JPH11316977A - Phase change recording medium - Google Patents

Abstract

(57) [Problem] To provide a phase change medium having high contrast and high sensitivity. [Constitution] In a phase change recording medium which performs recording by thermally changing a crystal state of a recording layer provided on a substrate via a dielectric layer to change light reflectance, a reflection layer is formed on the recording layer. And the reflective layer is formed of Al _1-x M _x (M is T
a, at least one element selected from Ti, Zr, V, Pt, Mo, and Cr, and x is a number from 0.01 to 0.15), and the dielectric layer contains SiO ₂ ; A phase change recording medium provided so as to enhance an interference effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a phase change recording medium. More specifically, the present invention relates to an optical recording medium using a phase-change recording layer as a recording layer.

[0002]

2. Description of the Related Art In a phase change recording medium, information is recorded using an effect in which the crystal phase of the medium changes (for example, from crystal to amorphous) by heating with a laser beam, and the information is recorded based on the difference in the light reflectance of each crystal phase. Can be read. The phase change recording medium includes both a writable type (write-once type) and a rewritable type (erasable type), and is a recording medium with remarkable progress in recent years. The carrier level (CL) of the phase change recording medium increases as the contrast of the light reflectance between the recorded state and the erased state increases. There has been proposed a method in which a recording layer is thinned in order to increase contrast, and a reflective layer is provided thereunder to utilize the interference effect of light (for example, Autumn Applied Physics Society of Japan, 1987, 18p-ZP-12).

[0003]

In order to enhance the interference effect, it is necessary to increase the light reflectance of the reflection layer. However, if a material having a high reflectance (eg, Au, Ag, Cu, Al, etc.) is used. In general, the thermal conductivity is large and the sensitivity is lowered.

[0004]

The present inventors have made intensive studies to provide a high-contrast, high-sensitivity phase-change recording medium which overcomes the above-mentioned disadvantages, and as a result, have reached the present invention. . That is, the gist of the present invention is to provide a phase-change recording medium that performs recording by thermally changing the crystal state of a recording layer provided on a substrate via a dielectric layer to change light reflectance. Provided with a reflective layer,
The reflective layer was formed of Al _1-x M _x (M is Ta, Ti, Zr, V,
At least one element selected from Pt, Mo, and Cr;
x is a number from 0.01 to 0.15), and the dielectric layer contains SiO ₂ and is provided so as to enhance the interference effect.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail. The phase-change optical recording medium according to the present invention is produced by a normal thin film forming apparatus such as vacuum evaporation or sputtering. As the substrate, a low heat conductive material such as PMMA or PC (polycarbonate) is usually desirable from the viewpoint of preventing heat from dissipating to the substrate. By forming an organic film such as a photosensitive resin thereon, heat dissipation can be prevented. The thickness of the substrate is generally about 1 to 2 mm, usually about 1.2 mm.

In the present invention, a dielectric layer, a recording layer, and a reflective layer are sequentially provided on a substrate. GeTe based recording layer,
InSb-based, TeO ₂ -based or the like is used. The film thickness of the recording layer is optimized from the refractive index before and after recording and the refractive index of the reflective layer so as to obtain the best contrast.
00-600 °. In the present invention, an Al alloy containing one or more elements selected from Ta, Ti, Zr, V, Pt, Mo, and Cr is used as the reflective layer. The content of the additional metal is 1 to 15 at% (atomic%), and more preferably 2 to 10 at%. Preferred additional metals are Ta, Ti and Zr among the above. The thickness of the reflective layer is selected in such a range that the reflectance does not decrease and the sensitivity does not decrease significantly, but is preferably about 300 to 500 °. In order to further enhance the interference effect, a high refractive index S
A dielectric containing iO ₂ is provided. Further, it is more effective to provide a dielectric material having a high refractive index in contact with the reflective layer side of the recording layer. Other dielectric materials such as ZnS, Ta
₂ O ₅ , SiO ₂ , SiO, ZrO ₂ , Si ₃ N ₄ , A
1N or the like is used. When a dielectric is provided on one or both sides of the recording layer, the thickness of the recording layer is determined by the entire interference effect including the dielectric.

[0007]

EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A polycarbonate disk was used as a substrate, and R
An SiO ₂ layer was formed to a thickness of 1000 ° by the F sputtering method. A recording layer is formed on the Ge target as a recording layer.
e, Bi chips were arranged and formed by sputtering. The film formation rate was 10 ° / sec, and the film was formed to a thickness of 400 °. The composition of the recording layer was Ge ₅₀ Te ₅₀ Bi ₃ . Next, a Ta chip was arranged on an Al target to form an alloy of 300 ° Al and Ta as a reflective layer. The amount of Ta in the reflective layer was adjusted by the number of Ta chips. As a comparative example, a similar disk having a reflective layer made of only Al was prepared.

[0009] 1800 is added to the disc created as described above.
When recording was performed under the conditions of rpm and 0.5 MHz duty 50%, the result as shown in FIG. 1 was obtained. The optimum recording power secondary distortion C ₂ and the ratio of carrier level C C ₂ /
The recording power at which C was minimized was set. As is clear from FIG. 1, the sensitivity can be increased without lowering the carrier level by adding a small amount of Ta to Al. A similar effect is obtained in addition to Al and Ta, in addition to Al and Ti, Zr, V, P
It was also recognized when an alloy with t, Mo, Cr, etc. was used.

[0010]

The phase change recording medium according to the present invention has a C / N ratio.
It shows good characteristics in both ratio and sensitivity.

[Brief description of the drawings]

FIG. 1 shows a Ta content in a reflective film, an optimum recording power, and
5 is a graph showing carrier level correlation.

Claims (2)

[Claims] 1. A phase change recording medium in which recording is performed by thermally changing a crystal state of a recording layer provided on a substrate via a dielectric layer to thereby change light reflectance, and to reflect light on the recording layer. And the reflective layer is formed of Al _1-x M _x (M
Is formed of at least one element selected from Ta, Ti, Zr, V, Pt, Mo, and Cr, and x is a number from 0.01 to 0.15), and the dielectric layer contains SiO ₂ ; A phase change recording medium provided to enhance an interference effect. 2. The phase change recording medium according to claim 1, wherein the thickness of the recording layer is 600 ° or less.