WO2003074579A1

WO2003074579A1 - Curable liquid resin composition

Info

Publication number: WO2003074579A1
Application number: PCT/NL2003/000149
Authority: WO
Inventors: Shuichi Sugawara; Masanobu Sugimoto; Zen Komiya; Abe Noriko
Original assignee: DSM NV
Current assignee: Koninklijke DSM NV
Priority date: 2002-03-04
Filing date: 2003-02-27
Publication date: 2003-09-12
Anticipated expiration: 2004-09-04
Also published as: JP3958201B2; AU2003215964A1; JP2003327637A

Abstract

A conventional curable liquid resin composition comprising (a) a urethane (meth)acrylate, and (c) a phosphorus-containing photoinitiator, can show haze after aging and other changes in properties upon aging. The present invention provides a solution to that problem by using (b) a Group IV metal compound in the synthesis of the urethane acrylate. The curable liquid resin composition of the present invention excels in high-speed curability and produces a uniform and transparent cured product. The present invention provides an optically uniform and highly transparent coating material for optical fibers, and a surface coating material and adhesive for various types of optical components.

Description

CURABLE LIQUID RESIN COMPOSITION

Detailed Description of the Invention Field of the Invention

The present invention relates to a curable liquid resin composition comprising a urethane (meth)acrylate. The curable liquid resin composition of the present invention is extremely useful as a coating material for optical fibers. Moreover, the curable liquid resin composition can be used as a surface coating material and as an adhesive for various types of optical components.

Background Art Liquid curable resins having different viscosities can be prepared using a urethane (meth)acrylate by combining a photoinitiator and various types of monomers. A cured product of such a liquid curable resin exhibits sufficient strength and flexibility, shows a small degree of change in properties over a wide range of temperature change, excels in heat resistance and hydrolysis resistance, excels in long-term reliability due to a small degree of change in properties over time, excels in resistance to chemicals such as acids and alkalis, has a small degree of hygroscopicity and water absorption, excels in light resistance and oil resistance, and exhibits adhesion to substrates. Such liquid curable resins are widely used as a protective film material and as an adhesive material for various types of substrates such as glass, ceramics, metal, paper, and wood by utilizing these characteristics.

In order to deal with a recent increase in productivity, high-speed curability has been demanded for such a protective or adhesive film. Since the demand for a surface protective or adhesive film has increased, such a film is more often used in a state in which the film is exposed on the surface. This increases the demand for improvement of the appearance of such film. As a result, a protective or adhesive film formed of a uniform and highly transparent cured product that is superior to a conventional protective or adhesive film or the like has been demanded.

Problems to be Solved by the Invention In view of the above situation, an object of the present invention is to provide a curable liquid resin composition having the same characteristics as those of a conventional composition, excelling in high-speed curability in comparison with a conventional composition, and capable of forming a uniform protective or adhesive film having high transparency.

Means for Solving the Problems The present inventors have conducted extensive studies to achieve the above object. As a result, the present inventors have found that a curable liquid resin composition excelling in high-speed curability in comparison with a conventional composition and capable of forming a uniform and highly transparent protective or adhesive film or the like can be produced by using a phosphorus-containing photoinitiator excelling in high-speed curability and using a Group IV metal catalyst as a urethanization catalyst during the production of a urethane (meth)acrylate. This finding has led to the completion of the present invention. The curable liquid resin composition of the present invention and a cured product of the composition excel in thermal stability because the viscosity of the composition and the Young's modulus of the cured product are stable over time during storage at high temperatures.

Specifically, the present invention provides a curable liquid resin composition comprising (a) a urethane (meth)acrylate, (b) a Group IV metal compound, and (c) a phosphorus-containing photoinitiator.

The present invention also provides a cured product obtained by curing the curable liquid resin composition using radiation and a process for producing the same. More in particular, such cured products can be primary coatings, adhesives in photonic art, matrix materials, adhesives for DVD's etc.

The present invention further provides a catalyst for the synthesis of urethane (meth)acrylate comprising one or more compounds selected from the group consisting of zirconium tetraacetylacetonate, zirconium tris(acetylacetonate)ethylacetoacetate, and zirconium bis(acetylacetonate)bis(ethylacetoacetate), and the method of manufacturing urethane (meth)acrylate using the same.

Preferred Embodiment of the Invention

The urethane (meth)acrylate (a) used in the present invention is produced by a reaction in the presence of a Group IV metal catalyst. The urethane (meth)acrylate is preferably produced by reacting a polyisocyanate and a hydroxyl group-containing (meth)acrylate in the presence of a Group IV metal catalyst, and even more preferably produced by reacting a polyol, a polyisocyanate, and a hydroxyl group- containing (meth)acrylate in the presence of a Group IV metal catalyst. Specifically, the urethane (meth)acrylate is produced by reacting the isocyanate groups of a polyisocyanate with the hydroxyl groups of a diol and a hydroxyl group-containing (meth)acrylate in the presence of a Group IV metal catalyst. Preferably, the urethane(meth)acrylate is a urethaneacrylate.

Methods of reacting these compounds include a method of reacting a diol, a polyisocyanate, and a hydroxyl group-containing (meth)acrylate all together; a method of reacting a diol with a polyisocyanate, and reacting the resulting product with a hydroxyl group-containing (meth)acrylate; a method of reacting a polyisocyanate with a hydroxyl group-containing (meth)acrylate, and reacting the resulting product with a diol; a method of reacting a polyisocyanate with a hydroxyl group-containing (meth)acrylate, reacting the resulting product with a diol, and further reacting the resulting product with a hydroxyl group-containing (meth)acrylate.

The reaction temperature is usually 5-90°C, and preferably 10-80°C. As the types of polyol, polyisocyanate, and hydroxyl group-containing

(meth)acrylate to be used in the present invention, those well known in the art (e.g. Japanese Patent Application Laid-open No. 2001-316434) may be used without any limitations. Preferably the resulting urethane (meth)acrylate comprises a polyether, a polyester and/or a polycarbonate. More preferably, the urethane(meth)acrylate comprises polyether only, or a combination of the polyether and either polycarbonate or polyester.

As examples of the polyol, polyether diols such as an aliphatic polyether diol, alicyclic polyether diol, and aromatic polyether diol, polyester diols, polycarbonate diols, polycaprolactone diols, and the like can be given. These polyols may be used either individually or in combinations of two or more. Polyols with a tri or more valence, which are synthesized by reacting a diol compound and a polyisocyanate, can also be used as the above polyols. There are no specific limitations to the manner of polymerization of the structural units of these polyols, which may be any of random polymerization, block polymerization, and graft polymerization. As examples of aliphatic polyether diols, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, polyheptamethylene glycol, polydecamethylene glycol, polyether diols obtained by the ring-opening copolymerization of two or more ion-polymerizable cyclic compounds, and the like can be given. As examples of the ion-polymerizable cyclic compounds, cyclic ethers such as ethylene oxide, propylene oxide, butene-1 -oxide, isobutene oxide, 3,3-bischloromethyloxetane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, dioxane, trioxane, tetraoxane, cyclohexene oxide, styrene oxide, epichlorohydrin, glycidyl methacrylate, allyl glycidyl ether, ally] glycidyl carbonate, butadiene monoxide, isoprene monoxide, vinyl oxetane, vinyl tetrahydrofuran, vinyl cyclohexene oxide, phenyl glycidyl ether, butyl glycidyl ether, and glycidyl benzoate can be given.

As specific examples of the polyether diols obtained by the ring- opening copolymerization of two or more ion-polymerizable cyclic compounds, binary copolymers obtained by the ring-opening copolymerization of a combination of monomers such as tetrahydrofuran and propylene oxide, tetrahydrofuran and 2- methyltetrahydrofuran, tetrahydrofuran and 3-methyl tetrahydrofuran, tetrahydrofuran and ethylene oxide, propylene oxide and ethylene oxide, and butene-1 -oxide and ethylene oxide, ternary copolymers obtained by the ring-opening copolymerization of a combination of monomers such as tetrahydrofuran, butene-1 -oxide, and ethylene oxide, and the like can be given.

Polyether diols obtained by the ring-opening copolymerization of these ion-polymerizable cyclic compounds with cyclic imines such as ethyleneimine, cyclic lactonic acids such as β-propyolactone or glycolic acid lactide, or dimethylcyclopolysiloxanes may be used.

The aliphatic polyether diols are commercially available as PTMG650, PTMG1000, PTMG2000 (manufactured by Mitsubishi Chemical Corp.), PPG400, PPG1000, EXCENOL 720, 1020, 2020 (manufactured by Asahi Glass Co., Ltd.), PEG1000, Unisafe DC1100, DC1800 (manufactured by Nippon Oil and Fats Co., Ltd.), PPTG2000, PPTG1000, PTG400, PTGL2000 (manufactured by Hodogaya Chemical Co., Ltd.), EO/BO500, EO/BO1000, EO/BO2000, EO/BO3000, and EO/BO4000 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the like.

As examples of alicyclic polyether diols, alkylene oxide addition diols of hydrogenated bisphenol A, alkylene oxide addition diols of hydrogenated bisphenol F, alkylene oxide addition diols of 1 ,4-cyclohexanediol, and the like can be given.

As examples of the aromatic polyether diols, alkylene oxide addition diol of bisphenol A, alkylene oxide addition diol of bisphenol F, alkylene oxide addition diol of hydroquinone, alkylene oxide addition diol of naphthohydroquinone, alkylene oxide addition diol of anthrahydroquinone, and the like can be given. The aromatic polyether diols are commercially available as Uniol DA400, DA700, DA1000, DA4000, DAB400, DAB800, DAB1000, DAB2000, DB400, DB800, DB1000, DB2000 (manufactured by Nippon Oil and Fats Co., Ltd.), and the like.

As examples of the polyester diols, polyester diols obtained by reacting a polyhydric alcohol with a polybasic acid, and the like can be given. Examples of the polyhydric alcohol include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1 ,6-hexanediol, neopentyl glycol, 1 ,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1 ,8-octanediol, and the like. As examples of the polybasic acids, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, and the like can be given.

As examples of commercially available products of the above polyester diols, Kurapol P-2010, P-1010, L-2010, L-1010, A-2010, A-1010, F-2020, F- 1010, PMIPA-2000, PKA-A, PNOA-2010, PNOA-1010 (manufactured by Kuraray Co., Ltd.), and the like can be given. As examples of the polycarbonate diols, polycarbonate of polytetrahydrofuran, polycarbonate of 1 ,6-hexanediol, commercially available products such as DN-980, 981 , 982, 983 (manufactured by Nippon Polyurethane Industry Co., Ltd.), PC-8000 (manufactured by PPG), PC-THF-CD (manufactured by BASF), and the like can be given. As examples of polycaprolactone diols, polycaprolactone diol obtained by reacting γ-caprolactone and a diol and the like can be given. Examples of such diols used for the reaction with γ-caprolactone include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1 ,2-polybutylene glycol, 1 ,6-hexanediol, neopentyl glycol, 1 ,4-cyclohexanedimethanol, 1,4-butanediol, and the like. The polycaprolactone diols are commercially available as PLACCEL 205, 205AL, 212, 212AL, 220, 220AL (manufactured by Daicel Chemical Industries, Ltd.), and the like.

As examples of the polyisocyanate compound, aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, and the like can be given. As examples of the aromatic polyisocyanates, 2,4-tolylene diisocyanate, 2,6- tolylene diisocyanate, 1 ,3-xylylene diisocyanate, 1 ,4-xylylene diisocyanate, 1 ,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethylphenylene diisocyanate, 4,4'-biphenylene diisocyanate, bis(2-isocyanateethyl)fumarate, 6-isopropyl-1 ,3-phenyl diisocyanate, 4-diphenylpropane diisocyanate, tetramethylxylylene diisocyanate, and the like can be given. Examples of alicyclic polyisocyanates include isophorone diisocyanate, methylenebis(4-cyclohexylisocyanate), hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, 2,5-bis(isocyanatemethyl)-bicyclo[2.2.1]heptane, 2,6-bis(isocyanatemethyl)-bicyclo[2.2.1]heptane, and the like. As examples of aliphatic polyisocyanates, 1 ,6-hexane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like can be given. Of these diisocyanates, 2,4-tolylene diisocyanate is preferable because of low cost and selectivity in reaction. However, from a performance point of view aliphatic isocyanates aid in preventing discoloration. Hence, aliphatic isocyanates such as isophorone diisocyanate, methylenebis(4- cyclohexylisocyanate) and hydrogenated diphenylmethane diisocyanate are preferred, of which isophorone diisocyanate is particularly preferable. These polyisocyanates may be used either individually or in combination of two or more. As the hydroxyl group-containing (meth)acrylate, (meth)acrylate containing a hydroxyl group bonded to the primary carbon atom (hereinafter referred to as "primary hydroxyl group-containing (meth)acrylate") and (meth)acrylate containing a hydroxyl group bonded to the secondary carbon atom (hereinafter referred to as "secondary hydroxyl group-containing (meth)acrylate") are preferable. The (meth)acrylate containing a hydroxyl group bonded to a tertiary carbon atom

(hereinafter designated as "tertiary hydroxyl group-containing (meth) acrylate") is not preferred because of its inferior reactivity with an isocyanate group.

As examples of the primary hydroxyl group-containing (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1 ,6-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, neopentyl glycol mono(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate, and (meth)acrylates of the following formula (1):

CH₂=C(R¹)-COOCH₂CH₂-(OCOCH₂CH₂CH₂CH₂CH₂)_n-OH (1)

wherein R¹ represents a hydrogen atom or a methyl group and n is an integer from 1 to 3; and the like can be given.

As examples of the secondary hydroxyl group-containing (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, a compound obtained by the addition reaction of (meth)acrylic acid and a compound containing a glycidyl group such as alkyl glycidyl ether, allyl glycidyl ether, or glycidyl (meth)acrylate, and the like can be given. Furthermore, a urethane (meth)acrylate can be prepared by reacting, for example, one mol of polyisocyanate and two mols of a hydroxyl group-containing (meth)acrylate compound. As examples of such a urethane (meth)acrylate, a reaction product of hydroxyethyl (meth)acrylate and 2,5-(or 2,6-)bis(isocyanatemethyl)- bicyclo[2.2.1]heptane, a reaction product of hydroxyethyl (meth)acrylate and 2,4- tolylene diisocyanate, a reaction product of hydroxyethyl (meth)acrylate and isophorone diisocyanate, a reaction product of hydroxypropyl (meth)acrylate and 2,4- tolylene diisocyanate, and a reaction product of hydroxypropyl (meth)acrylate and isophorone diisocyanate can be given.

In the present invention, the urethane (meth)acrylate (a) is usually included in the curable liquid resin composition in an amount of 5-99 wt%, and preferably in an amount of 20-90 wt% to ensure proper coatability, flexibility of the coating material after hardening, and long-term reliability.

Preferably, the number average molecular weight of the urethane(meth)acrylate oligomer is at least about 700 and at most about 10,000 Daltons. More preferably, the molecular weight is between about 1 ,000 and about 6,000 Daltons.

The proportions of the polyol, diisocyanate, and (meth)acrylate containing a hydroxyl group are preferably designed so that the isocyanate group contained in the diisocyanate and the hydroxyl group contained in the (meth)acrylate containing hydroxyl group are from 1.1 to 3 equivalents (preferably 1.2-3 and most preferred 2-1.5) and from 0.2 to 1.5 equivalents, respectively, to one equivalent of hydroxyl group contained in the polyol. It is particularly preferable that the equivalent of hydroxyl groups in the polyol and acrylate is almost the same as the equivalent of the isocyanate group in diisocyanate. The Group IV metal compound (b) used in the present invention can be used stoichiometrically and catalytically in various synthetic reactions as a catalyst due to its high reactivity as compared with other early transition metal compounds. Preferably, the Group IV metal compound (b) is used in catalytic amounts. Of these Group IV metal compounds, titanium and zirconium compounds are preferably used as catalysts in synthetic reactions for producing urethane (meth)acrylate on an industrial scale due to their high activity and capability of increasing the reaction speed.

The Group IV metal compounds (particularly Ti and Zr) preferably comprise one or more ligands choosen from the group consisting of acetoacetonate type groups, alkoxy groups and alkoxylate groups. These compounds generally have 2-4 ligands, comprising together 4 binding sites to the metal. The total number of carbon atoms of the compound generally is 30 carbon atoms or less, preferably 20 carbon atoms or less.

Suitable examples of such compounds include as titanium catalyst, titanium allyl acetoacetate triisopropoxide, titanium n-butoxide, titanium isopropoxide, titanium methacrylate triisopropoxide, titanium methacryloxyethyl acetoacetate triisopropoxide, and the like.

Suitable examples of such compounds include as zirconium catalyst, tetra-n-propoxy zirconium, tetraisopropoxy zirconium (also known as zirconium isopropoxide), tetra-n-butoxy zirconium (also known as zirconium n-butoxide), zirconyl acetate, zirconium tributoxystearate, zirconium tetraacetylacetonate (also known as zirconium 2,4-pentanedionate), zirconium tributoxyacetylacetonate, zirconium dibutoxy bis(acetylacetonate), zirconium tributoxyethylacetoacetate, zirconium butoxy acetylacetonate bis(ethylacetoacetate), zirconium bisbutoxy bis(ethylacetoacetate), zirconium acetylacetonate tris(triethanolamine), zirconium ris(acetylacetonate)ethyl- acetoacetate, zirconium bis(acetylacetonate)bis(ethylacetoacetate), zirconium acetylacetonate tris(ethylacetoacetate), zirconium diisopropoxide bis(2,2,6,6- tetramethyl-3,5-heptanedionate), zirconium hexafluoropentanedionate, zirconium 2,2,6,6-tetramethyl-3,5-heptanedionate, zirconium trifluoropentanedionate, and the like. Other suitable Group IV metal compounds include, as a hafnium catalyst, hafnium isopropoxide, hafnium n-butoxide, hafnium 2,4-pentanedionate, and the like. Of these, titanium compounds such as titanium n-butoxide and zirconium compounds are preferable. Furthermore, one or more compounds selected from zirconium tetraacetylacetonate, zirconium tris(acetylacetonate)ethylacetoacetate, and zirconium bis(acetylacetonate)bis(ethylacetoacetate) are particularly preferable in view of excellent reactivity and solubility.

As examples of commercially available products of the above zirconium catalysts, Alcofine ZRA402-80 (manufactured by Kawaken Fine Chemicals Co., Ltd.), AKZ948, AKZ953, AKZ980, AKZ985 (manufactured by Azmax Co., Ltd.), and the like can be given. These catalysts are preferably incorporated in an amount of 0.01-1 wt% of the total amount of the curable liquid resin composition, with 0.03-0.10 wt% being particularly preferable.

In the synthesis of urethane(meth)acrylate, a urethanization catalyst known in the art selected from the group consisting of Group VII metal compounds such as manganese 2,4-pentanedionate Group VIM metal compounds such as iron 2,4- pentanedionate Group IX metal compounds such as cobalt naphthenate Group X metal compounds such as nickel 2,4-pentanedionate Group XI metal compounds such as copper naphthenate Group XII metal compounds such as zinc naphthenate triethylamine, 1 ,4-diazabicyclo[2.2.2]octane, 2,6,7-trimethyl-1 ,4- diazabicyclo[2.2.2]octane, and the like may be used in combination with the catalyst of the present invention. For the amount of the urethanization catalyst to be combined with the Group IV metal compound, less than 10 wt% of the total amount of the curable liquid resin composition is preferable, with less 1 wt% being more preferable, and less than 0.1 wt% being particularly preferable. If the amount of the urethanization catalyst exceeds this range, the transparency of the cured product obtained from the curable liquid resin composition could decrease. It is most preferred to not use other than Group IV metal catalyst. Hence, less than 0.03 wt% more preferably less than 0.01 wt% of other than Group IV catalytically active metal compounds is most preferred. The curable liquid resin composition of the present invention contains the Group IV metal catalyst used as the urethanization catalyst in the manufacture of the urethane(meth)acrylate.

A urethane (meth)acrylate obtained by reacting 1 mol of polyisocyanate with 2 mols of hydroxyl group-containing (meth)acrylate compound may also be added to the curable liquid resin composition of the present invention. As examples of such a urethane (meth)acrylate, a reaction product of hydroxyethyl (meth)acrylate and 2,5(or 2,6)-bis(isocyanatemethyl)-bicyclo[2.2.1]heptane, a reaction product of hydroxyethyl (meth)acrylate and 2,4-tolylene diisocyanate, a reaction product of hydroxyethyl (meth)acrylate and isophorone diisocyanate, a reaction product of hydroxypropyl (meth)acrylate and 2,4-tolylene diisocyanate, and a reaction product of hydroxypropyl (meth)acrylate and isophorone diisocyanate can be given.

The phosphorous-containing photoinitiator (c) is used for initiating curing the curable liquid resin composition of the present invention.

The phosphorous-containing photoinitiator (c) preferably is a phosphine oxide type compound. The photoinitiator (c) preferably comprises phosphorous and at least one acyl group, more preferably one acyl group. As acyl group, aromatic groups are preferred, such as for example benzoyl groups in particular Cι-C₁₀ alkyl or alkoxy substituted aromatic groups. Often substituted benzoyl groups are used in practise, such as trimethylbenzoyl or 2,6 dimethoxybenzoyl. The other substituents to the phosphine group are cyclic aliphatic or aromatic groups with 5-20 carbon atoms.

Suitable examples of the phosphorous-containing photoinitiator (c) include, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)- 2,4,4-trimethylpentyl phosphine oxide, and derivatives thereof. The use of 2,4,6- trimethylbenzoyl diphenylphosphine oxide is preferred. Commercially available products of these compounds include Lucirin TPO-X (manufactured by BASF), Irgacure 819, 1700, 1800, 1850 (manufactured by Ciba Specialty Chemicals Co., Ltd.), and the like.

The phosphorous-containing photoinitiator (c) is incorporated in the curable liquid resin composition preferably in an amount of 0.1-10 wt%, with 0.5-7 wt% being particularly preferable.

The curable liquid resin composition of the present invention may further contain a non-phosphorous photoinitiator. As examples of the non-phosphorous photoinitiator, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4- chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyl methyl ketal, 1-(4- isopropylphenyl)-2-hydroxy-2-methylpropan-1 -one, 2-hydroxy-2-methyl-1 - phenylpropan-1-one, thioxanethone, diethylthioxanthone,

2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1 -[4-(methylthio)phenyl]-2- morpholino-propan-1-one, and the like can be given. Examples of commercially available products of these compounds include Irgacure 184, 369, 651, 500, 907, CGI403, CGI1700, CGI1750, CGI1850, CG24-61 (manufactured by Ciba Specialty Chemicals Co., Ltd.); Darocure 1116, 1173 (manufactured by Merck Ltd.); Ubecryl P36 (manufactured by UCB); and the like.

Also, when necessary, it is preferable that the curable liquid resin composition further contain a photosensitizer. As examples of the photosensitizer, triethylamine, diethylamine, N-methyldiethanoleamine, ethanolamine, 4- dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate; Ubecryl P102, 103, 104, 105 (manufactured by UCB); and the like can be given.

In addition to the photopolymerization initiator, the curable liquid resin composition of the present invention may contain a thermal polymerization initiator. As the thermal polymerization initiator, a peroxide, azo compound, and the like may be used. Specific examples include benzoyl peroxide, t-butyloxybenzoate, azobisisobutyronitrile, and the like.

In addition to the urethane(meth)acrylate, Group IV metal compound, and phosphorous-containing photoinitiator, other curable oligomers or polymers, reactive diluents, monofunctional or polyfunctional polymerizable monomers, or other additives may be added to the curable liquid resin composition of the present invention, insofar as the characteristics of the curable liquid resin composition are not impaired. These components are mixed at a temperature of usually 20-90°C, and preferably 50- 70°C. As examples of other curable oligomers or polymers, polyester

(meth)acrylate, epoxy (meth)acrylate, polyamide (meth)acrylate, a siloxane polymer having a (meth)acryloyloxy group, a reactive polymer obtained by reacting acrylic acid and a copolymer of glycidyl methacrylate and other vinyl monomers, and the like can be given. Given as examples of such polymerizable monofunctional compounds are vinyl group-containing lactam such as N-vi ny I pyrrol idone and N-vinylcaprolactam; alicyclic structure-containing (meth)acrylates such as isobornyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and cyclohexyl (meth)acrylate; benzyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, acryloylmorpholine, vinylimidazole, vinylpyridine, and the like. Further examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3- phenoxypropyl acrylate, 2-hydroxy butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl

(meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, iso-stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, methoxy polypropylene glycol (meth)acrylate, diacetone (meth)acrylamide, isobutoxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, t-octyl (meth)acrylamide, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 7-amino-3,7-dimethyloctyl (meth)acrylate, N,N-diethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, hydroxybutyl vinyl ether, lauryl vinyl ether, cetyl vinyl ether, 2-ethylhexyl vinyl ether, and compounds of the following formulas (2) to (4):

wherein R² represents a hydrogen atom or a methyl group, R³ represents an alkylene group having 2-6, and preferably 2-4 carbon atoms, R⁴ represents a hydrogen atom or an alkyl group having 1-12, and preferably 1-9 carbon atoms, and s is an integer from 0 to 12, and preferably from 1 to 8;

wherein R² is the same as defined above, R⁵ represents an alkylene group having 2-8, and preferably 2-5 carbon atoms, and p is an integer from 0 to 8, and preferably from 1 to 4;

wherein, R⁶ represents a hydrogen atom or a methyl group, R⁷ represents an alkylene group having 2-8, and preferably 2-5 carbon atoms, R⁸to R¹³ individually represent a hydrogen atom or a methyl group, and q is an integer from 0 to 8, and preferably from 1 to 4.

As examples of commercially available products, Aronix M111, M113, M114, M117 (manufactured by Toagosei Co., Ltd.), KAYARAD TC110S, R629, R644 (manufactured by Nippon Kayaku Co., Ltd.), Viscoat #320, and lauryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) can be given.

Examples of polyfunctional compounds include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4- butanediol di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol hydroxypivalate, trimethylolpropanetrioxyethyl (meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, di(meth)acrylate of diol of ethylene oxide or propylene oxide adduct of bisphenol A, di(meth)acrylate of diol of ethylene oxide or propylene oxide adduct of hydrogenated bisphenol A, epoxy(meth)acrylate obtained by the addition of (meth)acrylate to diglycidyl ether of bisphenol A, triethylene glycol divinyl ether, and the like.

Examples of commercially available products include Yupimer UV SA1002, SA2007 (manufactured by Mitsubishi Chemical Corp.), Viscoat 700 (manufactured by Osaka Organic Chemical Industry, Ltd.), Ripoxy VR-77 (manufactured by Showa Highpolymer Co., Ltd.), KAYARAD R-604, DPCA-20, DPCA- 30, DPCA-60, DPCA-120, HX-620, D-310, D-330, MANDA (manufactured by Nippon Kayaku Co., Ltd.), ARONIX M-210, M-215, M-315, M-325 (manufactured by Toagosei Co., Ltd.), and the like. Of these, Ripoxy VR-77, KAYARAD MANDA, and Viscoat 700 are particularly preferable.

These polymerizable monomers are contained in the curable liquid resin composition preferably in an amount of 5-85 wt%, with 10-80 wt% being particularly preferable. If less than 5 wt%, applicability of the composition is impaired due to increased viscosity, and if the amount exceeds 85 wt%, toughness of the cured product may be impaired.

As other additives that can be added to the curable liquid resin composition of the present invention in addition to the above components, antioxidants, coloring agents, UV absorbers, light stabilizers, silane coupling agents, heat polymerization inhibitors, leveling agents, surfactants, preservatives, plasticizers, lubricants, solvents, fillers, aging preventives, wettability improvers, and the like can be given. Examples of antioxidants include IRGANOX1010, 1035, 1076, 1222 (manufactured by Ciba Specialty Chemicals Co., Ltd.), ANTIGENE P, 3C, FR, Sumilizer GA-80 (manufactured by Sumitomo Chemical Industries Co., Ltd.) and the like. Examples of UV absorbers include TINUVIN P, 234, 320, 326, 327, 328, 329, 213 (manufactured by Ciba Specialty Chemicals Co., Ltd.), Seesorb 102, 103, 501, 202, 712, 704 (manufactured by Sypro Chemical Co.), and the like. Examples of light stabilizers include TINUVIN 292, 144, 622LD (manufactured by Ciba Specialty Chemicals Co., Ltd.), Sanol LS770 (manufactured by Sankyo Co., Ltd.), Sumisorb TM- 061 (manufactured by Sumitomo Chemical Industries Co., Ltd.), and the like. Examples of silane coupling agents include γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like, and commercially available products such as SH6062 and 6030 (manufactured by Toray-Dow Corning Silicone Co., Ltd.), and KBE903, 603, 403 (manufactured by Shin- Etsu Chemical Co., Ltd.).

The curable liquid resin composition of the present invention may be cured by radiation using the photoinitiator or may be cured using a combination of radiation and heat. Radiation used herein refers to infrared rays, visible rays, ultraviolet rays, X-rays, electron beams, α-rays, β-rays, γ-rays, and the like. Visible and ultraviolet rays are particularly preferred.

Preferably, the radiation-curable compositions can be cured by conventional means. For example, the radiation source can be a conventional light source such as, for example, UV lamps available from Fusion Systems Corp. In addition, low-, medium-, and high-pressure mercury lamps, superactinic fluorescent tubes or pulse lamps are suitable. UV cure of compositions according to the present invention are preferred.

The curable liquid resin composition of the present invention possesses high-speed curability that is superior to conventional compositions and can form a uniform and highly transparent overcoat. The viscosity of the liquid curable resin composition of the present invention is usually in the range of 200-20,000 cp at 25°C, and preferably 1,500-15,000 cp at 25°C.

The composition after curing should have a Young's modulus of 10 to 250 kg/mm² when used as a secondary coating material of elemental optical fibers or a bundling material of optical fiber ribbon matrix. When it is used as a primary coating material for elemental optical fibers, it is preferable that the Young modulus of the cured product be from 0.05 to 0.3 kg/mm². Use of the present invented composition in primary coating compositions is particularly preferred. The curable liquid resin composition of the present invention and a cured product of the composition excel in thermal stability because the viscosity of the composition and the Young's modulus of the cured product are stable over time during storage at high temperatures. The rate of viscosity change for this composition is usually less than ±13%, and preferably less than ±10% upon aging as described below. The rate of change of the Young's modulus of elasticity for the cured product is usually less than ±15%, preferably less than ±13%, and particularly preferably less than ±10% upon aging as described below. The haze value upon aging as described below preferably is about 2 or less, more preferably about 1 or less.

Examples

The present invention is described below in more detail by examples. However, the present invention is not limited to the examples. In the following description, part(s) means part(s) by weight.

Synthesis of urethane (meth)acrylate Synthesis Example 1

A reaction vessel equipped with a stirrer was charged with 50.968 parts of polypropylene glycol with a number average molecular weight of 2000 ("ACCLAIM 2200" manufactured by Sumitomo Bayer Urethane Co., Ltd.), 7.920 parts of isophorone diisocyanate, 0.015 parts of 2,6-di-t-butyl-p-cresol, and 0.005 parts of phenothiazine. The mixture was cooled to 15°C while stirring. After the addition of 0.049 parts of zirconium tetraacetylacetonate, the mixture was slowly heated to 35°C while stirring for one hour. The mixture was heated to 50°C and allowed to react. After the residual isocyanate concentration decreased to 1.45 wt% or less of the total amount of the reactants, 2.365 parts of 2-hydroxyethyl acrylate was added. The mixture was allowed to react at about 60°C while stirring. The reaction was terminated when the concentration of the residual isocyanate group was 0.1 wt% or less. The urethane (meth)acrylate obtained is identified as "UA1". Synthesis Example 2

Urethane (meth)acrylate "UA2" was obtained in the same manner as in Example 1 , except that the urethanization catalyst zirconium tetraacetylacetonate was replaced with an equal amount of tetra-n-butoxy zirconium.

Synthesis Example 3

Urethane (meth)acrylate "UA3" was obtained in the same manner as in Example 1 , except that the urethanization catalyst zirconium tetraacetylacetonate was replaced with an equal amount of zirconium tris(acetylacetonate)ethylacetoacetate.

Comparative Synthesis Example 1

Urethane (meth)acrylate "UA4" was obtained in the same manner as in Example 1 , except that the urethanization catalyst zirconium tetraacetylacetonate was replaced with an equal amount of dibutyl tin dilaurate.

(Production of liguid resin composition) Example 1

14.325 parts of isobornyl acrylate, 13.831 parts of polyoxyethylene nonylphenylether acrylate (M113, manufactured by Toagosei Co., Ltd.), 7.410 parts of vinyl caprolactam, 1.284 parts of Lucirin TPO-X (manufactured by BASF), 0.593 parts of Irganox 1035 (manufactured by Ciba Specialty Chemicals Co., Ltd.), 0.148 part of SEESORB 101 (manufactured by Sypro Chemical Co.), 0.988 part of mercaptopropyl trimethoxysilane (SH6062, manufactured by Toray-Dow Corning Silicone Co., Ltd.), and 0.099 part of diethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) were added to 61.322 parts of UA1. The mixture was stirred to homogenize, thereby obtaining the curable liquid resin composition of the present invention.

Example 2 A curable liquid resin composition was obtained in the same manner as in Example 1 , except that UA1 was replaced with an equal amount of UA2.

Example 3

A curable liquid resin composition was obtained in the same manner as in Example 1 , except that UA1 was replaced with an equal amount of UA3. Comparative Example 1

A curable liquid resin composition was obtained in the same manner as in Example 1 , except that UA1 was replaced with an equal amount of UA4.

Comparative Example 2

A curable liquid resin composition was obtained in the same manner as in Example 1 , except that Lucirin TPO-X was replaced with an equal amount of Irgacure 184 (manufactured by Ciba Specialty Chemicals Co., Ltd.).

Comparative Example 3

A curable liquid resin composition was obtained in the same manner as in Example 1 , except that UA1 was replaced with an equal amount of UA4 and Lucirin TPO-X was replaced with an equal amount of Irgacure 184.

(1) Method for measuring viscosity

The viscosity of the compositions obtained in the Examples and Comparative Examples at 25°C was measured using a B8H-BII viscometer (manufactured by TOKIMEC Inc.). Next, the composition was subjected to a durability test wherein the composition was placed in a 60°C oven for 60 days, then the viscosity of the composition was measured again (hereinafter referred to as "viscosity after duration"). The heat stability of the curable liquid resin composition was evaluated by calculating the variation between the initial viscosity and the viscosity after duration using the following formula (1 ). Viscosity variation (%) = 100-(initial viscosity/viscosity after duration) x 100 (1)

(2) Measurement of Young's modulus

The Young's modulus of the cured materials made from the compositions obtained in the Examples and Comparative Examples was measured. The curable liquid resin compositions were applied to glass sheets using an applicator bar for the preparation of films with a 354 μm thickness. The coatings were cured by irradiation of ultraviolet light at a dose of 1 J/cm² in the air, thereby producing test films. A sample in the shape of a strip with a width of 6 mm and a length of 25 mm was prepared from the cured film. A tensile test was conducted in accordance with JIS K7127 using an AGS-1KND tensile testing machine (manufactured by Shimadzu Corporation) under the conditions of 23°C and 50% humidity. The Young's modulus was calculated from the tensile strength at 2.5% strain at a drawing rate of 1 mm/min. Next, the cured film was subjected to a durability test, wherein the composition was placed in a 100°C oven for 60 days, then the Young's modulus of the composition was measured again (hereinafter referred to as "Young's modulus after duration"). Heat stability of the cured product was evaluated by calculating the variation between the initial Young's modulus and the Young's modulus after duration using the following formula (2).

Young's modulus variation (%) = 100-(initial Young's modulus/Young's modulus after duration) x 100 (2)

(3) Method for measuring cure speed The cure speed of the compositions obtained in the Examples and

Comparative Examples was measured. The curable liquid resin compositions were applied to glass sheets using an applicator bar for the preparation of films with a 354 μm thickness. The coatings were cured by irradiation of ultraviolet light at doses of 20 mJ/cm² and 500 mJ/cm² in the air, thereby producing two types of test films. Test specimens in the shape of a strip with a width of 6 mm and a length of 25 mm were prepared from the two types of cured films. A tensile test was conducted in accordance with JIS K7127 using an AGS-1KND tensile testing machine (manufactured by Shimadzu Corporation) under the conditions of 23°C and 50% humidity. The Young's modulus was calculated from the tensile strength at 2.5% strain at a drawing rate of 1 mm/min. Cure speed of the compositions was evaluated by calculating the variation between the Young's modulus of the test film cured at a dose of 20 mJ/cm² and the Young's modulus of the test film cured at a dose of 500 mJ/cm² using the following formula (3).

Cure speed(%)= Young's modulus of 20 mJ/cm² cured film / Young's modulus of 500 mJ/cm² cured film (3)

(4) Method of observing transparency of cured film

Transparency of the cured materials made from the compositions obtained in the Examples and Comparative Examples was observed. The curable liquid resin compositions were applied to glass sheets using an applicator bar for the preparation of films with a 354 μm thickness. The coatings were cured by irradiation of ultraviolet light at a dose of 1 J/cm² in the air, thereby producing test films. The cured films were heated in an oven at 120°C for 12 hours, then allowed to cool to room temperature. Transparency of the films was evaluated by observing the presence of microscopic white spots using an optical microscope and the haze value was measured in accordance with JIS K7136 using an SC-3H color haze meter (manufactured by Suga Test Instruments Co., Ltd.).

Evaluation method

The results as shown in table 1 were evaluated in accordance with the following standards.

The films having a cure speed of 0.8% or more, not possessing microscopic white spots when observed by an optical microscope, and having a haze value of 1.0% or less were regarded as acceptable products.

As is clear from Table 1 , the cured product obtained from the curable liquid resin composition of the present invention containing a Group IV metal compound displayed no microscopic white spots, was uniform, and transparent. It is also clear that the composition of the present invention exhibited limited change in viscosity, and the cured product of the present invention had a stable Young's modulus over time and excellent heat stability.

[Table 1]

Claims

1. A curable liquid resin composition comprising (a) a urethane (meth)acrylate, (b) a Group IV metal compound, and (c) a phosphorus-containing photoinitiator.

2. The curable liquid resin composition according to claim 1 , wherein the Group IV metal compound (b) is either a titanium compound or a zirconium compound.

3. Composition according to anyone of claims 1-2 wherein the urethane (meth)acrylate comprises a polyether, a polyester and/or a polycarbonate.

4. Composition according to anyone of claims 1-3 wherein the urethane (meth)acrylate is included in said composition in an amount of 5-99 wt%

5. Composition according to anyone of claims 1-4 wherein the urethane (meth)acrylate has a number average molecular weight of 700-10,000 Dalton.

6. Composition according to anyone of claims 1-5 wherein said Group IV metal compound comprises one or more ligands choosen from the group consisting of acetoacetonate type groups, alkoxy groups and alkoxylate groups.

7. Composition according to anyone of claims 1-6 wherein said Group IV metal compound has a number of carbon atoms of 30 or less.

8. Composition according to anyone of claims 1-7 wherein the Group IV metal compound is included in said composition in an amount of 0.01-1 wt%.

9. Composition according to anyone of claims 1-8 wherein photoinitiator (c) is a phosphine oxide type compound.

10. Composition according to anyone of claims 1-9 wherein photoinitiator (c) comprises at least one acylgroup.

11. Composition according to claim 10 wherein photoinitiator (c) comprises one acyl group.

12. Composition according to anyone of claims 1-11 wherein photoinitiator (c) further comprises as other substituents cyclic or aromatic groups with 5-20 carbon atoms.

13. Composition according to anyone of claims 1-12 wherein the composition further comprises one or more reactive diluents.

14. Composition according to claim 13 wherein the reactive diluent is included in the composition in an amount of 5-85 wt%.

15. Composition according to anyone of claims 1-14 wherein the composition has a viscosity in the range of 200-20,000 cp at 25°C.

16. Composition according to claim 15 wherein the change in viscosity upon aging the composition at 60°C for 60 days is + 13% or less.

17. A method for producing a cured product comprising curing the curable liquid resin composition according to anyone of claims 1-16 using radiation.

18. A cured product obtained by curing the curable liquid resin composition according to anyone of claims 1-16 using radiation.

19. Cured product of claim 18 having a Youngs modulus of 10-250 kg/mm².

20. Cured product of claim 18 having a Youngs modulus of 0.05-0.3 kg/mm².

21. Cured product according to anyone of claims 18-20 wherein the change in

Youngs modulus upon aging at 100°C for 60 days is + 15% of less.

22. Cured product according to anyone of claims 18-21 wherein the haze value of a 354 μm thin film upon aging at 120°C for 12 hours is 2 or less.

23. Coated optical glass fiber or ribbon comprising coated optical glass fibers having one or more covering layers wherein at least one covering layer is a cured product according to anyone of claims 18-22.

24. Coated optical glass fiber wherein the primary coating is a cured product according to anyone of claims 18-22.

25. Use of a curable resin composition according to anyone of claims 1-16 as an adhesive.

26. A catalyst for synthesizing urethane (meth)acrylate comprising one or more compounds selected from the group consisting of zirconium tetraacetylacetonate, zirconium tris(acetylacetonate)ethylacetoacetate, and zirconium bis(acetylacetonate)bis(ethylacetoacetate).

27. A method of manufacturing urethane (meth)acrylate characterized by reacting a polyisocyanate and a hydroxyl-group containing (meth)acrylate or a polyol, a polyisocyanate, and a hydroxyl-group containing (meth)acrylate in the presence of the catalyst for synthesizing urethane (meth)acrylate of claim 5.