JPH0292683A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain durability, oxidation resistance and to record with high contrast by forming a recording film made of a thin alloy film containing noble metal element and chalcogen on a nitrocellulose layer made of nitrocellulose or its derivative formed on a substrate. CONSTITUTION:A recording film made of a thin alloy film containing noble metal element and chalcogen is formed on a nitrocellulose layer made of nitrocellulose or its derivative formed on a substrate. The content of the noble metal element of the recording film is 0.1 to 90% by atomic percentage, and the substrate formed out of the recording film adheres to the whole surface of the substrate material with adhesive. For example, when information is recorded by a laser light, the thin film layer absorbs a light to heat the cellulose layer. Then, the cellulose layer serves as an initiator to deform the thin film layer, thereby forming bits, etc. and causing recording. Accordingly, the boundary of bits is clarified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium on which information is recorded and reproduced by irradiation with laser light.

[Prior Art] Optical recording media that record and reproduce information using laser light have recently become more popular due to improvements in basic technologies such as semiconductor lasers, recording materials, and film formation methods, as well as the ability to perform WIk recording. The path to practical application is rapidly opening. Recording methods for the above-mentioned optical recording medium include (1) deforming the recording film to form pits or bubbles, and (2) changing optical properties such as reflectance of the recording film using thermal energy from laser beam irradiation. Methods to change this have been proposed.

On the other hand, the structure of optical recording media is (a) an air sandwich type in which only a part of the substrate, such as the inner and outer periphery, is bonded with adhesive, and (+1) the entire surface of the substrate is bonded with adhesive. There are also fully laminated types.

Conventional recording materials used in the recording method (1) above include those containing chalcogens such as Te, Se, and S as main components. However, many chalcogens are mechanically unstable, and recording films containing chalcogen as a main component tend to crack in a high-humidity atmosphere. Various improvements have been made to solve this problem, including P in chalcogen.
b, 5bTechniques for improving the film quality of recording films by adding SSn, Ge, etc. were disclosed, for example, in Japanese Patent Publication No. 59-35356.
No., Special Publication No. 57-45'676, Special Publication No. 57-791
No. 9, Japanese Patent Publication No. 15483-1983, and Japanese Patent Application Publication No. 1983-15483.
No. 66996 and the like.

[Problem to be solved by the invention] However, in the conventional technology of adding elements such as Pb,
There is a problem in that the addition of the above elements reduces the oxidation resistance of the recording film.

By the way, in the case of the recording method (1) above, if the optical recording medium has the structure (b) above, in which the entire surface of the substrate is bonded via an adhesive, the adhesive layer becomes a major hindrance to changes in the shape of the recording film. Therefore, there is a problem in that the above-mentioned conventional recording materials either cannot record at all, or even if they can record, a very large recording power is required.

This invention was made in view of the above problems, and includes a recording film formed on a substrate, which strongly absorbs light in a predetermined wavelength range.
Optical recording media in which data is written by melting and removing the recording film and deforming it with the light and forming bits on the recording film have good recording and reproducing characteristics, and have good durability against external mechanical forces. The objective is to provide an optical recording medium with excellent stability such as oxidation resistance. In particular, even when the substrate is bonded to the entire surface of the recording film via a protective layer made of adhesive,
We are trying to provide an optical recording medium that can record with high contrast.

[Means for Solving the Problem] In order to achieve the above object, in the optical recording medium of claim (1) of this application, the recording film is an alloy thin film containing a noble metal element and chalcogen; It is formed on a nitrocellulose layer made of nitrocellulose or a derivative thereof provided on a substrate. In the above optical recording medium, the alloy thin film layer absorbs light (for example, semiconductor laser light),
Heat the nitrocellulose layer. Then, the nitrocellulose m layer acts as a detonator and deforms the alloy thin film layer to form bits and the like, and recording is performed. Therefore, conventional Te
Unlike a recording film that melts and then spreads due to surface tension to form bits, the boundaries of the bits become clear.

In the invention of claim (2), in claim (1), the content of the noble metal element in the recording film is 0.1% or more and 95% or less in terms of atomic percent.

In claim (3), the nitrocellulose-induced M of claim (1)
The entire surface of the substrate and the substrate on which the layer and recording film are formed are bonded together with an adhesive.

As the nitrocellulose derivative in this invention, a derivative in which the hydrogen atom of the hydroxyl group of nitrocellulose is replaced with some other group is used. Cellulose derivatives that do not contain nitrate esters, such as cellulose acetate, are not used. The degree of nitrification of the above nitrocellulose layer is 1% or more1
It is preferably in the range of 3% or less. If the amount exceeds this range and is too small, the effect as a detonator will be diminished, and if it is too large, the thermal stability of the nitrocellulose m-layer will decrease.

The content of the noble metal element contained in the recording film may be 0.1% or more and 95% or less in terms of atomic percent.

If the amount exceeds the above range, the sensitivity during recording will decrease, and if it is too small, the durability of the recording film against external mechanical forces will decrease. In addition to noble metal elements and chalcogen, the recording film contains B1
1Pb, and! It may contain an element of the 1st grade. Especially B
Adding i improves the shape of the bit and further improves the oxidation resistance of chalcogens such as Te.

As claimed in claim (3), the optical recording medium of the present application has a sufficiently high explosive power due to the nitrocellulose layer even when the base material is bonded to the entire surface of the recording film via an adhesive that serves as a protective layer. It maintains recording sensitivity and enables recording with high contrast. As for the above-mentioned adhesives, urethane-based, acrylic-based, and silicone-based adhesives are particularly preferable in terms of writing sensitivity. Phenol-based and melamine-based adhesives are so hard that they either cannot record at all or require high power for recording. Undesirable.

In the present invention, gold or platinum is exemplified as the most preferable noble metal element, but platinum group elements can also be exemplified. Further, in the present invention, examples of chalcogen include selenium and tellurium, and selenium is particularly preferred because it has a large stabilizing effect. Each of these elements may be used alone or in combination in an amount within a predetermined range. Representative combinations of elements in the present invention include Pt-Se-Bi system, Pt-Te-S
An example is the e-series.

In an optical recording medium, the reflectance before recording when a laser beam is incident is usually in the range of 5 to 60%.

If the reflectance is too low, tracking cannot be performed sufficiently during recording and reproduction, making stable recording and reproduction difficult. On the other hand, if it is too high, it will not be able to absorb enough light and recording will not be possible at all, or high power will be required for recording. It is particularly desirable to set the reflectance before recording in the range of 10 to 50%. In order for the above-mentioned alloy thin film to have such a reflectance, it generally has a film thickness of 5 to 200n+i, although it varies depending on the element composition.

In the present invention, the method for forming the recording film is not particularly limited, and existing film forming methods such as sputtering, vacuum evaporation, and ion blating can be used. For example, when forming a film by sputtering, a film with a desired composition can be obtained by controlling the power applied to targets of each constituent element, an alloy target between them, or a composite target.

As the substrate and the base material, for example, glass, polyester resin, polyolefin resin, polyamide resin, polycarbonate resin, polymethacrylic resin, etc. can be used. The substrate or base material on the side irradiated with the laser light must be sufficiently transparent to transmit the laser light, but the other substrate or base material may be opaque. The shape of the substrate and base material may be circular, rectangular, etc., or may be disk-shaped, card-shaped, etc.

The substrate may have irregularities such as guide grooves for tracking and the like.

The wavelength of the laser beam used for recording etc. is not particularly limited, but one of 11000 nm or less is suitable for use. Therefore, with current semiconductor lasers, the wavelength is 75
Those in the 0 to 850 nm region are effectively used. In this case, the power used during recording is generally in the range of about 1 to 15 mW.

The present invention will be explained in more detail with reference to Examples below.

[Example 1] A card-shaped transparent substrate made of polycarbonate having land portions serving as recording portions and group portions serving as track guide grooves was molded by a hot press method.

A film obtained by dissolving nitrocellulose with a degree of nitrification of 12% in an ethanol/ether solution was formed on the above substrate by a spin cord method. Next, on top of this nitrocellulose layer, pt%
A recording film made of an alloy thin film of Se and Bi was formed by sputtering. The film forming conditions are shown below.

First, the inside of the chamber was evacuated, and then Ar gas was introduced, and the gas pressure was set at 5×1.0 −3 Torr. In terms of atomic ratio, Ses. Baa. By applying high frequency power to a Pt alloy target and direct current power to a Pt sputtering target, a Pt-T-
A 5e-Bi alloy thin film was formed. ES the above alloy thin film
When the composition was analyzed by CA, the atomic ratio was Pt7o (Se
,. B140) '10. A card-shaped optical recording medium was prepared by bonding the transparent substrate on which the recording film was formed and a white polycarbonate plate using a urethane adhesive.

As a result of evaluating the recording and reproducing characteristics of this card-shaped optical recording medium, the reflectance before recording was 45%, while the reflectance after recording was 15%, and high contrast recording was possible. An accelerated deterioration test was conducted under the condition that the optical recording medium was held at 75 ° C 185% R) for 1000 hours,
Archival life and archival life were measured, but recording and reproducing characteristics did not deteriorate. In addition, a mechanical durability test of the recording film was conducted by subjecting the optical recording medium to bending, twisting, etc., but no cracks were generated and the recording characteristics were not affected.

[Example 2] Nitrocellulose with a degree of nitrification of 12% was coated with ethanol on a disc-shaped polycarbonate transparent circular substrate having land portions as recording portions and group portions as track guide grooves.
A film was formed using a solution dissolved in an ether solution using a spin code method. Next, on top of this nitrocellulose layer, Pt, Te
A recording film consisting of an alloy thin film of , and Se was formed by a sputtering method. The film forming conditions are shown below. First, the inside of the chamber is evacuated, and then ^r gas is introduced.
Gas pressure was set at 5x 10-'Torr. Tea in atomic ratio. Set.

A binary spat alloy thin film was formed by applying high frequency power to the alloy target and applying DC power to the PT target. When the composition of the alloy thin film was analyzed by ESCA, it was found to be Pt5s (TeaoSeto)is in terms of atomic ratio. The evaluation results of the recording and reproducing characteristics of the disc-shaped optical recording medium manufactured by the above method showed that the maximum CNR was 50 dB, and from 4 mW to 4
Writing was possible at 5 dB. An accelerated deterioration test was performed on the above optical recording medium under conditions of holding it at 75° C. and 85% RH for 1000 hours, and the archival life and shelf life were measured, but the characteristics did not deteriorate.

[Effects of the Invention] As explained above, according to the present invention, in an optical recording medium in which information is recorded by deforming the recording film by irradiation with light, a nitrocellulose-based 11ff1 layer, a noble metal element and a chalcogen are combined. Since a recording film made of an alloy thin film containing . In particular, it is preferable to set the content of the noble metal element within the range of claim (2), as this increases the recording sensitivity and the above-mentioned durability.

The optical recording medium of this application allows recording with high contrast even when the substrate and any base material are bonded together over the entire surface with an adhesive. In addition, since it has high durability against external mechanical forces, the present invention provides a fully laminated optical card with good recording and reproducing characteristics.

Patent applicant RiRashi Co., Ltd.

Claims (3)

[Claims] (1) An optical recording medium that records information by deforming a recording film by irradiating it with light, the recording film being an alloy thin film containing a noble metal element and chalcogen, and the recording film is provided on a substrate. An optical recording medium characterized in that the optical recording medium is formed on a nitrocellulose layer made of nitrocellulose or a derivative thereof. (2) The optical recording medium according to claim 1, wherein the content of the noble metal element in the recording film is 0.1% or more and 95% or less in terms of atomic percent. (3) Claim 1, wherein the substrate on which the recording film is formed and the entire surface of the base material are bonded together with an adhesive.
Or the optical recording medium according to 2.