the digital data is as described in the above the 7 bit digital data 7 bit digital data r 7 bit digital data g and 7 bit digital data b produced by the digital data converting circuit 114 are inputted to the time division gray scale data signal generating circuit 113 the time division gray scale data signal generating circuit 113 is a circuit for converting 7 bit digital data into digital data for carrying out time division gray scale and for generating a timing pulse and the like necessary for carrying out time division gray scale display here the time division gray scale data signal generating circuit 113 comprises means for dividing one frame into seven subframes corresponding to the 7 bit gray scales means for selecting an address time period and a sustain time period for each of the seven subframes and means for setting the sustain time periods such that ts 1 ts 2 ts 3 ts 4 tss ts 6 ts 7 1 1 2 1 4 1 8 1 16 1 32 1 64 it is to be noted that in case n 1 bit digital data is inputted to the time division gray scale data signal generating circuit 113 the time division gray scale data signal generating circuit 113 comprises means for dividing one.