JPS60164937A - information recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical reflection type or transmission type video mask, digital audio mask, etc., and is particularly suitable for writing arbitrary information on a disk. 1j Regarding Information Recording Media [Background of the Invention] An information recording medium capable of loading and reading information 17 by irradiation with a laser beam is used to record information with optical properties, such as reflectance. , a method of recording changes in transmittance, refractive index, etc. has been proposed. Among these, there are two types: the light absorption layer, which has good light absorption properties for laser light and has the effect of converting light into heat, and the phase change layer, whose optical properties change when heated.
Information recording media whose recording film is composed of layers have a high sensitivity.
High-density recording is possible. Such a recording film 2 may include, for example, selenium Se or S as a phase change layer.
Bismuth Bi, tellurium Te, or a compound thereof is used as the light absorption layer, and the thickness thereof is 50 to 1500 Å. When putting an information recording medium having this recording film into practical use, -
It is essential to protect the thin recording film as described above.

Conventionally, as shown in FIG. 1, a phase change layer 1 is formed on a transparent substrate 3 made of glass or acrylic resin, and a light absorption layer 2 and a layer 4 made of KSiOz, Al2O3, resin, etc. are formed thereon. The stability and reliability of the information recording film is improved by recording information by irradiating laser light from the substrate side.

However, by forming the protective layer 4, the recording sensitivity is reduced to less than half, and in order to omit information, more than twice the laser power is required as in the case without the protective layer 7. The output of a semiconductor laser, which is normally used as a laser light source, has a limit, and the recording sensitivity decreases, making it impossible to record information.1. As described above, the conventional technology has the disadvantage that it is not possible to form an effective protective layer without significantly reducing recording sensitivity.

[Purpose of the invention]

An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide an information recording medium with high recording sensitivity and good stability.

[Summary of the invention]

The present invention focuses on the fact that in conventional information recording films, heat from the light absorption layer is used only on the side in contact with the phase change layer, and the heat escaping from the opposite side in contact with the protective film is not effectively utilized. death,
By sequentially forming a first phase change layer, a light absorption layer, and a second phase change layer on a substrate, and forming a protective layer thereon, the heat utilization rate from the light absorption layer is doubled, and recording It is characterized by improved sensitivity.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 2 shows the structure of the recording film in the present invention.

A light-transmitting glass substrate or a resin substrate 3 made of acrylic resin or the like has a low light absorption rate for writing light, for example, semiconductor laser light with a wavelength of 830 nm, and its reflectance, transmittance, refractive index, etc. are mainly affected by heat. The optical properties of
A first phase change layer 1 having a change of 0% or more is provided, and a light absorption layer 2 is provided thereon, which has a high light absorption rate for the laser light and has the effect of converting the light into heat by absorption,
Furthermore, a second phase change layer 5 similar to the first is provided thereon,
The recording film has a three-layer structure.

This recording film is protected by a protective layer 4 made of 5i02, Al2O3, resin, or the like. The first and second phase change layers are made of a material whose optical properties change upon heating, such as Se or Sb2Se3.
A Be compound or Se alloy such as TeSe2, TnSe, or CdSe is used as the light absorption layer, and the layer is made of a material that melts or softens at a temperature (for example, 2000 C) that can change the optical properties of the first and second phase change layers. Bi, Te without causing undesirable physicalization or chemical changes
Alternatively, in order to write information on such an information recording medium using an alloy of these, a semiconductor laser (with an output of approximately 10 mW) is used from the transparent substrate 3 side.
A light beam (wavelength: 830 nm) is scanned in stages according to the recording pattern. At this time, most of the laser light passes through the first phase change layer and reaches the light absorption layer 2, but since the absorption rate here is small, the light is absorbed and converted into heat, and the laser light irradiation area The temperature of the light absorption layer rises to about 2006C, and the first and second phase change layers in contact with this portion are locally heated. The heated first and second phase-change coal layers change their optical properties, such as their reflectance, so that a difference in reflectance occurs between the parts irradiated with the laser beam and the parts not irradiated with the laser beam, making it impossible to record optical information. Ru. To read this, like writing, a semiconductor laser is used. In this case, the reading power is sufficiently lower than the power at the time of writing, for example, 1 mW, and reading with this low power prevents rewriting.

In the present invention, the thicknesses of the first and second phase change layers and absorption layer described above are at the same angle. That is, in order to efficiently read out changes in optical properties in the first and second mutualizing layers using the thin film interference effect, it is necessary to set the film thickness of each layer to a majority value. When Sb2Se3 is used for the phase change layer and Bj is used for the light absorption layer, the thickness of each 1- and the reflectance 10 before information writing and the reflectance 20 after writing are 3rd to 5th.
As shown in the figure. In Figure 3, the Bi layer is 20OA and the second Sb2
The Se3 layer is 40OA and the thickness is 30μ as a protective layer.
12 shows the change in reflectance with respect to the thickness of the first Sb2Se3 layer when m resin layers are provided. First Sb2S
The reflectance changes depending on the film thickness of the e3 layer is due to the interference effect of the film, and when the film thickness is around 500A, the reflectance before writing is 5% and increases to 30% after writing. Therefore, if this film thickness is selected, extremely good readout of recorded information becomes possible.

Further, FIG. 4 shows the change in reflectance with respect to the change in the thickness of the Bi layer when the thicknesses of the first and second Sb2Se3 layers were set to 500λ and 400A, respectively. Bi layer thickness is 40
When the temperature exceeds 0 A, light absorption is large, so the Bi layer does not have any interference effect as a film, and the reflectance does not depend on the film thickness (in the present invention).

It was chosen to also take advantage of the interference effect from the second Sb2Se3 layer. Furthermore, the thickness of the second Sb2. FIG. 5 shows the change in reflectance with respect to the change in the thickness of the Se3 layer. The thickness of the second Sb2Se3 layer is 1
When the value is 00 to 5ooX, the reflectance 20 after writing is more than twice the reflectance 10 before writing, and good information can be written and read. As described above, the first Sb2Se3 layers 400 to 700A, B are formed on the transparent substrate.
i-layer 100-400A1 and second Sb2Se3 layer 1
It can be seen that the information recording medium in which a three-layer recording film of 00 to 800 A is formed and protected by a resin layer can obtain a good change in reflectance and is suitable for engraving with laser light.

On the other hand, FIG. 6' shows the relationship between the reflectance ratio (after iiF writing/before writing) with respect to the laser power of the above three-layer recording film 40 and the conventional two-layer recording film 30.

Figure 6 shows the reflectance ratio with respect to the laser power when the above recording medium was made into a disk shape, rotated at 1800 rpm, and a signal of a constant level was written at a position with a radius of 130wn, and the thickness of each layer was First Sb2Se350
0A, Bi200A1 and second 5b2Se3
It is 400X. As shown in FIG. 6, 3 according to the present invention
It can be seen that the layered recording film can obtain a constant reflectance ratio with a smaller laser power than the conventional two-layered recording film, that is, has a high recording sensitivity.

As mentioned above, the three-layer recording film according to the present invention has high recording sensitivity during writing even with the formation of a protective film, and a large reflectance ratio can be obtained, so it can be used for optical video discs, digital audio discs, etc. Great effect on improving performance and reliability In the above embodiments, a reflective information recording medium was explained, but it is easy to understand that the structure of the present invention can also be used as is as a transmissive type. Good morning.

Moreover, as an effect of the present invention, in addition to the above-mentioned improvement in recording sensitivity, in a reflective type double-sided laminated disk as shown in FIG. 7, it has a great effect in reducing noise due to backside reflection. That is, when the conventional two-layer recording film shown in FIG. 1 is used, for example, Sb2Se3 as the phase change layer and Bi as the light absorption layer, the transmittance of the recording film is 10% even if the thickness of the Bi layer is about 4ooA. Moreover, since the surface reflectance of the Bi layer is high (50 to 60%), during the time when the information is read by irradiating the laser beam, ~ portion of the read light is reflected by the B of the reflective side disk.
When reflected back from the i-layer, it becomes noise and deteriorates the performance of the disk. However, in the three-layer recording film according to the present invention, the optical absorption layer is almost optically symmetrical, and as can be inferred from FIG. 3, the second Sb2Se3
It is easy to reduce the reflectance of the side to 10% or less. Therefore, it is possible to significantly reduce the return light from the opposite disk, which has a great effect on noise reduction.

In the above embodiment, the S protection layer and the disk adhesive layer were used as both, but it is clear that the present invention can be applied even if an independent protective layer and adhesive layer are used, if each is transparent.

〔Effect of the invention〕

According to the present invention, the sensitivity of an information recording medium on which a purulent membrane has been formed can be greatly improved, and therefore there is a great effect on improving the performance and reliability of the information recording medium.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a cross section of a conventional information recording medium;
The figure is a schematic diagram showing a cross section of an information recording medium according to the present invention, Figure 3 is a diagram showing the relationship between the film thickness and reflectance of the first S b 2 Se three layer, and Figure 4 is a diagram showing the film thickness of the Bi layer. Figure 5 is a diagram showing the relationship between the film thickness of the second Sb2Se3 layer and reflectance, Figure 6 is a diagram showing the relationship between laser power and reflectance ratio, and Figure 7 is a diagram showing the relationship between reflectance and reflectance ratio. FIG. 1 is a schematic diagram showing a cross section of a double-sided laminated disk according to the present invention. 1. First phase change layer 2... Light absorption layer 3... Transparent substrate 4... Protective layer 5 - Second phase change 1 composition 1 Figure 2 Figure 3 Figure 1 5 b 2 St Hiro layer Separate reference 1 (A) Figure 10 β/'January odor, 4 (A) Figure 5 Figure 2 L-zagwar (mvr)

Claims (1)

[Claims] An information recording medium If (": :l♂") is formed by forming an information recording film and its security film on a substrate, and the information recording film is separated from the first layer, the second layer, the third layer, the first layer and the third layer. The second layer is made of a material whose optical properties change when heated, and the second layer is made of a material that has optical absorption properties for blind light. recoding media.