JPS61190739A - Optical recording medium - Google Patents

Abstract

PURPOSE:To facilitate tracking even in the case of using a recording material which cannot form a pregroup by constituting a light reflective film of two kinds of materials having different reflectivities. CONSTITUTION:An optical recording medium consists of a transparent hard substrate 1, an optical recording film 2 and the light reflective film consisting of two kinds of the materials 3, 4 having different light reflectivies. Either 3 or 4 of two kinds of the materials constitutes an optical guide track. A light beam is irradiated from the substrate 1 side on such recording medium, then the intensity of the reflected light changes when the light beam deviates from the track and therefore the tracking is possible by detecting the change thereof. The tracking is possible according to such constitution as the formation of two kinds of the materials onto a Bi-substd. garnet film to a pattern shape even in the case of using the Bi-substd. garnet film formed on, for example, GdGa garnet as a recording material.

Description

[Detailed Description of the Invention] [Summary] Even when using an optical recording material that is difficult to form on a pregroup, light reflection can be achieved by configuring a light reflection film with two types of substances with different reflectances. Tracking can be performed using the difference in rate.

[Industrial application field]

The present invention relates to optical recording media, and more particularly to a method for tracking a magneto-optical disk.

[Conventional technology]

Conventionally, in a magneto-optical disk, tracking is performed using a laser beam guide groove called a pre-group. Generally, pre-groups are transferred directly from a stamper to a plastic substrate, or by 2P (photo-polymer) between a stamper and a substrate such as a glass substrate.
) It is formed by sandwiching resin and curing it with ultraviolet light. Usually, a recording medium such as a rare earth-transition metal amorphous alloy is formed on the substrate with the pregroups by sputtering or vapor deposition.

[Problem that the invention seeks to solve]

Depending on the recording material, it may be impossible to form a recording film on a substrate on which pregroups are formed as described above. For example, gadolinium gallium garnesoto<GGG
) is used as a recording material. Although it is possible to form a bismuth-substituted garnet film on a flat glass substrate,
In that case, the problem is the same.

Therefore, an object of the present invention is to enable tracking even when using a recording material in which pre-groups cannot generally be formed.

[Means for solving problems]

Referring to FIG. 1, the optical recording medium according to the present invention comprises a transparent hard substrate 1, an optical recording film (usually a semi-transparent material) 2, and two types of materials 3.4 having different light reflectances. It consists of a reflective film, and one of the two types of materials (3
or 4) constitutes a light guide trunk. For example, the material 1.2 is formed into a concentric or spiral shape. Data information is formed in area a (or b).

[For production]

If a light beam is irradiated onto this optical recording medium from the transparent hard substrate 1 side with the beam spot diameter narrowed to approximately the trunk width (for example, b in Figure 1), the reflected light intensity will change when the light beam deviates from the track. Therefore, tracking can be performed by detecting this change.

With this configuration of the optical recording medium, for example, even when a bismuth-substituted garnet film formed on GGG is used as a recording material, it is easy to form two types of substances in a pattern on the bismuth-substituted garnet film. Therefore, tracking becomes possible.

It is preferable that the two types of substances 3.4 have significantly different light reflectances in visible or near infrared light. Although metals are excellent as materials with high light reflectance, materials with low light reflectance do not necessarily have to be metals, and may be resins or other materials. Further, one of the members may be a stand instead of a light reflecting material. Although the area where information is recorded does not necessarily have to have a high light reflectance, it is necessary that the area where optical recording is performed has a certain degree of light reflectance.

〔Example〕

The following method using photolithography can be used to form a disk having the structure shown in FIG. An example will be shown in which a recording medium is bismuth-substituted garnet 6 formed on GGGs.

First, a chromium (Cr) film 7 is formed to a thickness of about 0.1 μm by sputtering or vacuum evaporation, and then a photoresist 8 is applied (FIG. 2(a)). This is exposed to an Ar laser in concentric circles with a width of about 0.6 μm and an interval of about 1.6 μm, and developed (FIG. 2(b)). Next, the exposed Cr portion is completely removed by reactive etching using plasma (FIG. 3(C)). Here, the photoresist 8 is removed using an organic solvent, and then an aluminum film 9 is applied to the entire surface by sputtering or vacuum evaporation to a thickness of about 0.2 μm (FIG. 2(d)).

Regarding light with a wavelength of 800 nm. The reflectances of l and Cr are 90% and 44%, respectively, and tracking using a semiconductor laser (LD) is possible.

〔Effect of the invention〕

In the optical recording medium of the present invention, tracking can be performed even when using a recording material that cannot be formed on a pregroup, such as bismuth-substituted garnet formed on GGG.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an optical recording medium of the present invention, and FIG. 2 is a cross-sectional view of the optical recording medium in the order of steps in an embodiment of the present invention. 1... Transparent substrate, 2... Optical recording film, 3.4
...Two types of substances with different light reflectance, 5...GGG
, 6... Bismuth-substituted garnet film, 7... Chromium film, 9... Aluminum film.

Claims (1)

[Claims] 1. Consists of a transparent hard substrate, an optical recording film formed on the transparent hard substrate, and a light reflecting film formed on the surface of the optical recording film opposite to the transparent hard substrate, and the light reflecting film has a light reflectance. 1. An optical recording medium that is formed of two types of materials with different materials, and a pattern of one of the two types of materials functions as a light guide track due to the difference in light reflectance of the two types of materials.