JPH0126357B2 - - 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 store high-density information in the form of optically detectable small (e.g., approximately 1μ) pits formed in a thin recording layer provided on a substrate in the form of spiral or circular tracks. I can do it. 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 shaped into a spiral or circular track. to form. The laser sensitive layer can absorb laser energy to form optically detectable pits. For example, in the heat mode recording method,
The laser-sensitive layer absorbs thermal energy and can form small pits at that location by evaporation or melting. In another heat mode recording method, absorption of irradiated laser energy can form pits with optically detectable density differences at the locations. 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 ~600nm, 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 thin films whose optical properties 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 sublimation, so it is not always possible to develop organic thin films that are 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 thin film having an absorption band on the long wavelength side. Another object of the present invention is to provide an optical recording medium having a thermally stable organic thin film. The organic thin film of the present invention is characterized in that it contains a pyrylium dye represented by the following general formula (1). General formula (1) In the formula, X ₁ and X ₂ represent a sulfur atom, an oxygen atom or a selenium atom. Z ₁ is optionally substituted pyrylium, thiopyrylium, selenapyrylium,
Indicates a hydrocarbon group consisting of the atomic group necessary to complete benzopyrylium, benzothiopyrylium, benzoselenapyrylium, naphthopyryllium, naphthothiopyrylium or naphthoselenapyrylium, and Z ₂ is an optionally substituted pyran. , thiopyran,
Indicates a hydrocarbon group consisting of the atomic group necessary to complete selenapyran, benzopyran, benzothiopyran, benzoselenapyran, naphthopyran, naphthothiopyran, or naphthoselenapyran. Examples of substituents include halogen atoms such as chlorine, bromine, and fluorine atoms, alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, amyl, isoamyl, hexyl, octyl, nonyl, and dodecyl, and methoxy. , alkoxy groups such as ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, aryl groups such as phenyl, α-naphthyl, β-naphthyl, tolyl,
xylyl, biphenyl, ethyl phenyl, methoxyphenyl, ethoxyphenyl, amyloxyphenyl, dimethoxyphenyl, diethoxyphenyl, hydroxyphenyl, chlorophenyl, dichlorophenyl, bromophenyl, dibromophenyl, nitrophenyl, diethylaminophenyl,
Examples include substituted aryl groups such as dimethylaminophenyl and dibenzylaminophenyl. R ₁ , R ₂ , R ₃ and R ₄ each represent (a) a hydrogen atom, (b) an alkyl group, particularly an alkyl group having 1 to 15 carbon atoms: for example, methyl, ethyl, propyl, isopropyl, butyl, t- Butyl, amyl, isoamyl, hexyl, octyl, nonyl, dodecyl (c) Aryl group: phenyl, α-naphthyl, β-
Naphthyl (d) substituted aryl group: tolyl, xylyl, biphenyl, ethyl phenyl, methoxyphenyl, ethoxyphenyl, amyloxyphenyl, dimethoxyphenyl, diethoxyphenyl, hydroxyphenyl, chlorophenyl, dichlorophenyl, bromophenyl, Dibromophenyl, nitrophenyl, diethylaminophenyl, dimethylaminophenyl, dibenzylaminophenyl R ₅ , R ₆ and R ₇ are hydrogen atoms, halogen atoms (chlorine atom, bromine atom, fluorine atom) substituted or unsubstituted Alkyl groups (methyl, ethyl, propyl, butyl, amyl, hydroxyethyl, methoxyethyl, carboxypropyl), substituted or unsubstituted aryl groups (phenyl, tolyl, xylyl, hydroxyphenyl, carboxyphenyl,
α-naphthyl, β-naphthyl) or substituted or unsubstituted aralkyl groups (benzyl, phenethyl,
3-phenylpropyl, methoxybenzyl, methylbenzyl). A is an anion such as perchlorate, fluoroborate, iodide, chloride, bromide, sulfate, periodide, P-
Represents toluene sulfonate, etc. m and l represent 1 or 2. n represents 0, 1 or 2. However, when n is 2, R ₅ may be the same or different, or
R ₆ may also be the same or different. Typical pyrylium dyes represented by general formula (1) are as follows.

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[Table] The optical recording medium of the present invention can have a structure as shown in FIG. 1, for example. The optical recording medium shown in FIG. 1 can be formed by providing on a substrate 1 an organic thin film 2 containing the aforementioned pyrylium dye. 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. The organic thin film 2 can be formed by vacuum evaporation of the cyanine dye described above, and a coating solution containing the cyanine dye described above in a binder is applied to the substrate 2.
It can be formed by coating 1. When forming a thin film with a cyanine dye together with a binder, the cyanine dye may be contained in the binder in a dispersed state or in an amorphous state. You can choose from resins. Specifically, cellulose nitro, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate,
Cellulose esters such as cellulose myristate, cellulose palmitate, cellulose acetate/propionate, cellulose acetate/butyrate, cellulose ethers such as methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl Copolymerization of vinyl resins such as butyral, polyvinyl acetal, polyvinyl alcohol, polyvinylpyrrolidone, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate copolymer, etc. Resins, acrylic resins such as polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyacrylonitrile, polyesters such as polyethylene terephthalate, poly(4,4'-isopropylidene) Diphenylene-co-1,4-cyclohexylene dimethylene carbonate), poly(ethylenedioxy-3,3'-phenylenethiocarbonate),
Poly(4,4'-isopropylidene diphenylene carbonate-coterephthalate), poly(4,4'-isopropylidene diphenylene carbonate-coterephthalate),
Polyarylate resins such as 4'-isopropylidene diphenylene carbonate), poly(4,4'-sec-butylidene diphenylene carbonate), and poly(4,4'-isopropylidene diphenylene carbonate block-oxyethylene) or polyolefins such as polyamides, polyimides, epoxy resins, phenolic resins, polyethylene, polypropylene, and chlorinated polyethylene. The organic solvent used during coating varies depending on the type of binder and whether the cyanine dye is dispersed or amorphous in the binder, but generally alcohols such as methanol, ethanol, isopropanol, etc. Ketones such as acetone, methyl ethyl ketone, cyclohexanone, N,
Amides such as N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran,
Ethers such as dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichlorethylene, benzene, toluene, Aromatics such as xylene, ligroin, monochlorobenzene, dichlorobenzene, methyl cellosolve, 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. The above-mentioned pyrylium dye contained in the organic thin film 2 is 1 to 90% by weight, preferably 20 to 70% by weight. Further, the dry thickness of the organic thin film 2 is 10 microns or less, preferably 2 microns or less. Further, in the optical recording medium of the present invention, a reflective layer 3 can be provided between the substrate 1 and the organic thin film 2, as shown in FIG. The reflective layer 3 is made of aluminum, silver,
It can be a deposited or laminated layer of a reflective metal such as chromium. The organic thin film 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 pit 5 the same as the thickness of the two organic thin films, 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 a lower intensity is used, the reading light is largely reflected in the bit area, but is absorbed in the non-pit area. Another method is to perform real-time writing with a laser beam of a first wavelength that is absorbed by the organic thin film 2, and use a laser beam of a second wavelength that substantially passes through the organic thin film 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 optical recording medium of the present invention can also be recorded by irradiation with a gas laser such as an argon laser (oscillation wavelength 488 nm), a helium-neon laser (oscillation wavelength 633 nm), or a helium-cadmium laser (oscillation wavelength 442 nm). Yes, but preferably
Lasers with a wavelength of 750 nm or more, especially gallium-aluminum-arsenic semiconductor lasers (oscillation wavelength
A method of recording by irradiation with a laser beam having an oscillation wavelength in the near-infrared or infrared region such as 830 nm) is suitable. Furthermore, the aforementioned laser beam can be used for reading. On this occasion,
Writing and reading can be performed with lasers of the same wavelength, or can be performed with lasers of different wavelengths. According to the present invention, it is possible to obtain a sufficiently improved S/N ratio, and the organic thin film 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. be able to. 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 Oherase Ratsker Nitrocellulose 25wt% methyl ethyl ketone solution) 12 parts by weight,
3 parts by weight of thiopyrylium dye No. (18) and 150 parts by weight of tetrahydrofuran were mixed and then dissolved. Apply this solution onto the Pyrex substrate at 500 rpm.
After applying by spinner coating method,
It was dried at a temperature of 100° C. for 2 hours to obtain a recording layer of 0.7 g/m ² . The optical 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
5mW and 8MHz gallium-aluminum-arsenic semiconductor laser beam focused at 0.8μ (oscillation wavelength
Recording was performed by irradiating the surface of the recording layer with light (830 nm) in the form of a track. When the recorded surface of the optical disk was observed using a scanning electron microscope, clear bits were observed. In addition, this optical disk has low output gallium.
When an aluminum-arsenic semiconductor laser was input and reflected light was detected, a waveform with a sufficient S/N ratio was obtained. Example 2 Nitrocellulose solution (Daicel Chemical Industries, Ltd.)
Manufactured by Ohares Ratsker, nitrocellulose
25wt% methyl ethyl ketone solution) 10 parts by weight No.
3 parts by weight of the benzopyrylium dye (12) was mixed with 100 parts by weight of monochlorobenzene and thoroughly stirred to dissolve. Next, this solution was applied onto a Pyrex substrate using a spinner at 500 rpm so that the coating amount after drying was 0.6 g/m ² , and then applied at a temperature of 100°C for 2 hours.
A recording layer was formed by drying for a period of time. When this recording layer was irradiated with the same laser beam as in Example 1,
Similar results as in Example 1 were obtained. Example 3 500 mg of benzothiopyrylium dye No. (11) was placed in a molybdenum boat for vapor deposition, and after evacuated to 1×10 ^-6 mmHg or less, it was vapor-deposited on a Pyrex substrate.
During the deposition, the heater was controlled so that the pressure within the vacuum chamber did not rise above 10 ^-5 . In this way, an organic thin film was formed on the Pyrex substrate to prepare an optical recording medium. When the recording layer made of this organic thin film was irradiated with the same laser beam as in Example 1, the same results as in Example 1 were obtained. Example 4 An optical recording medium was prepared in exactly the same manner as in Example 1, except that thiopyrylium dye No. (19) was used in place of thiopyrylium dye No. (18) used in Example 1. After that, when the same laser beam was irradiated, the same results as in Example 1 were obtained. Example 5 An optical recording medium was prepared in exactly the same manner as in Example 1, except that benzopyrylium dye No. (14) was used instead of thiopyrylium dye No. (18) used in Example 1. After the preparation, the same laser beam was irradiated, and the same results as in Example 1 were obtained. Example 6 An optical recording medium was prepared in exactly the same manner as in Example 1, except that thiopyrylium dye No. (21) was used instead of thiopyrylium dye No. (18) used in Example 1. After that, when the same laser beam was irradiated, the same results as in Example 1 were obtained. Example 7 An optical recording medium was prepared in exactly the same manner as in Example 1, except that thiopyrylium dye No. (22) was used instead of thiopyrylium dye No. (18) used in Example 1. When the same laser beam was irradiated from the sample, the same results as in Example 1 were obtained.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the optical recording medium of the present invention, and FIG. 3 is an explanatory diagram showing an embodiment using the optical recording medium of the present invention. 1: Substrate, 2: Organic thin film, 3: Reflective layer, 4: Laser beam, 5: Pits.

Claims (1)

[Scope of Claims] 1. An optical recording medium characterized by having an organic thin film containing a pyrylium dye represented by the following general formula (1). General formula (1) In the formula, X ₁ and X ₂ represent a sulfur atom, an oxygen atom or a selenium atom. Z ₁ : Consists of the necessary atomic group to complete pyrylium, thiopyrylium, selenapyrylium, benzopyrylium, benzothiopyrylium, benzoselenapyrylium, naphtopyrylium, naphthothiopyrylium, or naphthoselenapyrylium, which may be substituted Indicates a hydrocarbon group. _Z2 : optionally substituted pyran, thiopyran, selenapyran, benzopyran, benzothiopyran,
Indicates a hydrocarbon group consisting of the atomic group necessary to complete benzoselenapyran, naphthopyran, naphthothiopyran, or naphthoselenapyran. R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. R ₅ , R ₆ and R ₇ represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group. m and l: Indicates 1 or 2. n: Indicates 0, 1 or 2. However, when n is 2,
R ₅ may be the same or different, and R ₆ may be the same or different. A: Indicates an anion.