Compositions – Liquid crystal compositions – Cholesteric liquid crystal composition containing a sterol...
Reexamination Certificate
1999-07-30
2001-02-06
Wu, Shean C. (Department: 1756)
Compositions
Liquid crystal compositions
Cholesteric liquid crystal composition containing a sterol...
C349S002000, C359S003000, C430S020000, C552S544000
Reexamination Certificate
active
06183666
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cholesteryl compound with liquid crystalline properties, and a rewritable full-color thermosensitive recording material comprising the above-mentioned cholesteryl compound.
2. Discussion of Background
Color photographs and photocopiers are known as recording materials capable of recording a full-color image, but not capable of rewriting the recorded image. On the other hand, there are known recording materials capable of rewriting the recorded information, but not capable of achieving full-color recording, for example, a thermosensitive recording material comprising a long-chain alkyl carboxylic acid derivative such as behenic acid; an optical recording material comprising a photochromic compound such as a spiropyran derivative; and a magnetic and magneto-optical memory material.
As shown in the above-mentioned conventional recording materials, full-color recording and rewritable recording are not achieved at the same time.
Some image display materials, for example, television devices and liquid crystal devices can display full-color changeable images. However, these image display materials cannot be made compact, for instance, into a thin card that can be kept in a wallet. In addition, the color image displayed in the above-mentioned display materials cannot be stably maintained without a power source. For these reasons, the above-mentioned image display materials cannot be used as recording materials.
Achievement of rewritable full-color recording using liquid crystalline compounds is reported (N. Tamaoki et al. Advanced Materials 9 (14), 1102 (1997)). In this case, however, the peak of the reflection band of the reflection spectrum is, at most, 610 nm on the long wavelength side, so that it is difficult for the above-mentioned liquid crystalline compounds to assume a red color.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a liquid crystalline compound that is useful as a rewritable full-color thermosensitive recording material.
A second object of the present invention is to provide a rewritable full-color thermosensitive recording material using the above-mentioned liquid crystalline compound.
The above-mentioned first object of the present invention can be achieved by a cholesteryl compound of the following formula (1):
YO—CO(CH
2
)
n
—A—(CH
2
)
n
CO—OY (1)
wherein A is a 1,5-hexadienylene group represented by the formula —C(R)═CHCH
2
CH
2
CH═C(R)—, in which R is a hydrogen atom or methyl group; Y is a cholesterol residue obtained by removing a hydroxyl group from cholesterol; and n is an integer of 5 to 7.
The second object of the present invention can be achieved by a rewritable full-color thermosensitive recording material comprising a cholesteryl compound of the following formula (1):
YO—CO(CH
2
)
n
—A—(CH
2
)
n
CO—OY (1)
wherein A is a 1,5-hexadienylene group represented by the formula —C(R)═CHCH
2
CH
2
CH═C(R)—, in which R is a hydrogen atom or methyl group; Y is a cholesterol residue obtained by removing a hydroxyl group from cholesterol; and n is an integer of 5 to 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The cholesteryl compound of formula (1) according to the present invention is obtained by a condensation reaction of a long-chain dibasic acid comprising a 1,5-hexadienylene group (hereinafter simply referred to as a long-chain dibasic acid) and cholesterol.
The above-mentioned long-chain dibasic acid, which is represented by the following formula (2), has 18 to 24 carbon atoms in its molecule.
HOOC—(CH
2
)
n
—A—(CH
2
)
n
—COOH (2)
wherein A is a 1,5-hexadienylene group, and n is an integer of 5 to 7.
To be more specific, the moiety A in the above formula (2), that is, the 1,5-hexadienylene group is represented by the following formula (3):
wherein R is a hydrogen atom or methyl group.
The previously mentioned long-chain dibasic acid is conventionally known, and can be synthesized by the method of Kida et al., as reported in j. Jpn. Oil Chem. Soc. (YUKAGAKU) Kida et al., 41,385 (1992).
According to the above-mentioned synthesis method, cycloalkanones are treated with hydrogen peroxide in methanol, whereby hydroperoxides with methoxy group are obtained. This reaction is shown by the following reaction scheme (4):
Thereafter, a mixture of the above obtained hydroperoxide and 1,3-butadiene or 2-methyl-1,3-butadiene is allowed to react with iron(II) salts, thereby providing a long-chain dibasic acid ester comprising a 1,5-hexadienylene group. The thus obtained ester is subjected to saponification, whereby the long-chain dibasic acid of formula (2) is obtained.
In the condensation reaction of the long-chain dibasic acid of formula (2) and cholesterol, 2 to 4 moles, preferably 2 to 3 moles of the cholesterol may be allowed to react with one mole of the long-chain dibasic acid.
The above-mentioned condensation reaction is carried out in the presence of dicyclohexyl carbodiimide and 4-dimethylaminopyridine in a reaction solvent such as methylene chloride at room temperature for approximately 12 hours, with stirring.
In this case, dicyclohexyl carbodiimide has a function of activating the long-chain dibasic acid and may be employed in an amount of 1 to 2 moles with respect to one mole of cholesterol. 4-dimethylaminopyridine, which serves as a condensation catalyst, may be employed in an amount of 0.1 to 0.2 moles with respect to 1 mole of cholesterol.
The cholesteryl compound represented by formula (1) has liquid crystalline properties, and is capable of reproducing iridescent colors that can be selected from the whole visible region according to the temperature to which the compound is heated. Namely, the cholesteryl compound of the present invention assumes a dark red color at 110° C. In the measurement of the reflection spectrum, it is confirmed that the cholesteryl compound assuming a red color reflects the light with a peak reflection band at 750 nm. When the above-mentioned cholesteryl compound of the present invention is heated to 112° C., 113° C., 117° C., 124° C. and 132° C. and maintained at the respective temperatures, it is confirmed by the reflection spectra of the compound that the peak reflection band is respectively at 660, 570, 490, 450 and 400 nm.
Furthermore, the cholesteryl compound according to the present invention can be used for a full-color thermosensitive recording (and displaying) material because the colors of the cholesteryl compound can be fixed.
When the cholesteryl compound of the present invention is used for the full-color thermosensitive recording material, the cholesteryl compound may be, for example, interposed between two supports, thereby providing a recording medium. In this case, a thin glass plate, a polymeric film and a metal plate are usable as the support. At least one of the two supports is required to have transparency capable of transmitting at least a portion of the light therethrough. Further, it is desirable that one of the supports have light absorbing properties when information is recorded in the recording medium and erased therefrom using the application of light.
When the recording medium is fabricated by interposing the cholesteryl compound of the present invention between two supports, the cholesteryl compound (or a mixture comprising the cholesteryl compound) is first heated to such a degree that the cholesteryl compound can assume a fused phase or liquid crystalline phase, and the cholesteryl compound in such a state is coated on one support. Thereafter the other support is overlaid thereon. Alternatively, two supports are disposed in parallel, and the cholesteryl compound in the above-mentioned state is sucked into the gap between the two supports under reduced pressure or by means of capillarity. In this case, the gap between the two supports is not particularly limited, but preferably in the range of several microns to approximately 100 &mgr;m.
Further, the cholesteryl compound of the present invention is not always nec
Kida Yoshishige
Matsuda Hiroo
Tamaoki Nobuyuki
Oblon, Spivak, McCleland, Maier & Neustadt, P.C.
Ricoh & Company, Ltd.
Wu Shean C.
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