JPS63140435A - Information recording medium - Google Patents

Abstract

PURPOSE:To easily obtain an optical disk which is stable in both physical and chemical characteristics and permits rewriting by sticking and forming a thin amorphous film consisting of a mixture composed of tellurium, tin, zinc sulfide, and copper on a substrate, thereby constituting said disk. CONSTITUTION:The thin film 2 of a recording material formed on the substrate 1 is constituted of the thin amorphous film consisting of the mixture composed of the tellurium, tin, zinc sulfide, and copper. More specifically, the powders of zinc sulfide (ZnS), tellurium (Te), tin (Sn), and copper (Cu) are put into respectively separate tungsten boats and are electrically heated in a vacuum atmosphere. The powders in said boats are co-deposited by evaporation on the pregrooved disk-shaped acrylic or glass substrate installed in the vacuum atmosphere by which the thin amorphous film 2 consisting of the recording material having nearly 100nm film thickness is formed. The information recording medium with which the amorphous state is maintained for a long period of time, and which has the stable characteristics, permits rewriting and is suppressed in the oxidation of the tellurium is thereby obtd.

Description

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

(Prior Art) In recent years, high-density recording and reproduction has been required in various technical fields, and high-density recording and reproduction has been carried out using various types of information recording media. Research on rewritable information recording media using recording materials that reversibly undergo a phase transition between an amorphous state and a crystalline state has also become active.

Conventionally, in order to construct a rewritable information recording medium, a recording material that undergoes a reversible phase transition between an amorphous state and a crystalline state has been announced. For example, Te0x-Ge-5n, 5
n-Te-8s, etc. These recording materials are formed into a thin film of a predetermined thickness on a plastic substrate or a glass substrate, and then subjected to rapid heating and cooling conditions or heat removal and slow cooling conditions. By alternately irradiating it with laser light under cold conditions, the optical properties of the thin film of the recording material were reversibly changed, allowing it to be used as a rewritable information recording medium.

(Problems to be Solved by the Invention) However, recording materials that have been previously announced as rewritable recording materials that utilize the reversible phase transition between an amorphous state and a crystalline state Due to the low crystallization temperature of conventional recording materials, a phase transition from an amorphous state to a crystalline state easily occurs, resulting in the loss of recorded information. Furthermore, since the tellurium used in the recording material is easily oxidized, the oxidation of tellurium causes deterioration of the recording characteristics over time, which has become a problem.

(Means for Solving the Problems) The present invention provides an information recording medium in which an amorphous thin film made of a mixture of tellurium, tin, zinc sulfide, and copper is adhered to a substrate, that is, an amorphous state and a crystalline state. This is a rewritable recording material that can reliably undergo a phase transition between the amorphous state and the amorphous state. To solve the above-mentioned conventional problems by providing a stable rewritable information recording medium with characteristics such that the state can be maintained for a long period of time, and in which oxidation of tellurium is suppressed. This is what I did.

(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.

In FIG. 1, 1 is a substrate, and 2 is a thin film formed on the substrate 1 using a recording material.The thin film 2 of this recording material contains tellurium, tin, zinc sulfide, and copper in the state at the time of film formation. It is made into an amorphous thin film consisting of a mixture of

The information signal recording medium of the present invention, that is, an amorphous thin film 2 made of a mixture of tellurium, tin, zinc sulfide, and copper is deposited on a substrate 1.
The information recording medium formed by adhering to the substrate is produced, for example, in the following manner.

Zinc sulfide (ZnS) powder, tellurium (Te) powder, tin (Sn) powder, and copper (Cu) powder.

Each in a separate tungsten boat, I
The powder in the four boats described above is co-deposited by electrical heating in a vacuum atmosphere with a vacuum degree of IO'Pa onto a disc-shaped acrylic substrate or glass substrate with a pre-group installed in the vacuum atmosphere. Then, an amorphous thin film 2 of a recording material having a film thickness of approximately 1100 nm is formed on the substrate 1 with the pre-groups.

The amorphous thin film 2 of the recording material deposited on the substrate 1 as described above is an amorphous thin film 2 made of a mixture of tellurium, tin, zinc sulfide, and copper, and FIG. D of the amorphous thin film of the recording material described above by a differential scanning calorimeter
It is an SC curve.

According to FIG. 2, the amorphous thin film 2 of the recording material described above, that is, the amorphous thin film made of a mixture of tellurium, tin, zinc sulfide, and copper, transitions from an amorphous state to a crystalline state at around 170°C. An exothermic peak is observed during this phase transition, but the temperature at which this phase transition occurs (crystallization temperature Tx) increases as the amount of one or both of zinc sulfide and copper increases.

The higher the crystallization temperature Tx mentioned above, the more difficult it is for phase transition from an amorphous state to a crystalline state to occur.
Deterioration of recorded information is reduced, making it possible to preserve information for a long period of time.

The above-mentioned zinc sulfide has a phase transition temperature (crystallization temperature T).
x), which not only stabilizes the amorphous state (the state immediately after film formation), but also significantly improves humidity resistance and oxidation resistance.

In the information recording medium of the present invention, in which an amorphous thin film 2 made of a mixture of tellurium, tin, zinc sulfide, and copper is deposited on a substrate 1, first, the amorphous thin film 2 of the recording material is coated with, for example, By applying optical energy using a flash lamp, initialization (or initial crystallization) that changes the phase from the amorphous state immediately after film formation to the crystalline state is performed, which changes the optical properties of the thin film 2. do.

Figure 3 shows the light reflectance of an amorphous thin film 2 made of a mixture of tellurium, tin, zinc sulfide, and copper, and the light emissivity of the thin film in the initial crystallized state as described above. FIG. Thin film 2 shown in this FIG.
According to the characteristic curve of light reflectance, it can be seen that the reflectance of light with a wavelength of 780 nm to 830 nm increases due to initial crystallization.

The information recording medium having the thin film 2 made of the recording material brought into a crystalline state by the initialization has an output of 5 to 9 mW when it is rotated at a predetermined rotation speed (for example, 1800 revolutions per minute). A laser beam whose intensity is modulated by an information signal from a semiconductor laser (
When the thin film 2 made of the recording material in the crystalline state is irradiated with a light spot with a wavelength of 780 nm, the portion of the thin film 2 of the recording material irradiated with the laser beam returns to the amorphous state due to a phase transition, and the information is transferred. Recording of the signal takes place.

Next, reduce the rotation speed of the information recording medium to about 1/4, and
When irradiated with a laser beam of ~15 mw, the information signal recording portion in the amorphous state undergoes a phase transition again to the crystalline state, and the information signal is erased. Recording and erasing operations are 1
It is possible to repeat this process 00 times or more.

The thin film 2 of the recording material described above, that is, the amorphous thin film 2 made of a mixture of tellurium, zinc sulfide, and copper, has its optical properties changed by applying optical energy to it. Not only does the electrical conductivity change significantly, but at the same time electrical conductivity etc. also change significantly. Therefore, when recording and reproducing information signals using the information recording medium of the present invention, it is necessary to use not only optical energy but also electrical conductivity during recording. ,Electrical,
It is also possible to record information signals using thermal energy, and optical techniques such as detecting changes in light transmittance (light reflectance) can be used to reproduce information signals from information recording media. In addition to using means for detecting changes in physical characteristics, it is also possible to reproduce information signals using other detection means, such as detecting changes in electrical resistance or changes in capacitance. .

To give an example of the composition of the thin film 2 described above in the information recording medium of the present invention in which the amorphous thin film 2 made of a mixture of tellurium, tin, zinc sulfide, and copper is deposited on the substrate 1, zinc sulfide is 12 atom%.

Tellurium is 55 at% to 60 at%, tin is 14 at% to 2
0! JK % and # are 10 atomic % to 20 atomic %.

(Effects of the Invention) As is clear from the above detailed explanation, the information recording medium of the present invention has an amorphous thin film made of a mixture of tellurium, &l, zinc sulfide, and copper deposited on a substrate. With this configuration, it is possible to easily provide a rewritable optical disc with stable physical and chemical properties.According to the information recording medium of the present invention, the above-mentioned All the problems of the prior art have been successfully solved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional side view of a part of the information recording medium of the present invention, FIG. 2 is a DSC curve of a thin film 2 of recording material, and FIG. 3I3! is the reflectance characteristic curve of the thin film for light. 1...Substrate, 2...Thin film of recording material.

Claims (1)

[Claims] An information recording medium in which an amorphous thin film made of a mixture of tellurium, tin, zinc sulfide, and copper is adhered to a substrate.