JPS59171041A - Information recording medium - Google Patents

Abstract

PURPOSE:To prevent the deformation of the substrate of an information recording medium due to moisture and the deterioration of the recording layer by using transparent plastics as the material of the substrate of the recording medium suitable for writing and reading with laser light and by graft-polymerizing a monomer which gives water repellency on a surface of the substrate opposite to the recording layer. CONSTITUTION:A recording layer of a metal (alloy) such as Te, In or Bi is formed on one side of a transparent plastic sheet, and a water-repellent layer is formed on the other side by graft-polymerizing a monomer contg. Si or F such as vinyltrichlorosilane or fluorinated decyl acrylate. The graft polymn. is carried out by bringing vapor of said monomer into contact with the surface of the substrate activated by glow discharge. Thus, the deformation of the substrate due to moisture and the deterioration of the recording layer due to corrosion (oxidation) are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information recording medium on which information is written and/or read using laser light.

Conventionally, there are recording media that use a beam with high energy density, such as a laser beam. In such thermal recording media,
The recording layer has a high optical density and absorbs the irradiated high energy density light beam, causing a local temperature increase,
Information is recorded when the optical properties of the area irradiated with light change due to physical or chemical changes.

It has many advantages, such as being able to perform high-density recording on multiple recording media, being able to write and read information at high speed, short access time, and excellent long-term storage stability.

In two ways, recording on such a recording medium is performed by converting the information to be recorded into an electrical time-series signal and scanning the recording medium with a laser beam whose intensity is modulated according to that signal. In this case, there is an advantage that recorded images can be obtained in real time.

As such a recording layer (heat mode recording layer),
Generally, a thin film of a metal, semimetal, or semiconductor such as Bi, Sn, In, Te, etc., formed by vapor deposition or the like on a glass or transparent plastic substrate is used.

On the other hand, there is also a type of information recording medium that records information during manufacturing, that is, a reproduction-only information recording medium.
Supports coatings with high reflectivity such as

In addition, during handling or storage of these recording media, scratches may occur on the surface of the recording layer, or foreign matter such as dust may adhere, which may adversely affect recording and reading. Inch type (full-surface adhesive type) or air sand 1 inch type information recording media are used.

Plastics such as polymethyl methacrylate are usually used as the material for the substrate in terms of optical properties, ease of handling, and cost, but these plastics generally have a large hygroscopic expansion and therefore have the disadvantage of being deformed by moisture absorption. For example, in a substrate with a recording layer deposited on one side, the rate of moisture absorption differs between the recording layer side and the non-recording layer side, so moisture absorption basically causes zero shearing during handling and storage, which adversely affects recording and reading. In the case of a sand-inch type or air-sand inch type structure, the recording layer may deteriorate due to deformation due to moisture absorption or moisture permeation of the substrate.

Traditionally, a protective layer has been formed by applying a polymer solution in an organic solvent to the substrate surface and drying it, but although this conventional measure improves scratch resistance, it is difficult to obtain sufficient moisture resistance. Therefore, an object of the present invention is to provide an optical information recording medium having a substrate with improved moisture resistance.

The present invention provides an information recording medium having a recording layer on which information can be written and/or read by a laser on a transparent plastic substrate, wherein the surface of the substrate opposite to the recording layer is made water repellent by surface grafting. This is an information recording medium characterized by the following.

The present invention will be explained in detail below.

As the plastic substrate used in the present invention, a transparent plastic plate or sheet such as polyethylene terephthalate, polycarbonate, acrylic resin (polymethyl methacrylate, etc.) is used.

The thickness of the substrate is generally 0.3 tan or more, especially 1.0 to
1.5 constant is preferred, and is generally used in the form of a disk.

The material used for the recording layer is not particularly limited, and may be a material used in the technical field, such as Te.

Zn, In, Sn, Zr, At, C! u,
Metals such as Ga; metalloids such as Bi, As, and Sb; semiconductors such as Ge and Si, and alloys or combinations thereof.

Vapor deposition, sputtering, ion blating, etc. are used to provide a recording layer of these materials on the above substrate, and the optical density required for optical information recording is 600A~.
A thickness of 1500A is suitable.

In the present invention, the surface of the substrate of the information recording medium opposite the recording layer is made water repellent by grafting a monomer capable of imparting water repellency to the surface of the substrate. The monomer used here differs depending on the type of substrate, but for example, monomers such as decene and octadecene, which have a double bond at one end and the other end is nonpolar, are used. Compounds containing Sl or F in their moieties are preferably used. Examples of the JL form fTJ of compounds such as 1 and r include evinyltrichloro7lane, trimethylvinylsilane, alino lS° methylsilane, and fluorinated decyl acrylate.

In order to graft these monomers onto the substrate surface, the surface of the plastic substrate to be grafted is subjected to glow discharge treatment in a vacuum chamber, and then the monomer gas is introduced into the vacuum chamber. The preferred conditions for glow discharge treatment are 0.01~
Under reduced pressure of 0.5 Torr, 1, o o ay ~! 1
, 000V is applied to the glow discharge electrode. The voltage to be applied may be direct current, alternating current, or high/frequency. The discharge atmosphere was air, 02°N2. It is carried out in an atmosphere of an active gas such as Ar or an inert gas under reduced pressure as described above. The discharge treatment time is from several seconds to several minutes, but preferably about 60 seconds. It is preferable to introduce the monomer gas into the vacuum chamber after the glow discharge treatment, but in the case of monomers that are difficult to gasify, the monomer and substrate surface can be removed by removing the substrate from the vacuum chamber and applying the monomer. may be brought into contact with. In either case, it is necessary to bring the activated surface of the plastic substrate into contact with the monomer due to the glow discharge, and the monomer is grafted onto the substrate surface here.
A water-repellent graft layer is formed... The water-repellent treatment of the present invention can be applied to single-plate type optical information media, sandwich type or air sandwich type optical information media, and prevents deformation due to moisture absorption of the substrate. In addition, in the latter type, deterioration of the recording layer due to water permeation can be prevented.

EXAMPLE A polymethyl methacrylate disk substrate having a thickness of 1.50 mm and having a Te recording layer formed thereon to a thickness of 50× by vacuum deposition was placed in a vacuum chamber equipped with a glow discharge electrode, and the opposite side of the recording layer was subjected to glow discharge treatment.

The conditions are r105Torr, f5004 (5[]Hz).

It was 50 seconds. After stopping the discharge, octadecene gas was introduced into the vacuum chamber from the gas introduction boat until the pressure reached the saturated vapor pressure. Additionally, the Okukujinmine U hot water bath was used to facilitate warming and gasification. Next, the inside of the Pelger was leaked, and the substrate made water repellent by the graft was taken out.

The two substrates thus produced were bonded with an adhesive with the recording layer inside, with a spacer interposed therebetween, to produce an air sundry type disk. For comparison, an air sandwich type disk was made using a similar substrate without water repellent treatment.

When both were left in an atmosphere of 40° C. and 90° RH for one week and the deformation (amount of warpage) of each substrate was measured, the amount of deformation was clearly smaller in the water-repellent disk.

The deterioration of the recording layer was caused by placing both in an atmosphere of 60°C and 90φRH.
When the optical density of the recording layer was examined after leaving it for 1000 hours, the decrease in density was smaller in the one treated with water repellent treatment.

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Claims (1)

[Claims] 1) An information recording medium having a recording layer on which information can be written and/or read by a laser on a transparent plastic substrate, wherein the surface of the substrate opposite the recording layer is formed by surface grafting. An information recording medium characterized by being water repellent. 2) The information recording medium according to claim 1, wherein the surface grafting is performed by subjecting the substrate surface to glow discharge treatment and then contacting it with a monomer capable of imparting water repellency.