JPS60131650A - Optical memory disk and its manufacture - Google Patents

Abstract

PURPOSE:To enhance the recording sensitivity and stability by forming a recording thin film having MOx composition ratio of metal or semi-metal M to oxygen O on a disk substrate, and setting so that the part far from the disk substrate may contain a larger amt. of oxygen than the part near the substrate in the thicknesswise direction of the thin film. CONSTITUTION:A TeOx sintered body 5 which is a vapor deposition source is set on a hearth 4, and an electron beam 6 is concentrated on the body 5 to evaporate the vapor deposition substance by local heating. A disk substrate 8 is rotated above the sintered body 5 to vapor-deposit a TeOx thin film on the surface having a grooved track 7. When the TeOx sintered body 5 is heated by the electron beam, a film rich in Te is formed by reducing the power to decrease the vapor depositing speed. Conversely, a film rich in TeO2 is formed by increasing the vapor depositing speed. Then when the TeOx thin film is vapor- deposited, the composition rich in Te can be continuously changed to the composition rich in TeO2 from the part near the substrate toward the part far from the substrate by increasing continuously the vapor depositing speed at least at the initial stage. The disk having excellent recording sensitivity and stability can be obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION The field of industrial application is an optical memory disk in which bits of information are recorded on a recording film by laser beam irradiation, and a method for manufacturing the same.

2. Description of the Related Art Structures and Problems Therein In recent years, optical memory disks capable of recording and reproducing data in real time have been highly anticipated as large-capacity, high-density memories. In this method, for example, a laser beam is irradiated onto a disk rotating at high speed, bits are recorded on the recording film, and the bits are read out using the same laser beam. Since recording and playback is performed without contact, it has the advantages of not damaging the pickup or disc, and of allowing high-speed access to work information.

As a recording film that makes such an optical memory disk possible, there is a T eo, x (, C) (x (j) thin film. This TeOx is a mixture of T e O2 and Te. This thin film A phase transformation occurs due to the heat caused by the recording bit, and recording bits are formed by increasing the reflectance and decreasing the transmittance.

The most suitable method for forming the TeOx' thin film is vacuum evaporation, and an example of this evaporation method will be explained in FIG. T
An e-evaporation source 1 and a T e O2 evaporation source 2 are provided, and while the disk substrate 3 is being rotated, the temperatures of the respective evaporation sources 1 and 2 are controlled to perform evaporation.

The properties of a TeOx thin film vary greatly depending on its composition, that is, the value of X in TeOx. FIG. 2 shows the measurement of the difference in thermal transition temperature depending on the composition of the TeOx thin film. When the transmittance of these films deposited on a glass substrate is measured while being heated, a transition in transmittance is observed at a specific temperature. A composition with a large TeO2 component (a composition with a small TeO2 component value) has a low thermal transition temperature, whereas a composition with a large TeO2 component (a composition with a large TeOx thin film value) has a high thermal transition temperature. When the film is heated and heated by laser light to undergo phase transformation to form recording bits, it can be said that the lower the transition temperature, the higher the recording sensitivity of the material.

From this, the composition with a large amount of Te component (hereinafter, Te ri'c
(referred to as a high composition) can result in a highly sensitive recording film.

Next, FIG. 3 shows the results of examining the stability of these TeOx thin films. Te with different compositions deposited on a glass substrate
The Ox thin film was left at 40°C and a humidity of EO% for a long time, and the change in transmittance was measured. A film with T'erich composition shows a significant change in transmittance within a few hours, but T e O2
A rich film shows no changes at all and is very stable.

From the above results, for TeOx thin films, a Toτich composition is advantageous in terms of recording sensitivity and variation, but a TeO2-rich composition is superior in terms of stability, and both have their advantages and disadvantages. have.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems, and aims to provide an optical memory disk with high recording sensitivity and excellent stability, and a method for manufacturing the same. The composition ratio of metalloid M and oxygen 0 is MO
A thin film for recording is formed on a disk substrate, and the thin film is This is an optical memory disk in which the amount of oxygen is set to be greater in a portion far from the disk substrate than in a portion close to the disk substrate in the thickness direction of the disk.
A sintered body containing Ox as a main component is used as an evaporation source, and the evaporation rate is continuously increased at least in the initial stage of evaporating Mow onto the disk substrate.

Example 1 Case of an optical disc in which bit recording is performed by increasing the output of a laser beam during recording, and the change in reflectance of the bit portion caused by heating and thermal transformation is reproduced by a laser beam with a lower output.
．． The composition of the recording film on the side that is irradiated with the laser beam is a major factor that influences the characteristics of the optical disc. Therefore, the TeO on the side irradiated with laser light, that is, near the disk substrate
x In the thin film, as it approaches the disk substrate, T,
By continuously changing the composition to a rich one, the recording sensitivity is increased, and in other areas of the TeOx thin film, the T e
The O2 rich table composition is designed to enhance stability.

Next, a manufacturing method that enables the above-mentioned TeOx thin film structure will be described. FIG. 4 is a schematic diagram showing the manufacturing method. A TeOx sintered body 5, which is a vapor deposition source, is set in the nozzle 4. This TeOx sintered body 5 is intensively irradiated with an electron beam 6, and the deposited material is evaporated by the extreme heating. A disk substrate 8 having groove tracks 7 for guiding laser light is rotating above the TeOx sintered body 6, and a TeOx thin film is deposited on the surface having the groove tracks 7.

When heating the TeOx sintered body 5 with an electron beam,
When the power of the electron beam is lowered and the deposition rate is lowered,
A tertiary film is formed. Conversely, if the power is increased to increase the deposition rate, a T e O2 rich film is formed. This is because the evaporation temperature of Te is 450'C, whereas the evaporation temperature of T e O2 is as high as 733°C. Therefore, when the heating temperature is lowered, only Te is evaporated and a Te rich film is formed, but when the heating temperature is raised, T e O2 is also less likely to evaporate and a Te02 rich film is formed.

Therefore, when depositing a TeOx thin film on a disk substrate, at least in the initial stage, by continuously increasing the deposition rate, the composition changes continuously from Te rich to Te02 rich from the side closer to the substrate to the side farther away from the substrate. can be done.

TeO was deposited on a disk substrate 9 made of acrylic or the like on which the groove tracks shown in FIG.
FIG. 2 is a schematic diagram of a completed disk in which a thin film 1o is formed with a thickness of about 120 nm, and a protective substrate 11 is made into an adhesive structure with an adhesive layer 12 interposed therebetween. FIG. 5 shows a disk in which a hard coat layer 13 is provided on a resin coating 12 similarly applied to a thin film. This disk was rotated at 1800 rpm, and a laser beam was irradiated from the direction of arrow 14 to record a unit frequency of 5 MHz. As a result, a C/N ratio exceeding 5 sdB was obtained, and at 40'C
.

Even after being left in an atmosphere with a humidity of 90%, no significant changes were observed for more than 6 years.

Note that although a TeOx sintered body was used as the vapor deposition source, the same effect can be obtained even in a TeOx sintered body to which other components such as Ge and Sn are added, as long as the main component is the TeOx sintered body. .

Instead of continuously increasing the amount of oxygen, a film with higher stability can be obtained by forming a film component containing more oxygen in a stepwise manner, so to speak, in the form of a multilayer film.

In the above embodiment, T e Ox was used as an example, but Ge
0x(0(x(2), 5nOx(0<)C<2).

In0x(0(x(1,5), B10x(0(x<1.
5) The composition ratio of equal metal or metal M and oxygen 0 is MOx
(0(x (A, A is the value expressed as a stoichiometric ratio of the amount of oxygen 0 when the amount of M is 1)).

Effects of the Invention As described above, according to the present invention, since the amount of oxygen is greater in the parts far from the disc substrate than in the parts close to the disc substrate, it is possible to obtain an optical disc with good recording sensitivity and excellent stability. Moreover, since it is only necessary to control the deposition rate during production, it can be easily carried out.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing an example of a conventional method for forming a TeOx thin film, Figure 2 is a characteristic diagram showing the thermal transition temperature of TeOx thin films with different compositions, and Figure 3 is TeOx with different compositions.
A characteristic diagram showing the stability of the thin film, FIG. 4 is a principle diagram of an apparatus implementing the method for manufacturing an optical memory disk of the present invention, and FIGS. 6 a and b are cross-sectional front views of optical memory disks in embodiments of the present invention, respectively. , FIG. 6 is a characteristic diagram showing an example of temporal changes in the deposition rate in the apparatus of FIG. 4. 8.9...disc substrate, 5...Te
Ox sintered body, 1o... TeOx thin film, 11...
...Protection board. Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Diagram 1c 41 t-c King 1+'Wi (12!iW) Diagram ρ

Claims (1)

[Claims] (1) The composition ratio of metal or metalloid M and oxygen O is MOx
A thin film for recording is formed on the disk substrate 1, and the thickness of the thin film is In the direction of
The optical memory disk is configured such that the amount of oxygen is greater in a portion far from the disk substrate than in a portion closer to the disk substrate. (2) GeOx (0(x (2),
S nc)x(0<x(2), Te0x(0<x<2
),' In0x(0(x〈1.6 ), B10x(
0(x(1, 5)). (3) The value of A is continuous from the side closer to the disk substrate to the side farther from the disk substrate. The optical memory disk according to claim 1 or 2, which is set to have a large size.When forming a thin film for recording on a disk substrate, , a sintered body containing MOx as a main component is used as a deposition source, and MOx is deposited on the disk substrate.
1. A method for manufacturing an optical memory disk, characterized in that at least in the initial stage of vapor deposition, the vapor deposition rate is continuously increased. (6) A method for manufacturing an optical memory sensor 9 as set forth in claim 1, characterized in that an electron beam evaporation method is used to deposit MOx on the disk substrate 1c.