JPH02195538A - Component for optical information recording, reproducing and erasing - Google Patents

Abstract

PURPOSE:To improve cycle characteristics for bit error property by causing symmetric thermal expansion in a heat-resistant layer in the front and rear parts of a mark when the mark is formed by melting, with the intention of preventing the material transfer accompanied with melting of the recording thin film material. CONSTITUTION:The component consists of a lower heat-resistant layer, a recording thin film layer and an upper heat-resistant layer. In the process of forming the mark by melting the film with laser light, the front and back parts of the mark in the heat-resistant layer are made symmetric thermal expansion. These films are crystallized by irradiating with laser light to heat and by gradually cooling. By irradiating these crystallized films with high power laser light to heat over the melting point thereof, the heated area melts and rapidly cools to an amorphous state, which forms a mark. By selecting the constitution of layers and the method for heating, thermal expansion of the heat-resistant layer can be reduced and thermal expansion in the front and rear parts of the mark is made symmetric with less difference of expansion. Thus, deterioration of the component for recording caused by material transfer in the record ing thin film can be prevented.

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 containing Te and TeO2 as main components. Furthermore, by heating a thin film with a laser beam, melting it, and rapidly cooling it, it becomes amorphous and records information, and by heating and slowly cooling it, it crystallizes and erases it. ,S.RoO
Chalcogen materials such as Ge 15Te81Sb2S2 by Nis R. Opshinsky et al. are known. Furthermore, thin films made of a combination of a chalcogen element such as As2S3, As2Se3, or 5b2Sea and a group V element of the periodic table or a group V element such as Ge are widely known. In order to record information on these thin films with laser light and erase the information, the thin film is crystallized in advance, and a laser light focused on 2Φ1 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 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. A known method for erasing this information is to irradiate a long spot light in the direction of the rotating track of the disk to heat the thin film to raise its temperature, and then crystallize it again by the slow cooling effect of the long spot light.

Problems 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 and quenching it into an amorphous state, and heating and heating it to crystallize it, is to solve the following problem: The signal quality fluctuates. The cause of this variation is thermal and mechanical scratches on 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. Furthermore, there is thermal and mechanical damage to the recording thin film. For recording thin films, when heated above their melting point, the volume expands due to melting, and depending on the constituent elements, the vapor pressure of the thin film's constituent materials increases, and the composition and film thickness change due to the movement of constituents due to evaporation. In some cases. At the same time, the heat-resistant layers on the upper and lower surfaces of the recording thin film rise in temperature and expand asymmetrically, facilitating the movement of the recording thin film material.

If the substrate or recording film undergoes any of the above changes,
In the recording/reproducing/erasing cycle, there is a problem in that noise increases and cycle characteristics deteriorate.

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 through irradiation with laser light or the like, which includes a heat-resistant layer and a recording thin film layer on the bottom surface, and a heat-resistant layer on the top surface. The present invention provides an optical information recording/reproducing/erasing member which has a structure in which the amount of thermal expansion of the front and rear parts of the mark on the heat-resistant layer is symmetrical when the melted mark is formed by a laser beam. be.

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 achieved by irradiating these films with laser light and gradually increasing the temperature. This temperature is - crystallization temperature lower than the melting point of boat fishing. In addition, when this crystallized film is irradiated with a high-power laser beam and heated above its melting point, that part melts, rapidly cools, becomes amorphous again, and a mark can be formed.At this time, First, the temperature of the recording thin film rises and it melts and expands, and the recording thin film layer becomes a heat source and heats the heat-resistant layers on the upper and lower surfaces.If the amount of expansion of this heat-resistant layer is asymmetric between the front and rear parts of the mark, A movement of the recording thin film material occurs corresponding to the volume difference.The amount of expansion of the heat-resistant layer is reduced, the expansion of the front and rear parts is symmetrical, and the heating method is configured so as to make a difference in the amount of expansion. By choosing
Deterioration of the recording member due to transfer of recording thin film substances can be prevented.

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

Example 1 As a substrate on which a thin film serving as a recording layer is formed, a resin substrate made of polycarbonate or the like, or a glass plate, on which grooves or pit rows for guiding laser light are formed in advance is used. A first inorganic dielectric layer of ZnS, SiO2 or the like having excellent heat resistance is formed on this surface in advance.

This dielectric layer is preferably a ZnS dielectric layer containing 15 mol % or more of SiO2. For example, the coefficient of linear expansion is Z
In nS, it is 7.5X10-67'C. For SiO2, it is as small as 5.5XIO-7/'C.

A thin alloy film made of Te-Ge-3b is formed on this. 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 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 this thin film. Furthermore, a polycarbonate plate is attached with adhesive as a protective plate.

As a 130mm disc, r at 1800rpm rotation.
1 = 3.43 MHz signal and f 2 = 1.0-Hz
Measure the override characteristics of the signal. The override is a modulation between a high power level of 14 mW and a low power level of 6 mW using one circle spora l-5Φ1 μm laser beam, forming an amorphous mark at a high power level and forming an amorphous mark at a low power level. This is a simultaneous erasure method that crystallizes and erases amorphous marks.

FIG. 1 shows the relationship between the thickness of the recording thin film and the recording cycle characteristics. The thickness of the recording thin film is 80nm, 40nm, 20nm.
m, and 10 nm. The recording characteristics are pit error rate. The initial values of the first cycle, that is, the pit error rates, are all in the 10-6 range. When the recording film thickness is as thick as 80 nm, the pit error rate is 1000 nm.
An increase is seen beyond 0 cycles.

In the case of 40 nm, the pit error rate is 100,000
An increase is seen over cycles. 20nm, 10n
In the recording thin film layer of m, the thermal expansion is small, the difference in the amount of expansion is small, and no increase in pit error rate is observed after 1,000,000 cycles or more. These do not suffer from deterioration due to movement of components, which causes shading of the film within the recording track.

Example 2 A semiconductor laser was used as a laser light source for recording, erasing and reproducing information, and as a pulse waveform for forming recording marks, the first high power level was selected to melt the recording thin film, and the bias power level was selected to melt the recording thin film. Choose a lower power level to crystallize and choose to override information at least at these two power levels. Furthermore, for the second highest power level, a pulse waveform is selected in which the power level at the start of pulse irradiation for recording mark formation is 50% higher than the power level at the end of irradiation, as shown in FIG. The structure of the recording member consists of a recording thin film with a heat-resistant layer provided on the lower and upper surfaces. The recording cycle characteristics are evaluated by bit error characteristics, and the film thickness of Record Book II is 40 nm.
Characteristics of 1,000,000 cycles or more can be obtained in a thick region of 1,000,000 cycles or more. In the case of a rectangular pulse waveform, due to heat conduction, the temperature at the end of irradiation, that is, the front of the recording mark becomes higher than the temperature at the beginning of irradiation, that is, the rear of the recording mark, and the asymmetry of thermal expansion is large. On the other hand, by selecting a pulse waveform, the symmetry of thermal expansion is improved and cycle characteristics are improved.

Effects of the Invention With the configuration described above, it is possible to prevent changes due to material transfer accompanying melting of the recording thin film material, and the cycle characteristics of bit error characteristics are improved to more than 1 million cycles.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the film thickness and cycle characteristics of a recording thin film according to the configuration of the present invention, and FIG. 2 is an explanatory diagram showing a laser irradiation pulse waveform in the configuration of the present invention. ■...Film thickness 80 nm, 2...Film thickness 40
nm, 3... Film thickness 20 nm, 4... High power melting power level irradiation start part, 5... High power melting power level irradiation end part, 6... ...Low power crystallization power level, 7...Low power regeneration power level. Name of agent: Patent attorney Shigetaka Awano Haka 1 person 1 - 1
1 KBOnm e-rs Thickness 40 nm

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 modulating the intensity of laser light, which has a heat-resistant layer on the upper and lower surfaces of the recording thin film layer, and when forming the melting mark, the amount of thermal expansion of the heat-resistant layer at the front and rear parts of the mark; An optical information recording/reproducing/erasing member characterized in that a configuration is selected that makes the symmetrical structure. (2) The optical information recording/reproducing/erasing member according to claim (1), wherein the recording thin film layer is selected to have a thickness of 200 Å or less. (3) The first heat-resistant layer and the second heat-resistant layer are formed by forming a dielectric material having a coefficient of thermal expansion of 1×10^-^5/°C or less. Optical information recording/reproducing/erasing member. (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) As described in claim (1), the power level at the start of irradiation is selected to be higher than the power level at the end of irradiation as the irradiation pulse waveform of the laser light for melting and rapidly cooling the recording film and forming marks. Optical information recording/reproducing/erasing member.