JPH0696347B2 - Optical recording body - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical recording body for an optical disc.

2. Description of the Related Art As an optical recording medium for an optical disc, it is necessary to efficiently absorb the energy of laser light. Therefore, the absorption of laser light of a specific wavelength used for recording is large, and accurate reproduction of information is required. It is necessary that the reflectance with respect to a laser beam of a specific wavelength used for reproduction is high.

As such an optical recording material, various metals,
Inorganic compounds such as metal compounds and chalcogenides have been proposed, but these thin films are susceptible to air oxidation, difficult to store for a long period of time, and sensitive to light in the ultraviolet or visible region. However, there were some defects such as weakness in sunlight and other light.

As a recording material using an organic compound, a cyanine dye,
Squarylium dyes, naphthoquinone dyes, phthalocyanine dyes, etc. have been proposed. Of these, cyanine dyes, squarylium dyes, and naphthoquinone dyes
Generally, there are drawbacks such as poor stability, difficulty in storage for a long period of time, and difficulty in reading information due to low reflectance.

Some of the phthalocyanine dyes also have absorption at the wavelength of the semiconductor laser (around 800 nm), but have the drawback that the absorption changes easily along with the crystal transformation. For example, the absorption around 720 nm in a vapor-deposited film of vanadyl phthalocyanine changes to 815 nm by heating (Molecular
Crystals and Liquid Crystals 33 , 149-170 (197
6)).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide an optical recording material of an organic material, which has a high writing sensitivity to laser light, particularly a semiconductor laser light, and has good storage stability.

Means for Solving the Problems The gist of the present invention is an optical recording material comprising a substrate and a recording layer containing a light absorbing substance represented by the following general formula [I].

General formula [I] (In the formula, ring Z ¹ to ring Z ⁴ represent an optionally substituted thiophenene ring, pyridine ring, pyrazine ring or imidazole ring, and A represents Group IB, Group IIA of the periodic table, No. I
It represents a metal belonging to Group IB, Group IIIA, Group IIIB, Group IVA, Group IVB, Group VB or Group VIII or a compound containing the metal. ) In the light absorbing material represented by the general formula [I] in the optical recording material of the present invention, examples of the substituents of the thiophene ring, the pyridine ring, the pyrazine ring or the imidazole ring of the ring Z ¹ to the ring Z ⁴ include a methyl group. , Ethyl group, trifluoromethyl group,
Included are hydroxy groups, fluorine, chlorine or bromine.

In addition, A group IB, IIA group, IIIA group, IIIB group, I group
Examples of metals related to Group VA, Group IVB, Group VB or Group VIII include Cu, Mg, Zn, Sn, Pb, Fe, Co or Ni, and compounds containing the metal include AlCl , In
Examples include Cl, TiO, SnCl _{2 and the} like.

In the optical recording material of the present invention, it is particularly preferable that rings Z ¹ to Z ⁴ are thiophene rings and A is SnCl ₂ , InCl, VO or TiO.

The light-absorbing substance represented by the above general formula [I] is obtained by a known method such as dicyanothiophene, dicyanopyridines, dicyanopyrazine or dicyanoimidazole and a metal or a metal compound, for example, 2,3-dicyanothiophene. And stannous chloride can be easily synthesized by heating.

Examples of the substrate of the present invention include glass and plastics. Plastics are preferable in terms of safety and lightness. Examples of the plastics include acrylic resin, methacrylic resin, polycarbonate resin, vinyl chloride resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, polyamide resin, polystyrene resin, and epoxy resin.

Examples of the method for forming the recording layer include known methods such as a method of vacuum deposition on a substrate, a method of coating with a resin solution and a method of dissolving in a solvent and coating or dipping. In particular, the vacuum vapor deposition method is preferable.

As the vacuum deposition method, 1 × 10 ⁻⁴ Torr or more, preferably,
There can be mentioned a method of heating the compound represented by the general formula [I] by resistance heating or the like at a high vacuum of 2 × 10 ⁻⁵ Torr or more to obtain a vacuum deposited film on the substrate. Film thickness is 500-3000
Å, especially 1000 to 2500Å is preferred.

The film formation by coating can be obtained by spin-coating the compound represented by the general formula [I] with a binder dissolved or dispersed in a solvent. As the binder, polyimide resin, polyamide resin, polystyrene resin, acrylic resin, polyester resin, polycarbonate resin, polysulfone resin, phenol resin, polyether resin, silicone resin, cellulose ester, cellulose ether, polyvinyl acetate resin, polyvinyl chloride resin , Polyvinylidene chloride resin, polyurethane resin and copolymers thereof.

At that time, the ratio of the light absorbing substance to the resin is preferably 10 wt% or more.

As the solvent, various solvents such as dimethylformamide, tetrahydrofuran, dichloromethane and chlorobenzene can be used, but dimethylformamide is preferable in terms of solubility.

The recording layer of the optical recording medium of the present invention may be provided on both sides of the substrate, or may be provided on only one side.

Recording on the recording medium obtained as described above is performed by irradiating a recording layer provided on both sides or one side of the substrate with a laser beam focused to about 1 μm, preferably a semiconductor laser beam. In the portion irradiated with laser light, thermal deformation of the recording layer such as decomposition, evaporation, and melting occurs due to absorption of laser energy.

The recorded information is reproduced by using a laser beam to read the difference in reflectance between a portion where thermal deformation has occurred and a portion where thermal deformation has not occurred.

As the light source, various lasers such as He-Ne laser, Ar laser, and semiconductor laser can be used, but the semiconductor laser is particularly preferable in terms of cost and size.

As a semiconductor laser, the central wavelength is 830 nm and the central wavelength is 780.
nm and shorter wavelength lasers can be used.

Example 1 1.34 g of 2,3-dicyanothiophene (mp 118-122 ° C.) and 1.13 g of stannous chloride were dispersed in 2 ml of chloronaphthalene,
The reaction was carried out at 250 ° C. for 5 hours while heating under reflux. The obtained reaction solution was cooled to room temperature, 50 ml of methanol was added, and the mixture was stirred under reflux for 3 hours. The reaction solution was heated and the obtained crystals were dispersed in 100 ml of N-methyl-2-pyrrolidone, stirred at 200 ° C for 2 hours and then cooled to 100 ° C to separate the crystals. Further, the same operation using N-methyl-2-pyrrolidone was repeated twice to obtain 0.96 g of a compound represented by the following structural formula (λmax700 nm in an α-chloronaphthalene solvent).

The light-absorbing substance of the present invention represented by the above structural formula is added at 1 × 10 ⁻⁵ To
It was heated to 300 ° C to 400 ° C in a vacuum of rr and vacuum-deposited on a methacrylic resin plate having a plate thickness of 12 mm. The film thickness measured by the crystal vibration type film thickness meter was 2000Å. The maximum absorption wavelength of the deposited film is
It was 720 nm and the peak was wide. 33 reflectance at 830 nm
It was in%.

This vapor-deposited film was irradiated with a semiconductor laser beam having a central wavelength of 780 nm at an output of 4 mW and a beam diameter of about 1 μm, and the width was about 1 μm.
m, a very clear contoured hole (pit) having a pit length of about 2 μm was formed. Carrier level / noise level (C /
The N) ratio was 50 dB.

Examples 2 to 17 Light absorbing substances represented by structural formulas [III] to [XVIII] were synthesized according to Example 1, and the obtained light absorbing substances were treated under substantially the same conditions as in Example 1 with a methacrylic resin plate. Evaporated on top. The film thickness measured by the crystal vibration type film thickness meter was within the range of 2000 ± 100Å.

The maximum absorption wavelength of these light-absorbing substances of the present invention in the α-chloronaphthalene solvent, the maximum absorption wavelength of the thin film, the C / N ratio during semiconductor laser recording, and the storage stability are shown in Table 1 together with the results of Example 1 above. Shown in. In the table, the storage stability indicates the writing performance (C / N ratio) by a semiconductor laser after storage for 10 days in a constant temperature and humidity chamber at 60 ° C and 80%.

Claims (3)

[Claims] 1. An optical recording material comprising a substrate and a recording layer containing a light absorbing substance represented by the following general formula [I]. General formula [I] (In the formula, ring Z ¹ to ring Z ⁴ represent an optionally substituted thiophenene ring, pyridine ring, pyrazine ring or imidazole ring, and A represents Group IB, Group IIA of the periodic table, No. I
Group IB, Group IIIA, Group IIIB, Group IVA, Group IVB, Group VB
Represents a metal belonging to Group VIII or Group VIII or a compound containing the metal) 2. The optical recording material according to claim 1, wherein the light absorbing substance is represented by the following general formula [II]. General formula (II) (In the formula, ring Z ¹ to ring Z ⁴ represent a hydrogen atom, an alkyl group, a halogenated alkyl group, a hydroxy group or a thiophene ring optionally substituted with a halogen atom, a pyridine ring, a pyrazine ring or an imidazole ring, and A is Sn, Sn
Cl ₂ , Pb, Fe, Ni, Co, VO, InCl, TiO, Cu, Mg, Zn or AlCl) 3. The optical recording material according to claim 1, wherein the light absorbing substance is represented by the following general formula [III]. General formula (III) (In the formula, A represents SnCl ₂ , Pb, Fe, Ni, Co, VO, InCl, TiO or Zn)