Compositions – Liquid crystal compositions – Containing pleochroic dye
Patent
1988-06-08
1990-06-12
Gron, Teddy S.
Compositions
Liquid crystal compositions
Containing pleochroic dye
350349, 544294, 546285, 549373, 552256, C09K 1900, G02F 113, C07C10375, C07C 5036
Patent
active
049331043
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The present invention relates to dichroic dyes with negative dichroism and, more particularly, to a novel derivative of anthraquinone as a dichroic dye for a liquid-crystal material, liquid-crystal derivative and an electrooptical device.
PRIOR ART
Known in the art are anthraquinone derivatives (SU, A, No. 1089084) of the general formula ##STR5## where R is 4-alkylphenyl, 4-(4'-alkylphenyl)phenyl, or trans-4-alkylcyclohexyl group;
A, B, D are --NHCOR, --OCOR, --OH, --OR.sup.1, --NHR.sup.1, or --NR.sup.1 R.sup.2 group, and B and D can also be a hydrogen atom; negative dichroism in liquid crystals, a liquid-crystal material containing the above anthraquinone derivatives, and an electrooptical device based on the "guest-host" effect and containing this material as a working body.
The above anthraquinone derivatives in a liquid-crystal matrix ZK-807 based on 4-n-alkyl- and 4-n-alkoxy-4'-cyanobiphenyls has negative dichroism from -0.04 to -0.36 and a low limiting solubility in liquid crystals varying for the best samples from 0.1 to 2.3 mass %. In a liquid crystal 3010 ("La Roshe", Switzerland) the use of even a mixture of two dyes of the above formula does not produce the desired result since the total limiting solubility does not exceed 1.5 mass %. The liquid-crystal material containing (mass %) 0.1-2.5 anthraquinone derivative of the above formula and 97.6-99.9 crystal matrix has an optical density at the maximum of the long-wave absorption band equal to D.sub.1 =0.25-0.53. The electrooptical device based on the "guest-host" effect in which the above liquid-crystal material is used as a working body has an image luminance N=0.16-0.31. A low solubility of the described anthraquinone derivative does not allow one to obtain a liquid-crystal material with a high optical density (D.sub.1) at the maximum of a long-wave absorption band and, correspondingly, an electrooptical device based on the "guest-host" effect with a high intensity of symbol coloration.
DISCLOSURE OF THE INVENTION
It is an object of the invention to design a novel anthraquinone derivative as a dichroic dye negative dichroism possessing a high solubility in a liquid-crystal matrix, a liquid-crystal material containing said dichroic dye and having a high optical density at the maximum of the long-wave absorption band, and electrooptical device based on the "guest-host" effect with the above liquid-crystal material as a dichroic working body and characterized by a high image luminance.
Said object is accomplished by that a novel anthraquinone derivative of the general formula is proposed ##STR6## where A, B and D are simultaneously or independently --NHCOR.sup.1, --NHCOAlk, -- --OCOAlk, --OCOR.sup.1, --OH, --OAlk, --NHAlk groups or H, where ##STR7## R.sup.4 are the groups ##STR8## where Alk=C.sub.1 -C.sub.18 ; R.sup.5 are the groups ##STR9## where Alk=C.sub.1 -C.sub.18 ; R.sup.6 is hydrogen or --Alk=C.sub.1 -C.sub.8 ; dichroism for a liquid-crystal material.
Also proposed is a liquid-crystal material containing a liquid-crystal matrix and a dichroic dye with negative dichroism, said liquid-crystal material, according to the invention, contains at least one anthraquinone derivative of general formula /1/ as a dichroic dye with negative dichroism.
To ensure a maximum optical density of the liquid-crystal material, it is expedient to have the content of the anthraquinone derivative of general formula /1/ 1-15 mass %.
The proposed anthraquinone derivative of general formula /1/ , due to the structure, has a good solubility in liquid-crystal matrices (up to 15 mass %) and high dichroism (up to S=-0.39) which makes it possible to design a liquid-crystal material with a high optical density at a long-wave absorption band maximum.
The proposed liquid-crystal material provides the preparation of symbols of any color on a colorless or weakly-coloured background or on the background of any other colour with high gamma of the image in the corresponding electrooptical device.
Also proposed is an electrooptical device with a dichroic wor
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patent: 4136100 (1979-01-01), Epple
patent: 4176113 (1979-11-01), Wick et al.
patent: 4391489 (1983-07-01), Harrison et al.
patent: 4530572 (1985-07-01), Huffman
patent: 4702561 (1987-10-01), Huffman
Ivanshenko, A. V., et al., Mol. Cryst. Liq. Cryst., vol. 129, pp. 259-266 & 277-283, (1985).
Ivaschenko Alexandr V.
Lazareva Valentina T.
Pljusnina Tamara S.
Prudnikova Elena K.
Rumyantsev Vladimir G.
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