Optical recording medium and manufacturing method thereof

Details Optical recording medium and manufacturing method thereof Optical recording medium and manufacturing method thereof

1999-02-04

2001-02-27

Evans, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064400, C428S064500, C428S064600, C428S913000, C430S270130, C430S495100, C430S945000, C369S283000, C369S288000

Reexamination Certificate

active

06194046

ABSTRACT:

RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10 028677 filed Feb. 10, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical recording medium and a manufacturing method thereof. More particularly, it relates to an optical recording medium a recording layer of which is heated by illumination of light, such as laser light, to raise its temperature to produce phase change therein to record or erase the information to optically read out information signals, and a manufacturing method thereof.
2. Description of the Related Art
In the field of data recording, investigations into the optical data recording system are proceeding briskly. This optical data recording system has a number of advantages, such as non-contact recording/reproduction, a recording density higher by one digit of magnitude than in the magnetic recording system, and adaptability to memory configurations such as read-only, write-once or overwrite memory configurations, and is finding a wide field of application ranging from the industrial usage to the domestic usage as a system enabling realization of an inexpensive large-capacity file.
The optical data recording system, adapted for the overwrite memory configuration, may be enumerated by a magneto-optical disc and a phase-change optical disc.
The phase change optical disc, associated with the overwrite memory configuration, has the following structure: That is, a transparent dielectric film of ZnS etc is formed on a major surface of a transparent substrate, and subsequently a phase-change recording film of ZnS etc and a reflective film, such as an aluminum film, are formed thereon.
The chalcogen-based alloy material may be enumerated by a Ge—The—, Ge—The—Sb—, In—Sb—The— or Ge—S—Te-based materials. These materials permit information recording/erasure by exploiting transition between the crystal-amorphous and crystal-crystal phases. Of these materials, those having a specified composition of the Ge—Sb—Te-based material, as disclosed in JP Patent Kokai JP-A-62-53886, 3-80635 and 63-225934 and in JP Patent Kokoku JP-B-8-32482, or those having a specified composition of the Ag—In—Sb—Te-based material, as disclosed in JP Patent Kokai JP-A-6-166268 and 4-232779, are well-known.
[0006]
When recording the information on the phase-change optical disc, the light, such as the laser light, is illuminated from the transparent substrate side on the phase-change recording film to raise its temperature in a spot fashion to change the state of a portion of the phase-change recording film to effect the recording. The above-mentioned material is amorphous on rapid heating or quenching, and is crystallized on gradual cooling, depending on the heating temperature. Thus, the information is recorded by forming an amorphous portion and a crystalline portion.
For reproducing the information from the phase-change optical disc, the laser light, for example, which will not produce changes in the phase-change recording film, is illuminated to the phase-change recording film, from the side of the transparent substrate, to detect the information depending on the difference between the return light from the crystalline portion and that from the amorphous portion.
Meanwhile, the above-mentioned phase-change optical disc cannot be said to be sufficient in signal properties or recording durability for high linear velocity and for high recording density, such that the properties of the phase-change optical disc need to be improved further.
Also, the phase-change optical disc is adapted to the overwrite memory configuration, so that the phase-change optical disc is to be improved further in recording/erasure characteristics and in repetition durability.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical recording medium having sufficient signal characteristics and recording durability in high linear velocity and in recording density, and also having sufficient repetition recording durability as well as sufficient recording/erasure and repetition characteristics particularly required as the overwrite memory.
It is another object of the present invention to provide a manufacturing method for this type of the optical recording medium.
In one aspect, the present invention provides an optical recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer and a reflective layer are layered on a substrate, and in which the recording layer is reversibly changed from a crystalline state to an amorphous state or vice versa to record or erase the information, wherein the recording layer is made up of two thin films having different crystallization start temperatures.
The crystallization start temperature is now explained with reference to
FIG. 5
showing the relation between the time and the temperature. In
FIG. 5
, the abscissa denotes time, the ordinate denotes the temperature and the reflectivity level, a broken line denotes the state of temperature changes and a solid line denotes the state of reflectivity level changes. The crystallization start temperature is the temperature T
1
corresponding to a point R
1
at which the reflectivity level is abruptly changed at the time of transition from the amorphous state to the crystalline state.
A specified example of the two thin films making up the recording layer is a phase-change recording film formed of, for example, chalcogen-based alloy materials. The chalcogen-based alloy materials maybe enumerated by Ge—Te—, Ge—Te—Sb—, In—Sb—Te— and Ge—Sn—Te-based materials. Most preferred is the Ag—In—Sb—Te-based material.
In the optical recording medium of the present invention, one of the two thin films making up the recording layer preferably contains nitrogen or oxygen.
In producing the optical recording medium according to the present invention, the recording layer made up of two thin films may be formed by sputtering under an atmosphere of argon containing not more than 15% of nitrogen or under an atmosphere containing not more than 15% of oxygen.
Also, in the optical recording medium of the present invention, it is more preferred for the substrate side thin film of the recording layer to contain nitrogen or oxygen. In producing this optical recording medium, it is also more preferred for the crystallization start temperature of the substrate side thin film of the recording layer to be higher by not less than 20° C. than that of the opposite side thin film.
Moreover, in the optical recording medium of the present invention, the two thin films of the recording layer are preferably of a thickness not less than 3 nm.
In the optical recording medium of the present invention, in which the recording layer, adapted for recording or erasing the information by reversibly changing the recording layer from the crystalline state to the amorphous state or vice versa, is made up of two thin films having different crystallization start temperatures, the recording/erasure characteristics can be assured by the thin film of higher crystallization start temperature, while the repetition durability can be assured by the thin film of lower crystallization start temperature. This reciprocal effect assures optimum repetition recording durability.


REFERENCES:
patent: 5948496 (1999-09-01), Kinoshita
patent: 0 201 860 A2 (1986-05-01), None
Patent Abstracts of Japan Application No. 62317034 dated Dec. 15, 1987.
Patent Abstracts of Japan Application No. 05236891 dated Sep. 22, 1993.
Patent Abstracts of Japan Application No. 60034754 dated Feb. 22, 1985.

Affiliated with

Also associated with

Rating

Optical recording medium and manufacturing method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical recording medium and manufacturing method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical recording medium and manufacturing method thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2599114