JPH02270145A - Optical information recording, reproducing and erasing member - Google Patents

Abstract

PURPOSE:To improve recording and erasing characteristics and to stabilize cycle characteristics by changing the material of a dielectric layer of a rear surface and a dielectric layer of a front surface and adopting the constitution to select the film thickness on a substrate side large and the thermal conductivity small on the rear surface side. CONSTITUTION:The 1st inorg. dielectric layer 1 on the rear surface which has the heat conductivity as small as 1.6.10<3>Cal/Cm. deg.C and consists essentially of ZnS is previously formed as the dielectric material having excellent heat resistance on, for example, the front surface and an alloy thin film 2 consisting of Te-Ge-Sb is formed thereon. The 2nd inorg. dielectric layer 3 of the front surface is further provided on this recording thin film layer and the different dielectric material is used. Particularly the film essentially consisting of AIN having the large heat conductivity is selected. A reflecting layer 4 above-mentioned consisting of Al is provided thereon and the dielectric material 1 for the rear surface is selected at <=200nm as the film thickness. The dielectric material 3 of the front surface is selected at <=100nm. The C/N of the recording signal obtd. in this way is >=55dB and the erasing characteristics obtd. are >=30dB overwriting erasing.

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 TeOx (0<x<2.0) thin film whose main components are Te and Te02. Furthermore, by heating the thin film with a laser beam, melting it, and rapidly cooling it, it became amorphous and recorded information.A material that can be crystallized and erased by heating and slowly cooling it is S. ,R,0
Chalcogen materials such as Ge15Te81Sb2S2 by Nis R. Opshinsky et al. are known.

Also, As2S3, As2Se3 or Sb2Se3
Thin films made of a combination of an isochalcogenic element and an element from group Ⅰ of the periodic table or a group ① element such as Ge are widely known. These thin films can be formed on a substrate provided with a groove for guiding laser light and used as an optical disk. In order to record information on these disks with laser light and erase that information, a thin film is crystallized in advance, and a laser light focused to ~1 μm is intensity-modulated in accordance with the information, for example. A disc-shaped recording disk is rotated and irradiated, and the area irradiated with the peak power laser beam is heated to a temperature higher than the melting point of the thin film and rapidly cooled, so that information can be recorded as an amorphous mark. The area irradiated with the modulated bias power laser beam is heated to a temperature higher than the crystallization temperature of the thin film, and has the function of erasing the green signal information, which can be overridden.

The laser beam raises the temperature of the recording thin film above its melting point and also above its crystallization temperature. For this purpose, a dielectric material with excellent heat resistance is provided on the upper and lower surfaces of the recording thin film, and a protective layer for the substrate and adhesive layer is provided.

Depending on the thermal properties of these dielectrics, heating, rapid cooling, and cooling characteristics change, and recording and erasing characteristics can be selected.

Problems to be Solved by the Invention The first problem in information recording and erasable override recording media that use means of heating a thin film to raise its temperature, melting, rapidly cooling, and crystallizing by heating and heating is the erasing property. .

The second issue is the cycle characteristics of recording and erasing.

An object of the present invention is to provide an optical disc with excellent recording/erasing characteristics and stable cycle characteristics.

Means for Solving the Problems The present invention provides a material for recording and erasing information by thermally changing the state of a thin film through irradiation with laser light, etc. On the contrary, we provide an optical information recording/reproducing/erasing member characterized in that the thickness of the film on the substrate side is increased on the lower surface side, and the thermal conductivity thereof is selected to be smaller than that of the material of the dielectric layer on the upper surface. 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°C to 900°C.

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 heated above its melting point with a laser beam of a high power level, that part melts, rapidly cools, becomes amorphous again, and marks can be formed.

When an amorphous recording mark is selected, the recording thin film melts, and the faster the cooling rate, the more uniform the amorphous state is obtained and the signal amplitude is improved. If the cooling rate is slow, there will be a difference in the degree of amorphization between the center and the periphery of the mark. Next, during crystallization erasing, the temperature of the amorphous mark portion on which recording has already been performed is raised to a temperature higher than the crystallization temperature by irradiation with a laser beam, thereby crystallizing and erasing the mark.

At this time, when the mark is uniformly crystallized, the erasing characteristics are improved. However, if the recorded marks are non-uniform, the state of crystallization and erasure will be non-uniform, and the erasing characteristics will deteriorate.

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

As shown in Figure 1, the substrate on which the thin film that is the recording layer is formed may be a resin substrate such as polycarbonate on which grooves for guiding laser light are formed in advance, a glass plate on which grooves are formed using the 2P method, or a glass plate. A substrate with grooves formed directly on it is used. This surface is preliminarily coated with a dielectric material with excellent heat resistance, which has a thermal conductivity of 1.6 ・10' Cal.
A first inorganic dielectric layer 1 on the lower surface, which is mainly composed of ZnS and has a small value of /Cm-'C, is formed. This linear expansion coefficient is 7.5×10 4 /′C. On top of this, Te-Ge-
3b is formed. Furthermore, a second 1a-free dielectric layer 3 on the upper surface is provided on this recording thin film layer.

For this dielectric layer, different dielectrics are used as the material for the lower surface. In particular, a film whose main component is AIN, which has high thermal conductivity, is selected. Thermal conductivity is approximately 6.10 (which makes it possible to improve the cooling rate.Furthermore, a reflective layer 4 made of Af is provided on top of this.The thickness of the dielectric on the bottom surface is 200 nm or less. Select and set the top dielectric to 110
Select 0n or less. As a method for forming a thin film, vacuum evaporation or sputtering can be used. Sensitivity can also be improved by providing a reflective layer on the second inorganic dielectric layer. It is important to select a thin film thickness region of 20 nm or less as the film thickness of the recording thin film. Furthermore, a polycarbonate plate is attached with adhesive as a protective plate.

130III11 disc, 1800rpm
Rotation fl-3,43MI (z(7) signal and f2=1
．． Measure the override characteristics of the 0MHz signal. The override is a modulation between the power levels of a high power level of 1 mW and an i.m. power level of 8 mW using a laser beam of one circle spot of 1 m, forming an amorphous mark at a high power level and forming an amorphous mark at a low power level. This is a simultaneous recording method in which the amorphous mark is crystallized and erased.

A C/N ratio of 55 dB or more can be obtained for the recording signal. Furthermore, as an erasure characteristic, override erasure is 30dB.
The above is obtained.

The override cycle characteristics of the groove-shaped phase change optical disk configured according to the present invention will be evaluated.

In particular, the characteristics of pit error rate are measured.

No deterioration was observed after 1,000,000 cycles or more.

Effect of the invention The above configuration has the following effects.

(1) Recording signal amplitude increases, C/N ratio is 55dB
Improve above.

(2) Recorded marks are uniform and the override erasure rate is 3
Improved by more than 0dB.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the groove shape of an optical information recording/reproducing/erasing member in one embodiment of the present invention. 1...First inorganic dielectric layer, 2...T
An alloy thin film made of c-Ge-5b, 3... second inorganic dielectric layer, 4... reflective layer made of AI. Name of agent: Patent attorney Shigetaka Awano, 1 person/---1 father-in-law, 1 call, 1 call, and ---Te -Ge -ASbtr+%riA-Fri, R) II. 3--First: n Fukko Takuritsu 1 4-nh Parrot ro Mugizo 1 Figure 1

Claims (7)

[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 laser light has a dielectric layer on the upper surface of the recording thin film layer and the lower surface which is the laser light incident side, and the dielectric layer has different dielectric layers on the upper surface and the lower surface. An optical information recording/reproducing/erasing member characterized by using a body. (2) The optical information recording/reproducing/erasing member according to claim (1), wherein the dielectric material is selected such that the thickness of the lower surface is larger than that of the upper surface. (3) Claim (1) characterized in that the dielectric material is selected such that the thermal conductivity of the lower surface is smaller than that of the upper surface.
) The optical information recording/reproducing/erasing member described in ). (4) The optical information recording/reproducing/erasing member according to claim (1), wherein as the dielectric, a film mainly composed of ZnS is used on the lower surface, and a film mainly composed of AIN is used on the upper surface. (5) The optical information recording/reproducing/erasing member according to claim (1), further comprising a reflective film having high thermal conductivity provided on the upper dielectric. (6) 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. (7) The optical information recording/reproducing/erasing member according to claim (1), wherein the recording thin film layer has a thickness of 20 nm or less.