Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
1999-07-16
2001-09-18
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064200, C428S064500, C428S064800, C428S913000, C430S205000, C430S270200, C430S495100, C430S945000, C369S283000, C369S288000
Reexamination Certificate
active
06291045
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical information recording medium of write once (through a heat mode) type such as DVD-R, which is capable of performing a recording or reading data by means of a laser beam of a shorter wavelength region.
With respect to the means for recording and reading data such as images of character and graphic, picture or voice, an optical disc having a recording layer containing a pentamethine-based cyanine dye is known as a CD-R which is capable of recording and reading with a laser beam of 770 to 830 nm in wavelength. Recently however, DVD-R (a digital video disc-recordable, or a digital versatile disc-recordable), which is capable of recording and reading in high density with a red laser beam of 620 to 690 nm in wavelength for instance, which is shorter than the laser beam employed in the aforementioned CD-R, is now propagated as new media of the next generation.
As shown in Japanese Patent Unexamined Application H10-181211, the present applicants have proposed an optical information recording medium having a recording layer containing a specific kind of trimethine-based cyanine dye as being useful for such a DVD-R.
However, a trimethine-based cyanine dye having a benzene ring or a naphthalene ring, both being bonded to indole ring as shown in the aforementioned Japanese Patent Application, is accompanied with problems that when a substituent group in the benzene ring or naphthalene ring is hydrogen atom, etc. other than nitro group, the absorption spectrum of the recording layer having a dye layer containing such a dye becomes as shown in FIG.
1
. Namely, the absorbance h
2
of a second peak “b” representing an absorption due to the interaction and association between the dye molecules becomes too large in relative to the absorbance hl of the main peak “a” representing an absorption by the dye molecule itself which is based on the band gap energy in the dye molecule. As a result, the peak consisting of the main peak “a” and the second peak “b” fails to become sharp, and a half value width “d” of the spectrum (the width of the spectrum consisting of the main peak “a” and the second peak “b” in relative to the absorbance of h
1
/2) which represents the degree of the sharpness of peak also fails to become sufficiently small.
If the spectrum fails to become sufficiently sharp as mentioned above, the recording sensitivity or the absorbance per unit film thickness of a recording layer at the occasion of forming pits by making use of the irradiation of laser beam onto a recording layer cannot be sufficiently increased. This invites not only the problems that the thickness of the dye layer is required to be increased, the recording power is required to be increased, or the recording speed is required to be decreased, but also the problems that a so-called heat interference (wherein the deformation of the configuration of the pits may be caused due to the accumulation of heat at the space between the pits) tends to be brought about at the occasion of recording, thus giving a bad influence to the characteristics of the recording layer such as modulation amplitude or jitter.
BRIEF SUMMARY OF THE INVENTION
Therefore a first object of this invention is to provide an optical information recording medium having a recording layer which is capable of improving the ratio between the absorbance peak of a dye molecule and the association peak due to an association of the molecules in relative to a laser beam of shorter wavelength for the recording of the DVD in particular.
A second object of this invention is to provide an optical information recording medium which makes it possible to realize a recording material which is thin in film thickness and high in recording sensitivity to a laser beam of shorter wavelength for the recording of the DVD in particular.
A third object of this invention is to provide an optical information recording medium which is excellent in characteristics in terms of modulation amplitude, jitter, etc. in relative to a laser beam of shorter wavelength for the recording of the DVD in particular.
A fourth object of this invention is to provide an optical information recording medium which makes it possible to perform a high-speed recording with a small power in relative to a laser beam of shorter wavelength for the recording of the DVD in particular.
The present inventors have made an intensive study to solve the aforementioned problems and have finally found that a recording layer having a dye layer containing a trimethine-based cyanine dye having nitro group attached to a benzene ring or to a naphthalene ring, both being bonded to indole ring, is capable of minimizing the second peak in relative to the main peak shown in
FIG. 1
, thus enabling the spectrum consisting of a main peak and a second peak to become sharp.
Namely, according to this invention, there is provided (1) an optical information recording medium comprising a substrate on which a recording layer including a dye layer is formed; which is characterized in that said dye layer contains a trimethine-based cyanine dye represented by the following general formula [1]; and that said recording layer enables a recording and reading to be effected with a laser beam having a wavelength falling within a range of 620 nm to 690 nm.
wherein “A” represents any one of the following general formulas [2], [3], [4] and [5];
“A′” represents any one of the following general formulas [6], [7], [8] and [9];
“A” and “A′” may be the same or different from each other (where m and n respectively represents an integer of 1 or more); R and R′ may be the same or different from each other and are individually substituted or unsubstituted alkyl, carboxyl, alkoxycarbonyl, alkylcarboxyl, alkoxyl, alkylhydroxyl, aralkyl, alkenyl, alkylamide, alkylamino, alkylsufonamide, alkylcarbamoyl, alkylsulfamoyl, hydroxyl, halogen atoms, alkylalkoxyl, alkyl halide, alkylsulfonyl, alkylcarboxyl or alkylsulfonyl which are bonded to a metallic ion or alkyl, phenyl, benzyl, alkylphenyl, or phenoxyalkyl group (the hydrogen atom in the benzene ring portion and/or alkyl group portion may be substituted by a substituent group other than a metallic ion, such as alkyl, carboxyl, hydroxyl and a halogen atom); and X- is an anion selected from the group consisting of halogen atoms, PF6-, SbF6-, H3PO4, perchloric acid, hydroborofluoric acid, benzenesulfonic acid, toluenesulfonic acid, alkylsulfonic acid, benzenecarboxylic acid, alkylcarboxylic acid, trifluoromethylcarboxylic acid, periodic acid, SCN-, tetraphenyl borate and tungstic acid.
This invention also provides (2) an optical information recording medium of the aforementioned (1) wherein said dye layer further comprises, in addition to the trimethine-based cyanine dye represented by the aforementioned general formula [1], other kinds of dye at a ratio where the trimethine-based cyanine dye represented by the aforementioned general formula [1] occupies at least 50% by weight based on the total quantity of dyes.
This invention also provides (3) an optical information recording medium of the aforementioned (1) or (2) wherein said recording layer further comprises a metal complex.
In this invention, the recording layer is formed so as to enable the recording and reading to be effected with a laser beam having a wavelength falling within a range of 620 nm to 690 nm. This, in turn, means that the recording layer is made available for use in DVD-R.
The expression of the “recording layer” means in this invention not only a recording layer comprising a single or plural dye layers enabling pits to be formed thereon with a laser beam, but also an enhancing layer made of a resin for instance for adjusting the refractive index or film thickness of the optical information recording medium with a view to adjust the optical property of the optical information recording medium, and also an intermediate layer to be interposed between a subst
Fujii Toru
Hamada Emiko
Tajima Toshiaki
Tomizawa Yuji
Birch & Stewart Kolasch & Birch, LLP
Evans Elizabeth
Taiyo Yuden Co. Ltd.
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