LIGHT GUIDE PLATE USING DIFFRACTION GRATING, AND DIRECT BACKLIGHT DEVICE FOR LIQUID CRYSTAL TELEVISION

PROBLEM TO BE SOLVED: To provide a light guide plate, with which, efficient whitening is achieved by improving planar light emission efficiency and uniform light emitting property through enhancement and increase in functions of the light guide plate and by using a point light source LED group and diffusing light emitted from it, number of components, such as, many diffusion plates, diffusion sheets (films) and prism sheets which amplify Fresnel loss, an interference plate for reusing effective S-wave and P-wave, and a diffusion lens, can be reduced, and energy saving, cost reduction and thinning of a liquid crystal television can be achieved, and to provide a backlight device for a liquid crystal television using the same.SOLUTION: The backlight device is arranged right beneath a liquid crystal panel 5 for a liquid crystal television, includes a light guide plate formed of a pair of transparent bodies arranged in a lamination form with each other, and is structured of an upper light guide plate 1 and lower light guide plate 2 for forming the light guide plate, and an LED substrate 9 for a light source. Surface relief diffraction gratings 3, 4 are formed on emission surfaces of the respective transparent bodies. Anamorphic lens arrays 11, 12 are integrally arranged on the respective incident surface sides.