JP3058443B2 - Optical information recording medium - Google Patents

Description

The present invention relates to an optical information recording medium, in particular, a phase change type information recording medium, which causes a phase change in a recording layer material by irradiating a light beam, The present invention relates to an optical information recording medium on which information can be recorded, reproduced, and rewritable, and is applied to an optical memory-related device.

[Prior art] As one of optical memory media capable of recording, reproducing and erasing information by irradiating electromagnetic waves, particularly laser beams,
A so-called phase change type recording medium utilizing a transition between a crystal-amorphous layer or a crystal-crystal phase is well known.
In particular, overwriting with a single beam, which is difficult with a magneto-optical memory, is possible, and the drive-side optical system is simpler. Typical examples of the material include Ge-Te, Ge-Te-Sn, Ge-Te-S, Ge-Te as disclosed in US Pat. No. 3,530,441.
-Se-S, Ge-Se-Sb, Ge-As-Se, In-Te, Se-Te,
So-called chalcogen-based alloy materials such as Se-As can be used. In addition, for the purpose of improving stability and high-speed crystallization, Ge-Te
Au (JP-A-61-219692), Sn and Au (JP-A-61-27962)
[0190] For the purpose of proposing a material to which Pd (Japanese Patent Application Laid-Open No. 62-19490) is added and improving the recording / erasing repetition performance, Ge-Te-Se
There has also been proposed a material (JP-A-62-73438) in which the composition ratio of -Sb is specified. 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 reduction in erasing ratio due to erasing 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.

Japanese Patent Application Laid-Open No. 63-251290 proposes an optical recording medium having a recording layer composed of a single phase of a multi-component compound having a crystalline state of substantially three or more. Here, a ternary or higher ternary compound single phase is defined as a compound having a ternary or higher stoichiometric composition (eg, In ₃ SbTe ₂ ) in a recording layer of 90 atomic% or more. By using such a recording layer,
It is stated that recording and erasing characteristics can be improved. However, it has disadvantages such as a low erasing ratio and a laser power required for recording and erasing has not yet been sufficiently reduced. Under these circumstances, development of a recording material having a high erasing ratio and suitable for high-sensitivity recording and erasing has been desired.

[Problems to be Solved by the Invention] An object of the present invention is to provide an optical information recording medium in which the following points are improved as compared with the above-mentioned conventional technology.

(1) Dramatic improvement of erasing ratio (2) High-speed recording, improvement of erasing characteristics [Means for solving the problem] The inventors of the present invention have intensively studied for improvement, and as a result, a recording material capable of solving the above-mentioned problem. Was found. That is, the present invention is characterized in that a recording layer provided on a substrate contains a substance represented by the following general formula as a main component.

Ag _α In _β Te _γ Sb _δ where 5 ≦ α ≦ 17 (at,%) 6 ≦ β ≦ 18 (at,%) 13 ≦ γ ≦ 36 (at,%) 33 ≦ δ ≦ 77 (at,%) α + β + γ + δ = 100 where α, β, γ, and δ represent the average composition of each element contained in the recording film. These values are amounts measured by, for example, Auger electron spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, Rutherford backscattering analysis and the like.

Hereinafter, the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a configuration example of the present invention. A heat-resistant protective layer (2), a recording layer (3), a heat-resistant protective layer (4), and a reflective layer (5) are provided on a substrate (1). The heat-resistant protective layer does not necessarily need to be provided on both sides of the recording layer, and the heat-resistant protective layer (2)
Only, or only the heat-resistant protective layer (4) may be used. When the substrate is made of a material having low heat resistance such as polycarbonate resin, it is desirable to provide a heat-resistant protective layer (2).

The recording layer of the present invention can be formed by various vapor phase epitaxy 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. In addition to the vapor phase growth method, a wet process such as a sol-gel method can be applied. 200 to 100 as the thickness of the recording layer
00 °, preferably 500-3000 °. If the thickness is less than 200 mm, the light absorbing ability is remarkably reduced, and does not serve as a recording layer. On the other hand, if the thickness is more than 10,000 °, uniform phase change at high speed is unlikely to occur.

The material of the substrate is usually glass, ceramics, 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,
Examples include an ABS resin and a urethane resin, and a polycarbonate resin and an acrylic resin are preferable in view of workability, optical characteristics, and the like. The shape of the substrate may be a disk shape, a card shape or a sheet shape.

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, ZnS, In ₂ S ₃ , T
aS sulfides such as _{4, SiC, TaC, B 4} C, WC, TiC, mixtures carbide or diamond-like carbon, or their like ZrC and the like. These materials can be used alone as a protective layer, or as a mixture of each other. Further, it may contain impurities as needed. However, the melting point of the heat-resistant protective layer needs to be higher than the melting point of the recording layer. Such a heat-resistant protective layer can be formed by various vapor phase epitaxy 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, it is 500 to 3000 °. If it is thinner than 200 mm, it will not function as a heat-resistant protective layer.
When the thickness is more than 5000 mm, the sensitivity is lowered and the interface peeling is liable to occur. Further, if necessary, the protective layer can be multi-layered.

As the reflective layer, a metal material such as Al or Au, or an alloy thereof can be used, but it is not always necessary. Such a reflective layer is formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method,
It can be formed by an ion plating method, an electron beam evaporation method, or the like.

As the electromagnetic waves used for recording, reproducing and erasing, several types such as laser beam, electron beam, X-ray, ultraviolet ray, visible ray, infrared ray, microwave, etc. can be adopted, but when mounted on a drive, it is small and compact. Semiconductor lasers are best.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples. However, these examples do not limit the present invention at all.

Example 1 A heat-resistant protective layer, a recording layer, a heat-resistant protective layer, and a reflective layer were sequentially laminated by a rf sputtering method on a polycarbonate substrate having a pitch of 1.6 μm, a depth of 700 mm, a thickness of 1.2 mm, and a diameter of 86 mmφ for evaluation. An optical disk was manufactured. Ag ₁₁ In ₁₁ Te ₂₃ Sb ₅₅ was used as the recording material provided on the substrate, and the film thickness was 1000
Å The composition ratio of the elements contained in the film was determined by Auger electron spectroscopy. The reflective layer is made of Al and has a thickness of 500
Å The heat-resistant protective layer is made of Si ₃ N ₄ and the film thickness is 2000 on the substrate side.
Å, 1000Å on the reflective layer side.

For evaluation of optical discs, use 830 nm semiconductor laser light with NA =
The measurement was performed by squeezing the light through a 0.5 lens to a spot diameter of 1 μmφ on the medium surface and irradiating from the substrate side.

Although the recording film after film formation was amorphous, at the time of measurement, the entire surface of the disk was first sufficiently crystallized with 9 mW DC light on the medium surface, and was brought into an initial (unrecorded) state. The linear velocity of the disk at this time was 7 m / sec and 9 m / sec.

The recording conditions were a frequency of 4 MHz at a linear velocity of 7 m / sec, and 5.11 MHz at a linear velocity of 9 m / sec. Under these conditions, the mark length is constant at 0.88 μm.

The recording laser power (Pw) was changed from 4 mW to 19 mW. The erasing laser power (Pe) was 9 mW, which is the same as the power required for initialization. The reading power (Pr) was 1 mW.

2 and 3 show the relationship between the recording laser power (Pw) and the C / N (carrier to noise ratio) value of the mark recorded on the disc after initialization and the erasing ratio after erasing by DC light. . In the figure, ● indicates the C / N value during recording, and the length of the arrow is DC
Shows the C / N value erased by optical erasure.

As can be seen from these figures, 100% C / N erasure has been achieved at both linear velocities. Even when the linear velocity is increased, the maximum recording power at which the C / N is optimal is not so much shifted to the higher power side. From this, Ag ₁₁ In ₁₁ Te ₂₃
Recording of the disc is relatively fast with sb ₅₅ recording layer, it is understood that it is also sufficiently correspond to the erase characteristics.

Example 2 A disk using Ag ₁₅ In ₁₆ Te ₃₂ Sb ₃₇ as a recording layer was produced. The disc layer configuration is the same as in the first embodiment. The recording film after film formation is also amorphous. Measurement is linear velocity 5.6m
/ sec, 7m / sec, 9m / sec. DC light power required for initialization is 8 mW at a linear velocity of 5.6 m / sec, and linear velocity is 7 m / sec
Was 9 mW, and 10 mW at a linear velocity of 9 m / sec. The recording condition was a frequency of 3.18 at a linear velocity of 5.6 m / sec.
MHz, the frequency was 4 MHz at a linear velocity of 7 m / sec, and 5.11 MHz at a linear velocity of 9 m / sec. Under these conditions, the mark length is constant at 0.88 μm.

The recording laser power (Pw) was changed from 4 mW to 19 mW. The erasing laser power (Pe) was the same as the power required for initialization. The reading power (Pr) was 1 mW.

FIGS. 4, 5, and 6 show the linear velocity of 5.6 m / se, respectively.
c, Relationship between C / N (Carrier-to-Noise Ratio) value of mark recorded on disk after initialization at 7m / sec and 9m / sec and erasing ratio after erasing by DC light, and recording laser power (Pw) Is shown.

As can be seen from these figures, a disk using Ag ₁₅ In ₁₆ Te ₃₂ Sb ₃₇ as a recording layer can also erase 100% of the recorded C / N. Also, linear velocity from 9m / sec to 7m / sec, 5.6m
It can be seen that as the speed is reduced to / sec, the area where 100% erasure is possible gradually expands. Therefore, Ag ₁₅ In ₁₆ Te
It can be said that the ₃₂ Sb ₃₇ recording layer is suitable for relatively low-speed recording and erasing.

Comparative Example As a comparative example, a disk using Ag ₂₄ In ₂₅ Te ₄₁ Sb ₁₀ as a recording layer was produced. Example 1
Is the same as The recording film after film formation is also amorphous.
The measurement was performed at a linear velocity of 5.6 m / sec and 7 m / sec. The DC light power required for initialization was 8 mW at both linear velocities. The recording condition was a frequency of 3.18 at a linear velocity of 5.6 m / sec.
MHz and a frequency of 4 MHz at a linear velocity of 7 m / sec. Under these conditions, the mark length is constant at 0.88 μm.

The recording laser power (Pw) was changed from 4 mW to 19 mW. The erasing laser power (Pe) was the same as the power required for initialization. The reading power (Pr) was 1 mW.

Figs. 7 and 8 show the linear velocities of 5.6m / sec and 7m / sec, respectively.
C / N of the mark recorded on the disc after initialization in
The relationship between the (carrier-to-noise ratio) value, the erasing ratio after erasing by DC light, and the recording laser power (Pw) is shown.

As can be seen from these figures, in the disk using the Ag ₂₄ In ₂₅ Te ₄₁ Sb ₁₀ recording layer, the C / N was hardly changed after erasing compared to before the erasing. N100
It can be said that% erasure is very difficult.

[Effects of the Invention] As described above, the optical information recording medium of the present invention is excellent in exhibiting the following effects.

(1) Dramatic improvement in erasure rate (100% erasure) (2) Improvement in high-speed recording and erasure characteristics

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an information recording medium according to the present invention, and FIGS. 2 to 8 are C / N (carrier-to-noise ratio) values of marks recorded on a disk after initialization. 6 is a graph showing a relationship between an erasing ratio after erasing by DC light and recording laser power (Pw).

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiyuki Kageyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-60-177446 (JP, A) JP-A Heihei 1-277338 (JP, A) JP-A-2-35636 (JP, A) JP-A-3-197173 (JP, A) JP-A-3-231889 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/26 G11B 7/24 511

Claims (1)

(57) [Claims] 1. An optical information recording medium characterized in that a recording layer provided on a substrate contains a substance represented by the following general formula as a main component. Ag _α In _β Te _γ Sb _δ where 5 ≦ α ≦ 17 (at,%) 6 ≦ β ≦ 18 (at,%) 13 ≦ γ ≦ 36 (at,%) 33 ≦ δ ≦ 77 (at,%) α + β + γ + δ = 100