JPS5832238A - Disk type recording medium - Google Patents

Abstract

PURPOSE:To ensure the high stability to the change of the ambient temperature and humidity of a disk recording medium, by forming an impermeable wet recording medium layer or a reflecting film on one side of a transparent resin substrate and a transparent impermeable wet film on the other side of said substrate respectively. CONSTITUTION:A concentric or spiral signal track groove 2 is formed on one side of a substrate 1 made of a transparent resin material like polyvinyl chloride, polymethyl acrylate, etc. along with an impermeable wet recording medium layer 3 which changes its reflection factor or the like transmittance with irradiation of a recording light beam and a protecting layer 4, while a transparent impermeable wet film 5 of CaF2, SiO, etc. and a transparent protecting layer 6 are provided on the other side of the substrate 1. As a result, the balanced hygroscopicity is secured on both surfaces of the disk recording medium. At the same time, the warp is avoided for the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disk-shaped recorder 4B (hereinafter referred to as a disk) for reading pre-recorded information optically or for optically recording and reproducing information. be.

In recent years, disks have been used as large capacity memory for video.

It is put into practical use for audio and document files.

Conventionally, glass plates have been used as the base material for these discs, but with the spread of discs, transparent resin base materials have come to be used. Examples of this resin material include vinyl chloride and polymethyl methacrylate. In general, resin materials have a higher water absorption rate than glass by 2 −1 and are also more deformed due to water absorption. For this reason, in a disk that has a structure with an inorganic reflective film made of aluminum or the like on one side for signal reproduction, large circular warps occur due to changes in ambient temperature and humidity. It was found that this is due to the difference in moisture absorption characteristics between the reflective film surface having an inorganic reflective film and the incident surface having no similar film surface.

Conventionally, in order to practically prevent this warpage, a structure was adopted in which two disks having the above structure were bonded together facing each other, but this resulted in a loss of materials and man-hours and complicated the manufacturing process. .

In the present invention, in order to maintain a stable shape with a single disk without bonding two disks together against changes in temperature and humidity, CaF2. The present invention provides a disk structure in which a transparent moisture-impermeable film such as SiO is formed by means such as vapor deposition, thereby making it possible to balance moisture absorption characteristics on both surfaces of the disk.

An embodiment of the present invention will be described below with reference to the drawings. 3. The drawings show an embodiment of a disc on which information signals can be recorded and reproduced. 1 is a substrate made of a transparent resin material such as vinyl chloride or polymethyl acrylate, and one surface of this substrate 1 has concentric or spiral signal track grooves 2.
is formed.

A conventionally known moisture-impermeable recording medium layer 3 whose light transmittance or reflectance changes upon irradiation with a recording light beam is formed on this surface by vapor deposition or the like. A protective layer 4 is further provided on the recording medium layer 3, and the above structure is a conventionally known structure.

The feature of the present invention is that the other surface of the substrate 1 has CaF2°SiO
The transparent moisture-impermeable film 6 is provided by vapor deposition or the like.

In the embodiment, a transparent surface protection layer 6 is further provided on the transparent moisture-impermeable PL 6, but depending on the strength of the transparent moisture-impermeable film 6, this surface protection layer 6 is not particularly necessary.

Figure 2 shows the humidity range from 301 to 65 at a temperature of 30'C.
The amount of deviation in the height of the outer peripheral edge from the center reference plane of a disk with a diameter of 2001B was measured when changing the height to
Figure 1 shows an example of a veneer without a transparent impermeable film 6, and B shows an embodiment of the invention with a transparent impermeable film 6. 0, which indicates that the disk shifts in the direction of the reflective film 3 as a positive amount.
As described above, by forming a transparent moisture-impermeable film on the disc entrance surface, the present invention makes it possible to obtain a disc structure that is stable against changes in the temperature and humidity around the disc, without the need for a two-layer lamination structure. It is a purpose. This has great effects, such as saving disk materials, reducing man-hours by omitting the bonding work, and improving various properties such as slip-on properties by reducing the weight of the disk.

Various materials can be used as the transparent moisture-impermeable film 6. The first characteristic required is optical transparency. Regarding this, there is some coloring power; even if there is, it is necessary to make the film thinner or to use a material with an appropriate spectral absorption curve to make it difficult to absorb the laser light used to record signals on the disk or read out the recorded signals. is also possible. Next, it is resistant to humidity. That is, the moisture-impermeable film itself must not absorb moisture in the atmosphere and undergo hydrolysis, thereby causing optical unevenness. Finally, it is easy to manufacture. In general, inorganic substances such as oxides, nologides, and sulfides can be considered as materials having the above characteristics. The most convenient method for attaching these materials to a resin disk is a vacuum deposition method or a sputtering method. Therefore, it is desirable that the moisture-impermeable material is easy to manufacture, and a material that has a relatively low melting point or high vapor pressure is desirable.

A typical material that satisfies the above characteristics is CaF2
Another example is SiO. The properties of these substances are as follows.

Substance Color lJI (boiling point) Solubility of 100f in water at room temperature SiO Colorless (1700℃) Non-CaF2 is known as a protective layer for lenses etc.
It has extremely low solubility in water, that is, it does not easily undergo hydrolysis due to atmospheric moisture, and is optically transparent. Although SiO is known as an anti-reflection film, it does not dissolve in water, does not deteriorate significantly due to moisture, and is optically transparent.

These substances can be easily formed into a thin film by the above-mentioned vacuum evaporation method or sputtering method. In addition, in the example, an example of a disk provided with a recordable recording medium layer 3 is shown, Even in a configuration in which a reflective film made of aluminum or the like is provided after previously providing unevenness in accordance with recorded information on one surface of the substrate 1, the transparent moisture-impermeable film 6 may be provided in the same manner.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between disk humidity and warpage amount.

Claims (1)

[Claims] A disk-shaped recording medium characterized in that a moisture-impermeable recording medium layer or a reflective film is provided on one surface of a substrate made of a transparent resin material, and a transparent moisture-impermeable film is provided on the other surface of the substrate. .