Twisted nematic and super twisted nematic liquid crystal displays contain compounds having specified dielectric anisotropy values

摘要

Twisted nematic and super twisted nematic liquid crystal displays comprise a nematic liquid crystal mixture containing 15-80 wt.% of a liquid crystal component having a dielectric anisotropy of greater than +1.5, 20-85 wt.% of a liquid crystal component having a dielectric anisotropy of -1.5 to +1.5 and 0-20 wt.% of a liquid crystal component having a dielectric anisotropy of less than -1.5. Twisted nematic (TN) and super twisted nematic (STN) liquid crystal displays (I) comprise two substrate plates that with an edging, form a cell that contains a nematic liquid crystal mixture having positive dielectric anisotropy, electrode layers having orientation layers on the inner faces of the substrate plates, a pitch angle between the long axis of the molecule at the surface of the substrate plate and the substrate plate of 0-30 deg and a twist angle of the liquid crystal mixture in the cell from orientation layer to orientation layer of 22.5-600 deg . The nematic liquid crystal mixture comprises: (A) 15-80 wt.% of a liquid crystal component containing compounds having a dielectric anisotropy of greater than +1.5; (B) 0-85 wt.% of a liquid crystal component containing compounds having a dielectric anisotropy of -1.5 to +1.5; (C) 0-20 wt.% of a liquid crystal component containing compounds having a dielectric anisotropy of less than -1.5; and (D) optionally an optically active component in such an amount that the ratio between the layer thickness (gap between substrate plates) and the natural transition height of the chiral nematic liquid crystal mixture is 0.2-1.3 Component (A) comprises a compound of formula (1), (2) and (3). R1 = H or 1-12C alkyl whereby one or more non-neighboring CH2 groups is replaced by -O-, -CHCH-, -CO-, -OCO- or -COO-; L1 = H or F; R2, R3 = H, halogen, -CN, -NCS, -SF5 or 1-12C alkyl whereby one or more non-neighboring CH2 groups are replaced by -O-, -CHCH-, -CO-, -OCO- or -COO- and/or at least one H atom is optionally substituted by halogen and/or -CN; R4 = H or 1-12C alkyl whereby one or more non-neighboring CH2 groups are replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO-; X = -F-, -Cl, -OCF3, -OCHF2, -OCHFCF3 or -OCF2CHFCF3; L2 = H or F