Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Patent
1998-06-18
2000-07-11
Kelly, C. H.
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
25229901, 252582, 349 62, 349123, G02F 11335, G02F 11337, C09K 1952, F21V 900
Patent
active
060880775
ABSTRACT:
The invention is directed to a liquid crystalline display comprising a display cell containing liquid crystalline material and a retardation layer. The retardation layer comprises a, preferably slightly cross-linked, high-molecular weight material layer and a substrate, wherein the high-molecular weight material has a nematic phase above its Tg and a dynamic viscosity at the working temperature of at least 100 Pa.s. The difference of the Tc of the high-molecular weight material and the Tc of the low-molecular weight material of the display cell (TC.sub.cell) is in the range of -30.degree. C. to +30.degree. C., preferably in the range of -20.degree. C. to +20.degree. C., and more preferably in the range of -10.degree. C. to +10.degree. C.; and the Tg of the high-molecular weight liquid crystalline material is lower than 50.degree. C. It was found that if high-molecular weight material is used with a Tc comparable with that of the, preferably low-molecular weight, liquid crystalline material of the active cell, the temperature dependency of the retardation value of the retardation layer is comparable with that of the active cell. Thus, the retardation value of the retardation layer is comparable with that of the active cell within the temperature range in which displays are used. It was further found that by cross-linking of the high molecular weight liquid crystalline material, the retardation layers according to the invention become less susceptible to pinhole forming and unwanted variation of the twist, and have improved mechanical stability.
REFERENCES:
patent: 5380459 (1995-01-01), Kanemoto et al.
Bosma Martin
De Wit Paulus Pieter
Picken Stephen James
Steenbergen Andre
Akzo Nobel nv
Fennelly Richard
Kelly C. H.
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