JP2009185222A - Radiation-curable composition for optical recording medium, its cured product, and optical recording medium using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation-curable composition for an optical recording medium having low viscosity and excellent coating properties and giving a cured product having excellent transparency, balance between surface hardness and warpage resistance when formed into a laminate, or the like and improved load trace resistance, to provide its cured product and to provide the optical recording medium using the same. <P>SOLUTION: The radiation-curable composition for the optical recording medium containing a monomer or/and an oligomer having a radiation-curable group, having 300 to 10,000 mPa s viscosity at 25°C and ≥85% light transmittance per 0.1 mm optical path length in 400 nm wavelength as its cured product obtained by irradiation with radiation of 1J/cm<SP>2</SP>and having 100 μm film thickness has ≤15 wt.% content of the monofunctional monomer or/and the oligomer having the radiation-curable group. The radiation-cured product for the optical recording medium is obtained by curing the radiation-curable composition for the optical recording medium by irradiation with the radiation. The optical recording medium has a protective layer composed of the radiation-cured product for the optical recording medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiation curable composition for optical recording media, a cured product thereof, and an optical recording medium using the same. Specifically, it can give a cured product with low viscosity, excellent coating properties, transparency, and a balance between surface hardness and warpage resistance when made into a laminate, and improved load resistance. The present invention relates to a radiation curable composition for optical recording media capable of providing a cured product, a cured product thereof, and an optical recording medium using the same.

Many attempts have been made to use a radiation-curable composition for a protective layer of an information recording layer in an optical recording medium, and the present inventors have made, for example, a monomer or / and oligomer having a radiation-curable group, A specific amount of a monofunctional (meth) acrylate having an alicyclic skeleton and a composition containing other (meth) acrylate as necessary has excellent transparency and surface hardness as a cured product, and a curable composition. The inventors have found that a radiation curable composition excellent in the balance between the viscosity as a product and the heat resistance and moisture resistance as a cured product, and that cured product can be provided, and previously filed a patent application (see Patent Document 1). However, when this radiation-curable composition is used, for example, as a protective layer for an information recording layer in an optical recording medium, when the object having an uneven shape is pressed against the surface of the protective layer for a long time, The trace of the shape remains (in this specification, this phenomenon is referred to as “load trace property”), and it has been found that there is an inherent problem that the optical recording medium interferes with reading and writing of information. .
JP 2007-270119 A

  The present invention has been made to improve the load resistance in the above-described prior art. Therefore, the present invention has a low viscosity and excellent coatability, transparency, surface hardness and a laminate. Radiation curable composition for optical recording media capable of providing a cured product having an excellent balance with warpage resistance and the like, and capable of providing a cured product with improved load resistance, and cured product thereof, An object of the present invention is to provide an optical recording medium using the same.

As a result of intensive studies to solve the aforementioned problems, the present inventors have reduced the content of monofunctional monomers having a radiation curable group in the radiation curable composition from the conventionally known amount. It was found that the above object can be achieved by the present invention, and the present invention has been completed. That is, the gist of the present invention includes a monomer or / and oligomer having a radiation curable group at 25 ° C. The viscosity is 300 to 10,000 mPa · s, and the light transmittance per optical path length of 0.1 mm at a wavelength of 400 nm as a cured product having a film thickness of 100 μm obtained by irradiation with 1 J / cm ² of radiation is 85% or more. A radiation curable composition for optical recording media, wherein the content of the monofunctional monomer and / or oligomer having a radiation curable group is 15% by weight or less Composition, radiation cured product for optical recording medium obtained by curing radiation curable composition for optical recording medium by irradiation, and protection comprising radiation cured product for optical recording medium An optical recording medium having a layer.

  According to the present invention, it is possible to give a cured product having a low viscosity, excellent coating properties, transparency, and a balance between surface hardness and warpage resistance when made into a laminate, and load-bearing traces. The radiation curable composition for optical recording media which can give the hardened | cured material with improved property, its hardened | cured material, and an optical recording medium using the same can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention. it can.

1. Radiation curable composition for optical recording media The radiation curable composition for optical recording media of the present invention contains a monomer or / and oligomer having a radiation curable group. The radiation curable group is preferably a (meth) acryloyl group. As the monomer or / and oligomer having such a radiation curable group, a urethane (meth) acrylate having a urethane bond [hereinafter referred to as “component (A)”. " ] Is preferable. The other component contained in the radiation curable composition for optical recording media of the present invention is a monofunctional monomer or / and oligomer having one radiation curable group, preferably a (meth) acryloyl group, preferably Is a polyfunctional monomer or / and oligomer having a monofunctional (meth) acrylate and two or more radiation curable groups, preferably a (meth) acryloyl group, preferably a polyfunctional (meth) acrylate, etc. (A ) A monomer or / and oligomer having a radiation curable group other than the component, preferably (meth) acrylate [hereinafter sometimes referred to as “component (B)”. ], And a polymerization initiator for initiating radiation curing [hereinafter sometimes referred to as “component (C)”. ], Other auxiliary components, and the like.

1-1. Component (A): Urethane (meth) acrylate Urethane (meth) acrylate is usually obtained by reacting a polyisocyanate, a compound containing a hydroxyl group, and a (meth) acrylate containing a hydroxyl group. As the urethane (meth) acrylate in the present invention, urethane acrylate is preferable from the viewpoint of excellent surface curability as a composition and less stickiness (stickiness).

1-1-a. Polyisocyanate Polyisocyanate is a compound having two or more isocyanate groups in the molecule. Specific examples of the polyisocyanate include fats such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate. Aliphatic diisocyanates such as aromatic diisocyanate, bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, naphthalene diisocyanate, etc. Aromatic diisocyanates, and multimers thereof, and the like. One kind may be used alone, or two or more kinds may be used in combination. Among these, alicyclic diisocyanates such as bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, and isophorone diisocyanate are preferable in that the hue of the urethane (meth) acrylate obtained is good. preferable. In addition, ethylene diisocyanate trimer or / and pentamer, hexamethylene diisocyanate trimer or / and pentamer in terms of good surface hardness as a cured product of the radiation curable composition of the present invention. And trimers or / and pentamers of isophorone diisocyanate are preferred.

  The molecular weight of the polyisocyanate is preferably 100 or more, more preferably 150 or more, more preferably 1,000 or less, and even more preferably 500, in terms of the balance between the strength and elastic modulus of the cured product of the composition. It is preferable that:

1-1-b. Compound containing a hydroxyl group As the compound containing a hydroxyl group, polyols containing two or more hydroxyl groups are preferable, and specific examples thereof include ethylene glycol, 1,2-propanediol, and 1,3-propane. Diol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 3 -Methyl-1,5-pentanediol, 2,3,5-trimethyl-1,5-pentanediol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl -1,6-hexanediol, 1,8-octanediol, trimethylolpropane, pentaerythritol , Alkylene polyols such as sorbitol, mannitol, glycerin, 1,2-dimethylolcyclohexane, 1,3-dimethylolcyclohexane, 1,4-dimethylolcyclohexane, and the like.

  Among these, the above-mentioned polyols have an ether bond for forming a multimer etc., a polyether polyol, an ester bond by reaction with a polybasic acid, or an ester bond by ring-opening polymerization of a cyclic ester, polyester Polyol polyol having a carbonate bond by reaction with polyol or carbonate is preferable.

  Specific examples of the polyether polyol include polytetramethylene glycol as a ring-opening polymer of a cyclic ether such as tetrahydrofuran in addition to the multimers of the polyols, and ethylene oxide, propylene oxide, 1 , 2-butylene oxide, 1,3-butylene oxide, 2,3-butylene oxide, adducts of alkylene oxide such as tetrahydrofuran, epichlorohydrin, and the like.

  Specific examples of the polyester polyol include a reaction product of the polyol and a polybasic acid such as maleic acid, fumaric acid, adipic acid, sebacic acid and phthalic acid, and a ring opening weight of a cyclic ester such as caprolactone. Examples include polycaprolactone as a combination.

  Specific examples of the polycarbonate polyol include the polyols and alkylene carbonates such as ethylene carbonate, 1,2-propylene carbonate, and 1,2-butylene carbonate, or diphenyl carbonate, 4-methyldiphenyl carbonate, and 4-ethyl. Diphenyl carbonate, 4-propyl diphenyl carbonate, 4,4′-dimethyl diphenyl carbonate, 2-tolyl-4-tolyl carbonate, 4,4′-diethyl diphenyl carbonate, 4,4′-dipropyl diphenyl carbonate, phenyl toluyl carbonate, Diaryl carbonates such as bischlorophenyl carbonate, phenylchlorophenyl carbonate, phenyl naphthyl carbonate, dinaphthyl carbonate, or dimethyl Reaction with dialkyl carbonates such as carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, di-n-butyl carbonate, diisobutyl carbonate, di-t-butyl carbonate, di-n-amyl carbonate, diisoamyl carbonate, etc. Thing etc. are mentioned.

  These polyols may be used individually by 1 type, and may be used in combination of 2 or more type. Among these polyols, polyether polyol is preferable, among which polyalkylene glycol is more preferable, and polytetramethylene glycol is particularly preferable.

  The molecular weights of these polyols are low water absorption and low hygroscopicity as urethane (meth) acrylate, and therefore from the viewpoint of low corrosiveness of the metal layer when used as an optical recording medium as a cured product of the composition. The total number of polyols is preferably 15 mol% or more, more preferably 30 mol% or more, and the number average molecular weight is 200 or more, further 400 or more, 1,500 or less, and further 800 or less. preferable. Further, the number average molecular weight of the entire polyol is 3,500 or less, more preferably 2,500 or less, particularly 1,500 or less, optimally 1,000 or less, 200 or more, further 400 or more, In particular, it is preferably 600 or more.

1-1-c. (Meth) acrylate containing hydroxyl group (Meth) acrylate containing hydroxyl group is a compound having both a hydroxyl group and a (meth) acryloyl group. Specifically, hydroxyethyl (meth) acrylate, hydroxypropyl (Meth) acrylate, hydroxybutyl (meth) acrylate, addition reaction product of glycidyl ether and (meth) acrylic acid, mono (meth) acrylate of glycol, etc. may be mentioned, and one of these may be used alone. Moreover, you may use combining 2 or more types.

  The molecular weight of the hydroxyl group-containing (meth) acrylate is preferably 40 or more, more preferably 80 or more, and is preferably 800 or less, more preferably 400 or less.

1-1-d. Component (A): Method for Producing Urethane (Meth) acrylate The polyisocyanate, the compound containing the hydroxyl group, and the (meth) acrylate containing the hydroxyl group are subjected to an addition reaction to form a (meth) acryloyl group. Urethane (meth) acrylates having the following can be produced. At that time, the isocyanate group and the hydroxyl group are charged so as to have a stoichiometric amount. In particular, diols are used as a compound containing a hydroxyl group, and urethane (meth) acrylate having a (meth) acryloyl group further has an advantage that adhesion and surface curing degree are further increased as a cured product of the resulting composition. There is.

  In addition, when manufacturing urethane (meth) acrylate, the amount of the (meth) acrylate containing the hydroxyl group is combined with the compound containing the hydroxyl group and the (meth) acrylate containing the hydroxyl group. It is usually 20% by weight or more, preferably 40% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less, based on the total amount of hydroxyl group-containing compounds. According to the ratio, the molecular weight of the urethane (meth) acrylate obtained can be controlled.

  The addition reaction of these polyisocyanates with (meth) acrylates containing hydroxyl groups can be carried out by any known method. For example, a mixture of a polyisocyanate, a hydroxyl group-containing (meth) acrylate and an addition reaction catalyst is usually at 40 ° C or higher, preferably 50 ° C or higher, and usually 90 ° C or lower, preferably 75 ° C or lower. Mix under. As a mixing method at that time, it is preferable to drop a mixture of a hydroxyl group-containing (meth) acrylate and an addition reaction catalyst in the presence of polyisocyanate. In addition, as the addition reaction catalyst at this time, for example, dibutyltin laurate, dibutyltin dioctoate, dioctyltin dilaurate, and dioctyltin dioctoate are preferable, and one of these may be used alone, Two or more kinds may be used in combination.

  In addition, when manufacturing urethane (meth) acrylate, you may contain another component other than the said polyisocyanate, the compound containing the said hydroxyl group, and the (meth) acrylate containing the said hydroxyl group.

1-1-e. Component (A): Properties of Urethane (Meth) acrylate The urethane (meth) acrylate is preferably highly transparent, for example, a compound having no aromatic ring. When the urethane (meth) acrylate has an aromatic ring, the radiation curable composition having an aromatic ring and the cured product thereof are colored during storage even if the resulting product is a colored product or is not colored. Or coloring may increase (so-called yellowing). This is considered to be caused by the fact that the double bond part forming the aromatic ring irreversibly changes its structure by energy rays, and therefore urethane (meth) acrylate does not have an aromatic ring. By having the structure, there is an advantage that the hue is not deteriorated and the light transmittance is not lowered, and it is particularly suitable for application to an application requiring colorless and transparent such as an optical recording medium.

  For urethane (meth) acrylates that do not have aromatic rings, select polyisocyanates that do not have aromatic rings, compounds that contain hydroxyl groups that do not have aromatic rings, and (meth) acrylates that contain hydroxyl groups that do not have aromatic rings Specific examples of the polyisocyanate that can be produced by the process and have no aromatic ring include alicyclic diisocyanates such as bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, and isophorone diisocyanate. In addition, specific examples of the compound containing a hydroxyl group having no aromatic ring include alkylene polyol, alkylene polyester, and alkylene carbonate polyols, and the like, and a hydroxyl group having no aromatic ring. Specific examples of the content to (meth) acrylate, hydroxyalkyl (meth) acrylate. In addition, these 1 type may be used independently and may be used in combination of 2 or more type.

  The weight average molecular weight of these urethane (meth) acrylates is preferably 1,000 or more, more preferably 1,500 or more, and more preferably 10,000 or less, and more preferably from the viewpoint of the balance between viscosity and mechanical properties. It is preferably 5,000 or less.

  In the radiation curable composition for optical recording media of the present invention, the content of the urethane (meth) acrylate as the component (A) is preferably 25% by weight or more, and more preferably 30% by weight or more. In addition, it is preferably 95% by weight or less, and more preferably 90% by weight or less. If the content of the urethane (meth) acrylate as the component (A) is too small, moldability and mechanical strength when forming a cured product are lowered, and the cured product tends to be cracked. And the surface hardness of the cured product tends to decrease.

1-2. (B) component; (meth) acrylates other than the component (A) Among the (meth) acrylates other than the component (A), as the monofunctional (meth) acrylate, specifically, for example, N, N- (Meth) acrylamides such as dimethyl (meth) acrylamide, hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acryloylmorpholine, Examples include alicyclic (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, and (meth) acrylate having a tricyclodecane skeleton. Among these, Alicyclic (meth) acrylate Among them, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, and (meth) acrylate having a tricyclodecane skeleton are particularly preferable.

Examples of the polyfunctional (meth) acrylate compound include aliphatic poly (meth) acrylates, alicyclic poly (meth) acrylates, aromatic poly (meth) acrylates, and specific examples include polyethylene. Glycol di (meth) acrylate, 1,2-polypropylene glycol di (meth) acrylate, 1,3-polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, 1,2-polybutylene glycol di ( Of alkylene oxide adducts such as ethylene oxide, propylene oxide, or butylene oxide of bisphenol such as (meth) acrylate, polyisobutylene glycol di (meth) acrylate, bisphenol A, bisphenol F, or bisphenol S Di (meth) acrylates of hydrogenated derivatives of bisphenols such as (meth) acrylate, bisphenol A, bisphenol F, or bisphenol S, blocks of various polyether polyol compounds with other compounds, or random copolymer di (meta) ) (Meth) acrylates having a polyether skeleton such as acrylate, and hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, decanediol di (meth) acrylate, 2 , 2-bis [4- (meth) acryloyloxyphenyl] propane, 2,2-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] propane, bis (hydroxymethyl) tricyclo [5.2.1 .0 ^2,6 ] decane-di ( Bifunctional (meth) acrylates such as (meth) acrylate, p-bis [β- (meth) acryloyloxyethylthio] xylylene, 4,4′-bis [β- (meth) acryloyloxyethylthio] diphenylsulfone, Trifunctional (meth) acrylates such as trimethylolpropane tris (meth) acrylate, glycerin tris (meth) acrylate, pentaerythritol tris (meth) acrylate, and tetrafunctional (meth) acrylates such as pentaerythritol tetrakis (meth) acrylate And indefinite polyfunctional (meth) acrylates such as penta- or higher-functional (meth) acrylates such as dipentaerythritol hexa (meth) acrylate.

Of these, bifunctional (meth) acrylates are preferred because of the controllability of the cross-linking reaction. As the bifunctional (meth) acrylates, aliphatic poly (meth) acrylates and alicyclic poly (meth) acrylates are preferable, and hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, bis (Hydroxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane = di (meth) acrylate is preferred. Further, from the viewpoint of load resistance as a cured product, di (meth) acrylates of diols having 6 to 20 carbon atoms, and further 8 to 12 carbon atoms, specifically, hexanediol di (meth) acrylate, Particularly preferred are octanediol di (meth) acrylate and nonanediol di (meth) acrylate. In addition, from the viewpoint of load resistance as a cured product, tetrafunctional or higher (meth) acrylates, specifically, pentaerythritol tetrakis (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like are particularly preferable.

Furthermore, as the polyfunctional (meth) acrylate in the present invention, a side chain that is not related to crosslinking when it is made into a cured product, for example, a (meth) acryloyl group like an ethyl group in trimethylolpropane tri (meth) acrylate. When a crosslinked structure is formed, it is preferable not to have a molecular chain that is not directly involved in the formation of the crosslinked structure. From this viewpoint, polyethylene glycol di (meth) acrylate, 1,3-polypropylene glycol di (Meth) acrylate, polytetramethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, octanediol di (meth) acrylate, nonanediol di (meth) acrylate, decanediol di (meth) acrylate, bis (hydroxy Methyl) tricyclo [5. .1.0 ^2,6] include decane = di (meth) acrylate, glycerol tris (meth) acrylate, pentaerythritol tetrakis (meth) acrylate, as dipentaerythritol hexa (meth) acrylate are preferable polyfunctional (meth) acrylate It is done.

  In addition, the molecular weight of (meth) acrylates other than the component (A) is preferably 50 or more, more preferably 100 or more, from the viewpoint of the balance between the viscosity and the curing shrinkage as the composition, It is preferably 1,000 or less, more preferably 500 or less.

  These monofunctional (meth) acrylates and polyfunctional (meth) acrylates may be used alone or in combination of two or more. However, it is preferable that at least polyfunctional (meth) acrylate contains 1 or more types.

  In the radiation curable composition for optical recording media of the present invention, the content of the (meth) acrylate of the component (B) other than the component (A) is preferably 5% by weight or more, and preferably 10% by weight or more. More preferably, it is preferably 75% by weight or less, and more preferably 70% by weight or less. When the amount of the (B) component (meth) acrylate is too small, the viscosity of the radiation curable composition increases, and the surface hardness of the cured product tends to decrease. Formability and mechanical strength at the time of forming are lowered, and the cured product tends to be cracked.

  The content of the monofunctional (meth) acrylate in the component (B) is essential to be 15% by weight or less, more preferably 10% by weight or less, and 5% by weight or less. Is more preferably 2% by weight or less, and most preferably not contained. When the content of monofunctional (meth) acrylate is too large, when the surface of the radiation curable composition is pressed against the surface for a long time and a local stress is applied, The surface tends to be plastically deformed to leave uneven marks ("load mark property" in this specification). For this purpose, in reducing the content of monofunctional (meth) acrylate, the low-viscosity urethane (meth) acrylate as the component (A) is used, or the content of polyfunctional (meth) acrylate is reduced. It is necessary to balance the viscosity as the radiation curable composition and various physical properties as the cured product by increasing the amount or selecting the polyfunctional (meth) acrylate to be used.

1-3. (C) component; polymerization initiator The radiation curable composition for optical recording media of the present invention further starts polymerization for initiating a polymerization reaction that proceeds by radiation (for example, active energy rays, ultraviolet rays, electron beams, etc.). It is preferable to contain an agent. In particular, when the radiation is active energy rays or ultraviolet rays, it is preferable to contain a polymerization initiator. As the polymerization initiator, a radical generator which is a compound having a property of generating radicals by light is generally used, and any known radical generator can be used as long as the effects of the present invention are not significantly impaired.

  Specific examples of such radical generators include benzophenone, 2,4,6-trimethylbenzophenone, 4,4-bis (diethylamino) benzophenone, 4-phenylbenzophenone, methylorthobenzoylbenzoate, thioxanthone, diethylthioxanthone, isopropylthioxanthone. Chlorothioxanthone, 2-ethylanthraquinone, t-butylanthraquinone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, Benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, methylbenzoyl formate, 2-methyl-1- [4 (Methylthio) phenyl] -2-morpholinopropan-1-one, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4 , 4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] -2-methyl-propan-1-one and the like. Among them, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] -2-Methyl-propan-1-one is preferred.

  Among the above radical generators, benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-hydroxycyclohexyl are included in that the curing speed is high and the crosslinking density can be sufficiently increased. Phenylketone, 2-hydroxy-1- [4- {4- (2-hydroxy-2-methyl-propionyl) benzyl} phenyl] -2-methyl-propan-1-one, and 2,4,6-trimethyl Benzoyldiphenylphosphine oxide is preferred.

  In addition, when the cured product of the radiation curable composition of the present invention is used for an optical recording medium using a laser having a wavelength of 380 to 800 nm as a light source, the laser beam necessary for reading sufficiently passes through the cured product layer. Thus, it is preferable to select and use the type and amount of the radical generator. In this case, it is particularly preferable to use a short wavelength photosensitive radical generator in which the obtained cured product layer hardly absorbs laser light.

  Among the above radical generators, such short wavelength photosensitive radical generators include benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, methylorthobenzoylbenzoate, diethoxyacetophenone, 2-hydroxy -2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, methyl benzoyl formate, etc. Among them, those having a hydroxyl group such as 1-hydroxycyclohexyl phenyl ketone are particularly preferable.

  In addition, these radical generators may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the radical generator is usually 0.1 parts by weight or more, preferably 100 parts by weight or more, preferably (A) urethane (meth) acrylate and (B) (meth) acrylate. 1 part by weight or more, more preferably 2 parts by weight or more, and usually 10 parts by weight or less, preferably 9 parts by weight or less, more preferably 7 parts by weight or less, still more preferably 5 parts by weight or less, particularly preferably 4 parts by weight. It is as follows. If the amount added is too small, the radiation curable composition tends not to be cured sufficiently. On the other hand, if the amount is too large, the polymerization reaction proceeds rapidly, causing problems such as an increase in optical distortion. Or the hue tends to deteriorate.

  When a benzophenone polymerization initiator is used, it is usually 0.5 parts by weight or more, preferably 2 parts by weight or less, more preferably 1 part by weight or less. This is because when the amount of the benzophenone-based polymerization initiator is large, the volatile components in the cured product of the radiation curable composition increase, and the film thickness may be reduced in a high temperature and high humidity environment.

  In addition to these radical generators, for example, known sensitizers such as methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, amyl 4-dimethylaminobenzoate, 4-dimethylaminoacetophenone, etc. are used in combination. May be. A sensitizer may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the polymerization initiator other than the radical generator include an oxidizing agent, and these polymerization initiators may be used alone or in combination of two or more. The polymerization initiator may contain impurities such as a chlorine atom, a sulfur atom, a phosphorus atom, and a sodium atom, but the content of these impurities is preferably small, and each content is preferably It is 100 ppm or less, More preferably, it is 50 ppm or less, More preferably, it is 30 ppm or less, Most preferably, it is 10 ppm or less.

  In addition, when starting a polymerization reaction with an electron beam as radiation, the above polymerization initiator can be used, but since it is sufficiently cured without using a polymerization initiator, a radical generator or other polymerization initiator is used. It is preferable not to use.

1-4. Auxiliary components The radiation curable composition for optical recording media of the present invention may contain auxiliary components such as additives as necessary, as long as the effects of the present invention are not significantly impaired. Specific examples of the auxiliary components include stabilizers such as antioxidants, heat stabilizers, or light absorbers; glass fibers, glass beads, silica, alumina, zinc oxide, titanium oxide, mica, talc, kaolin, metal fibers, fillers metal powders and the like; carbon fiber, carbon black, graphite, carbon nanotube, a carbon material such as fullerene such as C ₆₀ (fillers, referred to as an inorganic component are collectively a carbon material such.); charge Modifiers such as inhibitors, plasticizers, mold release agents, antifoaming agents, leveling agents, anti-settling agents, surfactants, thixotropy imparting agents, epoxy group-containing compounds; pigments, dyes, hue modifiers, etc. Agents; monomers or / and oligomers thereof, or curing agents, catalysts, curing accelerators and the like necessary for the synthesis of inorganic components. These auxiliary components may be used alone or in combination. It may be used in combination of two or more. The content of these auxiliary components is usually 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less of the radiation curable composition.

  Among these, silica as fillers will be described in detail. In the radiation curable composition for optical recording media of the present invention, silica refers to silicon oxide in general, regardless of the ratio of silicon to oxygen and whether it is crystalline or amorphous. Examples of the silica particles include industrially produced silica particles dispersed in a solvent, or powdered silica particles; silica particles derived and synthesized from raw materials such as alkoxysilanes, and the like. Can do. Among them, when used in the radiation curable composition for optical recording media of the present invention, it is derived from a silica particle dispersed in a solvent or a raw material such as alkoxysilane, because of easy mixing and dispersion. Silica particles made are preferred.

  The particle diameter of the silica particles is arbitrary, but the number average particle diameter measured by morphological observation using a TEM (transmission electron microscope) or the like is preferably 0.5 nm or more, more preferably 1 nm or more, Further, it is preferably 50 nm or less, more preferably 40 nm or less, still more preferably 30 nm or less, particularly preferably 15 nm or less, and most preferably 12 nm or less. The silica particles are preferably ultrafine particles, but if they are too small, the cohesiveness of the ultrafine particles is extremely increased, and the transparency and mechanical strength of the cured product tend to be extremely decreased. This is because the characteristics tend not to be remarkable.

1-5. Production method and characteristics of radiation curable composition for optical recording medium 1-5-a. Method for producing radiation curable composition for optical recording medium The radiation curable composition for an optical recording medium of the present invention comprises the urethane (meth) acrylate as the component (A), the (meth) acrylate as the component (B), (C) It prepares by stirring and mixing uniformly the polymerization initiator of a component, and the said auxiliary component used as needed in the state which interrupted | blocked the radiation. The order of addition of each compound at that time is not particularly limited, but it is preferable to add a high viscosity liquid component and / or a solid component to a low viscosity liquid component and stir, and the polymerization initiator is Preferably added last.

  The stirring conditions at that time are not particularly limited, but the stirring temperature is usually room temperature, but it may be heated to a temperature of usually 90 ° C. or lower, preferably 70 ° C. or lower. The speed is usually 100 rpm or more, preferably 300 rpm or more, and usually 1,000 rpm or less, and the stirring time is usually 10 seconds or more, preferably 3 hours or more, and usually 24 hours or less.

1-5-b. Characteristics of radiation curable composition for optical recording medium In the present invention, the radiation curable composition for optical recording medium is measured at 25 ° C. measured by an E type viscometer, a B type viscometer, a vibration type viscometer, or the like. The viscosity is 300 mPa · s or more, preferably 500 mPa · s or more, and more preferably 1,000 mPa · s or more. Further, it is 10,000 mPa · s or less, preferably 7,000 mPa · s or less, more preferably 5,000 mPa · s or less, and particularly preferably 3,000 mPa · s or less. If the viscosity is too small, it is difficult to form a cured product having a film thickness of, for example, 50 μm or more. On the other hand, if the viscosity is too large, it is difficult to form a cured product having a smooth surface.

  As a method of adjusting the viscosity as the radiation curable composition, a method of adjusting each molecular weight of the urethane (meth) acrylate of the component (A) and the (meth) acrylate of the component (B), and an addition amount, Further, there are methods such as mixing a diluent, a solvent, a thickener, a rheology control agent, etc., among others, the urethane (meth) acrylate of the component (A) and the (meth) acrylate of the component (B). The method of adjusting each molecular weight or / and content of is particularly preferable.

  The radiation-curable composition for optical recording media of the present invention preferably contains substantially no solvent. This is to prevent bubbles from remaining and hindering reading and writing of information. “Contains substantially no solvent” means a state in which the content of a so-called organic solvent having volatility or a low boiling point is very low, and the solvent content in the radiation curable composition is usually 5% by weight or less. It is preferably 3% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.1% by weight or less. For simplicity, it means a state in which no odor of the organic solvent is observed.

2. 2. Cured product of radiation curable composition for optical recording medium 2-1. Method for producing cured product of radiation curable composition for optical recording medium The cured product of the radiation curable composition for optical recording medium in the present invention starts a polymerization reaction by irradiating with radiation (active energy ray or electron beam). It is obtained by so-called “radiation curing”. There is no restriction | limiting in particular in the form of a polymerization reaction, For example, well-known polymerization forms, such as radical polymerization, anionic polymerization, cationic polymerization, and coordination polymerization, can be used. Of these polymerization modes, radical polymerization is particularly preferable from the viewpoint of the homogeneity of the product and the like due to the initiation of the polymerization reaction proceeding homogeneously and in a short time within the polymerization system.

  Here, the term “radiation” refers to electromagnetic waves (gamma rays, X-rays, ultraviolet rays, visible rays, infrared rays, micro rays, which act on a polymerization initiator that initiates a necessary polymerization reaction to generate chemical species that initiate the polymerization reaction. Wave) or particle beam (electron beam, α-ray, neutron beam, various atomic beams, etc.). Examples of radiation preferably used in the present invention are preferably ultraviolet rays, visible rays, and electron beams, and most preferably ultraviolet rays and electron beams because energy and a general-purpose light source can be used.

  When ultraviolet rays are used as radiation, it is preferable to use a photoradical generator that generates radicals by ultraviolet rays within the above-described polymerization initiation as the polymerization initiator. At this time, a sensitizer may be used in combination as necessary. The wavelength of the ultraviolet rays is usually 200 nm or more, preferably 240 nm or more, and usually 400 nm or less, preferably 350 nm or less.

  As a device for irradiating ultraviolet rays, a known device such as a high-pressure mercury lamp, a metal halide lamp, or an ultraviolet lamp having a structure for generating ultraviolet rays by microwaves can be preferably used. The output of the apparatus is usually 10 W / cm or more, preferably 30 W / cm or more, and usually 200 W / cm or less, preferably 180 W / cm or less. The apparatus is usually 5 cm or more, preferably Is preferably at a distance of 30 cm or more, and usually 80 cm or less, preferably 60 cm or less, because the light deterioration, thermal deterioration, thermal deformation, etc. of the irradiated object are small.

The irradiation intensity of the radiation, usually 0.1 J / cm ² or more, preferably 0.2 J / cm ² or more, and usually 20 J / cm ² or less, preferably 10J / cm ² or less, more preferably 5 J / cm ² or less, more preferably 3J / cm ² or less, particularly preferably irradiated with 2J / cm ² or less. As long as the irradiation intensity is within this range, it can be appropriately selected depending on the type of radiation curable composition for optical recording media.

  The irradiation time of radiation is usually 1 second or longer, preferably 10 seconds or longer, and usually 3 hours or shorter, and preferably 1 hour or shorter in terms of promoting the reaction and productivity. When the irradiation energy or irradiation time of radiation is extremely small, the heat resistance and mechanical properties of the cured product may not be sufficiently exhibited due to incomplete polymerization. On the other hand, when it is extremely excessive, deterioration such as deterioration of hue due to light such as yellowing may occur.

  The irradiation of the radiation may be performed in one step or may be performed in a plurality of steps. As the radiation source, a diffusion radiation source in which radiation spreads in all directions is usually used. The irradiation of radiation is usually carried out by fixing and standing the radiation source in a state where the radiation curable composition for optical recording media shaped in the mold is fixed and left or transported by a conveyor. Moreover, the radiation curable composition for optical recording media is used as a coating liquid film on an appropriate substrate (for example, resin, metal, semiconductor, glass, paper, etc.), and the coating liquid film is cured by irradiating the radiation there. It is also possible.

  In addition, when an electron beam is used as radiation, the electron beam irradiation apparatus used for irradiation is not particularly limited, and examples thereof include a curtain type, an area beam type, a broad beam type, and a pulse beam type. The acceleration voltage at the time of irradiation is usually 10 kV or more, preferably 100 kV or more, and usually 1,000 kV or less, preferably 200 kV or less. Although the light source and irradiation device for electron beam irradiation are expensive, there are advantages that the use of a polymerization initiator can be omitted and that the polymerization is not hindered by oxygen and therefore the surface hardness is good. A cured product having excellent properties, particularly tensile elongation, can be obtained.

2-2. Characteristics of radiation-cured product for optical recording medium The cured product of the radiation-curable composition for optical recording medium of the present invention usually exhibits insoluble and infusible properties in a solvent or the like, and is an optical member even when it is thickened. It is preferable that the material has advantageous properties for the above-mentioned use and is excellent in adhesion and surface hardening. Specifically, it exhibits low optical distortion (low birefringence), high light transmittance, mechanical strength, dimensional stability, high adhesion, high surface hardness, and a certain level of heat and humidity resistance. preferable. Further, the smaller the curing shrinkage, the better.

  The film thickness of the radiation-cured product for optical recording media of the present invention is usually 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, still more preferably 70 μm or more, particularly preferably 85 μm or more, and usually 300 μm or less, preferably It is 130 μm or less, more preferably 115 μm or less. This is because the balance between the influence on the reading and writing of information due to dust and the transmittance is good.

The light transmittance of the radiation-cured product for optical recording media of the present invention is a light-transmittance per optical path length of 0.1 mm at a wavelength of 550 nm as a cured product having a film thickness of 100 μm obtained by irradiating 1 J / cm ² of radiation. 85% or more, preferably 89% or more, and there is no limit to the upper limit. Further, the light transmittance per optical path length of 0.1 mm at a wavelength of 400 nm is 85% or more, preferably 89% or more. If the light transmittance is too low, the transparency as a cured product is inferior, and errors increase when reading recorded information when used in an optical recording medium. The light transmittance can be measured at room temperature by a known method using, for example, an HP8453 type ultraviolet / visible absorptiometer manufactured by Hewlett-Packard Company.

  In order to set the light transmittance of the radiation-cured product for optical recording media of the present invention within the above range, it is preferable to use a component having a high light transmittance as each component constituting the radiation-curable composition for optical recording media. Furthermore, those having a small amount of impurities such as colored substances and decomposed substances in each component are preferred. Moreover, the thing with little catalyst amount at the time of manufacture is preferable. These are effective in order not to reduce the light transmittance in the visible light region. Furthermore, it is preferable to select an aliphatic or alicyclic skeleton having no aromatic ring in each component. These are effective in order not to reduce the light transmittance in the ultraviolet region.

The radiation cured product for optical recording media of the present invention is preferably a cured product having a film thickness of 100 μm obtained by irradiating with 1 J / cm ² of radiation, and has a tensile modulus of 500 MPa or more, preferably 1,000 MPa or more. More preferably, it is preferably 2,000 MPa or less, and more preferably 1,800 MPa or less. If the tensile modulus is too small, the load resistance tends to be insufficient, whereas if it is too large, the warping resistance is reduced, deformation occurs, and the layer tends to be peeled off when formed into a laminate. Become.

  The hardness of the radiation-cured product for optical recording media of the present invention is usually 6B or more, preferably 4B or more, more preferably B or more, and particularly preferably HB or more, as a surface hardness according to a pencil hardness test in accordance with JIS K5400. is there.

3. Optical Recording Medium The radiation curable composition and the radiation cured product of the present invention are suitably used as a material for an optical recording medium described below, particularly as a material for forming a protective layer of an information recording layer.

  Currently, optical recording media that are generally used include read-only media (ROM media), write-once media that can only be recorded once (Write Once media), and rewritable media that can be repeatedly erased. There is a type of medium (Rewritable medium) and the like, and the radiation curable composition for optical recording media and the radiation cured product thereof of the present invention can be applied to any of them.

  These optical recording media employ a layer structure according to their intended use. For example, in a read-only medium, a single layer containing, for example, a metal such as aluminum, silver, or gold is usually formed on a substrate on which unevenness for reproduction is formed, and in a write-once medium, A recording / reproducing functional layer in which a reflective layer containing a metal such as aluminum, silver, and gold and a recording layer containing an organic dye are laminated in this order on the substrate is usually formed. In a medium, a reflective layer containing a metal such as aluminum, silver, or gold, a dielectric layer, a recording layer containing an organic dye, and a dielectric layer are usually laminated in this order on a substrate. A recording / reproducing functional layer is formed and is configured respectively. The radiation curable composition for optical recording medium of the present invention and the radiation cured product thereof are formed on a single layer or a write-once medium of the read-only medium. Recording / playback functional layer , And it is suitable for use as a protective layer formed on the recording and reading layer in a rewritable medium.

  On the other hand, the wavelength of the laser beam as the recording / reproducing light for recording / reproducing of the optical recording medium is a light having an optimum wavelength depending on the standard such as CD, DVD, Blu-ray disc, HDDVD, etc. With the spread of rich content, the demand for higher density and higher capacity of optical recording media is increasing, and research using a blue laser with a shorter wavelength is being actively conducted. This next-generation high-density optical recording medium using a blue laser is an optical recording in which a recording / reproducing functional layer including a dielectric layer, a recording layer, a reflective layer, etc. is formed on a substrate, and a protective layer is formed thereon. This is an optical recording medium using recording / reproducing light having a wavelength of usually 350 nm or more, preferably 380 nm or more, and usually 450 nm or less, preferably 430 nm or less. The radiation curable composition for optical recording media of the invention and the radiation cured product thereof are particularly preferably used.

  The radiation curable composition for optical recording media of the present invention and the optical recording medium in which the radiation cured product is used have, for example, a two-layer structure having two recording layers and two reflective layers. It may be a thing. In the case of this two-layer type, one layer may be laminated on the substrate in order, or two layers obtained by laminating a pair of a recording layer and a reflective layer may be bonded together. Good. Further, a three-layer structure may be adopted, and the bonding may be performed through an adhesive layer. Furthermore, if necessary, a hub may be attached and incorporated in the cartridge.

  The thickness of the protective layer is usually 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, still more preferably 70 μm or more, particularly preferably 85 μm or more, and usually 300 μm or less, preferably 130 μm or less, more preferably 115 μm. It is as follows. If the film thickness is in such a range, the influence of dust and scratches attached to the surface of the protective layer can be reduced, and the thickness of the recording / reproducing functional layer is sufficient to protect the moisture from outside air and the like. be able to. Moreover, a uniform film thickness can be easily formed by a general coating method used in spin coating or the like.

Example 1
Isophorone diisocyanate (26.7 g) and dibutyltin laurate (40 mg) are placed in a four-necked flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, and heated to 70-80 ° C in an oil bath, and the temperature is constant. Gently stirred until When the temperature becomes constant, 19.6 g of polytetramethylene glycol having a number average molecular weight of 650 ("PTMG650" manufactured by Mitsubishi Chemical Corporation) and polytetramethylene glycol having a number average molecular weight of 2,000 ("PTMG2000" manufactured by Mitsubishi Chemical Corporation) A mixture of 59.8 g was added dropwise using a dropping funnel and stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 14.0 g of hydroxyethyl acrylate and 0.2 g of methoquinone is added dropwise with a dropping funnel, and when the addition is completed, the temperature is kept at 80 ° C. and stirred for 10 hours. Synthesized. After the temperature was lowered to 50 ° C., the synthesized urethane acrylate oligomer was mixed with 20.0 g of tetrahydrofurfuryl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.), 40.0 g of nonanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), dipentaerythritol hexaacrylate. Radiation-curable composition A was obtained by adding 20.0 g (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 7.0 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals) and stirring at room temperature for 3 hours. .

  The resulting radiation curable composition A had a urethane acrylate oligomer content of 58.0% by weight, a content of other acrylates of 38.6% by weight, of which a monofunctional acrylate content of 9.7% by weight. It was.

Moreover, when the viscosity of the obtained radiation curable composition A was measured by the method shown below, it was 2,500 mPa · s.
<Viscosity>
The measurement was performed using an E-type viscometer in a constant temperature and humidity chamber at 25 ° C. and 65% RH.

Further, a cured product was obtained by the method shown below, and the light transmittance of the obtained cured product was measured and found to be 89%.
<Light transmittance>
The obtained radiation curable composition was applied onto a 100 mm square, 3 mm thick glass plate coated with fluorine using a spin coater, and then using a high pressure mercury lamp ("J-cure 100" manufactured by JATEC). Then, it was cured by irradiating with an ultraviolet ray having an irradiation amount of 1 J / cm ² at a wavelength of 365 nm to form a cured product layer having a thickness of 100 μm. After the cured product layer is peeled from the glass plate, the peeled cured product layer is subjected to light transmission per optical path length of 0.1 mm at a wavelength of 400 nm using an ultraviolet / visible absorptiometer (manufactured by Hewlett-Packard; HP8453 type). The rate was measured.

Furthermore, it was 800 MPa when the tensile elastic modulus was measured about the obtained hardened | cured material by making it into hardened | cured material by the method shown below.
<Tensile modulus>
The obtained radiation curable composition was applied on a polyethylene terephthalate film affixed on a glass plate using a spin coater, and then a wavelength of 365 nm using a high-pressure mercury lamp (“J-cure 100” manufactured by JATEC). Was cured by irradiating with an ultraviolet ray having an irradiation amount of 1 J / cm ² to form a cured product layer having a thickness of 100 μm. After peeling the cured product layer from the polyethylene terephthalate film, 5 strips of 10 mm × 100 mm strips were cut out from the peeled cured product layer, and a tensile test was performed at a tensile speed of 1 mm / min using a tensile tester. The tensile modulus was measured and the average value was calculated.

Furthermore, an Ag—Cu—Au reflective layer having a thickness of 100 nm was formed by sputtering on a smooth polycarbonate substrate surface having a diameter of 120 mm and a thickness of 1.1 mm, and the obtained radiation-cured composition was formed on the surface of the reflective layer. After coating A using a spin coater, it was cured by irradiating with an ultraviolet ray with a dose of 1 J / cm ^{2 at} a wavelength of 365 nm using a high-pressure mercury lamp (“J-cure 100” manufactured by JATEC), and a film thickness of 100 μm. A test disk was prepared by forming a protective layer. When the obtained disk was evaluated for warpage resistance by the following method, it was “◯”.
<War resistance>
The prepared disc was allowed to stand in an environment set at 25 ° C. and 45% RH for 3 days, and then the displacement at a position 55 mm from the center of the disc was measured using a displacement sensor (“LT-9010” manufactured by Keyence Corporation). . However, the concave warp is added to the protective layer side, the convex warp is negative, and the absolute value is 0.3 mm or more, “x”, 0.1 mm or more and less than 0.3 mm, “△”, The case of less than 0.1 mm was evaluated as “◯”.

Further, when the obtained disk was evaluated for load resistance by the following method, it was “◯”.
<Load resistance>
Place the manufactured disk on a surface plate with the protective layer facing up, and stack a 100 mm square, 5 mm thick glass plate on the protective layer, and place a steel cork table with a weight of 200 g on it. After standing for 1 day, remove the cork base and glass plate, immediately observe the surface of the protective layer visually, and when the sand plast mark is visually observed in 75% or more of the total area, The case where it was visually observed in less than 75% of the area was evaluated as “Δ”, and the case where it was not visually observed was evaluated as “◯”.

Example 2
Into a four-necked flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, 36.8 g of isophorone diisocyanate and 40 mg of dibutyltin laurate are placed, heated in an oil bath to 70-80 ° C., and the temperature is constant. Gently stirred until When the temperature becomes constant, 4.5 g of 1,6-hexanediol, 19.6 g of polytetramethylene glycol having a number average molecular weight of 650 ("PTMG650" manufactured by Mitsubishi Chemical Corporation), and polytetramethylene having a number average molecular weight of 2,000 A mixture of 29.9 g of glycol ("PTMG2000" manufactured by Mitsubishi Chemical Corporation) was added dropwise using a dropping funnel, and the mixture was stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 19.3 g of hydroxyethyl acrylate and 0.2 g of methoquinone is added dropwise with a dropping funnel, and when the addition is completed, the temperature is kept at 80 ° C. and stirred for 10 hours. Synthesized. After the temperature was lowered to 50 ° C., the synthesized urethane acrylate oligomer was mixed with 20.0 g of tetrahydrofurfuryl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.), 50.0 g of nonanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), dipentaerythritol hexaacrylate. A radiation curable composition B was obtained by adding 20.0 g (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 7.0 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals) and stirring at room temperature for 3 hours. .

  The resulting radiation curable composition B had a urethane acrylate oligomer content of 53.2% by weight, a content of other acrylates of 43.4% by weight, of which a monofunctional acrylate content of 9.7% by weight. It was.

  The obtained radiation curable composition B was measured to have a viscosity of 2,000 mPa · s by the method described above. Furthermore, it was set as the hardened | cured material by the above-mentioned method, and when the light transmittance was measured about the obtained hardened | cured material, it was 89%. Further, the cured product was formed by the above-described method, and the tensile modulus of the obtained cured product was measured and found to be 2500 MPa.

  Further, when a test disk was prepared by the above-described method and the warpage resistance of the obtained disk was evaluated, it was “Δ”. Further, when the load resistance of the obtained disk was evaluated, it was “◯”.

Example 3
In a four-necked flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, 24.7 g of isophorone diisocyanate and 40 mg of dibutyltin laurate are placed, heated in an oil bath to 70-80 ° C., and the temperature is constant. Gently stirred until When the temperature becomes constant, 18.6 g of polytetramethylene glycol having a number average molecular weight of 650 ("PTMG650" manufactured by Mitsubishi Chemical Corporation) and polytetramethylene glycol having a number average molecular weight of 2,000 ("PTMG2000" manufactured by Mitsubishi Chemical Corporation) A mixture of 53.8 g was added dropwise using a dropping funnel, and the mixture was stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature is lowered to 70 ° C., a mixture of 12.9 g of hydroxyethyl acrylate and 0.2 g of methoquinone is added dropwise with a dropping funnel, and when the addition is completed, the temperature is kept at 80 ° C. and stirred for 10 hours. Synthesized. After the temperature was lowered to 50 ° C., the synthesized urethane acrylate oligomer was mixed with 34.0 g of 1,6-hexanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd.), 40.0 g of nonanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), A radiation curable composition was prepared by adding 16.0 g of pentaerythritol hexaacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 7.0 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals Co., Ltd.) and stirring at room temperature for 3 hours. C was obtained.

  The resulting radiation curable composition C had a urethane acrylate oligomer content of 53.1% by weight, a content of other acrylates of 43.5% by weight, of which a monofunctional acrylate content of 0.0% by weight. It was.

  The viscosity of the obtained radiation curable composition C measured by the method described above was 2,800 mPa · s. Furthermore, it was set as the hardened | cured material by the above-mentioned method, and when the light transmittance was measured about the obtained hardened | cured material, it was 89%. Moreover, it was 1,200 MPa when the tensile elasticity modulus was measured about the obtained hardened | cured material as a hardened | cured material by the above-mentioned method.

  Further, when a test disk was prepared by the above-described method and the warpage resistance of the obtained disk was evaluated, it was “◯”. Further, when the load resistance of the obtained disk was evaluated, it was “◯”.

Comparative Example 1
In a four-necked flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, 34.3 g of isophorone diisocyanate and 40 mg of dibutyltin laurate are placed and heated to 70-80 ° C. in an oil bath, and the temperature is constant. Gently stirred until When the temperature becomes constant, 3.3 g of 1,6-hexanediol, 19.6 g of polytetramethylene glycol having a number average molecular weight of 650 ("PTMG650" manufactured by Mitsubishi Chemical Corporation), and polytetramethylene having a number average molecular weight of 2,000 A mixture of 37.4 g of glycol ("PTMG2000" manufactured by Mitsubishi Chemical Corporation) was added dropwise using a dropping funnel, and the mixture was stirred for 2 hours while maintaining the temperature at 80 ° C. After the temperature was lowered to 70 ° C., a mixture of 17.9 g of hydroxyethyl acrylate and 0.2 g of methoquinone was added dropwise with a dropping funnel, and when the addition was completed, the temperature was kept at 80 ° C. and stirred for 10 hours. Synthesized. After the temperature was lowered to 50 ° C., the synthesized urethane acrylate oligomer was mixed with 37.5 g of tetrahydrofurfuryl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.), 30.0 g of nonanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.), dipentaerythritol hexaacrylate. Radiation curable composition C was obtained by adding 20.0 g (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 7.0 g of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals Co., Ltd.) and stirring at room temperature for 3 hours. .

  The resulting radiation curable composition C had a urethane acrylate oligomer content of 54.3% by weight, a content of other acrylates of 42.3% by weight, of which the monofunctional acrylate content was 18.1% by weight. It was.

  Further, the obtained radiation curable composition C was measured for viscosity by the above-described method, and it was 2,000 mPa · s. Further, a cured product was formed by the above-mentioned method, and the light transmittance of the obtained cured product was measured and found to be 89%. Moreover, it was set as the hardened | cured material by the above-mentioned method, and when the tensile elasticity modulus was measured about the obtained hardened | cured material, it was 1500 MPa.

  Further, when a test disk was prepared by the above-described method and the warpage resistance of the obtained disk was evaluated, it was “◯”. Further, when the load resistance of the obtained disk was evaluated, it was “x”.

Claims (9)

As a cured product having a film thickness of 100 μm, which contains a monomer or / and oligomer having a radiation curable group, has a viscosity at 25 ° C. of 300 to 10,000 mPa · s, and is irradiated with 1 J / cm ² of radiation. A radiation curable composition having a light transmittance of 85% or more per optical path length of 0.1 mm at a wavelength of 400 nm, wherein the content of a monofunctional monomer and / or oligomer having a radiation curable group is 15% by weight or less. A radiation curable composition for optical recording media, comprising: The radiation curable composition for optical recording media according to claim 1, wherein the radiation curable composition has a tensile elastic modulus of 500 to 2,000 MPa as a cured product having a film thickness of 100 µm obtained by irradiation with radiation of 1 J / cm ^2. Sex composition.   The radiation curable composition for optical recording media according to claim 1 or 2, comprising urethane (meth) acrylate as a monomer or / and oligomer having a radiation curable group in the radiation curable composition.   The radiation curable composition for optical recording media according to claim 3, wherein the urethane (meth) acrylate has a polyether skeleton.   The monofunctional monomer or / and oligomer having a radiation curable group in the radiation curable composition is a monofunctional (meth) acrylate, and further contains a polyfunctional (meth) acrylate. The radiation curable composition for optical recording media as described.   The radiation curable composition for optical recording media according to claim 5, comprising di (meth) acrylate of a diol having 6 to 20 carbon atoms as the polyfunctional (meth) acrylate.   The radiation curable composition for optical recording media according to claim 5 or 6, comprising a tetrafunctional or higher functional (meth) acrylate as the polyfunctional (meth) acrylate.   A radiation cured product for an optical recording medium, which is obtained by curing the radiation curable composition for an optical recording medium according to any one of claims 1 to 7 by radiation irradiation.   An optical recording medium comprising a protective layer made of the radiation-cured material for optical recording medium according to claim 8.