JPS61122950A - Substrate for optical disk - Google Patents

Abstract

PURPOSE:To obtain a substrate for an optical disk which obviates the camber of the substrate, the deformation of the guide track on the substrate, etc. by the effect of heat when a recording film is formed by a sputtering method, etc. on the substrate and has excellent heat resistance by using transparent ceramic as the substrate. CONSTITUTION:The optical recording film 3 is formed by a sputtering method, etc. on the transparent ceramic substrate 1 such as the transparent alumina substrate obtd. by pressing a stamper having the shape reverse from the shape of the guide track to a thin boehmite gel sheet obtd. by a sol-gel method to transfer the shape of the guide track to said sheet and calcining such sheet in an electric furnace. A protective layer 4 is then provided on the film 3 to obtain the optical disk. The excellent substrate for the optical disk which obviates the deformation by the effect of heat in the stage of forming the film 3 is thus obtd. by using the transparent ceramic substrate 1 in the above- mentioned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a substrate for an optical disk for optical recording used for recording and reproduction. Conventional technology Conventionally, substrates for optical disks have been made of polymethyl methacrylate, polycarbonate, etc. of polymeric materials (e.g.
JP-A-68-139342). The conventional optical disc substrate as described above will be explained below with reference to one drawing.

FIG. 2 shows a cross section of a conventional optical disc. In FIG. 2, 6 is a plastic substrate, 6 is a recording film, and 7 is a protective layer that prevents deterioration such as oxidation of the recording film.

The plastic substrate 5 is usually formed using a cell casting method, an injection molding method, a compression molding method, or a photopolymerization method (17).
p, p method).

Problems to be Solved by the Invention However, the above configuration has a problem in that the polymer material of the substrate has poor heat resistance. Usually, a metal recording film is formed on a substrate by sputtering or vapor deposition, but if the substrate material has poor heat resistance, the heat during sputtering or vapor deposition may cause damage.

The shape of the guide track on the board may be deformed or the board may warp. A guide track with a deformed shape or a warped substrate causes problems such as light deviating from a normal guide track. Therefore, it has been desired to develop a substrate that does not undergo deformation even when a recording film is formed by sputtering or vapor deposition.

In view of the above problems, the present invention provides an optical disk substrate having excellent heat resistance.

Means for Solving the Problems In order to achieve this object, the optical disk substrate of the present invention is a device made of highly heat-resistant transparent ceramics. This prevents the board from warping and the guide track from deforming due to heat.

EXAMPLE An example of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a substrate, 2 is a guide track section, 3 is a recording film, and 4 is a protective layer.

The substrate 1 is obtained from a sintered alumina body using a sol-gel method. That is, aluminum inopropoxide [B(t-C,H,O),'] is used as a starting material, 100 mol of distilled water is added to 1 mol of this material, and the mixture is stirred under heating to effect hydrolysis. Further, 0.1 mole of salt brew was added to 1 mole of monohydroxide produced by hydrolysis, and the mixture was left at 96°C for 4 days to obtain transparent Hiko sol. Transfer this sol to a concave Teflon container and slowly dry it to obtain a transparent boehmite gel thin plate with a thickness of 2.6 cm.Press an inverted-shaped guide track to this gel thin plate to form a guide track shape. Transfer is performed. This gel thin plate is fired in an electric furnace to obtain a 1.2 mm transparent alumina substrate. A recording film 3 is formed by sputtering or vapor deposition on this transparent alumina substrate with a guide track shape. Further, a protective layer 4 was provided on C. During sputtering or vapor deposition, this guide track portion 2 does not undergo any deformation.

As described above, according to this embodiment, by using transparent ceramics for the substrate, it is possible to form a highly heat-resistant substrate that is not deformed by heat during formation of a recording film by sputtering or vapor deposition.

Although transparent alumina was used as the ceramic in this example, other transparent ceramics such as PLZT (
A similar effect can be obtained with zirconate titanate/tan lead). In addition, in this example, the guide tracks were transferred to the gel obtained by the sol-gel method and sintered to obtain the substrate, but it is also possible to transfer the guide tracks to the green root before sintering without using the sol-gel method. By transferring and sintering, it is possible to obtain a transparent ceramic substrate.

Effects of the invention By using transparent ceramics for the substrate, the present invention achieves
No deformation occurs due to heat when forming a recording film by sputtering or vapor deposition. This makes it possible to realize an excellent optical disc substrate.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical disk substrate according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional optical disk substrate. 1...Transparent ceramic substrate, 2...
Guide track section, 3... Recording film, 4...
...Protective layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (1)

[Claims] An optical disc substrate characterized by using transparent ceramics as the substrate.