JPH0558915B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording method, and particularly to an optical recording method for a heat mode optical recording medium. Prior Art Optical recording media have the characteristic that the recording medium does not deteriorate due to wear since the medium and the writing or reading head are not in contact with each other, and for this reason, research and development of various optical recording media are being carried out. Among such optical recording media, heat mode optical recording media are being actively developed because they do not require development in a dark room. This heat mode optical recording medium is an optical recording medium that uses recording light as heat. One example is a heat mode optical recording medium that uses recording light such as a laser to melt or remove a part of the medium, which is called a pit. There is a pit-forming type in which writing is performed by forming small holes, information is recorded using the bits, and reading is performed by detecting the pits with a readout light. Until now, most of these pit-forming type media, especially those using a semiconductor laser as a light source that can make the device smaller, have a recording layer made of a material mainly composed of Te. However, in recent years, it has become clear that Te-based materials are harmful.
In addition, due to the need for higher sensitivity and lower manufacturing costs, Te
In place of conventional recording media, there are an increasing number of proposals and reports on media that use recording layers made of organic materials mainly containing dyes. For example, for He-Ne lasers, squalirium dye [Unexamined Japanese Patent Publication No. 56-46221 VBJipson
and CRJones, J.Vac.Sci.Technol., 18 (1)105
(1981)] and metal phthalocyanine dyes (Unexamined Japanese Patent Publication No. 1983)
-82094, 57-82095), etc. There is also an example of using metal phthalocyanine dyes for semiconductor lasers (Japanese Patent Application Laid-Open No. 86795/1986). In both of these, the recording layer is made into a thin film by vapor deposition of dye, and there is no major difference from the Te type in terms of medium production. However, the reflectance of the dye-deposited film to the laser is generally small, and the current conventional method of obtaining a readout signal from a change (decrease) in the amount of reflected light due to the pit cannot obtain a large S/N ratio. Can not. In addition, it is possible to use a transparent substrate carrying a recording layer as a medium with a so-called air sandwich structure in which the recording layers are integrated so that they face each other, and write and read data through the substrate without reducing the writing sensitivity. Although it is advantageous in that the recording layer can be protected and the recording density can be increased, such a recording and reproducing method is also difficult to use with a dye-deposited film. This is because a normal transparent resin substrate has a refractive index of a certain value (1.5 for polymethyl methacrylate), and the reflectance through the substrate of the recording layer is, for example, polymethyl methacrylate, relative to the wavelength of the semiconductor laser. This is because the recording layer exhibiting only a low reflectance cannot be detected because the reflectance is approximately 25% or less. Readout S/ of recording layer made of dye deposited film
In order to improve the N ratio, a vapor-deposited reflective film of Al or the like is usually interposed between the substrate and the recording layer. In this case, the vapor-deposited reflective film increases the reflectance and increases the S/
This is to improve the N ratio, and the reflective film is exposed by pit formation, increasing the reflectance, but as a matter of course, recording and reproduction cannot be performed through the substrate. Similarly, JP-A-55-161690 discloses a recording layer consisting of IR-132 dye (manufactured by Kodatsu) and polyvinyl acetate, and JP-A-57-74845 discloses 1,
A recording layer consisting of 1'-diethyl-2,2'-tricarbocyanine iodide and nitrocellulose, and further KYLaw, etal., Appl.Phys.Lett. 39 (9)718
(1981) described media in which a recording layer made of a dye and a resin was formed by a coating method, such as a recording layer made of 3,3'-diethyl-12-acetylthiatetracarbocyanine and polyvinyl acetate. Disclosed. However, these cases also have the same drawback as the dye-deposited film in that a reflective film is required between the substrate and the recording layer, and recording and reproduction cannot be performed from the back side of the substrate. As described above, in order to realize a medium having an organic material-based recording layer that allows recording and reproduction through the substrate, the organic material itself needs to exhibit a high reflectance. However, conventionally, there are very few examples of a single layer of organic material exhibiting high reflectance without laminating a reflective layer. It has been reported that a vapor-deposited film of vanadyl phthalocyanine exhibits a slightly high reflectance [P. Kivits, etal.
Appl.Phys.Part A 26 (2)101 (1981), Japanese Patent Application Publication No. 1987-
No. 97033], but the writing sensitivity is low, probably due to the high sublimation temperature. In addition, cyanine dyes and merocyanine dyes such as thiazole and quinoline dyes have been reported [Yamamoto et al., Proceedings of the 27th Japan Society of Applied Physics, 1p-P-9 (1980)], and a proposal based on this was published in JP-A-58. −112790
However, these dyes have low solubility in solvents, tend to crystallize, and are extremely unstable to readout light, resulting in immediate decolorization, especially when applied as a coating film, making them impractical. It cannot be offered to In view of these actual circumstances, the present inventors first
It is proposed that indolenine cyanine dyes, which have high solubility in solvents, little crystallization, thermal stability, and high reflectance of paint films, be used as a single layer film (Patent Application No. 1983). −134397, 57−
No. 134170). In addition, long-chain alkyl groups can be introduced into the molecules of other cyanine dyes such as indolenine, thiazole, quinoline, and selenazole to improve solubility and prevent crystallization. (Patent Application No. 57-182589, same)
57-177776, etc.). Furthermore, in order to improve photostability, and especially to prevent decolorization (reproduction deterioration) caused by readout light, we have proposed adding a transition metal compound quencher to cyanine dyes (Japanese Patent Application No. 166832/1983). 57
−168048, etc.) Furthermore, it forms an ionic bond between the dye and the quencher, thereby further reducing regeneration deterioration.
In addition, proposals have been made to improve stability (Patent Application No. 59-14848, Patent Application No. 59-18878, Patent Application No. 59-19715).
issue). By the way, in an optical recording film made of a dye or a dye composition, pits begin to form from the center of the irradiated light at the same time as it is irradiated with light, and in the latter half of the irradiated light pulse, pits are absorbed at the center of the irradiated light where the energy is most concentrated. It disappears. Therefore, the efficiency of energy use is low, which is the reason why the sensitivity cannot be improved beyond a certain value. Therefore, the present inventors have previously proposed that a film with a high melting point, such as a coating film of a colloidal particle dispersion of a silicon-based condensate, be applied as a surface layer (Japanese Patent Application No.
59-62386 etc.). According to this proposal, pits are not formed by irradiating light for a certain period of time, but the temperature rises during that time, and pits are formed all at once after reaching a sufficient temperature, resulting in extremely high sensitivity. However, since such pit formation is performed, there are disadvantages in that the intensity of the writing light is higher than the contrast obtained, and the medium running speed must be lower. In addition, in such a case, under normal conditions, when the pit is formed, the surface layer also breaks or breaks at the same time, and this is scattered to other tracks.
This has the disadvantage of lowering the S/N ratio and increasing the error rate. OBJECT OF THE INVENTION An object of the present invention is to provide an optical recording method using an optical recording medium having a recording layer made of a dye or a dye composition, by improving the surface layer of the medium and achieving high sensitivity.
Moreover, the objective is to have a high S/N ratio and a low error rate. DISCLOSURE OF THE INVENTION These objects are achieved by the invention described below. That is, the present invention has a recording layer made of a dye or a dye composition on a substrate, and on this recording layer,
When performing optical recording by irradiating writing light onto an optical recording medium that has a surface layer of an inorganic film with a higher melting point to form pits, recording is performed on the recording layer until sufficient energy can be absorbed by the surface layer. This is an optical recording method that improves sensitivity by preventing this from occurring, and also forms pits as recesses in a state where the surface layer is not substantially broken to prevent fragments from scattering during recording. Specific Configuration of the Invention The specific configuration of the present invention will be described in detail below. A dye is contained in the recording layer of the optical recording medium used in the present invention. There are no particular restrictions on the dyes used; cyanine,
Any of phthalocyanine-based, naphthalocyanine-based, tetradehydrocholine- or tetradehydrochorol-based dyes, anthraquinone-based, azo-based, triphenylmethane-based, biryllium or thiavirylium chlorine-based dyes can be used. Among these, cyanine dyes are primarily effective in the present invention. Among the cyanine dyes, those represented by the following formula [] are preferred. Formula [] φ−L=ψ (X ^- ) _n In the above formula [], ψ and φ are an indole ring, a thiazole ring, which may be fused with an aromatic ring, such as a benzene ring, a naphthalene ring, a phenanthrene ring, etc. Represents an oxazole ring, selenazole ring, imidazole ring, pyridine ring, etc. These φ and ψ may be the same or different, but are usually the same, and various substituents may be bonded to these rings. In addition,
In φ, the nitrogen atom in the ring has a positive charge, and in ψ, the nitrogen atom in the ring is neutral. The skeleton rings of these φ and ψ are preferably those represented by the following formulas [φ] to [φ]. In addition, in the following, the structure is shown in the form of φ. [φ] [φ] [φ] [φ] [φ] [φ] [φ] [φ] [φ] [φ] [φXI] [φXII] [φ] [φ] [φ] [φ] In these various rings, the group R ₁ (R ₁ , R ₁ ') bonded to the nitrogen atom in the ring (two nitrogen atoms in the imidazole ring) is a substituted or unsubstituted alkyl group or aryl group. . In such a ring, the group R ₁ bonded to the nitrogen atom,
There is no particular restriction on the number of carbon atoms in R ₁ '. Also,
If this group further has a substituent,
Examples of substituents include sulfonic acid groups, alkylcarbonyloxy groups, alkylamide groups, alkylsulfonamide groups, alkoxycarbonyl groups, alkylamino groups, alkylcarbamoyl groups, alkylsulfamoyl groups, hydroxyl groups, carboxy groups, halogen atoms, etc. It may be. In addition, when m described later is 0, the group R ₁ bonded to the nitrogen atom in φ is a substituted alkyl or aryl group and has a negative charge. Furthermore, when the rings φ and ψ are fused or non-fused indole rings (formulas [φ] to [φ]), two substituents R ₂ and R ₃ may be bonded to the 3-position. preferable. In this case, the two substituents R ₂ and R ₃ bonded to the 3-position are preferably an alkyl group or an aryl group. and,
Among these, unsubstituted alkyl groups having 1 or 2 carbon atoms, particularly 1, are preferred. On the other hand, another substituent R ₄ may be bonded to a predetermined position in the ring represented by φ and ψ. Such substituents include alkyl groups,
Aryl group, heterocyclic residue, halogen atom, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkylcarbonyl group, arylcarbonyl group, alkyloxycarbonyl group, aryloxycarbonyl group, alkylcarbonyloxy group, arylcarbonyloxy group , alkylamido group, arylamide group, alkylcarbamoyl group, arylcarbamoyl group, alkylamino group, arylamino group, alboxylic acid group, alkylsulfonyl group, arylsulfonyl group, alkylsulfonamide group, arylsulfonamide group,
It may be a variety of substituents such as an alkylsulfamoyl group, an arylsulfamoyl group, a cyano group, and a nitro group. Then, the number of these substituents (p, q, r,
s, t) are usually 0 or about 1 to 4. Note that when p, q, r, s, and t are 2 or more, the plurality of R ₄ may be different from each other. Furthermore, among these, the formula [φ] ~ [φ
It is preferable to have a fused or non-fused indole ring. These are the solubility in the solvent,
It has excellent coating properties and stability, exhibits an extremely high reflectance, and has an extremely high readout S/N ratio. On the other hand, L represents a linking group for forming a mono-, di-, tri- or tetracarbocyanine dye, and is particularly preferably one of formulas [L] to [L]. Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Formula [L] Here, Y represents a hydrogen atom or a monovalent group. In this case, monovalent groups include lower alkyl groups such as methyl groups, lower alkoxy groups such as methoxy groups, dimethylamino groups, diphenylamino groups, methylphenylamino groups, morpholino groups, imidazolidine groups, and ethoxycarbonylpiperazine groups. Preferable examples include di-substituted amino groups such as, alkylcarbonyloxy groups such as acetoxy groups, alkylthio groups such as methylthio groups, cyano groups, nitro groups, and halogen atoms such as Br and Cl. In addition, in these formulas [L] to [L],
Tricarbocyanine linking group, especially formula [L], [L
] is preferred. Furthermore, ^- is an anion, and preferable examples thereof include ^- , Br ^- , ClO ₄ ^- , BF ₄ ^- , [Formula] [Formula], and the like. Note that m is 0 or 1, but when m is 0, R ₁ of φ usually has ^{a −} charge and becomes an inner salt. Next, specific examples of the cyanine dye of the present invention will be given, but the present invention is not limited to these. [Table] [Table] [Table] [Table] [Table] [Table] Furthermore, the effect of the present invention is the second one.
It is a phthalocyanine dye. There are no particular restrictions on the phthalocyanine used.
Central atoms include Cu, Fe, Co, N, In, Ga,
Al, InCl, InBr, InI, GaCl, GaBr, GaI,
AlCl, AlBr, Ti, TiO, Si, Ge, H, H ₂ , Pb,
Vo, Mn, Sn, etc. are possible. In addition, -OH, halogen,
-COOH, _NH2 , -CoCl, -COOR', -OCOR' (where R' is various alkyl or aryl, etc.), _-SO2Cl , _-SO3H , _-CONH2 , -CN, _-NO2 , It may be bonded with various substituents such as -SCN, -SH, _-CH2Cl , etc. Next, specific examples of the light-absorbing dye of the present invention will be given, but the present invention is not limited to these. Such dyes can be easily synthesized according to the method described in Nitrogen-Containing Heterocyclic Compounds, page 432, Dai Organic Chemistry (Asakura Shoten). That is, first, the corresponding φ′−CH ₃ (φ′ is the above φ
represents the ring corresponding to . ) with excess R ₁ I (R ₁ is an alkyl group or an aryl group),
R ₁ is introduced into the nitrogen atom in φ' to obtain φ-CH ₃ I ^- . Next, this may be subjected to dehydration condensation with an unsaturated dialdehyde, unsaturated hydroxyaldehyde, pentadiene diallyl, isophorone, etc. using an alkali catalyst such as piperidine or trialkylamine, or acetic anhydride. Such a dye can also form a recording layer alone. Alternatively, a recording layer is formed together with resin. The resin used is preferably a self-oxidizing resin or a thermoplastic resin. The self-oxidizing resin contained in the recording layer undergoes oxidative decomposition when the temperature rises.
Among these, nitrocellulose is particularly suitable. Further, the thermoplastic resin is softened by increasing the temperature of the dye that has absorbed the recording light, and various known thermoplastic resins can be used as the thermoplastic resin. Among these, thermoplastic resins that can be particularly preferably used include the following. Polyolefin polyethylene, polypropylene, poly4-methylpentene-1, etc. Polyolefin copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-butene-1 copolymer,
Ethylene-maleic anhydride copolymer, ethylene propylene terpolymer (EPT), etc. In this case, the polymerization ratio of the comonomers can be arbitrary. Vinyl chloride copolymer, for example, vinyl acetate-vinyl chloride copolymer,
Vinyl chloride-vinylidene chloride copolymer, vinyl chloride-maleic anhydride copolymer, copolymer of acrylic acid ester or methacrylic acid ester and vinyl chloride, acrylonitrile-vinyl chloride copolymer, vinyl chloride ether copolymer,
Ethylene or propylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer with vinyl chloride graft polymerized, etc. In this case, the copolymerization ratio can be arbitrary. Vinylidene chloride copolymer Vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl chloride-acrylonitrile copolymer, vinylidene chloride-butadiene-vinyl halide copolymer, etc. In this case, the copolymerization ratio can be arbitrary. Polystyrene Styrene copolymer For example, styrene-acrylonitrile copolymer (AS resin), styrene-acrylonitrile-
Butadiene copolymer (ABS resin), styrene-
Maleic anhydride copolymer (SMA resin), styrene-acrylic acid ester-acrylamide copolymer, styrene-butadiene copolymer (SBR), styrene-vinylidene chloride copolymer,
Styrene-methyl methacrylate copolymer, etc. In this case, the copolymerization ratio can be arbitrary. Styrenic polymers such as α-methylstyrene, p-methylstyrene, 2,5-dichlorostyrene, α,β-
Vinylnaphthalene, α-vinylpyridine, acenaphthene, vinylanthracene, etc., or copolymers thereof, such as copolymers of α-methylstyrene and methacrylic acid ester. Chroman-indene resin A copolymer of coumaron-indene-styrene. Terpene resin or picolite For example, terpene resin which is a polymer of limonene obtained from α-pinene, or picolite obtained from β-pinene. Acrylic resin In particular, those containing an atomic group represented by the following formula are preferred. formula In the above formula, R ₁₀ represents a hydrogen atom or an alkyl group, and R ₂₀ represents a substituted or unsubstituted alkyl group. In this case, in the above formula,
R ₁₀ is preferably a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, particularly a hydrogen atom or a methyl group. Further, R ₂₀ may be a substituted or unsubstituted alkyl group, but the alkyl group preferably has 1 to 8 carbon atoms, and when R ₂₀ is a substituted alkyl group, the alkyl group preferably has 1 to 8 carbon atoms. The substituent for the group is preferably a hydroxyl group, a halogen atom, or an amino group (particularly a dialkylamino group). The atomic group represented by the above formula may form a copolymer with other repeating atomic groups to constitute various acrylic resins, but usually one type of atomic group represented by the above formula is used. Alternatively, an acrylic resin is formed by forming a homopolymer or copolymer having two or more repeating units. Polyacrylonitrile Acrylonitrile copolymer For example, acrylonitrile-vinyl acetate copolymer, acrylonitrile-vinyl chloride copolymer, acrylonitrile-styrene copolymer, acrylonitrile-vinylidene chloride copolymer, acrylonitrile-vinylpyridine copolymer, acrylonitrile-methacrylate acid methyl copolymer, acrylonitrile-butadiene copolymer,
Acrylonitrile-butyl acrylate copolymer, etc. In this case, the copolymerization ratio can be arbitrary. Diacetone acrylamide polymer Diacetone acrylamide polymer made by acetone acting on acrylonitrile. Polyvinyl acetate Vinyl acetate copolymer For example, a copolymer with acrylic acid ester, vinyl ether, ethylene, vinyl chloride, etc. The copolymerization ratio may be arbitrary. Polyvinyl ether For example, polyvinyl methyl ether, polyvinylethyl ether, polyvinyl butyl ether, etc. Polyamide In this case, polyamides include nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 9, nylon 11, nylon
In addition to regular homonylon such as 12 and nylon 13,
Nylon 6/6-6/6-10, Nylon 6/6
-6/12, nylon 6/6-6/11, or modified nylon in some cases. Polyesters such as oxalic acid, succinic acid, maleic acid,
Various dibasic acids such as aliphatic dibasic salts such as adipic acid and sebastenic acid, or aromatic dibasic acids such as isophthalic acid and terephthalic acid, ethylene glycol, tetramethylene glycol,
Condensates and co-condensates with glycols such as hexamethylene glycol are suitable. Among these, condensates of aliphatic dibasic acids and glycols and cocondensates of glycols and aliphatic dibasic acids are particularly suitable. Furthermore, for example, glyptal resin, which is a condensate of phthalic anhydride and glycerin, can be used as a fatty acid,
Modified glyptal resins that are esterified with natural resins and the like are also preferably used. Polyvinyl acetal resin Both polyvinyl formal and polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol are preferably used. In this case, the degree of acetalization of the polyvinyl acetal resin can be arbitrary. Polyurethane resin A thermoplastic polyurethane resin with urethane bonds. Particularly suitable are polyurethane resins obtained by condensation of glycols and diisocyanates, particularly polyurethane resins obtained by condensation of alkylene glycol and alkylene diisocyanate. Polyether Styrene-formalin resin, ring-opening polymer of cyclic acetal, polyethylene oxide and glycol, polypropylene oxide and glycol, propylene oxide-ethylene oxide copolymer, polyphenylene oxide, etc. Cellulose derivatives such as nitrocellulose, acetylcellulose, ethylcellulose, acetylbutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose,
Various esters and ethers of cellulose, such as ethylhydroxyethylcellulose, and mixtures thereof. Polycarbonate For example, various polycarbonates such as polydioxydiphenylmethane carbonate and dioxydiphenylpropane carbonate. Ionomers Na, Li, methacrylic acid, acrylic acid, etc.
Zn, Mg salt, etc. Ketone resin For example, a condensate of a cyclic ketone such as cyclohexanone or acetophenone and formaldehyde. Xylene resin For example, a condensate of m-xylene or mesitylene and formalin, or a modified product thereof. Petroleum resins _C5 type, _C9 type, _C5 - _C9 copolymer type, dicyclopentadiene type, or copolymers or modified products thereof. A blend of two or more of the above or a blend with other thermoplastic resins. Note that the self-oxidizing or thermoplastic resin may have various molecular weights. Such an autooxidizing compound or thermoplastic resin and the above-mentioned dye are usually in a weight ratio of 1:1.
Layers are laid in a wide range of ratios from 0.1 to 100. Preferably, such a recording layer further contains a quencher. This reduces reproduction deterioration and improves light resistance. Various types of quenchers can be used, but in particular, when the dye is excited and singlet oxygen is generated, it undergoes electron transfer or energy transfer from the singlet oxygen and becomes excited, returning to the ground state by itself. In addition, it is preferably a singlet oxygen quencher that converts singlet oxygen into a triplet state. Although various singlet oxygen quenchers can be used, transition metal chelate compounds are particularly preferred because they reduce acidic deterioration and have good compatibility with dyes. In this case, the central metals are Ni,
Co, Cu, Mn, Pd, Pt, etc. are preferred, and the following compounds are particularly preferred. 1 Acetylacetonate chelate system Q1-1 Ni () acetylacetonate Q1-2 Cu () acetylacetonate Q1-3 Mn () acetylacetonate Q1-4 Co () acetylacetonate 2 Bisdithio- represented by the following formula α-diketone system Here, R ¹ to ^{R 4} represent a substituted or unsubstituted alkyl group or aryl group, and M is Ni,
Represents transition metal atoms such as Co, Cu, Pd, and Pt. In this case, M has a negative charge and may form a salt with a cation (Cat) such as a quaternary ammonium ion. In addition, in the following description, Ph is a phenyl group,
φ represents a 1,4-phenylene group, φ' represents a 1,2-phenylene group, and benz represents that adjacent groups on the ring are bonded to each other to form a condensed benzene ring. [Table] 3 Bisphenyldithiol system represented by the following formula Here, R ⁵ to R ⁸ are hydrogen or methyl group,
It represents an alkyl group such as an ethyl group, a halogen atom such as Cl, or an amino group such as a dimethylamino group or a diethylamino group, and M represents a transition metal atom such as Ni, Co, Cu, Pd, or Pt. In addition, M in the above structure has a negative charge and may form a salt with a cation (Cat) such as a quaternary ammonium ion, and furthermore, other ligands may be bonded above and below M. Good too. Examples of this include the following: [Table] [Table] In addition, JP-A No. 50-45027 and Patent Application No. 58-
Such as those described in No. 163080. 4 Dithiocarbamate chelate system represented by the following formula Here, R ⁹ and R ¹⁰ represent an alkyl group. Further, M represents a transition metal such as Ni, Co, Cu, Pd, or Pt. Q4-1R ₉ , R ₁₀ /C ₄ H ₉ M/Ni 5 Represented by the following formula Here, M represents a transition metal atom, Q ¹ represents [Formula] or [Formula], and Cat represents a cation. [Table] Other items described in Japanese Patent Application No. 58-125654. 6 What is shown by the following formula Here, M represents a transition gold atom, A represents S, C< ^R11 _R12 or ^CQ2 , and ^R11 and ^R12 are CN, ^COR13 , respectively.
COOR ¹⁴ , CONR ¹⁵ , R ¹⁶ or SO ₂ R ¹⁷ represents ^a hydrogen atom or a substituted or unsubstituted alkyl group or aryl group, and Q ² represents a 5- or 6-membered ring ^. represents the atomic group necessary to form , Cat represents a cation, and n is 1 or 2. [Table] [Table] Other items described in Japanese Patent Application No. 127074/1982. 7 Compound represented by the following formula Here, M represents a transition metal atom, Cat represents a cation, and n is 1 or 2. M
Cat Q7−1 Ni
2 [(n-C ₄ H ₉ ) ₃ N] Q7-2 Ni
2 [n-C ₁₆ H ₃₃ (CH ₃ ) ₃ N] In addition, those described in Japanese Patent Application No. 58-127075. 8 Bisphenylthiol system Q8-1 Ni-bis(octyl phenyl) sulfide 9 Thiocatechol chelate system represented by the following formula Here, M represents a transition metal atom such as Ni, Co, Cu, Pd, Pt, etc. Further, M has a negative charge and may form a salt with a cation (Cat), and the benzene ring may have a substituent. M Cat Q9−1 Ni N ⁺ (C ₄ H ₉ ) ₄ 10 Compound represented by the following formula Here, R ¹⁸ represents a monovalent group, l is 0 to 6, M represents a transition metal atom, and Cat represents a cation. M R ¹⁸ l Cat Q10-1 Ni H 0 N (n-C ₄ H ₉ ) ₄ Q10-2 Ni CH ₃ 1 N (n-C ₄ H ₉ ) ₄ Described in Japanese Patent Application No. 143531/1982. 11 Compounds represented by both formulas below Here, in the above formula, R ²⁰ , R ²¹ , R ²² and R ²³ each represent a hydrogen atom or a monovalent group, and R ²⁴ , R ²⁵ , R ²⁶ and R ²⁷ represent a hydrogen atom or a monovalent group. R ²⁴ and R ²⁵ , R ²⁵ and R ²⁶ , and R ²⁶ and R ²⁷ may be bonded to each other to form a 6-membered ring. Moreover, M represents a transition metal atom. [Table] Other items described in Japanese Patent Application No. 145294/1982. 12 Compound represented by the following formula Here, M represents Pt, Ni or Pd,
X ₁ , X ₂ , X ₃ and X ₄ each represent O or S. M X ₁ X _{2 X 3} 13 Compound represented by the following formula Here, R ³¹ is a substituted or unsubstituted alkyl group or aryl group, and R ³² , R ³³ , R ³⁴ and R ³⁵ represent a hydrogen atom or a monovalent group, but R ³² and R ³³ , ^R33 and ^R34 , ^R34
and R ³⁵ may be combined with each other to form a 6-membered ring. Moreover, M represents a transition metal atom. [Table] Other items described in Japanese Patent Application No. 151928/1982. 14 Compounds represented by both formulas below R ⁴¹ , R ⁴¹ , R ⁴³ and R ⁴⁴ each represent a hydrogen atom or a monovalent group, but R ⁴¹ and R ⁴² , R ⁴² and R ⁴³ , R ⁴³ and R ⁴⁴ are bonded to each other and have six members. It may form a ring. Moreover, R ⁴⁵ and R ⁴⁶ represent a hydrogen atom or a monovalent group. Furthermore, M represents a transition metal atom. [Table] Other items described in Japanese Patent Application No. 151929/1982. 15 Compound represented by the following formula Here, R ⁵¹ , R ⁵² .R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ ,
and R ⁵⁸ each represent a hydrogen atom or a monovalent group, R ⁵¹ and R ⁵² , R ⁵² and R ⁵³ , R ⁵³ and R ⁵⁴ , R ⁵⁵ and R ⁵⁶ ,
R ⁵⁶ and R ⁵⁷ and R ⁵⁷ and R ⁵⁸ may be bonded to each other to form a 6-membered ring. X represents halogen. M represents a transition metal atom. [Table] Other items described in Japanese Patent Application No. 153392/1982. 16 Salicylaldehyde oxime system represented by the following formula Here, R ⁶⁰ and R ⁶¹ represent an alkyl group, and M represents a transition metal atom such as Ni, Co, Cu, Pd, or Pt. [Table] 17 Thiobisphenolate chelate system represented by the following formula Here, M is the same as above, R ⁶⁵ and
R ⁶⁶ represents an alkyl group. Further, M has a negative charge and may form a salt with a cation (Cat). [Table] 18 Phosphonous acid chelate system represented by the following formula Here, M is the same as above, R ⁷¹ and
R ⁷² represents a substituent such as an alkyl group or a hydroxyl group. R ⁷¹ , R ⁷² M Q18-1 3-t-C ₄ H ₉ , 5-t-C ₄ H ₉ , 6-
OH Ni 19 Compounds represented by the following formulas Here, R ⁸¹ , R ⁸² , R ⁸³ and R ⁸⁴ represent a hydrogen atom or a monovalent group, but R ⁸¹ and R ⁸² , R ⁸² and R ⁸³ , R ⁸³ and R ⁸⁴ are bonded to each other. , may form a 6-membered ring. R ⁸⁵ and R ⁸⁸ each represent a hydrogen atom or a substituted or unsubstituted alkyl group or aryl group. R ⁸⁶ represents a hydrogen atom, a hydroxyl group, or a substituted or unsubstituted alkyl group or aryl group. R ⁸⁷ represents a substituted or unsubstituted alkyl group or aryl group. Z represents a group of nonmetallic atoms necessary to form a 5- or 6-membered ring. M represents a transition metal atom. [Table] Other items described in Japanese Patent Application No. 153393/1982. 20 Compound represented by the following formula Here, R ⁹¹ and R ⁹² are each a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, an acyl group, an N-alkylcarbamoyl group, and an N-alkylcarbamoyl group.
- represents an arylcarbamoyl group, N-alkylsulfamoyl group, N-arylsulfamoyl group, alkoxycarbonyl group or aryloxycarbonyl group, and M represents a transition metal atom. R ⁹¹ , R ⁹² M Q20-1 nC ₄ H ₉ CH ₃ Ni Q20-2 CH ₃ CH ₃ O-φ-NHCO Ni In addition, those described in Japanese Patent Application No. 58-155359. In addition, other quenchers include the following. 21 Benzoate Q21-1 Existing chemical substance 3-3040 [Tinuvin-
120 (manufactured by Ciba Geigy)] 22 Hindered amine type Q22-1 Existing chemical substance 5-3732 [SANOLIS-770 (manufactured by Sankyo Pharmaceutical Co., Ltd.)] Each of these quenchers is
It is contained in an amount of about 0.01 to 12 moles, particularly about 0.05 to 1.2 moles. Note that the maximum absorption wavelength of the quencher is preferably greater than or equal to the maximum absorption wavelength of the dye used. This results in extremely low regeneration and deterioration. In this case, the difference between the two is preferably 0 or 350 nm or less. In order to miniaturize the device, it is preferable to use a 750,
780, 830nm semiconductor laser or 633nm
Since it is preferable to use a He-NE laser, etc., the maximum absorption wavelength of the singlet oxygen quencher is
The wavelength is preferably 680 nm or more, particularly 680 to 1500 nm, even more preferably 800 to 1500 nm. Furthermore, the absorption coefficients of the dye used (or its effective value when two or more types are used) and the singlet oxygen quencher at the wavelength of the readout light are εD, respectively.
and εQ, εD/εQ is preferably 3 or more. Note that when two or more types of dyes are used in combination, the absorption maximum wavelength and εD of the dyes are an arithmetic mean effective value depending on the concentration. With such a value, the excitation of the quencher during irradiation with readout light becomes extremely small, and the deterioration of regeneration due to singlet oxygen becomes extremely small. Additionally, the quencher may form an ionic conjugate with the dye. As the quencher dye ion conjugate, those described in Japanese Patent Application No. 59-14848 may be used. However, what can be more preferably used are the combinations of cyanine dye cations and quencher anions described in Japanese Patent Application Nos. 59-18878 and 59-19715. The cyanine dye cation used may be any of the cations listed above. In addition, the quencher anion is 3) above,
It may be any anion form among 5), 6), 7), 9), 10), and 17). A specific example is given below. In addition, in the following, D ⁺ is the corresponding cation of D, and Q ^- is the corresponding anion of the quencher. [Table] [Table] A quencher having such absorption characteristics is appropriately selected and used depending on the light source and dye used. In order to install such a recording layer, it is generally necessary to apply the coating according to a conventional method. The thickness of the recording layer is usually about 0.03 to 2 μm. Alternatively, when forming a recording layer using only a dye and a quencher, vapor deposition, sputtering, etc. may be used. The thickness of the recording layer is 0.04~0.12μm, especially 0.05~
Preferably, it is 0.08 μm. At 0.04 μm, particularly 0.03 μm or less, both absorption and reflection amount are small, and neither write sensitivity nor playback sensitivity can be increased. If it is 0.12 μm or more, the pre-group will be buried, making it difficult to obtain a tracking signal. Furthermore, it is not easy to form bits, and writing sensitivity decreases. In addition, such a recording layer may contain other dyes, other polymers or oligomers, various plasticizers, surfactants, antistatic agents, lubricants, flame retardants, stabilizers, dispersants, and antioxidants. , and may also contain a crosslinking agent and the like. To deposit such a recording layer, on the substrate,
What is necessary is just to apply|coat using a predetermined solvent and to dry. Examples of solvents used for coating include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, esters such as butyl acetate, ethyl acetate, carbitol acetate, and butyl carbitol acetate, and ethers such as methyl cellosolve and ethyl cellosolve. , aromatic systems such as toluene and xylene, halogenated alkyl systems such as dichloroethane, and alcohol systems. The substrate on which such a recording layer is provided is made of resin. Various materials are possible for the resin. However, in such resins, especially solvents for various coatings such as those mentioned above, especially ketone-based, ester-based,
Acrylic resins or polycarbonate resins are easily affected by alkyl halides and the like, and the effect of the underlayer of the present invention is particularly large. Since these are substantially transparent to writing and reading light, writing and reading can be performed from the back side of the substrate.
This is advantageous in terms of sensitivity, S/N ratio, etc., and is also advantageous in terms of implementation, such as dust countermeasures. Furthermore, since the moldability is good, it is easy to form tracking grooves. The acrylic resin is preferably a copolymer or homopolymer mainly composed of a methacrylic acid ester having a chain or cyclic alkyl group having 1 to 8 carbon atoms, such as polymethyl methacrylate. Furthermore, as the polycarbonate resin, bisphenol A type is preferred. When these acrylic resins or polycarbonate resins are formed by injection molding, the effect of the base layer of the present invention becomes even greater. Note that the number average degree of polymerization of these acrylic resins or polycarbonate resins is preferably about 800 to 6,000. The surface layer formed on the recording layer may be a film having a higher melting point than the recording layer and further a higher hardness than the recording layer. Therefore, vapor-phase deposited films of various oxide-based, nitride-based, and carbide-based inorganic substances, such as silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zirconium oxide, silicon nitride, and silicon carbide, may be used. Good too. Alternatively, it may be a hydrolyzed coating film mainly formed from silicon oxide, titanium oxide, acid zirconium, aluminum oxide, etc. formed from a chelate compound known as a so-called crosslinking agent. However, among these, the most active is the coating film of the colloidal particle dispersion of the silicon-based condensate. The colloidal particles of the silicon-based condensate are preferably silicon halides, particularly silicon tetrachloride, or hydrolyzed condensates of alkyl silicic acids, especially tetra-lower alkyl (methyl, ethyl) silicic acids. And the colloidal particle diameter is 30~100Å, especially
It is said to be about 50 to 80 Å. Further, as the fractional medium, an alcohol, particularly one aliphatic alcohol, an alkyl acetate, or a mixed solvent of these and an aromatic hydrocarbon is used. Moreover, for hydrolysis, a mineral acid is added as necessary. Then, a stabilizer such as ethylene glycol, a surfactant, etc. are added as necessary. An example of such a colloidal particle dispersion is one in which silicon tetrachloride (SiCl ₄ ) and a monohydric aliphatic alcohol are dissolved in acetic acid alkyl ester, which is described in Japanese Patent Publication No. 6533/1983. . Alternatively, 1 to 20 wt% of ethylene glycol may be added to a solution of tetraalkyl silicic acid, monovalent aliphatic alcohol, alkyl acetate, and mineral acid described in Japanese Patent Publication No. 36-4740. Furthermore, an alcoholic solution of tetra-lower alkylsilicic acid described in Japanese Patent Publication No. 45-35435 may also be used. In such cases, monohydric aliphatic alcohols to be used include methyl alcohol, ethyl alcohol, denatured alcohol, isopropyl alcohol, butyl alcohol, or mixtures thereof, and alkyl acetates include methyl acetate, ethyl acetate, amyl acetate, and acetic acid. Butyl or a mixture thereof may be used, and as the mineral acid, an aqueous solution of hydrochloric acid or sulfuric acid, which is commonly used in industry, may be used. In addition, these dispersions are applied according to the conventional method.
It may be applied with a spinner coat or the like. In this case, the diluting solvent includes, for example, a mixed solvent of a hydrocarbon type and an alcohol type. Then, drying may be performed at 40 to 80°C for about 20 minutes to 2 hours. The coating film thus formed is a silicon oxide coating film containing hydroxyl groups. The thickness of the above first surface layer is 0.005 to 0.03 μm. Particularly preferably, it is 0.08 to 0.12 μm. If the first surface layer is less than 0.003 μm, the effect of improving writing and reading sensitivity as an optical recording medium cannot be obtained. When the first surface layer exceeds 0.03 μm, the writing/reading sensitivity of the optical recording medium deteriorates.
It will drop. In an optical recording film made of a dye composition, pits are formed at the same time as the film is irradiated with light, and the subsequent irradiated light is no longer absorbed at the center where the energy is most concentrated. Therefore, the energy utilization efficiency is low, which is the reason why the sensitivity cannot be improved beyond a certain value. The surface layer of the present invention is a hard film with a high melting point, and is designed to prevent the formation of pits in response to irradiated light within a certain period of time. Even when forming a surface layer with a high melting point, by adjusting the intensity, pulse width, rotation speed, etc. of the writing light, the surface layer can be formed in a substantially continuous state and without substantially breaking. A recess will be formed. Therefore, while maintaining high sensitivity, a decrease in the S/N ratio and an increase in the error rate due to the scattering of fragments of the surface layer are prevented. Note that such writing conditions can be easily determined experimentally. Note that the fact that the surface layer is substantially continuous and unbroken means that the occurrence of pinholes that can be ignored with respect to the pit diameter is allowed. Moreover, such a surface layer may be a composite laminated film. Furthermore, a polymer film may be laminated as an upper layer on such a surface layer. The formation of such a polymer film also prevents the surface layer from breaking. Various polymers can be used, but in particular, the polymer should not invade the surface layer mentioned above and dissolve the dye, should have good adhesion, good uniformity, good coatability, and low viscosity. For these reasons, it is preferable to use a coating film of a polymer compound that is soluble in water or a water-alcohol mixed solvent and contains a hydroxyl group. In this case, being soluble in water or a water-alcohol mixed solvent means that it is soluble in water or a water-alcohol mixed solvent as described below by about 1% or more. Such a polymer compound may be a polysaccharide such as gum arabic, alginic acid, or gum tragacanth, but cellulose derivatives and vinyl alcohol unit-containing resins as described below are particularly suitable. 1 Cellulose derivatives Nitrorelulose, acetylcellulose, ethylcellulose, acetylbutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylhydroxyethylcellulose, etc. In this case, the hydroxyl group per repeating unit is
It is preferable that the average content is 1 or more. 2 Vinyl alcohol unit-containing resin A complete or partial hydrolyzate of polyvinyl alcohol, polyvinyl acetate, ethylene-vinyl acetate copolymer, etc. In this case, the vinyl alcohol unit is 70 mol%
As mentioned above, the content is preferably 80 mol% or more. Note that there is no particular restriction on the number average molecular weight of such a polymer compound. Such a polymer compound is usually dissolved in a water-alcohol mixed solvent and applied as a layer. In this case, the alcohol is methanol,
Ethanol, propanol, butanol, etc. alone or in combination are suitable. The mixing ratio of water and alcohol is about 1:0.5 to 3. Although water can be used alone as the coating solvent, a water-alcohol mixed solvent is superior in terms of coating properties on resin substrates. When applying such a protective layer, a crosslinking agent can be added to the coating solution to crosslink the polymer compound in the coating film. At this time, solvent resistance, water resistance, and heat resistance are improved, and the stability of the recording layer is improved. In this case, a surfactant, an antifoaming agent, an antistatic agent, etc. may be added to the coating liquid in order to prevent pinholes from forming, completely defoaming, and lower the viscosity. The crosslinking agent used is preferably an organic compound or chelate of titanium, zirconium, or aluminum, or an aldehyde, oxycarboxylic acid, or methylol-containing oligomer. Such a polymer membrane preferably has a thickness of 0.002 to 0.8 μm, more preferably 0.005 to 0.5 μm. If it is less than 0.002μm, there is no effective scattering prevention.
This is because the sensitivity decreases when it exceeds 0.8 μm. Furthermore, the recording layer having the surface layer of the present invention may be formed directly on the substrate, or may be provided via an underlayer. The underlayer may be of various known types, but it is preferably one that is produced in exactly the same manner as the first surface layer or polymer film described above. The thickness of the base layer is 0.005 to 0.05 μm. especially
It is preferably 0.008 to 0.03 μm. When the thickness of the underlayer is less than 0.005 μm, the effect of imparting solvent resistance and heat resistance to the substrate is insufficient. If it exceeds 0.05 μm, sensitivity decreases. By installing the base layer as described above,
The sensitivity as an optical recording medium has further increased, resulting in improved S/N
The ratio will further improve. A recording layer is usually provided directly on the underlayer, but if necessary, another intermediate layer may be provided between the underlayer and the recording layer. . Similarly, various uppermost protective layers, half mirror layers, reflective layers, etc. can also be provided on the surface layer. The medium of the present invention may have the above-mentioned recording layer on one side of such a substrate with an underlayer interposed therebetween, or may have recording layers on both sides thereof with an underlayer interposed therebetween. good. Also, two recording layers are coated on one surface of the substrate with an underlayer interposed therebetween, and these are placed so that the recording layers face each other with a predetermined gap between them.
It can also be sealed to prevent dust and scratches. In the recording method of the present invention, recording light is irradiated onto the medium in a pulsed manner while the medium is traveling or rotating. At this time, due to the heat generated by the dye in the recording layer, the self-oxidizing resin decomposes or the thermoplastic resin and the dye melt, forming pits. In this case, writing is preferably performed from the back side of the substrate. In particular, when a tri- or tetracarbocyanine dye is used, extremely good writing can be achieved when a recording semiconductor laser diode with a wavelength of 750, 780, or 830 nm is used. Also, when using phthalocyanine dyes,
Very good writing can be performed when using a recording semiconductor laser diode with a wavelength of 730 to 760 nm. The pits thus formed are read out by detecting reflected or transmitted light, especially reflected light, of the readout light of the above wavelength while the medium is running or rotating. In this case, it is preferable that the readout light is irradiated from the back side of the substrate and the reflected light is detected. Note that when a recording layer or a thermoplastic resin is used, pits once formed in the recording layer can be erased with light or heat and rewritten. In addition, He-
Ne laser etc. can also be used. In such a case, according to the present invention, pits are formed without substantially breaking the surface layer. FIG. 1 shows a cross-sectional view of the formed pit. In such a case, as described above, when forming a normal high melting point surface layer, the writing conditions are adjusted. In other words, the light intensity is slightly lowered,
In addition, the speed at which the irradiation light passes through the recording medium may be increased. At this time, high-speed recording can be performed at the same time. Furthermore, a polymer film may be formed on the surface layer to prevent the surface layer from breaking at the pit portion. Specific Effects of the Invention The present invention uses an optical recording medium having a surface layer with a high melting point in the recording layer made of a dye or a dye composition, and forms pits in such a manner that the surface layer does not break. , the intensity of the writing light to obtain the same contrast is reduced, and the medium running speed can be increased. By forming the polymer film and setting the writing conditions, breakage of the surface layer during pit formation and accompanying scattering can be prevented, so the S/N ratio is improved and the error rate is reduced. Specific Examples of the Invention Hereinafter, the present invention will be explained in further detail by giving examples of the present invention. Example Tetraethyl hydrochloric acid 4.2 parts Ethyl alcohol 43 parts Ethyl acetate 42 parts Concentrated hydrochloric acid 5.4 parts Ethylene glycol 5.4 parts were mixed into a PMMA (MFI=2) injection molded substrate with a base diameter of 30 cm to form a colloidal dispersion of 50 to 80 Å. , n-
It was diluted with propanol to prepare a coating solution. This was spin-coated and then treated at 60°C for 30 minutes. The film thickness is 0.01 μm. Then dye D-10 and quencher Q3-
8 (5:2) 1% solution of dye (dichloroethane,
A recording layer made of dichlorohexanone (6:5) was formed using a spinner. Furthermore, a surface layer was formed on this recording layer by applying a solution prepared by diluting the colloidal dispersion liquid with n-hexane using a spinner. The film thickness was approximately 0.006 μm. The above is designated as sample 1. Sample 1 without a surface layer is designated as sample 2. Furthermore, in Sample 1, a solution of polyvinyl alcohol PVA (Kuraray 205 hydrodispersity 88%) dissolved in methanol-water (1:1) at a concentration of 1% was applied onto the surface layer. and about
Sample 3 has a thickness of 0.01 μm. For the above samples, an 833nm semiconductor laser was used, the focusing part intensity was 8mW/10mW, and the pulse width was 100ns.
Then, writing was performed from the back side of the substrate at a predetermined medium speed, and the contrast of the signal was measured. In addition, the presence or absence of breakage of the surface layer at the pit portion and the presence or absence of scattering of the surface layer were observed using an electron microscope. The results are shown in Table 1. [Table] From the results shown in Table 1, the effects of the present invention are clear.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining a pit formed according to the present invention.

Claims (1)

[Claims] 1. Writing light is applied to an optical recording medium that has a recording layer made of a dye or a dye composition on a substrate, and a surface layer of an inorganic film having a higher melting point on the recording layer. When performing optical recording by forming bits by irradiation, the sensitivity is improved by preventing recording on the recording layer until sufficient energy can be absorbed by the surface layer, and the pits are An optical recording method that prevents fragments from scattering during recording by forming concave portions in a state where they do not break.