Edge light-type backlight device and light diffusion member

An edge light-type backlight device comprising:

• a light guide plate;
• a light source disposed at one end portion of the light guide plate;
• and
• a light diffusion sheet and a prism sheet successively disposed on a light-emitting surface of the light guide plate, wherein:
• the prism sheet has a refractive index of more than 1.60;
• a peak of an emitted light distribution on the light-emitting surface of the light diffusion sheet in a plane parallel to the one end portion of the light guide plate and orthogonal to the light-emitting surface is in angular ranges of 30 to 45° and −30 to −45° with respect to a normal direction of the light-emitting surface;
• and
• emitted light from the light-emitting surface of the light diffusion sheet is gradually decreased from the angular ranges of the peak of the emitted light distribution toward an emitting angle of −90° or 90° with respect to the normal direction.

A light diffusion member disposed on a light guide plate of an edge light-type backlight device including the light guide plate and a light source disposed at one end portion of the light guide plate, wherein:

• the light diffusion member includes a prism sheet and a light diffusion sheet;
• the prism sheet has a refractive index of more than 1.60;
• a peak of an emitted light distribution on the light-emitting surface of the light diffusion sheet in a plane parallel to the one end portion of the light guide plate and orthogonal to the light-emitting surface is in angular ranges of 30 to 45° and −30 to −45° with respect to a normal direction of the light-emitting surface;
• and
• emitted light from the light-emitting surface of the light diffusion sheet is gradually decreased from the angular ranges of the peak of the emitted light distribution toward an emitting angle of −90° or 90° with respect to the normal direction.