JPH0248989A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To enhance oxidation resistance of a recording medium and prolong useful life by providing on a base a recording film comprising a thin film containing Te as a main constituent and containing Cr, and heat-treating the recording film to produce an optical recording medium. CONSTITUTION:A recording film 12 comprising a thin film containing Te as a main constituent and containing Cr is provided on a base 11, and the recording film is heat-treated to produce an optical recording medium 10 for recording information by forming pits in the recording film through irradiation of the recording film with an energy beam. The content of Cr in the recording film is preferably 0.1-10atom.% based on the total number of atoms constituting the recording film. The heat treatment of the recording film is preferably carried out for at least 5sec at a temperature of 70 to 300 deg.C. With this method applied, a recording margin is broadened, and the recording sensitivity of the optical recording method obtained is further enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for manufacturing an optical recording medium in which information is recorded by forming pits in a recording film on a substrate by irradiating energy beams such as light or heat. .

Technical Background of the Invention and Problems There are two types of optical recording media: those that form physically changed parts such as holes or four parts in a part of the recording film by irradiation with an energy beam; There is a method of forming an optical characteristic changing section in which optical characteristics (refractive index, reflectance, etc.) are changed.

As a recording film in any type of optical recording medium, a recording film mainly composed of a low melting point metal such as tellurium (Te) has been known (Japanese Patent Laid-Open No. 71195/1983, -9234 publication). A Te film, which is a typical low-melting point metal film, can produce desired physical changes or optical property changes (hereinafter collectively referred to as "
It is extremely promising as a highly sensitive material. Sensitivity here is defined as the energy (mJ/c) required to form pits per unit area.

However, when Te is left in the atmosphere, it is oxidized by oxygen or moisture, increasing its light transmittance and becoming transparent. When such Te is used as a recording film, the film thickness is extremely thin, on the order of several hundred layers, so if the light transmittance increases due to oxidation of the film, the sensitivity will drop significantly. That is, when the film is oxidized, the melting temperature and evaporation temperature rise, and absorption of energy such as light decreases due to transparency, which increases the energy required to form pits, resulting in a significant decrease in sensitivity.

For example, when a Te film is left in an atmosphere with a temperature of 70° C. and a relative humidity of 85%, the sensitivity decreases by about 20% in about 5 hours and by about 50% in about 15 hours.

In order to solve these problems, various measures have been taken to prevent oxidation of the Te film. One known method is to coat the Te film with a stable inorganic substance, but although this method is effective in preventing ROM oxidation, it reduces sensitivity and is expensive, so it is not practical. has not been standardized. On the other hand, a method of coating the Te film with plastic is also known, but this method is advantageous because the degree of deterioration of sensitivity is small due to the low thermal conductivity of plastic, but it is advantageous because it allows oxygen and water to permeate relatively easily. , is not very useful in preventing oxidation of the Te film.

In addition, in order to solve the above-mentioned problems,
No. 63,038 discloses an optical recording medium having a recording film containing Te as a main component and Cr.

As disclosed in this publication, when Cr is contained in a recording film whose main component is Te, the oxidation resistance of the recording film improves in proportion to the content, extending the life of the optical recording medium. It is known that this can be achieved.

However, an optical recording medium having a recording film containing Te as a main component and Cr has the disadvantage that recording sensitivity decreases if a large amount of Cr is contained. Therefore, Cr contained in the recording film whose main component is Te.
From the viewpoint of improving oxidation resistance and recording sensitivity, the content of Cr is 5 to 15% by weight (total amount It was generally determined to be 11 to 27 atomic %).

However, the present inventors found that the recording sensitivity of an optical recording medium equipped with a Te-based recording film containing 5 to 15% by weight of Cr is still 17 lower than that of a recording film containing only a Te film. It was discovered by et al. The present inventors have discovered that such Te
After intensive study on optical recording media equipped with a recording film containing Cr as a main component, it was found that after forming a recording film containing Cr and containing Te as a main component on a substrate,
It has been found that heat treatment widens the recording margin and further improves the recording sensitivity. Here, "recording margin" refers to the width of the range of laser output used to form pits of a predetermined shape. The wider the recording margin, the more uniform pit formation becomes possible even when changing the laser output, and the wider the range of laser output that can be used when recording information.
The medium becomes unaffected by variations in laser output. Furthermore, the present inventors have found that such an effect is particularly noticeable when a recording film whose main component is Te containing a specific amount of Cr is heat-treated.

Purpose of the Invention The present invention was made based on these new findings, and aims to improve the oxidation resistance of the recording film, extend the life of the optical recording film, and record information with less energy. It is an object of the present invention to provide a method for manufacturing an optical recording medium that is highly sensitive and has a wide recording margin.

Summary of the Invention In order to achieve the above object, a method for manufacturing an optical recording medium according to the present invention comprises a substrate and a recording film formed on the substrate, and the recording film is irradiated with an energy beam. Accordingly, in a method for manufacturing an optical recording medium in which information is recorded by forming pits in this recording film, after forming a recording film made of a thin film containing Te as a main component and Cr on the substrate, A feature of this method is that this recording film is heat-treated.

The heat treatment is preferably performed at a temperature of 70 to 300°C for 5 seconds or more. Further, the content ratio of Cr contained in the recording film is 0.1 with respect to the total number of atoms constituting the recording film.
It is preferably in the range of ~40 at%, preferably 0.1-10 at%, more preferably 0.1-3.

According to the method for producing an optical recording medium according to the present invention, since the formed recording film is heat-treated, although the durability of the obtained optical recording medium is improved, the recording sensitivity is further reduced. improves. Moreover, the pit shape formed in the recording film can be made uniform, the recording margin can be widened, and the C/N ratio can be increased during information reproduction.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a schematic cross-sectional view of an optical recording medium obtained by a manufacturing method according to an embodiment of the present invention.

Before explaining the method for manufacturing an optical recording medium according to the present invention, first, the optical recording medium itself obtained by the method of the present invention will be explained.

As shown in FIG. 1, an optical recording medium 10 obtained by the manufacturing method according to the present invention is composed of a substrate 11 and a recording film 12 formed on the surface of this substrate.

In addition to inorganic materials such as glass or aluminum, the substrate 11 may be made of polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, such as ethylene and 1,4,5,8-dimethano-1,2,3,4. ,4a,5+8,8a-Copolymer of octahydronaphthalene (tetracyclododecene), ethylene and 2-methyl-1,4,5,8-dimethano-1,2,3,4,4a,5, 8.8a-Copolymer of octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1,4,5,8-dimethano-■.

2.3.4,4a,5.8.8a-Amorphous polyolefins, poly-4-
Organic materials such as methyl-1-pentene, epoxy resin, polyethersulfone, polysulfone, polyetherimide, etc. can be used. The thickness of this substrate 11 is
The thickness may be sufficient as long as it provides appropriate rigidity to the entire recording medium 10, preferably 0.5 to 2.5 mm, particularly preferably 1 to 1 mm. It is about 5 mm.

The recording film 12 according to the present invention is a thin film containing Te as a main component and Cr, and may also contain a low melting point metal other than Te or other components. Elements other than Te that can be included in the recording film 12 include "rI SMn,"
Nl, Zr5Nb, Ta.

Al, Pt5SraSBI In, Se, Pb.

Examples include Co, Sf, Pd5Sn, and Zn.

The content ratio of Cr contained in such a recording film 12 is not particularly limited, but is 0.1 to 40 at%, preferably 0.1 to 10 at%, based on the total number of atoms contained in the recording film. , particularly preferably 1 to 4 atom%, even more preferably 1
It is preferably in the range of 3 atomic %. By including Cr in such a range, although the oxidation resistance of the recording film 12 is improved, the recording sensitivity does not decrease.
This is because recording sensitivity can be improved in some cases.

The content of each element contained in the recording film 12 is measured, for example, by ICP emission spectrometry (inductively coupled plasma emission spectrometry) for metal elements.

To write information on the recording film 12 having the above composition, the recording film 12 is irradiated with an energy beam such as a laser beam that is modulated (on/off) depending on the information to be recorded. A pit may be formed in the irradiated portion. This pit may be a physically changed part such as a hole or a recess, or it may be an optical property changed part where optical properties such as refractive index or reflectance are changed.

The thickness of the recording film 12 needs to be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity. Specifically, when forming a physically changed part such as a hole in the recording film 12, the thickness of the recording film is 100 to 1.
[mu]m is preferably about 100 to 5,000 people, more preferably about 150 to 500 people. Further, when forming an optical characteristic changing portion such as reflectance or refractive index on the recording film 12, the film thickness of the recording film is 100 μm to 1 μm, preferably 100 μm to 1 μm.
~5000 people, more preferably about 200~2000 people.

Next, the manufacturing method of the present invention will be specifically explained.

The recording film 12 is formed on the surface of the substrate 11, for example, as follows. The recording film 12 can be formed on the substrate 11 by preparing Te and Cr as targets and employing a conventionally known film forming method such as a vacuum evaporation method, a sputtering method, or an electron beam evaporation method.

When forming the recording film 12 on the substrate 11, Te and Cr can be used as separate targets, but an alloy of Te and Cr can also be used as the target.

Next, in the present invention, after forming the recording film 12 on the substrate 11 as described above, the recording medium or the recording film 12 consisting of the substrate 11 and the recording film 12 is heated with an inert gas, a reducing gas, or Heat treatment is performed in a gas atmosphere containing oxygen. The specific method of heat treatment is not particularly limited,
For example, there is a method of heat-treating the recording film by leaving the recording medium or the recording film under a predetermined heat treatment temperature for a predetermined period of time. The heat treatment temperature needs to be below the melting point of Te contained in the recording film, preferably 70 to 30
A temperature range of 0°C, especially 90 to 150°C is preferable. The heat treatment time is preferably 5 seconds or more, particularly preferably 5 seconds to 10 seconds.
time, most preferably 5 minutes to 2 hours.

In this way, by heat-treating the recording film 12 or the recording medium composed of the substrate 11 and the recording film 12 after forming the recording film 12 on the substrate 11, the recording sensitivity of the recording film may be improved. For example, as shown by curve B in FIG.
-2.0 (atomic %) when the Cr content X-
It was confirmed that the recording energy output could be significantly reduced and the recording sensitivity would be improved compared to the non-heat-treated Te-only recording film (indicated by point A in the figure) of 0 (atomic %). In addition, regardless of the Cr content, in the heat-treated recording film according to the present invention, the shape of pits formed during recording due to heat treatment is comparable to that of pits formed in an untreated recording film. It has been confirmed that the recording energy output range can be widened (the recording margin is widened).

Note that, as shown by curve B in FIG. 2, the recording film according to the present invention has a Cr content of 0.1 to 3 at%, in particular,
It was confirmed that the recording energy output was small and the recording sensitivity was improved.

Furthermore, according to the present invention, as shown in FIG. 3, for example, the Cr content (
Atomic %: expressed as Te Cr 100-x
The change in reflectance after 100 hours in an environment of 70°C and 85% relative humidity with respect to the value of X when
It was confirmed that the oxidation resistance of the recording film according to the present invention was improved compared to the case where the r content was −0).

Effects of the Invention According to the method for manufacturing an optical recording medium according to the present invention, since heat treatment is performed after the recording film is formed, the recording margin is widened, and furthermore, at a predetermined Cr content ratio, the resulting optical recording medium Recording sensitivity is further improved.

Furthermore, in the present invention, since the recording film containing Te as a main component contains Cr, the oxidation resistance of the recording film is improved, and it is expected that the life of the optical recording medium will be extended.

[Examples] The present invention will be described below based on more specific examples, but the present invention is not limited to these examples.

Example 1 After evacuating the vacuum container, introduce gas A and increase the internal pressure by 6x.
1, Q -3 Torr. In this state, To and Cr were used as targets and simultaneously spucked. At that time, by controlling the voltage applied to each target and controlling the sputtering time using a shutter, T e 98 Cr 2 was deposited on the amorphous polyolefin substrate.
A film with a thickness of 250 mm was obtained.

After that, this recording medium (recording film) was placed in a nitrogen gas atmosphere for 1 hour.
The recording film was left at a temperature of 00°C for 20 minutes, and the recording film was heated to 100°C.
Heat treatment was performed for 20 minutes.

Example 2 A heat-treated recording film made of Te Cr and having a film thickness of 250 mm was obtained in the same manner as in Example 1.

Example 3 A heat-treated recording film made of Te Cr and having a film thickness of 250 mm was obtained in the same manner as in Example 1.

Example 4 A heat-treated recording film of Te913''4 and a film thickness of 200 mm was obtained in the same manner as in Example 1 except that an alloy of Te and Cr was used as the target.

Comparative Example 1 A sputtered Te film with a thickness of 250 mm was obtained in the same manner as in Example 1 except that only To was used as the target and no heat treatment was performed.

Comparative Example 2 Te C was prepared in the same manner as in Example 1 except that no heat treatment was performed.
A recording film with a film thickness of 250 was obtained.

Example 5 An alloy target of Te and Nl as a target and C
A heat-treated recording film made of TeNiCr and having a film thickness of 230 mm was obtained in the same manner as in Example 1, except that a target of R was used.

Example 6 To and In alloy targets and C as targets
A heat-treated recording film made of Te In Cr and having a film thickness of 250 mm was obtained in the same manner as in Example 1 except that a target of R was used.

Example 7 Te 9□Se was produced in the same manner as in Example 1 except that a TesSe alloy target and a Cr target were used.
A heat-treated recording film of Cr and a film thickness of 240 was obtained.

[Test Results] (1) Changes in reflectance in Examples 1 to 3 and Comparative Example 1 when the reflectance after being left in an atmosphere of 70°C and 85% RH for 100 hours is R1 and the initial reflectance is R6 Rate (R-R
) xlOO/R6 values are shown in Table 1.

The results are shown in Table 2.

Table 2 Table 1 (2) The energy required for recording using a laser beam with a frequency of 3.7 MHz is expressed as 1.0 in Comparative Example 1, and is expressed in increments of 0.05 below. , refers to the wide range of laser output used to form pits of a predetermined shape.

The wider the margin, the more uniform pits can be formed without being affected by fluctuations in laser output.

4,

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention, and Figures 2 and 3 are graphs showing the differences in function and effect between the optical recording medium according to the present invention and conventional optical recording media. be. 0... Optical recording medium 1... Substrate 2... Recording film

Claims (1)

[Scope of Claims] 1) Consisting of a substrate and a recording film formed on the substrate, the recording film is irradiated with an energy beam to form pits in the recording film and record information. A method for producing an optical recording medium according to the present invention, comprising: forming a recording film made of a thin film containing Te as a main component and containing Cr on the substrate, and then heat-treating the recording film. . 2) The content ratio of Cr contained in the recording film is in the range of 0.1 to 10 atomic % with respect to the total number of atoms constituting the recording film. A method for manufacturing an optical recording medium. 3) The method for manufacturing an optical recording medium according to claim 1 or 2, wherein the heat treatment is performed at a temperature of 70 to 300°C for 5 seconds or more.