JPS6050640A - Disc base plate - Google Patents

Abstract

PURPOSE:To obtain easily a recording layer having a uniform thickness without intrusion of a coating liquid for the recording layer to the central side by forming a solventphilic undercoating layer having the inside circumferential diameter larger than the diameter of the central hole of the solventphobic base plate then forming an optical information recording layer thereon. CONSTITUTION:A solventphilic undercoating layer 2 consisting of an acrylic curable resin, etc. is coated on an ''Acrylite AR'' base plate 1 formed by coating a solventphobic material such as an isobutyrene rubber or fluroresin on the surface of a base plate consisting of polymethacrylate or the like. The central part of the plate 1 is masked with a circular mask 8 and UV light 9 is irradiated thereto in such a way that the inside circumferential diameter of the layer 2 is larger by about 5-25mm. than the central hole diameter B of the base plate. The uncured resin in the central part is washed away by a solvent. A coating liquid for forming a recording layer is dropped onto the layer 2 from the inside to the outside and is then spin-coated and dried to form a recording layer 3. The layer 3 is thereby formed to a uniform film thickness and the inside circumferential diameter C of the layer 3 is constituted to the same diameter as the inside circumference A of the layer 2. the high-accuracy disc is thus obtd.

Description

[Detailed description of the invention] Technical field The present invention relates to a disk substrate for an optical information recording medium.

More specifically, the present invention relates to a disk substrate suitable for an optical information recording medium in which a recording material is coated.

In the conventional optical signal recording and reproducing method, high-density recording and reproducing is performed by concentrating light into a minute spot using a lens optical system. Therefore, if there is dust, foreign matter, scratches, irregularities, etc. on the substrate, noise, This causes problems such as dropouts and is a practical hindrance. Therefore, it has been proposed to provide a subbing layer such as a resin on the substrate to eliminate or reduce the influence of dust, foreign matter, etc. existing on the substrate, thereby making it possible to record and reproduce optical signals with high precision. In addition, the subbing layer has the effect of smoothing out scratches and unevenness on the substrate surface, and the recording layer provided on top of it has a smoother surface, which further reduces noise. Become. on the other hand,
As shown in FIG. 1, when the recording layer 3 is provided on the undercoat layer 2, the inner circumferential diameter A of the recording layer 3 is set to be smaller than the center hole diameter B in order to avoid uneven coating due to the effect of the center hole 4 of the substrate 1. also needs to be made larger. However, since the conventional undercoat layer 2 is provided over the entire surface of the substrate 1 as shown in FIG. 1, it is difficult to accurately determine the inner diameter A of the recording layer 3. Therefore, there was a problem that uneven coating occurred.

Purpose The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce unevenness in spin coating and to improve uniformity in optical information recording media (optical disk memory) in which a recording material is coated on a disk substrate. It is an object of the present invention to provide a disk substrate on which coating can be easily achieved.

Structure The disk substrate of the present invention is characterized in that it consists of a solvophobic substrate and a solvophilic subbing layer, and that the inner peripheral diameter of the subbing layer is Q larger than the diameter of the center hole of the substrate. .

Here, "a solvophobic substrate" means a case where only the surface of the substrate is made of a solvophobic material or a case where the entire substrate is made of a solvophobic material. Typically, a substrate with a solvophobic material applied to its surface is used. Examples of the solvophobic material include inbutylene rubber, fluorine resin, and the like. The solvophobic substrate can be obtained by applying a thin film of inbutylene rubber to the surface of a substrate made of plastic or the like by a conventional coating method such as roller coating, dipping, or spin coating. In addition, a plastic plate (for example, Acrylai made by Mitsubishi Rayon) AR with a solvent-phobic material such as inbutylene rubber attached as a mining sheet
) can be used as is for the purpose of the present invention.

Most synthetic resins can be used as the solvent-philic subbing layer, but photocurable resins are suitable in terms of solvent resistance when coating the recording layer and ease of forming the innermost layer. . As the photocurable resin, for example, an acrylic photocurable resin, a mixture of polyene and a polythiol compound, etc. are used.

Next, the structure of the disk substrate of the present invention will be explained with reference to the drawings.

As shown in FIG. 2, the disk substrate of the present invention is composed of a solvophobic substrate 1 and a solvophilic undercoat layer 2. As shown in FIG. The inner circumferential diameter C of the undercoat layer 2 is arbitrary, as long as it is larger than the center hole diameter B of the substrate 1.

However, if the inner circumferential diameter C of the undercoat layer 2 is made too large, the recording area of the recording layer 3 will become small.
An appropriate inner diameter CII'i of about 40 to 60 mm is suitable. Further, as shown in FIG. 3, it is more effective to provide an annular projection 5 on the inner periphery of the undercoat layer.

In addition, in the present invention, since the substrate surface is solvent-phobic, the coating liquid 6 of the recording material is applied inside the inner periphery 7 of the undercoat layer 2 (center side) when forming the recording layer 3, as shown in FIG. It is applied based on the inner periphery 7 without entering K. As a result, a uniform recording layer can be obtained. Furthermore, since the undercoat layer is solvent-philic, the coating liquid spreads over the undercoat layer to form a uniform recording layer.

EXAMPLES The present invention will be further described below with reference to Examples as well as comparative examples, but the present invention is not limited thereto.

Example 1 As shown in FIG. 5, an acrylic photocurable resin was applied as an undercoat layer 2 to an acrylic AR substrate (manufactured by Mitsubishi Rayon) 1 having a solvent-phobic surface, and a circular mask was formed around the center. 8 and irradiated with ultraviolet light 9. The uncured resin in the center was washed away with a solvent to produce a disk substrate of the present invention. Next, a recording material coating liquid consisting of 10% nitrocellulose, 95% water blue, and 80.5% acetone was dropped onto the outside of the inner periphery of the undercoat layer of the substrate, and the coating liquid was then applied by rotation to form a recording layer. did.

After drying, the thickness unevenness of the recording layer was measured and found to be within ±5 inches.

Comparative Example 1 A disk substrate was produced in the same manner as in Example 1, except that the acrylic photocurable resin of the undercoat layer was cured on the entire surface without using a mask. Next, the coating liquid of the same recording material as in Example 1 was applied to this substrate, and the film thickness unevenness of the recording layer was measured.
It was 10chi.

Example 2 A plasma polymerized film of tetrafluoroethylene (thickness: 0.1 μm) was formed on an acrylic substrate, and an undercoat layer was formed thereon in the same manner as in Example 1 to obtain a disk substrate of the present invention. . The entire recording layer was formed in the same manner as in Example 1. After drying, the film thickness unevenness of the recording layer was measured and found to be within +4%.

Effects: By using the disk substrate of the present invention constructed as described above, a uniform recording layer can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a conventional optical disk memory, FIGS. 2 to 5 are sectional views explaining the present invention, and FIG. 2 shows the structure of a disk substrate, and FIG. is a partially enlarged view when the subbing layer has an annular projection;
The figure shows how the recording material coating liquid is applied to the undercoat layer of the disk substrate, and the figure p+;s shows the method of forming the undercoat layer. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Undercoat layer, 3... Recording layer, 4...
... Center hole, 5 ... Annular projection, 6 ... Recording material coating liquid, 7 ... Inner periphery of subbing layer, 8 ... Circular mask, 9 ...
...Ultraviolet light, A...Inner circumference diameter of the recording layer, B...Center hole diameter, C...Inner circumference diameter of the first downward layer. Patent applicant Rico Co., Ltd. −

Claims (1)

[Claims] What is claimed is: 1. A disk substrate comprising a solvophobic substrate and a solvophilic undercoat layer, and further comprising an inner peripheral diameter of the undercoat layer that is larger than a diameter of a center hole of the substrate.