Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1986-06-17
1988-04-12
Gron, Teddy S.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
2522995, 350350R, G02F 113, C09K 1934, C09K 1954
Patent
active
047373121
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to liquid crystal compositions suitable for use in electro-optical matrix displays of the twisted nematic cell type, and to an electro-optical matrix display using the liquid crystal composition mentioned above.
There is still a great demand for liquid crystal compositions (LC compositions) suitable for matrix displays having an electrooptical characteristic (contrast/voltage curve) as steep as possible and simultaneously a low threshold voltage. In such matrix displays, each "display point" of an electrode grid can be selectively triggered by applying a voltage to a first electrode layer, consisting of a multiplicity of horizontral rows of conductors, and to another electrode layer, consisting of a multiplicity of vertical rows of conductors (multiplex drive). The highr the multiplex ratio and the lower the maximum voltage of the available drivers, the lower the threshold voltage of the LC composition has to be. A disadvantage of these matrix display elements is the partial activation of display points in the immediate vicinity of a triggered display point, which partial activation is called "crosstalk" and reduces the contrast of the display in an undesirable manner. The steeper the electro-optical characteristic of the LC composition used in a display element of this type, the less such crosstalk is then observed. As a rule, the steepness of the electro-optical characteristic of a LC composition is given as the ratio of the control voltages V which must be applied to a given display element in order to obtain 10% of the maximum contrast (V.sub.10) and 50% of the maximum contrast (V.sub.50).
The steepness of the electro-optical characteristic is the greater, the smaller the ratio ##EQU1## Till today the steepness of the electro-optical characteristic can only be determined by experiment, because all theoretical predictions ended up to now in rather wrong results.
Besides of a decrease of the contrast with increasing multiplex ratio, there is also a strongly increasing viewing-angle dependence of the contrast. This dependence is defined as ##EQU2## wherein V.sub.x,y,z is the applied control voltage at x % contrast, viewing angle y and temperature z.degree. C.
The smaller .beta., the better is the optical performance of the matrix display.
SUMMARY OF THE INVENTION
It has now been found that LC compositions according to the invention result in surprisingly steep electro-optical characteristics and surprisingly low viewing-angle dependence of the contrast at simultaneously acceptable threshold voltages for commercially available drivers and multiplex ratios up to 1:100 when used in matrix displays.
The invention thus relates to a liquid crystal composition, characterized in that it contains at least one compound of the formula I trans-1,3-dioxane-2,5-diyl and Ph is 1,4-phenylene, and at least one compound of each of the following groups A to D: trans-1,4-cyclohexylene and Ph is 1,4-phenylene, and Ph have the meanings indicated above, meanings indicated above, and Ph have the meanings indicated above, and, in addition in a total amount of 10 to 26% by weight at least five compounds of the formula E pyrimidine-2,5-diyl and Ph has the meaning indicated above, the meaning indicated above, meaning indicated above. indicated above. has the meaning indicated above, fluorinated 1,4-phenylene and Ph has the meaning indicated above, liquid crystal composition according to the above.
The LC compositions according to the invention preferably contain at least two compounds of the formula I preferably in a total amount of 10 to 25, preferably 11,5 to 20% by weight.
The LC compositions according to the first aspect of the invention preferably contain only one compound of the formula A preferably in an amount of 5 to 15% by weight, preferably at least two compounds of the formula B preferably in an total amount of 15 to 25% by weight and preferably only one compound of the formula C preferably in an amount of 5 to 10% by weight. These LC compositions according to the inv
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Matsumoto Shoichi
Sage Ian C.
Scheuble Bernhard
Tomii Hitoshi
Weber Georg
Gron Teddy S.
Merck Patent Gesellschaft mit beschrankter Haftung
Toshiba Corporation
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