JP2010157295A - Curable resin composition for optical disk, and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curable resin composition for an optical disk, which has high transparency, with which recording and reproducing with high reliability are achieved, and which is superior in long term storage stability (low warpage in a preservation test in high and low temperature surroundings, film retention in high temperature surroundings, scarcity of permanent deformation such as recesses), with respect to an optical disk (e.g., Blu-ray Disc (R)) having a reflection film to reflect a laser beam for information reading on a substrate and a protective layer (a transparent cover layer) with thickness of 10-150 μm on the reflection film, and the optical disk using the curable resin composition as the protective layer. <P>SOLUTION: The curable resin composition is used for the optical disk having the reflection film to reflect a laser beam for information reading on the substrate and the protective layer on the reflection film with thickness of 20-150 μm, and contains (a) 20-60 mass% of an oligomer or a polymer which has a radical polymerizable group, of which the cured product has a glass transition temperature of -10 to 45°C, and an elastic coefficient of 50-900 MPa at 25°C; (b) 30-80 mass% of (meth)acrylates with an average acrylic equivalent of 280-500; and (c) a photo-polymerization initiator. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a curable resin composition for optical disks and an optical disk. More specifically, in an optical disc (for example, a Blu-ray disc) having a reflective film that reflects a laser beam for reading information on a substrate and a protective layer having a thickness of 20 to 150 μm on the reflective film, the optical disc is cured. Optical discs using a protective resin composition as a protective layer are highly transparent and reliable for recording and playback, and have long-term storage stability (low warpage and high temperature in storage tests under high and low temperature environments). It is excellent in that the residual film property under the environment) and the amount of permanent deformation of the dent after the protective layer is pushed in are small.

  In recent years, high-definition digital high-definition broadcasting has begun, and high-definition, high-screen LCDs and plasma TVs have become widespread. However, a DVD (digital versatile disc), which is a conventional optical recording medium, has a small recording capacity, and thus cannot record a high-quality moving image for a long time. To meet this demand, a Blu-ray disc that records and reproduces information with blue laser light has been developed and sold as a standard for a new optical recording medium having a recording capacity more than five times that of DVD.

  In this new standard, in order to increase the capacity of optical recording media, blue laser light with a wavelength of 405 nm is used, and the numerical aperture (NA) of the recording / reproducing optical system objective lens is increased to 0.85. The laser beam spot diameter is reduced to about 0.44 times that of DVD, and the track pitch (interval) on which signals are recorded is reduced to about 0.43 times to increase the recording capacity by more than 5 times. Is realized.

Another technique adopted as a technique for increasing the capacity will be described below. The disk surface seen from the laser incident side is provided with a protective layer to protect the reflective film and recording layer. The thickness of the protective layer (distance between the disk surface and the signal recording surface) The DVD is about 600 μm, but the Blu-ray disc is about 100 μm. In this way, by reducing the thickness of the protective layer of the Blu-ray disc, distortion (blurring) of the laser beam spot caused by tilt due to the warp of the disc or the like is suppressed, and highly reliable recording / reproduction can be realized.
Patent Document 1 describes that the thickness of the protective layer (light-transmitting film) has a large problem in recording and reproducing information, and therefore high uniformity is required for the thickness of the protective layer. Patent Document 2 describes the necessity of controlling the thickness of the protective layer (transparent cover layer) to 100 μm ± 2 μm. Patent Document 3 describes that the laser spot position may fluctuate due to scratches (permanent deformation) such as dents in the recording medium, which may cause problems in recording and reproducing information. ing. From the viewpoint of long-term stable information recording and reproduction, it is desired that the change in the thickness of the protective layer is small when the recording medium is stored. Patent Document 4 describes a technique for preventing the protective layer (light transmission layer) from being damaged or deformed so as not to hinder the recording and reproduction. As a method for measuring the amount of deformation, a method of measuring the load and displacement during deformation while pushing a minute diamond indenter is adopted.
Further, in Patent Document 5 and Patent Document 6, if the optical recording medium is warped in a high temperature / high humidity environment or a low temperature environment, the loading to the driving device may be hindered or twisted. It is described that since a reading error occurs when a warp occurs, an optical recording medium with less warp occurring in various environments is required.
There are mainly two methods for forming the protective layer. There are a sheet bonding method in which a polycarbonate sheet is bonded with an ultraviolet curable adhesive and a spin coating method in which an ultraviolet curable resin is applied by spin coating, and the resin is cured by irradiating ultraviolet rays. Currently, the spin coating method has become mainstream from the viewpoint of cost. However, when the protective layer is formed using an ultraviolet curable resin, in addition to the above-described film thickness uniformity being required, the optical recording medium is warped mainly due to the curing shrinkage of the ultraviolet curable resin. Happens. For this reason, when a method for applying and curing an ultraviolet curable resin by previously forming a warp in a direction opposite to the warp caused by curing shrinkage of the recording medium substrate is performed, correction by a reproducing / recording device is performed, etc. In some cases, however, if the warpage exceeds the allowable range (correctable range), accurate data recording and playback on the optical recording medium may not be possible, and it may not be possible to insert / remove to / from the playback / recording device. is there. In addition, this warpage is not only required to have a small initial warpage, but also does not increase during a test to confirm long-term stability (storage test in a high temperature environment or a low temperature environment). Small).

  Further, in Patent Document 7, in order to obtain an optical disc having a protective layer (light transmission layer) excellent in transparency, abrasion resistance, and mechanical properties, it is desirable that the tensile elastic modulus of the protective layer be in a specific range. It is described. Patent Document 8 discloses an optical recording medium excellent in dimensional stability against environmental changes of a cured coating film obtained by ultraviolet irradiation. However, in an optical disc having a protective layer (light transmissive layer) on the reflective film (for example, a Blu-ray disc that reads information with blue laser light), long-term storage stability (high temperature environment or low temperature environment) In order to reduce the amount of permanent deformation due to dents after pressing the protective layer and low warpage in the storage test and the remaining film property under high temperature environment), further improvements need to be studied.

JP 2006-351102 A JP 2007-115356 A JP 2008-126518 A JP 2000-322768 A JP 2002-157782 A JP 2003-132596 A JP 2003-263780 A JP 2007-213744 A

  Under the circumstances described above, the problems to be solved by the present invention are a reflective film for reflecting laser light for reading information on a substrate, and a protective layer (transparent cover layer) having a thickness of 20 to 150 μm on the reflective film. ) (For example, a Blu-ray disc that reads information with a blue laser beam) can be recorded and played back with high transparency and reliability, and can be stored for a long period of time (under high or low temperature environments). Provide a curable resin composition for optical discs excellent in that the amount of permanent deformation such as low warpage and residual film properties in a high temperature environment) and dents is small, and an optical disc using the same as a protective layer There is.

  As a result of intensive studies, the present inventors have determined that radically polymerizable oligomers and / or polymers to be used in a curable resin composition for optical disks (hereinafter sometimes simply referred to as “composition”), (meta) By specifying acrylic acid esters, high transparency and long-term storage stability (low warpage in high-temperature and low-temperature storage tests and residual film properties under high-temperature environments) and a protective layer are pushed in. The present inventors have found that an optical disk excellent in that the amount of permanent deformation such as a later dent is small can be obtained, and the present invention has been achieved.

  That is, the curable resin composition for an optical disk of the present invention is present on a substrate and reflects a laser beam for reading information, and is present on the reflective film and has a thickness of 20 to 150 μm. A curable resin composition used for an optical disc having a protective layer, wherein (a) the glass transition temperature of the cured product is −10 to 45 ° C. and the elastic modulus at 25 ° C. 20 to 60% by mass of an oligomer and / or polymer having a radically polymerizable group of 50 to 900 MPa, and (b) (meth) acrylic acid esters having an average acrylic equivalent other than 280 to 500 of 280 to 500 It contains 80% by mass and (c) a photopolymerization initiator.

  It is preferable to use a diacrylate of an alkylene oxide adduct of bisphenol A having a molecular weight of 550 or more as the (meth) acrylic acid esters.

  Moreover, it is preferable that the viscosity in 25 degreeC of the curable resin composition of this invention is 800-3500 mPa * s.

  The optical disk of the present invention preferably has a protective layer formed by curing the above curable resin composition for optical disks.

  According to the present invention, an optical disc using the curable resin composition for an optical disc as a protective layer can realize high-transparency and reliable recording / reproduction and long-term storage stability (in a high temperature environment or a low temperature environment). The low warpage property and the remaining film property in a high temperature environment) and the amount of permanent deformation such as a dent after the protective layer is pushed in are excellent.

<< Curable resin composition for optical disk >>
<(A) Oligomer and / or polymer having radical polymerizability>
The curable resin composition for an optical disk of the present invention comprises (a) an oligomer having a radical polymerizable group having a glass transition temperature of −10 to 45 ° C. and an elastic modulus of 50 to 900 MPa at 25 ° C. and / or A polymer (hereinafter sometimes referred to simply as a radically polymerized group-containing oligomer / polymer) is contained in a curable resin composition in an amount of 20 to 70% by mass. These components are each contained in one kind or two or more kinds. can do. The cured product of the radical polymerized group-containing oligomer / polymer is preferably prepared under the curing conditions described below by adding and mixing a photopolymerization initiator employed in preparing the protective layer to the oligomer / polymer. The cured product obtained by curing the oligomer / polymer has a glass point transition temperature of −10 to 45 ° C. This is preferably -10 to 40 ° C, most preferably -5 to 40 ° C. The glass point transition temperature is a value obtained by dynamic viscoelasticity measurement, and a temperature having a maximum tan δ value is adopted. As the measurement conditions, a tensile mode, a frequency of 1 Hz, a clamp distance of 25 mm, an amplitude of 0.1%, and a heating rate of 5 ° C./min are employed. When the glass point transition temperature is higher than 45 ° C., the warp of the optical disk may increase. On the other hand, when the temperature is lower than −10 ° C., the optical disk may be recessed, and the long-term storage stability may be deteriorated. The elastic modulus of the oligomer / polymer cured product is the value of the storage elastic modulus E at 25 ° C. obtained by dynamic viscoelasticity measurement using the similarly obtained cured product. The elastic modulus of the cured product is 50 to 900 MPa. The pressure is preferably 50 to 850 MPa, more preferably 55 to 850 MPa, and most preferably 55 to 800 MPa. When the elastic modulus is smaller than 50 MPa, the long-term storage stability of the optical disk may be deteriorated. In particular, when the protective layer is pushed in, a dent is formed. When the elastic modulus is greater than 900 MPa, the warp of the obtained optical disk may increase or the long-term storage stability may deteriorate.

  The radical polymerized group-containing oligomer / polymer is one that is cured by heat and / or active energy rays such as ultraviolet rays, electron beams, and gamma rays. As the radical polymerized group-containing oligomer / polymer, saturated or unsaturated polybasic acid or anhydride acid thereof (for example, maleic acid, succinic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, etc.) And a saturated or unsaturated polyhydric alcohol (for example, ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, polyethylene glycol, Polyester (meth) acrylate obtained by reaction of (polypropylene glycol, 1,4-dimethylolbenzene, trimethylolpropane, pentaerythritol, etc.) and (meth) acrylic acid; saturated or unsaturated polyhydric alcohol (for example, ethylene glycol) , Neopen Glycol, polytetramethylene glycol, polyester polyol, polycaprolactone polyol, etc.) and organic polyisocyanates (eg, tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, etc.) and hydroxyl group-containing (meth) acrylates (eg, 2-hydroxyethyl ( Urethane) poly (meth) acrylate obtained by reaction with (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 1,4-butanediol mono (meth) acrylate, etc .; reaction between polysiloxane and (meth) acrylic acid Polysiloxane poly (meth) acrylate obtained by polyamide; polyamide poly (meth) acrylate obtained by reaction of polyamide with (meth) acrylic acid; vinyl ether group-containing (meth) (Meth) acryloyl group pendant polymers obtained by reaction of crylic acid esters with cationically polymerizable compounds (eg vinyl ethers, alkylene oxides, glycidyl ethers, etc.); multi-branched reactions such as dendrimers and hyperbranched polymers (Meth) acrylate compounds. Examples of the oligomer and / or polymer having an ion polymerizable group include polyphenols having at least one aromatic nucleus (for example, bisphenol compounds such as bisphenol A, bisphenol F, and bisphenol S, or bisphenol compounds) or alkylene oxides thereof (for example, , Ethylene oxide, propylene oxide, butylene oxide, etc.) and novolak type epoxy resins obtained by the reaction of epichlorohydrin (for example, phenol novolac type epoxy resin, cresol novolak type epoxy resin, bromine phenol novolak) Type epoxy resin), aromatic epoxy resin such as trisphenolmethane triglycidyl ether; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane Alicyclic epoxy resins such as boxylate, bis- (3,4-epoxycyclohexylmethyl) adipate, bis (2,3-epoxycyclopentyl) ether, EHPE-3150 (trade name, manufactured by Daicel Chemical Industries); polyhydric alcohol (For example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerin, trimethylolpropane, etc.) its alkylene side (for example, ethylene oxide, propylene oxide, butylene oxide, etc.) adduct and epi Aliphatic epoxy resin obtained by reaction with chlorohydrin. Among these, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and (meth) acryloyl group pendant polymer are preferable.

  In particular, when urethane (meth) acrylate is used, a polyvalent isocyanate having an alicyclic skeleton or an aromatic ring skeleton is preferable as an isocyanate component, and a divalent isocyanate having an alicyclic skeleton is particularly preferable. Examples of the divalent isocyanate having an alicyclic skeleton include isophorone diisocyanate. A polyhydric alcohol having an oxyalkylene skeleton is preferred as the polyhydric alcohol component, and a dihydric alcohol is more preferred. Examples of the dihydric alcohol having an oxyalkylene skeleton include oligoethylene glycol, oligopropylene glycol, oligobutylene glycol, and oligo (ethylene-propylene) glycol, and oligoethylene glycol and oligo (ethylene-propylene) glycol are particularly preferable. The number of repeating oxyalkylene skeletons is preferably 4 to 12, and more preferably 6 to 10. The hydroxyl group-containing (meth) acrylate component is preferably a hydroxyl group-containing acrylate, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 1,4-butanediol monoacrylate. Among these, 2-hydroxyethyl acrylate is particularly preferable. . The urethane (meth) acrylate may contain a urethane (meth) acrylate in which the isocyanate component and the hydroxyl group-containing (meth) acrylate component are directly urethanized during the composition. The preferred isocyanate component and hydroxyl group-containing (meth) acrylate component in the case where the isocyanate component and the hydroxyl group-containing (meth) acrylate component contain urethane (meth) acrylate directly urethanized are the same as described above. Urethane (meth) acrylate is 15 to 30 parts by weight of raw material isocyanate component, 45 to 65 parts by weight of raw material polyhydric alcohol component, and 5 to 40 parts by weight of raw material hydroxyl group-containing (meth) acrylate component in 100 parts by weight of raw material composition. The raw material isocyanate component is preferably 18 to 25 parts by weight, the raw material polyhydric alcohol component is 50 to 60 parts by weight, and the raw material hydroxyl group-containing (meth) acrylate component is more preferably 15 to 32 parts by weight. Moreover, when the isocyanate component and the hydroxyl group-containing (meth) acrylate component contain urethane (meth) acrylate directly urethanized, the total of 100 parts by weight of urethane (meth) acrylate having a polyhydric alcohol component is 1 It is preferable to mix | blend -20 weight part, and it is especially preferable that it is 5-15 weight part.

  The method for synthesizing urethane (meth) acrylate is not particularly limited. For example, a method in which a raw material isocyanate component and a raw material hydroxyl group-containing (meth) acrylate are reacted and then reacted in the order of a polyhydric alcohol component; ) A method in which an acrylate and a polyhydric alcohol component are charged together and reacted; a method in which a raw material isocyanate component and a polyhydric alcohol component are reacted, and then a hydroxyl group-containing (meth) acrylate is reacted. Among these, the isocyanate component and the hydroxyl group-containing (meth) acrylate component were directly urethanized by using a method in which the raw material isocyanate component and the raw material hydroxyl group-containing (meth) acrylate were reacted and then reacted in the order of the polyhydric alcohol component. Since urethane (meth) acrylate can also be synthesized at the same time, it is particularly preferable because productivity is improved. In addition, when adopting a method in which the raw material isocyanate component and the raw material hydroxyl group-containing (meth) acrylate are reacted and then reacted in the order of the polyhydric alcohol component, the raw material hydroxyl group-containing (meth) acrylate is divided into initial addition and subsequent addition. It is also preferable to add part of the raw material hydroxyl group-containing (meth) acrylate after the addition of the monohydric alcohol component.

  The content of the radical polymerizable group-containing oligomer / polymer is 20 to 60% by mass with respect to the total amount of the curable resin composition. More preferably, it is 25-55 mass%. If the total content is less than 20% by mass, the long-term storage stability of the optical disk may be inferior.

  When physical properties require high hardness, the (a) radical polymerizable group-containing oligomer / polymer is represented by the following formula (1):

[Wherein R ¹ is an alkylene group having 2 to 8 carbon atoms, R ² is a hydrogen atom or a methyl group, and m is a positive integer]
It is also possible to contain a vinyl polymer having a repeating unit represented by:

<Vinyl polymer>
In the vinyl polymer represented by the above formula (1), when the low molecular weight component increases, the strength of the cured film layer may decrease. The number average molecular weight (Mn) of the vinyl polymer is preferably 500 or more, more preferably 1000 to 20000, and still more preferably 1500 to 10,000. When the number average molecular weight (Mn) of the vinyl polymer is less than 500, the curing rate may be decreased and the strength of the cured product may be decreased. Further, if it exceeds 20000, the wettability with the base material is reduced, the mixing time is extended when the composition is adjusted, the viscosity increases, the workability at the time of coating is reduced, and further, for example, it is applied to a plastic base material and cured. In some cases, the warpage of the laminated body obtained by the treatment increases. Here, the number average molecular weight (Mn), the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) are tetrahydrofuran (THF) as a mobile phase under the conditions of a temperature of 40 ° C. and a flow rate of 0.3 mL / min. It is a value obtained by a gel permeation chromatography (GPC) apparatus HLC-8220GPC manufactured by Tosoh Corporation using two columns TSK-gel SuperHM-H and one TSK-gel SuperH2000 manufactured by Tosoh Corporation and converted to standard polystyrene. .

  The vinyl polymer represented by the above formula (1) can be obtained as a liquid viscous material except in the case of a polymer having a large solid monomer content. If it is a liquid viscous body, since the solubility to a (meth) acrylate type monomer etc. is good, the improvement of work efficiency can be aimed at when adjusting a composition.

In the above formula (1), examples of the alkylene group having 2 to 8 carbon atoms represented by R ¹ include an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, and a heptamethylene group. , Octamethylene group, cyclohexylene group, 1,4-dimethylcyclohexane-α, α′-diyl group, 1,3-dimethylcyclohexane-α, α′-diyl group, 1,2-dimethylcyclohexane-α, α ′ -Diyl group, 1,4-dimethylphenyl-α, α'-diyl group, 1,3-dimethylphenyl-α, α'-diyl group, 1,2-dimethylphenyl-α, α'-diyl group, etc. Can be mentioned. There are m substituents represented by R ¹ in the above formula (1), but they may be the same or different.

  In said formula (1), m is a positive integer, Preferably it is an integer of 1-20, More preferably, it is an integer of 1-10, More preferably, it is an integer of 1-5.

<Preparation of vinyl polymer>
The vinyl polymer represented by the above formula (1) has the following formula (2):

[Wherein R ¹ , R ² and m are as defined in the above formula (1)]
Can be prepared by conventionally known cationic polymerization, and can be easily performed by living cationic polymerization by the method described in JP-A-2006-241189. It can also be prepared. At this time, the different polymerizable monomers represented by the above formula (2) may be used alone or in combination of two or more. In the latter case, the resulting copolymer may be a random copolymer, an alternating copolymer, a periodic copolymer, a block copolymer, or a combination thereof. Moreover, a graft copolymer may be sufficient.

  Specific examples of the heteropolymerizable monomer represented by the above formula (2) include, for example, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, and 2-vinyloxypropyl (meth) acrylate. 1-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 2- (meth) acrylic acid 2- Vinyloxybutyl, 1-methyl-3-vinyloxypropyl (meth) acrylate, 2-methyl-3-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxypropyl (meth) acrylate, (meth) 1,1-dimethyl-2-vinyloxyethyl acrylate, 6-vinyloxyhexyl (meth) acrylate, (Meth) acrylic acid 4-vinyloxycyclohexyl, (meth) acrylic acid 4-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 3-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 2-vinyloxymethylcyclohexylmethyl, 4-vinyloxymethylphenylmethyl (meth) acrylate, 3-vinyloxymethylphenylmethyl (meth) acrylate, 2-vinyloxymethylphenylmethyl (meth) acrylate, 2- (2-vinyloxy) (meth) acrylate Ethoxy) ethyl, 2- (2-vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (2-vinyloxyethoxy) propyl (meth) acrylate, 2- (2-vinyloxyiso) (meth) acrylate Propoxy) propyl, (meth) acrylic acid 2- (2-vinyloxy) Ethoxy) isopropyl, (meth) acrylic acid 2- (2-vinyloxyisopropoxy) isopropyl, (meth) acrylic acid 2- {2- (2-vinyloxyethoxy) ethoxy} ethyl, (meth) acrylic acid 2- { 2- (2-vinyloxyisopropoxy) ethoxy} ethyl, 2- (2- (2-vinyloxyisopropoxy) isopropoxy} ethyl (meth) acrylate, 2- (2- (2- (2- Vinyloxyethoxy) ethoxy} propyl, 2- (2- (2-vinyloxyethoxy) isopropoxy} propyl (meth) acrylate, 2- {2- (2-vinyloxyisopropoxy) ethoxy} (meth) acrylate} Propyl, 2- (2- (2-vinyloxyisopropoxy) isopropoxy} propyl (meth) acrylic acid, (meth) acrylic acid 2 -{2- (2-vinyloxyethoxy) ethoxy} isopropyl, (meth) acrylic acid 2- {2- (2-vinyloxyethoxy) isopropoxy} isopropyl, (meth) acrylic acid 2- {2- (2- Vinyloxyisopropoxy) ethoxy} isopropyl, 2- (2- (2-vinyloxyisopropoxy) isopropoxy} isopropyl (meth) acrylate, 2- [2- {2- (2-vinyloxy) (meth) acrylate Ethoxy) ethoxy} ethoxy] ethyl, 2- (2- {2- (2-vinyloxyisopropoxy) ethoxy} ethoxy] ethyl (meth) acrylate, 2- (2- [2- {2) (meth) acrylate -(2-vinyloxyethoxy) ethoxy} ethoxy] ethoxy) ethyl; and the like. Among these different polymerizable monomers, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxyethyl (meth) acrylate, 2-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate 4-vinyloxybutyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxycyclohexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, (meth) acrylic acid 2- (2-vinyloxyethoxy) ethyl, 2- (2-vinyloxyisopropoxy) propyl (meth) acrylate and 2- {2- (2-vinyloxyethoxy) ethoxy} ethyl (meth) acrylate are preferred It is.

The heteropolymerizable monomer represented by the above formula (2) can be produced using a conventionally known method. For example, in the above formula (2), when R ¹ is an ethylene group and m is 1, a metal salt of (meth) acrylic acid and 2-halogenoethyl vinyl ether are condensed, or methyl (meth) acrylate and , 2-hydroxyethyl vinyl ether can be transesterified, or (meth) acrylic acid halide and 2-hydroxyethyl vinyl ether can be condensed. In the above formula (2), when R ¹ is an ethylene group and m is 2, a metal salt of (meth) acrylic acid and 2- (2-halogenoethoxy) ethyl vinyl ether are condensed or (meta ) By transesterifying methyl acrylate with 2- (2-hydroxyethoxy) ethyl vinyl ether or condensing (meth) acrylic acid halide with 2- (2-hydroxyethoxy) ethyl vinyl ether, Can be manufactured.

  When the vinyl polymer represented by the above formula (1) is a copolymer having a structural unit derived from a monomer capable of cationic polymerization, the copolymer is a heteropolymerizable monomer represented by the above formula (2). And a cationically polymerizable monomer can be easily prepared by cationic polymerization or living cationic polymerization. At this time, the different polymerizable monomers represented by the above formula (2) may be used alone or in combination of two or more. The resulting copolymer may be a random copolymer, an alternating copolymer, a periodic copolymer, a block copolymer, or a combination thereof. Moreover, a graft copolymer may be sufficient.

  Examples of the monomer capable of cationic polymerization include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, octadecyl vinyl ether, 2- Vinyl ether compounds such as chloroethyl vinyl ether, 4-hydroxybutyl vinyl ether, dihydrofuran; styrene, 4-methylstyrene, 3-methylstyrene, 2-methylstyrene, 2,5-dimethylstyrene, 2,4-dimethylstyrene, 2, 4,6-trimethylstyrene, 4-t-butylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 4- Styrene derivatives such as toxistyrene and 4-chloromethylstyrene; N-vinyl compounds such as N-vinylcarbazole and N-vinylpyrrolidone; divinyl compounds such as isopropenylstyrene, 2-vinyloxyethyl cinnamate and 2-vinyloxyethyl sorbate; Trivinyl compounds; and the like. These cationically polymerizable monomers may be used alone or in combination of two or more. Of these cationically polymerizable monomers, vinyl ether compounds such as isobutyl vinyl ether, cyclohexyl vinyl ether, dihydrofuran and 2-ethylhexyl vinyl ether are preferred.

  The heterogeneous polymerizable monomer represented by the above formula (2) has a radically polymerizable or anionically polymerizable (meth) acryloyl group and a cationically polymerizable vinyl ether group at the same time. A polymer having a (meth) acryloyl group or a vinyl ether group as a pendant group is obtained. In the present invention, the (meth) acryloyl group is obtained by cationic polymerization or living cationic polymerization of the vinyl ether group of the heteropolymerizable monomer represented by the above formula (2) alone or together with a cationic polymerizable monomer. A vinyl polymer represented by the above formula (1) having a pendant group is obtained.

  When the heteropolymerizable monomer represented by the above formula (2) and the cationically polymerizable monomer are subjected to cationic polymerization or living cationic polymerization, the molar ratio of the monomers (cationic polymerizable monomer / heterogeneous represented by the above formula (2) The polymerizable monomer) is preferably in the range of 0.1 to 10, more preferably 0.5 to 8, and still more preferably 0.8 to 5. By adjusting the heteropolymerizable monomer represented by the above formula (2) to the above copolymerization ratio, it is possible to obtain a composition having excellent curability, high cross-linking density of the cured product and excellent surface hardness.

<(B) (Meth) acrylic acid esters>
In addition to the above-mentioned (a) radical polymerized group-containing oligomer / polymer, the composition of the present invention comprises (b) (meth) acrylates having an average acrylic equivalent other than (a) of 280 to 500 (hereinafter simply referred to as ( (Sometimes referred to as “meth) acrylic acid esters”) as an essential component. By including (meth) acrylic acid esters, the liquid viscosity and the physical properties of the cured product can be adjusted.

(B) As (meth) acrylic acid esters, those having at least one radical polymerizable group are used so that the average acrylic equivalent to the total of (meth) acrylic acid esters is 280 to 500. There is no particular limitation. The average acrylic equivalent of the present invention is calculated as follows. When there is one (meth) acryloyl group, the molecular weight value is Mx. When there are two or more (meth) acryloyl groups, the molecular weight of (meth) acrylic acid esters / (meth) acryloyl group number is Mx. A total amount of (meth) acrylic acid esters is A (parts by mass), and the amount of (meth) acrylic acid ester X is Ax (parts by mass). The average acrylic equivalent is determined by the sum of Mx × Ax ÷ A. The average acrylic equivalent is 280-500. Preferably it is 280-450, Most preferably, it is 280-400. When the average acrylic equivalent is smaller than 280, the warp of the optical disk may increase. On the other hand, if it is larger than 500, the optical disk may be dented, and the long-term storage stability may be deteriorated.
Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1 -Adamantyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (Meth) acrylate, methoxydiethylene glycol (meth) acrylate, butoxydiethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate Monofunctional (eg, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate) (Meth) acrylate compounds; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meta) ) Acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate , Pentacyclopentadecane dimethanol di (meth) acrylate, di (meth) acrylic acid adduct of bisphenol A diglycidyl ether, cyclohexanedimethanol di (meth) acrylate, norbornane dimethanol di (meth) acrylate, p-menthane 1,8-diol di (meth) acrylate, p-menthan-2,8-diol di (meth) acrylate, p-menthan-3,8-diol di (meth) acrylate, bicyclo [2.2.2] -octane-1 -Methyl-4-isopropyl-5,6-dimethylol di (meth) acrylate, hydroxypivalic acid neopentyl glycol ester di (meth) acrylate, lactone-modified hydroxypivalic acid neopentyl glycol ester di (meth) acrylate, al Bifunctional (meth) acrylate compounds such as xylene oxide modified hydroxypivalic acid neopentyl glycol ester di (meth) acrylate, bis ((meth) acryloxyneopentyl glycol) adipate; trimethylolpropane tri (meth) acrylate, trimethylolpropane Tri (meth) acrylate, trimethylolethane tri (meth) acrylate, glycerol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, (Meth) acrylate compounds, (meth) acrylic acid derivatives; methoxyethyl (meth) acrylate, 2-methoxy-2-methylethyl (meth) acrylate, 2-meth Ci-1-methylethyl (meth) acrylate, ethoxyethyl (meth) acrylate, 2-ethoxy-2-methylethyl (meth) acrylate, 2-ethoxy-1-methylethyl (meth) acrylate, propoxyethyl (meth) acrylate , Propoxypropyl (meth) acrylate, isopropoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylol (Meth) acrylic derivatives having ether structure such as tri (meth) acrylate of propane ethylene oxide adduct and di (meth) acrylate of bisphenol A ethylene oxide adduct 4- (meth) acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4- (meth) acryloyloxymethyl-2-methyl-2-isobutyl-1,3-dioxolane, 4- (meth) ) 1,3-dioxolane-based monomers such as acryloyloxymethyl-2-cyclohexyl-1,3-dioxolane and 4- (meth) acryloyloxymethyl-2,2-dimethyl-1,3-dioxolane; . These polymerizable monomers may be used alone or in combination of two or more. Among these (meth) acrylic acid esters, (meth) acrylic acid esters having a molecular weight of 550 or more are preferable, more preferably 580 or more, and still more preferably 600 or more. The upper limit of the molecular weight is not particularly limited, but is preferably 100,000 or less, more preferably 50,000 or less, still more preferably 10,000 or less, and most preferably 5000 or less. (Meth) acrylic acid esters include di (meth) acrylate of ethylene oxide adduct of bisphenol A, tri (meth) acrylate of ethylene oxide adduct of trimethylolpropane, and lactone-modified hydroxypivalic acid neopentyl glycol ester di (meth) acrylate. It has good curability and can be used suitably.

As the bifunctional or higher functional (meth) acrylic ester compound, typically, di (meth) acrylate having a linear or branched alkylene group is preferably used. In the case of a linear alkylene group, the number of carbon atoms is preferably 4 or more, more preferably 6 or more. Di (meth) acrylate having a linear alkylene group having 4 or more carbon atoms is useful for adjusting the storage elastic modulus. The di (meth) acrylate having a branched alkylene group preferably has a neopentyl glycol skeleton, more preferably a hydroxypivalate neopentyl glycol ester skeleton.
A (meth) acrylic derivative having an ether structure is useful for adjusting the storage elastic modulus. When the ether structure increases, the storage elastic modulus decreases, and when the amount of acrylic group increases, the storage elastic modulus increases. The (meth) acrylic derivative having an ether structure is preferably a bifunctional or trifunctional acrylate, and the ether structure preferably has a dihydric alcohol moiety having an oxyalkylene skeleton. Examples of the dihydric alcohol having an oxyalkylene skeleton include oligoethylene glycol, oligopropylene glycol, oligobutylene glycol, and oligo (ethylene-propylene) glycol, and oligoethylene glycol and oligo (ethylene-propylene) glycol are particularly preferable. The number of repeating oxyalkylene skeletons in the (meth) acrylic derivative is preferably 4 to 16, and more preferably 6 to 14. Among these, di (meth) acrylate of 10 mol adduct of bisphenol A with ethylene oxide is particularly preferable.

Furthermore, from the viewpoint of good adhesion to a polycarbonate substrate that is usually used, a heteropolymerizable monomer can be suitably used. Among them, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxyethyl (meth) acrylate, ( 2-vinyloxypropyl (meth) acrylate, 1-methyl-2-vinyloxyethyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 6-vinyloxyhexyl (meth) acrylate, 4- (meth) acrylic acid 4- Vinyloxycyclohexyl, (meth) acrylic acid 4-vinyloxymethylcyclohexylmethyl, (meth) acrylic acid 2- (2-vinyloxyethoxy) ethyl, (meth) acrylic acid 2- (2-vinyloxyisopropoxy) propyl, (Meth) acrylic acid 2- {2- (2-vinyloxyethoxy) ethoxy} ethyl It can be suitably used.
The compounding quantity of (meth) acrylic acid ester whose average acrylic equivalent is 280-500 is 30-80 mass% with respect to the total amount of a curable composition. Preferably it is 35-80 mass%, More preferably, it is 35-75 mass%. When the blending amount exceeds 80% by mass, the curing shrinkage rate and internal strain increase, and for example, when the warp of the optical disk increases or the protective layer is cracked or cracked. When the blending amount is less than 30% by mass, the optical disk may be dented, and the long-term storage stability may be deteriorated.
<(C) Photopolymerization initiator>
The composition of the present invention comprises (a) a radical polymerization group-containing oligomer / polymer, (b) (meth) acrylic acid esters other than (a), and (c) a photopolymerization initiator as an essential component. To do. By including the photopolymerization initiator, there is an effect that it can be quickly cured by light irradiation.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2 -Propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholino Phenyl) butanone, oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone}, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpionyl) ) Benzyl] phenyl} -2-methylpropan-1-one and other acetophenones; Benzoins such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3, 3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ) Ethyl] benzenemethananium bromide, benzophenones such as (4-benzoylbenzyl) trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxa And thioxanthones such as 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride And so on. These radical photopolymerization initiators may be used alone or in combination of two or more. Of these photoradical polymerization initiators, acetophenones are preferred, specifically 1-hydroxycyclohexyl phenyl ketone, oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl]. ] Propanone}, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] phenyl} -2-methyl Propan-1-one is preferred. Among them, oligo {2-hydroxy-2-methyl-1- is preferable because it improves the durability of an optical disk using the curable resin composition for an optical disk as a protective layer and suppresses an increase in warpage during a heat resistance test. [4- (1-methylvinyl) phenyl] propanone} is particularly preferred.

<Ingredients other than (a), (b), (c)>
The composition of the present invention comprises (a) a radical polymerizable group-containing oligomer / polymer, (b) (meth) acrylates having an average acrylic equivalent other than 280 to 500, and (c) light. In addition to the polymerization initiator, an ultraviolet absorber and a thermal polymerization initiator may be included. In the case where the ultraviolet absorber is included, there are effects that the recyclability of the composition can be improved, the curing speed can be adjusted, and the warp of the optical disk can be reduced.

  Examples of the UV absorber include benzotriazole UV absorbers, hydroxyphenyltriazine UV absorbers, benzophenone UV absorbers, salicylic acid UV absorbers, and inorganic oxide UV absorbers. Specifically, phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone, glycol salicylate, t-butylmethoxydibenzoylmethane, ethylhexyl methoxycinnamate, dimethyl PABA ( Para-aminobenzoic acid) octyl, dimethyl PABA ethylhexyl, etc., conventionally known ultraviolet absorbers may be mentioned. In addition, the ultraviolet absorber is 2- (2-hydroxy-5-t-butylphenyl) -2H-benzotriazole (trade name “TINUBIN PS”, manufactured by Ciba Specialty Chemicals, Inc. ), 2- {2-hydroxy-4- (1-octyloxycarbonylethoxy) phenyl} -4,6-bis (4-phenylphenyl) -1,3,5-triazine (trade name “TINUBIN 479”, Ciba・ Specialty Chemicals Co., Ltd.), 2- {2-hydroxy-5- (2-methacryloyloxyethyl) phenyl} benzotriazole (trade name “RUVA93”, manufactured by Otsuka Chemical Co., Ltd.), octyl-3- {3- t-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole-2-yl) phenyl} pro Pionic acid, 2-ethylhexyl-3- {3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl} propionic acid (trade name “TINUBIN 109”, Ciba Specialty Chemicals Co., Ltd.) is preferable.

  The addition amount of the ultraviolet absorber is 0.03 to 0.4 parts by mass, preferably 0.03 to 0.3 parts by mass, and most preferably 0.05 to the entire curable resin composition. It is -0.2 mass part.

  As the thermal polymerization initiator, a thermal radical polymerization initiator that generates a polymerization initiation radical by heating is suitable. When the thermal polymerization initiator is included, there is an effect that the heat generated when the composition is cured with ultraviolet rays can be used to further promote the curing.

  Examples of the thermal polymerization initiator include methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1 , 1-bis (t-hexylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) -2-methylcyclohexane 1,1-bis (t-butylperoxy) -cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 1,1-bis (t-butylperoxy) butane, 2,2-bis (4 4-di-t-butylperoxy Chlohexyl) propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α, α'- Bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5 -Dimethyl-2,5-bis (t-butylperoxy) hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, Succinic acid peroxide, m-toluoyl benzoyl peroxide, benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate , Di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, di (3-methyl-3-methoxybutyl) peroxydicarbonate, α, α′- Bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methyl Tylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutyl Peroxy 2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexanoate, 1-cyclohexyl-1-methylethylperoxy 2-ethylhexanoate, t-hexylperoxy- 2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxysopropyl monocarbonate, t-butylperoxysobutyrate, t-butylperoxymalate, t-butylperoxy-3, 5,5-trimethylhexano Tate, t-butylperoxylaurate, t-butylperoxysopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxyacetate, t-butylperoxy-m-toluylbenzoate, t-butylperoxy Benzoate, bis (t-butylperoxy) isophthalate, 2,5-dimethyl-2,5-bis (m-toluylperoxy) hexane, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoyl) Peroxy) hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 2,3-dimethyl-2,3-diphenylbutene Organic peroxide initiators such as tan; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1-cyano-1-methylethyl) azo] formamide, 1,1′-azobis (Cyclohexane-1-carbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile) ), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis (2-methyl-) N-phenylpropionamidine) dihydrochloride, 2,2′-azobis [N- (4-chlorophenyl) -2-methylpropionamidine]] dihydrochloride, 2,2′-azobis [N (4-Hydrophenyl) -2-methylpropionamidine]] dihydrochloride, 2,2′-azobis [2-methyl-N- (phenylmethyl) propionamidine] dihydrochloride, 2,2′-azobis [2 -Methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine]] dihydrochloride, 2,2'-azobis [2- (5-Methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2 ′ -Azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (3,4,5, 6-tetrahydropyrimidine- -Yl) propane] dihydrochloride, 2,2'-azobis [2- (5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2, 2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [1,1-bis (Hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (2-methylpropionamide), 2,2 '-Azo Bis (2,4,4-trimethylpentane), 2,2′-azobis (2-methylpropane), 2,2-azobis (2-methylpropionic acid) dimethyl, 4,4′-azobis (4-cyanopentane) Acid) and azo initiators such as 2,2′-azobis [2- (hydroxymethyl) propionitrile]; and the like. These thermal radical initiators may be used alone or in combination of two or more. Among these thermal radical initiators, radicals can be efficiently generated by the catalytic action of metal soaps such as methyl ethyl ketone peroxide, cyclohexanone peroxide, cumene hydroperoxide, t-butylperoxybenzoate, benzoyl peroxide, and / or amine compounds. Preferred compounds are 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile).

  The blending amount of the thermal polymerization accelerator is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass or more, further preferably 0.05 to 3% by mass, based on the total amount of the composition. Is within the range. When the blending amount of the thermal polymerization accelerator is within such a range, it is preferable from the viewpoints of curability of the composition, physical properties of the cured product, and economical efficiency.

  The composition of the present invention uses a photosensitizer that can transfer excitation energy from an excited state generated by photoexcitation to a photopolymerization initiator and promote decomposition of the photopolymerization initiator to effectively generate radicals. be able to. Examples of the photosensitizer include 2-chlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone. These photosensitizers may be used alone or in combination of two or more.

  The blending amount of the photosensitizer is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, and still more preferably 0.2 to 10% by mass with respect to the total amount of the composition. Within range. If the compounding quantity of a photosensitizer is in such a range, it is preferable at the point of sclerosis | hardenability of a composition, the physical property of hardened | cured material, and economical efficiency.

  In the composition of the present invention, a photopolymerization accelerator capable of promoting the decomposition of the photopolymerization initiator and generating radicals effectively can be used. Examples of the photopolymerization accelerator include triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and 4-dimethylaminobenzoic acid. Examples include 2-n-butoxyethyl, 2-dimethylaminoethyl benzoate, N, N-dimethylparatoluidine, 4,4′-dimethylaminobenzophenone, and 4,4′-diethylaminobenzophenone. These photopolymerization accelerators may be used alone or in combination of two or more. Of these photopolymerization accelerators, triethanolamine, methyldiethanolamine, and triisopropanolamine are preferable.

  The blending amount of the photopolymerization accelerator is preferably 0.05 to 20% by mass, more preferably 0.1 to 15% by mass, and still more preferably 0.2 to 10% by mass with respect to the total amount of the composition. Within range. When the blending amount of the photopolymerization accelerator is within such a range, it is preferable from the viewpoint of the curability of the composition, the physical properties of the cured product, and the economical efficiency.

  The composition of the present invention may contain a surface function modifier as necessary. By adding the surface conditioner, the fingerprint removal resistance is improved. Generally, fluorine-based compounds and silicone-based compounds are used as the surface function modifier. In the present invention, polyether-modified fluorine-based compounds and polyethers having a reactive group (for example, (meth) acrylate) are used depending on the application. Any of modified fluorine compounds, non-reactive silicones, reactive (eg (meth) acrylate) silicones, polymeric silicones, and macromonomer silicones can be used.

  The composition of the present invention may further contain, as necessary, an inorganic filler, a low shrinkage agent (reactive oligomer or polymer, non-reactive oligomer or polymer), a color pigment, a plasticizer, a chain transfer agent, Polymerization inhibitor, near-infrared absorber, light stabilizer, antioxidant, flame retardant, matting agent, dye, antifoaming agent, leveling agent, antistatic agent, dispersant, slip agent, surface modifier, A thixotropic agent, a thixotropic agent, and the like can be added. The presence of these additives does not particularly affect the effects of the present invention. These additives may be used alone or in combination of two or more.

  The compounding amount of the additive may be appropriately set according to the type and purpose of use of the additive, the use and usage of the composition, and is not particularly limited. For example, the compounding amount of the inorganic filler is preferably in the range of 1 to 80% by mass, more preferably 10 to 60% by mass, and still more preferably 20 to 50% by mass with respect to the total amount of the composition. The amount of the low shrinkage agent, the color pigment, the plasticizer or the auxiliary change agent is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, and still more preferably 10 to 10% by mass with respect to the total amount of the composition. It is in the range of 25% by mass. The amount of polymerization inhibitor, antioxidant, matting agent, dye, antifoaming agent, leveling agent, antistatic agent, dispersant, slip agent, surface modifier or auxiliary agent is the total amount of the composition On the other hand, it is preferably 0.0001 to 10% by mass, more preferably 0.001 to 5% by mass, and still more preferably 0.01 to 3% by mass.

<Method for producing composition and curing method thereof>
The curable resin composition of the present invention can be obtained by mixing and stirring by a known method. The viscosity of the composition of the present invention is preferably 800 mPa · S or more and 3500 mPa · S or less at 25 ° C. More preferably, it is 1000 mPa · S or more and 2500 mPa · S or less. Here, the viscosity is a value calculated using a B-type viscometer (model “RB80L”: manufactured by Toki Sangyo Co., Ltd.) under the condition of a temperature of 25 ° C. If the viscosity falls outside the range of 800 mPa · s to 3500 mPa · s, the thickness of the protective layer may not be controlled to 100 μm ± 2 μm. Specifically, when the thickness of the protective layer at the center is thinner, The protective layer may be thick.

The composition of the present invention can be cured by irradiation with ultraviolet rays. Curing here refers to a state without fluidity. The wavelength of the ultraviolet rays used may be in the range of 150 to 450 nm. Examples of the light source that emits such a wavelength include sunlight, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a gallium lamp, a xenon lamp, a flash type xenon lamp, and a carbon arc lamp. Together with these light sources, it is possible to use heat by infrared rays, far infrared rays, hot air, high-frequency heating or the like. The integrated irradiation light amount is preferably in the range of 0.1 to 3 J / cm ² , more preferably 0.2 to 2.0 J / cm ² , and still more preferably 0.3 to 1.0 J / cm ² .

  In the case of curing by heating as well as curing by light irradiation, infrared rays, far infrared rays, hot air, high-frequency heating or the like may be used. The heating temperature may be appropriately adjusted according to the type of the substrate, and is not particularly limited, but is preferably 80 to 200 ° C, more preferably 90 to 180 ° C, and still more preferably 100 to 170 ° C. Within range. The heating time may be appropriately adjusted according to the application area and the like, and is not particularly limited, but is preferably 1 minute to 24 hours, more preferably 10 minutes to 12 hours, and even more preferably 30 minutes to 6 hours. Is within the range.

  When curing by electron beam irradiation is performed together with curing by light irradiation, an electron beam having an acceleration voltage of preferably 0 to 500 kV, more preferably 20 to 300 kV, and even more preferably 30 to 200 kV may be used. The irradiation amount is preferably in the range of 2 to 500 kGy, more preferably 3 to 300 kGy, and still more preferably 4 to 200 kGy.

The cured product obtained by curing the curable resin composition of the present invention has (A) a light transmittance of 85% or more at 405 nm with a thickness of 100 μm. More preferably, it is 88% or more, More preferably, it is 89% or more. The light transmittance is a value measured by a spectrophotometer using the obtained cured product. The cured product obtained by curing the composition of the present invention contains an oligomer and / or polymer having a radical polymerizable group, a (meth) acrylic acid ester, a photopolymerization initiator, and is sufficient depending on predetermined curing conditions and methods. The above light transmittance was able to be achieved by performing proper curing. If the light transmittance is lower than 85%, the transparency is inferior, so that errors may increase when reading recorded information.
The cured product obtained by curing the curable resin composition of the present invention has a mass loss of 0.1 when held in an oven at 70 ° C. for 100 hours (hereinafter may be simply referred to as mass reduction). It is preferable that they are mass% or more and 2.0 mass% or less. Furthermore, 0.1 mass% or more and 1.5 mass% or less are more preferable, 0.1 mass% or more and 1.0 mass% or less are the most preferable. The thickness of the cured product to be measured is 100 μ ± 2 μm. The cause of the decrease in mass is thought to be due to unreacted (meth) acrylic acid ester components, initiator residues and decomposition products thereof, or low molecular weight additives, but oligomers and / or polymers having radical polymerizable groups , (Meth) acrylic acid esters and a photopolymerization initiator are contained, and sufficient curing can be performed according to predetermined curing conditions and methods, thereby allowing the above-mentioned range. In order to reduce the mass by less than 0.1% by mass, a drying (decompression) step of the cured product is required, resulting in an increase in cost. When it is greater than 2.0% by mass, the volatile component bleeds out to the cured product surface. In addition, errors may increase during reading of recorded information due to a change in the thickness of the protective layer, or the long-term storage stability of the optical disk may deteriorate. That is, when the weight loss is 0.2% by mass or more and 2.0% by mass or less, for example, in optical disks, not only does the surface accuracy decrease with time and the storage stability is improved, but it is also used in automobiles. And can be saved.

  The cured product obtained by curing the curable resin composition of the present invention preferably has a storage elastic modulus E at 25 ° C. of 10 MPa to 150 MPa. More preferably, it is 10 MPa or more and 120 MPa or less, and most preferably 20 MPa or more and 100 MPa or less. The storage elastic modulus E is a value obtained by dynamic viscoelasticity measurement using the cured product obtained in the same manner as described above. A cured product having a storage elastic modulus of E10 MPa or more and 150 MPa or less could be obtained by sufficiently curing the curable resin composition under a predetermined curing condition or curing method. When the storage elastic modulus E is less than 10 MPa, the long-term storage stability of the optical disk may be deteriorated. In particular, there are dents. Further, when the storage elastic modulus is larger than 150 MPa, the warp of the obtained optical disk may increase or the long-term storage stability may deteriorate.

  The cured product obtained by curing the curable resin composition of the present invention preferably has a loss tangent tan δ at 25 ° C. of 0.10 to 0.70. More preferably, it is 0.10 or more and 0.60 or less, and most preferably 0.10 or more and 0.40 or less. The loss tangent tan δ is a value obtained by dynamic viscoelasticity measurement in the same manner as the storage elastic modulus E. The same measurement conditions are used. When the loss tangent tan δ is larger than 0.70, the long-term storage stability of the optical disk may be deteriorated. In particular, there are dents. On the other hand, if it is smaller than 0.10, the warp of the obtained optical disk may increase or the long-term storage stability may deteriorate.

  The cured product obtained by curing the curable resin composition of the present invention preferably has a glass point transition temperature of 0 ° C. or higher and 30 ° C. or lower. More preferably, it is 5 ° C. or higher and 30 ° C. or lower, and most preferably 10 ° C. or higher and 30 ° C. or lower. The glass point transition temperature is a value obtained by dynamic viscoelasticity measurement similar to the storage elastic modulus E, and the temperature of the maximum tan δ value is adopted. The measurement conditions are the same as the storage elastic modulus E. When the glass point transition temperature is higher than 30 ° C., the warp of the optical disk may increase. On the other hand, when the temperature is lower than 0 ° C., the optical disk may be recessed, and the long-term storage stability may be deteriorated.

  The cured product obtained by curing the curable resin composition of the present invention has a thickness of 20 to 150 μm. This thickness is preferably 20 to 120 μm, and more preferably 30 to 105 μm. That is, the upper limit of the thickness of the cured product obtained from the composition of the present invention is 150 μm or less, preferably 120 μm or less, more preferably 105 μm or less. On the other hand, the lower limit is 20 μm or more, preferably 30 μm or more.

≪Optical disc≫
The optical disk of the present invention can be obtained by having a protective layer formed by curing the curable resin composition for an optical disk of the present invention on a reflective film formed on a substrate. Among the optical disk manufacturing methods of the present invention, a conventionally known optical disk manufacturing method is used except for the protective layer manufacturing method. In the present invention, the term “on the reflective film” means not only a mode in which a protective layer is directly laminated on the reflective film, but also a functional layer such as a recording layer or a dielectric layer laminated on the reflective film, and the protective layer is protected on that functional layer. The form by which a layer is laminated | stacked is also meant. Further, in order to increase the recording capacity of the disc, a disc having a multilayer structure having two or more information recording layers has been created. An intermediate layer obtained by curing a transparent ultraviolet curable resin with ultraviolet rays is formed between the information recording layers. The composition of the present invention is suitable for forming a protective layer in an optical disc, but may be used as an ultraviolet curable resin for this intermediate layer. Examples of the optical disc of the present invention include a Blu-ray disc. Protective layers for Blu-ray discs generally have low warpage (low shrinkage), transparency (light transmission), adhesion to polycarbonate substrates, low corrosivity, recyclability, and fast curability (productivity) ), Dimensional stability (change in warpage during accelerated test, residual film property, small amount of permanent deformation such as dents) and the like are required. The optical disk of the present invention satisfies all the above characteristics. In addition, this invention is not limited to embodiment mentioned above, A various change is possible in the range shown to the claim. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  In the present invention, when further performance improvement is required, a layer such as an antistatic layer, a water repellent layer, an oil repellent layer, or a hard coat layer may be formed on the protective layer.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by the following examples and comparative examples, and is suitable within a range that can meet the purpose described above and below. It is also possible to carry out with modification, and they are all included in the technical scope of the present invention.

≪Evaluation method≫
<Viscosity>
Values obtained by measuring the obtained curable resin composition using a B-type viscometer (model “RB80L”: manufactured by Toki Sangyo Co., Ltd.) under a temperature of 25 ° C. were used.
<Transparency of protective layer>
Only the protective layer (cured film of the composition) was peeled off from the obtained substrate / protective layer laminate with a predetermined size, and the light transmittance at 405 nm was measured with a spectrophotometer (model UV-3100, manufactured by Shimadzu Corporation). ). Air was employed as a blank. Next, the calculated light transmittance value was evaluated according to the following criteria.
A: The transmittance is 89% or more. B: The transmittance is 85% or more. X: The transmittance is less than 85%.
<Weight loss>
Only the protective layer (cured film of the composition) is peeled off from the obtained substrate / protective layer laminate at a predetermined size, and the weight loss (%) before and after the heating acceleration test (held in an oven at 70 ° C. for 100 hours) Was calculated by (mass before test−mass after test) / mass before test × 100. Next, the calculated light transmittance value was evaluated according to the following criteria.
A: Weight loss is 1.0% or less. O: Weight loss is 2.0% or less. X: Weight loss is 2.0 or more.
<Residual film properties>
The thickness of the protective layer before and after the heating acceleration test (held in an oven at 70 ° C. for 100 hours) was measured using a laser focus displacement meter, and the remaining film ratio (%) was determined (film thickness after heating acceleration test / heating acceleration). The film thickness before the test × 100) was calculated, and the remaining film property was evaluated according to the following criteria.
○: Remaining film ratio is 98.0% or more and less than 102% ×: Remaining film ratio is less than 98.0% or 102% or more <Initial warpage increase>
The obtained substrate / protective layer laminate was placed on a horizontal glass plate so that the protective layer (cured film of the composition) was on the upper surface side, and then the warp of the laser displacement reading method manufactured by Nippon Shokubai Co., Ltd. Using an angle measuring device, the radial tilt value at a radius of 58 mm was measured in an environment of a temperature of 25 ° C. and a relative humidity of 50%. As the initial warpage increase amount, the warpage change amount before and after coating was adopted.
<War increase after heating acceleration test>
The obtained substrate / protective layer laminate was held for 100 hours in an environment of 80 ° C. and 85% relative humidity, and further warped when left in an environment of 25 ° C. and 50% relative humidity for 48 hours. The radial tilt value was measured in the same manner as the initial warpage increase. Thereby, the amount of warpage increase before and after the heating acceleration test was obtained.
<Increase in warpage after cold test>
The obtained substrate / protective layer laminate was measured for a radial tilt value in the same manner as the initial amount of warpage when the warpage value when left for 30 minutes in a thermostatic chamber at 0 ° C. was measured. Thereby, the amount of warpage increase after the cold test was determined.
<Overall evaluation of warpage>
Evaluation was made on the basis of the following criteria based on the warpage amount A obtained by adding the initial warpage increase amount and the warpage increase amount after the heating acceleration test, and the warpage amount B obtained by adding the initial warpage increase amount and the warpage increase amount after the cold test.
○: Both A and B are less than 0.8 ° Δ: Either A or B is 0.8 ° or more ×: Both A and B are 0.8 ° or more
If there is a warp of 0.8 ° or more, there is a risk that it will be difficult to improve the warp within the warp specification even if the manufacturing process is devised or the transparent cover resin is improved.
<Storage elastic modulus E at 25 ° C.>
The protective layer (cured film of the composition) or the cured product layer is peeled off from the obtained substrate / protective layer laminate or the substrate / oligomer or polymer cured product laminate, and dynamic viscoelasticity measurement by TA Instruments is performed. Measurement was performed under the following measurement conditions using the apparatus RSAIII.
(1) Sample size: width 8mm, length 50mm
(2) Clamp distance 25mm
(3) Measurement mode: Pull (4) Frequency: 1 Hz
(5) Width: 0.1%
(6) Temperature rising rate: 5 ° C./minute Dynamic viscoelasticity was measured, and the obtained value of the storage elastic modulus E at 25 ° C. was adopted.
<Loss tangent tan δ at 25 ° C.>
The value obtained by the same measurement method and conditions as the storage elastic modulus E at 25 ° C. was adopted.
<Glass point transfer temperature Tg>
A value obtained by the same measurement method and conditions as the storage elastic modulus E at 25 ° C., and the temperature of the maximum tan δ value was adopted.
<Permanent deformation amount>
Using the obtained substrate / protective layer laminate, using a micro-compression tester (manufactured by Shimadzu Corporation, model MCT-W500), the test conditions were as follows: use indenter 50 μm diameter, load speed 20 mN / sec, maximum load 300 mN, A value obtained by measuring the amount of deformation remaining in the substrate / protective layer laminate when the holding time at the maximum load was 90 seconds, the unloading speed was 20 mN / sec, and the holding time after complete unloading was 90 seconds was adopted. In this test, when the amount of permanent deformation exceeds 1 μm, reading errors due to laser light are likely to occur due to dents or the like, and the long-term storage stability may be poor.
≪Production Example 1≫
150 g of ethyl acetate was added to a four-necked flask equipped with a stir bar, thermometer, dropping line, and nitrogen / air mixed gas introduction tube, and the temperature was raised to 50 ° C. After the temperature rise, a mixture of 100 g of 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA, Nippon Shokubai Co., Ltd.) and 100 g of cyclohexyl vinyl ether (CHVE), and a mixed solution of 25 g of ethyl acetate and 13 mg of phosphotungstic acid , Each was added dropwise over 3 hours for polymerization. After completion of the polymerization, the reaction was terminated by adding triethylamine. Subsequently, after concentrating with an evaporator, the vinyl polymer P (VEEA-CHVE) was obtained. The reaction rate of the monomer is 99.5% by analyzing the mixed solution after the reaction is stopped by gas chromatography (GC), and the ethyl acetate content is 0.1%. There was found. Moreover, the number average molecular weight (Mn) of the obtained vinyl polymer was 2360, and molecular weight distribution (Mw / Mn) was 1.64.

Table 1 shows the glass transition temperature and the elastic modulus at 25 ° C. of the cured product of the oligomer and / or polymer having a radical polymerizable group used in the examples. Table 1 also shows the average acrylyl equivalent of (meth) acrylic acid esters.
Example 1
40 parts by mass of urethane acrylate as an oligomer (trade name “purple light UV-6640B”, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), diacrylate of 10 mol of bisphenol A ethylene oxide adduct as a (meth) acrylic acid ester (trade name “SR” -602 ", manufactured by Sartomer Co., Ltd., average molecular weight of 776) 20 parts by mass and diacrylate of ε-caprolactone 2-mol adduct of hydroxypivalic acid neopent glycol (trade name“ HX-220 ”, manufactured by Nippon Kayaku Co., Ltd.) 25 parts by mass, 15 parts by mass of 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), oligo {2-hydroxy-2-methyl-1- [4- (1- Methylvinyl) phenyl] propanone} (trade name “Escure ONE”, manufactured by Lamberti) Parts were mixed and stirred to prepare an optical disc curable resin composition.

Next, a curable resin composition for an optical disk was applied on a polycarbonate substrate having a thickness of 1 mm and dimensions of 120 mm × 120 mm with a spin coater at a thickness of 100 μm. The obtained polycarbonate substrate was cured by irradiation 15 times at a lamp height of 2 cm using a UV irradiator having a xenon flash UV lamp (model RC-742 manufactured by Xenon, USA). In addition, the irradiation integrated light quantity in 320-390 nm was about 0.6 J / cm < ² >. The thickness of the protective layer was 100 ± 2 μm. Table 1 shows the evaluation results of the obtained curable resin composition and laminate.
<< Other Examples and Comparative Examples >>
In the same manner as in Example 1, the components were mixed and stirred at the ratios shown in Tables 1 and 2 to obtain a curable resin composition for optical disks. The obtained composition was evaluated by the above evaluation method. The evaluation results are shown in Table 1. Abbreviations in Table 1 are as follows.
UV-6640B: urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
UV-6100B: urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
UV-7000B: urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
CN-981: Urethane acrylate (Sartomer Co., Ltd.)
CN-978: Urethane acrylate (Sartomer Co., Ltd.)
CN-991: Urethane acrylate (Sartomer Co., Ltd.)
P (VEEA-CHVE): Vinyl polymer of Production Example 1 IB-XA: Isobornyl acrylate (trade name “Light acrylate IB-XA”, manufactured by Kyoeisha Chemical Co., Ltd.)
DCP-A: Tricyclodecane diacrylate (trade name “Light acrylate DCP-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
Bis4EO-A: Diacrylate of ethylene oxide 4 mol adduct of bisphenol A (trade name “Light acrylate BP-4EA”, manufactured by Kyoeisha Chemical Co., Ltd.)
Bis10EO-A: Diacrylate of ethylene oxide 10 mol adduct of bisphenol A (trade name “SR-602”, manufactured by Sartomer Co., Ltd.)
・ PEGDA-9: Polyethylene glycol diacrylate (manufactured by Nippon Shokubai)
HX-220: Diacrylate of ε-caprolactone 2-mol adduct of hydroxypivalic acid neopen glycol (trade name “Kayarad HX-220”, manufactured by Nippon Kayaku Co., Ltd.)
HX-620: Diacrylate of ε-caprolactone 4 mol adduct of hydroxypivalic acid neopenglycol (trade name “Kayarad HX-620”, manufactured by Nippon Kayaku Co., Ltd.)
HPP-A: hydroxypivalic acid neopen glycol diacrylate (trade name “Light acrylate HPP-A”, manufactured by Kyoeisha Chemical Co., Ltd.)
VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
TMP-6EO-A: Triacrylate of trimethylolpropane ethylene oxide 6 mol adduct (trade name “SR-499”, manufactured by Sartomer Co., Ltd.)
TMP-9EO-A: Triacrylate of trimethylolpropane ethylene oxide 9 mol adduct (trade name “SR-502”, manufactured by Sartomer Co., Ltd.)
Irg184: 1-hydroxy-cyclohexyl-phenyl-ketone (trade name “Irgacure 184”, manufactured by Ciba Specialty Chemicals Co., Ltd.)
Esacure-one oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone}
(Product name "Esacure ONE", manufactured by Lamberti)

  The curable resin composition for an optical disc of the present invention has transparency and suppresses warpage of the entire optical disc, and further has long-term storage stability (low warpage and high temperature environment in a storage test under a high temperature environment and a low temperature environment). It is possible to use for an optical disc, for example, a Blu-ray disc, which is excellent in the residual film property below and the amount of permanent deformation such as dents).

Claims (4)

A curable resin composition used for an optical disc having a reflective film that is present on a substrate and reflects a laser beam for reading information, and a protective layer that is present on the reflective film and has a thickness of 20 to 150 μm. And (a) an oligomer having a radical polymerizable group having a glass transition temperature of −10 to 45 ° C. and an elastic modulus at 25 ° C. of 50 to 900 MPa in the curable resin composition and / or The polymer contains 20 to 70% by mass, (b) 30 to 80% by mass of (meth) acrylic acid esters having an average acrylic equivalent other than 280 to 500a, and (c) a photopolymerization initiator. A curable resin composition for optical discs.   2. The curable resin composition for an optical disk according to claim 1, wherein a diacrylate of an alkylene oxide adduct of bisphenol A having a molecular weight of 550 or more is used as the (meth) acrylic acid esters (b). .   The curable resin composition for an optical disc according to claim 1 or 2, wherein the curable resin composition has a viscosity at 25 ° C of from 800 to 3500 mPa · s.   An optical disc comprising a protective layer formed by curing the curable resin composition for an optical disc according to claim 1.