Area light source device and liquid crystal display device

An area light source device comprising:

• a light source;
• a light guide plate,
• wherein the light guide plate is arranged at a position facing the light source, for introducing light of the light source from a light incident end face and exiting the light to the outside from a light exit surface;
• wherein the light guide plate comprises:
• a light guide substrate made of translucent material,
• a low refraction index layer having a lower index of refraction than the light guide substrate,
• wherein the low refraction index layer being closely attached to a surface on a side opposite to the light exit surface of the light guide substrate,
• a high refraction index layer having a higher index of refraction than the low refraction index layer,
• wherein the high refraction index layer being closely attached to a surface on a side opposite to the light exit surface of the low refraction index layer, and
• a reflection layer closely attached to a surface on a side opposite to the light exit surface of the high refraction index layer;
• wherein the light guide substrate comprises:
• a light introducing section arranged at a position facing the light source, and
• a light guide plate main body comprising the light exit surface for exiting the light introduced from the light introducing section to the outside integrally configured;
• a directivity conversion unit for enclosing the light entered into the light introducing section from the light incident end face in the light guide substrate,
• wherein the directivity conversion unit is arranged on a surface on the light exit side of the light introducing section or a surface on the opposite side;
• a light control pattern for reflecting the light in the light guide plate main body and leaking the light to the low refraction index layer side from the surface on the side opposite to the light exit surface of the light guide plate main body,
• wherein the light control pattern is formed on the light exit surface side of the light guide plate main body;
• and
• a light exit unit for reflecting the light leaked to the high refraction index layer and exiting the light from the light exit surface,
• wherein the light exit unit is formed on an interface of the high refraction index layer and the reflection layer or on a surface on the side opposite to the interface of the reflection layer.