JPS62119756A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of the titled medium without deteriorating the characteristic as a recording medium by forming a film consisting of the oxide of at least one substance among magnesium, beryllium, and calcium on an optical recording layer. CONSTITUTION:The film consisting of the oxide of at least one substance among magnesium, beryllium, and calcium is formed on one or both sides of the optical recording layer. The oxide film is formed by vapor deposition or sputtering. Electron beam vapor deposition and RF sputtering are especially appropriate for magnesium oxide and beryllium oxide, and electron beam vapor deposition is appropriate for calcium oxide. An UV curing resin layer, etc., is provided between the oxide film and a glass sheet with the object of forming an optical guide groove when glass is used for the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium on which recording and reproduction can be performed using a light beam.

[Conventional technology]

Conventionally, optical recording media used in optical disks include rare earth-transition metal alloy thin films, reducing oxide thin films such as chalcogen compounds that utilize phase transition from amorphous to crystalline, heat mode recording media, and thermostats. For example, as a magneto-optical recording medium formed of a rare earth-transition metal alloy thin film, there are known plastic recording media such as MnB1°MnCuB1. Polycrystalline thin films such as GdCo.

GdFe, TbFe, DyFe, GdTbFe.

Amorphous FJ films such as TbDyFe and single crystal thin films such as GdIG are known.

Among these thin films, the film forming efficiency when manufacturing a large-area thin film at a temperature near room temperature, the writing efficiency for writing signals with small photothermal energy, and the write signal S
Considering readout efficiency etc. to read out with good /N ratio,
Recently, the amorphous vfXl! 2 is considered to be excellent as a photothermal magnetic recording medium. GdTbFe has a large Kerr rotation angle and has a single Curie point around 150°C, making it suitable as a photothermal magnetic recording medium. Furthermore, as a result of research aimed at improving the Kerr rotation angle, the inventors found that GdT
It has been found that bFeCo is a magneto-optical recording medium that has a sufficiently large Kerr rotation angle and can be read with a good S/N ratio.

[Problem that the invention seeks to solve]

However, amorphous magnetic materials used in magnetic recording media, including magneto-optical recording media such as GdTbFe, generally have a drawback of poor corrosion resistance. That is, when it comes into contact with the atmosphere or water vapor, it becomes oxidized and becomes transparent. Furthermore, this problem is common not only to magneto-optical recording media but also to the optical recording media described above.

In order to eliminate this drawback, conventionally a protective cover made of, for example, a transparent material, such as 5i02. Si
Although disc-shaped recording media with an air sandwich structure or a laminated structure in which a protective layer of O is provided or the recording layer is further sealed with an inert gas have been proposed, sufficient corrosion resistance for practical use has not been obtained.

The present invention has been made in view of the above problems, and an object thereof is to provide an optical recording medium with improved corrosion resistance without impairing the characteristics of the recording medium.

[Means for Solving the Problems] The above object of the present invention is to provide an optical recording medium having an optical recording layer on a substrate, in which magnesium, beryllium, or calcium is added to one or both sides of the optical recording layer. This is achieved by an optical recording medium formed with a film made of an oxide of at least one of the following.

That is, the effect of preventing oxidation of the optical recording layer is 5i02. An optical recording medium using magnesium oxide, beryllium oxide, and calcium oxide, which are larger than SiO, is provided.

The above-mentioned oxide films are all formed by a vapor deposition method or a sputtering method. In particular, electron beam evaporation or RF sputtering is suitable for magnesium oxide and beryllium oxide. Electron beam evaporation is suitable for calcium oxide. When glass is used for the substrate, an ultraviolet curing resin (2P) layer or the like is provided between the oxide film and the glass plate for the purpose of forming optical guide grooves.

In the present invention, when forming an oxide film following the optical recording layer, it is desirable to form the oxide film continuously without breaking the vacuum after forming the recording layer by a method such as sputtering. Even when forming an oxide film on the substrate-E, forming an optical recording layer thereon, and then forming an oxide film, it is better to form the films continuously in the same tank without breaking the vacuum.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples and can be applied in various ways. For example, the optical recording layer can be applied not only to magneto-optical recording but also to ,
Any optical recording material may be used, such as those mentioned in the prior art section. Furthermore, the corrosion resistance can be further improved by forming the optical recording medium constructed according to the present invention into a well-known air sandwich structure or a structure in which it is bonded to a glass plate or the like.

Example I In an RF sputtering device, a 1-inch square white glass plate was used as a substrate, and a 100 mmφ iron-cobalt alloy (Fe7C
o3) GdTbFe was sputtered using a composite target of 5 mm square small pieces of gadolinium terbium alloy (Gd, Tb,) arranged uniformly on a plate.
An optical recording layer made of a Co quaternary amorphous magnetic film and having a thickness of too much was formed. Subsequently, 4X 1 in the vacuum chamber
(After evacuation to about 1' Pa, argon (Ar) gas was introduced to about 4X 10' Pa, and using magnesium oxide as a second target, a magnesium oxide film was formed on the recording layer to a thickness of 2000 mm by sputtering. was deposited.

Example 2 In an RF sputtering device, the temperature in the vacuum chamber was 4×1O′″4
After evacuating to about Pa, 4×10 argon (Ar) gas was
' It was introduced to the level of Pa. Then, a UV-curable resin (2P) layer (epoxy acrylate) (1
0 to 100JI11) was formed as the first substrate.
Using magnesium oxide as a target, a magnesium oxide film with a thickness of 200 mm was formed on the substrate by sputtering. On top of that are the same Gd, Tb, and Fe as in Example 1.

A recording layer with a thickness of 1000 mm was formed by sputtering using a CO composite target as a second target.

Furthermore, after evacuating the inside of the tank to about 4×1(]' Pa, argon (Ar) gas was introduced to about 4×10' Pa, and using the first target, a thickness of 2×2 was deposited on the recording layer.
A magnesium oxide film of 00OA was formed.

Examples 3 to 6 Optical recording media were prepared in which protective films made of beryllium oxide and calcium oxide were provided in place of magnesium oxide in Examples 1 and 2, respectively. As an optical recording layer, the thickness is 100 mm.
An OA(7)GdTbaFeC0(7) quaternary amorphous magnetic film was used, and all oxide films were formed using an RF sputtering device.

Example 7 In an RF sputtering device, the pressure in the vacuum chamber was 4×10″Pa.
After exhausting the air to a certain extent, add argon (At) gas to 4×10'
It was introduced up to about Pa. Then, using polymethyl methacrylate (PMMA) as a substrate and using magnesium oxide as a first target, a magnesium oxide film with a thickness of 200 mm was formed on the substrate by sputtering. On top of that, the same Gd, Tb, and F as in Example 1 are successively added.
e, Coc7) A recording layer with a thickness of 100 OA was formed by sputtering using the composite target as a second target. Furthermore, after evacuating the tank to about 4X 1 (1'Pa), argon (Ar) gas was introduced to about 4X 1O-IPa, and a magnesium oxide film with a thickness of 2000A was formed on the recording layer using the first target. was formed.

Example 8 In an RF sputtering device, the pressure in the vacuum chamber was 4×10″Pa.
After evacuation to a certain extent, argon (Ar) gas was added to 4×1O−1
It was introduced up to about Pa. And polycarbonate (PC)
) was used as a substrate and magnesium oxide was used as the first target, and a thickness of 200 mm was deposited on the substrate by sputtering.
A magnesium oxide film of A was formed. Subsequently, a recording layer having a thickness of 1000 Å was formed thereon by sputtering using the same composite target of Gd, Tb, Fe, and Co as in Example 1 as a second target. Furthermore, after evacuating the inside of the tank to about 4X104Pa, argon (A'r
) Gas was introduced to about 4XlO-IPa, and the first
using the target.

A magnesium oxide film with a thickness of 2000 A was formed on the recording layer.

Examples 9 to 12 Optical recording media were prepared in which protective films made of helium oxide and calcium oxide were provided in place of magnesium oxide in Examples 7 and 8, respectively. The optical recording layer has a thickness of 100
A quaternary amorphous magnetic film of OA(7)G dT b Fe Co was used, and all oxide films were formed by an RF sputtering device.

Example 13 In an RF sputtering device, a 1-inch square white plate glass was used as a substrate, and the same Gd as in Example 1 was used.

A recording layer with a thickness of 200 mm was formed by sputtering using a composite target of Tb, Fe, and Co. Next, after evacuating the vacuum chamber to about 4×1 (1' Pa),
Argon (Ar) gas is introduced to about 4X 1O-1Pa, magnesium oxide is used as a second target, and a thickness of 100 mm is formed on the recording layer by sputtering.
A magnesium oxide film was formed on the substrate. Next, after evacuating the vacuum chamber to about 2×1 (1″4 Pa), aluminum (AI) was evaporated using an electron beam evaporation source, and an AI film with a thickness of 500 mm was formed as a reflective film on the magnesium oxide film. A protective film made of this fermented magnesium was formed to a thickness of 2000A by sputtering.

Example 14 In an RF sputtering device, 4×1 (1'
After evacuation to about Pa, argon (Ar) gas was added to 4×1O
-Introduced up to about IPa. Then, a layer of ultraviolet curable resin (2P) (epoxy acrylate) (
A magnesium oxide film with a thickness of 200 μm was formed on the substrate by sputtering using magnesium oxide as a first target. On top of that, the same Gd, Tb, Fe, and C as in Example 1 were successively added.

Using this composite target as a second target, a recording layer having a thickness of 200 mm was formed by sputtering. Furthermore, after evacuating the vacuum chamber to approximately 4×1O→Pa, argon (A
r) Introduce gas to about 4X 1O-IPa and
A magnesium oxide film with a thickness of 100 OA was formed on the recording layer using the target. Then 2X in the vacuum chamber
After evacuation to about 1' Pa, aluminum (A1) is evaporated using an electron beam evaporation source to form an A1 film with a thickness of 500A as a reflective film on the magnesium oxide film, and finally a protective film made of this magnesium oxide is applied. A film of 200 OA was formed by sputtering.

Examples 15 to 18 Optical recording media were prepared in which protective films were provided with beryllium oxide and calcium oxide in place of magnesium oxide in Examples 13 and 14, respectively. The optical recording layer has a thickness of 2
A quaternary amorphous magnetic film of GdTbFeCo of 0.00 A was used, and all oxide films were formed using an RF sputtering device.

Example 19 In an RF sputtering device, 4×10″4P in a vacuum chamber
After evacuation to about a degree, argon (Ar) gas was
It was introduced to the level of IPa. Then, using polymethyl methacrylate (PMMA) as a substrate and using magnesium oxide as a first target, a magnesium oxide film with a thickness of 200 mm was formed on the substrate by sputtering.

On top of that, the same Gd, Tb as in Example 1,
A recording layer having a thickness of 200 mm was formed by sputtering using a Fe, CoC7) composite target as a second target. Furthermore, after evacuating the tank to about 4X 10" Pa, argon (Ar) gas was introduced to about 4X 1G-' Pa, and a magnesium oxide film with a thickness of 100 OA was formed on the recording layer using the first target. Subsequently, after evacuating the vacuum chamber to approximately 2×1 G' Pa, aluminum (AI) was evaporated using an electron beam evaporation source.
Example 20 An AI film with a thickness of 500 A was formed as a reflective film on the magnesium oxide film, and finally a protective film made of this magnesium oxide was formed to a thickness of 2000 A by sputtering. 104Pa
After exhausting the air to a certain extent, add argon (Ar) gas to 4×10'
It was introduced up to about Pa. and Polycarponei) (
PC) as a substrate and magnesium oxide as the first target, a thickness of 2 mm was deposited on the substrate by sputtering.
A magnesium oxide film was formed on 00. Subsequently, using the same composite target of Gd, Tb, Fe, and Co as in Example 1 as a second target, a recording layer having a thickness of 200 mm was formed thereon by sputtering. Furthermore, after evacuating the inside of the tank to about 4X10'Pa, argon (A'') gas was introduced to about 4X10-'Pa, and a magnesium oxide film with a thickness of 100OA was formed on the recording layer using the first target. Then, 2X 10'' was placed in the vacuum chamber.
After evacuation to about 4 Pa, aluminum (AI) was evaporated using an electron beam evaporation source, and an A1 film with a thickness of 500 mm was formed as a reflective film on the magnesium oxide film.Finally, a protective film made of magnesium oxide was applied on top of this. Examples 21 to 24 Films were formed in 2000 by sputtering. Optical recording media were prepared in which protective films were formed of beryllium oxide and calcium oxide in place of magnesium oxide in Examples 19 and 20, respectively. The optical recording layer has a thickness L
A quaternary amorphous magnetic film of QQOA(7)G dT b Fe Co was used, and all oxide films were formed by an RF sputtering device.

Comparative Example 1 300OA instead of 2000A thick MgO layer (1)
An optical recording medium was produced in the same manner as in Example 1 except that the Sin layer was provided.

Comparative Example 2 An optical recording medium was produced in the same manner as in Example 1 except that the 2000A MgO layer was not provided.

Comparative Example 3 An optical recording medium was produced in the same manner as in Example 13 except that SiO was used instead of Mg0.

Comparative Example 4 An optical recording medium was produced in the same manner as in Example 13, except that the retention mM and reflective layer were not provided.

Corrosion Resistance Test The optical recording media prepared according to Examples 1 to 24 and Comparative Examples 1 to 4 described above were placed in a constant temperature and humidity chamber at 70° C. and 85% RH to conduct a corrosion resistance test. Examples 1 and 13
The results of Comparative Examples 1 to 4 are shown in Figs. 1 and 2. In Figs. 1 and 2, the horizontal axis represents the test time [unit: hours].
H)], and the vertical axis shows the change in coercive force Hc as a ratio of the coercive force to the initial value Hco. Here, the more the coercive force decreases, the more the corrosion progresses.Examples 2 to 1
The results of Example 2 were almost the same as those of Example 1, and the results of Examples 14 to 24 were almost the same as Example 13.

As can be seen from FIGS. 1 and 2, when magnesium oxide, beryllium oxide, or calcium oxide is used as a protective layer, the corrosion resistance of the optical recording medium can be improved.

〔Effect of the invention〕

According to the present invention, an optical recording medium with excellent corrosion resistance was obtained.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams showing the results of a corrosion resistance test of an optical recording medium based on the present invention, respectively. Coercive force curve 2 of Example 1: Coercive force curve 3 of Comparative example 1: Coercive force curve 4 of Comparative example 2: Coercive force curve 5 of Example 13: Coercive force curve 6 of Comparative example 3: Comparative example 4 coercive force curve of

Claims (1)

[Claims] In an optical recording medium having an optical recording layer on a substrate, a film made of an oxide of at least one of magnesium, beryllium, and calcium is formed on one or both sides of the optical recording layer. An optical recording medium characterized by: