Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-11-27
2003-12-09
Ramsuer, Robert W. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C369S275200, C428S064100, C428S064800, C428S064900, C430S213000, C430S270140
Reexamination Certificate
active
06660867
ABSTRACT:
TECHNICAL FIELD
The present invention relates to squarylium compounds which can be used in the optical recording field, and to optical recording media using the same.
BACKGROUND ART
In recent years, development of a digital versatile disc-recordable (DVD-R) as a recordable optical recording medium having a higher recording density than that of a compact disc-recordable (CD-R) has been under going. Both of CD-R and DVD-R are similar to each other in that an organic dye is utilized therein as a recording material and are also similar to each other in a principle of recording and reproducing of a signal (information). Therefore, the organic dyes developed for CD-R can basically comply with the various requirements (light resistance, solubility, and thermal decomposition properties) for the recording material of DVD-R other than spectroscopic properties. However, an oscillation wavelength of a semiconductor laser, which is used for recording the signal to DVD-R or for reproducing the signal from DVD-R, is in the range of 600-700 nm, which is shorter than that of the semiconductor laser which is used for CD-R. Accordingly, the recording material utilized for DVD-R should have an absorbance end of a longer wavelength side shorter than that of CD-R when it exists in the form of a membrane. Therefore, the dyes developed for CD-R such as cyanine dyes, azaannulene dyes and indoaniline-metal chelate dyes (“Electronics Related Dyes”, CMC, 1998) can not be used as the recording material for DVD-R.
The present inventors have developed squarylium compounds having two different kinds of aromatic substituents in a molecule. Such squarylium compounds have a squaric acid skeleton at a center of the molecule and substituents comprising an aromatic compound on carbon atoms at two catercornered positions of the skeleton. Squarylium compounds having two same aromatic substituents are conveniently referred to as symmetric squarylium compounds (or symmetric squarylium dyes), whereas those having two different kinds of substituents are referred to as asymmetric squarylium compounds (or asymmetric squarylium dyes).
A squarylium compound known in the art wherein a metal atom is coordinated thereby forming a chelate structure is a symmetric squarylium compound having an aniline derivative represented by the formula (A) as an aromatic substituent (
Chem. Ber
. vol. 103, 3553-3562, 1970).
However, this compound does not have a structure in which a plurality of squarylium compounds coordinate to one metal atom, and nitrogen atoms between the aromatic ring and the squaric acid skeleton are involved in coordination.
In addition, a known compound in which a plurality of squarylium analogues coordinate to one metal atom to form a chelate structure is a compound represented by the formula (B) (“OXOCARBONS”, ACADEMIC PRESS 1980, p. 210, edited by Robert West).
However, in this compound, the substituents on the squaric acid skeleton are changed from an oxygen atom to an sulfur atom, and nitrogen atoms between the aromatic ring and the squaric acid skeleton are involved in coordination.
Further, a complex of a compound represented by the formula (C) and a metal is known as an example which has an atom involved in coordination as a substituent on the aromatic ring, and in which a plurality of squarylium compounds and one metal atom form a complex. This complex may be used, for example, for a near infrared-ray absorbing agent, a filter for a plasma display, and the like (JP-A 2000-159776).
(wherein X and X′ represent a group having active hydrogen, Y
1
and Y
2
represent an hydrogen atom, an alkylamino group, or the like, and k and k′ represent an integer of 1 to 4)
However, the above reference discloses specifically only a compound represented by the formula (D) as a squarylium compound corresponding to the formula (C). Further, no specific structure for the complex is shown therein.
(wherein Z
1
-Z
6
represent a hydrogen atom, an alkyl group, or the like)
Squarylium compounds having a structure in which a plurality of squarylium compounds coordinate to one metal atom, and in which atoms involved in coordination are an oxygen atom being a substituent on the squaric acid skeleton and an atom in a substituent on an aromatic ring, have not been known yet.
In view of an oscillation wavelength of the semiconductor laser used for DVD-R, for spectroscopic properties of the recording material, which have the close relation with recording and reproducing sensitivities of the signal, it is desirable that the maximum absorption wavelength (&lgr;
max
) of the recording material measured in a solution state is within the range of 550-600 nm and log &egr; (&egr; is a molar extinction coefficient) at the maximum absorption wavelength is 5 or larger.
In addition, for thermal decomposition properties of the recording material, which have the close relation with the recording sensitivity, it is desirable that the recording material decomposes within the temperature range of 250-350° C.
Furthermore, although light resistance and solubility in a solvent which is necessary for membrane formation are also required as the property of the recording material, when the known squarylium compounds are used in a recording material for DVD-R, the obtained recording material for DVD-R is not sufficient for practical use in view of spectroscopic properties, light resistance, solubility and thermal decomposition properties. The above-mentioned compound A has a melting point of 350° C. or higher, and the compound C has a maximum absorption wavelength of 830 nm or longer. There are no property data for the compound B.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide squarylium compounds having spectroscopic properties, light resistance, solubility and thermal decomposition properties suitable for a recording material for DVD-R, and optical recording media using the same.
In view of the above situation, the present inventors intensively investigated and, as the result, we have found that a suqarylium compound having hydroxypyrazole as an aromatic substituent and a metal atom with a coordination ability form a chelate complex, and obtained a finding that compounds obtained by forming such a chelate complex have properties suitable for a recording material for DVD-R.
The present invention was done based on such a finding, and provides squarylium compounds represented by the formula (I):
wherein, R
1
and R
2
are the same or different, and represent an alkyl group optionally having a substituent, an aralkyl group optionally having a substituent, an aryl group optionally having a substituent, or a heterocyclic group optionally having a substituent; Q represents a metal atom with a coordination ability; q represents 2 or 3; and A represents an aryl group optionally having a substituent, a heterocyclic group optionally having a substituent, or Y═CH— wherein Y represents an aryl group optionally having a substituent or a heterocyclic group optionally having a substituent, and optical recording media which has a recording layer comprising said squarylium compound.
The present invention will be illustrated below, and herein the compound represented by the formula (I) is referred to as a compound (I). This is also applicable to compounds with other formula numbers added.
First, in the definitions of the respective groups in the above formula (I) or the formula (II) described below, an alkyl part of the alkyl and alkoxy groups includes straight or branched alkyl groups having from 1 to 6 carbon atoms and cyclic alkyl groups having from 3 to 8 carbon atoms, such as methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, iso-pentyl, 1-methylbutyl, 2-methylbutyl, tert-pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl groups, and the like.
Examples of the aralkyl group include aralkyl groups having from 7 to 15 carbon atoms, such as benzyl, phenethyl, phenylpropyl and naphthylmethyl groups, and the like.
Examples of the aryl group include phenyl
Kinugasa Motoharu
Noguchi Soh
Satoh Tsutomu
Shimizu Ikuo
Tomura Tatsuya
Kyowa Hakko Kogyo Co. Ltd.
Ramsuer Robert W.
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