JPH03162733A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To realize massproduction of the medium by successively forming a dielectric protective film on a substrate by CVD (chemical vapor depositon) method in vacuum, a recording film by magnetron sputtering method, and further a dielectric protective film by CVD method. CONSTITUTION:The medium is produced by successively forming a dielectric protective film 2 on a substrate 1 by CVD method in high vacuum, a recording film 3 by magnetron sputtering method, and further a dielectric protective film 4 by CVD method. On performing CVD method, ECR (electron cyclotron resonance) plasma CVD method is applied considering that by this method temp. of the substrate 1 does not elevate during forming the film, films can be formed under low gas pressure, the only a little amt. of impurities intrudes in the protective film 2, and high film formation rate can be obtained. Thus, the medium can be massproduced.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing an optical recording medium.

[Prior Art] Optical recording media on which information can be erased and rewritten include magneto-optical recording media and phase-change optical recording media.

Magneto-optical recording media generally have a protective film on a transparent substrate.
It has a structure in which a recording film having perpendicular magnetic anisotropy and a protective film are laminated in this order, or it has a structure in which a reflective film is further laminated on the upper protective film. The material for forming the recording film is preferably an amorphous alloy of rare earth elements and transition metals, such as TbFeCo.
, NdDyFeCo, GdTbFe, and other alloys are used. The properties of these alloy materials may change if oxygen is mixed in during film formation or if they are exposed to high humidity. Therefore, in order to improve the durability of the recording film, Cr, Pt, and Ti are added to the above-mentioned apricot materials.
A method of adding such as however,
This method cannot sufficiently increase the durability of the recording film, and the current situation is that the upper and lower protective films are still required to have high gas barrier properties and moisture barrier properties.

Also, what are the common materials used to form the recording film of phase-change optical recording media? In this case, chalcogenide alloys such as InSbTe and GeTeSb, whose optical properties change due to a crystal-amorphous transition, are used.

Since these alloy materials have low thermal stability and the volume of the recording film changes during the crystal-amorphous phase transition, phase-change optical recording media usually have a protective film on a transparent substrate. , has a structure in which a recording film and a protective film are laminated in this order.

Materials for forming the protective film in the above-mentioned magneto-optical recording medium and phase-change optical recording medium include Sin, SiO
Dielectric materials such as Z, Aff, AffSiN, and SiN are used. The protective film made of this dielectric material is Si
, ^1! It is generally formed by a reactive sputtering method using a target such as Si or AQ in a mixed gas of 8R gas and O2 gas or N2 gas.

In this case, an in-line sputtering apparatus having a film-forming chamber for forming a protective film, a film-forming chamber for forming a recording film, etc. is often used. The film forming rate when forming the protective film made of the above oxide or nitride by the reactive sputtering method is usually about 1/10 to 1/4 of the film forming rate of the above recording film. Since the time required for the process of forming the protective film becomes long, the production efficiency of the magneto-optical recording medium or the phase change type optical recording medium decreases. In order to increase the deposition rate of the protective film using the above-mentioned reactive sputtering method, it is possible to increase the applied sputtering power or lower the partial pressure of the introduced oxygen gas or nitrogen gas1, but in either case, the temperature of the substrate The problem arises that the protective film becomes opaque because the increased or unreacted ^Q or Si remains in the film. Therefore, it is not possible to make the film formation rate of the protective film sufficiently high by these methods.

An object of the present invention is to provide a method for mass-producing optical recording media provided with a dielectric protective film.

[Means for Solving the Problems] According to the present invention, the above object is achieved by forming a dielectric protective film on a substrate in a high vacuum using chemical vapor deposition (CVD).
This is achieved by providing a method for manufacturing an optical recording medium in which the recording film is formed by a porDeposit ion method and has a magnetic feature.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A schematic cross-sectional view of an example of an optical recording medium manufactured according to the present invention is shown in FIG. This optical recording medium is manufactured by forming a dielectric protective film 2 on a substrate 1 in a high vacuum using the CVD method, and then forming a recording film 3 on a substrate 1 in a high vacuum.
is formed by magnetron sputtering method, and dielectric protective film 4 is formed by CVD method, which are sequentially laminated.

CVD methods include thermal CVD method, high frequency (e.g. 3.7
MHz), and ECR (Elec
A plasma CVD method (cyclotron resonance) or the like is employed. Among these methods, ECR plasma CVD has the following advantages: the temperature of the substrate does not rise during film formation, the film can be formed at low gas pressure, there are few impurities mixed into the protective film, and a high film formation rate can be obtained.
It is preferable to adopt the law.

When forming a protective film made of Si nitride and a protective film made of Si oxide by thermal CVD method or plasma CVD method, the gas introduced into the film forming chamber of the film forming apparatus and its gas pressure; Table 1 shows an example of forming the above-mentioned protective film by the ECR plasma CVD method.

N
Microwave power and protective film when forming a protective film made of SiN by the ECR plasma CVD method, which is performed by introducing gas and introducing SiHa gas so that the gas pressure becomes 0.2 mTorr into the film forming chamber. FIG. 2 shows the relationship between the film forming rate and the relationship between the microwave power and the refractive index of the obtained protective film.

Comparative Example 1 Reactive sputtering using a target made of Si and introducing Hz gas (gas pressure: 0.3a+Torr) and Ar gas (gas pressure = 0.9+nTorr) into the film forming chamber and The relationship between the refractive index and the refractive index of the obtained protective film is shown in FIG.

As is clear from comparing FIG. 2 and FIG. 3, when the protective film is formed by ECR plasma CVD, it has the same refractive index as when it is formed by reactive sputtering. A protective film can be obtained at a film formation rate that is 10 times or more.

The film forming apparatus used in the present invention is equipped with a film forming chamber for forming a protective film by the CVD method and a film forming chamber for forming the recording film by the magnetron sputtering method, and sequentially forms the protective film and the recording film in a high vacuum. It is preferable to have a film forming chamber for forming an upper protective film and a film forming chamber for forming a lower protective film. Further, it is preferable that the film forming apparatus is provided with a buffer chamber for preliminary vacuum as in the conventional in-line sputtering apparatus.

Materials for forming the recording film 3 include TbFeCo, Nd
Erasing and rewriting of information is possible in magneto-optical recording materials made of amorphous alloys of rare earth elements and transition metals such as DyFeCo and GdTbFe, and phase-change optical recording materials made of chalcogenide-based amorphous alloys such as InSbTe and GeTeSb. It is preferable to use a material on which information can be written, such as cyanine dye, TeC, TeO, or TeSePb.

The thickness of the protective film and the recording film can be determined depending on their optical properties, but usually the thickness of the lower protective film is in the range of 600 to 1,500, and the thickness of the recording film is 10.
The thickness of the upper protective film is preferably in the range of 200 to 1000 people.

As the substrate 1, a polycarbonate resin substrate, a non-quality polyolefin resin substrate, a polymethyl methacrylate resin substrate, a glass substrate, etc. are used.

[Effects of the Invention] According to the present invention, optical recording media provided with a protective film made of a dielectric material can be mass-produced.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of an optical recording medium manufactured according to the present invention, and FIG.
Figure 3 shows the relationship between the microwave power and the film formation rate of the protective film when forming a protective film made of iN, and the relationship between the microwave power and the refractive index of the resulting protective film. FIG. 3 is a diagram showing the relationship between the refractive index and the spa protective film. 1... Substrate, 2.4... Protective film, 3... Recording film.

Claims (1)

[Claims] The method is characterized in that a dielectric protective film is formed on a substrate in a high vacuum by a CVD method, a recording film is formed by a magnetron sputtering method, and a dielectric protective film is formed by a CVD method, and these are sequentially laminated. A method for manufacturing an optical recording medium.