JPH05342631A - Optical information recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To provide a stable optical information recording medium excellent in recording and erasing characteristics and capable of withstanding thermal shocks at the time of recording and due to environmental changes. CONSTITUTION:Tantalum oxide, tantalum nitride or tantalum oxynitride is used as the material of first and second dielectric layers 2, 6 and a middle layer 7 based on zinc sulfide is formed at the interface between the second dielectric layer 6 and a reflecting layer 8. The bonding strength of the tantalum oxide, tantalum nitride or tantalum oxynitride to the reflecting layer 8 is increased and the resulting recording medium withstands thermal shocks at the time of recording and due to environmental changes and has improved recording and erasing characteristics.

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 large capacity by using a laser beam or the like.

[0002]

2. Description of the Related Art Te and T
There is a write-once disc using a TeOx (0 <x <2.0) thin film containing eO ₂ as a main component. Repeated recording
Erase discs that can be erased are being put to practical use. This erase disk heats a recording thin film with laser light, melts it, and cools it rapidly to make it amorphous and record information.
Further, it can be crystallized and erased by heating and gradually cooling it. R. Ovshinsky's chalcogen material Ge ₁₅ Te ₈₁ Sb ₂
S ₂ etc. are known. Further, thin films and the like made of a combination of a chalcogen element such as As ₂ S ₃ , As ₂ Se ₃ or Sb ₂ Se ₃ and a group IV element such as Group V or Ge of the Periodic Table 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 with laser light and erasing the information, the recording thin film is crystallized in advance, and the laser light focused to about 1 μm is made to correspond to the information intensity. When modulation is applied and, for example, a disk-shaped recording disk is rotated and irradiated, this 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, and information is recorded as an amorphized mark. You can record. Further, 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 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.

[0004]

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 and amorphization and heating and temperature rising crystallization is a problem in the heating cycle. Corresponding variation in signal quality. Factors of this variation include thermal and mechanical damage to the disk substrate or the dielectric layer due to repeated stimulus 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 structure such as the material of the dielectric layer or the film thickness of the dielectric layer. To increase the cooling rate, tantalum oxide is used as the dielectric material,
By using tantalum nitride and tantalum oxynitride, the thermal shock due to repeated recording and erasing can be reduced, and the cycle characteristics are greatly improved. Also, tantalum oxide, tantalum nitride,
Since tantalum oxynitride has a weak adhesion to the recording layer, the adhesion was improved by providing a thin intermediate layer containing zinc sulfide as a main component at the interface in contact with the recording layer. However, since tantalum oxide, tantalum nitride, and tantalum oxynitride have weak adhesion to the reflective layer, there is a problem that peeling or the like occurs during recording and due to environmental changes.

An object of the present invention is to provide an optical disk which has excellent recording / erasing characteristics and can withstand thermal shock due to recording and environmental changes.

[0007]

According to the present invention, a first dielectric layer made of tantalum oxide, tantalum nitride, or tantalum oxynitride is formed on one surface of a transparent substrate, and a first layer containing zinc sulfide as a main component. The recording layer has the property of absorbing the energy of the intermediate layer and irradiating it with laser light to heat up, melt, and rapidly cool to become amorphous, and the property of crystallizing by heating the amorphous state. Layer and a second layer based on zinc sulfide
Second intermediate layer and second dielectric layer made of the same material as the first dielectric layer
The dielectric layer, the third intermediate layer containing zinc sulfide as a main component, and the reflective layer are sequentially formed.

[0008]

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

[0009]

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 a groove for guiding laser light is formed in advance, or a glass plate in which a groove is formed by the 2p method,
It may be a substrate in which grooves are directly formed on a glass plate. A first dielectric layer 2 is made of tantalum oxide Ta ₂ O ₅ and has a thickness of about 150 nm. Intermediate layers 3, 5 and 7 are zinc sulfide containing 20% of SiO ₂ as an oxide and have a film thickness of 30 nm. 6 is a recording layer, Te-G
It is made of e-Sb and has a film thickness of about 30 nm. Reference numeral 8 is a reflective layer made of AL alloy and has a film thickness of about 100 nm. A protective plate 10 is attached to the reflective layer 8 with an adhesive 9. As a method of forming the dielectric layers 2 and 6, the intermediate layers 3, 5 and 7, the recording layer 4 and the reflective layer 8, generally, vacuum deposition or sputtering is used.

In this embodiment, a method of forming tantalum oxide as a dielectric layer will be described. The tantalum oxide target is formed by a sputtering method using a mixed gas of argon gas and oxygen. The sputtering pressure at this time is 5 × 10 ⁻⁴ To
rr 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 ⁻⁵ Tor.
A range of r to 6 × 10 ^-2 Torr is suitable. 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.

The disk configuration of this embodiment has an outer diameter of 130 m.
m, 1800 rpm rotation, linear velocity 8 m / sec, f1 =
The overwrite characteristics of the signal of 3.43 MHz and the signal of f2 = 1.0 MHz were measured. Overwrite is modulation between a high power level of 16 mW and a low power level of 8 mW by a laser beam of about 1 μm with one circle spot, forms an amorphized mark at a high power level, and a non-amorphous mark at a low power level The simultaneous erasure method was used to crystallize and erase the crystallized marks.

As a result, as the C / N ratio of the recording signal,
55 dB or more was obtained, and an overwrite erasing rate of 30 dB or more was obtained as the erasing property. As for the overwrite cycle characteristics, in particular, 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. ..

In the present embodiment, the first and second dielectric materials are tantalum oxide dielectric layers, but they may be tantalum nitride or tantalum oxynitride. Further, it is determined by the thickness teeth of each layer, the magnitude of the reproduction signal due to the optical interference effect, and the heat diffusion speed, and the thickness of the first dielectric layer is
The range of 150 to 200 nm is preferable. The thickness of the second dielectric layer is preferably in the range of 20 to 50 nm. 1st, 2nd, 3rd
The thickness of the intermediate layer is preferably in the range of 1 to 5 nm.

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

At this time, sputtering pressure, nitrogen partial pressure, oxygen content
The pressure may be the above-mentioned value, and the sputtering pressure may be 5 × 10.^-FourTo
rr ~ 5 x 10^-3Torr, nitrogen partial pressure and oxygen partial pressure are 5 ×
10 ^-FiveTorr ~ 6 x 10^-2Forming a dielectric layer with Torr
To do.

[0017]

As described above, according to the present invention, an optical information recording medium having stable recording / 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 reflecting layer. 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 sectional view of an optical 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 Third Intermediate Layer 8 Reflective Layer 9 Adhesive 10 Protective Plate

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

Claims (2)

[Claims] 1. A first dielectric layer made of a tantalum compound, a first intermediate layer containing zinc sulfide as a main component, and its energy absorbed by a laser beam to rise 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 raising a temperature of the amorphous state; a second intermediate layer containing zinc sulfide as a main component; A second dielectric layer made of the same material as the first dielectric layer;
An optical information recording medium, wherein a third intermediate layer containing zinc sulfide as a main component and a reflecting layer are sequentially formed. 2. A first dielectric layer made of a tantalum compound, a first intermediate layer containing zinc sulfide as a main component, and its energy absorbed by a laser beam to rise 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 raising a temperature of the amorphous state; a second intermediate layer containing zinc sulfide as a main component; A second dielectric layer made of the same material as the first dielectric layer;
A method for manufacturing an optical information recording medium in which a third intermediate layer containing zinc sulfide as a main component and a reflective layer are sequentially formed,
The second dielectric layer is sputtered at a sputter pressure of 5
× 10 ^-4 Torr~5 × and 10 ^-3 Torr, the manufacturing method of the optical information recording medium and forming an oxygen partial pressure ^{5 × 10 -5 Torr~1 × 10 -4} Torr.