JPH01113936A - Member for recording information - Google Patents

Abstract

PURPOSE:To shorten the time for crystallization and to obtain a high information transfer rate by providing a polycrystal film in contact with a recording film. CONSTITUTION:An underlying film 2 having grooves for tracking is formed on a glass substrate 1 and, for example, a ZnO film 3 is formed thereon. The ZnO film 3 has a high m.p., is nearly transparent and is small in crystal size and is, therefore, optimum as the polycrystal film. The optical recording film 4 is deposited by evaporation on the ZnO film 3 and finally a protective film 5 is provided thereon. The information is recorded by irradiation of high-power laser light, etc., on the crystallized recording film 4. The irradiated part is then made into the amorphous or poor crystalline part. The original crystalline state is restored if the information is erased by the irradiation of the low-power laser light, etc. If the polycrystal film 3 exists in contact with the recording film 4 at this time, the irradiated part is more easily crystallized by receiving the influence thereof. Since the time for the crystallization is thereby shortened, the higher information transfer rate is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information recording member that can be rewritten by irradiation with an energy beam such as a light beam or an electron beam.
In particular, the present invention relates to a recording member that utilizes a change in reflectance due to a phase change between crystals in an amorphous or poorly crystalline state.

[Conventional technology]

The conventional recording/reproducing method for phase-change optical disk media is as shown in Japanese Patent Laid-Open No. 59-71140. Recording is performed by converging a beam spot sufficiently and irradiating it for a short time, then rapidly heating and cooling it. This is done by making the film completely amorphous, and the recording is erased by returning the amorphous recorded portion to a completely crystalline state by slow heating using an elliptical spot that is long in the track direction. I was going. In this way, two different beam spots were used for recording and erasing. This is because the time required for erasing is longer than the time required for recording. In other words, the crystallization time of the recorded portion is long. However, recently, Applied Physics Letters No. 50
Volume 11, 191117, pages 667 to 669 (Appl, Phys, Lett, 50(11) 198
As shown in No. 7, PP667-669), a recording film capable of high-speed erasing and crystallization in approximately the same time as the laser irradiation time required for recording has been developed. By using this film, it became possible to rewrite information with a single beam spot during one revolution of the optical disk substrate by simply changing the laser power.

[Problem that the invention seeks to solve]

- Using the above conventional recording film, it is possible to override with a single laser or a single light spot, but it is also possible to increase the rotational speed of the disk to increase the linear velocity and achieve a high information transfer rate. For this purpose, it is necessary to further shorten the crystallization time.

An object of the present invention is to further shorten the crystallization time compared to the conventional method.

[Means for solving problems]

The above object is achieved by providing a polycrystalline film in contact with a recording film.

This polycrystalline film is a film such as ZnO or ZnS that does not evaporate, melt, or deform due to laser beam irradiation, and is not affected by expansion or contraction of the SS, that is, a film that has a high melting point and Use a membrane with high hardness. A preferable range of the crystal size of the polycrystalline film is 5 nm or more and 1100 nm or less, more preferably 5 nm or more and 50 nm or less. Further, the thickness of the polycrystalline film is preferably 10 nm to 1 μm, and more preferably 1100 nm to 400 nm.
It is more preferable that the polycrystalline film is transparent.

Further, it is desirable that the recording film used in the present invention has a shortest crystallization time during laser beam irradiation of 1 μs or less and a high crystallization temperature of 200° C. or higher.

If the film structure is the same as that of a polycrystalline film, the crystallization time can be further shortened.

[Effect]

If information is recorded on a crystallized recording film by irradiation with a high-power laser beam, etc., that portion becomes amorphous or has poor crystallinity.Next, if this recorded portion is erased by irradiation with a low-power laser beam, etc. Returns to the original crystalline state. If there is a polycrystalline film in contact with the recording film at this time, the recording film is likely to be influenced by the polycrystalline film and crystallize. That is, the time required for transition from an amorphous or poorly crystalline state to a crystalline state becomes shorter.

This polycrystalline film is effective because it shortens the crystallization time and also functions as a reflective layer or a protective layer.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a cross-sectional view of the structure of the optical disc in this embodiment.

First, a base film 2 having tracking grooves was formed using an ultraviolet curing resin on a glass substrate 1 having a diameter of 5 inches. Then, ZnO is deposited on top of this by ion beam sputtering.
Film 3 was formed to a thickness of 1100 nm. This ZnO film 3 has a high melting point of 1800° C., is nearly transparent, and has a small crystal size, so it is optimal as a polycrystalline film used in the present invention. 5n-T as an optical I#c film on this Zn0wAs.
An o-8s recording film 4 was deposited to a thickness of 1100 nm. Finally, an ultraviolet curing resin layer with a thickness of about 100 μm was provided as a protective film 5. In a disk medium with this structure,
A semiconductor laser beam sufficiently converged by a focusing lens 6 from the substrate 1 side was held on the tracking groove, and a recording portion with a diameter of about 1 μm was formed on the recording film 4 while automatic focusing was performed. Erasing was performed by heating this recorded portion with semiconductor laser light to a temperature slightly lower than the melting point. At this time.

Erasing time is reduced by 1 compared to conventional disks without ZnO film 3.
It was found that the time was reduced by more than an order of magnitude (~1 μs or less).

Furthermore, erasing time can also be shortened in a disk structure in which the optical recording film 4 and the ZnO film 3 are formed in the reverse order as shown in Fig. 2, or in a structure in which the optical recording film 4 is sandwiched between the ZnO films 3 as shown in Fig. 3. We were able to.

In this example, a transparent film such as the ZnO film 3 was used as the polycrystalline film, but the same effect could be obtained by using an opaque film such as Pd or PT. Furthermore, since these opaque films also have an effect as a reflective layer, they are also useful for improving recording sensitivity and shortening erasing time.

As for the size of the crystal grains used in these, it is preferable to have a smaller size because electrical noise will be smaller.

When the thickness is less than 5 nm, the effect of shortening the erasing time becomes weaker.

〔Effect of the invention〕

According to the present invention, from an amorphous (recording) state to a crystalline (erasing)
Since the time required to change the state, that is, the crystallization (erase) time can be shortened, there is an effect that the information transfer rate can be increased. Furthermore, this polycrystalline film also has the effect of serving as a reflective layer and a protective layer, so it is useful for improving reliability.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are longitudinal cross-sectional views of an optical disk according to an embodiment of the present invention. l...Glass substrate, 2... Base film, 3... Polycrystalline film, 4... Optical recording film, 5... Protective film, 6... Aperture lens.

Claims (1)

[Scope of Claims] 1. An information recording member capable of rewriting information by irradiation with an energy beam, characterized in that a polycrystalline film is provided in contact with the recording film. 2. The information recording member according to claim 1, wherein the polycrystalline film has a crystal grain size of 5 nm or more and 100 nm or less.