JPH02203437A - Optical information recording, reproducing and erasing member - Google Patents

Abstract

PURPOSE:To obtain the member which is stable in cycle characteristic by selecting the combination of the film thicknesses of a dielectric material and thin recording film which increase in the absorption of laser light with an increase in the film thickness of the thin recording film layer in the constitution consisting of the dielectric layer of the rear surface and thin recording film layer and the dielectric layer of the front surface. CONSTITUTION:The crystallized film is irradiated with laser light and is thereby heated to the m. p. thereof or above. This part is then melted and is rapidly cooled, by which the part is converted to an amorphous state and a mark 8 is formed. The increase of the film thickness of the thin recording film 3 is generated in the parts before and after the mark 8 and the light absorbing sensitivity of the part 10 where the film thickness is increased changes. The respective combinations of the dielectric materials 2, 4 and the thin recording film 3 which increase in sensitivity with an increase in the film thickness are, therefore, previously selected. The recording marks are formed stably with cycles in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording/reproducing/erasing member capable of recording, reproducing, and erasing information with high density and large capacity using a laser beam or the like.

Regarding conventional optical disk memories, there is a write-once type disk using a TeaX (0<x<2.0) thin film whose main components are Te and Te02. Furthermore, by heating a thin film with a laser beam, melting it, and rapidly cooling it, it becomes amorphous and records an information number, and by heating and slowly cooling it, it crystallizes and erases it.S ,R,0vs
Chalcogen material G e B T e a + S by Mr. Hinsky (Nis R. Opsinsky) et al.
b 2 S 2 and the like are known. Also, As2 S8
or As, Se8 or 5b2Se.

Thin films made of a combination of an isochalcogenic element and a group V element of the periodic table or a group V element such as Ge are widely known. Generally, the method of recording and erasing information using laser light is
A thin film is crystallized in advance, and this is ~φ1 μm.
Intensity modulation is applied to the focused laser beam to correspond to the information.
For example, by rotating a disk-shaped recording disk and irradiating it,
The area irradiated with the laser beam is heated to a temperature higher than the melting point of the thin film and then rapidly cooled, so that information can be recorded as an amorphous mark. When erasing this information, a long spot light is irradiated in the direction of the rotation track of the disk.
A method is known in which a thin film is heated to an elevated temperature and re-crystallized by the slow cooling effect of a long spotlight.

'Problem to be Solved by the Invention The first problem with information recording and erasable recording media that uses means of heating a thin film to raise its temperature, melting it, turning it into a cold amorphous state, and heating it up to crystallize it is the heating cycle. There is a corresponding variation in signal quality. In particular, fluctuations in bit error characteristics are a problem. The cause of this variation is the thermal effect of the substrate material due to repeated stimulation of rapid heating and cooling of 400°C or more by the recording spot light and the erasing spot light.

There is mechanical damage. When a recording thin film is heated above its melting point, its volume expands due to melting, and depending on its constituent elements, the vapor pressure of the thin film's constituent materials increases, and the composition changes due to evaporation and flow of the constituent components.

Changes in film thickness may occur due to movement of components.

If the substrate or recording film undergoes any of the above changes,
During the recording, reproducing, and erasing cycles, sensitivity decreases, noise increases, or bits of recorded marks are dropped. There was a problem that deterioration of cycle characteristics occurred.

An object of the present invention is to provide a member with stable cycle characteristics.

Means for Solving the Problems The present invention provides a member for recording and erasing information by thermally changing the state of a thin film by irradiation with a laser beam or the like. Provided is an optical information recording/reproducing/erasing member which has a structure consisting of a body layer and is characterized by selecting a combination of a dielectric material and a recording thin film thickness such that absorption of laser light increases as the thickness of the recording thin film layer increases. It is something to do.

The melting point of an amorphous film containing active Te is typically 40
It has a wide temperature range from 0℃ to 900℃.

Crystallization can be performed by irradiating these films with laser light and gradually increasing the temperature and cooling. This temperature is in the crystallization temperature range below the melting point. Furthermore, when this crystallized film is irradiated with a laser beam of a high power level and heated above its melting point, that part melts, rapidly cools, becomes amorphous again, and marks can be formed.

At this time, due to melting, evaporation, etc. of the recording thin film, slight movement of the recording thin film material may occur in the recording mark portion. When the substance moves, the thickness of the recording thin film increases at the front or rear of the mark. Therefore, the light absorption sensitivity of the increased film thickness changes. If the sensitivity of this part decreases, it will no longer be possible to form a mark in this part when recording a mark next time.

In the present invention, by selecting a combination of a dielectric material and a recording thin film whose sensitivity increases with respect to an increase in film thickness, recording marks can be formed stably over cycles.

This is particularly effective in the override method, where a mark in the previous signal overlaps with the mark in the next signal because the mark has already been recorded, so it is not affected by the thinning of the film.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

As the substrate on which the thin film serving as the recording layer is formed, a resin substrate such as polycarbonate or a glass plate is used, on which grooves or pits for guiding laser light are formed in advance.

The configuration of the recording member is as shown in FIG.
．． lower layer dielectric; 3. recording film, 4. upper N dielectric, 51 reflective layer, and 6. consisting of an adhesive protective layer.

A first inorganic dielectric layer such as ZnS or 5i02 having excellent heat resistance is formed on the surface of the substrate in advance. This dielectric layer is preferably a ZnS dielectric layer containing 15 mol% or more of 5IO2. For example, 5i02 by 20%
When it is included, the refractive index becomes n-2.0. On top of this, a thin alloy film made of Te-Ge-5b is formed.

Furthermore, heat resistance can be improved by providing a second inorganic dielectric layer on this recording thin film layer.

As a method for forming a thin film, vacuum evaporation or a spunter method can be used. Sensitivity can also be improved by providing a reflective layer on the second inorganic dielectric layer.

As a 130■ disk, fl rotates at 1800 rpm.
-3,43MI (z(7) signal and f2=1.0MHz
Measure the override characteristics of the signal. Override is done by laser beam with 1 circle spot 1m.
Simultaneous erasure method of forming an amorphous mark at a high power level and crystallizing and erasing the amorphous mark at a low power level by modulating between a high power level of 14 mW and a low power level of 6 mW. It is.

FIG. 2 shows recording marks of overridden tracks, respectively. Recording track, 8. Amorphous recording mark, 9. Crystallization erasure section, 10. This is the thickened portion of the recording film.

The optical characteristic (light absorption sensitivity A) of a recording member can be determined by the optical constants (refractive index n, extinction coefficient k) of the constituent materials and the respective film thicknesses d. In particular, the upper and lower dielectric layers (n, ni, dl, d2), the recording thin film in the amorphous state (nl, kl, d buttons, the crystalline state (n2., 2.d3), and the reflective layer) (n, to, d4) is important.

Figures 3(a) and (b) show the recording film thickness and light absorption sensitivity A.
In case (a), the light absorption sensitivity A decreases due to an increase in the thickness of the recording film; in case (a),
An example will be shown in which light absorption sensitivity increases as the thickness of the recording film increases.

The slope of these light absorption sensitivities varies depending on the thickness structure of the dielectric layer, the thickness region of the recording film, and the like.

As shown in FIG. 2, when an amorphous mark is formed, a slight increase in film thickness occurs at the front or rear part of the mark. By selecting the configuration of the recording member as shown in FIG. 3(b), it becomes possible to form the next signal mark in this portion.

Effects of the Invention With the configuration described above, it is possible to prevent a decrease in recording sensitivity against changes in sensitivity due to mass transfer of the recording thin film, and improve cycle characteristics of pit error characteristics.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the recording member, FIG. 2 is an explanatory diagram of overridden tracks, and FIG. 3(a) is a relationship between recording film thickness and light absorption sensitivity ((when IJI is negative). Figure 3 (b) is a diagram showing the relationship between the film thickness of the recording film and the light absorption sensitivity (when the slope is positive). 1...Substrate, 2...Lower dielectric, 3・
...Recording film, 4...Upper layer dielectric, 5...
... Reflective layer, 6... Adhesive protective layer. Name of agent: Patent attorney Shigetaka Awano 1 person, 1 figure, 1 figure, 1 record of electronic data (d3) Recording FjN (d3)

Claims (6)

[Claims] (1) Using a recording thin film that has the property of absorbing the energy of laser light, heating up, melting, rapidly cooling, and becoming amorphous, and the property of crystallizing an amorphous state by heating it. , the member for recording information by intensity modulation of the laser beam has a transparent dielectric layer on the upper and lower surfaces of the recording thin film layer, and absorption of the laser beam increases as the thickness of the recording thin film layer increases. , an optical information recording/reproducing/erasing member characterized by selecting a combination of film thicknesses of a dielectric material and a recording thin film. (2) Claim (1) characterized in that the combination of the film thicknesses of the dielectric material and the recording thin film is selected such that when the recording thin film is in a crystalline state, the absorption of laser light increases as the film thickness increases. The optical information recording/reproducing/erasing member described above. (3) The optical information recording/reproducing/erasing member according to claim (1), wherein the recording thin film layer has a thickness of 800 Å or less. (4) The optical information recording/reproducing/erasing member according to claim (1), wherein ZnS containing SiO_2 is used as the heat-resistant layer. (5) The optical information recording/reproducing/erasing member according to claim (1), wherein a material consisting of Te, Ge, and Sb is used for the recording thin film layer. (6) The optical information recording/reproducing/erasing member according to claim (1), wherein the wavelength of the laser beam for recording or erasing is selected so that its absorption increases as the thickness of the recording thin film increases. .