JPS63312888A - Optical recording medium - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of an optical recording medium, by producing the optical recording medium through providing on a substrate a recording layer comprising a phthalocyanine compound of a specified formula for recording and reading by use of laser radiation. CONSTITUTION:A phthalocyanine compound of the formula, wherein one of X and Y linked directly to each of four benzene rings is SR (R is a 1-20C straight chain alkyl), while the other is H, and M is a metallic atom, is dissolved in an appropriate solvent to prepare a coating liquid. The coating liquid is applied to a substrate to provide a recording layer, thereby producing an optical recording medium. Writing and reproduction of information from the optical recording medium is preferably conducted from the substrate side. Therefore, the substrate is preferably made from a transparent material such as a glass, a poly(meth)acrylic resin and a polyester resin.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a write-once optical recording medium using a semiconductor radar.

(Prior art and its problems) Conventionally, tellurium-based compounds have been used as inorganic recording media, but since the recording layer is formed by vacuum evaporation or sputtering, they suffer from low productivity and toxicity. There was a problem of concern. Many studies have been reported in which organic dyes, which are considered to be advantageous in these respects, are used in recording media. Such organic dyes include polymethine dyes, naphthoquinone dyes, dithiol metal complexes,
Phthalocyanine pigments are known. However, these organic dyes do not sufficiently have the following properties required for use as write-once optical recording media, and there is still room for improvement.

1. In order to convert laser light energy into thermal energy, it must have sufficient absorption intensity in the near-infrared region. 2. Since signal detection is based on changes in reflectance, it must have a sufficiently high reflectance for semiconductor radar light. 3. , The writing threshold must be clear, and changes due to heat, that is, thermal decomposition behavior, must be sharp against humidity changes in order to reduce damage caused by reading light. 4. In order to form a uniform recording layer with high productivity, A coating type is best; for this purpose, the dye must be soluble in a solvent5 and have sufficient durability (light resistance, moisture resistance) for repeated reproduction or storage.

Among the organic dyes mentioned above, phthalocyanine dyes have extremely large molecular absorption coefficients and are highly durable, so they can be used as high-performance optical recording media. There were problems in that special treatment was required to match the light, and chemical modification was somewhat difficult. In order to improve these drawbacks, we have recently developed a soluble 7-talocyanine with a substituent that absorbs in the near-infrared region (Japanese Patent Laid-Open No. 61-246091).
and naphthalocyanine (JP-A-61-163891.61
-268487) has been disclosed, but these compounds have the disadvantage that their synthesis involves multiple steps and the yield is low, leading to an increase in the cost of the recording medium. Ah nine.

(Means and Actions for Solving the Problems) The present inventors have taken into account the problems of optical recording media using organic dyes as described in the previous section, and have attempted to solve the problems easily. As a result of various studies on optical recording media with 1# and high performance, formula (I)
The present invention was completed by discovering that an optical recording medium containing a substituted phthalocyanine dye represented by the formula satisfies the above-mentioned characteristics.

(In the formula (D), only one of X and Y directly connected to the four benzene rings is 5R (R represents a straight-chain alkyl group having 1 to 20 carbon atoms), and the other is H. M represents a metal atom. In the present invention, rcnJ means that the number of carbon atoms is n. It can be obtained by a normal purification method such as recrystallization or column separation using an appropriate solvent after heating condensation with a metal oxide etc.The raw material 4-alkylthiophthalonitrile is
It is obtained by reacting 4-nitrophthalonitrile with an alkylthiol in the presence of a suitable catalyst. That is, as shown in the reference examples described below, the two-stage reaction provides a high yield of kanashi, which has the advantage of leading to cost reduction as an optical recording medium. The advantages of forming a recording medium using the phthalocyanine compound represented by formula (I) and as a recording medium are listed below.

1. Regarding absorption in the near-infrared region, due to substituent effects, the absorption maximum shifts to longer wavelengths compared to ordinary phthalocyanine dyes, so Mg T Ti is used as the central metal.
p V s Mn IF's * Ru * Co
+Nl e Cu p Zn p Atp Ga r
Any commonly known atoms such as In HSi * Go + Sn and Pb (including axial ligands such as oxygen atoms and halodane atoms in the case of trivalent or higher valent metals) may be used, but in particular 'rto, vo = kLCL
, InCt, 5iCt2°Ge, Sn, and Pb. In addition, as the chain length of the alkyl group becomes longer, the absorption rate decreases, so the length is 01~
C8 is preferred, and C4 to C6 are particularly preferred.

2. When the recording layer is made of substantially only phthalocyanine dye, the reflectance in the near-infrared region is high. Therefore, when this recording layer is used, it is possible to record and reproduce signals through the substrate alone without further providing a so-called reflective layer in the recording layer. In particular, in order to obtain a sufficiently high reflectance, the central metal and alkyl group chain length of the phthalocyanine dye are preferably those described in the previous section.

3. Judging the thermal decomposition behavior from the TG-DTA Fitl line, all of them show sharp thermal decomposition behavior. The degree of this effect is almost unaffected by the alkyl group chain length and depends on the type of central metal.Among the central metals listed as preferable in terms of absorption and reflectance, TiO, VO
is particularly preferred.

4,7 Talocyanine dyes are inherently robust but have poor solubility; however, the phthalocyanine dye of the present invention has an alkylthio group and is therefore soluble in bath agents such as chloroform, dichloromethane, benzene, toluene, and tetrahydro-7rane. It is.

The solubility is affected by the chain length of the alkyl group, but in order for the solubility to be about 11t or more, it is desirable that the alkyl group has a length of 02 or more. Further, as the ta-alkyl group chain length increases, the melting point of the phthalocyanine dye decreases, so in order to have sufficient strength as a recording medium, it is more preferable that the alkyl group chain length is 0.6 or less.

As mentioned above, in order to satisfactorily satisfy the critical absorption and reflectance in the near-infrared region, sharp thermal decomposition behavior, solubility, and durability, which are important factors when used as a recording medium, Among the 7 thalocyanine dyes represented by formula (I), the central metal is vO or TiO,
-Also, those in which the alkyl group is C2 to C6 are particularly preferred.

The basic structure of the Wf-containing optical recording medium containing 7-thalocyanine represented by formula (I) is that a thin film of 7-thalocyanine alone is formed on a substrate. Since it is desirable to write and read from the board side, the board material is glass, I (
Transparent resins such as meth)acrylic resin, polyester resin, polycarnate resin, and epoxy resin can be used.The form of the resin may be a sheet, a sheet, etc., and guide grooves are formed in advance on the surface of the substrate. You can also set it up. An inorganic or polymer layer may be provided as an undercoat layer on the substrate for the purpose of protecting the substrate and improving adhesion. Further, a protective layer made of the same material as the undercoat layer may be provided on the recording layer.

As mentioned above, since the recording material of the present invention has a high reflectance, there is no need to provide a reflective layer. However, on the other hand,
Formula (7) Using talocyanine diluted with a resin binder as the recording layer Since the reflectance can be controlled to be low, in this case, a two-layer structure in which the reflective layer is provided between the substrate and the recording layer is used. In either structure, the recording layer may be provided only on one side of the base material.
It may be provided on both sides, or it may be provided on one side to form a two-air sandwich structure.

(Example) Examples are shown below.

Reference Example As a reference example, a phthalocyaninated nitrile represented by formula (I) was synthesized. The synthesis conditions, yields, and melting points of the alkylthiophthalonitriles of Reference Examples 1 to 3 are shown in Table 1.

(Scheme 1) *1.8-Diazabicyclo(5,4,0)-7-undecene-N,N-dimethylformamide 119 Synthesis example of 4-alkylthiophthalonitrile Thiometal phthalocyanine was synthesized. The synthesis conditions, yields, and elemental analyzes of the tetrakisalkylthiometal phthalocyanines of Reference Examples 4 to 9 are shown in Table 2.

(Scheme 2) (In formula (I), X and Y directly connected to four benzene rings
In each of these, only one is 5R (R represents a straight-chain alkyl group having 1 to 20 carbon atoms), the other is H, and M represents a metal atom. 1 to 10 wt of each of the seven talocyanine compounds obtained in Examples 4 to 9 was dissolved in mochloroform, dichloromethane, benzene, toluene, tetrahydrofuran, or the like.

Example 1 (I) Spin coating (4000 rpm x 15 seconds) on a methyl lyacrylate resin substrate using a 1 wt% chloroform homogeneous solution of tetrakis ethylthiovanadyl phthalocyanine of Reference Example 4 shown in Table 2 of Reference Examples.
Finally, a thin film consisting only of phthalocyanine dye and having a thickness of 80 nm was obtained. This thin film was strong enough not to easily peel off even when rubbed with fingers. The maximum absorption wavelength of this thin film was λmax = 750 (am), and the absorption rate of light at 800 nm was 42 cm. On the other hand, the reflectance of 800 nm light incident on the substrate was 20 cm.

(2) When the TG-DTA curve of tetrakis ethylthiovanadyl phthalocyanine was measured in air,
The decomposition start temperature (DTin) is 305℃, and the decomposition end temperature (DTin) is 305℃.
DTf) is 480℃, TG curve is 2 steps higher,
The M amount reduction rate of 16 degrees in the first stage approximately corresponds to the amount of eliminated substituted ethyl groups. The maximum exothermic temperature associated with the first stage decomposition that appeared on the DTA curve was 385°C, and that of the second stage decomposition was 455°C.
Met. The TG-DTA curve is shown in FIG.

(3) Next, a semiconductor laser beam with a wavelength of 790 nm was applied to the recording medium shown in (I)K from the substrate side while rotating at 600 rpm, with a focusing output of 6 mW and a recording frequency of I MH.
When information was written with z and then the signal was reproduced with the laser condensing output set to 1-, the ratio was 58 dB.

Examples 2 to 6 Regarding the results of the same measurements as in Example 1 for each of the phthalocyanine compounds of Reference Examples 4 to 9 shown in Table 2 of Reference Examples, the film thickness, maximum absorption wavelength, and absorption of light at 800 nm were determined. index and reflectance, thermal decomposition temperature (DTin, DT
f) and the cfi ratio are shown in Table 3 together with the results of Example 1.

[Brief explanation of the drawing]

FIG. 1 is the TG-DTA m line of tetrakisethylthiovanadyl phthalocyanine of Reference Example 4 in Table 2.

Claims (1)

[Claims] 1. In an optical recording system in which recording and reading are performed using a laser beam, a recording medium provided on a substrate has the following formula (I
) An optical recording medium comprising a phthalocyanine compound represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) (In formula (I), only one of X and Y directly connected to the four benzene rings is SR (R is a carbon number of 1 to 20) (represents a straight-chain alkyl group), the others are H, and M represents a metal atom.)