JP2007175968A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which shows successful initial characteristics as an optical recording medium using an oxonol coloring matter in a recording layer. <P>SOLUTION: This optical recording medium has the recording layer, formed on a substrate, which contains the oxonol coloring matter and an azo coloring matter. In addition, the content of the azo coloring matter accounts for 1 to 15 mass% of the total coloring matter in the recording layer. Thus it is possible to ameliorate the initial characteristics of the optical recording medium by consuming a specified amount of the azo coloring matter along with the oxonol coloring matter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium capable of high density recording.

  Conventionally, it is called a write-once digital vasatile disc (so-called DVD-R) capable of recording information only once by laser light for recording and reproducing a large amount of character information, image information, audio information, and the like. Optical discs have been proposed. This DVD-R is a transparent formed with a narrow track pitch of a guide groove (pre-groove) for tracking the irradiated laser beam, which is narrower than half (0.74 to 0.8 μm) compared to a CD-R. Two discs with a recording layer made of a dye on a disc-shaped substrate, and usually a light reflecting layer on the recording layer, and further a protective layer if necessary, or a disc-shaped protection having the same shape as the disc It has a structure in which the substrate is bonded with an adhesive with the recording layer inside. Information recording / reproduction on a DVD-R is performed by irradiating visible laser light (usually laser light having a wavelength in the range of 630 to 680 nm), and recording at a higher density than CD-R is possible. Has been.

  Recently, networks such as the Internet and high-definition TV are rapidly spreading. Further, HDTV (High Definition Television) will be broadcast soon, and there is an increasing demand for a large-capacity recording medium for recording image information inexpensively and easily. Although the DVD-R is secured to a certain extent as a large-capacity recording medium, it cannot be said that the DVD-R has a large enough recording capacity to meet future requirements. Therefore, development of an optical disc having a higher recording capacity by using a laser beam having a shorter wavelength than that of DVD-R is being promoted. For example, a Blu-ray disc using a blue laser beam having a wavelength of 405 nm An optical recording disk to be called and a write-once type HD DVD having almost the same configuration as DVD ± R have been proposed (for example, see Non-Patent Documents 1 and 2).

In such an optical recording medium, for example, an oxonol dye is used as a dye of the recording layer, and information is recorded / reproduced by irradiating a blue (wavelength 400 to 430 nm, 488 nm) or blue-green (wavelength 515 nm) laser light. An information recording / reproducing method to be performed has been proposed. Oxonol dyes can be used more favorably than phthalocyanines having a refractive index of more than 2 and about 1.9. However, according to the study of the present inventors, good initial characteristics have not been obtained with a recording layer containing an oxonol skeleton dye. For example, in a medium having an HD DVD structure, a PRSNR (Partial Response Signal to Noise Ratio) value of 20 is obtained. There was room for improvement.
"ISOM2000", pages 210-211 “Nikkei Electronics October 13 issue”, Nikkei Business Publications, October 13, 2003, p126-134

This invention is made | formed in view of the above conventional trouble, and makes it a subject to achieve the following objectives. That is,
An object of the present invention is to provide an optical recording medium having good initial characteristics in an optical recording medium using an oxonol dye in a recording layer.

Means for solving the problems are as follows. That is,
<1> An optical recording medium having a recording layer on a substrate, wherein the recording layer contains an oxonol dye and an azo compound, and the content of the azo compound is 1 to 15 mass of the total dye in the recording layer % Of the optical recording medium.
In the present invention, the oxonol dye is defined as a polymethine dye having an anionic chromophore.

<2> The optical recording medium according to <1>, wherein the oxonol dye is represented by the following general formula (1).

［一般式（１）中、Ａ、Ｂ、Ｃ及びＤは、ＡとＢのハメットのσp 値の合計及びＣとＤのハメットのσp 値の合計がそれぞれ０．６以上となる電子吸引性基であり、ＡとＢもしくはＣとＤは連結して環を形成していてもよく、Ｒはメチン炭素上の置換基を表し、mは０乃至３の整数を表し、ｎは０乃至２ｍ＋１の整数を表し、ｎが２以上の整数のとき、複数個のＲは互いに同一でも異なっていてもよく、また互いに連結して環を形成していてもよく、Ｙ^t+はｔ価のカチオンを表し、ｔは１乃至１０の整数を表す。］

[In the general formula (1), A, B, C and D are electron-withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m represents an integer of 0 to 3, and n represents 0 to 2m + 1. Represents an integer, and when n is an integer of 2 or more, a plurality of R may be the same or different from each other, and may be linked to each other to form a ring, and Y ^{t +} represents a t-valent cation. , T represents an integer of 1 to 10. ]

<3> The azo dye is a metal chelate compound obtained from an azo compound represented by the following general formula (2 ″) and a metal salt, and the maximum absorption wavelength λmax is 500 nm <λmax <650 nm. The optical recording medium according to claim 1 or 2, characterized in that:
General formula (2 ")
A−N = N−B
[In the general formula (2 ″), A represents a monovalent group derived from a coupler component, and B represents a monovalent group derived from a diazonium salt.]

<4> The optical recording medium according to any one of claims 1 to 3, wherein the optical recording medium is recorded and reproduced by laser light having a wavelength of 350 to 450 nm.

  According to the present invention, it is possible to provide an optical recording medium having good initial characteristics in an optical recording medium using an oxonol dye in a recording layer.

The optical recording medium of the present invention is an optical recording medium having a recording layer on a substrate, wherein the recording layer contains an oxonol dye and an azo compound, and the content of the azo compound is all the dyes in the recording layer. It is characterized by being 1 to 15% by mass.
Hereinafter, each component of the optical recording medium of the present invention will be described first.

  As the layer structure of the optical recording medium of the present invention, a structure in which at least a recording layer and a reflective layer are sequentially provided on a first substrate, and the second substrate is bonded via an adhesive layer, so-called “ The present invention can be suitably applied to a configuration of “HD DVD” or a configuration having a reflective layer, a recording layer, and a cover layer on a substrate, so-called “Blu-ray Disc”. In any case, the recording layer contains an oxonol dye and an azo dye, and the content of the azo compound is 1 to 15% by mass of the total dye in the recording layer. Thus, the initial characteristics can be improved by using an azo dye having a content in the above-mentioned range in combination, instead of using the oxonol dye alone.

  Hereinafter, each layer in the layer configuration of the optical recording medium of the present invention will be described. First, the layer structure of HD DVD will be described. The layer structure of the HD DVD is the structure of the first substrate / recording layer / reflective layer / protective layer / adhesive layer / second substrate, even if a part is omitted or another different layer is added. It doesn't matter.

[First substrate]
The first substrate of the optical recording medium of the present invention can be arbitrarily selected from various materials used as substrates for conventional optical disks.
Examples of substrate materials include acrylic resins such as glass, polycarbonate, and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, amorphous polyolefins, and polyesters. You may use them together. Among the above materials, polycarbonate is preferable from the viewpoint of moisture resistance, dimensional stability, price, and the like.
The thickness of the first substrate is preferably 0.5 to 0.8 mm, and more preferably 0.55 to 0.75 mm.

In the present invention, the pregroove formed on the first substrate has a track pitch of 0.1 to 0.6 μm and a groove depth of 20 to 200 nm in order to achieve high density recording. It is essential to be. The track pitch is more preferably in the range of 0.33 to 0.50 μm. Further, the groove depth is preferably in the range of 50 to 130 nm, and more preferably in the range of 70 to 100 nm.
Furthermore, the groove width (half-value width) of the pregroove formed on the first substrate is preferably in the range of 140 to 260 nm, and more preferably in the range of 120 to 250 nm.
In addition, the groove inclination angle of the pregroove is preferably in the range of 20 to 80 °, and more preferably in the range of 30 to 70 °.

An undercoat layer may be provided on the surface of the substrate on which the recording layer is provided (the surface side on which the pregroove is formed) for the purpose of improving flatness, improving adhesive force, and preventing alteration of the recording layer. .
Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated. High molecular substances such as polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, and silane coupling agents And the like. The undercoat layer is formed by dissolving or dispersing the above substances in a suitable solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do.
The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

[Middle layer]
The intermediate layer is provided between the substrate and a reflective layer described later for the purpose of adjusting the thermal conductivity and improving the storage stability of the recording layer.
The material used for the intermediate layer is not particularly limited as long as it is a material that transmits laser light used for recording and reproduction and can express the above functions. It is a material with low moisture permeability and is preferably a dielectric.
Specifically, a material made of nitride, oxide, carbide, sulfide such as Zn, Si, Ti, Te, Sn, Mo, Ge, Nb is preferable, and ZnS, MoO ₂ , GeO ₂ , TeO, SiO ₂ are preferable. , TiO ₂ , ZnO, ZnS—SiO ₂ , SnO ₂ , ZnO—Ga ₂ O ₃ , and NbO ₂ are preferable, and SnO ₂ , ZnO—Ga ₂ O _{3, and} SiO ₂ are more preferable.

The intermediate layer can be formed by a vacuum film forming method such as vacuum deposition, DC sputtering, RF sputtering, or ion plating. Among these, it is more preferable to use sputtering.
The thickness of the intermediate layer in the present invention is preferably in the range of 1 to 200 nm, more preferably in the range of 5 to 100 nm, from the viewpoint of controlling the diffusion of heat at the time of recording pit formation. More preferably, it is in the range of 40 nm.

[Recording layer]
The recording layer is a layer containing a dye capable of absorbing laser light used for recording and reproduction, and is recorded with code information (coded information) such as digital information.
In the present invention, as described above, an oxonol dye and an azo compound are used as the dye contained in the recording layer, and other dyes may be used in combination. Examples of dyes that can be used in combination include cyanine dyes, metal complex dyes, and phthalocyanine dyes.

-Oxonol dye-
The oxonol dye used in the present invention will be described. In the present invention, an oxonol dye represented by the following general formula (1) is particularly preferably used as the oxonol dye because of its excellent recording characteristics.

［一般式（１）中、Ａ、Ｂ、Ｃ及びＤは、ＡとＢのハメットのσp 値の合計及びＣとＤのハメットのσp値の合計がそれぞれ０．６以上となる電子吸引性基であり、ＡとＢもしくはＣとＤは連結して環を形成していてもよく、Ｒはメチン炭素上の置換基を表し、mは０乃至３の整数を表し、ｎは０乃至２ｍ＋１の整数を表し、ｎが２以上の整数のとき、複数個のＲは互いに同一でも異なっていてもよく、また互いに連結して環を形成していてもよく、Ｙ^t+はｔ価のカチオンを表し、ｔは１乃至１０の整数を表す。］

[In the general formula (1), A, B, C and D are electron-withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m represents an integer of 0 to 3, and n represents 0 to 2m + 1. Represents an integer, and when n is an integer of 2 or more, a plurality of R may be the same or different from each other, and may be linked to each other to form a ring, and Y ^{t +} represents a t-valent cation. , T represents an integer of 1 to 10. ]

  The general formula (1) includes a plurality of tautomers due to differences in the notation of the local position of the anion. In particular, any one of A, B, C, and D is —CO—E (E is a substituent). In some cases, it is common to describe a localized negative charge on an oxygen atom. For example, when D is -CO-E, the following general formula (2) is common as the notation, and such notation is also included in the general formula (1).

The definitions of A, B, C, R, m, n, Y ^{t +} and t in the general formula (2) are the same as those in the general formula (1).

  Hereinafter, the oxonol dye represented by the general formula (1) will be described. In the general formula (1), A, B, C, and D each have a sum of Hammett's substituent constants σp values of A and B and a sum of Hammett's substituent constants σp values of C and D of 0.6 or more, respectively. Represents an electron-withdrawing group. A, B, C and D may be the same or different. A and B or C and D may be linked to form a ring. The Hammett substituent constant σp value of the electron-withdrawing group represented by A, B, C and D is preferably independently in the range of 0.30 to 0.85, more preferably 0.35. It is in the range of ~ 0.80.

  Hammett's substituent constant σp value (hereinafter referred to as σp value) is described, for example, in Chem. Rev. 91, 165 (1991) and references cited therein, and those not described can be obtained by the method described in the same document. When A and B (C and D) are linked to form a ring, the σp value of A (C) means the σp value of the group -A-B-H (-C-10 DH). The σp value of B (D) means the σp value of the group -BAH (-DCH). In this case, both have different σp values because of different coupling directions.

  Preferable specific examples of the electron-withdrawing group represented by A, B, C and D include a cyano group, a nitro group, and an acyl group having 1 to 10 carbon atoms (eg, acetyl, propionyl, butyryl, pivaloyl, benzoyl). An alkoxycarbonyl group having 2 to 12 carbon atoms (eg, methoxycarbonyl, ethoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, decyloxycarbonyl), an aryloxycarbonyl group having 7 to 11 carbon atoms (eg, phenoxycarbonyl), A carbamoyl group having 1 to 10 carbon atoms (eg, methylcarbamoyl, ethylcarbamoyl, phenylcarbamoyl), an alkylsulfonyl group having 1 to 10 carbon atoms (eg, methanesulfonyl), an arylsulfonyl group having 6 to 10 carbon atoms ( Example: benzenesulfonyl), charcoal An alkoxysulfonyl group having 1 to 10 atoms (eg, methoxysulfonyl), a sulfamoyl group having 1 to 10 carbon atoms (eg, ethylsulfamoyl, phenylsulfamoyl), an alkylsulfinyl group having 1 to 10 carbon atoms ( Examples, methanesulfinyl, ethanesulfinyl), arylsulfinyl groups having 6 to 10 carbon atoms (eg, benzenesulfinyl), alkylsulfenyl groups having 1 to 10 carbon atoms (eg, methanesulfenyl, ethanesulfenyl), carbon Arylsulfenyl group having 6 to 10 atoms (eg, benzenesulfenyl), halogen atom, alkynyl group having 2 to 10 carbon atoms (eg, ethynyl), diacylamino group having 2 to 10 carbon atoms (eg, diacetyl) Amino), phosphoryl group, carboxyl group, 5-membered or Membered Hajime Tamaki (e.g., 2-benzothiazolyl, 2-benzoxazolyl, 3-pyridyl, 5-(IH) - tetrazolyl, 4-pyrimidyl) can be exemplified.

  In the general formula (1), examples of the substituent on the methine carbon represented by R include those described below. A linear or cyclic alkyl group having 1 to 20 carbon atoms (for example, methyl, ethyl, n-propyl, isopropyl, n-butyl), a substituted or unsubstituted aryl group having 6 to 18 carbon atoms (for example, phenyl) , Chlorophenyl, anisyl, toluyl, 2,4-di-t-amyl, 1-naphthyl), alkenyl group (for example, vinyl, 2-methylvinyl), alkynyl group (for example, ethynyl, 2-methylethynyl, 2-phenyl) Ethynyl), halogen atom (eg, F, Cl, Br, I), cyano group, hydroxyl group, carboxyl group, acyl group (eg, acetyl, benzoyl, salicyloyl, pivaloyl), alkoxy group (eg, methoxy, butoxy, cyclohexyl) Oxy), aryloxy groups (eg, phenoxy, 1-naphthoxy), alkylthio Group (e.g., methylthio, butylthio, benzylthio, 3-methoxypropylthio), an arylthio group (e.g., phenylthio, 4-chlorophenylthio)

  An alkylsulfonyl group (for example, methanesulfonyl, butanesulfonyl), an arylsulfonyl group (for example, benzenesulfonyl, paratoluenesulfonyl), a carbamoyl group having 1 to 10 carbon atoms, an amide group having 1 to 10 carbon atoms, and the number of carbon atoms 2-12 imide groups, C2-C10 acyloxy groups, C2-C10 alkoxycarbonyl groups, heterocyclic groups (e.g., pyridyl, thienyl, furyl, thiazolyl, imidazolyl, pyrazolyl and other heteroaromatics) Ring, pyrrolidine ring, piperidine ring, morpholine ring, pyran ring, thiopyran ring, dioxane ring, dithiolane ring and other aliphatic heterocycles).

  R is preferably a halogen atom, a linear or cyclic alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or 6 to 10 carbon atoms. An aryloxy group, a heterocyclic group having 3 to 10 carbon atoms, particularly a chlorine atom, an alkyl group having 1 to 4 carbon atoms (eg, methyl, ethyl, isopropyl), phenyl, 1 to 4 carbon atoms Alkoxy groups (eg, methoxy, ethoxy), phenoxy, and nitrogen-containing heterocyclic groups having 4 to 8 carbon atoms (eg, 4-pyridyl, benzoxazol-2-yl, benzothiazol-2-yl) are preferable.

  n represents an integer of 0 to 2m + 1. When n is an integer of 2 or more, a plurality of Rs may be the same as or different from each other, and may be connected to each other to form a ring. At this time, the number of ring members is preferably 4 to 8, particularly preferably 5 or 6, and the constituent atoms of the ring are preferably carbon atoms, oxygen atoms or nitrogen atoms, and particularly preferably carbon atoms.

  A, B, C, D and R may further have a substituent, and examples of the substituent include those described above as examples of the monovalent substituent represented by R in the general formula (1). The same thing can be mentioned.

As the dye used for the optical disk, it is preferable that A and B or C and D are connected to form a ring from the viewpoint of thermal decomposability. Examples of such a ring include the following. Incidentally, in ^examples, R a, ^{R b} and ^{R c} are each independently represent a hydrogen atom or a substituent.

  Preferred rings are (8), (9), (10), (11), (12), (13), (14), (16), (17), (36), (39), (41 ), (54), (57) and (61). More preferably, it is shown by (8), (9), (10), (13), (14), (16), (17), (57) and (61). Most preferred are those represented by (9), (10), (13), (17), (57) and (61).

The substituents represented by R ^a , R ^b and R ^c have the same meanings as those exemplified as the substituent represented by R. R ^a , R ^b and R ^c may be connected to each other to form a carbocyclic or heterocyclic ring. Examples of the carbocycle include saturated or unsaturated 4- to 7-membered carbocycles such as a cyclohexyl ring, cyclopentyl ring, cyclohexene ring, and benzene ring. Examples of the heterocyclic ring include saturated or unsaturated 4- to 7-membered heterocyclic rings such as piperidine ring, piperazine ring, morpholine ring, tetrahydrofuran ring, furan ring, thiophene ring, pyridine ring, and pyrazine ring. it can. These carbocycles or heterocycles may be further substituted. Further, the group which can be substituted has the same meaning as the substituents represented by R.

  In the general formula (1), m is an integer of 0 to 3, and the absorption wavelength of the oxonol dye varies greatly depending on the value of m. Although it is necessary to design a dye having an optimum absorption wavelength according to the oscillation wavelength of the laser used for recording and reproduction, the selection of the value of m is important in this respect. When the center oscillation wavelength of the laser used for recording / reproduction is 780 nm (semiconductor laser for CD-R recording), in the general formula (1), m is preferably 2 or 3, and when the center oscillation wavelength is 635 nm or 650 nm (DVD- R is a semiconductor laser for recording, and m is preferably 1 or 2, and m is preferably 0 or 1 when the center oscillation wavelength is 550 nm or less (for example, a blue-violet semiconductor laser having a center oscillation wavelength of 405 nm).

In the general formula (1), the t-valent cation represented by Y ^{t +} may be either an inorganic or organic cation. Examples of the inorganic cation include a hydrogen ion, a metal ion, and an ammonium ion (NH ₄ ⁺ ). Preferably, it is a metal ion, and an alkali metal ion (eg, Li ⁺ , Na ⁺ , K ⁺ ) or a transition metal ion (eg, Cu ²⁺ , Co ²⁺ ) is particularly preferred. In the case of a transition metal ion, an organic ligand may be coordinated.

As the t-valent organic cation represented by Y ^{t +} , an onium ion is preferable, and a compound represented by the following general formula (3) is particularly preferable. These compounds can be prepared by the Mentokin reaction between the corresponding dipyridyl and a halide having the desired substituent (see, for example, JP-A-61-148162), or JP-A-51-16675 and JP-A-1-96171. It can be easily obtained by an arylation reaction according to the method described in the publication.

［一般式（３）中、Ｒ^３１およびＲ^３２はそれぞれ独立にアルキル基、アルケニル基、アルキニル基、アリール基又はヘテロ環基を表し、Ｒ^３３は置換基を表し、ｓは０乃至８の整数を表し、ｓが２以上の整数のとき、複数個のＲ^３３はそれぞれ同一でも異なっていてもよく、また互いに連結して環を形成していてもよい。］

[In General Formula (3), R ³¹ and R ³² each independently represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, R ³³ represents a substituent, and s is an integer of 0 to 8 And when s is an integer of 2 or more, the plurality of R ³³ may be the same or different from each other, and may be linked to each other to form a ring. ]

In the general formula (3), the alkyl group represented by R ³¹ or R ³² preferably has 1 to 18 carbon atoms, more preferably 1 to 8 carbon atoms, and may be linear, branched or cyclic, Examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, isoamyl, n-hexyl, cyclohexyl, 2-ethylhexyl, and n-octyl.

In the general formula (3), the alkenyl group represented by R ³¹ or R ³² preferably has 2 to 18 carbon atoms, more preferably 2 to 8 carbon atoms, such as vinyl, 2-propenyl, 2-methylpropenyl, 1 , 3-butadienyl.

In the general formula (3), the alkynyl group represented by R ³¹ or R ³² preferably has 2 to 18 carbon atoms, more preferably 2 to 8 carbon atoms. For example, ethynyl, propynyl, 3,3-dimethylbutynyl Can be mentioned.

In the general formula (3), the aryl group represented by R ³¹ or R ³² preferably has 6 to 18 carbon atoms, more preferably 6 to 10 carbon atoms, and examples thereof include phenyl, 1-naphthyl, and 2-naphthyl. Can do.

In the general formula (3), the heterocyclic group represented by R ³¹ or R ³² is preferably a saturated or unsaturated heterocyclic group having 4 to 7 carbon atoms, and the hetero atom contained therein is a nitrogen atom or an oxygen atom. A sulfur atom, for example, 4-pyridyl, 2-pyridyl, 2-pyrazyl, 2-pyrimidyl, 4-pyrimidyl, 2-imidazolyl, 2-furyl, 2-thiophenyl, 2-benzoxazolyl, 2-benzothi Mention may be made of oxazolyl.

R ³¹ and R ^{32 in} the general formula (3) may further have a substituent, and examples of the substituent include the same as those exemplified as the substituent representing R in the general formula (I). it can.

The substituent represented by R ³³ in the general formula (3) has the same meaning as R in the general formula (2), preferably an alkyl group having 1 to 18 carbon atoms, more preferably 1 to 8 carbon atoms. An unsubstituted alkyl group.

In the general formula (3), s represents an integer of 0 to 8, but s is preferably 0 to 4, more preferably 0 to 2, and particularly preferably 0. When s is an integer of 2 or more, the plurality of R ³³ may be the same or different from each other, and may be connected to each other to form a ring. In the general formula (3), the two pyridine rings may be linked at any position, but are preferably linked at the 2-position or 4-position of the pyridine ring, particularly at the 4-positions of both pyridine rings. It is preferable to connect.

  The oxonol dye represented by the general formula (1) may be bonded at an arbitrary position to form a multimer, and in this case, each unit may be the same as or different from each other, and polystyrene, polymethacrylate It may be bonded to a polymer chain such as polyvinyl alcohol or cellulose.

  Specific examples of the oxonol dye represented by the general formula (1) used in the present invention include JP-A Nos. 63-209995, 10-297103, 11-78106, and 11-348420. Specific examples of the oxonol dyes described in JP-A No. 2000-52658 and JP-A No. 11-78106 can be given. Some of the compounds are exemplified below.

  In the present invention, a predetermined amount of an azo dye is added to the recording layer in addition to the above oxonol. The azo dye will be described below.

The azo dye used in the present invention is preferably a metal chelate compound obtained from an azo compound represented by the following general formula (2 ″) and a metal salt.
General formula (2 ")
A−N = N−B
[In the general formula (2 ″), A represents a monovalent group derived from a coupler component, and B represents a monovalent group derived from a diazonium salt.]
Hereinafter, each of the azo compound and the metal salt will be described.

-Azo compounds-
An azo compound is a compound synthesized by reacting an aryl or heteroaryl diazonium salt (diazo component) with a compound (coupler component) having an acidic hydrogen atom that forms an azo coupling reaction with the diazonium salt. It is. The azo compound used in the present invention is preferably a compound having a structure represented by the following general formula (2 ″).
General formula (2 ")
A−N = N−B
[In the general formula (2 ″), A represents a monovalent group derived from a coupler component, and B represents a monovalent group derived from a diazonium salt.]

  The azo compound having a structure represented by the general formula (2 ″) is preferably a compound represented by the following general formula (A).

［一般式（Ａ）中、Ａ^１はそれが結合している炭素原子および窒素原子と一緒になって複素環を形成する残基を表わし、Ｘは水素原子、アルキル基、アルコキシ基、ハロゲン原子を表わし、Ｙは炭素数１〜６の鎖状または分岐のアルキル基を表わし、Ｒ^１、Ｒ^２はそれぞれ独立に置換基を有してもよいアルキル基を表し、Ｒ^１とＲ^２とが結合して環を形成していてもよい。］

[In the general formula (A), A ¹ represents a residue which forms a heterocyclic ring together with the carbon atom and nitrogen atom to which it is bonded, and X represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom. Y represents a linear or branched alkyl group having 1 to 6 carbon atoms, R ¹ and R ² each independently represents an alkyl group which may have a substituent, and R ¹ and R ² are It may combine to form a ring. ]

  The azo compound having a structure represented by the general formula (2 ″) is preferably a compound represented by the following general formula (4 ″).

［Ａ^１、Ｂ^２は、各々独立に、置換もしくは無置換の芳香族炭化水素環、置換もしくは無置換の芳香族ヘテロ環を形成する原子団を表す。Ｇは、金属イオンに配位する能力をもつ一価の基を表す。］

[A ¹ and B ² each independently represents an atomic group that forms a substituted or unsubstituted aromatic hydrocarbon ring or a substituted or unsubstituted aromatic heterocycle. G represents a monovalent group having the ability to coordinate to a metal ion. ]

The azo compound having a structure represented by the general formulas (2 ″) and (4 ″) will be described. A is a monovalent group derived from the residue of a compound (coupler component) having an acidic hydrogen atom that forms an azo coupling reaction with a diazonium salt, that is, a coupler component. A is preferably a substituted or unsubstituted aryl group, a 5-membered carbon group having 1 to 20 carbon atoms containing a nitrogen atom, or a 6-membered heterocyclic group having 2 to 20 carbon atoms containing a nitrogen atom. In the general formula (4 ") azo compounds represented by structure, A ¹ together with the carbon atoms to which they are attached represent an atomic group forming an aromatic hydrocarbon ring or aromatic hetero ring, formed by A ¹ Examples of the ring include an aromatic hydrocarbon ring having a substituent (preferably a substituted benzene ring), a 5-membered carbon atom having 1 to 20 carbon atoms or a 6-membered carbon atom having 2 to 20 carbon atoms. And an aromatic hydrocarbon ring having a substituent (preferably a substituted benzene ring) is more preferable.
Examples of structures formed by the substituent A or A ¹ are shown below.

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² are each independently a hydrogen atom or a monovalent substituent. It is.

Among the above ring structures, preferred are formulas (IV), (V), and (VI).
In the above general formula, R ¹¹ and R ¹³ are preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a cyano group, and 1 to 20 carbon atoms. A substituted or unsubstituted alkoxycarbonyl group, or a substituted or unsubstituted aminocarbonyl group having 2 to 20 carbon atoms. R ¹⁴ is preferably a cyano group, a substituted or unsubstituted alkoxycarbonyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 20 carbon atoms or a substituted or unsubstituted 2 to 20 carbon atoms, Of the aminocarbonyl group. R ¹⁵ is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted aminocarbonylamino group having 1 to 20 carbon atoms.
Particularly preferably, R ¹³ is a cyano group, R ¹⁴ is an alkoxycarbonyl group having 1 to 20 carbon atoms, R ¹⁵ is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or 6 to 20 carbon atoms. A substituted or unsubstituted aryl group.

B represents a monovalent group derived from a diazonium salt, preferably a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group. That is, B is a diazo component. The diazo component is a partial structure that can be introduced by converting a heterocyclic compound having an amino group as a substituent or a benzene derivative into a diazo compound (diazonium salt) and diazo coupling reaction with a coupler. It is a frequently used concept in the field. In other words, it is an amino-substituted heterocyclic compound capable of diazotization reaction or a substituent that is a monovalent group by removing the amino group of the benzene derivative. B is preferably the case of the ring formed by B ^2. B ² represents an atomic group forming a substituted or unsubstituted aromatic hydrocarbon ring or a substituted or unsubstituted aromatic heterocycle. Examples of the ring formed by B ² include an aromatic hydrocarbon ring having a substituent (preferably a benzene ring having a substituent), a 5-membered member having 1 to 20 carbon atoms containing a nitrogen atom, or a carbon number of 2 to 2 containing a nitrogen atom. A 20-membered 6-membered heterocyclic ring is preferable, a 5-membered carbon atom having 1 to 20 carbon atoms including a nitrogen atom or a 6-membered heterocyclic ring having 2 to 20 carbon atoms including a nitrogen atom is more preferable, and a 1-carbon atom including a nitrogen atom is preferable. More preferred are 20 5-membered heterocycles.
Examples of the monovalent heterocyclic group of A and B include the following (AB-1) to (AB-25).

In the formula, R ^{21 to} R ⁵⁰ each independently represent a hydrogen atom or a monovalent substituent. Examples of the substituent are those described in the description of R ^a , R ^b , and R ^c .
In (AB-1) to (AB-25),
b and c are integers from 0 to 6.
a, p, q, r are integers from 0 to 4.
d, e, f, g, t, and u are integers from 0 to 3.
h, i, j, k, l, and o are integers from 0 to 2.
When a to u are 2 or more, two or more substituents represented by R ^{21 to} R ⁵⁰ may be the same or different.
Among the structures of B, the following structures (a) -1, (a) -2, and (b) to (l) are preferable.

In the formula, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ^{61 to} R ⁶⁶ , R ⁷¹ , R ⁷² are each independently a hydrogen atom or a substituent. Examples of the substituent are those described in the description of R ^a , R ^b , and R ^c .
G represents a monovalent group having the ability to coordinate to a metal ion. Examples of G include hydroxyl group, carboxyl group, amino group (including alkylamino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkyl or aryl Examples include sulfonylamino group, mercapto group, sulfamoyl group, sulfo group, alkyl and arylsulfinyl group, carbamoyl group, aryl and heterocyclic azo group, phosphino group and phosphinyl group. G is preferably an alkylsulfonylamino group.

The azo dye according to the present invention is preferably an azo metal chelate dye coordinated with a metal ion. In particular, chelate dyes are superior in light resistance and are preferable. The metal ions used as the metal chelate dye are preferably Ni, Cu, Zn, Al, Ti, Fe, B, Cr, and Co. Among these, Ni, Co, and Al are more preferable.
In the case of a chelate structure, if a stable complex cannot be formed due to a shortage of ligands with respect to the central metal, a molecule other than the dye of the general formula (2 ″) is added as a ligand to form a stable chelate dye The ligand added separately is preferably a compound containing nitrogen, oxygen, or sulfur atom, among which an amine compound (including aniline) or a heterocyclic compound containing at least one nitrogen atom is preferred. A 5-membered or 6-membered amine compound having 3 to 20 carbon atoms is most preferred.
Specific examples of the azo dye used in the present invention are given below. The present invention is not limited by this specific example.

As for the synthesis method of the azo dyes, JP-A-3-268994, JP-A-361088, JP-A-7-161069, JP-A-7-251567, JP-A-10-204070, JP-A-11-12483, JP-A-11-12483. 11-166125, JP-A-2001-199169, JP-A-2001-152040, and JP-A-2002-114922.
The dye compound represented by the general formula (1 ′) according to the present invention has a complex refractive index coefficient n (real part: refractive index) and k (imaginary part: extinction) at the recording laser wavelength due to the optical characteristics of the amorphous film. The attenuation coefficient is preferably 2.0 ≦ n ≦ 3.0 and 0.00 ≦ k ≦ 0.20. More preferably, 2.1 ≦ n ≦ 2.7 and 0.00 ≦ k ≦ 0.10. Most preferably, 2.15 ≦ n ≦ 2.50 and 0.00 ≦ k ≦ 0.05.
The azo dye compound according to the present invention preferably has a thermal decomposition temperature in the range of 100 ° C to 350 ° C. Furthermore, what is in the range of 150 to 300 degreeC is preferable. Furthermore, the thing in the range of 200 to 300 degreeC is preferable.

  The maximum absorption wavelength λmax of the azo dye according to the present invention, that is, the metal chelate compound obtained from the azo compound represented by the general formula (A) and the metal salt is preferably 550 nm <λmax <650 nm, 560 nm It is more preferable that <λmax <640 nm.

  In the present invention, the content of the azo dye in the recording layer is 1 to 15% by mass, preferably 5 to 15% by mass, based on all the dyes in the recording layer. When the content of the azo dye is less than 1% by mass, the effect of improving the characteristics is not observed, and when it exceeds 15% by mass, the characteristics deteriorate.

  The recording layer can contain various anti-fading agents in order to further improve the light resistance of the recording layer. Examples of the antifading agent include organic oxidants and singlet oxygen quenchers. As the organic oxidizing agent used as the anti-fading agent, compounds described in JP-A-10-151861 are preferable. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used. Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19588, 60-35054, 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, 60-47069, 63-209995, JP No. 4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent No. 350399, and the Journal of the Chemical Society of Japan, October 1992, page 1141, etc. be able to.

  Examples of preferred singlet oxygen quenchers include compounds represented by the following general formula (4).

［但し、Ｒ^４１は置換基を有していてもよいアルキル基を表わし、Ｑ^-はアニオンを表わす。］

[However, R ⁴¹ represents an alkyl group which may have a substituent, and Q ⁻ represents an anion. ]

In the general formula (4), R ⁴¹ is generally an optionally substituted alkyl group having 1 to 8 carbon atoms, and is preferably an unsubstituted alkyl group having 1 to 6 carbon atoms. Examples of the substituent for the alkyl group include a halogen atom (eg, F, Cl), an alkoxy group (eg, methoxy, ethoxy), an alkylthio group (eg, methylthio, ethylthio), an acyl group (eg, acetyl, propionyl), an acyloxy group (Eg, acetoxy, propionyloxy), hydroxy group, alkoxycarbonyl group (eg, methoxycarbonyl, ethoxycarbonyl), alkenyl group (eg, vinyl), aryl group (eg, phenyl, naphthyl). Among these, a halogen atom, an alkoxy group, an alkylthio group, and an alkoxycarbonyl group are preferable. As examples of the anion of Q ⁻ , ClO ⁴⁻ , AsF ⁶⁻ , BF ⁴⁻ , and SbF ⁶⁻ are preferable.

The recording layer can be formed by a method such as vapor deposition, sputtering, CVD, or solvent coating, but solvent coating is preferred.
As a method for forming the recording layer by solvent coating, first, a recording material such as a dye is dissolved in an appropriate solvent together with a binder or the like to prepare a coating solution, and then this coating solution is coated on a substrate. There is a method of drying after forming a coating film.
The concentration of the recording substance (the above-mentioned dyes and compounds) in the coating solution is generally in the range of 0.01 to 15% by mass, preferably in the range of 0.1 to 10% by mass, more preferably 0.5 to 5%. It is in the range of mass%, most preferably in the range of 0.5-3 mass%.

Examples of the solvent for the coating solution include esters such as butyl acetate, ethyl lactate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; dimethylformamide and the like Amides; Hydrocarbons such as methylcyclohexane; Ethers such as dibutyl ether, diethyl ether, tetrahydrofuran, and dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol, and diacetone alcohol; 2,2,3,3- Fluorinated solvents such as tetrafluoropropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. And the like can be mentioned recall ethers.
The said solvent can be used individually or in combination of 2 or more types in consideration of the solubility of the pigment | dye to be used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.

  When a binder is used, examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene; Vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer; acrylic resins such as polymethyl acrylate and polymethyl methacrylate; polyvinyl alcohol, chlorinated polyethylene, epoxy resin, bunalal resin, Examples include synthetic organic polymers such as rubber derivatives and initial condensates of thermosetting resins such as phenol / formaldehyde resins.

  When a binder is used in combination as a material for the recording layer, the amount of binder used is generally in the range of 0.01 to 50 times the mass of the dye, preferably 0.1 to 5 times the amount. Is in range.

Examples of the solvent application method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method.
The thickness of the recording layer is generally preferably in the range of 10 to 150 nm, more preferably in the range of 15 to 140 nm, and still more preferably in the range of 20 to 130 nm.
The recording layer may be a single layer or a multilayer.

  The recording layer can contain various anti-fading agents in order to improve the light resistance of the recording layer. As the anti-fading agent, a singlet oxygen quencher is generally used. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used. Specific examples thereof include JP-A Nos. 58-175893, 59-31194, 60-18387, 60-19586, 60-19588, 60-35054, 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, 60-47069, 68-209995, JP Listed in publications such as Nos. 4-25492, 1-38680, and 6-26028, German Patent No. 350399, and the Chemical Society of Japan, October 1992, page 1141 Can do.

  The amount of the anti-fading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 50% by mass, preferably in the range of 0.5 to 45% by mass, more preferably , In the range of 3 to 40% by mass, particularly preferably in the range of 5 to 25% by mass.

[Reflective layer]
A reflective layer is provided adjacent to the recording layer for the purpose of improving the reflectance during information reproduction. The light-reflective substance that is the material of the reflective layer is a substance having a high reflectivity with respect to laser light. Examples thereof include Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. , Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi Mention may be made of metals such as metals and metalloids or stainless steel. These substances may be used alone or in combination of two or more or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred are Au metal, Ag metal, Al metal or alloys thereof, and most preferred are Ag metal, Al metal or alloys thereof.
The reflective layer can be formed on the substrate or the recording layer, for example, by vapor deposition, sputtering or ion plating of the light reflective material.
The thickness of the reflective layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.

[Adhesive layer]
The adhesive layer is formed to bond the reflective layer and the second substrate.
As a material constituting the adhesive layer, a photo-curing resin is preferable, and among them, a material having a small curing shrinkage rate is preferable in order to prevent the disk from warping. Examples of such a photocurable resin include UV curable resins (UV curable adhesive) such as “SD-640” and “SD-661” manufactured by Dainippon Ink and Chemicals, Inc. it can.
The thickness of the adhesive layer is preferably in the range of 1 to 1000 μm, more preferably in the range of 5 to 500 μm, and particularly preferably in the range of 10 to 100 μm in order to give elasticity.

[Second substrate]
The second substrate can be made of the same material and shape as the first substrate except that no pregroove is formed.
Further, a pre-groove similar to that of the first substrate may be formed on the second substrate, and a recording layer may be formed on the bonding surface. Furthermore, an intermediate layer may be provided between the second substrate and the recording layer, or a reflective layer may be provided on the surface of the recording layer opposite to the substrate. Note that the intermediate layer, the recording layer, and the reflective layer provided on the second substrate side are similar to the above-described layers. As described above, the laminate in which the recording layer is formed on the second substrate side and the laminate in which the intermediate layer, the recording layer, and the reflective layer are formed in this order on the first substrate as described above. An optical recording medium capable of recording and reproducing information on both sides can be obtained by adhering a body and an adhesive layer with both substrates facing outside.

[Protective layer]
In the optical recording medium of the present invention, a protective layer may be provided adjacent to the recording layer for the purpose of physically and chemically protecting the recording layer. Even when a recording layer is formed on the second substrate side, a protective layer may be provided adjacent to the recording layer.

Examples of materials used for the protective layer include inorganic substances such as ZnS, ZnS—SiO ₂ , SiO, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , thermoplastic resins, thermosetting resins, and UV curable materials. Organic substances such as resins can be mentioned. The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic on the reflective layer via an adhesive. Or you may provide by methods, such as vacuum evaporation, sputtering, and application | coating.

  In the case of a thermoplastic resin or a thermosetting resin, it can also be formed by dissolving these in a suitable solvent to prepare a coating solution, and then applying and drying the coating solution. In the case of a UV curable resin, it can also be formed by applying this coating solution and curing it by irradiation with UV light. In these coating liquids, various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added according to the purpose. The thickness of the protective layer is generally in the range of 0.1 μm to 1 mm.

  Next, the layer structure of the Blu-ray disc will be described. As described above, the layer structure of the Blu-ray disc is the structure of the substrate / recording layer / intermediate layer / adhesive layer / cover layer, and other different layers may be added. Below, each layer is demonstrated.

<Board>
As the substrate, a material similar to the material described for the first substrate of the HD DVD described above can be used. The thickness of the substrate is preferably 0.5 to 1.4 mm.

  The substrate is provided with irregularities (pregrooves) representing information such as tracking guide grooves or address signals. The track pitch of the pregroove is 250 to 400 nm. The depth of the pregroove (groove depth) is in the range of 10 to 150 nm, preferably 15 to 100 nm, more preferably 20 to 80 nm, and most preferably 20 to 60 nm.

In addition, it is preferable to form an undercoat layer on the surface of the substrate on the side where a reflective layer, which will be described later, is provided, for the purpose of improving planarity and adhesion.
Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, and chloro. Polymer materials such as sulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc .; silane coupling Surface modifiers such as agents;
The undercoat layer is formed by dissolving or dispersing the above materials in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, and preferably in the range of 0.01 to 10 μm.

<Reflective layer>
The reflective layer can be made of the same material as that described for the reflective layer of HD DVD described above, and can be formed by the same method.

The thickness of the reflective layer is generally in the range of 10 to 300 nm and preferably in the range of 50 to 200 nm.
The above reflective layers are not necessarily required when the reflectance of the following recording layers is sufficiently high.

<Recording layer>
The recording layer can be formed by the same method using the same dye as the HD DVD described above. The thickness of the recording layer is generally in the range of 10 to 300 nm, preferably in the range of 15 to 200 nm, and more preferably in the range of 20 to 150 nm.

  In the Blu-ray disc, a cover sheet, which will be described later, is bonded onto the above-described intermediate layer via a pressure-sensitive adhesive layer or an adhesive layer described below. A cover layer is formed by the cover sheet and the pressure-sensitive adhesive layer or the adhesive layer.

<Adhesive layer>
An adhesive layer is a layer formed in order to adhere | attach the light transmissive layer mentioned later, A conventionally well-known thing can be used widely. As the pressure-sensitive adhesive, acrylic pressure-sensitive adhesive, natural rubber, styrene-isoprene-styrene copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), and other rubber-based pressure-sensitive adhesives are appropriately selected and used. Can do. It is preferable that the said adhesive is previously apply | coated to the bonding surface of a light transmissive layer. The thickness of the pressure-sensitive adhesive layer is in the range of 1 to 50 μm, particularly preferably in the range of 2 to 45 μm.

<Adhesive layer>
Similar to the pressure-sensitive adhesive layer, the adhesive layer is a layer formed to adhere a light transmission layer described later. Examples of the material constituting the adhesive layer include a photocurable resin, a two-component curable adhesive, and the like. Among these, a photocurable resin is preferable, and a material having a low curing shrinkage rate is preferable in order to prevent warping of the disk. Examples of such a photocurable resin include UV curable resins (UV curable adhesive) such as “SD-640” and “SD-661” manufactured by Dainippon Ink and Chemicals, Inc. Can do. The thickness of the adhesive layer is preferably in the range of 1 to 50 μm, more preferably in the range of 2 to 40 μm, and particularly preferably in the range of 3 to 35 μm. In the Blu-ray disc, since the recording / reproducing light is transmitted through the adhesive layer, the uniformity of the recording characteristics is improved by reducing the thickness and reducing the thickness unevenness of the adhesive layer.

  Other examples of the material for forming the adhesive layer will be given. The material is a resin that can be cured by radiation irradiation, and has two or more radiation-functional double bonds in the molecule, and includes acrylic acid esters, acrylamides, methacrylic acid esters, and methacrylic acid. Examples include amides, allyl compounds, vinyl ethers, and vinyl esters. Preferred are bifunctional or higher acrylate compounds and methacrylate compounds.

  Specific examples of the bifunctional include ethylene glycol diacrylate, propylene glycol diacrylate, butanediol diacrylate, hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, Tripropylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, tripropylene Guri Aliphatic diols acrylic acid typified over dimethacrylate, it can be used those obtained by adding methacrylic acid.

Acrylic acid can also be added to polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Polyether acrylates with addition of acrylic acid and methacrylic acid, polyether methacrylates, known dibasic acids, and polyester polyols obtained from glycols. Polyester acrylate and polyester methacrylate to which methacrylic acid is added can also be used.
Furthermore, polyurethanes obtained by adding acrylic acid or methacrylic acid to polyurethane obtained by reacting known polyols, diols and polyisocyanates may be used.

  Also, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and those obtained by adding acrylic acid or methacrylic acid to these alkylene oxide adducts, isocyanuric acid alkylene oxide modified diacrylate, isocyanuric acid alkylene oxide modified diacrylate Those having a cyclic structure such as methacrylate, tricyclodecane dimethanol diacrylate and tricyclodecane dimethanol dimethacrylate can also be used.

  As said radiation, an electron beam and an ultraviolet-ray can be used. When ultraviolet rays are used, it is necessary to add a photopolymerization initiator to the following compounds. An aromatic ketone is used as a photopolymerization initiator. The aromatic ketone is not particularly limited, but an aromatic ketone having a relatively large extinction coefficient at a wavelength of 254, 313, and 865 nm, which generates an emission line spectrum of a mercury lamp usually used as an ultraviolet irradiation light source, is preferable. Typical examples include acetophenone, benzophenone, benzoin ethyl ether, benzyl methyl ketal, benzyl ethyl ketal, benzoin isobutyl ketone, hydroxydimethylphenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2,2-diethoxyacetophenone, Micheler's ketone. Various aromatic ketones can be used. Moreover, what added the photoinitiator beforehand as an ultraviolet curable adhesive is marketed, and you may use it. A mercury lamp is used as the ultraviolet light source. The mercury lamp is a 20 to 200 W / cm lamp and is used at a speed of 0.3 m / min to 20 m / min. In general, the distance between the substrate and the mercury lamp is preferably 1 to 30 cm.

  As the electron beam accelerator, a scanning system, a double scanning system, or a curtain beam system can be adopted, but a curtain beam system that can obtain a large output at a relatively low cost is preferable. As the electron beam characteristics, the acceleration voltage is 100 to 1000 kV, preferably 150 to 300 kV, and the absorbed dose is 0.5 to 20 Mrad, preferably 1 to 10 Mrad. When the acceleration voltage is 10 kV or less, the amount of transmitted energy is insufficient, and when the acceleration voltage exceeds 1000 kV, the energy efficiency used for polymerization is lowered, which is not preferable in terms of cost.

<Cover sheet>
The material for forming the cover sheet is not particularly limited as long as it is a transparent material, but the material is preferably polycarbonate, cellulose triacetate, or an acrylic polymer. Moreover, it is preferable that the material has a moisture absorption rate of 5% or less at 23 ° C. and 50% RH. Furthermore, the cover sheet preferably has a surface roughness of 5 nm or less and a birefringence of 10 nm or less.
“Transparent” means that the laser beam to be recorded / reproduced is so transparent that the light is transmitted (transmittance: 80% or more).
The thickness of the cover sheet is preferably in the range of 0.01 to 0.2 mm, more preferably in the range of 0.03 to 0.1 mm, and still more preferably in the range of 0.05 to 0.095 mm.

  As a method of sticking the cover sheet on the intermediate layer using the pressure-sensitive adhesive layer, after applying the pressure-sensitive adhesive on the cover sheet and drying the solvent, the cover sheet is formed on the intermediate layer via the pressure-sensitive adhesive. And a method of attaching the cover sheet by applying pressure with a roller.

  The application temperature of the pressure-sensitive adhesive is preferably in the range of 23 to 50 ° C, more preferably in the range of 24 to 40 ° C, and still more preferably in the range of 25 to 37 ° C for viscosity control. . After application, the film is preferably dried at 50 to 300 ° C, more preferably 80 to 200 ° C, and still more preferably 100 to 150 ° C. Moreover, as temperature at the time of bonding a cover sheet, it is preferable that it is the range of 0-100 degreeC, and it is more preferable that it is the range of 15-50 degreeC.

  In addition, after applying the adhesive on the release film having releasability to the adhesive to be used and drying the solvent, the cover sheet is pasted, and the release film is then peeled off on the cover sheet. A cover sheet can also be stuck by sticking on a barrier layer after providing an adhesive. This method is desirable particularly when the solvent contained in the adhesive dissolves the cover sheet.

When using a cover sheet provided with a pressure-sensitive adhesive layer on a release film, the film used as a substrate is not particularly limited as long as it is insoluble in the solvent contained in the pressure-sensitive adhesive. Plastic films such as polyethylene terephthalate, polypropylene, polyethylene, vinyl chloride, kraft paper, fine paper, crecote paper, paper such as Japanese paper, rayon, nonwoven fabric such as polyester, woven fabric made of synthetic fibers such as polyester, nylon, acrylic, Metal foils such as aluminum, copper, and stainless steel are used, but a plastic film is preferable from the viewpoint that a release agent layer is continuously and thinly applied uniformly on the film.
Moreover, as a mold release agent used, various mold release agents conventionally used, such as a silicone type mold release agent and a long-chain alkyl type mold release agent, can be selected suitably, and can be used.

<Surface coat layer>
In the optical recording medium of the present invention, a surface coat layer may be provided on the cover layer. As described above, the surface coat layer has a function of preventing peeling of the cover layer by being provided on the cover layer. Examples of the material for the surface coat layer include a photocurable resin such as an ultraviolet curable resin and an electron beam curable resin, and a humidity curable resin. Among them, the curing shrinkage is 15% or less (preferably 12% or less), the hardness is H or more (preferably 2H or more) in pencil hardness, and the transmittance for laser light in the recording wavelength region is 70% or more (preferably 75). % Or more) is preferable.

  For example, when an ultraviolet curable resin is used, the surface coat layer is formed by applying the ultraviolet curable resin to the inner peripheral portion of the substrate, rotating the substrate at a high speed and extending the substrate to the outer peripheral side, and then irradiating the ultraviolet rays. be able to.

  The layer thickness of the surface coat layer is preferably 0.1 to 50 μm, more preferably 0.5 to 40 μm, and even more preferably 1 to 30 μm.

[Recording method]
A method for recording information (digital information) on the optical recording medium of the present invention will be described.
For recording information on the optical recording medium of the present invention, a recording apparatus having at least a laser pickup for emitting laser light and a rotating mechanism for rotating the optical recording medium is used. First, using a rotating mechanism, laser light is emitted from a laser pickup while rotating an unrecorded optical recording medium at a predetermined recording linear velocity. By this irradiation light, the dye in the recording layer absorbs the light and the temperature rises locally. For example, information is recorded by generating pits and changing their optical characteristics.
The recorded information is reproduced by irradiating a laser beam from a laser pickup toward the recording layer of the rotated optical recording medium.

The recording waveform of the laser beam may be a pulse train or one pulse when one pit is formed. The ratio to the actual recording length (pit length) is important.
The pulse width of the laser beam is preferably in the range of 20 to 95%, more preferably in the range of 30 to 90%, and still more preferably in the range of 35 to 85% with respect to the length to be actually recorded. Here, when the recording waveform is a pulse train, the sum is in the above range.

The power of the laser beam varies depending on the recording linear velocity, but when the recording linear velocity is 6.61 m / s, the range of 1 to 15 mW is preferable, the range of 2 to 12 mW is more preferable, and the range of 3 to 10 mW is further increased. preferable. When the recording linear velocity is doubled, the preferable range of the laser beam power is ^21/2 times, respectively.

In order to increase the recording density, the NA of the objective lens used for the pickup is preferably 0.55 or more, and more preferably 0.60 or more.
In the present invention, a semiconductor laser having an oscillation wavelength in the range of 350 to 450 nm can be used as a light source for recording and reproduction.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to a following example.

[Example 1]
A substrate having a thickness of 0.6 mm was molded by injection molding using a polycarbonate resin (MD1500) manufactured by Teijin Chemicals Limited. The groove track pitch of the substrate was 400 nm, the groove depth was 90 nm, and the groove width was 180 nm.

  0.09 g of oxonol dye represented by the following structural formula and 0.01 g of azo dye represented by the following structural formula with respect to 14.8 g of TFP (2,2,3,3-tetrafluoro-1-propanol) Weighed and dissolved. The solution was irradiated with ultrasonic waves for 2 hours to dissolve the dye, and then allowed to stand in an environment of 23 ° C. and 50% for 0.5 hours or longer, and filtered through a 0.2 μm filter to prepare a recording layer forming coating solution. A recording layer having a thickness of 40 nm was formed on the substrate by spin coating using this recording layer forming coating solution.

  After forming the recording layer, it was heated in a clean oven at 80 ° C. for 1 hour. A reflective layer was formed to a thickness of 100 nm by DC sputtering using a target composed of 98.4 parts of Ag, 0.7 parts of Nd, and 0.9 parts of Cu on the heat-treated sample. The input power was 2 kW and the Ar flow rate was 5 sccm.

  After forming the reflective layer, a 0.6 mm thick polycarbonate substrate was bonded using a UV curable resin (SD-640) manufactured by Dainippon Ink & Chemicals, Inc. to produce an optical recording medium.

[Evaluation]
The produced optical recording medium was set in ODU-1000 (manufactured by Pulstec Industrial Co., Ltd.) equipped with a laser optical system having a wavelength of 405 nm and NA = 0.65, and a random signal (2T to 11T) was recorded at 10 mW. PRSNR was evaluated by reproducing with a power of 0.5 mW. At this time, the linear velocity was 6.61 m / s, and the laser emission pattern during recording was optimized, and the PRSNR, 11T signal Hi level (I11H), and Lo level (I11L) were measured. The results are shown in Table 1. In Table 1, I11 = I11H−I11L.
In Table 1, the determination was made according to the following criteria based on the PRSNR value.
-Criteria-
○: 31 or more ○ △: 21-30
Δ: Less than 20 ×: Measurement not possible

[Example 2]
Except that 0.095 g of the oxonol dye and 0.005 g of the azo dye were weighed and dissolved with respect to 14.8 g of TFP to prepare a recording layer forming coating solution, and a recording layer was formed using it. An optical recording medium was prepared in the same manner as in Example 1 and evaluated in the same manner.

[Comparative Example 1]
Optical recording was carried out in the same manner as in Example 1 except that 0.1 g of the oxonol dye was weighed and dissolved in 14.8 g of TFP to prepare a recording layer-forming coating solution, and a recording layer was formed using it. A medium was prepared and evaluated in the same manner.

[Comparative Example 2]
Except that 0.08 g of the oxonol dye and 0.02 g of the azo dye were weighed and dissolved with respect to 14.8 g of TFP to prepare a recording layer forming coating solution, which was used to form a recording layer. An optical recording medium was prepared in the same manner as in Example 1 and evaluated in the same manner.

  From the results of Table 1, the optical recording media of Examples 1 and 2 gave good results in PRSNR values, whereas Comparative Example 1 using an oxonol dye alone had a small PRSNR value. Although an azo dye was used in combination, measurement was impossible in Comparative Example 2 in which the addition amount of the azo dye was 20%. That is, it can be seen that an optical recording medium having a good PRSNR can be obtained by using an oxonol dye and a predetermined amount of an azo dye in combination.

Claims (4)

An optical recording medium having a recording layer on a substrate,
The optical recording medium, wherein the recording layer contains an oxonol dye and an azo dye, and the content of the azo dye is 1 to 15% by mass of the total dye in the recording layer. The optical recording medium according to claim 1, wherein the oxonol dye is represented by the following general formula (1).

[In the general formula (1), A, B, C and D are electron-withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m represents an integer of 0 to 3, and n represents 0 to 2m + 1. Represents an integer, and when n is an integer of 2 or more, a plurality of R may be the same or different from each other, and may be linked to each other to form a ring, and Y ^{t +} represents a t-valent cation. , T represents an integer of 1 to 10. ] The azo dye is a metal chelate compound obtained from an azo compound represented by the following general formula (2 ″) and a metal salt, and the maximum absorption wavelength λmax is 500 nm <λmax <650 nm. The optical recording medium according to claim 1.
General formula (2 ")
A−N = N−B
[In the general formula (2 ″), A represents a monovalent group derived from a coupler component, and B represents a monovalent group derived from a diazonium salt.]   The optical recording medium according to any one of claims 1 to 3, wherein the optical recording medium is recorded and reproduced by a laser beam having a wavelength of 350 to 450 nm.