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LIQUID EJECTION HEAD AND APPARATUS, AND
MANUFACTURING METHOD FOR THE LIQUID EJECTION HEAD
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a liquid
ejecting head wherein liquid is ejected by generation
of a bubble created by application of thermal energy
to the liquid, more particularly to such a head having
a movable member displaced by the generation of the
bubble.
In this specification, "recording" means not
only forming an image of letter, figure or the like
having specific meanings, but also includes forming an
image of a pattern not having a specific meaning.
An ink jet recording method of so-called
bubble jet type is known in which an instantaneous
state change resulting in an instantaneous volume
change (bubble generation) is caused by application of
energy such as heat to the ink, so as to eject the ink
through the ejection outlet by the force resulted from
the state change by which the ink is ejected to and
deposited on the recording material to form an image
formation. As disclosed in U.S. Patent No. 4,723,129
and so on, a recording device using the bubble jet
recording method comprises an ejection outlet for
ejecting the ink, an ink flow path in fluid
communication with the ejection outlet, and an
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electrothermal transducer as energy generating means
disposed in the ink flow path.
With such a recording method is advantageous
in that, a high quality image, can be recorded at high
speed and with low noise, and a plurality of such
ejection outlets can be posited at high density, and
therefore, small size recording apparatus capable of
providing a high resolution can be provided, and color
images can be easily formed. Therefore, the bubble
jet recording method is now widely used in printers,
copying machines, facsimile machines or another office
equipment, and for industrial systems such as textile
printing device or the like.
With the increase of the wide needs for the
bubble jet technique, various demands are imposed
thereon, recently.
For example, adjustment of a thickness of a
protecting film is considered to optimize the heat
generating element to meet the demand for the
improvement in the ejection efficiency. This method
is effective in that propagation efficiency of the
generated heat to the liquid is improved.
In order to provide high quality images,
driving conditions have been proposed by which the ink
ejection speed is increased, and/or the bubble
generation is stabilized to accomplish better ink
ejection. As another example, from the standpoint of
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increasing the recording speed, flow passage
configuration improvements have been proposed by which
the speed of liquid filling (refilling) into the
liquid flow path is increased.
Japanese Laid Open Patent Application No.
SHO-63-199972 and so on discloses a flow passage
structure shown in Figure 6, (a), (b). The flow
passage structure or the head manufacturing method
disclosed in this publication has been made noting a
backward wave (the pressure wave directed away from
the ejection outlet, more particularly, toward a
liquid chamber 12) generated in accordance with
generation of the bubble.
Figure 6, (a) and (b) disclose a valve 10
spaced from a generating region of the bubble
generated by the heat generating element 2 in a
direction away from the ejection outlet 11.
In Figure 6, (b), the valve 55 is
manufactured from a plate and has an initial position
as if it is stuck on the ceiling of the liquid flow
path 10. It lowers into the liquid flow path 10 by
generation of the bubble.
Japanese Laid Open Patent Application No.
SHO-63-199972 discloses a head wherein refilling of
the recording liquid is improvement so that frequency
responsivity is high.
On the other hand, in the bubble jet
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recording method, the heating is repeated with the
heat generating element contacted with the ink, and
therefore, a burnt material is deposited on the
surface of the heat generating element due to burnt
deposit of the ink. However, the amount of the
deposition may be large depending on the materials of
the ink. If this occurs, the ink ejection becomes
unstable._ Additionally, even when the liquid to be
ejected is the one easily deteriorated by heat or even
when the liquid is the one with which the bubble
generated is not sufficient, the liquid is desired to
be ejected in good order without property change.
Japanese Laid Open Patent Application No.
SHO-61-69467, Japanese Laid Open Patent Application
No. SHO-55-81172 and US Patent No. 4,480,259 disclose
that different liquids are used for the liquid
generating the bubble by the heat (bubble generating
liquid) and for the liquid to be ejected (ejection
liquid). In these publications, the ink as the
ejection liquid and the bubble generation liquid are
completely separated by a flexible film of silicone
rubber or the like so as to prevent direct contact of
the ejection liquid to the heat generating element
while propagating the pressure resulting from the
bubble generation of the bubble generation liquid to
the ejection liquid by the deformation of the flexible
film. The prevention of the deposition of the
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material on the surface of the heat generating element
and the increase of the selection latitude of the
ejection liquid are accomplished, by such a structure.
However, with this structure in which the
ejection liquid and the bubble generation liquid are
completely separated, the pressure by the bubble
generation is propagated to the ejection liquid
through the expansion-contraction deformation of the
flexible film, and therefore, the pressure is absorbed
by the flexible film to a quite high degree. In
addition, the deformation of the flexible film is not
so large, and therefore, the energy use efficiency and
the ejection force are deteriorated although the some
effect is provided by the provision between the
ejection liquid and the bubble generation liquid.
Further improvement of liquid ejecting head
is desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to
provide a liquid ejecting head wherein back wave is
suppressed by a valve mechanism of a movable member,
and a resistance applied to the ejection liquid by the
liquid flow path is reduced to improve the refilling
performance .
It is another object of the present invention
to provide a liquid ejecting head or the like wherein
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an inertia, due to a backward wave, in a direction
opposite from the liquid supply direction is
suppressed, and simultaneously therewith, a meniscus
retraction amount is reduced by a valve function of a
movable member, so that refilling frequency is
increased, and therefore, the printing speed or the
like is improved.
It is a further object of the present
invention to provide a liquid ejecting head wherein
when the valve mechanism of the movable member
operates by the generation ~f the bubble, the
resistance applied by the liquid flow path is reduced
to improve the ejection efficiency.
Lt is a further object of. the present
invention to provide a liquid ejecting head wherein
the heat accumulation in the liquid on the heat
generating element is significantly reduced, and the
residual bubble on the heat generating element can be
reduced, while the ejection efficiency and the
ejection pressure are improved.
It is a further object of the present
invention to provide a liquid ejecting head and so on
wherein deposition of residual material on the heat
generating element is reduced, and the range of the
usable liquid is widened, and in addition, the
ejection efficiency and the ejection force are
significantly increased.
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It is a further object of the present
invention to provide a liquid ejecting method, a
liquid ejecting head and so on, wherein the choice of
the liquid to be ejected is made greater.
It is a further object of the present
invention to provide a manufacturing method for a
liquid ejecting head with which such a liquid ejecting
head is easily manufactured.
It is a further object of the present
invention to provide an inexpensive liquid ejecting
head and a manufacturing method therefor wherein the
number of parts constituting the liquid ejecting head
is small.
According to an aspect of the present
15- invention, there is provided a liquid ejection head
comprising: an ejection outlet for ejecting liquid; a
bubble generating region for generating a bubble; a
movable member disposed faced to the bubble generating
region and movable between a first position and a
second position which is farther form the bubble
generating region than the first position; wherein the
movable member moves from the first position to the
second position by pressure produced by the gene-ration
of the bubble to permit expansion of the bubble more
in a downstream side closer to the ejection outlet
than in an upstream side; and a first common liquid
chamber having a height, measured in a direction
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perpendicular to a plane including the movable member
at rest, which is larger than that of the first liquid
flow path, wherein the movable member has a fulcrum in
the first common liquid chamber and a free end in the
first liquid flow path.
According to another aspect of the present
invention, there is provided a liquid ejection head
comprising: an ejection outlet for ejecting liquid; a
liquid path having a heat generating element for
generating a bubble in the liquid by application of
heat to the liquid, and a supply passage for supplying
the liquid to the heat generating element from
upstream side thereof; a movable member, disposed
faced to the heat generating element and having a free
end adjacent the ejection outlet, for directing a
pressure produced by generation of the bubble, toward
the ejection outlet, on the basis of the pressure
produced by the generation of the bubble; and a first
common liquid chamber having a height, measured in a
direction perpendicular to a plane including the
movable member at rest, which is larger than that of
the first liquid flow path, wherein the movable member
has a fulcrum in the first common liquid chamber and a
free end in the first liquid flow path.
According to a further aspect of the present
invention, there is provided a liquid ejection head
comprising: an ejection outlet for ejecting liquid; a
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heat generating element for generating a bubble in the
liquid by application of heat to the liquid; a movable
member, disposed faced to the heat generating element
and having a free end adjacent the ejection outlet,
for directing a pressure produced by generation of the
bubble, toward the ejection outlet; a supply passage
for supplying the liquid to the heat generating
element from an upstream thereof along a surface of
the movable member adjacent the heat generating
element; a first common liquid chamber having a
height, measured in a direction perpendicular to a
plane including the movable member at rest, which is
larger than that of the first liquid flow path,
wherein the movable member has a fulcrum in the first
common liquid chamber and a free end in the first
liquid flow path.
According to a further aspect of the present
invention, there is provided a liquid ejection head
comprising: a first liquid flow path in fluid
communication with an ejection outlet; a second liquid
flow path having bubble generation region for
generating the bubble in the liquid by applying heat
to the liquid; a movable member, disposed between the
first liquid flow path and the bubble generating
region and having a free end adjacent the ejection
outlet, for directing a pressure produced by
generation of the bubble, toward the ejection outlet
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of the first liquid flow path, by movement of the free
end into the first liquid flow path on the basis of
pressure produced by generation of the bubble the
bubble generating region; a first common liquid
chamber having a height, measured in a direction
perpendicular to a plane including the movable member
at rest, which is larger than that of the first liquid
flow path,, wherein the movable member has a fulcrum in
the first common liquid chamber and a free end in the
first liquid flow path.
According to a further aspect of the present
invention, there is provided a plurality of grooves
for constituting a plurality of first liquid flow
paths in direct fluid communication with associated
ones of .the ejection outlets; a recess for
constituting a first common liquid chamber for
supplying the liquid to the first liquid flow paths;
wherein the grooves and the recess are formed in a
grooved member; an element substrate having a
plurality of heat generating elements for generating
the bubble in the liquid by applying heat to the
liquid; and a partition wall disposed between the
grooved member and the element substrate and forming a
part of walls of second liquid flow paths
corresponding to the heat generating elements, and a
movable member movable into the first liquid flow
paths by pressure produced by the generation of the
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bubble, the movable member being faced to the heat
generating element; and a first common liquid chamber
having a height, measured in a direction perpendicular
to a plane including the movable member at rest, which
is larger than that of the first liquid flow path,
wherein the movable member has a fulcrum in the first
common liquid chamber and a free end in the first
liquid flow path.
According to an aspect of the present
invention, the fulcrum of the movable member is placed
in the first common chamber, so that resistance
against the displacement of the movable member by the
ceiling wall of the ejection flow path can be
minimized.
Since the first liquid flow path is short so
that flow path resistance against the ejection liquid
is small, by which height viscosity recording liquid
which has been difficult to eject heretofore, can be
ejected.
In an aspect of improving the refilling
property, the responsivity, the stabilized growth of
the bubble and stabilization of the liquid droplet
during the continuous ejections are accomplished, thus
permitting high speed recording. The ejection
efficiency can be improved as compared with a
conventional bubble jet type ejection head since the
liquid adjacent to the ejection outlet can be
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efficiently ejected by the synergistic effect between
the generated bubble and the movable member
displacement thereby. For example, in the most
desirable type of the present invention, the ejection
5 efficiency is increased even to twice the conventional
one.
In another aspect of the present invention,
even if the printing operation is started after the
recording head is left in a low temperature or low
humidity condition for a long term, the ejection
failure can be avoided. Even if the ejection failure
occurs, the normal operation is recovered by a small
scale recovery process including a preliminary
ejection and sucking recovery.
These and other objects,.features and
advantages of the present invention will become more
apparent upon a consideration of the following
description of the preferred embodiments of the
present invention taken in conjunction with the
2p accompanying drawings.
In this specification, "upstream" and
"downstream" are defined with respect to a general
liquid flow from a liquid supply source to the
ejection outlet through the bubble generation region
(movable member).
As regards the bubble per se, the
"downstream" is defined as toward the ejection outlet
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side of the bubble which directly function to eject
the liquid droplet. More particularly, it generally
means a downstream from the center of the bubble with
respect to the direction of the general liquid flow,
or a downstream from the center of the area of the
heat generating element with respect to the same.
In this specification, "substantially sealed"
generally means a sealed state in such a degree that
when the bubble grows, the bubble does not escape
through a gap (slit) around the movable member before
motion of the movable member.
In this specification, "separation wall" may
mean a wall (which may include the movable member)
interposed to separate the regionin direct fluid
communication with the ejection outlet from the bubble
generation region, and more specifically means a wall
separating the flow path including the bubble
generation region from the liquid flow path in direct
fluid communication with the ejection outlet, thus
preventing mixture of the liquids in the liquid flow
paths.
In this specification, "comb" or "comb-like"
means a structure in which the fulcrum portions of the
movable member is common, but the free end portions
are open.
BRIEF DESCRIPTION OF THE DRAWINGS
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Figure 1 is a schematic sectional view
showing an example of a liquid ejecting head according
to an embodiment of the present invention.
Figure 2 is a partly broken perspective view
of a liquid ejecting head according to an embodiment
of the present invention.
Figure 3 is a schematic view showing pressure
propagation from a bubble in a conventional head.
Figure 4 is a schematic view showing pressure
propagation from a bubble in a head according to an
embodiment of the present invention.
Figure 5 is a schematic view illustrating
flow of liquid in an embodiment of the present
invention.
Figure 6 illustrates a flow passage structure
of a conventional liquid ejecting head.
Figure 7 is a schematic sectional view
showing force applied from the ceiling of the liquid
flow path to the movable member in a liquid ejecting
head according to the present invention.
Figure 8 is a schematic sectional view of a
liquid ejecting head according to an embodiment of the
present invention.
Figure 9 is a schematic sectional view of a
liquid ejecting head according to an embodiment of the
present invention.
Figure 10 is schematic sectional view of a
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liquid ejecting head according to an embodiment of the
present invention.
Figure 11 is schematic sectional view of a
liquid ejecting head according to an embodiment of the
present invention.
Figure 12 is schematic sectional view of a
liquid ejecting head according to an embodiment of the
present invention.
Figure 13 illustrates a comb-like movable
membe r .
Figure 14 illustrates an operation of a
movable member.
Figure 15 illustrates another configuration
of a movable member.
Figure 16 shows a relation between an area of
a heat generating element and an ink ejection amount.
Figure 17 is a longitudinal sectional view of
a liquid ejecting head of the present invention.
Figure 18 is a schematic view showing a
configuration of a driving pulse.
Figure 19 is an exploded perspective view of
a head of the present invention.
Figure 20 is a schematic illustration of a
liquid ejecting apparatus.
Figure 21 is a block Figure of an apparatus.
Figure 22 is a series of schematic sectional
views of a liquid ejecting head according to a second
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embodiment of the present invention.
Figure 23 is partly broken perspective view
of a liquid ejecting head of Figure 22.
Figure 24 is a schematic cross-sectional view
of a liquid ejecting head according to Embodiment 3 of
the present invention, for illustration of the
operation.
Figure 25 illustrates a positional relation
between movable member and the second liquid flow path
of a liquid ejecting head according to an embodiment
of the present invention.
Figure 26 is shows another configuration of a
movable member of a liquid ejecting head according to
an embodiment of the present invention.
Figure 27 is and illustration of a feature
during manufacturing of the movable member, according
to an embodiment of the present invention.
Figure 28 is perspective view illustrating a
manufacturing method of a liquid ejecting head,
according to Embodiment 4 of the present invention.
Figure 29 is a schematic view showing a
movable member and a grooved member according to
Embodiment 5.
Figure 30 is a schematic view showing a
manufacturing method of a liquid ejecting head
according to Embodiment 5 of the present invention.
Figure 31 is schematic view showing a
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modified example of Embodiment 5.
Figure 32 is schematic view showing a
modified example of Embodiment 5.
Figure 33 is a schematic view showing another
embodiment of the reference portion of the grooved
member.
Figure 34 is a schematic view showing a
manufacturing method of a liquid ejecting head
according to Embodiment 5 of the present invention.
Figure 35 is perspective view illustrating a
manufacturing method of a liquid ejecting head,
according to Embodiment 7 of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Second bubble generation step of generating
at least one other bubble in said bubble generating
region to eject the liquid through the ejection
outlet.
Referring the accompanying drawings, the
ejection principle used in the present invention will
be described.
Figure 1 is a schematic sectional view of a
liquid ejecting head taken along a liquid flow path
according to this embodiment, and Figure 3 is a partly
broken perspective view of the liquid ejecting head.
The liquid ejecting head of this embodiment
comprises a heat generating element 2 (comprising a
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first heat generating element 2A and a second heat
generating element 2B and having a dimension of 40 pm
x 105 dun as a whole in this embodiment) as the
ejection energy generating element for supplying
thermal energy to the liquid to eject the liquid, an
element substrate l on which said heat generating
element 2 is provided, and a liquid flow path 10
formed above the element substrate correspondingly to
the heat generating element 2. The liquid flow path
10 is in fluid communication with a common liquid
chamber 13 for supplying the liquid to a plurality of
such liquid flow paths 10 which is in fluid
communication with a plurality of the ejection outlets
1$, respectively.
Above the element substrate in the liquid
flow path 10, a movable member or plate 31 in the form
of a cantilever of an elastic material such as metal
is provided faced to the heat generating element 2.
One end of the movable member is fixed to a foundation
(supporting member) or the like provided by patterning
of photosensitivity resin material on the wall of the
liquid flow path 10 or the element substrate. By this
structure, the movable member is supported, and a
fulcrum (fulcrum portion) 33 is constituted.
The movable member 31 is so positioned that
it has a fulcrum (fulcrum portion which is a fixed
end) 33 in an upstream side with respect to a general
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flow of the liquid from the common liquid chamber 13
toward the ejection outlet 18 through the movable
member 31 caused by the ejecting operation and so that
it has a free end (free end portion) 32 in a
5 downstream side of the fulcrum 33. The movable member
31 is faced to the heat generating element 2 with a
gap of 15 um approx. as if it covers the heat
generating element 2. A bubble generation region is
constituted between the heat generating element and
10 movable member. The type, configuration or position
of the heat generating element or the movable member
is not limited to the ones described above, but may be
changed as long as the growth of the bubble and the
propagation of the pressure can be controlled. For
15 the purpose of easy understanding of the.flow of the
liquid which will be described hereinafter, the liquid
flow path 10 is divided by the movable member 31 into
a first liquid flow path 14 which is directly in
communication with the ejection outlet 18 and a second
20 liquid flow path 16 having the bubble generation
region 11 and the liquid supply port 12.
Hy causing heat generation of the heat
generating element 2, the heat is applied to the
liquid in the bubble generation region 11 between the
25 movable member 31 and the heat generating element 2,
by which a bubble is generated by the film boiling
phenomenon as disclosed in U.S. Patent No. 4,723,129.
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The bubble and the pressure caused by the generation
of the bubble act mainly on the movable member, so
that movable member 31 moves or displaces to widely
open toward the ejection outlet side about the fulcrum
33, as shown in Figure 2, (b) and (c) or in Figure 2.
By the displacement of the movable member 31 or the
state after the displacement, the propagation of the
pressure caused by the generation of the bubble and
the growth of the bubble per se are directed toward
the ejection outlet.
The description will be made as to one of
fundamental ejection principle usable with the present
invention. One of important principles of this
invention is that movable member disposed faced to the
bubble is displaced from the normal first position to
the displaced second position on the basis of the
pressure of the bubble generation or the bubble per
se, and the displacing or displaced movable member 31
is effective to direct the pressure produced by the
generation of the bubble and/or the growth of the
bubble per se toward the ejection outlet 18
(downstream).
More detailed description will be made with
comparison between the conventional liquid flow
passage structure not using the movable member (Figure
4) and the present invention (Figure 5). Here, the
direction of propagation of the pressure toward the
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ejection outlet is indicated by VA, and the direction
of propagation of the pressure toward the upstream is
indicated by VB.
In a conventional head as shown in Figure 3,
there is not any structural element effective to
regulate the direction of the propagation of the
pressure produced by the bubble 40 generation.
Therefore, the direction of the pressure propagation
of the is normal to the surface of the bubble as
indicated by V1 - V8, and therefore, is widely
directed in the passage. Among these directions,
those of the pressure propagation from substantially
the half portion of the bubble closer to the ejection
outlet (V1 - V4), have the pressure components in the
VA direction which is most effective for the liquid
ejection. This portion is important since it is
directly contributable to the liquid ejection
efficiency, the liquid ejection pressure and the
ejection speed. Furthermore, the component V1 is
closest to the direction of VA which is the ejection
direction, and therefore, the component is most
effective, and the V4 has a relatively small component
in the direction VA.
On the other hand, in the case of the present
invention, shown in Figure 5, the movable member 31 is
effective to direct, to the downstream (ejection
outlet side), the pressure propagation directions V1 -
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V4 of the bubble which otherwise are toward various
directions. Thus, the pressure propagations of bubble
40 are concentrated so that pressure of the bubble 40
is directly and efficiently contributable to the
ejection. The growth direction per se of the bubble
is directed downstream similarly to the pressure
propagation directions V1 - V4, and the bubble grows
more in the downstream side than in the upstream side.
Thus, the growth direction per se of the bubble is
controlled by the movable member, and the pressure
propagation direction from the bubble is controlled
thereby, so that ejection efficiency, ejection force
and ejection speed or the like are fundamentally
improved.
. Referring back to Figure 1, the description
will be made as to ejecting operation in the liquid
ejecting head of this embodiment.
Figure 12, (a) shows a state before the
energy such as electric energy is applied to the heat
generating element 2, and therefore, no heat has yet
been generated. It should be noted that movable
member 31 is so positioned as to be faced at least to
the downstream portion of the bubble generated by the
heat generation of the heat generating element. In
other words, in order that downstream portion of the
bubble acts on the movable member, the liquid flow
passage structure is such that movable member 31
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extends at least to the position downstream
(downstream of a line passing through the center 3 of
the area of the heat generating element and
perpendicular to the length of the flow path) of the
center 3 of the area of the heat generating element.
Figure 1; (b) shows a state wherein the heat
generation of heat generating element 2 occurs by the
application of the electric energy to the heat
generating element 2, and a part of the liquid filled
in the bubble generation region 11 is heated by the
thus generated heat so that bubble is generated as a
result of film boiling.
At this time, the movable member 31 is
displaced from the first position to the second
position by the pressure produced by the generation of
the bubble 40 so as to guide the propagation of the
pressure toward the ejection outlet. It should be
noted that, as described hereinbefore, the free end 32
of the movable member 31 is disposed in the downstream
side (ejection outlet side), and the fulcrum 33 is
disposed in the upstream side (common liquid chamber
side), so that at least a part of the movable member
is faced to the downstream portion of the bubble, that
is, the downstream portion of the heat generating
element.
Figure 1, (c) shows a state in which the
bubble 40 has further grown by the pressure resulting
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from the bubble 40 generation, the movable member 31
is displaced further. The generated bubble grows more
downstream than upstream, and it expands greatly
beyond a first position (broken line position) of the
movable member. Thus, it is understood that in
accordance with the growth of the bubble 40, the
movable member 31 gradually displaces, by which the
pressure propagation direction of the bubble 40, the
direction in which the volume movement is easy,
namely, the growth direction of the bubble, are
directed uniformly toward the ejection outlet, so that
ejection efficiency is increased. When the movable
member guides the bubble and the bubble generation
pressure toward the ejection outlet, it hardly
obstructs propagation and growth, and can efficiently
control the propagation direction of the pressure and
the growth direction of the bubble in accordance with
the degree of the pressure.
Figure 1, (d) shows the bubble 40 contracting
and extinguishing by the decrease of the internal
pressure of the bubble after the film boiling.
The movable member 31 having been displaced
to the second position returns to the initial position
(first position) of Figure 2, (a) by the restoring
force provided by the spring property of the movable
member per se and the negative pressure due to the
contraction of the bubble. Upon the collapse of
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bubble, the liquid flows back from the common liquid
chamber side as indicated by VD1 and VD2 and from the
ejection outlet side as indicated by Vc so as to
compensate for the volume reduction of the bubble in
the bubble generation region 11 and to compensate for
the volume of the ejected liquid.
In the foregoing, the description has been
made as to the operation of the movable member 31 with
the generation of the bubble and the ejecting
operation of the liquid. Now, the description will be
made as to the refilling of the liquid in the liquid
ejecting head of the present invention.
When the bubble 40 enters the bubble
collapsing process after the maximum volume thereof
(Figure 2, (c)), a volume of the liquid enough to
compensate for the collapsing bubbling volume flows
into the bubble generation region from the ejection
outlet 18 side of the first liquid flow path 14 and
from the bubble generation region of the second liquid
flow path 16. In the case of conventional liquid flow
passage structure not having the movable member 31,
the amount of the liquid from the ejection outlet side
to the bubble collapse position and the amount of the
liquid from the common liquid chamber thereinto,
correspond to the flow resistances of the portion
closer to the ejection outlet than the bubble
generation region and the portion closer to the common
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liquid chamber (flow path resistances and the inertia
of the liquid).
Therefore, when the flow resistance at the
ejection outlet side is small, a large amount of the
liquid flows into the bubble collapse position from
the ejection outlet side, with the result that
meniscus retraction is large. With the reduction of
the flow resistance in the ejection outlet for the
purpose of increasing the ejection efficiency, the
meniscus retraction increases upon the collapse of
bubble with the result of longer refilling time
period, thus making high speed printing difficult.
According to this embodiment, because of the
provision of the movable member 31, the meniscus
retraction stops at the time when the movable member
returns to the initial position upon the collapse of
bubble, and thereafter, the supply of the liquid to
fill a volume W2 is accomplished by the flow through
the second flow path 16 (W1 is a volume of an upper
side of the bubble volume W beyond the first position
of the movable member 31, and W2 is a volume of a
bubble generation region 11 side thereof). In the
prior art, a half of the volume of the bubble volume W
is the volume of the meniscus retraction, but
according to this embodiment, only about one half (W1)
is the volume of the meniscus retraction.
Additionally, the liquid supply for the
CA 02333841 2001-02-13
-27-
volume W2 is forced to be effected mainly from the
upstream of the second liquid flow path along the
surface of the heat generating element side of the
movable member 31 using the pressure upon the collapse
of bubble, and therefore, more speedy refilling action
is accomplished.
When the high speed refilling using the
pressure upon the collapse of bubble is carried out in
a conventional head, the vibration of the meniscus is
expanded with the result of the deterioration of the
image quality. However, according to this embodiment,
the flows of the liquid in the first liquid flow path
14 at the ejection outlet side and the ejection outlet
side of the bubble generation region 11 are
suppressed, so that vibration of the meniscus is
reduced.
Thus, according to this embodiment, the high
speed refilling is accomplished by the forced
refilling to the bubble generation region through the
liquid supply passage 12 of the second flow path 16
and by the suppression of the meniscus retraction and
vibration. Therefore, the stabilization of ejection
and high speed repeated ejections are accomplished,
and when the embodiment is used in the field of
recording, the improvement in the image quality and in
the~recording speed can be accomplished.
The embodiment provides the following
CA 02333841 2001-02-13
-28-
effective function, too. It is a suppression of the
propagation of the pressure to the upstream side (back
wave) produced by the generation of the bubble. The
pressure due to the common liquid chamber 13 side
(upstream) of the bubble generated on the heat
generating element 2 mostly has resulted in force
which pushes the liquid back to the upstream side
(back wave). The back wave deteriorates the refilling
of the liquid into the liquid flow path by the
pressure at the upstream side, the resulting motion of
the liquid and the inertia force. In this embodiment,
these actions to the upstream side are suppressed by
the movable member 31, so that refilling performance
is further improved.
Additional description will be made as to the
structure and effect in the present invention.
With this structure, the supply of the liquid
to the surface of the heat generating element 2 and
the bubble generation region 11 occurs along the
surface of the movable member 31 at the position
closer to the bubble generation region 11. With this
structure, the supply of the liquid to the surface of
the heat generating element 2 and the bubble
generation region 11 occurs along the surface of the
movable member 31 at the position closer to the bubble
generation region 11 as indicated by VD2-
Accordingly, stagnation of the liquid on the surface
CA 02333841 2001-02-13
-29-
of the heat generating element 2 is suppressed, so
that precipitation of the gas dissolved in the liquid
is suppressed, and the residual bubbles not
extinguished are removed without difficulty, and in
addition, the heat accumulation in the liquid is not
too much. Therefore, more stabilized generation of
the bubble can be repeated at high speed. In this
embodiment., the liquid supply passage 12 has a
substantially flat internal wall, but this is not
limiting, and the liquid supply passage is
satisfactory if it has an internal wall with such a
configuration smoothly extended from the surface of
the heat generating element that stagnation of the
liquid occurs on the heat generating element, and eddy
flow is not significantly caused in the supply of the
liquid.
The supply of the liquid into the bubble
generation region may occur through a gap at a side
portion of the movable member (slit 35) as indicated
by VD1. In order to direct the pressure upon the
bubble generation further effectively to the ejection
outlet, a large movable member covering the entirety
of the bubble generation region (covering the surface
of the heat generating element) may be used, as shown
in Figure 2. Then, the flow resistance for the liquid
between the bubble generation region 11 and the region
of the first liquid flow path 14 close to the ejection
CA 02333841 2001-02-13
-30-
outlet is increased by the restoration of the movable
member to the first position, so that flow of the
liquid to the bubble generation region 11 along VD1
can be suppressed. However, according to the head
structure of this embodiment, there is a flow
effective to supply the liquid to the bubble
generation region, the supply performance of the
liquid is.greatly increased, and therefore, even if
the movable member 31 covers the bubble generation
region 11 to improve the ejection efficiency, the
supply performance of the liquid is not deteriorated.
The positional relation between the free end
32 and the fulcrum 33 of the movable member 31 is such
that free end is at a downstream position of the
fulcrum as shown in Figure 8, for example. With this
structure, the function and effect of guiding the
pressure propagation direction and the direction of
the growth of the bubble to the ejection outlet side
or the like can be efficiently assured upon the bubble
generation. Additionally, the positional relation is
effective to accomplish not only the function or
effect relating to the ejection but also the reduction
of the flow resistance through the liquid flow path 10
upon the supply of the liquid thus permitting the high
speed refilling. When the meniscus M retracted b the
ejection as shown in Figure 8, returns to the ejection
outlet 18 by capillary force or when the liquid supply
CA 02333841 2001-02-13
-31-
is effected to compensate for the collapse of bubble,
the positions of the free end and the fulcrum 33 are
such that flows S1, S2 and S3 through the liquid flow
path 10 including the first liquid flow path 14 and
the second liquid flow path 16, are not impeded.
More particularly, in this embodiment, as
described hereinbefore, the free end 32 of the movable
member 3 is faced to a downstream position of the
center 3 of the area which divides the heat generating
element 2 into an upstream region and a downstream
region (the line passing through the center (central
portion) of the area of the heat generating element
and perpendicular to a direction of the length of the
liquid flow path). The movable member 31 receives the
pressure and the bubble which are greatly
contributable to the ejection of the liquid at the
downstream side of the area center position 3 of the
heat generating element, and it guides the force to
the ejection outlet side, thus fundamentally improving
the ejection efficiency or the ejection force.
Further advantageous effects are provided
using the upstream side of the bubble, as described
hereinbefore.
Furthermore, it is considered that in the
structure of this embodiment, the instantaneous
mechanical movement of the free end of the movable
member 31, contributes to the ejection of the liquid.
CA 02333841 2001-02-13
-32-
Embodiment 1
The liquid ejection principle in this
embodiment is the same as the principle described
above. In this embodiment and thereafter, the present
invention is described with reference to a head in
which the first and second liquid flow paths 14 and 16
are separated with the separation wall 30. However,
the present invention is not limited to this type of
head; it is also applicable to those heads mentioned
in the preceding description of liquid ejection
principle.
The head structure in this embodiment is
characterized by the following function, in addition
to those described above. That is, the flow
resistance of the first liquid flow path 14 is
minimized to refill the liquid at a higher speed.
According to this embodiment, the upstream side end of
the first liquid flow path 14 is on the ejection
outlet side of the free end of the movable member 31
having moved to the second position, since the
pressure which tends to wastefully dissipate can be
directed toward the ejection outlet side by the
movable member 31, as described above. With the
implementation of this structure, the repulsive force
which the movable member 31 receives as it moves to
the second position can be reduced.
Hereinafter, the structure and effects which
CA 02333841 2001-02-13
-33-
characterize this embodiment will be described.
Figure 7 depicts the effect of the ceiling of
the first liquid flow path 14 upon the pivotal
displacement of the movable member 31. In Figure 7,
(a), the upstream side end of the first liquid flow
path 14 is on the downstream side of the position to
which the free end of the movable member reaches as
the movable member 31 moves to the second position,
and in Figure 7, (b), the upstream side end of the
first liquid flow path 14 is on the upstream side of
the supporting point 33 of the movable member 31. As
the movable member 31 moves toward the second
position, it is subjected to the repulsive force, that
is, the force which works in the direction opposite to
the direction in which the movable member 31 moves,
from the ceiling of the common liquid chamber 13 or
first liquid flow path 14. This is why it is
desirable that the upstream side end of the first
liquid flow path 14 is on the downstream side of the
Position to which the free end of the movable member
13 reaches as the movable member 13 moves to the
second position.
Figures 8 - 12 show the positional
relationship among the movable member 13, first liquid
flow path, and common liquid chamber 13, wherein in
each figure, (a) is a horizontal section of the nozzle
portion as seen from the first liquid flow path side,
CA 02333841 2001-02-13
-34-
depicting the positional relationship among the
movable member 31, first liquid flow path 14, a post
52 to which the supporting point 33 of the movable
member 13 is fixed, and the side walls 53 of the first
liquid flow path 14, and (b) is a vertical section of
the nozzle portion, depicting the configuration of the
side wall 53 of the first liquid flow path 14.
Figure 8 shows the structure of a nozzle in
which the downstream side end of the first common
liquid chamber 13 is on the upstream side of the
position to which the free end of the movable member
31 reaches as the movable member 31 moves to the
second position, and which has a post 52 to which the
supporting point of the movable member 31 is fixed.
With this structure, the repulsive force
which comes from the ceiling as the movable member 31
is pivotally displaced is negligible, and therefore,
the power from bubble generation can be efficiently
converted into ejective force. It should be noted
here that when a certain type of material is used as
the material for the movable member 31, the supporting
point 33 of the movable member 31 may be lifted into
the first common liquid chamber 33, and as a result,
the movable member 31 in a nozzle may be affected by
the movement of the movable member 31 in the adjacent
nozzles. Therefore, it is desirable that the
supporting point 33 of the movable member 31 is fixed
CA 02333841 2001-02-13
-35-
as described in this embodiment.
Figure 9 depicts a nozzle in which the
upstream side end of the first liquid flow path 14 is
on the further upstream side of the position to which
the free end of the movable member 31 reaches as the
movable member 3l is pivotally displaced, compared to
the preceding nozzle. In this case, the supporting
point 33 of the movable member 31 is also in the first
common liquid chamber 33, but is not fixed. Yet, the
arrangement is effective to improve the liquid
refilling efficiency as well as the liquid ejection
efficiency. This arrangement is also effective in the
case of a liquid ejection head illustrated in Figure
13, in which the bubble generation liquid and ejection
. liquid are the same liquid, and the movable member 31
is formed like a tooth of a comb.
Figure 10 depi~t~ a liquid ejection head in
which the ceiling of the first liquid flow path 14
becomes abruptly higher on the upstream side of the
position to which the free end of the movable member
31 reaches as the movable member 31 is moved to the
second position, and the side wall 53 of the first
liquid flow path 14, which separates the adjacent two
nozzles, vertically extends as high as the straight
line connecting the point at which the free end of the
movable member 31 is when the movable member 31 is at
the second position, and the supporting point 33.
CA 02333841 2001-02-13
-36-
This structural arrangement is effective to prevent a
bubble from expanding in the horizontal direction, and
therefore, the power from bubble generation can be
converted into ejective force more effectively than in
the preceding arrangement.
Figure 11 depicts a liquid ejection head in
which the side wall 53 of the first liquid path 14
also horizontally extends as far as the wall 53 in
the preceding arrangement, except that the wall 53 in
this arrangement vertically extends to the ceiling of
the first liquid flow path 14 at all points. With the
implementation of this structural arrangement, merely
raising the ceiling of the first liquid flow path 14
is effective to reduce the repulsive force against the
pivotal displacement of the movable member 31, to
improve the liquid refilling efficiency, and to impede
the lateral expansion of a bubble.
Figure 12 depicts a nozzle structure in which
the free end of the movable member 31 is allowed to
move into the first common liquid chamber 13 as the
movable member 31 is pivotally moved to the second
position. The liquid refilling efficiency, and the
liquid ejection efficiency, can be effectively
improved by the implementation of even this nozzle
structure, the only notable feature of which is that
the free end of the movable member 31 is in the first
liquid flow path 14 at least when the movable member
CA 02333841 2001-02-13
-37-
is stationary.
Embodiment 2
In this embodiment, a nozzle structure in
which a pivotally movable member is constituted of a
portion of separation wall 30, which is formed like a
tooth of a comb, at the front edge of the separation
wall 30, will be described in more detail.
Figure 22, (a - d), are longitudinal
sectional views of the liquid ejection head in this
embodiment, taken along the liquid flow path,
sequentially depicting various stages of liquid
ejection. Figure 3 is a partially cutaway perspective
view of the liquid ejection head illustrated in Figure
22.
The liquid ejecting head of this embodiment
comprises a heat generating element 2 (a heat
generating resistor of 40 Nm x 105 dun in this
embodiment) as the ejection energy generating element
for supplying thermal energy to the liquid to eject
the liquid, an element substrate 1 on which said heat
generating element 2 is provided, and a liquid flow
path 10 formed above the element substrate
correspondingly to the heat generating element 2. The
liquid flow path l0 is in fluid communication with a
common liquid chamber 13 for supplying the liquid to a
plurality of such liquid flow paths 10 which is in
fluid commun~cat~.o~ w~.tY~ a plurality of the ejection
CA 02333841 2001-02-13
-38-
outlets 18. It receives liquid from the common liquid
chamber 13, by the amount equivalent to the amount of
liquid ejected from the ejection outlet.
Above the element substrate in the liquid
flow path 10, a movable member or a plate 31 in the
form of a cantilever, or a tooth of a comb, of an
elastic material such as metal is provided faced
toward the heat generating element 2. The supporting
end of the movable member is fixed to a foundation
(supporting member) 34 or the like provided by
patterning of photosensitive resin material on the
wall of the liquid flow path 10 or the element
substrate. By this structure, the movable member is
supported, and a fulcrum (fulcrum portion) is
constituted.
Since the movable member 31 in this
embodiment is formed like a tooth of a comb, not only
can it be easily and inexpensively formed, but.also it
can be easily aligned relative to the foundation 34.
The movable member 31 is so positioned that
it has a fulcrum (fulcrum portion which is the fixed
end) 33 on the upstream side with respect to the
general flow of the liquid from the common liquid
chamber 13 toward the ejection outlet 18 through the
movable member 31 caused by the ejecting operation and
that it has a free end (free end portion) 32 on the
downstream side of the fulcrum 33. The movable member
CA 02333841 2001-02-13
-39-
31 is faced toward the heat generating element 2 with
a gap of 15 pm approx. so that it covers the heat
generating element 2. A bubble generation region is
constituted between the heat generating element and
movable member. The type, configuration or position
of the heat generating element or the movable member
is not limited to the ones described above, but may be
changed as long as the growth of the bubble and the
propagation of the pressure can be controlled.
According to the present invention, the tip of the
free end portion of the movable member 31 is given a
specific width, and therefore, the power from bubble
generation can be more easily guided toward the
ejection outlet 18. For the purpose of easy
understanding of the flow of the liquid which will be
described hereinafter, the liquid flow path 10 is
divided by the movable member 31 into a first liquid
flow path 14 which is directly in communication with
the ejection outlet 18 and a second liquid flow path
16 having the bubble generation region 11 and the
liquid supply port 12.
By causing heat generation of the heat
generating element 2, the heat is applied to the
liquid in the bubble generation region 11 between the
movable member 31 and the heat generating element 2,
by which a bubble is generated by the film boiling
phenomenon as disclosed in U.S. Patent No. 4,723,129.
CA 02333841 2001-02-13
-40-
The bubble and the pressure caused by the generation
of the bubble act mainly on the movable member, so
that the movable member 31 moves or displaces to
widely open toward the ejection outlet side about the
fulcrum 33, as shown in Figure 22, (b) and (c) or in
Figure 23. By the displacement of the movable member
31 or the state after the displacement, the
propagation of the pressure caused by the generation
of the bubble and the growth of the bubble per se are
directed toward the ejection outlet. Further, since
the tip of the free end portion 32 is given a specific
width, the power from bubble generation can be more
easily guided toward the ejection outlet 18.
Embodiment 3
. Next, the third embodiment of the present
invention will be described.
The liquid ejection principle in this
embodiment is substantially the same as the one
described in the preceding embodiments. However, in
this embodiment, the liquid flow path is divided into
two smaller parts, so that the liquid (bubble
generation liquid) to which heat is applied to
generate bubbles, and the liquid (ejection liquid)
which is the primary liquid to be ejected, can be
separated from each other.
Figures 24, (a and c) are schematic
longitudinal sections of the liquid ejection head in
CA 02333841 2001-02-13
-41-
this embodiment, Figure 24, (b) being the cross
section at an A-A line in (a), and Figure 24, (d)
being the cross section at a B-B line in (c).
In the case of the liquid ejection head in
this embodiment, a second liquid flow path 16 for
bubble generation is on the element substrate 1
comprising the heat generating member 2 which
generates thermal energy for generating a bubble in
the liquid, and on the second liquid flow path 16, a
first liquid flow path 14 for the ejection liquid is
disposed. The first liquid flow path directly leads
to the ejection outlet 18. The upstream side of the
first liquid flow path 14 is connected to the first
common liquid chamber 15 which supplies a plurality of
first liquid flow paths with the ejection liquid, and
the upstream side of the second liquid is connected to
the second common liquid chamber 17 which supplies a
plurality of second liquid flow paths with the bubble
generation liquid.
It should be noted here that when the bubble
generation liquid and the ejection liquid are
identical, a single liquid chamber may be shared by
both liquid flow paths.
Between the first and second liquid flow
paths, a separation wall 30 is disposed, which is
formed of elastic material such as metal, and
separates the common liquid chamber 15 for the first
CA 02333841 2001-02-13
-42-
liquid flow path, from the common liquid chamber 17
for the second liquid flow path. When it is desirable
that the bubble generation liquid and the ejection
liquid mix with each other as little as possible, the
first liquid flow path 14 and the second liquid flow
path 16 should be separated as completely as possible
to prevent the liquid flow between the two liquid flow
paths. However, when a certain degree of mixture
between the bubble generation liquid and the ejection
liquid does not create a problem, it is unnecessary to
give the separation wall the capability to completely
separate the two liquid flow paths.
A portion of the separation wall, which is in
the space directly above the top surface of the heat
generating member (hereinafter, ejection pressure
generating region, that is, a bubble generating region
11 constituted of A region and B region in Figure 24),
is shaped like the tooth side of a comb, each oblong
piece constituting the movable member 31 whose free
end is on the ejection outlet side (downstream side of
the liquid flow), and whose supporting point 31 is on
the common liquid chamber (15, 17) side. In other
words, each movable member 31 extends like a
cantilever from the supporting point 31 toward the
ejection outlet. Since the bottom surface of the
movable member 31 faces the bubble generating region
11(B), the movable member 31 is opened into the first
CA 02333841 2001-02-13
-43-
liquid flow path from the ejection outlet side by the
bubble generation in the bubble generation liquid.
Also, since the tip of the free end portion is given a
specific width, the power from bubble generation can
be easily guided toward the ejection outlet. When the
movable member 3l is in the state depicted in Figure
24, (a), the liquid flow between the first and second
liquid flow path is impeded most.
The positional relationship among the free
end 32 and supporting point 33 of the movable member
31, and the heat generating member is the same as the
one described in the preceding embodiment.
Also, the structural relationship between the
second liquid flow path 16 and the heat generating
member 2 in this embodiment is the same as the
structural relationship between the liquid supply path
12 and the heat generating member 2 described in one
of the preceding. embodiments.
Next,~the operation of the liquid ejection
head in this embodiment will be described with
reference to Figure 24.
In this embodiment, the ejection liquid
supplied to the first liquid flow path 14 and the
bubble generation liquid supplied to the second liquid
flow path 16 are water based inks, and they are
identical.
As the heat generating member 2 is driven,
CA 02333841 2001-02-13
-44-
heat is generated. This heat triggers such a film
boiling phenomenon as that disclosed in U.S. Patent
No. 4,723,129, in the bubble generation liquid within
the bubble generating region of the second liquid flow
path, generating a bubble 40. Up to this point, the
operation is the same as the one described in the
preceding embodiments.
However, in this embodiment, the escape path
for the pressure from bubble generation is blocked in
all three directions except for the upward direction
of the bubble generating region. Therefore, the
pressure from bubble generation is concentrated on the
movable member 31 disposed to oppose the ejection
pressure generating region, pivotally displacing the
movable member 31 into the first liquid flow path,
starting from the position depicted in Figure 24, (a)
to the position depicted in Figure 24, (b) as the
bubble grows. This pivotal displacement of the
movable member 31 creates a large path between the
first and second liquid flow paths 14 and 16, allowing
the pressure from bubble generation to propagate
toward the ejection outlet of the first liquid flow
path 14 (in the direction of an arrow mark A). Since
the tip of the free end portion of the movable member
31 is given a specific width, the power from bubble
generation can be more effectively guided toward the
ejection outlet 18. With this pressure propagation
CA 02333841 2001-02-13
-45-
and the aforementioned mechanical displacement of the
movable member 31, the liquid is desirably ejected
from the ejection outlet.
Next, as the bubble contracts, the movable
member 31 returns to the position depicted in Figure
24, (a). At the same time, the ejection liquid is
supplied into the first liquid flow path 14 from the
upstream side, by the amount matching the amount of
the ejected ejection liquid. Also in this embodiment,
since the ejection liquid is supplied in the direction
harmonious with the closing direction of the movable
member 31, the refilling of the ejection liquid is not
interfered by the movable member 31.
In terms of the propagation of the pressure
which occurs as the movable member 31 is pivotally
displaced, the controlling of the bubble growth
direction, the prevention of back wave, the
operations and effects of the essential portion of the
liquid ejection head in this embodiment are the same
as those described in the preceding embodiments, but
the liquid ejection head in this embodiment employing
the structure with two liquid flow paths enjoys the
following advantage in addition to those described
above.
That is, according to the structure described
in this embodiment, the liquid used as the ejection
liquid can be different from the liquid used as the
CA 02333841 2001-02-13
-46-
bubble generation liquid. In other words, the
ejection liquid can be ejected by the pressure from a
bubble generated in the bubble generation liquid
different from the ejection liquid. Therefore, high
viscosity liquid such as polyethylene glycol, which
has been difficult- to eject due to the fact that in
high viscosity liquid, application of heat does not
trigger bubble generation intense enough to generate
pressure sufficient for liquid ejection, can be
desirably ejected by filling the high viscosity liquid
in the first liquid flow path, and filling the second
liquid flow path with the bubble generation liquid,
for example, liquid in which bubbles can be desirably
generated or liquid with a low boiling point, more
specifically, mixture of ethanol and water
(ethanol: water = 4:6; viscosity: 1 - 2 cP).
Further, choosing as the bubble generation
liquid such liquid that does not leave baked deposit
or the like on the surface of the heat generating
member even when subjected to heat stabilizes bubble
generation, making it possible to accomplish desirable
ejection.
Further, the liquid ejection head in this
embodiment which employs the head structure in
accordance with the present invention enjoys not only
the advantage described in this embodiment, but also
the advantages described in the preceding embodiments,
CA 02333841 2001-02-13
-47-
and therefore, can eject the high viscosity liquid or
the like with additional ejection efficiency and
ejection force.
Further, liquid that is inferior in heat
resistance can be ejected with high ejection
efficiency and high ejection force, as described
above, without thermally damaging the liquid, simply
by filling the first liquid flow path with such
liquid, and the second liquid flow path with such
liquid that is not likely to be thermally denatured,
and is capable of desirably generating bubbles.
<Positional relation between second liquid flow path
and movable member>
Figure 25 is an illustration of the
Positional relation between the above-described
movable member 31 and second liquid flow path 16, and
(a) is a view of the movable member 31 position of the
partition wall 30 as seen from the above, and (b) is a
view of the second liquid flow path 16 as seen from
the above without partition wall 30. Figure 14, (c)
is a schematic view of the positional relation between
the movable member 31 and the second liquid flow path
16 wherein the elements are overlaid. In these
drawings, the bottom is a front side having the
ejection outlets.
The second liquid flow path 16 of this
embodiment has a throat portion 19 on the upstream
CA 02333841 2001-02-13
-4$-
side of the heat generating element 2 with respect to
the general flow of the liquid from the second common
liquid chamber side to the ejection outlet through the
heat generating element position, and the movable
member position along the first flow path, so as to
provide a chamber-(bubble generation chamber)
effective to suppress easy escape, toward the upstream
side, of the pressure produced upon the bubble
generation in the second liquid flow path 16.
In the case of the conventional head wherein
the flow path where the bubble generation occurs and
the flow path from which the liquid is ejected, are
the same, a throat portion may be provided to prevent
the escape of the pressure generated by the heat
generating element toward the liquid chamber. In such
a case, the cross-sectional area of the throat portion
should not be too small in consideration of the
sufficient refilling of the liquid.
However, in the case of this embodiment, much
or most of the ejected liquid is from the first liquid
flow path, and the bubble generation liquid in the
second liquid flow path having the heat generating
element is not consumed much, so that the filling
amount of the bubble generation liquid to the bubble
generation region 11 may be small. Therefore, the
clearance at the throat portion 19 can be made very
small, for example, as small as several pm - ten and
CA 02333841 2001-02-13
-49-
several dun, so that the escape of the pressure
produced in the second liquid flow path can be further
suppressed to further concentrate it to the movable
member side. The pressure can be used as the ejection
pressure through the movable member 31, and therefore,
high ejection energy use efficiency and high ejection
pressure can be accomplished. The configuration of
the second liquid flow path 16 is not limited to the
one described above, but may be any if the pressure
Produced by the bubble generation is effectively
transmitted to the movable member side.
As shown in Figure 25, (c), the lateral sides
of the movable member 31 cover respective parts of the
walls constituting a part of the second liquid flow
Path so that the falling of the movable member 31 into
the second liquid flow path is prevented. Hy doing
so, the above-described separation between the
ejection liquid and the bubble generation liquid is
further assured. Furthermore, the escape of the
bubble through the slit can be suppressed so that
ejection pressure and ejection efficiency are further
increased. Moreover, the above-described effect of
the refilling from the upstream side by the pressure
upon the collapse of the bubble, can be further
enhanced.
In Figure 24, (b), with the pivotal
displacement of the movable member 6 into the first
CA 02333841 2001-02-13
-50-
liquid flow path 14, a part of the bubble generated in
the bubble generation region of the second liquid flow
path 4 extends into the first liquid flow path 14
side. By giving the second flow path a height that
permits such extension of the bubble, the ejection
force is further improved as compared with the case
without such extension of the bubble. To provide such
extending of the bubble into the first liquid flow
path 14, the height of the second liquid flow path 16
is preferably lower than the height of the largest
bubble, more particularly, the height is preferably
several ucn - 30 ucn, for example. In this example, the
height is 15 dun.
<Movable Member and Partition Wall>
Figure 26 shows another example of the
movable member 31, wherein reference numeral 35
designates a slit formed in the partition wall, and
the slit is effective to provide the movable member
31. The fulcrum 33 side of the movable member is a
common member, and the front free end 32 side is open
(comb-like), so that first liquid flow paths and
second liquid flow paths can be provided only by the
top plate with the advantage of large tolerance in the
positioning precision in the direction of the liquid
flow.
In the foregoing embodiment, the comb-like
movable member 31 and the separation wall 30 having
CA 02333841 2001-02-13
-51-
the movable member is of nickel having a thickness of
pm, but this is not limited to this example, but it
may be any if it has anti-solvent property against the
bubble generation liquid and the ejection liquid, and
5 if the elasticity is enough to permit the operation of
the movable member, and if the required fine slit can
be formed.
Preferable examples of the materials for the
movable member include durable materials such as metal
such as silver, nickel, gold, iron, titanium,
aluminum, platinum, tantalum, stainless steel,
phosphor bronze or the like, alloy thereof, or resin
material having nytril group such as acrylonitrile,
butadiene, stylene or the like, resin material having
amide group such as polyamide or the like, resin
material having carboxyl such as polycarbonate or the
like, resin material having aldehyde group such as
polyacetal or the like; resin material having sulfon
group such as poly--sulfone, resin material such as
liquid crystal polymer or the like, or chemical
compound thereof; or materials having durability
against the ink, such as metal such as gold, tungsten,
tantalum, nickel, stainless steel, titanium, alloy
thereof, materials coated with such metal, resin
material having amide group such as polyamide, resin
material having aldehyde group such as polyacetal,
resin material having ketone group such as
CA 02333841 2001-02-13
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polyetheretherketone, resin material having imide
group such as polyimide, resin material having
hydroxyl group such as phenolic resin, resin material
having ethyl group such as polyethylene, resin
material having alkyl group such as polypropylene,
resin material having epoxy group such as epoxy resin
material, resin material having amino group such as
melamine resin material, resin material having
methylol group such as xylene resin material, chemical
compound thereof, ceramic material such as silicon
dioxide or chemical compound thereof.
Preferable examples of partition or division
wall include resin material having high heat-
resistive, high anti-solvent property and high molding
Property, more particularly recent engineering plastic
resin materials such as polyethylene, polypropylene,
polyamide, polyethylene terephthalate, melamine resin
material, phenolic resin, epoxy resin material,
polybutadiene, polyurethane, polyetheretherketone,
polyether sulfone, polyallylate, polyimide,
polysulfone, liquid crystal polymer (LCP), or chemical
compound thereof, or metal such as silicon diode,
silicon nitride, nickel, gold, stainless steel, alloy
thereof, chemical compound thereof, or materials
coated with titanium or gold.
The thickness of the separation wall is
determined depending on the used material and
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configuration from the standpoint of sufficient
strength as the wall and sufficient operativity as the
movable member, and generally, 0.5 um - 10 dun approx.
is desirable.
When the separated bubble generation liquid
and ejection liquid are used as has been described
hereinbefore, the movable member functions in effect
as the separation member. When the movable member
moves in accordance with generation of the bubble, a
small amount of the bubble generation liquid may be
mixed into the ejection liquid. Usually, the ejection
liquid for forming an image in the case of the ink jet
recording, contains 3 $ to 5 $ approx. of the coloring
material, and therefore, if content of the leaked
bubble generation liquid in the ejection liquid is not
more than 20 $, no significant density change results.
Therefore, the present invention covers the case where
the mixture ratio of the bubble generation liquid of
not more than 20 $.
In the foregoing embodiment, the mixing of
the bubble generation liquid is at most 15 $, even if
the viscosity thereof is changed, and in the case of
the bubble generation liquid having the viscosity not
more than 5 cP, the mixing ratio was at most 10 $
approx., although it is different depending on the
driving frequency.
The ratio of the mixed liquid can be reduced
CA 02333841 2001-02-13
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by reducing the viscosity of the ejection liquid in
the range below 20 cps (for example not more than 5
<Manufacturing of the Liquid Ejection Head>
The description will be made as to a
manufacturing step of the liquid ejecting head
according to an embodiment of the present invention.
Ln the case of the liquid ejecting head as
shown in Figure 23, the foundation 34 for forming the
movable member 31 on the element substrate 1 is
provided by patterning a DRY FILM or the like, and a
movable member 31 is bonded or welded on the
foundation 34. Thereafter, the grooved member having
a plurality of grooves constituting the liquid flow
paths 10, the ejection outlets 18 and a recess
constituting the common liquid chamber 13, is
connected to the element substrate 1 so that grooves
and the movable members are aligned.
Since the movable member is comb-like form
wherein the fulcrum side is integral, and the free end
side is open, so that first liquid flow paths and the
second liquid flow paths are provided only by the top
plate, thus avoiding the complicated structure of the
two passage structure.
In addition, since the movable member is
comb-like, the tolerance in the accuracy of the
positioning is eased in the liquid flow path
CA 02333841 2001-02-13
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direction. The comb-like form may be provided by
forming slits by laser machining or cutting in a
plate. In such a case, as shown in Figure 27(a), if
the positioning accuracy is not high enough, excess
portion at the front free end portion of the movable
member may be faced to the bubble generating region
with the result of lowering of the ejection
efficiency. However, according to the present
invention, the free end of the movable member is open,
so that ejection efficiency is high even if the
positioning accuracy is relatively poor in the
direction of the liquid flow path, as shown in Figure
27(b). Additionally, since the excess front end
portion (ejection outlet side) is not required, the
free end can be easily made closer to the ejection
outlet side as shown in Figure 27(c), so that latitude
in the design with respect to the nozzle length is
enhanced.
Figures 28 - 35 are schematic drawings of the
liquid ejection heads in the fourth to seventh
embodiments, which are produced using the method in
accordance with the present invention.
Figure 28 is a schematic perspective view of
the liquid ejection head in the fourth embodiment of
the present invention, depicting a separation wall
inclusive of a plurality of pivotally movable members,
and a grooved member with a plurality of grooves which
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are to become liquid flow paths, each of which is
correspondent to one of the plurality of pivotally
movable members.
In Figure 28, a reference numeral 50
designates a grooved member (top plate) with a
plurality of grooves (recessed portions) which are to
become a plurality of liquid flow paths, each leading
to its own, ejection outlet, and a reference numeral 30
designates a separation wall, one edge of which forms
a plurality of pivotally movable members 31, rendering
the separation wall resemblant to a comb. The grooved
member 50 is constituted of two portions: a thick
portion 50a on the downstream side and a thin portion
50b on the upstream side. The vertical surface of the
15. upstream end, relative to the liquid flow direction,
of the thick portion 50a, that is, the vertical plane
which divides the thick downstream portion 50a and the
thin upstream portion 50b serves as a contact type
positioning reference 54, with which the separation
wall 30 is placed in contact to be aligned with the
top plate 50 in the direction indicated by an arrow
mark Y. The plurality of grooves for forming the
plurality of liquid flow paths 14 extend substantially
in parallel in the direction perpendicular to the
contact type frontal positioning reference 54. The
cross section of each liquid flow path 14 is in the
form of an inverted isosceles trapezoid, narrowing
CA 02333841 2001-02-13
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toward the bottom, and is separated from the adjacent
ones by the liquid flow path walls 14a whose cross
section is in the form of an isosceles trapezoid.
Further, the grooved member 50 is provided with a
contact type lateral positioning reference 55, with
which the separation wall 30 is placed in contact to
be aligned with the grooved member 50 in the direction
indicated by an arrow mark X. The contact type
lateral positioning reference 55 is perpendicularly
erected from the top surface of the thin rear portion
50b of the grooved member 50, at the lateral edge.
The downstream side of the separation wall 30
forms the plurality of the pivotally movable members
31, resembling the tooth side of a comb, and as the
separation wall 30 is aligned with the groove member
50, each of the plurality of pivotally movable member
31 opposes the corresponding liquid flow path 14.
The liquid ejection head in accordance with
the present invention is manufactured by combining the
grooved member 50 and separation wall 30, which are
structured as described above, in the following
manner. First, the separation wall 30 must be aligned
with the grooved member 50. This is accomplished by
vibrating the grooved member 50 with the use of a
vibrating means such as a vibrator after placing the
separation wall 30 on the grooved member 50 in such a
manner that each of the movable members 30 is disposed
CA 02333841 2001-02-13
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in the corresponding liquid flow path 14 (groove) or
on the liquid flow path wall 14a adjacent to the
corresponding liquid flow paths 14 (grooves). More
specifically, first, the grooved member 50 is vibrated
to cause the movable members 31 of the separation wall
30 to settle down into the corresponding liquid flow
paths 14 (grooves) of the grooved member 50. Next,
the grooved member 50 is tilted so that the upstream
side, xelative to the liquid flow direction, of the
liquid flow path wall 14a is raised, and then, the
grooved member 50 is vibrated again to place the
separation wall 30 in contact with the contact type
frontal positioning reference 54 and the contact type
lateral positioning reference 55. Thus, the
separation wall 30 and the grooved member 50. are
accurately positioned, or fitted, relative to each
other. At this point, the separation wall 30 may be
fixed to the grooved member 50. Fixing the two
components together renders the following assembly
steps easier.
According to this embodiment, each of the
movable members 31 is fitted in the corresponding
groove which is to become the liquid flow path 14, and
therefore, there is little possibility that the
movable members 13 are damaged while the grooved
member 50 is aligned with the element substrate.
Figure 30 is a schematic drawing which
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depicts another method for manufacturing the liquid
ejection head in accordance with the present
invention.
In the preceding manufacturing method, the
grooved member 50 was vibrated to let the separation
wall 30 be properly positioned relative to the grooved
member 50. However, in this embodiment, another
method is described, according to which the separation
wall 30 is lifted by compressed air so that the
separation wall 30 settles down on the grooved member
50 in alignment with the grooved member 50 by its own
weight.
More specifically, the separation wall 30 is
first placed on the grooved member 50 in such a manner
that each of the movable members 31 of the separation .
wall 30 is disposed on the liquid flow path wall 14a
adjacent to the corresponding liquid flow path 14
(groove), and then, the grooved member 50 is tilted so
that the upstream side, relative to the liquid flow
direction, of the liquid flow path wall 14a is raised,
as described in the preceding embodiment. Next, the
separation wall 30 is caused to hover with the use of
compressed air, allowing the separation wall 30 to be
accurately positioned by its own weight, in alignment
with the grooved member 50, with the movable members
31 of the separation wall 30 being fitted in the
corresponding grooves of the grooved member 50, which
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are to become the liquid flow paths 14.
Figure 31 is a schematic perspective drawing
which depicts the fifth embodiment of the present
invention, in which compressed air is sent in through
the liquid supply port 20 of the grooved member 5Q.
By sending compressed air through the liquid
supply port 20 as described above, the separation wall
30 can be made to hover in a desirable member, and
therefore, the separation 30 and the grooved member 50
can be accurately positioned relative to each other
with ease.
Figures 32 and 33 illustrate the contact type
frontal positioning references 54a and 54b,
respectively, with which the grooved member 50 is
provided. Figure 32 depicts an arrangement in which
the grooved member 50 is shaved off apt two portions,
which constitute the laterally outward wall portion of
the laterally outermost liquid flow path, so that only
the rearward facing vertical surface 54a of the liquid
flow path wall 14a is allowed to serve as the contact
type frontal positioning reference, whereas Figure 33
depicts another arrangement in which only the rearward
facing vertical surface 54b of the laterally outward
wall portion of the laterally outermost liquid flow
path is allowed to serve as the contact type frontal
positioning reference. In either case, the separation
wall 30 and the grooved member 50 can be properly
CA 02333841 2001-02-13
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positioned relative each other with ease. However,
the structure illustrated in Figure 33 allows the
liquid to be supplied through the relatively larger
gap formed between the separation wall 30 and the
rearward facing surface of the liquid flow path wall
14a, improving thereby the refilling speed for the
liquid ejection head.
Figure 34 is a schematic drawing which
depicts the manufacturing method for the liquid
ejection head in the sixth embodiment of the present
invention.
Also in this embodiment, the upstream side
portion 54c of the liquid flow path wall 14a of the
grooved member 50 is used as the contact type frontal
positioning reference. However, in this embodiment,
the upstream side portion 54c is modified to give it a
semicircular horizontal section, and the contact
portion 54d, that is, the portion at the base of the
movable member 31 comparable to a tooth of a comb,
which is placed in contact with the contact type
frontal positioning reference 54c, is modified to give
it a V-shaped horizontal section, so that the
separation wall 30 and the grooved member 50 can be
aligned in two directions through a single step. More
specifically, as illustrated, the separation wall 30
is first placed on the grooved member 50 in such a
manner that the movable member 31 of the separation
CA 02333841 2001-02-13
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wall 30, resembling a comb tooth, is fitted within the
groove of the grooved member 50, which is to become
the liquid flow path 14. Then, the V-shaped contact
type frontal positioning reference 54d of the
separation wall 30, located between the adjacent
movable members 31 of the separation wall 30, is
placed in contact with the contact type frontal
positioning reference portion 54c of the liquid flow
path wall 14a of the grooved member 50, having a
semicircular horizontal section. As a result, the
separation wall 30 and the grooved member 50 are
desirably positioned relative to each other. In this
positioning, the contact type positioning reference
portion 54c of the liquid flow path wall 14a of the
grooved member 50 has a semicircular horizontal
section, whereas the contact type positioning
reference portion 54d of the separation wall 30,
located between the adjacent two movable members 31 of
the separation wall 30, has a V-shaped horizontal
section, and therefore, as both are placed in contact
with each other, the separation wall 30 and the
grooved member 50 are accurately aligned in two
directions, that is, the lateral direction and the
frontward-backward direction, through a single step.
Figure 35 is a schematic perspective drawing
which depicts the manufacturing method for the liquid
ejection head in the seventh embodiment of the present
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invention.
In this embodiment, the grooved member 50 is
provided with a pair of contact type referential pins
7, and the separation wall 30 is provided with a pair
of contact type elongated referential windows 8 which
correspond to the referential pin 7, so that the
separation wall 30 can be aligned with the grooved
member 50 with the use of the referential pin 7 and
the referential window 8.
First, the separation wall 30 is placed on
the grooved member 50 in such a manner that each
movable member 31 of the separation wall 30,
comparable to a comb tooth, is fitted in the
corresponding groove of the grooved member 50, which
is to become the liquid flow path 14. Substantially
at the same time, the contact type referential pin 7
of the grooved member 50 is inserted into the contact
type referential window 8 of the separation wall 30.
Then, the edge of the contact type referential window
8 is placed in contact with the contact type
referential pin 7 of the grooved member 50 to
desirably position the separation wall 30 relative to
the grooved member 50.
As described above, according to the present
invention, a liquid ejection head employs a pivotally
movable member to eject liquid based on an innovative
ejection principle. Also, in order to accurately
CA 02333841 2001-02-13
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align a separation wall with an element substrate when
joining them, all that is necessary is to place the
contact type positioning reference of the separation
wall in contact with the contact type positioning
reference of the element substrate, and therefore,
accurate positioning can be done with the use of a
small, simple, and inexpensive apparatus. Further,
the liquid adjacent to an ejection outlet can be
effectively ejected due to the synergistic effect from
bubble growth and the pivotal movement of a movable
member caused by the bubble growth, and therefore,
ejection efficiency is improved compared with the
conventional bubble jet system, conventional ejection
method, conventional head, or the like.
(Other Embodiment)
In the foregoing, the description has been
made as to the major parts of the liquid ejecting head
and the liquid ejecting method according to the
embodiments of the present invention. The description
will now be made as to further detailed embodiments
usable with the foregoing embodiments. The following
examples are usable with both of the single-flow-path
type and two-flow-path type without specific
statement.
Referring to Figure 14, the description will
be made as to the operation of the liquid ejecting
head according to this embodiment.
CA 02333841 2001-02-13
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In this case, the bubble generation liquid
supplied to the second liquid flow path 16 and the
ejection liquid supplied to the first liquid flow path
14 were both water type ink.
By the heat generated by the heat generating
element 2, the bubble generation liquid in the bubble
generation region in the second liquid flow path
generates a bubble 40, by film boiling phenomenon as
described hereinbefore.
In this embodiment, the bubble generation
pressure is not released in the three directions
except for the upstream side in the bubble generation
region, so that pressure produced by the bubble
generation is propagated concentratedly on the movable
member 6 side in the ejection pressure generation
portion, by which the movable member 6 is displaced
from the position indicated in Figure 14, (a) toward
the first liquid flow path side as indicated in Figure
14, (b) with the growth of the bubble.
Similarly to the foregoing embodiment, when
the movable member 31 is displaced as a result of the
generation of the bubble, and the movable member 31
receives the resistance in the direction opposite from
the displacement, but the resistance is sufficiently
small as compared with the case in which the fulcrum
of the movable member 31 is in the first liquid flow
path 14 as in Figure 14(c). Additionally, the
CA 02333841 2001-02-13
a~
-66-
refilling property is good, so the high viscosity
liquid can be ejected.
By the operation of the movable member, the
first liquid flow path 14 and the second liquid flow
path 16 are in wide fluid communication with each
other, and the pressure produced by the generation of
the bubble is mainly propagated toward the ejection
outlet in the first liquid flow path (direction A).
By the propagation of the pressure and the mechanical
displacement of the movable member, the liquid is
ejected through the ejection outlet.
Then, with the contraction of the bubble, the
movable member 31 returns to the position indicated in
Figure 17, (a), and correspondingly, an amount of the
liquid corresponding to the ejection liquid is
supplied from the upstream in the first liquid flow
path 14. In this embodiment, the direction of the
liquid supply is codirectional with the closing of the
movable member as in the foregoing embodiments, the
refilling of the liquid is not impeded by the movable
member.
<Movable Member and Separation Wall>
Figure 21 shows another example of the
movable member 31, wherein reference numeral 35
designates a slit formed in the partition wall, and
the slit is effective to provide the movable member
31. In the Figure, (a), the movable member has a
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rectangular configuration, and in (b), it is narrower
in the fulcrum side to permit increased mobility of
the movable member, and in (c), it has a wider fulcrum
side to enhance the durability of the movable member.
The configuration narrowed and arcuated at the fulcrum
side is desirable as shown in Figure 20, (a), since
both of easiness of motion and durability are
satisfied. However, the configuration of the movable
member is not limited to the one described above, but
it may be any if it does not enter the second liquid
flow path side, and motion is easy with high
durability.
In the foregoing embodiments, the plate or
film movable member 31 and the separation wall 5
having this movable member was made of a nickel having
a thickness of 5 um, but this is not limited to this
example, but it may be any if it has anti-solvent
property against the bubble generation liquid and the
ejection liquid, and if the elasticity is enough to
permit the operation of the movable member, and if the
required fine slit can be formed.
The thickness of the separation wall is
determined depending on the used material and
configuration from the standpoint of sufficient
strength as the wall and sufficient operativity as the
movable member, and generally, 0.5 dun - 10 um approx.
is desirable.
CA 02333841 2001-02-13
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The width of the slit 35 for providing the
movable member 31 is 2 dam in the embodiments. When
the bubble generation liquid and ejection liquid are
different materials, and mixture of the liquids is to
be avoided, the gap is determined so as to form a
meniscus between the liquids, thus avoiding mixture
therebetween. For example, when the bubble generation
liquid has a viscosity about 2 cP, and the ejection
liquid has a viscosity not less than 100 cP, 5 um
approx. Slit is enough to avoid the liquid mixture,
but not more than 3 pm is desirable.
In this invention, the movable member has a
thickness of dun order as preferable thickness, and a
movable member having a thickness of cm order is not
used in usual cases. When the movable member having a
thickness of the order of microns, and the slit width
is also of the order of microns, a certain degree of
consideration is to be paid to the manufacturing
variation.
When the thickness of the member opposed to
the free end and/or lateral edge of the movable member
formed by a slit, is equivalent to the thickness of
the movable member (Figures 13, 14 or the like), the
relation between the slit width and the thickness is
preferably as follows in consideration of the
variation in the manufacturing to stably suppress the
liquid mixture between the bubble generation liquid
CA 02333841 2001-02-13
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and the ejection liquid. When the bubble generation
liquid has a viscosity not more than 3 cp, and a high
viscous ink (5 cp, 10 cp or the like) is used as the
ejection liquid, the mixture of the 2 liquids can be
suppressed for a long term if W/t S 1 is satisfied.
The slit providing the "substantial sealing",
preferably has several microns width, since the liquid
mixture prevention is assured.
When the bubble generation liquid and the
ejection liquid are used for the respective functions,
the movable member functions as a separation member in
effect. When the movable member moves due to the
generation of the bubble, a small amount of the bubble
generation liquid may be mixed into the ejection
liquid. Since the ejection liquid for forming an
image usually contains approximately 3 $ to 5 $ of
coloring agent, no significant density change occurs
even if the content of the bubble generation liquid in
the ejected droplet is not more than 20 ~. Such a
case is within the split of the present invention,
therefore.
In the foregoing embodiments, the maximum
mixture ratio of the bubble generation liquid was 15 ~
even when various viscosities are used. With the
bubble generation liquid having the viscosity not more
than 5 cps, the mixture ratio was 10 ~ approx. at the
maximum, although it is different if the driving
CA 02333841 2001-02-13
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frequency is different.
The mixed liquid can be reduced by reducing
the viscosity of the ejection liquid in the range
below 20 cps (for example not more than 5 $).
The description will be made as to positional
relation between the heat generating element and the
movable member in this head. The configuration,
dimension and number of the movable member and the
heat generating element are not limited to the
following example. Hy an optimum arrangement of the
heat generating element and the movable member, the
pressure upon bubble generation by the heat generating
element, can be effectively used as the ejection
pressure.
In a conventional bubble jet recording
method, energy such as heat is applied to the ink to
generate instantaneous volume change (generation of
bubble) in the ink, so that ink is ejected through an
ejection outlet onto a recording material to effect
printing. In this case, the area of the heat
generating element and the ink ejection amount are
proportional to each other. However, there is a non-
bubble-generation region S not contributable to the
ink ejection. This fact is confirmed from observation
of burnt deposit on the heat generating element, that
is, the non-bubble-generation area S extends in the
marginal area of the heat generating element. It is
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understood that marginal approx. 4 dun width is not
contributable to the bubble generation.
In order to effectively use the bubble
generation pressure, it is preferable that movable
range of the movable member covers the effective
bubble generating region of the heat generating
element, namely, the inside area beyond the marginal
approx. 4 Nm width. In this embodiment, the effective
bubble generating region is approx. 4 um and inside
thereof, but this is different if the heat generating
element and forming method is different.
<Element Substrate>
The description will be made as to a
structure of the element substrate provided with the
1,5 heat generating element for.heating the liquid.
Figure 22 is a longitudinal section of the
liquid ejecting head according to an embodiment of the
present invention.
On the element substrate 1, a grooved member
50 is mounted, the member 50 having second liquid flow
paths 16, separation walls 30, first liquid flow paths
14 and grooves for constituting the first liquid flow
path.
The element substrate 1 has, as shown in
Figure 12, patterned wiring electrode (0.2 - 1.0 dun
thick) of aluminum or the like and patterned electric
resistance layer 105 (0.01 - 0.2 ucn thick) of hafnium
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boride (HfB2), tantalum nitride (TaN), tantalum
aluminum (TaAl) or the like constituting the heat
generating element on a silicon oxide film or silicon
nitride film 106 for insulation and heat accumulation,
which in turn is on the substrate 107 of silicon or
the like. A voltage is applied to the resistance
layer 105 through the two wiring electrodes 104 to
flow a current through the resistance layer to effect
heat generation. Between the wiring electrode, a
protection layer of silicon oxide, silicon nitride or
the like of 0.1 - 2.0 dun thick is provided on the
resistance layer, and in addition, an anti-cavitation
layer of tantalum or the like (0.1 - 0.6 Nm thick) is
formed thereon to protect the resistance layer 105
from various liquid such as ink.
The pressure and shock wave generated upon
the bubble generation and collapse is so strong that
durability of the oxide film which is relatively
fragile is deteriorated. Therefore, metal material
such as tantalum (Ta) or the like is used as the anti-
cavitation layer.
The protection layer may be omitted depending
on the combination of liquid, liquid flow path
structure and resistance material. One of such
examples is shown in Figure 17, (b). The material of
the resistance layer not requiring the protection
layer, includes, for example, iridium-tantalum-
CA 02333841 2001-02-13
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aluminum alloy or the like.
Thus, the structure of the heat generating
element in the foregoing embodiments may include only
the resistance layer (heat generation portion) or may
include a protection layer for protecting the
resistance layer.
In the embodiment, the heat generating
element has a heat generation portion having the
resistance layer which generates heat in response to
the electric signal. This is not limiting, and it
will suffice if a bubble enough to eject the ejection
liquid is created in the bubble generation liquid.
For example, heat generation portion may be in the
form of a photothermal transducerwhich generates heat
upon receiving light such as laser, or the one which
generates heat upon receiving high frequency wave.
On the element substrate 1, function elements
such as a transistor, a diode, a latch, a shift
register and so on for selectively driving the
electrothermal transducer element may also be
integrally built in, in addition to the resistance
layer 105 constituting the heat generation portion and
the electrothermal transducer constituted by the
wiring electrode 104 for supplying the electric signal
to the resistance layer.
In order to eject the liquid by driving the
heat generation portion of the electrothermal
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transducer on the above-described element substrate 1,
the resistance layer 105 is supplied through the
wiring electrode 104 with rectangular pulses as shown
in Figure 23 to cause instantaneous heat generation in
the resistance layer 105 between the wiring electrode.
In the case of the heads of the foregoing embodiments,
the applied energy has a voltage of 24 V, a pulse
width of 7 usec, a current of 150 mA and a frequency
of 6kHz to drive the heat generating element, by which
the liquid ink is ejected through the ejection outlet
through the process described hereinbefore. However,
the driving signal conditions are not limited to this,
but may be any if the bubble generation liquid is
properly capable of bubble generation.
<Ejection Liquid and Bubble Generation Liquid>
As described in the foregoing embodiment,
according to the present invention, by the structure
having the movable member described above, the liquid
can be ejected at higher ejection force or ejection
efficiency than the conventional liquid ejecting head.
When the same liquid is used for the bubble generation
liquid and the ejection liquid, it is possible that
liquid is not deteriorated, and that deposition on the
heat generating element due to heating can be reduced.
Therefore, a reversible state change is accomplished
by repeating the gassification and condensation. So,
various liquids are usable, if the liquid is the one
CA 02333841 2001-02-13
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not deteriorating the liquid flow passage, movable
member or separation wall or the like.
Among such liquids, the one having the
ingredient as used in conventional bubble jet device,
can be used as a recording liquid.
When the two-flow-path structure of the
present invention is used with different ejection
liquid and bubble generation liquid, the bubble
generation liquid having the above-described property
is used, more particularly, the examples includes:
methanol, ethanol, n-propyl alcohol, isopropyl
alcohol, n-hexane, n-heptane, n-octane, toluene,
xylene, methylene dichloride, trichloroethylene, Freon
TF, Freon BF, ethyl ether, dioxane, cyclohexane,
methyl acetate, ethyl acetate, acetone, methyl ethyl
ketone, water, or the like, and a mixture thereof.
As for the ejection liquid, various liquids
are usable without paying attention to the degree of
bubble generation property or thermal property. The
liquids which have not been conventionally usable,
because of low bubble generation property and/or
easiness of property change due to heat, are usable.
However, it is desired that ejection liquid
by itself or by reaction with the bubble generation
liquid, does not impede the ejection, the bubble
generation or the operation of the movable member or
the like.
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As for the recording ejection liquid, high
viscous ink or the like is usable. As for another
ejection liquid, pharmaceuticals and perfume or the
like having a nature easily deteriorated by heat is
usable.
The ink of the following ingredient was used
as the recording liquid usable for both of the
ejection liquid and the bubble generation liquid, and
the recording operation was carried out. Since the
ejection speed of the ink is increased, the shot
accuracy of the liquid droplets is improved, and
therefore, highly desirable images were recorded.
Dye ink viscosity of 2 cp
(C.I. Food black 2) dye 3 wt. $
Ethylene glycol 10 wt.
Thiodiglycol 5 wt. $
Ethanol 5 wt.
Water 77 wt.
Recording operations were also carried out
using the following combination of the liquids for the
bubble generation liquid and the ejection liquid. As
a result, the liquid having ten cps viscosity, which
was unable to be ejected heretofore, was properly
ejected, and even 150 cps liquid was properly ejected
to provide high quality image.
Bubble generation liquid 1:
Ethanol 40 wt.
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Water 60 wt.
Bubble generation liquid 2:
Water 100 wt.
Bubble generation liquid:
Isopropylalcohol 10 wt.
Water 10 wt. g
Ejection liquid 1 (Pigment ink; approx. 1 5 cp):
Carbon black 5 wt.
Stylene-acrylate-acrylate ethyl
copolymer resin material 1 wt. $
dispersion material (oxide = 140,
weight average molecular weight = 80 00)
Mono-ethanol amine 0.25 wt. ~
Glyceline 69 wt. g
Thiodiglycol 5 wt.
Ethanol 3 wt.
Water 16.75 wt. ~
Ejection liquid 2 (55 cp):
Polyethylene glycol 200 100 wt.
Ejection liquid 3 (55 cp):
Polyethylene glycol 600 100 wt.
In the case of the liquid which has not been
easily ejected, the ejection speed is low, an d
therefore, the variation in the ejection dire ction
is
expanded on the recording paper with the resu lt of
poor shot accuracy. Additionally, variation of
ejection amount occurs due to the ejection
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instability, thus preventing the recording of high
quality image. However, according to the embodiments,
the use of the bubble generation liquid permits
sufficient and stabilized generation of the bubble.
Thus, the improvement in the shot accuracy of the
liquid droplet and the stabilization of the ink
ejection amount can be accomplished, thus improving
the recorded image quality remarkably.
<Head Structure for 2 Flow Path >
Figure 19 is an exploded perspective view of
a two-flow-path structure head according to an
embodiment of the present invention.
The element substrate 1 is disposed on a
supporting member 70 of aluminum or the like. A wall
for the second liquid flow path 16 and a wall for the
second common liquid chamber 17, thereon, and a
separation wall 30 having the movable member 31 is
provided further thereon. There is further provided,
on the separation wall 30, a grooved member 50
including a plurality of grooves for constituting the
first liquid flow paths 14, the first common liquid
chamber 13, the supply passage 20 for supplying the
first liquid to the first common liquid chamber 13,
and the supply passage 21 for supplying the second
liquid to the second common liquid chamber 17, thus
constituting two-path head.
<Liquid Ejecting Device>
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Figure 27 is a schematic illustration of a
liquid ejecting device used with the above-described
liquid ejecting head. In this example, the ejection
liquid is ink. The apparatus is an ink ejection
recording apparatus. The liquid ejecting device
comprises a carriage HC to which the head cartridge
comprising a liquid container portion 90 and liquid
ejecting head portion 201 which are detachably
connectable with each other, is mountable. The
carriage HC is reciprocable in a direction of width of
the recording material 150 such as a recording sheet
or the like fed by a recording material transporting
means.
When a driving signal is supplied to the
liquid ejecting meanfi on the carriage from unshown
driving signal supply means, the recording liquid is
ejected to the recording material from the liquid
ejecting head 201 in response to the signal.
The liquid ejecting apparatus of this
embodiment comprises a motor 111 as a driving source
for driving the recording material transporting means
and the carriage, gears 112, 113 for transmitting the
power from the driving source to the carriage, and
carriage shaft 115 and so on. By the recording device
and the liquid ejecting method using this recording
device, good prints can be provided by ejecting the
liquid to the various recording material.
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Figure 28 is a block diagram of the entirety
of the device for carrying out ink ejection recording
using the liquid ejecting head and the liquid ejecting
method of the present invention.
The recording apparatus receives printing
data in the form of a control signal from a host
computer 300. The printing data is temporarily stored
in an input interface 301 of the printing apparatus,
and at the same time, is converted into processable
data to be inputted to a CPU 302, which doubles as
means for supplying a head driving signal. The CPU
302 processes the aforementioned data inputted to the
CPU 302, into printable data (image data), by
processing them with the use of peripheral units such
as RAMS 304 or the like, following control programs
stored in a ROM 303.
The CPU 302 processes the aforementioned data
inputted to the CPU 302, into printable data (image
data), by processing them with the use of peripheral
units such as RAMs 304 or the like, following control
programs stored in a ROM 303. The image data and the
motor driving data are transmitted to a head200 and a
driving motor 306 through a head driver 307 and a
motor driver 305, respectively, which are controlled
with the proper timings for forming a image.
As for recording material, to which liquid
such as ink is adhered, and which is usable with a
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recording apparatus such as the one described above,
the following can be listed; various sheets of paper;
OHP sheets; plastic material used for forming compact
disks, ornamental plates, or the like; fabric;
metallic material such as aluminum, copper, or the
like; leather material such as cow hide, pig hide,
synthetic leather, or the like; lumber material such
as solid wood, plywood, and the like; bamboo material;
ceramic material such as tile; and material such as
sponge which has a three dimensional structure.
The aforementioned recording apparatus
includes a printing apparatus for various sheets of
paper or OHP sheet, a recording apparatus for plastic
material such as plastic material used for forming a
compact disk or the like, a recording apparatus for
metallic plate or the like, a recording apparatus for
leather material, a recording apparatus for lumber, a
recording apparatus for ceramic material, a recording
apparatus for three dimensional recording material
such as sponge or the like, a textile printing
apparatus for recording images on fabric, and the like
recording apparatuses.
As for the ejection liquid usable with the
liquid ejecting apparatus, it is selected properly by
skilled in the art, in consideration of the recording
material and the recording condition.
The present invention is applicable to a so-
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called side shooter type head, wherein the liquid is
ejected in a direction perpendicular the heater
surf ace .
According to an aspect of the present
invention, the fulcrum is provided in the first common
chamber, so that produced pressure is efficiently
directed toward the ejection outlet. In addition, the
influence of the back-wave can be suppressed, thus
minimizing the flow resistance of the first liquid
passage. Thus, the refiling of the liquid is
improved, and the high ejection efficiency and high
ejection pressure can be provided. The first liquid
flow path for the ejection of the liquid and the
second liquid flow path for the generation of the
bubble, and the portion where the bubble is generated
is in the form of a chamber, so that bubble generation
efficiency isimproved, and the above advantage is
further enhanced.
According to the structure using the ejection
principle, the synergetic effect of the bubble and the
movable member is provided so that liquid adjacent the
ejection outlet can be ejected efficiently, thus
improving the ejection efficiency.
The ejection failure can be avoided even
after long term non-use under low temperature and low
humidity conditions, and even if the ejection failure
occurs, the normal state is restored by small scale
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refreshing process such as preliminary ejection or
suction recovery. According to the present invention,
the time required for the recovery can be reduced, and
the loss of the liquid by the recovery operation is
reduced, so that running cost can be reduced.
In an aspect of improving the refilling
property, the responsivity, the stabilized growth of
the bubble and stabilization of the liquid droplet
during the continuous ejections are accomplished, thus
permitting high speed recording.
By the comb-like configuration of the movable
member, the accuracy of connection is assured in the
direction of the liquid flow path, thus permitting
easy and less expensive manufacturing of the liquid
ejecting head.
With the head of the two-flow-path structure,
the latitude of selection of the ejection liquid is
wide since the bubble generation liquid may be the one
with which the bubble generation is easy and with
which the deposited material (burnt deposit or the
like) is easily produced. Therefore, the liquids
which have not been easily ejected through the
conventional bubble jet ejecting method, such as high
viscosity liquid with which bubble generation is
difficult or a liquid which tends to produce burned
deposit on the heater, can be ejected in goad order.
Furthermore, a liquid which is easy
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influenced by heat can be ejected without adverse
influence.
Accordingly, the liquid which has to be
painted because of its high viscosity can be printed
as dots.
While the invention has been described with
reference to the structures disclosed herein, it is
not confined to the details set forth and this
application is intended to cover such modifications or
changes as may come within the purposes of the
improvements or the scope of the following claims.
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