JPH03252929A - Optical disk only for reproduction - Google Patents

Abstract

PURPOSE:To prevent decrease in reflection for a long time by constituting a reflecting film of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium. CONSTITUTION:The reflecting film of the reproduction only optical disk 1 consists of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium. The amt. of at least element selected from hafnium, niobium, tantalum, and zirconium is 0.1-10 atm.% in total, and preferably 0.5-5 atm.%. By this method, the reflecting film is almost free from pin holes and corrosion and has excellent reflection. Thereby, decrease in the reflection is prevented even when the disk is used for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a read-only optical disc equipped with a reflective film,
More specifically, the present invention relates to a read-only optical disc equipped with a reflective film that is excellent in corrosion resistance or moisture resistance and has a high reflectance.

Technical background of the invention Information recording media that use light, such as compact discs, read-only optical discs such as laser discs, optical discs such as write-once discs, and even rewritable magneto-optical discs, are used for purposes such as increasing playback sensitivity. in,
A reflective film is often provided.

For example, in a read-only optical disc such as a compact disc, a substrate on which an information pattern is recorded, a reflective film, and a protective film are provided in this order.

Conventionally, reflective films made of aluminum metal have been widely used as reflective films in such information recording media. However, a reflective film made of aluminum metal has poor corrosion resistance, and as a result, the aluminum crystallizes, resulting in a decrease in planar smoothness and a decrease in the reflectance of the reflective film.

In order to solve such problems, for example,
7-186244 discloses an information recording medium having a reflective film made of an aluminum alloy containing chromium. However, reflective films made of aluminum alloys containing chromium do not have sufficient corrosion resistance, and pinholes may occur in the reflective film or the reflectance of the reflective film may decrease. There were times when I ended up doing this.

Also, for example, in Japanese Patent Application Laid-Open No. 62-137743,
An information recording medium having a reflective film made of an aluminum alloy containing at least 0.1 to 10% by weight of titanium is disclosed. However, the corrosion resistance of a reflective film made of an aluminum alloy containing only titanium is still not satisfactory, and pinholes may occur in the reflective film or the reflectance may decrease. Ta.

Thus, there is a desire for a read-only disk that has a reflective film that is excellent in corrosion resistance or long-term stability and that does not cause a decrease in reflectance.

In view of the above-mentioned prior art, the inventors of the present invention conducted extensive studies on reflective films for read-only discs, and found that they are made of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium. The present invention was completed based on the discovery that the reflective film has a high reflectance, excellent corrosion resistance and moisture resistance, and the reflectance hardly decreases even when used for a long period of time.

Purpose of the Invention The present invention is intended to solve the problems associated with the prior art as described above. It is an object of the present invention to provide a read-only optical disc having a reflective film that does not cause a decrease in optical performance.

SUMMARY OF THE INVENTION In order to achieve the above object, a read-only optical disk according to the present invention is a read-only optical disk provided with a reflective film, in which the reflective film is made of hafnium, niobium, tantalum, hafnium, niobium, tantalum,
and zirconium.

The read-only optical disc according to the present invention has a reflective film made of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium, and therefore has a high reflectance and high durability. It has excellent corrosion and moisture resistance, so the reflectance will not decrease even after long-term use.

DETAILED DESCRIPTION OF THE INVENTION The read-only optical disc according to the present invention will be specifically described below.

FIG. 1 is a schematic cross-sectional view of a read-only optical disc 1 according to the present invention.

In the read-only optical disc 1 according to the present invention, information patterns are recorded depending on the presence or absence of pits formed on the substrate 2. To reproduce recorded information, the presence or absence of pits is identified using light such as a laser beam, and this is marked as "0" or "0".
This is done by making it correspond to the "1" signal.

Specific examples of such a read-only optical disc 1 include a compact disc, a racer disc, a read-only digital memory, and the like.

The read-only optical disc 1 according to the present invention includes, for example, a first
As shown in the figure, a substrate 2 on which an information pattern is recorded
, a reflective film 3, and a protective film 4 are laminated in this order.

In the present invention, the material of the substrate 2 as described above is not particularly limited, but when the laser beam is incident from the substrate 2 side (arrow A), a transparent substrate is preferable, and specifically, a transparent substrate is used. In addition to inorganic materials such as polymethyl methacrylate, polycarbonate, polymer alloys of polycarbonate and polystyrene, cyclic olefin polymers such as those shown in U.S. Pat. No. 4,614,778, e.g. , 2.3.4
．． 4a 588a-Copolymer of octahydronaphthalene (tetracyclododecene), ethylene and 2-methyl-
1458-dimethano-1,2,3,4,4a, 5.8
．． Copolymer of 8a-octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1,
4,5,8-dimethano-] 2.3.4.4a, 5.
Copolymers with 8.8a-octahydronaphthalene, etc.
Organic materials such as poly-4-methyl-1-pentene, epoxy resin, polyethersulfone, polysulfone, and polyetherimide can be used.

In the present invention, an information pattern is recorded on such a substrate 2 depending on the presence or absence of pits, and the presence or absence of pits is determined by "
The recorded information is reproduced by reading the signals as "0" and "1" signals. During reproduction, the presence or absence of pits is identified using light such as a laser beam, and at this time, the reproduction sensitivity can be improved by providing a reflective film 3 with a high reflectance.

In the present invention, such a reflective film 3 is formed from an aluminum alloy containing at least one element selected from nophnium, niobium, tantalum, and zirconium.

At least one element selected from hafnium, niobium, tantalum, and zirconium contained in the aluminum alloy has a total content of 0.1 to 10 atomic%, preferably 0.
．． It is desirable that the content is 5 to 5 at%.

By having a total content of at least one element selected from nophnium, niobium, tantalum, and zirconium within the above range (0.1 to 10 atomic %, preferably 0.5 to 5 atomic %), ■There are very few pinholes in the reflective film, making it less susceptible to corrosion.■The reflective film also has excellent reflectance.

Further, the reflective film 3 as described above is made of at least one member selected from hafnium, niobium, tantalum, and zirconium.
In addition to the seed element and aluminum (AI), small amounts of one or more other metals (elements) can also be included. Examples of such metals include titanium (T1), chromium (C+), silicon (Si), copper (Cu), tungsten (W), manganese (Mn), and magnesium (Mg[
However, this does not apply to aluminum-hafnium alloys.
, vanadium (■), etc., and such other metals may be contained in a proportion of usually 2 atomic % or less, preferably 1 atomic % or less.

The thickness of the reflective film 3 as described above is 100 to 5,000 λ, particularly preferably 200 to 2,000 λ.

The read-only optical disc according to the present invention is constructed by further providing a protective film 4 on the reflective film 3. As such a protective film 4, 513N4, SiNx (0<x
<4/3), AI N5ZnSe.

Inorganic compound film such as ZnS, Si or CdS, or
Examples include organic compound films such as ethylene vinyl acetate and acrylic resin. The thickness of such a protective film 4 is not particularly limited, but is preferably 0.1 to 100 μm1.
It is about 20 μm.

Effects of the Invention The read-only optical disc according to the present invention has a reflective film made of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium, and therefore has corrosion resistance and It has excellent moisture resistance and its reflectance does not decrease even after long-term use.

[Examples] The present invention will be described below using more specific examples, but the present invention is not limited to these examples.

Example 1 A reflective film made of an aluminum-hafnium alloy with a thickness of 700 mm was deposited on a polycarbonate read-only optical disk substrate by sputtering using an aluminum-hafnium composite target. The content of hafnium in the aluminum alloy (layer) constituting the obtained reflective film was 4 atomic %.

This reflective film was immersed in a 10% by weight aqueous sodium chloride solution at 60° C. for 4 hours, and the change in reflectance was measured.

The reflectance of the reflective film did not change before and after immersion in the sodium chloride aqueous solution.

Example 2 A reflective film made of an aluminum-niobium alloy having a thickness of 700λ was deposited on a polycarbonate read-only optical disk substrate by sputtering using a composite target of aluminum niobium. The content of niobium in the aluminum alloy (jl) constituting the obtained reflective film was 4
It was atomic%.

This reflective film was immersed in a 10% by weight aqueous sodium chloride solution at 60° C. for 4 hours, and the change in reflectance was measured.

The reflectance of the reflective film did not change before and after immersion in the sodium chloride aqueous solution.

Example 3 The same operation as in Example 2 was performed except that tantalum was used instead of niobium.

This reflective film was immersed in a 10% by weight aqueous sodium chloride solution at a temperature of 60° C. for 4 hours, and changes in reflectance were measured.

The reflectance of the reflective film did not change before and after immersion in the sodium chloride aqueous solution.

Example 4 The same operation as in Example 2 was performed except that zirconium was used instead of niobium.

This reflective film was immersed in a 0% by weight aqueous sodium chloride solution at a temperature of 60° C. for 4 hours, and the change in reflectance was measured.

The reflectance of the reflective film did not change before and after immersion in the sodium chloride aqueous solution.

Comparative Example 1 A reflective film made of aluminum having a thickness of 700λ was deposited on a polycarbonate read-only optical disk substrate by sputtering using an aluminum target.

This reflective film was immersed in a 10% by weight aqueous sodium chloride solution at 60° C. for 4 hours, and the change in reflectance was measured.

The reflectance of the reflective film after being immersed in an aqueous sodium chloride solution was approximately 30% lower than before immersion.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a read-only optical disc according to the present invention. 1... Optical disk for playback only 2... Board 3...
Reflective film 4...Protective film A...Laser light Fig. 1

Claims (1)

[Claims] 1) A read-only optical disc equipped with a reflective film, characterized in that the reflective film is made of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium. A playback-only optical disc. 2) The reflective film is made of an aluminum alloy containing at least one element selected from hafnium, niobium, tantalum, and zirconium in a total proportion of 0.1 to 10 atomic %. The read-only optical disc according to item 1.