JPS62246158A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium which has high reproduction C/N, in inexpensive and is suitable for mass production by detecting a change of the electric resistance value of a recording layer, the electric resistance value of which is changed by the impression of light, heat or electric heat thereto as a change of the electrostatic capacity thereof, thereby executing reading out of an information signal. CONSTITUTION:Recording by a phase change is executed on the recording layer 3 when laser light focused by a condenser lens 5 is projected on the information recording medium formed with an amorphous thin film consisting of a mixture composed of antimony and zinc sulfide as the recording layer 3 on a substrate 1. The result that the electric resistance value of the recording layer 3a in the part cooled after heating decreases by about 4 digits is obtd. when the recording layer is cooled after heating. The reproduction signal exhibiting the good C/N when reproduced is obtd. when the information recording medium subjected to the recording is reproduced by a reproducing device of the type to detect the change of the electrostatic capacity.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an information recording medium.

(Prior Art) As the demand for recording various information signals at high recording densities has increased, various configurations have been developed in recent years.
x Principles and operations; (High-density recording and reproduction of information signals has become possible using information recording media made based on principles. A recorded optical disc (a playback-only optical disc) is copied from a master disk on which information signals are recorded.
It has been commercialized as video discs, compact discs, etc., and has already begun to become popular in ordinary households.In addition, electrically conductive It is well known that pre-recorded discs (information recording media that detect changes in capacitance for playback only), which are reproduced on discs with In addition, in order to meet the demands for high-density recording and reproduction in various technical fields, information can be transferred to the recording layer of an information recording medium by irradiating the recording layer of the information recording medium with a recording beam whose intensity is modulated by an information signal. Research has also begun on information recording media in which information signals are recorded by causing physical or chemical changes in response to the signal. rate.

It has two or more stable structural states with different absorption coefficients, electrical resistance, and other properties, and can be changed into the stable structural state 1 by applying external optical, atmospheric, or thermal energy. Regarding information recording media belonging to the phase change type, in which the recording layer is formed by applying a vapor deposition method or sputtering method to a material that causes a transition between
For example, an office file memory is used as an information recording medium that can be additionally recorded by a user only once (write-once type information recording medium) or an erasable information recording medium.

Active research and development is being carried out for practical use in other applications.

By the way, as mentioned above, read-only pre-recorded information recording media on which information numbers are recorded at a high density are becoming popular in general households, and information From an economic point of view, it is extremely desirable that a reproducing device used for reproducing signals can also be used for reproducing information signals recorded on the above-mentioned write-once information recording medium, for example. For this purpose, write-once information recording media and erasable information recording media that can reproduce information signals using a reproduction device for reproducing information signals from the various types of recorded information recording media exclusively for reproduction described above are available. Possible information recording media have started to attract attention.

Among the reproducing devices used for reproducing information signals from the recorded information recording medium for reproduction only,
A device in which the reproduction of an information signal from an information recording medium is performed by detecting a change in capacitance value;
When reproducing information signals from an information recording medium, a reproducing needle 7 with an electrode as shown in FIG. 2 is used, but the Wltis provided on the reproducing needle 7 has an extremely thin thickness. This has the advantage that information signals from the information recording medium 6 recorded at an extremely high recording density can be easily reproduced. A playback device for a recorded information recording medium (recorded information recording medium that detects changes in capacitance value for reproduction only) from an X disc on which information signals are recorded using bits that are reproduced on a conductive disk. That is, research has been carried out on write-once information recording media that can reproduce information signals using a capacitance change detection type reproduction device.

FIGS. 3 to 5 show conventional information recording media considered as configuration examples of write-once information recording media that can reproduce information signals using a capacitance change detection type reproduction device. In the information recording medium shown in FIG. 3, first, a recording layer 10 made of a conductive material is deposited on a substrate 9, and a protection layer 1111 made of an insulating material is formed on the above-mentioned WJ10. In the information recording medium shown in the third figure, the laser beam focused by the condensing lens 5 is projected onto the recording layer 10 made of the above-mentioned conductive material through the substrate 9. The portion of the recording layer 10 onto which the laser beam described above is projected; Jll
ill is dissolved and removed to form an array of bits 12 corresponding to the information signal on the recording layer of the information recording medium.

The conventional information recording medium shown in FIG.

It has a structure in which a conductive layer 11113 made of a conductive material is deposited on the substrate 9, and a recording layer 14 made of an insulating material is deposited on the aforementioned conductive fttllilla.
In the information recording medium shown in FIG.
By being projected on 3.

The portion of the recording layer 14 onto which the laser beam is projected is dissolved and removed, so that an array of bits 15 corresponding to the information signal is formed on the recording layer of the information recording medium.

Furthermore, the conventional information recording medium shown in FIG.
A conductive film 13 made of a conductive material is deposited on the substrate 9, a recording layer 14 made of an insulating material is deposited on the conductive film 13, and a protective film made of an insulating material is further deposited on the recording layer 14. In the information recording medium shown in FIG. By doing so, the portion of the recording layer 14 onto which the laser beam is projected is
and the protective film 11 are dissolved and removed, and an array of bits 16 corresponding to the information signal is formed on the recording layer of the information recording medium.

(Problems to be Solved by the Invention) In any of the information recording media shown in Figs. Information on the presence or absence of bits formed in the recording layer of a recording medium can be detected as a change in capacitance value, but as mentioned above, information obtained by focusing a laser beam and dissolving and removing the recording layer can be detected. When bits corresponding to signals are configured, bulges occur around the bits, causing problems such as dust on the reproduction needle when the information signal is reproduced using the reproduction needle.

(Means for Solving the Problems) The present invention provides an information recording medium using an m-film made of a phase-change material whose electrical resistance changes by applying optical, electrical, or thermal energy from the outside. Focusing on the fact that the above problems can be solved by using an amorphous thin film made of a mixture of antimony and zinc sulfide, or an amorphous thin film made of a mixture of antimony and tellurium oxide, The present invention provides an information recording medium configured as a recording layer on a substrate.

(Example) Hereinafter, specific contents of the information recording medium of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional side view of a part of the information recording medium of the present invention, and in this FIG. 1, 1 is a substrate, and this substrate 1
For example, a substrate 1 made of a suitable material transparent to the light used for recording and reproduction, such as an acrylic plate or a glass plate, is used.

Further, 2 is a transparent conductive film, and this transparent conductive film 2 is a well-known transparent conductive film! A film such as Nesa's U film or an ITO thin film can be used, and a nickel thin film may also be used. 3 is a recording layer, and this recording layer 3 is made of antimony (SB) and zinc sulfide. (ZnS) or a mixture of antimony (sb) and tellurium oxide (Ta02).

To deposit and form the recording layer 3 made of an amorphous thin film made of a mixture of antimony and zinc sulfide or the recording layer 3 made of an amorphous thin film made of a mixture of antimony and tellurium oxide on the substrate 1, the following steps are taken. By using a well-known film forming method such as a well-known vapor deposition method, a sputtering method, or an ion-blating method, an appropriate film thickness (eg.

A recording layer 3 having a thickness of several hundred angstroms to a thousand angstroms can be formed.

What is the mixing ratio of zinc sulfide and antimony when the recording layer 3 is formed of an amorphous thin film made of a mixture of antimony and zinc sulfide?

The weight ratio of (ZnS/5b) can be appropriately selected within the range of 0.2 to 0.8, and tellurium can be appropriately selected in the range of (ZnS/5b) = 0.2 to 0.8. The mixing ratio of the oxide and antimony can be appropriately selected within the range of (Te02/5b)=0.3 to 0.8 at a weight ratio of 1.

In the recording layer 3 of an information recording medium in which an amorphous thin film made of a mixture of antimony and zinc sulfide or an amorphous thin film made of a mixture of antimony and tellurium oxide is formed on the substrate 1 as the recording layer 3, When a laser beam with a wavelength of 7,800 angstroms is projected by a condenser lens 5 through the substrate 1 and the transparent conductive film 2, the radius of the disk is 6.
It was confirmed that recording was performed in the recording layer 3 by phase change using a laser beam with a power of about 3 milliwatts to 3.5 milliwatts in the vicinity of 01 Peng, but no film deformation occurred in the recording layer 3. Ta. Then, the portion of the recording layer 3 east irradiated by the laser beam is heated by the laser beam spot and then cooled, so that the electrical resistance value of the recording layer 3q in that portion becomes the same as that of the portion not irradiated by the laser beam spot. The result was that the electrical resistance value was lowered by about 4 times compared to the electrical resistance value of the recording layer 3.

Each information recording medium disk has an amorphous thin film made of a mixture of antimony and zinc sulfide or an amorphous thin film made of a mixture of antimony and tellurium oxide formed on the substrate 1 as the recording layer 3. Rotate for 900 minutes, then 4M
Laser light with a wavelength of 78oO angstroms, which is intermittent with a rectangular wave having a repetition frequency of Hz, is focused by a condenser lens 5 and passed through the substrate 1 and the transparent conductive film 2 to the recording layer 3.
After recording a signal on the recording layer 3 by projecting the signal onto the recording layer 3, the recorded information recording medium was played back by a playback device that detects changes in capacitance value, as shown in FIGS. 6 and 7. A reproduced signal showing a good C/N ratio was obtained.

That is, FIG. 6 shows a large number of sample disks in which an amorphous thin film with a thickness of approximately 1000 angstroms was formed as the recording layer 3 by a mixture of antimony and zinc sulfide with different mixing ratios of antimony and zinc sulfide. Prepare and run it at 900 speeds per minute for each individual sample disk.
The substrate 1 and the transparent conductive film 2 are rotated, and a laser beam having a wavelength of 7,800 angstroms, which is intermittent with a rectangular wave having a repetition frequency of 4 MHz, is focused by a condensing lens 5.
C of a reproduced signal when a signal is recorded on the recording layer 3 by projecting it onto the recording layer 3 through the /N, the horizontal axis shows the mixing ratio of zinc sulfide and antimony in weight ratio, and the vertical axis shows the regenerated C/N ratio.

Furthermore, FIG. 7 shows a large number of amorphous thin films each having a thickness of about 1000 angstroms formed as the recording layer 3 by a mixture of antimony and tellurium oxides with different mixing ratios of antimony and tellurium oxides. Sample disks were prepared, each sample disk was rotated at 900 revolutions per minute, and a laser beam having a wavelength of 7800 angstroms interrupted by a rectangular wave having a repetition frequency of 4 MHz was passed through a condenser lens 5. is focused and projected onto the recording layer 3 through the substrate 1 and the transparent conductor 1tWA2.
FIG. 2 is a diagram showing the C/N of a reproduced signal when each recorded sample disk is reproduced by a capacitance change detection type reproducing device after recording a signal on the disc. indicates the mixing ratio of tellurium oxide and antimony in weight ratio, and also.

The vertical axis shows the reproduction C/N ratio.

Looking at FIGS. 6 and 7, it can be seen that the information recording medium of the present invention provides a good reproduction C/N over a wide composition range of the constituent materials of the recording layer.

(Effect) As is clear from the detailed explanation above, light,
An information recording medium in which an information signal is read by detecting a change in electrical resistance in a recording layer as a change in capacitance in a recording layer whose electrical resistance changes due to the application of heat or a TL field. The information recording medium of the present invention has a recording layer on a substrate of an amorphous Nll formed from a mixture of antimony and zinc sulfide or an amorphous thin film formed from a mixture of an oxide of antimony and tellurium. It has a high reproduction C/N over a wide composition range of the constituent materials of the layer, and since there is no unevenness in the recording layer of a recorded recording medium, there is no dust on the reproduction needle. The information recording medium of the present invention has many advantages such as being inexpensive and suitable for large-scale production, and the various drawbacks of conventional information recording media can be satisfactorily solved.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional side view of a part of the information recording medium of the present invention, and FIG. FIG. 5 is a sectional view of a conventional example, and FIGS. 6 and 7 are diagrams showing reproduction C/N characteristics of the information recording medium of the present invention.

Claims (1)

[Claims] An information recording medium in which an information signal is read by detecting a change in electrical resistance in a recording layer as a change in capacitance in a recording layer whose electrical resistance changes when light, heat, or an electric field is applied. An information recording medium comprising an amorphous thin film made of a mixture of antimony and zinc sulfide or an amorphous thin film made of a mixture of antimony and tellurium oxide as a recording layer on a substrate.