Patent DE-19922723-A1 (DE)
Title: Active display matrix e.g. for flat screens contains a chiral/smectic liquid crystal mixture giving high maximum transmission, high contrast and constant threshold voltage over a wide temperature range
Inventor: NONAKA TOSHIAKI
IPC: C09K19/34
Filed: 1999-05-18
Abstract: An active matrix display with an asymmetric cell contains a \-3- component monostable liquid crystal domain in which the chiral-smectic liquid crystal (LC) mixture has an I-N asterisk -SmC asterisk phase sequence, a spontaneous polarization in the region of the operating temperature below 40 nC/cm<2>, a pitch at the nematic phase temperature above 20  mu  and a declination between the monostable position and the rubbing orientation of less than 10 deg at the operating temperature.  An active matrix display with an asymmetric cell contains a monostable liquid crystal domain in which the chiral-smectic liquid crystal (LC) mixture has an I-N asterisk -SmC asterisk phase sequence, a spontaneous polarization in the region of the operating temperature below 40 nC/cm<2>, a pitch at the nematic phase temperature above 20  mu  and a declination or tilt between the monostable position and the rubbing orientation of less than 10 deg  at the operating temperature, the LC mixture comprising at least one of each of the compounds of formula (A) and (B) and 0.05-50 wt.% one or more compounds of formula (C). R<12>-(A<14>-M<14>)a-(A<15>-M<15>)b-(M<16>-A<16>)c-M<17>-A<17>)d-R<13> (B) R<20>-M<18>-(A<14>-M<14>)a-(A<15>-M<15>)b-(M<16>-A<16>)c-(M<17>-A<17>) d-M<19>-R<21> (C) R<5> and R<6>  = H or 2-18C alkyl or alkoxy with 1 or 2 non-terminal -CH2- groups optionally replaced by -O-, -Si(CH3)2- or -CH(Cl)- and/or 1 or 2 -CH2- groups optionally replaced by -CH=CH- or -C equivalent to C- and where 1 or more H is optionally replaced by F and with the provisos that only 1 of R<5> and R<6> is H and that 2 adjacent -CH2- groups cannot be replaced by -O-;  X<3> and Y<4>  = -O-, -OC(O)-, -C(O)O-, -OC(O)O- or a single bond;  Z<1>  = -OC(O)-, -C(O)O-, -OC(O)O-, -OCH2-, -CH2O-, or -OC(O)CH2CH2-;  ring F and ring G  = phenylene-1,4-diyl (optionally 1-3 times substituted by F), pyrimidine-2,5-diyl, pyridine-2,5-diyl or pyridazine-2,5-diyl (each of these last 3 optionally substituted once by F);  ring K  = cyclohexane-1,4-diyl, dioxane-2,5-diyl, cyclohex-1-ene-1,4-diyl or cyclohex-2-ene-1,4-diyl (each of these last-named 4 optionally substituted once by F, CN or CH3), bicyclo(2.2.2)octane-diyl, bicyclo(2.2.1)heptane-diyl, 1-alkyl-1-silacyclohexane-1,4-diyl, thiophene-2,4-(or 2,5)-diyl, furan-2,4-(or 2,5-)-diyl or phenylene-1,4-diyl (optionally substituted once or twice by F, CN or CH3);  R<12> and R<13>  = (a) H or 2-12C alkyl or alkoxy with 1 or 2 -CH2- groups optionally replaced by -CH=CH-, -OC(O)-, -(O)CO- or -Si(CH3)2- and also \-1 H optionally replaced by F; or (b) 1-18C alkyl or alkoxy in which 1 -CH2- group is replaced by -CH=CH-, cyclopropane-1,2-diyl, cyclobutane-1,3-diyl, bicyclo(1.1.1)pentane-1,3-diyl, -C(CH3)2- or -CH(CH3)- or, when a terminal -CH2- group, by -C(CH3)3 and where a further -CH2- group is optionally replaced by -O-, -OC(O)- or -(O)CO- and \-1 H can be replaced by F; with the proviso that R<12> and/or R<13> is as per (b);  R<20> and R<21>  = (a) as per (a) for R<12> and R<13>; or (b) a group with \-1 asymmetric C atom which is either (i) a part of a 3-6C alkyl group in which 1-4 -CH2- groups are optionally replaced by -O-, -OC(O)- or -(O)CO- and the asymmetric C has -CH3, -CF3, -OCH3, -CH3 (sic), -Cl, -CN or -F as a substituent or (ii) part of a 3-7-membered carbon cycle (with 1 or 2 non-adjacent -CH2- groups optionally replaced by -O- or 1 -CH2- group optionally replaced by -OC(O)- or -(O)CO-) with \-1 of R<20> and R<21> being (b);  M<18> and M<19>  = a single bond when the group with an asymmetric C is an alkyl chain; A<14>-A<17>  = 1,3- or 1,4-phenylene (optionally substituted once or twice by F or Cl), cyclohexane-1,4-diyl (optionally substituted once by F or CN), cyclohex-1(or 2)-ene-1,4-diyl, 2-oxocyclohexane-1,4-diyl, 2-cyclohexene-1-one-3,6-diyl, 1-alkyl-1-sila-cyclohexane-1,4-diyl, bicyclo(2.2.2)octane-diyl, spiro(4.5)decane-2,8-diyl, spiro(5.5)undecane-3,9-diyl, indane-2,6-diyl, naphthylene-2,6-diyl (optionally substituted once or twice by F or CN), pyrimidine-, pyridine- or pyrazine-2,5-diyl (optionally substituted once by F), pyridazine-3,6-diyl, quinoline-2,6 (or 3,7)-diyl, isoquinoline-3,7-diyl, quinazoline-2,6-diyl, quinoxaline-2,6-diyl, 1,3-dioxane-2,5-diyl, thiophene-2,4 (or 2,5)-diyl, 1,3-thiazole-2,4 (or 2,5)-diyl, isoxazole-3,5-diyl, benzothiazole-2,6-diyl (optionally substituted once or more by F), 1,3,4-thiadiazole-2,5-diyl or piperidine- or piperazine-2,5-diyl;  M<14>-M<17>  = a single bond, -OC(O)-, -(O)CO-, -OCH2-, -CH2O-, -CH2CH2-, -CH2CH2CH2CH2- or -C=C-;  M<18> and M<19> = -OC(O)-, -(O)CO-, -OCH2-, -CH2CH2- or a single bond;  a, b, c and d = 0 or 1, with the provisos that a + b + c + d is 1-3 and (-Ax-Mx-) is a single bond when the index is zero An Independent claim is also included for the LC mixture.