Optical recording medium and method of information...

Details Optical recording medium and method of information... Optical recording medium and method of information...

1999-11-05

2002-01-15

Evans, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064800, C430S270160

Reexamination Certificate

active

06338888

ABSTRACT:

FIELD OF THE INVENTION
The present invention related to an optical recording medium, and particularly to an optical recording medium which is able to record and/or reproduce while using a plurality of laser beam wavelengths as well as a method of recording and/or reproducing information in which such an optical recording medium is used.
BACKGROUND ART
Recently, an optical recording medium (such as CD-R, CD-RW (re-writable) and the like) of a single substrate type has been proposed and developed which is capable of recording information (including recording other information in addition to already recorded information) according to the specification for compact disc (hereinafter referred to as CD) and which has a high beam reflection ratio (or reflectance).
As one example of the above optical recording mediums, CD-R will be explained below. As schematically shown in
FIG. 4
which shows a portion of a cross section perpendicular to the disc surface, this optical recording medium comprises a transparent substrate
1
having grooves
6
on which a recording layer
2
, a reflection layer
3
and a protection layer
4
are laminated in the listed order. A reflectance at the groove
6
is not less than 65% before recording, which is reduced by a laser beam having a high power (i.e. a recording beam) to form pits since the recording layer has been changed physically and/or chemically. Thus formed pits have the reduced reflectances, so that portions having such different reflectances resulted with the irradiated laser beam make it possible to record information. Also, reproduction of the information can be carried out by irradiating a laser beam having a less power onto portions of the optical recording medium and detecting reflectance changes.
For the recording/reproducing with the optical recording medium, a laser beam having a wavelength in the range between 770 nm and 830 nm is generally used. However, a laser beam having a wavelength in the range between 620 nm and 690 nm is used for DVD which has been recently available as an optical recording medium having a larger capacity. Reflectances of the mediums conventionally used for CD for AV (audio-visual) or CD-ROM for computers are less dependent on the laser beam wavelengths so that those mediums are readily used for reproduction by DVD players.
On the other hand, since pigments (or dyes) are used in the conventional CD-R mediums, the reflectances of the mediums are more dependent on the laser beam wavelengths: The reflectance is not less than 65% at a laser beam wavelength of around 780 nm. However, since the pigments used for the recording layer absorb a larger amount of beam having a wavelength in the range between about 620 nm and 690 nm, the reflectance for such a beam is as small as around 10%. Therefore, it is very difficult to reproduce information which is recorded in a CD-R according to the CD specification using a DVD player. In order to overcome the above interchangeability problem (i.e. that the DVD player is not able to reproduce the information recorded according to the CD specification), there have been attempts to provide a plurality of enhancing layers having different optical constants of inorganic materials (such as SiO
2
) between the substrate and the recording layer, so that the reflectance at a laser beam wavelength in the range between about 620 nm and 690 nm is improved by means of an interference effect.
However, it is not necessarily easy to merely use the enhancing layers having the different optical constants as described to sufficiently improve the reflectance. Further, even though the reflectance is improved by some degree, no sufficient modulation is obtained, and recording sensitivity is lowered so that signal qualities are not satisfactory. Due to the reasons as described, it has been very difficult to provide an optical recording medium having interchangeability between the CD player and the DVD player (that is, an optical recording medium form which the recorded information is able to be reproduced using either player).
SUMMARY OF THE INVENTION
In order to achieve the object as described above, the present invention provides an optical medium comprising a transparent substrate which contains thereon at least a recording layer, a recording supplemental (or auxiliary) layer, a reflection layer and a protection layer, wherein: the recording layer and the recording supplement layer contain organic pigments as their main components; the optical recording medium is able to record and/or reproduce using a laser beam having a wavelength of &lgr;
1
, and also able to record and/or reproduce using a laser beam having a wavelength of &lgr;
2
which is shorter than &lgr;
1
; the recording layer has a spectral (or spectroscopic) absorbance in the range between 5% and 35% at a wavelength of &lgr;
1
and a spectral absorbance in the range not less than 15% at a wavelength of &lgr;
2
; and the recording supplemental layer has a peak of a spectral reflectance at a wavelength in the vicinity of &lgr;
2
.
the recording supplemental layer has a peak of a spectral reflectance at a wavelength in the vicinity of &lgr;
2
.
With the optical recording medium according to the present invention, it is preferable that the spectral (or spectroscopic) reflectance measured through the substrate varies with a wavelength of the beam, and that the spectral reflectance shows a maximum peak at a wavelength in the vicinity of &lgr;
2
, and as the wavelength is increased from &lgr;
2
thereafter, and the spectral reflectance is decreased and shows a minimum peak at a wavelength between &lgr;
1
and &lgr;
2
followed by being increased.
It is to be noted that the optical recording medium according to the present invention may be in any of the following embodiments:
(1) An embodiment in which recording/reproducing by means of a laser beam having a wavelength of &lgr;
1
as well as recording/reproducing by means of a laser beam having a wavelength of &lgr;
2
is possible;
(2) An embodiment in which recording by means of a laser beam having a wavelength of &lgr;
1
as well as reproducing by means of a laser beam having a wavelength of &lgr;
2
is possible; and
(3) An embodiment in which recording by means of a laser beam having a wavelength of &lgr;
2
as well as reproducing by means of a laser beam having a wavelength of &lgr;
1
is possible. That is, with the optical recording medium according to the present invention, both of recording and reproducing are possible with respect to two kinds of wavelengths &lgr;
1
and &lgr;
2
, and alternatively recording is possible with respect to one wavelength of &lgr;
1
and &lgr;
2
and reproducing is possible with respect to the other wavelength of &lgr;
2
and &lgr;
1
. In any embodiment, the optical recording medium according to the present invention may be referred to as an “optical recording medium applicable to two kinds of wavelengths” since it is used with respect to the two kinds of wavelengths.


REFERENCES:
patent: 5328741 (1994-07-01), Yanagisawa et al.
patent: 5627817 (1997-05-01), Rosen et al.
patent: 676 751 (1995-10-01), None
patent: 755 052 (1997-01-01), None
patent: 8-263873 (1996-10-01), None
patent: 8-273193 (1996-10-01), None
patent: 8-339573 (1996-12-01), None
patent: 9-54979 (1997-02-01), None

Affiliated with

Also associated with

Rating

Optical recording medium and method of information... 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 information..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical recording medium and method of information... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2871049