JPH02206588A - Optical recording medium - Google Patents

Abstract

PURPOSE:To minimize a deterioration in regeneration by a method wherein an optical recording medium is formed by laminating a recording film layer containing an organic dye, such as triphenylmethane, having a melting point, a sublimating temperature, or a decomposition temperature of 200 deg.C or more on a substrate. CONSTITUTION:A recording film layer-forming coating liquid is prepared by dissolving an organic dye having a melting point, a sublimating temperature, or a decomposition temperature of 200 deg.C or more in an organic solvent. As the organic dye, triphenylmethane, polymethine, quinone, squarylium, indophenol, azulenium, indoaniline, pyrylium, thiopyrylium, aminium, cyanine, phthalocyanine, naphthalocyanine, or other dyes are used. This coating liquid is applied on a substrate, such as cellophane, synthetic resin, and glass, and dried to form a recording film. Thus, an optical recording medium is produced. In addition, the recording film preferably has a reflectance of 20% or more.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to optical recording media.

(Conventional technology) In recent years, semiconductor lasers have become increasingly smaller and cheaper.
It is popular as a light source for various recording devices.

Research is being conducted on various optical recording media. Among these optical recording media, it is easy to handle and record.

It is said to be relatively easy to reproduce and has a good shelf life.

Recording is performed by forming pits due to the thermal effect of laser light. 2. Description of the Related Art Optical recording media, so-called heat mode perforated optical recording media, have been developed.

The principle is as follows.

First, recording information is recorded by irradiating the recording film layer with a laser beam modulated with an information signal to be recorded. A hole called a pit is formed.

When reproducing this data, an information signal is obtained by irradiating a continuous laser beam that is weaker than that used during recording and detecting the difference in optical density, mainly the difference in reflectance, between the pit-formed area and the non-pit-formed area. It is something. For this reason, it is known to use, in the recording layer, an organic dye that absorbs the recording laser beam and exhibits one reflection at the wavelength of the laser beam during recording and reproduction.

(Problems to be Solved by the Invention) The organic substance used in the recording film layer of a heat mode optical recording medium needs to absorb the laser light used for recording. Generally, when such a heat mode optical recording medium is used, the light sources for recording laser light and reproduction laser light are usually the same in order to simplify and downsize the mechanism. Although the reproduction laser beam is made weaker than the recording laser beam, since it has the same wavelength, it is absorbed by the organic substance of the recording film layer. As a result, even during playback.

Heat is generated in the recording film layer irradiated with the reproduction laser beam. When reproduction is repeated, the recording film layer may gradually melt due to this heat, deform the bits due to sublimation and decomposition, and change the quality of the recording film layer itself. If such a phenomenon occurs, , deterioration or loss of recorded content, that is, reproduction deterioration occurs.

In order to prevent this reproduction deterioration, it is easy to think of reducing the reproduction laser light output to a very low level to reduce the heat generated in the recording film layer. However, in such cases, the reflected light from the recording film layer also becomes very weak, making it susceptible to interference from external light and electromagnetic noise entering the photoelectric conversion section, which increases the readout error rate. .

It is disadvantageous. In order to reduce the reading error rate of records, lenses with large apertures and light-receiving elements with large photoelectric conversion capabilities must be used, resulting in larger and more complex mechanical parts.
There are problems with track followability and cost.

(l! Means for Solving the Problem) As a result of intensive studies to solve the above problem, the present inventors have found that the organic dye used in the recording film layer of an optical recording medium has a negative melting point, sublimation point or It has been found that when the decomposition point is 200° C. or higher, regeneration deterioration is reduced.

That is, 9 the present invention has a melting point, sublimation point or decomposition point of 200°C.
The present invention relates to an optical recording medium having a recording film layer containing the above organic dye on a substrate.

It is necessary that the melting point, sublimation point or decomposition point is 200°C or higher. The melting point, sublimation point, or decomposition point is preferably 230°C or higher from the viewpoint of increasing the reproducible life.9 If the laser beam during regeneration must be strengthened due to mechanical system reasons, the melting point of the organic dye, Sublimation point or decomposition point is 25
More preferably, the temperature is 0°C or higher.

Here, the melting point, sublimation point or decomposition point is measured using a melting point measuring device, DE
It can be measured by a conventional method using C.

The melting point and sublimation point change depending on the temperature. In other words, solids change into liquids and solids change into gases, but the molecular structure of organic dyes remains unchanged before and after the changes. On the other hand, at one decomposition point, the molecular structure of the organic dye changes before and after that temperature, whether or not the form changes at that temperature.

Examples of organic dyes used in the recording film layer include triphenylmethanes, polymethines, quinones, squaliriums, and indophenols.

These include azuleniums, indoanilines, pyryliums, thiopyryliums, aminiums, cyanines, phthalocyanines, and suphthalocyanines. These dyes can fulfill the intended purpose if their melting point, sublimation point, or decomposition point is 200°C or higher, but among these organic dyes, phthalocyanines and naphthalocyanines are preferable. It is. Compounds with a phthalocyanine or naphthalocyanine skeleton in their structure are chemically stable and are less susceptible to deterioration due to light or oxidation. For this reason, it can be seen in quinones and cyanines.

It is excellent in that it does not impair its optical properties due to coloring due to oxidation or photobleaching. I also especially like tL Inoke,
Naphthalocyanines have light absorption and reflection wavelengths in the near-infrared region compared to phthalocyanines, so semiconductor lasers can be used as recording and reproducing laser light sources. For these reasons, an optical recording medium with excellent storage stability can be obtained, and a device equipped with the same can be easily made smaller and lighter.

The recording film layer is formed by coating an organic dye on a substrate or by vapor deposition.

Alternatively, a combination or mixture of a resin and an organic dye may be applied and formed on the substrate.

It is preferable that the reflectance of the recording film layer is 20% or more; if the reflectance is lower than this, the reflected light during reading is weak;
Records tend to be difficult to read.

Examples of materials for the substrate include cellophane, polyester resin, silicone resin, and acrylic resin.

Polycarbonate resin, polyvinyl chloride resin, polyacetal resin, nylon resin, epoxy resin.

Phenolic resin, melamine resin, vinyl acetate resin.

Examples include, but are not limited to, glass and ceramics.

Examples of resins to be combined with or mixed with organic dyes include acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyacetal resin, nylon resin, epoxy resin,
Examples include, but are not limited to, phenol resin, melamine resin, vinyl acetate resin, and silicone resin. Application methods include spin code method, dipping method,
Examples include, but are not limited to, brush coating methods, spray coating methods, and the like. Further, a leveling agent, an antioxidant, an ultraviolet absorber, a plasticizer, etc. can be added to the recording layer film as necessary.

The recording film layer formed on the substrate has various properties such as improving adhesion between the recording film layer and the substrate, preventing the substrate from deteriorating due to a solvent when forming the recording film layer by a coating method, etc. One or more layers may be formed for this purpose. Furthermore, one or more layers may be formed on the recording film layer for the purpose of adjusting the protection 1 reflectance of the recording film layer.

In the optical recording medium thus formed, the writing or reading laser beam may be irradiated from the recording film layer side or the substrate side. however.

When irradiating a laser beam from the substrate side, it is obvious that the substrate needs to be transparent to the laser beam.

Note that this optical recording medium may have a structure in which the recording film layer is placed inside and a lid is placed on that side to prevent dust from adhering to the recording film layer, or an air sandwich structure is used.

The laser used for writing and reading records.

Examples include, but are not limited to, semiconductor lasers, krypton lasers, argon lasers, helium neon lasers, and dye lasers. however.

The maximum laser output may be 5 mW or more, and the repetitive switching frequency of the laser beam may be 1 MHz or more.

This is desirable in that it can be matched with the standards applied to current compact discs, etc.

(Example) The invention will be explained by examples.

Example 1 Organic dye A shown in Table 1 was used and dissolved in cyclohexanone (Wako Pure Chemical Industries, Ltd., 2% grade IK) at a weight percentage of 9%.
A 3% solution was prepared. Using 20 cc of this solution, it was applied by a spin code method onto an optical disk substrate made of polymethyl methacrylate resin on which groups had been formed in advance, to form a recording film layer with a film thickness of 800λ. , as an optical recording medium.

Recording and reproduction were performed on this optical recording medium using an optical recording medium measuring device (hereinafter abbreviated as evaluation device). Figure 1 shows an overview of the evaluation device. For recording, a semiconductor laser with an output of 8 mW and an oscillation wavelength of 830 was used. Laser spot diameter on recording film surface is 0
．． Recording was performed by irradiating the entire circumference of one track with a modulated laser beam having a waveform shown in FIG. Next, reproduction was performed by continuously irradiating the recorded track with a laser beam. In the reproduced signal at this time. FIG. 3 shows the relationship between the ratio of the voltage level of the frequency component of the recording signal to the voltage level of the other frequency components of the recording signal (hereinafter abbreviated as CN ratio) and the number of reproductions. Note that the output of the laser beam for reproduction at this time is also shown in the figure (numerical value with unit of mW).

Example 2 The organic dye used was changed to the organic dye B in Table 1.
An experiment was conducted in the same manner as in Example 1.

The results are shown in Figure 4.

Example 3 Using the organic dye C in Table 1 as the organic dye, a film with a thickness of 70 mm was deposited by vapor deposition on an optical disk substrate (1.2 ml thick) made of a polymethyl methacrylate resin on which groups had been formed in advance.
The same experiment as in Example 1 was conducted except that a 0A recording film layer was formed and an optical recording medium was used. The results are shown in Figure 5.

Example 4 Except that the organic dye was changed to organic dye D in Table 1.

An experiment was conducted in the same manner as in Example 1. The results are shown in FIG.

Optical recording media using organic dyes with melting points, sublimation points, or decomposition points of 200°C or higher showed no playback deterioration up to a laser beam power of 1.1 mW, and were found to be excellent optical recording media. .

(Effects of the Invention) The optical recording medium of the present invention is excellent in that there is little reproduction deterioration.

[Brief explanation of the drawing]

FIG. 1 shows an outline of an optical information recording medium evaluation apparatus. FIG. 2 shows an outline of an optical information recording medium evaluation apparatus used for recording. Graphs showing waveforms of modulated laser light, and FIGS. 3 to 6Fi. 3 is a graph showing the relationship between the CN ratio and the number of reproductions in Examples 1 to 4, respectively. Explanation of symbols 1...Spectrum analyzer 2...Low noise wideband amplifier 3...Reproduction signal 4...Head drive signal 5...Head control circuit 6...Disk rotation speed control circuit 7... Laser light signal source 8... Laser diode 9... Detection section 10... Substrate 11...
・Recording film layer 12...Recording laser beam 13...
・Regenerated laser beam 14...Reflected light agent Patent attorney Kunihiko Wakabayashi Figure 2 Number of views (X/θ5[]) Figure Regenerated teaching (X705 times) Figure Regenerated teaching (X705 times) ) No. Δ

Claims (1)

[Claims] 1. An optical recording medium having, on a substrate, a recording film layer containing an organic dye having a melting point, sublimation point or decomposition point of 200° C. or higher. 2. The organic pigment is triphenylmethanes, polymethines, quinones, squarylium pigments, indophenols, azuleniums, indoanilines, pyryliums, thiopyryliums, aminiums, cyanines, phthalocyanines, or naphthalocyanines. The optical recording medium according to claim 1. 3. The optical recording medium according to claim 1, wherein the organic dye is a phthalocyanine or a naphthalocyanine.