JPH01292645A - Production of information recording medium - Google Patents

Abstract

PURPOSE:To decrease the internal stress of a formed film structural body by exerting external force to a plastic substrate and maintaining the same to an elastically deformed state, then forming the film structural body thereon, and removing the external force to restore the plastic substrate. CONSTITUTION:The plastic substrate 1 is fixed while the substrate is warped to recess the film forming side by a disk holder 5 constituted of a disk supporting table 6, a center mask 7 and an outside peripheral mask 8 and an underlying protective layer, magneto-optical recording layer and overlying protective layer are successively formed in this state on the substrate. The magneto- optical disk formed with the film in such a manner is released from the disk holder 5 to restore the substrate. The residual internal stresses of the film structural body on the plastic substrate 1 produced in such a manner are decreased and the warpage of the substrate 1 is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an information recording medium using a plastic substrate.

[Prior Art] Conventionally, when manufacturing information recording media using plastic substrates, a molded plastic substrate is held in an undeformed state, and a film structure having an information recording function is deposited on it using a vapor deposition method or the like. The film was formed by sputtering method, spin code method, etc.

[Problems to be Solved by the Invention] However, internal stress generally occurs in films formed by vapor deposition, sputtering, spin-coding, or the like.

For this reason, when a film structure is formed on a substrate, the internal stress generated in the film may deform the plastic substrate after the film is formed, resulting in warping, or the equilibrium state with the restoring force generated due to the elastic deformation of the substrate. There have been problems such as film cracking and film peeling due to residual internal stress in the film.

The present invention has been made to solve the above problems, and its purpose is to provide a method for manufacturing a highly reliable information recording medium with less deformation of the substrate and less residual internal stress in the film structure. There is a particular thing.

[Means to solve the problem]

The above purpose is to provide a method for manufacturing an information recording medium by providing a film structure having an information recording function on a plastic substrate, in which the plastic material has a restoring effect in the direction of relieving the internal stress generated in the film structure. This can be achieved by applying an external force to the substrate to keep it in an elastically deformed state, forming a membrane structure on the plastic substrate in the elastically deforming state, and then removing the external force and restoring the plastic substrate.

To apply the external force, a method such as using a disk holder with a concave or convex surface to hold the flat substrate is used.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A magneto-optical disk as shown in FIG. 3 was manufactured by the method described below.

A base protective layer 2, a magneto-optical recording layer 3, and a top protective layer 4 were sequentially formed on an injection-molded flat polycarbonate substrate 1 having a diameter of 130 mm by a sputtering method. At this time, the upper and base protective layers 2.4 were formed using silicon nitride as a material in an Ar gas atmosphere of 0.0 IPa, and each had a film thickness of 1000 A.

The magneto-optical recording layer 3 was formed by a two-dimensional simultaneous sputtering method using a Tb-Fe amorphous alloy thin film as a material.
The film thickness was set to A.

Here, during film formation, the polycarbonate substrate was held while being elastically deformed into the shape shown in FIG. That is,
A flat polycarbonate substrate l is held at the edge of the substrate (r=65 mm) with respect to the tangential plane at the center of the substrate by a disk holder 5 whose main components include a disk support table 6, a center mask 7, and an outer peripheral mask 8. The substrate was fixed with a concave warp on the film-forming surface side so that the amount of warpage defined by the amount of displacement was 5 mm. In this state, when each film is formed and laminated as described above, strong compressive stress is generated in the film. This internal stress acts on the substrate in a direction in which the film structure tends to expand, that is, in a direction in which the substrate is deformed into a convex shape toward the film-forming surface. Furthermore, when the film itself expands, the compressive stress in the film decreases and is relaxed as the film expands.

Now, when the magneto-optical disk formed by the above method is released from the disk holder 5 and restored, the film structure expands compared to the state immediately after the film formation, and the internal stress is relaxed.

When the amount of warpage of the single plate of the magneto-optical disk manufactured in this manner was measured as defined above, it was found that 10 μm was warped in a convex shape on the outer surface side.

Comparative Example 1 For comparison, a magneto-optical disk with the same configuration was manufactured using the same materials and method as in Example 1, except that each film was formed while holding the polycarbonate substrate 1 in an undeformed state. The amount was 150 μm in the convex shape on the membrane surface side.

(Durability test) Furthermore, the magneto-optical disks of Example 1 and Comparative Example 1 were
When the magneto-optical disk of Comparative Example 1 was placed in a constant temperature and humidity chamber at 90% relative humidity and subjected to a 1,000-hour durability test, film cracking occurred on the entire surface of the magneto-optical disk, but the optical disk of Example 1 did not. No change was observed in the appearance of the magnetic disk.

Example 2 The magneto-optical disk produced in Example 1 was protective coated with an ultraviolet curable resin as follows.

After spin-coding uncured resin on the film-forming surface of the magneto-optical disk using a conventional method, the magneto-optical disk 9 was held while being elastically deformed into the shape shown in FIG. That is, the disk holder 5 holds a convex 10J on the film forming surface side of the substrate.
Im further tested the disk of Example 1 with which warp by 3
It was elastically deformed into a state with a warp of about mm and then fixed using a vacuum chuck with an exhaust hole 10. In this state, when the applied UV curable resin is cured with UV 11,
Due to curing and shrinkage of the protective coat layer, tensile stress that tends to shrink is generated in the protective coat layer. This internal stress is reduced and relaxed as the protective coating layer shrinks.

When the magneto-optical disk on which the protective coat layer has been formed by the above method is released from the disk holder 5 and restored, the protective coat layer contracts compared to the state immediately after formation, and the internal stress is relaxed.

The amount of warpage of the thus manufactured magneto-optical disk whose film surface was coated with a protective coating layer was measured, but no warp was measured within the measurement accuracy.

Comparative Example 2 For comparison, a magneto-optical disk with a protective coating layer was manufactured by applying an uncured resin to the magneto-optical disk of Example 1 and then curing it in that state without applying any external force.
The amount of warpage was 100 μm in the concave shape on the coated surface side. [Effects of the Invention] As explained in detail above, according to the method for manufacturing an information recording medium of the present invention, the film structure formed on the plastic substrate The internal stress of the substrate can be reduced, and the environmental resistance of the information recording medium can be improved, as well as the warpage of the substrate can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the holding state of the substrate during film formation in the case of implementing Example 1 of the present invention, and FIG. FIG. 3 is a schematic cross-sectional view of an information recording medium manufactured according to an embodiment of the present invention. Substrate 2: Base protective layer 3: Magneto-optical recording layer 4: Upper protective layer 5: Disk holder 6: Disk support table 7: Center mask 8: Perimeter mask 9: Magneto-optical disk 10 coated with uncured resin : Vacuum chuck exhaust hole 11: Irradiation ultraviolet rays

Claims (1)

[Claims] 1) In a method of manufacturing an information recording medium by providing a film structure having an information recording function on a plastic substrate, an external force is applied to the plastic substrate so that a restoring effect acts in the direction of relieving the internal stress generated in the film structure. A method for producing an information recording medium, which comprises: applying and holding the plastic substrate in an elastically deformed state, forming a film structure on the elastically deformed plastic substrate, and then removing an external force to restore the plastic substrate to its original state.