JPH0373384A - Optical information recording member - Google Patents

Abstract

PURPOSE:To prolong the life and improve the recording sensitivity of a recording component by a method wherein a compound composing a recording layer consists of Ib-IIIb-IVb2 or IIb-IVb-Vb2, and crystal variation thereof consists of a phase transition between a chalcopyrite structure and a zinc blende structure. CONSTITUTION:An optical information recording component has a recording layer composed of a compound of which a crystal structure is varied when irradiated by optical beams, and can record and erase information by variation of the crystal structure of this compound. The compounds in the recording layer are Ib-III-b-IVb2 or IIb-IVb-Vb2, and the crystal structure variation thereof is a phase transition between a chalcopyrite structure and a zincblende structure. Such a crystal structural transition improves recording sensitivity of a phase variation type recording material and can make it have long life. Further, 700 to 2000Angstrom should be preferable as a film thickness of the recording layer, and beams of a small compact semiconductor are optimum when attached to a drive as an electromagnetic wave to be used for recording, reproducing, and erazing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical information recording member, particularly an optical information recording member that utilizes a change in the crystal structure of a material constituting a recording layer.

[Prior Art] As an optical memory medium that can record, reproduce, and erase information by irradiation with electromagnetic waves, especially laser beams, it utilizes transitions between crystal and amorphous phases or between crystal and crystal phases.
So-called phase change recording media are well known. In particular, it is possible to override with a single beam, which is difficult to do with optical and magnetic memory, and the optical system on the drive side is also simpler, so research and development on this topic has been active recently.

As a typical material example, USP 3.530,44
Ge-Te5Ge-Te-5 as disclosed in 1
,Ge-5e-8SGe-5e-SbSGe-As-5
eS I n-Te.

Examples include chalcogen-based alloy materials such as 5e-Te and 5e-As. In addition, Au is added to the Ge-Te system for the purpose of improving stability, high-speed crystallization, etc.
, S n and Au (JP-A-61-270190) Pd (
Proposals for materials containing additives such as JP-A-62-19490),
Ge-Te-5 for the purpose of improving repeated recording/erasing performance.
Material with specified composition ratio of e-Sb (Japanese Patent Application Laid-open No. 62-734
38) has also been proposed.

However, none of them can satisfy all the characteristics required of a phase change type rewritable optical memory medium.

Conventional phase change recording media mainly utilize phase change between crystalline and amorphous states. To record such information, it is necessary to raise the temperature of the recording material close to its melting point and irradiate it with a laser that provides enough energy to break the bonds between the atoms that make up the crystal.

Therefore, it is necessary to increase the output of the laser or to lengthen the time for irradiating the recording material. Increasing the output of a laser requires a high output that can only be achieved by maximizing the output of currently used semiconductor lasers, so there is a need for something that can write and erase with low energy. On the other hand, the problem of increasing the irradiation time becomes a serious hindrance to the challenges of high recording density and high-speed access, which are considered to be major advantages of optical information recording materials. Furthermore, the amorphous phase formed in this manner is not in a thermally stable state and is therefore susceptible to changes over time.

As a result, the C/N may decrease after long-term storage.

In particular, the most important issues to be solved are improving recording sensitivity and erasing sensitivity, preventing a decrease in erasing ratio due to unerased areas during overwriting, and extending the lifespan of recorded and unrecorded areas.

The present inventor has discovered that a compound having a chalcopyrite structure is effective as a phase change type recording material that utilizes an amorphous-crystalline phase transition. is required.

[Problems to be Solved by the Invention] A further object of the present invention is to provide an optical information recording member that has an increased service life and improved recording sensitivity.

[Means for Solving the Problems] In order to solve the above problems, the present invention utilizes a crystal-crystal phase transition rather than a crystal-amorphous phase change.
This is based on the idea of taking advantage of the characteristics of the material, which is lower in temperature than its melting point, requires less energy for writing and erasing, and has high thermal stability because both the recorded and unrecorded areas are crystalline. It is.

Further research has revealed the chalcopyrite-type structure and sphalerite (Zln).
It has been found that the crystal structure transition between the cblene) type structures is an effective phase transition that can significantly improve the problems of improved recording sensitivity and longer life required for phase change recording materials.

That is, the structure of the present invention is an optical information recording member that has a recording layer made of a compound whose crystal structure changes when irradiated with a light beam, and in which information can be recorded and erased by the change in the crystal structure of the compound. The compound is Ib-111
b-VIb2 or b-IVb-Vb2, and the crystal structure change thereof is a phase transition between a chalcopyrite structure and a sphalerite structure.

Additional elements may be added to the recording material. Examples of the additive element include those selected from the Ib group, ■-b group, ■b group, nb group, IVb group, and Vb group other than transition metals and compound constituent elements.

The information recording medium of the present invention may be provided with auxiliary layers such as a heat-resistant protective layer, a surface protective layer, a reflective layer, and an adhesive layer, if necessary. The substrate used in the present invention is usually made of glass, ceramics, or resin, and resin substrates are preferable in terms of moldability, cost, and the like. Typical examples of resins include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin,
Examples include fluororesins, ABS resins, urethane resins, etc., but polycarbonate resins and acrylic resins are preferable in terms of processability, optical properties, etc. Further, the shape of the substrate may be a disk, a card, or a sheet.

The material for the heat-resistant protective layer is Sin.

5iOz, ZnO, SnO2, Al2O3, TiOz,
Metal oxides such as In2O3, Mg0SZr02, Si:
+N4, AIN, TtN.

Nitride such as BNSZrN, SiC, TaC.

B 4 CSW Cs T iCSZ r Carbide such as C, diamond-like carbon, or a mixture thereof (
Can be mentioned. Further, it may contain impurities as necessary. Such a heat-resistant protective layer can be formed by various film-forming methods, such as vacuum evaporation, snow-cover method, plasma CVD method,
It can be formed by a photo-CVD method, ion blating method, electron beam evaporation method, or the like.

The thickness of the heat-resistant protective layer is 200 to 5000X.

The preferred range is 500 to 3000 μm. 200λ
If it becomes thinner, it will no longer function as a heat-resistant protective layer, and if it becomes thicker than 5000λ, sensitivity will decrease or interfacial peeling will easily occur.

Moreover, the protective layer can be multi-layered if necessary.

The phase change material is not limited to a single layer, but may also be a multilayer film or a phase change material in the form of ultrafine particles dispersed in a heat-resistant matrix.

As a method for producing the latter type of recording film, a wet process such as a sol-gel method can also be applied in addition to the above-mentioned vapor phase film formation.

The thickness of the recording layer is 200 to 10,000, preferably 500 to 3000λ, most preferably 700 to 2000λ.

Various types of electromagnetic waves can be used for recording, reproducing, and erasing, such as laser light, electron beams, X-rays, ultraviolet rays, visible light, infrared rays, and microwaves. A laser beam is best.

[Example] The present invention will be specifically explained with reference to Examples.

However, these Examples do not limit the present invention in any way.

Example 1 AgInTe2 was used as a recording material. The phase diagram of this system is shown in Figure 1. The γ phase in the figure shows a chalcopyrite structure, and the 6 phases show a sphalerite structure.

Thin films were deposited on glass substrates by conventional RF sputtering methods in argon plasma.

The film thickness is approximately 2,000 mm. An amorphous phase was obtained during film formation.

Figure 2 shows differential scanning calorimetry (PSC) of the prepared thin film.
) is the result. The temperature increase rate is 15° C./win. 2
A transition from an amorphous phase to a crystalline phase is observed at 02°C. As a result of the phase diagram and X-ray diffraction, this crystal phase has a chalcopyrite-type structure.
I n Te, 2.

An endothermic peak is observed at 353°C. This is the transition point from a chalcopyrite-type structure to a sphalerite-type structure.

In the phase diagram, the transition point is approximately 530°C, but the observed transition point is about 180°C lower than this. This is considered to be because the thinning of Ag1nTe2 makes it easier to achieve a state of high entropy. or,
The melting point of this thin film is close to the melting point obtained from the phase diagram <630℃
It is.

From this, a crystal-crystal phase transition is possible at a temperature 280° C. lower than the transition point when utilizing an amorphous-crystal transition.

Example 2 Zn was used instead of AgInTe2 in Example 1 as a recording material.
A thin film was formed on a glass substrate under the same conditions as in Example 1 except that 5nAsz was used.

The recording material was in an amorphous phase.

This was analyzed and tested under the same conditions as in Example 1.

FIG. 3 shows the results of differential scanning calorimetry (DSC) of the produced thin film.

The transition from the amorphous phase to the crystalline phase is about 20 L'C, and this crystalline phase is Zn5nAs2 with a chalcopyrite structure.

The endothermic peak observed at about 412° C. is the transition point from the chalcopyrite structure to the zincblende structure. In the phase diagram, the transition point is approximately 630°C, but the observed transition point is about 220°C.
The temperature is getting lower.

This is considered to be because Zn5nAsz is a thin film. Further, the melting point of this thin film is approximately 770° C., which is close to the melting point obtained from the phase diagram.

This makes it possible to perform a crystal-crystal phase transition at a temperature 360° C. lower than the transition point when utilizing an amorphous-crystal transition.

[Effects of the Invention] As explained above, the optical information recording member of the present invention has the following improvements.

1) Since a phase transition at a temperature lower than the melting point can be utilized, writing and erasing can be performed with low power.

2) Since it utilizes crystal-crystal mass transition, it is a thermally stable and long-life optical information recording member.

[Brief explanation of drawings]

Figure 1 is a phase diagram of the material of Example 1, Figure 2 is a graph showing the results of differential scanning calorimetry of the above material, and Figure 3 is a graph showing the results of differential scanning calorimetry of the material of Example 2. be.

Claims (1)

[Claims] In an optical information recording member that has a recording layer made of a compound whose crystal structure changes when irradiated with a light beam and is capable of recording and erasing information by changing the crystal structure of the compound, the compound of the recording layer is Ib-IIIb- VIb_2 or IIb-I
Vb-Vb_2, and these crystal structure changes are phase transitions between a chalcopyrite structure and a sphalerite structure.