To provide a backlight system which can evenly illuminate information display element of portable object, such as a wrist watch, from behind.

The backlight system 1 contains a lightguide plate 7 equipped with a light reflector 6 on its backside, optical diffusion film 9 on its surface, a rectifying film 11 and a visible light source 2. The visible light source 2 provides outside edge of the lightguide plate 7 with light ray, allowing the light ray to transparent between both sides of the lightguide plate 7. Layers of the optical diffusion film 9, etc. have a zone 10' whose opacity declines from the limitation 25 located near the borderline of the lightguide plate 7, which receives light from the light source, to attenuate light intensity throughout the zone 10'. This opacity declined zone 10' is a metallic coating, comprising translucent metallic coatings of various thicknesses deposited on the optical diffusion film and porous metallic coatings or a plurality of metal dots, wherein by having the light partially reflected and then returned to the lightguide plate 7, loss in useful photons reduced.