U.S. patent application number 09/735269 was filed with the patent office on 2002-08-15 for impact resistant uv curable hardcoatings.
Invention is credited to Lin, Shi, Ram, Sunder.
Application Number | 20020111390 09/735269 |
Document ID | / |
Family ID | 24955059 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020111390 |
Kind Code |
A1 |
Lin, Shi ; et al. |
August 15, 2002 |
IMPACT RESISTANT UV CURABLE HARDCOATINGS
Abstract
Curable compositions that are particularly suitable for coating
plastic ophthalmic lenses includes (a) 20% to 80% of a first
acrylated aliphatic urethane; (b) 5% to 50% of a monofunctional
acrylate; (c) (i) 2% to 30% of a second acrylated aliphatic
urethane or (ii) 2% or 25% of a multifunctional acrylate or (iii) a
combination of (i) and (ii); (d) 1% to 30% of a colloidal metal
oxide; (e) 1% to 20% of a photoinitiator; and (f) a solvent, with
the percentages based on weight. The cured composition provides
superior abrasion and impact resistance as well as protection
against environmental and chemical agents. In addition, the UV
curable compositions are capable of forming films on various
substrates; the film has excellent compatibility and adhesion to AR
coatings that are applied thereon. No primer coating is
required.
Inventors: |
Lin, Shi; (Petaluma, CA)
; Ram, Sunder; (Petaluma, CA) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
24955059 |
Appl. No.: |
09/735269 |
Filed: |
December 11, 2000 |
Current U.S.
Class: |
522/83 |
Current CPC
Class: |
Y10T 428/24421 20150115;
Y10T 428/24355 20150115; G02B 1/14 20150115; G02B 1/105 20130101;
Y10T 428/2438 20150115; C09D 4/06 20130101; Y10T 428/24372
20150115; C09D 175/16 20130101; Y10T 428/31573 20150401; Y10T
428/31507 20150401; Y10T 428/24405 20150115; Y10T 428/24364
20150115; Y10T 428/24388 20150115; C09D 4/06 20130101; C08F 290/147
20130101; C09D 4/06 20130101; C08F 290/067 20130101 |
Class at
Publication: |
522/83 |
International
Class: |
C08K 003/00 |
Claims
What is claimed is:
1. A radiation curable composition that comprises: (a) 20% to 80%
of a first acrylated aliphatic urethane; (b) 5% to 50% of a
monofunctional acrylate; (c) (i) 2% to 30% of a second acrylated
aliphatic urethane or (ii) 2% to 25% of a multifunctional acrylate
or (iii) a combination of (i) and (ii); (d) 1% to 30% of a
colloidal metal oxide; (e) 1% to 20% of a photoinitiator; and (f) a
solvent, wherein the percentages are by weight.
2. The radiation curable composition of claim 1 wherein the first
acrylated aliphatic urethane is a difunctional acrylated aliphatic
urethane.
3. The radiation curable composition of claim 1 wherein the first
acrylated aliphatic urethane has a molecular weight of between 2500
to 4500 Dalton.
4. The radiation curable composition of claim 1 wherein the
monofunctional acrylate comprises an acryloyl or a methacryloyl
moiety.
5. The radiation curable composition of claim 1 wherein the second
acrylated aliphatic urethane contains 3 or more polymerizable
unsaturated moieties per molecule.
6. The radiation curable composition of claim 1 wherein the second
acrylated aliphatic urethane has a molecular weight of between 500
to 1600 Dalton.
7. The radiation curable composition of claim 1 wherein the
multifunctional acrylate comprises a moiety having a hydroxyl group
and three or more acryloyl groups.
8. The radiation curable composition of claim 1 further comprising
at least one of (i) an effective amount of a light stabilizer, (ii)
dye, or (iii) a flow additive.
9. A transparent article which comprises: (a) a substrate; and (b)
an impact resistant coating on a surface of said substrate wherein
the coating is formed by radiation curing a composition that
comprises: (i) 20% to 80% of a first acrylated aliphatic urethane;
(ii) 5% to 50% of a monofunctional acrylate; (iii) (1) 2% to 30% of
a second acrylated aliphatic urethane or (2) 2% to 25% of a
multifunctional acrylate or (3) a combination of (1) and (2); (iv)
1% to 30% of a colloidal metal oxide; (v) 1% to 20% of a
photoinitiator; and (vi) a solvent, wherein the percentages are by
weight.
10. The transparent article of claim 9 wherein the first acrylated
aliphatic urethane is a difunctional acrylated aliphatic
urethane.
11. The transparent article of claim 9 wherein the first acrylated
aliphatic urethane has a molecular weight of between 2500 to 4500
Dalton.
12. The transparent article of claim 9 wherein the monofunctional
acrylate comprises an acryloyl or a methacryloyl moiety.
13. The transparent article of claim 9 wherein the second acrylated
aliphatic urethane contains 3 or more polymerizable unsaturated
moieties per molecule.
14. The transparent article of claim 9 wherein the second acrylated
aliphatic urethane has a molecular weight of between 500 to 1600
Dalton.
15. The transparent article of claim 9 wherein the multifunctional
acrylate comprises a moiety having a hydroxyl group and three or
more acryloyl groups.
16. The transparent article of claim 9 wherein the composition
further comprises at least one of (i) an effective amount of a
light stabilizer, (ii) dye, or (iii) a flow additive.
17. The transparent article of claim 9 wherein the substrate is an
ophthalmic lens.
18. The transparent article of claim 9 wherein the impact resistant
coating has a thickness of about 1 .mu.m to 6 .mu.m.
19. The transparent article of claim 9 wherein the ophthalmic lens
is made of polycarbonates, diethylene glycol bis(allyl carbonate),
or acrylic.
20. The transparent article of claim 9 wherein the ophthalmic lens
is made of a plastic material having an index of refraction of at
least 1.59.
21. The transparent article of claim 9 further comprising a hard
coating that is formed on the impact resistant coating.
22. The transparent article of claim 9 wherein there is no adhesion
layer between the coating and the substrate.
23. A method of fabricating a plastic ophthalmic lens which
comprises the steps of: (a) providing a plastic ophthalmic lens
substrate having a front surface and a back surface wherein the
front surface is covered with a hard coating and an antireflection
coating; (b) grinding the back side of the substrate to produce an
ophthalmic lens with a desired prescription; thereafter, (c)
forming an impact resistant coating onto the back surface of the
substrate by: (i) applying a radiation curable composition onto the
surface wherein the composition comprises: (1) 20% to 80% of a
first acrylated aliphatic urethane; (2) 5% to 50% of monofunctional
acrylate; (3) (i) 2% to 30% of a second acrylated aliphatic
urethane or (ii) 2% to 25% of a multifunctional acrylate (iii) or
combination of both (i) and (ii); (4) 1% to 30% of a colloidal
metal oxide; (5) 1% to 20% of a photoinitiator; and (5) a solvent,
wherein the percentages are by weight. (ii) curing the
composition.
24. The method of 23 wherein the first acrylated aliphatic urethane
is a difunctional acrylated aliphatic urethane.
25. The method of claim 23 wherein the first acrylated aliphatic
urethane has a molecular weight of between 2500 to 4500 Dalton.
26. The method of claim 23 wherein the monofunctional acrylate
comprises an acryloyl or a methacryloyl group.
27. The method of claim 23 wherein the second acrylated aliphatic
urethane contains 3 or more polymerizable unsaturated moieties per
molecule.
28. The method of claim 23 wherein the second acrylated aliphatic
urethane has a molecular weight of between 500 to 1600 Dalton.
29. The method of claim 23 wherein the multifunctional acrylate
comprises a moiety having a hydroxyl group and three or more
acryloyl groups.
30. The method of claim 23 further comprising at least one of (i)
an effective amount of a light stabilizer, (ii) dye, or (iii) a
flow additive.
31. The method of claim 23 wherein the impact resistant coating has
a thickness of about 1 .mu.m to 6 .mu.m.
32. The method of claim 23 wherein the plastic ophthalmic lens is
made of polycarbonate, diethylene glycol bis(allyl carbonate), or
acrylic.
33. The method of claim 23 wherein the ophthalmic lens is made of a
plastic material having an index of refraction of at least 1.59.
Description
FIELD OF THE INVENTION
[0001] The invention relates to radiation curable coating
compositions for plastic articles and particularly to coating
compositions for ophthalmic lenses that exhibit improved abrasion
resistance, excellent impact resistance, excellent adhesion to
various substrates and compatibility with anti-reflective
coatings.
BACKGROUND OF THE INVENTION
[0002] Plastic materials have been used as substitutes for glass
lenses in the ophthalmic industry because of their unique
properties such as lighter weight, superior shatter resistance, and
ease of fabrication. Commercially available plastic ophthalmic
lenses may contain diethylene glycol bis(allylcarbonate),
polycarbonate, acrylic, polyurethane and other high index
materials. Since most plastic ophthalmic lenses are soft and
susceptible to scratching, they are commonly coated with a thin
polymeric abrasion resistance hard coating.
[0003] Anti-reflective (AR) coatings on plastic ophthalmic lenses
have been employed to eliminate the light reflection that would
otherwise cause images to flicker. AR coatings can be created by
vacuum depositing a film of inorganic materials on the hard coating
layer of a plastic ophthalmic lens, but the addition of the hard
anti-reflective coatings can greatly reduce the impact resistance
of plastic lenses. Moreover, the Food and Drug Administration (FDA)
requires that plastic ophthalmic lenses must meet a minimum impact
strength of 0.2 Joules.
[0004] In an attempt to improve the impact resistance of plastic
lenses, primer coatings that are applied to the plastic lens before
the hard coating layer have been used. For instance, U.S. Pat. No.
5,310,577 describes a primer coating composition composed mainly of
a blocked polyisocyanate and a polyol that forms a primer layer of
a thermoset polyurethane. Similarly, U.S. Pat. No. 5,619,288
describes a method for imparting impact resistance to a plastic
ophthalmic lens, that consists of applying a coating of a
multifunctional acrylate in a solvent mixture to the back surface
of lens and curing the multifunctional acrylate to form an impact
resistance primer coat. A hard coat is then applied on top of the
primer coat layer to provide abrasion resistance. While the use of
a primer coating may improve impact resistance, it also adds an
extra step in the fabricating process of semi-finished lenses. This
is not desirable, especially in an Rx laboratory.
[0005] Another concern in fabricating semi-finished lenses is that
an Rx laboratory must apply different coating formulations to
different substrates or use pretreatment to address the adhesion
problem. It would be advantageous to have a coating which has
excellent adhesion to various substrates.
[0006] Accordingly, the art is in search of hard coatings which
exhibit excellent adhesion to various substrates without the need
for pretreatment of the substrates or of a primer coating. The hard
coatings should also exhibit excellent impact resistant and
compatibility with AR coatings, also without the need for a primer
coating on the AR coatings.
SUMMARY OF THE INVENTION
[0007] The present invention is based in part on the development of
a novel UV curable composition that is particularly suitable for
coating plastic ophthalmic lenses. The cured composition provides
superior abrasion and impact resistance as well as protection
against environmental and chemical agents. In addition, the UV
curable compositions are capable of forming films on various
substrates; the film has excellent compatibility and adhesion to AR
coatings that are applied thereon. No primer coating is
required.
[0008] Accordingly, in one aspect, the invention is directed to a
radiation curable composition that includes:
[0009] (a) 20% to 80% of a first acrylated aliphatic urethane;
[0010] (b) 5% to 50% of a monofunctional acrylate;
[0011] (c) (i) 2% to 30% of a second acrylated aliphatic urethane
or (ii) 2% to 25% of a multifunctional acrylate or a combination of
(i) and (ii);
[0012] (d) 1% to 30% of a colloidal metal oxide;
[0013] (e) 1% to 20% of a photoinitiator; and
[0014] (f) a solvent, wherein the percentages are by weight.
[0015] In one embodiment, the radiation curable composition further
includes at least one of (i) an effective amount of a light
stabilizer, (ii) dye, or (iii) a flow additive.
[0016] In another aspect, the invention is directed to a
transparent article which includes:
[0017] (a) a substrate; and
[0018] (b) an impact resistant coating on a surface of said
substrate wherein the coating is formed by radiation curing the
above described radiation curable composition.
[0019] In a further aspect, the invention is directed method of
fabricating a semi-finished plastic ophthalmic lens which includes
the steps of:
[0020] (a) providing a plastic ophthalmic lens substrate having a
front surface and a back surface wherein the front surface is
covered with a hard coating and an antireflection coating;
[0021] (b) grinding the back side of the substrate to produce an
ophthalmic lens with a desired prescription; thereafter,
[0022] (c) forming an impact resistant coating onto the back
surface of the substrate by:
[0023] (i) applying the above described radiation curable
composition onto the surface; and
[0024] (ii) curing the composition; and
[0025] (d) forming an antireflection coating onto the impact
resistant coating.
DETAILED DESCRIPTION OF THE INVENTION
[0026] This invention is directed to a UV curable composition that
provides durable films with improved abrasion resistance, impact
resistance, and excellent adhesion on various plastic substrates.
Furthermore, the films are also compatible with anti-reflective
coatings. The radiation curable composition comprises: (a) 20% to
80% of a first acrylated aliphatic urethane; (b) 5% to 50% of a
monofunctional acrylate; (c) (i) 2% to 30% of a second acrylated
aliphatic urethane or (ii) 2% to 25% of a multifunctional acrylate
or (iii) a combination of (i) and (ii); (d) 1% to 30% of a
colloidal metal oxide; (e) 1% to 20% of a photoinitiator; and (f) a
solvent. The percentages are based on weight. The radiation curable
composition may further include effective amounts of at least one
of (i) a light stabilizer, (ii) a dye, or (iii) a flow
additive.
[0027] However, prior to describing the invention is further
detail, the following terms will be defined:
[0028] The term "first acrylated aliphatic urethane" refers to
difunctional aliphatic urethane wherein the functional groups are
either an aryloyl or a methacryloyl moiety, or combinations
thereof. Typically the amount of first acrylated aliphatic urethane
present in the radiation curable composition ranges from about 20%
to 80% and preferably from about 40% to 70%. The average molecule
weight typically ranges from about 2500 to 4500 Dalton. Preferred
first acrylated aliphatic urethanes include difunctional aliphatic
acrylated urethanes such as, for example, those sold under the
trademarks CN 962, CN 964, CN 965 and CN 966 from Sartomer Co. and
EBECRYL 230 and 270 from UCB Chemicals.
[0029] The term "second acrylated aliphatic urethane" refers to
trifunctional or higher functional aliphatic urethane wherein the
functional groups are either acryloyl or methacryloyl moieties or
combinations thereof. Typically when employed the amount of second
acrylated aliphatic urethane present in the radiation curable
composition ranges from about 2% to 30% and preferably from about
5% to 20%. The average molecule weight typically ranges from about
500 to 1600 Dalton. Preferred second acrylated aliphatic urethanes
include highly functional acrylated urethanes such as, for example,
CN 968 from Sartomer Company and EBECRYL 8301 and 1290 from UCB
Chemicals.
[0030] The term "monofunctional acrylate" refers to an acrylate
monomer that contains only one acryloyl or methacryloyl moiety.
Typically the amount of monofunctional acarylate present in the
radiation curable composition ranges from about 5% to 50% and
preferably from about 15% to 40%.
[0031] The term "multifunctional acrylate" refers to an acrylate
monomer or oligomer that contains at least three or more acryloyl
or methacryloyl moieties or combinations thereof. Typically, when
employed, the amount of multifunctional acrylate present in the
radiation curable composition ranges from about 2% to 25% and
preferably from about 5% to 15%. Preferred multifunctional
(meth)acrylate monomers or oligomers which may be used to provide
film hardness include pentaerythritol tetraacrylate,
dipentaerythritol pentaacrylate, di-trimethylolpropane
tetraacrylate, pentaerythritol triacrylate, tris(2-hydroxy ethyl)
isocyanurate triacrylate. All of these work to improve
cross-linking stability, with concomitant improvements in impact
and abrasion resistance.
[0032] The term "colloidal metal oxide" refers to metal oxide
particles in acrylates or organic solvents. Suitable metal oxides
include, for example, silicon oxide. Typically the metal oxide
particles have diameters that range from 2 nm to 60 nm and
preferably from 5 nm to 50 nm. Suitable colloidal silica include
acrylic and methacrylic based silica organols that are commercially
available, for example, as HIGHLINK OG108-32 and OG100-31 from
Clariant Corporation, MEK-ST and IPA-ST from Nissan Chemical, and
FCS 100 from General Electric Company. The HIGHLINK OG108-32 is a
liquid suspension of colloidal silica in tripropylene glycol
diacrylate. Partially hydrolyzed alkoxysilylacrylates such as
acryloxypropyltrimethoxysilane may also be used. Typically, the
amount of functionalized colloidal metal oxide present in the
radiation curable composition ranges from about 1% to 30% and
preferably from about 3%to 20%.
[0033] The term "photoinitiator" refers to agents that catalyze the
polymerization of monomer systems. Suitable photoinitiators
include, for example, benzophenone, 1-hydroxycyclohexyl phenyl
ketone (methanone), acetophenone, and the like, and mixtures
thereof. A mixture of 1-hydroxycyclohexyl phenyl ketone and
benzophenone (available under the tradename IRGACURE 500 from Ciba
Giegy) is particularly preferred. Typically, the amount of
photoinitiator present in the radiation curable composition ranges
from about 1% to 20% and preferably from about 5% to 15%.
[0034] The term "light stabilizer" refers to compounds that enhance
the color of the coating by selecting absorbing radiation.
Preferred light stabilizers include, for example, substituted
benzophenones, benzotriazoles, hindered amines and diphenyl
acrylates. A particularly preferred light stabilizer is
2,2',4,4'-tetrahydroxy benzophenone, available as UVINUL 3050 from
BASF Corporation which exhibited excellent compatibility with the
acrylated aliphatic urethanes. Typically, when employed, the amount
of light stabilizer present in the radiation curable composition
ranges from about 1% to 20% and preferably from about 2% to
10%.
[0035] The term "dye" refers to any suitable substance that
neutralizes the yellow color caused by some UV absorbing materials.
Preferred dyes include, for example, blue dyes or a mixture of
solvent soluble dyes imparting a blue hue. The blue dye is used in
combination with the dihydroxy benzophenones to obtain a neutral
color. UV absorbers and dyes are described, for example, in U.S.
Pat. No. 5,949,518 which is incorporated herein by reference.
Typically, when employed, the amount of dye present in the
radiation curable composition ranges from about 0.01% to 5% and
preferably from about 0.05% to 1%.
[0036] The term "flow additive" refers to materials that enhance
the rheology of the radiation curable composition. Acrylic or
silicone containing surface additives are the preferred flow
additives, e.g., BYK 371, BYK 358, both from BYK-Chemie USA, and
FC430 from 3M Company. Typically, when employed, the amount of flow
additive present in the radiation curable composition ranges from
about 0.01% to 3% and preferably from about 0.05% to 0.5%.
[0037] The term "substrate" refers to a material which preferably
has superior structural and optical properties. Plastics, including
high index materials available under the tradename FINALITE, from
Sola International, are preferred substrate materials. Preferably,
the index of refraction of the substrate is at least 1.59.
Substrates include ophthalmic lenses (including sunglasses).
Preferred ophthalmic lenses also include laminated lenses that are
fabricated by bonding two lens wafers (i.e., a front wafer and a
back wafer) together with a transparent adhesive. As used herein
the term "lens" refers to both single integral body and laminated
types. Laminated lens wafers are described, for example, in U.S.
Pat. Nos. 5,149,181 and 4,645,317 and U.K. Patent Application, GB
2,260,937A, all of which are incorporated herein.
[0038] The term "anti-reflection coating" or "AR coating" refers to
a substantially transparent multilayer film that is applied to
optical systems (e.g., surfaces thereof) to substantially eliminate
reflection over a relatively wide portion of the visible spectrum,
and thereby increase the transmission of light and reduce surface
reflectance. Known anti-reflection coatings include multilayer
films comprising alternating high and low refractive index
materials (e.g., metal oxides) as described, for instance, in U.S.
Pat. Nos. 3,432,225, 3,565,509, 4,022,947, and 5,332,618, all of
which are incorporated herein. AR coatings can also employ one or
more electrically conductive high and/or electrically conductive
low refractive index layers which are further described in U.S.
Pat. No. 5,719,705 which is incorporated herein by reference. The
thickness of the AR coating will depend on the thickness of each
individual layer in the multilayer film and the total number of
layers in the multilayer film. Preferably, the AR coating for the
ophthalmic lens that is formed on the impact resistance UV cured
hard coating has about 3 to about 12 layers. Preferably, the AR
coating is about 100 to about 750 nm thick. For use with ophthalmic
lenses, the AR coating is preferably about 220 to about 500 nm
thick. Inorganic anti-reflective coatings can be single-layer
systems, but more generally are multi-layer anti-reflective stacks
deposited by vacuum evaporation, deposition, sputtering, ion
plating, and/or ion bean assisted methods.
[0039] The term "solvent" is meant to include a single solvent or a
mixture of solvents that dissolves the first acrylated aliphatic
urethane, monofunctional acrylate, the second acrylated urethane
and/or multifunctional acrylated so that the coating composition
can be readily applied. Particularly preferred solvents include,
for example, methyl ethyl ketone, acetone, methyl isobutyl ketone,
methyl propyl ketone, cyclohexanone, cyclopentanone, butyrolactone,
methanol, ethanol, isopropanol, butanol, tetrahydrofuran, N-methyl
pyrrolidone, tetrahydrofurfural alcohol, and mixtures thereof.
Ketones are particularly preferred because they exhibit excellent
solubility of the first and second acrylated aliphatic urethanes
and photoinitiator as well.
[0040] The amount of solvent used will depend on, among other
things, the particularly components employed to formulate the
coating composition, the temperature of the coating composition,
the coating thickness, and the coating technique to be used.
Typically, the solvent will comprise from about 30% to 85% of the
radiation curable coating composition. For spin coating
application, the solvent will preferably range from about 40% to
75% of the radiation curable coating composition.
Formulation of Coating Composition
[0041] The radiation curable coating composition is preferably
formulated by blending together the first acrylated aliphatic
urethane, monofunctional acrylate, the second acrylated urethane
and/or multifunctional acrylated, colloidal metal oxide, and
photoinitiator in a suitable organic solvent. Optional components
such as the light stabilizer, dye, and/or flow additive, can also
be added at this stage.
[0042] The curable coating compositions can be applied to various
substrates by conventional coating methods such as, for example,
spinning, dipping, spraying and the like. No surface pretreatment
of the substrate or formation of an adhesive or primer layer on the
substrate prior to coating is required. Spin coating is
particularly preferred because it readily creates a uniform film
which when cured is relatively defect free. The thickness of the
coating of curable coating composition that is applied will depend
on the particular substrate and application. In the case of
ophthalmic plastic lenses the thickness of the film should be
sufficient so that when the composition is cured, the impact
resistant layer will have a final thickness that ranges from about
1 to about 12 .mu.m and preferably from about 1.5 to about 8 .mu.m.
Thicker protective layers can lead to crazing and other defects
over time, however, thinner layers often do not provide enough
surface material to be resistant. Additionally, it is often
advantageous to have a coating that is thick enough to cover minor
blemishes on the surface of the lens.
[0043] The curable coating compositions can be cured by radiation,
e.g., UV radiation. Sources of UV radiation include, for example,
plasma arc discharges, mercury vapor lamps, etc. A preferred source
of UV irradiation is a Fusion 300 watt/in H lamp.
[0044] Finally, an anti-reflective coating can be formed on the
impact resistant layer, if desired. No surface pretreatment or
formation of an adhesive or primer layer on the protective layer is
required.
Experimental
[0045] Table 1 sets forth the amount (i.e., parts) of various
components of coating compositions that were tested on acrylic
lenses that were commercially available under the tradename
SPECTRALITE from SOLA Optical USA, Petaluma Calif., and which have
a hard coating PGII coated on the front (or convex) side.
1TABLE 1 Sample CN CN 964 CN IRGUCURE HIGHLINK HIGHLINK BYK BLUE
UNINUL No. 962 H60 968 HEMA MIBK Methanone DPHPA 500 OG 100-31 OG
108-32 371 DYE 3050 1 50 20 30 233 5 2 60 10 30 233 5 3 60 10 30
223 10 4 50 20 30 223 10 5 50 20 30 233 10 10 6 50 30 233 20 10 5 7
45 18 121 30 10 10 0.242 0.036 8 8 45 18 121 30 10 10 0.242 0.036 8
9 50 30 233 20 10 5
[0046] For Examples 1 and 2, the coating compositions were prepared
by initially dissolving the CN 964 H60, CN 968, and hydroxyethyl
methacrylate (HEMA) in methyl isobutyl ketone (MIBK) and mixing for
2 hours. Thereafter, 1-hydroxycyclohexyl phenyl ketone (methanone)
was added and the mixture was mixed for another 15 minutes.
[0047] For Examples 3 and 4, the coating compositions were prepared
by initially dissolving the CN 962, CN 968, and HEMA in MIBK and
mixing for 2 hours. Thereafter, the IRGACURE 500 was added and the
mixture was mixed for another 15 minutes.
[0048] For Example 5, the coating composition was prepared by
initially dissolving the CN 962, CN 968, HEMA, and HIGHLIK OG108-32
in MIBK and mixing for 2 hours. Thereafter, the IRGACURE 500 was
added and the mixture was mixed for another 15 minutes.
[0049] For Example 6, the coating composition was prepared by the
same procedure for Example 5 except that the formulation contained
dipentaerythritol pentaacrylate (DPHPA) instead of CN 968.
[0050] For Examples 7 and 8, the coating compositions were prepared
by initially dissolving the CN 962, CN 968, DPHPA, HEMA, HIGHLIK
OG108-31 in MIBK and mixing for 2 hours. Thereafter, IRGACURE 500
and UNINUL 3050 were added and the mixture was mixed for another 30
minutes. Finally, the BYK 371 and blue dye were added to the resin
solution and stirred for 30 minutes.
[0051] For Example 9, the curable composition used was identical to
that of Example 6.
[0052] Coating of Lenses with Curable Compositions
[0053] The back (or concave) side of the semi-finished lenses (from
SPECTRALITE) were initially surfaced and polished to 1.5 mm nominal
center thickness. After being wiped clean with isopropanol, each
lens back surface was then coated with one of the radiation curable
compositions of Examples 1-6. Specifically, two micron thick
coatings were applied on the back side by spinning coating before
being cured. In some cases, antireflection (AR) coatings were also
applied to both the front and back surfaces of the lenses using a
vacuum deposition process to deposit a multi-layer anti-reflective
film. Each AR coating comprised a film having 5 layers comprising
alternating layers of titanium oxide and silicon oxide, with
silicon oxide being the first, third, and fifth layers. Thereafter,
the lenses were subjected to adhesion and impact tests. (The
conditions of these test are described herein.) Table 2 sets forth
the results of the tests. As is apparent, all of the lenses with
the impact resistant coatings demonstrated good adhesion and impact
strength.
2TABLE 2 Coating Comp. Adhesiveness AR coat Impact Resistance
(Joules) 1 100/100 No 1.6 1 100/100 Yes 0.5 2 100/100 No 1.2 2
100/100 Yes 0.7 3 100/100 No 2.0 3 100/100 Yes 0.8 4 100/100 No 1.2
5 100/100 No 1.8 6 100/100 No 1.4 6 100/100 Yes 1.0
[0054] Adhesion Test
[0055] The cross-cut tape test, where 6 parallel lines each in two
perpendicularly crossing directions are cut with a six blade cutter
was employed. The lines are cut at fixed intervals of approximately
1 mm, on the surface of the coating of a given sample to produce a
total of 49 squares. Thereafter, adhesive cellophane tape is
applied to the cut squares, the tape is peeled, and the squares on
which the coat film are counted. The adhesion is measured by the
number of squares remaining.
[0056] Impact Test
[0057] The impact resistance of the coated lenses were measured
using an impact tester from American Optical Corporation based on
U.S. Pat. No. 3,896,657. The tester utilizes a 5/8" diameter
stainless steel ball supported by a magnet vertically above the
anvil on which a lens is mounted at a fixed distance from the ball.
The ball can be accelerated by different velocities using
compressed air to allow for variable impact energy of the ball
against the lens being tested when the ball is aimed to strike at
the center of the lens. The results of this test are measured in
Joules.
[0058] The curable compositions of Examples 7-9 were tested with
various substrates including: (1) CR-39 lenses which are fabricated
from polymerized diethylene glycol bis(ally carbonate) having a
silicone hard coating on front surface, (2) polycarbonate (POLY),
(3) three lenses made by Sola Optical USA, under the trademarks (i)
CR Transitions (CRT), (ii) Spectralite Transitions (SPT), and (iii)
High Index Finalite (Finalite). 1.5 or 2 micron thick curable
compositions were coated onto the back surface of each lens which
were then cured. Lenses were tested with and without antireflective
coatings on both the front and back of the lens. The impact
resistances of the coated lenses are set forth in Table 3. As is
apparent, the lenses exhibited good impact strength.
3TABLE 3 Coating Coating Impact Comp Substrate thickness (.mu.m) AR
Coat Resistance (Joules) 7 CR39 2.0 No 1.0 7 CR39 2.0 Yes 1.0 8
POLY 2.0 No >2.0 8 POLY 2.0 Yes >2.0 9 SPT 1.5 No 0.7 9 SPT
1.5 Yes 0.8 9 CRT 2.0 No 0.7 9 CRT 2.0 Yes 1.2 9 FINALITE 1.5 No
0.8 9 FINALITE 1.5 Yes 0.9
[0059] Although only preferred embodiments of the invention are
specifically disclosed and described above, it will be appreciated
that many modifications and variations of the present invention are
possible in light of the above teachings and within the purview of
the appended claims without departing from the spirit and intended
scope of the invention.
* * * * *