GB2283241A

GB2283241A - Curable coating compositions having improved adhesion

Info

Publication number: GB2283241A
Application number: GB9419625A
Authority: GB
Inventors: George Fredric Medford; James Robert Piazza; Randall Joseph Rocheleau
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1993-10-13
Filing date: 1994-09-29
Publication date: 1995-05-03
Anticipated expiration: 2014-09-29
Also published as: FR2711141A1; DE4435712A1; GB2283241B; GB9419625D0; FR2711141B1; JPH07207189A

Description

2283241 CURABLE COATING COMPOSITIONS HAVING IMPROVED ADHESION

BACKGROUND OF THE INVENTION

The present invention relates to radiation curable coating compositions and to a method for producing radiation curable hardcoat coating compositions. More particularly the present invention relates to acrylate containing ultra-violet light (UV) curable hardcoat compositions exhibiting improved adhesion to plastic resin substrates such as diethyleneglycol bis(allylearbonate) known generically and referred to herein as CR39 resin or substrate a registered trademark of PPG Industries. There is a tendency for acrylate-containing coating compositions to exhibit poor adhesion to CR39 resin, and in particular, to ophthalmic lenses made from CR39 resin, particularly after radiation cure. It is known in the art that soaking CR39 plastic lenses in hot caustic can enhance adhesion of some coatings. However, hot causticjs difficult and potentially dangerous to work with.

It has been found that by contacting the ophthalmic lens with an organic acid, improved adhesion is obtained. Further enhancement can be achieved by curing at slow lines speeds which heats the substrate surface to at least about 9011C and by using thin coatings, or by pre-heating the lens.

Additionally, it has been found that applying organic acid, heat, or a combination of organic acid and heat can improve coating adhesion to substrates. Other physical properties including flexibility and abrasion resistance can also be improved.

United States Patent Numbers 4,486,504 to Chung and 4,455,205 to Olson et al. relate to formulations of weatherable and non-weatherable UV curable hardcoat compositions.

A method for producing curable coating compositions and particularly to gel-free curable coating compositions is described in European Patent Application V0. 9409983.5.

United States Patent Number 5,221,560 to Perkins et al. relates to radiation-curable coating compositions that form transparent, abrasion resistant tintable coatings.

SUMMARY OF INVENTION

The present invention is directed to radiation curable acrylic coating compositions comprising an organic acid pre-treatment or an organic acid solvent or co-solvent and to a method for making curable hardcoat coating compositions, wherein an organic acid is brought into contact with a plastic substrate. Another embodiment includes preparing a coated substrate and then applying heat to the coated substrate, then curing.

DETAILED DESCRIPTION OF THE INVENTION

The radiation curable hardcoat coating compositions of the present invention are made from low molecular weight acrylate monomers. Acrylate monomers generally include octylacrylate, decylacrylate, blends of octylacrylate and decylacrylate (ODA), isodecylacrylate (IDA), tetra hydrafu rfu ra lacryl ate (THFA), hexanedioldiacrylate (HDDA), butanedioldiacrylate, and the like. One type of acrylate'monomer contemplated for use in the present invention can generally be represented by the following formula- (1) 0 (1 ((R)2C---CR1-C-0)nR2 Wherein each R is hydrogen, each R1 independently is hydrogen, a C(1-8) alkylene radical, or mixtures thereof, each R2 is independently hydrogen, a C(1-20) alkyl radical, branched C(2-8) aikylene radicals, branched halogenated C(2-8) aikylene radicals, branched hydroxyiated C(2-8) aikyiene radicals, branched acryiate radicals, C(6- 13) arylene radicals, halogenated C(6-13) arylene radicals, and the like, and where n is an integer from 1 to 3 inclusive.

I.

41 A In formula (1), each R1 is more particularly hydrogen or a C(,20) aikyi, such as methyl, ethyl, propyi, butVi, and the like; an aryi radical or halogenated aryl radical, for example, phenyl, tolVI, xylyi, naphthVI, chiorophenyi, and the like. R2 is more particularly R1 or a divalent aikylene radical, for example, methylene, ethylene, trimethyiene, tetramethylene or Cffi-13) arylene radicals, for example, phenylene, tolylene, naphthalene, and the like. Specific examples of monoacrylate monomers include:

CH3 1 2 CH:3, CH2:-- C-COO(CH2)m CH2 = CH COO(CH2)m CH3.

CH3 CHy-CH2 1 -12 = C COOCH2 CH CH2 0 11 C1-12,_' CH2 = CHCOCH2CH 1-1 0, CH2 -CH2 where m is an integer from 1-19.

Formula (1) includes acrylate monomers, for example, diacrylates of the formulas:

CH3 CH3 - i - 1 .,12---;1;00-CH2-OOCC--CH2' CH---CHCOO-CH2-CH2-0OCCH--CHT CH2--CHCOO-CH2-CHOHCH2-OOCCH--CH2#' CH3 CH 3 1 1 CH 2 ---CHCOO-(CH 2) -OWCH---CH 2' OOCH--CH CH---CHCOO-CH2-Cr12 -LM-WIX 2 CH3 C1-12--CHCOOOOCCH--CH 2' cl Br CH 2 --CHCOO -OOCCH--CH 2' and the like, and A triacryiates of the formulas:

OOCCH--CH9 CH 2---CHCOO-CH2 CH 2' 1;t11;M2-0OCCH--CH 2' CH --CHCOO-CH 2 j 2 CH 2--CHCOO-CH 2 -C-CH2CH3, 1 CH2--CHCOO-CH 2 CH 2 OH 1 CH2 --CHCOO-CH:z-k -CH2 -OOCCH---CH2.

CH 2-OOCCH--CH2 CH 3 0 C. i C1-12---CI-IC 01 C OOCCH--CH 2, and the like.

Low molecular weight acrylate monomers refer to monomers having a molecular weight of about 1,000 or below and preferably 5 about 500 or below.

In one embodiment of the present invention a necessary ingredient is an organic acid, in addition to the low molecular weight acrylate monomer. The organic acid can be any organic acid generally known to the art. Specific examples include glacial acetic acid and acrylic acid. The amount of organic acid used when applied as a solvent or co-solvent is generally from about 20 to about 99% by weight and preferably from 50% to about 95% by weight of combined organic acid and non-volatiles.

In an embodiment of the present invention, an ophthalmic lens is pretreated by soaking in an organic acid. The amount of organic acid used for soaking is generally an amount sufficient to completely cover the ophthalmic lens being pre-treated. The time required for presoak is from about 10 seconds to about 30 minutes, and preferably from about 60 seconds to about 120 seconds. During this pre-soak, it has been shown that increasing the temperature can give improved adhesion.

The temperature during this pre-soak can range from ambient temperature to about 12011C and preferably is from about 25"C to about 118C. After the pre-soak, the ophthalmic lens is then contacted with the curable coating composition.

Other ingredients that can be added in addition to the low molecular weight acrylate monomers and the organic acid include higher molecular weight acrylates and acrylated oligomers. One such high molecular weight acrylate includes acrylated silica which is generally formed from silyl acrylates and colloidal silica.

Representative formulas of siiyl acrylates include the following:

CH2---CCH3C02-CH2CH2-Si(OCH2CH3)3, C1-12--CHCO2-CH2C1-12-Si(OCH3)3, CH2--CCH3C02-CH2CH2CH2-Si(OCH2CH3)3, CH2---CHCO2-CH2C1-12-Si(OCH2CH3), CH2--CCH3C02-CH2CH2CH2-Si(OCH3)3, CH2---CHCO2-CH2CH2CH2-Si(OCH3)3, CH2---CCH3C02-CH2CH2CH2-Si(OCH2CH3)3, CH2--CHCO2-CH2CH2CH2-Si(OCH2CH3)3, CH2--CCH3C02-CH2CH2CH2CH2-Si(OCH3)3, CH2--CHCO2-CH2CH2CH2CH2-Si(OCH3)3, C1-12--CCH3C02-CH2CH2CH2C- 1-12-Si(OCH2CH3):3, CH2--CHCO2-CH2CH2CH2CH2-Si(OCH2CH3)3, and the like.

Colloidal silica, is a dispersion of submicron-sized silica (Si02) particles in an aqueous or other solvent medium and is generally 1 9 added to from the silyl acrylate. The Si02 provides quadri-functional (Q) silicon atoms. When mixed with tri-functional M silicon containing acrylates, TQ mixtures are formed.

Dispersions of colloidal silica are available from chemical manufacturers such as DuPont and Nalco Chemical Company.

Colloidal silica is available in either acidic or basic form. However, for purposes of the present invention it is preferable that the acidic form be utilized. It has been found that superior hardcoat properties can be achieved with acidic colloidal silica (i.e., dispersions with low sodium content). Alkaline colloidal silica also may be converted to acidic colloidal silica with additions of acids such as HC1 or H2SO4 along with high agitation.

Nalcoag 10340 is an example of a satisfactory colloidal silica for use in these coating compositions, available from Nalco Chemical Company, Chicago, Ill. Nalcoag 1034AG is a high purity, acidic pH aqueous colloidal silica dispersion having a low Na20 content, a pH of approximately 3.1 and an Si02 content of approximately 34 percent by weight. In the examples given below, the weight in grams or parts by weight of the colloidal silica includes its aqueous medium. Thus, for example, 520 grams of Nalcoag 10340 colloidal silica represents, approximately, 177 grams Of Si02 by weight. It should be noted, however, that the aqueous medium is a convenient way of handling the colloidal silica and does not form a necessary part of the hardcoat compositions of the present invention.

However, since water is required for the SiOR hydrolysis, some water must be added to non-aqueous colloidal silica.

Other high molecular weight acrylates include pentaerythritoi triacrylate, pentaerythritol tetracrViate, dipentaerythritolpentaacrylate, and the like.

AcrVlated oligomers include acrVlated epoxies, acrylated urethanes, and the like.

One skilled in the art would recognize that all of the above high molecular weight acrVlates and acrylated oligomers can be used -aindividually or in combinations and mixed with the tow molecular weight acryiates described above.

The coating compositions of the present invention may be formulated without any additional curing agent If desired, the coating compositions may be cured by exposure to electron-beam (EB) radiation. In the case of exposure to EB, it is desirable to have a thin coating. Preferably this coating is less than 2.5 cm (1 in.) in thickness, and preferably less than 25 micron. (111 000th in.) This material may be further formulated to contain curing agents. One such curing agent is a photoinitiator. The composition may than be cured by exposure to a UV light source. It is desirable to have a coating of about 25 microns (111000 in.) in thickness, preferably less than about 10 microns in thickness, and most preferably less than about 5 microns in thickness.

Although the coating compositions may contain only one of said low molecular weight acrylate monomers, the coating compositions can contain a mixture of two or more low molecular weight monomers. The UV curable compositions of the present invention can contain nonacrylic UV curable aliphatically unsaturated organic monomers in amounts up to 50% by weight of the UV curable hardcoat compositions which include, for example, such materials as N- vinyl pyrrolidone, styrene, vinyl ether/maleate blends, tetra- and penta- f unctional acrylates and the like.

The coating compositions contain a sufficient amount of low molecular weight acrylate monomers to give an acceptable level of adhesion to the CR39 substrate. An acceptable level of adhesion generally means a value of 4B using the test method ASTM D3359.

One preferred low molecular weight acrylate is HDDA. Compositions comprise between about 5 and 90 parts by weight of HDDA based on the total weight of nonvolatile material in the coating compositions, and preferably comprise between about 5 and 50 parts by weight of HDDA.

The photocurable coating compositions also contain a photosensitizing amount of photoinitiator, i.e., an amount effective to effect the photocure, of the coating composition. Generally, this amount is from about 0.01 to about 15 parts by weight, and preferably from about 0.1 to about 10 parts by weight based upon the total of colloidal silica, hydrolysis and condensation reaction product of a silyl acrylate of formula (1) and an acrylate monomer of formula (2).

As shown in U.S. Patent No. 4,491,508, certain blends of ketone-type and hindered amine type materials are photoinitlators effective for crosslinking the above described coating compositions in air to form suitable hard coatings upon exposure to UV radiation.

That patent is herein incorporated by reference.

One ketone-type photoinitiator used is aa diethoxyacetophenone. Another photoinitiator is methylbenzoylformate, having a molecular weight of 164, and used at 5 parts by weight or more. At 5.7 parts by weight methylbenzoylformate, 50 mole percent more photoinitiator is available in the formulations than the mole percent available then when using 5 parts by weight of the higher molecular weight a a diethoxyacetop hen one. Methylbenzoylformate is available as Vicure 550 from Akzo Chemicals, Inc., Chicago, Illinois. According to an embodiment of the present invention, 35 millimoles of photoinitiator per 100 g of coating is used. A wider range of substrates can be coated using a higher level of photoinitiator. The photoinitiators break down to free radicals when exposed to UV light. The free radicals then open the double bonds between carbon atoms in acrylate groups.

The amount of photoinitiator added to the compositions is typically 1-10 parts by weight based on 100 parts by weight of non volatile components.

The coating compositions of the instant invention may also optionally contain UV absorbers or stabilizers such as resorcinol monobenzoate, 2-methVI resorcinol dibenzoate, and the like. The stabilizers can be present in an amount, based upon the weight of the coating compositions, exclusive of any additional solvent which may optionally be present, from about 0.1 to 25 parts by weight, preferably from about 3 to about 18 parts by weight based on colloidal silica, hydrolysis and condensation reaction product of a silyl acrylate of formula (2) and an acrylate monomer of formula (1).

The UV curable coating composition can contain from about 1 to about 25 parts by weight of stabilizers based on non-volatile material.

Solvents can optionally be added if needed, for example, to ease application. Suitable solvents include any water-miscible alcohol or water-solvent azeotrope. Examples of solvents include isopropyl alcohol (IPA), 4-methoxypropanol, n-butanol, 2-butanol, ethanol and the like.

The coating compositions of the present invention may also optionally contain various flattening agents, surface active agents, thixotropic agents, UV light stabilizers, hindered amine light stabilizers (HALS) dyes, and tintable reactive diluents. All of these additives are well known in the art and do not require extensive discussions. Therefore, only a limited number will be referred to, is being understood that any of these compounds can be used so long as they do not deleteriously affect the photocuring of the coating compositions and do not adversely affect the non-opaque character of the coating. Tintability additives that are contemplated for use in the present invention include any compatible, functionalized compound which imparts tintability, including compounds containing alkylated amine formaldehyde, polyhydroxyl-functionality, ethylenically unsaturated functionality, alkanol amine functionality and polyfunctional, polymerizable non-acrylate functional-ethers, and the like.

The various surface-active agents, including anionic, cationic and nonionic surface-active agents are described in Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 19, Interscience Publishers, New York, 1969, pp. 507-593, and Encyclopedia of Polymer Science and Technology, Vol. 13, Interscience Publishers, New York, 1970, pp. 477-486, both of which are incorporated herein by reference. Also, flow control and leveling additives such as BYK3008 and BYK31 00 from BYK Chemie, Wallingford, CT, may be added in amounts of from 0.01 to 6 parts by weight based on colloidal silica, hydrolysis and condensation reaction product of a silyl acrylate of formula (1) and an acrylate monomer of formula (2).

The radiation curable coating compositions are generally prepared by blending the low molecular weight acrylate or acrylates with silica acrylate and with other acrylates and photoinitiator. In one embodiment of the present invention, this formulation is diluted with an organic acid and applied to an ophthalmic lens.

Factors that may contribute to the adhesion of the hardcoat of an ophthalmic lens include line speed and coating thickness. The coating thickness is preferably 0.1 micron to about 20 microns, and more preferably from about 1 micron to about 8 microns.

Adhesion may also be related to line speed. Generally a hotter temperature substrate surface can be achieved with a slower line speed can that can lead to improved adhesion. Typical lines speeds are from about 1 fpm to about 5 fpm, with two 300 Watt/inch Fusion H lamps. Also, pre-heating the lens alone or in combination with acetic acid or slow line speeds or both.

Additional factors can also include lamp distance. One skilled in the art would realize it is possible to vary these conditions in order to achieve the desired combination of cure and substrate surface temperatures over about 9011C. It is recognized by those skilled in the art that factors changing the substrate surface hardness, such as the ratio of inputs, and the time a temperature or cure, may be varied to get the desired combination of properties. Therefore, 3011C is merely a preferred lower boundary.

Adhesion will generally be described in terms of scribe adhesion. Scribe adhesion is measure in accordance with ASTM D3359 and is known to skill artisans. Good adhesion means a classification of 36 or higher. This means that better then 50% adhesion occurs. Preferable a classification of 4B is obtained, meaning substantially all of the coating adheres.

The coating compositions of the present invention can be applied to a variety of solid substrates by conventional methods, such as flowing, spraying or dipping, to form a continuous surface film. Substrates which are especially contemplated herein are transparent and non-transparent plastics and metals. More particularly, these include synthetic organic polymeric substrates such as acrylic polymers like poly(methylmethacrylate); polyesters, such as poly(ethylene terephthalate), poly(butylene terephthalate), oriented polyesters; polyamides; polyimides; acrylonitrile-styrene copolymers; styrene-acrylonitrile-butadiene copolymers; polyvinyl chloride; butyrates; polyethylene, low and high density polyethylene; polypropylene; filled polymers; nylon; urethane; melamine, enamel coatings such as polyester-epoxy enamel; glass; polysulfone; acrylic copolymers; acrylic polymers; and metal substrates such as aluminum, chromium and sputtered alloys. By choice of the proper formulation, application conditions and pretreatment of the substrate, including the use of primers, the coatings can be adhered to substantially all solid substrates.

EXAMPLES STANDARD COATING FORMULA In a 50 gallon reactor, fitted with a heating mantle, a stirrer, a dip leg, and a reflux condenser, 266 pounds. isopropyl alcohol (IPA), 54. 5 pounds Nalco's Nalcoag 1034A colloidal silica, and 19.6 g. paramethoxV phenol were mixed for a few minutes. An addition of 8.2 pounds methacrVIoxVpropVltrimethoxVsilane (MAPTMS) was then made over a period of a 2-3 minutes. This hydrolysis mixture was then heated and held at ref lux, while bleeding air to the solution, for 2 hours. After this cook, 22.8 pounds hexanedioldiacrViate (HDDA) (SR238 from Sartomer) was added and stripping was begun, finishing up at 150-200 mm Hg, with a jacket temperature of 75"C. During the strip, a 5% oxygen sparge was bled to the bottom of the kettle. The strip was continued for one hour after the over head flow had ceased. At the end of the strip, the silica acrVIate, a TQMDDA blend was recovered, having a viscosity of 41 cps. A 100g sample of the silica acryiate was blended with 100g trimethylolpropanetriacrylate (TMPTA from Radcyre Specialties), 12g Vicure 55 photoinitiator to make the standard formulation.

EXAMPLE 1

The standard formulation was diluted to 30% in glacial acetic acid and was applied by flow coat to a CR39 PLASIIC ophthalmic lens. The coating was allowed to flash for 2 minutes.at 2511C. The coating was then cured with two passes at 20 fpm through a Fusion Systems Processor (2 - 300 Watt per inch, H lamps, 1.9 inches from the coating). The coating had good abrasion resistance rubs with #000 steel wool, but it failed scribed tape-pull adhesion. The same coating similarly coated and cured on a second lens, was allowed to flash for 30 seconds at 250C. The results were the same. Thus, diluting in acetic acid alone does not improve adhesion to lenses.

EXAMPLE 2

The standard formulation was diluted to 30% in isopropyl alcohol and was applied by flow coat to a ophthalmic lens which had been pre-treated by soaking it for 15 minutes in glacial acetic acid at 55'C. The coating was allowed to flash for 30 seconds at 250C. The coating was then cured with two passes at 20 fpm through a Fusion Systems Processor (2-300 Watt per inch, H lamps, 1.9 inches from the coating). The coating had good abrasion resistance rubs with #000 steel wool, and it passed scribed tape-pull adhesion. Thus, an elevated temperature soak in acetic acid gave good adhesion using isopropyl alcohol to the coating solvent.

EXAMPLE 3

A coating similar to the standard formulation, but without acrylated silica was made by combining 50g TMPTA, 25g HDDA, and 4.5g Vicure 5. This coating was diluted to 30% in isopropyi alcohol, and was applied by flow coat to a ophthalmic lens which had been pretreated as in Example 2. the coating was flashed and cured as in Example 2, and exhibited good abrasion resistance, and scribed tape- pull adhesion. When the same coating was diluted in glacial acetic acid to 30%, and was applied to an untreated lens, a flash and cure as above resulted in failed scribed adhesion. Thus, the benefits of acetic acid soak are extended to non-silicone containing acrylate coatings as well.

EXAMPLE 4 An ophthalmic lens was prepared for coating by soaking it in glacial acetic acid at 25C for 2 minutes. The standard formulation, diluted to 30% in isopropyl alcohol, was then applied by flow cost to the lens. The coating was allowed to flash for 90 seconds at 2511C. The coating was then cured with two passes at 5 fpm at 1.9 inches. The coating had good abrasion resistance, and it passed scribed tape-pull adhesion. The coated lens was then placed in boiling water for three hours. Upon drying and cooling to 250C, the lens was tested for adhesion over the same scribe mark and was found to have 100% adhesion of the coating. A different ophthalmic lens was pre-treated and coated and cured in the same manner with the same results. A third lens was coated with the standard formulation, diluted to 30% in IPA, with no acetic acid treatment Upon curing as above, the lens was found to have poor scribed tape pull adhesion.

EXAMPLE 5 Ophthalmic lenses were prepared for coating by soaking in glacial acetic acid at 250C. Some lenses were then rinsed with isopropyl alcohol and were allowed to flash for 1 minute at 25"C. The standard formulation, diluted to 30% in isopropyl alcohol, was then applied by flow coat to each lens. The coating was allowed to flash fro 90 seconds at 25"C. The coating was soaked for 2 minutes and cured at 5 fpm at 1.9 inches. The coating had good abrasion resistance, and passed scribed tape-pull adhesion. Thin coatings at the top of the lenses passed scribed adhesion after a less strenuous cure, but thicker coatings at the bottom of the lenses required slower cure speeds when using the mild acetic acid soak condition.

f' Coatinq # Acetic Acid Soak (min) Cure Speed ft Initial After 3 Hrs.

per min(fpm) Adhesion Boil A 120 1 x20 fail B -- 2nd pass --- U7.5 fail B, OK T OK T B 120 1X10 fail B 2nd pass --- 1x5 OK B -OK B - c 120 1 x7.5 fail B, OK T OK T D 120 1x5 OK E 120 (IPA 1 x5 OK -30/ofaii B Rinse) F 30 (IPA Rinse) 1 X5 fail B, OK T OK T G 60 (IPA Rinse) 1X5 fail B, OK T OK T B = Bottom T = Top EXAMPLE 6 Ophthalmic lenses were prepared and coated as above. The standard formulation, diluted to 30% in isopropyl alcohol was used, but the cure was with lamps at 3.9 inches from the lens surface. Thus, the slower speeds are preferred at these mild soak conditions, even at 32' lamp distance.

Coating # HOAc Soak (min) Cure Speed A B 2nd pass c 2nd pass (IPA Rinse) (IPA Rinse) (fpm) 1X5 1X10 Adhesion Boil 1 OKT&B OK T&B fail T & B + 1X10 OK T, fail B OK T 1X5 + 1X5 fail T & B OKT&B OK T, fail B EXAMPLE 7

Ophthalmic lenses were pre-treated in glacial acetic acid for 2 minutes at 250C, and coated, as above. The standard formulation was altered in the level of Vicure 55 it contained, and was diluted to 30% in isopropyl alcohol. The cure was with lamps at 3.9 inches from the tens surface. Thus, the adhesion of the coating to the lenses requires a minimum amount of photoinitiator when prepared and cured in this manner.

Coating # Vicure (ppm Cure Speed Adhesion (fPm) A 2 1 x5 fail B uncured T B 4 1X5 fail T & B c 6 1 X5 OK T, -20% fail B D 9 1 x5 OK T, 20% fail B E 9 1 x20 fail T & B + 1X5 OK T, fail B EXAMPLE 8

Ophthalmic lenses were prepared and coated as above. The standard formulation, diluted to 30% in isopropyl alcohol was used. The cure was with 1-600 W Fusion H lamps focused at 2.1" Coatinq # Acetic Acid Coatinq A B c Dip (min) Flash (min) 2 2 2 Cure Speed AdhesionBoil (fPM) U2.5 1X5 1X10 OK OK fail - The same pattern of adhesion at speeds below 10 fpm holds for 1600 W Fusion H lamp.

f OK EXAMPLE 9

Ophthalmic lenses were prepared and coated as above. The standard formulation, diluted to 30% in isopropyl alcohol was used. The cure was with 1-600 W Fusion H lamps. The preparation differed in that lenses were heated in an oven only, and were not contacted with acetic acid.

Coatinq # Pre-Heat Temp (IC1 Cure Speed Adhesion Boil (fPM) 1X5 A B cured @2.1 inches 110 96 91 1X10 OK 20% Fail 20% Fail Fail -

Claims

1. A comprising:

is radiation curable coating composition (a) acrylate monomers; and (b) an organic acid in an amount sufficient to increase adhesion of said composition to a substrate when cured.

2. A radiation curable coating composition as in Claim 1, wherein said acrylate monomers are ODA,, THFAr IDA, EDDA or mixtures thereof.

3. A radiation curable coating composition as in Claim 1 wherein said substrate is a CR39 substrate.

4. A radiation curable coating composition as in Claim 1 wherein said substrate is PET.

5. A radiation curable coating composition as in Claim 1, wherein said organic acid is glacial acetic acid.

6. A radiation curable coating composition of Claim 1, where a temperature sufficient to improve adhesion to equal or greater than 4B as defined in ASTM D-3359 is applied during the cure of said composition.

7. The radiation curable coating composition of Claim 6 wherein a temperature of at least WC is applied during the cure of said composition.

8. A radiation curable coating composition as in Claim 2 further comprising silica acrylate.

9. A radiation curable coating composition as in Claim 1 further comprising:

(c) a photoinitiator.

1.

is

10. A radiation curable coating composition as in Claim 9. wherein the coating is substantially translucent.

11. A UV curable hardcoat composition as in Claim 9, which comprises: colloidal silica; a mixture resulting from the hydrolysis and condensation reaction of a silyl acrylate of the formula (M8 R2 0 R2 1 1 (R0)4-a-bSi(C(R2) HR3C) 11 =C(R2)2)b 2C C-C acrylic monomer of the formula:

0 (M2)2C=CR U 2-d-0)nR4 wherein R is a CO-13) monovalent organic radical, R1 is a C(,-8) alkyl radical, R2 is selected from hydrogen, R and mixtures thereof, R is a %- 8) alkylene radical, R is a polyvalent organic radical, a is whole number equal to 0-2 inclusive, b is an integer equal to 1-3 inclusive, the sum of a + b is equal to 1-3, n is an integer from 2 to 6 inclusive, and wherein the total of the silyl acrylate and acrylic monomer equals 100 parts by weight; and wherein said photoinitiator comprises methylbenzoylformate.

12. A method for making a radiation curable coating composition having increased adhesion to a substrate comprising:

(a) mixing acrylic monomers; (b) contacting a substrate with an organic acid; and (c) coating said substrate with said acrylic monomers.

13.

A method for making a radiation curable coating composition comprising:

(a) mixing acrylic monomers; and (b) adding an organic acid solvent or co-solvent

14. A method for preparing a coated CR39 plastic lens comprising:

(a) coating said lens with a coating composition comprising acrylate monomers; (b) heating said coated lens to a temperature of at least 900C while effecting radiation cure.

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