U.S. patent application number 10/057020 was filed with the patent office on 2002-09-12 for organic-inorganic hybrid polymer and method of making same.
Invention is credited to Jin, Dan L., Singh, Brij P..
Application Number | 20020127330 10/057020 |
Document ID | / |
Family ID | 24104984 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020127330 |
Kind Code |
A1 |
Jin, Dan L. ; et
al. |
September 12, 2002 |
Organic-inorganic hybrid polymer and method of making same
Abstract
An optically clear protective thin film having covalent chemical
bonds on a molecular level between organic polymer and in situ
generated silica molecules is formed from a hydrolyzed coating
solution of tetraalkyl orthosilicate, epoxyalkylalkoxy silanes,
(math)acryloxyalkylalkoxy silanes and solvent.
Inventors: |
Jin, Dan L.; (Bedford,
OH) ; Singh, Brij P.; (North Royalton, OH) |
Correspondence
Address: |
H. Duane Switzer
Jones, Day, Reavis & Pogue
North Point
901 Lakeside Avenue
Cleveland
OH
44114-1190
US
|
Family ID: |
24104984 |
Appl. No.: |
10/057020 |
Filed: |
January 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10057020 |
Jan 24, 2002 |
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09870221 |
May 30, 2001 |
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09870221 |
May 30, 2001 |
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09528276 |
Mar 17, 2000 |
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Current U.S.
Class: |
427/162 ;
427/376.2; 427/387; 427/407.1 |
Current CPC
Class: |
C08G 77/02 20130101;
C08G 77/20 20130101; B32B 27/08 20130101; Y10T 428/249978 20150401;
Y10T 428/31663 20150401; C09D 4/00 20130101; Y10T 428/31667
20150401; C09D 4/00 20130101; Y10T 428/31507 20150401; C09D 183/14
20130101; C09D 4/00 20130101; Y10T 428/26 20150115; Y10T 428/249979
20150401; C09D 183/06 20130101 |
Class at
Publication: |
427/162 ;
427/376.2; 427/387; 427/407.1 |
International
Class: |
B05D 005/06; B05D
003/02; B05D 001/36 |
Claims
What is claimed:
1. A thermally curable coating solution for applying optically
clear protective thin films to substrate surfaces, said solution
including oligomers from hydrolysis of tetraalkyl orthosilicate,
epoxyalkylalkoxy silanes, (math)acryloxyalkylalkoxy silanes, and
solvent, and having a pH of 4-6.
2. The solution of claim 1 wherein said tetraalkyl orthosilicate,
said epoxyalkylalkoxy silanes and said (math)acryloxyalkylalkoxy
silanes together comprise 20-50 weight percent of said
solution.
3. The solution of claim 1 wherein said solution contains a
surfactant and a catalyst, said solvent being 20-80 weight percent
of said solution, and 20-50 weight percent of said solvent being
water.
4. The solution of claim 1 wherein said tetraalkyl orthosilicate is
present in an amount greater than said epoxyalkylalkoxy silanes,
and said epoxyalkylalkoxy silanes is present in an amount greater
than said (math)acryloxyalkylalkoxy silanes.
5. The solution of claim 1 wherein the ratio of the amount of said
epoxyalkylalkoxy silanes in said solution to the amount of said
(math)acryloxyalkylalkoxy silanes in said solution is between 15 to
1 and 0.2 to 1.
6. The solution of claim 5 wherein said ratio is between 13 to 1
and 1 to 1.
7. The solution of claim 1 wherein the molar ratio of said water to
the combination of said epoxyalkylalkoxy silanes and
(math)acryloxyalkylalkox- y silanes is between 1 to 4 and 3 to
1.
8. The solution of claim 7 wherein said ratio is between 1 to 2 and
2to 1.
9. The solution of claim 1 including a curing agent present in an
amount between 0.2 to 0.5 weight percent of said solution.
10. The solution of claim 9 wherein said curing agent is present in
an amount between 0.3 to 0.4 weight percent of the solution.
11. The solution of claim 9 wherein said curing agent comprises one
or more of titanium acetylacetonate, aluminum acetylacetonate,
dibutyltin dilaurate and zinc napthenate.
12. The solution of claim 1 wherein said solvent comprises one or
more of acetonitrile, acetone, methyl ethyl ketone, 2-heptanone,
ethanol, isopropyl alcohol, n-butanol, iso-butanol, 2-ethoxyethanol
and 2-butoxyethanol.
13. The solution of claim 1 wherein said tetraalkyl orthosilicate
comprises one or more of tetramethyl orthosilicate, tetraethyl
orthosilicate, tetrapropyl orthosilicate and tetrabutyl
orthosilicate.
14. The solution of claim 1 wherein said (math)acryloxyalkylalkoxy
silanes comprise one or more of
2-methacryloxypropyltriethoxysilane,
3-acryloxypropyltrimethoxysilane, 2-acryloxypropyltriethoxysilane,
3-methacryloxypropylmethyldimethoxysilane,
2-methacryloxypropylmethyldiet- hoxysilane,
3-acryloxypropylmethyldimethoxysilane, 2-acryloxypropylmethyld-
iethoxysilane, 3-methacryloxypropyltrimethoxysilane and
methacryloxypropyltris(methoxyethoxy)methoxysilane.
15. The solution of claim 1 wherein said epoxyalkylalkoxy silanes
comprise one or more of glycidoxymethyltrimethoxysilane,
glycidoxymethyltriethoxys- ilane, 2-glycidoxyethyltrimethoxysilane,
2-glycidoxyethyltriethoxysilane, 1-glycidoxyethyltrimethoxysilane,
1-glycidoxyethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane,
3-glycidoxypropyltriethoxysilane,
2-glycidoxypropyltrimethoxysilane,
2-glycidoxypropyltriethoxysilane,
1-glycidoxypropyltrimethoxysilane,
2-glycidoxypropyltriethoxysilane, 4-glycidoxybutyltrimethoxysilane,
4-glycidoxybutyltriethoxysilane, 3-glycidoxybutyltrimethoxysilane,
2-glycidoxybutyltrimethoxysilane, 2-glycidoxybutyltriethoxysilane,
1-glycidoxybutyltrimethoxysilane, 1-glycidoxybutyltriethoxysilane,
(3,4-epoxycyclohexyl)methyltrimethoxysil- ane.
(3,4-epoxycyclohexyl)methyltriethoxysilane,
glycidoxymethylmethyldime- thoxysilane,
glycidoxymethylmethyldiethoxysilane, 2-glycidoxyethylmethyldi-
methoxysilane, 2-glycidoxyethylmethyldiethoxysilane,
1-glycidoxyethylmethyldimethoxysilane,
1-glycidoxyethylmethyldiethoxysila- ne,
3-glycidoxypropylmethyldimethoxysilane,
3-glycidoxypropylmethyldiethox- ysilane,
2-glycidoxypropylmethyldimethoxysilane, 2-glycidoxypropylmethyldi-
ethoxysilane, 1-glycidoxypropylmethyldimethoxysilane,
1-glycidoxypropylmethyldiethoxysilane,
4-glycidoxybutylmethyldimethoxysil- ane,
4-glycidoxybutylmethyldiethoxysilane,
3-glycidoxybutylmethyldimethoxy- silane,
3-glycidoxybutylmethyldiethoxysilane, 2-glycidoxybutylmethyldimeth-
oxysilane, 2-glycidoxybutylmethyldiethoxysilane,
1-glycidoxybutylmethyldim- ethoxysilane,
1-glycidoxybutylmethyldiethoxysilane,
(3,4-epoxycyclohexyl)methylmethyldimethoxysilane, and
(3,4-epoxycyclohexyl)methylmethyldiethoxysilane.
16. The solution of claim 1 wherein said tetraalkyl orthosilicate,
said epoxyalkylalkoxy silanes and said (math)acryloxyalkylalkoxy
silanes together comprise a polymerizable component that is 20-50
weight percent of said solution, said tetraalkyl orthosilicate
being present in an amount greater than said epoxyalkylalkoxy
silanes, and said epoxyalkylalkoxy silanes being present in an
amount greater than said (math)acryloxyalkylalkoxy silanes.
17. The solution of claim 16 wherein said tetraalkyl orthosilicate
is 40-75 weight percent of said polymerizable component, said
epoxyalkylalkoxy silanes is 20-45 weight percent of said
polymerizable component and said (math)acryloxyalkylalkoxy silanes
is 5-15 weight percent of said polymerizable component.
18. The solution of claim 1 wherein 0.1-0.5 weight percent of said
solution is 2M HCl and 0.5-2.0 weight percent of said solution is
acetic acid.
19. A curable coating solution for applying optically clear
protective thin films to substrate surfaces, said coating solution
having a polymerizable component that is 20-50 weight percent of
the total solution and consists essentially of tetraalkyl
orthosilicate, epoxyalkylalkoxy silanes and
(math)acryloxyalkylalkoxy silanes.
20. The solution of claim 19 wherein said tetraalkyl orthosilicate
is 40-75 weight percent of said polymerizable component, said
epoxyalkylalkoxy silanes is 20-45 weight percent of said
polymerizable component and said (math)acryloxyalkylalkoxy silanes
is 5-15 weight percent of said polymerizable component.
21. The solution of claim 19 wherein 0.1-0.5 weight percent of said
solution is 2M HCl and 0.5-2.0 weight percent of said solution is
acetic acid.
22. The solution of claim 21 wherein 0.01-1.0 weight percent of
said solution is a wetting agent and 0.2-0.5 weight percent of said
solution is a curing agent.
23. The solution of claim 22 wherein the remainder of said solution
is solvent and 20-50 weight percent of the solvent is water, the
remainder of the solvent being one or more of alcohols and organic
solvents.
24. An optically clear protective film having organic polymer and
generated silica molecules chemically bonded together by covalent
bonds, said film having pores smaller than five angstroms.
25. The film of claim 24 wherein said film is bonded to a plastic
substrate surface and said film suffers no visible crazing after
undergoing a Boiling Salt Water Test or a Thermal Test.
26. The film of claim 25 wherein said plastic substrate surface is
on a plastic substrate selected from polycarbonate, high index or
CR-39.
27. The film of claim 26 wherein said plastic substrate is an
eyeglass lens.
28. The film of claim 25 wherein said plastic substrate surface is
on a plastic substrate selected from polycarbonate or high index,
and a primer layer interposed between said film and said substrate
surface.
29. The film of claim 24 including an antireflective coating bonded
to said film.
30. The film of claim 29 including an hydrophobic film of
amphiphillic molecules bonded to said antireflective coating.
31. The film of claim 24 wherein said film has a thickness not
greater than 7 .mu.m.
32. A plastic substrate having a thin film bonded thereto, said
thin film having organic polymer and generated silica molecules
chemically bonded together by covalent bonds, and said film having
a thickness not greater than 7 .mu.m.
33. The substrate of claim 32 wherein said substrate is a plastic
eyeglass lens selected from polycarbonate, high index or CR-39.
34. The substrate of claim 33 including an antireflective coating
bonded to said film.
35. The substrate of claim 34 including an optically clear
hydrophobic film of amphiphillic molecules bonded to said thin
film.
36. The substrate of claim 32 wherein said substrate is a plastic
eyeglass lens selected from polycarbonate or high index, and a
primer layer interposed between said lens and said thin film.
37. A method of providing a protective thin film on ophthalmic
lenses comprising the steps of: preparing a coating solution by
mixing together tetraalkyl orthosilicate, epoxyalkylalkoxy silanes,
(math)acryloxyalkylalkoxy silanes, solvent, HCl and acetic acid;
stirring the solution to partially hydrolyze the silane groups;
heating the solution while continuing to stir to completely
hydrolyze the silane groups; cooling the solution followed by
dissolving a wetting agent and a catalyst in the solution; applying
a coating of the solution to a substrate surface; and heating the
substrate to cure the coating and bond same to the substrate
surface as a protective thin film in which polymer and silica
molecules are chemically bonded together by covalent bonds.
38. The method of claim 37 wherein said step of heating the
substrate to cure the coating is carried out at a temperature of
90-120.degree. C. for 30-60 minutes.
39. The method of claim 37 wherein said step of applying a coating
of the solution to a substrate surface is carried out by applying
the coating to an eyeglass lens of a material selected from
polycarbonate, high index or CR-39.
40. The method of claim 37 including the step of applying a primer
layer to the substrate surface prior to said step of applying a
coating of the solution thereto.
41. The method of claim 37 including the step of applying an
antireflective coating to said protective thin film.
42. The method of claim 41 including the step of applying an
hydrophobic film of amphiphillic molecules to said antireflective
coating.
43. The method of claim 37 wherein said step of applying a coating
of the solution to a substrate is carried out by applying a
solution coating that provides a cured protective thin film having
a thickness not greater than 7 .mu.m.
Description
RELATED APPLICATIONS
[0001] This application is a division of copending U.S. Serial No.
09/870,221 filed May 30, 2001 which is a division of copending U.S.
Ser. No. 09/528,276 filed Mar. 17, 2000.
BACKGROUND OF THE INVENTION
[0002] This application relates to the art of compositions and,
more particularly, to an organic-inorganic hybrid polymer
composition and a method of making same. The invention is
particularly applicable to compositions for applying optically
clear protective thin films to the surfaces of plastic eyeglass
lenses and will be described with specific reference thereto.
However, it will be appreciated that the invention has broader
aspects and that the composition can be used for other purposes as
well as for coating other plastic substrate surfaces, such as
transparent display cases, windows and crystals for covering faces
of clocks, watches and other instruments.
[0003] Plastic materials commonly are used for ophthalmic lenses
because they are lighter, easier to process and provide better
impact resistance than glass. However, the surfaces of the plastic
materials used in ophthalmic lenses are relatively soft and porous
compared to glass, and this frequently results in reduced optical
clarity due to abrasion and staining of the lens surface. This
problem may be alleviated by coating the lens surfaces with an
abrasion and stain resistant thin film that commonly is known as a
hardcoat.
[0004] The most desirable materials for hardcoating lenses are
inorganic oxides such as quartz, fused silica, glass, aluminum
dioxide, titanium dioxide and other ceramics. Because thin films of
these inorganic oxides are best applied in traditional processes
that reach 1000.degree. C. or more, they cannot be used with lenses
that are made of organic polymers which will decompose at such
temperatures.
[0005] Inorganic oxides can be applied to organic polymers by such
processes as chemical vapor deposition and the sol-gel process but
it is difficult to achieve a good bond because of the inherent
incompatibility between the inorganic coating and the organic
substrate. The different coefficients of thermal expansion for the
inorganic coating and the organic substrate tend to cause
delamination. Inorganic films with sufficient thickness to
adequately protect relatively soft plastic substrate surfaces may
become brittle and are prone to crazing. Equipment for chemical
vapor deposition also requires a large capital investment and,
because the necessary high vacuum chamber is relatively small, the
numbers and sizes of articles that can be processed is limited.
[0006] Polymer coating materials have been developed that provide
better abrasion and stain resistance than the surfaces of the
plastic materials that are used for ophthalmic lenses, and many of
these coating materials include an inorganic component for
enhancing the abrasion resistance of the coating. The abrasion
resistant properties of these polymer coating materials increase
with increasing crosslinking of the polymer molecules because the
density and hardness of the protective film that is formed from the
coating material increases. Most abrasion resistant polymer
coatings are formed by either thermal or radiation curing. The
thermal process involves a condensation reaction of reactive
monomers or oligomers, while the radiation process involves free
radical polymerization.
[0007] One measure of the degree of crosslinking, hardness,
abrasion resistance and porosity of a coating is whether or not a
protective film applied to a lens is tintable. Protective films
formed from known polymer coating materials are tintable because
the pores of the film are larger than the dye pigment molecules. In
a known wet molecular adsorption tinting process, a coated lens is
submerged in a dye bath or organic dye molecules and water
maintained at 95-100.degree. C., and this elevated temperature
expands the size of the pores in the protective film by different
amounts depending on the degree of crosslinking in the coating
polymer. In known protective films, the pores are large enough to
be penetrated by the dye molecules which range in size between
about 5-30 angstroms.
[0008] Highly crosslinked polymer coatings that are more abrasion
resistant than the polymers used for ophthalmic lenses are
disclosed in many U.S. patents, several of which are mentioned
hereafter by way of example. U.S. Pat, No. 4,407,855 discloses a
pentaerythritol-based polyacrylate or polymethacrylate composition.
U.S. Pat. No. 4,954,591 discloses a tintable coating composition of
polyfunctional acrylate, n-vinyl derivatives and ethylenically
unsaturated copolymer. U.S. Pat. No. 5,246,728 discloses a
composition of tri- and tetra-acrylates in butanol. U.S. Pat. No.
5,401,541 discloses a highly crosslinked acrylic copolymer that is
derived from a multifunctional aliphatic acrylate monomer. U.S.
Pat. No. 5,459,176 discloses a tintable composition of
polyacryloylated alkane polyols.
[0009] Although polymer coating compositions of the type described
in the above patents form protective films that are much harder
than the surfaces of the polymeric ophthalmic lenses, the nature of
the carbon-carbon and carbon-hydrogen bonds in the films is not
changed. In addition, the improvement in abrasion resistance does
not approach the abrasion resistance provided by protective films
of inorganic oxides.
[0010] The hardness and abrasion resistance of organic polymer
coatings is improved by mixing an inorganic oxide, such as silica,
with the composition that is used to form the coating. These
compositions may be thermally cured or may be cured by ultraviolet
radiation depending on the polymer that is used. Film coatings
produced with such compositions are clear provided the individual
silica particles are well dispersed and smaller than the visible
wavelengths of light.
[0011] The amount of silica that can be added to a coating material
for ophthalmic lenses is limited by the requirements of avoiding
agglomeration of silica particles and insuring good dispersion so
that the silica particles will not be visible in the protective
film. Polymer compositions that include colloidal silica are
disclosed in many U.S. patents, several of which are mentioned
hereafter by way of example. U.S. Pat. No. 4,499,217 discloses a
dispersion of colloidal silica in a thermosetting polymer. U.S.
Pat. Nos. 4,973,612, 5,075,348 and 5,188,900 disclose blends of
multifunctional acrylates, unsaturated organic compounds and
colloidal silica. U.S. Pat. No. 5,104,929 discloses a blend of
colloidal silica in ethylenically unsaturated aliphatic and/or
cycloaliphatic monomers. These compositions do not have chemical
bonding between the silica and the polymer, and protective thin
film coatings formed with such compositions tend to fail in a
relatively short time.
[0012] Attempts to alleviate the problems inherent in the lack of a
chemical bond between the colloidal silica and the polymer have
included the addition of reactive silane compounds to the
composition for modifying the surfaces of the colloidal silica
particles or for reacting with same. Disclosures of such
compositions may be found in many U.S. patents, several of which
are mentioned hereafter by way of example. U.S. Pat. No. 4,348,462
discloses a radiation curable composition that includes colloidal
silica, acryloxy or glycidoxy functional silanes, non-silyl
acrylates, and catalytic amounts of ultraviolet light sensitive
cationic and radical type photoinitiators. This composition is said
to cure to a transparent hard coating with improved abrasion
resistance. U.S. Pat. No. 3,986,997 discloses a composition that
includes colloidal silica, hydroxylated organosiloxanes and a
silanol condensation catalyst. U.S. Pat. No. 4,478,876 discloses a
composition that includes a blend of acrylate monomer, colloidal
silica and acryloxy functional silane. U.S. Pat. No. 5,426,131
discloses a composition that includes acrylic monomers,
functionalized colloidal silica and acrylated urethane. U.S. Pat.
No. 4,177,315 discloses the generation of silica within the
composition by hydrolyzing tetraethyl orthosilicate and aging the
composition followed by the addition of organic silanol compounds
to modify the preformed silica. U.S. Pat. No. 4,211,823 discloses a
composition that has one or more compounds selected from a group
that includes an epoxy group, a silanol group and a siloxane group,
plus silica particles and an aluminum chelate. U.S. Pat. Nos.
4,242,416 and 4,177,175 disclose a composition that includes an
organothiol containing siloxane resin and colloidal silica. U.S.
Pat. No. 4,355,135 discloses a composition that includes siloxane
and colloidal silica, and that forms a protective thin film coating
that is readily tintable by conventional dyes. U.S. Pat. No.
4,486,504 discloses a composition that includes hydrolysis products
of acryloxy functional silanes and/or glycidoxy functional silanes,
and colloidal silica. U.S. Pat. No. 5,102,695 discloses a
composition that includes colloidal silica, polysiloxane and
alkylated amine formaldehyde, and that forms a thin film coating
that is highly tintable by conventional dyes.
[0013] In the compositions of the aforementioned U.S. patents,
silica is used to impart inorganic properties to organic polymers
for improving the hardness and abrasion resistance of the
compositions. The silica usually is colloidal silica having a
particle size of 1-100 .mu.m and is dispersed in water or solvent.
As previously mentioned, the silica particles sometimes become
visible in the protective thin film coatings formed from the
compositions or otherwise interfere with the optical clarity of the
lenses on which the coatings are applied.
[0014] Preformed colloidal silica particles are very porous and
have a density that usually is in the range of 1.0-1.5 g/cm.sup.3
depending on the process used to form the particles. In comparison,
fused silica has a density of 2.0-2.1 g/cm.sup.3. Because of this
relatively low density and the accompanying high porosity of the
preformed silica particles, thin film coatings formed with
compositions that contain such particles are readily tintable by
conventional dyes. The relatively porous preformed silica particles
also are relatively fragile and do not significantly alter the
relatively soft nature of the plastic matrix. By way of example,
the structure of a thin film that is formed from a composition that
includes a polymer and colloidal silica particles may be
represented in a simplified form as fragile balls enveloped by
relatively soft plastic resin.
[0015] For the above reasons, it would be desirable to have a film
forming composition wherein a silica component is self-generated in
situ within the solution during preparation of the composition, and
is covalently bonded with an organic polymer component of the
solution on a molecular level to provide an essentially single
phase state that has no interface problems.
[0016] U.S. Pat. Nos. 4,173,490, 4,186,026 and 4,229,228 disclose
compositions wherein tetraethyl orthosilicate,
methyltrimethoxysilane and glycidoxypropyltrimethoxysilane are
cohydrolized with water and acid, and wherein the amount of
methyltrimethoxysilane is very high, such as about 50 weight
percent. However, methyl is an inert organic group that
dramatically reduces the possible degree of crosslinking bonds.
Large amounts of methyl or phenyl groups commonly are included in
these types of film forming compositions to reduce brittleness and
minimize cracking at the sacrifice of film hardness. Decreased
crosslinking reduces the density of a film formed by the
composition so that it remains relatively porous and does not have
optimum hardness. The absence of any curing compound also reduces
the possible crosslinking reactions by silanol condensation and by
ring opening polymerization of epoxy groups. Therefore, these
compositions form thin films having a porosity such that the films
also are readily tintable by conventional organic dyes. U.S. Pat.
No. 4,547,397 also discloses a coating composition that includes
tetraethyl orthosilicate, methacryloxytrimethoxy and/or
vinyltriethoxysilane. Thin film coatings formed by this composition
also do not provide optimum abrasion resistance to the surface.
[0017] It would be desirable to provide a composition that can be
used to form protective thin film coatings having such a high
density and low porosity that they cannot be tinted by the use of
conventional dyes. Thus, the thin film coating would have a pore
size at 95-100.degree. C. and below that is smaller than 5
angstroms so that the pores cannot be penetrated by conventional
dye molecules in a wet molecular adsorption tinting process. Such
coatings provide high optimum abrasion and stain resistance that
are superior to the abrasion and stain resistance of known
protective thin film coatings.
[0018] This application will refer to several standard tests that
are used in the ophthalmic lens industry to quantify the abrasion
resistance and adhesion of lens coatings, and a brief description
of each test follows.
Bayer Abrasion Test
[0019] The Bayer test is one in a series of standard procedures for
determining the abrasion resistance of coated lenses. An abrasive
media is oscillated back and forth over the surface of a coated
lens under specified conditions. The abrasive media is 500 g of
Alumdum 1524, and a complete test process is 600 cycles at a speed
of 150 cycles/min. The quantification of abrasion resistance is
based on the optical measurement of haze gain due to scratches
formed on the coated lens by the oscillating abrasive media. The
quantification of abrasion resistance is based on a normalized
difference of the haze gain measured on the coated test lens
compared to the haze gain measured on an uncoated plano lens of
CR-39 resin provided as a reference by the International Standards
Organization, also known as the ISO. CR-39 is trademark of PPG
Industries, Inc., for allyl diglycol carbonate monomer or
diethylene glycol bis(allyl carbonate) resin.
Steel Wool Test
[0020] The steel wool test is one in a series of standard
procedures for determining the abrasion resistance of coated
ophthalmic lenses. A standard #000 steel wool pad with 5 pounds of
weight on top of it is oscillated across a coated lens at a speed
of 100 cycles per minute for 200 cycles. The quantification of
abrasion resistance is based on a visual comparison of the test
lens to a standardized series of reference lenses. The
quantification of abrasion resistance is based on a ratio of the
haze gain measured on the coated lens compared to the haze gain
measured on an ISO reference lens of uncoated piano CR-39.
Cross Hatch Test
[0021] This standard procedure is for evaluating the adhesion of a
hardcoat or an antireflective coating on a lens. Using a cutting
device such as a razor blade, six parallel cuts 1.5 mm .+-.0.5 mm
apart and approximately 15 to 20 mm in length are made in the
coating on the front or convex surface of the lens. Another six
parallel cuts 1.5 mm .+-.0.5 mm apart are made in the coating
perpendicular to the first set. This forms a cross-hatched pattern
of squares over which tape is applied, such as 3M Scotch brand #600
and 8981. The tape then is pulled rapidly as close to an angle of
180 degrees as possible, and the percent adhesion is quantified by
the amount of coating removed from the squares in the cross-hatched
pattern. The 180 degree reference means that the tape is pulled
back over itself in a direction that is nearly parallel to the lens
surface.
Boiling Salt Water Test
[0022] This standard procedure evaluates the ability of a hardcoat
or an antireflective coating to adhere to a lens and the
susceptibility of the coating to crazing. A coated lens is
subjected to ten cycles of thermal shock by submersing the coated
lens for two minutes in a boiling salt water solution which
comprises 3.5 liters of deionized water, 157.5 grams of sodium
chloride, and 29.2 grams of sodium dihydrogen orthophosphate,
followed by submersing the coated lens for one minute in water at
18-24.degree. C. Coating performance is quantified by whether or
not coating layer detachment or complete delamination from the lens
occurs, and by whether or not crazing of the coating occurs.
Thermal Test
[0023] This standard procedure evaluates the ability of a hardcoat,
an antireflective coating or a combination of both to adhere to a
lens, and the susceptibility of the coating to crazing at an
elevated temperature. A coated lens is subjected to six hours of
thermal aging in an air circulating oven at 80.degree. C. and
coating performance is quantified by whether or not crazing of the
coating occurs.
SUMMARY OF THE INVENTION
[0024] An optically clear protective thin film for polymeric
eyeglass lenses and other polymeric substrate surfaces has covalent
chemical bonds between polymer and silica molecules.
[0025] The protective thin film preferably has a thickness that is
between 1-7 .mu.m and most preferably between 1.5-5.0 .mu.m.
[0026] A protective film in accordance with the present application
has a very high density and a very high hardness to provide
excellent abrasion and stain resistance. The high density and
hardness are achieved by a high degree of cross linking between
organic molecules and inorganic silica.
[0027] The improved film has such a high density that it cannot be
tinted with the use of conventional dyes that are used for tinting
eyeglasses.
[0028] The improved film is formed from a coating solution that
includes tetraalkyl orthosilicate, epoxyalkylalkoxy silanes,
(math)acryloxyalkylalkoxy silanes and solvents.
[0029] In a preferred arrangement, a polymerizable component of the
coating solution is 20-50 weight percent of the entire solution.
The tetraalkyl orthosilicate comprises 40-75 weight percent of the
polymerizable component, the epoxyalkylalkoxy silanes comprises
20-45 weight percent of the polymerizable component, and the
(math)acryloxyalkylalkoxy silanes comprises 5-15 weight percent of
the polymerizable component.
[0030] Between 20-80 weight percent of the solution is solvent, and
20-50 weight percent of the solvent is water.
[0031] From 0.1-0.5 weight percent of the solution is 2M HCl, and
0.5-2.0 weight percent of the solution is acetic acid to provide a
solution pH that is 3-6.
[0032] A surfactant or wetting agent comprises 0.1-1.0 weight
percent of the solution, and a catalyst or curing agent comprises
0.2-0.5 weight percent of the solution.
[0033] In one arrangement, the ratio of the amount by weight of
epoxyalkylalkoxy silanes in the solution to the amount by weight of
(math)acryloxyalkylalkoxy silanes in the solution is between 15 to
1 and 0.2 to 1, and more preferably between 13 to 1 and 1 to 1.
[0034] In another arrangement, the molar ratio of water to the
combined epoxyalkylalkoxy silanes and (math)acryloxyalkylalkoxy
silanes is between 1 to 4 and 3 to 1, and more preferably between 1
to 2 and 2 to 1.
[0035] The coating solution is prepared by mixing together
tetraalkyl orthosilicate, epoxyalkylalkoxy silanes,
(math)acryloxyalkylalkoxy silanes, solvent, HCl and acetic acid,
and stirring at room temperature to partially hydrolyze the silane
groups until the solution appears to be clear by visual inspection.
The solution then is heated to 60-70.degree. C. and stirred for 1-2
hours to completely hydrolyze all silane groups and form
organic-inorganic hybrid oligmers.
[0036] The solution then is cooled back down to room temperature,
followed by the addition of the surfactant and the catalyst, and
stirring to completely dissolve the surfactant and catalyst.
[0037] The coating solution is applied to the surfaces of polymeric
lenses which then are baked in an air circulating oven at a
temperature of 90-120.degree. C. to completely polymerize the
coating and form an optically clear protective film.
[0038] It is a principal object of the present invention to provide
an improved coating solution for use in applying optically clear
protective thin films to the surfaces of plastic eyeglass lenses
and other polymeric substrates.
[0039] It is another object of the invention to provide an improved
method of making a coating composition wherein silica is generated
in situ within the coating solution mix during processing from the
solution constituents.
[0040] It is still another object of the invention to provide a
protective thin film in which organic and self-generated inorganic
molecules are bonded together on a molecular level with covalent
chemical bonds.
[0041] It is an additional object of the invention to provide a
coating solution that does not contain preformed silica but that
forms protective thin films that include self-generated silica
molecules as part of a polymer hybrid.
[0042] It is a further object of the invention to provide an
improved method for preparing a coating solution and for applying
same to substrate surfaces in a protective thin film.
[0043] It also is an object of the invention to provide a
protective base coat as a foundation or primer on plastic lens
surfaces and other substrates beneath multilayer inorganic films
deposited by chemical vapor deposition or sputtering methods.
[0044] It is a further object of the invention to provide a
composition that cures faster on plastic surfaces.
BRIEF DESCRIPTION OF THE DRAWING
[0045] The drawing illustrates the general formula for the
protective film of the present application with covalent chemical
bonds between organic and inorganic molecules, and with the areas
circled in dotted lines representing links between organic and
inorganic components.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0046] A film forming composition in accordance with the present
application is made by mixing tetraalkyl orthosilicate, organic
epoxies, one or more of functional trialkoxy silanes and/or
methacryloxy and/or acryloxy type silanes, solvent, acetic acid and
hydrochloric acid.
[0047] The solution is stirred at room temperature, which may be
10-38.degree. C. and more commonly is 18-24.degree. C., to
partially hydrolyze the silane groups. The solution is cloudy or
hazy when stirring begins, and stirring is continued at room
temperature until the solution becomes clear. Once the solution
becomes clear, it is heated to a temperature of 60-70.degree. C.
while stirring continues for one to two hours to completely
hydrolyze all silane groups. The solution then is cooled back down
to room temperature followed by the addition of a surfactant and a
catalyst. Stirring is continued to dissolve the surfactant and
catalyst, and to obtain a clear and homogeneous solution. The
composition now is ready for use in applying an optically clear
protective film to lenses or other surfaces.
[0048] The composition is applied to lens surfaces in any known
manner, such as by dipping or spin coating. By way of example, a
lens may be immersed in the coating solution and withdrawn at a
uniform rate of 5-15 cm/min. to control the film thickness. Instead
of withdrawing the lens from the solution, the solution may be
drained to expose the lens at the same uniform rate of 5-15 cm/min.
During withdrawal of the lens from the solution or during lowering
of the solution level, the lens is positioned with its surfaces
extending generally perpendicular to the solution surface i.e., the
lens is edgewise to the solution surface so that the lens surface
to be coated progressively exits the solution as the lens is lifted
or the solution is drained. The coating then is thermally cured by
placing the coated lens in an air circulating oven maintained at
90-120.degree. C. for 30-120 minutes, and more preferably for 30-60
minutes.
[0049] The above procedure provides the lens with an optically
clear protective film in which silica and polymer molecules are
chemically bonded together. The chemical bonding between organic
and inorganic molecules, along with a high degree of crosslinking,
provides a film that has a very high density and a low porosity.
The film cannot be tinted by conventional dyes using conventional
tinting processes, and this is a measure of the very high density
and very low density that is achieved. Although the size of the
pores themselves have not been measured, the inability of dye
molecules to penetrate the pores at a temperature of 95-100.degree.
C. indicates that the pores in the protective film are smaller than
5 angstroms at and below a temperature of 95-100.degree. C.
[0050] In many previous compositions for use in hardcoating lenses,
large amounts of methyl and/or phenyl groups having inert and loose
end groups are included to reduce brittleness and cracking of the
hardcoat film. Because the inert and loose end groups result in
less crosslinking within the composition, lens hardcoats formed
from such compositions do not have optimum hardness and are readily
tintable with conventional dyes using conventional tinting
processes. This indicates that prior protective films have pores
that are larger than 5 angstroms at and above a temperature of
95.degree. C.
[0051] In contrast to prior compositions of the type described, all
of the film forming constituents of a composition in accordance
with the present application have highly reactive end groups so
that every molecule has multiple reactive groups for crosslinking.
The large number of reactive end groups participate in crosslinking
at an elevated temperature, and provide a chemical bond between
inorganic silica molecules and organic polymer molecules. The
organic components always have reactive groups at both ends, and
short and linear organic groups function as tight springs to
enhance the toughness of a fully cured film that is formed from the
composition. In a most preferred form of the composition of the
present application, nonreactive free organic groups are excluded
from the composition in order to achieve the hardest film.
[0052] In the composition of the present application, the component
of tetraalkyl orthosilicate is a source of silica. The component of
organic epoxies is a source of silica, and also provides epoxy for
hardening of the film and adhesive bonding of same to a lens
surface. The component of one or more of functional trialkoxy
silanes and/or methacryloxy and/or acryloxy type silanes is a
source of silica, and also provides acrylic to enhance film
toughness and adhesive bonding of the film to a lens surface. This
latter component may be termed an organofunctional group that
promotes adhesion of the composition and a film formed therefrom to
a lens surface along with controlling brittleness. Selection of the
compounds and the amounts of them that are used in the latter
component makes it possible to vary the flexibility of a film that
is formed from the composition and thereby adjust the film
hardness, brittleness and resistance to crazing. The component of
acetic acid adjusts the pH of the solution which desirably is below
six. The component of hydrochloric acid is a catalyst that promotes
hydrolysis of the silane groups. During curing of a coating into an
abrasion resistant protective thin film on a lens surface,
tetra-silanol groups that are generated from hydrolyzed tetraalkyl
orthosilicate, along with silanol groups from hydrolyzed
organosilanes, proceed with a condensation reaction which is
promoted by a metal chelate catalyst.
[0053] In the composition of the present application, examples of
tetraalkyl orthosilicate include tetramethyl orthosilicate,
tetraethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl
orthosilicate. The weight percent of generated silica or silicate
from tetraalkyl orthosilicate should be between 60-25 weight
percent of all solids in the solution, and preferably between 50-35
weight percent of all solids in the solution.
[0054] The total amount of epoxy and mathacryloxy type silanes
should be between 40-75 weight percent of the total solids in
solution and preferably 50-65 weight percent of all solids in the
solution. The ratio of epoxy type silanes to methacryloxy type
silanes should be between 15:1 to 0.2:1, and preferably between
13:1 to 1:1.
[0055] Examples of epoxy type silanes include
glycidoxymethyltrimethoxysil- ane, glycidoxymethyltriethoxysilane,
2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane,
1-glycidoxyethyltrimethoxysilane, 1-glycidoxyethyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane,
3-glycidoxypropyltriethoxysilane,
2-glycidoxypropyltrimethoxysilane,
2-glycidoxypropyltriethoxysilane,
1-glycidoxypropyltrimethoxysilane,
1-glycidoxypropyltriethoxysilane, 4-glycidoxybutyltrimethoxysilane,
4-glycidoxybutyltriethoxysilane, 3-glycidoxybutyltrimethoxysilane,
2-glycidoxybutyltrimethoxysilane, 2-glycidoxybutyltriethoxysilane,
1-glycidoxybutyltrimethoxysilane, 1-glycidoxybutyltriethoxysilane,
(3,4-epoxycyclohexyl)methyltrimethoxysilane.
(3,4-epoxycyclohexyl)methylt- riethoxysilane,
glycidoxymethylmethyldimethoxysilane,
glycidoxymethylmethyldiethoxysilane,
2-glycidoxyethylmethyldimethoxysilan- e,
2-glycidoxyethylmethyldiethoxysilane,
1-glycidoxyethylmethyldimethoxysi- lane,
1-glycidoxyethylmethyldiethoxysilane,
3-glycidoxypropylmethyldimetho- xysilane,
3-glycidoxypropylmethyldiethoxysilane, 2-glycidoxypropylmethyldi-
methoxysilane, 2-glycidoxypropylmethyldiethoxysilane,
1-glycidoxypropylmethyldimethoxysilane,
1-glycidoxypropylmethyldiethoxysi- lane,
4-glycidoxybutylmethyldimethoxysilane,
4-glycidoxybutylmethyldiethox- ysilane,
3-glycidoxybutylmethyldimethoxysilane, 3-glycidoxybutylmethyldiet-
hoxysilane, 2-glycidoxybutylmethyldimethoxysilane,
2-glycidoxybutylmethyld- iethoxysilane,
1-glycidoxybutylmethyldimethoxysilane,
1-glycidoxybutylmethyldiethoxysilane,
(3,4-epoxycyclohexyl)methylmethyldi- methoxysilane, and
(3,4-epoxycyclohexyl)methylmethyldiethoxysilane.
[0056] Examples of methacryloxy or acryloxy type silanes include
2-methacryloxypropyltriethoxysilane,
3-acryloxypropyltrimethoxysilane, 2-acryloxypropyltriethoxysilane,
3-methacryloxypropylmethyldimethoxysilan- e,
2-methacryloxypropylmethyldiethoxysilane,
3-acryloxypropylmethyldimetho- xysilane,
2-acryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltrimet-
hoxysilane, methacryloxypropyltris(methoxyethoxy)methoxysilane.
[0057] Water is used to hydrolyze all silane groups in the
compounds that are present in the coating solution of the present
application. The molar ratio of water to all silanes should be from
1:4 to 3:1, and preferably from 1:2 to 2:1. A small amount of
acetic acid and hydrochloric acid is introduced to the composition
to assist the hydrolysis of silanes. The pH value of the solution
should be from 3-6, and more preferably 4-5.
[0058] Many different solvents can be used, including alkyl
alcohols such as methanol, ethanol, n-propanol, iso-propanol,
n-butanol and iso-butanol, and many other polar solvents such as
ketone types, acetonitrile, tetrahydrofuran, 2-ethoxyethanol, and
2-butoxyethanol. Wetting agents such as DuPont FSN, polydimethyl
siloxane type, and non-ionic surfactants such as polyethylene
oxides, Brij.RTM.92 and Brij.RTM.98 may be used in the
composition.
[0059] Many different metal complex compounds can be used as curing
agents, such as titanium acetylacetonate, aluminum acetylacetonate,
dibutyltin dilaurate, and zinc napthenate. The amount of curing
agent used is from 0.4-5.0 weight percent of all solids contained
in the solution, and more preferably from 1.0-3.0 weight percent of
all solids in the solution.
[0060] Because the protective film of the present application is
extremely hard, it can be very thin while still providing the
desired protection to a lens surface. The film may have a thickness
between 1-7 .mu.m, and more preferably between 1.5-5.0 .mu.m. The
thickness of the film can be controlled by one or more of adjusting
the concentration of the coating solution, by adjusting the speed
at which a lens is pulled from immersion in the coating solution,
by adjusting the coating solution temperature and by adjusting the
coating solution viscosity. Adjusting the speed at which the lens
is pulled from immersion in a coating solution bath is a convenient
way to control the film thickness.
[0061] The film thickness also depends on the solids content of the
coating solution and on the viscosity of the coating solution, the
latter being affected by the temperature of the coating solution
when the lens is immersed and pulled. Higher solids content results
in a higher viscosity and a thicker film, and also reduces the
shelf life of the coating solution. Lower solids content may result
in a thinner film. The recommended solids content is between 15-50
weight percent of the entire coating solution, more preferably
20-50 weight percent of the entire coating solution and most
preferably between 20-40 weight percent of the entire coating
solution.
[0062] The shelf life or pot life of the coating solution depends
on several factors including solution temperature, pH value,
organic-to-inorganic ratio and solids content. In the preferred
composition of the present application, all end groups of the
organic-inorganic oligomers are either silanols or epoxy which can
react at ambient temperature, and the reaction rate depends on the
temperature of the coating solution. As is known from sol-gel
chemistry, silanol groups continuously proceed with a condensation
reaction and this reduces the shelf life of the coating solution.
As a result of this condensation reaction, the molecular weight of
the organic-inorganic oligomers increases and the coating solution
becomes more viscous. It is well-known that the condensation
reaction proceeds slowly at a solution pH that is between 3-6 and
at lower temperatures. Low temperature storage will extend the
shelf life of the coating solution. The epoxy groups are relatively
stable at ambient temperature, and ring opening polymerization
proceeds faster at an elevated temperature when a coating on a lens
is undergoing thermal curing during final film formation.
[0063] The structure of organic-inorganic oligomers in the coating
solution of the present application can be described as follows:
due to the high reactivity and concentration of silanols after
hydrolysis of tetraethyl orthosilicate and organoalkoxysilane, the
formation of O--Si--O prevails. The reactivity of R.sub.4 -x
Si(OH).sub.x(x=1-3) and Si--(OH).sub.4 are similar. R groups limit
or stop the silanol condensation reaction process due to steric
effects. The core of the organic-inorganic oligomers may have more
O--Si--O--Si three-dimensional net structure, and the outer layer
may have more organic component. It is believed that the transition
from the core to the outer layer is gradual. As a result, the
composition of the present application is relatively stable. At
room temperature, the gelation time of the coating solution is more
than six months. If the coating solution is maintained between
0-15.degree. C., it can be used after more than three months of
storage.
[0064] The coating solution of the present application preferably
is maintained at a temperature of 10-15.degree. C. to provide
stability of the coating solution and uniform quality of protective
films that are formed therefrom. The coating solution may be at
room temperature during coating of lenses but is not recommended,
and the temperature also depends on the coating process that is
used.
[0065] The quality of the protective film and its adhesion to a
plastic substrate depend on careful control of the coating process.
Great care should be taken and stringent efforts must be made at
all stages of the coating process to avoid contamination and ensure
cleanliness of the substrate surface, the coating solution and the
coating environment.
[0066] The cleanliness and smoothness of the substrate surface is
essential to the whole operation because a good coating will be
obtained only if the substrate is wetted uniformly and completely
by the coating solution. Any defect or dust on the substrate
surface will interrupt the coating film and produce a coating flaw.
There are some cleaning operations that can be carried out to
ensure that uniform wetting takes place. Cleaning with solvents is
a standard procedure that can include washing with a mild aqueous
detergent followed by washing with organic solvents such as
ethanol. The solvent that is used should not dissolve the
substrate. In some cases, a preliminary treatment involving a
chemical etch with an acid and a base, ultrasonic treatment, high
pressure spray and heat can be used individually or in combination.
Surface roughness or scratches that can interrupt the uniform flow
of coating solution will produce coating flaws. Therefore, highly
polished surfaces are most desirable.
[0067] Clean and dry plastic lenses or other plastic substrates may
be provided with an optically clear protective film by immersing
the entire article in the coating solution followed by pulling the
article from the solution at a rate of 5-15 cm/min. to form a
coating on the substrate surface. The article then is placed in an
air circulating oven that is maintained at a temperature of
90-120.degree. C. for 30-120 minutes to thermally cure the coating
to a protective thin film. Other coatings may be provided over the
protective film with no further cleaning or activation of the
surface of the protective film. For example, a hydrophobic film may
be applied over the protective film. The protective film also may
serve as a base coat for deposition of an antireflective film by
chemical vapor deposition or sputtering, and a hydrophobic film may
be applied over the antireflective film.
[0068] An example of applying a protective film to a lens in
accordance with the present application follows:
EXAMPLE I
[0069] A coating solution is prepared by mixing 104.0 g of
tetraethyl orthosilicate, 45.0 g of
glycidoxypropyltrimethoxysilane, 5.0 g
methacryloxypropyltrimethoxysilane, 119.0 g of isopropyl alcohol,
43.0 g of water, 0.4 g of 2M HCl and 3.2 g of 2M acetic acid. The
solution is stirred at room temperature to partially hydrolyze the
silane groups until a clear solution is obtained. The solution is
then heated up to and maintained at 60-70.degree. C. for 1-2 hours
while continuing the stirring to completely hydrolyze all silane
groups. The solution is then cooled to room temperature, followed
by the addition of 1.6 g of Brij.RTM.98 surfactant and 1.2 g of
aluminum acetylacetonate catalyst. The solution then is stirred to
dissolve the solids, and to obtain a homogeneous and clear
solution.
[0070] A CR-39 lens is cleaned dried and immersed into the coating
solution and withdrawn edgewise with the lens surfaces generally
perpendicular to the solution surface at a rate of 5-15 cm/min. In
the alternative, the coating solution may be drained to expose the
lens at the same rate of 5-15 cm/min. The coated lens is placed in
an air circulating oven maintained at 90-120.degree. C. for 30-120
minutes to cure the coating.
[0071] After cooling down to room temperature, the coated lens is
subjected to 600 cycles of Bayer abrasion testing. The coated lens
measures 3-4% haze, compared with 20-25% haze for an uncoated CR-39
lens after 600 cycles of Bayer abrasion testing. Table 1 gives the
results of a Bayer test on commercially available lenses and on a
lens that has the hybrid organic-inorganic hardcoat of the present
application in accordance with Example 1.
1TABLE 1 Base Lens Bayer Haze after Lens Material Ratio Bayer (%)
Manufacturer Bare CR-39 CR-39 -- 20-25 Essilor CR-39 Truetint CR-39
2.06 10.9 Essilor CR-39 Permagard CR-39 2.30 9.8 Sola Poly-Orcolite
Polycarbonate 1.13 20.0 Vision-Ease Poly-Gentax PDQ Polycarbonate
1.36 16.6 Gentax Poly-Gentax GLC Polycarbonate 3.04 7.4 Gentax
Example I CR-39 7.5-4.5 3-4 Applicant
[0072] The coating solution does not provide satisfactory adhesion
to all types of lens materials, such as high index and
polycarbonate, and an activator or primer layer may be required
before applying the coating in order to insure a good bond to the
lens surface. The bonding layer usually comprises coupling agents
such as 3-aminopropyltrimethoxysilane,
2-aminoethyl-3-amino-propyltriethoxysilane,
3-aminopropylmethyldimethoxys- ilane,
2-aminoethyl-3-amino-propylmethyldiethoxysilane, etc. The use of
coupling agents should not interrupt the flow of the coating
solution on the lens surface.
[0073] The following is an example of the coating composition of
the present application used as a base coat for other inorganic
films, such as antireflective films, deposited by any known process
such as chemical vapor deposition or sputtering.
EXAMPLE II
[0074] A scratch resist coating solution is prepared by mixing 313
g of tetraethyl orthosilicate, 200 g of
glycidoxypropyltrimethoxysilane, 40 g
methacryloxypropyltrimethoxysilane, 472 g of isopropyl alcohol, 144
g of water, 1.2 g of 2M HCl and 10.8 g 2M HAc. The solution is
stirred at room temperature to partially hydrolyze the silane
groups until a clear solution is obtained. The solution is then
heated up to and maintained at 60-70.degree. C. for 1-2 hours while
continuing the stirring to completely hydrolyze all silane groups.
The solution is then cooled to room temperature followed by the
addition of 6.0 g of Brij.RTM.98 surfactant and 4.0 g of aluminum
acetylacetonate catalyst. The solution is then stirred to dissolve
the solids, and obtain a homogeneous and clear solution.
[0075] A CR-39 lens is cleaned, dried and immersed into the coating
solution followed by withdrawal edgewise with the lens surfaces
generally perpendicular to the solution surface at a rate of 5-15
cm/min. The coated lens is placed in an air circulating oven at
90-120.degree. C. for 30-120 minutes to cure the coating. A
polycarbonate lens is cleaned and dried, primed with a solution of
0.5-5 weight percent aminosilane in methanol, or ethyl alcohol, or
isopropyl alcohol, or a mixture of them. The polycarbonate lens
then is immersed into the coating solution and withdrawn at a rate
of 5-15 cm/min. An antireflective film can be deposited immediately
after curing of the coating, and a hydrophobic film is then applied
on top of the antireflective film. The hydrophobic film may be of
the type described in U.S. Pat. No. 5,219,654 to Singh et al, the
disclosure of which is hereby incorporated herein by reference. The
lens coated with a base coat of the present application along with
the antireflective film and an hydrophobic film is subjected to 600
cycles of Bayer abrasion testing, the steel wool test, the boiling
salt water test, and the thermal test. The tape cross hatch test is
carried out both after curing of the base coat and after
application of the antireflective film but before application of
the hydrophobic film. The test results are summarized in Table 2
where AR means that the lens included an antireflective
coating.
2TABLE 2 Bayer Haze after Lens Material Ratio Bayer (%)
Manufacturer Bare CR-39 1.00 20-25 Essilor Bare CR-39 w/AR 1.36
16.5 Essilor CR-39 Truetint 2.06 10.9 Essilor CR-39 Truetint
w/(Zeiss)AR 1.61 10.3 Essilor CR-39 Permagard 2.30 9.8 Sola CR-39
Permagard 1.18 19.0 Sola w/(Zeiss)AR CR-39 Truetint TD.sub.2 4.09
5.5 Essilor CR-39 Truetint TD.sub.2 1.13 20.0 Essilor w/(Zeiss)AR
CR-39 Crizal w/AR 2.37 9.5 Essilor CR-39 UTMC w/AR 2.50 9.0 Sola
Bare Polycarbonate 0.4-0.6 40-60 Oracle Poly-Diamonex 3.46 6.5
Diamonex Poly-Diamonex w/AR 2.27 9.9 Diamonex Poly-Sola-Multi C
w/AR 2.53 8.9 Sola Example II CR-39 + Base 7.5-4.5 3-5 Applicant
Coat + AR Example II Polycarbonate + 5.5-3.7 4-6 Applicant Base
Coat + AR Glass Lens w/AR (MgF.sub.2) 10.71 2.1 Zeiss Glass Lens
w/AR 3.13 7.2 Zeiss
[0076] From Table 2, the Bayer test results indicate that an
antireflective film applied on top of any hardcoat impairs the
scratch-resistance of the lens. For example, the haze reading after
Bayer tests on a CR-39 Permagard lens is 9.8% without an
antireflective film and is 19.0% with an antireflective coating.
The CR-39 Truetint, CR-39 TD.sub.2 and Poly-Diamonex lenses all
show the same phenomenon. This could be due to physical and/or
chemical incompatibilities between the antireflective film and the
base hardcoat even after surface activation procedures are
performed. In contrast, an antireflective film applied to a base
hardcoat in accordance with the present application provides much
better results. As shown in Table 2, the haze reading after the
Bayer test for a CR-39 lens having an antireflective film applied
over a base hardcoat in accordance with the present application is
only 3-5, and for a polycarbonate lens it is 4-6. It is believed
that this improvement is due in part to the excellent compatibility
between the physical and chemical properties of antireflective
films and films formed with the coating solution of the present
application. This provides superior adhesion of the antireflective
film to the base hardcoat of the present application without
requiring any surface activation procedures on the base hardcoat.
Scratches on lenses coated with the improved protective film of the
present application are much finer and less visible than scratches
on lenses with prior art coatings.
[0077] Thermal tests such as the boiling salt water test serve to
evaluate the adhesion between an antireflective film and a base
layer, as well as between a base layer and plastic substrates to
which the base layer is applied. Table 3 tabulates the tests on
lenses coated in accordance with Example II in comparison to tests
on commercially available lenses. The most significant improvements
provided by the coating of the present application are in the
boiling salt water test and the thermal test. Antireflective lenses
having a base hardcoat in accordance with the present application
are the only ones that grade 5 in the boiling salt water test and
this compares to a grade of 0 for the other lenses.
3TABLE 3 Example Test Lens A Lens B Lens C II Lens Bayer Ratio 2.46
.+-. 4.43 .+-. 4.14 .+-. 8.84 .+-. 0.28 0.32 0.44 0.33 Steel Wool
haze gain 1.1 0.2 0.5 0.3 Boiling Salt Water A Effects A0 A0 A0 A5
B Effects B5 B5 B5 B5 C Effects C5 C5 C5 C5 Crosshatch Adhesion 5 5
5 5 Thermal Test A Effects A0 A0 A0 A5 B Effects B5 B5 B5 B5 C
Effects C5 C5 C5 C5
[0078] The following is an explanation of the meaning of the codes
and designations used in Table 3. CR-39 is a registered trademark
of PPG Industries, Inc., for allyl diglycol carbonate. Lens A is a
lens of CR-39 that has a manufacture hardcoat, an antireflective
film and a hydrophobic film, and is marketed under the trademark
Carat, a trademark of Carl-Zeiss-Stiftung. Lens B is a lens of
CR-39 that has a manufacture hardcoat and an antireflective film,
and is marketed under the trademark UTMC, a trademark of Pilkington
Visioncare, Inc. for ophthalmic lenses. Lens C is a lens of CR-39
with a manufacture hardcoat, an antireflective film and a
hydrophobic film, and is marketed under the trademark Crizal, a
trademark of Essilor International for ophthalmic lenses; namely,
spectacle lenses, spectacle lenses of plastics material, sunglass
lenses, tinted spectacle lenses, photosensitive spectacle lenses;
spectacle frames; contact lenses; cases for the aforesaid goods.
The Example II lens is the CR-39 lens coated according to Example
II with the protective base hardcoat film of the present
application plus an antireflective film and an hydrophobic film.
The Bayer Ratio is the ratio of haze gain on International
Standards Organization lenses divided by the haze gain of tested
lenses. The results are based on ten tested samples.
[0079] In Table 3, A Effects for the Boiling Salt Water test and
the Thermal Test is the quantification of crazing results. A5 means
no visible crazing, A4 means barely visible points, cracks or
hairline crazing, A3 means hairline crazing on up to 25% of the
lens surface, A2 means hairline crazing on up to 75% of the lens
surface, A1 means hairline crazing over the entire lens surface,
and A0 means severe fern-like or matt-like crazing over any region
of the lens.
[0080] In Table 3, B Effects for the Boiling Salt Water Test and
the Thermal Test is the quantification of results for delamination
by interlayer detachment. B5 means no delamination of individual
layers over the entire lens surface, B4 means partial delamination
of individual layers on up to 25% of the surface, B3 means partial
delamination of individual layers on up to 75% of the surface, and
B2 means total delamination of individual layers over the entire
lens surface.
[0081] In Table 3, C Effects for the Boiling Salt Water Test and
the Thermal Test is the quantification of results for delamination
by complete coating detachment. C5 means no coating delamination of
all layers from the lens surface, C4 means delamination of all
layers up to 25% of the surface, C3 means delamination of all
layers up to 75% of the surface, and C2 means complete coating
delamination over the entire lens surface.
[0082] In Table 3, the results of the Crosshatch Adhesion test are
graded between 0-5. A grade of 5 means that the edges of the cuts
are completely smooth and none of the squares in the cross hatched
area are detached; a grade of 0 means the coating has flaked along
the edges of the cuts in large ribbons and whole squares are
detached in an affected area that is greater than 65% of the lens
surface area.
[0083] In a most preformed form of the present application, the
composition and the film formed therefrom contains no preformed
silica, such as colloidal silica. Thus, all of the silica in the
composition and the cured film is self-generated in situ during
preparation of the composition from silica precursor components
that are used to prepare the composition. Preformed colloidal
silica has a density of 1.0-1.5 g/cm.sup.3, and the self-generated
silica in the composition of the present application is believed to
have a density that is significantly greater than 1.5 g/cm. The
self-generated silica is believed to have a density somewhat less
than the density of 2.0-2.1 g/cm.sup.3 for fused silica. Thus, the
self-generated silica is believed to have a density intermediate
1.5 g/cm.sup.3 to 2.1 g/cm.sup.3, and to be closer to 2.1
g/cm.sup.3 than to 1.5 g/cm.sup.3.
[0084] Although the cured film was not tintable by organic
molecules in a wet molecular adsorption process, it may be possible
to add dyes to the solution during mixing of the composition in
order to produce a film that is tinted instead of being optically
clear.
[0085] The film of the present application can be cured much faster
than previous films, a full cure being achieved in less than one
hour and most preferably in not more than thirty minutes. Although
the size of the pores in the cured film has not been measured, it
is believed to be less than five angstroms because that is believed
to be the smallest size of the organic molecules in the dyes that
are used for tinting eyeglass lenses in a wet molecular adsorption
process.
[0086] Although the invention has been described with reference to
a preferred embodiment, it is obvious that equivalent alterations
and modifications will occur to others skilled in the art upon the
reading and understanding of this specification. The present
invention includes all such equivalent alterations and
modifications, and is limited only by the scope of the claims.
* * * * *