WO2010143568A1 - Optical disc and ultraviolet-curable composition for intermediate layer of optical disc - Google Patents

Abstract

Disclosed is an optical disc comprising a substrate and, successively formed thereon, at least a first light-reflecting layer, an intermediate layer comprising a cured film formed of a ultraviolet-curable composition, a second light-reflecting layer and a light-transmitting layer, wherein the intermediate layer comprising a cured film formed of a ultraviolet-curable composition is laminated directly on the second light-reflecting layer and a blue laser beam is inputted from the light-transmitting layer side to regenerate data. By this optical disc, wherein the cured film of the ultraviolet-curable composition constituting the intermediate layer, that is equipped with the second light-reflecting layer laminated thereon, shows a weight loss of 3.5 mass% or less when cured with ultraviolet light and then allowed to stand in an environment at 110°C for 1 hour, appropriate signal characteristics can be maintained even in a high-temperature environment.

Description

Optical disk and ultraviolet curable composition for optical disk intermediate layer

The present invention provides an optical disc that has at least two or more light reflecting layers and performs recording or reproduction with a semiconductor laser (hereinafter referred to as a blue laser) having an oscillation wavelength in the range of 370 nm to 430 nm, and the light reflecting layer. The present invention relates to an ultraviolet curable composition suitable for an intermediate layer.

A DVD (Digital Versatile Disc), which is the mainstream as an optical disk capable of high density recording, has a structure in which two substrates with a thickness of 0.6 mm are bonded together with an adhesive. In order to achieve high density in a DVD, a 650 nm laser having a shorter wavelength is used compared to a CD (Compact Disc), and the optical system has a high numerical aperture.

However, it is necessary to further increase the density in order to record or reproduce high-definition video or the like corresponding to HDTV (high definition television). High-density recording methods and optical discs for the next generation of DVD have been studied, and high-density recording using a new optical disc structure using a blue laser with a shorter wavelength and a high numerical aperture optical system than DVD. A scheme has been proposed. Even in such a high-density recording type optical disk, a multilayer optical disk having two or more information recording portions is required in order to realize further higher density.

In a high-density recording type multi-layer optical disc, a concavo-convex pattern such as pits and grooves is usually formed on a substrate, and a light reflecting layer is laminated on the substrate to form a first information recording portion. An intermediate layer is provided on the recording layer with a cured film of an ultraviolet curable composition or the like, and a second unevenness pattern is formed on the intermediate layer to provide a second information recording portion.

In such a multilayer optical disc, the intermediate layer on which the concave / convex pattern is provided is composed of, for example, an ultraviolet curable composition containing a trifunctional or higher functional urethane (meth) acrylate and a tetrafunctional or higher functional polyfunctional (meth) acrylate. (Refer to Patent Document 1), or composed of an ultraviolet curable composition containing a specific amount of polyfunctional (meth) acrylate, monofunctional (meth) acrylate, alicyclic (meth) acrylate and methacrylate (refer to Patent Document 2) Is disclosed.

The intermediate layer made of these ultraviolet curable compositions has a very good releasability and is preferably a composition capable of forming an uneven pattern such as pits and grooves, and is formed from the intermediate layer made of the composition. An optical disk exhibits suitable signal characteristics. However, when applied to an optical disk that is recorded or reproduced by a blue laser, the signal characteristics may be deteriorated in a high temperature environment.

Japanese Patent No. 4193916 Japanese Patent No. 4247696

The problem to be solved by the present invention is to provide an optical disc capable of suitably maintaining signal characteristics even in a high temperature environment.

Furthermore, it is possible to provide an ultraviolet curable composition capable of suppressing the generation of volatile components even in a high temperature environment, providing an optical disc capable of suitably maintaining signal characteristics, and capable of forming an intermediate layer having good peelability from a stamper. It is in.

In the present invention, the substrate has at least a first light reflection layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflective layer, and a light transmission layer in this order, and the ultraviolet curable composition An optical disc in which an intermediate layer composed of a cured film of an object is directly laminated with the second light reflecting layer and reproduces information by entering a blue laser from the light transmitting layer side, wherein the second light reflecting layer The cured film of the ultraviolet curable composition forming the intermediate layer on which is laminated has a weight reduction rate of 3.5% by mass or less when left in an environment of 110 ° C. for 1 hour after ultraviolet curing. An optical disc is provided.

The present invention further includes, on the substrate, at least a first light reflection layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflection layer, and a light transmission layer in this order. An intermediate layer made of a cured film of a curable composition is directly laminated with the second light reflecting layer, and the second cured film of the optical disc that reproduces information by injecting a blue laser from the light transmitting layer side. An ultraviolet curable composition to be formed, comprising an ultraviolet curable compound and a polymerization initiator, wherein the content of the polymerization initiator with respect to 100 parts by mass of the ultraviolet curable compound is 2 to 10 parts by mass, and the molecular weight is Provided is an ultraviolet curable composition for an optical disc intermediate layer, wherein the content of a polymerization initiator of 215 or less is 5% by mass or less.

The optical disc of the present invention hardly deteriorates signal characteristics even in a high temperature environment, and can suitably reproduce a signal. In addition, according to the ultraviolet curable composition for an optical disc intermediate layer of the present invention, since generation of volatile components can be suppressed even under a high temperature environment, there is little pollution to the environment and the releasability from the stamper is good. Furthermore, since the weight loss due to the generation of volatile components can be suppressed, it is possible to realize an optical disc that can suitably maintain signal characteristics even in a high temperature environment.

The optical disk of the present invention comprises, on the substrate, at least a first light reflecting layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflecting layer and a light transmitting layer in this order, and the ultraviolet curable type An intermediate layer made of a cured film of the composition is directly laminated with the second light reflecting layer, and is an optical disc that reproduces information by injecting a blue laser from the light transmitting layer side, and the second light reflecting layer The cured film of the ultraviolet curable composition forming the intermediate layer on which is laminated is an optical disc having a weight reduction rate of 3.5% by mass or less when left in a 110 ° C. environment for 1 hour after ultraviolet curing. In the present specification, (meth) acrylate refers to acrylate or methacrylate, and similarly, (meth) acryloyl group refers to acryloyl group or methacryloyl group. The intermediate layer is a layer that is provided in a portion other than the surface layer of the optical disc and has other layers on the front and back surfaces.

[substrate]
As the substrate used in the optical disk of the present invention, a disk-shaped circular resin substrate can be used, and polycarbonate can be preferably used as the resin. When the optical disk is read-only, pits for recording information on the substrate are formed on the surface laminated with the light reflecting layer. When used as a Blu-ray disc for reading information with a blue laser having a laser light oscillation wavelength of 370 to 430 nm, a substrate having a thickness of about 1.1 mm can be used.

[Light reflection layer]
As the light reflecting layer used in the optical disk of the present invention, both the first light reflecting layer and the second light reflecting layer may be any one that can reflect a laser beam and form an optical disk that can be recorded and reproduced. For example, a metal such as gold, copper, or aluminum or an alloy thereof, or an inorganic compound such as silicon can be used. Of these, silver or an alloy containing silver as a main component is preferably used because of the high reflectance of light in the vicinity of 400 nm. The thickness of the light reflecting layer is preferably about 10 to 60 nm. In addition, when a third, fourth, etc. light reflecting layer is provided by further multilayering of the optical disk, the same light reflecting layer can be suitably used.

[Middle layer]
In the optical disk of the present invention, a cured film of an ultraviolet curable composition is provided as an intermediate layer provided between the first light reflecting layer and the second light reflecting layer and directly laminated with the second light reflecting layer. Having an intermediate layer. The intermediate layer on which the second light reflecting layer is laminated is an intermediate layer on which a concave and convex pattern such as pits and grooves is formed on the surface, and is a layer that forms an information recording site together with the second light reflecting layer. . When the optical disc is read-only, pits for recording information are provided on the surface of the intermediate layer.

In the present invention, as the intermediate layer on which the second light reflection layer is laminated, the weight reduction rate when left in a 110 ° C. environment for 1 hour after ultraviolet curing is 3.5% by mass or less, preferably 3. A cured film of an ultraviolet curable composition of 0% by mass or less, more preferably 2.5% by mass or less is used. By setting the weight reduction rate of the cured film of the ultraviolet curable composition used for the intermediate layer in this range, signal characteristics are hardly deteriorated even in a high temperature environment, and signal reproduction can be suitably performed.

The weight reduction rate after standing for 1 hour in a 110 ° C. environment after UV curing can be measured according to ASTM Designation: D5403.
In ASTM D5403, the weight loss rate after standing for 1 hour in a 110 ° C. environment after UV curing is expressed as Potential Volatiles, and is determined from the following equation.
Potential Volatiles = 100 [(CD) / (BA)]
Here, A: weight of glass substrate, B: glass substrate + intermediate layer before curing, C: glass substrate + intermediate layer after curing, D: glass substrate + intermediate layer after standing for 1 hour in 110 ° C. environment .

The cured film of the ultraviolet curable composition forming the intermediate layer on which the second light reflecting layer is laminated preferably has an elastic modulus at 25 ° C. of 800 to 3000 MPa, and more preferably 1500 to 2500 MPa. By setting the elastic modulus of the cured film used for the intermediate layer within the above range, the disk can be easily peeled off from the stamper and has a small warpage during curing.

As the ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated, a composition containing an ultraviolet curable compound and a polymerization initiator and capable of obtaining a cured film having the above characteristics. The UV-curable compound may be used as a UV-curable compound (meth) acrylate having three or more (meth) acryloyl groups in one molecule (hereinafter abbreviated as trifunctional (meth) acrylate) or in one molecule. (Meth) acrylate having two (meth) acryloyl groups (hereinafter abbreviated as bifunctional (meth) acrylate), (meth) acrylate having one (meth) acryloyl group in one molecule (Meth) acrylate monomers such as monofunctional (meth) acrylate), and (meth) such as epoxy (meth) acrylate and urethane (meth) acrylate The chestnut rate oligomers can be used.

Examples of the tri- or higher functional (meth) acrylate used in the present invention include bis (2-acryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-acryloyloxypropyl) hydroxypropyl isocyanurate, and bis (2-acryloyloxy). Butyl) hydroxybutyl isocyanurate, bis (2-methacryloyloxyethyl) hydroxyethyl isocyanurate, bis (2-methacryloyloxypropyl) hydroxypropyl isocyanurate, bis (2-methacryloyloxybutyl) hydroxybutyl isocyanurate, tris (2- Acryloyloxyethyl) isocyanurate, tris (2-acryloyloxypropyl) isocyanurate, tris (2-acryloyloxybutyl) isocyanurate Tris (2-methacryloyloxyethyl) isocyanurate, tris (2-methacryloyloxypropyl) isocyanurate, tris (2-methacryloyloxybutyl) isocyanurate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropanetetra (meth) ) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 3 moles of ethylene oxide per mole of trimethylolpropane or Diol or tri (meth) acrylate of triol obtained by adding propylene oxide, poly (meth) acrylate of dipentaerythritol Polyfunctional (meth) acrylates such as bets, and the like can be used.

Among them, trifunctional (meth) acrylate can be preferably used, and triol di- or tri (meth) acrylate obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane is an elastic property after curing. It is more preferable because the rate can be adjusted high.

Examples of the bifunctional (meth) acrylate include 1,4-butanediol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, and 1,6-hexanediol di (meth) acrylate. Neopentyl glycol di (meth) acrylate, 2-methyl-1,8-octanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, ethylene glycol di ( Obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol Gio Di (meth) acrylate, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkyl phosphate di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (Meth) acrylate, polyether (meth) acrylate, diethylaminoethyl (meth) acrylate, and (meth) acrylate having an alicyclic structure include alicyclic bifunctional (meth) acrylate, norbornane dimethanol di (meth) ) Acrylate, norbornane diethanol di (meth) acrylate, norbornane dimethanol, 2 mol of ethylene oxide or propylene oxide, di (meth) acrylate Didecane (meth) acrylate, pentacyclopentadecane dimethanol obtained by adding 2 mol of ethylene oxide or propylene oxide to rhodecane dimethanol di (meth) acrylate, tricyclodecane diethanol di (meth) acrylate, tricyclodecane dimethanol Di (meth) acrylate, pentacyclopentadecanediethanol di (meth) acrylate, di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to pentacyclopentadecanedimethanol, ethylene oxide or pentacyclopentadecanediethanol Di (meth) acrylate of diol obtained by adding 2 mol of propylene oxide, dimethylol dicyclopentane di (meth) acrylate, hydroxy Pivalaldehyde modified trimethylolpropane di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, ethylene oxide modified bisphenol A di (meth) acrylate, propylene oxide modified bisphenol A di (meth) acrylate, etc. can be used. .

Of these, dipropylene glycol di (meth) acrylate is particularly preferable.

Further, ultraviolet curable compounds such as N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl ether monomer, and phosphate group-containing (meth) acrylate can be used as necessary.

Examples of monofunctional (meth) acrylates include ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl. (Meth) acrylate, isoamyl (meth) acrylate, isodecyl (meth) acrylate, isostearyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-chloro-2-hydroxypropyl ( Aliphatic (meth) acrylates such as (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, 2- Roxy-3-phenoxypropyl (meth) acrylate, phenoxyethyl (meth) acrylate, aromatic (meth) acrylate such as benzyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, di Cyclopentenyloxyethyl (meth) acrylate, tetracyclododecanyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, alicyclic (meth) acrylate such as glycidyl (meth) acrylate, caprolactone modified tetrahydro Furfuryl (meth) acrylate, acryloylmorpholine, isobornyl (meth) acrylate, norbornyl (meth) acrylate, 2- (meth) acryloyloxymethyl-2 Methyl Bicycloheptane adamantyl (meth) acrylate, and the like can be used.

As an ultraviolet curable compound in the ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated, a (meth) acrylate monomer having three or more (meth) acryloyl groups in one molecule is ultraviolet. A composition containing 40 to 80% by mass in the ultraviolet curable compound contained in the curable composition and containing 10% by mass or less of a (meth) acrylate monomer having one (meth) acryloyl group in one molecule. The product is preferable because it is easy to adjust the weight reduction rate, elastic modulus, or viscosity range.

The content of trifunctional (meth) acrylate is more preferably 50 to 70% by mass. Further, the content of the monofunctional (meth) acrylate is more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

Further, a (meth) acrylate oligomer may be used in combination with these monomer components. The (meth) acrylate oligomer is not particularly limited, and various urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) acrylates, and polyether (meth) acrylates can be used. Among these, urethane (meth) acrylate and epoxy (meth) acrylate can be preferably used because the (meth) acryloyl group concentration of the ultraviolet curable composition and the elastic modulus after curing are easily adjusted to a suitable range. Among these, when urethane (meth) acrylate is used, the number of cross-linking points, distance between cross-linking points, and cross-linking structure of the cured film can be suitably controlled, and curing with less change in shape such as warping can be achieved by imparting appropriate flexibility to the cured film. A film can be formed.

The urethane (meth) acrylate used in the present invention includes a compound having two or more isocyanate groups in the molecule, a compound having a hydroxyl group and a (meth) acryloyl group, and two or more hydroxyl groups in the molecule. A urethane (meth) acrylate obtained from a compound having a diol can be preferably used. Further, urethane (meth) acrylate obtained by reacting a compound having a hydroxyl group and a (meth) acryloyl group with a compound having two isocyanate groups in the molecule can also be preferably used.

Examples of compounds having two or more isocyanate groups in the molecule include tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, bis (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, bis (isocyanatocyclohexyl) methane, and isophorone. Examples thereof include polyisocyanates such as diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and m-phenylene diisocyanate. Among them, a diisocyanate compound having two isocyanate groups in the molecule can be preferably used, and tolylene diisocyanate is particularly preferable because it does not deteriorate the hue and does not decrease the light transmittance.

Examples of the compound having a hydroxyl group and a (meth) acryloyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and these (meth) acrylates and 2 A compound obtained by reacting with a compound having at least one hydroxyl group may also be used. Alternatively, it may be a compound obtained by reacting a compound having two or more hydroxyl groups with (meth) acrylic acid. For example, an addition reaction product of a glycidyl ether compound and (meth) acrylic acid, or a mono (meth) glycol compound (meta) ) Acrylate and the like.

Polyols are preferably used as the compound having two or more hydroxyl groups, and specific examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3- Propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,5-pentanediol, eopentyl 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, sorbitol, mannitol, glycerin, 1, - dimethylolcyclohexane, 1,3-dimethylolcyclohexane, polymer polyol as multimers such as alkylene polyols such as 1,4-dimethylol cyclohexane.

Among them, polyether polyols having ether bonds, polyester polyols having ester bonds obtained by reaction with polybasic acids and ring-opening polymerization of cyclic esters, or polycarbonate polyols having carbonate bonds obtained by reaction with carbonates. Preferably there is. At least a part of these polyols, preferably 15 mol% or more in the total amount of polyols, more preferably 30 mol% or more in the total amount of polyols, preferably has a molecular weight of 500-2500.

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 polyol, propylene oxide, 1 , 2-butylene oxide, 1,3-butylene oxide, 2,3-butylene oxide, tetrahydrofuran, styrene oxide, an adduct of alkylene oxide such as epichlorohydrin, and the like.

Examples of the polyester polyol include a reaction product of the above polyols with a polybasic acid such as maleic acid, fumaric acid, adipic acid, sebacic acid, and phthalic acid, and a ring-opening polymer of a cyclic ester such as caprolactone. Examples include polycaprolactone.

Examples of the polycarbonate polyol include the above polyols and alkylene carbonates such as ethylene carbonate, 1,2-propylene carbonate, and 1,2-butylene carbonate, or diphenyl carbonate, 4-methyldiphenyl carbonate, 4-ethyldiphenyl carbonate, 4-propyldiphenyl carbonate, 4,4'-dimethyldiphenyl carbonate, 2-tolyl-4-tolyl carbonate, 4,4'-diethyldiphenyl carbonate, 4,4'-dipropyldiphenyl carbonate, phenyltoluyl carbonate, bischlorophenyl carbonate Diaryl carbonates such as phenyl chlorophenyl carbonate, phenyl naphthyl carbonate, dinaphthyl carbonate, etc. Dialkyl carbonate such as dicarbonate, 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. Examples include reactants.

The polyol to be used may be one kind or two or more kinds may be used in combination, but urethane (meth) acrylate using two or more kinds of polyether polyol, polyester polyol and polycarbonate polyol is preferable, and two kinds are used in combination. More preferably. By using these polyols in combination, it becomes easy to suitably adjust the deformation resistance and surface hardness of the obtained cured film in a high temperature and high humidity environment. As an example of two types of combined use, in the case of increasing the surface hardness, the combined use of polyester polyol and polycarbonate polyol is preferable, and in the case of improving the heat and humidity resistance, it is preferable to use a polyether polyol in combination. . In order to achieve these intermediate characteristics, it is preferable to use a polyether polyol and a polycarbonate polyol in combination.

The content of each polyol when used in combination with the polyol is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, based on the total amount of polyol used. The polyester polyol content is preferably 10 to 70% by mass, more preferably 20 to 60% by mass. By making content of polyether polyol or polyester polyol into the said range, the surface hardness and heat-and-moisture resistant property of hardened | cured material are easy to be obtained.

In addition, the urethane (meth) acrylate used in the present invention is preferably a structure having no aromatic ring, since the transparency becomes high.

As urethane (meth) acrylate used in the present invention, polyether skeleton urethane acrylate, DIC Corporation FAU-742TP, FAU-306, polyester skeleton urethane acrylate, Cognis Japan Co., Ltd. Photomer Preferred examples include -6892 and Ebecryl-8405 manufactured by Daicel Cytec Co., Ltd.

The content of urethane (meth) acrylate in the ultraviolet curable composition of the present invention is preferably 20% by mass or less in the ultraviolet curable compound contained in the ultraviolet curable composition, and is preferably 5 to 15% by mass. It is particularly preferred. By setting the urethane (meth) acrylate content in the above range, it is possible to impart an appropriate flexibility to the cured film, and in particular, a change in warp when a humidity shock is applied becomes small.

The molecular weight (Mw) measured by gel permeation chromatography (GPC) of urethane (meth) acrylate used in the present invention is preferably 1000 to 20000, and more preferably 1500 to 10,000. Thereby, the durability and light resistance of the optical disk using the ultraviolet curable composition of the present invention are further improved. If the molecular weight is high, the viscosity becomes high and handling becomes difficult. On the other hand, when the molecular weight is low, the distance between cross-linking points is shortened, so that the curing shrinkage is increased. The GPC uses HLC-8020 manufactured by Tosoh Corporation, the column uses GMHxl-GMHxl-G200Hxl-G1000Hxlw, the solvent uses THF, and the column temperature is 40 ° C. at a flow rate of 1.0 ml / min. The detector temperature is 30 ° C., and the molecular weight is measured in terms of standard polystyrene.

When the urethane (meth) acrylate is used, it is used at 40% by mass or less in the ultraviolet curable compound contained in the ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated. It is particularly preferable that the content is 20% by mass or less. By setting the content of urethane (meth) acrylate within the above range, it is possible to impart appropriate flexibility to the cured film, and in particular, it is possible to realize a cured film with less warpage when the wet heat environment changes.

As the epoxy (meth) acrylate used in the present invention, any epoxy (meth) acrylate having the above characteristics can be used. For example, bisphenol type epoxy (meth) acrylate represented by the following formula (1) can be used.

(In the formula, Y represents —SO ₂ —, —CH ₂ —, —CH (CH ₃ ) — or —C (CH ₃ ) ₂ —, and each Z independently represents a hydrogen atom or —CH ₃ . , N represents 0 or an integer of 1 or more.

Examples of such bisphenol type epoxy (meth) acrylate include bisphenol A type epoxy resins such as Epicoat 802, 1001, and 1004 manufactured by Yuka Shell Epoxy, and bisphenol F type epoxy resins such as Epicoat 4001P, 4002P, and 4003P, ) Epoxy acrylate obtained by reaction with acrylic acid.

Among them, Y is -C (CH ₃₎ 2 _- a, more that n is bisphenol A type epoxy (meth) acrylate to the addition polymer of the structure is an integer of 0 or 1 to 6 and the main constituent preferable.

Moreover, epoxy (meth) acrylates such as hydrogenated bisphenol A type and bisphenol F type can also be suitably used.

The molecular weight (Mw) measured by gel permeation chromatography (GPC) of the epoxy (meth) acrylate used in the present invention is preferably 500 to 3000, more preferably 800 to 1500. By setting the structure and molecular weight of the epoxy (meth) acrylate within the above ranges, the durability and light resistance of the optical disk using the ultraviolet curable composition of the present invention are further improved. The GPC used was Sakai HLC-8020 manufactured by Tosoh Corporation, and the column used was GMHxl-GMHxl-G200Hxl-G1000Hxlw. The solvent used was THF, the column temperature was 40 ° C., the detector temperature was 30 ° C., and the molecular weight was measured in terms of standard polystyrene at a flow rate of 1.0 ml / min.

The ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated preferably has a B-type viscosity at 25 ° C. of 1000 mPa or less, particularly preferably 50 to 500 mPa. The thickness of the intermediate layer between the reflective films in the optical disk is formed with a thickness of about 5 to 30 μm. By setting the viscosity range, the intermediate layer with the thickness can be suitably formed.

Further, the (meth) acryloyl group concentration of the ultraviolet curable composition is preferably 4 to 10 mmol / g.

[Initiator]
In the ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated, the content of the polymerization initiator used with respect to 100 parts by mass of the ultraviolet curable compound contained in the ultraviolet curable composition. Is preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass. Moreover, it is preferable to make content of the polymerization initiator whose molecular weight is 215 or less into the said polymerization initiator into 5 mass parts or less, and it is still more preferable to set it as 4 mass parts or less. The polymerization initiator having a molecular weight exceeding 215 is preferably contained in an amount of 1 part by mass or more, more preferably 1 to 5 parts by mass, and more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the ultraviolet curable compound. It is particularly preferred. A polymerization initiator having a molecular weight of 215 or less may not be contained, but it is preferable to use 1 part by mass or more in combination with a polymerization initiator having a molecular weight exceeding 215 because stable signal characteristics can be easily obtained. In the present invention, by adjusting the polymerization initiator in the ultraviolet curable composition forming the intermediate layer on which the second light reflecting layer is laminated as described above, when exposed to high temperatures during the production process. However, it is difficult to reduce the weight of the optical disk, and stable signal characteristics can be obtained even in a high temperature and high humidity environment when the optical disk is formed. Further, it is possible to reduce the contamination of the exhaust equipment due to volatile components during the production of the optical disk.

Examples of the polymerization initiator having a molecular weight exceeding 215 include benzoin isobutyl ether, benzyl, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one. 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-hydroxy- 1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-Hydroxy-2-methyl-1-propan-1-one, phenylglyoxyl Molecular cleavage types such as acid methyl ester, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone, benzophenone, Examples include hydrogen abstraction-type photopolymerization initiators such as 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide, 2,4-diethylthioxanthone, and 2-isopropylthioxanthone.

Among them, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone And at least one selected from 2,4,6-trimethylbenzoyldiphenylphosphine can be preferably used. Also, since the curability is particularly good, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone and 2,4,6-trimethylbenzoyldiphenylphosphine It is preferable to use these, and it is particularly preferable to use these in combination.

Examples of the polymerization initiator having a molecular weight of 215 or less include 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin methyl ether, benzophenone, benzyl, phenyl Examples include glyoxylic acid methyl ester. Of these, 1-hydroxy-cyclohexyl-phenyl-ketone is preferably used in combination with a polymerization initiator having a molecular weight exceeding 215.

[Additive]
In the ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated, as necessary, a surfactant, a leveling agent, a thermal polymerization inhibitor, a hindered phenol, a phosphate, Antioxidants such as phyto, and light stabilizers such as hindered amines can also be used. Examples of sensitizers include trimethylamine, methyldimethanolamine, triethanolamine, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzylamine and 4,4′-bis (diethylamino) benzophenone or the like can be used, and further, an amine that does not cause an addition reaction can be used in combination with the photopolymerizable compound.

In the optical disc of the present invention, the intermediate layer made of the cured film of the ultraviolet curable composition on which the second light reflecting layer is laminated may be directly laminated with the first light reflecting layer. An intermediate layer composed of a cured film of an ultraviolet curable composition on which a light reflecting layer is laminated, and a second intermediate layer composed of a cured film of an ultraviolet curable composition between the first light reflecting layer and a first intermediate layer. It may be provided so as to be directly laminated with one light reflecting layer. In addition to the intermediate layer on which the second light reflecting layer is laminated, it has a second intermediate layer laminated on the first light reflecting layer, so that suitable pit formation and light reflecting layer and field adhesion can be achieved. Or, it becomes easy to suitably adjust a plurality of required characteristics such as suppression of warpage of the optical disk.

In the present invention, it is preferable to use an intermediate layer formed from a cured film of an ultraviolet curable composition as the second intermediate layer laminated with the first light reflecting layer. The cured film of the ultraviolet curable composition used for the first intermediate layer preferably has an elastic modulus at 25 ° C. of 500 to 3000 MPa, more preferably 1000 to 2000 MPa. By setting the elastic modulus of the cured film used for the second intermediate layer within the above range, the adhesive force with the first light reflecting layer is good, and the disc has a small warp during curing. The second intermediate layer is preferably 300 MPa or more, preferably 500 MPa or more lower than the intermediate layer on which the second light reflecting layer is laminated.

In addition, the thickness of the intermediate layer between the reflective films in the optical disk is formed with a thickness of about 5 to 30 μm. When the intermediate layer is composed of a plurality of layers, the second intermediate layer is By forming the second light reflection layer to be thicker than the intermediate layer on which the second light reflection layer is laminated, it becomes easy to reduce the warp suitably. Therefore, the thickness of the intermediate layer on which the second light reflecting layer is laminated is set to 10 μm or less, preferably 2 to 5 μm, and the thickness of the second intermediate layer is set to about 3 to 25 μm thicker than this. It is preferable.

The ultraviolet curable composition used for the second intermediate layer preferably has a B-type viscosity at 25 ° C. of 1000 mPa or less, particularly preferably 50 to 600 mPa. By setting the viscosity within the above range, an intermediate layer on which the second light reflecting layer is laminated can be suitably laminated on the second intermediate layer.

Further, it is preferable that the second intermediate layer has a higher surface tension than the intermediate layer on which the second light reflecting layer is laminated. Thereby, the intermediate layer in which the second light reflection layer is laminated on the first intermediate layer can be suitably applied.

The UV curable composition used for the second intermediate layer can be suitably used from the UV curable compounds listed as the UV curable compounds used for the intermediate layer on which the second light reflecting layer is laminated.

In particular, when the ultraviolet curable compound contains 40 to 80% by mass of a (meth) acrylate monomer having three or more (meth) acryloyl groups in one molecule and urethane (meth) acrylate is used, It is preferable that it is below mass%.

Further, the polymerization initiator to be used is not particularly limited, and various polymerization initiators listed as polymerization initiators used for the intermediate layer on which the second light reflecting layer is laminated can be used. The content of the polymerization initiator is preferably 2 to 10% by mass.

Also in the additives, those listed as additives used for the intermediate layer on which the second light reflecting layer is laminated can be suitably used.

[Light transmission layer]
In the optical disk of the present invention, a light transmission layer is formed directly on the second light reflection layer on the intermediate layer on which the second light reflection layer is laminated or via another layer. As the light transmission layer, it is preferable to efficiently transmit a blue laser having an oscillation wavelength of laser light of 370 to 430 nm, and a transmittance of 405 nm light is preferably 85% or more at a thickness of 100 μm. 90% or more is particularly preferable.

The thickness of the light transmission layer in the optical disk of the present invention may be appropriately adjusted according to the structure of the optical disk, and the total thickness of the intermediate layer and the light transmission layer formed in the optical disk is preferably 70 to 110 μm. The thickness of the light transmission layer is usually set to about 100 μm, but the thickness greatly affects the light transmittance and signal reading and recording, and therefore needs to be sufficiently managed. The light transmission layer may be formed of a single cured layer having the thickness or a plurality of layers may be laminated.

The light-transmitting layer in the optical disk of the present invention is less likely to warp during curing, and the error of the reproduction signal does not increase easily even when a load is applied for a long time, and the signal can be suitably reproduced by recovering the error over time. It is preferable to provide a simple optical disc.

As such a light transmission layer, for example, an elastic modulus (25 ° C.) obtained by pressing with a load of 100 mN using a Vickers indenter with a ridge angle of 136 ° is 1500 MPa or less, preferably 50 to 1300 MPa, more preferably 400. A light-transmitting layer having a pressure of ˜900 MPa, most preferably 400-600 MPa can be preferably used. The light transmission layer is less likely to warp during UV curing, and deformation is easily recovered even with a long-time load, so that information can be recorded / reproduced satisfactorily.

The elastic modulus using a Vickers indenter can be measured according to ISO standard ISO14577.
In ISO14577, the elastic modulus obtained by pressing a Vickers indenter with a ridge-to-ridge angle of 136 ° is expressed as indentation elastic modulus _EIT . The plastic deformation rate is expressed as indentation creep _CIT and is obtained from the following equation.

Here, h1: indentation depth when the load reaches 100 mN, h2: indentation depth when the load is held for 60 seconds after reaching the load of 100 mN.

As a measuring instrument according to ISO14577, measurement can be performed using a Fisherscope HM2000 manufactured by Fischer Instruments.

The light transmission layer used in the present invention preferably has a plastic deformation rate of 30 to 90% when pressed with a load of 100 mN and held for 60 seconds using a Vickers indenter with a ridge angle of 136 °, and 40 to It is more preferably 90%, particularly preferably 40 to 60%. By setting the plastic deformation rate within the above range, deformation caused by a long-time load is easily recovered with time.

The loss elastic modulus (E ″) at 60 ° C. in the dynamic viscoelastic spectrum measured at a frequency of 3.5 Hz of the light transmission layer is preferably 10 MPa or less, and preferably 0.1 to 7 MPa. More preferred is 1-7 MPa. . When the loss elastic modulus at 60 ° C. is in this range, the error of the reproduction signal hardly increases even when a load is applied for a long time, and the signal is preferably easily reproduced by recovering the error with time.

When measuring the dynamic viscoelastic spectrum, the light transmission layer was punched into a JIS K 7127 test piece type 5 shape with a dumbbell cutter, and this test piece was used to measure dynamic viscoelasticity manufactured by Rheometrics. It can be measured with an apparatus RSA-II (frequency 3.5 Hz, temperature rising rate 3 ° C./min).

Further, the loss tangent (tan δ) at 60 ° C. in the dynamic viscoelasticity spectrum measured above is preferably a light transmission layer of 0.25 or less, and preferably 0.01 to 0.20 or less. Particularly preferred. When the loss tangent at 60 ° C. is within this range, even when a load is applied for a long time, the error of the reproduction signal hardly increases, and the error is recovered over time, so that the signal reproduction is easily facilitated.

In addition, the intermediate layer and the light transmission layer of the optical disk of the present invention preferably efficiently transmit a blue laser having a laser light oscillation wavelength of 370 to 430 nm, and have a light transmittance of 405 nm at a thickness of 100 μm of 85. % Or more is preferable, and 90% or more is particularly preferable.

[Configuration of optical disc]
The optical disk of the present invention comprises, on the substrate, at least a first light reflecting layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflecting layer and a light transmitting layer in this order, and the ultraviolet curable type An optical disc in which an intermediate layer made of a cured film of the composition is directly laminated with the second light reflection layer, and information is reproduced by making a blue laser incident from the light transmission layer side.

The optical disc of the present invention may be either a reproduction-only disc or a recordable / reproducible disc. In the case of a read-only optical disc, information recording pits are provided on the substrate and an intermediate layer on which the second light reflecting layer is laminated. Specifically, a guide groove for tracking a laser beam called a recording track (groove), which is an information recording portion, is provided when a single circular resin substrate is injection-molded, and then on the substrate having the recording track. The first light reflecting layer, the intermediate layer composed of the cured film of the ultraviolet curable composition, and the second light reflecting layer are sequentially laminated, and at least the light transmitting layer is provided on the second light reflecting layer. In this case, pits are formed on the second intermediate layer. A configuration in which a second intermediate layer made of a cured film of an ultraviolet curable composition is further provided between the first light reflecting layer and the intermediate layer made of a cured film of the ultraviolet curable composition is also preferable. Can be used.

Further, the recordable / reproducible disc has a configuration in which an information recording layer is provided between the substrate and the first light reflecting layer and between the second intermediate layer and the second light reflecting layer. Specifically, a first light reflecting layer is formed on one circular resin substrate, then a first information recording layer such as a phase change film or a magneto-optical recording film is provided, and the first light reflecting layer is further provided. By forming an intermediate layer composed of a cured film of an ultraviolet curable composition on the layer, a second light reflecting layer, and a second information recording layer, and further forming a light transmitting layer on the layer, It can be set as the structure which has two layers of information recording layers. In this configuration as well, as described above, a second intermediate layer made of a cured film of an ultraviolet curable composition is further interposed between the first light reflecting layer and the intermediate layer made of a cured film of the ultraviolet curable composition. May be provided. Alternatively, both the read-only disc and the recordable / reproducible disc may have a structure in which three or more layers of information recording portions and information recording layers are further laminated.

In the case of curing the ultraviolet curable composition applied in forming the intermediate layer or the light transmitting layer by irradiating with ultraviolet rays, for example, it can be performed by a continuous light irradiation method using a metal halide lamp, a high pressure mercury lamp, or the like, and described in US Pat. No. 5,904,795. It can also be performed by the flash irradiation method. The flash irradiation method is more preferable in that it can be cured efficiently.

When irradiating with ultraviolet rays, it is preferable to control the accumulated light amount to be 0.05 to 1 J / cm ² . More preferably accumulated light amount is 0.05 ~ 0.8J / cm ^2, particularly preferably 0.05 ~ 0.6J / cm ^2. The ultraviolet curable composition used for the optical disk of the present invention is sufficiently cured even when the integrated light quantity is small, and does not cause tacking of the end face or surface of the optical disk, and further does not cause warping or distortion of the optical disk.

In the case of a writable optical disc, an information recording layer is provided on the light reflecting layer. The information recording layer only needs to be capable of recording / reproducing information, and may be any of a phase change recording layer, a magneto-optical recording layer, and an organic dye recording layer.

When the information recording layer is a phase change recording layer, the information recording layer is usually composed of a dielectric layer and a phase change film. The dielectric layer is required to have a function of buffering heat generated in the phase change layer and a function of adjusting the reflectivity of the disk, and a mixed composition of ZnS and SiO ₂ is used. The phase change film causes a difference in reflectance between the amorphous state and the crystalline state due to the phase change of the film, and uses a Ge—Sb—Te, Sb—Te, or Ag—In—Sb—Te alloy. Can do.

In the optical disc of the present invention, the light transmission layer may be the outermost layer, but a hard coat layer may be further provided on the surface layer. The hard coat layer is preferably thin from the viewpoint of warping of the optical disc, and is preferably 5 μm or less.

In the optical disc of the present invention, it is preferable that the signal error SER after applying a load to the surface of the light transmission layer is 10 ⁻² or less because there are few signal reproduction failures.

[Embodiment]
Hereinafter, as a specific example of the optical disc of the present invention, an example of a specific configuration of a two-layer optical disc is shown below.

As a preferred embodiment of the two-layer type optical disc, for example, as shown in FIG. 1, a first light reflecting layer 2 and an intermediate layer 3 made of a cured film of an ultraviolet curable composition are formed on a substrate 1. A two-layer type optical disc in which a second light reflecting layer 4 and a light transmitting layer 5 are stacked thereon, and a blue laser is incident from the light transmitting layer 5 side to record or reproduce information. The configuration can be exemplified. As the thickness of the layer, the sum of the thickness of the light transmission layer 5 and the thickness of the intermediate layer 3 is in the range of 100 ± 10 μm. The thickness of the substrate 1 is about 1.1 mm, and the light reflecting film is a thin film such as silver.

In this configuration, as shown in FIG. 2, a hard coat layer 6 may be provided as the outermost layer. The hard coat layer 6 is preferably a layer having high hardness and excellent wear resistance. The thickness of the hard coat layer is preferably 1 to 5 μm, and more preferably 3 to 5 μm. Further, as shown in FIG. 3, an intermediate made of a cured film of an ultraviolet curable composition laminated with the second light reflecting layer 4 between the first light reflecting layer 2 and the second light reflecting layer 4. A configuration in which the layer 3 and the second intermediate layer 7 laminated with the first light reflection layer 2 are also preferable.

A method for manufacturing the optical disk shown in FIG. 1 will be described below.
First, a substrate 1 having a guide groove for tracking a laser beam called a recording track (groove) is manufactured by injection molding a polycarbonate resin. Next, the first light reflecting layer 2 is formed on the surface of the substrate 1 on the recording track side by sputtering or vapor-depositing a silver alloy or the like. An ultraviolet curable composition for forming the intermediate layer 3 having a recording track is applied thereon, and a mold for forming a recording track (groove) is bonded thereon, from one or both sides of the bonded disk. The ultraviolet curable composition is cured by irradiating with ultraviolet rays. Thereafter, the mold is peeled off, and the second light reflecting layer 4 is formed on the surface of the intermediate layer 3 on the side having the recording track (groove) by sputtering or vapor deposition of silver alloy or the like. After applying the ultraviolet curable composition, it is cured by ultraviolet irradiation to form the light transmission layer 5, thereby producing the optical disk of FIG. In the case of the optical disk of FIG. 2, a hard coat layer 6 is further formed thereon by spin coating or the like.

A method for manufacturing the optical disk shown in FIG. 3 will be described below.
First, a substrate 1 having a guide groove for tracking laser light called a recording track (groove) is manufactured by injection molding polycarbonate resin. Next, the first light reflecting layer 2 is formed on the surface of the substrate 1 on the recording track side by sputtering or vapor-depositing a silver alloy or the like.

An intermediate layer is formed thereon. First, a second intermediate layer 7 for laminating an intermediate layer 3 having a recording track is formed on the first light reflecting layer 2 formed on the substrate 1. . The second intermediate layer 7 is formed by applying an ultraviolet curable composition, irradiating ultraviolet rays from one or both sides of the disk, curing or semi-curing the ultraviolet curable composition, and having a recording track thereon. An ultraviolet curable composition for forming the layer 3 is applied, a mold for forming a recording track (groove) is bonded thereon, and ultraviolet light is irradiated from one or both surfaces of the bonded disk, The ultraviolet curable composition is cured. Thereafter, the mold is peeled off, and the second light reflecting layer 4 is formed on the surface of the intermediate layer 3 on the side having the recording track (groove) by sputtering or vapor deposition of silver alloy or the like. The optical disk shown in FIG. 3 can be produced by applying the ultraviolet curable composition and then curing it by ultraviolet irradiation to form the light transmission layer 5. Even when a phase change recording layer is used for the light reflection layer, an optical disc can be produced by the same method as described above.

Next, the present invention will be described in detail with reference to synthesis examples and examples, but the present invention is not limited to these examples. Hereinafter, “parts” in the examples represent “parts by mass”.

Each composition formulated according to the composition shown in Table 1 below (the numerical values in the table represent parts by mass) were heated and dissolved at 60 ° C. for 3 hours to obtain Examples 1 to 3 and Comparative Examples 1 to 3. The ultraviolet curable composition of each Example and the comparative example was prepared. The obtained composition was evaluated as follows, and the obtained results are shown in Table 1.

<Test method: Method for measuring viscosity>
About the ultraviolet curable composition, the viscosity in 25 degreeC was measured using the B-type viscosity meter (the Tokyo Keiki make, BM type | mold).

<Test method: Measurement method of elastic modulus>
The UV curable composition was applied on a glass plate so that the cured coating film was 100 ± 10 μm, and then 500 mJ / cm ² in a nitrogen atmosphere using a metal halide lamp (with a cold mirror, lamp output 120 W / cm). And cured. The elastic modulus of this cured coating film was measured with an automatic dynamic viscoelasticity measuring apparatus manufactured by TA Instruments Inc., and the dynamic elastic modulus E ′ at 25 ° C. was defined as the elastic modulus.

<Test method: Potential Volatiles>
The weight reduction rate when allowed to stand in an environment of 110 ° C. for 1 hour after UV curing was measured according to ASTM specification Design: D5403.
In ASTM D5403, the weight reduction rate after standing for 1 hour in a 110 ° C. environment after UV curing was expressed as Potential Volatiles, and was determined from the following equation.
Potential Volatiles = 100 [(CD) / (BA)]
Here, A: weight of glass substrate, B: glass substrate + intermediate layer before curing, C: glass substrate + intermediate layer after curing, D: glass substrate + intermediate layer after standing for 1 hour in 110 ° C. environment .

<Test method: optical disk durability test>
The recording disk (groove) is formed and applied to the polycarbonate disk on which the reflective film made of an alloy containing silver as a main component is laminated with the ultraviolet curable composition dispenser of each example and each comparative example, and the transparent polycarbonate disk is stacked. Combined. Subsequently, it was rotated with a spin coater so that the film thickness of the cured coating film became 10 to 20 μm. Next, using a “flash irradiation device RC-800” manufactured by XENON, 15-shot ultraviolet rays were irradiated in air from the transparent substrate side to prepare optical disk samples using the respective compositions.

The number of PI errors of each obtained sample was measured, and then an environmental test was performed at 80 ° C. and 85% RH 96 hours using “Etac constant temperature and high humidity device SD01” manufactured by Espec. After the test, the number of PI errors in each sample was measured.

PI error ratio was measured by “SA300” manufactured by Audio Dev Co., Ltd. The PI error ratio (number of PI errors after the environmental test / number of PI errors before the environmental test) was determined from the number of PI errors before and after the environmental test.

The oligomers in the table are as follows.
FAU-742TP: urethane acrylate (urethane acrylate obtained by reacting tolylene diisocyanate / hydroxyethyl acrylate on both ends of polytetramethylene glycol having a molecular weight of 850) Molecular weight Mw: 3700, manufactured by DIC Corporation
V5530: Bisphenol A type epoxy acrylate (epoxy acrylate in which acrylic acid is reacted on both ends of bisphenol A type epoxy resin having a molecular weight of 850) DIC Corporation TMP (3EO) TA: 3 mol of ethylene oxide per 1 mol of trimethylolpropane Triol of triol obtained by addition DPGDA: Dipropylene glycol diacrylate Photor 4094: Glyceryl [4PO] triacrylate Cognis Japan Co., Ltd. Photomer 4017: Hexadidiol diacrylate Cognis Japan Co., Ltd. THFA: Tetrahydrofurfuryl acrylate -Hydroxy-cyclohexyl-phenyl-ketone (molecular weight: 204.3) Ciba Specialte Initiator B: 2-Methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (molecular weight: 279.4) Ciba Specialty Chemicals Co., Ltd. Manufactured initiator C: KIP150: oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone represented by the following formula (i) (mixture of m = 2 and 3, molecular weight) : 469)

(In formula (i), R represents a hydrogen atom or a methyl group, and m is 2 to 3.)
Initiator D: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (molecular weight: 348)
Initiator E: 2-hydroxy-2-methyl-1-phenyl-propan-1-one (molecular weight: 164.2) Ciba Specialty Chemicals Co., gallic acid: (Dainippon Sumitomo Pharma Co., Ltd.)

As shown in Table 1, the optical discs of Examples 1 to 10 having a low weight loss rate of the intermediate layer had a small PI error ratio and good durability under a high temperature and high humidity environment. On the other hand, Comparative Examples 1 to 4 had a large PI error ratio and were not durable in a high temperature and high humidity environment.

It is a figure which shows an example of the optical disk of this invention. It is a figure which shows an example of the optical disk of this invention which has a hard-coat layer. It is a figure which shows an example of the optical disk of this invention which has a 2 layer intermediate | middle layer.

DESCRIPTION OF SYMBOLS 1 Substrate 2 First light reflection layer 3 Intermediate layer 4 Second light reflection layer 5 Light transmission layer 6 Hard coat layer 7 Second intermediate layer

Claims (13)

1. On the substrate, at least a first light reflection layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflective layer, and a light transmission layer in that order, from the cured film of the ultraviolet curable composition An intermediate layer is directly laminated with the second light reflecting layer, and reproduces information by injecting a blue laser from the light transmitting layer side,
   The cured film of the ultraviolet curable composition forming the intermediate layer on which the second light reflecting layer is laminated has a weight reduction rate of 3.5% by mass when left in an environment of 110 ° C. for 1 hour after ultraviolet curing. An optical disc characterized by:
2. 2. The optical disk according to claim 1, wherein the cured film of the ultraviolet curable composition forming the intermediate layer on which the second light reflecting layer is laminated has an elastic modulus at 25 ° C. of 800 to 3000 MPa.
3. The ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated contains an ultraviolet curable compound and a polymerization initiator,
   (UV) curable compound containing 50% by mass or more of (meth) acrylate monomer having two or more (meth) acryloyl groups in one molecule, and (meth) acrylate having one (meth) acryloyl group in one molecule The optical disk according to claim 1, wherein the monomer content is 10% by mass or less.
4. The ultraviolet curable composition used for the intermediate layer on which the second light reflecting layer is laminated has a polymerization initiator content of 2 to 10 parts by mass and a molecular weight of 215 with respect to 100 parts by mass of the ultraviolet curable compound. The optical disk according to any one of claims 1 to 3, wherein the content of the following polymerization initiator is 5 parts by mass or less.
5. The optical disk according to claim 4, wherein the content of the polymerization initiator having a molecular weight exceeding 215 with respect to 100 parts by mass of the ultraviolet curable composition is 1 part by mass or more.
6. 6. The optical disc according to claim 1, wherein the ultraviolet curable composition has a B-type viscosity at 25 ° C. of 1000 mPa · s or less.
7. A second layer made of a cured film of an ultraviolet curable composition is interposed between the first light reflective layer and an intermediate layer made of a cured film of an ultraviolet curable composition on which the second light reflective layer is laminated. The optical disc according to any one of claims 1 to 6, wherein an intermediate layer is provided so as to be directly laminated on the first light reflecting layer.
8. 8. The cured film of the ultraviolet curable composition forming the second intermediate layer has an elastic modulus at 25 ° C. of 500 to 3000 MPa, and a B-type viscosity at 25 ° C. of 1000 mPa · s or less. optical disk.
9. On the substrate, at least a first light reflection layer, an intermediate layer composed of a cured film of an ultraviolet curable composition, a second light reflective layer, and a light transmission layer in that order, from the cured film of the ultraviolet curable composition An intermediate layer is directly laminated with the second light reflecting layer, and an ultraviolet curable composition for forming the second cured film of the optical disc that reproduces information by entering a blue laser from the light transmitting layer side. There,
   Containing an ultraviolet curable compound and a polymerization initiator,
   The content of the polymerization initiator with respect to 100 parts by mass of the ultraviolet curable compound is 2 to 10 parts by mass, and the content of the polymerization initiator with a molecular weight of 215 or less is 5 parts by mass or less. UV curable composition for layers.
10. The ultraviolet curable compound contains 50% by mass of (meth) acrylate monomer having two or more (meth) acryloyl groups in one molecule, and (meth) acrylate having one (meth) acryloyl group in one molecule. The ultraviolet curable composition for an optical disc intermediate layer according to claim 9, wherein the monomer content is 10% by mass or less.
11. The ultraviolet curable composition for an optical disc intermediate layer according to claim 9 or 10, wherein the content of the polymerization initiator having a molecular weight exceeding 215 is 1% by mass or more.
12. The polymerization initiator having a molecular weight exceeding 215 is 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, oligo [2-hydroxy-2-methyl-1- [4 12. The ultraviolet curable composition for an optical disc intermediate layer according to claim 11, which is at least one selected from-(1-methylvinyl) phenyl] propanone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
13. The ultraviolet curable composition for optical disc intermediate layer according to any one of claims 9 to 12, wherein the ultraviolet curable composition contains gallic acid.

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