Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-04-20
2001-06-12
Tran, Thang V. (Department: 2752)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S275200, C369S275400, C369S283000, C369S288000, C428S064400, C428S064900
Reexamination Certificate
active
06246656
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical recording medium having a guide groove, a reflective film, an organic dye recording layer, and a light transmissive layer where information is read therefrom or recorded thereon by irradiation of light. More particularly, the present invention relates to an optical recording medium which can achieve a higher storage capacity by determining the relationship between the thickness of the light transmissive layer, the thickness unevenness of the light transmissive layer, and the skew margin (bend or warp). The present invention further relates to an optical disk apparatus for recording and/or reproducing the optical recording medium described herein.
BACKGROUND OF THE INVENTION
An optical recording medium capable of recording and/or reproducing NTSC signal data of up to four hours on one side thereof has been proposed for optical disks of the next generation. This proposed optical recording medium thereby allows a home-use video disk recorder to record and reproduce data for up to four hours, thereby functioning as a new recording medium which can be replaced with a cassette used in a current video cassette recorder (VCR).
Since the above optical recording medium has the same shape and size as a compact disc (CD), even a user accustomed to easy handling and operability of a CD will feel similar ease with use of this medium. Moreover, if the fast access feature of this optical recording medium is utilized, an optical disc apparatus is provided which not only serves as a small-sized and easily operable recorder but also has various functions such as video recording, playback, a trick play, edition, etc. that can be performed instantaneously.
It has been found that such an optical disc apparatus requires an optical recording medium having a storage capacity of at least 8 GB or more. However, optical recording mediums currently available do not have storage capacities of 8 GB or more.
A digital versatile disc (DVD) only has a storage capacity of 4.7 GB (ROM) when a wavelength &mgr; is 0.65 &mgr;m and a numerical aperture (N.A.) is 0.6.
If a higher storage capacity is desired without any change of signal format, such as an error correction code (ECC), a modulation system or the like, establishment of the following equation (1) is required for obtaining a storage capacity of 8 GB or more.
4.7×((0.65/0.60×(N.A./&lgr;))
2
≧8 (1)
According to the above equation (1), N.A./&lgr;≧1.20 must be established. As a result, it is necessary to set the wavelength &lgr; of the laser light utilized by the optical disc apparatus shorter or set the N.A. higher wherein N.A. represents the numerical aperture of an optical head device of the optical disc apparatus.
In order to satisfy the above condition, if the value of N.A. is set higher, it is necessary to decrease the thickness of the light transmissive layer of the optical recording medium through which irradiated reproduction light is transmitted. This reduced thickness is necessary to compensate for a consequent reduction in the allowance for a tilt angle wherein the disk surface is displaced from a surface perpendicular to the optical axis of the optical pickup. Specifically, the tilt angle is easily affected by optical aberrations resulting from the thickness of the base of the optical recording medium.
For a similar reason, unevenness of the thickness of the light transmissive layer must be reduced to no more than a predetermined value.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide an optical recording medium which avoids the aforementioned disadvantage of the prior art.
An additional object of the present invention is to provide an optical recording medium which permits use of an optical head device for an optical disc apparatus having a relatively high numerical aperture (N.A.) and which provides for a recordable storage capacity of 8 GB or more.
According to an aspect of the present invention, an optical recording medium includes a base formed of thermoplastic resin having a thickness ranging from between approximately 0.3 to 1.2 mm, a guide groove formed on the base, an information recording layer formed of at least a reflective film and an organic dye recording layer provided on the guide groove, and a light transmissive layer having a thickness ranging from between approximately 3 to 177 &mgr;m. For this optical recording medium, the unevenness &Dgr;t of the thickness of the light transmissive layer is set within the range of:
&Dgr;t≦±5.26(&lgr;/N.A.
4
)(&mgr;m)
wherein N.A. represents a numerical aperture of the optical head device of the optical disc recording and/or reproducing apparatus and &lgr; represents the wavelength of laser light utilized by the optical disc recording and/or reproducing apparatus.
Accordingly, an optical recording medium has been provided which achieves a storage recording capacity of at least 8 GB or more with excellent signal characteristics.
REFERENCES:
patent: 4711798 (1987-12-01), Ueda et al.
patent: 5079135 (1992-01-01), Matsuzawa et al.
patent: 5168031 (1992-12-01), Buckingham et al.
patent: 5569517 (1996-10-01), Tominaga et al.
patent: 5817389 (1998-10-01), Ono
patent: 5846626 (1998-12-01), Kashiwagi et al.
patent: 6054199 (2000-04-01), Sugiyama et al.
patent: 3-225650 (1991-10-01), None
Kaneko Masahiko
Kashiwagi Toshiyuki
Kawakubo Osamu
Yasuda Koichi
Chu Kim-Kwok
Frommer William S.
Frommer Lawrence & Haug LLP.
Ryan Matthew K.
Sony Corporation
LandOfFree
Reduced thickness of a light transmissive layer for a high... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reduced thickness of a light transmissive layer for a high..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reduced thickness of a light transmissive layer for a high... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2517593