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
1999-01-22
2001-06-26
McPherson, John A. (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
C430S270120, C430S945000, C428S064400, C204S192260
Reexamination Certificate
active
06251561
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Application No.10-11485 filed Jan. 23, 1998, and No.10-163885 filed Jun. 11, 1998, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium for recording information on a recording film by irradiating a recording laser beam and to a manufacturing method thereof. The optical information recording medium includes an optical disk, an optical card and the like.
2. Description of the Related Art
A one-time write CD (compact disk) which is compatible with a normal CD in reproducing information is now commercialized as an optical information recording medium. It is formed by providing an organic pigment recording film, an Au reflecting film and an UV (ultraviolet) resin protecting film on a transparent plastic substrate. Signals are recorded thereon by selectively lowering reflectance of a recording section, which is caused by deformation of the substrate due to thermal decomposition of the organic pigment recording film caused when the recording laser beam is irradiated.
However, the conventional one-time write CD has a problem that because the organic pigment is applied on the transparent substrate by a spin-coater, the film-forming conditions vary depending on the ambient temperature and humidity of the spin-coater, thus lowering the production yield.
With respect to this problem, Japanese Patent Publication (JP-B-) No. Hei. 3-57540 discloses a recording medium in which an energy absorbing recording film is formed on a substrate by means of sputtering. A film in which a low melting point metal such as Te and In is combined with an element such as N and
0
is used as the energy absorbing recording film. When a laser beam is irradiated onto the recording film, gas generates from the inside of the recording film by spot heating. As a result, the raising deformation of the recording film is caused by the generated gas so that signals are recorded on the recording film.
Although the production yield improves since sputtering is used in manufacturing the optical information recording medium, no reflecting film nor protecting film can be coated on the recording film and no single-plate disk such as a CD can be formed because the raising deformation of the recording film is used to record signals. It is not also suited to signal recording according to a recording mark length modulating method because the length of a recording mark becomes inaccurate when the deformation of the film occurs.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems, it is an object of the present invention to provide an optical information recording medium which can be yielded well and on which signals can be recorded while causing almost no raising deformation therein.
In order to achieve the fore-going object, according to the present invention, a recording film is formed by means of vacuum film formation process. The recording film contains a substance which is thermally decomposed when a recording laser beam is irradiated thereto. When the thermal decomposition of the substance is caused by irradiation of the recording laser beam, a change in complex index of refraction is caused predominantly over the raising deformation in the recording film. As a result, information is recorded in the recording film.
The recording media can be yielded well since the recording film is formed by means of vacuum film formation process. As the vacuum film formation process, sputtering, evaporation and ion-plating methods can be used.
Because the recording film contains the substance which is thermally decomposed, when the recording laser beam is irradiated to the recording film, the thermal decomposition of the substance is caused. As a result, the substance generated by the thermal decomposition is precipitated within the recording film, and therefore the complex index of refraction of the recording film changes. At this time, the change in the complex index of refraction occurs predominantly over the raising deformation in the recording film. That is, information may be recorded in the recording film while causing almost no raising deformation thereof.
Compounds of metal and nitrogen such as Cu—N, Sn—N, Ag—N and Ni—N may be used as the thermally-decomposed substance. When such a compound is used, Cu, Sn, Ag or Ni produced due to the thermal decomposition of the compound is precipitated within the recording film when the recording laser beam is irradiated.
It is also preferable that the recording film contains a substance which disperses the substance produced by the thermal decomposition within the recording film. Such a substance may be an organic substance formed by using gas containing at least one of C, H, F, S, O, Cl, N, P, I and Br.
Further, when the recording film contains a substance for controlling light absorptivity, light reflected from the reflecting film may effectively pass through the recording film, and therefore the reflectance of the recording medium may be enhanced. In this case, the reflectance may be controlled readily by regulating an amount of the light absorptivity controlling substance to be mixed in.
When sputtering is used as the vacuum film formation process, the recording film may be formed by means of reactive sputtering which is carried out in a state that a raw material substance for forming the thermally-decomposed substance is used as a target, a raw material gas to be combined with the raw material substance to form the thermally-decomposed substance and a gas containing at least one of C, H, F, S, O, Cl, N, P, I and Br are introduced into a furnace.
Cu, Sn, Ag or Ni may be used as the raw material substance for forming the thermally-decomposed substance, and N
2
gas may be used as the raw material gas to be combined with the raw material substance to form the thermally-decomposed substance.
Further, the recording film can be formed while containing the substance for controlling the light absorptivity of the recording film, when reactive sputtering is carried out in a state that the raw material substance for forming the thermally-decomposed substance and the substance for controlling the light absorptivity are used as different targets.
Beside the single-layer single-sided disk in which the recording film, the reflecting film and the protecting film are formed on the substrate, the above-mentioned optical information recording medium may be a dual-layer single-sided disk in which recording films are provided on the both substrates and signals of the two films are read from one side or a dual-layer dual-sided disk in which substrates having two recording films are laminated and signals recorded in the films are read from both sides, in the dual-layered disks such as DVDs.
The specific nature of the invention, as well as other objects, uses and advantages thereof, will clearly appear from the following description and from the following drawings in which like numerals refer to like parts.
REFERENCES:
patent: 4647947 (1987-03-01), Takeoka et al.
patent: 4702991 (1987-10-01), Takeoka et al.
patent: 4883741 (1989-11-01), Takahashi et al.
patent: 4940618 (1990-07-01), Hamada et al.
patent: 5090009 (1992-02-01), Hamada et al.
patent: 58-009231 (1983-01-01), None
patent: 61-178745 (1986-08-01), None
English Language Abstract of JP 58-009231, Jan. 1983.
Kawai Shoichi
Kuno Hironari
Sano Naoki
Sugawara Ryoichi
Denso Corporation
McPherson John A.
Pillsbury & Winthrop LLP
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