JP2000343824A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium capable of recording and reproducing in a high density by a blue laser. SOLUTION: The optical recording medium comprises a recording layer containing a compound represented by the formula, wherein a ring A is an aromatic hydrocarbon ring or an aromatic heterocycle which may be substituted, rings B, C are each 5-membered ring which may have a substituent, or may form a condensed ring together with C1 and C2, C1' and C2' and another group, wherein X, X' are each independently a nitrogen atom, or C-R1, Y, Y' are each independently an oxygen atom, a sulfur atom or N-R2, wherein R1 is a hydrogen atom, a substituted or nonsubstituted alkyl group, a substituted or nonsubstituted alkoxy group, a substituted or nonsubstituted alkenyl group, a substituted or nonsubstituted amino group, a substituted or nonsubstituted alkylthio group, an alkylcarbonyl group, an alkoxycarbonyl group or the like, and R2 is a hydrogen atom, a substituted or nonsubstituted alkyl group or a substituted or nonsubsituted alkenyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel write-once optical recording medium using an organic dye for a recording layer. Further, the present invention relates to an optical recording medium which can be written and read by a blue laser.

[0002]

2. Description of the Related Art In recent years, semiconductor lasers having a short oscillation wavelength have been developed, and there has been a demand for an optical recording medium capable of high-density recording and reproduction using a laser beam having a shorter wavelength than the conventional 780 nm or 830 nm. Conventionally proposed optical recording media include magneto-optical recording media, phase-change recording media,
There are chalcogen oxide optical recording media, organic dye optical recording media, and the like. Among these, the organic dye-based optical recording medium is considered to have an advantage in that it is inexpensive and advantageous in the manufacturing process.

At present, an organic dye-based optical recording medium has a C type in which a metal layer having high reflectivity is laminated on the organic dye layer.
DR is mass-produced and widely known. A high-density organic dye-based optical recording medium (DVD-R) for recording with a red semiconductor laser having a shorter wavelength than this has been developed and put into practical use.
It is considered that an optical recording medium capable of recording and reproducing with a blue semiconductor laser having a shorter wavelength than -R is required.

[0004]

Generally, CD-R, D
The recording medium used in each of the VD-Rs has a problem that when recording and reproducing with a blue semiconductor laser having a short wavelength, the reflectivity is low and recording and reproducing cannot be performed. An object of the present invention is to provide a novel optical recording medium that can correspond to a blue semiconductor laser.

[0005]

Means for Solving the Problems The present inventors include a compound represented by the above general formula (1) in a recording layer,
Find an optical recording medium corresponding to the blue semiconductor laser,
The present invention has been reached. That is, the present invention is characterized in that, in an optical recording medium provided with a recording layer on which information can be written / read by a laser on a substrate, the recording layer contains a compound represented by the following general formula (1). The gist of the invention is an optical recording medium.

[0006]

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Wherein ring A is an optionally substituted aromatic carbon
Represents a hydrogenated ring or an aromatic heterocyclic ring, and ring B and ring C are
Represents a 5-membered ring which may have a substituent,¹ And C
^Two , C ¹'And C^Two'And other groups may form a condensed ring.
No. Here, X and X 'are each independently a nitrogen atom, C
-R¹ Y and Y ′ are each independently an oxygen atom,
Sulfur atom, NR^Two Represents Where R¹ Is a hydrogen atom,
Substituted or unsubstituted alkyl group, substituted or unsubstituted alkyl group
Oxy, substituted or unsubstituted alkenyl, substituted or unsubstituted
Is an unsubstituted amino group, a substituted or unsubstituted alkylthio
Group, alkylcarbonyl group, alkoxycarbonyl group,
Alkylsulfonyl group, carboxylate group, carba
Moyl group, sulfamoyl group, sulfonate group,
Aryl group, halogen atom, formyl group, hydroxy
Group, carboxyl group, sulfonic group, nitro group, cyano
Represents a group. R^Two Is a hydrogen atom, a substituted or unsubstituted alkyl
Represents a substituted or unsubstituted alkenyl group. )

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the general formula (1), ring B and ring C are each a 5-membered ring which may have a substituent, or C ¹ and C ² ,
Represents a condensed ring formed together with C ¹ ′ and C ² ′ and others, and is not particularly limited as long as it is a group thereof, but preferably includes the following.

[0009]

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(Wherein E¹ ~ E⁶ Is the general formula (1)
R described¹ A substituent represented by E ⁷ ~ E^TenIs R^Two so
Is a substituent represented by¹ ~ F¹²And G¹ ~ G^{twenty four}Is water
Represents an element atom or an optional substituent. ) R¹ Is a substitution within the range described in the general formula (1).
It is not particularly limited as long as it is a group.
Child; halogen atom such as fluorine atom, chlorine atom and bromine atom
Child; formyl group; hydroxy group; carboxyl group;
Sulfonic acid group; nitro group; cyano group; methyl group, ethyl group,
n-propyl group, isopropyl group, n-butyl group, te
1 to 10 carbon atoms such as rt-butyl group and sec-butyl group
Linear or branched alkyl groups; cyclopropyl groups,
Clobutyl, cyclopentyl, cyclohexyl, etc.
A cyclic alkyl group having 3 to 6 carbon atoms;
As the kill group, a 2-hydroxyethyl group, 3-hydro
Xypropyl group, 4-hydroxybutyl group, 2-hydro
Hydroxy-substituted alkyl groups such as xypropyl groups;
Xymethyl group, 2-carboxyethyl group, 3-carboxy
Carboxy-substituted alkyl groups such as cypropyl groups; cyanome
Cyano-substituted alkyl such as tyl group and 2-cyanoethyl group
An amino-substituted alkyl group such as a 2-aminoethyl group; 2
-Chloroethyl group, 3-chloropropyl group, 2-chloro
Propyl, 2,2,2-trifluoroethyl, tri
Fluoromethyl group, pentafluoroethyl group, perful
A halogen-substituted alkyl group such as an o-n-propyl group; 2
-Methoxyethyl group, 2-ethoxyethyl group, 2-n-propyl
Ropoxyethyl group, 2-n-butoxyethyl group, 2-is
o-butoxyethyl group, 2- (2-ethylhexyloxy)
B) ethyl group, 3-methoxypropyl group, 4-methoxy
Alkoxy substitution such as butyl group and 2-methoxypropyl group
Alkyl group; alkenyl such as 2-allyloxyethyl group
An oxy-substituted alkyl group; a 2-acetyloxyethyl group,
2-propionyloxyethyl group, 2-n-butyrylo
A xyethyl group, a 2-iso-butyryloxyethyl group,
Acyloxy such as 2-trifluoroacetyloxyethyl group
A xy-substituted alkyl group, a methoxycarbonylmethyl group,
C 3-7 carbon atoms such as a sopropoxycarbonylethyl group;
And alkoxycarbonylalkyl groups.

Also, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, ter
C 1 to C 1 such as t-butoxy group and sec-butoxy group
0 straight-chain or branched alkoxy groups; and substituted alkoxy groups include 2-chloroethoxy, 3-chloropropoxy, 2-chloropropoxy, 2,2,2
-Trifluoroethoxy group, trifluoromethoxy group,
Examples include a halogen-substituted alkoxy group such as a pentafluoroethoxy group and a perfluoro-n-propoxy group.

A linear or branched alkenyl group having 2 to 10 carbon atoms such as a vinyl group, an allyl group, a propenyl group, a butenyl group or a pentenyl group; a carbon atom having a carbon number of 3 such as a cyclopentenyl group or a cyclohexynyl group; And a substituted alkenyl group such as a halogen-substituted group such as a 2-bromovinyl group, a 2,2-dichlorovinyl group, a 1,2-dibromovinyl group, and a 1,2-dibromopropenyl group. An alkenyl group and the like can be mentioned.

Further, methylthio, ethylthio, n-
A linear or branched alkylthio group having 1 to 10 carbon atoms, such as a propylthio group, an isopropylthio group, an n-butylthio group, a tert-butylthio group, a sec-butylthio group, and the like. Halogen-substituted alkylthio groups such as an ethylthio group, a 3-chloropropylthio group, a 2-chloropropylthio group, a 2,2,2-trifluoroethylthio group, a trifluoromethylthio group, and a pentafluoroethylthio group; .

In addition to the amino group, examples of the substituted amino group include a methylamino group, an ethylamino group, an n-propylamino group, a dimethylamino group, a diethylamino group, and a di-amino group.
Examples thereof include an alkyl-substituted amino group such as an n-propylamino group, an acylamino group, and a sulfoamino group. In addition, acetyl group, propio group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, pivaloyl group,
An alkylcarbonyl group having 2 to 7 carbon atoms such as a hexanoyl group and a heptanoyl group; methoxycarbonyl group, ethoxycarbonyl group, n-propoxycarbonyl group, isopropoxycarbonyl group, n-butoxycarbonyl group, te
There is an alkoxycarbonyl group having 2 to 7 carbon atoms such as an rt-butoxycarbonyl group and a sec-butoxycarbonyl group. Further, methylsulfonyl group, ethylsulfonyl group,
C 1-6 such as n-propylsulfonyl group, isopropylsulfonyl group, n-butylsulfonyl group, tert-butylsulfonyl group, sec-butylsulfonyl group
A carboxyyl group; a carbamoyl group; a sulfamoyl group; a sulfonic ester group; and an aryl group having 6 to 16 carbon atoms which may have a substituent such as a phenyl group or a naphthyl group.

R ¹ is preferably a hydrogen atom; a halogen atom; a nitro group; a cyano group; a formyl group; a linear or branched alkyl group having 1 to 6 carbon atoms; a halogen-substituted alkyl group having 1 to 6 carbon atoms; An alkoxy group having 1 to 5 carbon atoms; an alkylthio group having 1 to 5 carbon atoms. Particularly preferred are a hydrogen atom; a linear or branched alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 3 carbon atoms;
Is an alkylthio group.

R ² may be any substituent as long as it is in the range described in the general formula (1), and is not particularly limited. Examples thereof include a hydrogen atom or the substituted or unsubstituted alkyl group mentioned above in R ¹ , Examples include the same as the substituted or unsubstituted alkenyl groups. Particularly preferred are a hydrogen atom; a linear or branched alkyl group having 1 to 4 carbon atoms; and a halogen-substituted alkyl group having 1 to 4 carbon atoms. Substituents on rings B and C (for example, F ¹ to F shown in the above structural formula)
¹²⁾ is not particularly limited, it is the same as those for R ^1. When the rings B and C represent a condensed ring, the substituents of the condensed ring (for example, G ¹ to
G ²⁴ ) is not particularly limited, and examples thereof include the same as R ¹ . In the general formula (1), the ring B and the ring C may be a compound having the same ring and having symmetry or a compound having different rings and having asymmetricity, and are not particularly limited. Ring A may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and is not particularly limited as long as it is in those groups, but preferably includes the following.

[0017]

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(Wherein D ^{1 to} D ¹⁰ and D ^{13 to} D ²⁹ are not particularly limited, and include the same as R ¹ described above. D ¹¹ and D ¹² are the same as R ² Preferred examples of the compound represented by the general formula (1) include the following.

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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The optical recording medium of the present invention is basically composed of a substrate and a recording layer containing the above compound. If necessary, a subbing layer, a metal reflective layer, a protective layer, A layer or the like may be provided. An example of a preferable layer configuration includes a medium having a high reflectance in which a metal reflective layer such as gold, silver, and aluminum and a protective layer are provided on the recording layer. Hereinafter, the optical recording medium of the present invention will be described using a medium having this structure as an example.

The material of the substrate in the optical recording medium of the present invention is basically required to be transparent at the wavelength of recording light and reproducing light. For example, acrylic resin, methacrylic resin,
Polycarbonate resin, vinyl chloride resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, epoxy resin, and the like.Injection molded polycarbonate resin from the viewpoint of high productivity, cost, and moisture absorption resistance Substrates are particularly preferred.

These substrate materials are formed into substrates in a disk shape by an injection molding method or the like. If necessary, guide grooves or pits may be formed on the substrate surface. Such guide grooves and pits are preferably provided at the time of molding the substrate, but may also be provided on the substrate using an ultraviolet curable resin layer. When the guide groove is spiral, the groove pitch is preferably about 0.5 to 1.2 μm. A recording layer containing the compound specified in the present invention is formed on a substrate or, if necessary, on a subbing layer. Examples of the method for forming the recording layer include thin film forming methods generally used such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method. The coating method is particularly preferred.

In the case of film formation by spin coating, the number of revolutions is preferably 500 to 5000 rpm. After spin coating, a treatment such as heating or exposure to a solvent vapor may be performed in some cases. When forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, and a dipping method, the coating solvent is not particularly limited as long as it does not attack the substrate. For example, ketone alcohol solvents such as diacetone alcohol and 2-hydroxy-3-methyl 2-butanone; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; n-hexane;
chain hydrocarbon solvents such as n-octane; cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, t
cyclic hydrocarbon solvents such as tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohol solvents such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol; hydroxycarboxylic acids such as methyl lactate, ethyl lactate and methyl isobutyrate Ester solvents and the like.

In order to improve the stability and light resistance of the recording layer, a transition metal chelate compound (eg, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) is used as a singlet oxygen quencher. And a recording sensitivity improver such as a metal compound for improving the recording sensitivity. Here, the metal compound refers to a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, and the like.Examples include an ethylenediamine complex, an azomethine complex, a phenylhydroxyamine complex, a phenanthroline complex, Organometallic compounds such as dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetonate-based complexes, metallocene-based complexes, and porphyrin-based complexes are exemplified. The metal atom is not particularly limited, but is preferably a transition metal.

Further, if necessary, other types of dyes can be used in combination. Other types of dyes mainly absorb in the laser wavelength range for recording, and absorb heat of the irradiated laser light to cause heat, such as decomposition, evaporation, and dissolution, on the recording layer, reflective layer, or substrate at that location. There is no particular limitation as long as pits are formed with a substantial deformation. Also,
Near-infrared laser having a wavelength selected from 770 to 830 nm such as CD-R and 620 to 690 such as DVD-R
A dye suitable for recording with a red laser selected from nm can also be used in combination to provide an optical recording medium compatible with laser recording in a plurality of wavelength ranges. Other types of dyes include metal-containing azo dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, Azurenium dye, naphthoquinone dye, anthraquinone dye,
Examples include indophenol dyes, xanthene dyes, oxazine dyes, and pyrylium dyes.

Further, if necessary, a binder, a leveling agent, an antifoaming agent and the like can be used in combination. Preferred binders include polyvinyl alcohol, polyvinylpyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

The thickness of the dye may vary depending on the recording method, and is not particularly limited, but is preferably 50 to 300 nm. Next, a reflective layer having a thickness of preferably 50 to 300 nm is formed on the recording layer. As a material of the reflection layer, one having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, N
The metals i, Pt, Ta, Cr and Pd can be used alone or as an alloy. Among them, Au, A
1 and Ag have high reflectance and are suitable as a material for the reflective layer. In addition, the following may be included. For example, Mg, Se, Hf, V, Nb, Ru, W, Mn, R
e, Fe, Co, Rh, Ir, Cu, Zn, Cd, G
a, In, Si, Ge, Te, Pb, Po, Sn, Bi
And metal and semimetals. Among them, those containing Ag as a main component are particularly preferable in that they are inexpensive, easily reflect a high reflectance, and when a print receiving layer described later is provided, a beautiful white ground color can be obtained. . Here, the main component means one having a content of 50% or more. It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal, and use it as a reflective layer.

As a method of forming the reflection layer, for example,
Examples include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or under the reflective layer to improve the reflectance, the recording characteristics, and the adhesion. The material of the protective layer formed on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. As the organic substance, thermoplastic resin, thermosetting resin, electron beam curable resin, UV Curable resins and the like can be mentioned. Further, as the inorganic substance, SiO ₂ , Si
N ₄ , MgF ₂ , SnO _{2 and the} like can be mentioned. A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying.
The UV-curable resin can be formed by applying the coating solution as it is or after dissolving it in an appropriate solvent to prepare a coating solution, and irradiating with UV light to cure the coating solution. As the UV-curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used.
These materials may be used alone or as a mixture, or may be used as a multilayer film instead of a single layer.

As a method for forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method or the like is used as in the case of the recording layer. Of these, the spin coating method is preferable. The thickness of the protective layer is generally set at 0.1.
Although it is in the range of 1 to 100 μm, in the present invention, it is 3 μm.
-30 μm is preferred. Alternatively, a method may be used in which a substrate is bonded to the reflective layer surface, or two optical recording media are bonded to each other with the reflective layer surfaces facing each other. An ultraviolet curable resin, an inorganic thin film, or the like may be formed on the mirror surface of the substrate to protect the surface or prevent adhesion of dust and the like. A print-receiving layer can be further formed on a protective layer provided on the reflective layer, on a substrate bonded to the reflective layer surface, or the like.

The laser beam used for the optical recording medium of the present invention is preferably shorter in wavelength for high-density recording, but is more preferably 350 to 530 nm.
A typical example of such a laser beam is a center wavelength 410 n
m, 515 nm laser light. Wavelength 350
An example of the laser light in the range of to 530 can be obtained by using a high-power semiconductor laser of 410 nm blue or 515 nm turquoise. In addition, for example, (a) the fundamental oscillation wavelength of 740 to 960 nm A semiconductor laser capable of continuous oscillation; or (b) a semiconductor laser excited by the semiconductor laser and having a fundamental oscillation wavelength of 740 to 960 nm.
Can be obtained by converting the wavelength of any of the solid-state lasers capable of continuous oscillation from the second harmonic generation element (SHG).

The SHG may be any piezo element that does not have inversion symmetry.
ADP, BNN, KN, LBO, compound semiconductor, and the like are preferable. As a specific example of the second harmonic, in the case of a semiconductor laser having a fundamental oscillation wavelength of 860 nm, 430 of its harmonic is used.
nm, and in the case of a solid-state laser pumped by a semiconductor laser, a Cr-doped LiSrAlF ₆ crystal (fundamental oscillation wavelength 860
430 nm, which is a harmonic of 430 nm. Recording on the optical recording medium obtained as described above is performed by irradiating the recording layer provided on both sides or one side of the substrate with laser light focused to about 0.4 to 0.6 μm. Thermal deformation of the recording layer such as decomposition, heat generation, and melting occurs due to absorption of laser light energy in the portion irradiated with the laser light. Reproduction of recorded information is performed by laser light.
This is performed by reading the difference in reflectance between the portion where the thermal change has occurred and the portion where the thermal change has not occurred.

[0044]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention unless it exceeds the gist thereof.

Example 1 A compound represented by the following structural formula (a) (λmax = 377 nm in chloroform, molar extinction coefficient: 4.93 × 10
⁴ ) was dissolved in octafluoropentanol to adjust the concentration to 1.0% by weight. A solution obtained by filtering the solution was dropped on an injection-molded polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm, applied by a spinner method, and then dried at 100 ° C. for 30 minutes. The maximum absorption wavelength (λmax) of this coating film was 383 nm.

[0046]

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On this coating film, a reflective layer is formed by forming a silver film by a sputtering method or the like, and a UV-curable resin is further applied by spin coating or the like and cured by UV irradiation to form a protective layer. By doing so, an optical recording medium can be obtained. From this optical recording medium, it can be seen from the value of λmax of the coating film that recording and reproduction can be performed by a semiconductor laser having a center wavelength of 410 nm, for example.

[0048]

The optical recording medium obtained according to the present invention comprises:
This is an optical recording medium capable of high-density recording and reproduction using a blue laser.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G11B 7/24 516 G11B 7/24 516 4C069 // C07D 207/34 C07D 207/34 4H056 263/32 263 / 32 5D029 263/56 263/56 277/22 277/22 277/32 277/32 277/56 277/56 277/66 277/66 307/42 307/42 333/18 333/18 333/54 333/54 403/10 403/10 403/14 403/14 405/14 405/14 409/10 409/10 409/14 409/14 413/10 413/10 413/14 413/14 417/10 417/10 417 / 14 417/14 F term (reference) 2H111 EA03 EA12 EA22 EA25 EA32 EA43 FA01 FB42 4C033 AD06 AD09 AD10 4C037 GA02 GA05 HA08 4C056 BA03 BA20 CA03 CA09 CC01 CC10 CD02 4C063 AA01 AA03 BB01 CC52 DD67 DD DD DD DD DD DD DD DD DD DD DD DD DD EE05 4C069 AC07 4H056 DD12 DD23 DE02 FA06 5D029 JA04 JB28

Claims (3)

[Claims] 1. Writing information on a substrate by laser
Optical recording provided with a readable recording layer
In the medium, the recording layer is represented by the following general formula (1)
An optical recording medium comprising a compound. Embedded image(Wherein ring A is an optionally substituted aromatic hydrocarbon ring,
Or an aromatic heterocyclic ring, wherein ring B and ring C have a substituent
Also represents a good five-membered ring,¹ And C^Two , C ¹'And C
^TwoAnd a fused ring with other groups. here,
X and X ′ each independently represent a nitrogen atom, C—R¹ The table
And Y and Y ′ each independently represent an oxygen atom, a sulfur atom,
NR^Two Represents Where R¹ Is a hydrogen atom, substituted or unsubstituted
A substituted alkyl group, a substituted or unsubstituted alkoxy group,
Substituted or unsubstituted alkenyl group, substituted or unsubstituted
Amino group, substituted or unsubstituted alkylthio group, alkyl
Carbonyl group, alkoxycarbonyl group, alkyls
Rufonyl group, carboxylate group, carbamoyl group,
Sulfamoyl group, sulfonate group, aryl
Group, halogen atom, formyl group, hydroxy group, carbo
Represents a xyl group, a sulfonic group, a nitro group, and a cyano group.
R^Two Is a hydrogen atom, a substituted or unsubstituted alkyl group,
Or an unsubstituted alkenyl group. ) 2. The optical recording medium according to claim 1, wherein the ring A is a benzene ring, a 5-membered or 6-membered aromatic heterocycle. 3. The optical recording medium according to claim 1, wherein a laser wavelength for writing and reading is from 350 nm to 530 nm.