JPH07105575A - Optical recording medium - Google Patents

Abstract

PURPOSE:To produce a high reliability optical recording medium excellent in resistance to high temp. and humidity at a low cost. CONSTITUTION:A light absorbing layer contg. an org. coloring material, a light reflecting layer and a protective layer are successively laminated on a transparent substrate. The light reflecting layer is based on silver and contains 0.1-5 atomic % at least one kind of element selected from among Rh, Pd, Pt, Ti, Mo, Ta, Zr, V and W.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical recording medium.
More specifically, the present invention relates to a writable optical disc that is compatible with a so-called compact disc (CD).

[0002]

2. Description of the Related Art Compact discs are 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 produce a compact disc, a die for transferring the recording is required on the transparent substrate, and when producing about 100 discs or less, the cost per die is required for producing the compact disc. The cost will be considerably higher.

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 through a mold. ing. A recordable compact disc is recordable and has the same reflectivity as a read-only compact disc, so that it can be played back by a read-only compact disc player or drive after recording.

This recordable compact disc 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 been put to practical use and is on the market, in order to obtain a high reflectance of 65% or more and a high corrosion resistance with respect to the wavelength of a read laser beam, a light reflection is required. Although gold and an alloy containing gold as the main component are used for the layer, the cost is a major problem because gold is expensive.

On the other hand, silver, which is inexpensive and has a high reflectance comparable to that of gold,
When a metal such as copper or aluminum and an alloy containing them as a main component are used as the light reflecting layer, a change over time in disk characteristics such as a decrease in reflectance and an increase in error due to corrosion of the light reflecting layer is likely to occur. It was difficult to produce a recordable compact disc with sufficient reliability for the usage environment.

On the other hand, it has been proposed to use a corrosion resistant alloy such as stainless steel in order to improve the corrosion resistance, but most of them have a large amount of additive components necessary for exhibiting the corrosion resistance. , The reflectance of the alloy will be low. Further, since the anticorrosion mechanism forms a passivation film on the surface of the alloy, a decrease in reflectance is unavoidable when used as a reflection film.

[0008]

The present invention solves the above-mentioned problems of the prior art, and maintains the life and reliability equivalent to that of a recordable optical disc using gold having a high corrosion resistance as a light reflecting layer, and An object of the present invention is to provide a low-cost optical disc suitable for a recordable compact disc by making it possible to use an inexpensive metal as a light reflecting layer.

Usually, a recordable compact disc is
Since the protective layer is formed on the light reflecting layer, the light reflecting layer is not exposed to the extreme corrosive environment of the metal. Therefore, it is meaningless to impart durability to an acidic / alkaline or oxidative / reducing substance more than necessary, and it is possible to reduce the amount of added element. Therefore, in order to overcome the above-mentioned problems, the present inventors have diligently studied a combination of a high-reflectance elemental metal and a trace additive element that effectively imparts corrosion resistance thereto, and as a result, rhodium containing silver as a main component High reflectivity by using an alloy containing 0.1 to 5 atom% of at least one element selected from the group consisting of palladium, platinum, titanium, molybdenum, tantalum, zirconium, vanadium and tungsten in the light reflecting layer. It was found that an optical recording medium having a high reflectance and a small decrease in reflectance with time can be obtained, and the present invention has been completed.

That is, the gist of the present invention is to provide an optical recording medium in which a light absorbing layer containing an organic dye, a light reflecting layer and a protective layer are sequentially laminated on a transparent substrate, and the light reflecting layer contains silver as a main component. 0.1 to at least one element selected from the group consisting of rhodium, palladium, platinum, titanium, molybdenum, tantalum, zirconium, vanadium and tungsten.
The optical recording medium is characterized by containing 5 atomic%.

The optical recording medium of the present invention will be described in detail below. The optical recording medium of the present invention comprises a transparent substrate, a light absorbing layer, a silver or light reflecting layer containing silver as a main component, and a protective layer, which are sequentially laminated. As the material of the transparent substrate,
Examples thereof include plastics such as polycarbonate, polymethylmethacrylate, and amorphous polyolefin, or glass. As these transparent substrates, those having a thickness of about 1 to 2 mm and spiral guide grooves are used.

Materials for the light absorbing layer include organic dyes such as cyanine dyes, squarylium dyes, croconium dyes, azurenium dyes, triarylamine dyes, anthraquinone dyes, metal-containing azo dyes, and dithiol metal complex salt dyes. Indoaniline metal complex dyes, phthalocyanine dyes, naphthalocyanine dyes, intermolecular CT dyes, and the like are preferable, and they are used alone or in a mixture, or in the form of addition of a deterioration inhibitor, a binder, and the like.

As a method for forming a light absorbing layer containing an organic dye, a method in which an organic dye is dissolved in an organic solvent and spin-coated directly or through another layer on a transparent substrate is preferably used, and phthalocyanine is used. A vapor deposition method can also be used for a dye having a sublimation property such as a system dye. The film thickness of the light absorption layer is appropriately selected according to the wavelength to be used, the optical constant of the reflection layer, the material of the light absorption layer, etc., in consideration of the recording sensitivity to the power of recording light such as laser light, the performance coefficient, and the like. Usually, it is in the range of 100Å to 5 μm. The light absorption layer may be provided on both sides of the transparent substrate or may be provided on one side.

The light reflection layer is a metal thin film of an alloy containing silver as a main component and containing at least one element selected from the group consisting of rhodium, palladium, platinum, titanium, molybdenum, tantalum, zirconium, vanadium and tungsten. To use. This improves the corrosion resistance as compared with the case where silver is used alone. Rhodium is most effective as a component of the additive element, and then palladium, platinum, and titanium are effective, and an appropriate one can be selected from the above additive elements depending on the material of the adjacent light absorption layer. . The total amount of the additive elements is preferably 0.1 to 5 atom%, more preferably 0.1 to 3 atom%,
The composition can be easily confirmed by a fluorescent X-ray analysis method. The light-reflecting layer is formed on the light-absorbing layer directly or through another layer by a sputtering method or a vacuum deposition method.
It is preferable to use a polycrystalline film having a film thickness of 200 nm.

If necessary, the surface of the light reflecting layer may be surface-treated with a surface-treating agent such as a triazine thiol compound. As the protective layer formed on the light-reflecting layer, it is preferable to use a hard material such as an acrylic UV-curable resin. Usually, a spin coating method is applied directly on the light-reflecting layer or through another layer. Thickness 2 to 20 μm
And then cured by irradiation with ultraviolet rays.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative 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 meandering tracking groove for a compact recordable disk, having a diameter of 120 mm,
A polycarbonate substrate having a thickness of 1.2 mm was used.

The light-absorbing layer was prepared by dissolving the metal-containing azo dye represented by the structural formula in methyl cellosolve at 2.2% by weight (weight with respect to the solvent), filtering the solution, and spin-coating it on the substrate. Filmed After applying the dye layer, the solvent in the dye layer is completely evaporated in an oven at 80 ° C. for 10 hours.
It was dried for a minute. The film thickness of the dye layer was selected to have a high reflectance and was set to 120 nm.

[0018]

[Chemical 1]

Then, as a light reflecting layer on the light absorbing layer,
100 nm thick silver-rhodium alloy (rhodium content:
2 atomic%) was formed by DC magnetron sputtering in argon gas. Further, a UV-curing agent SD-318 (manufactured by Dainippon Ink and Chemicals, Inc.) was applied on the light-reflecting layer by a spin coating method to a thickness of 3 μm, and was cured by irradiating it with ultraviolet rays by an ultraviolet irradiating device to form a protective layer. Was formed.

With respect to the obtained recordable compact disc, an EFM signal was recorded by an optical disc evaluation device DDU-1000 (manufactured by Pulstec Co.) and subjected to a high temperature and high humidity test for 500 hours under the conditions of temperature 85 ° C. and humidity 85%. When changes in reflectance and C1 error (average value of the number of error occurrences per second) before and after were measured, a slight decrease in reflectance and an increase in C1 error were observed. The results are shown in Table-1. Example 2 Same as Example 1 except that a silver-titanium-molybdenum alloy having a thickness of 100 nm (titanium content: 1.8 at%, molybdenum content: 0.2 at%) was used as the light reflecting layer. Then, a recordable compact disc was manufactured.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. The results are shown in Table-1. Example 3 Except that a 100 nm thick silver-palladium-tungsten alloy (palladium content: 2.8 atom%, tungsten content: 0.2 atom%) was used as the light reflecting layer.
A recordable compact disc was manufactured in the same manner as in Example 1.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1
Only an increase in error was seen. The results are shown in Table-1. Example 4 A silver-platinum-molybdenum alloy having a thickness of 100 nm as a light reflection layer (platinum content: 4.7 atomic%, molybdenum content:
A recordable compact disc was prepared in the same manner as in Example 1 except that 0.3 atom%) was used.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. The results are shown in Table-1. Example 5 A recordable compact disc was produced in the same manner as in Example 1 except that a 100 nm thick silver-titanium alloy (titanium content: 1.1 atom%) was used as the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. The results are shown in Table-1. Example 6 A recordable compact disc was prepared in the same manner as in Example 1 except that a silver-tantalum alloy (tantalum content: 0.8 atom%) having a thickness of 100 nm was used as the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1
Only an increase in error was seen. The results are shown in Table-1. Example 7 A cyanine dye represented by the structural formula was used as a light absorbing layer, and a silver-rhodium-tantalum alloy having a thickness of 100 nm was used as a light reflecting layer (rhodium content: 1.5 atomic%, tantalum content: 0.5). Example 1 except that (atomic%) was used.
A recordable compact disc was prepared in the same manner as in.

[0026]

[Chemical 2]

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. The results are shown in Table-1. Example 8 The same as Example 3 except that a 100 nm thick silver-palladium-zirconium alloy (palladium content: 3.5 atom%, zirconium content 0.5 atom%) was used as the light reflection layer. A recordable compact disc was manufactured.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. The results are shown in Table-1. Example 9 Same as Example 3 except that a 100 nm thick silver-titanium-vanadium alloy (titanium content: 1.2 atom%, vanadium content: 0.1 atom%) was used as the light reflecting layer. Then, a recordable compact disc was manufactured.

When the obtained disk was tested in the same manner as in Example 1, a slight decrease in reflectance and C1 were observed.
Only an increase in error was seen. 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 silver (purity 99.99%) was used for the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, a decrease in reflectance and an enormous increase in C1 error were observed. The results are shown in Table-1. Comparative Example 2 A recordable compact disc was produced in the same manner as in Example 3 except that silver (purity 99.99%) was used for the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, the reflectance was less than 65%, and a huge increase in C1 error was observed. The results are shown in Table-1. Comparative Example 3 A recordable compact disc was prepared in the same manner as in Example 1 except that a 100 nm thick silver-rhodium alloy (rhodium content: 5.5 atom%) was used as the light reflecting layer.

When the obtained disk was tested in the same manner as in Example 1, both the reflectance and the C1 error hardly changed, but the reflectance was less than 65% and the C
The characteristics required for D compatibility were not satisfied. The results are shown in Table-1.

[0033]

[Table 1] The following is clear from Table-1.

In Comparative Examples 1 and 2, after the high temperature and high humidity test, the reflectance was lowered due to the corrosion of the light reflecting layer and a large amount of C1.
An increase in errors is seen. On the other hand, in Examples 1 to 3 to which the present invention is applied, the decrease in reflectance and the increase in C1 error are small even after the high temperature and high humidity test. On the other hand, when rhodium is added in an amount of more than 5 atomic%, the decrease in reflectance and the increase in C1 error are suppressed, but the reflectance required for CD compatibility is 65%.
You can see that it has not reached.

[0035]

Industrial Applicability According to the present invention, a highly reliable optical recording medium excellent in high temperature and high humidity resistance can be produced at low cost, and is industrially very useful. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Kuriwada 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd.

Claims (1)

[Claims] 1. An optical recording medium in which a light absorbing layer containing an organic dye, a light reflecting layer and a protective layer are sequentially laminated on a transparent substrate, wherein the light reflecting layer contains silver as a main component and rhodium, palladium or platinum. An optical recording medium containing 0.1 to 5 atomic% of at least one element selected from the group consisting of titanium, molybdenum, tantalum, zirconium, vanadium and tungsten.