JPS63228433A - Optical information recording/reproducing/erasing member - Google Patents

Abstract

PURPOSE:To obtain a recording member having high sensitivity and stabilized cycle characteristics by using a GeTe-Sb2Te3-excess Sb mixture. CONSTITUTION:When Sb2Te3 having 622 deg.C m.p. is into a thin film, the film has recording action by conversion into an amorphous phase and crystallization but the film has a low blackening (accompanied by crystallization) temp. and low thermal stability. By mixing the Sb2Te3 with GeTe having a higher m.p. and 725 deg.C Tm, the crystallization temp. is raised and superior thermal stability is provided. An Sb2Te3-GeTe film is, however, liable to cause the deterioration of signal quality in the cycle of heat recording (conversion into an amorphous phase) and erasing (crystallization) or in the cycle of recording and erasing in the reverse mode due to the phase separation of GeTe from Sb2Te3. I order to prevent the phase separation and to improve the cycle characteristics, excess Sb is added and an Sb2Te3-GeTe-excess Sb mixture is used.

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 memory, T e Ox (0< x < 2-0) whose main components are To and T e O2
There is a write-once type disc that uses a thin film. Furthermore, by heating a thin film with a laser beam, melting it, and rapidly cooling it, it becomes amorphous, recording information, and then heating it, slowly cooling it, crystallizes it, and erases it. , S, R, 0vshinsky (x R. Opshinsky) et al., chalcogen material G e 15Te
81Sb2S2 and the like are known. Also, A82S3,
Thin films made of a combination of a chalcogen element such as As Se or Sb2Se3 and an element of Group V or Group II of the periodic table, such as Go, are widely known. The method of recording information on these thin films with laser light and erasing that information is to crystallize the thin film in advance.
A laser beam focused by 1 μm in diameter is applied with intensity modulation according to the information, and is irradiated by rotating a disc-shaped recording disk, for example, and the area irradiated with the laser beam is heated to a temperature higher than the melting point of the thin film. Information can then be recorded as dots that are rapidly cooled and made amorphous. When deleting this information,
A method is known in which the thin film is heated and heated by irradiating it with a long spot light in the direction of the rotational track of the disk, and then crystallized again by the slow cooling effect of the long spot light.

In an information recording and erasable recording medium using means such as heating a thin film at a high temperature, melting and rapidly cooling it, and heating and gradually cooling it, the signal quality is improved in accordance with the heating cycle. may vary. A possible cause of this variation is thermal and mechanical damage to the substrate material due to repeated stimulation of rapid heating to 400'C or more and cooling by the recording spot light and the erasing spot light many times. Furthermore, the thermal 1 of the recording thin film
Mechanical damage may also occur. Regarding the recording thin film, depending on its composition, local changes in the composition and components in the film, so-called segregation, may occur.

When the substrate or the recording film undergoes such changes, there is a problem in that noise increases during recording/reproducing and erasing cycles, resulting in deterioration of cycle characteristics.

Means for Solving the Problems The present invention aims to improve the cycle characteristics of recording and erasing in a member that records and erases information by thermally changing the state of a thin film by irradiating it with laser light or the like. , as a thin film material, G o T .

The present invention provides an optical information recording/reproducing/erasing member characterized in that a material is selected from a mixture of Sb2T03 and Sb2T03 containing an excessive amount of Sb, and the material is formed on a substrate.

Function Sb2T03 (melting point: 622° C.) can be made into a thin film to obtain an amorphous film, and has a recording action of amorphization and crystallization. However, its blackening temperature (accompanied by crystallization) is as low as ~100° C., and its thermal stability is low. Therefore,
By mixing G o To with a high melting point of Tm = 725°C, this blackening (crystallization) temperature can be raised to 180°C or higher.

Although this mixed film has excellent thermal stability, signal quality is likely to deteriorate during cycles of heating recording (amorphization) and erasing (crystallization) or the reverse mode of recording and erasing.

Therefore, in the present invention, by including excessive Sb, Sb2Te
This method is characterized by using a mixture consisting of 3-GoTo-3b. This excess sb has the effect of inhibiting phase separation of the GoTo component and the Sb2Te3 component during the crystallization and amorphization process, resulting in improved cycle times. At the same time, crystallization nuclei can be expected to play a role in crystallization, resulting in improved recording and erasing sensitivity.

EXAMPLES The substrate on which the thin film serving as the recording layer is formed is a resin substrate on which a laser beam guide groove has been formed in advance, and the surface of this resin substrate is coated with ZnS or St, which has excellent heat resistance.
An inorganic dielectric layer such as O2 is formed in advance. This dielectric layer is preferably a ZnS dielectric layer containing 16 or more moles of S102.

On top of this, Sb2Te3. A mixed thin film consisting of GeTe and excess sb is formed.

As a method for forming a thin film, vacuum evaporation or sputtering can be used. The composition of this thin film is Sb2Te3. In the triangular diagram consisting of GeTe and sb, AAs b2Te3 (36%),
GeTe (41%), Sb (24%).

8 points Sb2Te3 (27%), GoTo (5
1%), Sb (22%), CA Sb2
Te3 (42%)-GoTo (29%).

It is desirable to select a region 1 containing Sb (29%).

This is converted into G e T e for Sb2Tθ3, respectively.
.

When expressed as the ratio and the ratio of excess Sb, 0.5<GoT
e/Sb2Te3<2.0 and 1o<excess Sb
Chi/Sb2Te3 will be selected at 30. In the triangular diagram, the composition region is centered around line 2, where the excess Sb moltenness is about 25%. This 26-line composition point group is the most important.

FIG. 2 shows the relationship between the sensitivity and composition of each film. In this figure, G e T e /S b 2T e 3 out of 1
．． 2, the values of excess S b /S b 2 T e 3 are shown for those of 10,18.30. As excess Sb increases, the C/N ratio in the low power region of 6 mW, curve 3, increases, and sensitivity is improved. However, at a laser power of 9 mW, the C/N ratio is approximately 55 at any composition point as shown in curve 4.
The value is in dB.

The ratio of G o T e / S b 2 T e 3 increases and GoT.

The richer it gets, the lower the sensitivity becomes. Furthermore, the relationship between cycle characteristics and composition is the amount of change in C with respect to the cycle and d
c/N, and the value of excess Sb/Sb2Tθ3 is dc
The magnitude of /H is in the following order.

dC/N1゜<dC/N18≦dCc. . Therefore, it is preferable to select Sb/Sb2Te3>20.

In the triangular diagram of Fig. 1, at points E and H where excess sb is less than the Sb2s% line, the deterioration of cycle characteristics is greater. At one point, the deterioration of the cycle characteristics increases again.

In addition, recording sensitivity decreases at the composition point where there is more sb.

A decrease in C/N ratio occurs.

Effects of the invention In a recording member that performs recording, reproducing and erasing using a laser beam, G
A recording thin film having a composition of eTeSb2Te3-excess sb has the following effects. In other words, the types of stable alloys in the thin film decrease and the excess S
The function of b makes it difficult for composition separation to occur in the thin film during recording and erasing cycles, improving cycle characteristics. Furthermore, depending on the amount of excess Sb, a recording member that simultaneously satisfies high sensitivity and stable cycle characteristics can be obtained.

[Brief explanation of drawings]

Figure 1 is a triangular diagram of the composition of a recording thin film used in an optical information recording/reproducing/erasing member in one embodiment of the present invention, and Figure 2 is a diagram showing the recording sensitivity (C/N ratio) of the same member, with excess Sb/Sb.
FIG. 3 is a characteristic diagram showing b2Te3 ratio dependence. 1... Composition region with good characteristics, 2...
Sb25% line, 3... Laser nozzle 6.
C/N ratio at 6 mW, 4... C ratio at laser power 9 mW. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 6Q-cho ε Figure 2

Claims (5)

[Claims] (1) An optical information recording/reproducing/erasing member in which a thin film whose state is thermally changed by irradiation with laser light or the like is formed on a substrate by adding an excess of Sb to a mixture of GeTe and Sb_2Te_3. (2) Let the amount of excess Sb be +Sbat%, Sb_2
The ratio with Te_3mol% is 10<+Sbat%/Sb
The optical information recording/reproducing/erasing member according to claim 1, characterized in that _2Te_3 mol%<30. (3) The amount of GeTe is 0.6<GeTemol%/S
The optical information recording/reproducing/erasing member according to claim 1, wherein b_2Te_3mol%<2.0. (4) A dielectric layer is formed on the substrate in advance, a thin film made of GeTe-Sb_2Te_3-Sb is formed on top of the dielectric layer, a dielectric layer is formed on top of that, and then a dielectric layer is formed on top of that. The optical information recording/reproducing/erasing member according to claim 1, characterized in that the optical information recording/reproducing/erasing member is formed with a reflective layer. (5) A thin film made of Sb_2Te_3-GeTe-excess Sb is contacted on at least one surface by a mixed dielectric layer of ZnS and SiO_2 having low thermal conductivity. The optical information recording/reproducing/erasing member described in 2.