a wave height of 10v was impressed as a result change in the intensity of transmitted light was observed the response time was sought from the change in the intensity of transmitted light at that time to give 34 u03bcsec at 25 u00b0 c as described above it was seen that when a compound of the present invention was added to a compound or a composition having sc phase exhibiting no ferro electricity a ferroelectric liquid crystal composition exhibiting very high speed response properties was obtained to the liquid crystal composition a of example 5 was added the following compound as a compound of the present invention no 1 in table 1 in an amount of 20 by weight str34 as a result sc phase exhibiting ferroelectricity appeared in a temperature range of 5 u00b0 c to 45 u00b0 c this composition had a spontaneous polarization at 25 u00b0 c of 11 1 nc cm 2 and a tilt angle of 13 u00b0 this composition was filled in a cell the same as in example 5 and placed between two crossed polarizers and a square wave having a wave height of 10v was impressed as a result change in the intensity of transmitted light was observed the response time was light to give 43 u03bcsec at 25 u00b0 c as described above it is seen that when the compound of the present invention is used a ferroelectric liquid crystal composition exhibiting very high speed response properties is obtained to the liquid crystal composition a of example 5 was added the following compound as a compound of the present invention no 11 in table 1 in an amount of 20 by weight str35 as a result sc phase appeared in a.