LIGHT DIFFUSION PLATE AND BACKLIGHT DEVICE

摘要

A light diffusion plate (30) includes a rectangular body portion (31) containing a valid portion serving as an effective plane of a backlight device (1) and a peripheral portion (32) formed at the periphery of the body portion (31) and serving as a non-effective plane of the backlight device (1). The body portion (31) has a diagonal line having a length equal to or longer than 500 mm. In the peripheral portion (32), a rectangular boundary line (30X) is formed so as to adjust the position of the light diffusion plate (30) with respect to a case (20). On the case (20), arrows (21X, 21Y) are formed to be matched with two sides (A, B) of one apex angle of the rectangular boundary line (30X).