Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2001-11-28
2003-07-29
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064800, C430S270140
Reexamination Certificate
active
06599605
ABSTRACT:
TECHNICAL FIELD
The present invention relates to novel 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 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, 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 different two 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 different two kinds of substituents are referred to as asymmetric squarylium compounds (or asymmetric squarylium dyes).
The asymmetric squarylium compound having as a substituent an aromatic ring bound to a squaric acid skeleton with a carbon atom of the aromatic ring and an aromatic amine bound to the squaric acid skeleton with an amino group has been previously known (Japanese Unexamined Patent Publication No. 92914/1994). OXOCARBONS (Academic Press, 1980) describes a compound in which an aromatic substituent bound to the squaric acid skeleton with a carbon atom is phenyl. However, since the color of these compounds is yellow, brown or red, it is believed that the maximum absorption wavelength of these compounds is 500 nm or shorter and, therefore, these compounds can be scarcely used as a recording material for DVD-R from a viewpoint of the spectroscopic properties.
In addition, Japanese Unexamined Patent Publication No. 92914/1994 describes a compound in which an aromatic substituent bound to the squaric acid skeleton with a carbon atom is an azulenyl group. However, the molar extinction coefficient of such a compound is 4.8 or smaller and, therefore, the compound is unsuitable for the recording material for DVD-R from a viewpoint of the spectroscopic properties.
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 its solution is within the range of 550-600 nm and log &egr; thereat (&egr; is a molar extinction coefficient) is 5 or greater. In addition, for thermal decomposition properties of the recording material, which have the close relation with the recording sensitivity, it is desirable that a significant loss in weight is observed 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, there is no recording material having suitable properties for DVD-R, such as spectroscopic properties, light resistance, solubility and thermal decomposition properties, in the known squarylium compounds.
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 as a recording material for DVD-R, and optical recording media using the same.
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 a hydrogen atom, 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, or R
1
and R
2
may be taken together with an adjacent nitrogen atom to form a heterocycle, wherein the heterocycle may have a substituent, and R
3
represents the general formula (II):
wherein, R
4
and R
5
are the same or different, and represent a hydrogen atom or an alkyl group, or R
4
and R
5
may be taken together with an adjacent nitrogen atom to form a heterocycle, and R
6
, R
7
, R
8
and R
9
are the same or different, and represent a hydrogen atom, an alkyl group optionally having a substituent, an alkoxy group optionally having a substituent, a hydroxyl group or a halogen atom, or R
4
and R
6
or R
5
and R
7
may be taken together with adjacent N—C—C to form a heterocycle, wherein the heterocycle may have a substituent; or the general formula (III):
wherein, R
10
represents a carbon or nitrogen atom, R
11
and R
12
are the same or different, and represent a hydrogen atom, an alkyl group optionally having a substituent, an aryl group optionally having a substituent, an aralkyl group optionally having a substituent, or a hydroxyl group (provided that, when R
10
is a nitrogen atom, then R
12
is not present), R
13
represents a hydrogen atom, an alkyl group optionally having a substituent, an aryl group optionally having a substituent or an aralkyl group optionally having a substituent, and R
14
and R
15
are the same or different, and represent a hydrogen atom, an alkyl group optionally having a substituent, an alkoxy group or a halogen atom, or R
14
and R
15
may be taken together with two adjacent carbon atoms to form an alicyclic hydrocarbon group, an aromatic ring optionally having a substituent or a heterocycle optionally having a substituent.
Also, the present invention provides optical recording media having a recording layer comprising said squarylium compound.
REFERENCES:
patent: 60-260549 (1985-12-01), None
patent: 06-092914 (1994-04-01), None
Z. Lu et al.; “Studies on Synthesis and El Properties of Several Novel Squaraines”; Synthetic Metals, vol. 91, No. 1-3, pp. 233-235, 1997.
N. Liu et al.; “Synthesis of New Squarains Used as Organic Electroluminescent Materials”; Chinese Chemical Letters, vol. 8, No. 5 pp. 403-406, 1997.
Oxocarbons, pp. 204-207 (1980).
Ikuta Masanori
Kinugasa Motoharu
Mutoh Kenji
Satoh Tsutomu
Shimizu Ikuo
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kyowa Hakko Kogyo Co. Ltd.
Mulvaney Elizabeth
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