JPH05151617A - Optical information recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a stable optical information optical recording medium which is superior in recording and erase characteristics and withstands an thermal impact due to an environmental variation and at the time of recording. CONSTITUTION:Tantalum oxide, taltalum nitride or tantalum-nitride-oxide is used as first and second dielectric layer 2, 6 and first and second middle layers 3, 5 which consist essentially of zinc sulfide, are formed on a boundary which comes into contact with a recording layer 4. Thus a sticking strength between tantalum oxide, tantalum nitride or tantalum-nitride-oxide and the recording layer is improved and the medium withstands a thermal impact due to an environmental variation and at the time of recording and the recording and erase characteristics are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium capable of recording / reproducing and erasing information with high density and high capacity by using a laser beam and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Te and Te for optical disk memory
There is a write-once disc that uses a TeO _x (0 <x <2.0) thin film containing O ₂ as a main component. Further, an erasing disk capable of repeatedly recording and erasing is being put to practical use. This erase disk heats a recording thin film (called a recording layer) with laser light,
It is possible to record information by making it amorphous by melting and quenching, and crystallizing and erasing by heating and gradually cooling it. The chalcogen materials Ge ₁₅ Te ₈₁ Sb ₂ S ₂ etc. of R. Ovshinsky and others are known.

Further, As ₂ S ₃ , As ₂ Se ₃ or Sb ₂ Se
Chalcogen elements such as ₃ and the periodic table, Group V or Ge, etc.
Thin films and the like made of a combination of group IV elements are widely known. These recording thin films can be formed on a substrate provided with a groove for laser light guide and used as an optical disc.

As a method of recording information on these discs by laser light and erasing the information, a certain recording thin film is crystallized, and laser light focused at about 1 μm is made to correspond to the information. When the intensity is modulated by irradiation, for example, when a disk-shaped recording disk is rotated and irradiated, the peak power laser light irradiation site is heated to a temperature equal to or higher than the melting point of the recording thin film and rapidly cooled to form an amorphized mark. Information can be recorded. In addition, this modulated bias power laser light irradiation site has a function of erasing the recorded signal information by raising the temperature above the crystallization temperature of the recording thin film and can be overwritten.

As described above, the recording thin film is heated to the melting point or higher and also to the crystallization temperature or higher by the laser beam. For this reason, a dielectric layer having excellent heat resistance is generally provided on the lower surface and the upper surface of the recording thin film as a protective layer for the substrate and the adhesive layer. Since the characteristics of temperature rise, rapid cooling, and gradual cooling change depending on the heat conduction characteristics of these dielectric layers, the recording and erasing characteristics can be determined by selecting the material or layer structure of the dielectric layer. Is.

[0006]

The problem in the information recording and erasable overwrite recording medium using the means of heating and raising the temperature of the recording thin film, melt quenching amorphization, and heating and temperature rising crystallization is a problem in the heating cycle. Corresponding variation in signal quality. Factors of this fluctuation include thermal and mechanical damage to the disk substrate or the dielectric layer due to repeated stimuli of rapid heating and cooling of 400 ° C. or more by the recording spot light. When the disk substrate or the dielectric layer is thermally damaged, there is a problem that noise is increased in the recording / reproducing and erasing cycles and the cycle characteristics are deteriorated.

The other is that the erasing disk utilizing the phase change is thermal recording as described above, and therefore the cooling rate at the time of recording or erasing influences the characteristics.
That is, the cooling rate depends on the disk configuration such as the material of the dielectric layer or the film thickness of the dielectric layer, and tantalum oxide, tantalum nitride, or tantalum oxynitride is used as the material of the dielectric plate to increase the cooling rate. The thermal shock due to repeated recording and erasing can be reduced, and the cycle characteristics have been greatly improved. However, since tantalum oxide, tantalum nitride, and tantalum oxynitride have weak adhesion to the recording layer, there is a problem that peeling or the like occurs during recording or due to environmental changes.

An object of the present invention is to provide an optical information recording medium excellent in recording and erasing characteristics and capable of withstanding thermal shock during recording and environmental changes, and a method for manufacturing the same.

[0009]

According to the present invention, a first dielectric layer made of tantalum oxide, tantalum nitride, or tantalum oxynitride is provided on one surface of a transparent substrate, and a first dielectric layer containing zinc sulfide as a main component. By the irradiation of the intermediate layer of 1 and the laser beam,
A recording layer containing zinc sulfide as a main component, which has the property of absorbing the energy, heating, melting, and rapidly cooling to become amorphous, and the ability to crystallize by heating the amorphous state A second intermediate layer, a second dielectric layer made of the same material as the first dielectric layer, and a reflective layer are sequentially formed.

[0010]

According to the present invention, tantalum oxide, tantalum nitride and tantalum oxynitride have weak adhesion to the recording layer,
By providing a thin intermediate layer containing zinc sulfide as a main component at the interface in contact with the recording layer, this adhesive force is improved and it is possible to withstand thermal shock due to recording and environmental changes.

Therefore, according to the present invention, the above-described structure provides an optical information recording medium which is excellent in recording / erasing characteristics and can endure many rewritings and environmental changes.

[0012]

FIG. 1 is a sectional view of an optical information recording medium according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a disk substrate made of a resin substrate such as polycarbonate. The disk substrate 1 is a resin substrate in which grooves for guiding laser light are formed in advance, or a glass plate in which grooves are formed by the 2P method,
Alternatively, it may be a substrate in which grooves are directly formed on a glass plate. The first dielectric layer 2 is made of tantalum oxide Ta ₂ O ₅ and has a thickness of about 150 nm. Reference numeral 3 is a first intermediate layer made of ZnS—SiO ₂ and having a film thickness of 3 nm. A recording layer 4 is made of Te-Ge-Sb and has a film thickness of about 30 nm. Reference numeral 5 is a second intermediate layer made of the same material as the first intermediate layer 3, and 6 is a second dielectric layer made of the same material as the first dielectric layer 2. Reference numeral 7 is a reflective layer made of Al alloy and has a film thickness of about 100 nm. Reference numeral 8 is an adhesive material, and 9 is a protective plate, which is attached to the reflection layer 7 with an adhesive agent 8. As a method of forming the dielectric layers 2 and 6, the intermediate layers 3 and 5, the recording layer 4 and the reflective layer 7, vacuum deposition or sputtering is generally used.

In this embodiment, a method of forming tantalum oxide Ta ₂ O ₅ as a dielectric layer will be described. A sputtering method using a mixed gas of Algol and oxygen is used as a target of tantalum oxide. Sputter pressure at this time is 5 × 10 ~ ⁴
Torr is set to 5 × 10 ³ Torr, and the oxygen partial pressure at this time is important in determining the characteristics or film quality. Therefore, in the case of a dielectric film, the oxygen partial pressure during sputtering is 5 × 10 to ⁵ Torr to 1 × 10.
A range of ~ ⁴ Torr is appropriate. If the pressure is less than this partial pressure, the film will be colored, and laser light will be absorbed during signal recording and reproduction. Further, if the number is large, there is no problem that the film is colored, but there is a problem that the adhesiveness with the disk substrate 1 is deteriorated and peeling or cracks occur due to environmental changes.

With the disk configuration of this embodiment, the outer diameter is 130 nm, 1
Signal of f1 = 3.43MHz at 800rpm rotation and linear velocity 8m / sec,
The overwrite characteristic of the signal of f2 = 1.0 MHz was measured.
Overwriting is about 1 μm with one circle spot.
Simultaneous erasing to form an amorphized mark at a high power level and to crystallize and erase the amorphized mark at a low power level by modulation between a high power level of 16 mW and a low power level of 8 mW by the laser light of I went by the method of recording.

As a result, the reproduction noise ratio C / N of the recording signal
As a result, an overwrite erase rate of 30 dB or more was obtained as the erase characteristic. Regarding the overwrite cycle characteristics, the bit error rate characteristics were measured, and as a result, no deterioration was observed for more than 1 million cycles.

Further, even when the optical information recording medium was put into and taken out from a room temperature environment in a constant temperature bath kept at 90 ° C., no damage such as peeling or cracking between layers occurred. .

Although tantalum oxide is used as the first and second dielectric materials in this embodiment, tantalum nitride or tantalum oxynitride may be used. Also, the film thickness of each layer is determined by the size of the reproduction signal due to the optical interference effect and the heat diffusion rate, and the film thickness of the first dielectric layer is in the range of 150 to 200 nm. Is good. The thickness of the second dielectric layer is preferably in the range of 20 to 50 nm. The thickness of the first and second intermediate layers is preferably in the range of 1 to 5 nm.

As a method of forming the dielectric layer of the above optical information recording medium, there is a sputtering method using a mixed gas of argon and oxygen for the above-mentioned target of tantalum oxide. In addition to this, tantalum nitride or tantalum nitride is also used. A mixed gas of argon and nitrogen, or a mixed gas of argon, oxygen and nitrogen may be used as the target of nitric oxide.

At this time, the sputter pressure, the nitrogen partial pressure, and the oxygen partial pressure may be the above-mentioned values, and the sputter pressure is 5 × 10 ⁴ Torr
5 × 10 ~ ³ Torr, nitrogen partial pressure and oxygen partial pressure are 5 × 10 ~ ⁵ Torr〜1
A dielectric layer is formed with × 10 to ⁴ Torr.

[0020]

As described above, according to the present invention, an optical information recording medium having stable recording and erasing cycle characteristics can be obtained by providing a thin intermediate layer containing zinc sulfide as a main component at the interface in contact with the recording film. It is possible to realize an optical information recording medium that can be obtained and can withstand many rewritings and environmental changes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical information recording medium showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Disk substrate, 2 ... First dielectric layer, 3 ... First
Intermediate layer, 4 ... recording layer, 5 ... second intermediate layer, 6 ...
Second dielectric layer, 7 ... Reflective layer, 8 ... Adhesive, 9 ... Protective plate.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takeo Ota 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A first dielectric layer made of tantalum oxide, a first intermediate layer containing zinc sulfide as a main component, and laser light irradiation for absorbing the energy on one surface of a transparent substrate. A recording layer having a property of being heated, melted, and rapidly cooled to be amorphous, and having a property of being crystallized by heating an amorphous state; and a second intermediate layer containing zinc sulfide as a main component. An optical information recording medium, wherein a second dielectric layer made of the same material as the first dielectric layer and a reflective layer are sequentially formed. 2. The optical information recording medium according to claim 1, wherein the first and second dielectric layers made of tantalum nitride are formed on one surface of the transparent substrate. 3. The optical information recording medium according to claim 1, wherein the first and second dielectric layers made of tantalum oxynitride are formed on one surface of the transparent substrate. 4. The optical information recording medium according to claim 1, wherein the film thickness of the first dielectric layer is 150 to 200 nm. 5. The optical information recording medium according to claim 1, wherein the thickness of the second dielectric layer is 20 to 50 nm. 6. The optical information recording medium according to claim 1, wherein the first and second intermediate layers have a thickness of 1 to 5 nm. 7. The optical information recording medium according to claim 1, wherein Te, Ge, Sb is used as a recording film material. 8. A sputtering method using a mixed gas of argon and oxygen with a target of tantalum oxide for the first and second dielectric layers, and a sputtering pressure of 5 × 10 to ⁴ Torr to 5 × 10 to ³ Torr.
2. The method for producing an optical information recording medium according to claim 1, wherein the oxygen partial pressure is 5 × 10 ⁵ Torr to 1 × 10 ⁴ Torr. 9. The first and second dielectric layers are formed by a sputtering method using a mixed gas of argon and nitrogen with a tantalum nitride target, and the sputtering pressure is 5 × 10 to ⁴ Torr to 5 × 10 to ² Torr.
3. The method for manufacturing an optical information recording medium according to claim 2, wherein the nitrogen partial pressure is 5 × 10 ⁵ Torr to 1 × 10 ⁴ Torr. 10. The first and second dielectric layers are formed by a sputtering method using a mixed gas of argon, oxygen and nitrogen with a target of tantalum oxynitride, and the sputtering pressure is 5 × 10 ⁴ Torr.
5 × 10 to ³ Torr, both oxygen partial pressure and nitrogen partial pressure are 5 × 10
^{4. The} method for producing an optical information recording medium according to claim 3, wherein the optical information recording medium is formed with ⁵ Torr to 1 × 10 ⁴ Torr.