U.S. patent application number 13/786235 was filed with the patent office on 2014-09-11 for thermally stable oleophobic anti-wetting coating for inkjet printhead face.
This patent application is currently assigned to XEROX CORPORATION. The applicant listed for this patent is XEROX CORPORATION. Invention is credited to Santokh S. Badesha, David J. Gervasi, Peter M. Gulvin, Mandakini Kanungo, Varun Sambhy.
Application Number | 20140255610 13/786235 |
Document ID | / |
Family ID | 51385740 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140255610 |
Kind Code |
A1 |
Sambhy; Varun ; et
al. |
September 11, 2014 |
THERMALLY STABLE OLEOPHOBIC ANTI-WETTING COATING FOR INKJET
PRINTHEAD FACE
Abstract
A coating for an ink jet printhead front face, wherein the
coating comprises an oleophobic anti-wetting coating having high
thermal stability and maintaining good contact and sliding angle
performance. In particular, the coating comprises fluorinated
silicone.
Inventors: |
Sambhy; Varun; (Penfield,
NY) ; Badesha; Santokh S.; (Pittsford, NY) ;
Kanungo; Mandakini; (Penfield, NY) ; Gulvin; Peter
M.; (Webster, NY) ; Gervasi; David J.;
(Pittsford, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
Norwalk |
CT |
US |
|
|
Assignee: |
XEROX CORPORATION
NORWALK
CT
|
Family ID: |
51385740 |
Appl. No.: |
13/786235 |
Filed: |
March 5, 2013 |
Current U.S.
Class: |
427/387 ;
524/588 |
Current CPC
Class: |
C08G 77/24 20130101;
C09D 183/08 20130101 |
Class at
Publication: |
427/387 ;
524/588 |
International
Class: |
C09D 183/08 20060101
C09D183/08 |
Claims
1. A coating for an ink jet printhead front face, wherein the
coating comprises: a crosslinked dimethyl methyltrifluoropropyl
siloxane polymer further comprising a methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker having the
general formula ##STR00005## wherein each x and y is independently
an integer from about 1 to about 100, wherein the coating has high
thermal stability as indicated by less than about 15 percent weight
loss when heated to up to a temperature of 290.degree. C. at a
pressure of up to 350 psi.
2. (canceled)
3. The coating of claim 1, wherein a drop of ultra-violet (UV) gel
ink or a drop of solid ink exhibits a contact angle of greater than
about 40.degree..
4. The coating of claim 1, wherein the coating has a sliding angle
of less than about 30.degree..
5. The coating of claim 1, wherein the coating maintains the
contact angle and sliding angle with the drop of ultra-violet (UV)
gel ink or the drop of solid ink after the coating has been soaked
in molten UV gel ink or solid ink at a temperature of at least
140.degree. C. for a period of at least two days.
6. The coating of claim 1 wherein the coating loses less than 15%
of the total weight of the coating after heating to 300.degree. C.
and for 60 minutes.
7. The coating of claim 1 maintaining a drool pressure of from
about 1.5 to about 8 inches of water.
8. The coating of claim 1, wherein the crosslinked dimethyl
methyltrifluoropropyl siloxane polymer is prepared a reaction
between a vinyl terminated dimethyl methyltrifluoropropyl silioxane
polymer and a methylhydrogen methyltrifluoropropyl siloxane polymer
cross-linker in presence of a platinum catalyst.
9. (canceled)
10. (canceled)
11. (canceled)
12. The coating of claim 1, wherein the crosslinked fluorosilicone
polymer is present in an amount of from about 10 to about 100
percent by weight of the total weight of the cured coating.
13. The coating of claim 1, wherein the crosslinked fluorosilicone
polymer is formed from a hydrosilylation reaction of a polymer
containing vinyl groups and a crosslinking agent containing Si--H
groups.
14. (canceled)
15. The coating of claim 13, wherein the drop of UV gel ink or the
drop of solid ink exhibits a contact angle of greater than about
40.degree. and a sliding angle of less than about 30.degree. with a
surface of the coating.
16. The coating of claim 13 maintaining a drool pressure of from
about 1.5 to about 8 inches of water.
17. A process of forming an oleophobic anti-wetting coating for an
ink jet printhead front face, comprising: coating a reactant
mixture comprising a polymer containing vinyl groups and a
crosslinking agent containing Si--H groups onto a substrate;
subjecting the coated reactant mixture to a curing treatment at a
first temperature, wherein the polymer is a vinyl terminated
dimethyl methyltrifluoropropyl silioxane polymer having the
structure ##STR00006## wherein n is between 30 and 100 and m is
between 1 and 10.
18. (canceled)
19. The process of claim 17, wherein the crosslinking agent is
methylhydrogen methyltrifluoropropyl siloxane polymer cross-linker
having the structure ##STR00007## wherein x is between 1 and 5 and
y is between 1 and 10.
20. The process of claim 17, wherein the polymer containing vinyl
groups and a crosslinking agent containing Si--H groups are reacted
in a weight ratio of from about 20:1 to about 5:1.
21. A coating for an ink jet printhead front face, wherein the
coating comprises: a crosslinked dimethyl methyltrifluoropropyl
siloxane polymer being a vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer having the structure
##STR00008## wherein n is between 30 and 100 and m is between 1 and
10, wherein the coating has high thermal stability as indicated by
less than about 15 percent weight loss when heated to up to a
temperature of 290.degree. C. at a pressure of up to 350 psi.
22. The coating of claim 21, wherein the weight ratio between the
vinyl terminated dimethyl methyltrifluoropropyl silioxane polymer
and the methylhydrogen methyltrifluoropropyl siloxane polymer
cross-linker is from about 100:1 to about 20:1
Description
BACKGROUND
[0001] Inkjet printers produce images by jetting or ejecting
droplets of liquid ink from an inkjet printhead onto a recording
substrate (e.g., paper). The printhead typically has a front face
with a nozzle opening defined therein, through which liquid ink is
ejected as droplets onto the recording substrate.
[0002] The front face of an inkjet printhead can become
contaminated by wetting or drooling of ink. Such contamination can
cause or contribute to partial or complete blocking of the nozzle
opening within the front fact of the inkjet printhead, cause under-
or over-sized ink droplets to be ejected from the inkjet printhead,
alter the intended trajectory of ejected ink droplets onto the
recording substrate, and the like, all of which degrade the print
quality of inkjet printers.
[0003] The front fact of an inkjet printhead is typically coated
with a material such as polytetrafluoroethylene (PTFE) (e.g.,
Teflon.RTM.) or perfluoroalkoxy (PFA), to protect it. Current
printheads have good initial performance with solid ink, including
those commercially available from Xerox Corporation. However, over
the operational lifetime, the performance degrades and ink does not
readily slide over the printhead front face coatings at typical
ink-ejecting temperatures. Rather, the ink tends to adhere and flow
along the printhead front face coating, leaving a residual ink film
which can partially or completely block the nozzle opening within
the front face of the inkjet printhead. FIG. 1 is a photograph of
the front face of an inkjet printhead after a printing run showing
wetting and contamination of a solid ink over most of the area of
the front face surrounding nozzle openings. Thus, oleophobic
anti-wetting coatings which prevent drooling failure are important
to improve robustness and reliability, provide for new market
penetration for future solid inks.
[0004] Solid inks are those characterized by being solid at room
temperature and molten at an elevated temperature at which the
molten ink is applied to a substrate. Solid inks generally comprise
an ink vehicle, one or more waxes, an optional colorant, and one or
more optional additives such as viscosity modifiers, antioxidant,
plasticizer, and the like. UV curable inks generally comprise a
photoinitiator package, a curable carrier material, an optional
colorant, and one or more optional additives such as viscosity
modifiers, dispersant, synergist, and the like. UV curable phase
change inks, a subset of UV curable inks, may also include a
gellant and optionally a curable wax. The term "curable" refers,
for example, to the component or combination being polymerizable,
that is, a material that may be cured via polymerization,
including, for example, free radical routes, and/or in which
polymerization is photoinitiated though use of a radiation
sensitive photoinitiator. For example, the curable carrier material
may be one or more curable monomers or a curable wax.
[0005] Contamination of an inkjet printhead front face can be
minimized somewhat by adopting purging and/or wiping procedures.
However, these procedures can undesirably consume time and/or use
excessive amounts of ink, thereby decreasing the useful life of the
inkjet printhead. Contamination of an inkjet printhead front face
can also be minimized somewhat by providing an oleophobic
anti-wetting printhead front face coating that does not wet
significantly with ink ejected from nozzle openings of the
printhead. When heated to temperatures typically encountered during
printhead fabrication processes, however, the surface property
characteristics of known oleophobic anti-wetting printhead front
face coatings degrade to the point that they cannot be relied upon
to minimize contamination of the inkjet printhead front face. Hence
a thermally stable oleophobic anti-wetting coating that does not
degrade in surface properties upon exposure to high fabrication
temperatures is needed for printheads.
[0006] Other oleophobic printhead front face coatings found to be
thermally stable comprise siloxyfluorocarbon (SFC) and are
disclosed in U.S. patent application Ser. No. 13/069,304 filed Mar.
22, 2011, U.S. patent application Ser. No. 13/275,255 filed Oct.
17, 2011 and U.S. Patent Publication No. 2012/0044298, which are
hereby incorporated by reference in their entirety. These coatings
show good surface properties, such as high contact angle/low slide
angle, with inks in stacking and ink aging tests even after
exposure to high fabrication temperatures. However, these coatings
may be expensive to manufacture and implement in printheads. Also
the thermal stability of these coatings (as shown by onset of
decomposition temperature in Thermal Gravimetric Analysis (TGA)
scans) only slightly above printhead fabrication temperatures of
290.degree. C., and may lead to less reliability and robustness of
printhead fabrication steps.
[0007] As such, there is desired an alternative to the conventional
print head face plate coatings that are used that would avoid the
problems described above. The advantages of such a coating would be
fewer printhead related defects, longer front face life, and
reduced manufacturing costs for producing the coating. In
particular, a robust and reliable anti-wetting coating for piezo
print heads is especially important for image quality performance
with organic-based inks.
SUMMARY
[0008] According to the embodiments illustrated herein, there is
provided a novel composition for use in printhead assemblies.
[0009] In particular, the present embodiments provide a coating for
an ink jet printhead front face, wherein the coating comprises a
crosslinked dimethyl methyltrifluoropropyl siloxane polymer,
wherein the coating has high thermal stability as indicated by less
than about 15 percent weight loss when heated to up to a
temperature of 290.degree. C. at a pressure of up to 350 psi.
[0010] In further embodiments, there is provided a coating for an
ink jet printhead front face, wherein the coating comprises a
crosslinked dimethyl methyltrifluoropropyl siloxane polymer
comprises repeating units having Formula I
##STR00001##
wherein a is an integer between 10 and 1000; and b is an integer
between 1 and 500, wherein a drop of UV gel ink or a drop of solid
ink exhibits a contact angle of greater than about 40.degree. with
the surface of the coating after the coating has been exposed to a
temperature of up to 290.degree. C. for at least 30 minutes.
[0011] In yet other embodiments, there is provided a process of
forming an oleophobic anti-wetting coating for an ink jet printhead
front face, comprising coating a reactant mixture comprising a
polymer containing vinyl groups and a crosslinking agent containing
Si--H groups onto a substrate; subjecting the coated reactant
mixture to a curing treatment at a first temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a better understanding of the present embodiments,
reference may be had to the accompanying figures.
[0013] FIG. 1 is a photograph showing contamination of a solid ink
over a nozzle area of a printhead having a PTFE coating after a
printing run;
[0014] FIG. 2 is a cross-sectional view of an inkjet printhead
according to the present embodiments;
[0015] FIG. 3 is a schematic of a crosslinked fluorosilicone
polymer produced by a hydrosilyation reaction according to the
present embodiments;
[0016] FIG. 4 is a graph illustrating the thermal stability of a
thermally stable oleophobic anti-wetting coating for the inkjet
printhead according to the present embodiments.
DETAILED DESCRIPTION
[0017] In the following description, it is understood that other
embodiments may be utilized and structural and operational changes
may be made without departure from the scope of the present
embodiments disclosed herein.
[0018] The present embodiments provide a novel composition for use
as a print head face plate coating to avoid many issues faced with
conventional face plates, such as drooling or flooding. In
addition, the novel composition provides a thermally stable
oleophobic anti-wetting coating for the printhead frontface, and
methods for making the same. In embodiments, the coating
composition comprises a cross-linked fluorinated Room Temperature
Vulcanizing (RTV) silicone. The fluorosilicone coatings
demonstrated desirable properties for print head performance. For
example, the TGA profile of these fluorosilicone coatings in air
shows that the coating composition has exceptional thermal
stability (30-300.degree. C. weight loss of only 1%, and onset of
decomposition 316.degree. C.). These coatings retain good surface
properties (both high contact angle and low sliding angle) after
stacking (290.degree. C./350 psi) and soaking in a mixture of Cyan
Magenta Yellow Black (CMYK) inks for two days at 140.degree. C.
conditions as well. Notably, these fluorosilicone coatings showed
very little thickness and mass decrease after exposure to
290.degree. C. Any anti-wetting coating will be exposed to
290.degree. C. during printhead fabrication steps and needs to be
able to withstand these conditions. Moreover, such coatings can be
especially attractive candidates as anti-wetting coatings for piezo
print heads.
[0019] The adhesion of an ink drop towards a surface can be
determined by measuring the sliding angle of the ink drop (i.e.,
the angle at which a surface is inclined relative to a horizontal
position when the ink drop begins to slide over the surface without
leaving residue or stain behind). The lower the sliding angle, the
lower the adhesion between the ink drop and the surface. As used
herein, the term "low adhesion" means a low sliding angle of less
than about 30.degree. when measured with ultra-violet curable gel
ink or solid ink, with the printhead front face surface.
[0020] Embodiments described here include oleophobic anti-wetting
coatings usable for an inkjet printhead front face, wherein the
surface coatings comprise an oleophobic low adhesion polymeric
material. When an inkjet printhead front face surface has such a
coating, jetted drops of ultra-violet (UV) gel ink, referred to
also as "UV ink," or jetted drops of solid ink exhibit low adhesion
towards the surface coating. The adhesion of an ink drop towards a
surface can be determined by measuring the sliding angle of the ink
drop, where the sliding angle is the angle at which a surface is
inclined relative to a horizontal position when the ink drop begins
to slide over the surface without leaving residue or stain behind.
The lower the sliding angle, the lower the adhesion between the ink
drop and the surface.
[0021] In some embodiments, a low sliding angle has a value of less
than about 25.degree., in other embodiments the low sliding angle
has a value of less than about 20.degree., when measured with
ultra-violet curable gel ink or solid ink with the printhead front
face surface as the surface. In yet other embodiments, a low
sliding angle is greater than about 1.degree. when measured with
ultra-violet curable gel ink or solid ink, with the printhead front
face surface as the surface.
[0022] As used here, an oleophobic anti-wetting coating is
"thermally stable" when drops of ultra-violet gel ink or solid ink
exhibit low adhesion towards the surface coating after the surface
coating has been exposed to high temperatures, such as temperatures
in a range between 180.degree. C. and 325.degree. C., or in a range
between about 180.degree. C. and about 325.degree. C., and high
pressures, such as from between about 100 psi and about 400 psi, or
from between about 100 psi and about 400 psi) for extended periods
of time. Extended periods of time may lie in the range between 10
minutes and 2 hours, or in a range between about 10 minutes and
about 2 hours.
[0023] In one embodiment, the surface coating is thermally stable
after the surface coating has been exposed to a temperature of
about 290.degree. C. at a pressure of about 350 psi for about 30
minutes. The surface coating can be bonded to a stainless steel
aperture brace at high temperature and high pressure without any
degradation. Therefore the resulting printhead can prevent ink
contamination because ink droplets can roll off the printhead front
face, leaving behind no residue.
[0024] In some embodiments, a printing apparatus includes an inkjet
printhead having a front face and an oleophobic anti-wetting
coating disposed on a surface of the front face. The oleophobic
anti-wetting coating includes an oleophobic low adhesion polymeric
material configured such that jetted drops of ultra-violet gel ink
or jetted drops of solid ink exhibit a contact angle greater than
or about 40.degree., or greater than or about 45.degree.. In one
embodiment, jetted drops of ultra-violet gel ink or jetted drops of
solid ink exhibit a contact angle greater than or about 55.degree..
In another embodiment, jetted drops of ultra-violet gel ink or
jetted drops of solid ink exhibit a contact angle greater than or
about 65.degree.. In one embodiment, there is no upper limit to the
contact angle exhibited between the jetted drops of ultra-violet
gel ink or jetted drops of solid ink and the surface coating. In
another embodiment, the jetted drops of ultra-violet gel ink or
jetted drops of solid ink exhibit a contact angle less than or
about 150.degree.. In yet another embodiment, the jetted drops of
ultra-violet gel ink or jetted drops of solid ink exhibit a contact
angle less than or about 90.degree..
[0025] When ink is filled into the printhead, it is desired to
maintain the ink within the nozzle until it is time to eject the
ink. Generally, the greater the ink contact angle, the better
(meaning higher) the drool pressure. Drool pressure relates to the
ability of the aperture plate to avoid ink weeping out of the
nozzle opening when the pressure of the ink tank or the reservoir
increases. Maintaining a higher pressure without weeping is
necessary for printhead maintenance and also allows for faster
printing when a print command is given.
[0026] In some embodiments, the coatings are thermally stable and
are able to maintain the desire contact angle and sliding angle as
disclosed herein, even after exposure to high temperatures, such as
temperatures in a range between 180.degree. C. and 325.degree. C.,
or in a range between about 250.degree. C. and about 300.degree.
C., and high pressures, such as pressures in a range between 100
psi and 400 psi, or in a range between about 200 psi and about 350
psi, for extended periods of time, between 10 minutes and 2 hours,
or in a range between about 30 min and about 60 min. This maintains
high drool pressures.
[0027] In one embodiment, the coatings are thermally stable and are
able to maintain the desire contact angle and sliding angle as
disclosed herein, even after exposure to a temperature of about
290.degree. C. at pressures of about 300 psi for about 30 minutes,
allowing maintenance of high drool pressures. Advantageously, the
oleophobic anti-wetting coatings described herein provide, in
combination, low adhesion and high contact angle for ultra-violet
curable gel ink and solid ink, which further provides the benefit
of improved drool pressure or reduced or eliminated weeping of ink
out of the nozzle.
[0028] In one embodiment, the coatings of the present disclosure is
able to maintain the contact angle and sliding angle with a drop of
UV gel ink or a drop of solid ink of greater than about 40.degree.
with the surface of the coating after the coating has been exposed
to a temperature of up to 290.degree. C. for at least 30
minutes.
[0029] In one embodiment, the coatings of the present disclosure is
able to maintain the contact angle and sliding angle with a drop of
UV gel ink or a drop of solid ink of greater than about 40.degree.
and a sliding angle of less than about 30.degree. with a surface of
the coating.
[0030] In one embodiment, the coatings of the present disclosure is
able to maintain the contact angle and sliding angle with a drop of
UV gel ink or a drop of solid ink of greater than about 55.degree.
and a sliding angle of less than about 20.degree. with a surface of
the coating.
[0031] In one embodiment, the coating of the present disclosure is
able to maintain the contact angle and sliding angle with a drop of
UV gel ink or a drop of solid ink after the coating has been soaked
in molten UV gel ink or solid ink at a temperature of at least
140.degree. C. for a period of at least two days.
[0032] In embodiments, the crosslinked dimethyl
methyltrifluoropropyl siloxane polymer comprises repeating units
having Formula I,
##STR00002##
wherein a is an integer between 10 and 10,000; and b is an integer
between 1 and 1,000. In further embodiments, a is an integer
between 10 and 5,000, or an integer between 10 and 1,000. In
further embodiments, b is an integer between 1 and 500.
[0033] In embodiments, the oleophobic anti-wetting coating
comprises a crosslinked fluorosilicone polymer made by
hydrosilylation reaction between a vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer and a methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker.
[0034] In embodiments,the crosslinked fluorosilicone polymer is
present in an amount of from about 10 to about 100 percent, from
about 20 to about 70 percent, or from about 95 to about 100, by
weight of the total weight of the cured coating.
[0035] In embodiments, the vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer has the general formula
##STR00003##
wherein m and n are integers from about 1 to about 300, from about
10 to about 200, or from about 30 to about 100; One specific
example of the vinyl terminated fluorosilicone is CF3510 available
from Nusil Technology LLC.
[0036] In embodiments, the methylhydrogen methyltrifluoropropyl
siloxane polymer cross-linker has the general formula
##STR00004##
wherein m and n are integers from about 1 to about 100, from about
1 to about 30, or from about 30 to about 90. One specific example
of the hydrogen siloxane cross-linker is XL 150 available from
Nusil Technology LLC.
[0037] In embodiments, the crosslinked fluorosilicone polymer is
formed from a hydrosilylation reaction of a polymer containing
vinyl groups and a crosslinking agent containing Si--H groups.
[0038] In some embodiments, the oleophobic anti-wetting coating is
based on platinum-catalyzed addition curing of two components,
namely, vinyl terminated dimethyl methyltrifluoropropyl silioxane
polymer and methylhydrogen methyltrifluoropropyl siloxane polymer
cross-linker, via a hydrosilyation reaction, as shown in FIG.
3.
[0039] In embodiments, the vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer and the methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker, and the
platinum catalystare can be mixed together for a time of from about
1 minute to about 30 minutes, from about 30 minutes to about 180
minutes or from 180 minutes to about 5 hours.
[0040] Generally, the weight ratio of the vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer to the methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker is from about
100:1 to about 1:1, from about 70:1 to about 10:1, or from about
20:1 to about 5:1.
[0041] A platinum catalyst may be added to the reaction mixture to
increase the rate of the hydrosilyation reaction. Examples of the
platinum catalyst include, but are not limited to, chloroplatinic
acid and its derivatives e.g., Speier's catalyst, Karstedt
catalyst, platinum chloride-olefin complexes, platinum
cyclomethylvinylsiloxane, [PtCl2(cyclooctadiene)], and the like. In
embodiments, the catalyst is present in the hydrosilyation reaction
in an amount of from about 0.01 ppm to about 1 ppm, or of from
about 1 ppm to about 100 ppm, or of from about 100 ppm to about
1000 ppm.
[0042] In embodiments, the vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer or the methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker can be diluted
by a solvent, such as, trifluorotoluene, perfluoroalkanes,
perfluorofluoroketones, perfluoroalcohols, fluorinated
tetrahydrofuran, fluorinated ethers, Novec 7200 (3M Chemical
Company), Novec 7500(3M Chemical Company), Novec 7600 (3M Chemical
Company), FC-75 (3M Chemical Company), Asahikilin AK-225 (SPI
Supplies), chloroform, methylene chloride, methyl ethyl ketone,
ethyl acetate, ethers, butyl acetate, acetone, and mixtures
thereof. In embodiments the solvent can be present from about 1 to
about 95 percent, or from about 10 to about 70 percent, or from
about 75 to about 95 percent by weight.
[0043] In embodiments, the coating maintains a drool pressure of
from about 1.5 to about 8 inches of water, or of from about 2 to
about 8 inches of water, or of from about 2 to about 6 inches of
water.
[0044] When coated onto the front face of an inkjet printhead, the
oleophobic anti-wetting surface coating exhibits a sufficiently low
adhesion with respect to the inks that are ejected from the inkjet
printhead such that ink droplets remaining on the oleophobic
anti-wetting coating can slide off the printhead in a simple,
self-cleaning manner. Contaminants such as dust, paper particles,
etc., which are sometimes found on the front face of inkjet
printheads, can be carried away from the inkjet printhead front
face by a sliding ink droplet. The oleophobic anti-wetting
printhead front face coating can provide a self-cleaning,
contamination-free inkjet printhead.
[0045] As used herein, the oleophobic anti-wetting coating can
exhibit a "sufficiently low wettability" with respect to inks that
are ejected from an inkjet printhead when a contact angle between
an ink and the oleophobic anti-wetting coating is, in one
embodiment, greater than about 45.degree. and in another embodiment
greater than about 55.degree..
[0046] The oleophobic anti-wetting coating disclosed herein can be
employed as an oleophobic low adhesion printhead front face coating
for an inkjet printhead of any suitable inkjet printer, such as
continuous inkjet printers, thermal drop-on-demand (DOD) inkjet
printers, and piezoelectric DOD inkjet printers. As used here, the
term "printer" encompasses any apparatus, such as a digital copier,
bookmaking machine, facsimile machine, multi-function machine, and
the like, which performs a print outputting function for any
purpose.
[0047] The oleophobic anti-wetting coating disclosed herein can be
employed as an oleophobic low adhesion printhead front face coating
for an inkjet printhead configured to eject any suitable ink such
as, aqueous inks, solvent inks, UV-curable inks, dye sublimation
inks, solid inks, etc. An exemplary inkjet printhead suitable for
use with the oleophobic anti-wetting coating disclosed herein is
described with respect to FIG. 2.
[0048] A typical inkjet printhead 60 may include a nozzle plate 30
typically bonded to a support brace 25. FIG. 2 shows an embodiment
of a printhead jet stack having an anti-wetting coating 40. In this
embodiment, an oleophobic, anti-wetting coating 40 is bonded to a
nozzle plate 30. The nozzle plate may be a polymer film, such as a
polyimide film, bonded to an aperture support brace 25.
[0049] The support brace 25 is formed of any suitable material such
as stainless steel and include apertures 50 defined therein. The
apertures 50 may communicate with an ink source (not shown). The
nozzle plate 30 may be formed of any suitable material such as
polyimide and include nozzles 55 defined therein. The nozzles 55
may communicate with the ink source via the apertures 50 such that
ink 45 from the ink source is jettable from the printhead 60 onto a
recording substrate through a nozzle 50.
[0050] In the illustrated embodiment, the nozzle plate 30 is bonded
to the support brace 25 by an intervening adhesive material 35. The
adhesive material 35 may be provided as a thermoplastic adhesive
can be melted during a bonding process to bond the nozzle plate 30
to the support brace 25. Typically, the nozzle plate 30 and the
oleophobic anti-wetting coating 40 are also heated during the
bonding process. Depending on the material from which the
thermoplastic adhesive is formed, bonding temperature can be in a
range between 180.degree. C. and 325.degree. C.
[0051] Conventional oleophobic anti-wetting coatings tend to
degrade when exposed to temperatures encountered during typical
bonding processes or other high-temperature, high pressure
processes encountered during fabrication of inkjet printheads.
However, the oleophobic anti-wetting coating 40 disclosed herein
exhibits a sufficiently low adhesion (indicated by low sliding
angles) and high contact angle with respect to an ink after it has
been heated to the bonding temperature. The oleophobic anti-wetting
coating 40 can provide a self-cleaning, contamination-free inkjet
printhead 60 with high drool pressure. The ability of the
oleophobic anti-wetting coating 40 to resist substantial
degradation in desirable surface properties (e.g., including low
sliding angle and high contact angle) upon exposure to elevated
temperatures enables inkjet printheads having self-cleaning
abilities while maintaining high drool pressure, to be fabricated
using high-temperature and high pressure processes.
[0052] In one embodiment, the oleophobic anti-wetting coating may
be formed on the substrate by initially applying the reactant
mixture that, as described above, includes at least a polymer
containing vinyl groups and crosslinking agent containing Si--H
groups. After the reactant mixture is applied to the substrate, the
reactants are reacted together to form the oleophobic anti-wetting
coating. The reactants can be reacted together by, for example,
curing the reactant mixture. In one embodiment, the reactant
mixture is first cured at a temperature of about 160.degree. C. for
about 60 minutes to 4 hours. In another embodiment, the reaction
mixture is cured at room temperature for 24 hours.
[0053] In one embodiment, the reactant mixture may be applied to
the substrate 32 using any suitable method such as die extrusion
coating, dip coating, spray coating, spin coating, flow coating,
stamp printing, and blade techniques. An air atomization device
such as an air brush or an automated air/liquid spray can be used
to spray the reactant mixture. The air atomization device can be
mounted on an automated reciprocator that moves in a uniform
pattern to cover the surface of the substrate 32 with a uniform or
substantially uniform amount of the reactant mixture. The use of a
doctor blade is another technique that can be employed to apply the
reactant mixture. In flow coating, a programmable dispenser is used
to apply the reactant mixture.
[0054] The inks described herein are further illustrated in the
following examples. All parts and percentages are by weight unless
otherwise indicated.
[0055] It will be appreciated that several of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also, various presently unforeseen or unanticipated
alternatives, modifications, variations or improvements therein may
be subsequently made by those skilled in the art, and are also
intended to be encompassed by the following claims.
[0056] While the description above refers to particular
embodiments, it will be understood that many modifications may be
made without departing from the spirit thereof. The accompanying
claims are intended to cover such modifications as would fall
within the true scope and spirit of embodiments herein.
[0057] The presently disclosed embodiments are, therefore, to be
considered in all respects as illustrative and not restrictive, the
scope of embodiments being indicated by the appended claims rather
than the foregoing description. All changes that come within the
meaning of and range of equivalency of the claims are intended to
be embraced therein.
EXAMPLES
[0058] The examples set forth herein below and are illustrative of
different compositions and conditions that can be used in
practicing the present embodiments. All proportions are by weight
unless otherwise indicated. It will be apparent, however, that the
present embodiments can be practiced with many types of
compositions and can have many different uses in accordance with
the disclosure above and as pointed out hereinafter.
Example 1
[0059] Coating 1
[0060] For the evaluation of oleophobic anti-wetting coatings on
potential inkjet printhead front face substrates, coatings were
prepared as follows. In a representative reaction 3.63 g of CF3510
available from Nusil Technology--vinyl terminated dimethyl
methyltrifluoropropyl silioxane polymer and 0.41 g of XL 150
available from Nusil Technology--methylhydrogen
methyltrifluoropropyl siloxane polymer cross-linker) were measured
into a round bottom flask. Then 29 g of ethyl acetate solvent was
added to the flask and the contents were stirred under N.sub.2 at
61.degree. C. for 24 hours. The resulting formulation was coated on
polyimide substrate using a 0.005 mil drawbar coater. The wet films
were cured at 160.degree. C. for 4 hours to yield uniform defect
free anti-wetting coating.
Evaluations
[0061] A TGA decomposition profile in air also confirms the
extremely high thermal stability of these coatings, as shown in
FIG. 4. In a typical Thermogravimetric Analysis (TGA) experiment,
pieces of coating were heated in a furnace and weight loss due to
decomposition was plotted against temperature. A lower weight loss
% indicates higher thermally stable coating. The coatings showed
only 1% weight loss up to 316.degree. C., indicating high thermal
stability in conditions that would be encountered during printhead
fabrication. In another example, the coating was kept in an over at
300.degree. C. for 60 minutes. The coating lost only 3% of it's
weight after 300.degree. C./60 minutes indicating high thermal
stability. Thermal robustness of coating is necessary as it is
exposed to a temperature of from about 200.degree. C. to about
315.degree. C. for about 15 minutes to about 120 minutes during
printhead fabrication process. In summary, the coating of the
present embodiments loses less than 15% of the total weight of the
coating after heating to 300.degree. C. and for 60 minutes.
[0062] Coatings were evaluated for surface property towards solid
ink. Results are given in Table 1 below. These coatings maintained
high contact angle after stacking conditions (290.degree. C./350
psi with Teflon coverlay) which simulate press adhesive bonding
cycles of printhead fabrication. Also stacked coatings maintained
high contact angle after two days/140.degree. C./CYMK ink soak
aging. The coatings displayed low sliding angle indicating low ink
adhesion. Sliding angle of below 30 degree typically indicate that
ink has low adhesion to be cleand from surface without leaving a
residue. Additionally, when test coupons were pulled from ink soak
studies, the ink came cleanly off and no ink residue was observed
on the coatings. This suggests that ink may be wiped of cleanly by
wiper blade during printhead maintenance cycles.
TABLE-US-00001 TABLE 1 TGA weight Coating loss % thickness Surface
property between and CA (Sliding angle 30-300.degree. C. Mass
(.degree.)) range loss after Towards solid ink (Onset of exposure
Stacking Stacking + 2 major to 290.degree. C. 290.degree. C./ day
Inking at Coating decomposition) for 30 min 350 psi/30 min
140.degree. C. Coating 1 1% (316 C.) ~ 3-5% 61 (21) 60 (25)
SUMMARY
[0063] The present embodiments provide novel compositions for the
thermally stable, mechanically robust, oleophobic anti-wetting
coatings and the procedures to prepare the coating. The present
embodiments have been demonstrated to be especially well-suited for
piezo printheads. The anti-wetting coating exhibits the desirable
high ink contact angle and low sliding angle while having excellent
thermal stability. These coating also show very little thickness
and mass loss after 290.degree. C. temperature exposure.
[0064] The claims, as originally presented and as they may be
amended, encompass variations, alternatives, modifications,
improvements, equivalents, and substantial equivalents of the
embodiments and teachings disclosed herein, including those that
are presently unforeseen or unappreciated, and that, for example,
may arise from applicants/patentees and others. Unless specifically
recited in a claim, steps or components of claims should not be
implied or imported from the specification or any other claims as
to any particular order, number, position, size, shape, angle,
color, or material.
[0065] All the patents and applications referred to herein are
hereby specifically, and totally incorporated herein by reference
in their entirety in the instant specification.
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