PURPOSE: To reduce a change with the passage of time and to record information with relatively low energy, by making use of the phenomenon that a metallic hydride as the material of a thin film releases hydrogen and changes the property when irradiated with energy beams.
CONSTITUTION: A thin film 2 of a hydride MHx (M is a metal) having about 100W1μm thickness is formed on a substrate 1 by carrying out sputtering or vapor deposition using the metal M in an atmosphere contg. hydrogen. The surface of the thin hydride film is coated with a protective film 3 of plastics such as polyethylene. When the hydride film is heated with energy beams such as laser beams, hydrogen is released at a relatively low temp. such as ≤ several 100°C, and simultaneously the hydride changes the property, so the volume of the film is changed. By the released hydrogen and the change of the property of the film, the protective film 3 is protruded to form a protruded part 4. The part 4 corresponds to a piece of information.
TERAO MOTOYASU
TSUNODA YOSHITO
