JP2597517B2 - Information recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a novel information recording medium on which information can be written using a high energy density laser beam.

[Technical Background of the Invention] In recent years, information recording media using high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk,
It is used as a disk, an audio disk, a large-capacity still image file, and a disk memory for a large-capacity computer.

A DRAW (Direct Read After Write) type optical disk has a disk-shaped substrate made of glass, synthetic resin, and the like, and a metal or semimetal such as Bi, Sn, In, Te, etc. provided thereon, or cyanine. And a recording layer comprising a dye of a metal, metal complex, or quinone type. An intermediate layer made of a polymer substance is provided on the surface of the substrate on which the recording layer is provided, from the viewpoint of improving the flatness of the substrate, improving the adhesive force with the recording layer, or improving the sensitivity of the optical disc. There are cases. Writing information on an optical disc is performed by irradiating the optical disc with a laser beam. The irradiated portion of the recording layer absorbs the light and locally raises the temperature, causing a physical or chemical change (for example, a pit). Information is recorded by changing its optical properties. Reading of information is also performed by irradiating an optical disk with a laser beam, and information is reproduced by detecting reflected light or transmitted light corresponding to a change in the optical characteristics of the recording layer.

As the recording material for forming the recording layer of such an information recording medium, metals and dyes are known as described above. An information recording medium using a dye has advantages in characteristics of the recording medium itself, such as higher sensitivity than a recording material such as a metal, and also has a manufacturing advantage that a recording layer can be easily formed by a coating method. Has great advantages. Accordingly, dyes that can be used for such optical discs have been developed and have been put to practical use. Characteristics required for application to an optical disc include absorption of a dye in an oscillation wavelength region of a semiconductor laser of 700 to 900 nm, a large absorption coefficient, high reflectance, and the like. Research on expanding the oscillation wavelength range of semiconductor lasers and improvement and development of optical disk drives are being carried out, and with this, changes in the types of dyes that can be used and changes are expected. Therefore, enrichment of the types of dyes for optical disks is desired.

The recording layer made of such a dye generally has low reflectance, low C / N of a reproduction signal, and other characteristic problems, and disadvantages such as the dye recording layer being easily degraded over time by light irradiation. Have.

As a recording layer made of a dye having improved reflectance and C / N, an optical disc having a recording layer made of a cyanine dye having a benzoindolenine skeleton has been developed in Japanese Patent Application Laid-Open No. 40382/1988. However, although the information recording medium having such a dye recording layer has a relatively good C / N ratio, it does not have satisfactory reflectance and light resistance.

In general, a reflective layer is further provided on the dye recording layer in order to increase the reflectance. Such an example is described in Nikkei Electronics (p. 107, published on January 23, 1989). According to this, the dye used in the recording layer of the recording medium is unknown, but the recording method is described. However, it is disclosed that the dye is melted by laser absorption of the dye recording layer, whereby the plastic substrate is heated, and the substrate rises on the recording layer side to form pits, thereby forming a pit. It has been done. This reflection layer is a deposited film of gold. According to the studies of the present inventors, when the cyanine dye having the benzoindolenine skeleton is used for the dye recording layer, it is possible to obtain an optical disc having a relatively high C / N and an improved reflectance. it can.

Even in the case of DRAW type optical discs, in the case of high-density recording of CD format signals (CD-DRAW), it is necessary to record the above signals at a low linear speed of 1.2 to 1.4 m / sec. It is required to be played on a CD player. It is desirable that the reflectivity of the optical disk be at least 70% or more for reproduction by a CD player. However, even when a CD format signal is recorded on an optical disc having a recording layer of a cyanine dye having a benzoindolenine skeleton and a reflective layer, some CD players cannot reproduce the CD format signal.

Therefore, along with the demand for enriching the types of dyes for the optical disk, the reflectivity of the CD-DRAW is remarkably high (80%).
%) Is desired.

[Object of the Invention] An object of the present invention is to provide an information recording medium having a recording layer composed of a novel ianine dye.

Another object of the present invention is to provide an information recording medium having a recording layer and a reflective layer thereon, wherein the information recording medium has significantly improved C / N and reflectance.

Still another object of the present invention is to provide an information recording medium having a recording layer and a reflective layer thereon, wherein the C / N and the reflectance are remarkably improved and the information recording medium is excellent in light resistance. .

[Summary of the Invention] The present invention relates to a method for preparing a compound of the following general formula (I): [Wherein, A and A ′ each represent an atomic group for completing an aromatic ring which may have a substituent,
Represents a methine group which may have a substituent, or a trivalent linking group formed by linking 3, 5 or 7 methine groups which may have a substituent by a conjugated double bond. , R ¹ , R ² , R ¹¹ and R ¹² each represent a hydrogen atom or an alkyl group which may have a substituent, a phenyl group, an acyl group, an alkoxy group or a 5- or 6-membered heterocyclic group, R ³ and R ¹³ each represent an alkyl group which may have a substituent (which may be a substituent having an anion); X ^n- represents an anion;
Represents 2 or 3, m represents 1 or 0, and
When R ³ or R ¹³ has a group having an anion as a substituent, m is 0. ] An information recording medium provided with a recording layer on which information can be recorded by a laser containing a cyanine dye represented by the following formula:

Preferred embodiments of the information recording medium of the present invention are as follows.

1) A and A ′ in the general formula (I) may be substituted with a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a cyano group and an alkoxycarbonyl group having 1 to 4 carbon atoms. The above-mentioned information recording medium, which is an atomic group for completing a benzene ring or a naphthalene ring.

2) L in the general formula (I) is a halogen atom or an alkyl group having 1 to 4 carbon atoms (provided that these alkyl groups are linked to form a ring by binding to another methine group) Or a trivalent linking group formed by linking three or five methine groups, which may be substituted with a benzyl group and a phenyl group, with a conjugated double bond.

3) R ¹ , R ² , R ¹¹ and R ^{12 in the} general formula (I) are each an unsubstituted alkyl group having 1 to 8 hydrogen atoms, an unsubstituted phenyl group or a naphthyl group. The information recording medium described above.

4) R ³ and R ^{13 in} the general formula (I) are each an alkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1 to 4 carbon atoms, an alkoxycarbonyl group having 1 to 4 carbon atoms, and a carbon atom The above-mentioned information recording medium, wherein the information recording medium is an alkyl group having 1 to 18 carbon atoms which may be substituted by a sulfonyl group having 1 to 4 atoms, a halogen atom or a hydroxy group.

5) The information recording medium as described above, wherein X ^{n− in the} general formula (I) is a halogen ion, a sulfonate ion, ClO ₄ ⁻ , BF ₄ ⁻ , a metal complex ion or a phosphate ion.

6) The information recording medium as described above, wherein a reflective layer made of a metal is provided on the recording layer.

7) The recording layer is provided with a recording layer comprising a mixture of a cyanine dye represented by the above general formula (I) and a dye having an absorption maximum at a longer wavelength side than the absorption maximum of the dye. The information recording medium described above.

8) The information recording medium as described above, wherein the recording layer contains a quencher having an absorption maximum on a longer wavelength side than the absorption maximum wavelength of any of the dyes contained in the recording layer.

9) The information recording medium according to 7) above, wherein the absorption maximum of the dye is 20 nm or more longer than the absorption maximum of the cyanine dye represented by the general formula (I).

10) The information recording medium as described above, wherein the absorption maximum of the cyanine dye is on the longer wavelength side than 650 nm.

11) The information recording medium, wherein the material of the substrate is plastic.

12) The information recording medium according to 6), wherein the metal is at least one selected from the group consisting of Cr, Na, Pt, Cu, Ag, Au, Al and stainless steel.

Incidentally, the absorption maximum of the dye of the present invention refers to the absorption maximum of the dye layer formed on the substrate.

[Effect of the Invention] An optical disc obtained by using the specific cyanine dye of the present invention represented by the above general formula (I) as a material for a recording layer of an optical disc exhibits excellent recording / reproducing characteristics and high reflectance.

Further, when a recording layer comprising the specific cyanine dye of the present invention is provided on a substrate, and a reflective layer comprising a metal is further laminated on the recording layer, by adopting such a configuration, recording sensitivity, C The reflectance can be improved without substantially deteriorating the recording / reproducing characteristics such as / N and the degree of modulation.

In particular, when a recording layer made of a specific cyanine dye of the present invention and another dye having an absorption maximum on a longer wavelength side than the dye is provided, and a reflective layer made of a metal is further laminated on the recording layer, a high level is obtained. In addition to reflectance, recording sensitivity, C / N,
Recording / reproducing characteristics such as the degree of modulation can also be improved.

Further, the obtained optical disk has a remarkably high reflectance, so that a CD format signal can be recorded and reproduced by a commercially available CD player, so that the optical disk is useful as a CD-DRAW.

[Detailed Description of the Invention] The information recording medium of the present invention has a basic configuration in which a recording layer containing a cyanine dye represented by the general formula (I) is provided on a substrate.

Furthermore, an information recording medium according to another aspect of the present invention has a basic configuration in which a reflective layer is provided on the dye recording layer.

The present inventors have developed a dye capable of forming a recording layer by coating on a substrate, and to obtain a novel dye exhibiting excellent recording / reproducing characteristics such as high C / N and high reflectance when used as an optical disc. We have been working diligently.

As a result, it was found that the above characteristics can be realized by using the cyanine dye represented by the general formula (I) as the recording layer. Further, by further laminating a reflective layer made of metal on the recording layer made of the specific cyanine dye, the recording sensitivity, C / N, and the recording / reproducing characteristics such as the degree of modulation are almost reduced. It was also found that the reflectance could be improved.
In this case, in addition to the cyanine dye represented by the general formula (I), a recording layer made of a mixture of a dye having an absorption maximum on a longer wavelength side than the dye is provided, so that the above-described high reflectance can be obtained. It became clear that it became easy to improve the recording / reproducing characteristics such as the recording sensitivity, C / N, and the degree of modulation.

That is, the cyanine dye of the present invention represented by the general formula (I) can change its absorption maximum to a short wavelength side or a long wavelength side by changing its structure. The above dye is the oscillation wavelength of general laser light
In the wavelength band around 780 nm, many have characteristics of high reflectance and relatively high C / N and modulation. Among these compounds, a dye having an absorption maximum in a wavelength region shorter than 780 nm and a dye having high sensitivity in the laser wavelength region (that is, a dye having a maximum absorption on a longer wavelength side than the dye) are used in combination. In addition to the above high reflectance, it was found that recording / reproducing characteristics such as recording sensitivity, C / N, and modulation degree can be improved.

The information recording medium of the present invention can be manufactured, for example, by the method described below.

The substrate of the present invention can be arbitrarily selected from various materials used as a substrate of a conventional information recording medium. As the substrate material of the present invention, for example, glass; acrylic resin such as polymethyl methacrylate; polyvinyl chloride;
Examples thereof include vinyl chloride resins such as vinyl chloride copolymers; epoxy resins; amorphous polyolefins and polyesters, and may be used in combination if desired. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoint of moisture resistance, dimensional stability, cost, and the like.

On the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesive strength and preventing deterioration of the recording layer,
An undercoat layer may be provided. Examples of the material of the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleinanhydride copolymer,
Polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate Examples thereof include polymers, polymer substances such as polyethylene, polypropylene, and polycarbonate; and organic substances such as silane coupling agents.

The undercoat layer is prepared, for example, by dissolving or dispersing the above substance 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 be formed. The thickness of the undercoat layer is generally 0.005 to 20 μm
And preferably in the range of 0.01 to 10 μm.

Further, it is preferable that irregularities representing information such as tracking grooves or address signals are formed on the substrate (or the undercoat layer). When a resin material such as the above polycarbonate is used, it is preferable that the groove is provided directly on the substrate by injection molding or extrusion molding of the resin material.

The groove may be formed by providing a pre-groove layer. As the material of the pre-groove layer,
A mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used.

The pre-groove layer is formed by first applying a mixed solution composed of the above-mentioned acrylate and a polymerization initiator on a precisely formed master (stamper), and then placing a substrate on the coating solution layer. The liquid layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the liquid phase. Next, the substrate provided with the pre-groove layer is provided by peeling the substrate from the matrix.

The thickness of the pre-group layer is generally in the range from 0.05 to 100 μm, preferably in the range from 0.1 to 50 μm.

 The recording layer of the present invention is provided on the substrate.

The recording layer of the present invention is characterized by containing a cyanine dye represented by the following general formula (I).

[Wherein, A and A ′ each represent an atomic group for completing an aromatic ring which may have a substituent,
Represents a methine group which may have a substituent, or a trivalent linking group formed by linking 3, 5 or 7 methine groups which may have a substituent by a conjugated double bond. , R ¹ , R ² , R ¹¹ and R ¹² each represent a hydrogen atom or an alkyl group which may have a substituent, a phenyl group, an acyl group, an alkoxy group or a 5- or 6-membered heterocyclic group, R ³ and R ¹³ each represent an alkyl group which may have a substituent (which may be a substituent having an anion); X ^n- represents an anion;
Represents 2 or 3, m represents 1 or 0, and
When R ³ or R ¹³ has a group having an anion as a substituent, m is 0. The above general formula (I) used for the information recording medium of the present invention.
In the compound represented by, preferably, R ¹ and R ¹¹ , R ²
And R ¹² , R ³ and R ¹³ , R ⁴ and R ¹⁴ , and A and A ′, respectively.

The group of atoms for completing the aromatic ring represented by A and A 'is preferably an optionally substituted benzene ring or naphthalene ring. As the substituent, preferably, F, Cl
Such as a halogen atom, a cyano group, a nitro group, a carboxyl group, an acyl group, an alkylsulfonyl group having 1 to 8 carbon atoms, an arylsulfonyl group having 1 to 8 carbon atoms, an alkoxycarbonyl group having 1 to 8 carbon atoms, An amino group, an alkyl group having 1 to 8 carbon atoms, an aryl group, an alkoxy group having 1 to 8 carbon atoms, an aryloxy group having 1 to 8 carbon atoms, an alkylthio group having 1 to 8 carbon atoms, an arylthio group, Sulfamoyl group, N-substituted sulfamoyl group, carbamoyl group, N-substituted carbamoyl group and 5
Alternatively, a 6-membered heterocyclic group can be exemplified. Among these, a substituent having a positive Hammett's σ constant or a converted value thereof is more preferable. Most preferably, F, Cl
And halogenated alkyl groups having 1 to 4 carbon atoms (eg, trifluoromethyl group), cyano groups and alkoxycarbonyl groups having 1 to 4 carbon atoms (eg, ethoxycarbonyl group). .

Preferable as the linking group represented by L is a conjugated methine group which may have a substituent consisting of 3 or 5 methine groups, and the substituent is preferably a halogen atom or a C 1-8 methine group. Examples thereof include an alkyl group, an alkoxy group having 1 to 6 carbon atoms, and an aralkyl group. Among these substituents, more preferred are a halogen atom, an alkyl group having 1 to 4 carbon atoms, a benzyl group and a phenyl group. Most preferably, it is a halogen atom such as a methyl group, a benzyl group and Cl.

Preferred as the group represented by R ¹ , R ² , R ¹¹ and R ¹² is an optionally substituted alkyl group having 1 to 18 carbon atoms (eg, methyl, ethyl, butyl, isobutyl, 2-butyl
Ethylhexyl, dodecyl, trifluoromethyl, 2-
Ethoxyethyl, 2-hydroxyethyl, 3-sulfopropyl, 3-sulfobutyl, 2-sulfoethyl, etc.),
An optionally substituted phenyl or naphthyl group having 6 to 18 carbon atoms (eg, phenyl, 4-methylphenyl group)
3,5-dichlorophenyl, 4-methoxyphenyl, β-
Naphthyl, 2,5-di-t-amylphenyl, etc.). More preferably, it is an unsubstituted alkyl group having 1 to 8 carbon atoms or an unsubstituted phenyl group or naphthyl group, and most preferably, a methyl group, an ethyl group, an n-propyl group and a phenyl group can be exemplified. .

The groups represented by R ³ and R ¹³ are preferably an alkyl group having 1 to 18 (preferably 1 to 5) carbon atoms, each being an alkoxy group having 1 to 4 carbon atoms, and a group having 1 to 4 carbon atoms.
May be substituted by an alkylthio group having 1 to 4 carbon atoms, an alkoxycarbonyl group having 1 to 4 carbon atoms, a sulfonyl group having 1 to 4 carbon atoms, a halogen atom or a hydroxy group. More preferably, methyl, ethyl, isopropyl, sec-butyl, cyclohexyl, 2-ethylhexyl, benzyl, 2-phenylethyl, dodecyl, 2-ethoxyethyl, 3-ethoxypropyl, Hydroxyethyl group, 3-acetoxypropyl group, ethoxycarbonylmethyl group, 3-sulfopropyl group, 2,3-tetrafluoropropyl group, allyl group, 2-
Methylthioethyl group, 3-methoxypropyl group, phenyl group, 4-methylphenyl group, 3,5-dichlorophenyl group, 4-methoxyphenyl group, β-naphthyl group and 2,
5-di-t-amylphenyl. Most preferably,
Methyl group, ethyl group, sec-butyl group, 2-ethoxyethyl group, 3-ethoxypropyl group, 3-methoxypropyl group, hydroxyethyl group, 3-acetoxypropyl group, ethoxycarbonylmethyl group, 3-sulfopropyl group and It is a 2,3-tetrafluoropropyl group.

Preferred as the anion represented by X are halide ions (eg, Cl ⁻ , Br ⁻ , I ⁻ ) and sulfonate ions (eg, CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ) that are preferred as the anion to be formed. ^-, CH ₃ OSO ₃ ^-, Naphthalene-1,5-disulfonate ion), Cl
O ₄ ⁻ , BF ₄ ⁻ , metal complex ion (for example, And phosphate ions (for example, PF ₆ ^-, Can be mentioned.

Of these, particularly preferred anions are ClO ₄ ⁻ , PF ₆
^- and In a while, I used in the intermediate stage of the synthesis ^- Ya May be mixed in a trace amount.

Examples of the specific compound represented by the above general formula include the following I-1 to I-20.

The dye represented by the general formula (I) of the present invention can be obtained from Chemcal Ab
FSBabic, abstracted in Stracts, Volume 69, Section 60031V
Khim.Geterotsikl, heed and AFBabicheva, Soedin.
Journal, Vol. 1967, pp. 917-922.
And A 'is unsubstituted benzene ring, with ^{R 1, R 2, R 3} , R 11, R 12 and R ¹³ are all methyl groups, X ^n-it is ClO ₄ ^- a, L is a unsubstituted methine And L is a trimethine group and the other is a dye having the same structure as the former. However, there is no description about application of these dyes to an optical disk. Other dyes can also be synthesized with reference to these.

Next, the synthesis method will be specifically described with reference to synthesis examples of the dye represented by formula (I) of the present invention.

Synthesis Example 1 (Synthesis of Dye I-4) After dissolving 4.58 g of 5,6-dichloro-1-ethyl-2-methylbenzimidazole in 25 ml of acetone,
-3 ml of bromopropiophenone was added, and the mixture was heated under reflux for 100 minutes. After the acetone was distilled off, the mixture was heated at 100 ° C. for 1 hour. 100 ml of acetone was added to the reaction mixture, and the mixture was stirred. The resulting colorless crystals were collected by filtration, washed with acetone, and dried. Yield 5.
4g.

The crystals were added to an aqueous solution prepared from 1.3 g of sodium carbonate and 60 ml of water, and heated on a steam bath for 80 minutes. After cooling, the resulting crystals were collected by filtration and washed with water to give 4.8 g of colorless crystals.
The crystals were recrystallized from 600 ml of methanol to obtain 2 g of colorless needle crystals of 6,7-dichloro-4-ethyl-1-methyl-2.
-Phenylpyrrolo [1,2-a] benzimidazole was obtained.

To 1 g of these crystals, 20 ml of acetonitrile and 0.3 g of paratoluenesulfonic acid monohydrate were added and dissolved, and 1,3,3-
1 ml of trimethoxypropene was added, and the mixture was heated under reflux for 5 minutes. After cooling, the resulting crystals were collected by filtration and acetonitrile 25 ml
Then, 0.75 g of compound crystals was obtained.

247-249 ° C.

λ _Max. (methanol): 626 nm Synthesis Example 2 (Synthesis of Dye I-18) To 2.57 g of 5,6-dichloro-1-isopropyl-2-methylbenzimidazole was added α-bromopropiophenone
After 1.52 ml and 1 ml of anisole were added and heated on a steam bath for 2 hours, 50 ml of acetone was added.

The resulting crystals are collected by filtration and 2% aqueous sodium carbonate solution (40 ml)
Was added and heated on a steam bath for 80 minutes. After cooling, the resulting crystals were collected by filtration and washed with water to give 6,7-dichloro-4-isopropyl-1-methyl-2-phenylpyrrolo [1,2-a] benzimidazole.

To 0.6 g of these crystals were added 11 ml of acetonitrile, 0.17 g of paratoluenesulfonic acid monohydrate and 0.6 ml of 1,3,3-trimethoxypropene, and the mixture was heated under reflux for 15 minutes. After cooling, the resulting crystals were collected by filtration and washed with acetonitrile to obtain 0.2 g of a compound.

167 ° C.

λ _Max. (methanol): 626 nm Further, as described above, by using the above-mentioned dye in combination with a dye having high sensitivity at the laser wavelength (ie, a dye having a maximum absorption on a longer wavelength side than the above-mentioned dye), the above-mentioned high reflectance is obtained. In addition, it is possible to obtain an information recording medium having improved recording / reproducing characteristics such as recording sensitivity, C / N, and modulation degree. In particular, when a reflective layer made of gold or the like is provided, it is effective to use the dye of the recording layer in combination with another dye as described above.

An optical disk having a reflective layer provided on a recording layer, wherein a dye having an absorption maximum at a longer wavelength than the absorption maximum of the cyanine dye is used in combination with the cyanine dye represented by the general formula (I). The absorption maximum of such a dye is larger than the absorption maximum of the cyanine dye represented by the general formula (I).
It is preferable that the height is at least 20 nm in order to obtain high C / N and reflectivity.

Such a dye may be any type of dye as long as it satisfies the above conditions. However, in forming a uniform dye recording layer, the dye has excellent compatibility with the general formula (I). Dyes that can use the same organic solvent when dissolved are preferable. By forming a uniform dye layer, C /
The recording / reproducing characteristics such as N and the degree of modulation are excellent. Such dyes include cyanine dyes, oxonol dyes,
Polymethine dyes such as pyrylium dyes and thiopyrylium dyes are preferred.

In particular, in the case of an optical disk having a reflective layer provided on a recording layer, the recording layer has a relatively high reflectance among dyes, and
A specific cyanine dye having a benzoindolenine skeleton represented by the following general formula (II) which is excellent in recording / reproducing characteristics such as C / N and recording sensitivity; and a dye represented by the general formula (I) of the present invention. By providing a recording layer made of a mixture of the above, the recording / reproducing characteristics and the reflectance can be improved, which is preferable.

Therefore, the dye having the absorption maximum on the long wavelength side is preferably a cyanine dye having a benzoindolenine skeleton having a structure represented by the following general formula (II).

General formula (II); [Where, R ^21, R ²² and R ²³ each independently represent an alkyl group which may have a substituent carbon atoms in the range of 1 to 8, X ^P- represents an anion And p represents 1 or 2.] In the general formula (II), the alkyl group represented by R ²¹ is an alkyl group which may have a substituent having 1 to 8 carbon atoms. Examples thereof include groups such as methyl, ethyl, n-propyl, n-butyl, isobutyl and 2-ethylhexyl, and preferably an alkyl group having 1 to 6 carbon atoms (for example, methyl, ethyl, n-
Propyl, n-butyl and isobutyl), and examples of the substituent which may be substituted include a fluorine atom and an alkoxy group. Particularly preferred is an unsubstituted alkyl group.

Examples of the alkyl group represented by R ²² and R ²³ include an unsubstituted alkyl group having 1 to 8 carbon atoms (specific examples include methyl,
Ethyl and propyl), and particularly preferably a methyl group or an ethyl group.

Examples of specific compounds represented by the general formula (II) include the following II-1 to II-16.

The cyanine dye having an indolenine skeleton represented by the above general formula (II) as shown in the above specific examples is a dye used in the recording layer of the optical disc disclosed in the above-mentioned JP-A Nos. 64-40382 and 64-40387. Are included in the general formula.

In a preferred combination of the dye of the general formula (I) and the dye of the general formula (II), three optionally substituted methine groups in which L of the dye of the general formula (I) is linked by a conjugated double bond Wherein the mixing ratio of the dye of the general formula (I) to the compound of the general formula (II) is 9:91 to 80:20 by weight (dye of the general formula (I): Dyes) are preferred.

In order to improve light resistance, it is preferable to use various dyes known as a so-called singlet oxygen quencher, for example, a compound represented by the following general formula (III) or (IV).

(However, [Cat] ⁺ represents a nonmetallic cation such as tetraalkylammonium, M represents a transition metal atom such as Ni, Z and Z ′ are an optionally substituted benzene ring, 2-thioxo-1 Represents an atomic group for completing a 5- or 6-membered aromatic or heterocyclic ring such as a, 3-dithiol ring) [Wherein R represents an alkyl group which may have a substituent, and Q represents the same anion as that represented by X in the general formula (I)]. The above general formula (III) or (IV) Specific examples of the quencher represented by are PA-1006 (Mitsui Toatsu Fine Co., Ltd.) and IRG-023 (Nippon Kayaku Co., Ltd.).

The recording layer is formed by dissolving the dye, and optionally the quencher, the binder, and the like in a solvent to prepare a coating solution, and then coating the coating solution on the substrate surface to form a coating film and then drying. It can be done by doing.

Examples of the solvent for preparing the dye layer coating solution of the present invention include: esters such as ethyl acetate, butyl acetate, and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone;
Chlorinated hydrocarbons such as dichloroethane and chloroform;
Amides such as dimethylformamide; hydrocarbons such as cyclohexane; tetrahydrofuran, ethyl ether,
Ethers such as dioxane; alcohols such as ethanol, n-propanol, isopropanol and n-butanol; and fluorinated solvents such as 2,2,3,3-tetrafluoropropanol.

Antioxidants, UV absorbers, plasticizers,
Various additives such as a lubricant may be added according to the purpose.

When a binder is used, examples of the binder include natural organic high molecular substances such as gelatin, cellulose derivatives, dextran, rosin, and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene; and polyvinyl chloride. , Polyvinylidene chloride,
Vinyl resins such as polyvinyl chloride / polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins And the like. Synthetic organic polymer substances such as an initial condensate of a thermosetting resin.

When a binder is used as a material for the recording layer, the ratio of the dye to the binder is generally in the range of 0.01 to 99% (weight ratio), preferably in the range of 1.0 to 95% (weight ratio). The concentration of the coating solution prepared in this way is generally 0.
01 to 10% (weight ratio), preferably 0.1 to 5%
% (Weight ratio).

The recording layer may be a single layer or a multilayer, but the layer thickness is generally
It is in the range of 200-3000 °, preferably in the range of 500-2500 °. The recording layer may be provided not only on one side of the substrate but also on both sides.

Examples of the 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.

Further, in the information recording medium of the present invention, it is preferable to provide a reflective layer on the recording layer for the purpose of improving the reflectance at the time of reproducing information. Is a substance having a high reflectance to, for example, Mg, Se,
Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, F
e, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, C
Examples thereof include metals such as d, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi and semimetals or stainless steel. Of these, preferred are Cr, Ni, Pt, C
u, Ag, Au, Al and stainless steel. These substances may be used alone or in combination of two or more kinds or as an alloy.

The reflection layer can be formed on the recording layer by, for example, vapor deposition, sputtering, or ion plating of the above-mentioned light reflective substance. The thickness of the reflective layer is generally in the range from 100 to 3000 °.

Further, a protective layer may be provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the like. This protective layer may be provided on the side of the substrate on which the recording layer is not provided for the purpose of improving the scratch resistance and the moisture resistance.

Examples of materials used for the protective layer include SiO, SiO ₂ , M
gF _2, inorganic substances such as SnO _2, Si ₃ N _4; thermoplastic resins, thermosetting resins, and organic materials such as UV curable resin.

The protective layer can be formed, for example, by laminating a film obtained by extrusion processing of a plastic on a recording layer (or a silver salt layer or a reflective layer) and / or a substrate via an adhesive layer. Or vacuum deposition,
It may be provided by a method such as sputtering or coating. In the case of a thermoplastic resin or a thermosetting resin, they can also be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure. Various additives such as an antistatic agent, an antioxidant and a UV absorber may be added to these coating solutions according to the purpose.

 The thickness of the protective layer is generally in the range from 0.1 to 100 μm.

In the present invention, the information recording medium may be a single plate having the above-described configuration, or two substrates having the above-described configuration are arranged such that the recording layer faces inside,
By bonding using an adhesive or the like, a bonding type recording medium can also be manufactured. Alternatively, an air sandwich type recording medium is manufactured by joining a substrate having the above configuration to at least one of the two disk-shaped substrates via a ring-shaped inner spacer and a ring-shaped outer spacer. You can also.

The information recording medium of the present invention can be manufactured by the above method.

The thus obtained optical disk having extremely high reflectance and excellent recording / reproducing characteristics can maintain a desired reflectance even if a singlet quencher is added to improve light resistance. That is, when the quencher is added, the reflectivity of the optical disk generally decreases, but the information recording medium of the present invention has a remarkably high reflectivity of about 80%. The rate can be maintained and can be played on a commercially available CD player. Accordingly, an optical disk having high reflectance and excellent light resistance can be obtained.

A method for recording and reproducing information using the information recording medium is performed, for example, as follows.

First, recording light such as semiconductor laser light is irradiated from the substrate side while rotating the information recording medium at a constant linear velocity (1.2 to 1.4 m / sec in the case of a CD format) or a constant angular velocity. By this light irradiation, a cavity is formed at the interface between the recording layer and the reflection layer in the optical disc having the reflection layer (the cavity is formed by deformation of the recording layer or the reflection layer, or deformation of both layers). It is considered that the information is recorded when the substrate is overlaid or deformed, or when the refractive index changes due to discoloration or change in the association state of the recording layer. In an optical disc having only a recording layer without a reflective layer, information is generally recorded by forming bits (holes) in the recording layer.
Generally, a semiconductor laser beam having an oscillation wavelength in the range of 750 nm to 850 nm is used as the recording light.

Reproduction of information can be performed by irradiating a semiconductor laser beam from the substrate side while rotating the information recording medium at the same constant linear speed as described above, and detecting the reflected light.

Hereinafter, examples of the present invention will be described. However, these examples do not limit the present invention.

Example 1 2.0 g of the cyanine dye represented by the general formula (I) (the dye I-17) and a diimmonium dye having the following structural formula as a quencher (IRG-023, manufactured by Nippon Kayaku Co., Ltd.) 0.2 g was dissolved in 100 cc of 2,2,3,3-tetrafluoropropanol (structural formula: HCF ₂ CF ₂ CH ₂ OH) to prepare a dye layer coating solution.

On a disc-shaped polycarbonate substrate (outer diameter: 120 mm, inner diameter: 15 mm, thickness: 1.2 mm, track pitch: 1.6 μm, group width: 0.5 μm, group depth: 900 mm) provided with a tracking guide, The coating solution was applied at a rotation speed of 1,000 rpm by a spin coating method and dried for 30 seconds to form a recording layer having a layer thickness of 1300 °.

Thus, an information recording medium including the substrate and the recording layer was manufactured.

Example 2 In Example 1, Au was further DC-sputtered on the recording layer to form a reflective layer having a thickness of 1300 °, and a UV-curable resin (trade name: 3070) was formed as a protective layer on the reflective layer. , Manufactured by Three Bond Co., Ltd.) by spin coating at a rotation speed of 1500 rpm, and then irradiating it with a high-pressure mercury lamp to cure it to form a protective layer having a thickness of 3 μm. A recording medium was manufactured.

Example 3 Example 2 was repeated except that 2 g of the dye I-4 was used in place of 2 g of the cyanine dye represented by the general formula (I) (the dye I-17). In the same manner as in Example 2, an information recording medium was manufactured.

Example 4 In Example 3, instead of 2 g of the cyanine dye represented by Formula (I) (Dye I-4), 0.4 g of (Dye I-4) and the dye represented by Formula (I) were used. An information recording medium was produced in the same manner as in Example 3 except that 1.6 g of the dye represented by II) (the dye II-1) was used.

Example 5 Example 4 was the same as Example 4 except that the dye layer coating solution was prepared without adding the diimmonium dye to the dye coating solution.
An information recording medium was manufactured in the same manner as described above.

Example 6 In Example 4, 0.4 g of the cyanine dye represented by the general formula (I) (the dye I-4) was replaced with a substrate having a depth of 1600 ° instead of a substrate having a depth of 900 °. 1.0g
And a dye layer coating solution was prepared by changing 1.6 g of the cyanine dye represented by the general formula (II) as the dye B (the 1.6 g of the dye (II-1) to 1.0 g). 20
An information recording medium was manufactured in the same manner as in Example 4 except that the recording layer was formed so as to be 00 °.

Example 7 An information recording medium was prepared in the same manner as in Example 4 except that the dye (II-6) was used instead of the dye (II-1) represented by the general formula (II). Was manufactured.

Example 8 An information recording medium was prepared in the same manner as in Example 4 except that the dye (I-18) was used instead of the dye (I-4) represented by the general formula (I). Was manufactured.

[Comparative Example 1] In Example 5, 1.6 g of the dye A (the dye II-1) represented by the general formula (II) was changed to 2.0 g, and the cyanine dye represented by the general formula (I) ( Dye I-
An information recording medium was manufactured in the same manner as in Example 5, except that the dye coating solution was prepared without using 4).

Comparative Example 2 Comparative Example 1 was the same as Comparative Example 1, except that 0.2 g of the above diimmonium dye (IRG-023, manufactured by Nippon Kayaku Co., Ltd.) was added to the dye coating solution as a quencher to prepare a dye layer coating solution. An information recording medium was manufactured in the same manner as in Example 1.

Table 1 shows the compositions of the dye coating solutions obtained in the above Examples and Comparative Examples.

[Evaluation of Information Recording Medium] 1) Reflectivity The obtained information recording medium was irradiated with light having a wavelength of 780 nm from the substrate side using a spectrophotometer (manufactured by Hitachi, Ltd.) to reflect the unrecorded portion. The rate was measured.

2) C / N The information recording medium obtained above was subjected to a constant linear velocity of 1.3 m / sec and a recording power of 780 nm using a semiconductor laser beam.
At 7.0 mW, a signal with a modulation frequency of 720 kHz (duty: 33%) was recorded. Then, the recorded signal was reproduced with a reproduction power of 0.5 mW, and the C / N during the reproduction was measured using a spectrum analyzer (TR4135: manufactured by Advantest).

 Table 2 shows the measurement results.

As is clear from Table 2, the optical disk having the recording layer using the dye having the absorption maximum on the relatively long wavelength side among the specific cyanine dyes of the present invention (Example 1) has a high reflectance and a high C / N ratio. Shows a high level, and can be sufficiently used as a dye for an optical disk. The optical disc having the reflective layer provided on the recording layer (Example 2) has a relatively high reflectivity and has almost no decrease in C / N.
Also, an optical disc having a recording layer using a dye having an absorption maximum on a relatively short wavelength side among the specific cyanine dyes of the present invention, and a reflective layer provided on the recording layer (Example 3)
Has an extremely high reflectance and has almost no decrease in C / N. An optical disc (Examples 4 to 8) having a recording layer in which a specific cyanine dye of the present invention (the dye used in Example 3 or the like) and another dye having a maximum absorption on a longer wavelength side than the dye are combined It has an extremely high reflectance and maintains a high level of C / N. Therefore, in the case where a quencher was added in order to improve light resistance, Example 3,
High reflectivity can be maintained as shown by 4, 6, and 8.

On the other hand, an optical disk (Comparative Example 1) using only a dye having a benzoindolenine skeleton, which is generally known for having a high reflectance and excellent recording / reproducing characteristics, has a lower reflectance than the Examples. Therefore, it cannot be said that the reflectance is sufficiently satisfactory for reproducing information on a CD player. Therefore, when a quencher was added to improve the light resistance (Comparative Example 2), the result was that the reflectance was lower than 70%.

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein said substrate has the following general formula (I): [Wherein, A and A ′ each represent an atomic group for completing an aromatic ring which may have a substituent,
Represents a methine group which may have a substituent, or a trivalent linking group formed by linking 3, 5 or 7 methine groups which may have a substituent by a conjugated double bond. , R ¹ , R ² , R ¹¹ and R ¹² each represent a hydrogen atom or an alkyl group which may have a substituent, a phenyl group, an acyl group, an alkoxy group or a 5- or 6-membered heterocyclic group, R ³ and R ¹³ each represent an alkyl group which may have a substituent (which may be a substituent having an anion); X ^n- represents an anion;
Represents 2 or 3, m represents 1 or 0, and
When R ³ or R ¹³ has a group having an anion as a substituent, m is 0. ] An information recording medium comprising a recording layer capable of recording information with a laser containing a cyanine dye represented by the following formula: 2. An information recording medium according to claim 1, wherein a reflection layer is provided on said recording layer.