JPS62295232A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain durability even if a protective film is not coated on a metallic reflective film and to improve productivity by forming the metallic reflective film of an Al alloy reflective film having excellent corrosion resistance. CONSTITUTION:The metallic reflective film of an optical recording medium having a recording film to be subjected to optical reproducing and the metallic reflective film is formed of the corrosion resistant Al alloy. The corrosion resistant Al alloy to be used is the alloy formed by incorporating Mg and/or Si into Al. The metallic reflective film having the additionally higher corrosion resistance is obtd. by adding a slight amt. of Cr and/or Mn thereto. The ratio at which Mg or Si or both occupy in the entire part of the metallic reflective film is selected usually from a 1-20% range, more preferably from a 1-10% range. The ratio at which the Cr or Mn or both occupy in the entire part of the metallic reflective film is usually enough with a 0.1-0.5% range.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical recording medium capable of performing recorded number reproduction using a light beam.

[Conventional technology]

Conventionally, optical recording media used in optical discs 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, For example, as a magneto-optical recording medium formed of a rare earth-transition metal alloy a film, thermoplastic recording media etc. are known.
Bi,? ', n (1: polycrystalline thin film such as uEi, Gd
Ca, GdFe, TbFe, DyFe.

GdTbFe, TbDyFe, GdFeCa, T
amorphous thin films such as bFeCa, GdTbflll:a,
There are single crystal R films such as GdIG.

Among these thin films, there are various issues such as film formability when manufacturing large-area thin films at temperatures near room temperature, writing efficiency for writing signals with small photothermal energy, and readout of written signals with a good S/N ratio. In consideration of read efficiency and the like, the amorphous thin film has recently been considered to be excellent for use in magneto-optical recording media.

Furthermore, in order to increase the magneto-optical rotation angle θk and improve the figure of merit, both sides of the recording film are coated with an interference film made of a dielectric material of a certain thickness, and a metal reflective film is placed on one interference film. It is common to adopt a configuration in which a multiple interference effect or a Faraday effect is added to the Kerr effect.

[Problem that the invention seeks to solve]

However, when metals with high reflectance such as Al and Cu are used as the metal reflective film, they are easily corroded, so it is necessary to cover them with a protective film such as SiO and 5iC1SiN to protect them from corrosion. There is a problem that the number of manufacturing steps increases and productivity deteriorates.

The present invention has been made in view of the above-mentioned problems, and by providing a metal reflective film with high reflectance and excellent corrosion resistance, the metal reflective film itself has a corrosion prevention effect. An object of the present invention is to provide an optical recording medium that does not require coating with a protective film.

[Method for solving the problem] The above purpose is to provide a metal reflective film in an optical recording medium having a recording film that is optically reproduced and a metal reflective film on a substrate, as shown in the representative example below. This is achieved by forming it from a corrosion-resistant Al alloy.

That is, the erodible Al alloy used in the present invention is Al
It is an alloy containing Mg and/or Si. Furthermore, by adding a small amount of Cr and/or Mn, a metal reflective film with excellent -MFM eating properties can be obtained. Mg,
The proportion of Si or both in the entire metal reflective film is usually selected from the range of 1 to 20%, preferably from the range of 1 to 10%. Further, the proportion of Cr, Mn, or both of them in the entire metal reflective film is usually sufficient in the range of 0.1 to 0.5%.

Typical methods for forming the above metal reflective film include forming a metal reflective film with the above composition by high-frequency sputtering using an Al alloy target with an appropriate composition, and forming a metal reflective film with the above composition on a pure Al target. A method of forming a metal reflective film with the above composition by using a composite target with chips of the additive element arranged thereon and adjusting the area ratio of the chip of the additive element to the target surface, a method of forming a pure Al target and a target of the additive element simultaneously. There is a method of forming a metal reflective film having the above composition ratio by sputtering and adjusting the power distribution applied to each target.

The thickness of the metal reflective film may be approximately the same as that of a known metal reflective film.

Next, a schematic cross-sectional view of an embodiment of the optical recording medium of the present invention having a laminated structure is shown in FIG.
Writing side substrate 11 made of plastic, glass, etc.
On a, an undercoat layer 12° and a protective film 13 are sequentially formed. Magneto-optical recording film 14. Protective film 15. Interference film 1B and the above-mentioned metal 11
fi 17 is provided, and a protective substrate ob is further bonded thereon with an adhesive layer 18.

The magneto-optical recording film 14 can be used without any limitation as long as it exhibits the magneto-optical effect in addition to those described above.

The present invention is not limited to the magneto-optical recording medium as described above, but can also be applied to any other type of optical recording medium provided with a metal reflective film.

〔Example〕

The present invention will be explained in more detail below using examples.

Example 1 An optical recording medium having the structure shown in FIG. 1 was produced as follows. Polycarbonate plastic substrate 11
On a, an undercoat layer 12 made of 5i01fi with a thickness of about 100 Å and a protective film 13 made of ZnS with a thickness of about 300 Å are formed.
GdT is deposited on it by high frequency sputtering.
About 150 bFeCo films were deposited to form a magneto-optical recording film 14.Next, this was coated with a protective layer film 15 made of ZnS with a thickness of about 300A and an interference film 1 made of a 540 film with a thickness of about 100A.
Then, about 700 people formed a metal reflective film 17 made of Al-5% M8 alloy. This metal reflective film 17 was formed by high frequency sputtering using a composite target in which Mg chips on an Al target were arranged at an area ratio of 5%.

Finally, a protective plastic substrate ttb was bonded to the optical recording medium using an adhesive layer 18 made of hot melt adhesive.

At the rotation angle 51 of the obtained recording medium, the initial characteristics of coercive force Hc and reflectance H were measured, and the relative humidity was 99°C at 60°C.
A moisture resistance test was conducted for 1000 hours in a constant temperature constant temperature layer.

For comparison, pure Al with the same thickness as the metal reflective film 17 was used.
An optical recording medium having the same structure except that a film was formed (
A comparative medium) was also tested. The results are shown in Table 2, and although the optical recording medium of the present invention did not have a special protective coating on the metal reflective film, it did not cause corrosion of the metal reflective film, decrease in reflectance, No deterioration of magnetic properties occurred.

On the other hand, in the comparison medium made of a conventional metal reflective film, corrosion occurs and a decrease in reflectance is observed.

Examples 2 to 6 Optical recording media having the same film structure as in Example 1 were produced, except that the alloy film listed in Table 1 was used as the metal reflective M17. For each example, a moisture resistance test similar to Example 1 was conducted.

The results are shown in Table 2. The optical recording medium of the present invention in each example showed corrosion of the metal reflective film, decrease in reflectance,
No particular deterioration of magnetic properties was observed.

Table 1 Table 2 [Effects of the Invention] The optical recording medium of the present invention, in which the metal reflective film is an Al alloy reflective film with excellent corrosion resistance, has excellent properties even without directly coating the metal reflective film with a protective film. Durability φ indicates reliability.

Also, 115 can be directly attached to the metal reflective film! Since there is no need to coat the material, the process is saved and productivity is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the optical recording medium of the present invention. 11a, + to 11: Large substrate Recording film = 14 Metal reflection 119:1?

Claims (3)

[Claims] (1) An optical recording medium having an optically reproducible recording film and a metal reflective film on a substrate, wherein the metal reflective film is made of a corrosion-resistant Al alloy film. (2) The optical recording medium according to claim 1, wherein the corrosion-resistant Al alloy film is an alloy film containing Mg and/or Si in Al. (3) The optical recording medium according to claim 2, wherein Cr and/or Mn are added to the corrosion-resistant Al alloy film.