JPH061559B2 - Information recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical reflective or transmissive video disc, a digital disc, a disc for computer memory, etc., and is particularly suitable for writing arbitrary information on the disc. Information recording medium.

[Background of the Invention]

As an information recording medium in which information can be written and read by irradiation with laser light, information recording has optical characteristics,
For example, a method of recording the change in reflectance, transmittance, refractive index, etc. has been proposed. Among them, JP-A-57-159692
As described in JP-A-57-186243, a light absorbing layer having a good light absorbing property with respect to a laser beam and having an effect of converting light into heat, and a phase transition layer in which optical characteristics are changed by heating. An information recording medium having a recording film composed of a layer film has high sensitivity and enables high density recording. However, when the recording film has a two-layer film structure, no consideration was given to the fact that the substances constituting the two-layer film influence each other, heat resistance deteriorates, and the stability of the recording film deteriorates.

[Object of the Invention]

An object of the present invention is to provide an information recording medium having high recording sensitivity and good heat resistance and stability.

[Outline of Invention]

The present invention focuses on the fact that in an information recording medium having a two-layer structure of a phase transition layer and a light absorbing layer, the heat resistance of the medium deteriorates due to the mutual diffusion between the two layers, and the stability of the recording film deteriorates. A diffusion prevention layer is provided between the phase transition layer and the light absorption layer to prevent mutual diffusion of the two or to reduce the diffusion rate.

Example of Invention

 Examples of the present invention will be described below.

Example 1 The constitution of the recording film in the present invention is shown in FIG. As shown in FIG. 1, writing light, for example, a wavelength of 830 nm is formed on a light-transmissive glass substrate or a resin substrate 4 such as an acrylic resin.
The first layer (phase transition layer) consisting of a vapor-deposited film of antimony triselenide Sb ₂ Se ₃ whose optical absorptivity to semiconductor laser light is small and whose optical characteristics such as reflectance and transmittance are changed mainly by heat. ) 1 is deposited, and a third layer (diffusion prevention layer) 3 composed of an antimony Sb vapor-deposited film is deposited thereon, and further,
The second, which consists of a Bi vapor deposition film that has a high light absorption coefficient for writing light
An information recording medium was obtained by depositing the layer 2 (light absorbing layer). Where the thicknesses of the first and second layers are respectively
The thickness was 300 Å and 250 Å, and the thickness of the third layer as the diffusion preventing layer was set to 30 to 100 Å. When the temperature characteristic of the recording film transmittance at this time is measured, the curves 7 to 9 in FIG. 2 are obtained. FIG. 2 shows the transmittance of the recording film when the recording film is heated together with the substrate 4 while irradiating the semiconductor laser beam from the substrate 4 side, and a sharp decrease in the transmittance near 170 ° C. is caused by Sb ₂ Se ₃
This is due to the phase transition of the layers. As an information recording medium,
It is desirable that the transmittance be constant until the temperature of the recording film reaches the phase transition temperature, and the higher the temperature at which the transmittance starts to decrease, the higher the heat resistance. However, Sb ₂ Se ₃ phase transition layer and Bi
Recording film made of a double layer of the light absorbing layer, occurs mutual diffusion of Sb ₂ Se ₃ and Sb, transmittance begins to decrease from about 80 ° C. As shown by the dotted line 6 in FIG. 2, Sb ₂ Se _The transmittance continues to decrease greatly up to around 170 ° C when the phase transition of the _three layers is completed. Therefore, in such an information recording medium, it is necessary to keep the storage temperature at a low temperature of 40 ° C. or lower, heat resistance is insufficient, and in long-term storage, transmittance (or reflectance, The change in the refractive index becomes a problem. On the other hand, as in the present invention, when a diffusion preventing layer made of Sb is provided between the Sb ₂ Se ₃ layer and the Bi layer, the thickness of the Sb layer is 30, Å 60 Å and 10
Assuming 0Å, curves 7, 8 and 9 in FIG.
As shown in (4), the temperature characteristic of the recording film changes, and the temperature at which the transmittance remains constant is 120 ° C to 150 ° C. It can be seen that the thicker the Sb layer, the higher the heat resistance of the recording film.

FIG. 3 shows changes in reflectance of these recording films before and after recording.
The dotted line 10 in FIG. 3 shows the reflectance before recording with respect to the wavelength of the recording light, and the curves 11, 12, and 13 are Sb.
The reflectance after recording is shown when the thickness of the diffusion prevention layer is 30Å, 60Å and 100Å, respectively. It can be seen from FIG. 3 that the thinner the Sb diffusion preventing layer is, the larger the reflectance change ratio before and after recording can be made, and the better performance as an information recording medium can be obtained. However, as shown in FIG. 2, considering the heat resistance, the thickness of the Sb diffusion layer is 30 to 100.
Å is suitable, and in this case, the heat resistance of the information recording medium is 40 to 40 with almost no deterioration in recording sensitivity and C / N (carrier signal to noise ratio) as compared with the case where the Sb diffusion prevention layer is not used. It was possible to improve 70 ℃. As described above, according to this example, the three-layer structure recording film having the diffusion prevention layer has a great effect on improving the heat resistance and stability of the information recording medium without deteriorating the recording and reproducing performance. Have.

Example 2 A case will be described in which an aluminum Al diffusion prevention layer having a thickness of 10 to 50Å is used instead of the Sb diffusion prevention layer described in Example 1. In this case, the temperature characteristics of the recording film are as shown in FIG. 4, and the change in transmittance is small up to around 170 ° C. at which the Sb ₂ Se ₃ layer undergoes a phase transition, and extremely good heat resistance can be obtained.
However, since Al has a higher thermal conductivity than Sb, the recording sensitivity deteriorates rapidly when the thickness of the Al diffusion prevention layer increases. When the thickness of the Al layer is 10 to 50Å, the recording sensitivity is reduced by 10 to 40%, and it can be put to practical use.

Here, although Al was used as the diffusion prevention layer, in addition to this, Ti, Hf, Zr, Ni, Cr, Au, Sn, Zn, Cu, Mn, Si, Ge, Ta, Te or compounds containing these Al ₂ O ₃ , SiO ₂ , Si ₃ N ₄ or the like can be used, and in any case, the film thickness is suitably 10 to 100Å.

Further, as the phase transition layer, in addition to Sb ₂ Se ₃ , Se, Te, In, Sb and other compounds TeSe ₂ , Sb ₂ Te ₃ , InSe, In ₂ Te ₃ , In ₂ Se _3, etc.,
Even when tellurium Te or a compound thereof is used in addition to Bi as the light absorption layer, as described above, an interdiffusion preventive layer such as Sb, Al, Al ₂ O ₃ and SiO ₂ is provided as the intermediate layer. Thus, it can be easily understood that the heat resistance of the information recording medium can be increased and the optical characteristics thereof can be stabilized, and the effects of the present invention can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the heat resistance of the information recording medium can be improved and the stability thereof can be enhanced, so that the life of the optical disk and the extension of the application are greatly enhanced.

[Brief description of drawings]

FIG. 1 is a sectional view of an information recording medium according to the present invention, FIG. 2 is a characteristic diagram showing temperature dependence of transmittance of the information recording medium in the first embodiment, and FIG. 3 is recording according to the present invention. FIG. 4 is a characteristic diagram showing changes in reflectance before and after, and FIG. 4 is a characteristic diagram showing temperature dependence of transmittance in the second embodiment. 1 ... Phase change layer 2 ... Light absorption layer 3 ... Diffusion prevention layer 4 ... Substrate

Claims (2)

[Claims] 1. A first layer formed on a substrate, the first layer being made of a material whose optical characteristics change mainly by heating with respect to writing light.
And to prevent or reduce mutual diffusion of substances forming the first layer and the second layer in an information recording medium provided with a second layer made of a material having a light absorbing property for the writing light. An information recording medium, characterized in that the third layer is provided between the first layer and the second layer. 2. The first layer is a compound such as Se, Te, In, Sb,
The second layer is a material containing at least Bi or Te, and the third layer is at least Sb, Al, Ti, Hf, Zr, Ni, Cr, Au, Sn, Zn, C.
The information recording medium according to claim 1, which is a material containing u, Mn, Si, Ge, Ta, or Te.