JPS6329339A - Information carrier disk - Google Patents

Abstract

PURPOSE:To improve repetitive characteristics of recording and erasure by forming a recording medium on the track groove face of a disk-shaped transparent substrate, covering the recording medium layer with a protective layer and constituting the transparent substrate and the protective layer of a resin material having specific heat resistance. CONSTITUTION:The recording and erasure are executed by projecting laser light 15 from the direction of the disk substrate 9. The recording medium 11 is quickly heated and quickly cooled to form an amorphous state having a low reflectivity by which information bits are formed when the laser light of a high power density throttled down to about 1mum spot diameter is projected to the disk at the time of recording. The recording medium layer 11 is slowly heated and slowly cooled to form a crystalline state having a high reflectivity, by which the recording bits are erased when the laser light of the low power density formed to an elliptical shape is projected to the disk at the time of erasing. Reproduction is executed by reading the recorded information bits with the laser light of the power substantially lower than the power for the recording and erasure. The formation of microcracks is thereby prevented and the deterioration of the repetitive characteristics of recording and erasure is prevented.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an information carrier disk (hereinafter simply referred to as a disk) in which a recording medium layer is provided on a disk-shaped transparent substrate and information is optically recorded, reproduced, or erased. It is related to the structure of

Conventional technology Conventionally, a recording medium layer is formed on one side of a disc substrate made of a disc-shaped transparent substrate, and minute holes are formed in the recording medium layer by irradiating laser light from the disc substrate side, or optical Discs on which recording and reproduction are performed by forming bits with varying densities have been put into practical use. Furthermore, erasing disks that allow repeated recording and erasing by reversibly changing the optical density of the recording medium layer are being put into practical use.

In the case of this erasing disk, since recording and erasing are performed by heating the recording medium 1 with a laser beam above its melting point and then cooling it in air or gradually, the temperature reaches a high temperature, albeit in a small area of around 1 μm. If a resin material with low Niijima property was used for the disk substrate, the disk substrate would be deformed by this heat, making it impossible to repeat recording and erasing. Therefore, it is necessary to form a heat insulating layer between the disk substrate and the recording medium layer or between the recording medium layer and a protective layer that protects the recording medium layer to prevent thermal deformation. Various proposals have been made regarding the material of this heat insulating layer, but all of them are 5in2゜λgN, 5i5N4.
It was made of inorganic materials such as, and had a structure as shown in Figure 3. In FIG. 3, 1 is a disk substrate made of a transparent resin material, 2 is a track groove for guiding laser light formed on one surface of the disk substrate 1, and 3 is a first track groove formed on the track groove 2. A heat insulating layer 4 is a recording medium layer formed on the first heat insulating layer 3, on which a second heat insulating layer 5 is formed, and in order to further protect these layers, an adhesive 6 is placed between them. A protective board is attached. In the configuration shown in Fig. 3, recording, reproduction, and erasing are performed by irradiating laser light from the direction of arrow 8 (for example, in
Problems to be Solved by the Invention of Publication No. 110052 However, since the heat insulating layer is made of an inorganic material, there is a large difference in the coefficient of thermal expansion between the heat insulating layer and the disk substrate made of a resin material. Due to changes in the storage environment or repeated recording and erasing, the heat from the laser beam can cause the insulation layer to peel off from the disk substrate, resulting in small cracks. It is also made of inorganic material, and its thickness is 1
Methods for forming a heat insulating layer of about 100n include vapor deposition,
A thin film forming method such as a sputtering method is required, and there are production problems such as a long forming time or a large forming apparatus. The present invention aims to provide a disk that prevents scratches and minute cracks between the heat insulating layer and the disk substrate, has excellent repeatability of recording and erasing, and has excellent productivity.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a disk substrate integrally formed with track grooves for guiding laser light using a resin having heat resistance with a heat deformation temperature of 200'C or more. After a recording medium layer is formed on the surface of the trunk groove, a protective layer is formed to protect the recording medium layer using the same heat-resistant resin material as the disk substrate.

In other words, by protecting the recording medium layer formed on a heat-resistant disk substrate with a layer of heat-resistant resin, it is possible to prevent the disk substrate from deforming due to the heat of the laser beam during repeated recording and erasing. This makes it possible to obtain a reliable disk that does not require a heat insulating layer made of an inorganic material.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 9 denotes a disk substrate made of a heat-resistant resin material having a heat deformation temperature of 200 DEG C. or higher, and has track grooves 10 for guiding laser light formed on one surface thereof. 11 is TeOx, Ge, Sn formed on the surface of the track groove 10.
A phase change recording medium layer having a composition of can be formed by sputtering, vapor deposition, or the like.

Reference numeral 12 denotes a protective layer formed on the recording medium layer 11, which is made of a resin material having heat resistance at a heat distortion temperature of 200° C. or higher, similar to the disk substrate 9, and has a thickness of 1 μm.
Since a layer with a wide degree of thickness can prevent thermal deformation during recording and erasing, it can be easily formed by, for example, a spin coating method. Furthermore, as for the curing method, it is possible to cure the resin material in a short time by using an ultraviolet curing type material as the heat-resistant resin material. 13 is a protective plate and adhesive 14
The entire surface is filled and bonded together to form a disk. In the configuration shown in FIG. 1, recording and erasing are performed by irradiating a laser beam 15 from the direction of the disk substrate 9. That is, during recording, by irradiating a flat laser beam with a power density focused to a spot diameter of about 1 μm, the recording medium layer 11 is rapidly heated and cooled to an amorphous state with low reflectance, and information bits are formed. Ru. During erasing, the recording medium layer 11 is heated and slowly cooled by irradiation with a laser beam shaped into an ellipse and having a low power density, so that the recording medium layer 11 becomes a crystalline state with high reflectance, and the information bits are erased. In reproduction, the recorded information bits are read using a laser beam of sufficiently lower power than during recording/erasing.

In addition, the heat resistance of the disk substrate 9 and the protective layer 12 was checked by checking the thermal deformation temperature and the repeatability of recording and erasing as follows.

Example 1 Polycarbonate with a heat deformation temperature of about 130°C was used as a disk substrate, a recording medium layer was directly formed, and recording and erasing was carried out with a recording power of 8 mW and an erase puff of -16 mW. As a result, the substrate was completed after about 100 repetitions. thermal deformation occurred and the noise increased significantly.

Example 2 Heat deformation temperature of disk substrate and protective layer is 230'C
As a result of conducting the same evaluation as in Example 1 using alicyclic methacrylate, it was found that after 104 repetitions, there was no increase in noise due to thermal deformation and good repeatability was obtained.Example 3 Based on the results of 1.2, the composition ratio of alicyclic methacrylate was changed and the heat distortion temperature was set to 150'C and 170'C.
C. and 200.degree. C., and as a result, it was found that by setting the thermal deformation temperature to 200.degree. C. or higher, there was no increase in noise due to thermal deformation and good repeatability was obtained.

The above results indicate that by setting the thermal deformation temperature of the resin material to 200°C or higher, it is possible to prevent the thermal shock of laser light due to repeated recording and erasing without using a highly heat-resistant heat insulating layer made of inorganic material. found.

FIG. 2 shows another embodiment of the present invention, the basic configuration of which is the same as the embodiment of FIG. 1, but a reflective layer 16 made of a thin metal film is formed on the protective layer 12, It has a so-called three-layer structure that improves recording sensitivity by reflecting the laser light that has passed through it. In this case, the thickness of the protective layer 12 is important in achieving the effect of the three-layer structure, and although it is possible to use the above-mentioned spin coating method, it is also possible to form the film with high precision using a heat-resistant resin material, for example, by sputtering. It is possible.

In the above embodiments, an example of a phase change type original disk has been described, but the present invention can also be applied to a magneto-optical disk in which recording and erasing are performed using the heat of a laser beam and a magnetic field. It is also possible to form a double-sided disc by forming track grooves, a recording medium layer, and a protective layer on the protective plate.

Effects of the Invention The present invention forms a recording medium layer on a disk substrate having heat resistance with a heat distortion temperature of 200'C or more, and protects it with a heat resistant resin layer with a heat distortion temperature of 200C or more.
The conventional insulating layer made of inorganic materials can be removed,
It prevents peeling and minute cracks due to the difference in thermal expansion coefficient between the inorganic material heat insulating layer and the resin material disc substrate.
This can prevent deterioration of the erase repetition characteristics. Furthermore, by removing the heat insulating layer and replacing the protective layer with a heat-resistant resin layer that is easy to form, a disk with a simple structure and excellent productivity can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an information carrier disk in one embodiment of the present invention, FIG. 2 is a sectional view of an information carrier disk in another embodiment of the present invention, and FIG. 3 is a sectional view of a conventional information carrier disk. be. 9... Disc substrate, 10... Track groove, 11... Recording medium layer, 12...
protective layer. Name of agent: Patent attorney Toshio Nakao and 1 other M1
Figure 2

Claims (1)

[Claims] A disk-shaped transparent substrate with track grooves formed on one side.
A recording medium layer is formed on the track structure, this recording medium layer is covered with a protective layer, and the transparent substrate and the protective layer are made of a resin material having heat resistance with a heat distortion temperature of 200°C or higher. information carrier disk.