A robot arm assembly includes a supporting arm, first and second mechanical arms, a first driving member, a second driving member, a first transmission mechanism between the first mechanical arm and the first driving member, and a second transmission mechanism between the second mechanical arm and the second driving member. The liquid crystal panel 11 has a liquid crystal layer 50 between a pair of glass substrates 31 and 41. Each of the first and second inside rings has the same number of circumferentially disposed holding slots as the stator slots to hold one of each pair of straight portions.