JPS62138846A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium having the superior stability for a long period by forming an information recording layer contg. a charge-transfer complex. CONSTITUTION:An information recording layer contg. a charge-transfer complex is formed. The maximum absorption wavelength of the charge-transfer complex is preferably within the range of 700-900nm. The fact that the maximum absorption wavelength of a charge-transfer complex shifts generally to the longer wavelength side of the maximum absorption wavelengths of an electron donative compound and an electron accepting compound used is known. Accordingly, when the maximum absorption wavelength of the charge-transfer complex is within the range of 700-900nm, the maximum absorption wavelength of a used charge donative compound is preferably within the range of 500-800nm.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical information recording medium on which information can be recorded and reproduced using laser light. The present invention relates to an optical information recording medium using a charge transfer complex having the following as a recording layer.

[Prior Art and its Problems] Conventionally, the information recording layer of an optical information recording medium having a base, a polymer binder layer, and an information recording layer contains, for example, Te.
Alloys, inorganic compounds such as Te oxide, or organic dyes are used. Among these, organic dyes are generally highly sensitive to laser light, have a low possibility of causing pollution, and are inexpensive, so various compounds have been studied and are suitable for use in information recording layers. is being attempted.

For example, attempts to use phthalocyanine dyes, cyanine dyes, merocyanine dyes, naphthoquinone dyes, etc. as information recording layers have been proposed (Japanese Patent Laid-Open No. 55-9
No. 7033, JP 58412790, JP 58-
However, optical information recording media using these organic dyes have the disadvantage that the stability of the information recording layer is inferior to optical information recording media using inorganic compounds as the information recording layer. have. for example,
For optical information recording media that use cyanine dyes, azulene derivatives, etc. as the information recording layer, if information is written using laser light and then read out using laser light about 50 times, the readout accuracy may fall below the practical range. Therefore, it is difficult to call it a practical information recording medium.

For this reason, various studies have been made to improve the stability of the information recording layer, but an organic compound-based optical information recording medium with high sensitivity and good stability has not yet been developed.

SUMMARY OF THE INVENTION An object of the present invention is to improve the drawbacks of the prior art as described above and to provide an optical information recording medium with excellent long-term stability.

[Means for solving problems]

As a result of intensive studies to solve the above problems, the present inventors have discovered an optical information recording layer using a charge transfer complex consisting of an electron-donating compound and an electron-accepting compound in the information recording layer. The inventors have discovered that the medium responds to laser light with high sensitivity and exhibits long-term stability in reading information, leading to the present invention.

That is, the present invention provides an optical information recording medium comprising an information recording layer provided on a substrate, wherein the information recording layer contains a charge transfer complex. .

The charge transfer complex used in the present invention preferably has a maximum absorption wavelength in the range of 700 to 900 nm. -Finally, it is known that the maximum absorption wavelength of a charge transfer complex is shifted to a longer wavelength side than the maximum absorption wavelength of an electron donating compound and an electron accepting compound, so the maximum absorption wavelength of a charge transfer complex is Wavelength is 700-900n
In order to fall within the range of m, the maximum absorption wavelength of the electron donating compound is preferably within the range of 5 (10 to 800 nm).

500 to 800, preferably used in the present invention
Examples of the electron-donating compound having a maximum absorption wavelength within the nm range include compounds represented by the following (1) to (3).

Compound (1): Phenalene derivative However, R0 to R in (I), (II), and (III)
16 represents a hydrogen atom, a halogen atom, or a monovalent organic residue, and R1 to R1++ may be the same substituent or different substituents. n represents 0 to 2.

Compound (2): Thiopyran derivative However, R1 to RZ4 in (TV) and (V) represent a hydrogen atom, a halogen atom, or a monovalent organic residue, and R1-R
24 may be the same substituent or different substituents.

n represents O~2.

Compound (3): benzodithiol derivative provided that (VI)
, (■) R and -wRe represent a hydrogen atom, a halogen atom, or a monovalent organic residue, and R1 to R8 may be the same substituent or different substituents. n represents O~2.

As a specific example of compound (1), bis(phenalene-
1-ylidene)ethane, bis(2-methylphenalene-
1-ylidene)ethane, bis(5-methylphenalene-
1-ylidene)ethane, bis(phenalene-1-ylidene)ethane, bis(2,5-dimethylphenalene-1-
ylidene) ethane, bis(5-phenylphenalene-1
-ylidene) ethane, pentaleno (L2,3-cd
; 4,5.6-c'd') diphenalene, pentaleno (1,2,3-cd; 4,5.6-c'd'
) Dimethylphenalene, etc. can be mentioned.

A specific example of compound (2) is 1,2-bis(4
H-thiopyran-4-ylidene)ethane, 1,2-bis(2,6-diphenyl-4H-thiopyran-4-ylidene)ethane, 1,2-bis(3,5-dimethyl-2,6
-diphenyl-4H-thiopyran-4-ylidene)ethane, 1゜2-bis(thiodanthene-9-ylidene)ethane, 1,2-bis(2,8-dimethylthiosanthene-9)
-ylidene) ethane, etc.

Specific examples of compound (3) include cyclohexa-2
,5-diene-1,4-diylidene-1,3-benzodithiole, cyclohexa-2,5-diene-1,4
-diylidenebis-1,3-methylhenzodithiole and the like.

All of these compounds (11 to (3)) can be preferably used in the present invention.

As the electron-accepting compound used in the present invention,
For example, trinitrobenzene chloranil, tetracyanoethylene, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 2,3-dichloro-5,6-dicyanonyl-benzoquinone, trinitrofluorenone, tetrabromo-p-benzoquinone, tetrachloro-p -benzoquinone, diethyltetracyanoquinodimethane, dibromotetracyanoquinodimethane, etc.; among these, trinitrobenzenechloranil, tetracyanoethane, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 2, 3-dichloro-5,6-dicyano-p
-benzoquinone and trinitrofluorenone are preferred.

In order to form a charge transfer complex from the above-mentioned electron donating compound and electron accepting compound, the electron donating compound and the electron accepting compound are usually mixed in a suitable solvent, and the preferable mixing ratio is as follows. is the molar ratio, donor/
Receptor ranges from 5/1 to 115.

700 to 900, which can be preferably used in the present invention
A charge transfer complex with a maximum absorption wavelength in the nm range is
It exhibits a molar specific absorption coefficient ε of about 104 or more, and it is very preferable to use it in the recording layer of an optical information recording medium.

The charge transfer complex described above can be formed and installed on a substrate by a general thin film forming method such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spinner method, or a dipping method. A method in which a charge transfer complex is dispersed in a polymeric resin binder is deposited on a substrate.
This is preferable from the viewpoint of the manufacturing method and the stability of the information recording layer.

Examples of polymeric resin binders that can be used in this case include natural polymeric compounds such as gelatin, cellulose derivatives, dextran, and rosin, polyethylene, polypropylene, polystyrene, poly(meth)acrylate, polyester, polyurethane, Mention may be made of thermoplastic resins such as vinyl chloride polymers.

The mixing ratio of the charge transfer complex and the polymer resin binder in the information recording layer according to the present invention is 80:20 to 2 by weight.
0:80 is preferable, more preferably 70:3
0-30:70.

In addition, examples of the base include glass, plasti, etc. Typical plastics include:
Examples include vinyl chloride resin, acrylic resin, epoxy resin, vinyl ester resin, polycarbonate resin, and polyolefin resin.

The film thickness when applying the charge transfer complex onto the substrate using a polymer resin as a binder is not particularly limited, but from the viewpoint of sensitivity to laser light, etc., it is 0.1 to 5 fm, preferably 0.5 to 2 fm. - is in the range.

Furthermore, a protective layer may be further provided on the information recording layer, or a reflective layer may be provided between the base and the information recording layer. If a protective layer is provided, it should be transparent to laser light;
It is preferable to use a material that has high mechanical strength, reacts with the recording layer, and has good film-forming properties. Examples of inorganic compounds include AlzOl, Sin, SiO, MgO, and Zn.
Examples of organic compounds include polystyrene, polyester, polycarbonate, polyxylene, polyvinyl chloride, and polyacrylonitrile. Examples include organic polymer compounds such as polyacrylonitrile, poly(meth)acrylate, polyvinyl acetate, polyethylene, polypropylene, and polyamide.

When providing a reflective layer, it is preferable to use a substance with high reflectance, such as AI, Ag, Pb, or Cu.

A metal thin film such as Na, Cr, etc. can be used.

〔Example〕

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited only to these Examples.

Example I J, Amer, Chem, Soc, 104.143
2 (1982), CheIII.

Bis(phenalene-1) synthesized according to the method described in Letters, 969 (1982).
-ylidene) etheno (melting point 138℃, maximum absorption wavelength 72
0 nm, log ε = 3.86) and trinitrofluorenone in a 1:2 molar ratio in tetrahydrofuran to form a charge transfer complex. The maximum absorption wavelength of this material was 760 degrees, and logε=4.05. Dissolve nitrocellulose in this charge transfer complex solution and
% solution and coated on a polyethylene terephthalate film so that the solid content was 1.0 g/lri to obtain an optical information recording medium.

This recording medium was irradiated with semiconductor laser light (GaAs bonded laser) from the thin film surface with a beam diameter of 2.0- and the irradiation power at the irradiation surface was reduced by 5 m. 910 tri recording medium
As a result of recording while moving with /sec,
The recording sensitivity was 3 nJ/bit, and as a result of observation with an electron microscope, extremely clear grooves were formed.

After recording with the same laser beam, reading was repeated and the stability of the recording layer was evaluated, and it was found that the optical information recording medium of the present invention could perform normal recording and reading even after 50 repetitions of recording and reading. did it.

Note that the stability of the recording layer is determined by the semiconductor laser (0.7M1lz
) as the readout light and detect the reflected light through the board.
Evaluation was made by measuring the C/N ratio (signal-to-noise ratio) using a spectrum analyzer with a bandwidth of 30 and 2.

Example 2 J, Chem, Soc, Chem, Comm, ,
1,2-bis(2,6-diphenyl-4H-thiopyran-4-ylidene)etheno (melting point 211-212
°C1 maximum absorption wavelength 553 nm, log ε=4.9
9) and 2,3-dichloro-5,6-dicyazolebenzoquinone were mixed in toluene at a molar ratio of 3:4 to form a charge transfer complex. The maximum absorption wavelength of this substance is 80
6 nm and log ε-4.09. Dissolve cellulose acetate in this charge transfer complex solution to 50%
Make a solution and place this on a glass substrate with a solid content of 1.0.
An optical information recording medium was obtained by coating the film at a concentration of g/m.

Thereafter, recording was performed using a semiconductor laser in the same manner as in Example 1.

The recording sensitivity was 1 nJ/bit, and it was confirmed that extremely clear grooves were formed.

As in Example 1, after information was recorded with a laser beam, reading was repeated, and even after repeating recording and reading 50 times, the recording and reading could be successfully repeated.

Example 3 J, Chem, Soc, Chem, Comm, , 7
17 (1981), 1,2-bis(thiosanthen-9-ylidene)etheno (melting point 233 °C, maximum absorption wavelength 550 nm, lo
gε-4,70) and tetracyanoquinodimethane were mixed in a molar ratio of 1:2 in methyl ethyl ketone to form a charge transfer complex. The maximum absorption wavelength of this substance is 790
nm, and logε=4.10. Chlorinated polyethylene was dissolved in this charge transfer complex solution to make a 50% solution, and this solution was placed on an epoxy resin base with a solid content of 1.5%.
0 g/n (to obtain an optical information recording medium.

Thereafter, recording was performed using a semiconductor laser in the same manner as in Example 1.

The recording sensitivity was 1.8 nJ/bit, and it was confirmed that extremely clear grooves were formed.

As in Example 1, after information was recorded with a laser beam, reading was repeatedly performed, and even after repeating recording and reading 50 times, recording and reading could be repeated normally.

Example 4 J, Chem, Soc, Chem, Comm, +7
4 (1978), cyclohexa-2,5-diene-1,4-diylidenebis-1,3-methylbenzodithiole (melting point 170~
172°C or higher, maximum absorption wavelength 580 nm, lo
g t =4.83) and 2,3-dichloro-5,6-dicya2-henzoquinone in a molar ratio of 1:2 in toluene.
to form a charge transfer complex. The maximum absorption wavelength of this material was 762 nm, which was log ε-4.15. Cellulose acetate was dissolved in this charge transfer complex solution to make a 50% solution, and this solution was coated on a glass substrate so that the solid content was 1.0 g and 7 m to obtain an optical information recording medium.

Thereafter, recording was performed using a semiconductor laser in the same manner as in Example 1.

The recording sensitivity was 1.2'nJ/bit, and it was confirmed that clear grooves were formed.

As in Example 1, after information was recorded with a laser beam, reading was repeatedly performed, and even after repeating recording and reading 50 times, recording and reading could be repeated normally.

Example 5 J, Amer, Chem, Soc, 105.51
36 (1983), pentaleno (1,2,3-cd; 4,5.
6-c'd' ] Diphenalene (melting point 155-157°
C1 maximum absorption wavelength 666 nm, log e -5
, 13) and tetracyanoethylene were mixed in a molar ratio of 1:2 in tetrahydrofuran to form a charge transfer complex. The maximum absorption wavelength of this material was 795 nn+, and logε=4.5. Nitrocellulose was dissolved in this charge transfer complex solution to make a 50% solution, and this was deposited on a vinyl ester resin base with a solid content of o, a g.
/m to obtain an optical information recording medium.

Thereafter, recording was performed using a semiconductor laser in the same manner as in Example 1.

The recording sensitivity was 1.0 nJ/bit, and it was confirmed that extremely clear grooves were formed.

As in Example 1, after information was recorded with a laser beam, reading was repeatedly performed, and even after repeating recording and reading 50 times, recording and reading could be repeated normally.

Example 6 Pentaleno (1,2,3-cd;
4゜5,6-c'd' ] diphenalene and 2.3-
Dichloro-5,6-dicyazhenzoquinone was mixed in toluene in a molar ratio of 3:4 to form a charge transfer complex.

The maximum absorption wavelength of this substance is 825 nm, and log
ε=5.01. Cellulose acetate was dissolved in this charge transfer complex solution to make a 50% solution, and this solution was coated on a glass substrate so that the solid content was 1.0 g/m to obtain an optical information recording medium.

Thereafter, recording was performed using a semiconductor laser in the same manner as in Example 1.

The recording sensitivity was 1 nJ/bit, and it was confirmed that extremely clear grooves were formed.

As in Example 1, after information was recorded with a laser beam, reading was repeatedly performed, and even after repeating recording and reading 50 times, recording and reading could be repeated normally.

Comparative Example 1 According to Example 4 of JP-A-58-83344, 1
．． 3-bis[3-ethylbenzthiazonylidene-(2
)-Methyl]-phenalenium tetrafluoroborate was synthesized, an optical information recording medium was obtained in the same manner as in Example 1.

Thereafter, signals were recorded on this in the same manner as in Example 1, and as a result, the recording sensitivity was 1.6 nJ/bit, and it was confirmed that extremely clear grooves were formed.

As in Example 1, after recording information with a laser beam, reading was repeated and the stability of the recording layer was evaluated. After 50 repetitions of recording and reading, the read sensitivity was significantly lowered.

〔Effect of the invention〕

As specifically shown in the examples, the optical information recording medium of the present invention has high sensitivity when recording information, and furthermore, has long-term stability when reading the recorded information. There is. That is, the present invention provides an optical information recording medium of a practical level, and can meet strong demands in this field.

Claims (1)

[Scope of Claims] 1. An optical information recording medium comprising an information recording layer provided on a substrate, wherein the information recording layer contains a charge transfer complex. 2. The optical information recording medium according to claim 1, wherein the information recording layer is a layer in which a charge transfer complex is dispersed in a polymeric resin binder. 3. The optical information recording medium according to claim 1, wherein the charge transfer complex has a maximum absorption wavelength in the range of 700 to 900 nm. 4. The optical system according to claim 1, wherein the charge transfer complex comprises (a) an electron-donating compound having a maximum absorption wavelength in the range of 500 to 800 nm, and (b) an electron-accepting compound. information recording medium. 5. The electron-donating compound is selected from the group consisting of phenalene derivatives, thiopyran derivatives, and benzodithiol derivatives, and the electron-accepting compound is trinitrobenzenechloranyl, tetracyanoethylene, tetracyanquinodimethane, and tetrachloro. The optical information recording medium according to claim 4, which is selected from the group consisting of phthalic anhydride, 2,3-dichloro-5,6-dicyano-p-benzoquinone, and trinitrofluorenone.