JP2002002117A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium, which has an absorbency suitable for a blue semiconductor laser and in which coloring matter having a high solubility to a solvent is employed. SOLUTION: In the optical recording medium having a recording layer, on which a reversible recording of information by laser beams is possible, on a substrate, the recording layer includes a stilbene derivative having a specified substituent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a write-once optical recording medium using an organic dye for a recording layer, and more particularly to a write-once optical recording medium for a blue laser.

[0002]

2. Description of the Related Art In recent years, semiconductor lasers having a short oscillation wavelength have been developed, and the wavelength of a conventionally used laser has been reduced to 78 nm.
There is a demand for an optical recording medium capable of high-density recording and reproduction using laser light having a wavelength shorter than 0 nm and 830 nm. Conventionally proposed optical recording media include magneto-optical recording media,
There are phase change recording media, chalcogen oxide optical recording media, organic dye-based optical recording media, and the like. Among these, the organic dye-based optical recording medium is inexpensive in cost and easy to manufacture in process. Is considered to have an advantage.

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.
Although DR is mass-produced and widely known, this CD-R
A high-density organic dye-based optical recording medium (DVD-R) for recording with a red semiconductor laser having a shorter wavelength than the laser used for recording / reproducing has been developed and put into practical use. However, as laser oscillation of a shorter wavelength, such as a blue semiconductor laser (wavelength 350 nm to 530 nm), becomes possible, there is an increasing need for an optical recording medium capable of recording and reproducing using the laser.

[0004]

Generally, an optical recording medium used as a CD-R or DVD-R has a problem that, when recording and reproducing with a short-wavelength blue semiconductor laser, the reflectivity is low and recording and reproducing cannot be performed. Have. For this reason, it is necessary to use a dye having an appropriate absorbance at a wavelength used for recording and reproduction, in other words, a dye having a maximum absorption wavelength at a shorter wavelength. For example, a compound of the following structural formula (2):

Embedded image That is, unsubstituted stilbene has a maximum absorption wavelength in a chloroform solution of 298 nm (molar extinction coefficient of 2.7 × 10
⁴ ) is located in a relatively short wavelength region, but this is a little too short wavelength region to be applied to an optical recording medium recordable / reproducible with a blue semiconductor laser (wavelength 350 nm to 530 nm).
It is necessary to shift the absorption wavelength to the longer wavelength side. Further, this compound has poor solubility in a solvent generally used for spin coating as described later, and tends to crystallize when applied to a substrate.

In order to shift the absorption peak of stilbene toward longer wavelengths, it is known that it is effective to introduce a substituent at the para-position of the methine chain.
263939 discloses the following compound (6)

Embedded image (The absorption peak in chloroform is 37
It is described that by using 6.5 nm and a molar absorption coefficient of 8.7 × 10 ⁴ ), an optical recording medium which can be recorded and reproduced by a laser beam having a wavelength of 400 to 500 nm can be obtained. However, this compound has very low solubility in a solvent. The current organic dye-based optical recording media have great advantages in that the recording layer can be formed by a spin coating method, so that the production process is simple and the time required for production is short. In the case of a compound having low solubility in a solvent, it is difficult to produce an optical recording medium by a coating method, and even if it can be produced, there is a problem that a dye crystallizes on a substrate.

In the above formula (1), the benzene ring
Other than selecting the above substituents, R₁₁And R ₁₂The hydrogen atom of the shea
The wavelength can be shifted to longer wavelengths by substituting
Can be done.

[0007]

Means for Solving the Problems The present inventors have proposed a substitution at the p-position of the methine chain in the stilbene skeleton, which shifts the maximum absorption wavelength to a longer wavelength without deteriorating the solubility and makes crystallization less likely to occur. A compound having a group introduced therein, and finding that an optical recording medium corresponding to a blue semiconductor laser can be suitably obtained by using the compound in a recording layer,
The present invention has been completed. That is, the present invention relates to an optical recording medium provided with a recording layer capable of irreversibly recording information by laser on a substrate, wherein the recording layer contains a compound represented by the following general formula (1). Characteristic optical recording medium.

Embedded image (Wherein R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R
Each ₁₀ independently represents a hydrogen atom or an optional substituent. R ₃ and R ₈ each independently represent a hydrogen atom, an optionally substituted linear or branched alkyl group, an optionally substituted cyclic alkyl group, a halogen atom, a hydroxy group, a mercapto group, Alkylthio group, nitro group, cyano group, isothiocyanato group, carboxyl group, optionally substituted alkoxy group, optionally substituted amino group, optionally substituted acyl group, optionally substituted An acylamino group, an optionally substituted carbamate group, an optionally substituted carboxylate group, or an optionally substituted carbamoyl group, or R ₈ represents R ₇ and / or R
₉ or R ₃ binds to R ₂ and / or R ₄ to form a saturated ring fused to the benzene ring to which they are attached. However, at least one of R ₃ and R ₈ represents a group other than a hydrogen atom. R ₁₁ and R ₁₂ each independently represent a hydrogen atom or a cyano group. )

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the general formula (1), R ₁ , R ₂ , R ₄ , R ₅ ,
R ₆ , R ₇ , R ₉ and R ₁₀ represent a hydrogen atom or any substituent. Specifically, for example, a hydrogen atom; methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, se
a linear or branched alkyl group having 1 to 18 carbon atoms such as a c-butyl group, a tert-butyl group, or an n-heptyl group; and a carbon atom having 3 to 18 carbon atoms such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, and an adamantyl group. A cyclic alkyl group; a vinyl group,
A linear or branched alkenyl group having 2 to 18 carbon atoms such as a propenyl group or a hexenyl group; a cyclic alkenyl group having 3 to 18 carbon atoms such as a cyclopentenyl group or a cyclohexenyl group;
Heterocyclic groups such as 2-thienyl group, 2-pyridyl group and furfuryl group; aryl groups having 6 to 18 carbon atoms such as phenyl group, tolyl group, xylyl group and mesityl group; aralkyl groups such as benzyl group and phenethyl group A linear or branched acyl group having 2 to 18 carbon atoms such as an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group; a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, n A straight-chain or branched alkoxy group having 1 to 18 carbon atoms such as -butoxy group, sec-butoxy group and tert-butoxy group; a straight-chain or branched alkoxy group having 3 to 18 carbon atoms such as propenyloxy group, butenyloxy group and pentenyloxy group; Branched alkenyloxy group; methylthio group, ethylthio group, n-
Propylthio group, n-butylthio group, sec-butylthio group,
C1-C18 linear or branched alkylthio group such as tert-butylthio group; halogen atom such as fluorine atom, chlorine atom, bromine atom, iodine atom; nitro group; cyano group; isocyano group; cyanato group; isocyanato group Thiocyanato group; isothiocyanato group; mercapto group; hydroxy group; hydroxyamino group; hydroxyimino group;
Formyl group; a sulfonic group; a carboxyl group; -NR ₁₃
Acylamino group represented by -NHCOR _15;; amino group represented by R ₁₄ -; represented by -CONR ₁₈ R ₁₉ carbamate group represented by -NHCOOR ₁₆ ;; carboxylic acid ester group represented by COOR ₁₇ Carbamoyl group; -S
Sulfamoyl group represented by _{O 2 NR 20 R 21; -SO} 3 R
A sulfonic ester group represented by ₂₃ ; —NHSO ₂ R ₂₄
And the like. Of these, the alkyl group, alkylthio group, alkoxy group, acyl group, and aryl group may be substituted with a substituent described below.

Here, R _{13 to} R ₂₄ each represent a hydrogen atom,
Represents a linear or branched alkyl group, a cyclic alkyl group or an aryl group, which may be substituted with a substituent described below. When R ₁₃ and R ₁₄ in the amino group are an alkyl group, they may form a saturated ring by bonding to each other directly or via an oxygen atom. The saturated ring is preferably a 5- to 7-membered ring. As such a ring,
For example, the following examples are given.

Embedded image

R₁, R_Two, R_Four, R_Five, R₆, R₇, R₉Also
Is R_TenIs an alkyl group, an alkylthio group, an alkoxy group,
When it is an acyl group or an aryl group, and -NR₁₃
R₁₄, -NHCOR_Fifteen, -NHCOOR₁₆, -COOR
₁₇, -CONR₁₈R₁₉, -SO_TwoNR₂₀R_{twenty one}, -SO_ThreeR
_{twenty three}Or -NHSO_TwoR_{twenty four}And R_{1 Three}
~ R_{twenty four}Is an alkyl group or an aryl group,
And the like may have a methoxy group and an ethoxy group.
Group, n-propoxy group, isopropoxy group, n-butoxy
Group, sec-butoxy group, tert-butoxy group, etc.
10 alkoxy groups; methoxymethoxy group, ethoxyme
Toxic group, propoxymethoxy group, ethoxyethoxy
, Propoxyethoxy, methoxybutoxy, etc.
A C 2-12 alkoxyalkoxy group; methoxymeth
Xymethoxy group, methoxymethoxyethoxy group, methoxy
Siethoxymethoxy group, methoxymethoxyethoxy group,
Alcohols having 3 to 15 carbon atoms such as ethoxyethoxymethoxy groups
Oxyalkoxyalkoxy group; allyloxy group;
C6 to C12 alkyl groups such as a benzyl group, a tolyl group and a xylyl group;
Reel groups (these may be further substituted with substituents)
No. ); Phenoxy, tolyloxy, xylyloxy
Aryl having 6 to 12 carbon atoms, such as a cyclo group or a naphthyloxy group;
Oxy group; carbon number of allyloxy group, vinyloxy group, etc.
2 to 12 alkenyloxy groups; cyano groups; nitro groups;
Hydroxyl group; amino group; N, N-dimethylamino
Group, an N, N-diethylamino group, etc.
Alkylamino group; methylsulfonylamino group, ethyls
Such as a rufonylamino group and an n-propylsulfonylamino group
An alkylsulfonylamino group having 1 to 6 carbon atoms;
Halogen atom such as atom, chlorine atom and bromine atom; carboxy
A methoxycarbonyl group, an ethoxycarbonyl group,
n-propoxycarbonyl group, isopropoxycarbonyl
Alkoxy having 2 to 7 carbon atoms such as a group or n-butoxycarbonyl
Cicarbonyl group; methylcarbonyloxy group, ethylca
Rubonyloxy group, n-propylcarbonyloxy group, i
Isopropylcarbonyloxy group, n-butylcarbonyloxy group
C 2-7 alkylcarbonyloxy such as xyl group
Group: methoxycarbonyloxy group, ethoxycarbonyl
Oxy group, n-propoxycarbonyloxy group, isopro
Poxycarbonyloxy group, n-butoxycarbonyloxy
An alkoxycarbonyloxy group having 2 to 7 carbon atoms such as a silyl group
And the like. Also, R₁, R_Two, R_Four, R_Five, R₆,
R₇, R₉And R_TenOf adjacent groups
A saturated ring fused to the benzene ring to which these groups are attached
It may be formed. The saturated ring is a straight chain having 1 to 6 carbon atoms or
Is a branched alkyl, hydroxy, amino or
It may be substituted with an ano group or the like. R₁, R_Two, R_Four,
R_Five, R₆, R₇, R₉And R_TenAnd more preferably
A hydrogen atom, an optionally substituted linear or branched alkyl
Kill group, optionally substituted alkoxy group, halogen
Atom, nitro, cyano, hydroxy, or substituted
Any of the amino groups which may be substituted.

R in the general formula (1)_ThreeAnd R₈Is before
As described above, the maximum absorption wavelength of the compound is shifted to the longer wavelength side.
Can be crystallized and hardly crystallized
Group (ie, a group that improves solubility)
is there. R selected from such a viewpoint_ThreeAnd R₈Is
A hydrogen atom, an optionally substituted linear or branched alkyl
Kill group, optionally substituted cyclic alkyl group, halogen
Atom, hydroxy group, mercapto group, substituted
Alkylthio, nitro, cyano, isothio
A cyanate group, a carboxyl group, an optionally substituted
Lucoxy group, optionally substituted amino group, substituted
An optionally substituted acyl group, an optionally substituted acyl group
Amino group, an optionally substituted carbamate group,
An optionally substituted carboxylic acid ester group, or
A carbamoyl group which may be₈Is R₇and
/ Or R₉Or R_ThreeIs R _TwoAnd / or R_FourWhen
A saturated ring bonded to and fused to the benzene ring to which they are bonded
To form Specific examples of each group include R₁, R_Two, R_Four,
R_Five, R₆, R₇, R₉Or R_TenSame as above
Things. Note that R₈Is R₇And / or R₉
Or R_ThreeIs R_TwoAnd / or R_FourCombine with this
Form a saturated ring fused to the benzene ring to which they are attached
In this case, the saturated ring is a hydrocarbon ring or a heterocyclic ring,
Is also good. In terms of the position of the maximum absorption wavelength of the compound,
Preferably R_ThreeOr R₈Is a nitrogen atom, an oxygen atom, or
Bonded to the benzene ring at the sulfur atom
It is a saturated heterocyclic ring containing a B atom. Ring size is 5-8 members
A ring is preferable, and examples thereof include a ring structure shown below.
It is. In the following examples, the description of the substituent on the ring is omitted.
Although it is abbreviated, it is actually a straight or branched chain having 1 to 6 carbon atoms.
Alkyl group, hydroxy group, amino group or cyano group
May have a substituent.

Embedded image The benzene ring in the above structure represents a benzene ring bonded to both sides of the methine chain in the general formula (I). R
₃ and R ₈ are preferably a hydrogen atom, a linear or branched alkyl group which may be substituted, a halogen atom,
Hydroxy group, mercapto group, optionally substituted alkylthio group, nitro group, cyano group, optionally substituted alkoxy group, optionally substituted amino group, optionally substituted acyl group, substituted An optionally substituted acylamino group, an optionally substituted carbamate group,
An optionally substituted carboxylate group, an optionally substituted carbamoyl group, R ₈ is bonded to R ₇ and / or R ₉ , or R ₃ is bonded to R ₂ and / or R ₄ ; These form a saturated ring fused to the benzene ring to which they are bonded.

Among them, particularly preferred are a hydrogen atom, a linear or branched unsubstituted alkyl group, a halogen atom, a hydroxy group, a nitro group, an unsubstituted alkoxy group, an optionally substituted amino group, and a substituted or unsubstituted amino group. A good acyl group,
A carboxylate group which may be substituted,
R ₈ is bonded to R ₇ and / or R ₉ , or R ₃ is bonded to R ₂ and / or R ₄ to form a saturated ring fused to the benzene ring to which they are bonded.

R ₁₁ and R ₁₂ each represent a hydrogen atom or a cyano group, and the combination thereof is not limited, but both of them are preferably hydrogen atoms or one of them is a hydrogen atom and the other is a cyano group.

Preferred examples of the compound represented by the general formula (1) include the following.

Embedded image

Embedded image

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Embedded image

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Embedded image The compound represented by the general formula (1) has a maximum absorption wavelength at a position suitable for optical recording with a blue semiconductor laser beam,
Although crystallization hardly occurs, ketone alcohol solvents represented by the following formula (3), ketone solvents represented by the following formula (4), and hydroxycarboxylic acids represented by the following formula (5) are more preferable. A compound having a solubility of at least 1% by weight at 25 ° C. in at least one solvent selected from acid ester solvents.

Embedded image (Wherein R ₃₁ , R ₃₂ , R ₃₄ , R ₃₇ , R ₃₈ and R ₃₉ are each independently an alkyl group having 1 or 2 carbon atoms, and R ₃₅ and R ₃₆ are each independently an alkyl group having 1 to 5 carbon atoms. A linear or branched alkyl group, R ₃₃ represents a direct bond or an alkylene group having 1 or 2 carbon atoms.) Specifically, ketone alcohols such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone Solvents; ketone solvents such as methyl ethyl ketone, diisobutyl ketone, and methyl isobutyl ketone; and hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; their purity is usually 90% by weight or more. is there. These dyes of the present invention are extremely useful as dyes for use in the recording layer of an optical recording medium because they have excellent thin film forming properties when forming a recording layer from a solution containing the dye. Further, the dye of the present invention has a recording layer containing the dye in a shorter wavelength (350 nm to 500 nm) region having an absorption of an intensity suitable for recording / reproducing by a laser beam, so that recording corresponding to a short wavelength laser is performed. It is extremely useful as a dye for use in an optical recording medium for reproduction. The optical recording medium of the present invention is basically composed of a substrate and a recording layer containing the compound, and further includes an undercoat layer, a metal reflective layer, a protective layer, and the like on the substrate as necessary. 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 basically needs to be transparent at the wavelength of recording light and reproducing light. Examples of such a material include a resin such as an acrylic resin, a methacrylic resin, a polycarbonate resin, a polyolefin resin (especially an amorphous polyolefin), a polyester resin, a polystyrene resin, an epoxy resin, and a glass. Alternatively, a material in which a resin layer made of a radiation-curable resin such as a photo-curable resin is provided on glass can be used. In terms of high productivity, cost, and moisture absorption resistance, injection molded polycarbonate is preferred. Amorphous polyolefin is preferred from the viewpoints of chemical resistance, moisture absorption resistance, and the like. Further, a glass substrate is preferable from the viewpoint of high-speed response and the like. A resin substrate or a resin layer may be provided in contact with the recording layer, and a guide groove or pit for recording / reproducing light may be provided on the resin substrate or the resin layer. When the guide groove is spiral, this groove pitch is 0.5 ~ 1.2μm
It is preferred that it is about.

A recording layer containing the compound of the present invention is formed on a substrate or, if necessary, on an undercoat layer.
Examples of the method of 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. From the viewpoint of mass productivity and cost, the spin coating method is preferable, and it is also a method that makes the most of the properties of the compound according to the present invention. From the viewpoint that a recording layer having a uniform thickness can be obtained, a vacuum deposition method or the like is more preferable than a coating method.
In the case of film formation by spin coating, the number of rotations is 500 to 15000
After spin coating, a treatment such as heating or exposure to a solvent vapor may be performed after spin coating.

The coating solvent for 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 is not particularly limited as long as it does not attack the substrate. Further, the solvent does not necessarily need to be a solvent represented by the above-described general formulas (3) to (5), and may be any solvent that can sufficiently dissolve the dye used in the recording layer. For example, diacetone alcohol, 3-hydroxy-3
Ketone alcohol solvents such as -methyl-2-butanone; ketone solvents such as methyl ethyl ketone, diisobutyl ketone and methyl isobutyl ketone; hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate and methyl 2-hydroxyisobutyrate; methyl cellosolve , Ethyl cellosolve and the like; cellosolve solvents such as methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate and the like; ether solvents such as isoamyl ether;
Methoxy-1-butanol, 1,3-diethoxy-2-
Ether alcohol solvents such as propanol; ether carboxylic solvents such as 3-methoxypropionic acid;
Chain hydrocarbon solvents such as n-hexane and n-octane; cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; tetrafluoropropanol And perfluoroalkyl alcohol solvents such as octafluoropentanol and hexafluorobutanol. In the case of the vacuum evaporation method, for example, the compound of the present invention,
If necessary, other recording layer components such as other dyes and various additives,
After placing in a crucible placed in a vacuum vessel and evacuating the vacuum vessel to about 10 ⁻² to 10 ⁻⁵ Pa with a suitable vacuum pump, the crucible is heated to evaporate the recording layer components and face the crucible. By vapor deposition on the substrate placed
A recording layer is formed.

The recording layer is formed of a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α) as a singlet oxygen quencher in order to improve the stability and light resistance of the recording layer. -Diketone, etc.) or 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 an atom, an ion, a cluster, or the like. Dihydroxyazobenzene-based complex,
Dioxime-based complexes, nitrosoaminophenol-based complexes,
Organometallic compounds such as 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 are not particularly limited as long as they have appropriate absorption mainly in a recording laser wavelength range. Also, 770-8 like CD-R
Supports recording with laser light in multiple wavelength ranges by using a dye suitable for recording with a near-infrared laser with a wavelength selected from 30 nm or a red laser selected from 620 to 690 nm such as DVD-R The optical recording medium can also be used.

Other dyes include metal-containing azo dyes,
Phthalocyanine dye, naphthalocyanine dye, cyanine dye, azo dye, squarylium dye, metal-containing indoaniline dye, triarylmethane dye,
Examples include merocyanine dyes, azulenium dyes, naphthoquinone dyes, anthraquinone dyes, 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, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like. The thickness of the recording layer is
Although the suitable film thickness varies depending on the recording method and the like, it is not particularly limited, but is usually 50 to 300 nm.

A reflective layer may be formed on the recording layer, and its thickness is preferably 50 to 300 nm. As a material of the reflection layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta,
Cr and Pd metals can be used alone or as an alloy. Among them, Au, Al, and Ag have high reflectivity and are suitable as the material of the reflective layer. In addition to these as main components, the following may be included. For example, Mg, Se, H
f, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Z
Metals and metalloids such as n, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi can be mentioned. Among them, those containing Ag as a main component are particularly preferable because they are inexpensive, easily reflect a high reflectance, and when a print receiving layer described later is provided, a white and beautiful 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 of a material other than a metal and use it as a reflective layer. Examples of a method for forming the reflective layer 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 for improving reflectance, improving recording characteristics, improving adhesion, etc. on the substrate or below the reflective layer,
An adhesive layer can also be provided.

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. Examples of the organic material include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and a UV curable resin. Further, as inorganic substances, SiO ₂ , Si
N ₄ , MgF ₂ , SnO _{2 and the} like can be mentioned.

The thermoplastic resin, the thermosetting resin and the like can be formed by dissolving in a suitable solvent, applying a coating solution, and drying. The UV curable resin can 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 the resin. As 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 of 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 0.1 to 1
Although it is in the range of 00 μm, it is preferably 3 to 30 μm in the present invention.

Further, a substrate may be further bonded to the reflective layer surface, or two optical recording media may be bonded to each other with the reflective layer surfaces facing each other. An ultraviolet curable resin layer, 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. Note that a print receiving layer that can be written (printed) with various types of printers such as ink jet and thermal transfer, or various writing instruments may be provided on a surface other than the recording / reproducing light incident surface.

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. Representative examples of such laser light include laser light having center wavelengths of 410 nm and 515 nm. An example of laser light having a wavelength in the range of 350 to 530 nm can be obtained by using a high-power semiconductor laser of 410 nm blue or 515 nm turquoise.Others, for example, (a) a fundamental oscillation wavelength of 740 to 740 nm 960n
m, a semiconductor laser capable of continuous oscillation, or (b) excited by a semiconductor laser, and having a fundamental oscillation wavelength of 740 to 960.
It can also be obtained by wavelength conversion of any of solid-state lasers capable of continuous oscillation of nm using a 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, the fundamental oscillation wavelength is 86
In the case of a semiconductor laser of 0 nm, its harmonic is 430 nm, and in the case of a solid-state laser pumped by a semiconductor laser, it is 430 of a harmonic from a Cr-doped LiSrAlF ₆ crystal (a fundamental oscillation wavelength of 860 nm).
nm.

The recording on the optical recording medium of the present invention obtained as described above is carried out by irradiating a recording layer provided on both sides or one side of the substrate with a laser beam focused to about 0.4 to 0.6 μm. In the portion irradiated with the laser beam, thermal deformation of the recording layer such as decomposition, heat generation, and dissolution occurs due to absorption of the laser beam energy, and the optical characteristics change. Reproduction of recorded information is performed by reading the difference in reflectance between a portion where optical characteristics have changed and a portion where optical characteristics have not changed using a laser beam.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. Example 1

Embedded image The 4-amino-4 '-(N,
N-dimethylamino) stilbene (manufactured by Tokyo Chemical Industry Co., Ltd.
Λmax = 356 nm in chloroform, and the absorption spectrum is shown in FIG. The molar extinction coefficient was 3.5 × 10 ⁴ ) dissolved in propyl lactate and adjusted to 1.0 wt%. 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 362 nm. FIG. 2 shows the absorption spectrum.

Embodiment 2

Embedded image 4-methoxy-4'-nitrostilbene represented by the above structural formula (8) (manufactured by Tokyo Chemical Industry Co., Ltd .; λmax in chloroform = 377.5 nm; molar extinction coefficient: 2.6 × 1)
0 ^4. ) Was dissolved in propyl lactate and adjusted to 1.0 wt%.
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 is 383 nm.
Met.

Example 3 (a) Production Example

Embedded image 8.1 g (0.05 mol) of 4-nitrophenylacetonitrile represented by the above structural formula (9),
0) piperonal 7.5g (0.05mo)
1) 0.3 ml of piperidine was dissolved in 150 ml of methanol at room temperature. The solution was refluxed for 3 hours in a water bath, and after cooling, the solution was filtered, and the precipitated solid was separated by filtration. The solid was washed with methanol and then dried in a vacuum drier to obtain 14.5 g of a compound represented by the following structural formula (11) (yield: 99%).

Embedded image 14.5 g (0.05 mol) of this compound was dissolved in a 100 ml solution of tetrahydrofuran (THF), and the solution was cooled in an ice bath. In this solution, tin (II) chloride dihydrate 3
A solution of 3.8 g of 43 ml of concentrated hydrochloric acid was added dropwise at 30 ° C. or lower. After completion of the dropwise addition, the reaction solution was refluxed for 1 hour. After cooling, the reaction solution was neutralized with a 2 mol / l aqueous sodium hydroxide solution, and the precipitated solid was separated by filtration. The solid was washed with water and dried in a vacuum drier to obtain 12.5 g (yield: 96%) of a compound represented by the following structural formula (12).

Embedded image (B) Example of recording medium Compound of the above formula (12) (λmax = 3 in chloroform)
68 nm, molar extinction coefficient 2.6 × 10 ⁴ ) was dissolved in methyl lactate and adjusted to 1.0 wt%. 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 369.5 nm.

Comparative Example 1

Embedded image Trans-stilbene represented by the structural formula (2) (manufactured by Tokyo Chemical Industry Co., Ltd .; λmax = 298 nm in chloroform, absorption spectrum is shown in Fig. 3. The molar extinction coefficient is 2.7 × 1.
0 ^4. ) Was dissolved in diisobutyl ketone and adjusted to 1.0 wt%. The solution obtained by filtering this is 120 mm in diameter and thickness
Drop onto a 1.2 mm injection molded polycarbonate resin substrate, apply by spinner method, and apply
Dried for minutes. However, crystallization was observed on the surface of the substrate after the completion of the application, and no absorption peak was observed in the applied film.

Comparative Example 2

Embedded image 4,4'-bis (5-methylbenzoxazol-2-yl) stilbene represented by the structural formula (6) (λmax in chloroform = 376.5 nm, absorption spectrum is shown in Fig. 4. Molar extinction coefficient 8 0.7 × 10 ⁴ ) using methyl lactate, diacetone alcohol, diisobutyl ketone,
1 wt% solution using various solvents of hydroxyacetone, isoamyl ether, ethylene glycol-mono-n-hexyl ether, n-hexane, 1,3-diethoxy-2-propanol, octafluoropentanol, dipropylene glycol, dodecylbenzene Were tried but none of them dissolved. Of these samples, a solution obtained by filtering a suspension of compound (6) in diacetone alcohol was dropped onto an injection-molded polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm, and applied by a spinner method. Then, after coating, it was dried at 100 ° C. for 30 minutes. However, no absorption peak was observed in the coating film.

On the coating film formed in each of the above embodiments, a silver film is formed by a sputtering method or the like to form a reflective layer, and a UV curable resin is applied by spin coating or the like and cured by UV irradiation. Thus, a protective layer is formed to obtain an optical recording medium. It is clear from the value of λmax of the coating film that this optical recording medium can be recorded / reproduced by a semiconductor laser having a center wavelength of 410 nm, for example.

[0036]

The solution containing the compound of the present invention can form a coating film having an absorption suitable for recording / reproducing by short-wavelength laser light and has excellent film-forming properties.
A recording medium having a recording layer using the compound of the present invention is useful as an optical recording medium for recording and reproduction corresponding to a short wavelength laser.

[Brief description of the drawings]

FIG. 1 is an absorption spectrum of a compound (7) used in Example 1 in a chloroform solution.

FIG. 2 is an absorption spectrum of a coating film containing compound (7) used in Example 1.

FIG. 3 is an absorption spectrum of a compound (2) used in Comparative Example 1 in a chloroform solution.

FIG. 4 is an absorption spectrum of a compound (6) used in Comparative Example 2 in a chloroform solution.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kurose 1000-term Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa F-term in Yokohama Research Laboratory, Mitsubishi Chemical Corporation 2H111 EA03 FB42 5D029 JA04

Claims (7)

[Claims] 1. An optical recording medium having a recording layer on which information can be irreversibly recorded by a laser on a substrate, wherein the recording layer contains a compound represented by the following general formula (1). Characteristic optical recording medium. Embedded image (Wherein R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R
Each ₁₀ independently represents a hydrogen atom or an optional substituent. R ₃ and R ₈ each independently represent a hydrogen atom, an optionally substituted linear or branched alkyl group, an optionally substituted cyclic alkyl group, a halogen atom, a hydroxy group, a mercapto group, Alkylthio group, nitro group, cyano group, isothiocyanato group, carboxyl group, optionally substituted alkoxy group, optionally substituted amino group, optionally substituted acyl group, optionally substituted An acylamino group, an optionally substituted carbamate group, an optionally substituted carboxylate group, or an optionally substituted carbamoyl group, or R ₈ represents R ₇ and / or R
₉ or R ₃ binds to R ₂ and / or R ₄ to form a saturated ring fused to the benzene ring to which they are attached. However, at least one of R ₃ and R ₈ represents a group other than a hydrogen atom. R ₁₁ and R ₁₂ each independently represent a hydrogen atom or a cyano group. ) 2. R ₃ and R ₈ each independently represent a hydrogen atom,
An optionally substituted linear or branched alkyl group, halogen atom, hydroxy group, mercapto group, optionally substituted alkylthio group, nitro group, cyano group, optionally substituted alkoxy group, substituted Optionally substituted amino group, optionally substituted acyl group, optionally substituted acylamino group, optionally substituted carbamate group, optionally substituted carboxylate group, optionally substituted A carbamoyl group, R ₈ is bonded to R ₇ and / or R ₉ , or R ₃ is bonded to R ₂ and / or R ₄ to form a saturated ring fused to a benzene ring to which they are bonded The optical recording medium according to claim 1. 3. R ₃ and R ₈ each independently represent a hydrogen atom,
Linear or branched unsubstituted alkyl group, halogen atom,
A hydroxy group, a nitro group, an unsubstituted alkoxy group, an optionally substituted amino group, an optionally substituted acyl group, an optionally substituted carboxylate group, or R ₈ is _3. The optical recording medium according to claim 2, wherein R ₇ and / or R ₉ or R ₃ binds to R ₂ and / or R ₄ to form a saturated ring condensed with a benzene ring to which they are bound. 4. R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R ₁₀ are each independently a hydrogen atom, a linear or branched alkyl group which may be substituted, The optical recording medium according to any one of claims 1 to 3, wherein the optical recording medium is any of an optionally substituted alkoxy group, a halogen atom, a nitro group, a cyano group, a hydroxy group, and an optionally substituted amino group. 5. The optical recording medium according to claim 1, wherein one of R ₁₁ and R ₁₂ represents a hydrogen atom and the other represents a cyano group. 6. A ketone alcohol-based solvent represented by the following formula (3), a ketone-based solvent represented by the following formula (4), and a compound represented by the following formula (5) of the compound represented by the general formula (1): The optical recording medium according to any one of claims 1 to 5, wherein the solubility in at least one solvent selected from the group consisting of hydroxycarboxylic acid ester solvents represented by the formula is 1% by weight or more at 25 ° C. Embedded image (Wherein R ₃₁ , R ₃₂ , R ₃₄ , R ₃₇ , R ₃₈ and R ₃₉ each independently represent an alkyl group having 1 or 2 carbon atoms, R ₃₅ and R
₃₆ independently represents a linear or branched alkyl group having 1 to 5 carbon atoms, and R ₃₃ represents a direct bond or an alkylene group having 1 or 2 carbon atoms. ) 7. The optical recording medium according to claim 1, wherein information can be irreversibly recorded and reproduced with laser light having a wavelength of 350 to 530 nm.