JPH02276678A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enable recording or reproduction of signal without requiring additional reflection layer of metal or metal oxide film by employing specific phthalocyanin pigment in the recording layer of an optical recording medium thereby providing high absorption of semiconductor laser beam to the recording layer and sufficient reflection factor to the recording layer itself. CONSTITUTION:Optical recording medium substantially comprises a transparent injection molding resin substrate and a recording layer arranged on the substrate, where the recording layer contains phthalocyanin pigment shown by the formula. In the formula, Y<1>, Y<2>, Y<3>, Y<4> represent substituent or non- substituent hydrocarbon independently while X<1>, X<2>, X<3>, X<4>, X<5>, X<6>, X<7>, X<8> represent alkylthio group or arylthio group independently and M represents two hydrogens, bivalent metal atom or trivalent or tetravalent substituent metal atom. The substrate includes injection molding resin such as acrylic resin, polycarbonate resin or polyolefin resin which transmits signal recording/reproducing light and having light transmission factor higher than 85% and low optical anisotropy.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an optical recording medium having a recording layer made of an organic dye that can be used for additional recording using a focused beam of a laser, particularly a semiconductor laser, and more specifically for use in external memories of computers and images. The present invention relates to an optical recording medium having a recording layer made of an organic dye, which is used for recording various information such as audio.

[Conventional technology]

A write-once optical recording medium with an organic dye as a recording layer can be formed by a simple and highly productive method such as a spin code, and has the characteristics that the recording film hardly deteriorates in an oxidizing atmosphere. However, media with recording layers containing organic dyes that absorb in the semiconductor laser region, such as dithiol metal complexes, polymethine dyes, squalium dyes, naphthoquinone dyes, phthalocyanine dyes, and naphthalocyanine dyes, have been developed and some have been put into practical use. . The characteristics required for optical recording media are l) high reflectance, 2) good sensitivity, and 3) sharp threshold characteristics (
(reproduction light stability), and (4) excellent economic efficiency. Furthermore, a write-once type optical recording medium such as the one of the present invention is often used for storing information, etc., and is required to have long-term durability, for example, durability of 30 years or more. However, none of the optical recording media proposed so far in which the recording layer is an organic dye film satisfies all of the above characteristics. For example, media with recording layers made of cyanine dyes or squalium dyes have poor light resistance and moisture resistance, or have unclear threshold values during recording, making it impossible to increase the reproduction power. On the other hand, phthalocyanine dyes and naphthalocyanine dyes generally have excellent light resistance and threshold characteristics, but they have low reflectance and poor sensitivity.In order to improve these drawbacks, various methods have been developed. Media using phthalocyanine-based or naphthalocyanine-based dyes have been proposed. For example, JP-A-61-177287 discloses a medium that achieves high reflectance by using a naphthalocyanine dye in which a large substituent is introduced into the central metal as a recording layer. However, although this medium has a high reflectance, it has poor sensitivity during recording and is inferior in durability. On the other hand, phthalocyanine dyes are expected to have a higher reflectance, but their absorption wavelength is generally the oscillation wavelength of the semiconductor laser (7
80 to 840 nm), recording sensitivity is significantly lowered. As a method for bringing the absorption wavelength of phthalocyanine dyes closer to the near-infrared region, Japanese Patent Laid-Open No. 154888/1988 proposes a dye in which a substituent is introduced into the benzene ring of a phthalocyanine dye via an element such as sulfur. However, thioether group-substituted phthalocyanine dyes have poor solubility, and if a medium containing this dye as a recording layer is stored for a long period of time or the same track is repeatedly reproduced for a long period of time, This has the fatal disadvantage that not only the reflectance and absorption characteristics of the medium decrease, but also the noise of the medium increases. The reason for this is that the dye has crystallinity and is in an amorphous state at the time of coating, so there is no problem, but it gradually crystallizes and changes the optical properties (reflectance, absorption properties) of the recording layer. In addition to this, it is estimated that noise due to grain boundaries also increases. On the other hand, JP-A-61-197280 proposes a dye in which a substituent is introduced into the benzene ring of a phthalocyanine dye via an oxygen. However, media using such dyes vary depending on the type, number, and position of substituents on the dye.
In some cases, the reflectance is small, and in others, if the medium is stored for a long time or the same track is played continuously, the reflectance or absorption intensity may decrease due to dye crystallization. This has the fatal disadvantage that not only this occurs, but also the noise of the medium increases. As described above, conventional optical recording media using organic dyes as recording layers also have various drawbacks, and it has been desired to develop an optical recording medium that improves these drawbacks. [Basic idea] The present inventors have improved the drawbacks of conventional optical recording media using organic dyes as recording layers, while having the above-described characteristics of optical recording media using organic dyes as recording layers. As a result of investigating phthalocyanine dyes, we discovered a new substituted phthalocyanine dye in which ether substituents were introduced at the two α-positions of the benzene ring that constitutes the phthalocyanine dye.If this dye is used in the recording layer, it can be used directly. It can be applied to polycarbonate injection molded substrates, and has a high reflectance that could not be achieved with conventional optical recording media using organic dyes.
The present invention was completed by discovering that it is possible to create an optical recording medium that is highly durable, highly sensitive, and has a sharp recording threshold, so that the reproduction power can be increased. [Disclosure of the Invention] That is, the present invention provides an optical recording medium capable of recording and reproducing signals without having a reflective layer, which comprises a transparent injection molded resin substrate and a recording layer provided on the substrate. The optical recording medium is characterized in that the recording layer contains a phthalocyanine dye represented by the following general formula (1). [In formula (1), Yl, jp, Y3. Y4 each independently represents a substituted or unsubstituted hydrocarbon group, Xl, X
l, Xl. x', x', x8. x? , x8 each independently represent an alkylthio group or an arylthio group, M is 2 hydrogens, 2
represents a valent metal atom, a trivalent or tetravalent substituted metal atom] The substrate used in the optical recording medium of the present invention is preferably one that transmits light for recording and reproducing signals. It is desirable that the light transmittance is 85% or more and that the optical anisotropy is small. For example, acrylic resin, polycarbonate resin, allyl resin, polyester resin, polyamide resin, vinyl chloride resin, Preferred examples include plastics such as polyvinyl ester resins, epoxy resins, and polyolefin resins, and glass. Among these, injection molding resins such as acrylic resins, polycarbonate resins, and polyolefin resins are preferred from the viewpoint of mechanical strength of the board, ease of providing guide grooves and header signals, and economic efficiency, and polycarbonate resins are particularly preferred. Resins are more preferred. The shape of these substrates may be plate-like, film-like, circular or card-like, and of course the surface of the substrate may have guide grooves for indicating recording positions, bits for address signals, etc. It is preferable to provide such guide grooves, address signals, etc. when manufacturing the substrate by injection molding or casting, but it is preferable to apply an ultraviolet curable resin onto the substrate, overlap it with a stamper, and expose it to ultraviolet rays. It can also be given by In the present invention, the above-mentioned formula (1) is formed on such a substrate.
) is provided with a phthalocyanine dye layer. . In the phthalocyanine dye represented by the general formula (1) used in the recording layer of the present invention, yl, y2.
y3. y4 represents a substituted or unsubstituted hydrocarbon group,
Specific examples of unsubstituted hydrocarbon groups include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group,
n-hexyl group, n-hebutyl group, n-octyl group, n
- Straight chain alkyl groups such as nonyl group, n-decyl group, n-undecyl group, rhododecyl group, 1so-propyl group, 5
ec-butyl group, tert-butyl group, fso-pentyl group, 5ec-pentyl group, neopentyl group, 1-methylbutyl group, 2-methylbutyl group, 1.1-dimethylpropyl group, 1.2-dimethylpropyl group, etc. Branched pentyl group, methylpentyl group, ethylbutyl group, 2,3-dimethylbutyl group, branched hexyl group such as methylethylpropyl group, methylhexyl group, ethylpentyl group, dimethylpentyl group, pro-rubutyl group, methylethylbutyl group , branched hebutyl groups such as trimethylbutyl group and diethylpropyl group, ethylhexyl groups such as methylhebutyl group and 2-ethylhexyl group, branched octyl groups such as dimethylhexyl group, propylpentyl group, methylethylpentyl group, and trimethylpentyl group. , methyloctyl group, dimethylhebutyl group, ethylhexyl group, trimethylhexyl group such as 2.5.5-trimethylhexyl group, methylethylhexyl group, propylhexyl group, tetramethylpentyl group, methylpropylpentyl group, dimethylethyl group Pentyl group, diethylpentyl group, branched nonyl group such as methylpro and rubentyl group, methylnonyl group, ethyloctyl group such as 4-ethyloctyl group, dimethyloctyl group,
Propyl to butyl group, methylethyl to butyl group, trimethyl to butyl group, butylhexyl group, methylpro and lhexyl group, diethylhexyl group, 4,5-dimethyl-4
- Dimethylethylhexyl group such as ethylhexyl group, branched decyl group such as tetramethylhexyl group, methyldecyl group, ethylnonyl group, dimethylnonyl group, propyloctyl group, methylethyloctyl group, trimethyloctyl group, diethylhebutyl group, tetramethylheptyl group branched undecyl groups such as butylheptyl groups, methylundecyl groups, ethyldecyl groups, dimethyldecyl groups, methylethylnonyl groups, trimethylnonyl groups, butyloctyl groups such as 4-butyloctyl groups, 6.6-diethyloctyl groups branched dodecyl groups such as diethyl octyl groups such as, tetramethyloctyl groups such as 1,3,5.7-tetramethyloctyl groups, cyclohexyl groups, methylcyclohexyl groups,
Dimethylcyclohexyl group, cycloalkyl group, benzyl group, phenylethyl group, aralkyl group such as butylbenzyl group, allyl group, alkenyl group such as methylbutenyl group, phenyl group, methylphenyl group, ethylphenyl group,
Examples include aryl groups such as nonylphenyl group and naphthyl group. In addition, the substituted hydrocarbon group is a substituent formed by bonding the hydrocarbon groups together through atoms such as oxygen, nitrogen, and sulfur, and includes, for example, a methoxymethyl group, an ethoxymethyl group,
Butoxymethyl group, methoxyethyl group, ethoxyethyl group, ethoxyethoxyethyl group, methoxybutyl group, ethoxybutyl group, butoxybutyl group, ethoxyhexyl group, ethoxyoctyl group, ethylthioethoxyethyl group, dimethylaminoethoxyethyl group, etc. Alkoxyalkyl groups, phenoxyethyl groups, phenoxybutyl groups, aryloxyalkyl groups such as naphthoxyethyl groups, hydroxyalkyl groups such as hydroxyethyl groups, hydroxyethoxyethyl groups, dimethylaminomethyl groups, dimethylaminoethyl groups, dibutylaminoethyl groups, etc. Examples include alkylaminoalkyl groups, methylthiomethyl groups, alkylthioalkyl groups such as ethylthioethyl groups, and arylthioalkyl groups such as phenylthioethyl groups and naphthylthioethyl groups. In the present invention, the substituents Y' to Y4 may be the same or different in one molecule. In the present invention, the above-mentioned substituent Y I in one molecule,
If the total number of carbon atoms in Y 4 is less than 40, the solubility of the dye in the solvent is insufficient, so it cannot be applied directly to a polycarbonate injection molded substrate.On the other hand, if the total number of carbon atoms in the substituents is less than 96 If it exceeds this, it is undesirable because the reflectance from the recording layer decreases and the dye tends to crystallize.From the viewpoint of reflectance and crystallization, it is more preferable that the total carbon number is 80 or less, especially for 10 years or more. In consideration of long-term storage stability and ease of dye synthesis, substituents Y' to Y4 are particularly preferably substituted or unsubstituted hydrocarbon groups having 5 to 12 carbon atoms. On the other hand, in the general formula (1) of the present invention, x l, ,
The substituent represented by xa represents an alkylthio group or an arylthio group, and examples of the alkylthio group include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a hexylthio group, a pentylthio group, a nonylthio group,
Examples of the arylthio group include a decylthio group and a dodecylthio group, and examples of the arylthio group include a phenylthio group, a naphthylthio group, a methylphenylthio group, a dimethylphenylthio group, and a butylphenylthio group. On the other hand, M in the phthalocyanine dye represented by the general formula (1) of the present invention represents two hydrogen atoms, a divalent metal, or a trivalent or tetravalent substituted metal. Specific examples of divalent metals include:
Cu, Zn, Fe, Co, Ni, Ru. Rh, Pd, Pt, Mn, Mg, Ti, B
e, Ca, Ba, Cd, Hg. Examples include Pb and Sn. Trivalent substitution metals include AI, Ga, In, TI, Mn, Fe,
Halides (chlorine, bromine, iodine), hydroxides, alkoxides, aryl oxides of trivalent metals such as Ru,
Examples include silyl oxides, alkylated products, arylated products, and derivatives thereof. Examples of tetravalent substitution metals include Cr, Si, Ge, Sn, Ti, Zr,
Examples include dihalides, dihydroxides, dialkoxides, diaryl oxides, dialkylated products, dialkylated products, diarylated products, and oxides of tetravalent metals such as Mn and V. Cu, N, etc. are recommended as central metals because of their large absorption at the oscillation wavelength of semiconductor lasers and their durability.
Divalent metals such as i, Co, and Pd, and substituted metals such as v0 are preferred. The dye used in the present invention can be synthesized, for example, by the following route. X-11110 (I) There are various methods for synthesizing the dye used in the present invention in addition to the methods described above, and the methods are not limited to the methods described above. In the present invention, a recording layer made of a dye is fixed (formed) on a substrate.
In order to do this, it is preferable to dissolve the phthalocyanine dye in a solvent and form it by a coating method such as dipping or spin coating. To fix the recording layer by coating, a dye solution consisting of the above dye and an organic solvent is brought into contact with the substrate to fix the dye onto the substrate.More specifically, for example, the dye solution is caused to flow down onto the substrate. There is a method in which excess dye liquid is removed while rotating the substrate after the substrate surface is brought into contact with the liquid level of the dye liquid, or after the substrate surface is brought into contact with the liquid level of the dye liquid, and the excess dye liquid is removed while the substrate is rotated. There are methods. If necessary, forced drying may be performed after this. In the coating method, ordinary organic solvents can be used to dissolve the dye of the present invention, but in order to be able to directly coat the injection molded substrate used in the present invention, it is necessary to Solvents that do not cause damage, such as aliphatic or alicyclic hydrocarbons such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, methyl alcohol, ethyl alcohol, isopropyl alcohol, allyl alcohol, methyl cellosolve, etc. Alcohol-based solvents and ether-based solvents such as diethyl ether, dibutyl ether, and diisopropyl ether are preferred.The concentration of the dye solution when coating varies depending on the type of solvent and coating method, but is usually o, t-t.
o% by weight. In order to increase the reflectance of the recording layer or further increase the sensitivity in the optical recording medium of the present invention, other dyes may be added to the phthalocyanine dye of the present invention described above, for example, within a range that does not impede the effects of the present invention. Approximately 5 total pigments
It is also possible to use a mixture in a range of less than 0%. Examples of dyes that can be used in combination include known ones, such as aromatic or unsaturated aliphatic diamine metal complexes, aromatic or unsaturated aliphatic dithiol metal complexes, unsubstituted or substituted phthalocyanine or naphthalocyanine dyes, and polymethine dyes. , squalium dyes, naphthoquinone dyes, anthraquinone dyes, and the like. In the present invention, in order to improve the smoothness of the recording layer and reduce defects such as pinholes when forming the recording layer, resins such as nitrocellulose, ethylcellulose, acrylic resin, and polystyrene resin are used as the dye. The recording layer can also be formed by adding additives such as a leveling agent, an antifoaming agent, and the like. However, if a large amount of these resins or additives is added, the reflectance of the recording layer may decrease or the dye in the recording layer may become non-uniformly dispersed, which may impede the effects of the present invention. From these points of view, the amount of the resin and additives added in the recording layer is less than 20% by weight, preferably less than 10% by weight, and more preferably less than 5% by weight. Generally, in an optical recording medium, the thickness of the recording layer affects reflectance, recording sensitivity, etc., but the thickness of the recording layer in the present invention is preferably 30 to 250 nm, more preferably 40 nm.
~200 stops. As described above, it is preferable for the optical recording medium of the present invention to record and reproduce signals using a laser beam that passes through the substrate (a beam irradiated from the substrate side). Generally, in order to record a signal on an optical recording medium, when a laser beam is irradiated with a focused recording layer, the recording layer in the irradiated area absorbs the laser beam and generates heat. Recording is performed by changing the recording layer due to the generated heat and changing the reflectance. To reproduce the zero-order recorded signal, this change in reflectance is detected by a laser beam. If this change in reflectance is small, the signal-to-noise ratio (C/N) is small and undesirable.In order to increase this change in reflectance, the reflectance before recording must be increased.On the other hand, the sensitivity In order to make the recording layer more sensitive, the recording layer must absorb more laser light.In other words, the recording layer must have high reflectivity and high absorption for laser light. Optical (reflectance,
Absorption intensity) or physical changes are required. The most characteristic feature of the present invention is that when the phthalocyanine dye of the present invention is used as a recording layer, the recording layer has a large absorption in the oscillation wavelength range of a semiconductor laser, and the recording layer itself has a high reflectance. have Furthermore, the medium characteristics do not change even when subjected to reproduction light or long-term storage. When putting the optical recording medium of the present invention into practical use, in order to protect the recording layer, it is necessary to apply an ultraviolet curable resin or the like on the recording layer, paste a protective sheet on the surface of the recording layer, or place the surfaces of the recording layer together. You may also use a method such as pasting two sheets together with the inner side. At this time, it is preferable to provide an air gap above the recording layer and then bond the recording layer together. In addition, in the optical recording medium of the present invention, the laser beam used for recording and reproducing signals usually has a wavelength of 640 to 850.
A semiconductor laser having an oscillation wavelength in nm is preferable. For example, when recording at a linear velocity of 1 m/s, the laser output on the recording layer is set to about 5 to 12 mW, and when reproducing, the laser output at the time of recording is set to about 5 to 12 mW. It should be about 1/10.

【Example】

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In the center of the surface of an injection molded polycarbonate resin substrate having a spiral guide groove (depth 70 nm, width 0.6 μ, pitch 1.64) with a dog stand and a thickness of 1.2 mm and a diameter of 130 mm. In general formula (1), the substituent Y'NY
' is 3-methylbutyl group, x1 to x a are 4-tart
After dropping a 3% octane solution of a phthalocyanine dye having a structure in which -butylphenylthio group and M is Cu, the resin substrate was rotated once for 10 seconds at a speed of LOOORPM. Next, this resin substrate was dried in an atmosphere of 40° C. for 10 minutes to fix a recording layer consisting essentially only of the phthalocyanine dye on the resin substrate. The thickness of this recording layer is approximately 70n when measured in cross section using a microscope.
It was m. The absorption of light with a wavelength of 780 nm through the resin substrate was 43%, and the reflectance of focused light through the substrate was 33%. An optical recording medium was made by laminating two of the same recording plates thus produced with the recording layer surfaces facing each other and providing an air gap of 500 μm. Place this optical recording medium on a turntable and turn it at 1800 rpm.
While rotating at a speed of m, a drive having an optical head equipped with a semiconductor laser with an oscillation wavelength of 780 nm is used to control the laser beam to be focused on the recording layer on the guide groove through the resin substrate. A 3.7 MHz pulse signal (pulse width 90 ns) was recorded at the outermost periphery of the medium (linear velocity 11 m) using a laser output of 8 mW.
/s). Next, using the same device, the recorded signal was reproduced with the output of the semiconductor laser set to 1 mW on the recording surface. At this time, a signal-to-noise ratio (C/N) of 55 dB was obtained, and extremely good recording and reproduction could be performed. In order to investigate the reproduction light stability of this optical recording medium, the recorded signal was continuously reproduced over the same track 1 million times using 1 mW of reproduction light.
/N value showed no change at all. To check the durability of this optical recording medium, 60℃, 90%
After being left in an RH atmosphere for three months, the absorption characteristics and reflectance of the optical recording medium were measured, and there was almost no change from the initial state. Next, when I replayed the recorded signal, it showed 54 dB of C.
/N value was obtained, and there was almost no deterioration of the recording layer in the durability test. Examples 2 and 11 A medium was prepared using a dye having the structure shown in Table 1 instead of the phthalocyanine dye in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 2. As is clear from Example 1.2, the optical recording medium of the present invention has a high reflectance, and both have an excellent C/N of 50 dB or more.
It can be seen that the properties are very excellent, with almost no change even in the reproduction light stability and acceleration durability tests of up to 5,000 hours. [Effects of the Invention] By using a specific phthalocyanine dye in the recording layer of the optical recording medium of the present invention, the recording layer has a large absorption of semiconductor laser light, and the recording layer itself has sufficient reflectance. Therefore, it has high sensitivity and can record and reproduce signals without separately applying a reflective layer such as metal or metal oxide thin film, and has a large C/N value due to the high initial reflectance. is obtained. Further, the optical recording medium of the present invention can be easily mass-produced by a coating method, and has excellent reproduction light stability and durability, and can be used for a long period of time.

Claims (4)

[Claims] (1) An optical recording medium capable of recording and reproducing signals without having a reflective layer, which is substantially composed of a transparent injection molded resin substrate and a recording layer provided on the substrate; An optical recording medium characterized in that the layer contains a phthalocyanine dye represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) [In formula (I), Y^1, Y^2, Y^3, Y^4 each independently represent a substituted or unsubstituted hydrocarbon group, X^1
, X^2, X^3, X^4, X^5, X^6, X^7,
Each of X^8 independently represents an alkylthio group or an arylthio group, and M represents two hydrogen atoms, a divalent metal atom, or a trivalent or tetravalent substituted metal atom. ] (2) Substituents Y^1, Y^2, Y^3 in formula (I),
The optical recording medium according to claim 1, wherein the total number of carbon atoms in Y^4 is 40 to 96. (3) Y^1, Y^2, Y^3, Y^4 in formula (I)
3. The optical recording medium according to claim 2, wherein each of is independently a substituted or unsubstituted hydrocarbon group having 5 to 12 carbon atoms. (4) The optical recording medium according to claim 3, wherein the substrate is a polycarbonate resin substrate.