JPH02292743A - Reproduction only type optical disk - Google Patents

Abstract

PURPOSE:To obtain the optical disk having high reliability by providing an intermediate layer consisting of an oxide or nitride having a specific thickness between a reflecting layer and a substrate. CONSTITUTION:The intermediate layer consisting of the oxide or nitride and having <=1mum thickness is provided between the reflecting layer and the substrate. The adhesive property of the resin substrate and the reflecting layer is improved by the intermediate layer and the peeling of the reflecting layer arising from the expansion or contraction of the substrate by an environmental change is prevented. Since the permeation of moisture from the resin substrate side is shut off, the oxidation of the reflecting layer at and under a high temp. and high humidity is prevented. The weatherability is greatly improved in this way and the good use condition is assured in all environments. The reliability is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a read-only optical disc that performs optical reading, and more particularly to a read-only optical disc with significantly improved weather resistance.

[Prior Art] Read-only optical discs have already been widely put into practical use as low-cost, large-capacity recording media. It has become particularly popular for music playback and image playback. A read-only optical disc generally has a reflective film (
Usually, it has a structure in which an Afl layer) is vapor-deposited, and a protective coating of resin is further applied. [Problems to be Solved by the Invention] However, the read-only optical disc having the above structure has various problems due to insufficient weather resistance. That is, for example, when a sudden change in temperature or humidity is applied, the resin substrate expands or contracts, which causes the reflective film to peel off. There was also the problem that the reflective film was oxidized at high temperatures. Such peeling or oxidation of the reflective film directly causes an increase in the error rate, which greatly reduces the reliability of optical discs. Therefore, in order to obtain a more reliable read-only optical disc, or to obtain a read-only optical disc that can be used satisfactorily under special environments such as high and low temperatures, the issue of weather resistance of read-only optical discs must be addressed. This is considered a very important requirement to be resolved.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a highly reliable read-only optical disc that has excellent weather resistance and can be used in good condition even under special environments.

[A Thousand Steps to Solve the Problem] The read-only optical disc of claim (1) includes a transparent resin substrate on which unevenness (concavities and/or convexities) for recording information is formed, and a transparent resin substrate on the substrate. A read-only optical disc comprising a reflective layer provided therein is characterized in that an intermediate layer made of an oxide or nitride and having a thickness of 1 μm or less is provided between the reflective layer and the substrate.

A read-only optical disc according to claim (2) is characterized in that, in the above-mentioned read-only optical disc, a protective layer made of oxide or nitride is further provided on the reflective layer.

That is, the inventors of the present invention have made intensive studies to provide a read-only optical disc with high weather resistance that overcomes the above-mentioned drawbacks, and as a result, by interposing a specific intermediate layer between the substrate and the reflective layer. It was discovered that a read-only optical disc with significantly improved weather resistance could be obtained, and the present invention was completed.

The present invention will be explained in detail below.

In the read-only optical disc of the present invention, the substrate is made of a transparent resin, and its constituent resin materials include, for example, polycarbonate and PMMA.

These resins are molded by injection molding into a mold (stambar) on which information has been recorded in advance, and are molded into a substrate having irregularities (concave portions and/or convex portions) corresponding to recording signals formed on the surface. The thickness of this board is usually 1.2
mm is considered standard.

In the present invention, a reflective layer is provided on such a resin substrate via an intermediate layer made of oxide or nitride and having a thickness of 1 μm or less. In the present invention, the purpose of forming such an intermediate layer is to be located between the reflective layer and the resin substrate, and to increase the adhesion between the resin substrate and the reflective layer, and to block the transmission of moisture from the resin substrate side. It is in.

Among the substances constituting the intermediate layer, examples of oxides include StO2, Sin, Aj2203, Ta205, Ti
Examples include one or more selected from the group consisting of O3, Nb205, Zro2, etc. Further, as the nitride, 1f! selected from the group consisting of Si3N, AjlN, ZrN, etc. ! or 2 fffi or more. If the intermediate layer made of these oxides or nitrides is too thick, productivity will decrease and the cost of the product will increase. Therefore, in the present invention, the thickness of the intermediate layer is 1 μm or less. On the other hand, if the thickness of the intermediate layer is too thin, the original purpose of improving adhesion and blocking moisture cannot be fully achieved. Therefore, the thickness of the intermediate layer is preferably 50A or more. A more preferable thickness of the intermediate layer is 100~
SoooA.

The reflective layer formed on the resin substrate via such an intermediate layer is preferably made of a metal with high reflectance and excellent corrosion resistance. Examples of metals suitable as a constituent material of the reflective layer include AJ2, Au, Ag, PT, etc., but when considering cost, it is particularly preferable to use Afi. The layer thickness of the reflective layer is 300A to 1μm, especially 500A to So
It is preferable to make it Oo person.

In the read-only optical disc of claim (2), a protective layer made of oxide or nitride is further provided on such a reflective layer. As the material constituting the protective layer, the same material as used for the above-mentioned intermediate layer is preferably used.

The thickness of the protective layer is preferably about 300 to 5000A.

In a typical read-only optical disc, a coating layer made of resin is further formed on the reflective layer or the protective layer formed on the reflective layer. As the resin constituting this resin coating layer, ultraviolet curing type or hot melt type resin is preferably used. The layer thickness of this resin coating layer is 3 to 300 μm,
In particular, it is preferably 5 to 200 μm.

In addition, as a method for forming an intermediate layer, a reflective layer, and further a protective layer as necessary on the resin substrate, in the usual case,
Vacuum deposition methods such as thermal evaporation, electron beam evaporation, and sputter evaporation are preferably used. Further, as a method for forming the resin coating layer, a spin coating method, a roll coating method, etc. are used.

[Function] By forming a reflective layer on a resin substrate via an intermediate layer made of oxide or nitride, the adhesion between the resin substrate and the reflective layer is improved, and the expansion or contraction of the substrate due to environmental changes is prevented. The accompanying *US of the reflective layer can be prevented. Furthermore, since the intermediate layer blocks the transmission of moisture from the resin substrate side, oxidation of the reflective layer under high temperature and high humidity conditions is also prevented.

Therefore, according to the read-only optical disc of the present invention in which a reflective layer is provided on a resin substrate via an intermediate layer, the weather resistance is significantly improved, and it is possible to ensure good use under any environment. .

Note that the formation of this intermediate layer can be carried out continuously with the formation of the reflective layer, and since it is a thin film with a thickness of 1 μm or less, the formation of the intermediate layer does not reduce the productivity of read-only optical discs. Almost never happens.

Weather resistance is further improved by further forming a protective layer made of oxide or nitride on the reflective layer.

[Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 A polycarbonate substrate of 130 mmφ on which a group for tracking was formed was introduced into a sputtering device, and an 8xl
After evacuation to below O-7 Torr, the Si02 target was RF splattered with Ar gas to form an intermediate layer SiO2 film to a thickness of 50 OA. After that, while maintaining the vacuum, AIL target is used as a reflective layer.
℃ film is formed to a thickness of 100A, and Si is further added as a protective layer.
02 film was formed to a thickness of 50 OA.

When a tape peeling test was conducted using the mirror surface portion of the disc thus prepared, no peeling occurred at all.

In addition, we conducted an acceleration test on these disks for 1000 hours at 70°C and 90%RH, and calculated the drop-in error rate 1- (D/I (0)) using the following formula before acceleration.
) to the drop-in error rate (D/I (1000)) after 1000 hours of accelerated testing was determined, and the rate of increase was investigated. The results are shown in Table 1.

Comparative Example 1 Example 1 except that no intermediate layer and protective layer were formed.
A disk was prepared in the same manner as above, and a peel test and an acceleration test were conducted.

As a result, peeling occurred in the peel test, and corrosion occurred on the entire surface in the accelerated test, making it impossible to measure the error rate.

Table 1 Examples 2 to 5 Disks were prepared in the same manner as in Example 1, except that the intermediate layer and protective layer were made of the materials shown in Table 1, and a peel test and an acceleration test were conducted.

The results are shown in Table 1.

From Table 1, it is clear that the read-only optical disc of the present invention has no problem of peeling of the reflective layer, the increase in drop-in error rate is suppressed to less than double, and the weather resistance is extremely high.

[Effects of the Invention] As detailed above, the read-only optical disc of the present invention has the following advantages:
This is a highly reliable read-only optical disc with outstanding weather resistance and durability, and can be used in good condition for a long period of time in any environment.

In particular, according to the read-only optical disc of claim (2),
Its weather resistance is further improved.

Claims (1)

[Claims] (1) In a read-only optical disc comprising a transparent resin substrate with unevenness formed on the surface for recording information, and a reflective layer provided on the substrate, an oxide or nitride is provided between the reflective layer and the substrate. 1. A read-only optical disc characterized by comprising an intermediate layer having a thickness of 1 μm or less. (2) The read-only optical disc according to claim 1, further comprising a protective layer made of oxide or nitride provided on the reflective layer.