JPH02183443A - Optical recording medium - Google Patents

Abstract

PURPOSE:To allow recording, reproducing, and erasing from a flat substrate side and to enhance performance, such as C/N, by sticking a grooved substrate and flat substrate which are different in material from each other. CONSTITUTION:The above medium is constituted by providing a magneto-optical recording layer 3 sandwiched by protective layers 2 on the grooved substrate 1 consisting of polycarbonate or the like having good transferability and heat resistance and sticking the flat substrate 5 consisting of an acryl resin, etc., having a low double refractive index and optical characteristics thereon by an adhesive agent 4, such as UV adhesive agent. The both-face medium is constituted by providing the magneto-optical recording layer on the grooved substrate 6 consisting of the polycarbonate, etc., and sticking the flat substrate 7 consisting of the acrylic resin, etc., thereon, then further, sticking two sheets of the disks obtd. in such a manner by the adhesive agent 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical recording medium having a closely bonded structure in which information is recorded, read and erased using laser light.

[Summary of the Invention] The present invention provides an optical recording medium having a closely bonded structure of a groove substrate and a flat substrate, in which a material such as polycarbonate which has excellent groove transferability and good heat resistance is used as the groove substrate, The flat substrate is made of a material with low birefringence and excellent optical properties, such as PMMA, which is different from the material of the groove substrate.By performing recording, reproduction, and erasing from the flat substrate side by irradiating laser light, it can be used as an optical recording medium. The objective is to improve the performance of the optical recording medium and to manufacture an optical recording medium with improved productivity.

[Prior Art] Optical memories (optical recording media), which can record and reproduce larger amounts of information than magnetic memories, have been actively developed and commercialized as next-generation memories in recent years.

In optical recording media such as magneto-optical disks, a laser beam is irradiated onto the recording film to locally increase the temperature of the recording film, and a bias magnetic field is used to change the direction of magnetization, thereby reducing the Kerr effect or Faraday effect of the magnetic thin film. Use to record information.

The structure of a conventional optical recording medium is as shown in Figure 2.
A protective layer (10) was sandwiched on a plastic transparent substrate (9) in which a tracking groove was formed.

It has a structure in which an MO magneto-optical recording film (11) is formed by sputtering or the like, and a protective coating (12) is applied thereon.

In the structure of conventional magneto-optical recording media, recording, reproduction, and erasing are performed in order to eliminate the effects of scratches and contamination on the surface of the recording medium.
This was done by irradiating a laser from the flat side of the transparent substrate on which the tracking groove was formed.

Normally, the thickness of this plastic substrate is about 1.2 mats because it is necessary to increase the diameter of the laser incident surface.

[Problems to be Solved by the Invention] In the structure of the conventional magneto-optical recording medium as described above, the plastic transparent substrate on which the tracking groove is formed is
In molding, a stamper serving as a mold is required to have high transferability of the tracking groove, and it is also necessary to have excellent optical properties such as birefringence, heat resistance, and temperature resistance.

However, in reality, it is extremely difficult to satisfy all of these requirements due to the characteristics of the resin materials currently in use.

For example, polycarbonate resin, which is commonly used as a substrate for optical recording media (optical disks), has excellent heat resistance and moisture resistance, and good moldability, but if you try to improve transferability, There was a problem that stress became high and birefringence increased.

In the case of acrylic resin, it has low birefringence and excellent optical properties, but it has poor heat resistance and has the problem of deformation of the tracking groove by the heat of recording and erasing with laser light.

[Means for Solving the Problems] In order to solve the above problems and improve the performance as an optical recording medium, the optical recording medium of the present invention has a structure in which a groove substrate and a flat substrate are closely bonded, and furthermore, the groove substrate and the flat substrate are bonded together. The groove substrate is made of a material with excellent transferability and heat resistance even if the optical properties are poor, and the flat substrate is made of a material with excellent optical properties.
After the recording film is formed, the optical recording medium is completed by closely bonding with UV adhesive, and recording, reproduction, and erasing are performed from the flat substrate side using laser light.

[Function] According to the present invention, a material with excellent tracking groove transferability and heat resistance is used as a groove substrate, a material with excellent optical properties such as birefringence is used as a flat substrate, and a close bonding structure is formed with a UV adhesive. By doing so, recording, reproducing, and erasing can be performed from the flat plate side, and performance such as C/N ratio is improved.

[Example] FIGS. 1(a) and 1(b) are sectional views for explaining an example of the optical recording medium of the present invention.

In (a), the optical disk groove substrate (1) is manufactured by injection molding and has a thickness of 1. It is a 2ma+ polycarbonate (PC) board.

A TbFeCo magneto-optical recording film (3) sandwiched with a 5iAIN protective layer (2) on the groove surface of this substrate.
is formed by sputtering.

A cast 1 to 2 mm thick acrylic flat substrate (5) was adhered to this substrate using UV adhesive (4) to complete the process.

When this magneto-optical disk was recorded and reproduced using a laser beam from the flat substrate side, it was possible to improve the C/N ratio by more than 2 dB compared to a conventional disk.

(b) is an example of a double-sided media, which is also a PC groove board (
6) is manufactured by injection molding. In this case, the thickness of the substrate is 0. It is 5mm.

After forming a magneto-optical recording film on the surface of this groove as in the case (a), an acrylic flat substrate (7) is bonded with UV adhesive to form a single-sided medium disk.

These two disks are pasted together using a hot melt adhesive (8) to complete a double-sided medium.

[Effects of the Invention] As described above, the present invention provides an optical recording medium having a structure in which a groove substrate and a flat substrate are closely bonded.
The groove substrate is made of a material with excellent transferability and heat resistance, and the flat substrate is made of a material with excellent optical properties.By performing recording, reproduction, and erasing with laser light from the flat substrate side, C.
This aims to improve the performance as an optical recording medium, such as /N ratio, and improves productivity.

In the examples, the combination of PC resin and acrylic resin has been described, but other material combinations may also be used.
Any method that can provide similar effects is included in the present invention.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views showing the film structure and bonding structure of an embodiment of the optical recording medium of the present invention, and FIG. 2 is a cross-sectional view of a conventional optical recording medium. 1.6.9 Groove substrate 2.10 Protective layer 3, 1 5, 7 Magneto-optical recording layer UV adhesive Flat substrate Hot melt adhesive Protective coating Applicant Seiko Epson Corporation Attorney Masataka Shigamiyanagi (1 other person)

Claims (1)

[Scope of Claims] 1) An optical recording medium having a structure in which a groove substrate and a flat substrate are closely bonded together, wherein the groove substrate and the flat substrate are made of different materials. 2) Claim 1, characterized in that recording, reproduction, and erasing are performed from the flat substrate side by laser beam irradiation.
Optical recording medium as described in Section. 3) The optical recording medium according to claim 1, characterized in that the adhesive method for close bonding uses a UV adhesive.