JP2875275B2 - Information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an information recording medium, in particular, a phase change type information recording medium, which irradiates a light beam to cause a phase change in a recording layer material, and The present invention relates to an information recording medium that can record, reproduce, and rewrite information, and is applied to optical memory related devices.

[Prior art] Recording of information by irradiation of electromagnetic waves, particularly laser beams,
As one of the rewritable and erasable optical memory media, a so-called phase change type recording medium utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase is well known. In particular, overwriting with a single beam, which is difficult with a magneto-optical memory, is possible, and the optical system on the drive side is simple.

Typical examples of the material include Ge-Te, Ge-Te-Sb, Ge-Te-S, Ge-Se as disclosed in US Pat. No. 3,530,441.
-S, Ge-Se-Sb, Ge-As-Se, In-Te, Se-Te, Se-
So-called chalcogen-based alloy materials such as As are mentioned. or,
Au (Japanese Patent Application Laid-open No. Sho 62-219692), Sn and Au (Japanese Patent Application Laid-Open No. Sho 61-270190), Pd
(JP-A-62-19490) and a material (JP-A-62-73438) in which the composition ratio of Ge-Te-Se-Sb is specified for the purpose of improving the recording / erasing repeatability. Suggestions have been made.

However, none of them can satisfy all of the properties required for a phase-change rewritable optical memory medium. In particular, improvement of recording sensitivity and erasing sensitivity, prevention of a decrease in erasing ratio due to unerased portion at the time of overwriting, and extension of life of a recorded portion and an unrecorded portion are the most important issues to be solved.

[Problems to be Solved by the Invention] The present invention is to solve the above-mentioned problems of the prior art and to solve the following problems.

1) Improvement of erasing speed (crystallization speed), 2) Prolongation of life of recording portion (amorphous portion), 3) Improvement of reliability (oxidation resistance, corrosion resistance), 4) Improvement of physical strength of recording film [Means for Solving the Problems] Generally, the erasing speed and the life of the recording portion of a phase-change type optical information recording medium are determined by the activation energy Ea at the time of transition of crystalline amorphous.
And the frequency factor ν.

Ea and ν have a relationship represented by the reaction rate constant k of crystallization and Arrhenius equation. That is, It is.

When the amorphous portion is used as a recorded portion and the quality portion is used as an unrecorded portion, increasing k at a temperature higher than the crystallization transition point Tc leads to an improvement in the erasing speed, and decreasing at room temperature decreases the life of the recorded portion. It leads to extension. Ea and ν for k are obtained as follows.

That is, ν at a high temperature and Ea and ν at a low temperature greatly contribute to k. Therefore, in order to achieve the purpose of improving the erasing speed and extending the life of the recording section, ν,
A recording material that has a large value for both Ea is required.

In the present invention, an excellent optical information recording medium that achieves the above object by mixing oxygen into a recording material has been obtained. That is, the configuration of the present invention includes, in a recording layer provided on a substrate,
An information recording medium characterized by containing a compound represented by the following general formula as a main component, general formula, (X _o Y _p Z _q ) _1-x O _x , wherein X is selected from Group Ib elements of the periodic table Y is also one selected from group Vb elements, Z is also one selected from group VIb elements, 0.15 ≦ o ≦ 0.35 0.15 ≦ p ≦ 0.35 0.40 ≦ q ≦ 0.60 o + p + q = 1 0.05 ≦ x ≦ 0.20.

If the amount o of X in each of the above components is less than 0.15, Ea and ν
And the life of the recording portion (amorphous portion) also decreases as the crystallization speed decreases.

If it exceeds 0.35, Ea becomes too large to prevent high-speed crystallization.

If the amount p of Y is less than 0.15, the crystallization rate is reduced, and if it exceeds 0.35, the contrast at the time of recording is reduced. If the amount q of Z is less than 0.40, the contrast at the time of recording is reduced. Exceeding the range shortens the life of the recording portion (amorphous portion).

If the oxygen content is less than 5%, a remarkable effect is not recognized, while if it exceeds 20%, the contrast (reflectance change) before and after the phase transition decreases. So the oxygen content is 5-20%
Good to be.

The substrate used in the present invention is usually glass, ceramic or resin, and a resin substrate is suitable in terms of moldability, cost, and the like. Representative examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin and the like. Polycarbonate resin in terms of workability, optical properties, etc.,
Acrylic resins are preferred. Further, the shape of the substrate may be a disk shape, a card shape or a sheet shape.

If necessary, auxiliary layers such as a heat-resistant protective layer, a surface protective layer, a reflective layer, and an adhesive layer may be provided.

Representative examples of the recording layer material used in the present _{invention, (Ag o Sb p Te q} ) 1-x O x, (Ag o Bi p Te q) 1-x O x, (Ag o Sb p Se q) _{1-x O x, (Cu} o Sb p Te q) 1-x O x, (Ag o Sb p S q) 1-x O x, (Ag o Bi p Se q) 1-x O x, (Ag _{o Bi p S q) 1-} x O x, (Cu o Sb p Se q) 1-x O x, (Cu o Sb p S q) 1-x O x, (Cu o Bi p Se q) 1- _{x O x, (Cu o Bi} p S q) 1-x O x, (Ag o As p Te q) 1-x O x, (Ag o As p Se q) 1-x O x, (Ag o As _p S _q ) _1-x O _x , and the like.

Materials for the heat-resistant protective layer include SiO, SiO ₂ , ZnO, and Sn.
Metal oxides such as O ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO ₂ , S
i ₃ N ₄ , nitride such as AlN, TiN, BN, ZrN, SiC, TaC, B
₄ C, WC, TiC, a mixture of carbide and diamond-like carbon, or their like ZrC and the like. Further, it may contain impurities as needed. Such a heat-resistant protective layer can be formed by various vapor deposition methods, for example, a vacuum evaporation method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam evaporation method and the like.

The thickness of the heat-resistant protective layer is 200 to 5000 mm, preferably 5
It is good to be 00-3000Å. When the thickness is less than 200 mm, the layer does not function as a heat-resistant protective layer. On the other hand, when the thickness is more than 5000 mm, the sensitivity is lowered and the interface is apt to be peeled off. In addition, the protective layer can be multi-layered as necessary.

Various vapor-phase film formation methods such as a vacuum evaporation method, an electron beam evaporation method, a sputtering method, a CVD method, and an ion plating method can be used as a film formation method of the recording layer.

Further, not only the above-described single layer of the phase change material, but also a multi-layered or ultra-fine phase change material may be dispersed in a heat resistant matrix.

As a method for producing the latter recording film, a wet process such as a sol-gel method can be applied in addition to the vapor phase film forming method.

The thickness of the recording layer is 200 to 10,000 Å, preferably 50
0-3000Å, optimally 700-2000Å.

 Hereinafter, the present invention will be described specifically with reference to examples.

[Example] An AgSbTe ₂ ternary alloy target was prepared as a sputtering target, a recording layer was formed on a glass substrate under the conditions shown in (Table 1) below, and the composition in the film was analyzed by Auger electron spectroscopy. Crystallization temperature by differential scanning calorimeter (DSC) (T
c), crystallization activation energy (Ea) and frequency factor (ν) were evaluated.

Further, the difference (ΔR%) in reflectance at a wavelength of 800 nm before and after the heat treatment (200 ° C., 10 minutes) was measured by a spectrophotometer.
The results are shown below (Table 2).

After the five samples A to E were allowed to stand for 500 hours in an environment of 60 ° C. and 90% RH, the reflectance changes of all the samples B to E except for A were 3% or less. Sample E has a small change in reflectance (contrast) before and after the heat treatment.

In addition, the sample to which oxygen was added was less susceptible to damage than the sample A, and the physical strength of the film was clearly improved.

[Effects of the Invention] As described above, the following improvements can be made by the optical information recording medium of the present invention.

1) Improvement of the erasing speed with an increase in the frequency factor, 2) Improvement of the life of the recording section with an increase of the activation energy, 3) Improvement of oxidation resistance and corrosion resistance, 4) Improvement of physical strength.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroko Iwasaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-61-2594 (JP, A) JP-A Sho 63-160882 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41M 5/26

Claims (1)

(57) [Claims] 1. An information recording medium comprising a compound represented by the following general formula as a main component in a recording layer provided on a substrate, a general formula: (X _o Y _p Z _q ) _{1 -x} O _x However, X is one selected from the periodic table group Ib element, Y is also, one selected from the group Vb element, one Z is which also selected from the VIb group element, 0.15 ≦ o ≦ 0.35 0.15 ≦ p ≦ 0.35 0.40 ≦ q ≦ 0.60 o + p + q = 1 0.05 ≦ x ≦ 0.20.