Antiferroelectric liquid crystal composite material, process for preparing the same, and liquid crystal element using the same

A process for preparing an antiferroelectric liquid crystal composite material comprising a step of mixing an organic polymer and an antiferroelectric liquid crystal material, wherein the antiferroelectric liquid crystal material is represented by the following formula (I)

• R--X.sup.1 --(A.sup.1 --X.sup.2).sub.l --(A.sup.2 --X.sup.3).sub.m --(A.sup.3 --X.sup.4).sub.n --Q.sup.1 --C*H(Q.sup.2)--Q.sup.3(I)
• wherein R is an alkyl group of 4 to 20 carbon atoms or a polyfluoroalkyl group of 4 to 20 carbon toms, a part of --CH.sub.2 -- group or a --CF.sub.2 -- group present in said alkyl or polyfluoroalkyl group may be substituted with at least one group selected from --O--, --S--, --CO--, --CHX-- (wherein X is a halogen atom), --O--CO--, --O--COO--, --COO-- and --CH.dbd.CH-- so that hetero atoms are not bonded to each other, said alkyl or polyfluoroalkyl group may have optical activity;
• X.sup.1 is a group selected form --COO--, --O--CO-- and --O--, or a single bond;
• X.sup.2 and X.sup.3 are each independently a group selected from --COO--, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O-- and --OCH.sub.2 --;
• X.sup.4 is a group selected from --COO--, --CO--, --O-- and --O--CO--;
• A.sup.1, A.sup.2 and A.sup.3 are each independently a group selected from divalent groups represented by the following formulas:
• ##STR17## Q.sup.1 is --CH.sub.2).sub.q -- wherein q is an integer of 0 to 6;
• Q.sup.2 and Q.sup.3 are each independently an alkyl group of 1 to 10 carbon atoms or a halogen atom, Q.sup.2 and Q.sup.3 are different from each other, both of Q.sup.2 and Q.sup.3 are not halogen atoms, and a part of --CH.sub.2 -- group or --CF.sub.2 -- group present in Q.sup.1, Q.sup.2 and Q.sup.3 may be substituted with at least one group selected from --O--, --S--, --CO--, --CHX-- (wherein X is a halogen atom), --CHCN--, --O--CO--, --O--COO--, --COO-- and --CH.dbd.CH--so that hetero atoms are not bonded to each other;
• l, m and n each independently represent 0 or 1;
• and
• a difference in a refractive index between the organic polymer and the antiferroelectric liquid crystal material is in the range of 0 to .+-.0.15 in a transparent state of said composite material.

A liquid crystal element comprising a pair of electrodes facing each other at lest one of which is a transparent electrode and an antiferroelectric liquid crystal composite material filled between the electrodes, wherein the antiferroelectric liquid crystal composite material comprises an organic polymer and an antiferroelectric liquid crystal material, said organic polymer and said antiferroelectric liquid crystal material being in the dispersed state;

• said antiferroelectric liquid crystal material is represented by the following formula (I)
• R--X.sup.1 --(A.sup.1 --X.sup.2).sub.l --(A.sup.2 --X.sup.3).sub.m --(A.sup.3 --X.sup.4).sub.n --Q.sup.1 --C*H(Q.sup.2)--Q.sup.3(I)
• wherein R is an alkyl group of 4 to 20 carbon atoms or a polyfluoroalkyl group of 4 to 20 carbon atoms, a part of --CH.sub.2 -- group or a --CF.sub.2 -- group present in said alkyl or polyfluoroalkyl group can be substituted with at least one group selected from --O--, --S--, --CO--, --CHX-- (wherein X is a halogen atom), --O--CO--, --O--COO--, --COO-- and --CH.dbd.CH-- so that hetero atoms are not bonded to each other, said alkyl or polyfluoroalkyl group may have optical activity;
• X.sup.1 is a group selected form --COO--, --O--CO-- and --O--, or a single bond;
• X.sup.2 and X.sup.3 are each independently a group selected from --COO--, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O-- and --OCH.sub.2 --;
• X.sup.4 is a group selected from --COO--, --CO--, --O-- and --O--CO--;
• A.sup.1, A.sup.2 and A.sup.3 are each independently a group selected from divalent groups represented by the following formulas:
• ##STR18## Q.sup.1 is --(CH.sub.2).sub.q -- wherein q is an integer of 0 to 6;
• Q.sup.2 and Q.sup.3 are each independently an alkyl group of 1 to 10 carbon atoms or a halogen atom, Q.sup.2 and Q.sup.3 are different from each other, both of Q.sup.2 and Q.sup.3 are not halogen atoms, and a part of --CH.sub.2 -- group or --CF.sub.2 -- group present in Q.sup.1, Q.sup.2 and Q.sup.3 may be substituted with at least one group selected from --O--, --S--, --CO--, --CHX-- (wherein X is a halogen atom), --CHCN--, --O--CO--, --O--COO--, --COO-- and --CH.dbd.CH-- so that hetero atoms are not bonded to each other;
• l, m and n each independently represent 0 or 1;
• and
• a difference in a refractive index between the organic polymer and the antiferroelectric liquid crystal material is in the range of 0 to .+-.0.15 in a transparent state of said composite material.