U.S. patent application number 11/432685 was filed with the patent office on 2008-01-03 for antireflective coating compositions and methods for depositing such coatings.
This patent application is currently assigned to Yazaki Corporation. Invention is credited to Matthew Emilio Coda, Satyabrata Raychaudhuri, Yongan Yan.
Application Number | 20080003373 11/432685 |
Document ID | / |
Family ID | 36910829 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080003373 |
Kind Code |
A1 |
Yan; Yongan ; et
al. |
January 3, 2008 |
Antireflective coating compositions and methods for depositing such
coatings
Abstract
Coating compositions, and methods for depositing them on the
surface of an article to produce an antireflection coating, are
disclosed. In one embodiment, the coating composition includes a
(meth)acrylate-functional silicon alkoxide, silica particles, a
(meth)acrylate monomer, an epoxy(meth)acrylate oligomer, a
photoinitiator, a solvent, an acid, and water. The relative amounts
of these constituents are controlled such that, when the coating
composition is deposited onto the surface of an article and cured,
it has a refractive index less than about 1.60 at a wavelength of
510 nm. In another embodiment, the coating composition includes an
organo-metallic compound other than an organo-metallic compound of
silicon, an epoxy-functional silicon alkoxide, a
non-epoxy-functional silicon alkoxide, a curing agent compatible
with epoxy-functional molecules, a solvent, an inorganic acid, and
water. The relative amounts of these constituents are controlled
such that, when the coating composition is deposited onto the
surface of an article and cured, it has a refractive index greater
than about 1.70 at a wavelength of 510 nm. The coating compositions
are deposited in a process that produces an antireflection coating
in less than 90 minutes of processing time.
Inventors: |
Yan; Yongan; (Thousand Oaks,
CA) ; Raychaudhuri; Satyabrata; (Thousand Oaks,
CA) ; Coda; Matthew Emilio; (Ventura, CA) |
Correspondence
Address: |
SHEPPARD, MULLIN, RICHTER & HAMPTON LLP
333 SOUTH HOPE STREET
48TH FLOOR
LOS ANGELES
CA
90071-1448
US
|
Assignee: |
Yazaki Corporation
|
Family ID: |
36910829 |
Appl. No.: |
11/432685 |
Filed: |
May 10, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60680079 |
May 11, 2005 |
|
|
|
60701545 |
Jul 22, 2005 |
|
|
|
Current U.S.
Class: |
427/444 ;
106/287.1; 106/287.16 |
Current CPC
Class: |
C08F 290/064 20130101;
C09D 7/62 20180101; C09D 5/006 20130101; G02B 1/113 20130101; C08K
3/36 20130101; C09D 151/10 20130101; C08F 290/06 20130101; C08F
283/10 20130101; C09D 133/06 20130101; Y10S 977/773 20130101; C09D
151/10 20130101; C08L 2666/02 20130101 |
Class at
Publication: |
427/444 ;
106/287.1; 106/287.16 |
International
Class: |
B05D 3/00 20060101
B05D003/00; C04B 41/50 20060101 C04B041/50; C09D 183/04 20060101
C09D183/04 |
Claims
1. A coating process comprising the steps of: forming an
antireflection coating on a surface of an article, wherein the step
of forming includes a step of depositing a first coating layer onto
the surface of the article by using a first coating composition
that comprises at least one (meth)acrylate-functional silicon
alkoxide, silica particles, at least one (meth)acrylate monomer, at
least one epoxy (meth)acrylate oligomer, at least one
photoinitiator, at least one solvent, at least one acid, and water,
wherein the step of depositing the first coating layer includes
dispensing the first coating composition onto the surface of the
article, and curing the dispensed first coating composition, to
produce the first coating layer, wherein the first coating layer
has a refractive index less than about 1.60 at a wavelength of 510
nm; wherein the step of forming an antireflection coating has a
time duration of less than 90 minutes, and wherein the
antireflection coating has prescribed optical properties and
prescribed adhesion and abrasion resistance properties.
2. A coating process as defined in claim 1, wherein the step of
forming has a time duration of less than 30 minutes.
3. A coating process as defined in claim 1, wherein the step of
forming has a time duration of less than 10 minutes.
4. A coating process as defined in claim 1, wherein the first
coating layer deposited in the step of depositing has a refractive
index less than about 1.55 at a wavelength of 510 nm.
5. A coating process as defined in claim 1, wherein the first
coating layer deposited in the step of depositing has a refractive
index less than about 1.50 at a wavelength of 510 nm.
6. A coating process as defined in claim 1, wherein: the step of
forming further includes a step of depositing a second coating
layer onto the surface of the article by using a second coating
composition that comprises at least one organo-metallic compound
other than an organo-metallic compound of silicon, at least one
epoxy-functional silicon alkoxide, at least one
non-epoxy-functional silicon alkoxide, at least one curing agent
compatible with epoxy-functional molecules, at least one solvent,
at least one inorganic acid, and water, wherein the step of
depositing the second coating layer includes dispensing the second
coating composition onto the surface of the article, and curing the
dispensed second coating composition, to produce the second coating
layer, wherein the second coating layer has a refractive index
greater than about 1.70 at a wavelength of 510 nm.
7. A coating process as defined in claim 6, wherein the second
coating layer has a refractive index greater than about 1.80 at a
wavelength of 510 nm.
8. A coating process as defined in claim 6, wherein the second
coating layer has a refractive index greater than about 1.90 at a
wavelength of 510 nm.
9. A coating process as defined in claim 6, wherein the step of
depositing the second coating layer occurs before the step of
depositing the first coating layer.
10. A coating process as defined in claim 6, wherein the step of
depositing the second coating layer alternates with the step of
depositing the first coating layer, to produce an antireflection
coating having at least four layers.
11. A coating process as defined in claim 10, wherein at least one
of the alternating steps of depositing the second coating layer and
depositing the first coating layer includes a step of heat-treating
the dispensed coating composition prior to the step of curing such
dispensed coating composition.
12. A coating process as defined in claim 1, and further comprising
a step of depositing a hard-coat layer onto the surface of the
article prior to the step of forming the antireflection
coating.
13. A coating composition comprising at least one
(meth)acrylate-functional silicon alkoxide, silica particles, at
least one (meth)acrylate monomer, at least one epoxy(meth)acrylate
oligomer, at least one photoinitiator, at least one solvent, at
least one acid, and water; wherein the relative amounts of the
constituents of the coating composition are controlled such that,
when the coating composition is dispensed onto the surface of an
article and cured, it has a refractive index less than about 1.60
at a wavelength of 510 nm.
14. A coating composition as defined in claim 13, wherein the at
least one (meth)acrylate-functional silicon alkoxide is selected
from the group consisting of
(3-acryloxypropyl)dimethylmethoxysilane,
(3-acryloxypropyl)methlyldimethoxysilane,
(3-acryloxypropyl)trimethoxysilane,
(methacryloxymethyl)dimethylethoxysilane,
methacryloxymethyltriethoxysilane,
methacryloxymethyltrimethoxysilane,
methacryloxypropylmethyldiethoxysilane,
methacryloxypropylmethyldimethoxysilane,
(3-methacryloxypropyl)triethoxysilane,
(3-methacryloxypropyl)trimethoxysilane, and mixtures thereof.
15. A coating composition as defined in claim 13, wherein the at
least one (meth)acrylate-functional silicon alkoxide is
(3-acryloxypropyl)trimethoxysilane.
16. A coating composition as defined in claim 13, wherein the at
least one (meth)acrylate monomer is selected from the group
consisting of 2(2-ethoxyethoxy)ethyl acrylate, 2-phenoxyethyl
acrylate, 2-phenoxyethyl methacrylate, caprolactone acrylate,
dicyclopentadienyl methacrylate, tetrahydrofurfuryl acrylate,
tetrahydrofurfuryl methacrylate, 1,3-butylene glycol diacrylate,
1,4 butanediol dimethacrylate, diethylene glycol diacrylate,
ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A
dimethacrylate, ethylene glycol dimethacrylate, ethoxylated
trimethylolpropane triacrylate, pentaeryhritol triacrylate,
propoxylated glyceryl triacrylate, propoxylated trimethylolpropane
triacrylate, trimethylolpropane triacrylate, trimethylolpropane
trimethacrylate, tris(2-hydroxy ethyl) isocyanurate triacrylate,
and mixtures thereof.
17. A coating composition as defined in claim 13, wherein the at
least one (meth)acrylate monomer is selected from the group
consisting of ethoxylated trimethylolpropane triacrylate,
tris(2-hydroxy ethyl) isocyanurate triacrylate, and mixtures
thereof.
18. A coating composition as defined in claim 13, wherein the at
least one (meth)acrylate monomer is a mixture of ethoxylated
trimethylolpropane triacrylate and tris(2-hydroxy ethyl)
isocyanurate triacrylate.
19. A coating composition as defined in claim 13, wherein the at
least one photoinitiator is selected from the group consisting of
1-hydroxy-cyclohexyl-phenyl-ketone,
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone,
and mixtures thereof.
20. A coating composition as defined in claim 13, wherein the at
least one photoinitiator is a mixture of
1-hydroxy-cyclohexyl-phenyl-ketone and
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone.
21. A coating composition as defined in claim 13, wherein the at
least one solvent is selected from the group consisting of
isopropanol, ethyl acetate, 1-methoxy 2-propanol, and mixtures
thereof.
22. A coating composition as defined in claim 13, wherein the at
least one solvent is a mixture of isopropanol, ethyl acetate, and
1-methoxy 2-propanol.
23. A coating composition as defined in claim 13, wherein the at
least one inorganic acid is hydrochloric acid.
24. A coating composition as defined in claim 13, wherein the
relative amounts of the constituents of the coating composition are
controlled such that, when the composition is deposited onto the
surface of an article and cured, it has a refractive index less
than about 1.55 at a wavelength of 510 nm.
25. A coating composition as defined in claim 13, wherein the
relative amounts of the constituents of the coating composition are
controlled such that, when the composition is deposited onto the
surface of an article and cured, it has a refractive index less
than about 1.50 at a wavelength of 510 nm.
26. A coating composition comprising at least one organo-metallic
compound other than an organo-metallic compound of silicon, at
least one epoxy-functional silicon alkoxide, at least one
non-epoxy-functional silicon alkoxide, at least one curing agent
compatible with epoxy-functional molecules, at least one solvent,
at least one inorganic acid, and water; wherein the relative
amounts of the constituents of the coating composition are
controlled such that, when the coating composition is dispensed
onto the surface of an article and cured, it has a refractive index
greater than about 1.70 at a wavelength of 510 nm.
27. A coating composition as defined in claim 26, wherein the at
least one organo-metallic compound is selected from the group
consisting of organo-metallic compounds represented by formulas
R.sup.1.sub.xM.sup.1 (OR.sup.2).sub.4-x,
R.sup.1.sub.yM.sup.2(OR.sup.2).sub.3-y,
R.sup.1.sub.zNb(OR.sup.2).sub.5-z, and mixtures thereof; wherein
M.sup.1 is a metal selected from the group consisting of Ti, Zr,
Ge, and Sn; wherein M.sup.2 is a metal selected from the group
consisting of Al, In, and Sb; wherein R.sup.1 is an organic
functional group selected from the group consisting of
C.sub.1-C.sub.4 alkyl, vinyl, allyl, acryloxy, epoxide, and amino
groups; wherein R.sup.2 is C.sub.1-C.sub.4 alkyl group; and wherein
x is 0, 1, 2, or 3; y is 0, 1, or 2; and z is 0, 1, 2, 3, or 4.
28. A coating composition as defined in claim 26, wherein the at
least one organo-metallic compound is titanium isopropoxide.
29. A coating composition as defined in claim 26, wherein the at
least one epoxy-functional silicon alkoxide is selected from the
group consisting of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
5,6-epoxyhexyltriethoxysilane,
(3-glycidoxypropyl)dimethylethoxysilane,
(3-glycidoxypropyl)methyldiethoxysilane,
glycidoxypropyl)methyldimethoxysilane,
(3-glycidoxypropyl)trimethoxysilane,
glycidoxymethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,
3-cyanopropyltrimethoxysilane, and mixtures thereof.
30. A coating composition as defined in claim 26, wherein the at
least one epoxy-functional silicon alkoxide is
(3-glycidoxypropyl)trimethoxysilane.
31. A coating composition as defined in claim 26, wherein the at
least one non-epoxy-functional silicon alkoxide is represented by a
general formula (OFG).sub.w-Si--(OR.sup.3).sub.4-w, wherein OFG is
an organofunctional group; OR.sup.3 is a hydrolyzable alkoxy group;
R.sup.3 is an alkyl; and w is 0, 1, 2 or 3.
32. A coating composition as defined in claim 26, wherein the at
least one non-epoxy-functional silicon alkoxide is selected from
the group consisting of tetraethoxysilane, tetramethoxysilane, and
mixtures thereof.
33. A coating composition as defined in claim 26, wherein the at
least one non-epoxy-functional silicon alkoxide is a mixture of
tetraethoxysilane and tetramethoxysilane.
34. A coating composition as defined in claim 26, wherein the at
least one curing agent is selected from the group consisting of an
anhydride, a carboxylic acid, and mixtures thereof.
35. A coating composition as defined in claim 26, wherein at least
one curing agent is selected from the group consisting of acetic
anhydride, acrylic anhydride, cyclic anhydride, hexahydrophthalic
anhydride, methacrylic anhydride, propionic anhydride, acetic acid,
acrylic acid, formic acid, fumiaic acid, itaconic acid, maleic
acid, methacrylic acid, propionic acid, methylenesuccinic acid, and
mixtures thereof.
36. A coating composition as defined in claim 26, wherein the at
least one curing agent is hexahydrophthalic anhydride.
37. A coating composition as defined in claim 26, wherein the at
least one curing agent is methylenesuccinic acid.
38. A coating composition as defined in claim 26, wherein the at
least one solvent is selected from the group consisting of ethanol,
1-methoxy 2-propanol, and mixtures thereof.
39. A coating composition as defined in claim 26, wherein the at
least one solvent is a mixture of ethanol and 1-methoxy
2-propanol.
40. A coating composition as defined in claim 26, wherein the at
least one inorganic acid is hydrochloric acid.
41. A coating composition as defined in claim 26, wherein the
relative amounts of the constituents of the coating composition are
controlled such that, when the composition is dispensed onto the
surface of an article and cured, it has a refractive index greater
than about 1.80 at a wavelength of 510 nm.
42. A coating composition as defined in claim 26, wherein the
relative amounts of the constituents of the coating composition are
controlled such that, when the composition is dispensed onto the
surface of an article and cured, it has a refractive index greater
than about 1.90 at a wavelength of 510 nm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Priority is claimed from co-pending U.S. Provisional Patent
Application Ser. No. 60/680,079, filed May 11, 2005, and Ser. No.
60/701,545, filed Jul. 22, 2005, which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to antireflective coating
compositions and to methods for depositing such compositions onto
articles, especially transparent articles.
[0003] Antireflection coatings on transparent articles reduce the
reflectance of visible light from the articles and enhance the
transmission of such light into, or through, the articles. When the
articles are used as cover plates for display instruments, these
coatings enhance the brightness, contrast, and readability of the
displayed information, for a variety of lighting conditions.
Optical articles such as ophthalmic lenses frequently are coated
with antireflective coatings to decrease the level of reflected
light and thereby increase visibility and minimize eye fatigue.
[0004] Although various antireflection coatings have been generally
effective in providing reduced reflectivity over the visible
spectrum, the coatings are not considered to have been entirely
satisfactory for use in many applications. For example, some of the
coatings are highly susceptible to mechanical damage from abrasion
and exhibit poor adhesion to the underlying substrate. Moreover,
some of the processes used for depositing such coatings, including
electron beam deposition, reactive plasma sputtering, and
ion-assisted deposition, are relatively expensive to implement.
[0005] It should, therefore, be appreciated that there is a need
for improved antireflection coating compositions and for an
improved process for depositing such coating compositions onto
articles, especially transparent articles, in a variety of sizes
and configurations, with reduced expense and with reduced
susceptibility to mechanical damage. The present invention fulfills
this need and provides further related advantages.
SUMMARY OF THE INVENTION
[0006] The present invention resides in an improved antireflection
coating compositions and for an improved process for depositing
such coating compositions onto articles, especially transparent
articles, in a variety of sizes and configurations, with reduced
cost and with reduced susceptibility to mechanical damage.
[0007] More particularly, one coating composition in accordance
with the invention comprises at least one (meth)acrylate-functional
silicon alkoxide, silica particles, at least one (meth)acrylate
monomer, at least one epoxy(meth)acrylate oligomer, at least one
photoinitiator, at least one solvent, at least one acid, and water.
The relative amounts of the constituents of the coating composition
are controlled such that, when the coating composition is dispensed
onto the surface of an article and cured, it has a refractive index
less than about 1.60, or more preferably less than about 1.55, or
most preferably less than about 1.50, all at a wavelength of 510
nm.
[0008] In more detailed features of this embodiment of the
invention, the (meth)acrylate-functional silicon alkoxide is
selected from the group consisting of
(3-acryloxypropyl)dimethylmethoxysilane,
(3-acryloxypropyl)methlyldimethoxysilane,
(3-acryloxypropyl)trimethoxysilane,
(methacryloxymethyl)dimethylethoxysilane,
methacryloxymethyltriethoxysilane,
methacryloxymethyltrimethoxysilane,
methacryloxypropylmethyldiethoxysilane,
methacryloxypropylmethyldimethoxysilane,
(3-methacryloxypropyl)triethoxysilane,
(3-methacryloxypropyl)trimethoxysilane, and mixtures thereof.
Further, the (meth)acrylate monomer is selected from the group
consisting of 2(2-ethoxyethoxy)ethyl acrylate, 2-phenoxyethyl
acrylate, 2-phenoxyethyl methacrylate, caprolactone acrylate,
dicyclopentadienyl methacrylate, tetrahydrofurfuryl acrylate,
tetrahydrofurfuryl methacrylate, 1,3-butylene glycol diacrylate,
1,4 butanediol dimethacrylate, diethylene glycol diacrylate,
ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A
dimethacrylate, ethylene glycol dimethacrylate, ethoxylated
trimethylolpropane triacrylate, pentaeryhritol triacrylate,
propoxylated glyceryl triacrylate, propoxylated trimethylolpropane
triacrylate, trimethylolpropane triacrylate, trimethylolpropane
trimethacrylate, tris(2-hydroxy ethyl)isocyanurate triacrylate, and
mixtures thereof.
[0009] In other more detailed features of this embodiment of the
invention, the photoinitiator is selected from the group consisting
of 1-hydroxy-cyclohexyl-phenyl-ketone,
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone,
and mixtures thereof. Further, the solvent is selected from the
group consisting of isopropanol, ethyl acetate, 1-methoxy
2-propanol, and mixtures thereof. The inorganic acid is
hydrochloric acid.
[0010] In an alternative coating composition in accordance with the
invention, the coating composition comprises at least one
organo-metallic compound other than an organo-metallic compound of
silicon, at least one epoxy-functional silicon alkoxide, at least
one non-epoxy-functional silicon alkoxide, at least one curing
agent compatible with epoxy-functional molecules, at least one
solvent, at least one inorganic acid, and water. The relative
amounts of the constituents of this coating composition are
controlled such that, when the coating composition is deposited
onto the surface of an article and cured, it has a refractive index
greater than about 1.70, or more preferably greater than about
1.80, or most preferably greater than about 1.90, all at a
wavelength of 510 nm.
[0011] In more detailed features of this embodiment of the
invention, the organo-metallic compound is selected from the group
consisting of organo-metallic compounds represented by formulas
R.sup.1.sub.xM.sup.1 (OR.sup.2).sub.4-x,
R.sup.1.sub.yM.sup.2(OR.sup.2).sub.3-y,
R.sup.1.sub.zNb(OR.sup.2).sub.5-z, and mixtures thereof; wherein
M.sup.1 is a metal selected from the group consisting of Ti, Zr,
Ge, and Sn; wherein M.sup.2 is a metal selected from the group
consisting of Al, In, and Sb; wherein R.sup.1 is an organic
functional group selected from the group consisting of
C.sub.1-C.sub.4 alkyl, vinyl, allyl, acryloxy, epoxide, and amino
groups; wherein R.sup.2 is C.sub.1-C.sub.4 alkyl group; and wherein
x is 0, 1, 2, or 3; y is 0, 1, or 2; and z is 0, 1, 2, 3, or 4.
[0012] In other, more detailed features of this embodiment of the
invention, the epoxy-functional silicon alkoxide is selected from
the group consisting of
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
5,6-epoxyhexyltriethoxysilane,
(3-glycidoxypropyl)dimethylethoxysilane,
(3-glycidoxypropyl)methyldiethoxysilane,
glycidoxypropyl)methyldimethoxysilane,
(3-glycidoxypropyl)trimethoxysilane,
glycidoxymethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,
3-cyanopropyltrimethoxysilane, and mixtures thereof. Further, the
non-epoxy-functional silicon alkoxide is represented by a general
formula (OFG).sub.w-Si--(OR.sup.3).sub.4-w, wherein OFG is an
organo-functional group; OR.sup.3 is a hydrolyzable alkoxy group;
R.sup.3 is an alkyl; and w is 0, 1, 2 or 3. Preferably, the silicon
alkoxide is selected from the group consisting of
tetraethoxysilane, tetramethoxysilane, and mixtures thereof.
[0013] In yet other more detailed features of the invention, the
curing agent is selected from the group consisting of an anhydride,
a carboxylic acid, and mixtures thereof. Preferably, the curing
agent is selected from the group consisting of acetic anhydride,
acrylic anhydride, cyclic anhydride, hexahydrophthalic anhydride,
methacrylic anhydride, propionic anhydride, acetic acid, acrylic
acid, formic acid, fumaric acid, itaconic acid, maleic acid,
methacrylic acid, propionic acid, methylenesuccinic acid, and
mixtures thereof. Further, the solvent is selected from the group
consisting of ethanol, 1-methoxy 2-propanol, and mixtures thereof.
The inorganic acid preferably is hydrochloric acid.
[0014] The process of the invention includes the steps of providing
a first coating composition that includes at least one
(meth)acrylate-functional silicon alkoxide, silica particles, at
least one (meth)acrylate monomer, at least one epoxy(meth)acrylate
oligomer, at least one photoinitiator, at least one solvent, at
least one acid, and water, and forming an antireflection coating on
a surface of an article using the first coating composition. The
step of forming includes a step of depositing a first coating layer
onto the article's surface, including steps of (1) dispensing the
first coating composition onto the surface, and (2) curing the
dispensed first coating composition, to produce the first coating
layer. Preferably, this first coating layer has a refractive index
less than about 1.60, or more preferably less than about 1.55, or
most preferably less than about 1.50, all at a wavelength of 510
nm. The step of forming an antireflection coating has a preferred
time duration of less than 90 minutes, or more preferably less than
30 minutes, and most preferably less than 10 minutes. The resulting
antireflection coating has prescribed optical properties and
prescribed adhesion and abrasion resistance properties.
[0015] In other more detailed features of the invention, the
process further includes a step of providing a second coating
composition that includes at least one organo-metallic compound
other than an organo-metallic compound of silicon, at least one
epoxy-functional silicon alkoxide, at least one
non-epoxy-functional silicon alkoxide, at least one curing agent
compatible with epoxy-functional molecules, at least one solvent,
at least one inorganic acid, and water. The step of forming further
includes a step of depositing the second coating composition onto
the article's surface, including steps of (1) dispensing the second
coating composition onto the surface, and (2) curing the dispensed
second coating composition, to produce the second coating layer.
Preferably this second coating layer has a refractive index greater
than about 1.70, or more preferably greater than about 1.80, or
most preferably greater than about 1.90, all at a wavelength of 510
nm.
[0016] In one preferred embodiment, the AR coating includes
multiple layers, alternating between the second coating layer and
the first coating layer. When forming such an AR coating, the step
of depositing the second coating layer alternates with the step of
depositing the first coating layer, with the former step occurring
first, such that the lowest coating layer comprises the second
coating composition. In addition, at least one of the alternating
steps of depositing the second coating layer and depositing the
first coating layer can include a step of heat-treating the
dispensed coating composition prior to the step of curing such
dispensed coating composition.
[0017] Further, the coating process can further include a step of
depositing a hard-coat layer onto the surface of the article prior
to forming the antireflection coating.
[0018] Other features and advantages of the present invention
should become apparent from the following description of the
preferred embodiments and methods, taken in conjunction with the
accompanying drawings, which illustrate, by way of example, the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic cross-sectional view of a five-layer
antireflective (AR) coating deposited onto one surface of a
polycarbonate (PC) lens, as described in Example 12, below. The
hydrophobic coating layer of that Example is not shown.
[0020] FIG. 2 is a graph depicting the reflectance of a PC lens,
with the five-layer AR coating of Example 12 deposited onto both
its convex surface and its concave surface, and without such
coating, as a function of wavelength.
[0021] FIG. 3 is a graph depicting the reflectance of a PC lens,
with the four-layer AR coating of Example 13 deposited onto both
its convex surface and its concave surface, and without such
coating, as a function of wavelength.
[0022] FIG. 4 is a graph depicting the reflectance of a PC lens,
with the five-layer AR coating of Example 15 deposited onto both
its convex surface and its concave surface, and without such
coating, as a function of wavelength.
[0023] FIG. 5 is a schematic cross-sectional view of a four-layer
AR coating and a hard-coat deposited onto one surface of a
polymethylmethacrylate (PMMA) panel, as described in Example 16,
below.
[0024] FIG. 6 is a graph depicting the reflectance of a PMMA panel,
with the four-layer AR coating of Example 16 deposited onto both of
its surfaces, and without such coating, as a function of
wavelength.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND METHODS
[0025] This invention relates generally to antireflective (AR)
coating compositions that can be deposited onto transparent
articles within a very short processing time. The invention also
relates to processes for depositing such AR coating compositions
onto such transparent articles. The AR coatings deposited using
these coating compositions and processes have good mechanical
properties, i.e., good adherence, good hardness, and improved
abrasion resistance.
[0026] Transparent optical articles such as lenses, prisms, optical
windows, photomask substrates, pellicles used in photomask
assemblies, and the like may be coated with the coatings of the
invention, to provide antireflective properties. The transparent
articles also comprise cover plates of display devices such as
field emission displays, liquid crystal displays (LCDs), plasma
display panels (PDPs), electroluminescence displays (ELDs), cathode
ray tube displays (CRTs), fluorescence tube displays, meters,
clocks, and the like, used in the manufacture of televisions,
personal digital assistants (PDAs), cellular phones, vehicle
dashboards, projection screens, hand-held games, and the like.
[0027] The articles being coated may be of any shape, including
simple rectangular and flat shapes as well as complicated shapes
having curvatures and bends. The articles may comprise polymers,
glasses, ceramics, or hybrids of these materials. Polymeric
articles may comprise poly(methyl methacrylate) (PMMA),
polycarbonate (PC), poly(ethylene terephthalate) (PET),
polystyrene, poly(diethylene glycol-bis-allyl carbonate) (ADC) or
CR-39', triacetyl cellulose (TAC), poly(ethylene-2,6-naphthalate)
(PEN), or the like.
[0028] The AR coating is deposited onto at least one surface of
such articles using the coating compositions of this invention,
which are prepared using a liquid-based process. The deposition of
these compositions produces AR coating layers having higher
refractive indices (i.e., higher than 1.70, 1.80, or 1.90 at a
wavelength of about 510 nm) and lower refractive indices (i.e.,
lower than 1.60, 1.55, or 1.50 at a wavelength of about 510 nm),
each layer having a prescribed thickness in the range of 10 to 200
nm.
[0029] The AR coating comprises at least one AR layer. If the AR
coating includes just one layer, that layer is deposited using a
coating composition having a refractive index lower than that of
the article. On the other hand, if the AR coating includes multiple
layers, those layers may alternate between a layer having a
refractive index higher than 1.70, 1.80, or 1.90, at a wavelength
of about 510 nm, and a layer having a refractive index lower than
1.60, 1.55, or 1.50, at that same wavelength of about 510 nm.
[0030] Principles of providing coatings having antireflective
properties are described in a publication entitled "Antireflection
Coatings Made by Sol-Gel Processes," Solar Energy Materials and
Solar Cells, Volume 68 (2001), pages 313 to 336, by Dinguo Chen.
Two basic approaches to achieve low reflection are described. In
one approach, the surface of the antireflective layer is roughened
by etching, grinding, embossing, or like, or by incorporating
particles into the transparent matrix. This provides haze, or
diffuse reflection, and thereby reduces the reflection level.
Coatings obtained by this approach are commonly referred as
antiglare coatings. In the other approach, the refractive indices
and thicknesses of a series of coating layers are controlled to
provide destructive interference of the light reflected at the
interfaces between the successive layers and the article.
[0031] Antiglare coatings prepared by etching, grinding, embossing,
or like, generally have lower mechanical strength and abrasion
resistance than do antiglare coatings prepared by incorporating
particles into the coating matrix. The antiglare approach is
advantageous, because the reflection levels of such coatings are
less dependent on the wavelength of the incident light and because
the control of the thicknesses and refractive indices of the
coating's layers is relatively less critical.
[0032] On the other hand, the destructive interference approach
provides clearer coatings, with comparatively lower antireflection
levels. However, the reflection level of such coatings is more
dependent on the wavelength of the incident light. Although the
effect of this wavelength dependence may be decreased by having
multiple destructive interference layers, the manufacturing cost of
the coating increases with each additional layer. Furthermore, the
control of the thicknesses and refractive indices is relatively
more critical for the destructive interference type AR
coatings.
[0033] Thus, both approaches have relative advantages and
disadvantages. The choice between the two approaches depends on
desired antireflective property level and cost requirements of a
specific application. Both approaches, and a combination of the
approaches, are within the scope of this invention.
[0034] In one embodiment of the invention, the transparent articles
may also incorporate a hard-coat. This hard-coat is deposited onto
at least one surface of the article, before the AR coating is
deposited. The hard-coat layer is incorporated into the coating to
provide abrasion resistance not only for the article, but also for
the AR coating itself. Deposition of the hard-coat layer is carried
out using a suitable liquid hard-coat formulation. In general,
there are two types of liquid formulations: thermally curable and
radiation-energy-curable, particularly ultraviolet (UV)-curable
formulations. Both types of hard-coat formulations are within the
scope of this invention. The thermally curable formulations may
provide better abrasion resistance than do the UV-curable
formulations. However, the UV-curable formulations may be cured at
comparatively faster rates, thereby decreasing production costs.
The type of hard-coat formulation suitable for this invention may
be decided by considering abrasion resistance and production cost
requirements of a particular article.
[0035] In addition to the abrasion-resistance requirement, the
hard-coat layer may have a refractive index closely matching that
of the underlying article, to prevent the formation of interference
fringes. Further, the thickness of the hard-coat layer may be in
the range of 1 to 10 micrometers, or more preferably in the range
of 2 to 6 micrometers, to provide the described abrasion
resistance. If the thickness is less than 1 micrometer, the
hard-coat layer might not provide an abrasion resistance level
within the scope of this invention. On the other hand, if the
thickness is more than 10 micrometers, the deposition of the
hard-coat layer may result in formation of cracks, surface
non-uniformities, or the entrapment of bubbles, leading to
degradation of the coating's mechanical and optical properties.
[0036] The preparation and deposition of a variety of hard-coat
formulations providing abrasion resistance and refractive index
levels suitable for the AR coatings of this invention are well
described in the prior art. A few examples of such hard-coat
formulations are described in U.S. Pat. No. 4,478,876 to Chung;
U.S. Pat. No. 5,493,583 to Lake; and U.S. Pat. No. 6,001,163 to
Havey et al. Such formulations are commercially available from SDC
Corporation, of Anaheim, Calif., or Red Spot Corporation, of
Evansville, Ind. Commercial UV-curable formulations sold under
trademark MP1175UV by SDC Corporation and under the trademark
UVB510R6 by Red Spot Corporation, and a commercial thermally
curable formulation sold under trademark MP1154D by SDC
Corporation, may be used for depositing the hard-coat layer of the
present invention. Hard-coat deposition and curing techniques and
conditions described in the prior art, as well as in application
sheets of the commercial formulations, may be applied to provide
the hard-coat layer of this invention.
[0037] Before the deposition of the hard-coat layer, the surface of
the article may be modified by techniques well described in the
prior art. These techniques include corona discharge, chemical
etching (particularly using a NaOH or KOH solution), or deposition
of a primer layer to increase adhesion of the hard-coat layer to
the surface of the article. For this purpose, the transparent
article may further incorporate a primer layer deposited onto at
least one surface of the article, before the deposition of the
hard-coat. A commercial formulation sold under trademark PR1133 by
SDC Corporation is particularly suitable to deposit the primer
layer for the thermally curable MP1154D formulation.
[0038] In one embodiment, before deposition of an AR coating, the
surface of an article that has been pre-coated with the hard-coat
layer is modified by chemical etching or by corona discharge.
Chemical etching solutions, preferably prepared using NaOH or KOH
and water, may be used to modify the surface of the hard-coat
layer. This surface modification increases the adhesion between the
AR coating and the hard-coat layer. In another embodiment, the
article may further incorporate a primer layer deposited onto at
least one surface of the article after the hard-coat has been
deposited. This primer layer also may provide a better adherence of
the AR coating to the article surface.
A Low Refractive Index UV Curable Coating Composition
[0039] In one embodiment of the invention, a low refractive index
coating composition is used to deposit one AR layer. This coating
composition may be cured by exposing it to an actinic radiation,
e.g., ultra-violet (UV) radiation. This low refractive index
UV-curable coating composition is hereafter designated as the "LU"
composition. The LU composition comprises at least one
(meth)acrylate-functional silicon alkoxide, silica particles, at
least one (meth)acrylate monomer, at least one epoxy(meth)acrylate
oligomer, at least one photoinitiator, at least one solvent, at
least one inorganic acid, and water.
[0040] In this invention, the term (meth)acrylate is used to
designate chemical compounds having acrylate or methacrylate
functional groups.
[0041] Examples of a suitable silicon alkoxide with (meth)acrylate
functionalities, which may be used in preparation of the LU
composition, include (3-acryloxypropyl)dimethylmethoxysilane,
(3-acryloxypropyl)methlyldimethoxysilane,
(3-acryloxypropyl)trimethoxysilane,
(methacryloxymethyl)dimethylethoxysilane,
methacryloxymethyltriethoxysilane,
methacryloxymethyltrimethoxysilane,
methacryloxypropylmethyldiethoxysilane,
methacryloxypropylmethyldimethoxysilane,
(3-methacryloxypropyl)triethoxysilane,
(3-methacryloxypropyl)trimethoxysilane, mixtures thereof, and the
like. In one embodiment, the (meth)acrylate functional silicon
alkoxide is (3-acryloxypropyl)trimethoxysilane.
[0042] The silica particles may be any silica particles miscible
with the LU composition. In various embodiments, the average
particle size may be smaller than about 100 nm, or more preferably
smaller than about 50 nm. The silica particles may be added to a
coating composition in the form of a dry powder, or in a colloidal
dispersion in a suitable liquid, or in another form. Dry powders
and/or colloidal dispersions of silica particles in aqueous or
non-aqueous solutions are commercially available from various
sources including Nalco Company (Naperville, Ill.), Nyacol
Nano-Technologies Incorporated (Ashland, Mass.), Nissan Chemical
Industries (Tokyo, Japan), Grace Davison (Columbia, Md.), Clariant
Corporation (Charlotte, N.C.), Cabot Corporation (Billerica,
Mass.), Degussa Advanced Nanomaterials (Hanau-Wolfgang, Germany),
and Catalysts and Chemicals Industries (Tokyo, Japan).
[0043] In some cases, the silica particles have functional groups
on their surfaces that are suitable for increasing the miscibility
of the particles with the LU composition. Silica particles having
such functional groups may be commercially obtained from Nissan
Chemical Industries, Clariant Corporation, and Cabot Corporation.
Preparation of such particles is also described in references such
as U.S. Pat. No. 6,335,380 to Wilhelm, which describes a method for
surface modification of colloidal silica with a vinyl silane, and
European patent publication No. EP 0505737 to Tilley, which
describes preparation of (meth)acrylate functionalized colloidal
silica.
[0044] The (meth)acrylate monomer that may be used in preparation
of the LU composition may be any monofunctional or multifunctional
monomer. It may also be in any ethoxylated or propoxylated form.
Suitable examples of the (meth)acrylate monomer include
2(2-ethoxyethoxy)ethyl acrylate, 2-phenoxyethyl acrylate,
2-phenoxyethyl methacrylate, caprolactone acrylate,
dicyclopentadienyl methacrylate, tetrahydrofurfuryl acrylate,
tetrahydrofurfuryl methacrylate, 1,3-butylene glycol diacrylate,
1,4 butanediol dimethacrylate, diethylene glycol diacrylate,
ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A
dimethacrylate, ethylene glycol dimethacrylate, ethoxylated
trimethylolpropane triacrylate, pentaeryhritol triacrylate,
propoxylated glyceryl triacrylate, propoxylated trimethylolpropane
triacrylate, trimethylolpropane triacrylate, trimethylolpropane
trimethacrylate, tris(2-hydroxy ethyl) isocyanurate triacrylate,
mixtures thereof and the like. In one embodiment, the
(meth)acrylate monomer is ethoxylated trimethylolpropane
triacrylate, tris(2-hydroxy ethyl) isocyanurate triacrylate,
mixtures thereof, and the like. In another embodiment, the
(meth)acrylate monomer is a mixture of ethoxylated
trimethylolpropane triacrylate and tris(2-hydroxy ethyl)
isocyanurate triacrylate. The (meth)acrylate monomers are
commercially available, for example, from Sartomer Company (Exton,
Pa.).
[0045] The epoxy(meth)acrylate oligomer that may be used in
preparation of the LU composition may be any oligomer that has
(meth)acrylate and epoxy functional groups. Such
epoxy(meth)acrylate oligomers are commercially available, for
example, from Sartomer Company under catalog numbers CN190, CN120,
CNUVE151, CN120A75, CN112C60, and the like. Mixtures of such
oligomers also may be used.
[0046] The photoinitiator that may be used for preparation of the
LU composition may be any chemical compound that may initiate
polymerization of (meth)acrylate functional groups by actinic
radiation. Suitable photoinitiator examples are
1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone,
2-hydroxy-2-methyl-1-phenyl-1-propanone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone,
diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide, the mixtures
thereof, and the like. Photolatent base-type photoinitiators, for
example,
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone may
also be used as the photoinitiator. In one embodiment, the
photoinitiator is 1-hydroxy-cyclohexyl-phenyl-ketone,
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone,
mixtures thereof, and the like. In one embodiment, the
photoinitiator is a mixture of 1-hydroxy-cyclohexyl-phenyl-ketone
and
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone.
Such photoinitiators are commercially available, for example from
Ciba Specialty Chemicals (Tarrytown, N.Y.).
[0047] Suitable solvents that may be used to prepared the LU
composition, include methanol, ethanol, propanol, isopropanol,
butanol, isobutanol, secondary butanol, tertiary butanol,
cyclohexanol, pentanol, octanol, decanol, di-n-butylether, ethylene
glycol dimethyl ether, propylene glycol dimethyl ether, propylene
glycol methyl ether, dipropylene glycol methyl ether, tripropylene
glycol methyl ether, dipropylene glycol dimethyl ether,
tripropylene glycol dimethyl ether, ethylene glycol butyl ether,
diethylene glycol butyl ether, ethylene glycol dibutyl ether,
ethylene glycol methyl ether, diethylene glycol ethyl ether,
diethylene glycol dimethyl ether, ethylene glycol ethyl ether,
ethylene glycol diethyl ether, ethylene glycol, diethylene glycol,
triethylene glycol, propylene glycol, dipropylene glycol,
tripropylene glycol, butylene glycol, dibutylene glycol,
tributylene glycol, tetrahydrofuran, dioxane, acetone, diacetone
alcohol, methyl ethyl ketone, cyclohexanone, methyl isobutyl
ketone, ethyl acetate, n-propyl acetate, n-butyl acetate, t-butyl
acetate, propylene glycol monomethyl ether acetate, dipropylene
glycol methyl ether acetate, 1-methoxy-2-propanol, ethyl
3-ethoxypropionate, 2-propoxyethanol, ethylene glycol ethyl ether
acetate, mixtures thereof, and the like. In one embodiment, the
solvent is isopropanol, ethyl acetate, 1-methoxy 2-propanol,
mixtures thereof, and the like. In another embodiment, the solvent
is a mixture of isopropanol, ethyl acetate, and 1-methoxy
2-propanol.
[0048] The inorganic acid that may be used to prepare the LU
composition may be any acid that can catalyze the sol-gel
hydrolysis and polymerization reactions of the (meth)acrylate
functional silicon alkoxide. Suitable inorganic acids are
hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid,
mixtures thereof, and the like.
[0049] The relative amount of each chemical compound forming the LU
composition, i.e., the (meth)acrylate functional silicon alkoxide,
the silica particles, the (meth)acrylate monomer, the
epoxy(meth)acrylate oligomer, the photoinitiator, the photo latent
base, the solvent, and the water, is controlled such that when the
coating composition is deposited to form a low-index layer, the
layer has a refractive index less than 1.60, or more preferably
less than 1.55, or most preferably less than 1.50, at a wavelength
of 510 nm. Preparation of the LU composition is demonstrated by way
example in EXAMPLE 7, below.
[0050] After this coating composition has been applied to the
article but before it has been cured by exposure to the UV
radiation, the article may be heat-treated to improve the coating's
adhesion. In one embodiment, this heat treatment is carried out
after a fourth-layer of the AR coating has been applied using the
LU composition.
High Refractive Index Coating Composition
[0051] In one embodiment of the invention, a high refractive index
coating composition is used to deposit an AR layer having a
refractive index greater than 1.70, or more preferably greater than
1.80, or most preferably greater than 1.90. This high refractive
index coating composition is hereafter designated as the "HT"
composition. The HT composition comprises at least one
organo-metallic compound (but not an organo-metallic compound of
silicon), at least one epoxy-functional silicon alkoxide, at least
one non-epoxy-functional silicon alkoxide, at least one curing
agent that is compatible with epoxy-functional molecules, at least
one solvent, at least one inorganic acid, and water.
[0052] The organo-metallic compound that may be used to prepare the
HT composition may be any organo-metallic compound that can
increase the refractive index of the AR layer to a value greater
than 1.70, 1.80, or 1.90. Suitable examples of such an
organo-metallic compound may be described by formulas
R.sup.1.sub.xM.sup.1 (OR.sup.2).sub.4-x,
R.sup.1.sub.yM.sup.2(OR.sup.2).sub.3-y,
R.sup.1.sub.zNb(OR.sup.2).sub.5-z, and the like. Mixtures of such
organo-metallic compounds also are suitable for such purpose. In
these formulas, M.sup.1 is a metal selected from the group
consisting of Ti, Zr, Ge, and Sn; M.sup.2 is a metal selected from
the group consisting of Al, In, and Sb; R.sup.1 is an organic
functional group such as C.sub.1-C.sub.4 alkyl, vinyl, allyl,
(meth)acryloxy, epoxide, and amino groups; and R.sup.2 is
C.sub.1-C.sub.4 alkyl group. In these formulas, x is 0, 1, 2, or 3;
y is 0, 1, or 2; and z is 0, 1, 2, 3, or 4. Useful examples of such
organo-metallic compounds are aluminum acrylate, aluminum ethoxide,
aluminum isopropoxide, aluminum methacrylate, antimony III
n-Butoxide, antimony III ethoxide, antimony III methoxide,
germanium n-butoxide, germanium ethoxide, germanium isopropoxide,
germanium methoxide, methacryloxy triethyl germane, indium
methoxyethoxide, niobium V n-butoxide, niobium V ethoxide, tin II
ethoxide, tin II methoxide, di-n-butyldiacrylate tin;
di-n-butyldimethacrylate tin, titanium n-butoxide, titanium
ethoxide, titanium isobutoxide, titanium isopropoxide, titanium
methacrylate triisopropoxide, titanium
methacryloxyethylacetoacetate triisoproxide, titanium n-propoxide;
zirconium n-butoxide, zirconium t-butoxide, zirconium
dimethacrylate dibutoxide, zirconium ethoxide, zirconium
isopropoxide, zirconium methacrylate, zirconium
methacryloxyethylacetoacetate tri-n-butoxide, zirconyl
dimethacrylate, mixtures thereof, and the like. In one embodiment
of this invention, the organo-metallic compound is titanium
isopropoxide. Such metal alkoxides are commercially available, for
example from Gelest (Morrisville, Pa.) and Aldrich (St. Lois,
Mo.).
[0053] Suitable examples of the epoxy-functional silicon alkoxide
that may be used to prepare the HT composition are
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
5,6-epoxyhexyltriethoxysilane,
(3-glycidoxypropyl)dimethylethoxysilane,
(3-glycidoxypropyl)methyldiethoxysilane,
glycidoxypropyl)methyldimethoxysilane,
(3-glycidoxypropyl)trimethoxysilane,
glycidoxymethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,
3-cyanopropyltrimethoxysilane, mixtures thereof, and the like. In
one embodiment of the invention, the epoxy-functional silicon
alkoxide is (3-glycidoxypropyl)trimethoxysilane. Such epoxy
functional silicon alkoxides are commercially available, for
example, from Gelest.
[0054] A useful non-epoxy-functional silicon alkoxide that may be
used to prepare the HT composition may be represented by a general
formula (OFG).sub.w-Si--(OR.sup.3).sub.4-w; wherein w equals 0, 1,
2 or 3; OR.sup.3 is a hydrolyzable alkoxy group; R.sup.3 is an
alkyl; and OFG is an organofunctional group. In some embodiments,
each OFG independently includes at least one functional group
selected from the group consisting of acetyl, acrylate,
alkoxyalkyl, alkyl (straight, branched, or cyclic), amino,
aromatic, carbamate, carboxyl, cyano, ester, halogen, mercapto,
methacrylate, or vinyl functional groups. Each OFG should have at
least one carbon atom in addition to the functional group. In one
embodiment, each OFG independently has from 1 to 100 carbon atoms.
In another embodiment, each OFG independently has from 1 to 20
carbon atoms. In some embodiments, each alkyl group R.sup.3
independently has from 1 to 20 carbon atoms. In other embodiments,
each alkyl group R.sup.3 independently has from 1 to 4 carbon
atoms.
[0055] Suitable examples of the non-epoxy-functional silicon
alkoxide that may be used to prepare the HT composition are
acetoxypropyltrimethoxysilane; (3-acryloxypropyl) trimethoxysilane;
allyltrimethoxysilane; 3-aminopropyltrimethoxysilane;
3-aminopropyltris(methoxyethoxyethoxy)silane;
3-aminopropylmethyldiethoxysilane;
3-aminopropyldimethylethoxysilane; 3-aminopropyltriethoxysilane;
3-(N-allylamino) propyltrimethoxysilane;
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane;
2-cyanoethyltriethoxysilane; 3-cyanopropyltrimethoxysilane;
(heptadecafluoro-1,1,2,2-tetrahydrododecyl)triethoxysilane;
3-mercaptopropyltrimethoxysilane;
(3-methacryloxypropyl)trimethoxysilane;
(3-methacryloxypropyl)triethoxysilane;
methacryloxymethyltrimethoxysilane;
methacryloxymethyltriethoxysilane; tetraethoxysilane;
tetramethoxysilane; (tridecafluoro-1,1,2,2-tetrahydrooctyl)
triethoxysilane; (3,3,3-trifluoropropyl)trimethoxysilane;
vinyltrimethoxysilane; vinyltriethoxysilane; mixtures thereof; and
the like. In one embodiment of the invention, the
non-epoxy-functional silicon alkoxide is tetraethoxysilane,
tetramethoxysilane, or mixtures thereof. In another embodiment of
the invention, the non-epoxy-functional silicon alkoxide is a
mixture of tetraethoxysilane and tetramethoxysilane. Such
non-epoxy-functional silicon alkoxides are commercially available,
for example, from Gelest.
[0056] The curing agent that is used to prepare the HT composition
may be any curing agent that is compatible with epoxy functional
molecules. The curing agent may be an anhydride, a carboxylic acid,
mixtures thereof, or the like. Suitable examples of anhydrides are
acetic anhydride, acrylic anhydride, cyclic anhydride,
hexahydrophthalic anhydride, methacrylic anhydride, propionic
anhydride, mixtures thereof and the like. Possible carboxylic acid
components include acetic acid, acrylic acid, formic acid, fumaric
acid, itaconic acid, maleic acid, methacrylic acid, propionic acid,
methylenesuccinic acid, mixtures thereof, and the like. In one
embodiment of the invention, the curing agent is hexahydrophthalic
anhydride. In another embodiment of the invention, the curing agent
is methylenesuccinic acid.
[0057] Suitable solvents that may be used to prepare the HT
composition include methanol, ethanol, propanol, isopropanol,
butanol, isobutanol, secondary butanol, tertiary butanol,
cyclohexanol, pentanol, octanol, decanol, di-n-butylether, ethylene
glycol dimethyl ether, propylene glycol dimethyl ether, propylene
glycol methyl ether, dipropylene glycol methyl ether, tripropylene
glycol methyl ether, dipropylene glycol dimethyl ether,
tripropylene glycol dimethyl ether, ethylene glycol butyl ether,
diethylene glycol butyl ether, ethylene glycol dibutyl ether,
ethylene glycol methyl ether, diethylene glycol ethyl ether,
diethylene glycol dimethyl ether, ethylene glycol ethyl ether,
ethylene glycol diethyl ether, ethylene glycol, diethylene glycol,
triethylene glycol, propylene glycol, dipropylene glycol,
tripropylene glycol, butylene glycol, dibutylene glycol,
tributylene glycol, tetrahydrofuran, dioxane, acetone, diacetone
alcohol, methyl ethyl ketone, cyclohexanone, methyl isobutyl
ketone, ethyl acetate, n-propyl acetate, n-butyl acetate, t-butyl
acetate, propylene glycol monomethyl ether acetate, dipropylene
glycol methyl ether acetate, 1-methoxy-2-propanol, ethyl
3-ethoxypropionate, 2-propoxyethanol, ethylene glycol ethyl ether
acetate, mixtures thereof, and the like. In one embodiment of the
invention, the solvent is ethanol, 1-methoxy 2-propanol, or
mixtures thereof. In another embodiment of the invention, the
solvent is a mixture of ethanol and 1-methoxy 2-propanol.
[0058] The inorganic acid that may be used to prepare the HT
composition may be any acid that can catalyze the sol-gel
hydrolysis and polymerization reactions of the organo-metallic
compound, the epoxy-functional silicon alkoxide, and the
non-epoxy-functional silicon alkoxide. Suitable inorganic acids are
hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid,
mixtures thereof, and the like. In one embodiment of the invention,
the inorganic acid is hydrochloric acid.
[0059] The relative amount of each chemical compound forming the HT
composition, i.e., the organo-metallic compound, the
epoxy-functional silicon alkoxide, the non-epoxy-functional silicon
alkoxide, the curing agent, the solvent, the inorganic acid, and
the water, is controlled such that when the coating composition is
deposited to form a high-index layer, the layer has a refractive
index greater than 1.70, or more preferably greater than 1.80, or
most preferably greater than 1.90, at a wavelength of 510 nm. The
preparation of HT composition is demonstrated by way of example in
EXAMPLES 3-6, below.
[0060] The coating compositions of this invention all may be
deposited onto the article using any suitable coating technique
commonly known in the industry, including, for example, those
techniques described in a publication entitled "Antireflection
Coatings Made by Sol-Gel Processes," Solar Energy Materials and
Solar Cells, Volume 68 (2001), pages 313 to 336, by Dinguo Chen.
These coating techniques include spin-coating, dip-coating,
roll-coating, flow-coating, and meniscus-coating. Spray-coating is
less preferable, because it sometimes may be difficult to obtain
uniform coatings using this technique. As described in U.S. Pat.
No. RE 37,183 to Kawamura et al., coatings prepared by a
spray-coating technique generally are thicker at the periphery than
at the center. This non-uniformity may yield coatings providing
poorer antireflective properties.
[0061] In the spin-coating technique, the article is held down
steadily on a surface of a rotating chuck by application of vacuum.
A predetermined volume of the liquid coating composition is
dispensed onto the article surface, while the article is being
spun, typically at speeds higher than 1,000 rpm. The coating
composition thereby forms a thin layer or film on the article
surface and may partially be dried during spinning. The article
then may be cured on the chuck. Alternatively, the article may be
removed from the spin-coater and cured, for example, in an oven.
Typically, just one surface of the article is coated by the
spin-coating technique during each AR coating run.
[0062] In the dip-coating technique, the transparent article is
clamped to a cantilevered arm and dipped into a plastic container
containing a coating composition. The plastic container and the
cantilevered arm are enclosed within a chamber having controlled
humidity. A drive system moves the cantilevered arm and the article
down and up along a vertical or inclined axis. The range of motion
must be sufficient to dip the article fully into, and out of, the
container. Each AR layer is deposited by lowering the cantilevered
arm and article at a predetermined speed into the container. After
remaining submerged in the composition for a brief time duration,
the article then is withdrawn from the composition at a
predetermined speed. The drive system includes a suitably
programmed computer, for precisely controlling the withdrawal speed
of the arm and the article, so as to control the thickness of the
layer being deposited. In general, slow withdrawal speeds yield
thinner coating layers. The withdrawal speed is in the range of 0.1
cm/second to 0.5 cm/second. Typically, all of the article's
surfaces are coated by dip-coating technique during each coating
run.
[0063] For all of the identified coating techniques, the level of
reflection for the destructive interference-type AR coating
critically depends on the refractive index and thickness of each
layer. The composition of the coating solution affects both of
these parameters. The spin-speed of the spin-coater (or
withdrawal-speed of the dip-coater) yielding the desired level of
reflection is determined empirically by preparing a number of
coatings, each having an AR layer deposited at a different spin
speed (or withdrawal speed), and by then measuring the
antireflective property of each coating. The spin speed (or
withdrawal speed) yielding the best antireflective property then is
selected to produce the AR layer.
[0064] The coating compositions of this invention may be
heat-treated at any temperature for a time duration that does not
physically or chemically degrade the coating and/or the article.
For example, if the plastic article's glass transition temperature
is exceeded during the coating process, the article may deform,
rendering it useless for commercial purposes. At temperatures much
higher than the glass transition temperature, the plastic articles
may even chemically decompose. On the other hand, since these are
time-dependent phenomena, such physical or chemical degradation may
be avoided by shortening the heat treatment time. Thus, negative
effects of higher heat-treatment temperatures may be avoided by
shortening the processing time. The heat-treatment temperatures and
time durations that yield the best curing conditions, while
avoiding such degradation, may be determined empirically. This
heat-treatment may be applied as an aid to the curing of a coating
composition. For example, the LU composition may be heat-treated
after it has been dispensed onto the surface of an article but
before the curing by UV irradiation. Alternatively, this heat
treatment may be applied to fully cure the coating composition, as
in the case of the HT composition. This heat treatment also may be
applied to improve the AR coating's adhesion and the abrasion
resistance.
[0065] By using the coating compositions and the coating processes
described above, the AR coating may be formed on the surfaces of
transparent articles in a very short processing time. The
processing time for formation of an AR coating on at least one
surface of an article includes the time duration required for
cleaning and drying of the article before or after deposition of
each AR layer, as well as the time duration required for dispensing
a coating composition onto the article's surface and curing of the
coating composition. The processing time may also include the time
duration required for deposition of a hard coat and/or primer
layer. The processing time may also include the time duration
required for a surface treatment of any one layer, including the
hard coat. The processing time may further include the time
duration required for moving an article before or after each of
these individual processing steps. Thus, the processing time is a
total time duration required to coat at least one surface of an
article with the AR coating of this invention. The processing time
excludes the time duration required to deposit a hydrophobic layer
on the AR coating.
[0066] The processing time preferably is less than 90 minutes, more
preferably is less than 30 minutes, and most preferably is less
than 10 minutes. For example, using the process of the invention, a
fully cured five-layer AR coating may be formed on one surface of
an ophthalmic lens with a processing time of less than 7
minutes.
[0067] The method of the present invention may be better understood
by reference to the following illustrative examples:
EXAMPLE 1
Preparation of a Low Concentration Titania Coating Composition
[0068] A low concentration titania coating composition, prepared in
this Example, is hereafter designated as the "LoT" composition. The
preparation of the LoT composition is described in detail in U.S.
Pat. No. 5,856,018 to Chen et al., the contents of which are
incorporated herein by reference. This coating composition was
prepared as follows:
[0069] In a container, about 317.1 grams of a reagent-grade ethanol
(Fisher Scientific, Tustin, Calif., Catalog No. A995-4), about 5.9
grams of hydrochloric acid (about 36 wt % concentrated), and about
5.8 grams of water were mixed for about 5 minutes at about 200 rpm
at ambient temperature, to form a first mixture. Then, about 106.4
grams of titanium isopropoxide were added to the first mixture, to
form a second mixture. The second mixture was stirred for about 60
minutes at about 200 rpm. Then, about 1552.5 grams of the reagent
grade ethanol, about 2.1 grams of the hydrochloric acid, and about
10.4 grams of water were added to the second mixture, to form a
third mixture. After third mixture was stirred for about 5 hours at
about 200 rpm, it was filtered through a 0.2 .mu.m filter, to form
the LoT composition.
EXAMPLE 2
Preparation of a Medium Concentration Titania Coating
Composition
[0070] A medium concentration titania coating composition, prepared
in this Example, is hereafter designated as the "MdT" composition.
The preparation of the MdT composition is described in detail in
U.S. Pat. No. 5,856,018 to Chen et al. This coating composition was
prepared as follows:
[0071] In a container, about 448.17 grams of reagent grade ethanol,
about 8.31 grams of hydrochloric acid (about 36 wt % concentrated),
and about 8.13 grams of water were mixed for 5 minutes at about 200
rpm at ambient temperature, to form a first mixture. Then, about
150.34 grams of titanium isopropoxide were added to the first
mixture, to form a second mixture. This second mixture was stirred
for about 60 minutes at about 200 rpm. Then, about 1374.52 grams of
the reagent grade ethanol, about 2.93 grams of hydrochloric acid,
and about 7.61 grams of water were added to the second mixture to
form a third mixture. After the third mixture was stirred for about
5 hours at about 200 rpm, it was filtered through a 0.2-.mu.m
filter, to form the MdT composition.
EXAMPLE 3
Preparation of a High Refractive Index Titania Coating
Composition
[0072] A high refractive index titania coating composition,
prepared in this Example, is hereafter designated as the "HT1"
composition. The HT1 coating composition was prepared as
follows:
[0073] In a container, about 317.1 grams of reagent-grade ethanol,
about 5.9 grams of hydrochloric acid (36 wt %), and about 5.7 grams
of water were mixed for about 5 minutes, at about 200 rpm and at
ambient temperature, to form a first mixture. Then, about 106.4
grams of titanium tetraisopropoxide were added to the first
mixture, to form a second mixture, and this second mixture was
stirred for about 60 minutes, at about 200 rpm and at ambient
temperature. Then, about 1552.5 grams of reagent-grade ethanol,
about 2.1 grams of hydrochloric acid, and about 10.4 grams of water
were added to the second mixture, to form a third mixture.
[0074] A fourth mixture was prepared by stirring a solution
containing about 1.34 grams of 3-glycidoxypropyltrimethoxysilane
(GPTMOS) purchased from Aldrich (St. Louis, Mo.), about 0.95 grams
of hexahydrophthalic anhydride (HHPA) purchased from Lonza
Chemicals (Basel, Switzerland), about 1.58 grams of tetramethyl
orthosilicate (TMOS) purchased from Aldrich, about 1.98 grams of
1-methoxy 2-propanol purchased from Aldrich, about 1.4 grams of
water, and about 32 grams of reagent alcohol for about 1 hour, at
about 250 rpm and at ambient temperature.
[0075] A fifth mixture was prepared by adding the fourth mixture to
the third mixture. After the fifth mixture was stirred for about 5
hours, at about 200 rpm and at ambient temperature, it was filtered
through a 0.2-.mu.m filter, to form the coating composition
HT1.
EXAMPLE 4
Preparation of a Second High Refractive Index Titania Coating
Composition
[0076] The coating composition of this Example was prepared in the
same manner as described in EXAMPLE 3, except that the about 0.95
grams of hexahydrophthalic anhydride (HHPA) used in the fourth
mixture were replaced by about 1.70 grams of methylenesuccinic
acid.
EXAMPLE 5
Preparation of a Third High Refractive Index Titania Coating
Composition
[0077] A high refractive index titania coating composition,
prepared in this Example, is hereafter designated as the "HT3"
composition. The HT3 composition was prepared as follows:
[0078] In a container, about 310.3 grams of reagent-grade ethanol,
about 6.57 grams of hydrochloric acid (about 36 wt % concentrated),
and about 2.63 grams of water were mixed for about 5 minutes, at
about 200 rpm and at ambient temperature, to form a first mixture.
Then, about 117.5 grams of titanium tetraisopropoxide were added to
the first mixture, to form a second mixture. The second mixture was
stirred for about 60 minutes, at about 200 rpm and at ambient
temperature. Then, about 1146.6 grams of reagent-grade ethanol,
about 2.18 grams of hydrochloric acid, and about 15.5 grams of
water were added to the second mixture, to form a third
mixture.
[0079] A fourth mixture was prepared by stirring a solution
containing about 1.36 grams of 3-glycidoxypropyltrimethoxysilane
(GPTMOS) purchased from Aldrich, about 0.935 grams of
hexahydrophthalic anhydride (HHPA) purchased from Lonza Chemicals,
about 1.75 grams of tetramethyl orthosilicate (TMOS) purchased from
Aldrich, about 2.07 grams of 1-methoxy 2-propanol purchased from
Aldrich, about 1.56 grams of water, and about 33.3 grams of reagent
alcohol for about 1 hour, at about 250 rpm and at ambient
temperature.
[0080] A fifth mixture was prepared by adding the fourth mixture to
the third mixture. After stirring the fifth mixture for about 5
hours, at about 200 rpm and at ambient temperature, it was filtered
through a 0.2-.mu.m filter, to form the HT3 composition.
EXAMPLE 6
Preparation of a Fourth High Refractive Index Titania Coating
Composition
[0081] The coating of this Example was prepared in the same manner
as described in EXAMPLE 5, except that the about 0.935 grams of
hexahydrophthalic anhydride (HHPA) that was used in the fourth
mixture was replaced by about 1.87 grams of methylenesuccinic
acid.
EXAMPLE 7
Preparation of a Low Refractive Index UV-Curable Coating
Composition
[0082] An LU composition is prepared as follows: In a container,
about 21.056 grams of about 30 wt % colloidal silica solution in
isopropyl alcohol, purchased from Nissan Chemicals (Houston, Tex.,
catalog no. IPA-ST), about 7.579 grams of
(3-acryloxypropyl)trimethoxysilane, and about 0.664 grams of water
containing about 0.1 normal hydrochloric acid were mixed to form a
first mixture. The first mixture was then sealed in a closed
container and heated to about 45.degree. C. and held at that
temperature for about 60 minutes under sonication using Model
FS220H sonicator purchased from Fisher Scientific.
[0083] In a three-liter container, which is covered with an
aluminum sheet to prevent its contents from being exposed to
outside light, about 4.914 grams of ethoxylated trimethylolpropane
triacrylate purchased from Sartomer Corporation (Exton, Pa.) under
catalog number SR-454, about 4.914 grams of bisphenol-A epoxy
acrylate oligomer purchased from Sartomer Corporation under catalog
number CN120, about 2.541 grams of tris(2-hydroxy ethyl)
isocyanurate triacrylate, purchased from Sartomer Corporation under
catalog number SR-368D, about 0.847 grams of a photoinitiator
1-hydroxy-cyclohexyl-phenyl-ketone, purchased from Ciba Corporation
(Tarrytown, N.Y.) under catalog number Irgacure 184, and about
0.170 grams of a photo latent base
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone
purchased from Ciba Corporation under catalog number 907 were mixed
to form a second mixture. The second mixture was stirred for about
5 minutes at about 200 rpm. To the second mixture, about 110 grams
of ethyl acetate and about 305 grams of 1-methoxy-2-propanol were
added, to form a third mixture. The third mixture was stirred at
about 250 rpm for about 30 minutes, at ambient temperature.
[0084] A fourth mixture was formed by mixing together in a
container the third mixture, the first mixture, and about 1542.2
grams of isopropanol. The fourth mixture was sealed and stirred at
about 250 rpm for about 60 minutes, at ambient temperature. Then,
the fourth mixture was filtered through a 10-.mu.m filter, to form
the LU composition.
EXAMPLE 8
Preparation of a Low Refractive Index UV-Curable Organo-Siloxane
Coating Composition
[0085] A low refractive index UV-curable organo-siloxane coating
composition, prepared in this Example, is hereafter designated as
the "DMP11" composition. The DMP11 composition was prepared as
follows:
[0086] In a container covered by aluminum sheet to prevent its
contents from being exposed to outside light, about 135.8 grams of
a UV-curable organo-siloxane purchased from SDC Corporation,
Anaheim, Calif. under catalog number MP-1175, about 452.4 grams of
1-methoxy-2 propanol, about 1276.0 grams of isopropyl alcohol, and
about 135.8 grams of ethyl acetate were mixed to form a first
mixture. This first mixture was stirred at about 250 rpm for about
60 minutes, in ambient conditions. The first mixture then was
filtered through a 10-.mu.m filter, to form the DMP11
composition.
EXAMPLE 9
Preparation of a First Low Refractive Index Silica Coating
Composition
[0087] The Low Refractive Index Silica Coating Composition is
hereafter designated as the "LS2" composition. Preparation of the
LS2 composition is described in detail in U.S. Pat. No. 5,856,018
to Chen et al. The LS2 coating composition was prepared as follows.
In a container, about 28.3 grams of reagent-grade ethanol, about
52.6 grams of tetraethyl orthosilicate (TEOS) purchased from
Aldrich, about 2.6 grams of hydrochloric acid (about 36 wt %), and
about 15.3 grams of water were mixed for about 30 minutes, at about
200 rpm and at ambient temperature, to form a first mixture. Then,
about 901.2 grams of reagent-grade alcohol were added to the first
mixture, to form a second mixture. After the second mixture was
stirred for about 5 hours, at about 200 rpm and at ambient
temperature, it was filtered through a 0.2-.mu.m filter, to form
the LS2 composition.
EXAMPLE 10
Preparation of a Second Low Refractive Index Silica Coating
Composition
[0088] Another low refractive index silica coating composition is
hereafter designated as the "LS4" composition. A detailed
description of the preparation of the coating composition LS4 is
disclosed in U.S. Pat. No. 5,856,018 to Chen et al. The LS4 coating
composition was prepared as follows:
[0089] In a container, about 231.7 grams of reagent-grade ethanol,
about 136.8 grams of tetraethyl orthosilicate (TEOS) purchased from
Aldrich, about 4.7 grams of hydrochloric acid (about 36 wt %), and
about 40.7 grams of water were mixed for about 30 minutes, at about
200 rpm and at ambient temperature, to form a first mixture. Then,
about 586.1 grams of reagent alcohol were added to the first
mixture, to form a second mixture. After the second mixture was
stirred for about 5 hours, at about 200 rpm and at ambient
temperature, it was filtered through a 0.2-.mu.m filter, to form
the coating composition LS4.
EXAMPLE 11
Preparation of a Hydrophobic Coating Composition
[0090] The preparation of a hydrophobic coating composition used to
deposit a hydrophobic layer was described in detail in U.S. Pat.
No. 6,395,331 to Yan et al., the contents of which are incorporated
by reference. The hydrophobic coating composition was prepared in a
two-step procedure. First, in a container, about 38.5 grams of
isopropanol, about 2.8 grams of water, about 0.7 gram of
hydrochloric acid (about 36 wt % concentrated), and about 0.4 grams
of 1H, 1H, 2H, 2H,-perfluorodecyltriethoxysilane were mixed
together, to form a first mixture. This first mixture was stirred
for about 2 hours at about 250 rpm, at ambient temperature. The
first mixture then was mixed with about 0.1 gram of 1H, 1H, 2H,
2H,-perfluorodecyltriethoxysilane, about 495.3 grams of water,
about 418.3 grams of isopropanol, and about 44 grams of ethylene
glycol, to form a second mixture. The second mixture was stirred at
about 250 rpm for about 1 hour and then filtered through a
0.2-.mu.m filter to produce the hydrophobic coating
composition.
EXAMPLE 12
Five-Layer AR Coating with a Hydrophobic Layer on an Ophthalmic
Lens
[0091] In this example, the coating compositions were successively
deposited, using a conventional spin-coating process, to form a
five-layer AR coating on both the convex surface and the concave
surface of a polycarbonate (PC) ophthalmic lens. The spin coater
used in this experiment was manufactured by Gerber Coburn, South
Windsor, Conn., under the catalog name Stratum Lens Coating System.
The PC lens was purchased from Essilor Corporation, Dudley, Mass.
under the trademark Airwear. The lens, as purchased, had a
hard-coat on both of its surfaces. Before the deposition of the
first AR layer, the lens was cleaned by dispensing about 1 ml of
ethanol on a clean room cloth and then wiping both surfaces of the
lens with this cloth. The lens then was dried by blowing compressed
air.
[0092] First the convex surface of the lens was coated with a
five-layer AR coating using the process described below. This
process was then repeated for the lens' concave surface.
[0093] A first AR layer was deposited on the lens' convex surface
using the LoT composition prepared in EXAMPLE 1. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the convex surface, over a time
duration of about 20 seconds, while the lens was being spun at a
spin speed of about 2,800 rpm. This first AR layer was cured at
about 130.degree. C. within about 1 minute using a heat gun.
[0094] A second AR layer was deposited onto the lens' convex
surface using the LU composition prepared in EXAMPLE 7. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. This layer was cured in the spin coater by
first purging its chamber for about 15 seconds with nitrogen and
then exposing the lens to UV radiation for about 20 seconds. The UV
radiation energy received by the article was measured by placing a
radiometer in place of the lens. This radiometer is manufactured by
EIT Incorporated, Sterling, Va. with a trademark MicroCure. It was
found that about 20 seconds of exposure to the UV radiation caused
absorption of about 2.2 J/cm.sup.2 energy by the radiometer. The
temperature in the UV chamber was initially about 30.degree. C.,
but the temperature of the lens surface increased to about
230.degree. C. after having received the UV radiation, as measured
by a temperature tape manufactured by Paper Thermometer Co.,
Greenfield, N.H. Although this temperature exceeded the lens' glass
transition temperature, no warpage of the lens was visible.
[0095] A third AR layer was deposited onto the lens' convex surface
using the MdT composition prepared in EXAMPLE 2. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 1,400 rpm. This layer was cured at about 130.degree. C.
within about 1 minute using a heat gun.
[0096] A fourth AR layer was deposited onto the lens' convex
surface using the LU composition prepared in EXAMPLE 7. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. The deposited layer was heat treated at about
130.degree. C. for about 1 minute using a heat gun, and it was then
further cured in the spin coater by first purging its chamber for
about 15 seconds with nitrogen and then exposing the lens to UV
radiation for about 20 seconds.
[0097] A fifth AR layer was deposited onto the lens' convex surface
using the DMP11 composition prepared in EXAMPLE 8. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. This layer was cured in the spin coater by
first purging its chamber for about 15 seconds with nitrogen and
then exposing the lens to UV radiation for about 20 seconds.
[0098] After the deposition of the fifth AR layer on the convex
surface, the lens was removed from the spin coater, and the concave
surface was cleaned by dispensing about 1 ml of ethanol on a clean
room cloth and then wiping the concave surface of the lens with
this cloth. The lens then was dried by blowing compressed air.
Finally, the same deposition process was repeated to coat the lens'
concave surface with same five-layer AR coating.
[0099] The processing time for forming this five-layer AR coating
on one surface of the lens was less than 7 minutes. This five-layer
coating is depicted schematically in FIG. 1, deposited onto a
polycarbonate (PC) ophthalmic lens. The second and fourth layers of
the coating, which were deposited using the LU coating composition,
yielded a refractive index of less than 1.50. The LU coating
composition has a stable pot life longer than 90 days.
[0100] Finally, a hydrophobic layer was deposited onto the fifth
layer using the hydrophobic coating composition prepared in EXAMPLE
11. The liquid composition was applied to both surfaces of the lens
by manually dipping the lens into the composition for about 10
seconds. This layer was cured at about 130.degree. C. within about
1 minute using a heat gun.
[0101] The five-layer AR coating, with the hydrophobic over-layer,
was tested for its mechanical and optical properties. The adhesion
of the coating was tested using a cross-cut tape adhesion test
described in Japanese Industrial Standard JIS 5600-5-6. This test
was carried out using 3M No. 600 adhesion tape. The adhesion of the
AR coating was determined to be Y1, which is considered to be a
passing level of adhesion, within the scope of this invention. It
was found that the about one-minute heat treatment of the fourth
layer at 130.degree. C. using a heat gun, before the UV curing,
improved the AR coating's adhesion. When there was no heat
treatment, the AR coating failed at the cross-hatch adhesion test,
i.e., the adhesion was not Y1. This heat treatment allowed the AR
coating to pass the cross-hatch test.
[0102] This AR coating had at least 2H pencil hardness. The
antireflective property of this coating is shown in FIG. 2.
EXAMPLE 13
Four-Layer AR Coating on an Ophthalmic Lens
[0103] In this Example, the coating compositions were successively
deposited using a conventional spin-coating process, to form a
four-layer AR coating on both the convex surface and the concave
surface of a polycarbonate (PC) lens. Stratum Lens Coating System
was used in this Example. The PC lens was purchased from Essilor
Corporation under the trademark Airwear. The lens, as purchased,
had a hard-coat on both of its surfaces. Before the deposition of
the first AR layer, the lens was cleaned by dispensing about 1 ml
of ethanol on a clean room cloth and then wiping both surfaces of
the lens with the cloth. The lens then was dried by blowing
compressed air.
[0104] First, the convex surface of the lens was coated with a
four-layer AR coating using the process described below. This
process was then repeated for the concave surface.
[0105] A first AR layer was deposited onto the convex surface of
the lens using the HT1 composition prepared in EXAMPLE 4. The
liquid composition was applied by manually dispensing in the range
of 0.5 ml to 1 ml of solution onto the lens' convex surface, over a
time duration of about 20 seconds, while the lens was being spun at
a spin speed of about 2,800 rpm. This layer was cured at about
130.degree. C. within about 1 minute using a heat gun.
[0106] A second AR layer was deposited onto the lens' convex
surface using the LU composition prepared in EXAMPLE 7. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. The layer was cured in the spin coater by first
purging its chamber for about 15 seconds with nitrogen and then
exposing the lens to UV radiation for about 20 seconds.
[0107] A third AR layer was deposited onto the lens' convex surface
using the HT3 composition prepared in EXAMPLE 6. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 1,400 rpm. This layer was cured at about 130.degree. C.
within about 1 minute using a heat gun.
[0108] A fourth AR layer was deposited onto the lens' convex
surface using the LS4 composition prepared in EXAMPLE 10. The
liquid composition was applied by manually dispensing in the range
of 0.5 ml to 1 ml of solution onto the lens surface, over a time
duration of about 20 seconds, while the lens was being spun at a
spin speed of about 3,000 rpm. The layer then was cured in an oven
at about 100.degree. C. within about 7.5 minutes, after which the
layer was further cured in the oven at about 100.degree. C. in
about 75% relative humidity for about 10 minutes.
[0109] After the deposition of the fourth AR layer on the lens'
convex surface, the lens was removed from the spin coater and the
concave surface was cleaned by dispensing about 1 ml of ethanol on
a clean room cloth and then wiping the lens' concave surfaces with
the cloth. The lens was then dried by blowing compressed air.
Finally, the same deposition process was repeated to coat the lens'
concave surface with the same four-layer AR coating.
[0110] The processing time for forming this four-layer AR coating
on one surface of the lens was less than 22 minutes.
[0111] The AR coating of this Example was tested for its optical
and mechanical properties. As shown in FIG. 3, the coating had good
optical properties. As prepared, the AR coating passed the
crosshatch adhesion test using 3M No. 600 adhesion tape. In
addition, the coating was analyzed using an ellipsometer with a
model name Vase, manufactured by J. A. Woollam Corporation, Lincoln
Nebr., to determine the refractive index of each layer. The first
layer, deposited using the compositions HT1, was measured to have a
refractive index of about 1.96; the second layer, deposited using
the composition LU, was measured to have a refractive index of
about 1.50; the third layer, deposited using the composition HT3,
was measured to have a refractive index of about 1.95; and the
fourth layer, deposited using the composition LS4, was measured to
have a refractive index of about 1.44.
EXAMPLE 14
Four-Layer AR Coating with a Hydrophobic Layer on an Ophthalmic
Lens
[0112] In this Example, a four-layer AR coating was deposited onto
an ophthalmic lens in the same manner as described in EXAMPLE 13.
In this Example, a hydrophobic coating layer was deposited onto the
fourth layer onto both surfaces of the lens using the hydrophobic
coating composition prepared in EXAMPLE 11. The liquid composition
was applied to the lens surfaces by manually dipping the lens into
the composition for about 10 seconds. This layer was cured at about
130.degree. C. within about 1 minute using a heat gun.
[0113] The AR coating was tested for its optical and mechanical
properties. The coating had good optical properties, similar to
those shown in FIG. 3. As prepared, the AR coating passed the
crosshatch adhesion test using 3M No. 600 adhesion tape.
[0114] The water contact angle of the lens having a hydrophobic top
coating layer was about 110.degree.. After rubbing the lens using a
lens cleaning cloth identified by the trademark Buff-Off, purchased
from Quality Accessories Inc, Munster, Ind., for about 20,000
cycles, at about 3 psi pressure, the water contact angle was
reduced to about 102.degree.. No coating delamination occurred
during this cloth rub test. Both high contact angle and no
delamination after the rub test indicated that this coating had
very good abrasion resistance properties.
EXAMPLE 15
Five-Layer AR Coating with a Hydrophobic Layer on an Ophthalmic
Lens
[0115] In this Example, the coating compositions were successively
deposited using a conventional spin-coating process, to form a
five-layer AR coating on both the convex surface and the concave
surface of a polycarbonate (PC) ophthalmic lens. Stratum Lens
Coating System was used in this Example. The PC lens was purchased
from Essilor Corporation under the trademark Airwear. The lens, as
purchased, had a hard-coat on both of its surfaces. Before the
first AR layer was deposited, the lens was cleaned by dispensing
about 1 ml of ethanol onto a clean room cloth and then wiping both
lens surfaces with the cloth. The lens then was dried by blowing
compressed air.
[0116] First, the convex surface of the lens was coated with a
five-layer AR coating with a process described below. This process
was then repeated for the concave surface.
[0117] A first AR layer was deposited onto the lens' convex surface
using the HT1 composition prepared in EXAMPLE 4. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens' convex surface, over a time
duration of about 20 seconds, while the lens was being spun at a
spin speed of about 2,800 rpm. The layer was cured at about
130.degree. C. within about 1 minute using a heat gun.
[0118] A second AR layer was deposited onto the lens' convex
surface using the LU composition prepared in EXAMPLE 7. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. The layer was cured in the spin coater by first
purging its chamber for about 15 seconds with nitrogen and then
exposing the lens to UV radiation for about 20 seconds.
[0119] A third AR layer was deposited onto the lens' convex surface
using the HT3 composition prepared in EXAMPLE 6. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 1,400 rpm. This layer was cured at about 130.degree. C.
within about 1 minute using a heat gun.
[0120] A fourth AR layer was deposited onto the lens' convex
surface using the LU composition prepared in EXAMPLE 7. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. The layer was partially cured at about
130.degree. C. within about 1 minute using a heat gun, and it then
was further cured in the spin coater by first purging its chamber
for about 15 seconds with nitrogen and then exposing the lens to UV
radiation for about 20 seconds.
[0121] A fifth AR layer was deposited onto the lens' convex surface
using the DMP11 composition prepared in EXAMPLE 8. The liquid
composition was applied by manually dispensing in the range of 0.5
ml to 1 ml of solution onto the lens surface, over a time duration
of about 20 seconds, while the lens was being spun at a spin speed
of about 3,500 rpm. The layer was cured in the spin coater by first
purging its chamber for about 15 seconds with nitrogen and then
exposing the lens to UV radiation for about 20 seconds.
[0122] After the fifth AR layer was deposited, the lens was removed
from the spin coater and the concave surface was cleaned by
dispensing about 1 ml of ethanol onto a clean room cloth and then
wiping the lens' concave surface with the cloth. The lens then was
dried by blowing compressed air. Finally, the same deposition
process was repeated to coat the lens' concave surface with a
similar five-layer AR coating.
[0123] The processing time for forming the five-layer AR coating
for one surface of the lens was less than 7 minutes.
[0124] Finally, a hydrophobic layer was deposited onto the fifth
layers of the two five-layer AR coatings using the hydrophobic
coating composition prepared in EXAMPLE 11. The liquid composition
was applied to the lens surfaces by manually dipping the lens into
the composition for about 10 seconds. This layer was cured at about
130.degree. C. within about 1 minute using a heat gun.
[0125] The AR coating was tested for its optical and mechanical
properties. As shown in FIG. 4, the coating had good optical
properties. In addition, the coating was analyzed using the Vase
ellipsometer, to determine the refractive index of each layer. The
first layer, deposited using the compositions HT1, was measured to
have a refractive index of about 1.96; the second layer, deposited
using the composition LU, was measured to have a refractive index
of about 1.50; the third layer, deposited using the composition
HT3, was measured to have a refractive index of about 2.05; the
fourth layer, deposited using the composition LU, was measured to
have a refractive index of about 1.50; and the fifth layer,
deposited using the composition DMP11, was measured to have a
refractive index of about 1.53.
[0126] The AR-coated lens of this Example passed the crosshatch
tape-adhesion test, both before and after depositing the
hydrophobic layer. The water contact angle was measured to be
110.degree. after applying the hydrophobic layer. No delamination
occurred after a 20,000-cycle cloth rub test, at about 3 psi
pressure. The coated lens also passed the crosshatch tape-adhesion
test after the lens had been treated at about 95% relative
humidity, in an about 65.degree. C. oven, for about 24 hours. All
these tests indicated that this AR coating with hydrophobic layer
had very good optical and mechanical properties.
EXAMPLE 16
Four-Layer AR Coating on a Flat Panel
[0127] In this example, both surfaces of a flat poly(methyl
methacrylate) (PMMA) panel were coated with a four-layer AR coating
as follows. The coating compositions were successively deposited
onto the panel using a conventional dip-coating process. The PMMA
panel was purchased from Cyro Corporation, Macon, Ga., under the
trademark Acrylite. The panel thickness was about 2 mm, with a size
of about 20 cm.times.about 18 cm. Both surfaces of the PMMA panel
were first dip-coated with a basecoat of UVB510R6, manufactured by
Red Spot Corporation, to a thickness of about 4.5 micrometers.
[0128] A first AR layer then was deposited onto the panel using the
HT1 composition prepared in EXAMPLE 3. The dip-coating chamber was
controlled to have a temperature of about 23.degree. C. and a
relative humidity of about 60%. The panel was lowered into the HT1
composition at a speed of about 1 cm/second and kept submerged for
about 10 seconds. The panel then was withdrawn from the dip-coating
tank at a speed of about 0.2 cm/second. Finally, the layer was
cured in an oven, at about 100.degree. C. for about 10 minutes.
[0129] A second AR layer was deposited onto this panel using the
LS2 composition prepared in EXAMPLE 9. The dip-coating chamber was
controlled to have a temperature of about 23.degree. C. and a
relative humidity of about 25%. The panel was lowered into the LS2
composition at a speed of about 1 cm/second and kept submerged for
about 10 seconds. The panel then was withdrawn from the dip-coating
tank at a speed of about 0.11 cm/second. Finally, the layer was
cured in an oven, at about 100.degree. C. for about 15 minutes.
[0130] A third AR layer was deposited onto this panel using the HT3
composition prepared in EXAMPLE 5. The dip-coating chamber was
controlled to have a temperature of about 23.degree. C. and a
relative humidity of about 60%. The panel was lowered into the HT3
composition at a speed of about 1 cm/second and kept submerged for
about 10 seconds. The panel then was withdrawn from the dip-coating
tank at a speed of about 0.29 cm/second. Finally, the layer was
cured at about 100.degree. C. for about 10 minutes using a heat
gun.
[0131] A fourth AR layer was deposited onto this panel using the
LS4 composition prepared in EXAMPLE 10. The dip-coating chamber was
controlled to have a temperature of about 23.degree. C. and a
relative humidity of about 25%. The panel was lowered into the LS4
composition at a speed of about 1 cm/second and kept submerged for
about 10 seconds. The panel then was withdrawn from the dip-coating
tank at a speed of about 0.21 cm/second. The layer was cured in two
steps. First, the layer was cured in an oven at about 100.degree.
C. for about 5 minutes, and second, the layer was further cured in
the oven at about 100.degree. C. for about 20 minutes at about 75%
relative humidity.
[0132] The processing time for forming the four layers of this AR
coating, schematically shown in FIG. 5, was less than 80
minutes.
[0133] The AR coating of this Example was tested for its optical
and mechanical properties. As shown in FIG. 6, this coating had
good optical properties. In addition, the coating was analyzed
using the Vase ellipsometer, to determine the refractive index of
each layer. The first layer, deposited using the compositions HT1,
was measured to have a refractive index of about 1.95; the second
layer, deposited using the composition LS2, was measured to have a
refractive index of about 1.44; the third layer, deposited using
the composition HT3, was measured to have a refractive index of
about 1.95; and the fourth layer, deposited using the composition
LS4, was measured to have a refractive index of about 1.44. As
prepared, the AR coating passed the crosshatch adhesion test using
3M No. 600 adhesion tape.
[0134] Although several embodiments of the invention have been
described in detail above, those of ordinary skill in the art will
appreciate that various modifications may be made without departing
from the scope of the invention. Accordingly, the invention is
defined only by reference to the following claims.
* * * * *