TINTABLE CROSS-LINKABLE COMPOSITIONS

Abstract: A cross-linkable polymeric casting composition capable of producing an optical article exhibiting improved tint rate, the casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical-polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra-functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material.

Description: TINTABLE CROSS-LINKABLE COMPOSITIONS The present invention relates to the manufacture of plastic optical articles such as video discs and ophthalmic lenses. The most widely used plastic ophthalmic lens material is polymerised diethylene glycol bis (allyl carbonate). This polymer has proved a satisfactory material for the manufacture of ophthalmic lenses because of a combination of features, including excellent transmission, resistance to discolouration, high strength and high impact resistance. Further, in European Patent Application EP 0453149A2, the entire disclosure of which is incorporated herein by reference, applicant describes a cross-linkable casting composition including at least polyoxyalkylene glycol diacrylate or dimethacrylate, a high index bisphenol monomer and a urethane monomer. These copolymers have a high refractive index, a high Abbe number, and excellent impact strength. Whilst the lenses produced from the prior art compositions provide advances in the art, difficulties may be encountered in certain applications, an important characteristic in the manufacture of, for example, optical lenses is the ability to tint or dye the optical lens material. A particularly important characteristic is the tint rate or the rate at which a dye material is taken up by the optical lens material. This influences both final colour and time of manufacture. The prior art casting compositions have, in general, suffered from relatively low tint rates. The rigidity of a lens material (as determined by the free volume of the lens polymer which controls the diffusion coefficient of the dye in the polymer), and the chemical affinity of the material to dye molecules (as measured by the solubility coefficient) are important parameters controlling the tintability. At low rigidity, dye molecules can penetrate faster into the host material while at high rigidity, penetration becomes more difficult. Affinity refers to chemical compatibility, e.g. a more hydrophilic host material will have a faster uptake of dye molecules dispersed in an aqueous medium. It would accordingly be a significant advance in the art if the tint rate of optical lens materials could be increased and in particular without sacrificing other optical and mechanical properties of the optical lens material. It is accordingly an object of the present invention to overcome or at least alleviate one or more of the difficulties and deficiencies related to the prior art. Accordingly, the present invention provides a cross-linkable polymeric casting composition capable of producing an optical article exhibiting improved tint rate, the casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical- polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material. The cross-linkable polymeric casting composition may be modified such that other optical and mechanical properties of the optical article are reduced to a small extent only. Preferably other mechanical and optical properties may be maintained or even improved. The cross-linkable polymeric casting composition according to the present invention may be utilised for the preparation of a tinted optical article. The tinted optical article may be light-transmissible. The tinted optical article may be transparent. A photochromic optical article is preferred. The photochromic optical article may be characterised by having an improved tintability. The optical article may exhibit a high refractive index. The optical article may also retain good abrasion resistance and impact resistance. By the term "high refractive index" as used herein, we mean a polymer having a refractive index of at least approximately 1.55, preferably approximately 1.57, more preferably approximately 1.60. The polyoxyalkylene glycol diacrylate or dimethacrylate compound may be present in the polymeric casting composition in an increased amount relative to the casting compositions known in the prior art. As the polyalkylene glycol diacrylate or dimethacrylate is relatively flexible, such increased proportion thereof will provide a reduction in rigidity, and thus an increase in tint rate. The polyoxyalkylene glycol diacrylate or dimethacrylate compound may be present in amounts of from approximately 30% by weight to approximately 90% by weight, more preferably approximately 45% to 90% by weight, most preferably approximately 50% to 70% by weight, based on the total weight of the casting composition. For example, in a simple two component composition such as those consisting of a polyethylene glycol dimethacrylate (e.g. one designated in the trade as 9G) and a polyfunctional urethane acrylate (e.g. one designated in the trade as U4HA), the tint rate can be increased by simply increasing the amount of the more flexible component 9G. Conversely, an increase in the amount of the more rigid poly functional urethane acrylate will decrease the tint rate, e.g.: 9G/U4HA (wt ratio) % Transmission after tinting 100/0 3 80/20 11 60/40 51 50/50 74 NB: Tint rate is inversely proportional to % Transmission after tinting. Of course, we can also use this technique in compositions consisting of more than two components. The polyoxyalkylene glycol diacrylate or dimethacrylate compound includes ethylene oxide or propylene oxide repeating units in its backbone. An ethylene oxide derivative is preferred. The diacrylate or dimethacrylate monomer may include a monomer which exhibits an increased alkylene oxide chain length relative to the prior art. This will also provide a reduction in rigidity and in turn an increase in tint rate. Accordingly, preferably approximately 6 to 23 alkylene oxide repeating units may be included. Preferably the alkylene oxide chain length, n, is greater than or equal to approximately 9, preferably greater than or equal to approximately 14, more preferably greater than or equal to approximately 23. A polyethylene glycol dimethacrylate may be used. A polyethylene glycol dimethacrylate with an average molecular weight of the order of 600 is preferred. One suitable material is that sold under the trade name NKESTER 9G by Shin Nakamura which has an average molecular weight of 536. The average number of ethylene oxide polymerised units is 9. Preferably, an NK Ester 14G or 23G having an average number of 14 or 23 ethylene oxide polymerised units respectively may be used. For example, tint rate increases as the number of ethylene oxide groups between the reactive methacrylate end groups increases. For example, by using the analogues 3G, 4G, 6G, 9G, 14G and 23G as the glycol dimethacrylate component, it is possible to vary the tint rate from slow to fast for compositions containing these materials in that order, e.g. n G/ATM20*/U4HA (40/50/10) % Transmission after tinting value of n 4 70 9 43 14 23 23 9 * ATM20 Bisphenol A ethoxylated dimethacrylate Alternatively, or in addition, the polyalkylene glycol diacrylate or dimethacrylate component may be rendered more chemically compatible with a dye material. A diacrylate component may preferably be included as the diacrylates are generally more hydrophilic than the dimethacrylates. The polyoxyalkylene glycol diacrylate or dimethacrylate compound may be otherwise modified to increase hydrophilicity and thus its chemical affinity with a dye material. Accordingly, in a preferred aspect, the polyoxyalkylene glycol diacrylate or dimethacrylate component may include a copolymerisable hydrophilic monomer. The copolymerisable hydrophilic monomer may function to introduce polar groups, for example amine and hydroxy functional groups, into the structure of the starting diacrylate or dimethacrylate component. The copolymerisable hydrophilic molecule may be selected from the group consisting of dimethylamino ethyl acrylate or methacrylate, diethylamino ethyl acrylate or methacrylate or the glycidyl ester of a bisphenol such as bisphenol A. The copolymerisable hydrophilic monomer may be included in the cross- linkable polymeric casting composition in any suitable amounts. The copolymerisable hydrophilic monomer may be present in amounts of from 0 to approximately 20% by weight, based on the total weight of the cross-linkable polymeric casting composition, preferably approximately 2.5 to 15% by weight, more preferably approximately 5 to 10% by weight. Alternatively, or in addition, a particular cross-linkable polymeric casting composition may require a reduction in the tint rate to balance with other properties. Analogues of polyethylene glycol dimethacrylate which have generally equivalent chain lengths flexibility/free volume, but different chemical affinity to the dye molecules, for example polyethylene dimethacrylates, may be used. The high index bisphenol monomer component in the cross-linkable casting composition may include recurring units capable of forming a homopolymer having a refractive index of approximately 1.55, or greater. The high index bisphenol monomer component may be a polyacrylate or polymethacrylate ester of a bisphenol compound. The high index bisphenol monomer may be selected from compounds having the formula wherein R, is methyl, ethyl or hydrogen; R 2 is hydrogen, methyl or ethyl; R 3 is hydrogen, methyl or hydroxyl; R 4 is hydrogen, methyl or ethyl; X is hydrogen or a halogen, preferably chlorine, bromine or iodine, or hydrogen; and m and n are integers having a value of 2 to 20, preferably 4 to 8. The rigidity of the high index bisphenol monomer component may be reduced by increasing the value of m or n. This will in turn increase the tintability of the optical active formed therefrom. Accordingly m and n are preferably integers such that m + n = 4 to 30, more preferably from 10 to 30. For example the high index bisphenol monomer sold under the trade designation SR480 and available from Santomer and having the following formula has been found to be suitable. wherein m and n are integers between 2 and 8 such that m + n = 10, and X is hydrogen or a halogen, preferably chlorine, bromine or iodine, or hydrogen Similarly high index bisphenol monomers sold under the trade designations BPE-100, BPE-200, BPE-500 and BP-1300 from Shin-Nakamura Chemical Co. Ltd., wherein m + n = 2, 4, 10 and 30 respectively, have been found to be suitable. Alternatively, or in addition, the chemical affinity for a dye material may be increased by introducing a polar group into the molecule. A halogen is preferred. For example, substitution in the aromatic ring/s with halogens, e.g. using Br, as in the case of NK ester 534M, can be used to change both the diffusivity and the solubility coefficient. Representative monomers of the above-described class include: dimethacrylate and diacrylate esters of bisphenol A; dimethacrylate and diacrylate esters of 4,4'bishydroxyethoxy-bisphenol A and the like. A preferred high index bisphenol compound is bisphenol A ethoxylated dimethacrylate. A bisphenol A ethoxylated dimethacrylate sold under the trade designation ATM20 by Ancomer has been found to be suitable. A glycidyl ester of bisphenol A sold under the trade designation Bis GMA by Freeman Chemicals has been found to be suitable. Desirably the high index monomer includes a polar group, e.g. a halogen. Halogenated high index bisphenol compounds which may be used include those sold under the trade designation and NK Ester 534M by Shin Nakamura. High index brominated bisphenol monomers sold under the trade designations SR803, SR804, GX6099 and GX6094 by Dai-lchi-Kogyo Seiyaku (DKS) Co. Ltd. have also been found to be suitable. The high index bisphenol monomer may be present in amounts of from approximately 5 to 40% by weight, preferably 10 to 35% by weight based on the total weight of the casting composition. In addition, a secondary high index monomer other than a high index bisphenol monomer may be used in the casting composition according to the present invention in minor amounts. These include styrene, and derivatives thereof; high index acrylate and methacrylate esters including benzyl and phenyl methacrylate; n-vinyl pyrrolidone; and high index aromatic urethanes. The secondary high index monomer component may be included to modify overall refractive index of the optical article formed therefrom. The secondary high index monomer component may be present in amounts of from 0 to approximately 20% by weight based on the total weight of the casting composition. The secondary high index monomer component is present preferably in amounts of approximately 5% to 15% by weight, more preferably approximately 5 to 10% by weight. It is preferred that the secondary high index monomer component is not present in amounts greater than 20% since the optical article formed therefrom may exhibit reduced barcol hardness and/or reduced abrasion resistance. This may be compensated for, to some degree by increasing the amount of high index bisphenol monomer used. As stated above, the cross-linkable polymeric casting composition includes at least one urethane monomer having terminal acrylic and/or methacrylic groups. The number of such groups may vary from 2 to 6, preferably 2 to 4. In order to improve tint rates, the urethane monomer may be modified to decrease the rigidity thereof and/or to decrease the number of cross-linkable sites. An increase in the number of cross-linkable sites will give a tighter and more rigid network with lower free volume and consequently a slower tint rate. Conversely, a decrease in the number of cross-linkable sites will give a less rigid network with higher free volume and a faster tint rate, e.g. in the composition 9G/ATM20/Urethane acrylate in the ratio 40/50/10 the % transmission after tinting using U4HA (which contains two acrylate and two methacrylate groups per molecule) is 43% while that of U6HA (which contains six acrylate groups per molecule) is 39%. Whilst the U6HA exhibits a larger number of cross-linkable sites, it is structurally a more flexible molecule, thus permitting overall reduction in transmission rate and thus tint rate. Suitable materials falling within this definition include materials supplied under the trade names U-4H, U-4HA and U-6HA by Shin Nakamura, NF-201 and NF-202 by Mitsubishi Rayon. These monomers are included to improve physical toughness without causing the lens material to become too brittle. Impact resistance is improved without adversely affecting abrasion resistance. Certain urethane monomers, for example the aromatic urethane methacrylate NF202, are high refractive index components and may function alternatively or in addition as the or one of the secondary high index monomer component(s) of the casting composition. The structures contained within any particular monomer can be selected from those containing aliphatic, aromatic, and cyclic structures of other forms. We have found that in the formulations of the present invention, the tetracrylic urethane monomer gives particularly satisfactory results. The inclusion of the tetracrylic urethane monomer may provide a product of increased hardness. The tetracrylic urethane monomer according to a preferred aspect of the present invention may be a compound of the formula R 2 R 3 R 2 \ / C=C-C-0-C -C -C -0-C-C=C, A R' D 2 ? =0 NH X I NH wherein R, R 1 , R 2 and R 3 which may be the same or different are selected from hydrogen, alkyl of 1 to 6 carbon atoms or a substituted alkyl of 1 to 6 carbon atoms; and X is a relatively flexible organic residue having 1 to 20 carbon atoms. X may be an aliphatic, aiicyclic or aromatic residue. X may be selected from the group consisting of C C 20 alkyl, alkoxy, alkylamino, alkyl carbonyl alkoxy carbonyl, alkylamido or alkoxy amide. X may be substituted with one or more polar groups, e.g. halogen, hydroxyl, nitro or amino, alkyl to increase tint rate in the final optical article. The urethane monomer may be present in any suitable amount to provide a desired level of hardness. The urethane monomer may be present in amounts of from approximately 5 to approximately 25% by weight, preferably 5 to 15% by weight based on the total weight of the casting composition. The tri- or tetra-functional vinyl, acrylic or methacrylic monomer may function as a poly functional unsaturated cross-linking agent according to the present invention. The cross-linking agent may be a short chain monomer for example trimethylol propane trimethacrylate, pentaerythritol triacrylate or tetracrylate, or the like. Other polyfunctional cross-linking agents which may be used include NK Ester TMPT, NK Ester A-TMPT, NK Ester A-TMM-3, NK Ester A- TMMT, di-trimethylol propane tetraacrylate, trimethylolpropane triacrylate, pentaerythritrol tetramethacrylate, dipentaerythritol monohydroxypenta acrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylol-propane trimethacrylate. It is preferable to select as the polyfunctional unsaturated cross linking agent, material such as that sold under the trade name SR-454 which is an ethoxylated trimethylol propane triacrylate. A polyfunctional unsaturated cross- linking agent sold under the trade designation SR415 has been found to be particularly suitable. SR415 provides increased flexibility in that it includes ten (10) ethoxylated groups in each molecule. The poly functional unsaturated cross-linking agent may be present in amounts of from approximately 5 to 25% by weight, preferably approximately 10% to 20% by weight based on the total weight of the casting composition. The cross-linkable casting composition according to the present invention may further include a cross-linking initiator. The cross-linking initiator may be a heat and/or ultraviolet (UN.) initiator. The compositions are preferably cured by a combination of UN. radiation and heat. The combination of UN. radiation and heat may reduce the possibility of incomplete curing for example due to the phenomenon known as "radical trapping". The composition, with the addition of approximately 0.2 to 2.0% by weight of cross-linking initiator may be exposed to UN. radiation for between 0.5 and 10 seconds. Any commercially viable UN. curing system may be used. We have used a Fusion System with microwave driven lamps. A number of fusion bulbs with different output spectra may be considered. Presently we prefer the "D" bulb and the 'V bulb. One source we have found satisfactory is a 10 inch, 300 watt/inch mercury lamp. The mould assembly is then heated to 100°C for one hour or the lens may be removed from the assembly and heated in air for about one hour at 100°C. This means that fully cured lenses can be manufactured, if desired, in about one hour. Heat curing can also be used without any use of UN. radiation. Typically 2 - 4 passes under the UN. lamps plus an hour of heat treatment at 100°C completes the cure. Any suitable UN. initiator may be used. An initiator available under the trade designation Irgacure 184 has been found to be satisfactory. More than one curing agent may be present. It has been possible to operate with a relatively low level of initiator of between approximately 0.05 and 0.25% by weight. A range of photoinitiators available commercially can be used, depending on sample thickness, type of UN. lamp used and the absorption wavelength of the monomer mix. The following photoinitiators have been found to be suitable. Alcolac Vicure 10 - isobutyl benzoin ether Alcolac Vicure 30 - isopropyl benzoin ether Alcolac Vicure 55 (V55) - methyl phenyl glyoxylate Ciba Geigy Irgacure 184 - 1 - hydroxy cyclohexyl phenyl ketone • Ciba Geigy Irgacure 651 - benzildimethyl ketal Ciba Geigy Irgacure 907 - 2-methyl-1,[4-(methylthio)phenyl]-2-morpholino- propanone-1 Merck Darocur 1664 Rohm Catalyst 22 • Bis(t-butyl peroxide) diisopropylbenzene t-butyl perbenzoate t-butyl peroxy neodecanoate Amicure DBU Amicure BDMA A mixture of two or more of the above may also be used. Additionally, combination of photoiniator mixtures or photoinitiator mixtures with a heat induced free radical initiator such as peroxides, peroxypercabonates or an azo compound may also be employed. As an alternative to photo curing initiators, a heat curing initiator may be used, for example 1,1-di-tertbutylperoxy-3,3,5-trimethylcyclohexane or secondary isopropyl percarbonate. Other additives may be present which are conventionally used in casting compositions such as inhibitors, dyes, UN. stabilisers and materials capable of modifying refractive index. Mould release agents can be added but they are in general not required with the compositions used in the method of the present invention. Such additives may include: UN. Absorbers including • Ciba Geigy Tinuvin P - 2(2'-hydroxy-5'methyl phenyl) benzotriazole • Cyanamid Cyasorb W 531 -2-hydroxy-4-n-octoxybenzophenone • Cyanamid Cyasorb W 5411 -2(2-hydroxy-5-t-octylphenyl)benzotriazole • Cyanamid UV 2098 - 2 hydroxy-4-(2-acryloyloxyethoxy) benzophenone • National S + C Permasorb NA - 2 hydroxy-4-(2 hydroxy-3- methacryloxy)propoxy benzophenone • Cyanamid UV 24 - 2,2'-dihydroxy-4-methoxybenzophenone • BASF UVINUL 400 - 2,4 dihydroxy-benzophenone • BASF UVINUL D-49 - 2,2 , -dihydroxy-4,4' dimethoxy benzophenone • BASF UVINUL D-50 - 2,2', 4,4' tetrahydroxy benzophenone • BASF UVINUL D-35-ethyl-2-cyano-3,3-diphenyl acrylate • BASF UVINUL N-539-2-ethexyl-2-cyano-3,3-diphenyl acrylate • Ciba Geigy Tinuvin 213 Hindered amine light stabilisers (HALS) including • Ciba Geigy Tinuvin 765/292 - bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate • Ciba Geigy 770 - bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate Antioxidants including • Ciba Geigy Irganox 245 - triethylene glycol-bis-3-(3-tert butyl-4-hydroxy-5- methyl phenyl)propionate • Irganox 1010 -2,2-bis[[3-[3,4-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1- oxopropoxy]-methyl]-1,3-propanediyl 3,5-bis (1,1 -dimethyl ethyl)-4-hydroxy benzene propanoate • Irganox 1076 - octadecyl 3-(3 , ,5'-di-tert-butyl(-4'-hydroxy phenyl) propionate Anticolourino aαents including • Triphenyl phosphine • 10 dihydro-9-oxa-10-phosphaphenanthrene-1 -oxide Cure modifiers including • Dodecyl mercaptan • Butyl mercaptan • Thiophenol • A dimer of α-methyl styrene Other monomeric additives can be present in amounts up to 10% by weight as diluents, and include monomers such as methacrylic acid, vinyl silanes, methyl allyl, hydroxy ethyl, methacrylate. Other monomeric additives may be included to improve processing and/or material properties, these include: • methacrylic acid, maleic anhydride, acrylic acid • adhesion promoters/modifiers such as Sartomer 9008, Sartomer 9013, Sartomer 9015 etc. • dye-enhancing, pH-adjusting monomers like Alcolac SIPOMER 2MIM • a charge-reducing cationic monomer to render the material more antistatic, example Sipomer Q5-80 or Q9-75 • hydrophobic comonomers: Shin Nakamura NPG, P9-G etc. to reduce the water adsorption of the material • viscosity modifiers Accordingly, in a preferred aspect of the present invention the cross- linkable polymeric casting composition may further include at least one aliphatic glycol dimethacrylate or diacrylate. The aliphatic glycol dimethacrylate or diacrylate may function to reduce the viscosity of the composition and thus improve the processing characteristics of the composition. An ethylene, propylene, butylene or pentylene diacrylate or methacrylate may be used. A butylene glycol dimethacrylate is preferred. One suitable material is that sold under the trade designation NK ester BD by Shin Nakamura. A neopentyl glycol dimethacrylate may be used. One suitable material is that sold under the trade designation NK ester NPG by Shin Nakamura. The aliphatic glycol dimethacrylate or diacrylate may be present in amounts of approximately 1 to 10% by weight, preferably 2.5 to 5% by weight based on the total weight of the casting composition. In a further aspect of the present invention there is provided a tinted optical article including an optical article formed from a cross linkable casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical-polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material; and a dye material incorporated therein. The dye material utilised in the tinted optical article may be of any suitable type. A photochromic dye is preferred. The photochromic dyes utilised in the process of the present invention are generally activated by near UV light, in the range of wavelengths from approximately 320 nm to 450 nm. The pigment(s) or dye(s) including photochromic dye(s) may be selected from the group consisting of anthraquinones, phthalocyanines, spiro-oxazines, chromenes, pyrans including spiro-pyrans and fulgides. Examples of preferred photochromic dyes may be selected from the group consisting of • 1 ,3-dihydrospiro[2H-anthra[2,3-d]imidazole-2, 1 '-cyclohexane]-5, 10-dione • 1 ,3-dihydrospiro[2H-anthra[2,3-d]imidazole-2, 1 '-cyclohexane]-6, 11 -dione • 1 ,3-dihydro-4-(phenylthio)spiro[2H-anthra'1 ,2-d]imidazole-2, 1 '-cyclohexane]- 6,11 -dione • 1,3-dihydrospiro[2-H-anthra[1,2-d]imidazole-2,1 , -cycloheptane]-6,11-dione • 1.S.S-trimethylspiro'indole^.S'-tSHJnaphthop.l-bl-l ,4-oxazine] • Σ-methyl-S.S'-spirobpH-naphthop.l-blpyran] (2-Me) • 2-phenyl-3-methyl-7-methoxy-8'-nitrospiro[4H-1-benzopyran-4,3'-[3H]- naphtho]2,1-b]pyran • Spiro[2H-1 -benzopyran-2,9'-xanthene] • 8-methoxy-1',3 , -dimethylspiro(2H-1-benzopyran-2,2'-(1Η)-quinoline • 2,2'-Spirobi[2H-1-benzopyran] • 5'-amino-1 '^'.S'-trimethylspiropH-l -benzopyran-2,2'-indoline • Ethyl-β-methyl-β-(3 , I 3 , -dimethyl-6-nitrospiro(2H-1-benzopyran-2,2 , -indolin-r- yl)-propenoate • (l^-propanediy bisp^'-dimethyl-β-nitrospiropH-l-benzopyran^^'- indoline] • S.S'-dimethyl-δ-nitrospiropH-l-benzopyrao-Σ^'-benzoxazoline] • e'-methylthio-S.S'-dimethyl-e-methoxy-e-nitrospiropH-l-benzopyran^^'- benzothiozoline] • (1 ,2-ethanediyl)bis[8-methoxy-3-methyl-6-nitrospiro[2H-1 -benzopyran-2,2'- benzothiozoline] • N-N , -bis(3,3'-dimethyl-6-nitrospiro[2H-1-benzopyran-2,2'(3Η)-benzothioazol- 6'-yl)decanediamide • -α-(2,5-dimethyl-3-furyl)ethylidene(Z)-ethylidenesuccinic anhydride; α-(2,5- dimethyl-3-furyl)-α',δ-dimethylfulgide • 2,5-diphenyl-4-(2'-chlorophenyl)imidazole • [(2',4'-dinitrophenyl)methyl]-1 H-benzimidazole • N-N-diethyl-2-phenyl-2H-phenanthro[9, 10-d]imidazol-2-amine • 2-Nitro-3-aminofluoren 2-amino-4-(2'-furanyl)-6H-1 ,3-thiazine-6-thione The optical article may provide characteristics substantially equal to or greater than those achievable with articles made from diethylene glycol bis(allyl carbonate) but with improved dye take-up. The overall refractive index may be in the mid refractive index range of from approximately 1.51 to 1.57, preferably 1.53 to 1.57. The optical articles prepared by the method of this invention include camera lenses, ophthalmic lenses and video discs. The casting composition may be formed into an optical article by mixing in a convenient vessel the components making up the material, and then adding the curing catalyst and/or photo-initiator. The mixed material is then degassed or filtered. As the curing time is substantially reduced the casting process may be undertaken on a continuous or semi-continuous basis. The dye material, for example a photochromic dye or mixture of dyes, may be incorporated into the optical article so formed in any suitable manner. A surface imbibition technique may be used. The dye material may be incorporated by first positioning a polymeric or other carrier of photochromic dye physically against a surface of the optical article. Heat may then be applied (e.g. in the range 100 to 150°C) to cause the dyes to undergo sorption and diffusion into the lens. The depleted carrier is removed from the lens after the passage of sufficient time at elevated temperature, typically of the order 1/2 to 4 hours. It is found that adequate darkening is achieved with inclusion of 5 to 10 μg/mm 2 of surface diffused to a depth of about 50 μm. The average dye concentration in this region of the lens is in the range of approximately 0.1 to 0.2 mg/mm 3 , or approximately 7 to 14% (w/w) of the polymer weight in that region. In a still further aspect of the present invention, the optical article may be a coated optical article. The coated optical article may include an optical article formed from a cross-linkable casting composition as described above, and a polymeric coating including a dye, adhered thereto. The polymeric coating may exhibit improved adhesion to the substrate optical article. The optical article may be a lens or lens blank. The polymeric coating may be formed from a polymer of the type described above. The polymeric coating may be of the type described in copending Australian Provisional Patent Application entitled "Process for Preparing Optical Articles" the entire disclosure of which is incorporated herein by reference. In an alternative embodiment, the polymer coating may be cast to form a muitifocal, progressive or like region on the surface of a pre-formed lens or lens blank. Such techniques are disclosed for example in United States Patents 5,178,800 and 5,219,497 to Innotech Inc. In a preferred aspect, the polymeric coating may be cast on the optical article utilising front surface coating techniques. Such techniques are described for example in Australian Patent Application 80556/87 or Australian Patent 648,209 to applicants, the entire disclosures of which are incorporated herein by reference. As stated above, the polymeric coating includes a dye material. A photochromic dye, e.g. as described above, is preferred. A chromone photochromic dye is preferred. The dye may be incorporated directly or indirectly into the polymeric coating. The dye may be incorporated by surface imbibition as described above. The present invention will now be more fully described with reference to the accompanying examples. It should be understood, however, that the description following is illustrative only and should not be taken in any way as a restriction on the generality of the invention described above. EXAMPLE 1 (Comparative) A cross-linkable casting composition having the following components was prepared • 9G (polyethylene glycol dimethacrylate) 60 • TMPT (Trimethylol propane trimethacrylate) 20 • U4HA (urethane tetracrylate) 20 The monomer mix was prepared in a beaker together with 0.2% V55 as the UN. initiator. The casting material was used to fill the space between a pair of glass moulds separated by a plastic gasket at their periphery and held together by a clip. The mould was then passed 4 times under a UN. lamp. This was followed by a 1 hour extended cure at 100°C. A polymeric carrier bearing a chromone photochromic dye was placed in contact with the optical lens so formed and heated at 130°C for 2 hours. A tinted optical lens was produced. The lens showed relatively poor dye penetration as illustrated below. EXAMPLE 2 Example 1 was repeated under similar conditions with monomer mixes as designated in Table 1 below. The results achieved are also given in Table 1. Satisfactory tinted lenses were achieved in Examples 2, 3, 4, 6, 7, 8, 11 and 12. A thin cross section of a dye imbibed lens was allowed to soak in a solution of concentrated nitric acid (pH approximately 0-1) until a deep purple colour was obtained on the front surface. The section was then rinsed under water and the depth of penetration of the photochromic dye was measured by a microscope. TABLE 1 Example Formulations Dye % Yellowness Penetration Trans. Index (Microns) 14G/9G/TMPT/U4HA 1 (Comp.) 0/60/20/20 33 92.8 1.0 2 20/40/20/20 51 92.8 0.9 3 40/20/20/20 64 92.8 1.0 4 60/0/20/20 90 92.8 1.0 23G/9G/TMPT/U4HA 5 (Comp.) 0/60/20/20 33 92.8 1.0 6 20/40/20/20 83 92.8 0.9 7 40/20/20/20 125 92.9 0.9 8 60/0/20/20 290 92.6 0.8 9G/X/U4HA 45/50/5 X= 9 (Comp.) ATM20 13 92.6 1.0 10 (Comp.) BPE200 18 91.6 1.7 11 BPE 500 250 92.5 1.3 12 SR480 196 92.7 1.0 14G Polyethylene glycol dimethacrylate having on average 14 ethylene oxide polymerised units 23G Polyethylene glycol dimethacrylate having on average 23 ethylene oxide polymerised units ATM20 A bisphenol A ethoxylated dimethacrylate by Ancomer BPE200 High index bisphenol monomer wherein m + n is 10 from Shin- Nakamura BPE500 High index bisphenol monomer wherein m + n is 30 from Shin- Nakamura SR480 Highly ethoxylated bisphenol A dimethacrylate from Sartomer Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.

Claims: Claims 1. A cross-linkable polymeric casting composition capable of producing an optical article exhibiting improved tint rate, the casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical- polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material. 2. A cross-linkable polymeric casting composition according to Claim 1, wherein the polyoxyalkylene glycol diacrylate or dimethacrylate component is present in an increased amount of from approximately 30% by weight to approximately 90% by weight, based on the total weight of the casting composition. 3. A cross-linkable polymeric casting composition according to Claim 2, wherein the polyoxyalkylene glycol diacrylate or dimethacrylate component is present in an amount of from approximately 45% to 90% by weight, based on the total weight of the casting composition. 4. A cross-linkable polymeric casting composition according to Claim 1, wherein the polyoxyalkylene glycol diacrylate or dimethacrylate component includes a monomer which exhibits an increased alkylene oxide chain length of from approximately 6 to 23 alkylene oxide repeating units. 5. A cross-linkable polymeric casting composition according to Claim 4, wherein the polyoxyalkylene glycol diacrylate or dimethacrylate monomer includes approximately 9 to 23 alkylene oxide repeating units. 6. A cross-linkable polymeric casting composition according to Claim 1, wherein the polyoxyalkylene glycol diacrylate or dimethacrylate component includes approximately 2.5% to 20% by weight, based on the total weight of the casting composition, of a co-poiymerisable hydrophilic monomer. 7. A cross-linkable polymeric casting composition according to Claim 6, wherein the co-polymerisable hydrophilic monomer is selected from the group consisting of dimethylamino ethyl acrylate or methacrylate, diethylamino ethyl acrylate or methacrylate or the glycidyl ester of a bisphenol. 8. A cross-linkable polymeric casting composition according to Claim 1 , wherein the high index bisphenol monomer is selected from compounds having the formula wherein R is methyl, ethyl or hydrogen; R 2 is hydrogen, methyl or ethyl; R 3 is hydrogen, methyl or hydroxyl; R 4 is hydrogen, methyl or ethyl; X is hydrogen or a halogen, or hydrogen; and m and n are integers having a value of 2 to 20. 9. A cross-linkable polymeric casting composition according to Claim 8, wherein m and n are integers such that m + n = 10 to 30. 10. A cross-linkable polymeric casting composition according to Claim 8, wherein X is a halogen selected from one or more of chlorine, bromine or iodine. 11. A cross-linkable polymeric casting composition according to Claim 1 , wherein the urethane monomer is modified to decrease to rigidity thereof and/or to decrease the number of cross-linkable sites. 12. A cross-linkable polymeric casting composition according to Claim 11, wherein the urethane monomer is a compound of the formula wherein R, R 1 , R 2 and R 3 which may be the same or different are selected from hydrogen, alkyl of 1 to 6 carbon atoms or a substituted alkyl of 1 to 6 carbon atoms; and X is a relatively flexible organic residue having 1 to 20 carbon atoms. 13. A cross-linkable polymeric casting composition according to Claim 12, wherein X is selected from the group consisting of C^C^o alkyl, alkoxy, alkylamino, alkyl carbonyl alkoxy carbonyl, alkylamido or alkoxy amide, optionally substituted with one or more polar groups. 14. A cross-linkable polymeric casting composition according to Claim 1 , wherein the tri- or tetra functional vinyl, acrylic or methacrylic monomer is selected from the group consisting of trimethylol propane trimethacrylate, pentaerythritol triacrylate or tetracrylate, di-trimethylol propane tetraacrylate, trimethylolpropane triacrylate, pentaerythritrol tetramethacrylate, dipentaerythritol monohydroxypenta acrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylol-propane trimethacrylate. 15. A cross-linkable polymeric casting composition according to Claim 14, wherein the tri- or tetra functional monomer is an ethoxylated trimethylol propane triacrylate or trimethacrylate. 16. A tinted optical article including an optical article formed from a cross linkable casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical-polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material; and a dye material incorporated therein. 17. A tinted optical article according to Claim 16, wherein the dye material is a photochromic dye. 18. A coated optical article including an optical article an optical article formed from a cross linkable casting composition including a polyalkylene glycol diacrylate or dimethacrylate; a urethane monomer having terminal acrylic and/or methacrylic groups; and a monomer including a recurring unit derived from at least one radical-polymerisable bisphenol monomer capable of forming a homopolymer having a high refractive index; and/or a tri- or tetra functional vinyl, acrylic or methacrylic monomer, the cross-linkable polymeric casting composition being modified to reduce the rigidity of the optical article formed therefrom, and/or increase the chemical affinity of the components of the casting composition to a dye material; and a dye material incorporated therein, and a polymeric coating including a dye adhered thereto. 19. A coated optical article according to Claim 18 wherein the polymeric coating includes a photochromic dye.

Inventors: KOK CHONG MENG, PERROTT COLIN MAURICE, TOH HUAN KIAK, KOK, CHONG, MENG, PERROTT, COLIN, MAURICE, TOH, HUAN, KIAK
Applicants: KOK CHONG MENG, PERROTT COLIN MAURICE, SOLA INT HOLDINGS, TOH HUAN KIAK, KOK, CHONG, MENG, PERROTT, COLIN, MAURICE, SOLA INTERNATIONAL HOLDINGS LTD., TOH, HUAN, KIAK
Application year: 1996
Main classification: C08F265
IPC codes: C08F290