JPS62154246A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the generation of a blister by deterioration with lapse of time or thermal impact and to eliminate the possibility of generating a color flash and defective reading by depositing a thin film consisting of a metal having reflectivity by evaporation on the surface of a substrate on which information bits are formed. CONSTITUTION:The reflective thin film consisting of the metal such as aluminum or aluminum alloy is deposited by evaporation at a rate of <=15 Angstrom/ sec on the surface of the substrate on which the information signal bits are formed and which is made of a high polymer compd. consisting of a component such as acryl having a polar group at the side chain. Particularly the substrate 1 made of the high polymer compd., such as acrylic resin or epoxy resin, consisting of the component having the polar group at the side chain has high bonding strength to aluminum and therefore, the blister 6 is liable to arise. Generation of such blister is effectively prevented by making the crystal grain size smaller. This method is similarly applicable to the formation of the thin film consisting of metals having reflectivity such as aluminum alloy, silver and gold to be used for similar purposes.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention involves depositing a reflective metallic thin film on a substrate on which submicron information signal bits are formed. The present invention relates to a method of manufacturing optical recording media such as optical video discs and compact discs, which transmit information such as video, audio, characters, and graphics by directing a source from a source and reading information signal bits by the reflection.

[Conventional technology]

An optical video disk, which is a conventional optical recording medium of this type, is constructed as shown in FIGS. 1 and 2, and a method for manufacturing the same will be described below.

An information signal node 5 is formed on the surface of the group Fi1 of a polymer compound made of a component having a polar group in its side chain, such as an acrylic resin or an epoxy resin, using a stand bar or the like.

An aluminum thin film 2 is formed on the surface of the substrate 1 on which the information signal bits 5 are formed under a high vacuum of 10' Torr at a deposition rate of 20 angstroms/sec or more.

The degree of vacuum and deposition rate for this evaporation are recommended to obtain a beautiful appearance for general use.

A protective film 3 is coated on this aluminum thin film 2, and two substrates 1 coated with an adhesive 4 on this surface are polymerized and bonded.
The optical video disc is completed.

In this optical video disc, a beam such as a laser beam is irradiated from the surface of a substrate 1 with a diameter of about 1 micron, and the information signal bit 5 is read by the reflected light reflected by the aluminum thin film 2 to analyze the information. It is.

[Problems to be Solved by the Invention] When the aluminum thin film 2 is formed by vapor-depositing aluminum at a high speed as described above in a high vacuum as described above, the crystal grain size of the thin film 2 is usually 500 angstroms or more. It becomes.

In the optical recording medium that reads information signals as described above, the aluminum thin film 2 changes over time.
may peel off from the substrate 1, resulting in a bulge 6 as shown in FIG.

This bulge 6 causes the information signal bit 5 to be read incorrectly, resulting in color flash and poor reading.

[Purpose of the invention]

The present invention is intended to eliminate the above-mentioned drawbacks of conventional optical recording media, and the crystal grain size of the reflective thin film made of metal such as aluminum is set to 500 angstroms or less to prevent aging and thermal i. It is an object of the present invention to provide an optical recording medium that prevents the above-mentioned blistering from occurring due to i-blow and is free from the risk of color flash or reading failure.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention applies the above-mentioned reflective metallic thin film to the information bit forming surface of the substrate.
The gist is to deposit at a rate of angstroms/second or less and to have a crystal grain size of 500 angstroms or less.

[Embodiments of the invention]

The present invention originates from the fact that it was confirmed that the bulge 6 of the aluminum thin film 2 as described above causes color flash and reading failures in reading optical recording media.

It has been found that this bulge 6 has a large correlation with the crystal grain size of the thin film 2 formed on the substrate 1.

That is, two kinds of aluminum thin films 2 having a thickness of 400 to 800 angstroms were prepared, one having a crystal grain size of 200 to 300 angstroms or less, and one having a crystal grain size of 500 to 800 angstroms or more.

When this was left in a room for a long time and the resulting product was forced to deteriorate by heating and humidifying, the product with a large crystal grain size developed blistering 6, but the product with a small crystal grain size did not.

This phenomenon occurs because the difference in thermal expansion coefficient due to the difference in the materials of the aluminum thin film 2 and the substrate 1 results in a difference in expansion and contraction, which appears as strain, but when the crystal grain size is large, this strain is difficult to disperse, and this stress It is thought that the thin film 2 overcomes the bonding force between the substrate 1 and the thin film 2 and peels off, resulting in the appearance of a bulge 6.

On the other hand, when the crystal grain size is small, the above-mentioned strain is easily dispersed due to crystal sliding, etc., and it is considered that the stress does not cause the thin film 2 to peel off from the substrate 1.

In order to form the aluminum thin film 2 with such a small crystal grain size, it is formed when the deposition rate is 15 angstroms/second or less, and the degree of vacuum is 10 angstroms/second.
A °'Torr stand was found to be desirable.

An optical video disc on which the thin film 2 is formed under such conditions does not generate blisters 6 even under adverse conditions such as heating and humidification, and can provide high-quality images.

Therefore, reliability against changes over time is improved.

In particular, groups made from polymeric compounds such as acrylic resins and epoxy resins, which are made of components having polar groups in their side chains.
Since the polar group of No. 1 has a strong bonding force with aluminum, it tends to cause blistering 6, but reducing the crystal grain size is effective in preventing this as well.

Although the above description was made regarding an aluminum thin film, it can be similarly applied to the formation of a reflective metal thin film such as an aluminum alloy, silver, or gold used for the same purpose.

In addition to the above-mentioned optical video disc, the present invention also provides
Compact disc, DRAW disc, E-DRAW
It can also be carried out when manufacturing optical recording media such as disks.

Furthermore, the present invention can be applied to the production of an optical recording medium using a substrate having a strong bond between a polar group formed of a polymer compound having a polar group in a side chain, such as an acrylic resin or an epoxy resin, and aluminum. Implementing this method is extremely effective in preventing the aforementioned deterioration.

〔Effect of the invention〕

When using the manufacturing method of the present invention, when depositing a reflective metal-based thin film, the crystal grain size can be set to 500 angstroms or less.

With this crystal grain size, the difference in expansion and contraction between the substrate and the thin film due to aging, thermal shock, etc. is dispersed, and peeling and blistering of the thin film does not occur. The reliability is significantly improved.

In this manufacturing method, the deposition rate for forming a thin film is made slower than in the past, and it can also be performed in a low vacuum, so the productivity can be maintained.

Furthermore, conventionally attempts have been made to prevent blistering by delicately controlling external conditions such as moisture, but with this manufacturing method, this is no longer necessary and production efficiency can be greatly improved. can.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical video disc, FIG. 2 is an enlarged view of part A thereof, and FIG. 3 is an enlarged sectional view showing the bulge of the thin film. ■... Substrate, 2... Aluminum thin film, 3... Protective film, 4... Adhesive, 5... Information signal bit, 6...
...Bulge.

Claims (1)

[Claims] A reflective thin film of metal such as aluminum or aluminum alloy is applied to the surface of a substrate made of a polymer compound made of a component having a polar group in a side chain such as acrylic on which information signal bits are formed. 1. A method for producing an optical recording medium, characterized in that deposition is performed at a rate of 1/2 or less.