Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-09-22
2004-01-13
Maki, Steven D. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S219000, C156S267000, C264S001330, C264S293000
Reexamination Certificate
active
06676791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mutilayered optical information-recording medium (hereafter, optical disk) that has two or more information-recording surfaces in the thickness direction of a light transmitting substrate and a process for the manufacture thereof.
2. Description of the Prior Art
Optical disks which record optically readable information and allow reading of the recorded information using a laser beam spot have heretofore been available. Optical disks including compact disks (CDs) and CD-ROMs have become widespread in use, particularly over the recent years.
CD-ROMs recently have come to be used not only in computers but also in multimedia game CD-ROMs and are increasingly replacing magnetic disks (floppy disks) and ROM cartridges both in computer and game applications. Furthermore, a high density CD version called the DVD (digital videodisk) is about to enter the field of movies and multimedia.
Recently proposals have been made of multilayered optical disks that enable the recording of massive quantities of information. In contrast to the conventional CD that has a single-layer information-recording surface in which information signals are recorded only on one surface thereof on a substrate, the mutilayered optical disks are structured to have a multiple number of information-recording surfaces in the thickness direction of the substrate.
Referring to
FIG. 1
, the aforementioned multilayered optical disk is now described below.
FIG. 1
is a drawing illustrating the structure of a conventional multilayered optical disk.
FIG. 1
shows a partial cross-sectional view of the optical disk in its tracking direction.
As illustrated in
FIG. 1
, the conventional multilayered optical disk
101
has a first reflecting layer
105
, a transparent layer
106
, a second reflecting layer
107
, and a protective layer
108
laminated together in this sequence onto a light transmitting substrate
104
.
Crenulated pits
104
A corresponding to information are generated on the substrate
104
, and pits
104
B corresponding to information are generated on the above transparent layer
106
. In other words, the optical disk
101
has two information-recording surfaces in the thickness direction of the substrate
104
, where the surface on which pits
104
A are formed on the light transmitting substrate
104
is the first information-recording surface
102
, and the surface on which pits
104
B are formed on the light transmitting substrate
106
is the second information-recording surface
103
.
The first reflecting layer
105
which is formed between the first information-recording surface
102
and the second information-recording surface
103
is made of a material with a certain degree of light transmittance to enable light to be incident on the second information-recording surface
103
or to be reflected.
If three or more information-recording surfaces are to be formed, a second transparent layer is formed on the second reflecting layer
107
on the above transparent layer
106
, followed by forming the pits on the second transparent layer, generating a third recording surface, and a similar procedure is used to form a fourth information-recording surface and beyond.
Incident playback laser beam for reading information recorded on each of the above information-recording surfaces (
102
,
103
) is directed though the underside of the above substrate
104
. The playback light beam pickup is equipped to accurately recognize the spacing between adjacent information-recording surfaces, which may be as narrow as several tens of microns (&mgr;m), and to be focused onto the desired information-recording surface, so as to read out the information present on each information-recording surface.
As described above, the multilayered optical disk which is structured to have two or more information-recording surfaces in the thickness direction of substrate
104
can record a greater amount of information than can a conventional single layer structured optical disk.
Referring to FIG.
2
(A-E), a conventional process for the manufacture of optical disk
101
having the above construction is described as follows.
First, as illustrated in FIG.
2
(A), a stamper (not illustrated) with a pattern negative to pits
104
A on the first information-recording surface is used to mold, for example, by injection molding, an optical disk substrate
104
having pits
104
A on its surface.
Then, as illustrated in FIG.
2
(B), a first reflecting layer
105
is formed on the surface of substrate
104
having pits
104
A formed thereon by a film-forming method such as sputtering, vacuum vapor depositing, spin coating or the like. It should be recalled that as mentioned above, the first reflecting layer
105
is a reflecting film that has a certain degree of light transmittance.
Then, a second information-recording surface is formed on top of the above first reflecting layer
105
. The second information-recording surface is formed by the process well-known in the art as “the 2P process.”
That is, as illustrated in FIG.
2
(
c
), a stamper
141
with crenulated
141
A pattern negative to pits
104
B of the second information-recording surface is used a UV-curable resin
142
is deposited as a droplet onto the first reflecting layer
105
of the above substrate
104
, and then the stamper
141
is pressed at its signal-bearing surface against the substrate
104
having the UV-curable resin
142
deposited thereon so as to spread the UV-curable resin
142
to a uniform thickness.
Incidentally a nozzle (not illustrated) is used to suction off any resin that has overflown from the outer peripheral of substrate
104
as the stamper
141
is pressed.
Then, when the above UV-curable resin
142
is cured by irradiating UV from the substrate
104
side, followed by peeling off the s§tamper
141
, an optical disk substrate is obtained on which is generated pits
104
B that provide a second information-recording surface
103
, as illustrated in FIG.
2
(D).
Lastly, a second reflecting layer
107
is formed as a film of aluminum, gold or the like, by sputtering or by vacuum film formation such as vacuum vapor deposition or the like, followed by forming a protective film
108
onto the second reflecting layer
107
and print a label (not illustrated) on the protective layer
108
, thereby completing the formation of a multilayered optical disk as illustrated in FIG.
2
(E).
It should be noted that the playback principle imposed on a multilayered optical disk as described above requires that the spacing between adjacent information-recording surfaces be under strict control. For example, a 40 &mgr;m thick film spacing between adjacent information-recording surfaces allows a variation in thickness of only about ±2 &mgr;m.
However, “the 2P process” mentioned above even with improved precision could achieve at best a level of ±5 &mgr;m. In addition, “the 2P process” is inferior in productivity relative to that of injection molding, requiring as long as 2 minutes per surface for molding a second and subsequent information-recording surfaces.
It may be possible to increase in practice the molding rate of “the 2P process”, but that would lead to problems such as reduced film thickness precision, trapping of air bubbles, unsatisfactory suction-removal of the resin overflow, and the like.
That is, manufacture of the above multilayered optical disk by a conventional manufacturing process would be plagued with problems in terms of both precision and productivity.
BRIEF SUMMARY OF THE INVENTION
1. Object of the Invention
This invention relates to a multilayered optical disk with two or more information-recording surfaces in the thickness direction of a light transmitting substrate, and aims to provide a multilayered optical disk effective in terms of both precision and productivity and a process for the manufacture thereof.
2. Brief Summary
The first aspect of this invention provides an optical information-recording medium that has at least two or more information-recording s
Kondo Tetsuya
Nishizawa Akira
Anderson Kill & Olick P.C.
Corcoran Gladys
JVC - Victor Company of Japan, Ltd.
Maki Steven D.
Meller Michael N.
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