Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2001-09-26
2004-03-02
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064800, C430S270140
Reexamination Certificate
active
06699556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording medium and an information recording method and in particular to an optical information recording medium and an information recording method capable of recording and reproducing information by irradiation with laser rays. In particular, the present invention relates to an optical information recording medium suitable for recording information by irradiation with short-wavelength laser rays having wavelengths of 550 nm or less and an information recording method using this optical information recording medium.
2. Description of the Related Art
Heretofore, an optical information recording medium (optical disk) capable of recording information only once by laser rays has been known. This optical disk is also called addition writing-type CD (so-called CD-R), and this disk is structured typically by laminating a recording layer containing an organic colorant, a light-reflective layer consisting of a metal such as gold, and a protective layer made of resin in this order on a transparent disk-shaped substrate. Recording of information on this CD-R is conducted by irradiating the CD-R with near-infrared laser rays (usually laser rays with wavelengths in the vicinity of 780 nm), and the portion thus irradiated absorbs the rays to increase temperature locally thus undergoing a physical or chemical change (e.g., formation of pits) thereby changing the optical characteristics at that portion to record information. Reading (reproduction) of information is conducted by irradiating the CD-R with laser rays having the same wavelength as that of the recording laser rays and detecting a difference in reflectance between a portion where the optical characteristics of the recording layer were changed (recorded portion) and a portion where the characteristics were not changed (unrecorded portion).
Further, an optical disk called an addition writing-type digital versatile disk (so-called DVD-R) has been proposed and practically used as an optical information recording medium capable of higher density recording than CD-R. Usually, a DVD-R has either: a structure in which two disks each consisting of a recording layer containing an organic pigment, a light-reflective layer and a protective layer laminated in this order on a transparent disk-shaped substrate are laminated with their recording layers inside; or a structure in which said disk and a disk-shaped protective substrate of the same shape as said disk are laminated with the recording layer inside. On the transparent disk-shaped substrate, a guide groove (pre-groove) for tracking irradiation laser rays is formed with a groove width (0.74 to 0.8 &mgr;m) which is less than half the width of grooves on a CD-R. Recording and reproduction of information on the DVD-R is performed by irradiation of visible laser rays (usually, laser rays having wavelengths in the range of 630 nm to 680 nm) to achieve higher density recording than CD-Rs.
Recently, high-vision TV, networks such as the Internet and the like have been rapidly spreading. Further, the start of broadcasting of HDTV (high definition television) is near at hand. Under these circumstances, there is a strong demand for a high-capacity recording medium capable of recording image information easily and inexpensively. At present, DVD-R fulfills a satisfactory role as a high-capacity recording medium, but there is an increasing demand for higher capacity and higher density, and development of a recording medium for coping with such demand is also necessary. Accordingly, a recording medium of higher capacity capable of high-density recording with rays of shorter wavelengths than those for DVD-R is being developed.
For example, Japanese Patent Application Laid Open (JP-A) No. 4-74690, JP-A 8-127174, JP-A 11-53758, JP-11-334204, JP-A 11-334205, JP-A 11-334206, JP-A 11-334207, JP-A 2000-43424, JP-A 2000-108513, JP-A 2000-113504, JP-A 2000-149320 and JP-A 2000-158818 disclose a recording and reproduction method wherein an optical information recording medium having a recording layer containing an organic dye is irradiated with a laser having a wavelength of 530 nm or less in a direction from the recording layer toward the light-reflective layer, thus effecting recording and reproduction of information. In this method, an optical disk equipped with a recording layer containing a porphyrin compound, an azo type dye, a metal azo type dye, a quinophthalone type dye, a trimethine cyanine dye, a dicyanovinyl phenyl skeleton dye, a coumarin compound or the like is irradiated with a lasers of blue color (wavelengths of 430 nm and 488 nm) or bluish-green color (wavelength of 515 nm), thereby effecting the recording and reproduction of information.
However, investigations by the inventors of the present invention have revealed that the optical disks described in the above publications cannot achieve practically required sensitivity in the case of recording information by irradiation with short-wavelength laser rays, with wavelengths of 550 nm or less, and other recording characteristics such as reflectance and degree of modulation are not satisfactory, thus necessitating further improvements. In particular, the optical disks described in the above publications have lower recording characteristics when irradiated with laser rays having wavelengths of 450 nm or less.
SUMMARY OF THE INVENTION
The present invention was made in view of the problems in the prior art described above, and a first object of the present invention is to provide an optical information recording medium excellent in recording characteristics and capable of recording and reproducing information by irradiation with laser rays having wavelengths of 550 nm or less, particularly laser rays having wavelengths of 450 nm or less, which are shorter than wavelengths of laser rays used in recording and reproducing information on CD-R and DVD-R. A second object of the present invention is to provide an information recording method capable of high-density recording of information by irradiation with laser rays having wavelengths of 550 nm or less, particularly laser rays having wavelengths of 450 nm or less, which are shorter than wavelengths of laser rays used in recording and reproduction on CD-R and DVD-R. A first aspect of the present invention is directed to an optical information recording medium having: a substrate; and a recording layer on the substrate which is capable of recording information by irradiation with laser rays, the recording layer comprising a 1,2,3-triazole compound devoid of a condensate with 1,3-dimethylbarbituric acid. The second aspect of the present invention is directed to an information recording method including steps of: providing an optical information recording medium having, on a substrate, a recording layer capable of recording information by irradiation with laser rays, the recording layer comprising a 1,2,3-triazole compound devoid of a condensate with 1,3-dimethylbarbituric acid; and irradiating the optical information recording medium with a laser having a wavelength of at most 550 nm for recording information.
According to the present inventors' studies, an optical information recording medium having a recording layer on a substrate, which has good recording characteristics in having high sensitivity, high reflectance and high degrees of modulation even with respect to short-wavelength laser rays having wavelengths of 550 nm or less, and particularly wavelengths of 450 nm or less, can be obtained by inclusion of a 1,2,3-triazole compound in the recording layer, which is capable of recording information by irradiation with laser lays. Further, this optical information recording medium is capable of high-density recording of information by irradiation with laser rays having wavelengths of 550 nm or less, and particularly wavelengths of 450 nm or less.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Below, the embodiments of the optical information recording medium and the information recording method a
Fuji Photo Film Co. , Ltd.
Mulvaney Elizabeth
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