Liquid crystal compounds

A compound of formula (I)

• wherein
• SP1 and SP2 each independently from each other represents a spacer group of the formula —(CH2)p-,
• wherein p is an integer of 0 to 18,
• with the proviso that p is 0 only when X1 and X2 are each a single bond, and wherein, when p is 1 to 18, up to four —CH2— groups of said —(CH2)p- group are optionally replaced by groups selected from the group consisting of —CH═CH—, —O—, —S—, —NR′—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— and —OCONR′, with the further proviso that the spacer group does not contain two adjacent heteroatoms;
• X1 and X2 each independently from each other is selected from the group consisting of —O—, —S—, —NR′—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO—, —OCONR′ and a single bond;
• in which
• R′ is selected from the group consisting of hydrogen, a C1-C18 alkyl group;
• BP1 and BP2 each independently from each other represents a polymerizable group,
• R1, R2, R3 and R4 each independently from each other are selected from the group consisting of hydrogen, —OR5, —COOR5, —OCOR5, —CONR5, —OCOOR5, —OCONR5 and a C1-C18 alkyl group, wherein
• R5 is selected from the group consisting of a C1-C18 alkyl group, an aryl group, an aralkyl group and an alkylaryl group.