JPH0352139A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To allow good recording by overwriting by successively providing a recording layer having specific crystallization time, coating layers which are provided on both sides of this recording layer and consist of AlN having a specific film thickness, and a reflecting layer consisting of a metallic thin film. CONSTITUTION:The lower coating layer 2 consisting of the AlN layer having a high thermal conductivity and the upper coating layer 4 are provided at <=500Angstrom thickness on both sides of the recording layer 3. A material having 100nsec time required for crystallization is used as the recording layer 3. The reflecting layer 5 is provided on the upper coating layer 4. The AlN having the high thermal conductivity is formed on both sides of the recording film in such a manner and the film thickness is confined to <=500Angstrom , by which the cooling of the recording film is effectively executed and the generation of cracks is prevented. As a result, the good recording by overwriting is executed and the rewriting of many times is possible.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention records m-information with high density and large capacity using a laser beam or the like. reproduction. and an erasable optical information recording medium.

Conventional Technology Optical information recording media are attracting attention as large-capacity, high-density memories, and the development of so-called rewritable media that allows information to be erased and re-recorded is currently underway. As one of these rewritable optical information recording media, Te-G
Using an e-Sb alloy thin film as a recording layer, the recording layer is heated by irradiation with laser light, melted, and rapidly cooled to deteriorate the quality and record information. Also, by heating and gradually cooling it, crystallization is performed. There are things that erase information by changing it.

Figure 3 is a cross-sectional view of this rewritable optical information recording medium. In this figure, a subbing layer 22 made of a dielectric, a recording layer 23, an overcoating layer 24 made of a dielectric, and a reflective layer 25 made of a thin metal film are formed on a disk-shaped substrate 2l having a center hole. A protective Fi 27 is provided on top with an adhesive 26 interposed therebetween. Here, the recording layer 23 is made of Te-Ge-Sb.
When an alloy thin film is used, the crystallization speed is extremely fast, so that deterioration and crystallization can be achieved simply by modulating the intensity of a single laser beam and irradiating the film. Therefore, this rewrite type optical information recording medium allows information to be rewritten using a single laser beam, which is generally called overwriting.

Problems to be Solved by the Invention When the recording layer 23 having such a high crystallization rate is used, it is necessary to cool the recording layer 23 extremely rapidly in order to properly reduce quality during recording.

Furthermore, the recording layer 23 heated by the laser is heated above its melting point, reaching a high temperature of 600''C or above.At this time, if cooling is insufficient, the heated area of the recording film 23 will The temperature will become higher, the high temperature area will expand, or the time the temperature will remain high will increase.)
However, when the heat load increases, the rewriting costs 100,000 to 1
When repeated a large number of times, such as 1,000,000 times, the recording layer 23
suffered thermal damage, making it impossible to keep good records. For this reason as well, sufficient cooling of the recording layer 23 is required. These measures include, for example,
It is possible to increase the cooling effect by increasing the thermal conductivity of No. 4. Here, the upper layer 22 is separated so that the recording layer 23 and the reflective layer 25 do not react, and a stable dielectric material with a high melting point is used as a material that does not itself react with the recording layer 23 or the reflective layer 25. It will be done. A dielectric material with high thermal conductivity is /IN, which is effective in cooling the recording layer 23.

However, since the AffN thin film has high internal stress, for example 1
When the film thickness reaches approximately 1,000 mm, cracks may occur in the AlN thin film after a certain film, thermal distortion due to rapid heating and cooling during rewriting, or changes in the surrounding environment due to differences in linear expansion coefficient between each layer. There was a problem in that the occurrence of cracks was also observed in the strain that was generated.

It is an object of the present invention to solve the above-mentioned problems and provide an optical information recording medium that can perform good recording by overwriting and can be rewritten many times. Means for Solving the Problems The technical means of the present invention for solving the above problems are as follows. In other words, the time required for crystallization is loO
A coating layer made of AlN and having a thickness of 500 nm or less is provided on both sides of the recording layer, which has a speed of 500 nm or less.

Effect of the present invention With the above-described configuration, AfN having high thermal conductivity is formed on both sides of the recording film, and the film thickness is set to 500 μm or less, so that the recording film can be effectively cooled and cracks can be prevented. It can be prevented. As a result, it becomes an optical information recording medium that can perform good recording by overwriting and can be rewritten many times. Example (Example!) An optical information recording medium according to an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of the present invention. In the figure, a lower coating layer 2 made of AlN with a thickness of about 400 mm is formed on a transparent substrate l on a disk having a central hole, a recording layer 3 made of a Te-Ge-Sb alloy with a thickness of about 200 mm, and a recording layer 3 made of a Te-Ge-Sb alloy with a thickness of about 200 mm. An upper coating layer 4 of about 400 mm thick made of the same material as above, a warped T layer 5 of about 400 thick made of Au, and a protective plate 7 is provided via an adhesive 6 made of ultraviolet curing resin.

By rotating this optical information recording medium, the linear velocity is 5.5~
3 MHz and 1 MHz signals were recorded alternately using a laser beam with a wavelength of 830 nm in the range of 1.1 m/sec,
After overwriting 1 million times, a good playback signal was obtained. This is because the dielectric layer in contact with the recording layer is made of a material with low thermal conductivity, and the signal begins to deteriorate after approximately 300,000 cycles, and the upper coating layer 4 made of A2N is thin. If the thickness exceeds 500, the internal stress within the film increases, making it unable to withstand the thermal cycle of heating and cooling during rewriting, and cracks begin to appear after approximately 100,000 repetitions. From the above, the configuration of this embodiment has increased the number of rewrites by about three times as compared to the conventional configuration. However, in this example, the layer in contact with the recording layer is made of AI! which has high thermal conductivity. ．． The recording film This allows for rapid cooling of the material, making it possible to achieve good amorphization. Furthermore, even after repeated rewriting many times, no cranking occurs.

(Example 2) Regarding an optical information recording medium according to another example of the present invention,
This will be explained with reference to the drawings. FIG. 2 is a sectional view showing another embodiment of the present invention. In the figure, a protective layer made of ZnS-Sin2 with a thickness of about 1500 mm is placed on a transparent resin substrate made of polycarbonate having a central hole.
2. Approximately 400-layer thick bottom coating made of AeN
13, a recording layer of about 200 mm thick made of Te-Ge-Sb alloy l4, an upper coating of about 400 mm thick made of AffiN Iil5, a reflective layer of about 400 mm thick made of Au
6, and a protective plate l8 made of polycarbonate is attached via an ultraviolet curing adhesive l7. Here, resin materials that are easy to mold are often used as substrates for optical information recording media. However, resin substrates are sensitive to heat. In the structure of this embodiment, if there is no protective layer 12, the temperature of the recording layer l4 will be 600°C or higher during recording, and this heat will be conducted to the lower coating layer l3, so the resin substrate
11 surface is about 300 degrees or more. As a result, the resin board l1 was deformed, and the signal began to deteriorate after being rewritten several tens of thousands of times. In order to prevent deformation of the resin substrate 1l, the heat resistance effect is improved by making the lower coating layer l3 thicker, but since the coating layer is made of AlN, the thicker the layer, the greater the internal stress and the tendency for cracks to occur. Deterioration occurs. On the other hand, in this embodiment, a protective layer 12 of about 1,500 layers thick made of Zn S S I O 2 with low internal stress is provided on the resin substrate 11, so this serves as a heat-resistant layer and prevents the resin substrate 11 from deforming. Since a layer made of ANN with high thermal conductivity is provided on both sides of the recording medium 4,
It has a sufficient cooling effect and enables good quality reduction. As a result, good reproduction signals were obtained even after 1 million rewrites even on a resin substrate with a low heat distortion temperature. In this example, the recording layer 14 is made of TeGe-Sb.
Although an alloy thin film is used, other recording layer materials may also be used as long as the crystallization time is 100 nsec or less. Further, the protective layer and the reflective layer are not particularly limited as long as they are made of materials generally used in optical information recording media. Effects of the Invention As described above, according to the present invention, it is possible to provide an optical information recording medium that can perform good recording by overwriting with a simple structure and can be rewritten over one million times.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an optical information recording medium in one embodiment of the present invention, FIG. 2 is a cross-sectional view of an optical information recording medium in another embodiment of the present invention, and FIG. 3 is a conventional optical information recording medium. FIG. 2 is a cross-sectional view of a recording medium. 1...Substrate, 2. l3... Lower coating layer, 3, 14... Recording layer, 4.15...
...Top coating layer, 5.16...Reflection layer, 6, l7...Adhesive, 7 18...
- Protective plate, 11...Resin board.

Claims (2)

[Claims] (1) Information is recorded on the substrate by a change in the crystal state, and the time required for crystallization is 100 ns or less, and a recording layer made of a material with a film thickness of 500 Å or less on both sides of this recording layer. An optical information recording medium in which a coating layer and a reflective layer made of a thin metal film are sequentially formed. (2) The optical information recording medium according to claim 1, wherein the substrate material is resin, and a protective layer made of a dielectric material is provided on the substrate.