JPH02118935A - Magneto-optical disk - Google Patents

Abstract

PURPOSE:To enable the tracking necessary for high-density recording with the magneto-optical disk for which a Faraday effect is used by alternately concentrically or spirally forming high-reflectivity regions and low-reflectivity regions to the disk. CONSTITUTION:A recording system 2 consisting of garnet is formed on a glass substrate 1. An Al layer 3 is formed thereon. Resist patterns 5 are then concentrically formed on the layer 3. After chemical etching is executed, the resist 5 is removed to obtain the concentrical patterns of the layer 3. A layer 4 consisting of carbon is further formed thereon. The reflected films 3+4 formed alternately and concentrically with the high-reflectivity regions consisting of the carbon and the low-reflectivity regions consisting of the carbon on the reflecting surface are obtd. with the magneto-optical disk made of the garnet obtd. in such a manner. The tracking is enabled in this way and the disk is utilizable as the high-density recording medium.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a magneto-optical disk using the Faraday effect, which can perform tracking necessary for high-density recording.
The object of the present invention is to provide a magneto-optical disk using the Faraday effect, in which a high reflectance region having sufficient reflectance to obtain a necessary magneto-optical signal is provided on the reflective surface of the reflective film. and low reflectance regions having a reflectance lower than that of the high reflectance region by a sufficient difference for tracking are formed alternately in a concentric or spiral shape.

(Industrial Application Field) The present invention relates to a magneto-optical disk using the Faraday effect.

[Conventional technology]

Magneto-optical disks that use the Faraday effect are made by forming a recording film of a magnetic material (garnet, etc.) that has a Faraday effect on a transparent substrate (glass, etc.), and then forming a reflective film (A1, etc.) on top of it. It is composed of Linearly polarized light incident from the substrate side passes through the transparent substrate, and then when it passes through the recording film, the plane of polarization changes at an angle proportional to the magnetization strength and thickness of the recording film.
The light undergoes a Faraday rotation by θ, ), is reflected by the reflective film, and when it passes through the recording film again, is further rotated by the same angle (θf), and finally passes through the substrate and returns to the outside. Since the rotation angle can be doubled in this way, it has an advantage in reading sensitivity compared to the Kerr effect, in which polarized light rotates when reflected on the recording film surface, so magneto-optical disks that use the Faraday effect have a wide range of applications as recording media. is expected.

However, since magnetic materials having the Faraday effect generally have a high crystallization temperature, it has not been possible to form guide tracks for tracking required for high-density recording. That is, in other optical discs, groups are formed in photopolymer or polycarbonate on a glass substrate to serve as guide tracks. However, this method cannot be applied to magnetic materials that have the Faraday effect because this group is compensated for by high-temperature crystallization.
Therefore, there was a problem in that high-density recording requiring tracking could not be performed.

[Problem to be solved by the invention]

An object of the present invention is to provide a magneto-optical disk using the Faraday effect that can perform the tracking required for high-density recording.

[Means to solve the problem]

According to the present invention, in a magneto-optical disk using the Faraday effect, the reflective surface of the reflective film has a high reflectance area having sufficient reflectance to obtain a necessary magneto-optical signal, and a tracking area. This is achieved by a magneto-optical disk characterized in that low reflectance regions having a reflectance lower than that of the high reflectance region are alternately formed in a concentric or spiral shape with a sufficient difference between the two regions. Ru.

In order to obtain the necessary magneto-optical signal, conventionally, a reflector having a reflectance of about 20% or more is used. Metals such as AI and Ag are mainly used as such materials. The material constituting the high reflectance region of the reflective film of the present invention may be a material that is conventionally used as a reflective film of such a magneto-optical disk using the Faraday effect.

The low reflectance region needs to have a reflectance lower than the high reflectance region by a sufficient difference to enable tracking. The difference in reflectance for this purpose is the difference in reflectance (the difference between the peaks and valleys of the group) that is conventionally used when tracking by group on other optical discs.
is equivalent in principle. In the conventional group system, trunking is normally performed based on a difference in reflectance of about 10 to 30%.

The low reflectance 9M region can be formed of a material whose reflectance is sufficiently lower than that of the material forming the high reflectance region, as described above. In this case, if the material in the high reflectance region is expressed as H1, the material in the low reflectance region, the combination of H and L is H/
For example, when using an Ar laser, L may be Al/C,
8l/Au, Al/Cu, Ag/c, Ag
/Cu etc. are used. Since the order of reflectance is determined by the wavelength of the laser used, the combinations are set as appropriate depending on the laser wavelength.

It is also possible to form the high reflectance region and the low reflectance region with the same material, and process the reflective surface in a concentric or spiral shape using an appropriate method so that the reflectance has the required difference. .

[Function] The magneto-optical disk using the Faraday effect of the present invention has high reflectivity, by forming guide tracks by alternately forming regions with different reflectances in a concentric or spiral shape.
Tracking required for density recording can be performed.

Since this guide track does not have a step on the recording film unlike the guide tracks of the conventional group, the film quality of the recording film is also improved.

In the following, the invention will be explained in more detail by means of examples with reference to the accompanying drawings.

[Example] A garnet magneto-optical disk according to the present invention was manufactured by the steps shown in m1IF(a) to (e).

A garnet recording film 2 (thickness: 0.2 Jtm) was formed on a glass substrate 1 having a thickness of 1 m by sputtering (FIG. 1(a)). On top of this, an AI layer 3 having a thickness of 1 was formed by vapor deposition (FIG. 1(b)).

Next, a resist pattern 5 (thickness 100 m) is formed concentrically with a pitch of 2n on the AI layer 3 by photolithography.
) was formed (Fig. 1(C)). After chemical etching with hydrochloric acid in this state, the resist 5 was removed with an organic solvent to obtain a concentric pattern of the A1 layer 3 (see Fig. 1).
d)). Further, a carbon layer 4 is formed on this layer to a thickness of 2 mm by vapor deposition (FIG. 1(e)). In the thus obtained garnet magneto-optical disk, the high reflectance region (h) of A1 and the low reflectance region 61 (1) of carbon were formed alternately and concentrically at two pitches on the reflective surface. Reflective film (3+4)
has.

In this case, 3 may be formed as a carbon layer and 4 may be formed as an A (layer).

〔Effect of the invention〕

The magneto-optical disk using the Faraday effect of the present invention enables trunking and is therefore extremely useful as a high-density recording medium.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the manufacturing process of a garnet magneto-optical disk according to the present invention. 1... Glass substrate, 2... Garnet recording film, 3
...A1 layer, 4...carbon layer, 5...resist layer.

Claims (1)

[Claims] 1. In a magneto-optical disk using the Faraday effect,
On the reflective surface of the reflective film, there is a high reflectance area that has a reflectance sufficient to obtain the necessary magneto-optical signal, and a reflectance that is lower than the reflectance of the high reflectance area with a difference sufficient to perform tracking. 1. A magneto-optical disk characterized in that low reflectance areas having a low reflectivity are formed alternately in a concentric or spiral shape.