Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INKJET PRINTHEAD HAVING ISOLATED NOZZLES
FIELD OF THE INVENTION
The present invention relates to the field of inkjet printers and, discloses
an inkjet
printing system using printheads manufactured with microelectro-mechanical
systems
(MEMS) techniques.
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BACKGROUND OF THE INVENTION
Many different types of printing have been invented, a large number of which
are
presently in use. The known forms of print have a variety of methods for
marking the print
media with a relevant marking media. Commonly used forms of printing include
offset
printing, laser printing and copying devices, dot matrix type impact printers,
thermal paper
printers, film recorders, thermal wax printers, dye sublimation printers and
ink jet printers
both of the drop on demand and continuous flow type. Each type of printer has
its own
advantages and problems when considering cost, speed, quality, reliability,
simplicity of
construction and operation etc.
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In recent years, the field of ink jet printing, wherein each individual pixel
of ink is
derived from one or more ink nozzles has become increasingly popular primarily
due to its
inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey
of the
field, reference is made to an article by J Moore, "Non-Impact Printing:
Introduction and
Historical Perspective", Output Hard Copy Devices, Editors R Dubeck and S Shen-
, pages 207
- 220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a
continuous stream of ink in ink jet printing appears to date back to at least
1929 wherein US
Patent No. 1941001 by Hansell discloses a simple form of continuous stream
electro-static ink
jet printing.
US Patent 3596275 by Sweet also discloses a process of a continuous ink jet
printing
including the step wherein the ink jet stream is modulated by a high frequency
electro-static
field so as to cause drop separation. This technique is still utilized by
several manufacturers
including Elmjet and Scitex (see also US Patent No. 3373437 by Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet
printing
device. Piezoelectric systems are disclosed by Kyser et. al. in US Patent No.
3946398 (1970)
which utilizes a diaphragm mode of operation, by Zolten in US Patent 3683212
(1970) which
discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in US
Patent No.
3747120 (1972) discloses a bend mode of piezoelectric operation, Howkins in US
Patent No.
4459601 discloses a piezoelectric push mode actuation of the ink jet stream
and Fischbeck in
US 4584590 which discloses a shear mode type of piezoelectric transducer
element.
Recently, thermal ink jet printing has become an extremely popular form of ink
jet
printing. The ink jet printing techniques include those disclosed by Endo et
al in GB 2007162
(1979) and Vaught et al in US Patent 4490728. Both the aforementioned
references disclosed
ink jet printing techniques that rely upon the activation of an electrothermal
actuator which
results in the creation of a bubble in a constricted space, such as a nozzle,
which thereby
FIN
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causes the ejection of ink from an aperture connected to the confined space
onto a relevant
print media. Printing devices utilizing the electro-thermal actuator are
manufactured by
manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing
technologies are
available. Ideally, a printing technology should have a number of desirable
attributes. These
include inexpensive construction and operation, high speed operation, safe and
continuous
long term operation etc. Each technology may have its own advantages and
disadvantages in
the areas of cost, speed, quality, reliability, power usage, simplicity of
construction operation,
durability and consumables.
A problem with inkjet printheads, and especially inkjet printheads having a
high
nozzle density, is that ink can flood across the printhead surface
contaminating adjacent
nozzles. This is undesirable because it results in reduced print quality.
Moreover, cross-
contamination of ink across the printhead surface can potentially result in
electrolysis and
accelerated corrosion of nozzle actuators.
Previous attempts to minimize ink flooding across the printhead surface
typically
involve coating the printhead with a hydrophobic material. However,
hydrophobic coatings
have only had limited success in minimizing the extent of flooding.
A further problem with inkjet printheads, especially inkjet printheads having
senstitive MEMS nozzles formed on an ink ejection surface of the printhead, is
that the
nozzle structures can become damaged by cleaning the printhead surface.
Typically,
printheads are wiped regularly to remove particles of paper dust or paper
fibers, which
build up on the ink ejection surface. When a wiping mechanism comes into
contact with
nozzle structures on the printhead surface, there is an obvious risk of
damaging the nozzles.
It would be desirable to provide a printhead, which minimizes cross-
contamination
by ink flooding between adjacent nozzles. It would be further desirable to
provide a
printhead, which allows regular cleaning of the printhead surface by a wiping
mechanism
without risk of damaging nozzle structures on the printhead.
SUMMARY OF THE INVENTION
In a first aspect, there is provided a printhead comprising:
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a substrate including a plurality of nozzles for ejecting ink droplets onto a
print
medium, each nozzle having a nozzle aperture defined in an ink ejection
surface of the
substrate; and
a plurality of formations on the ink ejection surface, the surface formations
being
5 configured to isolate each nozzle from at least one adjacent nozzle.
In a second aspect, there is provided a method of operating a printhead,
whilst
minimizing cross-contamination of ink between adjacent nozzles, the method
comprising
the steps of
(a) providing a printhead comprising:
a substrate including a plurality of nozzles for ejecting ink droplets onto a
print
medium, each nozzles having a nozzle aperture defined in an ink ejection
surface of the
substrate; and
a plurality of formations on the ink ejection surface, the surface formations
being
configured to isolate each nozzle from at least one adjacent nozzle; and
(b) printing onto a print medium using said printhead.
In a third aspect, there is provided a method of fabricating a printhead
having
isolated nozzles, the method comprising the steps of:
(a) providing a substrate, the substrate including a plurality of nozzles for
ejecting
ink droplets onto a print medium, each nozzle having a nozzle aperture defined
in an ink
ejection surface of the substrate;
(b) depositing a layer of photoresist over the ink ejection surface;
(c) defining recesses in the photoresist, each recess revealing a portion of
the ink
ejection surface surrounding a respective nozzle aperture;
(d) depositing a roof material over the photoresist and into the recesses;
(e) etching the roof material to define a nozzle enclosure around each nozzle
aperture, each nozzle enclosure having an opening defined in a roof and
sidewalls
extending from the roof to the ink ejection surface; and
(f) removing the photoresist.
Optionally, the formations have a hydrophobic surface. Inkjet inks are
typically
aqueous-based inks and hydrophobic formations will repel any flooded ink.
Hence,
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hydrophobic formations minimize as far as possible any cross-contamination of
ink by
acting as a physical barrier and by intermolecular repulsive forces. Moreover,
hydrophobic
formations promote ingestion of any flooded ink back into respective nozzle
chambers and
ink supply channels. Since nozzle chambers are typically hydrophilic, ink will
tend to be
drawn back into the nozzle and away from a surrounding hydrophobic formation.
Optionally, the formations are arranged in a plurality of nozzle enclosures,
each
nozzle enclosure comprising sidewalls surrounding a respective nozzle, the
sidewalls
forming a seal with the ink ejection surface. Hence, each nozzle is isolated
from its adjacent
nozzles by a nozzle enclosure.
Optionally, each nozzle enclosure further comprises a roof spaced apart from
the
respective nozzle, the roof having a roof opening aligned with a respective
nozzle opening
for allowing ejected ink droplets to pass therethrough onto the print medium.
Hence, each
nozzle enclosure may typically take the form of a cap, which covers or
encapsulates an
individual nozzle on the ink ejection surface. The roof not only provides
additional
containment of any flooded ink, it also provides further protection of each
nozzle from, for
example, the potentially damaging effects of paper dust, paper fibers or
wiping.
Typically, the sidewalls extend from a perimeter region of each roof to the
ink
ejection surface. Sidewalls of adjacent nozzle enclosures are usually spaced
apart across the
ink ejection surface.
Optionally, the printhead is an inkjet printhead, such as a pagewidth inkjet
printhead. Optionally, the printhead has a nozzle density, which is sufficient
to print at up
to 1600 dpi. The present invention is particularly beneficial for printheads
having a high
nozzle density, because high density printheads are especially prone to
flooding between
adjacent nozzles.
BRIEF DESCRIPTION OF THE DRAWINGS
Notwithstanding any other forms that may fall within the scope of the present
invention, preferred forms of the invention will now be described, by way of
example only,
with reference to the accompanying drawings in which:
Fig. 1 is a schematic cross-sectional view through an ink chamber of a unit
cell of a
printhead according to an embodiment using a bubble forming heater element;
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Fig. 2 is a schematic cross-sectional view through the ink chamber Fig. 1, at
another
stage of operation;
Fig. 3 is a schematic cross-sectional view through the ink chamber Fig. 1, at
yet
another stage of operation;
Fig. 4 is a schematic cross-sectional view through the ink chamber Fig. 1, at
yet a
further stage of operation; and
Fig. 5 is a diagrammatic cross-sectional view through a unit cell of a
printhead in
accordance with an embodiment of the invention showing the collapse of a vapor
bubble.
Fig. 6 is a schematic, partially cut away, perspective view of a further
embodiment
of a unit cell of a printhead.
Figs. 7 to 20 are schematic perspective views of the unit cell shown in Fig.
6, at
various successive stages in the fabrication process of the printhead.
DESCRIPTION OF OPTIONAL EMBODIMENTS
Bubble Forming Heater Element Actuator
With reference to Figures 1 to 4, the unit cell 1 of one of the Applicant's
printheads
is shown. The unit cell 1 comprises a nozzle plate 2 with nozzles 3 therein,
the nozzles
having nozzle rims 4, and apertures 5 extending through the nozzle plate. The
nozzle plate
2 is plasma etched from a silicon nitride structure which is deposited, by way
of chemical
vapor deposition (CVD), over a sacrificial material which is subsequently
etched.
The printhead also includes, with respect to each nozzle 3, side walls 6 on
which the
nozzle plate is supported, a chamber 7 defined by the walls and the nozzle
plate 2, a multi-
layer substrate 8 and an inlet passage 9 extending through the multi-layer
substrate to the
far side (not shown) of the substrate. A looped, elongate heater element 10 is
suspended
within the chamber 7, so that the element is in the form of a suspended beam.
The
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printhead as shown is a microelectromechanical system (MEMS) structure, which
is formed
by a lithographic process which is described in more detail below.
When the printhead is in use, ink I 1 from a reservoir (not shown) enters the
chamber 7 via the inlet passage 9, so that the chamber fills to the level as
shown in Figure
1. Thereafter, the heater element 10 is heated for somewhat less than 1
microsecond, so
that the heating is in the form of a thermal pulse. It will be appreciated
that the heater
element 10 is in thermal contact with the ink 11 in the chamber 7 so that when
the element
is heated, this causes the generation of vapor bubbles 12 in the ink.
Accordingly, the ink 11
to constitutes a bubble forming liquid. Figure 1 shows the formation of a
bubble 12
approximately 1 microsecond after generation of the thermal pulse, that is,
when the bubble
has just nucleated on the heater elements 10. It will be appreciated that, as
the heat is
applied in the form of a pulse, all the energy necessary to generate the
bubble 12 is to be
supplied within that short time.
When the element 10 is heated as described above, the bubble 12 forms along
the
length of the element, this bubble appearing, in the cross-sectional view of
Figure 1, as four
bubble portions, one for each of the element portions shown in cross section.
The bubble 12, once generated, causes an increase in pressure within the
chamber 7,
which in turn causes the ejection of a drop 16 of the ink 11 through the
nozzle 3. The rim 4
assists in directing the drop 16 as it is ejected, so as to minimize the
chance of drop
misdirection.
The reason that there is only one nozzle 3 and chamber 7 per inlet passage 9
is so
that the pressure wave generated within the chamber, on heating of the element
10 and
forming of a bubble 12, does not affect adjacent chambers and their
corresponding nozzles.
The pressure wave generated within the chamber creates significant stresses in
the chamber
wall. Forming the chamber from an amorphous ceramic such as silicon nitride,
silicon
dioxide (glass) or silicon oxynitride, gives the chamber walls high strength
while avoiding
the use of material with a crystal structure. Crystalline defects can act as
stress
concentration points and therefore potential areas of weakness and ultimately
failure.
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Figures 2 and 3 show the unit cell 1 at two successive later stages of
operation of the
printhead. It can be seen that the bubble 12 generates further, and hence
grows, with the
resultant advancement of ink I 1 through the nozzle 3. The shape of the bubble
12 as it
grows, as shown in Figure 3, is determined by a combination of the inertial
dynamics and
the surface tension of the ink 11. The surface tension tends to minimize the
surface area of
the bubble 12 so that, by the time a certain amount of liquid has evaporated,
the bubble is
essentially disk-shaped.
The increase in pressure within the chamber 7 not only pushes ink 11 out
through
the nozzle 3, but also pushes some ink back through the inlet passage 9.
However, the inlet
passage 9 is approximately 200 to 300 microns in length, and is only
approximately 16
microns in diameter. Hence there is a substantial viscous drag. As a result,
the
predominant effect of the pressure rise in the chamber 7 is to force ink out
through the
nozzle 3 as an ejected drop 16, rather than back through the inlet passage 9.
Turning now to Figure 4, the printhead is shown at a still further successive
stage of
operation, in which the ink drop 16 that is being ejected is shown during its
"necking
phase" before the drop breaks off. At this stage, the bubble 12 has already
reached its
maximum size and has then begun to collapse towards the point of collapse 17,
as reflected
in more detail in Figure 21.
The collapsing of the bubble 12 towards the point of collapse 17 causes some
ink 11
to be drawn from within the nozzle 3 (from the sides 18 of the drop), and some
to be drawn
from the inlet passage 9, towards the point of collapse. Most of the ink 11
drawn in this
manner is drawn from the nozzle 3, forming an annular neck 19 at the base of
the drop 16
prior to its breaking off.
The drop 16 requires a certain amount of momentum to overcome surface tension
forces, in order to break off. As ink 11 is drawn from the nozzle 3 by the
collapse of the
bubble 12, the diameter of the neck 19 reduces thereby reducing the amount of
total surface
tension holding the drop, so that the momentum of the drop as it is ejected
out of the nozzle
is sufficient to allow the drop to break off.
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When the drop 16 breaks off, cavitation forces are caused as reflected by the
arrows
20, as the bubble 12 collapses to the point of collapse 17. It will be noted
that there are no
solid surfaces in the vicinity of the point of collapse 17 on which the
cavitation can have an
effect.
5
Advantages of Nozzle Enclosures
Referring to Figure 6, an embodiment of the unit cell 1 according to the
invention is
shown. The aperture 5 is surrounded by a nozzle enclosure 60, which isolates
adjacent
apertures on the printhead. The nozzle enclosure 60 has a roof 61 and
sidewalls 62, which
1o extend from the roof to the nozzle plate 2 and form a seal therewith. An
opening 63 is
defined in the roof 61, which allows ink droplets (not shown) to pass through
the nozzle
enclosure and onto a print medium (not shown).
The nozzle enclosure 60 minimize cross-contamination between adjacent
apertures
5 by containing any flooded ink in the immediate vicinity of each nozzle.
Flooding of ink
from each nozzle may be caused by a variety of reasons, such as nozzle
misfires or pressure
fluctuations in ink supply channels. The nozzle enclosure may be formed from
or coated
with a hydrophobic material during the fabrication process, which. further
minimizes the
risk of cross-contamination.
A further advantage of the printhead according to the invention is that it
allows the
nozzle plate 2 of the printhead to be wiped without risk of damaging the
sensitive nozzle
structures. Typically, inkjet printheads are cleaned by a wiping mechanism as
part of a
warm-up cycle. The nozzle enclosures 60 provide a protective barrier between
the nozzles
and the wiping mechanism (not shown).
Fabrication Process
In the interests of brevity, the fabrication stages have been shown for the
unit cell of
Figure 6 only (see Figures 7 to 20). It will be appreciated that the other
unit cells will use
the same fabrication stages with different masking.
Referring to Figure 7, there is shown the starting point for fabrication of
the thermal
inkjet nozzle shown in Figure 13. CMOS processing of a silicon wafer provides
a silicon
substrate 21 having drive circuitry 22, and an interlayer dielectric
("interconnect") 23. The
interconnect 23 comprises four metal layers, which together form a seal ring
for the inlet
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passage 9 to be etched through the interconnect. The top metal layer 26, which
forms an
upper portion of the seal ring, can be seen in Figure 7. The metal seal ring
prevents ink
moisture from seeping into the interconnect 23 when the inlet passage 9 is
filled with ink.
A passivation layer 24 is deposited onto the top metal layer 26 by plasma-
enhanced
chemical vapour deposition (PECVD). After deposition of the passivation layer
24, it is
etched to define a circular recess, which forms parts of the inlet passage 9.
At the same as
etching the recess, a plurality of vias 50 are also etched, which allow
electrical connection
through the passivation layer 24 to the top metal layer 26. The etch pattern
is defined by a
layer of patterned photoresist (not shown), which is removed by 02 ashing
after the etch.
Referring to Figure 8, in the next fabrication sequence, a layer of
photoresist is spun
onto the passivation later 24. The photoresist is exposed and developed to
define a circular
opening. With the patterned photoresist 51 in place, the dielectric
interconnect 23 is etched
as far as the silicon substrate 21 using a suitable oxide-etching gas
chemistry (e.g. 02/C4F8).
Etching through the silicon substrate is continued down to about 20 microns to
define a
front ink hole 52, using a suitable silicon-etching gas chemistry (e.g. `Bosch
etch'). The
same photoresist mask 51 can be used for both etching steps. Figure 9 shows
the unit cell
after etching the front ink hole 52 and removal of the photoresist 51.
Referring to Figure 10, in the next stage of fabrication, the front ink hole
52 is
plugged with photoresist to provide a front plug 53. At the same time, a layer
of photoresist
is deposited over the passivation layer 24. This layer of photoresist is
exposed and
developed to define a first sacrificial scaffold 54 over the front plug 53,
and scaffolding
tracks 35 around the perimeter of the unit cell. The first sacrificial
scaffold 54 is used for
subsequent deposition of heater material 38 thereon and is therefore formed
with a planar
upper surface to avoid any buckling in the heater element (see heater element
10 in Figure
10). The first sacrificial scaffold 54 is UV cured and hardbaked to prevent
reflow of the
photoresist during subsequent high-temperature deposition onto its upper
surface.
Importantly, the first sacrificial scaffold 54 has sloped or angled side faces
55.
These angled side faces 55 are formed by adjusting the focusing in the
exposure tool (e.g.
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stepper) when exposing the photoresist. The sloped side faces 55
advantageously allow
heater material 38 to be deposited substantially evenly over the first
sacrificial scaffold 54.
Referring to Figure 11, the next stage of fabrication deposits the heater
material 38
over the first sacrificial scaffold 54, the passivation layer 24 and the
perimeter scaffolding
tracks 35. The heater material 38 is typically a monolayer of TiA1N. However,
the heater
material 38 may alternatively comprise TiA1N sandwiched between upper and
lower
passivating materials, such as tantalum or tantalum nitride. Passivating
layers on the heater
element 10 minimize corrosion of the and improve heater longevity.
Referring to Figure 12, the heater material 38 is subsequently etched down to
the
first sacrificial scaffold 54 to define the heater element 10. At the same
time, contact
electrodes 15 are defined on either side of the heater element 10. The
electrodes 15 are in
contact with the top metal layer 26 and so provide electrical connection
between the CMOS
and the heater element 10. The sloped side faces of the first sacrificial
scaffold 54 ensure
good electrical connection between the heater element 10 and the electrodes
15, since the
heater material is deposited with sufficient thickness around the scaffold 54.
Any thin areas
of heater material (due to insufficient side face deposition) would increase
resistivity and
affect heater performance.
Adjacent unit cells are electrically insulated from each other by virtue of
grooves
etched around the perimeter of each unit cell. The grooves are etched at the
same time as
defining the heater element 10.
Referring to Figure 13, in the subsequent step a second sacrificial scaffold
39 of
photoresist is deposited over the heater material. The second sacrificial
scaffold 39 is
exposed and developed to define sidewalls for the cylindrical nozzle chamber
and perimeter
sidewalls for each unit cell. The second sacrificial scaffold 39 is also UV
cured and
hardbaked to prevent any reflow of the photoresist during subsequent high-
temperature
deposition of the silicon nitride roof material.
Referring to Figure 14, silicon nitride is deposited onto the second
sacrificial
scaffold 39 by plasma enhanced chemical vapour deposition. The silicon nitride
forms a
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roof 44 over each unit cell, which is the nozzle plate 2 for a row of nozzles.
Chamber
sidewalls 6 and unit cell sidewalls 56 are also formed by deposition of
silicon nitride.
Referring to Figure 15, the nozzle rim 4 is etched partially through the roof
44, by
placing a suitably patterned photoresist mask over the roof, etching for a
controlled period
of time and removing the photoresist by ashing.
Referring to Figure 16, the nozzle aperture 5 is etched through the roof 24
down to
the second sacrificial scaffold 39. Again, the etch is performed by placing a
suitably
patterned photoresist mask over the roof, etching down to the scaffold 39 and
removing the
photoresist mask.
Referring to Figure 17, in the next stage a third sacrificial scaffold 64 is
deposited
over the roof 44. The third sacrificial scaffold 64 is exposed and developed
to define
sidewalls for the cylindrical nozzle enclosure over each aperture 5. The third
sacrificial
scaffold 64 is also UV cured and hardbaked to prevent any reflow of the
photoresist during
subsequent high-temperature deposition of the nozzle enclosure material.
Referring to Figure 18, silicon nitride is deposited onto the third
sacrificial scaffold
64 by plasma enhanced chemical vapour deposition. The silicon nitride forms an
enclosure
roof 61 over each aperture 5. Enclosure sidewalls 62 are also formed by
deposition of
silicon nitride. Whilst silicon nitride is deposited in the embodiment shown,
the enclosure
roof 61 may equally be formed from silicon oxide, silicon oxynitride etc.
Optionally, a
layer of hydrophobic material (e.g. fluoropolymer) is deposited onto the
enclosure roof 61
after deposition. This extra deposition step may be performed at any stage
after deposition
(e.g. after etching or after ashing).
Referring to Figure 19, the nozzle enclosure 60 is formed by etching through
the
enclosure roof layer 61. The enclosure opening 63 is defined by this etch. In
addition, the
enclosure roof material which is located outside the enclosure sidewalls 62 is
removed. The
etch pattern is defined by standard photoresist masking.
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With the nozzle structure, including nozzle enclosure 60, now fully formed on
a
frontside of the silicon substrate 21, an ink supply channel 32 is etched from
the backside of
the substrate 21, which meets with the front plug 53.
Referring to Figure 20, after formation of the ink supply channel 32, the
first,
second and sacrificial scaffolds of photoresist, together with the front plug
53 are ashed off
using an 02 plasma. Accordingly, fluid connection is made from the ink supply
channel 32
through to the nozzle aperture 5 and the nozzle enclosure opening 63.
It should be noted that a portion of photoresist, on either side of the nozzle
chamber
sidewalls 6, remains encapsulated by the roof 44, the unit cell sidewalls 56
and the chamber
sidewalls 6. This portion of photoresist is sealed from the 02 ashing plasma
and, therefore,
remains intact after fabrication of the printhead. This encapsulated
photoresist
advantageously provides additional robustness for the printhead by supporting
the nozzle
plate 2. Hence, the printhead has a robust nozzle plate spanning continuously
over rows of
nozzles, and being supported by solid blocks of hardened photoresist, in
addition to support
walls.
Other Embodiments
The invention has been described above with reference to printheads using
bubble
forming heater elements. However, it is potentially suited to a wide range of
printing
system including: color and monochrome office printers, short run digital
printers, high
speed digital printers, offset press supplemental printers, low cost scanning
printers high
speed pagewidth printers, notebook computers with inbuilt pagewidth printers,
portable
color and monochrome printers, color and monochrome copiers, color and
monochrome
facsimile machines, combined printer, facsimile and copying machines, label
printers, large
format plotters, photograph copiers, printers for digital photographic
"minilabs", video
printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak
Company) printers, portable printers for PDAs, wallpaper printers, indoor sign
printers,
billboard printers, fabric printers, camera printers and fault tolerant
commercial printer
arrays.
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It will be appreciated by ordinary workers in this field that numerous
variations and/or
modifications may be made to the present invention as shown in the specific
embodiments
without departing from the spirit or scope of the invention as broadly
described. The present
embodiments are, therefore, to be considered in all respects to be
illustrative and not
5 restrictive.
Ink Jet Technologies
The embodiments of the invention use an ink jet printer type device. Of course
many
10 different devices could be used. However presently popular ink jet printing
technologies are
unlikely to be suitable.
The most significant problem with thermal ink jet is power consumption. This
is
approximately 100 times that required for high speed, and stems from the
energy-inefficient
15 means of drop ejection. This involves the rapid boiling of water to produce
a vapor bubble
which expels the ink. Water has a very high heat capacity, and must be
superheated in
thermal ink jet applications. In conventional thermal inkjet printheads, this
leads to an
efficiency of around 0.02%, from electricity input to drop momentum (and
increased
surface area) out.
The most significant problem with piezoelectric ink jet is size and cost.
Piezoelectric crystals have a very small deflection at reasonable drive
voltages, and
therefore require a large area for each nozzle. Also, each piezoelectric
actuator must be
connected to its drive circuit on a separate substrate. This is not a
significant problem at the
current limit of around 300 nozzles per printhead, but is a major impediment
to the
fabrication of pagewidth printheads with 19,200 nozzles.
Ideally, the ink jet technologies used meet the stringent requirements of in-
camera
digital color printing and other high quality, high speed, low cost printing
applications. To
meet the requirements of digital photography, new ink jet technologies have
been created. The
target features include:
low power (less than 10 Watts)
high resolution capability (1,600 dpi or more)
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photographic quality output
low manufacturing cost
small size (pagewidth times minimum cross section)
high speed (< 2 seconds per page).
All of these features can be met or exceeded by the ink jet systems described
below
with differing levels of difficulty. Forty-five different ink jet technologies
have been
developed by.the Assignee to give a wide range of choices for high volume
manufacture.
These technologies form part of separate applications assigned to the present
Assignee as set
out in the table under the heading Cross References to Related Applications.
The ink jet designs shown here are suitable for a wide range of digital
printing systems,
from battery powered one-time use digital cameras, through to desktop and
network printers,
and through to commercial printing systems.
For ease of manufacture using standard process equipment, the printhead is
designed to
be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color
photographic
applications, the printhead is 100 mm long, with a width which depends upon
the ink jet type.
The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip
area of 35
square mm. The printheads each contain 19,200 nozzles plus data and control
circuitry.
Ink is supplied to the back of the printhead by injection molded plastic ink
channels.
The molding requires 50 micron features, which can be created using a
lithographically
micromachined insert in a standard injection molding tool. Ink flows through
holes etched
through the wafer to the nozzle chambers fabricated on the front surface of
the wafer. The
printhead is connected to the camera circuitry by tape automated bonding.
Tables of Drop-on-Demand Ink Jets
Eleven important characteristics of the fundamental operation of individual
ink jet
nozzles have been identified. These characteristics are largely orthogonal,
and so can be
elucidated as an eleven dimensional matrix. Most of the eleven axes of this
matrix include
entries developed by the present assignee.
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The following tables form the axes of an eleven dimensional table of ink jet
types.
Actuator mechanism (18 types)
Basic operation mode (7 types)
Auxiliary mechanism (8 types)
Actuator amplification or modification method (17 types)
Actuator motion (19 types)
Nozzle refill method (4 types)
Method of restricting back-flow through inlet (10 types)
Nozzle clearing method (9 types)
Nozzle plate construction (9 types)
Drop ejection direction (5 types)
Ink type (7 types)
The complete eleven dimensional table represented by these axes contains 36.9
billion possible configurations of ink jet nozzle. While not all of the
possible combinations
result in a viable ink jet technology, many million configurations are viable.
It is clearly
impractical to elucidate all of the possible configurations. Instead, certain
ink jet types have
been investigated in detail. These are designated IJ01 to IJ45 above which
matches the
docket numbers in the table under the heading Cross References to Related
Applications.
Other ink jet configurations can readily be derived from these forty-five
examples
by substituting alternative configurations along one or more of the 11 axes.
Most of the
IJ01 to IJ45 examples can be made into ink jet printheads with characteristics
superior to
any currently available ink jet technology.
Where there are prior art examples known to the inventor, one or more of these
examples are listed in the examples column of the tables below. The IJ01 to
IJ45 series are
also listed in the examples column. In some cases, print technology may be
listed more than
once in a table, where it shares characteristics with more than one entry.
Suitable applications for the ink jet technologies include: Home printers,
Office
network printers, Short run digital printers, Commercial print systems, Fabric
printers,
Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide
format
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printers, Notebook PC printers, Fax machines, Industrial printing systems,
Photocopiers,
Photographic minilabs etc.
The information associated with the aforementioned 11 dimensional matrix are
set
out in the following tables.
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Thermal An electrothermal = Large force = High power = Canon Bubblejet
bubble heater heats the ink to generated = Ink carrier 1979 Endo et al GB
above boiling point, = Simple limited to water patent 2,007,162
transferring significant construction = Low efficiency = Xerox heater-in-
heat to the aqueous = No moving parts = High pit 1990 Hawkins et
ink. A bubble = Fast operation temperatures al USP 4,899,181
nucleates and quickly = Small chip area required = Hewlett-Packard
forms, expelling the required for actuator = High mechanical TIJ 1982 Vaught
et
ink. stress al USP 4,490,728
The efficiency of the = Unusual
process is low, with materials required
typically less than = Large drive
0.05% of the electrical transistors
energy being = Cavitation causes
transformed into actuator failure
kinetic energy of the = Kogation reduces
drop. bubble formation
= Large print heads
are difficult to
fabricate
Piezo- A piezoelectric crystal = Low power = Very large area = Kyser et al USP
electric such as lead consumption required for actuator 3,946,398
lanthanum zirconate = Many ink types = Difficult to = Zoltan USP
(PZT) is electrically can be used integrate with 3,683,212
activated, and either = Fast operation electronics = 1973 Stemme
expands, shears, or = High efficiency = High voltage USP 3,747,120
bends to apply drive transistors = Epson Stylus
pressure to the ink, required = Tektronix
ejecting drops. = Full pagewidth = IJ04
print heads
impractical due to
actuator size
= Requires
electrical poling in
high field strengths
during manufacture
Electro- An electric field is = Low power = Low maximum = Seiko Epson,
strictive used to activate consumption strain (approx. Usui et all JP
electrostriction in = Many ink types 0.01%) 253401/96
relaxor materials such can be used = Large area = IJ04
as lead lanthanum = Low thermal required for actuator
zirconate titanate expansion due to low strain
(PLZT) or lead = Electric field = Response speed
magnesium niobate strength required is marginal (- 10
(PMN). (approx. 3.5 V/ m) s)
can be generated = High voltage
without difficulty drive transistors
= Does not require required
electrical poling = Full pagewidth
print heads
impractical due to
actuator size
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Ferro- An electric field is = Low power = Difficult to = IJ04
electric used to induce a phase consumption integrate with
transition between the = Many ink types electronics
antiferroelectric (AFE) can be used = Unusual
and ferroelectric (FE) = Fast operation materials such as
phase. Perovskite (< 1 s) PLZSnT are
materials such as tin = Relatively high required
modified lead longitudinal strain = Actuators require
lanthanum zirconate = High efficiency a large area
titanate (PLZSnT) = Electric field
exhibit large strains of strength of around 3
up to 1% associated V/ m can be readily
with the AFE to FE provided
base transition.
Electro- Conductive plates are = Low power = Difficult to = IJ02, IJ04
static plates separated by a consumption operate electrostatic
compressible or fluid = Many ink types devices in an
dielectric (usually air). can be used aqueous
Upon application of a = Fast operation environment
voltage, the plates = The electrostatic
attract each other and actuator will
displace ink, causing normally need to be
drop ejection. The separated from the
conductive plates may ink
be in a comb or = Very large area
honeycomb structure, required to achieve
or stacked to increase high forces
the surface area and = High voltage
therefore the force. drive transistors
may be required
= Full pagewidth
print heads are not
competitive due to
actuator size
Electro- A strong electric field = Low current = High voltage = 1989 Saito et
al,
static pull is applied to the ink, consumption required USP 4,799,068
on ink whereupon = Low temperature = May be damaged = 1989 Miura et al,
electrostatic attraction by sparks due to air USP 4,810,954
accelerates the ink breakdown = Tone jet
towards the print = Required field
medium. strength increases as
the drop size
decreases
= High voltage
drive transistors
required
= Electrostatic field
attracts dust
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Permanent An electromagnet = Low power = Complex = IJ07, IJ10
magnet directly attracts a consumption fabrication
electro- permanent magnet, = Many ink types = Permanent
magnetic displacing ink and can be used magnetic material
causing drop ejection. = Fast operation such as Neodymium
Rare earth magnets = High efficiency Iron Boron (NdFeB)
with a field strength = Easy extension required.
around 1 Tesla can be from single nozzles = High local
used. Examples are: to pagewidth print currents required
Samarium Cobalt heads = Copper
(SaCo) and magnetic metalization should
materials in the be used for long
neodymium iron boron electromigration
family (NdFeB, lifetime and low
NdDyFeBNb, resistivity
NdDyFeB, etc) = Pigmented inks
are usually
infeasible
= Operating
temperature limited
to the Curie
temperature (around
540 K)
Soft A solenoid induced a = Low power = Complex = IN I, IJ05, IJ08,
magnetic magnetic field in a soft consumption fabrication IJ10, IJ12, IJ14,
core electro- magnetic core or yoke = Many ink types = Materials not IJ15,
IJ17
magnetic fabricated from a can be used usually present in a
ferrous material such = Fast operation CMOS fab such as
as electroplated iron = High efficiency NiFe, CoNiFe, or
alloys such as CoNiFe = Easy extension CoFe are required
[1], CoFe, or NiFe from single nozzles = High local
alloys. Typically, the to pagewidth print currents required
soft magnetic material heads = Copper
is in two parts, which = metalization should
are normally held be used for long
apart by a spring. electromigration
When the solenoid is lifetime and low
actuated, the two parts resistivity
attract, displacing the = Electroplating is
ink. required
= High saturation
flux density is
required (2.0-2.1 T
is achievable with
CoNiFe [1])
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Lorenz The Lorenz force = Low power = Force acts as a = IJ06, IJ11, IJ13,
force acting on a current consumption twisting motion IJ16
carrying wire in a = Many ink types = Typically, only a
magnetic field is can be used quarter of the
utilized. = Fast operation solenoid length
This allows the = High efficiency provides force in a
magnetic field to be = Easy extension useful direction
supplied externally to from single nozzles = High local
the print head, for to pagewidth print currents required
example with rare heads = Copper
earth permanent metalization should
magnets. be used for long
Only the current electromigration
carrying wire need be lifetime and low
fabricated on the print- resistivity
head, simplifying = Pigmented inks
materials are usually
re uirements. infeasible
Magneto- The actuator uses the = Many ink types = Force acts as a =
Fischenbeck,
striction giant magnetostrictive can be used twisting motion USP 4,032,929
effect of materials = Fast operation = Unusual = IJ25
such as Terfenol-D (an = Easy extension materials such as
alloy of terbium, from single nozzles Terfenol-D are
dysprosium and iron to pagewidth print required
developed at the Naval heads = High local
Ordnance Laboratory, = High force is currents required
hence Ter-Fe-NOL). available = Copper
For best efficiency, the metalization should
actuator should be pre- be used for long
stressed to approx. 8 electromigration
MPa. lifetime and low
resistivity
= Pre-stressing
may be required
Surface Ink under positive = Low power = Requires = Silverbrook, EP
tension pressure is held in a consumption supplementary force 0771 658 A2 and
reduction nozzle by surface = Simple to effect drop related patent
tension. The surface construction separation applications
tension of the ink is = No unusual = Requires special
reduced below the materials required in ink surfactants
bubble threshold, fabrication = Speed may be
causing the ink to = High efficiency limited by surfactant
egress from the = Easy extension properties
nozzle. from single nozzles
to pagewidth print
heads
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Viscosity The ink viscosity is = Simple = Requires = Silverbrook, EP
reduction locally reduced to construction supplementary force 0771 658 A2 and
select which drops are = No unusual to effect drop related patent
to be ejected. A materials required in separation applications
viscosity reduction can fabrication = Requires special
be achieved = Easy extension ink viscosity
electrothermally with from single nozzles properties
most inks, but special to pagewidth print = High speed is
inks can be engineered heads difficult to achieve
fora 100:1 viscosity = Requires
reduction. oscillating ink
pressure
= A high
temperature
difference (typically
80 degrees) is
required
Acoustic An acoustic wave is = Can operate = Complex drive = 1993 Hadimioglu
generated and without a nozzle circuitry et al, EUP 550,192
focussed upon the plate = Complex = 1993 Elrod et al,
drop ejection region. fabrication EUP 572,220
= Low efficiency
= Poor control of
drop position
= Poor control of
drop volume
Thermo- An actuator which = Low power = Efficient aqueous = IJ03, IJ09, IJ17,
elastic bend relies upon differential consumption operation requires a IJ18,
IJ19, IJ20,
actuator thermal expansion = Many ink types thermal insulator on IJ21, IJ22,
IJ23,
upon Joule heating is can be used the hot side IJ24, IJ27, IJ28,
used. = Simple planar = Corrosion IJ29, IJ30, 1J3 1,
fabrication prevention can be IJ32, IJ33, IJ34,
= Small chip area difficult IJ35, IJ36, IJ37,
required for each = Pigmented inks IJ38 ,IJ39, IJ40,
actuator may be infeasible, IJ41
= Fast operation as pigment particles
= High efficiency may jam the bend
= CMOS actuator
compatible voltages
and currents
= Standard MEMS
processes can be
used
= Easy extension
from single nozzles
to pagewidth print
heads
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
High CTE A material with a very = High force can = Requires special = IJ09,
IJ17, IJ18,
thermo- high coefficient of be generated material (e.g. PTFE) IJ20, IJ21,
IJ22,
elastic thermal expansion = Three methods of = Requires a PTFE IJ23, IJ24,
IJ27,
actuator (CTE) such as PTFE deposition are deposition process, IJ28, IJ29,
IJ30,
polytetrafluoroethylen under development: which is not yet IJ31, IJ42, IJ43,
e (PTFE) is used. As chemical vapor standard in ULSI IJ44
high CTE materials deposition (CVD), fabs
are usually non- spin coating, and = PTFE deposition
conductive, a heater evaporation cannot be followed
fabricated from a = PTFE is a with high
conductive material is candidate for low temperature (above
incorporated. A 50 pm dielectric constant 350 C) processing
long PTFE bend insulation in ULSI = Pigmented inks
actuator with = Very low power may be infeasible,
polysilicon heater and consumption as pigment particles
15 mW power input = Many ink types may jam the bend
can provide 180 N can be used actuator
force and 10 pm = Simple planar
deflection. Actuator fabrication
motions include: = Small chip area
Bend required for each
Push actuator
Buckle = Fast operation
Rotate = High efficiency
= CMOS
compatible voltages
and currents
= Easy extension
from single nozzles
to pagewidth print
heads
Conduct-ive A polymer with a high = High force can = Requires special = IJ24
polymer coefficient of thermal be generated materials
thermo- expansion (such as = Very low power development (High
elastic PTFE) is doped with consumption CTE conductive
actuator conducting substances = Many ink types polymer)
to increase its can be used = Requires a PTFE
conductivity to about 3 = Simple planar deposition process,
orders of magnitude fabrication which is not yet
below that of copper. = Small chip area standard in ULSI
The conducting required for each fabs
polymer expands actuator = PTFE deposition
when resistively = Fast operation cannot be followed
heated. = High efficiency with high
Examples of = CMOS temperature (above
conducting dopants compatible voltages 350 C) processing
include: and currents = Evaporation and
Carbon nanotubes = Easy extension CVD deposition
Metal fibers from single nozzles techniques cannot
Conductive polymers to pagewidth print be used
such as doped heads = Pigmented inks
polythiophene may be infeasible,
as pigment particles
Carbon granules may jam the bend
actuator
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ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS)
Description Advantages Disadvantages Examples
Shape A shape memory alloy = High force is = Fatigue limits = IJ26
memory such as TiNi (also available (stresses maximum number
alloy known as Nitinol - of hundreds of MPa) of cycles
Nickel Titanium alloy = Large strain is = Low strain (1%)
developed at the Naval available (more than is required to extend
Ordnance Laboratory) 3%) fatigue resistance
is thermally switched = High corrosion = Cycle rate
between its weak resistance limited by heat
martensitic state and = Simple removal
its high stiffness construction = Requires unusual
austenic state. The = Easy extension materials (TiNi)
shape of the actuator from single nozzles = The latent heat of
in its martensitic state to pagewidth print transformation must
is deformed relative to heads be provided
the austenic shape. = Low voltage = High current
The shape change operation operation
causes ejection of a = Requires pre-
drop. stressing to distort
the martensitic state
Linear Linear magnetic = Linear Magnetic = Requires unusual = IJ 12
Magnetic actuators include the actuators can be semiconductor
Actuator Linear Induction constructed with materials such as
Actuator (LIA), Linear high thrust, long soft magnetic alloys
Permanent Magnet travel, and high (e.g. CoNiFe)
Synchronous Actuator efficiency using = Some varieties
(LPMSA), Linear planar also require
Reluctance semiconductor permanent magnetic
Synchronous Actuator fabrication materials such as
(LRSA), Linear techniques Neodymium iron
Switched Reluctance = Long actuator boron (NdFeB)
Actuator (LSRA), and travel is available = Requires
the Linear Stepper = Medium force is complex multi-
Actuator (LSA). available phase drive circuitry
= Low voltage = High current
operation operation
BASIC OPERATION MODE
Description Advantages Disadvantages Examples
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BASIC OPERATION MODE
Description Advantages Disadvantages Examples
Actuator This is the simplest = Simple operation = Drop repetition = Thermal
ink jet
directly mode of operation: the = No external rate is usually = Piezoelectric
ink
pushes ink actuator directly fields required limited to around 10 jet
supplies sufficient = Satellite drops kHz. However, this = IJ01, IJ02,,IJ03,
kinetic energy to expel can be avoided if is not fundamental IJ04, IJ05, IJ06,
the drop. The drop drop velocity is less to the method, but is IJ07, IJ09,
IJ11,
must have a sufficient than 4 m/s related to the refill IJ12, IJ14, IJ16,
velocity to overcome = Can be efficient, method normally IJ20, IJ22, IJ23,
the surface tension. depending upon the used IJ24, IJ25, IJ26,
actuator used = All of the drop IJ27, IJ28, IJ29,
kinetic energy must IJ30, I331, IJ32,
be provided by the IJ33, IJ34, IJ35,
actuator IJ36, IJ37, IJ38,
= Satellite drops IJ39, IJ40, IJ41,
usually form if drop IJ42, IJ43, IJ44
velocity is greater
than 4.5 m/s
Proximity The drops to be = Very simple print = Requires close = Silverbrook,
EP
printed are selected by head fabrication can proximity between 0771 658 A2 and
some manner (e.g. be used the print head and related patent
thermally induced = The drop the print media or applications
surface tension selection means transfer roller
reduction of does not need to = May require two
pressurized ink). provide the energy print heads printing
Selected drops are required to separate alternate rows of the
separated from the ink the drop from the image
in the nozzle by nozzle = Monolithic color
contact with the print print heads are
medium or a transfer difficult
roller.
Electro- The drops to be = Very simple print = Requires very = Silverbrook, EP
static pull printed are selected by head fabrication can high electrostatic
0771 658 A2 and
on ink some manner (e.g. be used field related patent
thermally induced = The drop = Electrostatic field applications
surface tension selection means for small nozzle = Tone-Jet
reduction of does not need to sizes is above air
pressurized ink). provide the energy breakdown
Selected drops are required to separate = Electrostatic field
separated from the ink the drop from the may attract dust
in the nozzle by a nozzle
strong electric field.
Magnetic The drops to be = Very simple print = Requires = ' Silverbrook, EP
pull on ink printed are selected by head fabrication can magnetic ink 0771 658
A2 and
some manner (e.g. be used = Ink colors other related patent
thermally induced = The drop than black are applications
surface tension selection means difficult
reduction of does not need to = Requires very
pressurized ink). provide the energy high magnetic fields
Selected drops are required to separate
separated from the ink the drop from the
in the nozzle by a nozzle
strong magnetic field
acting on the magnetic
ink.
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BASIC OPERATION MODE
Description Advantages Disadvantages Examples
Shutter The actuator moves a = High speed (>50 = Moving parts are = IJ13,
IJ17, IJ21
shutter to block ink kHz) operation can required
flow to the nozzle. The be achieved due to = Requires ink
ink pressure is pulsed reduced refill time pressure modulator
at a multiple of the = Drop timing can = Friction and wear
drop ejection be very accurate must be considered
frequency. = The actuator = Stiction is
energy can be very possible
low
Shuttered The actuator moves a = Actuators with = Moving parts are = IJ08,
IJ15, IJ18,
grill shutter to block ink small travel can be required IJ19
flow through a grill to used = Requires ink
the nozzle. The shutter = Actuators with pressure modulator
movement need only small force can be = Friction and wear
be equal to the width used must be considered
of the grill holes. = High speed (>50 = Stiction is
kHz) operation can possible
be achieved
Pulsed A pulsed magnetic = Extremely low = Requires an = IJ 10
magnetic field attracts an `ink energy operation is external pulsed
pull on ink pusher' at the drop possible magnetic field
pusher ejection frequency. An = No heat = Requires special
actuator controls a dissipation materials for both
catch, which prevents problems the actuator and the
the ink pusher from ink pusher
moving when a drop is = Complex
not to be ejected. construction
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AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)
Description Advantages Disadvantages Examples
None The actuator directly = Simplicity of = Drop ejection = Most ink jets,
fires the ink drop, and construction energy must be including
there is no external = Simplicity of supplied by piezoelectric and
field or other operation individual nozzle thermal bubble.
mechanism required. = Small physical actuator = IJO1, IJ02, IJ03,
size IJ04, IJ05, IJ07,
IJ09, IJ11, IJ12,
IJ14, IJ20, IJ22,
IJ23, IJ24, IJ25,
IJ26, IJ27, IJ28,
IJ29, IJ30, IJ31,
IJ32, IJ33, IJ34,
IJ35, IJ36, IJ37,
IJ38, IJ39, IJ40,
IM 1, IJ42, IJ43,
IJ44
Oscillating The ink pressure = Oscillating ink = Requires external =
Silverbrook, EP
ink pressure oscillates, providing pressure can provide ink pressure 0771 658
A2 and
(including much of the drop a refill pulse, oscillator related patent
acoustic ejection energy. The allowing higher = Ink pressure applications
stimul- actuator selects which operating speed phase and amplitude = IJ08,
IJ13, IJ15,
ation) drops are to be fired = The actuators must be carefully IJ17, IJ18,
IJ19,
by selectively may operate with controlled IJ21
blocking or enabling much lower energy = Acoustic
nozzles. The ink = Acoustic lenses reflections in the ink
pressure oscillation can be used to focus chamber must be
may be achieved by the sound on the designed for
vibrating the print nozzles
head, or preferably by
an actuator in the ink
supply.
Media The print head is = Low power = Precision = Silverbrook, EP
proximity placed in close = High accuracy assembly required 0771 658 A2 and
proximity to the print = Simple print head = Paper fibers may related patent
medium. Selected construction cause problems applications
drops protrude from = Cannot print on
the print head further rough substrates
than unselected drops,
and contact the print
medium. The drop
soaks into the medium
fast enough to cause
dro se aration.
Transfer Drops are printed to a = High accuracy = Bulky = Silverbrook, EP
roller transfer roller instead = Wide range of = Expensive 0771 658 A2 and
of straight to the print print substrates can = Complex related patent
medium. A transfer be used construction applications
roller can also be used = Ink can be dried = Tektronix hot
for proximity drop on the transfer roller melt piezoelectric
separation. ink jet
= Any of the IJ
series
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AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES)
Description Advantages Disadvantages Examples
Electro- An electric field is = Low power = Field strength = Silverbrook, EP
static used to accelerate = Simple print head required for 0771 658 A2 and
selected drops towards construction separation of small related patent
the print medium. drops is near or applications
above air = Tone-Jet
breakdown
Direct A magnetic field is = Low power = Requires = Silverbrook, EP
magnetic used to accelerate = Simple print head magnetic ink 0771 658 A2 and
field selected drops of construction = Requires strong related patent
magnetic ink towards magnetic field applications
the print medium.
Cross The print head is = Does not require = Requires external = IJ06, IJ16
magnetic placed in a constant magnetic materials magnet
field magnetic field. The to be integrated in = Current densities
Lorenz force in a the print head may be high,
current carrying wire manufacturing resulting in
is used to move the process electromigration
actuator. problems
Pulsed A pulsed magnetic = Very low power = Complex print = IJ10
magnetic field is used to operation is possible head construction
field cyclically attract a = Small print head = Magnetic
paddle, which pushes size materials required in
on the ink. A small print head
actuator moves a
catch, which
selectively prevents
the paddle from
moving.
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ACTUATOR AMPLIFICATION OR MODIFICATION METHOD
Description Advantages Disadvantages Examples
None No actuator = Operational = Many actuator = Thermal Bubble
mechanical simplicity mechanisms have ink jet
amplification is used. insufficient travel, = IJO1, IJ02, IJ06,
The actuator directly or insufficient force, IJ07, IJ16, IJ25,
drives the drop to efficiently drive IJ26
ejection process. the drop ejection
process
Differential An actuator material = Provides greater = High stresses are =
Piezoelectric
expansion expands more on one travel in a reduced involved = IJ03, IJ09, IJ17,
bend side than on the other. print head area = Care must be IJ18, IJ19, IJ20,
actuator The expansion may be taken that the IJ21, IJ22, IJ23,
thermal, piezoelectric, materials do not IJ24, IJ27, IJ29,
magnetostrictive, or delaminate IJ30, IJ31, IJ32,
other mechanism. The = Residual bend IJ33, IJ34, IJ35,
bend actuator converts resulting from high IJ36, IJ37, IJ38,
a high force low travel temperature or high IJ39, IJ42, IJ43,
actuator mechanism to stress during IJ44
high travel, lower formation
force mechanism.
Transient A trilayer bend = Very good = High stresses are = IJ40, IJ41
bend actuator where the two temperature stability involved
actuator outside layers are = High speed, as a = Care must be
identical. This cancels new drop can be taken that the
bend due to ambient fired before heat materials do not
temperature and dissipates delaminate
residual stress. The = Cancels residual
actuator only responds stress of formation
to transient heating of
one side or the other.
Reverse The actuator loads a = Better coupling = Fabrication = IJ05, U11
spring spring. When the to the ink complexity
actuator is turned off, = High stress in the
the spring releases. spring
This can reverse the
force/distance curve of
the actuator to make it
compatible with the
force/time
requirements of the
dro ejection.
Actuator A series of thin = Increased travel = Increased = Some
stack actuators are stacked. = Reduced drive fabrication piezoelectric ink
jets
This can be voltage complexity = IJ04
appropriate where = Increased
actuators require high possibility of short
electric field strength, circuits due to
such as electrostatic pinholes
and piezoelectric
actuators.
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ACTUATOR AMPLIFICATION OR MODIFICATION METHOD
Description Advantages Disadvantages Examples
Multiple Multiple smaller = Increases the = Actuator forces = IJ12, IJ13,
IJ18,
actuators actuators are used force available from may not add IJ20, IJ22,
IJ28,
simultaneously to an actuator linearly, reducing IJ42,1J43
move the ink. Each = Multiple efficiency
actuator need provide actuators can be
only a portion of the positioned to control
force required. ink flow accurately
Linear A linear spring is used = Matches low = Requires print = IJ15
Spring to transform a motion travel actuator with head area for the
with small travel and higher travel spring
high force into a requirements
longer travel, lower = Non-contact
force motion. method of motion
transformation
Coiled A bend actuator is = Increases travel = Generally = IJ17, IJ21, IJ34,
actuator coiled to provide = Reduces chip restricted to planar IJ35
greater travel in a area implementations
reduced chip area. = Planar due to extreme
implementations are fabrication difficulty
relatively easy to in other orientations.
fabricate.
Flexure A bend actuator has a = Simple means of = Care must be = IJ10, IJ19,
IJ33
bend small region near the increasing travel of taken not to exceed
actuator fixture point, which a bend actuator the elastic limit in
flexes much more the flexure area
readily than the = Stress
remainder of the distribution is very
actuator. The actuator uneven
flexing is effectively = Difficult to
converted from an accurately model
even coiling to an with finite element
angular bend, resulting analysis
in greater travel of the
actuator ti .
Catch The actuator controls a = Very low = Complex = IJ10
small catch. The catch actuator energy construction
either enables or = Very small = Requires external
disables movement of actuator size force
an ink pusher that is = Unsuitable for
controlled in a bulk pigmented inks
manner.
Gears Gears can be used to = Low force, low = Moving parts are = IJ13
increase travel at the travel actuators can required
expense of duration. be used = Several actuator
Circular gears, rack = Can be fabricated cycles are required
and pinion, ratchets, using standard = More complex
and other gearing surface MEMS drive electronics
methods can be used. processes = Complex
construction
= Friction, friction,
and wear are
possible
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ACTUATOR AMPLIFICATION OR MODIFICATION METHOD
Description Advantages Disadvantages Examples
Buckle plate A buckle plate can be = Very fast = Must stay within = S. Hirata
et al,
used to change a slow movement elastic limits of the "An Ink jet Head
actuator into a fast achievable materials for long Using Diaphragm
motion. It can also device life Microactuator",
convert a high force, = High stresses Proc. IEEE MEMS,
low travel actuator involved Feb. 1996, pp 418-
into a high travel, = Generally high 423.
medium force motion. power requirement IJ18, U27
Tapered A tapered magnetic = Linearizes the = Complex = IJ14
magnetic pole can increase magnetic construction
pole travel at the expense force/distance curve
of force.
Lever A lever and fulcrum is = Matches low = High stress = IJ32, IJ36, IJ37
used to transform a travel actuator with around the fulcrum
motion with small higher travel
travel and high force requirements
into a motion with = Fulcrum area has
longer travel and no linear movement,
lower force. The lever and can be used for
can also reverse the a fluid seal
direction of travel.
Rotary The actuator is = High mechanical = Complex = IJ28
impeller connected to a rotary advantage construction
impeller. A small = The ratio of force = Unsuitable for
angular deflection of to travel of the pigmented inks
the actuator results in actuator can be
a rotation of the matched to the
impeller vanes, which nozzle requirements
push the ink against by varying the
stationary vanes and number of impeller
out of the nozzle. vanes
Acoustic A refractive or = No moving parts = Large area = 1993 Hadimioglu
lens diffractive (e.g. zone required et al, EUP 550,192
plate) acoustic lens is = Only relevant for = 1993 Elrod et al,
used to concentrate acoustic ink jets EUP 572,220
sound waves.
Sharp A sharp point is used = Simple = Difficult to = Tone jet
conductive to concentrate an construction fabricate using
point electrostatic field. standard VLSI
processes for a
surface ejecting ink-
jet
= Only relevant for
electrostatic ink jets
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ACTUATOR MOTION
Description Advantages Disadvantages Examples
Volume The volume of the = Simple = High energy is = Hewlett-Packard
expansion actuator changes, construction in the typically required to Thermal
Ink jet
pushing the ink in all case of thermal ink achieve volume = Canon Bubblejet
directions. jet expansion. This
leads to thermal
stress, cavitation,
and kogation in
thermal ink jet
implementations
Linear, The actuator moves in = Efficient .= High fabrication = IJO1, IJ02,
IJ04,
normal to a direction normal to coupling to ink complexity may be IJ07, IJ1 1,
IJ14
chip surface the print head surface. drops ejected required to achieve
The nozzle is typically normal to the perpendicular
in the line of surface motion
movement.
Parallel to The actuator moves = Suitable for = Fabrication = IJ12, IJ13,
IJ15,
chip surface parallel to the print planar fabrication complexity IJ33,, IJ34,
IJ35,
head surface. Drop = Friction IJ36
ejection may still be = Stiction
normal to the surface.
Membrane An actuator with a = The effective = Fabrication = 1982 Howkins
push high force but small area of the actuator complexity USP 4,459,601
area is used to push a becomes the = Actuator size
stiff membrane that is membrane area = Difficulty of
in contact with the ink. integration in a
VLSI process
Rotary The actuator causes = Rotary levers = Device = IJ05, IJ08, IJ13,
the rotation of some may be used to complexity IJ28
element, such a grill or increase travel = May have
impeller = Small chip area friction at a pivot
requirements point
Bend The actuator bends = A very small = Requires the = 1970 Kyser et al
when energized. This change in actuator to be made USP 3,946,398
may be due to dimensions can be from at least two = 1973 Stemme
differential thermal converted to a large distinct layers, or to USP 3,747,120
expansion, motion. have a thermal = IJ03, IJ09, IJ10,
piezoelectric difference across the IJ19, IJ23, IJ24,
expansion, actuator IJ25, IJ29, IJ30,
magnetostriction, or IJ31, IJ33, IJ34,
other form of relative IJ35
dimensional change.
Swivel The actuator swivels = Allows operation = Inefficient = IJ06
around a central pivot. where the net linear coupling to the ink
This motion is suitable force on the paddle motion
where there are is zero
opposite forces = Small chip area
applied to opposite requirements
sides of the paddle,
e. . Lorenz force.
Straighten The actuator is = Can be used with = Requires careful = IJ26, IJ32
normally bent, and shape memory balance of stresses
straightens when alloys where the to ensure that the
energized. austenic phase is quiescent bend is
planar accurate
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ACTUATOR MOTION
Description Advantages Disadvantages Examples
Double The actuator bends in = One actuator can = Difficult to make = IJ36,
IJ37, IJ38
bend one direction when be used to power the drops ejected by
one element is two nozzles. both bend directions
energized, and bends = Reduced chip identical.
the other way when size. = A small
another element is = Not sensitive to efficiency loss
energized. ambient temperature compared to
equivalent single
bend actuators.
Shear Energizing the = Can increase the = Not readily = 1985 Fishbeck
actuator causes a shear effective travel of applicable to other USP 4,584,590
motion in the actuator piezoelectric actuator
material. actuators mechanisms
Radial con- The actuator squeezes = Relatively easy = High force = 1970 Zoltan
USP
striction an ink reservoir, to fabricate single required 3,683,212
forcing ink from a nozzles from glass = Inefficient
constricted nozzle. tubing as = Difficult to
macroscopic integrate with VLSI
structures processes
Coil / uncoil A coiled actuator = Easy to fabricate = Difficult to = IJ17,
IJ21, IJ34,
uncoils or coils more as a planar VLSI fabricate for non- IJ35
tightly. The motion of process planar devices
the free end of the = Small area = Poor out-of-plane
actuator ejects the ink. required, therefore stiffness
low cost
Bow The actuator bows (or = Can increase the = Maximum travel = IJ16, IJ18,
IJ27
buckles) in the middle speed of travel is constrained
when energized. = Mechanically = High force
rigid required
Push-Pull Two actuators control = The structure is = Not readily = IJ18
a shutter. One actuator pinned at both ends, suitable for ink jets
pulls the shutter, and so has a high out-of- which directly push
the other pushes it. plane rigidity the ink
Curl A set of actuators curl = Good fluid flow = Design = IJ20, IJ42
inwards inwards to reduce the to the region behind complexity
volume of ink that the actuator
they enclose. increases efficiency
Curl A set of actuators curl = Relatively simple = Relatively large = IJ43
outwards outwards, pressurizing construction chip area
ink in a chamber
surrounding the
actuators, and
expelling ink from a
nozzle in the chamber.
Iris Multiple vanes enclose = High efficiency = High fabrication = IJ22
a volume of ink. These = Small chip area complexity
simultaneously rotate, = Not suitable for
reducing the volume pigmented inks
between the vanes.
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ACTUATOR MOTION
Description Advantages Disadvantages Examples
Acoustic The actuator vibrates = The actuator can = Large area = 1993
Hadimioglu
vibration at a high frequency. be physically distant required for et al, EUP
550,192
from the ink efficient operation = 1993 Elrod et al,
at useful frequencies EUP 572,220
= Acoustic
coupling and
crosstalk
= Complex drive
circuitry
= Poor control of
drop volume and
position
None In various ink jet = No moving parts = Various other = Silverbrook, EP
designs the actuator tradeoffs are 0771 658 A2 and
does not move. required to related patent
eliminate moving applications
parts = Tone-jet
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NOZZLE REFILL METHOD
Description Advantages Disadvantages Examples
Surface This is the normal way = Fabrication = Low speed = Thermal ink jet
tension that ink jets are simplicity = Surface tension = Piezoelectric ink
refilled. After the = Operational force relatively jet
actuator is energized, simplicity small compared to = IJO1-IJ07, IJ10-
it typically returns actuator force IJ14, IJ16, IJ20,
rapidly to its normal = Long refill time IJ22-IJ45
position. This rapid usually dominates
return sucks in air the total repetition
through the nozzle rate
opening. The ink
surface tension at the
nozzle then exerts a
small force restoring
the meniscus to a
minimum area. This
force refills the nozzle.
Shuttered Ink to the nozzle = High speed = Requires = IJ08, IJ13, IJ15,
oscillating chamber is provided at = Low actuator common ink IJ17, IJ18, IJ19,
ink pressure a pressure that energy, as the pressure oscillator IJ21
oscillates at twice the actuator need only = May not be
drop ejection open or close the suitable for
frequency. When a shutter, instead of pigmented inks
drop is to be ejected, ejecting the ink drop
the shutter is opened
for 3 half cycles: drop
ejection, actuator
return, and refill. The
shutter is then closed
to prevent the nozzle
chamber emptying
during the next
negative pressure
cycle.
Refill After the main = High speed, as = Requires two = IJ09
actuator actuator has ejected a the nozzle is independent
drop a second (refill) actively refilled actuators per nozzle
actuator is energized.
The refill actuator
pushes ink into the
nozzle chamber. The
refill actuator returns
slowly, to prevent its
return from emptying
the chamber again.
Positive ink The ink is held a slight = High refill rate, = Surface spill =
Silverbrook, EP
pressure positive pressure. therefore a high must be prevented 0771 658 A2 and
After the ink drop is drop repetition rate = Highly related patent
ejected, the nozzle is possible hydrophobic print applications
chamber fills quickly head surfaces are = Alternative for:,
as surface tension and required IJ01-IJ07, IJ10-IJ14,
ink pressure both IJ16, IJ20, IJ22-IJ45
operate to refill the
nozzle.
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METHOD OF RESTRICTING BACK-FLOW THROUGH INLET
Description Advantages Disadvantages Examples
Long inlet The ink inlet channel = Design simplicity = Restricts refill =
Thermal ink jet
channel to the nozzle chamber = Operational rate = Piezoelectric ink
is made long and simplicity = May result in a jet
relatively narrow, = Reduces relatively large chip = IJ42, IJ43
relying on viscous crosstalk area
drag to reduce inlet = Only partially
back-flow. effective
Positive ink The ink is under a = Drop selection = Requires a = Silverbrook,
EP
pressure positive pressure, so and separation method (such as a 0771 658 A2
and
that in the quiescent forces can be nozzle rim or related patent
state some of the ink reduced effective applications
drop already protrudes = Fast refill time hydrophobizing, or = Possible
from the nozzle. both) to prevent operation of the
This reduces the flooding of the following: 1301-
pressure in the nozzle ejection surface of IJ07, IJ09- IJ12,
chamber which is the print head. IJ14, IJ16, IJ20,
required to eject a IJ22, , IJ23-IJ34,
certain volume of ink. IJ36- IJ41, IJ44
The reduction in
chamber pressure
results in a reduction
in ink pushed out
through the inlet.
Baffle One or more baffles = The refill rate is = Design = HP Thermal Ink
are placed in the inlet not as restricted as complexity Jet
ink flow. When the the long inlet = May increase = Tektronix
actuator is energized, method. fabrication piezoelectric ink jet
the rapid ink = Reduces complexity (e.g.
movement creates crosstalk Tektronix hot melt
eddies which restrict Piezoelectric print
the flow through the heads).
inlet. The slower refill
process is unrestricted,
and does not result in
eddies.
Flexible flap In this method recently = Significantly = Not applicable to =
Canon
restricts disclosed by Canon, reduces back-flow most ink jet
inlet the expanding actuator for edge-shooter configurations
(bubble) pushes on a thermal ink jet = Increased
flexible flap that devices fabrication
restricts the inlet. complexity
= Inelastic
deformation of
polymer flap results
in creep over
extended use
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METHOD OF RESTRICTING BACK-FLOW THROUGH INLET
Description Advantages Disadvantages Examples
Inlet filter A filter is located = Additional = Restricts refill = IJ04, IJ12,
IJ24,
between the ink inlet advantage of ink rate IJ27, U29, IJ30
and the nozzle filtration = May result in
chamber. The filter = Ink filter may be complex
has a multitude of fabricated with no construction
small holes or slots, additional process
restricting ink flow. steps
The filter also removes
particles which may
block the nozzle.
Small inlet The ink inlet channel = Design simplicity = Restricts refill =
IJ02, IJ37, IJ44
compared to the nozzle chamber rate
to nozzle has a substantially = May result in a
smaller cross section relatively large chip
than that of the nozzle area
, resulting in easier ink = Only partially
egress out of the effective
nozzle than out of the
inlet.
Inlet shutter A secondary actuator = Increases speed = Requires separate =
IJ09
controls the position of of the ink jet print refill actuator and
a shutter, closing off head operation drive circuit
the ink inlet when the
main actuator is
energized.
The inlet is The method avoids the = Back-flow = Requires careful = IJO1,
IJ03, 1J05,
located problem of inlet back- problem is design to minimize IJ06, U07, IJ10;
behind the flow by arranging the eliminated the negative IJ11, IJ14, IJ16,
ink-pushing ink-pushing surface of pressure behind the IJ22, IJ23, IJ25,
surface the actuator between paddle IJ28, IJ31, IJ32,
the inlet and the IJ33, IJ34, IJ35,
nozzle. IJ36, IJ39, IJ40,
IJ41
Part of the The actuator and a = Significant = Small increase in = IJ07, IJ20,
IJ26,
actuator wall of the ink reductions in back- fabrication IJ38
moves to chamber are arranged flow can be complexity
shut off the so that the motion of achieved
inlet the actuator closes off = Compact designs
the inlet. possible
Nozzle In some configurations = Ink back-flow = None related to = Silverbrook,
EP
actuator of ink jet, there is no problem is ink back-flow on 0771 658 A2 and
does not expansion or eliminated actuation related patent
result in ink movement of an applications
back-flow actuator which may = Valve jet
cause ink back-flow = Tone jet
through the inlet.
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NOZZLE CLEARING METHOD
Description Advantages Disadvantages Examples
Normal All of the nozzles are = No added = May not be = Most ink jet
nozzle firing fired periodically, complexity on the sufficient to systems
before the ink has a print head displace dried ink = IJO1, IJ02, IJ03,
chance to dry. When IJ04, IJ05, IJ06,
not in use the nozzles IJ07, IJ09, IJ10,
are sealed (capped) IJ11, IJ12, IJ14,
against air. IJ16, IJ20, IJ22,
The nozzle firing is IJ23, IJ24, IJ25,
usually performed IJ26, IJ27, IJ28,
during a special IJ29, IJ30, IJ31,
clearing cycle, after IJ32, IJ33, IJ34,
first moving the print IJ36, IJ37, IJ38,
head to a cleaning IJ39, IJ40,, IJ41,
station. IJ42, IJ43, IJ44,,
IJ45
Extra In systems which heat = Can be highly = Requires higher = Silverbrook,
EP
power to the ink, but do not boil effective if the drive voltage for 0771 658
A2 and
ink heater it under normal heater is adjacent to clearing related patent
situations, nozzle the nozzle = May require applications
clearing can be larger drive
achieved by over- transistors
powering the heater
and boiling ink at the
nozzle.
Rapid The actuator is fired in = Does not require = Effectiveness = May be
used
success-ion rapid succession. In extra drive circuits depends with: IJ01,
IJ02,
of actuator some configurations, on the print head substantially upon IJ03,
IJ04, IJ05,
pulses this may cause heat = Can be readily the configuration of IJ06, IJ07,
IJ09,
build-up at the nozzle controlled and the ink jet nozzle IJ10, U11, IJ14,
which boils the ink, initiated by digital IJ16, IJ20, IJ22,
clearing the nozzle. In logic IJ23, IJ24, IJ25,
other situations, it may IJ27, IJ28, IJ29,
cause sufficient IJ30, IJ31, IJ32,
vibrations to dislodge IJ33, IJ34, IJ36,
clogged nozzles. IJ37, IJ38, IJ39,
IJ40, IJ41, IJ42,
IJ43, IJ44, IJ45
Extra Where an actuator is = A simple = Not suitable = May be used
power to not normally driven to solution where where there is a with: IJ03,
IJ09,
ink pushing the limit of its motion, applicable hard limit to IJ 16, IJ20,
IJ23,
actuator nozzle clearing may be actuator movement IJ24, IJ25, IJ27,
assisted by providing IJ29, IJ30, IJ31,
an enhanced drive IJ32, IJ39, IJ40,
signal to the actuator. IM 1, IJ42, IJ43,
IJ44, IJ45
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NOZZLE CLEARING METHOD
Description Advantages Disadvantages Examples
Acoustic An ultrasonic wave is = A high nozzle = High = IJ08, IJ13, IJ15,
resonance applied to the ink clearing capability implementation cost IJ17,
IJ18, IJ19,
chamber. This wave is can be achieved if system does not IJ21
of an appropriate = May be already include an
amplitude and implemented at very acoustic actuator
frequency to cause low cost in systems
sufficient force at the which already
nozzle to clear include acoustic
blockages. This is actuators
easiest to achieve if
the ultrasonic wave is
at a resonant
frequency of the ink
cavity.
Nozzle A microfabricated = Can clear = Accurate = Silverbrook, EP
clearing plate is pushed against severely clogged mechanical 0771 658 A2 and
plate the nozzles. The plate nozzles alignment is related patent
has a post for every required applications
nozzle. A post moves = Moving parts are
through each nozzle, required
displacing dried ink. = There is risk of
damage to the
nozzles
= Accurate
fabrication is
required
Ink The pressure of the ink = May be effective = Requires = May be used
pressure is temporarily where other pressure pump or with all IJ series ink
pulse increased so that ink methods cannot be other pressure jets
streams from all of the used actuator
nozzles. This may be = Expensive
used in conjunction = Wasteful of ink
with actuator
energizing.
Print head A flexible `blade' is = Effective for = Difficult to use if = Many
ink jet
wiper wiped across the print planar print head print head surface is systems
head surface. The surfaces non-planar or very
blade is usually = Low cost fragile
fabricated from a = Requires
flexible polymer, e.g. mechanical parts
rubber or synthetic = Blade can wear
elastomer. out in high volume
print systems
Separate A separate heater is = Can be effective = Fabrication = Can be used
with
ink boiling provided at the nozzle where other nozzle complexity many IJ
series ink
heater although the normal clearing methods jets
drop e-ection cannot be used
mechanism does not = Can be
require it. The heaters implemented at no
do not require additional cost in
individual drive some ink jet
circuits, as many configurations
nozzles can be cleared
simultaneously, and no
imaging is required.
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NOZZLE CLEARING METHOD
I Description Advantages Disadvantages Examples
NOZZLE PLATE CONSTRUCTION
Description Advantages Disadvantages Examples
Electro- A nozzle plate is = Fabrication = High = Hewlett Packard
formed separately fabricated simplicity temperatures and Thermal Ink jet
nickel from electroformed pressures are
nickel, and bonded to required to bond
the print head chip. nozzle plate
= Minimum
thickness constraints
= Differential
thermal expansion
Laser Individual nozzle = No masks = Each hole must = Canon Bubblejet
ablated or holes are ablated by an required be individually = 1988 Sercel et
drilled intense UV laser in a = Can be quite fast formed al., SPIE, Vol. 998
polymer nozzle plate, which is = Some control = Special Excimer Beam
typically a polymer over nozzle profile equipment required Applications, pp.
such as polyimide or is possible = Slow where there 76-83
polysulphone = Equipment are many thousands = 1993 Watanabe
required is relatively of nozzles per print et al., USP
low cost head 5,208,604
= May produce thin
burrs at exit holes
Silicon A separate nozzle = High accuracy is = Two part = K. Bean, IEEE
micro- plate is attainable construction Transactions on
machined micromachined from = High cost Electron Devices,
single crystal silicon, = Requires Vol. ED-25, No. 10,
and bonded to the precision alignment 1978, pp 1185-1195
print head wafer. = Nozzles may be = Xerox 1990
clogged by adhesive Hawkins et al., USP
4,899,181
Glass Fine glass capillaries = No expensive = Very small = 1970 Zoltan USP
capillaries are drawn from glass equipment required nozzle sizes are 3,683,212
tubing. This method = Simple to make difficult to form
has been used for single nozzles = Not suited for
making individual mass production
nozzles, but is difficult
to use for bulk
manufacturing of print
heads with thousands
of nozzles.
Monolithic, The nozzle plate is = High accuracy = Requires = Silverbrook, EP
surface deposited as a layer (<1 m) sacrificial layer 0771 658 A2 and
micro- using standard VLSI = Monolithic under the nozzle related patent
machined deposition techniques. = Low cost plate to form the applications
using VLSI Nozzles are etched in = Existing nozzle chamber = IJO1, IJ02, IJ04,
litho- the nozzle plate using processes can be = Surface may be IJ11, IJ12,
IJ17,
graphic VLSI lithography and used fragile to the touch IJ 18, IJ20, IJ22,
processes etching. IJ24, IJ27, IJ28,
IJ29, IJ30, IJ31,
IJ32, IJ33, IJ34,
IJ36, IJ37, IJ38,
IJ39, IJ40, IJ41,
IJ42, IJ43, IJ44
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NOZZLE CLEARING METHOD
Description Advantages Disadvantages Examples
Monolithic, The nozzle plate is a = High accuracy = Requires long = IJ03,
IJ05, IJ06,
etched buried etch stop in the (<1 m) etch times IJ07, IJ08, IJ09,
through wafer. Nozzle = Monolithic = Requires a IJ10, IJ13, IJ14,
substrate chambers are etched in = Low cost support wafer IJ15, IJ16, IJ19,
the front of the wafer, = No differential IJ21, IJ23, IJ25,
and the wafer is expansion IJ26
thinned from the back
side. Nozzles are then
etched in the etch stop
layer.
No nozzle Various methods have = No nozzles to = Difficult to = Ricoh 1995
plate been tried to eliminate become clogged control drop Sekiya et al USP
the nozzles entirely, to position accurately 5,412,413
prevent nozzle = Crosstalk = 1993 Hadimioglu
clogging. These problems et al EUP 550,192
include thermal bubble = 1993 Elrod et al
mechanisms and EUP 572,220
acoustic lens
mechanisms
Trough Each drop ejector has = Reduced = Drop firing = IJ35
a trough through manufacturing direction is sensitive
which a paddle moves. complexity to wicking.
There is no nozzle = Monolithic
plate.
Nozzle slit The elimination of = NO nozzles to = Difficult to == 1989 Saito et
al
instead of nozzle holes and become clogged control drop USP 4,799,068
individual replacement by a slit position accurately
nozzles encompassing many = Crosstalk
actuator positions problems
reduces nozzle
clogging, but increases
crosstalk due to ink
surface waves
DROP EJECTION DIRECTION
Description Advantages Disadvantages Examples
Edge Ink flow is along the = Simple = Nozzles limited = Canon Bubblejet
('edge surface of the chip, construction to edge 1979 Endo et al GB
shooter') and ink drops are = No silicon = High resolution patent 2,007,162
ejected from the chip etching required is difficult = Xerox heater-in-
edge. = Good heat = Fast color pit 1990 Hawkins et
sinking via substrate printing requires al USP 4,899,181
= Mechanically one print head per = Tone jet
strong color
= Ease of chip
handing
Surface Ink flow is along the = No bulk silicon = Maximum ink = Hewlett-
Packard
('roof surface of the chip, etching required flow is severely TIJ 1982 Vaught
et
shooter') and ink drops are = Silicon can make restricted al USP 4,490,728
ejected from the chip an effective heat = IJ02, IJ11, IJ12,
surface, normal to the sink IJ20, IJ22
plane of the chip. = Mechanical
strength
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DROP EJECTION DIRECTION
Description Advantages Disadvantages Examples
Through Ink flow is through the = High ink flow = Requires bulk = Silverbrook,
EP
chip, chip, and ink drops are = Suitable for silicon etching 0771 658 A2 and
forward ejected from the front pagewidth print related patent
(pup surface of the chip. heads applications
shooter') = High nozzle = IJ04, IJ17, IJ18,
packing density IJ24, IJ27-IJ45
therefore low
manufacturing cost
Through Ink flow is through the = High ink flow = Requires wafer = IJ01, IJ03,
IJ05,
chip, chip, and ink drops are = Suitable for thinning IJ06, IJ07, IJ08,
reverse ejected from the rear pagewidth print = Requires special IJ09, IJ10,
IJ13,
('down surface of the chip. heads handling during IJ14, IJ15, IJ16,
shooter') = High nozzle manufacture IJ19, IJ21, IJ23,
packing density IJ25, IJ26
therefore low
manufacturing cost
Through Ink flow is through the = Suitable for = Pagewidth print = Epson
Stylus
actuator actuator, which is not piezoelectric print heads require = Tektronix
hot
fabricated as part of heads several thousand melt piezoelectric
the same substrate as connections to drive ink jets
the drive transistors. circuits
= Cannot be
manufactured in
standard CMOS
fabs
= Complex
assembly required
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INK TYPE
Description Advantages Disadvantages Examples
Aqueous, Water based ink which = Environmentally = Slow drying = Most existing
ink
dye typically contains: friendly = Corrosive jets
water, dye, surfactant, = No odor = Bleeds on paper = All IJ series ink
humectant, and = May jets
biocide. strikethrough = Silverbrook, EP
Modem ink dyes have = Cockles paper 0771 658 A2 and
high water-fastness, related patent
li t fastness applications
Aqueous, Water based ink which = Environmentally = Slow drying = IJ02, IJ04,
IJ21,
pigment typically contains: friendly = Corrosive IJ26, IJ27, IJ30
water, pigment, = No odor = Pigment may = Silverbrook, EP
surfactant, humectant, = Reduced bleed clog nozzles 0771 658 A2 and
and biocide. = Reduced wicking = Pigment may related patent
Pigments have an = Reduced clog actuator applications
advantage in reduced strikethrough mechanisms = Piezoelectric ink-
bleed, wicking and = Cockles paper jets
strikethrough. = Thermal ink jets
(with significant
restrictions)
Methyl MEK is a highly = Very fast drying = Odorous = All IJ series ink
Ethyl volatile solvent used = Prints on various = Flammable jets
Ketone for industrial printing substrates such as
(MEK) on difficult surfaces metals and plastics
such as aluminum
cans.
Alcohol Alcohol based inks = Fast drying = Slight odor = All IJ series ink
(ethanol, 2- can be used where the = Operates at sub- = Flammable jets
butanol, printer must operate at freezing
and others) temperatures below temperatures
the freezing point of = Reduced paper
water. An example of cockle
this is in-camera = Low cost
consumer
hoto a hic printing.
Phase The ink is solid at = No drying time- = High viscosity = Tektronix hot
change room temperature, and ink instantly freezes = Printed ink melt
piezoelectric
(hot melt) is melted in the print on the print medium typically has a ink jets
head before jetting. = Almost any print `waxy' feel = 1989 Nowak
Hot melt inks are medium can be used = Printed pages USP 4,820,346
usually wax based, = No paper cockle may `block' = All IJ series ink
with a melting point occurs = Ink temperature jets
around 80 C. After = No wicking may be above the
jetting the ink freezes occurs curie point of
almost instantly upon = No bleed occurs permanent magnets
contacting the print = No strikethrough = Ink heaters
medium or a transfer occurs consume power
roller. = Long warm-up
time
CA 02592267 2007-06-27
WO 2006/099652 PCT/AU2005/000392
INK TYPE
Description Advantages Disadvantages Examples
Oil Oil based inks are = High solubility = High viscosity: = All IJ series ink
extensively used in medium for some this is a significant jets
offset printing. They dyes limitation for use in
have advantages in = Does not cockle ink jets, which
improved paper usually require a
characteristics on = Does not wick low viscosity. Some
paper (especially no through paper short chain and
wicking or cockle). multi-branched oils
Oil soluble dies and have a sufficiently
pigments are required. low viscosity.
= Slow drying
Micro- A microemulsion is a = Stops ink bleed = Viscosity higher = All IJ
series ink
emulsion stable, self forming = High dye than water jets
emulsion of oil, water, solubility = Cost is slightly
and surfactant. The = Water, oil, and higher than water
characteristic drop size amphiphilic soluble based ink
is less than 100 nm, dies can be used = High surfactant
and is determined by = Can stabilize concentration
the preferred curvature pigment required (around
of the surfactant. suspensions 5%)
