JPS63197043A - optical disc - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical disc that records, reproduces, and erases information using a laser beam, and is particularly suitable for suppressing corrosion of an information recording medium. Regarding structure.

[Prior Art] In recent years, reversible optical disks that have high density, large capacity, and are capable of random access have been attracting attention. Reversible optical disks can be broadly classified into two types: 1) those that utilize phase change, and 2) those that utilize magneto-optic effects. Various companies are considering using plastic substrates to lower the cost and mass produce reversible optical discs. Further, a resin layer may also be present in the optical disc medium. These polymer materials contain water, by-products during material synthesis, solvents, etc. Therefore, prior to disk production, the resin substrate and resin thin film are vacuum baked at 80 to 100°C. However, with this method, no particular problem occurs immediately after the disc is created, but as time passes after the disc is created, the information recording film is corroded by the water absorbed by the resin and the impurities remaining in the resin, causing the disc characteristics to deteriorate significantly. There was a problem with the decline. JP-A-57-181447 can be mentioned as one of the measures to solve this problem. However, this only physically blocked the interface between the recording film and the substrate.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not give enough consideration to the corrosion of the recording medium due to water or impurity components that diffuse from the resin in the substrate or disk structure, especially the diffusion of 02°HxO in the protective film. As a result, there was a problem in that the disk life span was shortened due to changes in disk characteristics over time.

An object of the present invention is to provide a long-life reversible optical disk that suppresses deterioration of disk characteristics due to corrosion of a recording film caused by a resin substrate or a resin layer.

[Means for solving problems]

The above object is achieved by coating the surface of the resin substrate or resin layer with a transparent inorganic material.

[Effect]

The thin film of the above material is optically transparent, and the diffusion coefficient of 02, H20, or other substances in this film is extremely small, and the permeation of substances (mainly water and oxygen) due to film defects such as pinholes is also small. Therefore, corrosion of the chemically active magneto-optical information recording film can be suppressed, and there is no adverse optical effect on the disk.

As a result, a reversible optical disc with long life and high reliability can be obtained. Furthermore, since this inorganic material film exists between the substrate and the optical effect film or between the substrate and the magneto-optical information recording film, it is extremely effective in improving the adhesion between both layers and reducing stress.

〔Example〕

The details of the present invention will be explained below using Examples 1 to 3.

[Example 1] FIG. 1 shows a schematic diagram of the cross-sectional structure of the produced optical disc. The substrate 1 is made of polymethyl methacrylate (PMMA).
), polycarbonate (pc).

Epoxy resin (EP) and photocurable resin (Follow casting substrate: PHC) were used. Using an in-line magnetron sputtering device, a transparent inorganic compound thin film of S n O 2 or InzOs is deposited on top of this.
A film doped with AQ or Ti or an ITO film 2 was formed. For the sputter target, 5no2 or In
AQ or Ti chips placed on zOs or ITO were used, and Ar was used as the discharge gas.

In addition, the sputtering conditions are: discharge gas pressure: 5 x 10-
' (Torr), input RF electric crab IW/(!I?), and sputtering time is 10 minutes. The thickness of the created film is 1000. Next, on top of this, as optical effect film 3, A SisNa film was created by sputtering.A Si3N4 sintered target was used as the target, and Ar was used as the discharge gas.The sputtering conditions were the same as in the case of creating the transparent inorganic compound thin film. The thickness of the film is 850.Next, the magneto-optical recording film: Tb
27FeaaCozzNba 4 was prepared by sputtering. Tbx7FerhsCoxwNb on target
An s-alloy sintered target was used, and Ar was used as the discharge gas. The sputtering conditions are the same as in the case of creating the transparent inorganic compound thin film described above. The thickness of the produced thin film was 1000, the magneto-optical properties were Kerr rotation angle θ = 0.35'', coercive force Hc = 5 KOe, Curie temperature ``I'c =
200°C, compensation temperature: Tc; IIP = 120°C (magneto-optical recording film only). Finally, 5isNa as the protective film 5 was formed under the same conditions as in the case of forming the optical effect film. Here, only the sputtering time was set to 20 minutes, and the sputtering time was 20 minutes.
A film of 00 people was formed. For comparison, a magneto-optical disk not containing the transparent inorganic compound film of the present invention was also prepared.

Next, the created disc was heated to 80°C and 95% RH.
Kerr rotation angle when stored for 1000 hours in a table environment (
Changes in OKL coercive force (Hc) and reflectance (R) over time were measured. The results are shown in Table 1. First, by providing a transparent inorganic compound film between the substrate surface and the optical effect film, there was no decrease in optical properties such as reflectance, which remained constant at 28%. In addition, fluctuations in magneto-optical properties, especially Kerr rotation angle and coercive force, were almost suppressed. Here, the variation in coercive force is due to structural relaxation caused by storing the amorphous magneto-optical recording film at 80° C., and is not due to corrosion. On the other hand, in a magneto-optical disk in which a transparent inorganic compound thin film was not provided between the substrate and the optical effect film, both the Kerr rotation angle 9 reflectance and coercive force decreased. In particular, the coercive force fluctuates significantly, and the main cause of this is not simply structural relaxation, but a decrease in its value due to corrosion.

As described above, by providing the transparent inorganic compound thin film of the present invention on the substrate surface, it was possible to suppress variations in the magnetic and magneto-optical characteristics of the magneto-optical disk, and a highly reliable reversible optical disk was obtained.

The protective effect of the magnetic film was improved by about 20% when an amorphous transparent inorganic compound film was used compared to when a crystalline film was used.

[Example 2] The cross-sectional structure of the produced optical disc was the same as that of Example 1, and is as shown in FIG. The disk substrate l has a PMM
A, PC, EP, and PHC were used.

On this substrate, a transparent inorganic compound thin film was formed using an in-line thin film forming apparatus.
A thin film 2 was formed. The thin film was formed by vacuum evaporation, and the film thickness was 50 nm. The formation conditions at that time are
After the inside of the vacuum chamber was evacuated to below I x 10-6 (Torr), the resistance heating method was used. Subsequently, after lightly sputter etching the surface of this film, a SiO film was formed as an optical effect film 3 by sputtering. The conditions are as described below. In other words, a SiO sintered body was used as the target, and after exhausting to lXl0 B Torr, Ar was used as the discharge gas, and the pressure crab was
The resulting film, which was sputtered for 7 minutes at an input RF output of 2.5 W/cd, had a film thickness of 85 nm and a refractive index:
n=1.98.

Next, a magneto-optical recording film (T b Fe Co
A Nb amorphous thin film) 4 was formed to a thickness of 1100 nm by sputtering. The target and formation conditions at that time are the same as in Example 1. Finally, apply 1 layer of SiO protective film 5.
The film was formed to have a thickness of 50 nm. The conditions at that time were the same as in the case of forming the optical effect film previously, except that the sputtering time was 15 minutes. For comparison, a disk whose substrate surface was not covered with the transparent conductive thin film of the present invention was also prepared.

Next, when the prepared disk was stored in an environment of 80° C. and 95% RH for 1000 hours, the change over time of the reflectance R of the coercive crab Hc was measured at Kerr rotation angle=θ. The results are summarized in Table 2. From this table, it is possible to suppress variations in the magnetic and magneto-optical characteristics of the magneto-optical disk by covering the surface of the plastic substrate with a conductive film, thereby obtaining a highly reliable reversible optical disk.

Table 2 [Example 3] The cross-sectional structure of the produced magneto-optical disk was the same as that of Example 1, and its schematic diagram is as shown in FIG. The disc preparation procedure was performed using an in-line sputtering device in the order described below.

First, for the disk substrate 1, a PC or a PHC was used.

Pd is deposited on this substrate by ino-beam evaporation or sb
, or a SnO film 2 doped with Ti was formed by sputtering, a Pd film was formed by the EB method using a normal method, and a 5nOz film doped with Ti or sb was formed using SnO.
A mosaic-like composite target in which Ti or SB chips were removed using target bonding was used on an O2 plate.

Doping a large amount of these metals increases the absorption rate,
Care must be taken as this will cause a deterioration of the disc characteristics. The thickness of these transparent inorganic compounds is 50 nm. On the other hand, by providing this transparent inorganic compound film between the substrate and the optical effect film, it was effective not only to protect the magneto-optical recording film but also to improve the adhesion between the two films and reduce stress. Subsequently, a 5ixNa optical effect film 3 was formed on this film by sputtering. The sputtering conditions are the same as in Example 1.

The thickness of the created film was 85 nm, and the refractive index was 2.05.
Met. Next, as the magneto-optical information recording film 4 (Gdo+
aTbo,z)o,zz(Feo,eCoo,z)o,
7Jbo+oa was prepared by sputtering. The method was a ternary DC simultaneous sputtering method using GdTb alloy, FeCo alloy, and Nb plate as targets and rotating the substrate at a rotation speed of 12 rpm. The composition of the magneto-optical recording film was determined by controlling the applied power of the DC power supply. Also,
In order to improve the corrosion resistance of the recording film, the power applied to the Nb target was increased when the film thickness exceeded 60 nm, and the power applied to the other targets was decreased to provide a compositional gradient in Nb in the film thickness direction. Finally, a 5iaNa protective film 5 was formed to a thickness of 50 nm by magnetron sputtering. The sputtering conditions at this time are the same as in the case of forming the optical effect film described above.

For comparison, a magneto-optical disk was also manufactured in which the surface of the substrate was not covered with the thin film of the transparent inorganic compound of the present invention, but an optical effect film was directly covered on the disk substrate.

Next, the produced magneto-optical disk was stored in an environment of 80° C. and 95% RH for 1000 hours at a Kerr rotation angle of 20, and the change over time in the coercive crab Hct reflectance: R was measured.

Table 3 summarizes the changes in these characteristics from the initial stage of disc creation to after 1000 hours.

This table shows that by covering the plastic substrate surface with the transparent inorganic compound film of the present invention, fluctuations in the magnetic and magneto-optical properties of the magneto-optical disk can be suppressed, and a highly reliable magneto-optical disk can be obtained.

Table 3 [Effects of the Invention] According to the present invention, in forming a reversible optical disc using a plastic substrate or a substrate having a resin layer, by covering the resin surface with a transparent inorganic compound thin film,
Since it is possible to block substances that seep out of the resin or diffuse into the resin, it is possible to suppress recording membranous deterioration caused by these substances, and has the effect of extending the life of the disk.

Furthermore, this thin film has the effect of not only extending the life of the disk but also increasing the adhesive strength between the optical effect film and the substrate by reducing the stress between the two. In particular, if a transparent inorganic compound film with the same refractive index as the substrate material is used,
The influence on the optical path can be ignored, and the film thickness can be arbitrarily selected.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional structure of the produced optical disc. 1... Substrate, 2... Transparent inorganic compound film, 3...
Optical effect film, 4... Information recording film, 5... Protective film.

Claims (1)

[Scope of Claims] 1. An optical disc on which information is read and written using laser light, characterized in that a transparent inorganic layer is provided at the interface between a resin substrate or resin layer and an information recording medium. 2. The transparent inorganic layer is a CuI film or an A
Indium oxide film (ITO film) doped with at least one of u, Pd, Al, Ti, and tin, or Al
, antimony, a tin oxide film doped with Ti, or a cadmium tin oxide film (CTO film). The optical disc described. 3. The optical disc according to claim 1, wherein the transparent inorganic layer is a layer made of a thin film of a metal element. 4. The optical disc according to claim 1, 2 or 3, wherein the transparent inorganic layer is amorphous. 5. The optical disk according to claim 1, 2, 3, or 4, wherein the refractive index of the transparent inorganic layer is equal to the refractive index of the substrate material.