JPH0126879B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an optical recording medium suitable for writing and recording with a laser, particularly a semiconductor laser, and more particularly to an improved optical recording medium usable in optical disk technology. In general, optical disks are optically detectable small (e.g., approximately 1 microbit) tracks formed in a thin recording layer on a substrate in the form of spiral or circular tracks that can store high-density information. To write information on such a disk, a focused laser beam is scanned over the surface of the laser-sensitive layer, and only the surface irradiated with this laser beam forms a pit, which is then traced in a spiral or circular track. The laser-sensitive layer can absorb laser energy and form optically detectable pits.For example, in heat mode recording, the laser-sensitive layer absorbs thermal energy and creates optically detectable pits. Small pits can be formed by evaporation or melting.Another heat mode recording method uses
Absorption of the irradiated laser energy can form pits with optically detectable concentration differences at that location. The information recorded on this optical disk is detected by scanning a laser along the track and reading the optical changes in the pitted and non-pitted areas. For example, a laser is scanned along a track and the energy reflected by the disk is monitored by a photodetector. When pits are not formed, the output of the photodetector is reduced, while when pits are formed, the laser beam is sufficiently reflected by the underlying reflective surface and the output of the photodetector is increased. As a recording medium used for such optical discs,
So far, methods have been proposed that mainly use inorganic materials such as metal thin films such as aluminum vapor-deposited films, bismuth thin films, tellurium oxide thin films, and chalcogenite amorphous glass films. These thin films are generally 350
It is sensitive to wavelength light around ~800nm, and
Since the reflectance to laser light is high, there are drawbacks such as low utilization rate of laser light. For this reason, in recent years, research has been carried out on organic films whose optical dynamics can be changed by light energy of relatively long wavelengths (for example, 780 nm or more). Such an organic thin film is effective in that pits can be formed using, for example, a semiconductor laser whose oscillation wavelength is around 830 nm. However, organic compounds that generally have absorption characteristics on the long wavelength side are unstable to heat and have technical problems in terms of sublimability, so it is not always possible to develop an organic film that is satisfactory in terms of properties. The current situation is that it cannot be said that this is true. An object of the present invention is to provide an optical recording medium having an organic coating having an absorption band on the long wavelength side. Another object of the invention is to provide an optical recording medium having a thermally stable organic coating. The optical recording medium of the present invention is characterized by having an organic coating containing a polymethine compound represented by the following general formula (1). General formula (1) R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are hydrogen atoms or alkyl groups (e.g. methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-
Butyl group, iso-butyl group, t-butyl group, n-
amyl group, t-amyl group, n-hexyl group, n-
octyl group, t-octyl group, etc.), and further includes other alkyl groups, such as substituted alkyl groups (e.g., 2-hydroxyethyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 2-acetoxyethyl group, carboxy Methyl group, 2-carboxyethyl group, 3-carboxypropyl group, 2-
Sulfonyethyl group, 3-sulfopropyl group, 4-
Sulfobutyl group, 3-sulfatepropyl group,
4-sulfatebutyl group, N-(methylsulfonyl)-carbamylmethyl group, 3-(acetylsulfamyl)propyl group, 4-(acetylsulfamyl)butyl group, etc.), cyclic alkyl group (e.g. ,
cyclohexyl group, etc.), allyl group (CH ₂ = CH−
CH ₂ −), aralkyl group (e.g. benzyl group,
phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group, etc.), substituted aralkyl group (e.g.
carboxybenzyl group, sulfobenzyl group, hydroxybenzyl group, etc.). moreover,
R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are substituted or unsubstituted aryl groups (e.g., phenyl group, naphthyl group, tolyl group, xylyl group, methoxyphenyl group, dimethoxyphenyl group, trimethoxyphenyl group) enyl group, ethoxyphenyl group, dimethylaminophenyl group, diethylaminophenyl group, dipropylaminophenyl group, dibenzylaminophenyl group, diphenylaminophenyl group, etc.), substituted or unsubstituted heterocyclic group (For example, pyridyl group,
quinolyl group, lepidyl group, methylpyridyl group, furyl group, thienyl group, indolyl group, pyrrole group, carbazolyl group, N-ethylcarbazolyl group, etc.) or substituted or unsubstituted styryl group (e.g. styryl group, methoxystyryl group) group, dimethoxystyryl group, trimethoxystyryl group, ethoxystyryl group, dimethylaminostyryl group, diethylaminostyryl group, dipropylaminostyryl group, dibenzylaminostyryl group, diphenylaminostyryl group, 2,2-diphenylvinyl group, 2 -phenyl-2-methylvinyl group, 2-
(dimethylaminophenyl)-2-phenylvinyl group, 2-(diethylaminophenyl)-2-phenylvinyl group, 2-(dibenzylaminophenyl)-
2-phenyl vinyl group, 2,2-di(diethylaminophenyl) vinyl group, 2,2-di(methoxyphenyl) vinyl group, 2,2-di(ethoxyphenyl) vinyl group, 2-(dimethylaminophenyl) vinyl group enil)
-2-methylvinyl group, 2-(dimethylaminophenyl)-2-ethylvinyl group, etc.). m
is 0 or 1, and n is 0, 1 or 2.
X is a chloride ion, bromide ion, iodide ion, perchlorate ion, benzenesulfonate ion, P-toluenesulfonate ion, methylsulfate ion, ethylsulfate ion, propylsulfate ion, etc. Represents an anion. Next, representative examples of the polymethine compound represented by the general formula (1) will be listed.

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【table】

[Table] These polymethine compounds are described by Bernard S.
Wildi et al., J.Am.Chem.Soc (Journal of
American Chemical Society) 80 3772~
3777 (1958) and H. Schmidt et al.
It can be easily synthesized according to the synthesis method disclosed by Annalendel Chemie ) 623 204-216 or R. Wlzinger et al. can get. The organic coating of the present invention can be used for optical disc recording. For example, a substrate 1 as shown in FIG.
The recording medium can have the above-mentioned organic film 2 formed thereon. Such an organic film 2 can be formed by vacuum deposition of the compound represented by the above-mentioned general formula (1), or can also be formed by applying a coating liquid containing the above-mentioned polymethine compound in a binder. can do. When forming a film by coating, the above-mentioned polymethine compound may be contained in a binder in a dispersed state or in an amorphous state. Suitable binders can be selected from a wide variety of resins. Specifically, cellulose esters such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, cellulose acetate/propionate, cellulose acetate/butyrate, methyl cellulose, ethyl cellulose, propyl cellulose,
Cellulose ethers such as butyl cellulose, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, vinyl resins such as polyvinylpyrrolidone, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene. Copolymer resins such as acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyacrylic resin such as polyacrylonitrile, polystyrene terephthalate, etc. polyesters of , 4'-isopropylidene diphenylene carbonate co-terephthalate), poly(4,4'-isopropylidene diphenylene carbonate), poly(4,4'-sec-butylidene diphenylene carbonate), poly(4,4'-sec-butylidene diphenylene carbonate), ,4'-isopropylidene diphenylene carbonate block-
polyarylate resins such as oxyethylene),
Alternatively, polyamides, polyimides, epoxy resins, phenolic resins, polyolefins such as polyethylene, polypropylene, and chlorinated polyethylene can be used. The organic solvent that can be used during coating varies depending on the type of binder and whether the above-mentioned compound is contained in the binder in a dispersed or amorphous state, but in general, , alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N,N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, Ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, butyl acetate, resin group halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene,
Alternatively, aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. When forming the organic film 2 together with the binder,
The content of the polymethine compound mentioned above is the same as that of the organic coating 2.
It is 1 to 90% by weight, preferably 20 to 70% by weight. Further, the dry film thickness or vapor deposited film thickness of the organic film 2 is 10 microns or less, preferably 2 microns or less. As the substrate 1, plastics such as polyester, acrylic resin, polyolefin resin, phenolic resin, epoxy resin, polyamide, and polyimide, glass, or metals can be used. Further, in the present invention, a reflective layer 3 can be provided between the substrate 1 and the organic coating 2 as shown in FIG.
The reflective layer 3 can be a deposited layer or a laminate layer of a reflective metal such as aluminum, silver, or chromium. The organic coating 2 can be formed into pits 5 by irradiation with a focused laser beam 4 as shown in FIG. By making the depth of the pits 5 the same as the thickness of the organic coating 2, the reflectance in the pit region can be increased. When reading, if a laser beam having the same wavelength as the laser beam used for writing but with low intensity is used, the reading light will be largely reflected in pit areas, but will be absorbed in non-pit areas. Another method is to perform real-time writing with a laser beam of a first wavelength that is absorbed by the organic coating 2, and to use a laser beam of a second wavelength that is substantially transmitted through the organic coating 2 for reading. The readout laser beam can respond to changes in the reflection phase caused by different film thicknesses in pitted and non-pitted regions. The organic coating of the present invention can be used for Alcon laser (oscillation wavelength: 488 nm), helium-neon laser (oscillation wavelength: 488 nm), helium-neon laser (oscillation wavelength:
It is also possible to record by irradiation with a gas laser such as a helium-cadmium laser (oscillation wavelength: 442 nm), but preferably 750 nm).
Lasers with wavelengths longer than m, especially gallium-aluminum-arsenic semiconductor lasers (oscillation wavelength 780n)
A method of recording by irradiation with a laser beam having an oscillation wavelength in a near-infrared region such as m) is suitable. Furthermore, the aforementioned laser beam can be used for reading. At this time, writing and reading can be performed using a laser of the same wavelength, or can be performed using lasers of different wavelengths. According to the present invention, a sufficiently improved S/N ratio can be obtained, and the organic coating used in the present invention has small reciprocity law failure, making it possible to increase the utilization of intense energy beams such as laser beams. Can be done. Furthermore, it is possible to perform recording using a laser beam having an oscillation wavelength of 750 nm or more. Hereinafter, the present invention will be explained in detail according to examples. Example 1 Nitrocellulose solution (Daicel Chemical Industries, Ltd.)
Manufactured by Ohares Latzker: Nitrocellulose 25
12 parts by weight of methyl ethyl ketone solution), 3 parts by weight of the aforementioned compound No. (3), and 70 parts by weight of methyl ethyl ketone were thoroughly mixed in a ball mill. This mixed solution was applied onto an aluminum vapor-deposited glass plate using the dip coating method, and then dried.
A recording layer of 0.6 g/m ² was obtained. The optical disk recording medium created in this way is mounted on a turntable, and the turntable is driven by a motor.
Spot size while giving 1800rpm rotation
Recording was carried out by irradiating the surface of the recording layer in the form of a track with a 5 mW and 8 MHz gallium-aluminum-arsenide semiconductor laser (oscillation wavelength 780 nm) focused at 1.0 micron. When the recorded surface of the optical disc was observed using a scanning electron microscope, clear pits were observed. Furthermore, when a low-output gallium-aluminum-arsenic semiconductor laser was incident on this optical disk and reflected light was detected, a waveform with a sufficient S/N ratio was obtained. Example 2 The above-mentioned compound No. 5 was coated on an aluminum vapor-deposited glass plate by dip coating in the same manner as in Example 1 to produce an optical disk recording medium having a recording layer of 0.6 g/m ² . Created. When information was recorded on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 3 An optical disk recording having a recording layer of 0.6 g/m ² was prepared by applying the above compound No. (10) onto an aluminum vapor-deposited glass plate by dip coating in the same manner as in Example 1. Created a body. When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 4 An optical disk recording having a recording layer of 0.8 g/m ² was prepared by coating the above compound No. (14) on an aluminum vapor-deposited glass plate by dip coating in the same manner as in Example 1. Created a body. When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 5 An optical disk recording having a recording layer of 0.6 g/m ² was prepared by coating the above compound No. (17) on an aluminum vapor-deposited glass plate by dip coating in the same manner as in Example 1. Created a body. When information was recorded on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 6 An optical disk recording having a recording layer of 0.6 g/m ² was prepared by coating the above compound No. (20) on an aluminum vapor-deposited glass plate by dip coating in the same manner as in Example 1. Created a body. When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 7 500 mg of the above compound No. (1) was placed in a molybdenum boat for vapor deposition, and after evacuated to 1×10 ^-6 mmHg or less, it was vapor deposited on an aluminum vapor-deposited glass plate. During the deposition, a 0.2 micron deposited film was formed while controlling the heater so that the pressure in the vacuum chamber did not rise above 10 ^-5 mmHg. Example 1
When information was stored in the same manner as in Example 1, clear pits similar to those in Example 1 were observed, and information was reproduced in the same manner as in Example 1, but in this case, a sufficient S/N ratio was obtained. A waveform was observed. Example 8 The above-mentioned compound No. (5) was vapor-deposited on an aluminum vapor-deposited glass plate in the same manner as in Example 7.
An optical disc recording medium having a micron recording layer was prepared. When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed. Example 9 The above-mentioned compound No. (13) was deposited on an aluminum-deposited glass plate in the same manner as in Example 7, and
An optical disk recording medium having a recording layer of 0.2 microns was prepared. When information was stored on this optical disk recording medium in the same manner as in Example 1 and then reproduced, a waveform with a sufficient S/N ratio was observed. Further, when the surface of the recording layer after information was written was observed with a scanning electron microscope, clear pits were found to have been formed.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the optical disc recording body of the present invention, and FIG. 3 is an explanatory view showing an embodiment of this optical disc recording body. 1...Substrate, 2...Organic coating, 3...Reflection layer,
4... Laser beam, 5... Pit.

Claims (1)

[Scope of Claims] 1. An optical recording medium characterized by having an organic coating containing a compound represented by the following general formula (1). General formula (1) (In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted styryl group, or a substituted or unsubstituted styryl group) Represents a substituted heterocyclic group. m is 0 or 1, n is 0, 1 or 2
It is. X is an anion. )