JPS6357290A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium requiring no reflection layer composed of an inorganic compound, by employing a specific phthalo/ naphthalocyanine coloring matter in a recording layer and controlling the thickness of the recording layer to a proper level. CONSTITUTION:A recording layer provided on a transparent substrate is composed of less than 20wt% of resin binder and phthalo/naphthalocyanine coloring matter shown by formula I; in the formula, M represents a metal, a metal oxide or a metal halide, while L1, L2, L3 and L4 represent a benzene ring or naphthalene ring skeletons having no substituent or one or more univalent substituent Z. The substituent Z is selected from -SO2NR<1>R<2>, -COR<3>, -COOR<4>, -CONHR<5>, -NR<6>R<7>, -R<8>-OR<9>, -R<10>X and -X, where R<1>-R<10> represent hydrocarbon group having carbon number of 1-12, and X represents halogen. The total number of carbon in all substituent Z of one molecule of said coloring matter is in the range of 16-96. The thickness of the recording layer is 50-300nm, and a signal is recorded or read out by a light beam transmitted through the transparent substrate.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an optical recording medium that can be additionally recorded using a focused beam of a semiconductor laser, and more specifically relates to a computer external memory, various types of information such as images, audio, etc. The present invention relates to an optical recording medium used for recording information, and a method for recording and reading information using the recording medium.

[Prior art]

The above-mentioned recordable optical recording medium includes a recording medium having an inorganic recording layer made of a thin film of a low-melting metal such as tellurium, a tellurium alloy, and a bismuth alloy, and, for example, U.S. Pat.
A recording medium having a phthalocyanine dye film as a recording layer as disclosed in No. 75 has been proposed.

However, these recording media have low productivity because they require formation of the recording layer in a vacuum using vacuum evaporation, sputtering, etc., and media with inorganic recording layers have high thermal conductivity of the recording layer. has a limit in terms of recording density. Furthermore, since these use toxic substances such as tellurium, there are concerns about toxicity. On the other hand, in the case of media with a phthalocyanine dye as a recording layer, the optical properties of the recording layer do not match the oscillation wavelength of the semiconductor laser, so the recording film, which is usually obtained by vapor deposition, is exposed to heat or organic solvent vapor, which is called shifting. However, this shifting process is complicated and requires a long process time of 1 to 72 hours, so it has not been put to practical use.

In order to solve the above-mentioned problems, media have been proposed in which a recording film is formed using a coating method using a soluble organic dye. For example, methods have been developed to coat organic dyes such as dithiol metal complexes, polymethine dyes, squalium dyes, and naphthoquinone dyes that absorb in the semiconductor laser region and are soluble in organic solvents using a spin coding method, and some of them have been put into practical use. . However, among the dyes that have been proposed so far, for example, media with cyanine dyes or squalium dyes in the recording layer have poor durability. In addition, since the pigment film alone, such as a dithiol metal complex, has a wood-like low reflectance, a separate reflective layer made of an inorganic compound such as a metal thin film or a metal oxide thin film is required.

For example, U.S. Patent No. 4,492.750 relates to a medium using an alkyl-substituted naphthalocyanine dye. An optical recording medium provided with an optical recording layer composition in which alkyl-substituted naphthalocyanine dye particles having a particle size of 0.005 .mu.m to 0.1 .mu.m are dispersed in a resin binder has been disclosed. In this way, it is not possible to form a recording layer made of an organic dye directly on the substrate, and it is necessary to form a reflective layer made of an inorganic compound such as Heβ on the substrate separately from the recording layer using a vacuum process such as vapor deposition. The fact that there is no optical recording medium makes the manufacturing process of the optical recording medium more complicated. What is even more problematic is that organic pigment films inherently have low thermal conductivity.
It is expected that high recording sensitivity will be obtained, but if a metal-based or inorganic-based reflective layer with high thermal conductivity is provided, the recording layer will not be irradiated due to the high thermal conductivity of the metal-based reflective layer. Thermal energy generated by the laser beam for writing is dissipated through the metal reflective layer and is not effectively used to form the focus (irregularities corresponding to the signal).
This results in a significant decrease in recording sensitivity. Furthermore, AI
! Naturally, when a reflective layer made of an inorganic compound such as The light does not reach the recording layer because it is blocked by a metal reflective layer that does not substantially transmit it. Therefore, when a reflective layer is provided, signals cannot necessarily be recorded and reproduced through the substrate, but must be performed from the recording layer side. In such a case, even slight dust or scratches on the surface of the recording layer greatly interfere with normal recording and reproduction of signals made up of unevenness. Therefore, for practical use, an overcoat or the like is required as a protective layer on the recording layer.

If it is possible to record and reproduce signals by irradiating a laser beam through a transparent substrate, the presence of dust and scratches on the side where the laser beam enters, that is, on the medium surface before the laser beam is focused, will be eliminated from the substrate. The protective layer is not needed because the gap corresponding to the thickness does not substantially affect signal recording and reproduction. As described above, media provided with a reflective layer made of an inorganic (metallic) compound such as Heβ have a number of drawbacks, and it is not possible to record signals without separately providing a reflective layer made of an inorganic compound. It has been desired to develop an optical recording medium in which a recording layer is formed by a coating method using an organic dye that is reproducible and has excellent durability.

[Basic idea]

The inventors of the present invention have conducted intensive studies to improve the above-mentioned drawbacks of optical recording media with an organic dye film as a recording layer. By controlling the thickness of the layer to an appropriate thickness, it not only has durability that could not be achieved with conventional optical recording media using organic dyes, but also because the recording layer itself has the function of a reflective layer. In addition, the present invention was completed by discovering that an optical recording medium can be formed that does not require a separate reflective layer made of an inorganic compound as in the prior art.

[Disclosure of the invention]

That is, the present invention provides an optical recording medium capable of recording and reading signals without having a 411 reflective layer, which is substantially composed of a transparent substrate and a recording layer provided on the recording plate, The recording layer comprises less than 20% by weight of a resin binder and a compound represented by the following general formula (1) [wherein M represents a metal, a metal oxide or a metal halide, LI+L2. L3+ and L4 represent a benzene ring or naphthalene ring skeleton which is unsubstituted or has one or more monovalent substituents -Z. However, -2 is selected from the group consisting of the following substituents: SO□NR'R2°-COR3°-COOR'.

-CONHR5゜-NR6127゜-R"-0R9゜410x and The present invention provides the optical recording medium comprising a phthalo/naphthalocyanine dye having one or more -Z.

The transparent substrate used in the optical recording medium of the present invention preferably has a light transmittance of 85% or more for writing and reading signals, and has small optical anisotropy. Preferred examples include plastics such as acrylic resin, polycarbonate resin, allyl resin, polyester resin, polyamide resin, vinyl chloride resin, polyvinyl ester resin, epoxy resin, and polyolefin resin, and glass. Among these, plastics are particularly preferred from the viewpoints of mechanical strength of the substrate, ease of providing guide grooves, address signals, etc., and economic efficiency.

The shape of these transparent substrates may be plate-like or film-like, or may be circular or card-like.

Of course, the surface may have guide grooves indicating the recording position, irregularities for address signals, etc.

Such guide grooves, address signals, etc. can be added when the substrate is manufactured by injection molding or casting, or they can be added by applying an ultraviolet curable resin or the like onto the substrate, overlapping it with a stamper, and exposing it to ultraviolet rays. .

In the present invention, on such a substrate, a resin binder of less than 20% by weight and the following general formula (I) [wherein M is a metal,
Represents a metal oxide or metal halide, L, L
2. L3. and represent a benzene ring or naphculene ring skeleton that is unsubstituted or has one or more monovalent substituents -Z. However, -2 is SO□NR'R'' selected from the group consisting of the following substituents.

-Cot? 3゜ -COOR’.

-CON)IR5□ -NRhR'.

-R11-OR9゜-R10x and . ] A recording layer made of a phthalo/naphthalocyanine dye is provided.

In the phthalo/naphthalocyanine dye represented by the general formula (I) used in the recording layer in the present invention, specific examples of the hydrocarbon group represented by R+ and RIG in the substituent represented by -Z include a methyl group, Ethyl group, n-propyl group, 1so-propyl group, n-butyl group, 5ec-butyl group tert-butyl group, 1so-butyl group\n-
Pentyl group, 1so-pentyl group, 5ec-pentyl group, tert-pentyl group, n-hexyl group, 1so-
hexyl group, 1-methyl-1 ethylpropyl group, 1.1
-dimethylbutyl group, n-heptyl group, 1so-heptyl group, 5eC-heptyl group, tert-heptyl group,
Octyl group, 2-ethylhexyl group, nonyl group, decyl group, dodecyl group, cyclohexyl group, methylcyclo-1
2= Aliphatic hydrocarbon groups such as hexyl group, unsaturated aliphatic hydrocarbon groups such as allyl group, butene group, hexene group, octene group, dodecene group, cyclohexene group, methylcyclohexene group, and further phenyl group Specific examples of halogen Examples include fluorine, chlorine, bromine, and iodine.

More specific examples of the substituent -Z include ~5ONR'R
`` is a sulfonamide group such as dimethylsulfonamide group, diethylsulfonamide group, dibutylsulfonamide group, dioctylsulfonamide group, didodecylsulfonamide group, diphenylsulfonamide group; -COR' is an acetyl group, ethyl Acyl groups such as carbonyl group, butylcarbonyl group, octylcarbonyl group, dodecylcarbonyl group, benzoyl group; -COOR' includes methoxycarbonyl group, ethoxycarbonyl group, butoxycarbonyl group, octoxycarbonyl group, dodecyloxycarbonyl group, Ester groups such as benzyloxy groups; -CONHR5 includes methylcarboxamide groups,
-NR'R' is a dimethylamino group, a diethylamino group, a dibutylamino group, dioctylamino group,
Amino groups such as didodecylamino group and diphenylamino group; -R11-OR9 is a methoxymethyl group, methoxyethyl group, ethoxyethyl group, butoxyethyl group, phenoxyethyl group, etc.; -R''X is a chloromethyl group; , chloroethyl group,
Examples thereof include a chlorobutyl group, a chlorooctyl group, a chlordodecyl group, a chlorphenyl group, a bromoethyl group, a bromooctyl group, and a bromphenyl group.

On the other hand, specific examples of M in the phthalo/naphthalocyanine dye represented by the general formula (I) include Tb group metals of the periodic table such as Cu; Mg, Cas Sr, Zn,
Group ■ metals such as Cd; Aj2, Ga, In,
Tj! Group II metals such as Ge-, Sn, , Pb, T
Group II metals such as i; Sb, Bi, V, Nb
Group ■ metals such as 5Ta; Sex Te5Crs
MO% Group ■ metals such as W; Group ■ metals such as Mn, Tc; Fe, Co, Ni+ Ru, Rh,
Examples include group III metals such as Pd, Os, Ir, and Pt, and halides such as oxides, chlorides, bromides, and iodides of these metals. These metals, metal oxides, and metal halides are usually divalent, but may be a mixture of monovalent and trivalent. It may also form a dimer via oxygen. In the phthalo/naphthalocyanine dye of general formula (I), L1, L2. As mentioned above, L3 and L4 consist of a benzene ring or a naphthalene ring,
In terms of the absorption wavelength of the pigment film, 1, +, L2. L3. L4
It is preferable that three or more of them consist of the above-mentioned naphthalene rings, and all of them consist of the above-mentioned naphthalene rings = 15
- For example, a naphthalocyanine dye represented by the following general formula (II) is most preferred.

In addition, the total number of carbon atoms in all substituents represented by -Z in one molecule in the fucro/naphthalocyanine dye represented by the general formula (1) of the present invention is 16 or more from the viewpoint of solubility of the dye in a solvent. is preferred. On the other hand, if the total number of carbon atoms exceeds 96, the reflectance of the dye film formed becomes low, which is not preferable. -The number of -Z substituents in the molecule is not particularly limited, but from the viewpoint of solubility, it is preferably 3 or more, and 4
It is more preferable that the number is 1 or more.

There is no particular restriction on the way in which this -Z substituent is introduced, and it may be bonded to any position on the benzene ring or naphthalene ring, and if multiple -Z substituents are bonded in the molecule, it may be bonded to one benzene ring or naphthalene ring. Even if it is bonded to the ring on average, 1
It may be bonded to only one benzene ring or naphthalene ring. - When two or more -Z substituents are present in the molecule, they may be the same substituent or different types of substituents.

Moreover, M in general formula (I) is Cu, Ni, Mg,
Pd.

Co, Nb+ Sn, In, Ge, Ga, v
o, TsO, Aff, Ga.

Chlorides, bromides, and oxides of In are preferable from the viewpoint of absorption and reflection of semiconductor laser light by the dye film, especially VO, TiO+ In, and In-C7! + In-B
r+A A-C7! .

A A-Br, Ga-CI! ,,Ga-Br+A
/-0-8j! , Ga-0-Ga, and In-0-In are preferred.

In addition, the above-mentioned Fukuro/naphthalocyanine dye used in the present invention has a carbon number of 1 to 12 other than the above-mentioned -Z substituent.
It may have an alkyl group, an aryl group, an alkyl ether group, an aryl ether group, etc.

The Lid 0/naphthalocyanine dye used in the present invention can be produced by a known method. For example, naphthalocyanine dyes are described in Japanese Patent Application Laid-Open No. 60-23451 and Zh, Obs.
, Khim, 42, 696-699 (1972) and the like.

The expression "phthalo/naphthalo" in the phthalo/naphthalocyanine dye of the present invention refers to a specific combination of L+ Lx L+ in general formula (I), for example, when all of them are benzene rings (phthalocyanine dye). , all of them are naphthalene rings (naphthalocyanine dye), and there are combinations of mixed benzene rings and naphthalene rings, and it means that all of these are included.

In order to fix (form) the recording layer on the transparent substrate in the optical recording medium of the present invention, for example, phthalo/naphthalocyanine dyes can be fixed by methods such as vacuum evaporation, sputtering, and ion blating. Since the method (2) requires complicated operations and is inferior in productivity, a so-called coating method is most preferred.

To fix the recording layer by coating, a dye solution consisting of the above-described phthalo/naphthalocyanine dye and an organic solvent described below is brought into contact with the substrate to fix the dye on the substrate. There is a method in which the dye liquid is allowed to flow down, or after the surface of the substrate is brought into contact with the liquid level of the dye liquid and then pulled up, the excess liquid is removed while rotating the substrate. There are methods such as letting it flow down onto the substrate. If necessary, forced drying may be performed after this. The organic solvent used in this case may be a conventional solvent that dissolves the fucro/naphthalocyanine dye, such as benzene, toluene, xylene, ethylbenzene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetylacetone, ethyl acetate, butyl acetate, amyl acetate, cellosolve. , methyl cellosolve, butyl cellosolve, cellosolve acetate,
Examples include diglyme, chloroform, carbon tetrachloride, methylene chloride, methylchloroform, trichlene, dimethylformamide, methanol, ethanol, and butanol. In selecting a solvent, it is preferable to use a solvent that does not damage the guide grooves on the transparent substrate in addition to the solubility of the dye.

The concentration of the dye solution in the present invention varies depending on the type of solvent and coating method, but is usually 0.1 to 10% by weight, preferably 0.3 to 5% by weight. At this time, in the present invention, in order to increase the reflectance of the recording film or improve sensitivity, other soluble dyes may be added to the dye solution to the extent that the effects of the present invention are not impaired, for example, approximately less than 50% of the total amount of dyes used. It is also possible to use a mixture within the range of . Examples of dyes that can be used in combination include already known aromatic or unsaturated aliphatic diamine metal complexes, aromatic or unsaturated aliphatic dithiol metal complexes, alkyl-substituted phthalocyanine dyes such as tert-butyl, and alkyl-substituted naphthalocyanines. dyes, alkoxy-substituted phthalocyanine dyes, alkoxy-substituted naphthalocyanine dyes, trialkylsilyl-substituted naphthalocyanine dyes, phenoxy-substituted phthalocyanine dyes, phenoxy-substituted naphthalocyanine dyes,
Examples include polymethine dyes, squalium dyes, naphthoquinone dyes, and anthraquinone dyes.

In the present invention, in order to improve the smoothness of the recording film and reduce defects such as pinholes when forming the recording film, the bag/naphthalocyanine dye of the present invention and, if necessary, the bag/naphthalocyanine dye described above are used. In solution with other dyes, soluble resins such as nitrocellulose, ethylcellulose, acrylic resin, polystyrene, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinyl butyral, polyester resin, dimer acid polyamide, leveling agent, antifoaming Additives such as agents may also be added. However, when large amounts of these resins and additives are added, the reflectance of the recording layer decreases, and the dyes do not dissolve uniformly in the recording film and become dispersed, resulting in a decrease in recording sensitivity and a decrease in reflectance. do. From these points of view, the amount of the resin and additives added is less than 20% by weight of the recording film, preferably less than 10% by weight, and more preferably less than 5% by weight. In other words, in the present invention, the amount of phthalo/naphthalocyanine dye in the recording layer and the total amount of the dye that can be mixed and used as described above is at least 80% by weight to 100% by weight, preferably 90% by weight to It is 100% by weight, more preferably 95% to 100% by weight.

Regarding the optical recording medium of the present invention, as described above, it is preferable to record and reproduce signals using a laser beam (light beam irradiated from the substrate side) passing through a transparent substrate. In such a case, if the thickness of the recording layer becomes too thick, the writing light will be absorbed and attenuated considerably as it passes through the thick recording layer. It doesn't reach enough. Therefore, the amount of light on this surface is insufficient and the temperature rise is insufficient, making it impossible to satisfactorily form unevenness corresponding to the signal. As a result, the sensitivity decreases, and even if recording is possible, the S/N value (signal-to-noise ratio) value when reading out the signal is too small to be of practical use.

On the other hand, if the thickness of the recording layer is too thin, as will be described later, a sufficient reflectance in the recording layer cannot be obtained due to light interference, and therefore a large S/N value cannot be obtained.

Therefore, it is necessary to form a recording layer with an appropriate thickness, and the thickness of the recording layer in the optical recording medium of the present invention is preferably from 50 to 300 nm, more preferably from 60 to 250 nm.

There are various methods for measuring film thickness, and it is quite difficult to obtain accurate measured values. It is preferable to use Note that it is particularly difficult to measure the film thickness when there are guide grooves on the substrate;
It is also possible to use the film thickness obtained when the dye is fixed on a substrate that does not have e) as a substitute.

The most characteristic feature of the present invention is that the recording layer formed in this way has a fairly high reflectance, and therefore the recording layer itself also functions as a reflective layer. It is something that we have at the same time.

Therefore, the optical recording medium of the present invention is capable of controlling the focus of a laser beam when recording or reading signals without providing any reflective layer made of an inorganic compound such as a metal thin film, metal oxide, or metal alloy thin film as in the past. This makes it possible to control the trunk and the writing position of signals.

Generally, in order to write a signal on an optical recording medium, a laser beam is irradiated with a focused laser beam on the recording layer.

The dye in the recording layer in the irradiated area absorbs the laser beam and generates heat, causing the recording layer to change in quality, forming irregularities and changing the reflectance, thereby performing writing.

Signals are read by detecting this change in reflectance using a laser beam, but generally, if this change in reflectance is small, the signal-to-noise ratio (S/N) is undesirable.

However, what should be noted here is that the mode in which the reflectance of the optical recording medium changes when recording is performed, that is, the way in which the reflectance changes when unevenness is formed, is This is completely different depending on the configuration of the recording layer of the medium. For example, in the case of a medium consisting of two layers, a light-reflecting layer and a light-absorbing layer, as disclosed in U.S. Pat. The previously covered reflective layer is now exposed, and the reflectance of the uneven portions increases after recording. Therefore, in such a case, it is sufficient that the initial reflectance (that is, before the unevenness is formed) is such that the laser beam can be controlled. On the other hand, as in the present invention, the recording layer having a reflective layer is a so-called monolayer that serves as both a light reflective layer and a light absorbing layer.
The situation is completely opposite in the case of an optical recording medium consisting of a wafer, in which the reflectance of the area decreases due to the formation of concavities and convexities.

That is, the reflectance of the uneven portion becomes lower than the unique reflectance that the recording layer originally had. In such a case, in order to obtain a large S/N value, the original reflectance through the substrate is at least 10% or more, preferably 15% or more in the state before the signal is written. These 10
% or more, preferably 15% or more, can be achieved by using the dye of the present invention and appropriately selecting the film thickness of the recording layer. (It varies depending on the thickness.) This can be easily achieved. The reflectance in the present invention is determined by using a light source with the same wavelength as the oscillation wavelength of the semiconductor laser (for example, 830 nm), and fixing the recording layer on a transparent substrate that has no unevenness such as guide grooves. shall mean the value measured through a transparent substrate using an equipped spectrophotometer.

The medium of the present invention has sufficient reflectance as described above with only a single layer of dye, and the recording film has large absorption in the oscillation wavelength range of a semiconductor laser simply by coating the dye.

As disclosed in U.S. Pat. No. 4,492,750, the amount of resin binder is 40-99% by weight, preferably 60%
In the region where the amount is ~90% by weight, the dye is not uniformly dissolved in the binder and the dye particles become dispersed, so the spectral characteristics of the dye will not match the laser emission wavelength unless treated with organic solvent vapor. . On the other hand, in the case of the present invention, where the amount of resin binder is much smaller, from 0 to less than 20% by weight, surprisingly, even though similar dyes are used, organic solvent vapor treatment is not required. We also discovered that the material has large absorption in the laser emission wavelength range. Although the exact reason for this is unclear, it is probably because the state of association between dye molecules or the crystal structure varies greatly depending on the amount of resin binder. An even more significant feature of the present invention is that the resin binder (
It is also possible to form a recording layer using substantially only a phthalo/naphthalocyanine dye without using any binder (binder).

Usually, when a film made of an organic dye alone is formed by vacuum evaporation, the resulting film is inferior in mechanical strength. Therefore, although large amounts of resins have been added as Pai Goo to organic dyes to improve the mechanical strength of dye films, the specific dyes of the present invention have much lower amounts of binder or even no binder at all. It has been found that a recording film made essentially of only Fukuro/Naphthalocyanine dye has sufficient mechanical strength to be used as an optical recording medium.

When putting the optical recording medium of the present invention into practical use, an antireflection layer may be provided to improve the S/N value, or an ultraviolet curing resin or the like may be coated on the recording layer for the purpose of protecting the recording layer. Alternatively, a method such as pasting a protective sheet on the recording layer surface or pasting two sheets together with the recording layer surfaces inside may be used.

It is preferable to provide an air gap on the recording layer when laminating the recording layer.

In addition, the laser beam used for recording and reading in the present invention has a wavelength of 730 to 870 nm, preferably 75 nm.
It is a semiconductor laser with an emission wavelength of 0 to 860 nm. For example, when recording at 5 m/s, the laser output on the substrate surface should be about 4 mW to 12 mW, and the read output should be about 1710 when recording.
It may be about 0.4 mW to 1.2 mW.

[Preferred form for carrying out the invention]

Hereinafter, preferred embodiments of the present invention will be explained with reference to Examples.

Example 1 Spiral guide groove with thickness 1.2+nm and diameter 130mm (depth 70nm, width 0.6μ, pitch 1.6μ
After dropping a solution consisting of 1.2 parts by weight of tris-dihexylsulfonamide naphthalocyanine vanadyl dye and 98.8 parts by weight of carbon tetrachloride into the center of the surface having the guide groove of the acrylic resin plate having The resin plate was rotated for 10 seconds at a speed of 1100 Orp. Next, this acrylic resin plate was dried in an atmosphere of 40° C. for 10 minutes to fix a recording layer substantially consisting only of tris-dihexylsulfonamide-naphthalocyanine vanadyl dye to the acrylic resin plate. The thickness of this recording layer was 110 degrees when measured in cross section using a microscope. Also 83 through the acrylic resin plate
The reflectance of light with a wavelength of 0 nm was 22%. Further, the absorption rate of light at 830 nm was 54%.

The optical recording medium made in this way was placed on a turntable with the recording layer facing up, and while rotating at a speed of 900 rpm, the oscillation wavelength of 830 nm and the output at the substrate surface were 8 mW.
Using an optical head equipped with a semiconductor laser having
A 1 MHz pulse signal (50% duty) was recorded while controlling the laser beam to be focused on the recording layer through the acrylic resin plate from the lower side of the optical recording medium, that is, from the substrate side. Next, using the same device, the output of the semiconductor laser was set to 0.7 mW on the substrate surface, and the recorded signal was reproduced in the same manner. At this time, the signal-to-noise ratio (S/N
) was able to perform extremely good signal writing and reading at 53 decihers.

In order to investigate the durability of this optical recording medium, 60℃, 90χ
After leaving it in an RH atmosphere for 4 months, we recorded the signal on the unrecorded part using the same method as above, and reproduced the signal recorded before the durability test and the signal recorded on the 21ji (durability test). When tested, an S/N of 51.52 dB was obtained for each, and the changes caused by the durability test were sufficiently small.

The shape of the focus of the signal recording part after the durability test was observed using a scanning electron microscope, and the shape of the focus recorded before the durability test and the bit recorded after the durability test were almost the same. The bit shape was very clean, with almost no ridges on the edges of the focus, which is thought to occur due to the high thermal conductivity of optical recording media whose recording layer is an inorganic thin film such as a Te-based film, and which causes noise. Example 2, Comparative Example 1 Tris-dihexyl sulfonamide in Example 1
A recording layer consisting essentially only of naphthalocyanine dyes was prepared in the same manner as in Example 1 using a carbon tetrachloride solution of naphthalocyanine dyes having four substituents and M shown in Table 1 instead of naphthalocyanine dyes. We made an optical recording medium with a
/N was found. The results are summarized in Table 1.

It is clear from Table 1 that the S/N value is 48 to 53 dB in all the embodiments of the present invention.
In the comparative example, only 31 to 33 dB L was obtained. Normally, the S/N value required for optical recording media is at least 45 dB.
Based on the above, it can be seen that the comparative example cannot be put to practical use as a recording medium at all.

First expression □2: ■ * Derivation of the cross-section of the medium using a microscope. Comparative Example 2 An optical recording medium was prepared and evaluated in the same manner as in Example 1 using a carbon tetrachloride solution consisting of the dye used in Example 1 and a resin binder of the type and amount shown in Table 2. The thickness of the recording layer, the reflectance, and the S/N value determined by recording and reproduction are summarized in Table 2.

In Comparative Example 2 (experiment numbers 11 to 13) in Table 2, recording was impossible. That is, although it was possible to control the focus of the laser beam during recording and the formation of bits was physically observed, it was not possible to extract a signal during reproduction (reading). This is because in the comparative example, the amount of resin binder is much larger than in the example of the present invention, so the initial reflectance is originally small at 8 to 10%, and even if a focus is formed, the reflectance due to this is This seems to be due to the fact that the decrease in reflectance was slight, and therefore a change in reflectance that could be taken out as a signal was not obtained.

Table 2 A: Dimer acid polyamide Example 4 Except for using a phthalo/naphthalocyanine vanadyl dye which consists of an average of 3 naphthalene rings and 1 benzene ring and has an average of 3 dioctyl sulfonamide groups in the molecule. An optical recording medium was produced and evaluated in the same manner as in Example 1. Film thickness is 120nm, reflectance is 20%, absorption rate is 62
%, and the S/N value was 52 dB.

Comparative Example 3 After providing an aluminum reflective layer by vapor deposition on the acrylic resin plate used in Example 1, the same process as in Example 1 was carried out using the dye solutions of Experiment No. 1 and Experiment No. 8 on this reflective layer. and created an optical recording medium. The thicknesses of the resulting recording layers were 1100 nm and 350 nm, respectively, and the reflectances were 28% and 11%, respectively.

Using these optical recording media, signals were recorded and reproduced in the same manner as in Example 1 except that semiconductor laser light was irradiated from the recording layer side, and the S/N value was 25 clB for each.
, was extremely low at 21 dB. Next, when recording and reproducing the signal at a rotational speed of 450 rpm, the S/N value increased, but it was 38 dB and 38 dB, respectively.
It was still low at 1 dB.

From the above, if a reflective layer made of metal or the like is provided separately, the recording sensitivity decreases due to the high thermal conductivity of the reflective layer, making it impossible to record signals at high speed rotation, and even when recording at low speed rotation, the S/R is extremely small. It can be seen that only the N value can be obtained.

〔Effect of the invention〕

In the optical recording medium of the present invention, since the recording layer itself has sufficient reflectance, signals can be written and read without providing a reflective layer such as a thin metal film or a thin metal oxide film.
Moreover, since the reflectance is large, a large S/N ratio can be obtained. Furthermore, the shape of the focal point of the recording section shows no raised edges, which confirms that a large S/N can be obtained and at the same time indicates the possibility of improving the recording density.

The optical recording medium of the present invention can be easily mass-produced by a coating method, is stable against heat and humidity, and can be used for a long period of time.

Claims (1)

[Scope of Claims] (1) An optical recording medium capable of recording and reading signals without having a reflective layer, which essentially consists of a transparent substrate and a recording layer provided on the recording plate. The recording layer contains less than 20% by weight of a resin binder and the following general formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼ (I) [In the formula, M is a metal, a metal oxide, or a metal oxide. It represents a halide, and L_1, L_2, L_3, and L_4 represent a benzene ring or naphthalene ring skeleton that is unsubstituted or has one or more monovalent substituents -Z. where -Z is selected from the group consisting of the following substituents: -SO_2NR^1R^2, -COR^3 -COOR^4, -CONHR^5, -NR^6R^7, -R^8- OR^9, -R^1^0X and -X (wherein, R^1 to R^1^0 represent a hydrocarbon group having 1 to 12 carbon atoms, and X represents a halogen), and in one molecule has one or more substituents -Z. ] (2) The total number of carbon atoms in all substituents in one molecule in the phthalo/naphthalocyanine dye represented by the general formula (I) - Z The optical recording medium according to claim 1, wherein there are 16 to 96 pieces. (3) The optical recording medium according to claim 1, wherein three or more of L_1, L_2, L_3 and L_4 in the phthalo/naphthalocyanine dye represented by general formula (I) are naphthalene rings. (4) L_1, L_2, L_3, and L_4 in the phthalo/naphthalocyanine dye represented by general formula (I)
The optical recording medium according to claim 3, wherein is a naphthalene ring. (5) The optical recording medium according to claim 1, wherein the dye represented by formula (I) contains three or more -Z substituents in one molecule. (6) The optical recording medium according to claim 1, wherein the recording layer has a thickness of 50 to 300 nm. (7) The optical recording medium according to claim 1, wherein signals are recorded and read by a light beam passing through a transparent substrate.