JP2006265276A - Ultraviolet-curable composition for optical disk and optical disk obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet-curable composition for optical disks that is used between a translucent reflecting layer and a dye recording layer of a multilayered write-once-read-many optical disk and exhibits excellent durability under a high-temperature high-humidity condition. <P>SOLUTION: The ultraviolet-curable composition for optical disks comprises a (meth)acryloyl group-containing compound such as trimethylolpropane tri(meth)acrylate, glycerine triacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate or dipentaerythritol hexa(meth)acrylate, and forms a cured film having a dynamic modulus at 150°C of at least 1,000 MPa. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultraviolet curable composition for optical discs, and more particularly to an ultraviolet curable composition used for an optical disc having a structure in which a recording layer is provided in multiple layers, and an optical disc using the composition.

  A typical example of the bonded optical disk is a DVD (digital versatile disk or digital video disk). In this DVD, an optical disk substrate having a recording layer and an optical disk substrate having no information recording, or two disk substrates having a recording layer are connected via an intermediate resin layer. Are joined together.

  DVDs can be broadly classified into read-only types and recordable types. There are two types of recordable DVDs: write-once DVD-R and DVD + R, and rewritable DVD-RW, DVD + RW, and DVD-RAM. Among these DVDs, DVDs called write-once type DVD-R and DVD + R are different from other DVDs in that organic dyes are used in the recording layer. In a write-once optical disc, a recording layer is formed on a transparent substrate by irreversibly changing optical characteristics or forming a concavo-convex shape by laser light irradiation. As the recording layer, for example, a cyanine-based, phthalocyanine-based, or azo-based organic dye that is decomposed by heating by laser light irradiation, changes its optical constant, and causes deformation of the substrate by volume change is used.

  2. Description of the Related Art Conventional write-once DVDs are obtained by joining an optical disk substrate in which a recording layer made of an organic dye and a light reflection layer are laminated on a substrate and an optical disk substrate having no information recording layer. 1 was provided with one recording layer. In order to increase the recording capacity of an optical disk, an optical disk in which a multi-layer recording layer is provided on one optical disk has been proposed (for example, Patent Document 1). That is, a light reflecting layer of the first optical recording surface formed from the dye recording layer and the light reflecting layer provided on the substrate, and a second optical recording surface formed from the other dye recording layer and the light reflecting layer. A multilayer optical disk is shown in which a dye recording layer is bonded with a light-transmitting intermediate layer interposed therebetween. According to the optical disk described in this document, it is possible to irradiate a laser beam from one side, and to record and reproduce the recording layer on the first optical recording surface and further the recording layer on the second optical recording surface through the intermediate layer. It is.

  In addition, a method of manufacturing a multilayer write-once optical disc has been proposed in which an intermediate layer that joins the first optical recording surface and the second optical recording surface has a structure in which a plurality of resin layers are laminated (for example, Patent Document 2). . In these multilayer write-once optical discs, as described above, signals are recorded by irradiating an organic dye or the like with laser light. In this case, the organic dye or the like is locally heated and becomes a high temperature to cause a chemical change.

  By the way, as a known technique containing a compound having three or more (meth) acryloyl groups, a technique related to a resin composition for an optical disk using the same compound and 2-butyl-2-ethyl-1,3-propanediol diacrylate in combination. Is known (see, for example, Patent Document 3). This technique relates to an active energy ray-curable composition for optical discs capable of forming a cured product layer having excellent adhesion and heat-and-moisture resistance. Example 1 contains 27% by mass of pentaerythritol tetraacrylate and trimethylolpropane. A composition containing 9% by weight of triacrylate is described. In addition, an example in which this composition is used as a protective layer of an optical disk having an aluminum alloy reflective film is described. However, when this composition is used as a composition for an intermediate layer of a multi-layer write-once optical disc, a signal is written on the write-once optical disc with a laser beam, and an endurance test under high temperature and high humidity conditions is performed, compared to before Since the modulation and jitter are very poor, it has been difficult to obtain a multilayer write-once optical disc that is practically satisfactory.

JP 2003-331463 A (Claims) JP 2003-77191 A (Claims) JP 2002-3539 A (Claims, Example 1)

  Therefore, the object of the present invention is to use a multilayer write-once optical disc between a translucent reflective layer and a dye recording layer, even when a high temperature and high humidity durability test is performed on an optical disc on which a signal is written by a laser beam. Another object of the present invention is to provide an ultraviolet curable composition for optical discs capable of forming a resin layer with little change in signal characteristics. Another object of the present invention is to provide a multi-layer write-once optical disc with little change in signal characteristics and excellent reliability even when a high temperature and high humidity durability test is performed on an optical disc on which a signal is written by laser light. It is to provide.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is an ultraviolet curable composition for optical disks containing a compound (Y) having three or more (meth) acryloyl groups, wherein the compound (Y) is represented by the formula (1), the formula (2), Formula (3), Formula (4), Formula (5), or Formula (6)

（式中、Ｘは式(7)

(Where X is the formula (7)

（式中、Ｒ^１は分岐鎖を有していても良い炭素数２〜６のアルキレン基、Ｒ^２は水素原子又はメチル基を表し、ｍは１〜１０の整数を表す。）で表される基、Ｚは前記式(7)で表される基又は水素原子であるが、少なくとも３個のＺは前記式(7)で表される基である。）で表される化合物であり、且つ前記紫外線硬化型組成物により形成される硬化膜の１５０℃における動的弾性率が１０００ＭＰａ以上であることを特徴とする光ディスク用紫外線硬化型組成物を提供するものである。

(Wherein R ¹ represents an alkylene group having 2 to 6 carbon atoms which may have a branched chain, R ² represents a hydrogen atom or a methyl group, and m represents an integer of 1 to 10). Z is a group represented by the above formula (7) or a hydrogen atom, and at least three Z are groups represented by the above formula (7). And a cured film formed from the ultraviolet curable composition has a dynamic elastic modulus at 150 ° C. of 1000 MPa or more, and an ultraviolet curable composition for optical discs is provided. Is.

The present invention also provides:
(1) Dye recording layer (a), laminate A provided with a translucent light reflecting layer on one side of the dye recording layer (a), (2) Dye recording layer (b), and dye recording layer ( A laminate B provided with a light reflecting layer on one side of b)
(3) Provided is an optical disc having a structure in which the translucent light reflecting layer and the dye recording layer (b) are laminated via a cured resin layer of the above-mentioned ultraviolet curable composition for optical discs so as to face each other. It is.

  The cured film of the ultraviolet curable composition for optical disks of the present invention is presumed to act on the signal characteristics of the optical recording surface as follows. When a signal is recorded on the optical recording surface with laser light, the dye recording layer is irradiated with laser light to chemically change the dye at a high temperature. At this time, the resin layer in contact with the dye recording layer on the optical recording surface is also subjected to heat due to the chemical change of the laser and the dye, and the laser irradiation part is deformed to form a recording mark. However, when the conventional ultraviolet curable composition for optical discs is used, the signal mark deteriorates as a result of the recording marks and grooves formed on the resin layer being easily deformed in an environment of high temperature and high humidity. It was. On the other hand, the resin layer composed of the cured film of the ultraviolet curable composition for optical discs of the present invention is composed of a compound having three or more polyfunctional (meth) acryloyl groups, and further has a dynamic elastic modulus at 150 ° C. of 1000 MPa. Therefore, even in an environment of high temperature and high humidity, there is almost no deformation caused by it. Therefore, the recording marks and grooves formed on the resin layer are not deformed, and the signal characteristics are very little deteriorated.

  The compound (Y) having three or more (meth) acryloyl groups used in the ultraviolet curable composition for optical discs of the present invention brings about a high crosslinking density, and the resin layer is deformed under conditions of high temperature and high humidity. In addition to preventing the heat and heat resistance of the resin layer, the long-term reliability of the dye recording layer is imparted. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid, and the same applies to derivatives of acrylic acid or methacrylic acid.

As a specific example of the compound (Y),
As a compound represented by the formula (1);
Trimethylolpropane tri (meth) acrylate, (meth) acrylic acid ester of trimethylolpropane ethylene oxide adduct, (meth) acrylic acid ester of trimethylolpropane propylene oxide adduct ;
Glycerin triacrylate, (meth) acrylic acid ester of glycerin ethylene oxide adduct, (meth) acrylic acid ester of glycerin propylene oxide adduct as a compound represented by formula (3);
Ditrimethylolpropane tetra (meth) acrylate, (meth) acrylic acid ester of ditrimethylolpropane ethylene oxide adduct, (meth) acrylic acid ester of ditrimethylolpropane propylene oxide adduct as a compound represented by formula (4) ;
Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, (meth) acrylate ester of pentaerythritol ethylene oxide adduct, propylene oxide adduct of pentaerythritol (meth) acrylate formula (5) As a compound represented;
Dipentaerythritol penta (meth) acrylate, dipentaerythritol penta (meth) acrylate, (meth) acrylic ester of dipentaerythritol ethylene oxide adduct, (meth) acrylic ester formula of dipentaerythritol propylene oxide adduct As a compound represented by (6);
Tris (2-acryloyloxyethyl) isocyanurate, tris (2-acryloyloxypropyl) isocyanurate, tris (2-acryloyloxybutyl) isocyanurate, tris (2-methacryloyloxyethyl) isocyanurate, tris (2-methacryloyloxy) Propyl) isocyanurate, tris (2-methacryloyloxybutyl) isocyanurate, and the like.

  From these compounds, one or two or more compounds are used in combination so that the dynamic elastic modulus at 150 ° C. is 1000 MPa or more. It is preferable to select such that the crosslink density is high. Specifically, trimethylolpropane tri (meth) acrylate, glycerin triacrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylol. Propane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, or dipentaerythritol hexa (meth) acrylate is preferred.

  The dynamic elastic modulus is preferably 1000 to 4000 MPa, and more preferably 1500 to 3000 MPa. When the dynamic elastic modulus is greater than 4000 MPa, the warp of the optical disk increases and adversely affects signal characteristics. Moreover, in order to suppress the warp of the optical disk to be smaller, the elastic modulus is preferably 3000 MPa or less. In addition to the compound (Y) having three or more (meth) acryloyl groups described in the present invention, other radical polymerizable compounds can be used as long as the effects of the present invention are not impaired. Examples of the radical polymerizable compound include monofunctional (meth) acrylates, polyfunctional (meth) acrylates, and vinyl compounds.

  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, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-chloro-2 -Hydroxypropyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, tetrahydrofurf (Meth) acrylate, glycidyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, nonylphenoxyethyl tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate , Norbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (meth) acryloylmorpholine, and the like.

  Examples of the polyfunctional (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 (meth) Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene Oxa Modified alkylated phosphoric acid (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyether (meth) acrylate, diethylaminoethyl (meth) acrylate, Examples include norbornane dimethanol di (meth) acrylate, cyclohexane dimethanol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, and pentacyclopentadecane diethanol di (meth) acrylate.

  Examples of the vinyl compound include N-vinyl pyrrolidone, N-vinyl caprolactam, vinyl ether monomer, and the like.

  In this invention, a photoinitiator can be used as needed. As the photopolymerization initiator, any known and commonly used photopolymerization initiators can be used, but those of molecular cleavage type or hydrogen abstraction type are suitable as the photopolymerization initiator used in the present invention. Examples of the photopolymerization initiator used in the present invention include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, trimethylbenzoyldiphenylphosphine oxide, benzyl Dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, methylphenylglyoxylate, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one and 2- Molecular cleavage types such as methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diph It can be used hydrogen abstraction type photopolymerization initiators such as Nirusurufido.

  Moreover, as an arbitrary component at the time of comprising the composition of this invention, there exist the following, It can use within the range which does not impair the effect of this invention. That is, as a sensitizer for a photopolymerization initiator, for example, trimethylamine, methyldimethanolamine, triethanolamine, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N -Dimethylbenzylamine, 4,4'-bis (diethylamino) benzophenone, etc. Furthermore, amines that do not cause an addition reaction with the above-mentioned photopolymerizable compound can be used in combination. Of course, it is preferable to select and use those which are excellent in solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance. In addition, the ultraviolet curable resin composition of the present invention includes, as necessary, surfactants, leveling agents, thermal polymerization inhibitors, antioxidants such as hindered phenols and phosphites, hindered amines, and the like as necessary. Light stabilizers can also be used.

Next, the optical disk of the present invention will be described. An optical disk using the ultraviolet curable composition for an optical disk of the present invention,
(1) Dye recording layer (a), laminate A provided with a translucent light reflecting layer on one side of the dye recording layer (a), (2) Dye recording layer (b), and dye recording layer ( A laminate B provided with a light reflecting layer on one side of b)
(3) An optical disc having a structure in which the translucent light reflecting layer and the dye recording layer (b) are laminated via a cured resin layer of the ultraviolet curable composition for optical disc of the present invention so as to face each other. As a specific structure of such an optical disk, for example, there is an optical disk having the structure of FIG.

  The optical disk of FIG. 1 includes a translucent light reflecting layer 3, a cured resin layer 4 of an ultraviolet curable composition, a dye recording layer (b) 5, a light reflecting layer 6, and a substrate 7 on a substrate 1. Is an optical disc having a structure in which are sequentially stacked. In FIG. 1, the dye recording layer (a) 2 and the translucent light reflecting layer 3 form a laminate A21 (first recording layer), and the dye recording layer (b) 5 and the light reflecting layer 6 are laminated B22. (Second recording layer) is formed. Further, the dye recording layer (b) 5 and the dye recording layer (b) 5 are laminated via the cured resin layer 4 of the ultraviolet curable composition so that the cured resin layer 4 is an ultraviolet curable composition for optical discs of the present invention. Is a cured resin layer. Furthermore, the cured resin layer 4 may have a two-layer structure, in which case the cured resin layer (c) of the ultraviolet curable composition for optical discs of the present invention in contact with the dye recording layer (b) 5 and a translucent light It is constituted by a cured resin layer (d) of another ultraviolet curable composition in contact with the reflective layer 3. FIG. 1 also shows a convex recording track (groove) 11 in the first recording layer and a convex recording track (groove) 12 in the second recording layer.

In the optical disk of the present invention, an adhesive layer 8 may be provided between the light reflecting layer 6 and the substrate 7 (FIG. 2). Also, one or more of the laminates A _n have the same structure as the laminate A21 is a translucent light reflective layer 3 and the dye recording layer of each laminate A _n and the laminate A21 (a) 2 and face each other An optical disk having a laminated structure may be used. An example in which only one layer of the laminate A _n 23 having the same structure as the laminate A21 is further laminated on the laminate A21 in the optical disc shown in FIG.

  An optical disk using the ultraviolet curable composition for optical disks of the present invention can be produced, for example, by the following steps.

  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) 11 is manufactured by injection molding polycarbonate resin. Next, after the azo dye is dissolved in a solvent, the dye recording layer (a) 2 is formed on the surface of the substrate 1 on the recording track side by spin coating or the like. Further thereon, a semi-transparent light reflecting layer 3 is formed by sputtering or vapor-depositing a silver alloy or the like to produce a laminate A21 (first recording layer).

  Next, the substrate 7 having a guide groove for tracking laser light called a recording track (groove) 12 is manufactured by injection molding of polycarbonate resin. Next, the light reflecting layer 6 is formed by sputtering or vapor-depositing a silver alloy or the like. On this, an azo dye is dissolved in a solvent, and then a dye recording layer (b) 5 is formed on the surface of the substrate 1 on the recording track side by spin coating or the like to produce a laminate A22 (second recording layer). To do.

  The ultraviolet curable composition for optical discs of the present invention is applied to the surface of the translucent light reflecting layer 3 of the substrate 1 having the first recording layer, and the dye recording layer (b) 5 and spin of the substrate having the second recording layer are applied. Bonded by a coat or the like, and irradiated with ultraviolet rays from one or both sides of the bonded disc, the composition of the present invention is cured to form a cured resin layer 4, and the optical disc of FIG. 1 is produced.

  A method for manufacturing the optical disk shown in FIG. 2 will be described below.

  First, the substrate 1 having a guide groove for tracking a laser beam called a recording track (groove) 11 is manufactured by injection molding polycarbonate resin. Next, after the azo dye is dissolved in a solvent, the dye recording layer (a) 2 is formed on the surface of the substrate 1 on the recording track side by spin coating or the like. Further thereon, a semi-transparent light reflecting layer 3 is formed by sputtering or vapor-depositing a silver alloy or the like to produce a laminate A21 (first recording layer).

  On this, the cured resin layer 4 is formed. The cured resin layer of the ultraviolet curable composition for optical discs of the present invention may be formed directly, or a cured resin of another ultraviolet curable composition by spin coating or the like. After providing the layer, a cured resin layer of the ultraviolet curable composition for optical disks of the present invention may be formed. When forming the cured resin layer of the ultraviolet curable composition for optical discs of the present invention on the cured resin layer 4, the recording track (groove) 13 is transferred to the surface using a mold. The other ultraviolet curable composition preferably has a lower dynamic elastic modulus at 25 ° C. than the ultraviolet curable composition for optical discs of the present invention. By combining with the cured resin layer of the other ultraviolet curable composition, the optical disc There is an advantage that the warpage can be reduced. When combining the cured resin layer of the ultraviolet curable composition for optical disks of the present invention with the cured resin layer of other ultraviolet curable compositions, the film thickness of the cured resin layer of the ultraviolet curable composition for optical disks of the present invention Is preferably 3 to 25 μm. The process of transferring the recording track (groove) 13 is as follows. An ultraviolet curable composition for an optical disk of the present invention is applied on a semitransparent light reflecting layer 3 of a substrate 1 and bonded to a mold for forming a recording track (groove) 13 thereon, and this bonded disk The composition of the present invention is cured by irradiating ultraviolet rays from one or both sides. Thereafter, the mold is peeled off to prepare an optical disc substrate in which the recording track (groove) 13 is provided on the cured resin layer 4. In addition, as a type | mold, if it has sufficient peelability with respect to the cured resin layer 4, it can use without a restriction | limiting especially, However, From the surface of productivity and cost, a resin-made stamper is preferable. As the material of the resin stamper, for example, an acrylic resin, a methacrylic resin, a polycarbonate resin, a polyolefin resin (particularly amorphous polyolefin), a polyester resin, a polystyrene resin, an epoxy resin, or the like is used. it can. Since it is desired that the ultraviolet curable composition for optical disks of the present invention has low adhesion to the cured resin layer 4 and high releasability, polyolefin resins are preferred.

  Subsequently, after the azo dye is dissolved in a solvent on the surface of the cured resin layer 4 of the optical disk substrate having the recording track (groove) 13, the dye recording layer (b) 5 is formed by spin coating or the like. . Further, the light reflecting layer 6 is formed by sputtering or vapor-depositing a silver alloy or the like to produce a multilayer body B22 (second recording layer).

  Next, a substrate 7 having no recording layer is produced by injection molding of a polycarbonate resin. An ultraviolet curable adhesive is applied to the surface of the light reflecting layer 6 of the substrate having the two recording layers obtained as described above, and is bonded to the substrate 7. From one side or both sides of the bonded disc. The optical disk shown in FIG. 2 can be manufactured by irradiating ultraviolet rays to cure the ultraviolet curable adhesive to form the adhesive layer 8.

  A method for manufacturing the optical disk shown in FIG. 3 will be described below.

  Similar to the method of forming the laminate 21 and the cured resin layer 4 in the optical disc shown in FIG. 2, a laminate 23 is formed on the substrate 1 shown in FIG. 3, and a recording track (groove) is formed thereon. The cured resin layer 4 of the ultraviolet curable composition for optical discs of the present invention having the above is formed. Next, the laminate 21 of FIG. 3 is formed in the same manner as the method of forming the laminate 21 in the optical disc shown in FIG. On this, the cured resin layer 4 is formed in the same manner as described above, and further, the laminated body 22 is formed in the same manner as the method of forming the laminated body 22 in the optical disk shown in FIG.

  Finally, an ultraviolet curable adhesive is applied to the surface of the reflective film 6 of the laminate 22 and bonded to the polycarbonate resin substrate 7 having no recording layer, and ultraviolet light is irradiated from one or both sides of the bonded disk. Then, the ultraviolet curable adhesive is cured to form the adhesive layer 8, and the optical disk of FIG. 3 can be manufactured.

  As the organic dye used in the recording layer, in addition to the azo dye, any organic dye that can form pits by laser light used for recording can be used without particular limitation, for example, cyanine-based, phthalocyanine-based, naphthalocyanine-based, Anthraquinone, triphenylmethane, pyrylium or thiapyrylium salts, squarylium, croconium, formazan, metal complex dyes and the like can be mentioned. In addition, a singlet oxygen quencher may be mixed with the dye. The quencher is preferably a metal complex such as acetylacetonate, bisdithio-α-diketone or bisdithiol such as bisphenyldithiol, thiocatechol, salicylaldehyde oxime, or thiobisphenolate. An amine quencher such as an amine compound having a nitrogen radical cation or a hindered amine is also suitable. As the recording layer material, a phase change recording material can be used in place of the organic dye, and a chalcogen alloy can be used as the material, and examples thereof include GeSbTe and AgInSbTe.

  Further, the light reflecting layers of the first recording layer and the second recording layer can be used without particular limitation as long as they can reflect and record / reproduce laser light in addition to the silver alloy, for example, gold, copper In addition, a metal such as aluminum and an alloy thereof, and an inorganic compound such as silicon can be used. The light reflecting layer can be obtained by forming a thin film by a method such as sputtering or vapor deposition using these materials.

  The ultraviolet irradiation can be performed by a continuous light irradiation method using, for example, a metal halide lamp, a high pressure mercury lamp, or the like, or by a flash light irradiation method described in US Pat. No. 5,904,795. The flash irradiation method is more preferable in that it can be cured efficiently. The gel fraction of the cured product is preferably 70% to 100%, more preferably 85% to 100%. In addition, as a board | substrate used for the optical disk of this invention, what is normally used as a board | substrate for optical disks can be used, and especially a polycarbonate substrate can be used suitably.

  The ultraviolet curable composition for an optical disk of the present invention is not limited to the use of write-once DVD-R and DVD + R, but is a rewritable DVD-RW, DVD + RW, DVD-RAM or other DVD, or on an optical disk substrate. In addition, an optical disc in which a light transmission layer is formed by laminating a cured film of an ultraviolet curable composition, for example, a next generation type optical disc using a blue-violet laser beam as a laser beam for reading and writing information (trade name “Blu- ray "manufactured by Sony, trade name" HD-DVD ") and the like.

EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these Examples.
(Example 1 and Comparative Example 1)
<Preparation of composition and optical disc sample>
According to the blending composition shown in Table 1 below, each composition material was heated and dissolved at 60 ° C. for 3 hours to prepare UV curable compositions of Examples and Comparative Examples.

As another ultraviolet curable composition used together with the ultraviolet curable composition of the present invention, the following blended composition (Composition I) was prepared by heating and dissolving each composition material at 60 ° C. for 3 hours.
Acrylic acid adduct of bisphenol A diglycidyl ether 7 parts by mass Urethane acrylate UA-2 13 parts by mass BP (4EO) DA 47 parts by mass TCDDA 3 parts by mass Methylpentanediol diacrylate 10 parts by mass Lauryl acrylate 5 parts by mass Phenoxyethyl acrylate 3 Parts by mass tetrahydrofurfuryl acrylate 3 parts by mass TMP (3EO) TA 2 parts by mass HCPK 4 parts by mass TPO 1 part by mass BDK 1 part by mass Gallic acid 0.3 parts by mass
4,6-bis (octylthiomethyl) -o-cresol 0.1 parts by mass

Here, abbreviations indicate the following compounds.
UA-2: urethane acrylate obtained by reacting polytetramethylene glycol (molecular weight 850), tolylene diisocyanate and hydroxyethyl acrylate in a molar ratio of 1/2/2 BP (4EO) DA: ethylene oxide in 1 mol of bisphenol A Diacrylate of diol obtained by adding 4 mol. TCDDA: Tricyclodecane dimethanol diacrylate. TMP (3EO) TA: Triol triol obtained by adding 3 mol of ethylene oxide to 1 mol of trimethylolpropane. Acrylate, HCPK: 1-hydroxycyclohexyl phenyl ketone, TPO: Trimethylphenyldiphenylphosphine oxide, BDK: Benzyldimethyl ketal

  Next, the optical disk of FIG. 2 was produced by the method described above. First, the substrate 1 having a guide groove for tracking a laser beam called a recording track (groove) was manufactured by injection molding polycarbonate resin. Next, after the azo dye was dissolved in a solvent, the dye recording layer (a) 2 was formed on the surface of the substrate 1 on the recording track side by spin coating. Further thereon, a semi-transparent light reflecting layer 3 was formed by sputtering a silver alloy to produce a laminate A21 (first recording layer).

  On the translucent light reflecting layer 3 of the substrate 1, the composition I was applied by spin coating, and irradiated with ultraviolet rays to form a cured resin layer having a film thickness of about 45 μm. Next, the ultraviolet curable composition for optical discs of each of the above examples and comparative examples is applied, bonded to a resin stamper, and irradiated with ultraviolet rays from the resin stamper side of the bonded disc. The composition was cured. Thereafter, the resin stamper was peeled off to form a cured resin layer having a film thickness of about 10 μm on which the recording track (groove) was transferred. Thus, a cured resin layer 4 comprising a combination of the composition of the present invention and the composition A was formed. Here, the resin stamper was produced by injection molding a polyolefin-based resin. Subsequently, an azo dye was dissolved in a solvent on the surface of the cured resin layer 4 of the optical disk substrate having the recording track (groove), and then a dye recording layer (b) 5 was formed by spin coating. Further, the light reflecting layer 6 was formed by sputtering a silver alloy to produce a laminate B22 (second recording layer).

  Next, a substrate 7 having no recording layer is produced by injection molding of a polycarbonate resin. An ultraviolet curable adhesive Dicure Clear SD-694 (manufactured by Dainippon Ink & Chemicals, Inc.) is applied to the surface of the light reflecting layer 6 of the substrate having the two recording layers obtained as described above. Then, it was bonded to the substrate 7, and ultraviolet light was irradiated from the surface of the substrate 7 of the bonded disk to cure the ultraviolet curable adhesive, and the adhesive layer 8 was formed to produce the optical disk of FIG.

<Evaluation of signal characteristics>
First, in order to measure jitter and modulation, a signal was recorded at a linear velocity of 9.1 m / s with a laser beam having a wavelength of 657 nm on the second recording layer of each manufactured optical disk. Jitter and modulation of each optical disk were measured. Next, each optical disk was subjected to a 50-hour durability test at 80 ° C. and 85% RH, and jitter and modulation were measured again. Jitter and modulation measurements were performed with “DDU-1000” (Pulstec). Table 1 shows the compositions and evaluation results of Examples and Comparative Examples. In addition, before and after the endurance test, the smaller the change in jitter and modulation, the better the signal characteristics.

<Measurement of dynamic elastic modulus>
The ultraviolet curable compositions for optical disks of the above examples and comparative examples were applied on a glass plate so that the film thickness after curing was about 100 μm, and ultraviolet rays from a metal halide lamp (lamp power 120 W / cm) were applied. It hardened | cured by irradiation with the irradiation amount of 0.5 J / cm < ² >. The dynamic elastic modulus of this cured film was measured with a dynamic viscoelasticity measuring device RSA-3 (TE Instruments Co., Ltd.) under conditions of a temperature rising rate of 3 ° C./min and a frequency of 3.5 Hz. Asked.

The abbreviations in Table 1 represent the following compounds.
PETTA: pentaerythritol tetraacrylate TMPTA: trimethylolpropane triacrylate TMP (3EO) TA: triol triole obtained by adding 3 mol of ethylene oxide to 1 mol of trimethylolpropane TAEIC: tris (acryloyloxy) Ethyl) isocyanurate, NPGDA: neopentyl glycol diacrylate, TCDDA: tricyclodecane dimethanol diacrylate, UA-1: polytetramethylene glycol (molecular weight 1000), isophorone diisocyanate and hydroxyethyl acrylate Ratio of urethane acrylate, EP-1: acrylic acid adduct of bisphenol A diglycidyl ether, HCPK: 1-hydroxycyclohex Silphenyl ketone

≪Summary of evaluation results≫
As apparent from Table 1 above, when the ultraviolet curable compositions obtained in Examples 1 to 3 according to the present invention having a dynamic elastic modulus at 150 ° C. of 1000 MPa or more are used, the jitter of the second recording layer is Measurement was possible even after the durability test. Modulation showed little change before and after the durability test.

  On the other hand, Comparative Examples 1 to 3 contain Compound A having three or more acryloyl groups, but all have a dynamic elastic modulus at 150 ° C. of less than 1000 MPa. As a result, Comparative Examples 1 and 3 are durable. Jitter could not be measured after the test, the modulation was greatly reduced, and the characteristics as an optical disk were insufficient. In Comparative Example 2, neither jitter nor modulation could be measured after the durability test.

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. It is a figure which shows an example of the optical disk of this invention.

Explanation of symbols

1 Substrate 2 Dye recording layer (a)
3 Translucent light reflecting layer 4 Cured resin layer of UV curable composition 5 Dye recording layer (b)
6 Light reflecting layer 7 Substrate 8 Adhesive layer 11 Convex recording track (groove)
12 Convex recording track (groove)
13 Convex recording track (groove)
21 Dye recording layer (a) 2 and translucent light reflecting layer 3 are laminated body A
22 Dye recording layer (b) 5 and light reflecting layer 6 are laminated body B
23 Laminate _An

Claims (4)

An ultraviolet curable composition for optical discs containing a compound (Y) having three or more (meth) acryloyl groups, wherein the compound (Y) is represented by the formula (1), the formula (2), the formula (3), Formula (4), Formula (5), or Formula (6)

(Where X is the formula (7)

(Wherein R ¹ represents an alkylene group having 2 to 6 carbon atoms which may have a branched chain, R ² represents a hydrogen atom or a methyl group, and m represents an integer of 1 to 10). Z is a group represented by the above formula (7) or a hydrogen atom, and at least three Z are groups represented by the above formula (7). And a cured film formed from the ultraviolet curable composition has a dynamic elastic modulus at 150 ° C. of 1000 MPa or more. The compound (Y) is trimethylolpropane tri (meth) acrylate, glycerin triacrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta ( 2. The ultraviolet curable composition for optical disks according to claim 1, which is (meth) acrylate or dipentaerythritol hexa (meth) acrylate. (1) Dye recording layer (a), laminate A provided with a translucent light reflecting layer on one side of the dye recording layer (a), (2) Dye recording layer (b), and dye recording layer ( A laminate B provided with a light reflecting layer on one side of b)
(3) Laminated through the cured resin layer of the ultraviolet curable composition for optical discs according to claim 1 or 2 so that the translucent light reflecting layer and the dye recording layer (b) face each other Optical disc having the above structure. (1) Dye recording layer (a), laminate A provided with a translucent light reflecting layer on one side of the dye recording layer (a), (2) Dye recording layer (b), and dye recording layer ( A laminate B provided with a light reflecting layer on one side of b)
(3) An optical disc having a structure in which a translucent light reflecting layer and the dye recording layer (b) are laminated with a cured resin layer of an ultraviolet curable composition for an optical disc facing each other,
The cured resin layer of the ultraviolet curable composition has a two-layer structure comprising a cured resin layer (c) in contact with the dye recording layer (b) and a cured resin layer (d) in contact with the translucent light reflecting layer. A resin layer,
An optical disc, wherein the cured resin layer (c) is a cured resin layer of the ultraviolet curable composition for optical discs according to claim 1.

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