Optical information recording disc

Details Optical information recording disc Optical information recording disc

1999-10-26

2001-05-29

Evans, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064200, C428S064400, C428S064800, C428S457000, C428S913000, C430S270140, C430S945000, C369S283000, C369S288000

Reexamination Certificate

active

06238764

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical information recording disc, an apparatus for preparing an optical information recording disc, and a process for preparing an optical information recording disc. In particular, the invention relates to an optical information recording disc of DVD (Digital Video Disc) type.
BACKGROUND OF THE INVENTION
Recently, an optical information recording disc of DVD (Digital Video Disc) type has been paid an attention, because the information recording disc of DVD type can record a great amount of information in a limited space volume. The information recording discs of DVD type are classified into DVD-RCM (for read-out only), DVD-R (in which additional information is recordable), and DVD-RAM (in which a recorded information is rewritable).
The information recording disc of DVD type has a sandwich structure. In more detail, it comprises a pair of substrate discs having an information recorded layer from which the information is readable by applying thereto a laser beam or an information recordable layer in which Can information is recordable by applying thereto a laser beam or comprises a substrate disc having an information recorded layer from which the information is readable by applying thereto a laser beam or an information recordable layer in which an information is recordable by applying thereto a laser beam and a disc plate. The pair of substrates or the set of substrate and disc plate is combined using an adhesive layer under the condition that the information recorded layer or information recordable layer is placed between them.
Nikkei Electronics, No. 630 (1995, published Nihon Keizai Shimbunsha, namely, Japan Economic Journal), Specific Edition for “Optical Disc”, as well as Nikkei New Media, Specific Edition for “DVD” (1995, published Nihon Keizai Shimbunsha) illustrate a schematic structure of a representative optical information recording disc of DVD-R type, which is shown in
FIG. 1
of Drawings attached to this specification.
The representative information recording disc of DVD-R type of
FIG. 1
comprises a pair of substrate discs
1
a
,
1
b
having a pre-groove for tracking, information recordable layers
2
a
,
2
b
placed on the substrate discs
1
a
,
1
b
, respectively, laser beam reflective layers 3a, 3b placed on the information recordable layers
2
a
,
2
b
, respectively, protective layers
4
a
,
4
b
, placed on the reflective layers
3
a
,
3
b
, respectively, and an adhesive layer
5
combining the protective layer
4
a
and the protective layer
4
b
. This information recording disc is produced by combining a pair of substrate discs
1
a
,
1
b
which are provided thereon with the information recording layer
2
a
,
2
b
, the reflective layer
3
a
,
3
b
, and the protective layer
4
a
,
4
b
, using an adhesive material
5
.
The present inventor has studied the optical information recording disc of DVD-type and has noticed that the information recording disc of DVD-type sometimes shows poor mechanical strength as well as poor storage stability. A further study of the inventor has revealed that the poor mechanical strength and poor storage stability are caused by partial peeling of the edges of the substrates from the assembled recording disc structure. The peeling is sometimes observed between the substrate and the protective layer. The recording layer generally comprises a dye and, possibly, a small amount of a binder, and therefore, it has low cohesion strength. Moreover, the bonding strength between the reflective layer which is generally made of metal and the protective layer which is generally made of organic resin is low. Accordingly, the substrate disc easily separates from the protective layer at their outer peripheral ends when the information disc encounters physical shock or is stored for a long period under severe surrounding conditions. Particularly, if the substrate disc has a fin or flash at its outer or inner peripheral end, the separation occurs more easily when the information disc is brought into contact with other information disc or any other materials.
SUMMARY OF THE INVENTION
The present invention has an object to provide an optical information recording disc showing an improved mechanical strength and an improved storage stability.
The invention has a specific object to provide of an optical information recording disc of DVD-type having an improved mechanical strength and an improved storage stability.
In the first aspect, the present invention resides in an optical information recording disc comprising a pair of substrate discs which have a center hole and which are provided thereon with a recording layer, a reflective layer and a protective layer overlaid in order, the substrate discs being combined via an adhesive layer to place their protective layers between them, or comprising a substrate disc which has a center hole and which is provided thereon with a recording layer, a reflective layer and a protective layer overlaid in order and a disc plate, the substrate disc and the disc plate being combined via an adhesive layer to place the protective layer between them, wherein both the recording layer and reflective layer are retracted from the outer peripheral end of the substrate disc so that the substrate disc is exposed in the retracted area and the protective layer is kept in contact with the substrate disc in the exposed area.
In the above-mentioned information recording disc, it is preferred that both the recording layer and reflective layer are further retracted from the peripheral end of the center hole so that the substrate disc is exposed in thus retracted area and the protective layer is kept in contact with the substrate disc in thus exposed area. Further, it is preferred that the adhesive layer is also kept in contact with the substrate disc in the exposed area. The information recording layer preferably is a dye layer.
In the second aspect, the invention resides in an optical information recording disc comprising a pair of substrate discs which have a center hole and which are provided thereon with a recording layer, a reflective layer and a protective layer overlaid in order, the substrate discs being combined via an adhesive layer to place their protective layers between them, or comprising a substrate disc which has a center hole and which is provided thereon with a recording layer, a reflective layer and a protective layer overlaid in order and a disc plate, the substrate disc and the disc plate being combined via an adhesive layer to place the protective layer between them, wherein the substrate disc is processed at its outer peripheral end to form an enlarged surface area and the reflective layer is retracted from the outer peripheral end of the substrate.
In the above-mentioned information recording disc, wherein both the recording layer and reflective layer are preferably retracted from the outer peripheral end of the substrate disc so that the substrate disc is exposed in the retracted area and the protective layer is kept in contact with the substrate disc in the exposed area. It is further preferred that the substrate disc is further processed at its inner peripheral end to form an enlarged surface area, both the recording layer and reflective layer are further retracted from the inner peripheral end so that the substrate disc is exposed in thus retracted area, and the protective layer is kept in contact with the substrate disc in thus exposed area. It is further preferred that the adhesive layer is also kept in contact with the substrate disc in the exposed area. Thee processing for forming the enlarged surface area has been performed preferably by roughing or chamfering the outer peripheral end of the substrate disc. The recording layer preferably is a dye layer.
In the third aspect, the invention resides in an optical information recording disc comprising a pair of substrate discs which have a center hole and which are provided thereon with a recording layer and a reflective layer overlaid in order, the substrate discs being combined via a

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