JPH02276679A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide high absorption of semiconductor laser beam to a recording layer and high reflection factor to the recording layer itself and to eliminate additional reflection layer of metal or metal oxide film by employing specific phthalocyanin pigment in the recording layer of optical recording medium. 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>, Y<5>, Y<6>, Y<7>, Y<8> represent substituent or non-substituent hydrocarbon independently where Y<1>, Y<3>, Y<5>, Y<7> differ respectively from Y<2>, Y<4>, Y<6>, Y<8> while X<1>, X<2>, X<3>, X<4>, X<5>, X<6>, X<7>, X<8> represent hydrogen atom, 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 Application Field] The present invention relates to an optical recording medium in which glauconite is used as an organic dye that can be additionally recorded using a focused beam of a laser, particularly a semiconductor laser. is the computer's external memory, 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, a medium having a recording layer containing a cyanine dye or a squalium dye has poor light resistance or moisture resistance, or has an unclear threshold value during recording, making it impossible to increase the reproduction power.

On the other hand, phthalocyanine dyes and naphthalocyanine dyes are dyes that generally have excellent light resistance and excellent threshold characteristics, but have low reflectance and poor sensitivity. In order to improve these drawbacks, media using various phthalocyanine and naphthalocyanine 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 No. 61-19728 () proposes a dye in which a substituent is introduced into the benzene ring of a phthalocyanine dye via oxygen. However, the media using such dyes have a high f! Depending on the type, number, and location, some have low reflectance or poor solubility and cannot be dissolved in solvents that can be applied directly to polycarbonate injection molded substrates. In addition, when a medium is stored for a long period of time or the same track is played back continuously, not only does the reflectance and absorption intensity decrease, which is thought to be caused by dye crystallization, but also the noise of the medium occurs. It has the fatal disadvantage of increasing For example, if the number of carbon atoms in the ether group is 4 or less, the dye has poor solubility and can only be dissolved in solvents that would damage polycarbonate injection molded substrates when applied directly, such as toluene, as disclosed in the patent. . In addition, if the benzene ring has an aromatic substituent or a non-halogen atom such as hydrogen or an ether group is introduced at a position other than the α-position of the benzene ring, the reflectance may be low or the reflection may be due to crystallization. This results in a decrease in rate and absorption intensity and an increase in noise.

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 a recording layer, while having the above-described characteristics of optical recording media using organic dyes as a recording layer. As a result of studying phthalocyanine dyes, we discovered a new substituted phthalocyanine dye in which different ether substituents were introduced at the two 0-positions of the benzene ring constituting the phthalocyanine dye.If this dye was used in the recording layer, It can be applied directly to polycarbonate injection molded substrates, and has high reflectance, excellent durability, high sensitivity, and a sharp recording threshold, which was not possible with conventional optical recording media using organic dyes. They discovered that it is possible to create an optical recording medium that can increase the reproduction power, and completed the present invention.

[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), Y', Y2. Ytsu, Y', Y'
, Y', Y' and ya each independently represent a substituted or unsubstituted hydrocarbon group, and Y' and Y2. Y3 and Y4.
yS and YIs, Y? and Y8 are different from each other, and x'
, x'', x', x', x'', x', xfu,
X8 each independently represents a hydrogen atom, an alkylthio group, or an arylthio group, and M represents two hydrogens, a divalent metal atom, or 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, has a light transmittance of 85% or more, and has optical anisotropy. Preferably one with a small gender. Preferred examples include plastics such as acrylic resins, polycarbonate resins, allyl resins, polyester resins, polyamide resins, vinyl chloride resins, polyvinyl ester resins, epoxy resins, and polyolefin resins, and glass. . Among these, acrylic resin,
Injection molding resins such as polycarbonate resins and polyolefin resins are preferred, and polycarbonate resins are particularly preferred.

The shape of these substrates may be plate-like or film-like, or may be circular or card-like. Of course, the surface of the substrate may have guide grooves 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 by applying ultraviolet curable resin on the substrate, overlapping it with a stand bar, and exposing it to ultraviolet light. 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 (I) used in the recording layer of the present invention, Y', Y'',
Y', Y', Y', Y', Y7OyoUY'Ha substitution *ri represents an unsubstituted hydrocarbon group, and 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-nonyl group, n-
Straight chain alkyl groups such as decyl group, n-undecyl group, n-dodecyl group, 1so-propyl group, 5ec-butyl group,
tert-butyl group, 1so-pentyl group, 5ec-
Pentyl group, neopentyl group, l-methylbutyl group, 2
-Methylbutyl group, 1.1-dimethylpropyl group, 1.
Branched pentyl groups such as 2-dimethylpropyl group, methylpentyl group, ethylbutyl group, 2.3-dimethylbutyl group, branched hexyl group such as methylethylpropyl group, methylhexyl group, ethylpentyl group, dimethylpentyl group,
Branched hebutyl groups such as propylbutyl group, methylethylbutyl group, trimethylbutyl group, diethylpropyl group, ethylhexyl group such as methylhebutyl group, 2-ethylhexyl group, dimethylhexyl group, propylpentyl group, methylethylpentyl group, Branched octyl groups such as trimethylpentyl groups, methyloctyl groups, dimethylhebutyl groups,
Ethylhebutyl group, trimethylhexyl group such as 2.5.5-trimethylhexyl group, methylethylhexyl group, propylhexyl group, tetramethylpentyl group, methylpropylpentyl group, dimethylethylpentyl group, diethylpentyl group, methylpro and lupentyl group branched nonyl groups such as methylnonyl groups, ethyloctyl groups such as 4-ethyloctyl groups, dimethyloctyl groups, propylhebutyl groups, methylethylheptyl groups, trimethylhebutyl groups, butylhexyl groups, methylpropylhexyl groups, Ethylhexyl group, dimethylethylhexyl group such as 4.5-dimethyl-4-ethylhexyl group, branched decyl group such as tetramethylhexyl group, methyldecyl group, ethylnonyl group, dimethylnonyl group, propyloctyl group, methylethyloctyl group, trimethyloctyl group group, branched undecyl groups such as diethylheptyl group, tetramethylheptyl group, butylheptyl group, methylundecyl group, ethyldecyl group, dimethyldecyl group, methylethylnonyl group,
Branched dodecyl such as trimethylnonyl group, butyloctyl group such as 4-butyloctyl group, diethyloctyl group such as 6.6-diethyloctyl group, tetramethyloctyl group such as 1.3.5.7-tetramethyloctyl group groups, cyclohexyl groups, methylcyclohexyl groups, dimethylcyclohexyl groups, cycloalkyl groups, benzyl groups, phenylethyl groups, aralkyl groups such as butylbenzyl groups, allyl groups, alkenyl groups such as methylbutenyl groups, phenyl groups, methylphenyl groups, ethyl Examples include aryl groups such as phenyl group, 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, butyloctyl 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 of Yl and Ya are Yl and Y2.
The combinations of Y3 and Y', Y' and Yl, and Y7 and Y8 are different from each other. As a result, the optical recording medium of the present invention was subjected to an accelerated durability test (60°C, 9°C).
At 0% R11), crystallization of the dye does not occur over a long period of 5,000 hours, and therefore, the decrease in reflectance and absorption intensity that has conventionally been thought to be caused by this does not occur. Furthermore, regarding the stability of reproduction light, the increase in noise does not become a problem even after reproduction is repeated 10 million times.

In the present invention, the above-mentioned substituents Y1 to Y in one molecule
If the total number of carbon atoms in the substituent groups 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. If it exceeds the range, it is not preferable because the reflectance from the recording layer decreases and the dye tends to crystallize. From the viewpoint of reflectance and crystallization, substituents Y1 to Y8 are 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, the substituents represented by x1 to x8 represent an alkylthio group or an arylthio group, and examples of the alkylthio group include a methylthio group,
Examples of arylthio groups include ethylthio group, propylthio group, butylthio group, hexylthio group, bentylthio group, nonylthio group, decylthio group, dodecylthio group, and examples of arylthio group include phenylthio group, naphthylthio group, methylphenylthio group, and dimethylphenylthio group. , butylphenylthio group, etc.

On the other hand, M in the phthalocyanine dye represented by the general formula (I) of the present invention represents two hydrogens, a divalent metal, a trivalent or tetravalent substituted metal, and a specific example of a divalent metal. Examples include Cu, Zn, Fe, Co, Ni, and 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,
Examples include halides (chlorine, bromine, iodine) of trivalent metals such as Ru (chlorine, bromine, iodine), hydroxides, alkoxylated compounds, aryl group oxylated compounds, silyl group oxidized compounds, hydrocarbons, aryl group compounded compounds, and derivatives thereof. . Examples of the tetravalent substitution metal include Cr, Sf, Ge, button, Ti, and Z.
r.

Examples include dihalides, dihydroxides, sialyl group oxides, diaryl group oxides, disilyl group oxides, dihydrocarbons, diaryl group compounds and oxides of tetravalent metals such as Mn and V. Due to its large absorption at the oscillation wavelength of semiconductor lasers and its durability, it is recommended as a central metal.
Divalent metals such as Cu, Ni, Co, and Pd, and vO
Substituted metals such as are preferred.

The dye used in the present invention can be synthesized, for example, by the following route.

Note that there are various methods for synthesizing the dye used in the present invention in addition to the methods described above, and the method is 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 surface of the substrate is brought into contact with the liquid level of the dye liquid and the excess dye liquid is removed. 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 during coating varies depending on the type of solvent and coating method, but is usually 0.1 to 1.
It is about 0% 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 pigments, naphthoquinone pigments,
Examples include anthraquinone pigments.

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 mm, more preferably 40 to 250 mm.
It is 200 nm.

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 undesirably small. In order to increase this change in reflectance, the reflectance before recording must be increased.On the other hand, in order to make the recording layer more sensitive in terms of sensitivity, the recording layer must absorb more laser light. In other words, the recording layer must have high reflectivity and high absorption for laser light.Furthermore, the optical recording medium must have 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 preferred. For example, when recording at a linear velocity of 11 m/s, the laser output on the recording layer may be set to about 5 to 1'2 mW, and when reproducing, the laser output may be set to about 1/10 of that of recording.

[Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Fire 11 Hada 1 Spiral guide groove with a thickness of 1.2 mm and a diameter of 130 mm (depth 70 nm, width 0.6 pm, pitch 1.6 g)
) in the center of the surface having the guide groove of an injection molded polycarbonate resin substrate having a substituent Y1 in general formula (I)
, Y3, Y5 and Y7 are n-pentyl groups, Y2, Y4
, Y6 and Y8 are 2-ethylhexyl groups, x'-x"
After dropping a 3% octane solution of a phthalocyanine dye having a structure in which is a phenylthio group and M is Cυ, the resin substrate was rotated at a speed of 11,000 rpm for 10 seconds. 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. Further, 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 31%.

An optical recording medium was fabricated 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 JiIm.

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. Recording of a pulse signal (pulse width 90 ns) of 3.7 M) lz with a laser output of 10 mW was performed on the outermost part of the medium (linear velocity 1
1 m/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, the signal to noise ratio (C/N) is 56 dB
This resulted in extremely good recording and playback. In order to investigate the stability of the reproduction light of this optical recording medium, this recorded signal was continuously reproduced over the same track 10 million times using a reproduction light of 1 mW. /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 5,000 hours, the absorption characteristics and reflectance of the optical recording medium were measured, and there was almost no change from the initial state. Next, in order to investigate the durability of the recording characteristics, we replayed the recorded signal before conducting the durability test.
A C/N value of 4 dB was obtained, and there was almost no deterioration of the recording layer during the durability test.

2.1 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.
In addition, it can be seen that the characteristics are very excellent with almost no change even in the reproduction optical stability and acceleration durability tests of 5,000 hours.6 [Effect of the invention 1 The optical recording of the present invention By using a specific phthalocyanine dye in the recording layer of the medium, 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 the need for a separate 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 (1)

[Scope of Claims] (1) An optical recording medium capable of recording and reproducing signals without having a reflective layer, which consists of a transparent injection molded resin substrate and a recording layer provided on the substrate. An optical recording medium characterized in that the recording 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, Y
^5, Y^6, Y^7 and Y^8 each independently represent a substituted or unsubstituted hydrocarbon group, and Y^1, Y^2, Y^
3 and Y^4, Y^5 and Y^6, Y^7 and Y^8 are different from each other, X^1, X^2, X^3, X^4, X^5,
X^6, X^7, and X^8 each independently represent a hydrogen atom, an alkylthio group, or an arylthio group, and M is two hydrogens, 2
Represents a valent metal atom, 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, Y^5, Y^6, Y^7 and Y^8 is 40 to 96. (3) X^1, X^2, X^3, X^4 in formula (I)
, X^5, X^6, X^7 and X^8 have 1 to 1 carbon atoms
3. The optical recording medium according to claim 2, wherein 2 is a substituted or unsubstituted hydrocarbon group. (4) Y^1, Y^2, Y^3, Y^4 in formula (I)
, Y^5, Y^6, Y^7 and Y^8 have 5 to 1 carbon atoms
4. The optical recording medium according to claim 3, which is an alkylthio group or an arylthio group of 2. (5) The optical recording medium according to claim 4, wherein the substrate is a polycarbonate resin substrate.