JPS6362794A - Optical recording medium - Google Patents

Abstract

PURPOSE:To perform the writing or reading of a signal even when no reflecting layer is provided, by containing a specific phthalo/naphthalocyanine dye in a recording layer at least in a specific ratio or more. CONSTITUTION:An optical recording medium is constituted of a transparent substrate and the recording layer provided on a recording plate. The recording layer contains at least 80wt% or more of a phthalo/naphthalocyanine dye represented by formula (I). The transparent substrate to be used desirably has light transmissivity, for example, of 85% or more and low optical anisotropy. Since the recording layer has relatively high reflectivity itself and the recording layer itself also simultaneously has a function as a reflecting layer, a signal can be read even when no reflecting layer is provided and the focus control of laser beam or the track control of a signal writing position at the time of reading becomes possible.

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 the formation of the recording layer in a vacuum, such as by vacuum evaporation or sputtering, and media with an inorganic recording layer have a 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 by a coating method using a soluble organic dye. A method of coating an organic dye that absorbs in water and is soluble in organic solvents using a spin coding method has been developed and has been put into practical use to some extent. However, among the dyes that have been proposed so far, for example, cyanine dyes Media with a recording layer made of a squalium dye or a dithiol metal complex have poor durability, and since the dye film alone has inherently low reflectance, such as a dithiol metal complex, a separate inorganic film such as a metal thin film or a metal oxide thin film is used. A reflective layer made of a type compound was required.

For example, U.S. Pat. No. 4,492.750 relates to a medium using an alkyl-substituted naphthalocyanine dye. In this patent, a reflective layer such as AJ is provided on a glass or polymethyl methacrylate substrate, and an organic Solvent vapor treated. An optical recording medium provided with an optical recording layer composition in which alkyl-substituted naphthalocyanine dye particles having a particle size of , oosμ to 0.1μ are dispersed in a resin binder is disclosed. In this way, it is not possible to form a recording layer made of an organic dye directly on the substrate, and a reflective layer made of an inorganic compound such as Ajl must be formed 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 dye films inherently have low thermal conductivity, so they are expected to provide high recording sensitivity.
When a metallic or inorganic reflective layer with high thermal conductivity is provided, the thermal energy generated by the writing laser beam applied to the recording layer is transferred to the metal due to the high thermal conductivity of the metallic reflective layer. Since the light is dissipated through the reflective layer and is not effectively used to form pits (irregularities corresponding to signals), recording sensitivity is significantly reduced.

Furthermore, when a reflective layer made of an inorganic compound such as A1 is provided, if a laser beam for recording or reading signals is irradiated from the substrate side, the laser beam may be emitted even if the substrate itself is transparent. The beam does not reach the recording layer because it is blocked by a metal reflective layer that does not substantially transmit light. Therefore, if a reflective layer is provided, signals cannot necessarily be recorded or reproduced through the substrate. In such a case, where recording has to be performed from the recording layer side, 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. In this way, media with a reflective layer made of an inorganic (metallic) compound such as AI have a number of drawbacks, and it is not possible to record and reproduce signals without separately providing a reflective layer made of an inorganic compound. There has been a desire to develop an optical recording medium in which a recording layer is formed by coating an organic dye that is capable of coating 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 reflective layer, which is substantially composed of a transparent substrate and a recording layer provided on the recording plate; The recording layer has the following general formula (1). The above optical recording medium contains at least 80% by weight of a phthalo/naphthalocyanine dye represented by ) and representing a metal oxide or a metal halide in the represented molecule.

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 preferably has a 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 X inner grooves, address signals, etc., and economical 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 thereof may have an X inner groove representing a recording position or irregularities for an address signal, etc.

Such X inner grooves, address signals, etc. can be added when making the substrate by injection molding or casting, or by applying ultraviolet curable resin etc. on the substrate and overlapping it with a stamper and applying ultraviolet & infrared light etc. Can be granted.

In the present invention, the following general formula (representing ri, Ql+ Qt+ Qs+ Q*+ Q%+ Q
&+ Q? + Q@+ Q9 and R3 represent a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group, a phenyl group, or a substituted phenyl group, A recording layer containing a phthalo/naphthalocyanine dye represented by ), which represents an oxide or a metal halide, is provided.

In the phthalo/naphthalocyanine dye represented by the general formula (1) used in the recording layer in the present invention, Rt
Specific examples of the substituents represented by -Rg and R8 include methyl, ethyl, n-propyl, 1so-propyl, n-butyl, 1so-butyl, 5ec-butyl, ta
rt-butyl, n-amyl, 1so-amyl, 5ec-
Amyl, lert-amyl, rhohexyl, 1so-hexyl, 1-methyl-1-ethylpropyl, 1,1-dimethylbutyl, n-hebutyl, tert-heptyl, octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, etc. and substituted phenyl groups such as phenyl, tolyl (methylphenyl), and xylyl (dimethylphenyl).

On the other hand, specific examples of M in the phthalo/naphthalocyanine dye represented by the general formula
Group ■ metals such as; A1, Ga, In, T
1 m group metals such as HGe, Sns Pb%Ti
Group III metals such as; 5bSBi%V %Nb%Ta
Group V metals such as Se, T.

Group II metals such as %Crs MO%-; Mn%Tc
Group ■ metals such as Fe, Go, NL Ru+
Examples include group II metals such as Rh+ Pd+ Os+ Ir+ Pt, oxides of these metals, and halides such as chlorides, bromides, and iodides. These metals, metal oxides, and metal halides are usually divalent, but may be a mixture of monovalent and trivalent, or may form a dimer via oxygen. In the phthalo/naphthalocyanine dye of formula (1), Lt, Lx, LI, and 2 are composed of a benzene ring or a naphthalene ring as described above, but from the viewpoint of the absorption wavelength of the dye film, LI, LI L
It is preferable that three or more of them consist of the above-mentioned naphthalene rings, and it is most preferable that all of them consist of the above-mentioned naphthalene rings.

That is, this is a case where the general formula (1) is a naphthalocyanine dye represented by the following formula.

(In the formula, R+, Rt, R3 and R4 have 1 to 12 carbon atoms.
In terms of solubility, silyl groups represent straight-chain or branched alkyl groups, phenyl groups, or substituted phenyl groups, and these groups may be the same or different at the same time. 2 or more are preferable, 3 or more are more preferable, and R of the silyl substituent
+, Rs, If the number of carbon atoms in Rs exceeds 12, the reflectance of the recording layer containing it will decrease, which is undesirable, and M in the general formula (summer) is Cu, NL+ Mg+ P
d+ Co+ sb, Sn, In, Gat Ga
t VO+ TIO and A1. Chlorides, bromides and oxides of Ga and In are preferable from the viewpoint of absorption and reflection of semiconductor laser light by the dye film, especially VO+TiO
+In, In-CCIn-Br.

A I -CI, A l -Br, Ga-Cl, G
a-Br, A I -0-A I, Ga-0-Ga,
In-0-In is preferred.

The phthalo/naphthalocyanine dye used in the present invention can be produced by a known method.

For example, naphthalocyanine dyes are disclosed in JP-A No. 60-2345.
No. 1, Zh, Oba, Khim, 42.696-69
9 (1972) etc., for example, general formula (■) (where R represents a straight chain or branched alkyl group having 1 to 12 carbon atoms, a phenyl group, or a substituted phenyl group). It is produced by heating and reacting 6-silylated-2,3-dicyanonaphthalene represented by the formula with a metal chloride in urea. In addition, the compound represented by the general formula (If) can be used for fixing (forming) the recording layer on a suitable substrate in the optical recording medium of the present invention according to a known method, for example, as a phthalate. / Vacuum deposition of naphthalocyanine dye,
Although fixing can be carried out by methods such as sputtering and ion blasting, these methods require complicated operations and are inferior in terms of productivity, so 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, this may be followed by forced drying; the growing solvent used in this case may be any of the usual solvents that dissolve phthalo/naphthalocyanine dyes (e.g., benzene, toluene, xylene, ethylbenzene, methyl ethyl ketone, etc.). 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, and dimethylformamide. 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 IO% by weight, preferably 0.3χ 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 mixed with the dye liquid in an amount of 25 parts by weight or less per 100 parts by weight of the dye of the present invention. You can also do it. 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, alkyl-substituted phthalocyanine dyes such as [-butyl], and alkyl-substituted naphthalocyanines. Examples include alkoxy-substituted naphthalocyanine-based dyes, phenoxy-substituted naphthalocyanine-based dyes, polymethine-based dyes, squalium-based dyes, naphthoxynone-based dyes, and anthraquinone-based 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 phthalo/naphthalocyanine dye of the present invention and, if necessary, the phthalo/naphthalocyanine dye described above are used. Soluble resins such as nitrocellulose, ethylcellulose, acrylic mUL polystyrene, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinyl butyral, polyester resin, and additives such as leveling agents and antifoaming agents in solutions with other dyes. However, if large amounts of these resins or additives are added, the reflectance of the recording layer may decrease, or the dye may not be dissolved uniformly in the recording film and become dispersed, resulting in a decrease in recording sensitivity. Moreover, the reflectance also decreases. From these points, the amount of resin and additives added should be 20% in the recording film.
It is less than 1% by weight, preferably 10% by weight or less, more preferably 5% by weight or less. In other words, in the present invention, the amount of phthalo/naphthalocyanine dye in the recording layer is small (
80% to 100% by weight, preferably 90% by weight
~100% by weight, more preferably 95% by weight ~100% by weight
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) through a transparent substrate.In such a case, the recording layer If the film thickness becomes too thick, the writing light will be absorbed and attenuated considerably as it passes through the thick recording layer, and will not reach the surface of the recording layer (the surface in contact with air). Due to insufficient light intensity and insufficient temperature rise, it is not possible to satisfactorily form the unevenness corresponding to the signal.As a result, the sensitivity decreases, and even if recording is possible, the S/ The N value (signal-to-noise ratio) value is too small to be put to 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 50 to 400 nm, more preferably 60 to 250 nm.

There are various methods for measuring film thickness, and it is quite difficult to obtain accurate measured values. It is particularly difficult to measure the film thickness when there are guide grooves on the substrate, but it is preferable to use prsgroov
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 distinctive 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 does not require any reflective layer made of an inorganic compound such as a thin gold film, metal oxide, or metal alloy thin film as in the past, and can be used as a focal point of a laser beam when recording or reading signals. This makes it possible to control and track the signal writing position.

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, This completely depends 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 single layer (gonolayer) that serves as a light reflective layer and a light absorbing layer.
The situation is completely opposite in the case of an optical recording medium made of a material such that the reflectance of that portion decreases due to the formation of irregularities.

That is, the reflectance of the uneven portion is lower than the reflectance of the patent 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 easily achieved by using the dye of the present invention and by appropriately selecting the thickness of the recording layer. However, the reflectance changes depending on the film thickness due to interference of reflected light from the front and back sides of the recording layer.

For example, if we use tetra-6-trimethylsilyl2.
3--1-7 Figure 1 shows the results of measuring the relationship between film thickness and reflectance when a film consisting essentially only of talocyanine vanadyl is used for the recording layer. Using a light source with a wavelength of 830 nm, the recording layer was fixed on a transparent substrate free of unevenness such as guide grooves, and measurements were made through the transparent substrate using a spectrophotometric needle equipped with a 5-layer specular reflection accessory. However, the reflectance in the present invention means the value measured in this way. When light is irradiated through the substrate, reflection occurs at the interface between the substrate and the recording film and at the interface between the recording film and air. These two reflected lights interfere with each other, and depending on the thickness of the recording layer, the first
It changes as shown in the figure. Therefore, in the present invention, by appropriately selecting the film thickness, a sufficiently large reflectance can be obtained.

In addition, the recording layer measured through the acrylic resin plate when this 110 nm thick recording layer of tetra-6-trimethylsilyl-2,3-naphthalocyanine vanadyl was coated on a 1.2 m flat acrylic resin plate. Figure 2 shows the wavelength dependence of the reflectance and transmittance of this recording layer.
It has broad absorption from 0 to 850 n-. The wavelength range of this absorption closely matches the emission wavelength of the semiconductor laser.

Also, the reflectance in this wavelength range is over 13%, especially at 7.
It has a reflectance of 15% or more in the 80-850 nm region. As is clear from FIG. 2, it can be seen that the recording film of the present invention has large absorption and reflectance in the laser emission wavelength range even without some part being treated with organic solvent vapor.

The amount of resin binder is 40-99% by weight, preferably 60% by weight as disclosed in U.S. Pat.
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, organic solvent vapor treatment is not required, even though similar pigments are used for other purposes. We have discovered that even though it has a large absorption in the laser emission wavelength range. Although the exact reason for this is unknown, it is probably because the state of association between dye molecules or the crystal structure varies greatly depending on the amount of resin pine mites. An even more significant feature of this invention is that it is possible to form a recording layer using only phthalo/naphthalocyanine dyes without using a resin binder (binding agent).

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 the dye film, even though the amount of the specific dye binder of the present invention is much lower or not at all, It was found that a recording film containing only phthalo/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 facing inside may be used in combination.

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 having an emission wavelength of 0 to 860n-. For example, when recording at 5 m/s, the laser output on the substrate surface should be about 4+*W~12o+I4, and the read output should be about 1/10 of the recording output.
, 0.4 mW to about 1.2 mW.

(Preferred Mode for Carrying Out the Invention) Hereinafter, preferred embodiments of the present invention will be described with reference to Examples.

Example 1 (11) Tetra-6-driethylsilyl 2,3
- After dropping a solution consisting of 1 part by weight of naphthalocyanine vanadyl dye and 99 parts by weight of chloroform, the acrylic resin plate was rotated at a speed of 2000 rpm for 15 seconds.

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 the tetra-6-triethylsilyl-2,3-naphthalocyanine vanadyl dye on the acrylic resin plate. The thickness of this recording layer was 110 nm* as measured by an ellipsometer. The reflectance of light having a wavelength of 830 rho through the acrylic resin plate was 21%.

(2) Place the optical recording medium thus produced on a turntable with the recording layer facing up, and while rotating at a speed of 900 rpm, generate a semiconductor laser with an oscillation wavelength of 830 rom and an output of 8 mW at the substrate surface. Using an optical head equipped with a laser beam, a 1 MHz pulse signal (duty 50%
) was used to perform the recording, the output of the semiconductor laser was set to 0.7+wW on the substrate surface, and the recorded signal was reproduced in the same manner. The signal-to-noise ratio (5/N) at this time was 54 decibels, and very good signal writing and reading could be performed.

(3) 60°C to check the durability of this optical recording medium.
After being left in an atmosphere of 95χRH for 4 months, signals were recorded on the red recording section in the same manner as above, and the signals recorded before the durability test and the signals recorded after the durability test were played back. S of 52.53 dB each
/N was obtained, and the change due to the durability test was sufficiently small.

(4) The shape of the pits in the signal recording area after the durability test was observed using a scanning electron microscope, and the shapes of the bits recorded before the durability test and the pits recorded after the durability test were almost the same. In optical recording media whose recording layer is an inorganic thin film such as a Te-based film, there is almost no bulging at the edges of the pits, which is thought to occur due to the high thermal conductivity and causes noise, and the bit shape is very clean. Met.

Example 2, Comparative Example 1 An acrylic plate with a thickness of 1.2 mm and a diameter of 120 mm was used, and the naphthalocyanine dye having a silyl group and M shown in Table 1 was used, and carbon tetrachloride was used as a solvent to change the dye concentration. An optical recording medium having a recording layer consisting essentially of naphthalocyanine dye was prepared in the same manner as in Example 1, and the reflectance and S/N were examined. The results are summarized in Table 1.

As is clear from Table 1, S/N values of 47 to 53 dB are obtained in all the embodiments of the present invention;
In the comparative example, the S/N value required for an optical recording medium 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.

Table 1 Umbrella Umbrella The column of Examples of the present invention shows Example 2, and the column of Comparative Examples shows Comparative Example 1. Example 3 A spiral recording guide groove (width 0.8μ Practice, depth 0.07μ monk,
Tetra-6-drimethylsilyl-2.3-naphthalocyanine vanadyl 1 was applied to both the acrylic resin plate with a pitch interval of 2.5 μm and the acrylic resin plate without guide grooves.
A weight percent carbon tetrachloride liquid was applied and dried in the same manner as in Example 1 to produce an optical recording medium having a recording layer consisting essentially of tetra-6-trimethylsilyl-2,3-naphthalocyanine vanadyl. However, for the acrylic resin plate having guide grooves, layer ii was fixed on the surface having the guide grooves. The film thickness of this optical recording medium was measured with an ellipsometer and was 13.
0 nm, the reflectance was 22% (on a substrate without guide grooves).

Using these optical recording media, S/N measurements, durability tests, and pit observations were performed by writing and reading signals in the same manner as in Example 1.

The results are summarized in Table 2.

Example 4 An average of 3 trimethylsilylnaphthalene rings in the molecule and 1
Phthalo/naphthalocyanine InCj consisting of an unsubstituted benzene ring! An optical recording medium was prepared and evaluated in the same manner as in Example 1 except that the following was used. The film thickness is 120n- and the reflectance is 1.
9%, and the S/N value was 52 dB.

Example 5, Comparative Example 2 Acrylic resin plate with a thickness of 1.2 ms and a diameter of 120-1,
The same method as in Example 2 was carried out using a carbon tetrachloride solution consisting of tetra,6-drimethylsilyl-2,3-naphthalocyanine vanadyl as the dye and a resinus binder of the type and amount shown in Table 3. An optical recording medium was created. The thickness and reflectance of the recording layer are summarized in Table 3. Using this zero-order medium, signals were recorded and reproduced in the same manner as in Example 2. The results cannot be recorded in Comparative Example 2 (Experiment Nos. 12 to 13) in Table 3. Vinyl chloride %←weight)-vinyl acetate 17% copolymer Table 3. In other words, it was possible to control the focus of the laser beam during recording, and the formation of physical irregularities was observed;
It was not possible to extract the signal during playback (reading). In the comparative example, this is because the binder (resinu
Since the amount of s binder is much larger than that in the examples of the present invention, the initial reflectance is originally small at 7 to 9%.
This seems to be because even though the unevenness is formed, the amount of decrease in reflectance caused by this is small, and therefore a change in reflectance that can be taken out as a signal is obtained.

Comparative Example 3 An optical recording medium was prepared in the same manner as in Example 1 using the 5% chloroform solvent of the naphthalocyanine dye used in Example 3. The thickness of the recording layer in the obtained optical recording medium was 500 nm. Further, the reflectance was 10%. Using this optical recording medium, signals were recorded and reproduced in the same manner as in Example 1 to determine the S/N, but only 30 dB L was obtained and the noise was large.

Comparative Example 4 After providing an aluminum reflective layer by vapor deposition on the acrylic resin plate used in Example 1, Example 3 was applied on this reflective layer.
Using the dye solution of Comparative Example 1, an optical recording medium was produced in the same manner as in the example. The thicknesses of the resulting recording layers were 130 nm and 500 nm, respectively. Moreover, the reflectance was 27% and 12%, respectively.

When recording and reproducing signals using these optical recording media in the same manner as in Example 1 except for irradiating semiconductor laser light from the recording layer side, the S/N values were extremely high at 28 dB and 20 dB, respectively. It was low.

Next, when recording and reproducing signals with the rotational speed for recording set to 45 rpm, the S/N values increased, but were as low as before at 40 dB and 30 dB, respectively.

From the above, if a reflective layer made of metal or the like is separately provided, the recording performance will be reduced 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/N will be extremely small. It turns out that you can only get value.

〔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 pits in the recording section shows no raised edges, which supports the fact that a large S/N ratio 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.

[Brief explanation of drawings]

Figure 1 shows the film thickness dependence of reflectance when the tetra-6-drimethylsilyl-2,3-naphthalocyanine vanadyl dye of the present invention is used as a recording film when 830n- light is irradiated through the substrate. It is a graph. FIG. 2 is a graph showing the wavelength dependence of the transmittance and reflectance of the recording layer, which is the same as FIG. 1. Patent applicant: Mitsui Toatsu Chemical Co., Ltd.Drawing number: Figure 2: 600 TOO8) 0 900 Wavelength (nm)

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 has the following general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, L_1, L_2, L_3, L_4 are ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. Representing ▼, Q_1, Q_2, Q_3, Q_4, Q
_5, Q_6, Q_7, Q_8, Q_9 and Q_1_0
is hydrogen or a ▼ group with mathematical formulas, chemical formulas, tables, etc., and R_1, R_2, and R_3 represent a linear or branched alkyl group or alkenyl group having 1 to 12 carbon atoms, a phenyl group, or a substituted phenyl group. , has an average of two or more ▲ mathematical formulas, chemical formulas, tables, etc. ▼ groups in the molecule represented by general formula (I). Further, M represents a metal, a metal oxide, or a metal halide. ) The optical recording medium contains at least 80% by weight of a phthalo/naphthalocyanine dye. (2) Claim 1 in which 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▲There are mathematical formulas, chemical formulas, tables, etc.▼ The optical recording medium described. (3) 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 2, wherein is a naphthalene ring. (4) Optical recording medium (5) recording according to claim 1, characterized in that the dye represented by general formula (I) contains an average of 3 or more Si-R_2 groups in one molecule. Claim 1, wherein the layer thickness is 50 to 400 nm.
Optical recording medium described in Section 1. (6) The optical recording medium according to claim 1, wherein signals are recorded and read by a light beam passing through a transparent substrate.