Patent ID: 7349043

Claim:
A portable terminal device comprising: a planar light source, comprising: a backlight that emits light in a planar shape; a ray direction regulating element that regulates a direction of light made incident from the backlight and emits the light and in which a transparent area for transmitting light and an absorption area for absorbing light are formed alternately in a direction perpendicular to a light regulating direction thereof; and a transparent and scattering switching element that is switchable between a state in which light which is transmitted by the ray direction regulating element and made incident on said switching element is transmitted and a state in which the light is scattered; adjusting means for adjusting an amount of the backlight and the transparent and scattering states of the transparent and scattering switching element independently from each other; electric power accumulating means; residual amount detecting means for electric power accumulated in the electric power accumulating means; and control means that automatically changes an amount of light of the backlight and the transparent and scattering states of the transparent and scattering switching element on the basis of detected residual amount information.