Styryl compounds

A styryl compound of the formula (I) ##STR18## in which X is .dbd.CH.sub.2, --O--, --S-- or the grouping .dbd.NR.sub.3 wherein R.sub.3 is hydrogen or an alkyl group having 1 to 4 carbon atoms,

• Z is the --O-- or --S-- atom,
• A is a straight-chain or branched-chain alkylene group having 2 to 4 carbon atoms,
• R.sub.1 is lower alkyl unsubstituted or substituted by hydroxy, cyano, phenyl or phenoxy,
• R.sub.2 is hydrogen, C.sub.1 -C.sub.4 -alkyl unsubstituted or substituted by OH, CN, halogen or C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -alkoxy unsubstituted or substituted by OH, CN, halogen, lower alkyl or lower alkoxy, halogen or phenoxy unsubstituted or substituted by OH, CN, halogen, lower alkyl or lower alkoxy, and
• Y is --CN, --COOR.sub.4, --SO.sub.2 R.sub.4 or CONR.sub.3 R.sub.5, wherein R.sub.3 has the meaning given above, R.sub.4 is C.sub.1 -C.sub.4 -alkyl group or the phenyl group, R.sub.5 is hydrogen or is the same as R.sub.4,
• and the benzene rings B, C and D can be further substituted by alkyl of 1 to 4 carbon atoms, alkoxy or 1 to 4 carbon atoms, halogen, --CN, --NO.sub.2, --SO.sub.2 -alkyl, --SO.sub.2 NH.sub.2, --SO.sub.2 NH-alkyl (C.sub.1 -C.sub.4), --SO.sub.2 N (alkyl-C.sub.1 -C.sub.4).sub.2 or --COO-alkyl-(C.sub.1 -C.sub.4).