A coating composition for forming a transparent, abrasion-resistant coating upon eyeglass lenses or other transparent substrates, the composition comprising a binder component and a curing agent component and being substantially free of volatiles. The binder component comprises the hydrolysis product of an epoxy-functional alkoxy silane, a polyglycidyl ether, and an acrylic monomer having an acrylic functionality of not more than two. The curing agent component comprises a cationic photoinitiator and a free radical photoinitiator.

FIELD OF THE INVENTION 
The invention relates to the field of transparent coatings for transparent 
objects such as eyeglass lenses, windows and the like, and refers 
particularly to a coating having an index of refraction essentially equal 
to that of the substrate that is coated. 
BACKGROUND OF THE INVENTION 
Transparent plastic materials such as eyeglass lenses, television screen 
face plates and the protective coatings on photographic prints often are 
quite soft and are subject to becoming dull and hazy due to scratching and 
abrasion during use. Polycarbonate eyeglass lenses, for example, are 
strong and shatter resistant but also are relatively soft and susceptible 
to scratching. Television screen face plates similarly are made of 
flexible, shatter resistant plastic materials such as polycarbonate and 
poly (methylmethacrylate), and these also can be scratched or abraded. 
Various coatings have been proposed for eyeglasses and other transparent 
plastic materials to reduce their propensity to become scratched and 
abraded. One such composition is shown in U.S. Pat. No. 4,378,250 
(Treadway, et al.) granted Mar. 29, 1983. Other coatings are shown in U.S. 
Pat. Nos. 5,367,019 (Sawara), 4,855,180 (Kawamura), 4,895,767 (Mori et 
al.) and 4,719,146 (Hohage et al.) Besides being abrasion resistant, 
coatings for eyeglass lenses should also be capable of being tinted by 
treatment with a dye which becomes incorporated in the coating. As a 
general observation, the tintability of a coating tends to decrease as its 
hardness and scratch resistance increases, and vice-versa. 
Harasta, et al. U.S. Pat. No. 4,426,431 discusses a coating composition 
referred to as a "hybrid " system because it employs a solution, in a 
solvent such as propylene carbonate, an epoxy compound and a cationic 
initiator for it, and an acrylic compound and a free radical initiator for 
it. In general, coating compositions suitable for use in forming 
protective transparent coatings on eyeglass lenses and the like are 
provided in solution in a volatile solvent, the solvent serving as a low 
viscosity vehicle to enable the coating composition to be uniformly spread 
upon a surface and to accept dye treatments. The solvents that are 
employed are for the most part organic, and must be used and disposed of 
carefully. 
Perkins et al. U.S. Pat. No. 5,221,560 describes a coating composition 
containing a polyfunctional, polymerizable non-acrylate functional ether, 
a radiation-sensitive initiator, and colloidal silica in an amount 
providing at least 25% by weight of the total solids of the composition, 
the silica being reacted with a small amount of a hydrolyzed 
acryloxy-functional or glycidoxy-functional silane. 
It would be desirable to provide a coating composition that is capable of 
forming coatings having both excellent abrasion resistance and dye 
acceptance. 
SUMMARY OF THE INVENTION 
The present invention utilizes a coating composition that utilizes that 
accepts dye well, that provides exceptional abrasion-resistance, and that 
is substantially free of volatiles. The composition includes at least 10% 
by weight, solids basis, of an at least partially hydrolyzed 
epoxy-functional alkoxysilane. Included also in the composition is a 
polymerizable ether, desirably cationically polymerizable, selected from 
the group consisting of glycidyl ethers, allyl ethers and vinyl ethers, 
and an ethylenically unsaturated monomer component, desirably an acrylic 
monomer component that preferably includes a monomer having an acrylic 
functionality of not more than two. A cationic photoinitiator is employed 
to affect polymerization of the epoxy-functional components, and a free 
radical initiator is employed to initiate polymerization of the 
ethylenically unsaturated coating components, that is, the 
acrylic-functional component. The polymerizable ethers improve tintability 
of the resulting coating, and use of the acrylic monomer results in 
excellent adhesion to polycarbonate substrates. 
Hydrolysis of the alkoxysilane may but need not be complete, and 
preferably, the alkoxysilane is reacted with a stoichiometricly sufficient 
quantity of water to hydrolyze at least 50% of the alkoxy groups and most 
preferably from about 60% to about 70% of the alkoxy groups. In a 
preferred embodiment, the coating composition is substantially free of 
volatile solvents and also preferably is free of silica. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The epoxy functional alkoxy silane precursor of the at least partially 
hydrolyzed polymerizable ingredient is preferably an 
epoxyalkylalkoxysilane of the following structure: 
EQU Q-R.sub.1 -Si(R.sub.2).sub.m -(OR.sub.3).sub.3-m 
wherein R.sub.1 is a C.sub.1 -C.sub.14 alkylene group, R.sub.2 and R.sub.3 
independently are C.sub.1 -C.sub.4 alkyl groups and Q is a glycidoxy or 
epoxycyclohexyl group, and m is 0 or 1. The alkoxy groups are at least 
partially hydrolyzed to form silanol groups with the release of the 
R.sub.3 OH alcohol, and some condensation of the silanol groups occurs. 
Epoxy reactivity is preserved, however. Many epoxy-functional 
alkoxysilanes are suitable as hydrolysis precursors, including 
glycidoxymethyl-trimethoxysilane, glycidoxymethyltriethoxysilane, 
glycidoxymethyl-tripropoxysilane, glycidoxymethyl-tributoxysilane, 
b-glycidoxyethyltrimethoxysilane, b-glycidoxyethyltriethoxysilane, 
b-glycidoxyethyl-tripropoxysilane, b-glycidoxyethyl-tributoxysilane, 
b-glycidoxyethyltrimethoxysilane, a-glycidoxyethyl-triethoxysilane, 
a-glycidoxyethyl-tripropoxysilane, a-glycidoxyethyltributoxysilane, 
g-glycidoxypropyl-trimethoxysilane, g-glycidoxypropyl-triethoxysilane, 
g-glycidoxypropyl-tripropoxysilane, g-glycidoxypropyltributoxysilane, 
b-glycidoxypropyl-trimethoxysilane, b-glycidoxypropyl-triethoxysilane, 
b-glycidoxypropyl-tripropoxysilane, b-glycidoxypropyltributoxysilane, 
a-glycidoxypropyl-trimethoxysilane, a-glycidoxypropyl-triethoxysilane, a 
-glycidoxypropyl-tripropoxysilane, a-glycidoxypropyltributoxysilane, 
g-glycidoxybutyl-trimethoxysilane, d-glycidoxybutyl-triethoxysilane, 
d-glycidoxybutyl-tripropoxysilane, d-glycidoxybutyl-tributoxysilane, 
d-glycidoxybutyl-trimethoxysilane, g-glycidoxybutyl-triethoxysilane, 
g-glycidoxybutyl-tripropoxysilane, g-propoxybutyl-tributoxysilane, 
d-glycidoxybutyl-trimethoxysilane, d-glycidoxybutyl-triethoxysilane, 
d-glycidoxybutyl-tripropoxysilane, a-glycidoxybutyl-trimethoxysilane, 
a-glycidoxybutyl-triethoxysilane, a-glycidoxybutyl-tripropoxysilane, 
a-glycidoxybutyl-tributoxysilane, 
(3,4-epoxycyclohexyl)-methyl-trimethoxysilane, 
(3,4-epoxycyclohexyl)methyl-triethoxysilane, 
(3,4-epoxycyclohexyl)methyl-tripropoxysilane, 
(3,4-epoxycyclohexyl)-methyl-tributoxysilane, 
(3,4-epoxycyclohexyl)ethyl-triethoxysilane, 
(3,4-epoxycyclohexyl)ethyl-triethoxysilane, 
(3,4-epoxycyclohexyl)ethyl-tripropoxysilane, 
(3,4-epoxycyclohexyl)-ethyl-tributoxysilane, 
(3,4-epoxycyclohexyl)propyl-trimethoxysilane, 
(3,4-epoxycyclohexyl)propyl-triethoxysilane, 
(3,4-epoxycyclohexyl)propyl-tripropoxysilane, 
(3,4-epoxycyclohexyl)propyl-tributoxysilane, 
(3,4-epoxycyclohexyl)butyl-trimethoxysilane, 
(3,4-epoxycyclohexy)butyl-triethoxysilane, 
(3,4-epoxycyclohexyl)-butyl-tripropoxysilane, and 
(3,4-epoxycyclohexyl)butyl-tributoxysilane. 
A particularly preferred epoxyalkylalkoxysilane is .gamma.-glicidoxypropyl 
trimethoxy silane due to its wide commercial availability. 
Hydrolysis of the epoxy-functional alkoxysilane precursor may occur in an 
acidic environment, and reference is made to U.S. Pat. No. 4,378,250, the 
teachings of which are incorporated herein by reference. Hydrolysis of the 
alkoxy groups liberates the associated alcohol to form silanol groups; 
these, in turn, are relatively unstable and tend to condense 
spontaneously. Preferably, the alkoxysilane is reacted with a 
stoichiometricly sufficient quantity of water to hydrolyze at least 50% of 
the alkoxy groups and most preferably from about 60% to about 70% of the 
alkoxy groups. For the hydrolysis of an epoxy-functional trialkoxy silane, 
good results have been obtained by reacting the silane with a 
stoichiometricly sufficient quantity of water to hydrolyze two-thirds of 
the alkoxy groups. 
The at least partially hydrolyzed epoxy-functional silane is present in the 
coating compositions of the invention at a weight concentration (solids 
basis) of 10% to 75%, and preferably 20% to 50%. 
Useful cationic initiators for the purposes of this invention include the 
aromatic onium salts, including salts of Group Va elements, such as 
phosphonium salts, e.g., triphenyl phenacylphosphonium 
hexafluorophosphate, salts of Group VIa elements, such as sulfonium salts, 
e.g., triphenylsulfonium tetrafluoroborate, triphenylsulfonium 
hexafluorophosphate and triphenylsulfonium hexafluoroantimonate, and salts 
of Group VIIa elements, such as iodonium salts, e.g., diphenyliodonium 
chloride. The aromatic onium salts and their use as cationic initiators in 
the polymerization of epoxy compounds are described in detail in U.S. Pat. 
No. 4,058,401, "Photocurable Compositions Containing Group VIA Aromatic 
Onium Salts," by J. V. Crivello issued Nov. 15, 1977; U.S. Pat. No. 
4,069,055, "Photocurable Epoxy Compositions Containing Group VA Onium 
Salts," by J. V. Crivello issued Jan. 17, 1978; U.S. Pat. No. 4,101,513, 
"Catalyst For Condensation Of Hydrolyzable Silanes And Storage Stable 
Compositions Thereof," by F. J. Fox et al. issued Jul. 18, 1978; and U.S. 
Pat. No. 4,161,478, "Photoinitiators," by J. V. Crivello issued Jul. 17, 
1979, the disclosures of which are incorporated herein by reference. Other 
cationic initiators can also be used in addition to those referred to 
above; for example, the phenyldiazonium hexafluorophosphates containing 
alkoxy or benzyloxy radicals as substituents on the phenyl radical as 
described in U.S. Pat. No. 4,000,115, "Photopolymerization Of Epoxides," 
by Sanford S. Jacobs issued Dec. 28, 1976, the disclosure of which is 
incorporated herein by reference. Preferred cationic initiators for use in 
the compositions of this invention are the salts of Group VIa elements and 
especially the sulfonium salts. Particular cationic catalysts include 
diphenyl iodonium salts of tetrafluoro borate, hexafluoro phosphate, 
hexafluoro arsenate, and hexafluoro antimonate; and triphenyl sulfonium 
salts of tetrafluoroborate, hexafluoro phosphate, hexafluoro arsenate, and 
hexafluoro antimonate. 
The polymerizable ether component imparts tintability, and is selected from 
the group consisting of glycidyl ethers, allyl ethers and vinyl ethers. 
The polymerizable ethers may be monofunctional or polyfunctional, 
preferably polyfunctional, and desirably are cationically polymerizable. 
Mixtures of the polymerizable ethers may be used, particularly mixtures of 
glycidyl ethers and vinyl ethers. These ethers preferably are non-acrylate 
functional. 
Glycidyl ethers useful in the invention include triglycidyl ether, 
.gamma.-glycidoxypropyl trimethoxy silane, triglycidyl ether, 
1,4-butanediol diglycidyl ether, Bisphenol A diglycidyl ether, the C.sub.8 
-C.sub.14 alkyl glycidyl ethers, butyl glycidyl ether, cresyl glycidyl 
ether, phenyl glycidyl ether, nonylphenyl glycidyl ether, 
p-tert-butylphenyl glycidyl ether, 1,4-butanediol diglycidyl ether, 
neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, 
polyglycidyl ethers of aliphatic polyols, cyclohexane dimethanol 
diglycidyl ether, 2-ethylhexyl glycidyl ether, polyglycol diepoxide, 
polyglycidyl ether of castor oil, trimethylolethane triglycidyl ether, 
trimethylolpropane triglycidyl ether, dibromoneopentyl glycol diglycidyl 
ether, and 3,4-epoxycyclohexyl methyl-3,4-epoxycyclohexane carboxylate. 
Glycidyl ethers, if used alone as the polymerizable ether, are present 
preferably in a weight concentration (solids basis) of from about 10% to 
about 50%. 
Allyl ethers include 1,1,2,2,-tetraallyloxyethane, triallylcyanurate, 
polyallylglycidyl ether, and allylglycidyl ether. Allyl ethers, if used 
alone as the polymerizable ether, preferably are employed at a weight 
concentration (solids basis) of up to about 10%. 
Vinyl ethers include triethylene glycol divinyl ether, diethylene glycol 
divinyl ether, tetraethylene glycol divinyl ether, dipropylene glycol 
divinyl ether, tripropylene glycol divinyl ether, 1,4-divinyloxybutane, 
and, as a preferred ether, cyclohexane dimethanol divinyl ether. If used 
alone as the polymerizable ether, a vinyl ether preferably is employed at 
a weight concentration (solids basis) not greater than about 15%, and most 
preferably in the range of about 5% to about 10%. 
As noted above, the polymerizable ether ingredient may consist of a mixture 
of two or more ethers, the relative amounts of which are chosen so as to 
provide the cured coating with good tintability while maintaining 
acceptable adhesion to substrates. Employing too much of the polymerizable 
ether may tend to adversely affect adhesion of the coating to substrates, 
particularly polycarbonate substrates. 
Of the ethylenically unsaturated monomers, vinyl acetate contributes to 
good adhesion to polycarbonate substrates. However, acrylic-functional 
monomers and oligomers are preferred. Useful acrylic compounds for 
improving adhesion to polycarbonate substrates include both mono and 
di-functional monomers, but other or additional polyfunctional acrylic 
monomers may also be included. Examples of monofunctional acrylic monomers 
include acrylic and methacrylic esters such as ethyl acrylate, butyl 
acrylate, 2-hydroxypropyl acrylate, cyclohexyl acrylate, 2-ethylhexyl 
acrylate, methyl methacrylate, ethyl methacrylate, and the like. Examples 
of polyfunctional acrylic monomers, including both difunctional and tri 
and tetrafunctional monomers, include neopentylglycol diacrylate, 
pentaerythritol triacrylate, 1,6-hexanediol diacrylate, trimethylolpropane 
triacrylate, tetraethylene glycol diacrylate, 1,3-butylene glycol 
diacrylate, trimethylolpropane trimethacrylate, 1,3-butylene glycol 
dimethacrylate, ethylene glycol dimethacrylate, pentaerythritol 
tetraacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol 
dimethacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, 
glycerol diacrylate, glycerol triacrylate, 1,3-propanediol diacrylate, 
1,3-propanediol dimethacrylate, 1,2,4-butanetriol trimethacrylate, 
1,4-cyclohexanediol diacrylate, 1,4-cyclohexanediol dimethacrylate, 
pentaerythritol diacrylate, 1,5-pentanediol dimethacrylate, and the like. 
The acrylic-functional monomers and oligomers preferably are employed at a 
weight concentration of from about 10% to about 50% on a solids basis 
Although photoactivated free-radical initiator are preferred, thermally 
activated free radical initiators may also be used. Useful photoinitiators 
for this purpose are the haloalkylated aromatic ketones, 
chloromethylbenzophenones, certain benzoin ethers, certain acetophenone 
derivatives such as diethoxyacetophenone and 
2-hydroxy-2-methyl-1-phenylpropan-1-one. A preferred class of free-radical 
photoinitiators is the benzil ketals, which produce rapid cures. A 
preferred photoinitiator is .alpha.,.alpha.-dimethoxy-.alpha.-phenyl 
acetophenone (Iragacure.TM. 651, Ciba-Geigy, disclosed in U.S. Pat. Nos. 
3,715,293 and 3,801,329). The most preferred photoinitiator, in accordance 
with this invention, is 2-hydroxy-2-methyl-1-phenylpropane-1-one 
(Darocure.TM. 1173, Ciba-Geigy Corporation). Specific examples of 
photoinitiators include ethyl benzoin ether, isopropyl benzoin ether, 
dimethoxyphenyl acetophenone, diethoxy acetophenone, and benzophenone. 
The invention may be better understood by reference to the following 
non-limiting examples. Cured coatings were subjected to several tests, 
outlined as follows: 
Scratch Resistance 
The coated substrate is supported in a jig and a pad of 0000 grade steel 
wool attached to a support with a weight of 5 p.s.i. is rubbed across the 
surface automatically for 50 strokes, one stroke being forward and back. 
The change in haze is measured spectrophotometically, and is reported as 
the percentage loss in transmissivity. 
Adhesion 
Adhesion may be measured using the procedures of ASTM 3359. This test, in 
brief, provides for scoring of the cured coating with a sharp instrument 
in a cross-hatched fashion to leave diamond-shaped patches, followed by an 
attempt to lift the diamond-shaped patches from the substrate through the 
use of a pressure sensitive adhesive tape that is applied to the cross 
hatched surface and then pulled away. The degree to which the 
cross-hatched portions of the coating remain adhered to the substrate 
provides a measure of adhesion to that substrate, and is reported as the 
percentage of diamond-shapes that remain adhered to the substrate. 
Tintability 
A coated and cured sample is immersed in BPI Black Dye (Brain Power Inc.) 
at 98-102.degree. C. for 15 minutes and then rinsed with water and dried. 
Transmissivity is measured spectrophotometrically, and tintability is 
reported as percentage transmissivity.

EXAMPLE 1 
A master batch of the partial hydrolysis product of .gamma. glycidoxy 
propyl trimethoxy silane is prepared as follows: 
______________________________________ 
glycidoxy propyl trimethoxy silane 
868.3 gm 
Water. 131.2 gm 
Conc. HCL 0.5 gm 
______________________________________ 
The above ingredients are stirred together in a flask equipped with a 
condenser for 12-16 hours, during which substantially all of the volatiles 
are removed using a rotary evaporator. Sufficient water is used in this 
example to theoretically hydrolyze 2 of the 3 alkoxy groups. 
EXAMPLE 2 
______________________________________ 
Master batch of Example 1. 25.35 gm 
Butane diol diacrylate 23.47 gm 
Trimethylol Propane Triglycidyl Ether 
37.55 gm 
Mixed Triarylsulfonium Hexafluroantimonate Salts 
9.39 gm 
50% in Propylene Carbonate (UVI 6974, Union Carbide) 
2-hydroxy-2-methyl-1-phenylpropane-1-one 
2.35 gm 
(Darocure .TM. 1173, Ciba-Geigy Corporation) 
Acrylated Silicone Flow Control Agent 
1.89 gm 
(Ebecryl .TM. 1360, UCB Radcure Co.) 
______________________________________ 
The material was spin coated on a polycarbonate substrate and cured using a 
300 watt per inch mercury bulb. The cured film exhibited the following 
properties. 
______________________________________ 
Scratch Resistance 
&lt;1% haze 
Adhesion after tint 
100% (using 3M 600 tape) 
Tintability &lt;10% transmission. 
______________________________________ 
EXAMPLE 3 
______________________________________ 
Master batch of Example 1 
26.38 gm 
Butane diol diacrylate 34.2 gm 
Trimethylol Propane Triglycidyl Ether 
19.54 gm 
Trimethylol Propane Triacrylate 
9.77 
UVI 6974 4.88 
Darocure 1173 3.25 
Ebecryl 1360 1.98 
______________________________________ 
The coating composition was coated on a polycarbonate substrate and cured 
as in Example 1. Testing results were as follows: 
______________________________________ 
Scratch Resistance &lt;0.5% Haze 
Adhesion after tint 
100% 
Tintability &lt;16.0% transmissivity 
______________________________________ 
EXAMPLE 4 
______________________________________ 
Master batch of Ex. 1 26.87 
Butane Diol Diacrylate 
24.88 
Trimethylol Propane Triglycidyl Ether 
29.85 
Trimethylol Propane Triacrylate 
9.95 
UVI 6974 2.99 
Darocure 1173 3.48 
Ebecryl 1360 1.99 
Total 100.0 
______________________________________ 
The coating composition was coated and tested as in Example 1, yielding the 
following test results: 
______________________________________ 
Scratch resistance &lt;0.5% Haze 
Adhesion after tint 
100% 
Tintability &lt;15.0% Transmission 
______________________________________ 
EXAMPLE 5 
______________________________________ 
Master batch of Example 1 22.83 
Butane Diol Diacrylate 27.40 
Dipentaerythritol Hydroxy Pentacrylate 
22.83 
Cyclohane 1,4,Dimethylol Divinyl Ether 
18.26 
UVI 6974 2.28 
Darocure 1173 4.56 
Acrylated Silicone Flow Control Agent (BYK .TM. 371, BYK 
1.84 
Total 100.0 
______________________________________ 
The composition was coated and cured as in Example 1, and the following 
test results were obtained: 
______________________________________ 
Scratch Resistance &lt;1.0% Haze 
Adhesion after tint 
100k % 
Tintability &lt;6.0% Transmission 
______________________________________ 
EXAMPLE 5 
______________________________________ 
Master batch of Example 1 
27.40 
Butane Diol Diacrylate 27.40 
Dipentaerythritol Hydroxy Pentacrylate 
22.83 
Cyclohane 1,4,Dimethylol Divinyl Ether 
13.70 
UVI 6974 2.28 
Darocure 1173 4.57 
BYK 371 1.83 
Total 100.0 
______________________________________ 
The composition was coated on Polycarbonate as in Example 1. The following 
test results were obtained: 
______________________________________ 
Scratch Resistance &lt;0.8% Haze 
Adhesion after tint 
100% 
Tintability &lt;6.0% Transmission 
______________________________________ 
While a preferred embodiment of the present invention has been described, 
it should be understood that various changes, adaptations and 
modifications may be made therein without departing from the spirit of the 
invention and the scope of the appended claims.