applied (Figure 4B). In the case where
pulses having a constant peak value are employed, the
forming process is performed as follows.
In Figures 4A and 4B, T1 and T2 denote the
width and interval of the voltage pulses, respectively,
wherein T1 is set to a value in the range from 1 usec
to 10 msec, and T2 in the range from 10 usec to 100
msec. The peak voltage of the triangular waveform (the
CA 02295408 2000-O1-13
- 26 -
peak value of the forming voltage) is selected to a
proper value according to the type of the surface
conduction electron-emitting device. The forming is
performed in a vacuum at a pressure of for example 1 x
10-5 Torr wherein the voltage is applied for a time
period in the range from a few sec to a few ten min.
The waveform of the voltage applied between the
electrodes of the device it not limited to a triangular
waveform, and a rectangular wave or other proper
waveforms may also be employed.
In the case of the waveform shown in Figure 4B,
T1 and T2 are selected to similar values to those in
Figure 4A. In this case, the peak voltage of the
triangular waveform (the peak value of the forming
voltage) is increased in steps of for example 0.1 V and
applied to the device in a vacuum at a proper pressure.
During the forming process, a current is
measured in each pulse interval using a voltage small
enough, for example 0.1 V, not to locally destroy or
deform the electrically-conductive thin film 4, thereby
determining the resistance. When the resistance has
achieved a high value, for example 1 MS2 or greater, the
forming process is stopped.
After the forming process, it is desirable that
the device is further subjected to an activation
process.
In the activation process, as in the forming
CA 02295408 2000-O1-13
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process, a voltage pulse having a constant peak voltage
is applied repeatedly to the device in a vacuum at a
pressure of for example 10-" to 10-5 Torr so that carbon
or a carbon compound originating from an organic
substance present in the vacuum is deposited on the
electrically-conductive thin film thereby greatly
changing the device current If and the emission current
Ie. During the activation process, the device current
If and the emission current Ie are monitored, and the
process is stopped for example when the emission
current Ie has reached a saturated value. In the
activation process, the pulse applied to the device
preferably has a voltage equal to an operation driving
voltage.
In this, invention, the carbon and the carbon
compound refer to graphite (single crystal or
polycrystal) and amorphous carbon (mixture of amorphous
carbon and polycrystal graphite), respectively. The
film thickness thereof is preferably less than 500
and more preferably less than 300 ~1.
The electron-emitting device obtained in the
above-described manner is preferably operated in a
vacuum at a lower pressure than in the energization
forming process or the activation process.
Furthermore, it is desirable that the electron-emitting
device be used after heating it at a temperature of
80°C to 150°C in vacuum at a still lower pressure.
CA 02295408 2000-O1-13
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The "pressure lower than in the energization
forming process or the activation process" refers to
such a pressure less than about 10-6 Torr, and more
preferably refers to an ultra-low pressure so that
substantially no further deposition of carbon or carbon
compound occurs onto the electrically-conductive thin
film thereby obtaining stabilized device current If and
emission current I~.
In the present invention, the electron-emitting
device is of the surface conduction type which has a
simple structure and thus can be easily produced.
The surface conduction electron-emitting device
according to the present invention is basically of the
flat panel type.
A distinctive feature of the method of the
invention for producing an electron-emitting device is
in that a solution containing a metal element is
supplied in the form of a droplet onto a substrate
thereby forming an electrically-conductive thin film.
This can be achieved in various modes of the invention.
I. In a mode of the invention, the condition
associated with a droplet supplied on a substrate is
detected, and another droplet is supplied on the basis
of the obtained information of the condition. This
mode of the invention will be described in greater
detail below.
Figures 14, 16 and 17 are schematic diagrams
CA 02295408 2000-O1-13
- 29 -
illustrating various modes of the apparatus for
producing an electron-emitting device according to the
present embodiment of the invention. Figure 15 is a
flow chart associated with a process of producing an
electron-emitting device according to an embodiment of
the present invention.
In Figures 14, 16 and 17, reference numeral 7
denotes an ink-jet ejecting device, reference numeral 8
denotes light emitting means, reference numeral 9
denotes light receiving means, reference numeral 10
denotes a stage, reference numeral 11 denotes a
controller, and reference numeral 12 denotes control
means. In this invention, the light emitting means is
not limited to those which emit visual light, and
variety types of light emitting devices such as an LED,
an infrared laser, etc., may be employed. As for the
light receiving means, any type of light receiving
means may be employed as long as it can receive a
signal (light) emitted by the light emitting means. It
is required that the light emitting means and the light
receiving means be constructed and disposed so that a
signal (light) generated by the light emitting means is
reflected from or transmitted through an insulating
substrate and then the signal (light) is received by
the light receiving means.
In the method and apparatus for producing an
electron-emitting device according to the present
CA 02295408 2000-O1-13
- 30 -
embodiment, the conditions to be detected associated
with the droplet include the amount of a droplet
supplied into a gap or a recessed portion between a
pair of device electrodes, the position of the droplet,
the presence or the absence of the droplet, etc. On
the basis of the obtained information regarding such
the items, the control means controls the conditions
such as the number of times of ejecting operations, and
the ejecting position: Furthermore, in the case where
an ink-jet ejecting apparatus using a piezo-electric
device is employed, the ejecting conditions,, including
driving conditions, of the ink-jet ejecting apparatus
are also controlled.
Furthermore, it is desirable that the means of
detecting the above conditions include droplet
information detecting means for detecting whether a
droplet ejected from a nozzle by means of an ink-jet
technique is present in the gap between the electrodes
and further detecting its amount, and also include
arrival position detecting means for detecting the
droplet arrival position.
In this arrival position detecting means, the
droplet arrival position is detected by optically
detecting an electrode pattern or a dedicated alignment
mark before ejecting a droplet, or otherwise by
optically detecting the modulation of the transmittance
due to the droplet. The droplet position is determined
CA 02295408 2000-O1-13
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by detecting the transmittance at a plurality of points
in the gap and also in the vicinity of the gap and
further calculating the correlation among these points.
Furthermore, in the production apparatus of the
present embodiment, it is desirable that both the
droplet information and the droplet arrival position be
detected by the same single optical detecting system
without having another optical system dedicated for
detecting the position. In a more preferable mode,
both the droplet information and the position are
detected successively or at the same time using the
same optical system.
In the production method of the present
embodiment, as shown in Figure 15, the droplet
supplying position is determined by detecting, with the
light emitting means and the light receiving means,
light passing through or being reflected from the area
between the electrodes, and then the head of the
ink-jet ejecting device is moved to the position
between electrodes to which a droplet is to be supplied
(positioning step). A droplet is then supplied between
the electrodes using the ink-jet ejecting device
(droplet supplying step), and then, as in the
positioning step, it is determined whether a droplet
has been supplied between the electrodes (to_obtain
information regarding the presence or absence of the
droplet itself) on the basis of the signal passing
CA 02295408 2000-O1-13
- 32 -
through or being reflected from the area between the
electrodes (droplet detecting step). If it is
concluded in the droplet detecting step that a droplet
has been deposited successfully at a desired position
in a desired area, then the process goes to a next step
to perform positioning of a next point between another
pair of electrodes. On the other hand, if no droplet
has been supplied, a droplet is supplied again.
In the moving and carrying operation of the
ink-jet ejecting device and the stage, movement in the
direction of X, Y, and/or 8 may be performed for any
combination of the stage and the ink-jet ejecting
device, for example only for the stage, or only for the
ink-jet ejecting device, or otherwise for both of
these.
Furthermore, during the droplet supplying step,
the ink-jet ejecting device and the stage may be either
in motion or at rest. However, if the ink-jet ejecting
device or the stage is in motion during a process of
supplying a droplet, it is desirable that the movement
or carriage is performed at a speed slow enough not to
shift the droplet arrival position from a desired
position.
In the production apparatus of the present
embodiment, the optical detecting means may be realized
in various fashions. Among them, Figures 18A to 18C
illustrate types in which the optical system and the
CA 02295408 2000-O1-13
- 33 -
ejection nozzle are disposed so that the optical axis
of the optical system and the ejection axis of the
ejection nozzle intersect each other at the focal point
of the optical detecting system. In this type, it is
possible to alternately perform ejection of a solution
and detection of information of the supplied droplet
while maintaining the ejection nozzle 301, the optical
detecting system 302, and the device substrate
(insulating substrate) 1 at fixed locations relative to
each other. Figure 18A illustrates a vertical
reflection type in which an emission system and a
detection system are integrated in a compact fashion,
Figure 18B illustrates an oblique reflection type in
which an emission system and a detection system are
disposed so that an ejection nozzle is located between
them, and Figure 18C illustrates a vertical
transmission type in which an emission system and a
detection system are disposed so that a device
substrate is located between them.
Figures 19A and 19B and 20A and 20B illustrate
types in which the optical axis of the optical
detecting system and the ejection axis do not intersect
each other, wherein the one shown in Figures l9A and
19B is of a reflection type and the one shown in
Figures 20A and 20B is of a transmission type. In this
type, to perform alternate operations of ejecting a
droplet and detecting information thereof, it is
CA 02295408 2000-O1-13
- 34 -
required to move the displacement control mechanism 403
or 503 alternately in either direction denoted by an
arrow so that the axis of the optical detecting system
and the ejection axis alternately comes to the center
of the gap, as shown in the figures.
One technique of controlling the ejecting
operation is to use a difference component of the
detected signal associated with the droplet information
as a correction signal. In this technique, at least
one of parameters such as the height of the driving
pulse, the pulse width, the pulse timing, and the
number of pulses is fed back in real time to maintain
the detected signal associated with the droplet
information at an optimum value. Another technique is
to correct at least one of the parameters according to
a predetermined algorithm in response to the deviation
of the detected value from an optimum value.
In the example shown in these figures, a
droplet to be detected is formed between device
electrodes. However, the present invention is not
limited to such the mode. In a preliminary step, a
dummy droplet may be deposited at some location other
than a location between device electrodes, and this
dummy droplet may be detected. According to the
detection result, the ejection condition is optimized,
and then an actual droplet is ejected onto a location
between device electrodes.
CA 02295408 2000-O1-13
- 35 -
In another mode of the present embodiment,
there is provided droplet removing means for removing
at least a part of the deposited droplet. In this
mode, if the detected droplet information indicates
that the amount of the droplet deposited in the gap is
greater than an optimum value, a part of the droplet is
removed so that the remaining amount of the droplet
becomes optimum, or otherwise the entire droplet is
removed once and then another droplet is ejected.
The droplet removing means may include a
dedicated removing nozzle for ejecting a gas such as
nitrogen thereby blowing away a droplet from a gap. It
is desirable that the dedicated removing nozzle be
disposed near the ejection nozzle so that no additional
mechanism for control the position of the dedicated
removing nozzle is required. In the case where
ejection nozzles are disposed in a multi-array fashion,
dedicated removing nozzles may be disposed at periodic
locations over the array. In this mode, as described
above, in addition to the means for supplying a droplet
by means of ejection, there is also provided the means
for removing a droplet. Thus, in this mode, it is
possible to control the amount of the droplet more
accurately.
In the present embodiment, the production
apparatus includes means for optically detecting the
information of the droplet arrival position and also
CA 02295408 2000-O1-13
- 36 -
means for controlling the ejection position and
performing a finer position adjustment on the basis of
the detected positional information.
The position detecting means detects the
droplet arrival position by optically detecting an
electrode pattern or a dedicated alignment mark before
ejecting a droplet, or otherwise by optically detecting
the modulation of the transmittance due to the droplet.
The droplet position is determined by detecting the
transmittance at a plurality of points in the gap and
also in the vicinity of the gap and further calculating
the correlation among these points.
In the present embodiment, both the droplet
information and the droplet arrival position are
preferably detected by the same single optical
detecting system without having another optical system
dedicated for detecting the position. More preferably,
both the droplet information and the position are
detected successively or at the same time using the
same optical system.
II. In another mode of the invention, the diameter
of a droplet dot and the position at which the droplet
is supplied are determined in a distinctive fashion
according to the invention.
Figures 32A and 32B illustrate a multi-dot
pattern (pad) of a surface conduction type
electron-emitting device produced according to a
CA 02295408 2000-O1-13
- 37 -
production method of the present embodiment of the
invention. Figure 32A illustrates the distance between
adjacent dots, and the diameter of dots. Figure 32B
illustrates an example of a pad. In this invention,
the term "adjacent dots" refers to those dots which are
located adjacent to each other either in the horizontal
direction or in the vertical direction as shown in
Figure 32A, and those dots which are adjacent in an
oblique direction are not regarded as "adjacent dots".
In Figures 32A and 32B, reference numerals 2
and 3 denote a device electrode, reference numeral 4
denotes an electrically-conductive thin film, and
reference numeral 8 denotes a circular film (dot) in a
liquid phase or in a solid state formed after supplying
a droplet onto the substrate.
First, in a preliminary step, the diameter ~ of
a dot formed of the material described above is
determined. That is, an insulating substrate is
cleaned well with for example an organic solvent, and
then dried. A dot is then formed using a droplet
supplying mechanism, and the diameter ~ of the dot is
measured.
A plurality of dots are formed on the substrate
on which, after cleaned, device electrodes have been
formed by means of vacuum evaporation and
photolithography, thereby producing a multi-dot pattern
(pad), as shown in Figure 32B. In the above process,
CA 02295408 2000-O1-13
- 38 -
center-to-center distances P1 and Pz between dots are
set to a value less than the diameter ~ of one dot so
that adjacent dots overlap each other. As a result of
the above process, droplets deposited on the substrate
expand, and a pad having a substantially constant width
Wz is obtained. The width WZ of the pad is preferably
less than the width W1 of the device electrodes, and the
length T of the pad is preferably greater than the gap
L1, wherein the specific size of the pad is determined
also taking into account the resistance to be achieved,
the width of the device electrodes, the gap width, and
the alignment accuracy.
After forming the thin film in the
above-described manner, the substrate is heated at a
temperature in the range from 300°C to 600°C so that
the solvent is evaporated, thereby forming an
electrically-conductive thin film. After that, forming
and other processes are performed in a manner similar
to that described above.
III. In still another mode of the invention, the
surface of a substrate is subjected to a special
treatment before supplying a droplet thereon. More
specifically, the substrate surface on which a droplet
is to be deposited is subjected to a process for making
the substrate surface hydrophobic.
In this embodiment, before supplying a droplet
onto a substrate having device electrodes, the surface
CA 02295408 2000-O1-13
- 39 -
of the substrate is treated so that the surface of the
substrate becomes hydrophobic. More particularly, the
treatment for achieving hydrophobicity is performed
using a silane coupling agent such as
HMDS(hexamethyldisilazane), PHAMS, GMS, MAP, or PES.
The hydrophobicity treatment is performed by
coating a silane coupling agent on the substrate using
for example a spinner and then heating the substrate at
a temperature in the range from 100°C to 300°C (for
example 200°C) for a time duration in the range from a
few ten min to a few hours (for example 15 min).
This surface treatment ensures that when a
droplet is supplied onto the substrate using the
droplet supplying mechanism, good reproducibility in
the shape of the droplet on the substrate can be
obtained. Thus, the droplet on the substrate does not
expand into an irregular shape. This means that it is
possible to easily control the shape of the
electrically-conductive thin film by controlling the
amount and the shape of the droplet. As a result, it
is possible to obtain improved reproducibility or
uniformity in the size and thickness of the
electrically-conductive thin film. Thus, it is
possible to form a great number of electron-emitting
devices over a large area maintaining good uniformity
in the electron emission performance.
Now, an image-forming apparatus according to
CA 02295408 2000-O1-13
- 40 -
the present invention will be described below.
An electron source substrate for use in an
image-forming apparatus is produced by disposing a
plurality of surface conduction type electron-emitting
devices on a substrate.
One method of disposing surface conduction type
electron-emitting devices is to dispose them in
parallel to each other and connect each end of the
respective devices to each other into the form of a
ladder (hereafter referred to as a ladder-type electron
source substrate). Another method is to dispose
surface conduction type electron-emitting devices into
a simple matrix form in which each pair of device
electrodes are connected to each other via X-direction
interconnections and Y-direction interconnections
(hereafter referred to as a matrix-type electron source
substrate). In an image-forming apparatus constructed
with a ladder-type electron source substrate, a control
electrode (grid electrode) is required to control the
travel of electrons emitted from electron-emitting
devices.
The construction of an electron source produced
according to the present embodiment will be described
in great detail below with reference to Figure 6. In
Figure 6, reference numeral 91 denotes an electron
source substrate, reference numeral 92 denotes an
X-direction interconnection, reference numeral 93
CA 02295408 2000-O1-13
- 41 -
denotes a Y-direction interconnection, reference
numeral 94 denotes a surface conduction
electron-emitting device, and reference numeral 95
denotes an interconnection.
In Figure 6, a glass substrate or the like may
be employed as a substrate for the electron source
substrate 91, wherein its shape is selected according
to a particular application.
The X-direction wires 92 include m lines Dxl,
Dx2, ..., Dxm, and the Y-direction wires 93 include n
lines Dyl, Dy2, ..., Dyn.
The material, film thickness, wire width are
selected properly so that a voltage is supplied
substantially uniformly to a great number of surface
conduction type electron-emitting devices. These m
X-direction wires 92 and n Y-direction wires 93 are
electrically isolated from each other by an interlayer
insulating layer (not shown), and these wires are
disposed in a matrix form (m, n are both a positive
integer).
The interlayer insulating layer (not shown) is
formed over the X-direction wires 92 in the entire area
or in a desired part of the surface of the electron
source substrate 91. The X-direction wires 92 and the
Y-direction interconnections 93 are each connected to a
corresponding external terminal.
Furthermore, device electrodes (not shown) of
CA 02295408 2000-O1-13
- 42 -
surface conduction type electron-emitting devices 94
are electrically connected via m X-direction wires 92,
n Y-direction wires 93, and wires 95.
The surface conduction type electron-emitting
devices may be formed either directly on the substrate
or on the interlayer insulating layer (not shown).
As will be described in greater detail later,
the X-direction wires 92 are electrically connected to
scanning signal generation means (not shown) so that a
scanning signal generated by the scanning signal
generation means is applied via the X-direction wires
92 to the surface conduction type electron-emitting
devices 94 disposed in each X-direction row thereby
scanning these surface conduction type
electron-emitting devices in response to an input
signal.
On the other hand, the Y-direction wires 93 are
electrically connected to modulation signal generation
means (not shown) so that a modulation signal generated
by the modulation signal generation means is applied
via the Y-direction wires 93 to the~surface conduction
type electron-emitting devices 94 disposed in each
Y-direction column thereby modulating these surface
conduction electron-emitting devices according to the
input signal.
A voltage equal to the difference between the
scanning signal and the modulation signal is applied as
CA 02295408 2000-O1-13
- 43 -
a driving voltage across each surface conduction type
electron-emitting device.
In the arrangement described above, each device
can be driven independently via the wires in the simple
matrix form.
Referring to Figures 7, 8A and 8B, and 9, an
image-forming apparatus using an electron source
provided with simple matrix form wires produced in the
above-described manner will be described below. Figure
7 illustrates a basic construction of the image-forming
apparatus, and Figures 8A and 8B illustrate fluorescent
films. Figure 9 is a block diagram illustrating the
image-forming apparatus and a driving circuit for
driving it according to an NTSC TV signal.
In Figure 7, reference numeral 91 denotes an
electron source substrate obtained by forming
electron-emitting devices on a substrate, 1081 denotes
a rear plate on which the electron source substrate 91
is fixed, 1086 denotes a face plate consisting of a
glass substrate 1083 whose back surface is covered with
a fluorescent film 1084 which is further backed with a
metal (metal-back) 1085, and 1082 denotes a supporting
frame, wherein an envelope 1088 is formed with these
members.
Reference numeral 94 denotes an
electron-emitting device, and 92 and 93 denote an
CA 02295408 2000-O1-13
- 44 -
X-direction wires and a Y-direction wires,
respectively, connected to a pair of device electrodes
of each surface conduction type electron-emitting
device 94.
As described above, the envelope 1088 is
composed of the face plate 1086, the supporting frame
1082, and the rear plate 1081. The principal purpose
of the rear plate 1081 is to reinforce the mechanical
strength of the electron source substrate 91. If the
electron source substrate 91 itself has an enough
mechanical strength, the rear plate 1081 is no longer
necessary. In such a case, the supporting frame 1082
may be directly connected to the electron source
substrate 91 so that the envelope 1088 is formed with
the face plate 1086, the supporting frame 1082, and the
electron source substrate 91.
In Figures 8A and 8B, reference numeral 1092
denotes a phosphor. In the case of monochrome type,
the phosphor 1092 simply consists of the phosphor
itself. However, in the case of a color type, the
fluorescent film includes a phosphor 1092 and a black
conductor 1091, which is called a black stripe or a
black matrix depending on the arrangement of the
phosphor. In color display devices, black stripes
(black matrix) are disposed at boundaries between
phosphors 1092 of three primary colors so as to reduce
mixture of colors. The black stripes (black matrix)
CA 02295408 2000-O1-13
- 45 -
also prevent a reduction in contrast of the fluorescent
film 1084 due to reflection of external light.
The phosphor may be coated on the glass
substrate 1093 by means of deposition or printing in
either case of monochrome type or color type
fluorescent film.
The inner side of the fluorescent film 1084
(Figure 7) is usually covered with a metal-back 1085.
One purpose of the metal-back is to directly reflect
light, which is emitted by the phosphor toward the
inside, to the face plate 1086 thereby increasing the
brightness. Another purpose is to act as an electrode
to which an electron beam acceleration voltage is
applied. Furthermore, the metal-back protects the
phosphor from being damaged by collision of negative
ions generated in the envelope. The metal-back is
formed as follows. After forming a fluorescent film,
the inner surface of the fluorescent film is smoothed
(this smoothing process is usually called filming).
Then, Al is deposited on the fluorescent film by means
of for example evaporation.
The face plate 1086 may also be provided with a
transparent electrode (not shown) on the outer side of
the fluorescent film 1084 so as to increase the
conductivity of the fluorescent film 1084.
In the case of a color image forming apparatus,
when components are combined and sealed into a unit,
CA 02295408 2000-O1-13
- 46 -
phosphors of respective colors have to be disposed at
correct locations corresponding to electron-emitting
devices, and thus accurate positioning is required.
Sealing is performed after evacuating the
inside of the envelope 1088 via an exhaust pipe (not
shown) to a pressure of about 10-' Torr. To maintain
the pressure at a low enough value after sealing the
envelope 1088, Bettering may be performed. In the
Bettering process, a Better disposed at a proper
location (not shown) is heated either immediately
before or after the sealing of the envelope 1088
thereby evaporating a film. The Better usually
contains Ba as a main ingredient, and the film formed
by evaporating the Better has an adsorbent property.
With the Bettering, it is possible to maintain the
pressure as low as 1 x 10'5 Torr to 1 x 10'' Torr.
Processes of surface conduction electron-emitting
devices after the energization forming are determined
properly as required.
Figure 5 is-a schematic diagram of a measuring
system for evaluating the electron emission
performance. In Figure 5, 81 denotes a power source
for supplying a device voltage Vf to a device, 80
denotes an ammeter for measuring a device current If
flowing through the electrically-conductive thin film 4
between device electrodes 2 and 3, 84 denotes an anode
electrode for measuring an emission current IQ emitted
CA 02295408 2000-O1-13
_ 47 _
by the electron emission region of the device, 83
denotes a high-voltage power source for supplying a
voltage to the anode electrode 84, 82 denotes an
ammeter for measuring an emission current I~ emitted by
the electron emission region of the device, 85 denotes
a vacuum chamber, and 86 denotes a vacuum pump.
Referring to the block diagram shown in Figure
9, the circuit configuration of the driving circuit for
driving the image-forming apparatus provided with the
electron source of the simple matrix type so that a
television image is displayed thereon according to an
NTSC television signal will be described below. As
shown in Figure 9, the driving circuit includes a
display panel 1101, a scanning circuit 1102, a control
circuit 1103, a shift register 1104, a line memory
1105, a synchronizing signal extraction circuit 1106, a
modulation signal generator 1107, and DC voltage
sources Vx and Va.
These components will be described in detail
below.
The display panel 1101 is connected to external
electric circuits via terminals Doxl to Doxm, terminals
Doyl to Doyn, and a high-voltage terminal Hv. The
electron source disposed in the display panel is driven
via these terminals as follows. The surface conduction
electron-emitting devices arranged in the form of an m
x n matrix is driven row by row (n devices at a time)
CA 02295408 2000-O1-13
- 48 -
by a scanning signal applied via the terminals Doxl to
Doxm.
Via the terminals Doyl to Doyn, a modulation
signal is applied to each surface conduction type
electron-emitting device disposed in the line selected
by the above-described scanning signal, thereby
controlling the electron beam emitted by each device.
A DC voltage of for example 10 kV is supplied from the
DC voltage source Va via the high-voltage terminal Hv.
This voltage is used to accelerate the electron beam
emitted from each surface conduction type
electron-emitting device so that the electrons gain
high enough energy to excite the phosphor.
The scanning circuit 1102 operates as follows.
The scanning circuit 1102 includes m switching elements
(S1 to Sm in Figure 9). Each switching element selects
either the voltage Vx output by the DC voltage source
or 0 V (ground level) so that the selected voltage is
supplied to the display panel 1101 via the terminals
Doxl to Doxm. Each switching element S1 to Sm is
formed with a switching device such as an FET. These
switching elements S1 to Sm operate in response to the
control signal Tscan supplied by the control circuit
1103.
The output voltage of the DC voltage source Vx
is set to a fixed value so that devices which are not
scanned are supplied with a voltage less than the
CA 02295408 2000-O1-13
- 49 -
electron emission threshold voltage of the surface
conduction electron-emitting device.
The control circuit 1103 is responsible for
controlling various circuits so that an image is
correctly displayed according to an image signal
supplied from the external circuit. In response to the
synchronizing signal Tsync received from the
synchronizing signal extraction circuit 1106 which will
be described in greater detail below, the control
circuit 1103 generates control signals Tscan, Tsft, and
Tmry and sends these control signals to the
corresponding circuits.
The synchronizing signal extraction circuit
1106 is constructed with a common filter circuit in
such a manner as to extract a synchronizing signal
component and a luminance signal component from an NTSC
television signal supplied from an external circuit.
Although the synchronizing signal extracted by the
synchronizing signal extraction circuit 1106 is simply
denoted by Tsync in Figure 9, the practical
synchronizing signal consists of a vertical
synchronizing signal and a horizontal synchronizing
signal. The image luminance signal component extracted
from the television signal is denoted by DATA in Figure
9. This DATA signal is applied to the shift register
1104.
The shift register 1104 receives a DATA signal
CA 02295408 2000-O1-13
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in time sequence and converts it to a signal in
parallel form line by line of an image. The
above-described conversion operation of the shift
register 1104 is performed in response to the control
signal Tsft generated by the control circuit 1103 (this
means that the control signal Tsft acts as a shift
clock signal to the shift register 1104).
After being converted into the parallel form,
one line of image data consisting of parallel signals
Idl to Idn is output from the shift register 1104
(thereby driving n electron-emitting devices).
The line memory 1105 stores one line of image
data for a required time period. That is, the line
memory 1105 stores the data Idl to Idn under the
control of the control signal Tmry generated by the
control circuit 1103. The contents of the stored data
are output as data I'dl to I'dn from the line memory
1105 and applied to the modulation signal generator
1107.
The modulation signal generator 1107 generates
signals according to the respective image data I'dl to
I'dn so that each surface conduction electron-emitting
device is driven by the corresponding modulation
signals generated by the modulation signal generator
1107 wherein the output, signals of the modulation
signal generator 1107 are applied to the surface
conduction electron-emitting devices of the display
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panel 1101 via the terminal Doyl to Doyn.
The electron-emitting device used in the
present invention has fundamental characteristics in
terms of the emission current I~ as described below. In
the emission of electrons, there is a distinct
threshold voltage Vth. That is, only when a voltage
greater than the threshold voltage Vth is applied to an
electron-emitting device, the electron-emitting device
can emit electrons.
In the case where the voltage applied to the
electron-emitting device is greater than the threshold
voltage, the emission current varies with the variation
in the applied voltage. The electron emission
threshold voltage Vth and the dependence of the
emission current on the applied voltage may vary
depending on the materials, structure, and production
technique.
When the electron-emitting device is driven by
a pulse voltage, if the voltage is less than the
electron emission threshold voltage, no electrons are
emitted, while an electron beam is emitted when the
pulse voltage is greater than the threshold voltage.
Thus, it is possible to control the intensity of the
electron beam by varying the peak voltage Vm of the
pulse. Furthermore, it is also possible to control the
total amount of charge carried by the electron beam by
varying the pulse width Pw.
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As can be seen from the above discussion,
either technique based on the voltage modulation or
pulse width modulation may be employed to control the
electron-emitting device so that the electron-emitting
device emits electrons according to the input signal.
When the voltage modulation technique is employed, the
modulation signal generator 1107 is designed to
generate a pulse having a fixed width and having a peak
voltage which varies according to the input data.
On the other hand, if the pulse width
modulation technique is employed, the modulation signal
generator 1107 is designed to generate a pulse having a
fixed peak voltage and having a width which varies
according to the input data.
According to the above operation, a TV image is
displayed on the display panel 1101. In the above
circuit, the shift register 1104 and the line memory
1105 may be either of analog type or of digital type as
long as the serial-to-parallel conversion of the image
signal and the storage operation are correctly
performed at a desired rate.
When the digital technique is employed for
these circuits, an analog-to-digital converter is
required to be connected to the output of the
synchronizing signal extraction circuit 1106 so that
the output signal DATA of the synchronizing signal
extraction circuit 1106 is converted from analog form
CA 02295408 2000-O1-13
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to digital form. Furthermore, a proper type of
modulation signal generator 1107 should be selected
depending on whether the line memory 1105 outputs
digital signals or analog signals.
When a voltage modulation technique using
digital signals is employed, the modulation signal
generator 1107 is required to include a
digital-to-analog converter and an amplifier is added
as required.
In the case of the pulse width modulation, the
modulation signal generator 1107 is constructed for
example with a combination of a high speed signal
generator, a counter for counting the number of pulses
generated by the signal generator, and a comparator for
comparing the output value of the counter with the
output value of the above-described memory. If
required, an amplifier is further added to the above so
that the voltage of the pulse-width modulation signal
output by the comparator is amplified to a voltage
large enough to drive the surface conduction
electron-emitting devices.
On the other hand, in the case where a voltage
modulation technique using analog signals is employed,
an amplifier such as an operational amplifier is used
as the modulation signal generator 1107. A level
shifter is added to that if required. In the case
where the pulse width modulation technique is coupled
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with the analog technique, a voltage controlled
oscillator (VCO) can be used as the modulation signal
generator 907. If required, an amplifier is further
added to the above so that the output voltage of the
VC0 is amplified to a voltage large enough to drive the
surface conduction electron-emitting devices.
In the image display device constructed in the
above-described manner according to the present
invention, electrons are emitted by applying a voltage
to each electron-emitting device via the external
terminals Doxl to Doxm, and Doyl to Doyn. The emitted
electrons are accelerated by a high voltage which is
applied via the high voltage terminal Hv to a
back-metal 1085 or a transparent electrode (not shown).
The accelerated electrons strike a fluorescent film and
thus light is emitted from the fluorescent film. As a
result, an image is formed by light emitted from the
fluorescent film.
While the image-forming apparatus of the
present invention has been described above with
reference to a preferred embodiment thereof, the
invention is not limited to the details shown, since
various modifications in the construction or the
material are possible. Furthermore, although it is
assumed in the above description that an input signal
according to the NTSC standard is used, an input signal
according to another standard such as PAL, or SECAM may
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also be employed. A TV signal consisting of a greater
number of lines than those of the above standards may
also be employed (such standards include the MUSE and
other the high definition television standards).
The ladder-type electron source substrate and
an image display device using such the electron source
substrate will be described below with reference to
Figures 10 and 11.
In Figure 10, reference numeral 1110 denotes an
electron source substrate, 1111 denotes an
electron-emitting device, and 1112 denotes an
interconnection Dxl to DxlO for connecting
electron-emitting devices in common. In the
ladder-type electron source substrate, a plurality of
electron-emitting devices 1111 are disposed on a
substrate 1110 in a line along the X direction (this
line is referred to as a device row), and a plurality
of device lines are disposed on the substrate in
parallel. A driving voltage is applied separately to
each device row via a corresponding common
interconnection thereby driving each device row
independently. That is, if a voltage greater than an
electron emission threshold is applied to a device row
to be activated, an electron beam is emitted from this
device row. On the other hand, no electrons are
emitted by device rows which are applied with a voltage
less than the electron emission threshold. Some of the
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row interconnections, for example Dx2 and Dx3, may be
connected in common.
Figure 11 is a schematic diagram of an
image-forming apparatus provided with a ladder-type
electron source. In Figure 11, reference numeral 1120
denotes a grid electrode, 1121 denotes an opening
through which electrons may pass, 1122 denotes external
terminals Doxl, Dox2, ..., Dox extending toward the
outside of the case, 1123 denotes external terminals
G1, G2, ..., Gn connected to the grid electrodes 1120
and extending toward the outside, and 1124 denotes an
electron source substrate whose devices disposed in
each row are connected in common in the manner as
described above. In Figures 7 and 10, similar members
are denoted by similar reference numerals. The
image-forming apparatus of this embodiment differs from
the simple-matrix image-forming apparatus (Figure 7)
described above in that the grid electrode 1120 is
disposed between the electron source substrate 1110 and
the face plate 1086.
As described above, the grid electrode 1120 is
disposed in the middle between the substrate 1110 and
the face plate 1086. The grid electrode 1120 is used
to modulate the electron beam emitted by the surface
conduction electron-emitting devices. The grid
electrode 1120 includes stripe-shaped electrodes
extending in a direction perpendicular to the device
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rows arranged in the ladder-form wherein the
stripe-shaped electrodes have circular openings 1121
disposed at location corresponding to the respective
electron-emitting devices so that an electron beam may
pass through these openings. The shape and the
location of the grid is not limited to that shown in
Figure 11. For example, many openings may be disposed
in a mesh form. Furthermore, openings may also be
provided at locations in the vicinities of, or in
peripherals of, surface conduction electron-emitting
devices.
The terminals 1122 extending outward from the
case and the grid terminals 1123 extending outward from
the case are electrically connected to a control
circuit (not shown).
In this image-forming apparatus, one line of
image modulation signal is applied to a grid electrode
column in synchronization with the driving signal
applied row to row (scanning operation) thereby
controlling the irradiation of the electron beam to the
phosphor and thus displaying an image line to line.
The image-forming apparatus according to the
present invention can be applied not only to a
television system, but also to other display systems
such as a video conference system, a display for a
computer system, etc. Furthermore, the image-forming
apparatus according to the present invention can be
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coupled with a photosensitive drum and other elements
so as to form an optical printer.
EXAMPLES
Referring to specific examples, the present
invention will be described in further detail below.
Example 1
Using a photolithographic technique which will
be described in detail later, electron emission regions
were formed in areas 1201 assigned for the electron
emission regions on a substrate on which device
electrodes (X-direction wires 72 and Y-direction wires
73) are disposed in a matrix form as shown in Figure 12
so as to produce an electron source substrate on which
a plurality of surface conduction electron-emitting
devices are disposed.
The electrodes were formed so that, at wires of
the X-direction and Y-direction wires, they are
electrically isolated from each other by an insulator
(not shown). Figures lA to 1D illustrate a production
process flow associated with the surface conduction
type electron-emitting device. Figures 2A and 2B
illustrate a top view and a cross section of a surface
conduction type electron-emitting device produced.
Device electrodes were formed on a substrate by
means of photolithography according to the process
steps described below.
(1) A quartz substrate was employed as the
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insulating substrate 1. The quartz substrate was
cleaned well with an organic solvent. Then, electrodes
2 and 3 of Ni were formed on the substrate 1 using a
common evaporation technique and a photolithography
technique (Figure lA). The electrodes 2 were formed so
that the distance L1 between the electrodes was 2 um
the width W1 of the electrodes was 600 pm, and the
thickness thereof was 1000 A.
(2) Using an ink-jet ejecting device provided
with a piezo-electric device serving as the droplet
supplying mechanism 6, a 60 um3 droplet (one dot) of a
solution containing organic palladium (ccp-4230,
available from Okuno-Seiyaku Co., Ltd.) was deposited
between the electrodes 2 and 3 so that a thin film 4
having a width W2 of 300 um was formed (Figure 1B). In
this example, the volume of the recessed space formed
on the insulating substrate 1 between the electrodes 2
and 3 was 120 um3.
(3) Then, heat treatment was performed at 300°C
for 10 min so that a particle film serving as the thin
film 4 (Figure 1C) and consisting of palladium oxide
(Pd0) particles was formed. As described earlier, the
term "particle film" is used herein to refer to a film
composed of a plurality of particles, wherein the
particles may be dispersed in the film, or otherwise
the particles may be disposed so that they are adjacent
to each other or they overlap each other (or may be
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disposed in the form of islands).
(4) A voltage was applied across the electrodes
2 and 3 so that the thin film 4 was subjected to a
forming process (energization forming process) thereby
forming an electron emission region 5 (Figure 1D).
Using the electron source substrate produced in
the above-described manner, an envelope 1088 was formed
with a face plate 1086, a supporting frame 1082, and
rear plate 1081. Then the envelope 1088 was sealed.
Thus a display panel was obtained. Furthermore, an
image-forming apparatus provided with a driving circuit
capable of displaying a television image according to
an NTSC television signal, such as that shown in Figure
9, was produced.
The electron-emitting device produced according
to the method described above, the electron source
substrate produced using this electron-emitting device,
the display panel, and the image-forming apparatus all
showed good performance, and no problems were observed.
Furthermore, according to the method of producing a
surface conduction type electron-emitting device
described in the present example, the thin film 4 was
formed by supplying a droplet onto the substrate and
thus a process for patterning the thin film 4 was no
longer required. Furthermore, the thin film 4 was
formed with only one droplet (one dot) without
uselessly consuming the solution.
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Example 2
Device electrodes were formed on a substrate in
a ladder form so that the width (W1) of the device
electrodes was 600 um, the distance (L1) between the
device electrodes was 2 um, and the thickness of the
device electrodes was 1000 ~. Using this substrate
(Figure 13), surface conduction electron-emitting
devices were produced in a manner similar to that in
Example 1. In Figure 13, reference numeral 1301 denote
the substrate, and reference numeral 1302 denotes an
wire.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. The resultant
devices showed as good performance as in Example 1.
Example 3
Device electrodes were formed in a matrix form
on a substrate in the manner described above. Then,
surface conduction type electron-emitting devices were
produced on this substrate (Figure 12) using the
above-described ink-jet ejecting device of the bubble
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jet type in a manner similar to that in Example 1.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. The resultant
devices showed as good performance as in Example 1.
Example 4
Device electrodes were formed in a ladder form
on a substrate in the manner described above (Figure
13). Then, surface conduction type electron-emitting
devices were produced on this substrate using the
ink-jet ejecting device of the bubble jet type in a
manner similar to that in Example 1.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. The resultant
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devices showed as good performance as in Example 1.
Example 5
Surface conduction type electron-emitting
devices were produced in the same manner as in Example
1 except that the thin film 4 was formed of a 0.05 wt%
palladium acetate aqueous solution. Although the
solution used in this example was different from that
in Example 1, the obtained devices showed as good
performance as in Example 1.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. The resultant
devices showed as good performance as in Example 1.
Example 6
Surface conduction type electron-emitting
devices were produced in the same manner as in Example
1 except that the amount of one droplet was 30 um3 and
two droplets (two dots) were supplied for each device.
The obtained devices showed as good performance as in
Example 1. This means that if a proper amount of
solution is supplied, a desired thin film can be
CA 02295408 2000-O1-13
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formed.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. The resultant
devices showed as good performance as in Example 1.
Example 7
Surface conduction type electron-emitting
devices were produced in the same manner as in Example
1 except that the amount of one droplet was 200 um3.
Although the width of the thin film 4 became
greater than the width of the electrodes 2 and 3 as
shown in Figure 3, the resultant devices showed good
electron emission performance.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1081 in a manner
similar to that in Example 1. Then the envelope 1088
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
CA 02295408 2000-O1-13
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that shown in Figure 9, was produced. The resultant
devices showed similar performance to that in Example
1.
However, the increase in the length of the
electron emission region 5 exceeding the length of the
device electrodes resulted in a variation in the
performance and thus the picture quality was poor
relative to that in Examples 1 to 6.
Example 8
Electron-emitting devices were produced using
the apparatus shown in Figure 14. The process of
supplying a droplet was performed in the manner shown
in the flow chart of Figure 15.
In Figure 14, reference numeral 1 denotes an
insulating substrate, 2 and 3 denote an electrode, 4
denotes a droplet, 5 denotes a thin film, 6 denotes an
electron emission region, 7 denotes an ink-jet ejecting
device, 8 denotes light emitting means, 9 denotes light
receiving means, 10 denotes a stage, and 11 denotes a
controller.
The production was performed as follows.
(1) Electrode formation process
A flat glass substrate was employed as the
insulating substrate 1. The glass substrate was
cleaned well with an organic solvent. Then, electrodes
2 and 3 of Ni were formed on the substrate 1 using an
evaporation technique and a photolithography technique.
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The electrodes 2 were formed so that the distance
between the electrodes was 3 pm the width of the
electrodes was 500 yam, and the thickness thereof was
1000
(2) Positioning process
As for the ink-jet ejecting device 7, an
ink-jet print head capable of ejecting a droplet of
solution by bubble jet type ink-jet ejecting device was
employed. An optical sensor serving as the light
receiving means 9 for detecting an optical signal and
converting it into an electrical signal was disposed at
a side of the print head. An insulating substrate 1
having electrodes 2 and 3 was placed on the stage 10
and fixed thereon. The back face of the insulating
substrate 1 was illuminated by light emitted from a
light emitting diode serving as the light emitting
means 8. Under the control of the controller 11, the
stage 10 was moved while monitoring, with the light
receiving means 9, the light passing through the area
between the device electrodes 2 and 3 so that the ink
jet position comes to a correct position between the
device electrodes 2 and 3.
(3) Droplet supplying process
Using an ink-jet ejecting device 7, a droplet 4
of a solution containing organic palladium (ccp-4230
available from Okuno-Seiyaku Co., Ltd.) serving as a
material of a thin film (.particle film) 5 was deposited
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between the electrodes 2 and 3.
(4) Droplet detection process
In a manner similar to that in the positioning
process, it was checked whether a droplet 4 was
supplied properly.
While the droplet 4 was deposited at a correct
position in this example, if the droplet 4 was not
supplied between the device electrodes 2 and 3, the
droplet supplying process is performed repeatedly until
it is concluded in the droplet detection process that a
droplet 4 has been supplied successfully. This reduces
the number of defects which are produced in the thin
film 4 during the process of forming the thin film 4.
(5) Heating process
The insulating substrate 1 on which the droplet
4 was deposited was heated at 300°C for 10 min so that
a particle film consisting of palladium oxide (Pd0)
particles was formed. Thus, a thin film 5 was
obtained. The diameter of the resultant thin film was
150 pm and it was located at a substantially central
position between the device electrodes 2 and 3. The
thickness was 100 ~, and the sheet resistance was 5 x
10452/square .
As described earlier, the term "particle film"
is used here to refer to a film composed of a plurality
of particles, wherein the particles may be dispersed in
the film, or otherwise the particles may be disposed so
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that they are adjacent to each other or they overlap
each other (or may be disposed in the form of islands).
The surface conduction type electron-emitting
devices obtained in the above-described manner were
subjected to a forming process. The resultant devices
showed good performance.
Example 9
Figure 16 illustrates the droplet supplying
process using the production apparatus employed in this
example.
In this example,.electrodes were formed in a
manner similar to that in Example 8. Then, positioning
was performed in the same manner as in Example 8 except
that instead of moving the stage 10, the ink-jet
ejecting device 7 and the light receiving means 9
disposed adjacent to each other were moved by means of
control means 12. After that, a droplet supplying
process, a droplet detection process, and a heating
process were performed in the same manner as in Example
8 thereby obtaining surface conduction type
electron-emitting devices. In this example, the light
emitting means 8 was provided with a mechanism (not
shown) capable of moving in synchronization with the
movement of the light receiving means 9.
The surface conduction type electron-emitting
devices obtained in the above-described manner showed
as good device performance as in Example 8.
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Example 10
Figure 17 illustrates the droplet supplying
process using the production apparatus employed in this
example.
In this example, electrodes were formed in a
manner similar to that in Example 8. In this example,
the light emitting means, the ink-jet 7, and the light
receiving means 9 were located adjacent to each other,
and the position between the device electrodes 2 and 3
was detected by detecting the light emitted by the
light emitting means 8 and then reflected from the
substrate. After that, a droplet supplying process, a
droplet detection process, and a heating process were
performed in the same manner as in Example 8 thereby
obtaining surface conduction electron-emitting devices.
The surface conduction electron-emitting
devices obtained in the above-described manner showed
as good device performance as in Example 8.
Example 11
In this example, an electron beam generation
apparatus using an electron source substrate such as
that shown in Figure 21 was produced.
First, a plurality of electron-emitting devices
were formed on an insulating substrate 1 in a manner
similar to that in Example 8. A grid (modulation
electrode) 13 having electron transmission holes 14 was
disposed above the insulating substrate 1 so that the
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orientation of the grid 13 was perpendicular to the
device electrodes 2 and 3 thereby forming an electron
beam generation apparatus.
The performance of the electron source obtained
in the above-described manner was evaluated. The
electron beam emitted by the electron-emitting devices
was switched in an on-off fashion in response to
information signal applied to the grid 13. It was also
possible to continuously control the amount of
electrons of the electron beam according to information
signal applied to the grid 13. Furthermore, there was
a very small variation in the amount of electrons of
the electron beam among electron-emitting devices.
Example 12
Using a substrate on which a plurality of
electron-emitting devices were formed in a manner
similar to that in Example 11, an image-forming
apparatus provided with a grid such as that shown in
Figure 11 was produced. The resultant image-forming
apparatus showed good performance without having any
problems.
Example 13
Using a substrate on which a plurality of
electron-emitting devices were formed in a manner
similar to that in Example 8, an image-forming
apparatus such as that shown in Figure 7 was produced.
The resultant image-forming apparatus showed good
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performance without having any problems.
Example 14
According to the ink-jet method of the
invention, surface conduction electron-emitting devices
were formed on a substrate on which interconnections
were formed in a 10 x 10 matrix form, as shown in
Figure 22. Figure 31A is an enlarged view illustrating
each unit cell. Each unit cell is composed of: wires
241 and 242 extending in directions perpendicular to
each other; and device electrodes 2 and 3 disposed at
opposing locations wherein each device electrode is
connected to either wire. The wires 241 and 242 were
formed by means of a printing technique. At
intersections of these wires, they are electrically
isolated from each other by an insulator (not shown).
The opposing device electrodes 2 and 3 were formed of
an evaporated film which was patterned by means of
photolithography. The width of the gap between the
device electrodes was about 10 um, the gap length was
500 um, and the film thickness of the device electrodes
was 30 nm. According to the ink-jet method of the
invention, an ink droplet of a solution containing
organic palladium (Pd concentration of 0.5 wt%) was
ejected a few times onto the central position of the
gap between device electrodes thereby forming a droplet
7. Then, a drying process and a baking process (at
350°C for 30 min) were performed. Thus, an
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electrically-conductive thin film in a circular form
having a diameter of about 300 um and a thickness of 20
nm consisting of Pd0 particles was obtained.
Figure 23 is a block diagram of an ejection
control system used to form a thin film according to
the ink-jet method of the invention. In this figure,
reference numeral 1 denotes a substrate on which a unit
cell is formed. Reference numerals 2 and 3 denote
opposing device electrodes. Reference numeral 1501
denotes an ejection nozzle of the ink-jet ejecting
device, and 1502 denotes an optical system for
detecting information associated with a droplet.
Reference numeral 1503 denotes a displacement control
mechanism on which there are mounted the detection
optical system and an ink-jet cartridge composed of the
ejection nozzle, an ink tank, and a supplying system.
The displacement control mechanism 1503 includes: a
coarse adjustment mechanism responsible for movement
from a unit cell to another cell on a substrate
provided matrix-shaped wires; and a fine adjustment
mechanism responsible for horizontal positioning within
a unit cell and for adjustment of distance between the
substrate and the ejection nozzle. In this example, a
piezoelectric ink-jet ejecting device was employed as
the ink-jet ejecting device. As for the optical
detecting system, the vertical reflection type was
used.
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In this example, information associated with a
droplet is detected according to the method of the
invention, and the ejecting operation is controlled on
the basis of the detected information, as will be
described in detail below.
In this example, the amount of a droplet is
controlled by controlling the number of times of
ejecting operations while the amount of a droplet in
each ejecting operation is maintained to a fixed value.
In the piezoelectric ink-jet device, the amount of a
droplet ejected in each operation is controlled by
controlling the height and the width of a voltage pulse
applied to the piezoelectric element for ejecting a
droplet. In this specific example, the amount of a
droplet ejected through the ejecting nozzle in each
ejecting operation is set to 10 ng so that a droplet of
100 ng in total amount is obtained by 10 ejecting
operations.
The displacement control mechanism is driven on
the basis of preset coordinate information so that the
end of the ejection nozzle comes to a location at a
height of 5 mm above the center of a gap between
electrodes in a unit cell. Then, an ejecting operation
is started according to the given driving conditions.
At the same time, the optical detecting system starts
detecting droplet information at the center of a gap
between device electrodes.
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Figure 24 illustrates a detail of optical
detecting system of the vertical reflection type.
Linearly polarized light is emitted by a semiconductor
laser 161. The light is reflected by a mirror 162, and
then passes through a beam splitter 163, a 1/4~, plate
164, and a focusing lens 165. Finally, the light is
incident on a droplet at a right angle. After passing
through the droplet, a part of the light is reflected
at the surface of the substrate, and travels backward.
The reflected light passes again through the droplet
and is incident on the 1/4~, plate 164. As a result of
the second passage through the 1/4~, plate 164, the
reflected light becomes linearly polarized light whose
polarization direction is shifted by 90° relative to
that of the incident light. The reflected light is
further reflected by the beam splitter 163 into a
direction perpendicular to the previous path so that
the light is incident on a photo detector 166 such as a
photodiode. The intensity of the reflected light is
modulated by scattering and absorption during the two
times of passage through a droplet. Therefore, it is
possible to determine the thickness of the droplet from
the intensity of the reflected light.
The output of the photodiode is amplified by an
optical information detecting circuit 1504 and then
sent to a comparator 1505. The comparator 1505
compares the input signal with a reference value and
CA 02295408 2000-O1-13
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outputs a difference signal. The reference value is
set to a value determined experimentally so that the
film thickness becomes 20 nm after baked. The
intensity of the reflected light decreases as the
thickness of the droplet increases, and thus difference
signal defined as "(detection signal) - (reference
signal)" decreases as the thickness of the droplet
increases toward the optimum value. The difference
signal becomes zero when the droplet thickness reaches
the optimum value. If the droplet thickness increases
further exceeding the optimum value, the difference
signal has a negative value. The difference signal
output by the comparator 1505 is applied to an ejection
condition correcting circuit 1506. The ejection
condition correcting circuit 1506 outputs a HI-level
signal when the difference signal has a positive value,
while a LOW-level signal is output when the difference
signal has a negative value. The output of the
ejection condition correcting circuit 1506 is applied
to an ejection condition controlling circuit 1507. The
ejection condition controlling circuit 1507 performs an
ejecting operation under fixed conditions at fixed time
intervals as long as the output signal of the ejection
condition correcting circuit 1506 is maintained at a HI
level. If the output of the ejection condition
correcting circuit 1506 goes to a LOW level, the
ejection condition controlling circuit 1507 stops the
CA 02295408 2000-O1-13
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ejecting operation.
After depositing the droplet, the 10 x 10
matrix-electrode substrate was baked at 350°C for 30
min so that the droplet became a thin film consisting
of Pd0 particles. The resistance between the device
electrodes was measured. A normal resistance around 3
kS2 was observed even in those cells which needed an
unusual number of times of ejecting operations. A
forming process was then performed by applying a
forming voltage across the device electrodes from unit
cell to unit cell thereby forming an electron emission
region at the center of a gap between device electrodes
of each unit cell.
The electron source substrate obtained in the
above-described manner was set in the electron emission
characteristic measuring system shown in Figure 5, and
electron emission performance was evaluated. All of
100 devices showed uniform electron emission
performance. Furthermore, a greater number of cells
were formed on a large-sized substrate (such as that
shown in Figure 12), and a droplet was deposited on
each unit cell, in a manner similar to that in the case
of the substrate having 10 x 10 cells, using the
ejection control system shown in Figure 23, the
piezoelectric ink-jet ejecting device, and the optical
detecting system of the vertical reflection type. A
baking process was then performed at 350°C for 30 min.
CA 02295408 2000-O1-13
_ 77 _
Thus, a thin film consisting of Pd0 particles was
formed in all unit cells. The resistance between the
device electrodes was measured. A normal resistance
around 3 kS2 was observed even in those unit cells which
needed an unusual number of times of ejecting
operations. A forming process was then performed by
applying a forming voltage across the device electrodes
from cell to cell thereby forming an electron emission
region at the center of a gap between device electrodes
of each cell.
Using the electron source substrate obtained in
the above-described manner, an envelope 1088 was formed
with a face plate 1086, a supporting frame 1082, and
rear plate 1081, in the manner described above in
connection with Figure 7. Then the envelope 1088 was
sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit was produced. All devices, including
those which needed an unusual number of times of
ejecting operations, showed uniform characteristics.
Thus, the resultant image-forming apparatus showed good
performance in displaying a TV image with a small
variation in brightness.
In the present invention, as described above,
even in the case where deposition of a droplet needs an
unusual number of ejecting operations due to some
unusual condition in the ejection nozzle, wettability
CA 02295408 2000-O1-13
_ 7g _
of a substrate, droplet arrival location, etc., a thin
film can be formed in a gap between device electrodes
uniformly in the composition, homology, and thickness.
This indicates that the ejecting operation can be
controlled effectively according to the present
invention.
Example 15
In Example 14 described above, the ejecting
operation is controlled by controlling the number of
times of ejecting operations. Instead, in this
example, either the height or the width of the ejection
driving pulse is controlled. In the piezoelectric
ink-jet device, as described above, the amount of a
droplet ejected in each ejecting operation is
determined by the height and the width of a voltage
pulse applied to the piezoelectric element for ejecting
a droplet. Therefore, it is possible to control the
amount of a droplet to a desired value by controlling
at least either the height or the width of the driving
pulse on the basis of the information associated with
the droplet. In this example, the number of ejecting
operations is fixed to two, wherein the standard amount
of a droplet ejected in one ejecting operation is set
to 50 ng, and thus a droplet having a total amount of
100 ng is produced by two ejecting operations.
In this example, information associated with a
droplet is detected, and the ejecting operation is
CA 02295408 2000-O1-13
_ 79 _
controlled on the basis of the detected information, as
will be described in detail below with reference to
Figure 24: Except the method of controlling the
ejecting operation, the other parts of this example are
the same as those in Example 14. As for the optical
detecting system 1602, the vertical reflection type is
employed as in Example 14. The displacement control
mechanism 1603 is driven on the basis of preset
coordinate information so that the end of the ejection
nozzle 1601 comes to a location at a height of 5 mm
above the center of a gap between electrodes 2 and 3 in
a unit cell. Then, a first ejecting operation is
performed according to the 50-ng driving conditions
given previously. Then, information associated with a
droplet at the center of a gap between device
electrodes is detected with the optical detecting
system.
A signal including the information associated
with the droplet ejected in the first ejecting
operation is output by the photodiode and amplified by
an optical information detecting circuit 1604 and then
sent to a comparator 1605. The comparator 1605
compares the received signal with a reference value and
outputs a difference signal. The reference value is
determined experimentally so that the reference value
corresponds to the intensity of the light reflected
from a correct amount of droplet deposited in a first
CA 02295408 2000-O1-13
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ejecting operation so that, after a second droplet is
further deposited, the total amount of the deposited
droplet has a thickness of 20 nm when measured after
baked. The intensity of the reflected light decreases
as the thickness of the droplet increases, and thus
difference signal defined as "(detection signal) -
(reference signal)" changes as a function of the
deviation of the droplet thickness from an optimum
value. The difference signal output by the comparator
1605 is applied to an ejection condition correcting
circuit 1606. Correction signal data is experimentally
determined on the basis of the relationship between the
difference signal and the deviation in the droplet
amount and stored in the ejection condition correcting
circuit 1606. On the basis of this data, the ejection
condition correcting circuit 1606 calculates a
correction signal corresponding to the difference
signal and outputs the resultant correction signal to
an ejection condition controlling circuit 1607. The
ejection condition controlling circuit 1607 corrects
the height or the width of the driving pulse on the
basis of the correction signal received from the
ejection condition correcting circuit 1606, and
performs a second ejecting operation.
After completion of depositing the droplet, the
10 x 10 matrix-electrode substrate was baked at 350°C
for 30 min so that the droplet became a thin film
CA 02295408 2000-O1-13
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consisting of Pd0 particles. The resistance between
the device electrodes was measured. A normal
resistance around 3 kit was observed even in those cells
which showed an unusual operation in the first ejecting
operation. A forming process was then performed by
applying a forming voltage across the device electrodes
from unit cell to unit cell thereby forming an electron
emission region at the center of a gap between device
electrodes of each unit cell.
The electron source substrate obtained in the
above-described manner was set in the electron emission
characteristic measuring system shown in Figure 5, and
electron emission performance was evaluated. All of
100 devices showed uniform electron emission
performance.
Furthermore, a greater number of unit cells
were formed on a large-sized substrate (such as that
shown in Figure 12), and a droplet was deposited on
each cell, in a manner similar to that in the case for
the substrate having 10 x 10 cells, according to the
ejection control method shown in Figure 24, using a
piezoelectric ink-jet ejecting device. A baking
process was then performed at 350°C for 30 min. Thus,
a thin film consisting of Pd0 particles was formed in
all cells. The resistance between the device
electrodes was measured. A normal resistance around 3
kn was observed even in those cells which showed an
CA 02295408 2000-O1-13
- 82 -
unusual operation in the first ejecting operation. A
forming process was then performed by applying a
forming voltage across the device electrodes from cell
to cell thereby forming an electron emission region at
the center of a gap between device electrodes of each
unit cell.
Using the electron source substrate obtained in
the above-described manner, an envelope 1088 was formed
with a face plate 1086, a supporting frame 1082, and
rear plate 1081, in the manner described above in
connection with Figure 7. Then the envelope 1088 was
sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced. All devices,
including those which needed an unusual number of times
of ejecting operations, showed uniform characteristics.
Thus, the resultant image-forming apparatus showed good
performance in displaying a TV image with a small
variation in brightness.
In the present invention, as described above,
even in the case where deposition of a droplet needs an
unusual number of ejecting operations in a first
ejecting operation due to some unusual condition in the
ejection nozzle, wettability of a substrate, droplet
arrival location, etc., a thin film can be formed in a
CA 02295408 2000-O1-13
- 83 -
gap between device electrodes uniformly in the
composition, homology, and thickness.
Example 16
In Examples 14 and 15 described above, an
optical detecting system is employed as the means of
detecting information associated with a droplet.
Instead, in this example, an electrical detecting
system is employed. Except the detection method, the
other parts of this example are the same as those in
Example 7.
Referring to Figure 25, the method of forming a
thin film using an ink-jet ejecting system according to
the invention will be described in detail below. In
this figure, reference numeral 1 denotes a substrate on
which a unit cell is formed. Reference numerals 2 and
3 denote opposing device electrodes. Reference numeral
1801 denotes an ejection nozzle of the ink-jet ejecting
device, and 1808 denotes an electric system for
detecting an electrical property of a droplet.
Reference numeral 1803 denotes a displacement control
mechanism on which there is mounted an ink-jet
cartridge comprising the ejection nozzle, an ink tank,
and a supplying system. The displacement control
mechanism 1503 includes: a coarse adjustment mechanism
responsible for movement from a unit cell to another
cell on a matrix-shaped interconnection substrate;.and
a fine adjustment mechanism responsible for horizontal
CA 02295408 2000-O1-13
- 84 -
positioning within a unit cell and for adjustment of
distance between the substrate and the ejection nozzle.
In this example, a bubble-jet ejecting device is
employed as the ink-jet ejecting device.
In this example, information associated with a
droplet is detected, and the ejecting operation is
controlled on the basis of the detected information, as
will be described in detail below. In this example, as
in Example 14, the amount of a droplet is controlled by
controlling the number of times of ejecting operations
while the amount of a droplet in each ejecting
operation is maintained to a fixed value. In this
specific example, a droplet of 100 ng is formed by 10
ejecting operations.
The displacement control mechanism 1803 is
driven on the basis of preset coordinate information so
that the end of the ejection nozzle comes to a location
at a height of 5 mm above the center of a gap between
electrodes 2 and 3 in a unit cell. Then, an ejecting
operation is started according to the given driving
conditions. At the same time, the electric measuring
system 1808 starts detecting droplet information at the
center of a gap between device electrodes.
The electric measuring system 1808 detects
electrical properties of a droplet by measuring a
current which flows in response to a voltage applied
across device electrodes 2 and 3. Electrical
CA 02295408 2000-O1-13
- 85 -
properties to be detected include resistance of a
droplet, capacitance of a droplet, etc. The amount of
a droplet in a gap between device electrodes can be
estimated on the basis of the relationship between the
amount of a droplet and the electric properties.
Although a DC voltage may be employed as the applied
voltage for detection, an AC voltage having a
relatively small amplitude in the range from 10 mV to
500 mV at a relatively large frequency in the range
from 100 Hz to 100 kHz is more preferable to suppress a
chemical reaction such as generation of gas in a
solution. The AC voltage is phase-detected thereby
extracting a current component having the same phase as
that in the applied voltage and a current component
having a phase delayed by amount of 90°. This
technique allows simultaneous detection of both the
resistance and capacitance of a droplet. In this
specific example, only the resistance of a droplet is
detected. The type of ink is not limited to a special
one as long as it is possible to measure its
resistance. In this example, an aqueous solution
containing organic palladium (Pd concentration of 0.5
wto) exhibiting good ionic conduction is employed.
The current signal output by the electric
measuring system 1808 is applied to an electric
information detecting circuit 1809. In the electric
information detecting circuit 1809, the received
CA 02295408 2000-O1-13
- 86 -
current signal is converted into a voltage form and
amplified. Furthermore, the signal is phase-detected
with a lock-in amplifier. Then the resistance is
calculated and the result is sent to a comparator 1810.
The comparator 1810 compares the received signal with a
reference value and outputs a difference signal. The
reference value is experimentally determined so that
the reference value corresponds to a resistance which
will result in a final film thickness of 20 nm after
baked. In the case of the aqueous solution containing
organic palladium (Pd concentration of 0.5 wt~), the
reference value is set to 70 k~2. The resistance
decreases as the thickness of the droplet increases,
and thus difference signal defined as "(detection
signal) - (reference signal)" decreases as the
thickness of the droplet increases toward the optimum
value. The difference signal becomes zero when the
droplet thickness reaches the optimum value. If the
droplet thickness increases further exceeding the
optimum value, the difference signal has a negative
value. The difference signal output by the comparator
1810 is applied to an ejection condition correcting
circuit 1811. The ejection condition correcting
circuit 1811 outputs a HI-level signal when the
difference signal has a positive value, while a
LOW-level signal is output when the difference signal
has a negative value. The output of the ejection
CA 02295408 2000-O1-13
_ 87 _
condition correcting circuit 1811 is applied to an
ejection condition controlling circuit 1807. The
ejection condition controlling circuit 1807 performs an
ejecting operation under fixed conditions at fixed time
intervals as long as the output signal of the ejection
condition correcting circuit 1811 is maintained at a HI
level. If the output of the ejection condition
correcting circuit 1811 goes to a LOW level, the
ejection,condition controlling circuit 1807 stops the
ejecting operation.
The electron source substrate obtained in the
above-described manner was set in the electron emission
characteristic measuring system shown in Figure 5, and
electron emission performance was evaluated. All of
100 devices showed uniform electron emission
performance.
Furthermore, a greater number of cells were
formed on a large-sized substrate (such as that shown
in Figure 12), and a droplet was deposited on each unit
cell, in a manner similar to that in the case of the
substrate having 10 x 10 cells, using the ejection
control system shown in Figure 23, the piezoelectric
ink-jet ejecting device, and the optical detecting
system of the vertical reflection type. A baking
process was then performed at 350°C for 30 min. Thus,
a thin film consisting of Pd0 particles was formed in
all cells. The resistance between the device
CA 02295408 2000-O1-13
_ 88 _
electrodes was measured. A normal resistance around 3
kit was observed even in those cells which needed an
unusual number of times of ejecting operations. A
forming process was then performed by applying a
forming voltage across the device electrodes from cell
to cell thereby forming an electron emission region at
the center of a gap between device electrodes of each
cell.
In the present invention, as described above,
even in the case where deposition of a droplet needs an
unusual number of ejecting operations due to some
unusual condition in the ejection nozzle, wettability
of a substrate, droplet arrival location, etc., a thin
film can be formed in a gap between device electrodes
uniformly in the composition, morphology, and
thickness. This indicates that the ejecting operation
can be controlled effectively according to the present
invention.
Example 17
Figure 26 is a block diagram of a system for
controlling the ejection conditions while the system
includes two separate detection systems, an electric
detection system and an optical detecting system. In
this system, although a detailed description is not
given here, an error is compensated on the basis of
information obtained via the two detection systems and
thus more accurate control of the ejection operation is
CA 02295408 2000-O1-13
_ g9 _
possible according to hybrid information.
Example 18
In this example, there is provided a droplet
amount correcting system including a removal nozzle.
There are two techniques of correcting the amount of a
droplet using a removal nozzle. One technique is to
remove a part of a droplet so that the remaining amount
becomes optimum when the detected droplet information
indicates that the amount of the droplet present in a
gap is greater than the optimum value. Another
technique is to remove the entire droplet once and then
eject another droplet. The. removal of a droplet may be
performed either by sucking the droplet or by ejecting
a gas such as nitrogen thereby blowing away the droplet
from a gap. In this specific example, the entire
droplet is removed by sucking the droplet with a
removal nozzle.
Furthermore, in this example, information
associated with a droplet is detected, and the ejecting
operation is controlled on the basis of the detected
information, as will be described in detail below with
reference to Figure 27. Except the removal nozzle, the
other parts of this example are the same as those in
Example 14. The removal nozzle 2012 is mounted on the
same position control mechanism 2003 as that on which
an ejection nozzle and an optical detecting system are
mounted, without having an additional position control
CA 02295408 2000-O1-13
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mechanism dedicated for the removal nozzle. In this
example, the standard amount of a droplet ejected at a
time via the ejection nozzle is set to 100 ng, and thus
a 100 ng droplet is deposited by one ejecting
operation.
The displacement control mechanism 2103 is
driven on the basis of preset coordinate information so
that the end of the ejection nozzle 2001 comes to a
location at a height of 5 mm above the center of a gap
between electrodes 2 and 3 in a unit cell. An ejecting
operation is then performed according to the given
driving conditions. Then, information associated with
a droplet at the center of a gap between device
electrodes is detected with the optical detecting
system 2002.
A signal including the information associated
with the droplet is output by a photodiode and
amplified by an optical information detecting circuit
2004 and then sent to a comparator 2005. The
comparator 2005 compares the received signal with a
reference value and outputs a difference signal. The
reference value is experimentally determined so that
the reference value corresponds to the intensity of
reflected light which will result in a final film
thickness of 20 nm after baked. The intensity of the
reflected light decreases as the thickness of the
droplet increases, and thus difference signal defined
CA 02295408 2000-O1-13
- 91 -
as "(detection signal) - (reference signal)" changes as
a function of the deviation of the droplet thickness
from an optimum value. Therefore, the difference
signal decreases as the thickness of the droplet
increases toward the optimum value, and the difference
signal becomes zero when the droplet thickness reaches
the optimum value. If the droplet thickness increases
further exceeding the optimum value, the difference
signal has a negative value. The difference signal
output by the comparator 2005 is applied to an ejection
condition correcting circuit 2006. The ejection
condition correcting circuit 2006 outputs a LOW-level
signal when the difference signal has a positive value,
while a HI-level signal is output when the difference
signal has a negative value. The output of the
ejection condition correcting circuit 2006 a.s applied
to a removal nozzle control circuit 2013. On the basis
of correction signal data which represents the
relationship between the difference signal and the
deviation in the droplet amount from the optimum value,
the ejection condition correcting circuit 2006
calculates a correction signal corresponding to the
difference signal and outputs the resultant correction
signal to an ejection condition controlling circuit
2007. When the output signal is at a HI level, the
removal nozzle control circuit 2013 does not perform
any operation. In this case, during an ejecting
CA 02295408 2000-O1-13
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operation, the ejection condition controlling circuit
2007 controls the height or the width of the driving
pulse in response to the correction signal. On the
other hand, in the case where a LOW-level signal is
output, the removal nozzle control circuit 2013
operates first so as to remove the entire amount of a
droplet by sucking it with the removal nozzle 2012,
then an ejecting operation is performed under the
control of the ejection condition controlling circuit
2007.
A droplet was deposited on each of 100 unit
cells on a 10 x 10 matrix-electrode substrate according
to the technique described above. In almost all cells,
the thickness of the droplet obtained after the first
ejecting operation was in an allowable range. In a few
percent of unit cells, however, the thickness was
greater than the upper acceptable limit. In the
example shown in Figure 28A, an extremely great amount
of droplet was ejected in one ejecting operation and
thus the droplet thickness became greater than the
acceptable upper limit. In this case, the entire
droplet was sucked via the removal nozzle, and the
another droplet was ejected under corrected conditions.
As a result of the re-ejection, a droplet having a
thickness within the allowable range was deposited as
shown on the right side of Figure 28A. In the example
shown in Figure 28B, the wettability of the substrate
CA 02295408 2000-O1-13
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used was unusually low, and the droplet thickness
became greater than the acceptable upper limit although
the ejected amount was proper. Also in this case,
re-ejection was performed in a manner similar to that
in the case of Figure 28A, and the resultant thickness
fell within the allowable range.
After completion of depositing the droplet, the
x 10 matrix-electrode substrate was baked at 350°C
for 30 min. Thus, a thin film consisting of Pd0
10 particles was obtained. The resistance between the
device electrodes was measured. A normal resistance
around 3 kit was observed even in those cells which
showed an unusual operation in the first ejecting
operation. A forming process was then performed by
applying a forming voltage across the device electrodes
from unit cell to unit cell thereby forming an electron
emission region at the center of a gap between device
electrodes of each cell.
' The electron source substrate obtained in the
above-described manner was set in the electron emission
characteristic measuring system shown in Figure 5, and
electron emission performance was evaluated. All of
100 devices showed uniform electron emission
performance.
Furthermore, a greater number of cells were
formed on a large-sized substrate (such as that shown
in Figure 12), and a droplet was deposited on each
CA 02295408 2000-O1-13
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cell, in a manner similar to that in the case of the
substrate having 10 x 10 unit cells, using the ejection
control system including the removal nozzle shown in
Figure 27, and the piezoelectric ink-jet ejecting
device. A baking process was then performed at 350°C
for 30 min. Thus, a thin film consisting of Pd0
particles was formed in all unit cells. The resistance
between the device electrodes was measured. A normal
resistance around 3 k~2 was observed even in those cells
which needed an unusual number of times of ejecting
operations. A forming process was then performed by
applying a forming voltage across the device electrodes
from unit cell to unit cell thereby forming an electron
emission region at the center of a gap between device
electrodes of each cell.
Using the electron source substrate obtained in
the above-described manner, an envelope 1088 was formed
with a face plate 1086, a supporting frame 1082, and
rear plate 1081, in the manner described above in
connection with Figure 7. Then the envelope 1088 was
sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit was produced. All devices, including
those which needed an unusual number of times of
ejecting operations, showed uniform characteristics.
Thus, the resultant image-forming apparatus showed good
performance in displaying a TV image with a small
CA 02295408 2000-O1-13
- 95 -
variation in brightness.
In the present invention, as described above,
even in the case where deposition of a droplet needs an
unusual number of ejecting operations in a first
ejecting operation due to some unusual condition in the
ejection nozzle, wettability of a substrate, droplet
arrival location, etc., a thin film can be formed in a
gap between device electrodes uniformly in the
composition, morphology, and thickness.
Example 19
In this example, in.addition to the means of
controlling the ejection operation on the basis of the
information of.a droplet, there are also provided means
of optically detecting the droplet arrival position and
means of adjusting the ejection position on the basis
of the information of the droplet arrival position.
Figure 29 is a block diagram illustrating the
system of detecting the information of a droplet and
controlling the ejecting position on the basis of the
information of the droplet. Except the optical
detecting system, the other parts of this example are
the same as those in Example 14. Since the control of
the ejecting operation has been described in detail
above in connection with the previous examples, only
the control of the positioning operation will be
described herein below.
The optical detecting system 2202 used in this
CA 02295408 2000-O1-13
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example is of a vertical reflection type similar to
that used in Example 14. However, unlike the system in
Example 14, the optical detecting system 2202 uses two
beams, that is, a beam for detecting information of a
droplet, and a sub-beam for detecting the position.
This multi-beam type optical system is similar to an
optical detecting system which is broadly used to
achieve a tracking operation in a compact disk system.
A light beam emitted by a semiconductor laser is
divided by a diffraction grating into three beams
aligned in one line. These three beams are reflected
and modulated at different loc~.tions, and detected by
separate sensors. From the relationship among the
intensities of these reflected light beams, the
information of the position is detected.
The detection and the control of the position
may be performed either for an electrode pattern or a
dedicated alignment mark before ejecting a droplet, or
for a deposited droplet after completion of an ejecting
operation. The droplet arrival position may be
detected either by comparing the intensities of the
three reflected beams with each other after an ejecting
operation, or by comparing the intensities of the three
reflected beams before an ejecting operation with those
after the ejecting operation. The control of the
ejecting position may be either in a manner that a
preliminary ejection is performed first, and then an
CA 02295408 2000-O1-13
_ 97 _
actual ejection is performed at a position corrected on
the basis of the result of the preliminary ejection or
in a manner that a position is detected and a
corresponding correction is performed for each ejecting
operation.
Figure 30 illustrates an example of a manner in
which the droplet position is controlled. After a
first ejecting operation, the intensities of the three
beams aligned in a line perpendicular to a gap between
device electrodes are detected and compared with each
other. From the comparison result, the deviation of
the droplet arrival position from the center of the gap
between the device electrodes is determined. In
response to a correction signal representing the amount
of the deviation, the displacement control mechanism
2203 (Figure 29) corrects the ejecting position so that
a droplet is ejected at a correct position in a next
ejecting operation and also operations further
following that.
Example 20
In Examples 14 to 19 described above, one
droplet is ejected at a fixed position thereby forming
a thin film in an electron emission region. However,
the present invention is not limited to that, and
various modifications are possible. Figures 31A to 31C
illustrate some examples of possible device structures,
wherein Figure 31A illustrates the device structure
CA 02295408 2000-O1-13
_ 98 _
employed in Examples 14 to 19, Figure 31B illustrates a
device structure which is formed by ejecting a
plurality of droplets at different positions, and
Figure 31C illustrates a device structure which is
formed by ejecting a plurality of droplets so that not
only the thin film in the electron emission region but
also a part of each device electrode are formed of the
plurality of droplets. In any device structure, the
techniques of controlling the ejecting operation and
the techniques of controlling the ejecting position
used in Examples 14 to 19 descried above may be
employed.
Furthermore, in Examples 14 to 19, wires are
formed in a matrix fashion. However, the invention is
not limited to that. The wires may also be formed in
other shapes such as a ladder shape.
Example 21
A substrate having device electrodes connected
via matrix-shaped wires was prepared, and surface
conduction type electron-emitting devices were produced
thereon as described below. Figure 33A is a plan view
of the surface conduction electron-emitting device
obtained. Referring to Figures 32A and 32B and 33A to
33D, the production process will be described in detail
below.
(1) A quartz substrate was employed as an
insulating substrate. The quartz substrate was cleaned
CA 02295408 2000-O1-13
- 99 -
well with an organic solvent. Then the substrate was
dried at 120°C.
(2) Using an ink-jet ejecting device provided
with a piezo-electric device serving as the droplet
supplying mechanism, droplets of a solution containing
organic palladium (ccp-4230, available from
Okuno-Seiyaku Co., Ltd.) were deposited on the above
cleaned substrate. The measured diameter of the
obtained dots was 50 um (Figure 32A).
(3) Then, electrodes 2 and 3 of Ni were formed
on the substrate 1 using an evaporation technique and a
photolithography technique so that the gap length L1
between the device electrodes was 200 um, the width Wl
of the electrodes was 600 um, and the thickness of the
electrodes was 1000 A.
(4) Droplets of a solution containing organic
palladium (ccp-4230, available from Okuno-Seiyaku Co.,
Ltd.) described above were deposited between the device
electrodes 2 and 3 as shown in Figure 33A, using the
ink-jet ejecting device provided with the
piezo-electric device serving as the droplet supplying
mechanism, wherein the ejecting operation was
controlled so that the diameter of the resultant dots
became 50 um. Eleven dots having a diameter of 50 pm
described in (2) were formed in the gap of 200 um so
that the center-to-center distance P1 between adjacent
dots was 25 um and thus each dot overlaps adjacent dots
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at either sides by an amount of 25 um. The overlapping
areas expanded after the dots were deposited. As a
result, each edge along the length changed into a
straight line. Thus, a line of dots (pad) having a
width W2 of 50 pm and a length T of 300 um was
obtained.
(5) Then, heat treatment was performed at 300°C
for 10 min so that a particle film consisting of
palladium oxide (Pd0) particles was formed. Thus, a
thin film 4 was obtained.
(6) A voltage was applied across the electrodes
2 and 3 so that the thin film 4 was subjected to a
forming process (energization forming process) thereby
producing an electron emission region 5.
In the electron source substrate obtained in
the above-described manner, since the pad was formed of
dots overlapping each other, the width W2 of the pad
came to have a constant value along the length of the
pad. Furthermore, the variation in the thickness was
small and thus the variation in resistance was also
small.
In this technique, a pad consisting of a Pd0
particle film can be formed in a gap between device
electrodes with a margin of a few ten um in both
vertical and horizontal directions. Therefore, no
difficult alignment process is required. This allows a
reduction of defects due to an alignment error.
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It is not necessary that dots be deposited
successively from a dot to an adjacent dot from left to
right or in the opposite direction, and dots may be
deposited in an arbitrary order. For example, dots may
be deposited at every other dot locations first, and
then a dot may be further deposited in each space.
Furthermore, each dot was formed by ejecting
two droplets instead of one droplet. In this case, the
film thickness became about twice and the resistance
became about half. This means that it is possible to
control the resistance of the thin conductive film by
changing the number of droplets ejected.
Furthermore, each dot was formed by ejecting a
twice amount of droplet. The result was similar to
that obtained with two droplets each having the
original amount. This means that it is also possible
to form a thin conductive film having an arbitrary
resistance by controlling the amount of a droplet.
In the technique described in this example, it
is possible to produce a plurality of devices with
small variations in characteristics from device to
device, and thus it is possible to improve the
production yield. Furthermore, since no patterning
process is required to form a thin film 4, the
production cost can be reduced.
Using the electron source substrate having
matrixrshaped wires obtained in the above-described
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manner, an envelope was formed with a face plate, a
supporting frame, and rear plate. Then the envelope
was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image was produced. The resultant image-forming
apparatus had only a small number of defects, and
showed good performance in displaying a TV image with a
small variation in brightness.
Example 22
Device electrodes were formed in a ladder form
on a substrate so that the width W1 of the device
electrodes was 600 umm the gap length L1 between the
device electrodes was 200 um, and the thickness d of
the device electrodes was 1000 ~1. Then, surface
conduction type electron-emitting devices were produced
on this substrate in a manner similar to that in
Example 21. Using the obta~.ned electron source
substrate, an envelope was formed with a face plate, a
supporting frame, and rear plate. Then the envelope
was sealed. Thus, an image-forming apparatus was
obtained. The resultant image-forming apparatus showed
as good performance as in Example 21.
Example 23
As in Example 21, device electrodes were formed
on a substrate so that the width W1 of the device
electrodes was 600 umm the gap length L1 was 200 um,
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and the thickness d of the device electrodes was 1000
Then, droplets of a solution containing organic
palladium were deposited on the above substrate using
an ink-jet ejecting device similar to that used in
Example 21. In this example, the droplets were
deposited so that the shape of a pad became such as
that shown in Figure 35A2. Two lines of dots each
including eleven dots having a diameter (~) of 50 um
such as that described in (2) of Example 21 were formed
in'the gap of 200 um so that the center-to-center
distances P1 and P2 between adjacent dots were 25 um
(~/2) and thus each dot overlaps adjacent dots at
either sides by an amount of 25 um. As a result, a
rectangular pad having a width W2 of 75 um and a length
T of 300 um was obtained. Electron-emitting devices
were formed in the same manner as in Example 21 except
that pads were formed into a different shape. The
resultant devices showed good characteristics and the
variation in characteristics from device to device was
as small as in Example 21. In this example, since the
pad was formed of two lines of dots, the resultant
resistance was half that of a pad formed of one line of
dots. This means that it is possible to obtain a
desired resistance by changing the number of lines of
dots. That is, the width W2 of the pad is determined
so as to obtain a desired resistance within the upper
limitation equal to the width W1 of the device
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electrodes, wherein the alignment accuracy should be
also taken into account.
Example 24
Using a substrate which is similar to that used
in Example 21 except that the gap length between device
electrodes was 20um, droplets were deposited on the
substrate in such a manner as to obtain a pad having a
shape such as that shown in Figures 3581 and 3582. The
obtained devices showed as good characteristics as in
Example 21, and the variations in characteristics from
device to device was small. In this example, since the
gap length was as small as 20 um, the alignment in a
direction perpendicular to the gap was easier than
Examples 21, 22, and 23. Furthermore, devices having a
pad with a shape such as that shown in Figures 35C1 and
35C2 were also produced. The obtained devices also
showed good characteristics.
Example 25
In this example, instead of the ink-jet
ejecting device using a piezo-electric device employed
in Examples 21 to 24, a droplet supplying mechanism of
the bubble-jet type was employed to produce devices and
an image-forming apparatus. The obtained devices and
image-forming apparatus showed as good characteristics
as in Examples 21 to 24.
Example 26
Device electrodes were formed in a matrix form
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on a substrate by means of photolithography. Then,
surface conduction type electron-emitting devices were
produced on this substrate, thereby forming an electron
source substrate. Figure 40A is a plan view of a
surface conduction type electron-emitting device
produced, and Figure 40B is a cross-sectional view
thereof. Referring to Figures 40A and 40B, the
production process of the surface conduction
electron-emitting device will be described below.
Step 1: A quartz substrate was employed as an
insulating substrate 1. The quartz substrate was
cleaned well with an organic solvent. Then, electrodes
2 and 3 of Ni were formed on the substrate 1 using an
evaporation technique and a photolithography technique
so that the distance (L1) between the device~electrodes
was 2 um, the width (W1) of the device electrodes was
400 um, and the thickness of the device electrodes was
1000 A.
Step 2: The substrate on which the device
electrodes 2 and 3 were formed was cleaned by means of
ultrasonic with purified water. Then the substrate was
dried by pulling it up from hot pure water. The
hydrophobicity treatment was then performed using HMDS
(HMDS was coated on the substrate using a spinner and
then the substrate was heated in an oven at 200°C for
15 min) thereby making the surface of the substrate
hydrophobic. Using an ink-bet electing device provided
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with a piezo-electric device, one droplet of an aqueous
solution containing a 0.05 wt~ palladium acetate was
ejected toward a position between the device electrodes
2 and 3 formed on the substrate. After arriving on the
substrate, the droplet remained in a limited area
without expanding. This resulted in good stability and
good reproducibility.
Step 3: Heat treatment was then performed at
300°C for 10 min so that a particle film
(electrically-conductive film 4) consisting of
palladium oxide (Pd0) particles was formed.
The term "particle film" is used here to refer
to a film composed of a plurality of particles, wherein
the particles may be dispersed in the film, or
otherwise the particles may be disposed so that they
are adjacent to each other or they overlap each other
(or may be disposed in the form of islands). In this
technique, the width (W2) of the obtained thin film is
determined as a function of the shape of the droplet
deposited on the substrate. As described above, it is
possible to good reproducibility in the shape of the
droplet; and thus it is possible to obtain a small
variation in the width (W2) of the thin film.
Furthermore, in this technique, no patterning process
is required to form the electrically-conductive thin
film 4.
Step 4: A forming process was then performed by
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applying a voltage across the device electrodes 2 and 3
so that a current was passed through the
electrically-conductive thin film 4 thereby forming an
electron emission region 5.
Thus, an electron source substrate provided
with the above-described surface conduction
electron-emitting devices connected via matrix-shaped
interconnections was obtained. Using this electron
source substrate, an envelope 1088 was formed with a
face plate 1086, a supporting frame 1082, and rear
plate 1081, in the manner described above in connection
with Figure 7. Then the envelope 1088 was sealed.
Thus a display panel was obtained. Furthermore, an
image-forming apparatus provided with a driving circuit
capable of displaying a television image according to
an NTSC television signal, such as that shown in Figure
9, was produced.
The obtained image-forming apparatus showed
good performance in displaying a TV image with a small
variation in brightness over a large screen area.
Example 27
Device electrodes were formed on a substrate in
a ladder form so that the width (W1) of the device
electrodes was 600 pm, the distance (L1) between the
device electrodes was 2 um, and the thickness of the
device electrodes was 1000 ~. Using this substrate
(Figure 13), surface conduction electron-emitting
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devices were produced in a manner similar to that in
Example 21. Using the obtained electron source
substrate, an envelope was formed with a face plate
1286, a grid electrode 1120, a supporting frame 1082,
and rear plate 1124, in the same manner as described
above in connection with Figure 11. Then the envelope
1088 was sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced.
The resultant image-forming apparatus showed as
good characteristics as in Example 26.
Example 28
Device electrodes were formed in a matrix form
on a substrate by means of photolithography (Figure
13). Then, surface conduction electron-emitting
devices were produced on this substrate, thereby
forming an electron source substrate in a manner
similar to that in Example 26. Using the obtained
electron source substrate, as in Example 26, an
envelope 1088 was formed with an above-described face
plate 1086, a supporting frame 1082, and rear plate
1081. Then the envelope 1088 was sealed. Thus a
display panel was obtained. Furthermore, an
image-forming apparatus provided with a driving circuit
capable of displaying a television image according to
CA 02295408 2000-O1-13
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an NTSC television signal, such as that shown in Figure
9, was produced.
The resultant image-forming apparatus showed as
good characteristics as in Example 26.
Example 29
Device electrodes were formed in a ladder form
on a substrate by means of photolithography (Figure
13). Then, surface conduction electron-emitting
devices were produced on this substrate, thereby
forming an electron source substrate in a manner
similar to that in Example 26. Using the obtained
electron source substrate, a display panel was produced
in a manner similar to the previous examples.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC television signal, such as
that shown in Figure 9, was produced.
The resultant image-forming apparatus showed as
good characteristics as in Example 26.
Example 30
Device electrodes were formed in a matrix form
on a substrate by means of photolithography (Figure
13). Then, surface conduction type electron-emitting
devices were produced on this substrate, thereby
forming an electron source substrate. Figure 34 is a
plan view of a surface conduction type
electron-emitting device produced. The production
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process of the surface conduction electron-emitting
device will be described below.
Step 1: A quartz substrate was employed as an
insulating substrate 1. The quartz substrate was
cleaned well with an organic solvent. Then, electrodes
2 and 3 of Ni were formed on the substrate 1 using an
evaporation technique and a photolithography technique
so that the distance (Ll) between the device electrodes
was 2 um, the width (Wl) of the device electrodes was
600 um, and the thickness,of the device electrodes was
1000
Step 2: The substrate on which the device
electrodes 2 and 3 were formed was cleaned by means of
ultrasonic with purified water. Then the substrate was
dried by pulling it up from hot pure water. The
hydrophobicity treatment was then performed using HMDS
(HMDS was coated on the substrate using a spinner and
then the substrate was heated in an oven at 200°C for
15 min) thereby making the surface of the substrate
hydrophobic. Using an ink-jet ejecting device provided
with a piezo-electric device, two droplets of an
aqueous solution containing a 0.05 wto palladium
acetate were ejected toward positions located near each
other between the device electrodes 2 and 3 formed on
the substrate. After arriving on the substrate, the
droplet remained in a limited area without expanding.
This resulted in good stability and good
CA 02295408 2000-O1-13
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reproducibility.
Step 3: Heat treatment was then performed at
300°C for 10 min so that a particle film,
(electrically-conductive film 4) consisting of
palladium oxide (Pd0) particles was formed. The term
"particle film" is used here again to refer to a film
composed of a plurality of particles, wherein the
particles may be dispersed in the film, or otherwise
the particles may be disposed so that they are adjacent
to each other or they overlap each other (or may be
disposed in the form of islands). In this technique,
the width (W2) of the obtained thin film is determined
as a function of the shape of the droplet deposited on
the substrate. Therefore, as described above, it is
possible to good reproducibility in the shape of the
droplet, and thus it is possible to obtain a small
variation in the width (W2) of the thin film.
Furthermore, in this technique, no patterning process
is required to form the electrically-conductive thin
film 4.
Step 4: A forming process was then performed by
applying a voltage across the device electrodes 2 and 3
so that a current was passed through the
electrically-conductive thin film 4 thereby forming an
electron emission region 5.
Using the obtained electron source substrate,
an envelope 1088 was formed with a face plate 1086, a
CA 02295408 2000-O1-13
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supporting frame 1082, and rear plate 1081, in the same
manner as described above in connection with Figure 7.
Then the envelope 1088 was sealed. Thus a display
panel was obtained. Furthermore, an image-forming
apparatus provided with a driving circuit capable of
displaying a television image according to an NTSC
television signal, such as that shown in Figure 9, was
produced.
The resultant image-forming apparatus showed as
good characteristics as in Example 26.
Example 31
Device electrodes were formed in a matrix form
on a substrate by means of photolithography (Figure
12). Then, surface conduction type electron-emitting
devices were produced on this substrate, thereby
forming an electron source substrate in the same manner
as in Example 26 except that two droplets were ejected
to form one electrically-conductive thin film between
device electrodes. Droplets were ejected using the
same type of droplet supplying mechanism as that used
in Example 26 under the same conditions as those
employed in Example 26 and the amount of a solution
contained in each droplet (one dot) was also the same
as that in Example 26. The thickness of the obtained
electrically-conductive thin film was twice that
obtained in Example 26, since two droplets were ejected
for each electrically-conductive thin film in this
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example. From this result, it can be concluded that it
is possible to control the thickness of the
electrically-conductive thin film by changing the
amount of a droplet or by changing the number of
droplets ejected for each electrically-conductive thin
film.
Using the electron source substrate obtained in
the above-described manner, a display panel and an
image-forming apparatus were produced in a manner
similar to that in Example 26.
The obtained display panel and image-forming
apparatus showed as good characteristics as in Example
26.
Example 32
In the production of electron-emitting devices
in any example described above, device electrodes (or
device electrodes and interconnection electrodes) were
formed first, and then droplets were deposited, and
finally baking was performed. Instead, droplets may be
deposited first and then baking may be performed so as
to form electrically-conductive thin films. After that
device electrodes (or device electrodes and
interconnection electrodes) may be formed. A specific
example according to the latter production step order
will be described in detail below.
Figures 35A1 to 35C2 are schematic diagrams
illustrating the process of producing one device.
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A quartz substrate was employed as an
insulating substrate 1. The quartz substrate was
cleaned well with an organic solvent. Using an ink-jet
ejecting device provided with a piezo-electric device,
a droplet of an aqueous solution containing a 0.05 wto
palladium acetate was ejected toward a center of the
substrate (Figures 35A1 and 35A2). (The number of
droplets is not limited to one. As required, two or
more droplets may be ejected.)
After that, baking was performed at 300°C for
10 min thereby forming an electrically-conductive thin
film 5 in a circular shape consisting of palladium
oxide (Pd0) particles (Figures 35B1 and 35B2).
Using an evaporation technique and a
photolithography technique, electrodes 2 and 3 of Ni
(Figures 35C1 and 35C2) were formed on the substrate
having a dot of electrically-conductive thin film so
that the distance L1 between the device electrodes was
10 um, the width W1 of the device electrodes was 400
pm, and the thickness of the device electrodes was 1000
~. In the above process, the device electrodes 2 and 3
were formed at locations so that the center of the gap
between the device electrodes 2 and 3 was substantially
coincident with the center of the dot of the
electrically-conductive thin film.
A forming process was then performed by
applying a voltage across the device electrodes 2 and 3
CA 02295408 2000-O1-13
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so that a current was passed through the
electrically-conductive thin film 5 thereby forming an
electron emission region 6 (Figures 35C1 and 35C2).
Although only one device was produced on a
substrate in the above example, a .plurality of surface
conduction type electron-emitting devices may also be
produced on a substrate thereby producing an electron
source substrate having matrix-shaped wires as shown in
Figure 36. The matrix-shaped wires electrodes may be
produced by means of evaporation and photolithography.
In this structure, the X-direction wires and the
Y-direction wires are electrically isolated from each
other by an insulator (not shown) at~ each intersection.
Furthermore, an envelope 1088 was formed with a face
plate 1086, a supporting frame 1082, and rear plate
1081, in the same manner as described above in
connection with Figure 7. Then the envelope 1088 was
sealed. Thus a display panel was obtained.
Furthermore, an image-forming apparatus provided with a
driving circuit capable of displaying a television
image according to an NTSC.television signal, such as
that shown in Figure 9, was produced. As for the
electron source substrate, the type shown in Figure 37
may also be employed.
Also in this example, as in the previous
examples, the obtained image-forming apparatus showed
good performance in displaying a TV image with a small
CA 02295408 2000-O1-13
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variation in brightness over a large screen area.
Example 33
After forming a plurality of dot-shaped
electrically-conductive thin films on a substrate in
the same manner as in Example 32, device electrodes 2
and 3 as well as ladder-form interconnections were
formed on the substrate by means of evaporation and
photolithography so that the width W1 of the device
electrodes was 600 um, the distance between the device
electrodes was 10 um, and the thickness of the device
electrodes was 1000 ~ thereby forming an electron
source substrate as shown in Figure 39. Furthermore,
an envelope 1088 was formed with a face plate 1086, a
supporting frame 1082, and rear plate 1124, in the same
manner as described above in connection with Figure 11.
Then the envelope 1088 was sealed. Thus a display
panel was obtained. Furthermore; an image-forming
apparatus provided with a driving circuit capable of
displaying a television image according to an NTSC
television signal, such as that shown in Figure 9, was
produced.
Also in this example, as in Example 32, the
obtained image-forming apparatus showed good
performance in displaying an image.
Example 34
In Examples 32 and 33 described above, an
ink-jet ejecting device provided with a piezo-electric
CA 02295408 2000-O1-13
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device was employed. Instead, an ink-jet ejecting
device of the bubble-jet type in which a bubble is
generated by means of heat may also be employed. Using
this type of ink-jet ejecting device, an image-forming
apparatus with an electron source substrate having
matrix-shaped interconnections as well as an
image-forming apparatus with an electron source
substrate having ladder-shaped wires were produced.
The obtained image-forming apparatus showed as good
performance as in Examples 32 and 33.
