Supertwist liquid crystal display
AssigneeMerck Patent Gesellschaft mit beschraenkter Haftung
InventorsGeorg Weber, Herbert Plach, Volker Reiffenrath, Reinhard Hittich
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Abstract
Supertwist liquid crystal display elements with excellent steepness of the characteristic are obtained, if the nematic liquid crystal mixture satisfies the following conditions: a nematic phase range of at least 60.degree. C., a viscosity of 30 mPa.s or lower, and .DELTA..epsilon./.epsilon..perp.<2.0, where .DELTA..epsilon. is the dielectric anisotropy and .epsilon..perp. is the dielectric constant in the direction of the short axis of the liquid crystal molecules.
Claims17
A supertwist liquid crystal display comprising:
- two plane-parallel carrier plates which, with a border, form a cell;
- a nematic liquid crystal mixture, located in the cell, having a positive dielectric anisotropy and at least one chiral doping material;
- electrode layers with superposed orientation layers on the insides of the carrier plates;
- a tilt angle of 1.degree. to 30.degree. between the longitudinal axis of the molecules at the surface of the carrier plates and the carrier plates;
- and
- a twist angle of the liquid crystal mixture in the cell from orientation layer to orientation layer of between 160.degree. and 450.degree.,
- wherein the nematic liquid crystal mixture satisfies the following conditions:
- a nematic phase range of at least 60.degree. C.,
- a viscosity of 30 mPa.s or lower, and
- 0. 9.ltoreq..DELTA..epsilon./.epsilon..perp..ltoreq.2.0, where .DELTA..epsilon. is the dielectric anisotropy and .epsilon..perp. is the dielectric constant in the direction of the short axis of the liquid crystal molecule, and wherein the liquid crystal mixture contains at least one compound of the following formulae R and/or S:
- ##STR18## wherein R.sup.C and R.sup.D each independently of one another are n-alkyl having 1-10 C atoms or (trans)-n-alkenyl having 3-10 C atoms.
A display according to claim 6, wherein the liquid crystal mixture contains at least one compound of the following formulae H to K:
- ##STR21## wherein n is 1 or 2 and, in the case of n=2, the two fluorine atoms are adjacent, and R.sup.A and R.sup.B have the meaning given in claim 9.
A method of enhancing the steepness of the electrooptical characteristic curve of a supertwist liquid crystal display comprising employing as the nematic liquid crystal mixture of said display one which satisfies the following conditions:
- a nematic phase range of at least 60.degree. C.,
- a viscosity of 30 mPa.s or lower, and
- 0.9.ltoreq..DELTA..epsilon./.epsilon..perp..ltoreq.2.0, where .DELTA..epsilon. is the dielectric anisotropy and .epsilon..perp. is the dielectric constant in the direction of the short axis of the liquid crystal molecules,
- whereby high steepness of the characteristic curve is achieved, said display further comprising:
- two plane-parallel carrier plates which, with a border, form a cell;
- a nematic liquid crystal mixture, located in the cell, having a positive dielectric anisotropy and at least one chiral doping material;
- electrode layers with superposed orientation layers on the insides of the carrier plates;
- a tilt angle of about 1.degree. to 30.degree. between the longitudinal axis of the molecules at the surface of the carrier plates and the carrier plates;
- a twist angle of the liquid crystal mixture in the cell from orientation layer to orientation layer of between 160.degree. and 450.degree., and wherein the liquid crystal mixture contains at least one compound of the following formulae R and/or S:
- ##STR24## wherein R.sup.C and R.sup.D each independently of one another are n-alkyl having 1-10 C atoms or (trans)-n-alkenyl having 3-10 C atoms.
Dependencies are inferred from the claim text.