Dynamic information storage or retrieval – Storage medium structure – Layered
Reexamination Certificate
2000-02-08
2001-12-25
Cao, Allen (Department: 2754)
Dynamic information storage or retrieval
Storage medium structure
Layered
Reexamination Certificate
active
06333914
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical recording medium and a method of manufacturing such an optical recording medium.
2. Description of the Related Art
There have been known optical recording mediums such as optical disks, cards, etc. for recording and/or information such as audio information, video information, etc. with the application of light. It has been proposed to increase the amount of information that can be recorded on an optical recording medium by employing an information recording surface thereof which is of a multilayer structure.
One such proposal is illustrated in
FIG. 1
of the accompanying drawings. As shown in
FIG. 1
, an optical disk has a pair of first and second recording members
1
,
2
which comprises respective transparent substrates
1
S,
2
S, respective information areas
1
M,
2
M disposed on respective surfaces of the transparent substrates
1
S,
2
S and carrying recorded information in the form of information pits, and respective reflecting surfaces
1
R,
2
R of evaporated aluminum, for example, disposed respectively on the information areas
1
M,
2
M. The first and second recording members
1
,
2
are bonded to each other by an adhesive
3
with the information areas
1
M,
2
M facing each other.
For reading or reproducing recorded information from the information areas
1
M,
2
M, reading light (hereinafter referred to as reproducing light)
1
L is applied to the information area
1
M through the transparent substrate
1
S, and reproducing light
2
L is applied to the information area
2
M through the transparent substrate
2
S. Therefore, a drive unit for use with the optical disk has a double optical pickup structure including two playback optical pickups positioned in confronting relationship to the opposite surfaces of the optical recording medium for applying reproducing light to the respective information areas
1
M,
2
M, or alternatively, a single optical pickup for applying reproducing light to the information areas
1
M,
2
M which have selectively been brought into facing relationship to the optical pickup by reversing the optical disk.
The drive unit of the double optical pickup structure is large in size, made up of a large number of parts, and heavy in weight. The drive unit with the single optical pickup needs a complex mechanism for automatically reversing the optical disk in order to successively reproduce recorded information from the information areas
1
M,
2
M. Therefore, the drive unit with the single optical pickup is also large in size, made up of a large number of parts, and heavy in weight.
To avoid the above difficulties, there has been proposed an optical recording medium capable of reproducing information recorded on two-layered information recording areas with light applied from one side of the optical recording medium. The optical recording medium and a method of manufacturing same will be described below with reference to
FIGS. 2A through 2D
of the accompanying drawings.
As shown in
FIG. 2A
, a first transparent substrate
21
S is injection-molded of polycarbonate (hereinafter referred to as “PC”) which has a first information area
21
M comprising information pits representative of recorded information. Then, as shown in
FIG. 2B
, a semitransparent optical layer
23
, for example, a sputtered layer of SiN, is formed on the first information area
21
M for controlling the transmittance and reflectance in the first information area
1
M at desired values. Thereafter, a second information area is formed of an ultraviolet-curing resin on the semitransparent optical layer
23
by a photopolymerization process, e.g., a so-called
2
P process. More specifically, as shown in
FIG. 2C
, a stamper
25
having a pattern of convex and concave shapes for forming a second information area is pressed against the semitransparent optical layer
23
through an ultraviolet-curing resin
24
, and then the ultraviolet-curing resin
24
is cured by an ultraviolet radiation applied from the side of the first transparent substrate
21
S. Thereafter, as shown in
FIG. 2D
, the stamper
25
is removed, leaving a second information area
22
M, transferred from the pattern of convex and concave shapes of the stamper
25
, on the ultraviolet-curing resin
24
. A reflecting film
26
of evaporated aluminum or the like is deposited on the second information area
22
M, and then covered with a protective layer
27
of a photosetting resin or the like. In this manner, the optical recording medium with the first and second information areas
21
M,
22
M is manufactured.
For reproducing information recorded on the optical recording medium with light, the light is applied to the optical recording medium from the side of the transparent substrate
21
S. More specifically, as shown in
FIG. 2D
, to reproduce recorded information from the first information area
21
M, reproducing light
21
L which is focused on the first information area
21
M is applied from the side of the transparent substrate
21
S, and light reflected by the first information area
21
M is detected to read the information. To reproduce recorded information from the second information area
22
M, reproducing light
22
L which is focused on the second information area
22
M is applied from the side of the transparent substrate
21
S, and light reflected by the second information area
22
M is detected to read the information.
Since the information recorded on the first and second information areas
21
M,
22
M can be reproduced with light applied from one side, a drive unit for use with the optical-recording medium may have a single optical pickup. As the optical recording medium does not need to be reversed, the drive unit may be small in size, light in weight, simple in structure, and easy to assemble. However, because the information area
22
M is formed by the
2
P process, the optical recording medium is required to be formed in layers, and cannot be mass-produced efficiently.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical recording medium which allows information to be reproduced from and/or recorded on a plurality of layered information areas with light applied from one side of the optical recording medium, permits a drive unit for the optical recording medium to have a single optical pickup without the need for reversal of the optical recording medium, and can be mass-produced highly efficiently.
According to the present invention, there is provided an optical recording medium comprising a first recording member having a first light-transmissive substrate and a first semi-light-transmissive information area disposed on a surface of the first light-transmissive substrate, a second recording member having a second substrate and a second reflective information area disposed on a surface of the second substrate, and a transparent layer, the first recording member and the second recording member being joined to each other with the transparent layer interposed therebetween with the first and second information areas facing each other.
According to the present invention, there is also provided a method of manufacturing an optical recording medium, comprising the steps of separately fabricating a first recording member having a first light-transmissive substrate and a first semi-light-transmissive information area disposed on a surface of the first light-transmissive substrate, and a second recording member having a second substrate and a second reflective information area disposed on a surface of the second substrate, and joining the first recording member and the second recording member to each other with a transparent layer interposed therebetween with the first and second information areas facing each other.
The terms “light-transmissive”, “semi-light-transmissive”, “reflective”, and “transparent” used herein are intended to signify the properties capable of transmitting, partly transmitting, reflecting, and passing light that is applied to optically repr
Kashiwagi Toshiyuki
Ohki Hiroshi
Cao Allen
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
LandOfFree
Optical recording medium and method of manufacturing same 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 method of manufacturing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical recording medium and method of manufacturing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2596646