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Yellow Dyes for Liquid Crystal Displays

IP.com Disclosure Number: IPCOM000052258D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 27K

Publishing Venue

IBM

Related People

Clecak, NJ: AUTHOR [+2]

Abstract

In guest-host display systems in which a dye is dissolved in a liquid crystalline matrix, the dye which is used has a number of requirements which must be met in order that it will be useful in a practical manner. Among these requirements are adequate solubility in the liquid crystal host, chemical and photochemical stability, a high order parameter (which includes the angle that the transition dipole makes with the long axis of the molecule as well as the geometrical requirements of high aspect ratio), and a strong absorption in the visible portion of the spectrum. In an ideal case, we would like to have such a dye in which the absorption was broad enough to cover the whole visible spectrum, i.e.

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Yellow Dyes for Liquid Crystal Displays

In guest-host display systems in which a dye is dissolved in a liquid crystalline matrix, the dye which is used has a number of requirements which must be met in order that it will be useful in a practical manner. Among these requirements are adequate solubility in the liquid crystal host, chemical and photochemical stability, a high order parameter (which includes the angle that the transition dipole makes with the long axis of the molecule as well as the geometrical requirements of high aspect ratio), and a strong absorption in the visible portion of the spectrum. In an ideal case, we would like to have such a dye in which the absorption was broad enough to cover the whole visible spectrum, i.e., a black dye; however, as no such dye is presently available, it has been found necessary, if a black on white display is desired, to formulate the mixture with at least two dyes absorbing in different parts of the spectrum.

We have prepared, and have now found to be useful in guest-host display systems, a number of dyes with a variety of structures which absorb in the 400 to 500 nm portion of the spectrum. These dyes all meet the requirements of high order parameter, good solubility and, particularly, good stability - chemical, photochemical and electro-chemical.

The dyes in class 1 were prepared by us and represent new yellow dye structures. The method of preparation was the condensation between benzidine and p-nitrocinnamaldehyde.

The compounds in class 2, where n=l, are known compounds. Those with n=2 are new and were prepared in the following manner. Equimolar amounts of the aldehyde and p-nitrophenylacetic acid were dissolved in toluene, and a catalytic amount of piperidine was added....