U.S. patent application number 09/798716 was filed with the patent office on 2002-05-02 for ink jet nozzle assembly including meniscus pinning of a fluidic seal.
Invention is credited to Silverbrook, Kia.
Application Number | 20020051037 09/798716 |
Document ID | / |
Family ID | 27157930 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020051037 |
Kind Code |
A1 |
Silverbrook, Kia |
May 2, 2002 |
Ink jet nozzle assembly including meniscus pinning of a fluidic
seal
Abstract
An ink jet nozzle assembly includes a nozzle chamber having an
inlet receiving fluid from a reservoir and a nozzle through which
ink is ejected. The chamber includes a fixed portion, a movable
portion and a clearance space. Relative movement between the fixed
portion and the movable portion in an ejection phase reduces an
effective volume of the chamber. Alternative relative movement in a
refill phase enlarges the effective volume of the chamber. The
clearance space contains an air-ink interface, surface tension in
ink across a meniscus at the interface forms a fluidic seal between
the chamber and the atmosphere. The clearance space, nozzle and the
ink being dimensioned relative to one another such that ink is
ejected preferentially from the chamber through the nozzle in
droplet form in the ejection phase, and ink is alternately drawn
preferentially into the chamber from the reservoir through the
inlet in the refill phase without the fluidic seal breaking.
Inventors: |
Silverbrook, Kia; (Balmain,
AU) |
Correspondence
Address: |
SILVERBROOK RESEARCH PTY LTD
393 DARLING STREET
BALMAIN
2041
AU
|
Family ID: |
27157930 |
Appl. No.: |
09/798716 |
Filed: |
March 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09798716 |
Mar 2, 2001 |
|
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09112765 |
Jul 10, 1998 |
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6217153 |
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Current U.S.
Class: |
347/54 |
Current CPC
Class: |
B41J 2/1646 20130101;
H04N 1/2112 20130101; B41J 2/14427 20130101; B41J 2/1628 20130101;
B41J 2/1635 20130101; B41J 2/1642 20130101; B41J 2/1645 20130101;
B41J 2/1648 20130101; B41J 3/445 20130101; B41J 2/1631 20130101;
B41J 2/1623 20130101; B41J 2002/14435 20130101; B41J 2002/14346
20130101; B41J 2/1632 20130101; B41J 2/1639 20130101 |
Class at
Publication: |
347/54 |
International
Class: |
B41J 002/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 1998 |
AU |
PO1398 |
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 between two solid surfaces of said assembly that move
relative to one another when the assembly is activated in use, and
wherein at least one of said surfaces has a thin lip adjacent said
fluidic seal to hinder wicking of said ink along said at least one
surface.
2. An assembly according to claim 1 wherein said lip is less than
or equal to about 1 .mu.m thick.
3. An ink jet nozzle assembly including: a nozzle chamber having an
inlet in fluid communication with an ink reservoir and a nozzle in
fluid communication with a surrounding atmosphere; the chamber
including a fixed portion, a movable portion and a clearance space
therebetween, relative movement between the fixed portion and the
movable portion in an ejection phase reducing an effective volume
of the chamber, and alternate relative movement in a refill phase
enlarging the effective volume of the chamber; the clearance space
containing an ink/air interface, surface tension in ink across a
meniscus at the interface forming a fluidic seal between the
chamber and the atmosphere; wherein: the clearance space, the
nozzle and the inlet are dimensioned relative to one another such
that ink is ejected preferentially form the chamber through the
nozzle in droplet form in the ejection phase, and ink is
alternately drawn preferentially into the chamber from the
reservoir through the inlet in the refill phase without said
fluidic seal breaking.
4. An assembly according to claim 3 wherein the chamber
incorporates a rim extending outwardly adjacent at least a portion
of the fluidic seal and is disposed to minimise wicking of ink from
the chamber across the seal.
5. An assembly according to claim 3 wherein the movable portion
includes the nozzle and the fixed portion is mounted on a
substrate.
6. An assembly according to claim 3 wherein the fixed portion
includes the nozzle mounted on a substrate and the movable portion
includes an actuator.
7. An assembly according to claim 3 wherein a largest distance
between the fixed portion and the movable portion across the
clearance space is less than approximately 5 .mu.m.
8. An assembly according to claim 7 wherein said distance is less
than approximately 3 .mu.m.
9. An assembly according to claim 8 wherein said distance is less
than approximately 1 .mu.m.
10. An assembly according to claim 5 wherein said rim extends
substantially around a periphery of the fluidic seal, immediately
adjacent the clearance space.
11. An assembly according to claim 4 wherein a lower section of the
rim includes a ledge portion overhanging a recess adapted to
collect any residual ink wicking across the seal.
12. An assembly according to claim 3 including an outwardly
protruding lip extending around the nozzle to minimise wicking of
ink across an outer surface of the nozzle chamber.
13. An assembly according to claim 3 wherein at least one surface
adjacent the clearance space includes an hydrophobic coating to
enhance performance of the fluidic seal.
14. An assembly according to claim 13 wherein the hydrophobic
coating is formed substantially from polytetrafluoroethylene
(PTFE).
15. An assembly according to claim 3 wherein the ink jet nozzle
assembly is manufactured using micro-electro-mechanical-systems
(MEMS) techniques.
Description
[0001] This is a C-I-P of application Ser. No. 09/112,765 filed on
Jul. 10, 1998.
FIELD OF THE INVENTION
[0002] The field of the invention relates to the field of inkjet
printing devices and in particular, discloses a single bend
actuator cupped paddle inkjet printing device.
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 printing
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 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 Sherr, pages 207-220 (1988).
[0006] Ink Jet printers themselves come in many different types.
The utilisation of a continuous stream 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 electrostatic 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)
[0008] 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.
[0009] 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 disclose ink jet printing techniques 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 electro-thermal actuator are manufactured by
manufacturers such as Canon and Hewlett Packard.
[0010] 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.
[0011] When creating a large number of inkjet nozzles which
together form a printhead, it is necessary or desirable to ensure
that the printhead is of a compact form so as to ensure that the
printhead takes up as small a space as possible. Further, it is
desirable that any construction of a printhead is as simple as
possible and preferably, the number of steps in construction are
extremely low, therefore ensuring simplicity of manufacture.
Further, preferably each ink ejection nozzle is of a standard size
and the ink forces associates with the ejection are regular across
the nozzle.
[0012] Further, where the ink ejection mechanism is of a mechanical
type attached to an actuator device, it is important to ensure that
a substantial clearance is provided between an ink ejection nozzle
and the surface of the paddle. Unless a large clearance is provided
(of the order of 10.quadrature.m in the case of a 40.quadrature.m
nozzle) a number of consequential problems may arise. For example,
if a mechanical paddle ejection surface and nozzle chamber walls
are too close, insufficient ink will be acted on by the paddle
actuator so as to form a drop to be ejected. Further, high
pressures and drag is likely to occur where movement of a paddle
occurs close to nozzle chamber walls. Further, if the paddle is too
close to the nozzle, there is a danger that an unwanted meniscus
shape may occur after ejection of an ink drop with the ink meniscus
surface attaching to the surface of the paddle.
[0013] Further, should the ink ejection mechanism be formed on a
silicon wafer type device utilizing standard wafer processing
techniques, it is desirable to minimize the thickness of any layer
of material when forming the system. Due to differential thermal
expansions, it is desirable to ensure each layer is of minimal
thickness so as to reduce the likelihood of faults occurring during
the fabrication of a printhead system due to thermal stress. Hence,
it is desirable to construct a printhead system utilizing thin
layers in the construction process.
SUMMARY OF THE INVENTION
[0014] 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 between two
solid surfaces of said assembly that move relative to one another
when the assembly is activated in use, and wherein at least one of
said surfaces has a thin lip adjacent said fluidic seal to hinder
wicking of said ink along said at least one surface.
[0015] Preferably said lip is less than or equal to about 1 .mu.m
thick.
[0016] There is further disclosed herein an ink jet nozzle assembly
including:
[0017] a nozzle chamber having an inlet in fluid communication with
an ink reservoir and a nozzle in fluid communication with a
surrounding atmosphere;
[0018] the chamber including a fixed portion, a movable portion and
a clearance space therebetween, relative movement between the fixed
portion and the movable portion in an ejection phase reducing an
effective volume of the chamber, and alternate relative movement in
a refill phase enlarging the effective volume of the chamber;
[0019] the clearance space containing an ink/air interface, surface
tension in ink across a meniscus at the interface forming a fluidic
seal between the chamber and the atmosphere; wherein:
[0020] the clearance space, the nozzle and the inlet are
dimensioned relative to one another such that ink is ejected
preferentially form the chamber through the nozzle in droplet form
in the ejection phase, and ink is alternately drawn preferentially
into the chamber from the reservoir through the inlet in the refill
phase without said fluidic seal breaking.
[0021] Preferably the chamber incorporates a rim extending
outwardly adjacent at least a portion of the fluidic seal and is
disposed to minimise wicking of ink from the chamber across the
seal.
[0022] Preferably the movable portion includes the nozzle and the
fixed portion is mounted on a substrate.
[0023] Preferably the fixed portion includes the nozzle mounted on
a substrate and the movable portion includes an actuator.
[0024] Preferably a largest distance between the fixed portion and
the movable portion across the clearance space is less than
approximately 5 .mu.m.
[0025] Preferably said distance is less than approximately 3
.mu.m.
[0026] Preferably said distance is less than approximately 1
.mu.m.
[0027] Preferably said rim extends substantially around a periphery
of the fluidic seal, immediately adjacent the clearance space.
[0028] Preferably a lower section of the rim includes a ledge
portion overhanging a recess adapted to collect any residual ink
wicking across the seal.
[0029] Preferably an outwardly protruding lip extends around the
nozzle to minimise wicking of ink across an outer surface of the
nozzle chamber.
[0030] Preferably at least one surface adjacent the clearance space
includes an hydrophobic coating to enhance performance of the
fluidic seal.
[0031] Preferably the hydrophobic coating is formed substantially
from polytetrafluoroethylene (PTFE).
[0032] Preferably the ink jet nozzle assembly is manufactured using
micro-electro-mechanical-systems (MEMS) techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] 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:
[0034] FIGS. 1-3 are schematic illustrations of the operational
principles of the preferred embodiment;
[0035] FIG. 4 illustrates a perspective view, partly in section of
a single inkjet nozzle of the preferred embodiment;
[0036] FIG. 5 is a side perspective view of a single ink jet nozzle
of the preferred embodiment;
[0037] FIGS. 6-15 illustrate the various manufacturing processing
steps in the construction of the preferred embodiment;
[0038] FIG. 16 illustrates a portion of an array view of a
printhead having a large number of nozzles, each constructed in
accordance with the principles of the present invention.
[0039] FIG. 17 provides a legend of the materials indicated in
FIGS. 18 to 28;
[0040] FIG. 18 to FIG. 28 illustrate sectional views of the
manufacturing steps in one form of construction of an ink jet
printhead nozzle;
[0041] FIG. 29 shows a three dimensional, schematic view of a
nozzle assembly for an ink jet printhead in accordance with the
invention;
[0042] FIGS. 30 to 32 show a three dimensional, schematic
illustration of an operation of the nozzle assembly of FIG. 29;
[0043] FIG. 33 shows a three dimensional view of a nozzle array
constituting an ink jet printhead;
[0044] FIG. 34 shows, on an enlarged scale, part of the array of
FIG. 33;
[0045] FIG. 35 shows a three dimensional view of an ink jet
printhead including a nozzle guard;
[0046] FIGS. 36a to 36r show three-dimensional views of steps in
the manufacture of a nozzle assembly of an ink jet printhead;
[0047] FIGS. 37a to 37r show sectional side views of the
manufacturing steps;
[0048] FIGS. 38a to 38k show layouts of masks used in various steps
in the manufacturing process;
[0049] FIGS. 39a to 39c show three dimensional views of an
operation of the nozzle assembly manufactured according to the
method of FIGS. 36 and 37; and
[0050] FIGS. 40a to 40c show sectional side views of an operation
of the nozzle assembly manufactured according to the method of
FIGS. 36 and 37.
DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS
[0051] In the preferred embodiment, an inkjet printing system is
provided having an ink ejection nozzle arrangement such that a
paddle actuator type device is utilized to eject ink from a
refillable nozzle chamber. As a result of the construction
processes utilized, the paddle is generally of a "cupped" shape.
The cup shape provides for the alleviation of a number of the
aforementioned problems. The paddle is interconnected to a thermal
actuator device which is thermally actuated by means of passing a
current through a portion of the thermal actuator, so as to cause
the ejection of ink therefrom. Further, the cupped paddle allows
for a suitable construction process which does not require the
formation of thick surface layers during the process of
construction. This means that thermal stresses across a series of
devices constructed on a single wafer are minimized.
[0052] Turning initially to FIGS. 1-3, there will now be explained
the operational principles of the preferred embodiment. In FIG. 1
there is illustrated an inkjet nozzle arrangement 1 having a nozzle
chamber 2 which is normally filled with ink from a supply channel 3
such that a meniscus 4 forms across the ink ejection aperture of
the nozzle arrangement. Inside the nozzle arrangement, a cupped
paddle actuator 5 is provided and interconnected to an actuator arm
6 which, when in a quiescent position, is bent downwards. The lower
surface of the actuator arm 6 includes a heater element 8 which is
constructed of material having a high "bend efficiency".
[0053] Preferably, the heater element has a high bend efficiency
wherein the bend efficiency is defined as: 1 bend efficiency =
Young's Modulus .times. (Coefficient of thermal Expansion) Density
.times. Specific Heat Capacity
[0054] A suitable material can be a copper nickel alloy of 60%
copper and 40% nickel, hereinafter called (cupronickel). which can
be formed below a glass layer so as to bend the glass layer.
[0055] In its quiescent position, the arm 6 is bent down by the
element 8. When it is desired to eject a droplet of ink from the
nozzle chamber 2, a current is passed through the actuator arm 8 by
means of an interconnection provided by a post 9. The heater
element 8 is heated and expands with a high bend efficiency thereby
causing the arm 6 to move upwards as indicated in FIG. 2. The
upward movement of the actuator arm 6 causes the cupped paddle 5 to
also move up which results in a general increase in pressure within
the nozzle chamber 2 in the area surrounding the meniscus 4. This
results in a general outflow of ink and a bulging of the meniscus
4. Next, as indicated in FIG. 3, the heater element 8 is turned off
which results in the general return of the arm 6 to its quiescent
position which further results in a downward movement of the cupped
paddle 5. This results in a general sucking back 11 of the ink
within the nozzle chamber 2. The forward momentum of the ink
surrounding the meniscus and the backward momentum of the ink
results in a general necking of the meniscus and the formation of a
drop 12 which proceeds to the surface of the page. Subsequently,
the shape of the meniscus 4 results in a subsequent inflow of ink
via the inlet channel 3 which results in a refilling of the nozzle
chamber 2. Eventually, the state returns to that indicated by FIG.
1.
[0056] Turning now to FIG. 4, there is illustrated a side
perspective view partly in section of one form of construction, a
single nozzle arrangement 1 in greater detail. The nozzle
arrangement 1 includes a nozzle chamber 2 which is normally filled
with ink. Inside the nozzle chamber 2 is a paddle actuator 5 which
divides the nozzle chamber from an ink refill supply channel 3
which supplies ink from a back surface of a silicon wafer 14.
[0057] Outside of the nozzle chamber 2 is located an actuator arm 6
which includes a glass core portion and an external cupronickel
portion 8. The actuator arm 6 interconnects with the paddle 5 by
means of a slot 19 located in one wall of the nozzle chamber 2. The
slot 19 is of small dimensions such that surface tension
characteristics retain the ink within the nozzle chamber 2.
Preferably, the external portions of the arrangement 1 are further
treated so as to be strongly hydrophobic. Additionally, a pit 21 is
provided around the slot 19. The pit includes a ledge 22 with the
pit and ledge interacting so as to minimize the opportunities for
"wicking" along the actuator arm 6. Further, to assist of
minimizing of wicking, the arm 6 includes a thinned portion 24
adjacent to the nozzle chamber 2 in addition to a right angled wall
25.
[0058] The surface of the paddle actuator 5 includes a slot 12. The
slot 12 aids in allowing for the flow of ink from the back surface
of paddle actuator 5 to a front surface. This is especially the
case when initially the arrangement is filled with air and a liquid
is injected into the refill channel 3. The dimensions of the slot
are such that, during operation of the paddle for ejecting drops,
minimal flow of fluid occurs through the slot 11.
[0059] The paddle actuator 5 is housed within the nozzle chamber
and is actuated so as to eject ink from the nozzle 27 which in turn
includes a rim 28. The rim 28 assists in minimizing wicking across
the top of the nozzle chamber 2.
[0060] The cupronickel element 8 is interconnected through a post
portion 9 to a lower CMOS layer 15 which provides for the
electrical control of the actuator element.
[0061] Each nozzle arrangement 1, can be constructed as part of an
array of nozzles on a silicon wafer device and can be constructed
from the utilizing semiconductor processing techniques in addition
to micro machining and micro fabrication process technology (MEMS)
and a full familiarity with these technologies is hereinafter
assumed.
[0062] For a general introduction to a micro-electro mechanical
system (MEMS) reference is made to standard proceedings in this
field including the proceeding of the SPIE (International Society
for Optical Engineering) including volumes 2642 and 2882 which
contain the proceedings of recent advances and conferences in this
field.
[0063] Turning initially to FIGS. 6a and 6b, in FIG. 6b there is
shown an initial processing step which utilizes a mask having a
region as specified in FIG. 6a. The initial starting material is
preferably a silicon wafer 14 having a standard 0.25 .mu.m CMOS
layer 15 which includes drive electronics (not shown), the
structure of the drive on electronics being readily apparent to
those skilled in the art of CMOS integrated circuit designs.
[0064] The first step in the construction of a single nozzle is to
pattern and etch a pit 28 to a depth of 13 .mu.m using the mask
pattern having regions specified 29 as illustrated in FIG. 6a.
[0065] Next, as illustrated in FIG. 7b, a 3 .mu.m layer of the
sacrificial material 30 is deposited. The sacrificial material can
comprise aluminium. The sacrificial material 30 is then etched
utilizing a mask pattern having portions 31 and 32 as indicated at
FIG. 7a.
[0066] Next, as shown in FIG. 8b a very thin 0.1 .mu.m layer of a
corrosion barrier material (not shown) (for example, silicon
nitride) is deposited and subsequently etched so as to form the
heater element 35. The etch utilizes a third mask having mask
regions specified 36 and 37 in FIG. 8a.
[0067] Next, as shown intended in FIG. 9b, a 1.1 .mu.m layer of
heater material 39 which can comprise a 60% copper 40% nickel alloy
is deposited utilizing a mask having a resultant mask region 40 as
illustrated in FIG. 9a.
[0068] Next a 0.1 .mu.m corrosion layer is deposited over the
surface. The corrosion barrier can again comprise silicon
nitride.
[0069] Next, as illustrated in FIG. 10b, a 3.4 .mu.m layer of glass
42 is deposited. The glass and nitride can then be etched utilizing
a mask as specified 43 in FIG. 10a. The glass layer 42 includes, as
part of the deposition process, a portion 44 which is a result of
the deposition process following the lower surface profile.
[0070] Next, a 6 .mu.m layer of sacrificial material 45 such as
aluminium is deposited as indicated in FIG. 11b. This layer is
planarized to approximately 4 .mu.m minimum thickness utilizing a
Chemical Mechanical Planarization (CMP) process. Next, the
sacrificial material layer is etched utilizing a mask having
regions 48, 49 as illustrated in FIG. 11a so as to form portions of
the nozzle wall and post.
[0071] Next, as illustrated in FIG. 12b, a 3 .mu.m layer of glass
50 is deposited. The 3 .mu.m layer is patterned and etched to a
depth of 1 .mu.m using a mask having a region specified 51 as
illustrated in FIG. 12b so as to form a nozzle rim.
[0072] Next, as illustrated in FIG. 13b the glass layer is etched
utilizing a further mask as illustrated in FIG. 12a which leaves
glass portions e.g. 53 to form the nozzle chamber wall and post
portion 54.
[0073] Next, as illustrated in FIG. 14b the backside of the wafer
is patterned and etched so as to form an ink supply channel 3. The
mask utilized can have regions 56 as specified in FIG. 14a. The
etch through the backside of the wafer can preferably utilize a
high quality deep anisotropic etching system such as that available
from Silicon Technology Systems of the United Kingdom. Preferably,
the etching process also results in the dicing of the wafer into
its separate printheads at the same time.
[0074] Next, as illustrated in FIG. 15, the sacrificial material
can be etched away so as to release the actuator structure. Upon
release, the actuator 6 bends downwards due to its release from
thermal stresses built up during deposition. The printhead can then
be cleaned and mounted in a moulded ink supply system for the
supply of ink to the back surface of the wafer. A TAB film for
suppling electric control to an edge of the printhead can then be
bonded utilizing normal TAB bonding techniques. The surface area
can then be hydrophobically treated and finally the ink supply
channel and nozzle chamber filled with ink for testing.
[0075] Hence, as illustrated in FIG. 16, a pagewidth printhead
having a repetitive structure 60 can be constructed for full color
printing. FIG. 16 shows a portion of the final printhead structure
and includes three separate groupings 61-63 with one grouping for
each color and each grouping e.g. 63 in turn consisting of two
separate rows of inkjet nozzles 65, 66 which are spaced apart in an
interleaved pattern. The nozzle 65, 66 are fired at predetermined
times so as to form an output image as would be readily understood
by those skilled in the art of construction of inkjet printhead.
Each nozzle e.g. 68 includes its own actuator arm 69 which, in
order to form an extremely compact arrangement, is preferably
formed so as to be generally bent with respect to the line
perpendicular to the row of nozzles. Preferably, a three color
arrangement is provided which has one of the groups 61-63 dedicated
to cyan, magenta and another yellow color printing. Obviously, four
color printing arrangements can be constructed if required.
[0076] Preferably, at one side a series of bond pads e.g. 71 are
formed along the side for the insertion of a tape automated bonding
(TAB) strip which can be aligned by means of alignment rail e.g. 72
which is constructed along one edge of the printhead specifically
for this purpose.
[0077] One form of detailed manufacturing process which can be used
to fabricate monolithic ink jet print heads operating in accordance
with the principles taught by the present embodiment can proceed
utilizing the following steps:
[0078] 1. Using a double sided polished wafer 14, complete drive
transistors, data distribution, and timing circuits using a 0.5
micron, one poly, 2 metal CMOS process 15. This step is shown in
FIG. 18. For clarity, these diagrams may not be to scale, and may
not represent a cross section though any single plane of the
nozzle. FIG. 17 is a key to representations of various materials in
these manufacturing diagrams, and those of other cross referenced
ink jet configurations.
[0079] 2. Etch oxide down to silicon or aluminum using Mask 1. This
mask defines the pit underneath the paddle, as well as the edges of
the printheads chip.
[0080] 3. Etch silicon to a depth of 8 microns 80 using etched
oxide as a mask. The sidewall slope of this etch is not critical
(60 to 90 degrees is acceptable), so standard trench etchers can be
used. This step is shown in FIG. 19.
[0081] 4. Deposit 3 microns of sacrificial material 81 (e.g.
aluminum or polyimide)
[0082] 5. Etch the sacrificial layer using Mask 3, defining heater
vias 82 and nozzle chamber walls 83. This step is shown in FIG.
20.
[0083] 6. Deposit 0.2 microns of heater material 84, e.g. TiN.
[0084] 7. Etch the heater material using Mask 3, defining the
heater shape. This step is shown in FIG. 21.
[0085] 8. Wafer probe. All electrical connections are complete at
this point, bond pads are accessible, and the chips are not yet
separated.
[0086] 9. Deposit 3 microns of PECVD glass 85.
[0087] 10. Etch glass layer using Mask 4. This mask defines the
nozzle chamber wall, the paddle, and the actuator arm. This step is
shown in FIG. 22.
[0088] 11. Deposit 6 microns of sacrificial material 86.
[0089] 12. Etch the sacrificial material using Mask 5. This mask
defines the nozzle chamber wall. This step is shown in FIG. 23.
[0090] 13. Deposit 3 microns of PECVD glass 87.
[0091] 14. Etch to a depth of (approx.) 1 micron using Mask 6. This
mask defines the nozzle rim 28. This step is shown in FIG. 24.
[0092] 15. Etch down to the sacrificial layer using Mask 7. This
mask defines the roof of the nozzle chamber, and the nozzle 27
itself. This step is shown in FIG. 25.
[0093] 16. Back-etch completely through the silicon wafer (with,
for example, an ASE Advanced Silicon Etcher from Surface Technology
Systems) using Mask 8. This mask defines the ink inlets 3 which are
etched through the wafer. The wafer is also diced by this etch.
This step is shown in FIG. 26.
[0094] 17. Etch the sacrificial material. The nozzle chambers are
cleared, the actuators freed, and the chips are separated by this
etch. This step is shown in FIG. 27.
[0095] 18. 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.
[0096] 19. 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.
[0097] 20. Hydrophobize the front surface of the printheads.
[0098] 21. Fill the completed printheads with ink 88 and test them.
A filled nozzle is shown in FIG. 28.
[0099] Referring now to FIG. 29 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. 33 and 34) on a silicon substrate 116. The array
114 will be described in greater detail below.
[0100] 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.
[0101] 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.
[0102] As shown in greater detail in FIGS. 30 to 32 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.
30 to 32 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. 30) of a body of ink 140 in the nozzle
chamber 134.
[0103] An ink inlet aperture 142 (shown most clearly in FIG. 34) 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.
[0104] 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.
[0105] 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.
[0106] 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.
[0107] 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).
[0108] 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. 31 of the drawings. This causes an ejection of ink
through the nozzle opening 124 as shown at 162 in FIG. 31 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. 32 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. 32 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. 32 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. 30) is formed
in readiness for the next ink drop ejection from the nozzle
assembly 110.
[0109] Referring now to FIGS. 33 and 34 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. 34 of the
drawings.
[0110] 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.
[0111] Further, to facilitate close packing of the nozzles 122 in
the rows 172 and 174, each nozzle 122 is substantially hexagonally
shaped.
[0112] 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.
33 and 34 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.
[0113] Also, as shown in FIG. 33 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).
[0114] Referring to FIG. 35 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] 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.
[0119] 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.
[0120] Referring now to FIGS. 36 to 38 of the drawings, a process
for manufacturing the nozzle assemblies 110 is described.
[0121] 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.
[0122] 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.
[0123] In FIG. 36b 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).
[0124] 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.
[0125] 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.
[0126] In the next step, shown in FIG. 36e 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 sum 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.
[0127] 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.
[0128] 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.
[0129] Other materials which can be used instead of TiN are
TiB.sub.2, MoSi.sub.2 or (Ti, Al)N.
[0130] 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] 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.
[0135] As shown in FIG. 36l of the drawing a high Young's modulus
dielectric layer 232 is deposited. The layer 232 is constituted by
approximately 1 82 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.
[0136] 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.
[0137] The dielectric layer 232 is plasma etched down to the
sacrificial layer 228 taking care not to remove any of the
sacrificial layer 234.
[0138] This step defines the nozzle opening 124, the lever arm 126
and the anchor 154 of the nozzle assembly 110.
[0139] 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.
[0140] Then, as shown in FIG. 36p 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.
[0141] 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.
[0142] 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. 36r and 37r of the
drawings. For ease of reference, the reference numerals illustrated
in these two drawings are the same as those in FIG. 29 of the
drawings to indicate the relevant parts of the nozzle assembly 110.
FIGS. 39 and 40 show the operation of the nozzle assembly 110,
manufactured in accordance with the process described above with
reference to FIGS. 36 and 37, and these figures correspond to FIGS.
29 to 32 of the drawings.
[0143] 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, portable printers for PDAs, wallpaper printers, indoor
sign printers, billboard printers, fabric printers, camera printers
and fault tolerant commercial printer arrays.
[0144] The fully formed printhead being able to be utilized in a
wide range of printing systems.
[0145] 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 embodiment without departing
from the spirit or scope of the invention as broadly described. The
present embodiment is, therefore, to be considered in all respects
to be illustrative and not restrictive.
* * * * *