U.S. patent application number 09/798742 was filed with the patent office on 2001-07-19 for ink jet nozzle assembly including a fluidic seal.
Invention is credited to Silverbrook, Kia.
Application Number | 20010008408 09/798742 |
Document ID | / |
Family ID | 27158026 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008408 |
Kind Code |
A1 |
Silverbrook, Kia |
July 19, 2001 |
Ink jet nozzle assembly including a fluidic seal
Abstract
An ink jet print head includes a nozzle chamber for storage of
ink to be ejected from an ink ejection nozzle formed in one wall of
the nozzle chamber; and a movable paddle actuator mechanism formed
in a first wall of the nozzle chamber, one end of the paddle
actuator traversing along a second wall of the nozzle chamber, the
second wall being substantially perpendicular to the first wall;
the one end further including a flange having a surface abutting
the second wall, the movable paddle actuator mechanism being
operable to cause the ejection of ink from the ink ejection nozzle
with the flange moving substantially tangentially to the second
wall.
Inventors: |
Silverbrook, Kia; (Balmain,
AU) |
Correspondence
Address: |
SILVERBROOK RESEARCH PTY LTD
393 DARLING STREET
BALMAIN
2041
AU
|
Family ID: |
27158026 |
Appl. No.: |
09/798742 |
Filed: |
March 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09798742 |
Mar 2, 2001 |
|
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09112820 |
Jul 18, 1998 |
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Current U.S.
Class: |
347/54 ;
348/E5.024; 348/E5.055 |
Current CPC
Class: |
B41J 2/1645 20130101;
B41J 2/1639 20130101; B41J 2/1646 20130101; B41J 2002/041 20130101;
H04N 2101/00 20130101; B41J 2/1648 20130101; H04N 5/225 20130101;
H04N 5/2628 20130101; B41J 2/1628 20130101; B41J 2002/14346
20130101; B41J 2/16585 20130101; B41J 2002/14435 20130101; H04N
1/2154 20130101; B41J 2202/15 20130101; B41J 2/17596 20130101; B41J
2/1632 20130101; B41J 2/1631 20130101; B41J 2/14427 20130101; H04N
1/2112 20130101; B41J 2/1642 20130101 |
Class at
Publication: |
347/54 |
International
Class: |
B41J 002/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 1998 |
AU |
PP3985 |
Jul 15, 1997 |
AU |
PO7991 |
Claims
We claim:
1. An ink jet nozzle assembly including a nozzle chamber containing
ink to be ejected and a fluidic seal comprising a meniscus formed
by said ink across two solid surfaces of said assembly that move
relative to one another when the assembly is activated in use.
2. An ink jet nozzle assembly including: a nozzle chamber having an
inlet in fluid communication with an ink reservoir and a nozzle
through which ink from said chamber can be ejected; the chamber
including a fixed portion and a movable portion configured for
relative movement in an ejection phase and alternate relative
movement in a refill phase; the movable portion being formed in a
first wall of said nozzle chamber and having one end traversing
adjacent a second wall of said nozzle chamber, said second wall
being substantially perpendicular to said first wall; and the inlet
being positioned and dimensioned relative to the nozzle such that
ink is ejected preferentially from the chamber through the nozzle
in droplet form during the ejection phase, and ink is alternately
drawn preferentially into the chamber from the reservoir through
the inlet during the refill phase.
3. An assembly according to claim 2 wherein the movable portion
includes the nozzle and the fixed portion is mounted on a
substrate.
4. An assembly according to claim 2 wherein the fixed portion
includes the nozzle mounted on a substrate and a movable portion
includes an ejection paddle.
5. The assembly according to claim 2 wherein said one end of said
first wall further includes a flange including a surface adjacent
said second wall.
6. An assembly according to claim 5 wherein said flange is spaced
from said second wall by a slot.
7. The assembly according to claim 2 wherein said second wall of
said chamber forms one wall of said inlet.
8. An assembly according to claim 2 wherein said movable portion
includes a thermal bend actuator.
9. An assembly according to claim 2 formed on a silicon wafer.
10. An assembly according to claim 9 wherein said inlet is formed
by back etching a back surface of said silicon wafer.
11. An assembly according to claim 10 wherein said back etching
comprises a plasma etching of said back surface.
12. An assembly according to claim 2 wherein said movable portion,
in being actuated to be eject a drop of ink, restricts a flow of
ink into said chamber via said inlet.
13. An assembly according to claim 2 further including a slot
around a substantial portion of said movable portion, said slot
interconnecting said nozzle chamber with an external ambient
atmosphere, said slot being dimensioned to provide for fluid
movement during operation of said movable portion while not
allowing for the ejection of fluid therethrough.
14. An assembly according to claim 8 wherein said thermal bend
actuator comprises a conductive heater layer between layers of a
substantially non-conductive material having a higher coefficient
of thermal expansion.
15. An assembly according to claim 14 wherein said conductive
heater layer is arranged in a serpentine form so that, upon
conductive heating of said conductive heater layer, said conductive
heater layer forms a concertina so as to allow for substantially
unhindered expansion of said substantially non-conductive
material.
16. An assembly according to claim 14 wherein said substantially
non-conductive material comprises substantially
polytetra-fluoroethylene.
17. An assembly according to claim 9 wherein said silicon wafer is
initially processed utilizing a CMOS processing system so as to
form a electrical circuit required to operate said ink jet nozzle
assembly on said silicon wafer.
Description
[0001] This is a C-I-P of application Ser. No. 09/112,820 filed on
Jul. 10, 1998.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of inkjet
printing and, in particular, discloses a surface bend actuator
vented ink supply ink jet printer.
BACKGROUND OF THE INVENTION
[0003] Many different types of printing have been invented, a large
number of which are presently in use. The known forms of printers
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.
[0004] 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.
[0005] Many different techniques of 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 Sherr, pages 207-220 (1988).
[0006] 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 U.S. Pat. No.
1,941,001 by Hansell discloses a simple form of continuous stream
electro-static ink jet printing.
[0007] U.S. Pat. No. 3,596,275 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 U.S.
Pat. No. 3,373,437 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 U.S. Pat.
No. 3,946,398 (1970) which utilizes a diaphragm mode of operation,
by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a
squeeze mode of operation of a piezoelectric crystal, Stemme in
U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of
piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601
discloses a piezoelectric push mode actuation of the ink jet stream
and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear
mode type of piezoelectric transducer element.
[0008] 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 U.S. Pat. No. 4,490,728. Both the aforementioned
references disclosed ink jet printing techniques which 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 causes the ejection of ink from an aperture connected
to the confined space onto a relevant print media. Printing devices
utilizing the electrothermal actuator are manufactured by
manufacturers such as Canon and Hewlett Packard.
[0009] 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.
SUMMARY OF THE INVENTION
[0010] There is disclosed herein an ink jet nozzle assembly
including a nozzle chamber containing ink to be ejected and a
fluidic seal comprising a meniscus formed by said ink across two
solid surfaces of said assembly that move relative to one another
when the assembly is activated in use.
[0011] There is further disclosed herein an ink jet nozzle assembly
including:
[0012] a nozzle chamber having an inlet in fluid communication with
an ink reservoir and a nozzle through which ink from said chamber
can be ejected;
[0013] the chamber including a fixed portion and a movable portion
configured for relative movement in an ejection phase and alternate
relative movement in a refill phase;
[0014] the movable portion being formed in a first wall of said
nozzle chamber and having one end traversing adjacent a second wall
of said nozzle chamber, said second wall being substantially
perpendicular to said first wall; and
[0015] the inlet being positioned and dimensioned relative to the
nozzle such that ink is ejected preferentially from the chamber
through the nozzle in droplet form during the ejection phase, and
ink is alternately drawn preferentially into the chamber from the
reservoir through the inlet during the refill phase.
[0016] Preferably the movable portion includes the nozzle and the
fixed portion is mounted on a substrate.
[0017] Preferably the fixed portion includes the nozzle mounted on
a substrate and a movable portion includes an ejection paddle.
[0018] Preferably one end of said first wall further includes a
flange including a surface adjacent said second wall.
[0019] Preferably said flange is spaced from said second wall by a
slot.
[0020] Preferably said second wall of said chamber forms one wall
of said inlet.
[0021] Preferably said movable portion includes a thermal bend
actuator.
[0022] Preferably the assembly is formed on a silicon wafer.
[0023] Preferably said inlet is formed by back etching a back
surface of said silicon wafer.
[0024] Preferably said back etching comprises a plasma etching of
said back surface.
[0025] Preferably said movable portion, in being actuated to be
eject a drop of ink, restricts a flow of ink into said chamber via
said inlet.
[0026] Preferably the assembly further includes a slot around a
substantial portion of said movable portion, said slot
interconnecting said nozzle chamber with an external ambient
atmosphere, said slot being dimensioned to provide for fluid
movement during operation of said movable portion while not
allowing for the ejection of fluid therethrough.
[0027] Preferably said thermal bend actuator comprises a conductive
heater layer between layers of a substantially non-conductive
material having a higher coefficient of thermal expansion.
[0028] Preferably said conductive heater layer is arranged in a
serpentine form so that, upon conductive heating of said conductive
heater layer, said conductive heater layer forms a concertina so as
to allow for substantially unhindered expansion of said
substantially non-conductive material.
[0029] Preferably said substantially non-conductive material
comprises substantially polytetrafluoroethylene.
[0030] Preferably said silicon wafer is initially processed
utilizing a CMOS processing system so as to form a electrical
circuit required to operate said ink jet nozzle assembly on said
silicon wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Notwithstanding any other forms which 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:
[0032] FIG. 1 to FIG. 3 are schematic sectional views illustrating
the operational principles of the preferred embodiment;
[0033] FIG. 4a and FIG. 4b illustrate the operational principles of
the thermal actuator of the preferred embodiment;
[0034] FIG. 5 is a side perspective view of a single nozzle
arrangement of the preferred embodiment;
[0035] FIG. 6 illustrates an array view of a portion of a printhead
constructed in accordance with the principles of the preferred
embodiment.
[0036] FIG. 7 provides a legend of the materials indicated in FIGS.
8 to 16;
[0037] FIG. 8 to FIG. 17 illustrate sectional views of the
manufacturing steps in one form of construction of an ink jet
printhead nozzle;
[0038] FIG. 18 shows a three dimensional, schematic view of a
nozzle assembly for an ink jet printhead in accordance with another
embodiment of the invention;
[0039] FIGS. 19 to 21 show a three dimensional, schematic
illustration of an operation of the nozzle assembly of FIG. 18;
[0040] FIG. 22 shows a three dimensional view of a nozzle array
constituting an ink jet printhead;
[0041] FIG. 23 shows, on an enlarged scale, part of the array of
FIG. 22;
[0042] FIG. 24 shows a three dimensional view of an ink jet
printhead including a nozzle guard;
[0043] FIGS. 25a to 25r show three-dimensional views of steps in
the manufacture of a nozzle assembly of an ink jet printhead;
[0044] FIGS. 26a to 26r show sectional side views of the
manufacturing steps;
[0045] FIGS. 27a to 27k show layouts of masks used in various steps
in the manufacturing process;
[0046] FIGS. 28a to 28c show three dimensional views of an
operation of the nozzle assembly manufactured according to the
method of FIGS. 25 and 26; and
[0047] FIGS. 29a to 29c show sectional side views of an operation
of the nozzle assembly manufactured according to the method of
FIGS. 25 and 26.
DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
[0048] The preferred embodiment of the present invention discloses
an inkjet printing device made up of a series of nozzle
arrangements. Each nozzle arrangement includes a thermal surface
actuator device which includes an L-shaped cross sectional profile
and an air breathing edge such that actuation of the paddle
actuator results in a drop being ejected from a nozzle utilizing a
very low energy level.
[0049] Turning initially to FIG. 1 to FIG. 3, there will now be
described the operational principles of the preferred embodiment.
In FIG. 1, there is illustrated schematically a sectional view of a
single nozzle arrangement 1 which includes an ink nozzle chamber 2
containing an ink supply which is resupplied by means of an ink
supply channel 3. A nozzle rim 4 is provided, across which a
meniscus 5 forms, with a slight bulge when in the quiescent state.
A bend actuator device 7 is formed on the top surface of the nozzle
chamber and includes a side arm 8 which runs generally parallel to
the surface 9 of the nozzle chamber wall so as to form an "air
breathing slot" 10 which assists in the low energy actuation of the
bend actuator 7. Ideally, the front surface of the bend actuator 7
is hydrophobic such that a meniscus 12 forms between the bend
actuator 7 and the surface 9 leaving an air pocket in slot 10.
[0050] When it is desired to eject a drop via the nozzle rim 4, the
bend actuator 7 is actuated so as to rapidly bend down as
illustrated in FIG. 2. The rapid downward movement of the actuator
7 results in a general increase in pressure of the ink within the
nozzle chamber 2. This results in a outflow of ink around the
nozzle rim 4 and a general bulging of the meniscus 5. The meniscus
12 undergoes a low amount of movement.
[0051] The actuator device 7 is then turned off so as to slowly
return to its original position as illustrated in FIG. 3. The
return of the actuator 7 to its original position results in a
reduction in the pressure within the nozzle chamber 2 which results
in a general back flow of ink into the nozzle chamber 2. The
forward momentum of the ink outside the nozzle chamber in addition
to the back flow of ink 15 results in a general necking and
breaking off of the drop 14. Surface tension effects then draw
further ink into the nozzle chamber via ink supply channel 3. Ink
is drawn in the nozzle chamber 3 until the quiescent position of
FIG. 1 is again achieved.
[0052] The actuator device 7 can be a thermal actuator which is
heated by means of passing a current through a conductive core.
Preferably, the thermal actuator is provided with a conductive core
encased in a material such as polytetrafluoroethylene which has a
high level coefficient of expansion. As illustrated in FIG. 4, a
conductive core 23 is preferably of a serpentine form and encased
within a material 24 having a high coefficient of thermal
expansion. Hence, as illustrated in FIG. 4b, on heating of the
conductive core 23, the material 24 expands to a greater extent and
is therefore caused to bend down in accordance with
requirements.
[0053] Turning now to FIG. 5, there is illustrated a side
perspective view, partly in section, of a single nozzle arrangement
when in the state as described with reference to FIG. 2. The nozzle
arrangement 1 can be formed in practice on a semiconductor wafer 20
utilizing standard MEMS techniques.
[0054] The silicon wafer 20 preferably is processed so as to
include a CMOS layer 21 which can include the relevant electrical
circuitry required for the full control of a series of nozzle
arrangements 1 formed so as to form a printhead unit. On top of the
CMOS layer 21 is formed a glass layer 22 and an actuator 7 which is
driven by means of passing a current through a serpentine copper
coil 23 which is encased in the upper portions of a
polytetrafluoroethylene (PTFE) layer 24. Upon passing a current
through the coil 23, the coil 23 is heated as is the PTFE layer 24.
PTFE has a very high coefficient of thermal expansion and hence
expands rapidly. The coil 23 constructed in a serpentine nature is
able to expand substantially with the expansion of the PTFE layer
24. The PTFE layer 24 includes a lip portion 8 which upon
expansion, bends in a scooping motion as previously described. As a
result of the scooping motion, the meniscus 5 generally bulges and
results in a consequential ejection of a drop of ink. The nozzle
chamber 4 is later replenished by means of surface tension effects
in drawing ink through an ink supply channel 3 which is etched
through the wafer through the utilization of a highly an isotropic
silicon trench etcher. Hence, ink can be supplied to the back
surface of the wafer and ejected by means of actuation of the
actuator 7. The gap between the side arm 8 and chamber wall 9
allows for a substantial breathing effect which results in a low
level of energy being required for drop ejection.
[0055] A large number of arrangements 1 of FIG. 5 can be formed
together on a wafer with the arrangements being collected into
printheads which can be of various sizes in accordance with
requirements. Turning now to FIG. 6, there is illustrated one form
of an array 30 which is designed so as to provide three color
printing with each color providing two spaced apart rows of nozzle
arrangements 34. The three groupings can comprise groupings 31, 32
and 33 with each grouping supplied with a separate ink color so as
to provide for full color printing capability. Additionally, a
series of bond pads e.g. 36 are provided for TAB bonding control
signals to the printhead 30. Obviously, the arrangement 30 of FIG.
6 illustrates only a portion of a printhead which can be of a
length as determined by requirements.
[0056] One form of detailed manufacturing process which can be used
to fabricate monolithic ink jet printheads operating in accordance
with the principles taught by the present embodiment can proceed
utilizing the following steps:
[0057] 1. Using a double sided polished wafer 20, complete drive
transistors, data distribution, and timing circuits using a 0.5
micron, one poly, 2 metal CMOS process 21. Relevant features of the
wafer at this step are shown in FIG. 8. For clarity, these diagrams
may not be to scale, and may not represent a cross section though
any single plane of the nozzle. FIG. 7 is a key to representations
of various materials in these manufacturing diagrams, and those of
other cross referenced ink jet configurations.
[0058] 2. Etch the CMOS oxide layers down to silicon or second
level metal using Mask 1. This mask defines the nozzle cavity and
the edge of the chips. Relevant features of the wafer at this step
are shown in FIG. 8.
[0059] 3. Plasma etch the silicon to a depth of 20 microns using
the oxide as a mask. This step is shown in FIG. 9.
[0060] 4. Deposit 23 microns of sacrificial material 50 and
planarize down to oxide using CMP. This step is shown in FIG.
10.
[0061] 5. Etch the sacrificial material to a depth of 15 microns
using Mask 2. This mask defines the vertical paddle 8 at the end of
the actuator. This step is shown in FIG. 11.
[0062] 6. Deposit a thin layer (not shown) of a hydrophilic
polymer, and treat the surface of this polymer for PTFE
adherence.
[0063] 7. Deposit 1.5 microns of polytetrafluoroethylene (PTFE)
51.
[0064] 8. Etch the PTFE and CMOS oxide layers to second level metal
using Mask 3. This mask defines the contact vias 52 for the heater
electrodes. This step is shown in FIG. 12.
[0065] 9. Deposit and pattern 0.5 microns of gold 53 using a
lift-off process using Mask 4. This mask defines the heater
pattern. This step is shown in FIG. 13.
[0066] 10. Deposit 1.5 microns of PTFE 54.
[0067] 11. Etch 1 micron of PTFE using Mask 5. This mask defines
the nozzle rim 4 and the rim 4 at the edge of the nozzle chamber.
This step is shown in FIG. 14.
[0068] 12. Etch both layers of PTFE and the thin hydrophilic layer
down to the sacrificial layer using Mask 6. This mask defines the
gap 10 at the edges of the actuator and paddle. This step is shown
in FIG. 15.
[0069] 13. Back-etch through the silicon wafer to the sacrificial
layer (with, for example, an ASE Advanced Silicon Etcher from
Surface Technology Systems) using Mask 7. This mask defines the ink
inlets which 3 are etched through the wafer. This step is shown in
FIG. 16.
[0070] 14. Etch the sacrificial layers. The wafer is also diced by
this etch.
[0071] 15. Mount the printheads in their packaging, which may be a
molded plastic former incorporating ink channels which supply the
appropriate color ink to the ink inlets at the back of the
wafer.
[0072] 16. Connect the printheads to their interconnect systems.
For a low profile connection with minimum disruption of airflow,
TAB may be used. Wire bonding may also be used if the printer is to
be operated with sufficient clearance to the paper.
[0073] 17. Fill the completed printheads with ink 55 and test them.
A filled nozzle is shown in FIG. 17.
[0074] Referring now to FIG. 18 of the drawings, a nozzle assembly,
in accordance with a further embodiment of the invention is
designated generally by the reference numeral 110. An ink jet
printhead has a plurality of nozzle assemblies 110 arranged in an
array 114 (FIGS. 22 and 23) on a silicon substrate 116. The array
114 will be described in greater detail below.
[0075] The assembly 110 includes a silicon substrate or wafer 116
on which a dielectric layer 118 is deposited. A CMOS passivation
layer 120 is deposited on the dielectric layer 118.
[0076] Each nozzle assembly 110 includes a nozzle 122 defining a
nozzle opening 124, a connecting member in the form of a lever arm
126 and an actuator 128. The lever arm 126 connects the actuator
128 to the nozzle 122.
[0077] As shown in greater detail in FIGS. 19 to 21 of the
drawings, the nozzle 122 comprises a crown portion 130 with a skirt
portion 132 depending from the crown portion 130. The skirt portion
132 forms part of a peripheral wall of a nozzle chamber 134 (FIGS.
19 to 21 of the drawings). The nozzle opening 124 is in fluid
communication with the nozzle chamber 134. It is to be noted that
the nozzle opening 124 is surrounded by a raised rim 136 which
"pins" a meniscus 138 (FIG. 19) of a body of ink 140 in the nozzle
chamber 134.
[0078] An ink inlet aperture 142 (shown most clearly in FIG. 23) is
defined in a floor 146 of the nozzle chamber 134. The aperture 142
is in fluid communication with an ink inlet channel 148 defined
through the substrate 116.
[0079] A wall portion 150 bounds the aperture 142 and extends
upwardly from the floor portion 146. The skirt portion 132, as
indicated above, of the nozzle 122 defines a first part of a
peripheral wall of the nozzle chamber 134 and the wall portion 150
defines a second part of the peripheral wall of the nozzle chamber
134.
[0080] The wall 150 has an inwardly directed lip 152 at its free
end which serves as a fluidic seal which inhibits the escape of ink
when the nozzle 122 is displaced, as will be described in greater
detail below. It will be appreciated that, due to the viscosity of
the ink 140 and the small dimensions of the spacing between the lip
152 and the skirt portion 132, the inwardly directed lip 152 and
surface tension function as a seal for inhibiting the escape of ink
from the nozzle chamber 134.
[0081] The actuator 128 is a thermal bend actuator and is connected
to an anchor 154 extending upwardly from the substrate 116 or, more
particularly, from the CMOS passivation layer 120. The anchor 154
is mounted on conductive pads 156 which form an electrical
connection with the actuator 128.
[0082] The actuator 128 comprises a first, active beam 158 arranged
above a second, passive beam 160. In a preferred embodiment, both
beams 158 and 160 are of, or include, a conductive ceramic material
such as titanium nitride (TiN).
[0083] Both beams 158 and 160 have their first ends anchored to the
anchor 154 and their opposed ends connected to the arm 126. When a
current is caused to flow through the active beam 158 thermal
expansion of the beam 158 results. As the passive beam 160, through
which there is no current flow, does not expand at the same rate, a
bending moment is created causing the arm 126 and, hence, the
nozzle 122 to be displaced downwardly towards the substrate 116 as
shown in FIG. 20 of the drawings. This causes an ejection of ink
through the nozzle opening 124 as shown at 162 in FIG. 20 of the
drawings. When the source of heat is removed from the active beam
158, i.e. by stopping current flow, the nozzle 122 returns to its
quiescent position as shown in FIG. 21 of the drawings. When the
nozzle 122 returns to its quiescent position, an ink droplet 164 is
formed as a result of the breaking of an ink droplet neck as
illustrated at 166 in FIG. 21 of the drawings. The ink droplet 164
then travels on to the print media such as a sheet of paper. As a
result of the formation of the ink droplet 164, a "negative"
meniscus is formed as shown at 168 in FIG. 21 of the drawings. This
"negative" meniscus 168 results in an inflow of ink 140 into the
nozzle chamber 134 such that a new meniscus 138 (FIG. 19) is formed
in readiness for the next ink drop ejection from the nozzle
assembly 110.
[0084] Referring now to FIGS. 22 and 23 of the drawings, the nozzle
array 114 is described in greater detail. The array 114 is for a
four color printhead. Accordingly, the array 114 includes four
groups 170 of nozzle assemblies, one for each color. Each group 170
has its nozzle assemblies 110 arranged in two rows 172 and 174. One
of the groups 170 is shown in greater detail in FIG. 23 of the
drawings.
[0085] To facilitate close packing of the nozzle assemblies 110 in
the rows 172 and 174, the nozzle assemblies 110 in the row 174 are
offset or staggered with respect to the nozzle assemblies 110 in
the row 172. Also, the nozzle assemblies 110 in the row 172 are
spaced apart sufficiently far from each other to enable the lever
arms 126 of the nozzle assemblies 110 in the row 174 to pass
between adjacent nozzles 122 of the assemblies 110 in the row 172.
It is to be noted that each nozzle assembly 110 is substantially
dumbbell shaped so that the nozzles 122 in the row 172 nest between
the nozzles 122 and the actuators 128 of adjacent nozzle assemblies
110 in the row 174.
[0086] Further, to facilitate close packing of the nozzles 122 in
the rows 172 and 174, each nozzle 122 is substantially hexagonally
shaped.
[0087] It will be appreciated by those skilled in the art that,
when the nozzles 122 are displaced towards the substrate 116, in
use, due to the nozzle opening 124 being at a slight angle with
respect to the nozzle chamber 134 ink is ejected slightly off the
perpendicular. It is an advantage of the arrangement shown in FIGS.
22 and 23 of the drawings that the actuators 128 of the nozzle
assemblies 110 in the rows 172 and 174 extend in the same direction
to one side of the rows 172 and 174. Hence, the ink droplets
ejected from the nozzles 122 in the row 172 and the ink droplets
ejected from the nozzles 122 in the row 174 are parallel to one
another resulting in an improved print quality.
[0088] Also, as shown in FIG. 22 of the drawings, the substrate 116
has bond pads 176 arranged thereon which provide the electrical
connections, via the pads 156, to the actuators 128 of the nozzle
assemblies 110. These electrical connections are formed via the
CMOS layer (not shown).
[0089] Referring to FIG. 24 of the drawings, a development of the
invention is shown. With reference to the previous drawings, like
reference numerals refer to like parts, unless otherwise
specified.
[0090] In this development, a nozzle guard 180 is mounted on the
substrate 116 of the array 114. The nozzle guard 180 includes a
body member 182 having a plurality of passages 184 defined
therethrough. The passages 184 are in register with the nozzle
openings 124 of the nozzle assemblies 110 of the array 114 such
that, when ink is ejected from any one of the nozzle openings 124,
the ink passes through the associated passage 184 before striking
the print media.
[0091] The body member 182 is mounted in spaced relationship
relative to the nozzle assemblies 110 by limbs or struts 186. One
of the struts 186 has air inlet openings 188 defined therein.
[0092] In use, when the array 114 is in operation, air is charged
through the inlet openings 188 to be forced through the passages
184 together with ink travelling through the passages 184.
[0093] The ink is not entrained in the air as the air is charged
through the passages 184 at a different velocity from that of the
ink droplets 164. For example, the ink droplets 164 are ejected
from the nozzles 122 at a velocity of approximately 3 m/s. The air
is charged through the passages 184 at a velocity of approximately
1 m/s.
[0094] The purpose of the air is to maintain the passages 184 clear
of foreign particles. A danger exists that these foreign particles,
such as dust particles, could fall onto the nozzle assemblies 110
adversely affecting their operation. With the provision of the air
inlet openings 88 in the nozzle guard 180 this problem is, to a
large extent, obviated.
[0095] Referring now to FIGS. 25 to 27 of the drawings, a process
for manufacturing the nozzle assemblies 110 is described.
[0096] Starting with the silicon substrate or wafer 116, the
dielectric layer 118 is deposited on a surface of the wafer 116.
The dielectric layer 118 is in the form of approximately 1.5
microns of CVD oxide. Resist is spun on to the layer 118 and the
layer 118 is exposed to mask 200 and is subsequently developed.
[0097] After being developed, the layer 118 is plasma etched down
to the silicon layer 116. The resist is then stripped and the layer
118 is cleaned. This step defines the ink inlet aperture 142.
[0098] In FIG. 25b of the drawings, approximately 0.8 microns of
aluminum 202 is deposited on the layer 118. Resist is spun on and
the aluminum 202 is exposed to mask 204 and developed. The aluminum
202 is plasma etched down to the oxide layer 118, the resist is
stripped and the device is cleaned. This step provides the bond
pads and interconnects to the ink jet actuator 128. This
interconnect is to an NMOS drive transistor and a power plane with
connections made in the CMOS layer (not shown).
[0099] Approximately 0.5 microns of PECVD nitride is deposited as
the CMOS passivation layer 120. Resist is spun on and the layer 120
is exposed to mask 206 whereafter it is developed. After
development, the nitride is plasma etched down to the aluminum
layer 202 and the silicon layer 116 in the region of the inlet
aperture 142. The resist is stripped and the device cleaned.
[0100] A layer 208 of a sacrificial material is spun on to the
layer 120. The layer 208 is 6 microns of photo-sensitive polyimide
or approximately 4 .mu.m of high temperature resist. The layer 208
is softbaked and is then exposed to mask 210 whereafter it is
developed. The layer 208 is then hardbaked at 400.degree. C. for
one hour where the layer 208 is comprised of polyimide or at
greater than 300.degree. C. where the layer 208 is high temperature
resist. It is to be noted in the drawings that the
pattern-dependent distortion of the polyimide layer 208 caused by
shrinkage is taken into account in the design of the mask 210.
[0101] In the next step, shown in FIG. 25e of the drawings, a
second sacrificial layer 212 is applied. The layer 212 is either 2
.mu.m of photo-sensitive polyimide which is spun on or
approximately 1.3 .mu.m of high temperature resist. The layer 212
is softbaked and exposed to mask 214. After exposure to the mask
214, the layer 212 is developed. In the case of the layer 212 being
polyimide, the layer 212 is hardbaked at 400.degree. C. for
approximately one hour. Where the layer 212 is resist, it is
hardbaked at greater than 300.degree. C. for approximately one
hour.
[0102] A 0.2 micron multi-layer metal layer 216 is then deposited.
Part of this layer 216 forms the passive beam 160 of the actuator
128.
[0103] The layer 216 is formed by sputtering 1,000 .ANG. of
titanium nitride (TiN) at around 300.degree. C. followed by
sputtering 50 .ANG. of tantalum nitride (TaN). A further 1,000
.ANG. of TiN is sputtered on followed by 50 .ANG. of TaN and a
further 1,000 .ANG. of TiN.
[0104] Other materials which can be used instead of TiN are
TiB.sub.2, MoSi.sub.2 or (Ti, Al)N.
[0105] The layer 216 is then exposed to mask 218, developed and
plasma etched down to the layer 212 whereafter resist, applied for
the layer 216, is wet stripped taking care not to remove the cured
layers 208 or 212.
[0106] A third sacrificial layer 220 is applied by spinning on 4
.mu.m of photo-sensitive polyimide or approximately 2.6 .mu.m high
temperature resist. The layer 220 is softbaked whereafter it is
exposed to mask 222. The exposed layer is then developed followed
by hardbaking. In the case of polyimide, the layer 220 is hardbaked
at 400.degree. C. for approximately one hour or at greater than
300.degree. C. where the layer 220 comprises resist.
[0107] A second multi-layer metal layer 224 is applied to the layer
220. The constituents of the layer 224 are the same as the layer
216 and are applied in the same manner. It will be appreciated that
both layers 216 and 224 are electrically conductive layers.
[0108] The layer 224 is exposed to mask 226 and is then developed.
The layer 224 is plasma etched down to the polyimide or resist
layer 220 whereafter resist applied for the layer 224 is wet
stripped taking care not to remove the cured layers 208, 212 or
220. It will be noted that the remaining part of the layer 224
defines the active beam 158 of the actuator 128.
[0109] A fourth sacrificial layer 228 is applied by spinning on 4
.mu.m of photo-sensitive polyimide or approximately 2.6 .mu.m of
high temperature resist. The layer 228 is softbaked, exposed to the
mask 230 and is then developed to leave the island portions as
shown in FIG. 9k of the drawings. The remaining portions of the
layer 228 are hardbaked at 400.degree. C. for approximately one
hour in the case of polyimide or at greater than 300.degree. C. for
resist.
[0110] As shown in FIG. 251 of the drawing a high Young's modulus
dielectric layer 232 is deposited. The layer 232 is constituted by
approximately 1 .mu.m of silicon nitride or aluminum oxide. The
layer 232 is deposited at a temperature below the hardbaked
temperature of the sacrificial layers 208, 212, 220, 228. The
primary characteristics required for this dielectric layer 232 are
a high elastic modulus, chemical inertness and good adhesion to
TiN.
[0111] A fifth sacrificial layer 234 is applied by spinning on 2
.mu.m of photo-sensitive polyimide or approximately 1.3 .mu.m of
high temperature resist. The layer 234 is softbaked, exposed to
mask 236 and developed. The remaining portion of the layer 234 is
then hardbaked at 400.degree. C. for one hour in the case of the
polyimide or at greater than 300.degree. C. for the resist.
[0112] The dielectric layer 232 is plasma etched down to the
sacrificial layer 228 taking care not to remove any of the
sacrificial layer 234.
[0113] This step defines the nozzle opening 124, the lever arm 126
and the anchor 154 of the nozzle assembly 110.
[0114] A high Young's modulus dielectric layer 238 is deposited.
This layer 238 is formed by depositing 0.2 .mu.m of silicon nitride
or aluminum nitride at a temperature below the hardbaked
temperature of the sacrificial layers 208, 212, 220 and 228.
[0115] Then, as shown in FIG. 25p of the drawings, the layer 238 is
anisotropically plasma etched to a depth of 0.35 microns. This etch
is intended to clear the dielectric from all of the surface except
the side walls of the dielectric layer 232 and the sacrificial
layer 234. This step creates the nozzle rim 136 around the nozzle
opening 124 which "pins" the meniscus of ink, as described
above.
[0116] An ultraviolet (UV) release tape 240 is applied. 4 .mu.m of
resist is spun on to a rear of the silicon wafer 116. The wafer 116
is exposed to mask 242 to back etch the wafer 116 to define the ink
inlet channel 148. The resist is then stripped from the wafer
116.
[0117] A further UV release tape (not shown) is applied to a rear
of the wafer 16 and the tape 240 is removed. The sacrificial layers
208, 212, 220, 228 and 234 are stripped in oxygen plasma to provide
the final nozzle assembly 110 as shown in FIGS. 25r and 26r of the
drawings. For ease of reference, the reference numerals illustrated
in these two drawings are the same as those in FIG. 18 of the
drawings to indicate the relevant parts of the nozzle assembly 110.
FIGS. 28 and 29 show the operation of the nozzle assembly 110,
manufactured in accordance with the process described above with
reference to FIGS. 25 and 26, and these figures correspond to FIGS.
19 to 21 of the drawings.
[0118] The presently disclosed ink jet printing technology 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.
[0119] It would be appreciated by a person skilled in the art 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 restrictive.
* * * * *