JPH01191351A - Production of information recording medium - Google Patents

Abstract

PURPOSE:To improve durability by subjecting an information recording medium provided with a metallic recording layer on a substrate to a heating and humidifying treatment at and under a high temp. and high humidity. CONSTITUTION:A recording material consisting of a metal and metal sulfide is deposited by evaporation on the substrate to provide the metallic recording layer which allows writing and/or reading of information by a laser. This metallic recording layer is subjected to the heating and humidifying treatment. The metal and metal sulfide, etc., forming the metallic recording layer is subjected mainly to oxidation by the heating and humidifying treatment, by which the higher stability than the stability of the metal prior to the oxidation is imparted to said metal, etc. The degradation of the characteristics including recording sensitivity, C/N and jitters with age is thereby obviated and the durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method of manufacturing an information recording medium on which information can be written and/or read using a laser beam.

[Technical Background of the Invention] In recent years, information recording media using high energy density beams such as laser beams have been developed and put into practical use. This information recording medium is called an optical disc, and includes video discs, audio discs, large-capacity still image files, and large-capacity computer discs.
It can be used as memory.

The basic structure of optical discs is plastic.

It has a disk-shaped transparent substrate made of glass or the like, and a recording layer made of metal or semimetal such as Bi, Sn, In, Te, etc. provided thereon. Note that the surface of the substrate on which the recording layer is provided is usually coated with an undercoat layer or an undercoat layer made of a polymeric material in order to improve the flatness of the substrate, improve the adhesion with the recording layer, or improve the sensitivity of the optical disc. An intermediate layer is provided.

Information is written on an optical disk by, for example, irradiating the optical disk with a laser beam.
The irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in a physical or chemical change that changes its optical properties, thereby recording information. Also reading information from optical discs. This is performed by irradiating an optical disk with a laser beam, etc., and information is reproduced by detecting reflected light or transmitted light according to changes in the optical characteristics of the recording layer.

Recently, as a disk structure for protecting the recording layer, a recording layer is provided on at least one of the two disk-shaped substrates, and the recording layer is located inside the two disk-shaped substrates. Also, an air sandwich structure has been proposed in which a ring-shaped inner spacer and a ring-shaped outer spacer are joined to form a space. In optical discs with such a structure, the recording layer is not in direct contact with the outside air, and information is recorded and reproduced using laser light that passes through the substrate, so the recording layer is generally not susceptible to physical or chemical damage. There is no possibility that the recording or reproducing of information will be hindered by dust or dirt adhering to the surface.

As mentioned above, information recording media have extremely high utility value in various fields, but for example, they must have as high a sensitivity as possible during recording, and a high C/C ratio during playback.
It is desired to improve various properties such as good N and the like, and that the above properties do not change over time, that is, have excellent durability.

Among the above-mentioned issues, ways to improve durability in particular include structural improvements such as making the structure of the disk a sandwich structure, or providing an undercoat layer under the recording layer, or A method of forming a multilayer structure by providing a protective layer on top of the protective layer is known. Furthermore, as a method for improving the recording layer itself, a method of oxidizing a metal recording layer made of Te was proposed by Saletail (VF 1977-42-095).

However, although the above-mentioned information recording medium has excellent durability with little deterioration of the recording layer, it cannot be said that the characteristics such as recording sensitivity and C/N during reproduction are sufficiently excellent, and the disc It cannot be said that it is advantageous in manufacturing because the process is complicated.

[Objective of the Invention] The present invention provides a method for manufacturing an information recording medium with improved durability and read durability without deterioration of recording sensitivity, C/N, and jitter characteristics over time. Its purpose is to

[Summary of the Invention] The present invention provides a metal recording layer on which information can be written and/or read by laser by depositing a recording material made of metal and metal sulfide on the substrate, and then depositing the recording material on the substrate. A method for manufacturing an information recording medium characterized by subjecting a metal recording layer provided on the surface to a heating and humidifying process.

Incidentally, the above-mentioned vapor deposition means evaporating a metal or the like and depositing it on a substrate, and includes all methods such as vacuum vapor deposition, sputtering, and ion blating.

Preferred embodiments of the method for manufacturing an information recording medium of the present invention are as follows.

l) The method for manufacturing the information recording medium, wherein the heating and humidifying treatment is performed by leaving the medium in an atmosphere with a temperature of 50"0 or more and a humidity of 60% RH or more for one hour or more.

2) The information recording medium characterized in that the main component of the metal is In, and the main component of the metal sulfide is Ge5xC (where X is a number in the range of 0<x≦2). Production method.

3) The method for manufacturing the information recording medium, wherein the thickness of the metal recording layer is within a range of 300 to 1000 mm.

4) The method for manufacturing the information recording medium, wherein the substrate is made of at least one material selected from the group consisting of polycarbonate, polymethyl methacrylate, and glass.

5) The method for manufacturing the information recording medium, wherein the substrate is made of polycarbonate.

[Effects of the Invention] The method for manufacturing an information recording medium of the present invention is characterized in that after a metal recording layer made of metal and metal sulfide is provided on the surface of the substrate, a heating and humidifying treatment is further performed. Information recording media manufactured by this method have improved durability such as read durability because the metal recording layer is chemically and physically stabilized, and recording sensitivity, C/N, and jitter change over time. It is possible to obtain an information recording medium with improved durability with little change, and also to obtain an information recording medium with excellent durability without complicating the disk manufacturing process by the manufacturing method of the present invention. Can be done.

The above effect can be obtained when a metal recording layer consisting of a combination of In and Ge5x (where X is a number in the range of 0<X≦2) is provided on the surface of the polycarbonate x plate.
Author:

[Detailed Description of the Invention] The information recording medium of the present invention can be manufactured, for example, by the following method.

The substrate used in the present invention can be arbitrarily selected from various materials conventionally used as substrates for information recording media. In terms of the optical properties, flatness, workability, ease of handling, stability over time, and manufacturing costs, examples of substrate materials include glass for soda-lime glass caps, cell-cast polymethyl methacrylate, and injection-molded polymethyl. Examples include acrylic resins such as methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; and polycarbonates. Among these, polymethyl methacrylate, polycarbonate, and glass are preferred from the viewpoint of dimensional stability, transparency, flatness, etc., and polycarbonate resin is particularly preferred.

Pregrooves may be provided directly on the plastic substrate by injection molding, extrusion molding, or the like.

Next, a metal recording layer made of a combination of the metal of the present invention and a metal sulfide is provided on the surface of the substrate (or the undercoat layer or intermediate layer if desired).

Examples of the above metal materials include Te, S as low melting point metals.
n, Pb, Bi, etc.; other metals include Ag, An,
Go, Cu, Ga, Mo, Ni, St, V, Au, Be
, Cr, Fe, Mn.

Mention may be made of Nb, Pd, Ti and Zn. Preferably it is a low melting point metal.

Examples of metal sulfides used in combination with the above metals include Cry, Cr25. Cr253, MoS2. MnS,
FeS, FeS2, CoS, Co253, N
iS, Ni2S, PbS, Cu2S,
Ag2S, ZnS, In2S3, In25
2, SnS, SnS 2, As 2S,,sb 2S2
, Bi 2s, and the like.

The ratio of metal to metal sulfide is 99:l to 20 by weight.
: In the range of 80, preferably 95:5 to 75:
The range is 25.

More preferably, the material of the recording layer is In as a metal and GeSx as a metal sulfide (where X is 0<x≦2
) is used.

In addition to metal sulfides, materials for the recording layer used in combination with the above metals include MgF2, CaF2, RhF2,
Metal fluorides such as 3 and M.

Metal oxides such as O□0, In20, In2O3, and Ge01PbO may be used.

The recording layer is formed on the substrate using the above-mentioned materials by a method such as vapor deposition, sputtering, or ion blasting.

The thickness of the recording layer is generally in the range of 200 to 1,500 J in view of the optical density required for optical information recording.In the present invention, it is preferably in the range of 300 to 100 OX in view of the need to obtain a particularly high reflectance.

The manufacturing method of the present invention is characterized in that the information recording medium having the metal recording layer provided on the substrate is heated and humidified at high temperature and high humidity. Through this treatment, the metal recording layer is chemically and physically stabilized, and an information recording medium with excellent durability can be obtained. That is, by the heating and humidification treatment, the metal and metal sulfide forming the metal recording layer are mainly subjected to oxidation action.For example, when In is used as the metal and GeS is used as the metal sulfide, Some of the In is indium oxide.

It is assumed that some of GeS and H are converted to germanium oxide. The degree of this change is greater near the surface of the metal recording layer, and the stability of such a metal oxide is naturally better than that of the metal before oxidation. Therefore, this significantly improves durability such as reading durability.

However, the above-mentioned treatment may slightly reduce the characteristics of the metal recording layer, such as reflectance and recording sensitivity. In particular, there is a tendency for the reflectance to decrease.

For this reason, the metal recording layer obtained by the manufacturing method of the present invention has a layer thickness of a normal metal recording layer (i.e., especially the reflectance and C/N It is preferable to provide a metal recording layer that is slightly thicker than the layer thickness that provides the best characteristics with well-balanced characteristics.The degree of thickening varies depending on the type of metal used, but the metal recording layer Preferably, the layer thickness is within the range of 5 to 20% greater than the layer thickness that provides the best properties of the layer.

In this way, the manufacturing method of the present invention in which a metal recording layer (preferably slightly thicker than usual) is provided on a substrate and subjected to the heating and humidification treatment described above, can be used without impairing the best characteristics of the metal recording layer. It is possible to obtain an information recording medium with improved durability such as read durability, and with little change over time in recording sensitivity, C/N, and jitter.

The conditions for the heating and humidifying treatment of the present invention are as shown below, for example.

l) Heating conditions include 50℃ for 1 day or more, 60℃ for 12 hours or more, and 70℃ for 6 hours.
3 hours or more at 80℃.

2) The humidification conditions are 60% RH for 8 days or more and 90% RH for 4 days or more.The treatment may be performed under the above conditions 1) or 2) alone, but It is effective to perform the treatment by combining the conditions 1) and 2) above, and in the present invention, the treatment is performed under the combined conditions. That is, the metal recording layer of the present invention has at least 5
It is preferable to heat and humidify at 0° C. and 60% RH for 1 hour or more.

Particularly preferred conditions are, for example, 60° C., 90% RH for 1 to 4 days, or 80° C., 90% RH for 6 to 24 hours.

Before providing the metal recording layer on the plastic plate, the following undercoat layer, pregroove layer and/or intermediate layer may be provided.

The surface of the substrate on which the recording layer is provided has improved flatness,
For the purpose of improving adhesive strength and preventing deterioration of the recording layer, an undercoat layer may be provided. Examples of materials for the undercoat layer include polymethyl methacrylate and acrylic acid/methacrylic acid copolymer.

Polymer substances such as nitrocellulose, polyethylene, polypropylene, and polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (Si02, Al2
(O, etc.) and inorganic substances such as inorganic fluoride (MgFz).

A pre-groove layer may be provided on the substrate (or undercoat layer) for the purpose of forming tracking grooves or unevenness representing information such as address signals.The material for the pre-groove layer is acrylic acid. monoester, diester,
A mixture of at least one monomer (or oligomer) of triesters and tetraesters and a photopolymerization initiator can be used.

To form the pregroove layer, first, a mixed solution consisting of the above acrylic ester and a polymerization initiator was applied to a precisely made fil type (stambar) 1-, and then a substrate was placed on top of this coating solution layer. After that, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix to fix the substrate and the liquid phase.Next, by peeling the substrate from the matrix, a substrate provided with a pregroove layer is obtained. It will be done. The layer thickness of the pregroove layer is generally in the range from 0.05 to 100 lm, preferably in the range from O11 to 50 lm.

An intermediate layer made of various known materials such as chlorinated polyolefin is further provided on the substrate (or undercoat layer or pregroove layer), or on the pregroove if the pregroove is provided directly on the substrate. You can leave it there.

In particular, when the material of the intermediate layer is chlorinated polyolefin, it is possible to reduce the loss of thermal energy due to laser beam irradiation due to heat conduction from the recording layer to the substrate, etc. Gas is generated from the irradiated portion, making it easier to form pits, thereby further reducing the pit error rate and further improving the recording sensitivity.

The chlorinated polyolefin used as the intermediate layer material generally has a chlorination rate of 30% or more, preferably 5%.
i' in the range of 0% or less, particularly preferably in the range of 50 to 70%
! The rate of conversion to one element is the rate of total conversion. In addition, from the viewpoint of thermal stability and solubility, chlorinated polyethylene and chlorinated polypropylene are particularly preferred among these chlorinated polyolefins.The chlorinated polyolefin layer is formed by dissolving the above chlorinated polyolefin in a solvent and applying a coating solution. It is possible to prepare the coating liquid and then apply the coating liquid onto the substrate.

As a solvent for dissolving chlorinated polyolefin,
Examples include toluene, xylene, ethyl acetate, butyl acetate, cellosolve acetate, methyl ethyl ketone, 2-dichloroethane, methyl isobutyl ketone, cyclohexanone, cyclohexane, tetrahydrofuran, ethyl ether, and dioxane.

Various additives such as plasticizers and lubricants may also be added to these coating solutions depending on the purpose.

Examples of the coating method include a spray method, a spin code method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method.

A chlorinated polyolefin layer can be formed on the substrate (or undercoat layer) by applying it to the substrate surface (or undercoat layer) to form a coating film and then drying it. What is the layer thickness of the chlorinated polyolefin layer?

Generally 10 to ioo'o, preferably 100 to 50
It is within the range of 0 or more.

Note that the surface of the substrate opposite to the side on which the recording layer is provided is coated with inorganic substances such as silicon dioxide, tin oxide, and magnesium fluoride to improve scratch resistance and moisture resistance.
An fs film made of a polymer material such as a thermoplastic resin or a photocurable resin may be provided by a method such as vacuum deposition, sputtering, or coating.

In this way, an information recording medium having a basic configuration in which the substrate and the recording layer are laminated in this order can be manufactured.

Note that a bonded type recording medium can be manufactured by bonding two substrates having the above structure using an adhesive or the like.

Furthermore, an air sandwich type recording medium can be manufactured by joining two disk-shaped substrates, at least one of which has the above configuration, via a ring-shaped outer spacer and an inner spacer. can.

Next, Examples and Comparative Examples of the present invention will be described.

[Example 1] Disc-shaped polycarbonate substrate (outer diameter: 130 mm,
Inner diameter: 15 mm, thickness: 1.2 mm) On the surface, the substrate temperature was 90°C, the evaporation rate was 4/sec, and the degree of vacuum was 5 x 10-6.
A recording layer with a layer thickness of 660 mm was provided by co-evaporating GeS and In under Torr conditions.Next, the substrate on which the recording layer was provided was left in an atmosphere of 60° C. and 90% RH for 30 minutes. . In this way, an information recording medium consisting of a substrate and a recording layer was manufactured in this order.

[Comparative Example 1] In Example 1, the thickness of the recording layer was changed from 660 mm to 800 mm.
Example 1 except that the heating and humidifying conditions were changed from an atmosphere of 60°C and 90% RH to an atmosphere of normal temperature and normal humidity.
In the same manner as above, an information recording medium consisting of a substrate and a recording layer was manufactured in this order.

[Evaluation of Information Recording Medium] The recording and reproducing performance of the information recording media obtained in Example 1 and Comparative Example 1 was evaluated under the following conditions.

Semiconductor laser: Wavelength 830nm *Beam diameter
21.6pm Linear velocity: 5.5m/sec Recording power: 9mW Reproduction power: 1.2mW A fine pattern (100100...) of 2-7RLL code information was recorded at the above recording power, and a spectrum analyzer was used to record the fine pattern of 2-7RLL code information. The following measurements were performed at a width of 30 kHz.

(1) Decrease in reflectance When information recorded under the conditions described above was reproduced, the energy of the laser incident light and the energy of the reflected light were measured, and the ratio was determined as a percentage. After being left in an atmosphere of 60° C. and 90% RH for 10 days, 20 days, and 30 days, the reflectance was measured for each, and the rate of decrease was calculated.

(2) Decrease in C/N for 10 days, 20 days, and 30 days in an atmosphere of 60°C and 90% RH.
After being left for a day, each was reproduced under the above conditions, and the decrease in C/N was measured when the initial C/N before being left was set as OdB.

(3) Reading durability When reproduced under the above conditions, the initial C/N and the C/N after 2 hours of continuous reproduction were measured.

The results obtained are summarized in Table 1.

Table 1 Example 1 Comparative Example 1 Decrease in reflectance (z) Initial 00 10 days 0.4 2.5 20 days 0.6 3.7 30 days 0.7 4.4 Decrease in C/N (dB) Initial 00 10 days 0.4 1.8 20 days 0.7 2.8 30 days 0.9 3.5 Reading durability (dB) Initial 51.0 51.0 After 2 hours 50.7 48.9 In addition, With the decrease in reflectance shown in Table 1, initial reflectance measurement step 1
was 35.0% in both Example 1 and Comparative Example 1. As is clear from the results shown in Table 1, the information recording medium of the present invention (Example 1) was 35.0% in both Example 1 and Comparative Example 1. It can be seen that both the reflectance and the C/N ratio hardly decrease even after being left unused, and the C/N ratio after continuous playback also shows little decrease and is excellent in durability.

On the other hand, in Comparative Example 1 in which the information recording medium was not left in an atmosphere of 60° C. and 90% RH for 3 days, the durability was generally poor.

Claims (1)

[Claims] 1. After providing a metal recording layer on which information can be written and/or read by laser by depositing a recording material made of metal and metal sulfide on the substrate,
A method for manufacturing an information recording medium, comprising subjecting the metal recording layer to a heating and humidifying process.