Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2001-12-27
2004-05-11
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S321000, C430S945000, C369S275400, C216S024000
Reexamination Certificate
active
06733957
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a disk substrate having a pit and a groove with different depth formed separately in the inner and outer circumference of the disk substrate, and relates to a disk substrate manufactured by the manufacturing method and a disk manufactured by the disk substrate.
2. Description of the Related Art
There existed various types of optical disks such as a read only type, a recordable type and a rewritable type. An optical disk, which is provided with a read only area and a recordable area enabling to be recorded by a user in one substrate, has been proposed and practiced. In an optical disk having a pit area to be a read only area and a groove area to be a recordable area, generally, a pit depth is set to &lgr;/4n, which is the maximum amplitude of a sum signal of a reproduced signal, wherein “&lgr;” is a wavelength of a laser beam for recording and reproducing and “n” is a refractive index of a substrate of the optical disk. On the other hand, a groove depth is set to &lgr;/8n, which is the maximum amplitude of a differential signal of a tracking signal. In order to obtain such an optical disk substrate as being formed in one surface with a deep pit and a shallow groove, which are different in depth from each other, it is necessary for a pit and a groove to be varied in depth while forming a photoresist pattern as one process of manufacturing an optical disk master, which is a foundation of manufacturing the optical disk substrate.
Generally, in a process of forming such a photoresist pattern, there existed the method of changing each depth of pit and groove in one substrate such that using a laser beam in stronger intensity forms a pit and using a laser beam in weak intensity forms a groove. A depth of pit is determined by a film thickness of photoresist coated on a surface of substrate. However, a depth of groove depends on an intensity of laser beam and is apt to vary by a change of laser beam intensity or focus signal. A width of groove also depends on laser beam intensity, so that it is extremely hard to obtain an arbitrary width of groove. Further, a shape of groove obtained becomes approximately a V shaped one, so that a stable tracking signal can hardly be obtained. Furthermore, a recording power for recording a signal in a groove is necessary to be more powerful than that for recording in a conventional groove having a rectangular bottom, so that such a V shaped groove is a shape of unsuitable for recording in higher liner velocity.
In order to solve the problem mentioned above, there provided the prior arts such as a method of obtaining a pit and groove having a different depth from each other as mentioned above by using a photoresist pattern having a variety of depths as mentioned above and further by using the plasma etching and ashing processes.
SUMMARY OF THE INVENTION
Accordingly, in consideration of the above-mentioned problems of the related art, an object of the present invention is to provide a method for manufacturing a disk substrate for mass production of a phase change optical disk, wherein the disk substrate is provided with a pit having a first depth and a groove having a second depth allocated in an outer circumference area of the pit, the method including the steps of coating photoresist on a surface of a glass substrate (
1
) so as to form a resist layer (
2
) on the glass substrate (
1
), etching the surface of the resist layer (
2
) in atmosphere mixed with Argon and Oxygen in ratio of 10 to 90% under gas pressure of 0.1 to 1.5 Pa, wherein a pit (p
1
) having a first depth and a groove (g
1
) having a second depth are formed on the surface of the resist layer (
2
), forming a depression having a first and a second depth by cutting laser to be exposed on the surface of the resist layer (
2
), etching the depression having the first depth and the second depth from the surface of the resist layer of the disk substrate (
1
) in atmosphere mixed with Argon and Oxygen in voluminal ratio of 10 to 90% under gas pressure of 0.1 to 1.5 Pa, wherein the first and the second depth of the depression become predetermined value respectively, and ashing the resist layer (
2
) from the glass substrate (
1
).
Other object and further features of the present invention will be apparent from the following detailed description when lead-in conjunction with the accompanying drawings.
REFERENCES:
patent: 5204852 (1993-04-01), Nakagawa et al.
patent: 5246531 (1993-09-01), Junji et al.
patent: 5696758 (1997-12-01), Yanagimachi et al.
patent: 5923640 (1999-07-01), Takemura et al.
patent: 6221772 (2001-04-01), Yang et al.
patent: 6392350 (2002-05-01), Amano
patent: 6404713 (2002-06-01), Ueki
patent: 6510129 (2003-01-01), Hirokane et al.
patent: 6580678 (2003-06-01), Kondo et al.
patent: 0467716 (1992-01-01), None
patent: 04-286736 (1992-10-01), None
patent: 2000-82242 (2000-03-01), None
patent: 2000-260069 (2000-09-01), None
Machine translation of JP 2000-082242.*
J. Hirokane et al., “An Etched Glass Master and a Photomask for an Optical Disk Substrate”, International Progress In Precision Engineering, 1993, pp. 542-553.
Asanuma Toyohito
Shimomai Kenichi
Angebranndt Martin
Connolly Bove & Lodge & Hutz LLP
Victor Company of Japan
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