Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1997-02-27
2001-04-24
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S945000, C369S275500, C369S275200, C428S064500, C428S064600
Reexamination Certificate
active
06221557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium, more particularly to a phase-change type optical information recording medium.
2. Discussion of Background
There is conventionally known a phase-change type optical information recording medium which utilizes phase changes between a crystalline phase and an amorphous phase or between one crystalline phase and another crystalline phase as one of the optical recording media which are capable of recording, reproducing and erasing information, for instance, by the application of a laser beam thereto. This kind of phase-change type optical information recording medium is capable of overwriting information by the application of a single laser beam thereto.
Such a phase-change type optical information recording medium is generally composed of a substrate made of polycarbonate, a first protective layer provided on the substrate, a recording layer provided on the first protective layer, a second protective layer provided on the recording layer, and a light reflection and heat dissipation layer.
Representative examples of recording materials for use in the above-mentioned recording layer are the so-called chalcogen-based alloys, such as Ge-Te, Ge-Se-Sb and Ge-Te-Sn as disclosed in U.S. Pat. No. 3,530,441, and Ge-Te-Se-Sb and Ge-Te-Sb, with the composition ratios of such elements being specifically selected for improvement of the recording/erasing repetition performance thereof as proposed in Japanese Laid-Open Patent Applications 62-73438 and 63-228433.
Furthermore, as the materials for the above-mentioned protective layers, there are conventionally known oxides such as SiO and A1
2
O, and nitrides such as BN, Si
3
N
4
and AlN.
However, protective layers composed of such an oxide or nitride are known to have the shortcoming that the protective layers are thermally damaged by the heat applied thereto during the cycles of heating with the application of a laser beam and cooling, resulting in the reduction of the reliability of the performance of the optical information recording medium comprising such a protective layer.
In order to eliminate the above-mentioned shortcoming, mixed materials, such as a material composed of ZnS and SiO
2
, are proposed as disclosed in Japanese Laid-Open Patent Application 63-259855 and Japanese Patent Publication 4-74785. It is reported that by using such a material in the protective layer, the above-mentioned recording/erasing repetition performance can be significantly improved for high line speed recording media, but the recording/erasing repetition performance cannot be sufficiently improved for low line speed recording media such as compact disks.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a phase-change type optical information recording medium with high heat resistance.
A second object of the present invention is to provide a phase-change type optical information recording medium which has excellent recording, reproduction and erasing repetition performance (hereinafter referred to as repetition use performance), and high recording sensitivity.
A third object of the present invention is to provide a phase-change type optical information recording medium which has excellent repetition use performance, in particular, from low line speed operation through high line-speed operation.
These objects of the present invention can be achieved by an optical information recording medium comprising (a) a substrate with guide grooves thereon, (b) a recording layer provided on the substrate, comprising a recording material of which phase is reversibly changeable from a stable state to a semistable state and vice versa, (c) a heat-resistant dielectric protective layer provided on the recording layer, comprising a protective material which comprises Zn, Si, S and O, and (d) a light reflection and heat dissipation layer which is provided on the heat-resistant dielectric protective layer.
The desired heat resistance can be obtained by use of the above-mentioned heat-resistant dielectric protective layer. When the substrate is not sufficiently heat resistant for use in practice, an additional heat-resistant dielectric protective layer which may be the same as the above-mentioned heat-resistant dielectric protective layer may be provided between the substrate and the recording layer.
In the above optical information recording medium, it is preferable that the protective material for the heat-resistant dielectric protective layer comprise ZnS, ZnO and SiO
2
.
Furthermore, in the above protective material, it is preferable that the composition ratio of ZnS, ZnO and SiO
2
be such that the composition ratio thereof be represented by formula (I) in order to obtain excellent repetition use performance, in particular, from low line speed operation through high line speed operation:
(ZnS)
&agr;
(ZnO)
&bgr;
(SiO
2
)
&ggr;
(I)
provided that 30≦&agr;≦90, 55≦&bgr;≦50, and 5≦&ggr;≦30, and &agr;+&bgr;+&ggr;=100 mole %.
Furthermore, for achieving the above-mentioned object, it is also preferable that the protective material have a thermal conductivity in a range of 1.2 W/m·k to 24.0 W/m·k.
For obtaining a phase-change type optical information recording medium having excellent repetition use performance and high recording sensitivity, it is preferable that the recording material for the recording layer comprise Ag, In, Sb and Te.
Furthermore, it is preferable that the recording material for the recording layer further comprise at least one element selected from the group consisting of N and Cl.
Furthermore, it is preferable that the recording material for the recording layer comprise Ag, S, one of Sb or As, and at least one element selected from the group consisting of Zn, Si, Ge and Sn.
For achieving the above-mentioned objects, it is also preferable that the recording material for the recording layer comprise Ag and St and one element selected from the group consisting of Sb and As and be present in the form of Ag
3
SbS
3
or Ag
3
AsS
3
in a crystalline state in the stable state, and in an amorphous state in the somistable state.
In the above, it is preferable that the recording material be in an amorphous state in the semistable state, and initialization and erasing be performed in the crystalline state.
In the above, it is also preferable that the recording layer comprise Ag
3
SbS
3
or Ag
3
AsS
3
in the stable state, with at least one element selected from the group consisting of Zn, Si, Ge and Sn being added thereto.
Furthermore, in the above, it is preferable that the recording layer comprise a compound of formula (II) or a compound of formula (III):
(Ag
3
SbS
3
)
x
M
100−x
(II)
wherein M represents an element selected from the group consisting of Zn, Go, Si and Sn, and 92≦X≦99, X indicating mole %; and
(Ag
3
AsS
2
)
x
M
100−x
(III)
wherein M represents an element selected from the group consisting of Zn, Ge, Si and Sn, and 92≦X≦99, X indicating mole %.
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Japanese Journal of Applied Physics, vol. 32, No. 5A, Part 1, pp. 1980-1982, May 1, 1993, Junki Tominaga, et al., “V and Ti Doping Effect on In-Ag-Te-Sb Optical
Harigaya Makoto
Iwasaki Hiroko
Kageyama Yoshiyuki
Shinotsuka Michiaki
Angebranndt Martin
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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