JPH02199642A - Resin substrate for optical disk and production of optical disk - Google Patents

Abstract

PURPOSE:To eliminate the deterioration in characteristics and to improve the adhesiveness of an optical recording layer by using a resin substrate having a specific rate of the weight loss by a heating treatment. CONSTITUTION:The resin substrate having <=0.05wt.% rate of the weight loss by the heating treatment for one hour at 100 deg.C in air is used as the resin substrate at the time of forming the film of the optical recording layer by a vacuum film forming method on the resin substrate, thereby forming the optical disk. Since this resin substrate for the optical disk has the extremely low rate of the weight loss as compared to the conventional resin substrate for the optical disk, the characteristics of the optical disk are stable in the case of using th optical disk by using such resin substrate for the optical disk. The deterioration in the magneto-optical characteristics, such as Kerr rotating angle and coercive force, and the adhesive property of the substrate to the recording layer is substantially obviated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical disc useful as a recording medium for high-speed data files, video recording, etc., and particularly to an optical disc with excellent storage stability.

(Prior Art and its Problems) Optical recording has many characteristics such as high density, large capacity, and non-contact with a recording/reproducing head, and in recent years, its development and practical application have been actively promoted.

The recording medium, the optical disc, can be erased,
Magneto-optical disks, phase change optical disks, and the like are attracting attention because they are easy to read and record.

A magnetic material is used in the recording layer of a magneto-optical disk, and information is recorded as changes in magnetization, and the recorded information is read as changes in the polarization state of reproduction light. The magnetic material is Gd,
Amorphous rare earth transition metals (for example, G
dCo, CdFe, TbFe, D>”Fe, GdTbF
e, GdFeCo, TbFeCo, etc.) are common because they have excellent magneto-optic effects.

On the other hand, phase change type optical disks are generally of the crystal/amorphous phase change type, for example, and information is recorded in a heat mode and the recorded information is read from the change in reflectance accompanying the phase change. The recording layer includes Te-based and non-Te-based.

Glass, polycarbonate, polymethyl methacrylate, epoxy, and other resins are available as substrates for optical discs, but currently they have the advantages of being easy to process in mass production, easy to handle, and relatively inexpensive. Development is proceeding with a focus on resin substrates. Among them, JP-A No. 62-252545, JP-A No. 62-2
Polycarbonate substrates disclosed in JP-A No. 64463, JP-A No. 63-97627, etc. have excellent light transmittance, low birefringence on the surface, low hygroscopicity, and are inexpensive and suitable for use in magneto-optical recording media. It is seen as promising as a substrate for

The manufacturing process of this optical disk is usually vacuum deposition, sputtering, carbon dioxide, etc. on a transparent substrate such as glass or resin.
This is accomplished by providing the above-mentioned recording layer by a vacuum film forming method such as VD.

However, optical disks whose substrates are transparent resin substrates produced through such processes often have varying characteristics and are not consistently good.

For example, when the recording layer is made of a rare earth transition metal alloy, the magneto-optical properties such as Kerr rotation angle and coercive force may be significantly deteriorated.

In addition, the adhesion of the recording layer is often poor, and when aged under high temperature and high humidity, minute peeling occurs on the recording layer, which significantly increases the error rate.
There was a strong concern that this would reduce the durability and reliability of optical discs.

In order to improve this problem, Japanese Patent Application Laid-Open No. 63-300
446 and Japanese Patent Application Laid-Open No. 63-010357, attempts have been made to apply plasma or the like to the surface of a plastic substrate to improve the adhesion between the substrate and the recording layer.
An effective method for stabilizing the characteristics of optical discs has not yet been found.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to provide an optical disk having particularly stable magneto-optical characteristics and good adhesion of the recording layer. It is an object.

(Means for Solving the Problems) The object of the present invention is to provide a resin substrate for an optical disk, which has a weight reduction rate of 0.05% by weight or less when heated in air at 100°C for 1 hour. achieved.

That is, when manufacturing an optical disc in which an optical recording layer is formed on a resin substrate by a vacuum film forming method, the weight loss rate when the resin substrate is heated in air at 100°C for 1 hour is as follows.
The object of the present invention can be achieved by using a resin substrate containing 0.05% by weight or less.

The resin substrate for optical discs of the present invention can be heated at -100°C in air.
When heat treatment is performed for 1 hour, the weight reduction rate before and after the treatment is 0.05% by weight or less, which is extremely small compared to conventional resin substrates for optical discs. Therefore, when an optical disk is made using the resin substrate for optical disks of the present invention, its characteristics are stable, and there is almost no deterioration in magneto-optical characteristics such as Kerr rotation angle and coercive force, and in the adhesion of the recording layer to the substrate. .

The substances considered to be removed from the optical disc resin substrate by heat treatment at 100'C for 1 hour are water,
Possible sources include low molecular weight organic substances brought in from the raw materials for the resin substrate.

The advantage of the resin substrate for optical disks of the present invention is that if water or oligomers remain on the substrate, those substances will come out on the substrate surface during vacuum film formation and react with the rare earth transition metal alloy. The so-called Week boundary
The y layer is formed at the interface between the substrate and the magneto-optical recording layer.
Such a problem can be prevented by using the substrate of the present invention.

Materials for the resin substrate for optical disks of the present invention include polycarbonate, polymethyl methacrylate, epoxy resin, etc. Among them, polycarbonate is most desirable in terms of heat resistance and injection moldability for forming groups (guide grooves).

Generally, resin substrates for optical discs tend to contain water, and usually contain about 0.1 to 5.0% by weight of water.

The resin substrate for an optical disk of the present invention has a weight loss rate of 0.05% or less after heat treatment at 100° C. for 1 hour, and the water content therein is considered to be very small at 0.05%.

Methods for obtaining the resin substrate for an optical disk of the present invention include various methods such as heating, degassing, degassing in vacuum, and storing after injection molding so as not to absorb moisture.

The above method mainly removes moisture from the substrate,
Weight loss rate after heat treatment at 100℃ for 1 hour is 0.0
It is possible to obtain a resin substrate for optical discs having a content of 5% by weight or less.

Even if the resin substrate for an optical disk of the present invention is obtained by the above method, if it is left at room temperature, it will absorb moisture in the environment and the weight loss rate after heating at 100°C for 1 hour will be zero. Since the content exceeds .05% by weight, special attention must be paid to the storage environment of the resin substrate for optical discs of the present invention.

For example, an effective method is to store the recording layer under low humidity until immediately before forming the recording layer using a vacuum film forming method.

In the present invention, heat treatment at 100°C for 1 hour means that a 50+ mm square resin substrate as a measurement sample piece is placed in a cleanliness class 100 oven using a front-blown horizontal laminar flow circulation method and heated to 100°C. It is heat-treated for 1 hour.

The weight reduction rate is the calculated value of (Wl-W2)/WIX100 (wt%), where Wl is the weight of the measurement sample piece before heat treatment and W2 is the weight immediately after heat treatment. .

A thin film of an optical recording layer is formed on the resin substrate for an optical disc of the present invention by a vacuum film forming method such as a sputtering method. Film formation is performed in a high vacuum with almost no moisture, so the weight loss rate of the resin substrate for optical disks during heat treatment at 100'C for 1 hour when installed in the vacuum chamber of the vacuum film formation equipment is If it is 0.05% or less, the object of the present invention can be fully achieved.

In order to obtain a magneto-optical disk with good adhesion of the optical recording layer without deterioration of the magneto-optical properties, the objective of the present invention is to satisfy the conditions for the resin substrate for the optical disk of the present invention during vacuum deposition of the optical recording layer. is important. Conversely, after forming an optical recording layer on the resin substrate for an optical disk of the present invention, for example, the optical disk is placed under high temperature and high humidity, and the resin substrate absorbs moisture and is subjected to heat treatment at 100° C. for 1 hour. Even if the weight M-$i fraction exceeds 0.05%, the above object of the present invention can be fully achieved.

When obtaining a magneto-optical disk on the resin substrate for optical disks of the present invention, a thin film of a recording layer of rare earth transition metal alloy, a dielectric protective layer such as silicon nitride or aluminum nitride, and an enhancement layer are formed to protect the thin film of the recording layer. Filmed.

(Effects of the Invention) By using a resin substrate for an optical disc that has a weight loss rate of 0.05% by weight or less after heat treatment at 100°C for 1 hour, there is no deterioration in properties and the adhesion of the optical recording layer is improved. It is possible to obtain optical discs with good quality.

The novel effects of the present invention described above will be made clearer through the following Examples and Comparative Examples.

(Example-1) Outer diameter 130 nuwφ, inner diameter 15■φ, thickness 1.2mm with guide grooves (groups) provided on one side by injection molding
The polycarbonate substrate was heat treated at 130° C. for 2 hours using a class 100 clean oven.

50 from polycarbonate substrate subjected to the above heat treatment
A sample piece measuring mm square was cut out and its weight was measured, and it was found to be 3.5520 gr.

After that, put the measuring piece in the oven,
Heat treatment for measurement was performed at 100° C. for 1 hour.

Immediately after the heat treatment for this measurement was completed, the sample piece was taken out of the oven and its weight was measured, which was 3.55.
27 gr, and thus the weight loss rate of the polycarbonate substrate was determined to be 0.02% by weight.

After the polycarbonate substrate was heat-treated at 130° C. for 2 hours, it was immediately mounted on a substrate holder in a vacuum chamber of a magnetron sputtering device.

Next, the vacuum inside the vacuum chamber was set to 5X10-'Torr.
It was evacuated until .

Thereafter, Ar gas was introduced into the vacuum chamber until the vacuum level reached 1X10-'' Torr.

Next, a predetermined RF power is applied to each target, and a silicon nitride enhancement layer with a thickness of 100 OA is applied to the surface of the polycarbonate substrate where the guide groove is provided.
b A recording layer of Fe Co and a dielectric protective layer of silicon nitride having a film thickness of 1000 μm were sequentially formed in this order to form a magneto-optical recording layer having a three-layer structure, and a sample of a magneto-optical disk was obtained.

(Example-2) After heat treating a polycarbonate substrate, the temperature was 25°C and the humidity was 30°C.
A magneto-optical disk sample was prepared under the same conditions as Example 1, except that it was stored for 3 days in a desiccator whose humidity was adjusted to %RH.

The weight reduction rate of the polycarbonate substrate by heat treatment at 100° C. for 1 hour was 0.05% by weight.

(Example-3) After heat treatment of polycarbonate substrate, 50m5+Tor
Except that it was stored for 3 days in a vacuum drying group with an atmosphere of
A magneto-optical disk sample was prepared under the same conditions as in Example-1.

The weight reduction rate of the polycarbonate substrate by heat treatment at 100° C. for 1 hour was 0.02% by weight.

(Example 4) A magneto-optical disk sample was prepared under the same conditions as Example 1, except that a polycarbonate substrate that had been injection molded within 2 hours was used without heat treatment.

The weight reduction rate of the polycarbonate substrate by heat treatment at 100° C. for 1 hour was 0.02% by weight.

(Comparative Example-1) A magneto-optical disk sample was prepared under the same conditions as in Example-4, except that it was stored in a room at 25° C. and 60% RH for 3 days after injection molding.

The weight reduction rate of the polycarbonate substrate by heat treatment at 100° C. for 1 hour was 0.3% by weight.

(Comparative Example-2) After heat treatment of polycarbonate substrate, 25℃, temperature 60℃
Except that it was stored for 3 days in a room with an atmosphere of %RH.
A magneto-optical disk sample was prepared under the same conditions as in Example-1.

The weight reduction rate of the polycarbonate substrate by heat treatment at 100° C. for 1 hour was 0.3% by weight.

For the magneto-optical disk samples obtained as described above, the adhesion and magneto-optical properties of the magneto-optical recording layer were evaluated using the following measurement methods.

As for the magneto-optical characteristics, the coercive force He, which greatly affects the C/N of the magneto-optical disk, was measured.

The results obtained are shown in Table 1.

Evaluation of adhesion: A 5chotch #810 adhesive tape was adhered onto the magneto-optical recording layer, and the adhesive tape was adhered to the magneto-optical recording layer, and the adhesive tape was adhered to the adhesive tape No.
Measurement was performed using the peel-off method described on page 28.

The case where the magneto-optical recording layer peeled off from the substrate was shown as x, and the case where it did not peel off was shown as O.

Measurement of coercive force Hc: A curl loop measuring device was used under conditions of a maximum applied magnetic field of 15 KOe.

The magneto-optical disk samples of Comparative Example-1 and Comparative Example-2 in Table 1 were found to be heavy, probably due to moisture absorption during storage under relatively high humidity conditions after injection molding or heat treatment. The l reduction rate was increased by one order of magnitude compared to each treatment in the examples.

Moreover, both the adhesion and the coercive force decreased.

Claims (2)

[Claims] (1) A resin substrate for an optical disc, which has a weight loss rate of 0.05% by weight or less after heat treatment at 100° C. for 1 hour in air. (2) An optical disk manufacturing method in which an optical recording layer is formed on a resin substrate by a vacuum film forming method, wherein the resin substrate immediately before film formation is the optical disk resin substrate according to claim 1. manufacturing method.