Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Plural heating steps including sintering
Reexamination Certificate
2000-01-19
2001-08-28
Jenkins, Daniel (Department: 1742)
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Plural heating steps including sintering
C419S033000, C419S046000
Reexamination Certificate
active
06280684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sputtering target for fabricating a recording layer of an optical recording medium; a method of producing the sputtering target; a phase-change type optical recording medium comprising a recording material in a recording layer thereof, which recording material is capable of causing changes in the phase thereof by the application of a laser beam thereto, thereby recording, reproducing and overwriting information therein; and a method of fabricating the above-mentioned phase-change type optical recording medium by using the above-mentioned sputtering target.
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 by the application thereto of electromagnetic waves, such as a laser beam. This kind of phase-change type optical information recording medium enables the overwriting of information by the application of a single laser beam thereto, although such overwriting is difficult to conduct by the application of a single laser beam in magneto-optical memory using a magneto-optical recording medium. An optical system of a drive unit for the phase-change type optical information recording medium can be designed simpler than that for a magneto-optical recording medium, so that recently research and development of this kind of recording medium has been actively conducted.
As disclosed in U.S. Pat. No. 3,530,441, the so-called chalcogen-based alloys, such as Ge-Te, Ge-Te-Se, Ge-Te-S, Ge-Se-S, Ge-Se-Sb, Ge-As-Se, In-Te, Se-Te and Se-As, are conventionally used as recording materials for the phase-change type optical recording medium. In addition, it is proposed to add an element of Au to the above-mentioned Ge-Te based alloy to improve the stability and to increase the rate of crystallization of the recording material as disclosed in Japanese Laid-Open Patent Application 61-219692. Furthermore, the addition of Sn and Au to the Ge-Te based alloy, and the addition of Pd to the same are respectively proposed in Japanese Laid-Open Patent Applications 61-270190 and 62-19490 for the same purposes as mentioned above. Furthermore, recording materials comprising a mixture of Ge, Te, Se and Sb, and a mixture of Ge, Te and Sb are respectively disclosed in Japanese Laid-Open Patent Application 62-73438 and 63-228433, each of which has a specific composition in terms of atomic percent of each constituent element of the recording material for the improvement of the recording and erasing repetition properties of the obtained recording medium.
However, non of the above-mentioned conventional phase-change type optical recording media satisfies all the requirements for the phase-change type rewritable optical recording medium. In particular, most important points to be improved in the conventional phase-change type optical recording media are to improve the recording sensitivity and erasing sensitivity, and to prevent the decrease of the erasability in the course of the overwriting operation, which is caused by the portions remaining unerased.
For the above-mentioned improvements, a mixed-phase type recording material comprising as constituent elements Ag, In, Sb and Te is proposed, as disclosed in Japanese Laid-Open Patent Applications 3-240590, 4-78031, 4-232779 and 5-345478. Such a mixed-phase type recording material can show the recording and erasing sensitivities to the light with a peak power of 12 mW or less, and excellent erasability, so that it is effective when used in a recording layer for mark edge recording. However, conventional optical recording media employing the Ag-In-Sb-Te based recording materials are still insufficient with respect to the shelf stability and the repetition reliability.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a sputtering target for fabricating a recording layer of an optical recording medium with excellent C/N ratio, high erasability and sensitivities, minimum jitter, and sufficient shelf stability and repetition reliability.
A second object of the present invention is to provide a method of producing the above-mentioned sputtering target.
A third object of the present invention is to provide an optical recording medium with excellent C/N ratio, high erasability and sensitivities, minimum jitter, and sufficient shelf stability and repetition reliability.
A fourth object of the present invention is to provide a method of producing the above-mentioned optical recording medium.
The first object of the present invention can be achieved by a sputtering target for fabricating a recording layer of an optical recording medium capable of recording and erasing information by utilizing changes in the phase of a recording material in the recording layer, the sputtering target comprising a compound or mixture comprising as constituent elements Ag, In, Te and Sb with the respective atomic percent (atom. %) of &agr;, &bgr;, &ggr; and &dgr; thereof being in the relationship of 2≦&agr;≦30, 3≦&bgr;≦30, 10≦&ggr;≦50, 15≦&dgr;≦83, and &agr;+&bgr;+&ggr;+&dgr;=100.
It is preferable that the compound or mixture for use in the above-mentioned sputtering target comprise Sb, and AgInTe
2
with a stoichiometric composition and/or a nearly stoichiometric composition having a chalcopyrite structure, and it is preferable that the AgInTe
2
form crystallites with a particle size of 450 Å or less.
The second object of the present invention can be achieved by a method of producing a target for sputtering, comprising the steps of mixing Ag, In and Te elements to prepare a mixture of Ag, In and Te elements, fusing the mixture of Ag, In and Te elements at 600° C. or more to prepare a fused mixture, rapidly cooling the fused mixture to prepare a solid lump, pulverizing the solid lump to prepare finely-divided particles, mixing the finely-divided particles with Sb to prepare a mixture of the finely-divided particles and Sb, and sintering the mixture of the finely-divided particles and Sb.
Alternatively, the second object of the present invention can also be achieved by a method of producing a target for sputtering, comprising the steps of mixing Ag, In, Te and Sb elements to prepare a mixture of Ag, In, Te and Sb elements, fusing the mixture of Ag, In, Te and Sb elements at 600° C. or more to prepare a fused mixture, and rapidly cooling the fused mixture to prepare a solid lump, pulverizing the solid lump to prepare finely-divided particles, and sintering the finely-divided particles.
In either case, it is preferable that the method of producing the sputtering target further comprise the step of carrying out the heat treatment at a temperature not higher than the melting point of the mixture prior to the sintering step.
The third object of the present invention can be achieved by an optical recording medium comprising a recording layer capable of recording and erasing information by utilizing changes in the phase of a recording material in the recording layer, the recording layer comprising as constituent elements Ag, In, Te and Sb with the respective atomic percent of &agr;, &bgr;, &ggr; and &dgr; thereof being in the relationship of 0<&agr;≦30, 0<&bgr;≦30, 10≦&ggr;≦50, 10≦&dgr;≦80, and &agr;+&bgr;+&ggr;+&dgr;=100.
The third object can also be achieved by an optical recording medium comprising a recording layer capable of recording and erasing information by utilizing changes in the phase of a recording material in the recording layer, the recording layer comprising as constituent elements Ag, In, Te, Sb, and nitrogen and/or oxygen atom with the respective atomic percent of &agr;, &bgr;, &ggr;, &dgr; and &egr; thereof being in the relationship of 0<&agr;≦30,
Deguchi Hiroshi
Harigaya Makoto
Hayashi Yoshitaka
Ide Yukio
Iwasaki Hiroko
Cooper & Dunham LLP
Jenkins Daniel
Ricoh & Company, Ltd.
LandOfFree
Sputtering target, method of producing the target, optical... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sputtering target, method of producing the target, optical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sputtering target, method of producing the target, optical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2434701