AU728612B2 - Process for preparing optical articles - Google Patents

Description

WO 97/27223 PCT/AU97/00029 1 PROCESS FOR PREPARING OPTICAL ARTICLES The present invention relates to a process for 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 form optical materials having 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.

Attempts have been made in the prior art to produce lens materials of this type which absorb ultraviolet light, below a particular wavelength, that is they exhibit a high ultraviolet (UV) light cut-off, but substantially without success.

It has been proposed in the prior art to utilise long wavelength type photoinitiators. However the rate of reaction utilising such photoinitiators is normally too fast for proper cure to be achieved utilising ultraviolet light. Optical articles produced therefrom exhibit unacceptable stress/strain and increased yellowness, indicative of trapped free radicals therein. Moreover, the utilisation of photoinitiators such as Vicure 55 may lead to detrimental residues of such initiators being maintained in the final product. This may lead to fatigue difficulties in the final product.

It would accordingly be a significant advance in the art if optical lens materials could be provided which exhibit a high UV cut-off 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 WO 97/27223 PCT/AU97/00029 2 art.

Accordingly, the present invention provides a process for preparing an optical article which process includes providing a cross-linkable polymeric casting composition including an acrylate or methacrylate monomer, and optionally an ultra-violet (UV) absorber; a cure modifier; and a UV photoinitiator; mixing the casting composition, cure modifier and photoinitiator; and exposing the mixture to a source of ultraviolet (UV) radiation for a time sufficient to produce an optical article.

The optical article formed in the process according to the present invention may be light-transmissible. The optical article may be transparent.

The optical article may exhibit a high refractive index. A coated optical article is preferred. The optical article may also retain good abrasion resistance and impact resistance, and reduced fatigue. The optical article may exhibit reduced stress/strain and significantly reduced yellowness relative to prior art methods utilising long wavelength photoinitiators. A tinted optical article may be produced.

A photochromic optical article is preferred. The optical article may exhibit reduced fatigue utilising the process of the present invention in the photochromic layer or coating.

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 optical article may be an optical lens element. The lens element may be a relatively thick lens element.

By the term "lens element" as used herein we mean all forms of individual refractive optical bodies employed in the ophthalmic arts, including, but not limited to, lenses, lens wafers and semi-finished lens blanks requiring further finishing to a particular patient's prescription. Also included are formers used in the WO 97/27223 PCT/AU97/00029 3 manufacture of progressive glass lenses and moulds for the casting of progressive lenses in polymeric material such as the material sold under the trade designation CR39.

It has surprisingly been found that by combining the use of a photoinitiator with a cure modifier, it is possible to product an optical article which will tolerate increased volumes of ultraviolet light absorbers. The optical article may exhibit a higher UV cut-off than previously achievable in the prior art. Whilst we do not wish to be restricted by theory, it is postulated that the utilisation of a cure modifier slows the cure rate under UV light of the casting composition. This improves the fatigue properties of the article thus formed, and avoids problems of unwanted residues of initiators remaining in the final product due to incomplete cure.

The cure modifiers utilised in the process of the present invention may be of any suitable type. A transfer agent may be used. A transfer agent such as 2,4diphenyl-4-methyl-l-pentene Nofmer-MSD), dodecyl mercaptan, butyl mercaptan and thiophenol have been found to be suitable. A transfer agent such as di-isopropanyl benzene has been found to be suitable.

The transfer agent may be present in any suitable amounts. The transfer agent may be utilised in an amount of from approximately 0.001% by weight to 1% by weight, preferably 0.01% to 0.50%, more preferably approximately 0.1% to by weight, based on the total weight of the casting composition.

Nofmer and di-isopropanyl benzene are preferred.

The photoinitiator may be of any suitable type. A long wavelength photoinitiator may be used.

The long wavelength photoinitiator may be of any suitable type. By the term "long wavelength photoinitiator" as used herein, we mean a photoinitiator which reacts to light at a wavelength of approximately 400nm or above.

A range of photoinitiators available commercially can be used, depending on sample thickness, type of U.V. lamp used and the absorption wavelength of the monomer mix.

The following photoinitiators have been found to be suitable.

WO 97/27223 Lucirin TPO PCT/AU97/00029 2,4,6-trimethylbenzoyldiphenoylphosphime oxide

H

3

C'

Irgacure 907 (2-methyl-i -[4-(methylthio)phenyl]-2-morpholinopropane-1 -one) OC H 3 Ill1

OH

3 S j C-C-N 0 1 \VJ

CHN

3 (hydroxycyclohexyl) phenyl ketone Irgacure 184

HO

Irgacure 369 (2-benzyl-2-N-dimethylamino-1 -(4-morpholinophenyl)- I -butanone) O 0 CH 2

CH

3

II

N

H

3 C \CH 3 Lucirin BDK; Irgacure 651 (Benzil Dimethyl Ketal) 0 OCH 3

OCH

3 Vicure 30 isopropyl benzoin ether I *,CH 3 OCH

CH

WO 97/27223 PCT/AU97/00029 WB 4744 2-n-propoxy-9H-thioxanthen-9-one 0 O O O O--CH2CH2CH3

S

Quantacure EPD Ethyl 4-(dimethylamino)benzoate H1 3 C -O-CH2CH3 A mixture of two or more of the above may also be used. TPO Lucirin is preferred.

The photoinitiator may be present in any suitable amounts in the crosslinking casting composition. The photoinitiator may be present in amounts of from approximately 0.01% to 1.00% by weight, preferably approximately 0.10% to 0.5% by weight, based on the total weight of the casting composition.

The source of ultraviolet radiation may be of any suitable type. Any commercial UV 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.

One source we have found satisfactory is a 10 inch, 300 watt/inch mercury lamp. This means that fully cured lenses can be manufactured, if desired, in about 60 minutes.

Typically 2 4 passes under the U.V. completes the cure.

In a preferred aspect of the present invention the cross-linkable polymeric casting composition including a polyoxyalkylene glycol diacrylate or dimethacrylate; a monomer including a recurring unit derived from at least one radical polymerisable bis-phenol monomer capable of forming a homopolymer having a high refractive index; a urethane monomer having terminal acrylic and/or methacrylic groups; and a UV absorber.

WO 97/27223 PCT/AU97/00029 6 The polyoxyalkylene glycol diacrylate or dimethacrylate compound may be present in the polymeric casting composition in any suitable amount The polyoxyalkylene glycol diacrylate or dimethacrylate compound may be present in amounts of from approximately 10% by weight to approximately 60% by weight, preferably approximately 15% by weight to 55 by weight, more preferably approximately 20 to 45% by weight, based on the total weight of the casting composition.

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 3G or 4G having an average number of 3 to 5 ethylene oxide polymerised units respectively 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.

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.

WO 97/27223 PCT/AU97/00029 7 The high index bisphenol monomer may be present in amounts of from approximately 5 to 60% by weight, preferably 20 to 55% by weight, more preferably approximately 10 to 45% 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 four acrylate groups per molecule) is 43% while that of U6HA (which contains six acrylate groups per molecule) is 39%. Whilst the WO 97/27223 PCT/AU97/00029 8 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 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 2.5 to approximately 25% by weight, preferably 5 to 10% by weight based on the total weight of the casting composition.

In a further preferred aspect of the present invention the cross-linkable polymeric casting composition may further include an ultraviolet (UV) absorber.

As mentioned above, it has been found that the amount of UV absorber may be increased as interference with the photoinitiator is reduced in the process according to the present invention, particularly where the long wavelength photoinitiators are used. The UV absorber may be present in amounts of from approximately 0.05% to 0.5% by weight, preferably approximately 0.1% to 0.2% by weight based on the total weight of the casting composition.

The UV absorber may be selected from the group consisting of one or more of WO 97/27223 PCT/AU97/00029 9 Ciba Geigy Tinuvin P 2(2'-hydroxy-5'methyl phenyl) benzotriazole Cyanamid Cyasorb UV 531 -2-hydroxy-4-n-octoxybenzophenone Cyanamid Cyasorb UV 541 1-2(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 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 BASF UVINUL 511- Ciba Geigy Tinuvin 213 In a still further preferred aspect of the present invention the cross-linkable polymeric casting composition may further include at least one poly-functional unsaturated cross-linking agent.

The poly functional unsaturated cross-linking agent according to the present invention may be a tri- or tetra-functional vinyl, an acrylic or methacrylic monomer. 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, ditrimethylol propane tetraacrylate, trimethylolpropane triacrylate, pentaerythritrol tetramethacrylate, dipentaerythritol monohydroxypenta acrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane 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.

The poly functional unsaturated cross-linking agent may be present in amounts of from approximately 5 to 20% by weight, preferably approximately WO 97/27223 PCT/AU97/00029 by weight based on the total weight of the casting composition.

In a further 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.

Other additives may be present which are conventionally used in casting compositions such as inhibitors, dyes, U.V. 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: 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 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 WO 97/27223 PCT/AU97/00029 11 Anticolouring agents including 10 dihydro-9-oxa-10-phosphaphenanthrene-1 -oxide 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 In a further aspect of the present invention there is provided an optical article formed from a cross linkable casting composition including an acrylate or methacrylate monomer; optionally an ultra-violet (UV) absorber a cure modifier; and an ultra-violet (UV) photoinitiator.

Preferably the optical article further includes a dye material incorporated therein.

More preferably the cross linkable casting composition includes a polyalkylene glycol diacrylate or dimethacrylate; 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 a urethane monomer having terminal acrylic and/or methacrylic groups; and an ultra-violet (UV) absorber WO 97/27223 PCT/AU97/00029 12 a cure modifier; and an ultra-violet (UV) photoinitiator; and optionally a dye material incorporated therein.

The optical article may provide characteristics substantially equal to or greater than those achievable with industry standard articles, but with reduced stress/strain and reduced yellowing. The optical article may exhibit a relatively high UV cut-off.

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 photo-initiator. The mixed material is then degassed or filtered.

When present, 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 1,3,3-trimethylspiro'indole-2,3'-[3H]naphtho[2, 1-b]-1,4-oxazine] 2-methyl-3,3'-spirobi[3H-naphtho[2,1-b]pyran] (2-Me) 2-phenyl-3-methyl-7-methoxy-8'-nitrospiro[4H-1-benzopyran-4,3'-[3H]- WO 97/27223 PCT/AU97/00029 13 nap htho]2, 1-b]pyran Spiro[2H-1 -benzopyran-2,9'-xanthene] 8-methoxy-1 ',3'-dimethylspiro(2H-1 -benzopyran-2,2'-(l1'H)-quinoline 2,2'-Spirobi[2H-1 -benzopyran] 0 5'-amino-1 3'-trimethylspiro[2H-1 -benzopyran-2,2'-indoline Ethyl-13-methyl-f3-(3', 3'-d imethyl-6-n itrospi ro(2H-1 -benzopyran-2 ,2'-indolin-lI'yl)-propenoate 3-propanediyl)bis[3',3'-dimethyl-6-nitrospiro[2H-1 -benzopyran-2,2'indoline] 0 3, 3'-dimethyl-6-nitrospiro[2H-1 -benzopyrao-2 ,2'-benzoxazoline] 6'-methylthio-3,3'-dimethy-8-methoxy-6-nitrospiro[2H.1 -benzopyran-2,2'benzothiozoline] (1 ,2-ethanediyl)bis[8-methoxy-3-methyl-6-nitrospiro[2H.1 -benzopyran-2,2'benzothiozoline] N-N'-bis(3, 3'-d imethyl-6-nitrospiro[2H-1 -benzopyran-2,2'(3'H)-benzothioazol- 6'-yl)decanediamide -a-(2,5-dimethyl-3-furyl)ethylidene(Z)-ethylidenesuccinic anhydride; ct-(2, d imethyl-3-furyl)-&', &d imethylfu Igide 2,5-diphenyl-4-(2'-chlorophenyl)imidazole [(2',4'-dinitrophenyl)methyl]-1 H-benzimidazole N N-N-d iethyl-2-p henyl-2 H-phen anth ro[9, 1 0-d]imidazol-2-amine 2-Nitro-3-aminofluoren 2-amino-4-(2'-fu ranyl)-6H-1 ,3-thiazine-6-thione In a preferred aspect of the present invention the coated optical article may include an optical substrate; and a polymeric coating adhered to a portion of the optical article, the polymeric coating being prepared by a process as described above.

The polymeric coating may include a dye material. A photochromic dye, e.g. as described above is preferred. A chromene photochromic dye is preferred.

The dye may be incorporated directly or indirectly into the polymeric coating.

As stated above the polymeric coating prepared according to the process WO 97/27223 PCT/AU97/00029 14 of the present invention may exhibit an enhanced affinity to dye uptake. 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.

For example 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 in the range 100 to 1500) to cause the dyes to undergo sorption and diffuse 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 p gm/mm 2 of surface diffused to a depth of about 50p.m. The average dye concentration in this region of the lens is in the range of approximately 0.1 to 0.2 mgm/mm 3 or approximately 7 to 14% of the polymer weight in that region.

The polymeric coating is formed from a polymeric coating composition of the type described above.

The optical substrate may be a lens or lens blank. The optical substrate may be formed from the same polymeric material as, or different to, the polymeric material used in the polymeric coating.

The polymeric material utilised in the manufacture of the lens or lens blank may be of any suitable type. A polycarbonate material may be used. An optical material of the allyl diglycol carbonate type may be used. The optical substrate may be formed from cross-linkable polymeric casting compositions, for example as described in applicant's United States Patent 4,912,155, United States Patent Application No. 07/781,392, Australian Patent Applications 50581/93, 50582/93, European Patent Specification 543149A2, or co-pending Provisional Patent Applications PN0073 "Heat Responsive Articles" and PN0071 "Method of Preparing Photochromic Article", the entire disclosures of which are incorporated herein by reference.

Such cross-linkable polymeric casting compositions may include a diacrylate or dimethacrylate monomer (such as polyoxyalkylene glycol diacrylate WO 97/27223 PCT/AU97/00029 or dimethacrylate and a polymerisable comonomer, e.g. methacrylates, acrylates, vinyls, vinyl ethers, allyls, aromatic olefins, ethers, polythiols, epoxies and the like.

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.

The present invention will now be more fully described with reference to the accompanying examples and claims. 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.

In the drawings: Figures 1 to 8 are a series of graphs illustrating the effect of various amounts of cure modifier on heat flow during and under ultraviolet light.

Figure 9 is a graph illustrating the effect of various photoinitiators on heat flow during and under ultraviolet light.

EXAMPLE 1 A cross-linkable casting composition having the following components was prepared Percent 9G (polyethylene glycol dimethacrylate) ATM20 (high index: bisphenol A ethoxylated dimethacrylate) U4HA (urethane tetracrylate) Nofmer-MSD (2,4-diphenyl-4-methyl-1-pentene) The monomer mix was prepared in a beaker together with 0.4% Irgacure 907 long wavelength U.V. 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 U.V. lamp. Cure time was minutes.

A polymeric carrier bearing a chromene photochromic dye was placed in contact with the optical lens so formed and heated at 130°C for 2 hours.

WO 97/27223 PCT/AU97/00029 16 A tinted optical lens exhibiting reduced strain and improved yellowness index is thus achieved.

EXAMPLES 2-8 Example 1 was repeated under similar conditions with various photoinitiators and amounts of cure modifier as designated in Table 1 below. The results achieved are also given in Table 1 and satisfactory lenses were achieved in each case.

COMPARATIVE EXAMPLES 1-4 Examples were repeated with any photoinitiators, but omitting cure modifier as designated in Table 1 below.

TABLE I Effect of NOFMER on conversion of functional groups and some properties of SPECTRALITE Example Initiator Nofmer Conc. Barcol YI Tg Conversion C=C cUVII Final Comparative 1 Irgacure 907 0 20 1.9 107 71 94 1 Irgacure 907 0.1 20 1.7 41 94 2 Irgacure 907 0.5 16 1.4 105 12 94 Comparative 2 Irgacure 369 0 22 17.2 110 89 3 Irgacure 369 0.1 21 16.3 84 4 Irgacure 369 0.5 21 11.6 104 56 Comparative 3 Lucirin TPO 0 23 1.4 115 89 96 Lucirin TPO 0.1 23 1.2 86 96 6 Lucirin TPO 0.5 23 1.0 106 86 WO 97/27223 PCT/AU97/00029 18 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 (26)

1. A process for preparing an optical article which process includes: a) providing i) a cross-linkable polymeric casting composition including an acrylate or methacrylate monomer; and optionally an ultra-violet (UV) absorber; ii) a cure modifier that is present in an amount from 0.001% to 1% by weight; and iii) a UV photoinitiator; b) mixing the casting composition, cure modifier and photoinitiator; and c) exposing the mixture to a source of ultraviolet (UV) radiation for a time sufficient to produce an optical article. 15

2. A process according to claim 1 wherein the amount of cure modifier ranges from 0.01% to

3. A process according to claim 1 or claim 2 wherein the cure modifier is a transfer agent selected from 2,4-diphenyl-4-methyl-1-pentene, dodecyl mercaptan, butyl mercaptan, thiophenol or di-isopropanyl benzene. 20

4. A process according to claim 3 wherein the cure modifier is selected from 2,4-diphenyl-4-methyl-1-pentene or di-isopropanyl benzene.

5. A process according to claim 1 wherein the UV photoinitiator is a long wavelength photoinitiator (as hereinbefore defined).

6. A process according to claim 5 wherein the UV photoinitiator is selected from any one or more of the group consisting of 2,4,6-trimethylbenzoyldiphenoylphosphine oxide; (2-methyl-4-[4-(methylthio)phenyl]-2-morpholinopropane-1-one); (hydroxycyclohexyl) phenyl ketone; 2-benzyl-2-N-dimethylamino-1 -(4-morpholinophenyl)-1-butanone; Benzil Dimethyl Ketal; isopropyl benzoin ether; 2-n-propoxy-9H-thioxanthen-9-one; or Ethyl 4-(dimethylamino)benzoate. JMN W:\SPECI\PCT00029.doc

7. A process according to claim 6 wherein the UV photoinitiator is present in an amount from approximately 0.01% to 1.00% by weight.

8. A process according to claim 1 wherein the cross-linkable polymeric casting composition includes a polyoxyalkylene glycol diacrylate or dimethacrylate; a monomer including a recurring unit derived from at least one radical polymerisable bis-phenol monomer capable of forming a homopolymer having a high refractive index; and a urethane monomer having terminal acrylic and/or methacrylic groups.

9. A process according to claim 8 wherein an ultraviolet (UV) absorber is included in the casting composition.

10. A process according to claim 9 wherein the ultraviolet (UV) absorber is selected from any one or more of the group consisting of: 0 2(2'-hydroxy-5'methyl phenyl) benzotriazole; 15 2-hydroxy-4-n-octoxybenzophenone; 2(2-hydroxy-5-t-octylphenyl)benzotriazole; 2 hydroxy-4-(2-acryloyloxyethoxy) benzophenone; 2 hydroxy-4-(2-acryloyloxyethoxy) benzophenone; 2 hydroxy-4-(2 hydroxy-3-methacryloxy) propoxy benzophenone; 20 2,2'-dihydroxy-4-methoxybenzophenone; 2,4 dihydroxy-benzophenone; 2,2'-dihydroxy-4,4' dimethoxy benzophenone; tetrahydroxy benzophenone; ethyl-2-cyano-3,3-diphenyl acrylate; 2-ethexyl-2-cyano-3,3-diphenyl acrylate.

11. A process according to claim 10 wherein the ultraviolet (UV) absorber is present in an amount from approximately 0.05% to 0.5% by weight, based on the total weight of the casting composition.

12. An optical article formed from a cross linkable casting composition including an acrylate or methacrylate monomer; optionally an ultra-violet (UV) absorber; R a cure modifier wherein the cure modifier is present in an amount approximately 0.001% to 1% by weight; and JMN W:SPECl\pct00029.doc 21 an ultra-violet (UV) photoinitiator.

13. An optical article according to claim 12 wherein the amount of cure modifier ranges approximately from 0.0 1% to

14. An optical article according to claim 12 or claim 13 further including a dye material incorporated therein.

An optical according to claim 14 wherein the dye material is a photochronic dye selected from any one or more of the group consisting of: 1 ,3-d ihydrospiro[2H-anthra[2 ,3-d]imidazole-2,1I'-cyclohexane]-5,1 I -dione; 1, ,3-d ihyd rospiro[2 H-a nth ra[2 imidazole-2, I '-cyclohexa ne]-6, 1-dione; 1, 3-d ihyd ro-[4-(phenylth io)spi ro[2 H-anth ra'1 imid azole-2, 1'- cyclohexane]-6,1 1 -dione; I ,3-dihydrospiro[2-H-anthra[1 ,2-d]imidazole-2,1 '-cycloheptane]6,1 1 dione; I ,3,3-trimethylspiro'indole-2,3'-[3H]naphtho[2, 1 ,4-oxazine]; 15 2-methyl-3,3'-spirobi[3H-naphtho[2,1 -b]pyran] (2-Me); 2-phenyl-3-methyl-7-methoxy-8'-nitrospiro[4H-1 -benzopyran-4,3'-[3H]- naphtho]2,1I-b]pyran; ****:Spiro[2H-1 -benzopyran-2,9'-xanthene]; 8-methoxy-1 ',3'-dimethylspiro(2H-1 -benzopyran-2,2'-(1 'H)-quinoline; 20 2,2'-Spirobi[2H-1 -benzopyran]; 5'-amino-1 ',3',3'-trimethylspiro[2H-1 -benzopyran-2,2'-indoline]; ~Ethyl-p-methyl-f3-(3',3'-d imethyl-6-nitrospiro(2H-1I-benzopyran-2 ,2 indolin-1 '-yl)-propenoate; (1 ,3-propaned iyl)bis[3' ,3'-dimethyl-6-nitrospiro[2H-1 -benzopyran-2,2'- indoline]; 3 imethyl-6-nitrospiro[2 H-I -benzopyrao-2 ,2'-benzoxazoline]; 6'-methylthio-3,3'-dimethyl-8-methoxy-6-nitrospiro[2H-1 -benzopyran-2 benzothiozoline]; (1 ,2-ethanediyl)bis[8-methoxy-3-methyl-6-nitrospiro[2 H-i -benzopyran- 2,2'-benzothiozoline]; N-N'-bis(3 ,3'-dimethyl-6-nitrospiro[2H-1 -benzopyran-2 H)- benzothioazol- 6'yl)decanediamide; RA4~ a-(2 ,5-dimethyl-3-furyl)ethylidene(Z)-ethylidenesuccinic anhydride; a-(2 ,5-dimethyl-3-furyl)-a ,6-dimethylfulg ide; JMN WASPECPctOO02g.doc 22 2,5-diphenyl-4-(2'-chlorophenyl)imidazole; [(2',4'-dinitrophenyl)methyl]-1 H-benzimidazole; N-N-diethyl-2-phenyl-2H-phenanthro[9,10-d]imidazole-2-amine; 2-Nitro-3-aminofluoren 2-amino-4-(2'-furanyl)-6H-1,3-thiazine-6-thione.

16. An optical article according to claim 12 or claim 13 wherein the cure modifier is a transfer agent selected from 2,4-diphenyl-4-methyl-1-pentene, dodecyl mercaptan, butyl mercaptan, thiophenol or di-isopropanyl benzene.

17. An optical article according to claim 16 wherein the cure modifier is selected from 2,4-diphenyl-4-methyl-1-pentene or di-isopropanyl benzene.

18. An optical article according to claim 12 or claim 13 wherein the UV photoinitiator is a long wavelength photoinitiator is selected from one or more of the group consisting of 2,4,6-trimethylbenzoyldiphenoylphosphine oxide; (2-methyl-1 -[4-(methylthio)phenyl]-2-morpholinopropane-1 -one); 15 (hydroxycyclohexyl) phenyl ketone; (2-benzyl-2-N-dimethylamino-1-(4-morpholinophenyl)-1-butanone) Benzil Dimethyl Ketal; •isopropyl benzoin ether; 2-n-propoxy-9H-thioxanthen-9-one; or 20 Ethyl 4-(dimethylamino)benzoate.

19. An optical article according to claim 12 or claim 13 wherein the cross- linkable polymeric casting composition includes a polyoxyalkylene glycol diacrylate or dimethacrylate; a monomer including a recurring unit derived from at least one radical polymerisable bis-phenol monomer capable of forming a homopolymer having a high refractive index; and a urethane monomer having terminal acrylic and/or methacrylic groups.

An optical article according to claim 12 or claim 13 wherein the article is a lens element of relatively high thickness.

21. A coated optical article including a) an optical substrate; and b) a polymeric coating adhered to at least a portion of the substrate, Swherein the polymeric coating is formed from i) a cross-linkable polymeric casting composition including JMN W:\SPECIRPCT00029.doc 23 an acrylate or methacrylate monomer; and optionally an ultra-violet (UV) absorber; ii) a cure modifier wherein the cure modifier is present in an amount from approximately 0.001% to 1% by weight of the polymeric coating; and iii) an ultra-violet (UV) photoinitiator; and c) a dye material incorporated therein.

22. A coated optical article according to claim 21 wherein the amount of cure modifier ranges approximately from 0.01% to

23. A coated optical article according to claim 21 or claim 22 wherein the cross-linkable polymeric casting composition includes a polyoxyalkylene glycol diacrylate or dimethacrylate; a monomer including a recurring unit derived from at least one radical polymerisable bis-phenol monomer capable of forming a homopolymer having a 15 high refractive index; and a urethane monomer having terminal acrylic and/or methacrylic groups.

24. A coated optical article according to claim 21 or claim 22 wherein the cure modifier is a transfer agent selected from 2,4-diphenyl-4-methyl-1-pentene, dodecyl mercaptan, butyl mercaptan, thiophenol or di-isopropanyl benzene. 20

25. A coated optical article according to claim 21 or claim 22 wherein the cure modifier is selected from 2,4-diphenyl-4-methyl-1-pentene or di- isopropanyl benzene.

26. An optical article substantially as hereinbefore described with reference to any one of the examples. DATED 31 October, 2000 PHILLIPS ORMONDE FITZPATRICK Attorneys For: SOLA INTERNATIONAL HOLDINGS LTD JMN W:\SPECIpct00029.doc