JPH04177635A - Manufacture of optical disc - Google Patents

Abstract

PURPOSE:To prevent the warpage of a transparent plastic board by controlling the conditions of the plasma etching of the surface of the transparent plastic board so that the product of the power of etching and an etching time is kept within a specific range. CONSTITUTION:A silicon nitride film 1b is formed onto a transparent plastic board 2 through reactive sputtering. A TbFeCo film as a recording layer 3 is formed onto the film 1b. The surface and the rear of the board are turned over, and the surface on the side reverse to the layer 3 is plasma-etched. The surface of the board 2 is plasma-etched under conditions, in which the product of power density per the unit surface of an etching surface and an etching time is kept at a value from 0.02 to 1.00 on these plasma etching. A silicon nitride film 1a as a transparent thin-film layer is shaped in the same manner as the film 1b is formed. Accordingly, an optical disc having excellent adhesion and the transparent thin-film can be acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an optical disc having a transparent thin film on a transparent plastic substrate on which a recording film is formed.

[Conventional technology]

FIG. 4 is a schematic cross-sectional view showing a conventional optical disc disclosed in, for example, Japanese Patent Application Laid-open No. 197964/1982. A recording film 13 is a silicon nitride film formed on the other surface of the transparent plastic substrate 11.

It is a transparent thin film such as a silicon oxide film or an aluminum oxide film.

Next, the operation will be explained.

Since the above-mentioned optical disk is provided with a transparent thin film 13 on a transparent plastic substrate 11, moisture absorption of the transparent plastic substrate 11, which generally has a high water absorption rate, is prevented by this transparent thin film 13, and the transparent plastic substrate 11 is prevented from absorbing moisture due to humidity fluctuations.
can prevent warping. As described above, if these transparent thin films 13 have a dense structure, moisture does not pass therethrough and the transparent plastic substrate 11 can be prevented from absorbing moisture. However, if the adhesion of the transparent thin film 13 to the surface of the transparent plastic substrate 11 is weak, in the long term, it may cause deterioration of the surface of the transparent plastic substrate 11, etc.
The transparent thin film 13 may peel off from the transparent plastic substrate 11. Furthermore, in many cases, the surface of the transparent plastic substrate 11 on which the recording film 12 is formed has track grooves for guiding the light beam, increasing the surface area. On the other hand, since the surface of the transparent plastic substrate 11 on the opposite side to the recording film 12 is formed as smooth as possible to prevent diffuse reflection of the light beam, the adhesion force of the transparent thin film 13 tends to decrease. be.

Furthermore, one method for strengthening the adhesion is to plasma-etch the surface of the transparent plastic substrate 11 before forming the transparent thin film 13. For example, on pages 83 and 84 of the Proceedings of the Optical Memory Symposium '90, there is a report on a method for improving adhesion by etching the surface of a polycarbonate substrate with Ar plasma when forming a silicon nitride film on the surface of the substrate. ing.

However, the following experiment has revealed that under certain conditions, the transparent thin film 13 may peel off. In this experiment, before forming a silicon nitride film with a thickness of 1200 angstroms as the transparent thin film 13 on a transparent plastic substrate 11 with a diameter of 86 mm, the surface of the transparent plastic substrate 11 was etched with Ar plasma using various etching input power and etching time. I researched the optical buisfu created by

Figure 5 shows the results after etching was performed under various conditions of input power density P and etching time T, assuming that the input power density per unit surface area of the etched surface is P watts/cm2 and the etching time is T minutes. This is the front page showing the results of examining whether the formed transparent thin film 13 peels off or not. Here, marks 0, Δ, and 0 indicate cases in which no peeling of the transparent thin film 13 occurred immediately after the formation of the transparent thin film 13, cases in which peeling occurred on a part of the disk surface, and cases in which peeling occurred on the entire disk surface. Each indicates that peeling has occurred. Further, O marks, Δ marks, and - marks respectively indicate optical discs after the transparent thin film 13 has been formed.

30℃ in a constant temperature and humidity chamber at 80℃ and 90%RH atmosphere.
After conducting an accelerated test of holding for 00 hours, the transparent thin film 13
This indicates cases in which no peeling occurred at all, cases in which peeling occurred on a part of the disk surface, and cases in which peeling occurred on the entire surface of the disk. Also shown are the measured values of warpage of the disk after forming the transparent thin film. According to this, when the etching condition PXT is less than 0.2, peeling of the transparent thin layer 1113 occurs. This is the transparent thin film 13
This is because the adhesion force to the transparent plastic substrate 11 is not strong enough. Further, the warpage of the optical disk increases as the PXT increases, and even when the PXT exceeds 1.0, peeling occurs in all but a few cases. This is because during etching, only the surface of the transparent plastic substrate 11 exposed to plasma increases in temperature, so the transparent plastic substrate 11 warps, and after the transparent thin film 13 is formed,
This is due to different processes being performed on the front and back sides of the transparent plastic substrate 11, such as reversing the warpage of the transparent plastic substrate 11. Due to the deformation phenomenon of the transparent plastic substrate 11, stress was applied to the transparent thin film 13, and peeling occurred.

[Problem to be solved by the invention]

The conventional manufacturing method for optical discs is as described above.
If the product of the input power density P per unit surface area of the etched portion of the surface of the transparent plastic substrate 11 and the etching time T exceeds the set value range, the transparent plastic substrate 11 will warp and the transparent thin film will peel off, causing the optical head There were issues such as the inability to perform focus servo with high accuracy.

This invention was made to solve the above-mentioned problems, and the transparent thin film remains intact even when placed in a harsh environment of high temperature and high humidity for a long period of time! It is an object of the present invention to provide a method for manufacturing an optical disk that can manufacture an optical disk with little warpage and no warpage.

[Means to solve the problem]

The method for manufacturing an optical disc according to the present invention includes forming a recording film directly or via a transparent thin film on one surface of a transparent plastic substrate, and forming each transparent thin film when forming a transparent thin film on the other surface of the transparent plastic substrate. The surface of the transparent plastic substrate on the etching side is such that the product of the input power density per unit surface area of the etching surface and the etching time is 0.02 or more,
Plasma etching is performed under conditions that result in a value of 1.00 or less.

[Effect]

In the method for manufacturing an optical disk according to the present invention, from the viewpoint of controlling the energy applied to the transparent plastic substrate, the conditions for plasma etching the surface of the transparent plastic substrate are set such that the product of the input power for etching and the etching time is within a specified range. By controlling this, warpage of the plastic substrate is eliminated, and excellent adhesion of the transparent thin film to the plastic substrate is obtained, thereby preventing peeling of the transparent thin film.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, la and lb are silicon nitride films, which are formed as a transparent thin film layer and a protective layer, respectively, on a transparent plastic substrate 2 such as polycarbonate.

3 is a recording layer as a magnetic film made of TbFeCo or the like.

FIG. 2 is a schematic diagram showing a sputtering apparatus for manufacturing an optical disk used to carry out the method of the present invention. In the figure, 4 is a vacuum chamber, 5 is an Ar gas inlet, and 6 is an N gas inlet.
2 a gas inlet, 7 a substrate holder that connects and holds the transparent plastic substrate 2 to a rotating mechanism, 8 a silicon target, and 9 a TbFeCo target.

Next, a method for manufacturing an optical disk as shown in FIG. 1 using the sputtering apparatus shown in FIG. 2 will be described.

First, the substrate holder 7 holding the transparent plastic substrate 2 is rotated. Next, after introducing Ar gas and N2 gas from the inlets 5 and 6, respectively, a high DC voltage is applied to the silicon target 8 to form a silicon nitride film 1b by reactive sputtering. Next, after stopping the introduction of N2 gas, a DC high voltage was applied to the TbFeCo target 9.
and the recording layer 3 T b Fe Co II
form. Furthermore, the front and back of the transparent plastic substrate 2 are switched, the substrate holder 7 is reattached, and after evacuation is again performed, Ar gas is introduced.

Next, a high frequency high voltage is applied to the substrate holder 7 to generate Ar plasma. This plasma discharge causes A
The r ions plasma-etch the surface of the transparent plastic substrate 2 on the side opposite to the recording layer 3. At this time, the board holder 7
The surface area of one side of is 2500 square centimeters, and the input high frequency power is 500 watts, so the input power density P is.

0.2 watts/cm 2 and etching time T is 5 minutes. Therefore, the product of P and T is 1.0, which satisfies the condition of 0.02≦PXT≦1.00. After this etching step, N2 gas was introduced in addition to Ar gas to form a silicon nitride film 1a as a transparent thin film layer in the same manner as when the silicon nitride protective film 1b was formed. In this way, by keeping the product of the etching input power P and the etching time T within the specified range obtained from the above experimental results, it is possible to obtain an optical disk having a transparent thin film 9 with good adhesion.

Further, FIG. 3 is a schematic diagram of a sputtering apparatus for implementing another method of the present invention, in which 4a, 4b, 4c
are the first vacuum tank, the second vacuum tank, the third vacuum tank, and 5a, respectively.
, 5b, and 5c are Ar gas inlet ports provided in each of the vacuum chambers 4a, 4b, and 4c, respectively, and 6 is an N2 gas inlet port provided in the second vacuum chamber 4b. 8a and 8b are silicon targets, 9 is a TbFeCo target, 10a and 10b
is a dummy target for plasma etching.

In addition, the transparent plastic substrate 2 has a dot valve 11° 12
through each vacuum chamber 4a, 4b as indicated by the dotted line arrow.
, 4c, and the side of the transparent plastic substrate 2 on which the recording layer 3 is to be formed is
It is held by a substrate holder so as to face the T b Fe Co target 9 .

Next, a procedure for producing an optical disc using this sputtering apparatus will be described.

First, the transparent plastic substrate 2 is positioned between the two dummy targets 10a and the lob in the first vacuum chamber 4a, and the Ar gas inlet 4a is opened to introduce Ar gas. Further, a high frequency and high voltage is applied to the substrate holder (not shown) to generate Ar plasma. By this plasma discharge, Ar ions plasma-etch both the front and back surfaces of the transparent plastic substrate 2. At this time, the surface area of one side of the substrate holder 7 is 2000 square centimeters, and the surface area of both sides is 4000 square centimeters, and the input high frequency power is 600 watts.

The input power density P is 0.15 watts/cm2, and the etching time T is 4 minutes, so the product of P and T is 0.6. Therefore, this value 0°6 is 0.02≦P
XT≦1. Satisfies the conditions of OO.

Next, the transparent plastic substrate 2 is placed in the second vacuum chamber 4b.
located between two silicon targets 8a and 8b,
Ar gas and N2 gas are introduced, and a DC high voltage is applied to each of the two silicon targets 8a and 8b to generate plasma.

This causes reactive sputtering of silicon, and silicon nitride thin films 1a and lb are formed on both surfaces of plastic substrate 2, respectively.

Furthermore, the transparent plastic substrate 2 is placed in the T of the third vacuum chamber 4c.
It is positioned above the bFeCo target 9, Ar gas is introduced, and a DC high voltage is applied to the TbFeCo target 9 to generate plasma. As a result, T b F
e Co sputtering occurs, and the recording layer Tb
A FeCo thin film 3 is formed on one side of the transparent plastic substrate 2. As shown above, the transparent plastic substrate 2
Although it is desirable to form the silicon nitride films as transparent thin films on the front and back sides at the same time, if they cannot be formed at the same time due to some restrictions, they may be formed sequentially. In the optical disks manufactured according to the above two examples, no peeling of the silicon nitride film was observed either immediately after the manufacture or after being kept in an atmosphere of 80°C and 90% RH for 3000 hours, indicating that the high pressure was unreliable. showed that. Also, the second
The warpage of the optical disc obtained using the sputtering device shown in the figure is 2
．． The optical disc obtained using the sputtering apparatus shown in FIG. 3 shows a small value of 34 m r a d, which is not a problem in practice, and the warpage when silicon nitride films are sequentially formed on both sides of the transparent plastic substrate 2 is as follows. The warpage was 1.10 mrad, and when silicon nitride films were simultaneously formed on both sides of the transparent plastic substrate 2, the warpage was 0.88 mrad, which was an even better result.

In the above embodiment, the transparent thin WA1 on the opposite side of the recording layer 3
a and the transparent thin film 1b on the same side as the recording layer 3.

Both films are made of the same silicon nitride film, but these may be of different compositions, for example, films of materials with transparent and dense structures such as aluminum nitride film, silicon oxide film, aluminum oxide film, tantalum oxide film, etc. For example, effects similar to those of the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, a recording film is formed on one surface of a transparent plastic substrate directly or via a transparent thin film,
When forming a transparent thin film on the other surface of the transparent plastic substrate, the product of the input power density per unit surface area of the etched surface of the transparent plastic substrate on which each transparent thin film is to be formed and the etching time is 0.02. That's 1.00
Plasma etching was performed under the following conditions, which has the effect of producing highly reliable optical discs that do not cause warping of the transparent plastic substrate or peeling of the transparent thin film. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an optical disk manufactured by an optical disk manufacturing method according to an embodiment of the present invention, and FIG.
3 is a schematic diagram showing a sputtering apparatus used in a method for manufacturing an optical disk according to another embodiment of the present invention, FIG. 4 is a schematic diagram showing a sputtering apparatus used in a method for manufacturing an optical disk according to another embodiment of the present invention 5 is a schematic cross-sectional view showing a conventional optical disk, and FIG. 5 is a front view showing test results for peeling of the transparent thin film and warpage of the disk in the conventional optical disk. la and lb are transparent thin films, 2 is a transparent plastic substrate, 3
is the recording film. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 Figure 4 Figure 2 Figure 5 Procedural amendment (voluntary) 3.2.1 e Name of invention Method for manufacturing optical disks 3 Relationship with the case of the person making the amendment Patent applicant Address: 2-3 Sara-chome, Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 5, Subject of amendment 6, Contents of amendment (1) The scope of the claims will be amended as shown in the attached sheet. . (2) The specification shall be amended as follows. 7. List of attached documents A document stating the amended scope of claims One or more documents Amended claims A recording film is formed on one surface of a transparent plastic substrate directly or through a transparent thin film, and a recording film is formed on one surface of a transparent plastic substrate directly or through a transparent thin film, and In a method for manufacturing an optical disc in which a transparent thin film is formed on the other side,
The surface of the above-mentioned transparent plastic substrate on the side on which each of the above-mentioned transparent thin films is to be formed is etched so that the product of the input power density per unit surface area of the etching surface and the etching time is 0.02 watts' centimeter 2 l, 1.00 cm.・ ′ Sen
A method for manufacturing an optical disc, characterized in that plasma etching is carried out under conditions that result in a value of less than 200 nm.

Claims (1)

[Claims] In a method for manufacturing an optical disc, a recording film is formed on one surface of a transparent plastic substrate directly or via a transparent thin film, and a transparent thin film is formed on the other surface of the transparent plastic substrate,
The surface of the transparent plastic substrate on the side where each of the transparent thin films will be formed is etched so that the product of the input power density per unit surface area of the etched surface and the etching time is 0.02 or more, and the etching time is 1.02 or more.
A method for manufacturing an optical disc, characterized by performing plasma etching under the following conditions.