JPS62149050A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve heat absorption efficiency to a light beam by forming an optothermorecording medium layer and heat absorptive layer having the heat absorptivity larger than the heat absorptivity of said medium layer on a glass substrate. CONSTITUTION:The optothermorecording medium 2 and the heat absorptive layer 3 are formed on the glass substrate 1 and the light beam 4 is made incident thereon from the substrate side. The layer 3 is formed of a thin Bi2Te3 alloy film having low heat conductivity and excellent heat accumulating property. The surface reflectivity thereof is decreased to accumulate the heat energy of the light beam in the film. The layer 2 is formed of a thin Ag-Zn alloy film contg. 37.8wt% Zn and is heated by the heat conduction from the thin film 3. The film 2 is silver white at an ordinary temp. and has 95% reflectivity to light of about 800nm wavelength. The reflectivity thereof decreases to 80% when the layer is heated at >=285 deg.C by the heat of the light beam. The thermal efficiency to the light beam is thereby improved and the writing and reading of information are made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an optical recording medium, and in particular to an optical recording medium that performs recording by irradiating light to raise the temperature of the irradiated area and causing an M4j change. Concerning improvements in recording media.

[Technical contradiction of the invention and its problems] In recent years, optical disk devices that use laser beams etc. as recording and reproducing devices have
Because it has the potential to realize large-capacity ω memory at a relatively low cost, it has attracted attention from various quarters, and research toward practical application is progressing.

By the way, it is known that copper-aluminum (Cu-Al) alloy thin films, zinc-coated zinc (Ag-Zn) alloy thin films, etc. undergo eutectoid transformation when they have a certain time-determined alloy structure. Since it exhibits a reversible change in surface QJ ratio or color tone due to eutectoid transformation, its use as an optical recording medium such as an optical disk is being considered.

That is, the alloy thin film is irradiated with light energy such as a laser beam, and the thermal action of this light energy causes a detectable physical change - eutectoid transformation, which is then used for recording.

Conventionally, as an optical recording medium, Cu is used as a photothermal recording medium layer 12 on a support such as a glass substrate 11 as shown in FIG.
-Al alloy thin films and Ag-Zn alloy thin films are used, and recording is performed by light irradiation 13 from the substrate side.

However, these alloy thin films generally have a high surface reflectance and a poor heat absorption rate with respect to irradiated light, so they have the drawback of requiring a large amount of light energy for recording.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an optical recording medium with high heat absorption efficiency for light beams.

[Summary of the Invention] Therefore, the optical recording medium of the present invention is provided with a heat absorption layer made of a material having a higher heat absorption efficiency than the photothermal recording medium layer.

As a result, even when using a photothermal recording medium layer with poor heat absorption efficiency, such as a Cu-Al alloy thin film or an Aq-Zn alloy thin film, the thermal energy of the light beam can be efficiently transmitted to the photothermal recording medium layer.

In other words, the light beam efficiently absorbed by the heat absorption layer heats that area (of the heat absorption layer).

Thermal energy of the light beam is effectively stored and energized within the heat absorption layer, indirectly heating the photothermal recording medium.

In this way, the thermal energy of the light beam is efficiently supplied and the photothermal recording medium layer undergoes a 11111 change in the irradiated area 11-J, thereby achieving recording.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a cross-sectional structure of an optical recording medium for an optical disk according to an embodiment of the present invention.

This optical recording medium includes a glass substrate 1 and a photothermal recording medium layer 2.
As a heat absorbing layer 3, bismuth telluride (
B12Te3) alloy thin film is interposed therebetween.

Here, during recording, the light beam 4 is made to enter from the glass substrate 1 side.

Bi2Te3 has low thermal conductivity and excellent heat storage properties.
When the presence of the alloy thin film reduces the surface reflectance due to multiple interference effects and the light beam is effectively absorbed within this film, the heat of the light beam 4 is absorbed within this Bi2Te3 alloy thin film layer. Energy is effectively stored and AC+-37.8wt% in the area irradiated with the light beam.
The Zn alloy thin film 2 is heated indirectly by thermal conduction.

This AQ-37, 8 wt% Zn composite & Ajj film has a silver-white color tone at room temperature, and has a reflectance of approximately 95% for light with a wavelength of around 800 nm, but as mentioned above, the thermal energy of the light beam reduces the reflectance to 285%. When heated and rapidly cooled to temperatures above
00 nm (The reflectance near -j changes to about 80%. In this way, information is corrupted by eutectoid transformation due to heating, and during reproduction, this is read and reproduced by light. .

In this way, the light energy is effectively used to inject information into the photothermal recording medium layer, so that good recording can be performed with less light energy than in the past.

In addition, when processing the written information, the Ag-37.
The wt% Zn alloy film returns to its original silvery white color.

By the way, the melting point of this Bi21-63 alloy thin film is 585
°C, and even if the recorded temperature of the Ag-37.8 wt% Zn alloy thin film exceeds 285 °C, it will not melt.
In the recording mode, multiple interference effects can be preserved.

In addition, since the Bi2Te2 alloy thin model has low thermal conductivity,
12 recording time light beam i! 'Thermal energy extracted by DJ is 3i2Te, 3 which is heat absorption 1 book 3
The light diffuses within the alloy film and is conducted to the photothermal recording medium layer 2, which has a high thermal conductivity. Therefore, the thermal energy of the light beam is efficiently transmitted to the photothermal recording medium layer, enabling high-resolution recording.

In addition, in the example, Bi210 is used as the heat absorption layer.
3 alloy thin film was used, but it is not limited to this.
In addition, the photothermal recording medium layer may be selected from materials with high heat absorption, such as bismuth selenide (Bi2Se3) alloy thin film, antimony telluride (Sb2F'e3) alloy source pA, etc. At this point, heating and rapid cooling are required, so it is necessary to select the material for the heat absorbing layer while taking precautions.

Further, the heat absorption layer may have not only a single layer structure but also a multilayer structure.

Furthermore, in the actual Mb example, a heat absorption layer was interposed between the layer and the photothermal recording medium layer.

In addition, a photothermal recording medium layer 22 and a heat absorption layer 2 are provided on the substrate 21.
3 in this order (FIG. 2(a)), a substrate 31, a first heat absorption layer 33a, a photothermal recording medium layer 32,
The second heat absorption layer 33b was logging υ in the order of
)) etc. are also valid.

In addition, for the photothermal recording medium layer, Aq-37,8w
It goes without saying that it is effective when using other materials in addition to the t%Zn alloy thin film, but in particular Cu-Al alloy thin film, copper-aluminum-nickel (Cu-Al-Ni)
The structure of the present invention is effective when using a material having a poor 1R rate of ripening with a light beam, such as a thin film of an alloy.

〔Effect of the invention〕

As explained above, according to the present invention, since the heat absorption layer is removed, it is possible to provide an optical recording medium with high heat absorption efficiency for optical beams.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of an optical recording medium according to an embodiment of the present invention, FIGS. 2(a) and (b) are diagrams showing another embodiment of the present invention, and FIG. 3 is a diagram showing a conventional optical recording medium. 1 is a diagram showing a cross-sectional structure of an optical recording medium. 1.11.21.31...Substrate, 2.12, 22゜3
2... Photothermal recording medium [Tsuba, 3.23.33a, 33b
...Heat absorption layer, 4...Light beam. Figure 1 Figure 2 (a) Figure 2 (b) Figure 3

Claims (3)

[Claims] (1) An optical recording medium comprising a substrate, a photothermal recording medium layer, and a heat absorption layer made of a substance having a higher heat absorption coefficient than the photothermal recording medium layer. (2) The photothermal recording medium layer is made of copper-aluminum (Cu
-Al) based alloy thin film layer, copper-aluminum-nickel (
Cu-Al-Ni) based alloy thin film layer, silver-zinc (Ag-Z
n) An optical recording medium according to claim (1), characterized in that it is made of an alloy thin film having eutectoid transformation such as an alloy thin film. (3) The heat absorption layer is bismuth telluride (Bi_2T
e_3) Alloy thin film, antimony telluride (Sb_2Te
_3) Alloy thin film, bismuth selenide (Bi_2Se_3
2.) The optical recording medium according to claim 1 or 2, characterized in that it is made of an alloy thin film or an alloy thin film made of a combination thereof.