Compositions – Liquid crystal compositions
Patent
1993-08-16
1998-06-23
Wu, Shean C.
Compositions
Liquid crystal compositions
349 86, 349 88, 349 94, 349106, 428 1, C09K 1952, G02F 113
Patent
active
057693935
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a polymer dispersed liquid crystal display element wherein the liquid crystal and polymer are dispersed into one another, and, more particularly, to a display element applicable to user interfaces employed for computer displays and television and the method of producing such display elements.
2. Background of the Invention
With the introduction of computers to society in recent years, the development of user interfaces has accelerated. The development of displays is particularly fast paced, but currently the market depends primarily on twisted nematic liquid crystal display devices, which employ two polarizing plates providing a display that is dark. To solve these problems, polymer dispersed liquid crystal display devices have been recently developed. Since these systems do not require polarizing plates, the incident light to the display can be effectively employed. In particular, in operational modes that utilize dichroic dye, the appearance of the element is remarkable when employed as a reflecting type. For example, Fergason utilizes capsulated liquid crystal containing dichroic dye which is dispersed with polymers, as disclosed in Japanese Laid-Open Patent Publication 3-52843, hereinafter referred to as normal polymer PDLC mode. Also, Doane, et al., has proposed a production method whereby liquid crystal containing dichroic dye and polymer precursors are combined and the liquid crystal and polymer are phase separated into a sponge state as performed through polymerization, as disclosed in Japanese Patent Publication 61-502128, hereinafter referred to as normal polymer PDLC mode. Furthermore, employing polymer precursors which take on a liquid crystal state, Hikmet, et al., of Philips Corporation, provided a display element with a structure that was formed with polymer in an aligned state, which is achieved by irradiation with ultraviolet light while in a mixed condition with liquid crystal, and in which the liquid crystal was contained in a gel network, as disclosed in Mol. Cryst. Liq. Cryst., Vol. 213, pp. 117-131, 1992, hereinafter referred to as network type aligned PDLC mode. Unlike previously described modes, the display element of this mode scatters white when an electric field is applied. We have, however, independently developed technology that forms polymer into grains or macromolecules while they are in an aligned state as disclosed, for example, in EPO Publication 488116, hereinafter referred to as grain-aligned PDLC mode. However, sufficiently desired brightness and contrast level cannot be achieved in these modes. Moreover, the driving voltage is not of sufficiently desired low value.
The purpose of the invention is to offer a display element and associated manufacturing method wherein the liquid crystal and polymer are aligned and dispersed in one another providing high brightness and good contrast with low driving voltage.
SUMMARY OF THE INVENTION
According to this invention, a liquid crystal and polymer are aligned and dispersed in one another wherein the polymer or polymers employed are derived from one or more polymer precursors having a polymerizable portion. More particularly, such polymer precursors include at least one component as a polymer precursor having a polymerizable portion and a side chain portion. Alternatively, they may include polymer precursors having two or more polymerizable portions comprising at least one component. The polymer precursors may comprise either ester derivatives with methacrylic acid or acrylic acid, or they are amide derivatives with methacrylic acid or acrylic acid. The polymer precursors contain at least one component comprising a compound having an epoxy group. The polymer precursors may also contain at least one component comprising a compound having at least two aromatic rings, or at least one of the aromatic rings may by hydrogenated, and an ester group between the aromatic rings. The polymer precursors may also contain at least one component comprisi
REFERENCES:
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R. A. M. Hikmet, "Electrically Induced Light Scattering From Anisotropic Gels With Negative Dielectric Anisotropy", Mol. Cryst. Liq. Cryst., vol. 213, pp. 117-131, 1992.
D. K. Yang et al., "Cholesteric Liquid Crystal/Polymer Dispersion For Haze-Free Light Shutters", Applied Physics Letters, vol. 60(25), pp. 3102-3104, Jun. 22, 1992.
"Liquid crystal/liquid-crystalline network composite systems", by Dietrich Braun, Liquid Crystals, vol. 11, No. 6, Jun. 1992, London GB pp. 929-939.
Kobayashi Hidekazu
Samizu Kiyohiro
Seiko Epson Corporation
Wu Shean C.
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