JPS60160037A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable recording, reading and erasion with laser light by forming a phase transition recording layer of a material enabling reverside transition from an amorphous phase to a crystalline phase on a substrate and a layer of a material having a higher m.p. than the material of the recording layer and causing no reaction with the material of the recording layer even at the m.p. or above on the recording layer. CONSTITUTION:A recording layer 2 is formed on the surface of a substrate 1 of glass, acrylic resin or the like by vacuum-depositing a material which records information by transition from a crystalline phase to an amorphous phase by rapid heating and rapid cooling and can erase the information by reverse phase transition by removal of heat. The material includes Sb2Se3. A layer 3 of a material having a higher m.p. than the material of the layer 2 by >=300 deg.C and causing no reaction with the material of the layer 2 even at the m.p. or above is then formed on the layer 2 by vacuum deposition with electron beams or other method. The material of the layer 3 includes Mo. The thickness of the recording layer 2 can be reduced, and an optical information recording medium enabling sure recording and erasion with high sensitivity and small power at high speed is obtd. The medium is fit for repeated recording.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides for
Related to information recording media that optically record information, especially erasable and rewritable optical information recording media ◎ Background technology and its problems Magneto-optical recording media are known as erasable and rewritable optical information recording media. It is being However, in such a magneto-optical medium, the optical system is complicated because information is recorded, that is, the direction of magnetization is read out using polarized light.

Furthermore, since the erasure is performed using an external magnetic field, the device becomes complicated.

In contrast, by utilizing reversible phase transition from amorphous to crystalline and from crystalline to amorphous that does not rely on magnetic recording, phase transition from crystalline to amorphous by rapid heating and cooling is possible. For example, information is recorded by performing a phase transition from amorphous to crystalline using elm heat, and erasing is performed, for example, and the signal is A method of regeneration was proposed. For example, JP-A-55-28
No. 530 discloses information recording materials using low oxides such as reox (o<x<2), or JP-A-52-13814.
An As-To-Qa-based information recording material disclosed in Publication No. 5 has been proposed. In the case of a method of recording, erasing, and rewriting information through such a phase transition, the optical system is simplified because the recording and erasing are performed by making a phase transition between crystalline and amorphous depending on the amount of laser light and the irradiation time. It has the advantage of Further, this recording method using phase transition has the advantage that the amount of reproduced signals is much larger than the amount of reproduced signals using the above-mentioned magneto-optical material, and recording with a high contrast ratio can be performed.

In this way, information is recorded and erased through phase transition.

In information recording media that are rewritten, the phase transition from a crystalline state to an amorphous state, for example, requires rapid cooling for recording, so the heat capacity of the recording layer is required to be as small as possible. For example, when erasing due to the transition to a crystalline state, it is necessary to heat this recording layer to a temperature higher than its melting point. Therefore, the thermal efficiency is increased as much as possible to reduce the power of the irradiated light or to reduce the power of the irradiated light and information. In order to increase the relative running speed with the recording medium, such as the rotational speed of the disk, the recording layer is required to be formed as thin as possible. However, when trying to realize this with a single layer film in an information recording medium that records information using this phase transition,
The minimum film thickness that allows a change in optical constants before and after recording, that is, a large degree of modulation, is determined to be about 100 OX. Figure 1 shows
This shows the reflectance when a semiconductor laser source (wavelength 83011 m) is irradiated from the substrate side of an information recording medium obtained by depositing a recording layer such as SbyoS@3o on a glass substrate. In the same figure, the solid line curve represents the case where the recording layer is in the vapor deposition state, that is, the amorphous state, and the broken line curve represents the case where the recording layer is crystallized by heating and slow cooling, where the birefringence growth in the amorphous state = 4. 4-1.5 t, and in the crystalline state W = 4.9-2.8 t. As is clear from this, the minimum film thickness that can obtain the maximum reflectance difference before and after recording, that is, the maximum modulation degree, is about 1000X.

Purpose of the Invention The present invention provides an information recording medium based on the above-mentioned phase transition,
It is possible to make the thickness of the information recording layer sufficiently thin so that recording and erasing can be performed reliably with high sensitivity, low noise, and high speed rotation, and the degree of modulation after recording is increased. The purpose of this invention is to provide an information recording medium that enables the following.

SUMMARY OF THE INVENTION In the present invention, at least one layer and a second layer are formed on a substrate.
A layer is provided. The first layer is a phase change recording layer, that is, a recording material layer that can reversibly change between an amorphous state and a crystalline state, and the second layer is a constituent material of this first layer, that is, a recording layer. A stable high melting point material layer that has a melting point higher than the melting point of ) Configure.

Examples Example 1 As shown in FIG. 2, a first layer (
2), that is, as a recording layer, 5b2S03 is deposited to a thickness of 400X by vacuum evaporation using resistance heating, and on top of this, a second layer (3), that is, a high melting point layer, is formed by Mo f electron beam evaporation. It was deposited to a thickness of . These first and second layers (2) and (3) are formed by continuous evaporation by providing an evaporation source of Sb2Se3 by resistance heating and a evaporation source of Mo by electron beam bombardment in the same vacuum evaporation Pelzer. can do. The sample thus obtained was irradiated with a parallel beam of a semiconductor radar source (wavelength λ = s3o nm) from the substrate (1) side, and the sample was heated while monitoring the reflected light with a photodetector. I went. The measurement results of the relationship between heating temperature and reflectance in this case are shown in FIG. As is clear, in this case, the reflectance changes greatly due to heating around 180°C. This is 5 at this temperature
This is because the b2Ss3 recording layer (2) has transitioned from an amorphous state to a crystalline state, and almost no change in reflectance is observed even if the heating temperature is increased further. still,
Here, the melting point of S b 2 S s s is 5850', and even if the temperature is raised to about this temperature, the M of the second layer
No reaction with o occurred.

Example 2 A substrate (1) such as a glass disk having a thickness of 1.2 mm was provided, and a first layer (5b2S03) was coated thereon in the same manner as in Example 1.
2) and a second layer (3) made of Mo were deposited by vacuum evaporation using resistance heating and vacuum evaporation using electron beam bombardment, respectively, to obtain a disk. Heat this in the oven and
The layer, that is, the three Sb2Se layers of the recording layer, is crystallized to the high reflectance state shown in FIG. Recordings were made by direct current. The portion recorded in this manner became amorphous and its reflectance was reduced to about half. When this disk was heated and annealed again in the open, the recording portion was crystallized again. When recording was performed again using a direct current laser source in the same manner, the film became amorphous like P1 as described above, and it was confirmed that these phenomena were reversible.

Comparative example 1 5b2Se on a glass substrate as in Example IK.

A layer is formed to a thickness of 400X by vacuum evaporation with resistance heating, and on top of this, Nl' is deposited by electron beam evaporation.
2500X was formed. When the reflectance of the thus obtained sample was monitored while being heated in the same manner as in Example 1, changes in reflectance with respect to heating temperature were obtained as shown in FIG. As is clear from comparing FIG. 4 with FIG. 3, the sample according to Comparative Example 1 exhibits a complicated change in reflectance. This seems to be due to not only a change in the crystal state of 5b2Se in the recording layer but also an alloying reaction (diffusion reaction) between Sb2Se3 and 1IJi. In this case, it was impossible to return from the high reflectance state to the original low reflectance state, that is, the amorphous state of 5b2so, and recording, erasing, and rewriting were impossible.

Example 3 A substrate (1) such as a 1.2-thick acrylic substrate with a guide groove was prepared, and a film was formed thereon to a thickness of 5lo2t 1ooo l by resistance heating vapor deposition. Furthermore, a first recording layer of 8b-8o alloy @350 Mo is deposited as a second layer (3) on top of the jo 500 by electron beam evaporation.
It was deposited to a thickness of X. These 5iOz -5b-8
The s-alloy layer and the Mo layer can be deposited continuously in the same deposition Pelger. A similar transparent acrylic substrate was laminated with an ultraviolet curing resin on the side opposite to the substrate (1), with the vapor-deposited surface facing inside, to obtain a disk. The 5IO2 layer of the disk thus obtained is for obtaining a heat insulating effect.

That is, this 5so2N is a base (1
), the first and second layers are prevented from being deformed by heating during vapor deposition, and the recording material layer of the first layer is also prevented from being corroded. Further, the acrylic substrate laminated on the vapor deposition surface is used to protect the recording layer and to prevent deformation and evaporation of the recording material. A semiconductor laser source with a beam diameter of approximately 1
Recording and erasing was performed on the recording layer (2) by focusing the light to about μm. First, the disk was rotated at 45 rpm, and the recording layer was changed from an amorphous state to a crystalline layer with a direct current of 15 mW of surface power from a semiconductor laser, resulting in a high reflectance state. At this time, when the initial reflectance is 1, in a high reflectance state, it is 1
．． It became about 5 to 2 times. Next disk k 1800r
The output power at the laser source panel is rotated at a speed of 2 MHz with a maximum of 18.5 mW and a reference signal f of 2 MHz.
/? The pulse was modulated and recorded. At this time, playback No. 18 C
/N was measured with a spectrum analyzer and found to be 47 d
It was B. After that, the rotation speed of the disk f 450 r
pm and the previously recorded track again with a board power of 15.
It was erased with a lede power of mW.

When the reproduced signal of the erased portion was measured using a spectrum analyzer, it was confirmed that most of the signal had been erased, although there was about 10 dB left unerased.

Recording and erasing on this disk was reversible, and recording, erasing, and rewriting on the same track was possible multiple times. As described above, according to the present invention, although the first layer, that is, the recording layer, is made into a thin film of less than 100 OX, there is no large reflectance change during recording and erasing, that is, between the amorphous state and the crystalline state. is obtained. This is due to the multiple interference effect between each layer due to the two-layer structure or the multi-layer structure formed by providing the second layer. That is, now a first layer consisting of K5b7oSeso on a transparent substrate,
That is, in a two-layer structure in which a recording layer is deposited by resistance heating vacuum evaporation, and a second layer of 500× thick Mo(D) is deposited thereon by electron beam evaporation, the thickness of the first layer is The reflection output when the thickness of the 5b7oSeso layer is changed is as shown in Figure 5. In the figure, the solid line curve shows the reflectance of the amorphous state, and the dashed line curve shows the reflectance of the crystalline state. The difference is that the thickness of the S b 7 OS e s o layer is 300
It can be seen that a large difference, that is, a sufficiently large modulation degree, can be obtained at a thinness of about X.

According to the present invention described above, a large degree of modulation can be obtained even though the thickness of the recording layer is set to sufficient /J1, but recording interpolation using a SbSe compound is used as the first layer. It has been confirmed that by selecting the Se composition ratio in the range of 10 to 70 atoms, preferably 20 to 35 atoms, the recording layer can be reversibly crystallized and made amorphous. Ta. Also, as the second layer,
In addition to the MO mentioned above, W, Ta + Nb, Zr +
By using at least one metal selected from Hf*Tl or an alloy thereof, the interface between the first layer and the second layer can be maintained without deformation during the recording and erasing process. Ta.

Effects of the Invention As described above, according to the present invention, the recording layer, for example, 5bSs
Compared to the case of a single layer structure of a compound recording layer, by adopting a multilayer structure of two or more layers with a second layer of high melting point layer, the film thickness of the recording layer can be reduced to about one layer of that of a single layer structure. A sufficient modulation degree can be obtained by making the recording layer thinner, and since the recording layer can be made thinner, the heat capacity of the recording layer can be reduced, and the transition process from the crystalline state to the amorphous state can be reduced. The rapid heating and cooling conditions are satisfactory, and the recording sensitivity can be increased, and the laser source power can be reduced even in the amorphous to crystalline state, and the disk can rotate at high speed. has advantages. Further, by providing the high melting point material layer as the second layer, deformation of the recording layer can be effectively prevented and the effect of a protective film on the recording layer can be obtained.

In addition, when the recording layer has a single layer structure, this recording layer needs to have a certain amount of absorption for the laser source used, but when it has a two or more layer structure, the recording layer Since there is no need for the recording layer to absorb the laser source used, it is possible to use a recording layer made of a material that is highly transparent to the laser source, which increases the flexibility in selecting the material for the recording layer. There is also the practical effect of increasing.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the thickness of the recording layer and the reflectance, FIG. 2 is a cross-sectional view of the information recording medium according to the present invention, and FIG.
4 and 4 are reflectance characteristic curve diagrams of examples and comparative examples of the present invention, and FIG. 5 is a characteristic curve diagram showing the relationship between the thickness of the recording layer and the reflectance of the information recording medium according to the present invention. Ru. (1) is a base, (2) and (3) are first and second layers. 5bto 5ajo') 41! (7)-5bto
SamO #) Jl14 (S) Figure 3 Figure 4: IIL Maro (℃] -

Claims (1)

[Claims] The film is formed on a substrate by at least a first layer and a second layer, the first layer being a recording material layer capable of reversibly changing between an amorphous state and a crystalline state. The second layer has a melting point higher than the melting point of the first layer by 9300° C. or more, and reacts with the first layer when the temperature of the first layer is raised to its melting temperature. An information recording medium consisting of a layer of high melting point material that does not melt.