PURPOSE: To enable writing and erasing without any trouble and to enable displaying with good contrast by providing conductor layers contg. oxygen atoms on plural pieces of horizontal electrodes for thermal writing or erasing made of thin metallic films thereby performing orientation uniformly over the entire surface.

CONSTITUTION: The 1st layer, which is plural pieces of horizontal electrodes 11(5) playing the role of a heater, is provided on the inside wall surface of a back substrate 10(4). The 2nd layer 12 of indium oxide or tin oxide is superposed thereon and an orientation layer 6 formed of a silane coupling agent is stuck thereon. The layer 6 sticks chemically and securely on the electrodes 5(11) by the effect of the oxygen in tin oxide or indium oxide. Since tin oxide and indium oxide are conductors, no charge-up arises; therefore, not only the orientation is uniform but also the writing and erasing of signals are accomplished with good contrast without any trouble.