JP2000149327A - Optical disk capable of recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk capable of recording, excellent in high temperature and high humidity resistances, less liable to a change in characteristics with the lapse of time and having high reliability and a long service life. SOLUTION: A light absorbing layer, a silver-base light reflecting layer and a protective layer are successively laminated on a transparent substrate to obtain the objective optical disk capable of recording. The light reflecting layer comprises a silver-base alloy containing at least one metal selected from copper, gallium, aluminum, palladium and rhodium. Preferably the alloy further contains at least one metal selected from tungsten, magnesium and boron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recordable optical disk. For more information, so-called compact disc (CD)
The present invention relates to an optical disk which is compatible with a computer and is suitable for a writable optical disk.

[0002]

2. Description of the Related Art Compact disks have been widely used as audio software, computer game software, and electronic publishing media because of their large recording capacity and high productivity as software packages. However, in order to manufacture a compact disk, a mold for transferring a record on a transparent substrate is required. Due to the cost, when manufacturing about 100 or less disks, the cost per disk is reduced. It will be quite high.

In order to solve this problem, a compact disc having a recordable area that can be directly recorded on the disc, that is, a recordable compact disc, has been developed instead of producing a recording disc via a mold. . Recordable compact discs are recordable and show the same reflectance as a read-only compact disc.
It has the feature that it can be played back on a compact disc player or drive for playback after recording.

This recordable compact disk is usually manufactured by sequentially providing a light absorbing layer made of an organic dye, a light reflecting layer made of a metal, and a protective layer made of an ultraviolet curable resin on a transparent substrate.

[0005]

In a recordable compact disc which has already been put to practical use and is commercially available, the light reflection layer has a high reflectance of 65% or more with respect to the wavelength of the read laser beam and a high corrosion resistance. Although gold and alloys containing gold as a main component are used to obtain it, gold is expensive, which is a major problem in terms of cost.

On the other hand, when a metal such as silver, copper, aluminum or the like, which is inexpensive and has a high reflectance equivalent to that of gold, and an alloy containing them as a main component are used as the light reflecting layer, the light reflecting layer may be corroded. It is difficult to produce a recordable compact disk that is sufficiently reliable in the use environment because the characteristics of the disk such as a decrease in reflectivity and an increase in error tend to change with time.

The present invention solves the above-mentioned conventional problems and uses less expensive metal for the light reflecting layer without deteriorating the life and reliability of the recordable optical disk using expensive gold as the light reflecting layer. Therefore, it is an object of the present invention to provide a low-cost optical disk suitable for a recordable compact disk.

[0008]

As described above, when a metal such as silver, copper, aluminum or the like or an alloy containing these as a main component is used as a light reflecting layer instead of gold having high corrosion resistance, , Because the disc characteristics tend to change with time, such as a decrease in reflectance or an increase in error due to corrosion of the light reflection layer,
The present inventors have made intensive studies on the corrosion mode of silver and a light reflection layer containing silver as a main component, and as a result, the degree of progress of corrosion from the surface of the light reflection layer in contact with the protective layer determines the life of the entire disc. That led to the finding.

Based on this finding, as a result of further study on the prevention of the above-mentioned corrosion, the use of an ultraviolet-curable resin containing a triazine thiol-based compound as the protective layer significantly suppressed the progress of corrosion of the light reflecting layer. Have found that a recordable optical disk having the same disk reliability as that obtained by using gold as the light reflection layer can be obtained,
The present invention has been completed.

That is, the gist of the present invention is to provide a recordable optical disk having a light absorbing layer, a light reflecting layer containing silver or silver as a main component, and a protective layer sequentially laminated on a transparent substrate, wherein the protective layer is triazine thiol. A recordable optical disk comprising a UV-curable resin containing a system compound. Hereinafter, the recordable optical disk of the present invention will be described in detail.

Examples of the material of the transparent substrate used in the present invention include plastics such as polycarbonate, polymethyl methacrylate, and polyolefin; glass; and plastics formed on glass. These transparent substrates generally have a thickness of about 1 to 2 mm and have guide grooves formed spirally on the surface. As a constituent material of the light absorbing layer formed on the transparent substrate, a light absorbing organic dye is suitably used, and specifically, a cyanine dye, a squarylium dye, a pyrylium dye, a triarylamine dye, a metal-containing azo dye, And phthalocyanine dyes. As a method for forming the light absorbing layer, a method is usually employed in which an organic dye is dissolved in an organic solvent and spin-coated on the transparent substrate.

In the present invention, a thin film of silver or an alloy containing silver as a main component is used as the light reflecting layer. When an alloy containing silver as a main component is used as the light reflecting layer, the material is not particularly limited as long as it has a high reflectance of 65% or more with respect to the wavelength of the read laser light, but is preferably copper, gallium, or aluminum. , Palladium, rhodium and the like and silver and two or more alloys are used. Further, a small amount of elements such as tungsten, magnesium, and boron may be added for the purpose of corrosion resistance.

Silver or a metal thin film containing silver as a main component, which is a light reflection layer, is usually formed by a sputtering method or a vacuum evaporation method, and preferably has a thickness of 50 to 200 nm. In the present invention, an ultraviolet curing agent containing a triazinethiol-based compound is coated on the light reflecting layer thus formed, and cured by irradiation with ultraviolet light to form a protective layer.

As the triazinethiol compound, a compound represented by the following general formula [I] is preferable. In the general formula [I], -R represents -SR ¹ or ^{-NR 2 R 3, R 1,} R 2 and R ³ represents a hydrogen atom or a hydrocarbon group. Examples of the hydrocarbon group include an alkyl group, an alkenyl group,
Aryl groups are preferred.

[0015]

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As the ultraviolet curing agent, it is preferable to use an acrylic ultraviolet curing agent, and the triazine thiol compound is usually used in an amount of 0.001 to 0.05% by weight, preferably 0.01 to 0.03% by weight. Melt at the rate of weight%,
It is preferable to coat by a method such as spin coating or screen printing. The thickness of the protective layer can be arbitrarily set, but is preferably about 2 to 20 μm.

[0017]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 As a transparent substrate, a recording groove having a diameter of 120 mm provided with a periodically meandering tracking groove for a recordable compact disc,
A polycarbonate substrate having a thickness of 1.2 mm was used.

The light-absorbing layer is formed by dissolving a metal-containing azo dye represented by the following structural formula at 2.2% by weight (based on the weight of the solvent) in methylcellosolve, filtering, and spin-coating the substrate. A film was formed. After the dye application, drying was performed in an oven at 80 ° C. for 10 minutes to completely evaporate the solvent in the dye layer. The thickness of the dye layer was selected so as to increase the reflectance, and was 120 nm.

[0019]

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Next, a silver layer having a thickness of 100 nm was formed as a light reflecting layer on the light absorbing layer by DC magnetron sputtering in an argon gas. Next, a compound represented by the following structural formula is dissolved in an ultraviolet curing agent SD-318 (manufactured by Dainippon Ink and Chemicals, Inc.) at a ratio of 0.02% by weight, and then spin-coated, and irradiated with ultraviolet light by an ultraviolet irradiation device. And cured to form a protective layer.

[0021]

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The obtained recordable compact disc was subjected to EFM using DDU-1000 (Pulstec).
The signal is recorded, and the temperature is set to 85 ° C and the humidity is set to 85%.
After the high-temperature and high-humidity test for 00 hours, the data was played back with a commercially available CD player and the change in the C1 error was measured. As a result, only a slight increase in the C1 error was observed. The results are shown in Table 1. Example 2 A recordable compact disc was produced in the same manner as in Example 1 except that a 100 nm-thick silver / aluminum alloy (silver: 80 atomic%, aluminum: 20 atomic%) layer was formed as a light reflecting layer. Was.

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in the C1 error was found. The results are shown in Table 1. Example 3 A recordable compact disc was produced in the same manner as in Example 1 except that the ultraviolet curing agent SD-318 used for forming the protective layer contained a compound represented by the following structural formula.

[0024]

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When the obtained disk was tested in the same manner as in Example 1, only a slight increase in the C1 error was found. The results are shown in Table 1. Comparative Example 1 A recordable compact disc was produced in the same manner as in Example 1 except that the ultraviolet curing agent SD-318 used for forming the protective layer was used without containing a triazinethiol-based compound.

When the obtained disk was tested in the same manner as in Example 1, a tremendous increase in C1 error was found. The results are shown in Table 1. Comparative Example 2 A recordable compact disc was produced in the same manner as in Example 2 except that the ultraviolet curing agent SD-318 used for forming the protective layer was used without containing a triazinethiol compound.

When the obtained disk was tested in the same manner as in Example 1, a tremendous increase in C1 error was found. The results are shown in Table 1. Reference Example 3 A recordable compact disc was produced in the same manner as in Comparative Example 1 except that a gold layer having a thickness of 100 nm was formed as a light reflection layer.

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in the C1 error was found. The results are shown in Table 1. Reference Example 4 A recordable compact disc was produced in the same manner as in Example 1 except that a gold layer having a thickness of 100 nm was formed as a light reflection layer.

When the obtained disk was tested in the same manner as in Example 1, only a slight increase in C1 error was found. The results are shown in Table 1.

[0030]

[Table 1]

In Comparative Examples 1 and 2, after the high-temperature and high-humidity test, a large increase in the C1 error due to the corrosion of the light reflecting layer is observed. On the other hand, in Examples 1 to 3, even after the high-temperature and high-humidity test, the increase in the C1 error was small, and the disk reliability was equivalent to that of Reference Examples 3 and 4 using the gold layer as the light reflecting layer. Sex has been obtained.

[0032]

The recordable optical disk of the present invention comprises a light absorbing layer, a light reflecting layer containing silver or silver as a main component, and a protective layer which are sequentially laminated on a transparent substrate, and a triazinethiol compound is formed on the protective layer. By using an ultraviolet curable resin containing, the corrosion resistance of the light reflection layer is greatly improved, and the disk reliability is equivalent to that when gold is used as the light reflection layer. Therefore, a highly reliable and long-life recordable optical disk having excellent resistance to high temperature and high humidity and little change in characteristics over time can be manufactured at low cost.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Kuriwada 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Research Institute (72) Inventor Satoru Imamura 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Mitsubishi Chemical Research Institute Yokohama Research Laboratory

Claims (2)

[Claims] 1. A recordable optical disc comprising a light absorbing layer, a light reflecting layer mainly composed of silver, and a protective layer sequentially laminated on a transparent substrate, wherein the light reflecting layer is mainly composed of silver, copper,
A recordable optical disk comprising a binary alloy containing at least one metal selected from gallium, aluminum, palladium, and rhodium and silver. 2. The recordable optical disk according to claim 1, wherein the light reflection layer further comprises an alloy containing at least one metal selected from tungsten, magnesium, and boron.