A compound having a good durability against light and capable of producing desired liquid crystallinity after polymerization, and a polymerizable liquid crystal composition containing such a compound, are provided. Further, an optical element having a good durability against light, and an optical information writing/reading device employing such an element, are provided.
A compound represented by CH 2 =CR 1 -COO-R 2 -Cy-Ph-R 3 -OCO-CR 4 =CH 2 . R 1 and R 4 are each preferably a hydrogen atom. R 3 is preferably a C 1-6 alkylene group wherein an oxygen atom is present or not present at an end of the group to be bonded to a cyclic group, and wherein some or all of hydrogen atoms bonded to carbon atoms in the group may be substituted by fluorine atoms; or an alkylene group wherein an oxygen atom is present at an end of the group to be bonded to a cyclic group. A diffraction grating 2 produced by employing this liquid crystal compound has a good durability against light, and accordingly, it is possible to constitute an optical information writing/reading device suitable for large capacity recording by employing a blue laser as a light source 1.