Illuminating lens, lighting device, surface light source, and liquid-crystal display apparatus

An illuminating lens for spreading light emitted from a light source so that a surface to be irradiated is irradiated with the spread light, the lens comprising:

• a main body to be disposed over the light source;
• and
• a ring portion joined to a periphery of the main body so as to be located around the light source,
• wherein the main body includes:
• a light entrance surface through which the light emitted from the light source enters the lens;
• and a light exit surface through which the light that has entered the lens exits the lens,
• the light exit surface has a first light exit surface and a second light exit surface, the first light exit surface being recessed toward a point on an optical axis of the illuminating lens, and the second light exit surface extending outwardly from a periphery of the first light exit surface to form a convex surface,
• the first light exit surface has a transmissive region located in the center of the first light exit surface and a total reflection region located around the transmissive region, the transmissive region being capable of transmitting light that has been emitted from a starting point at a relatively small angle with respect to the optical axis and then reached the first light exit surface, when a position of the light source on the optical axis is defined as the starting point, and the total reflection region being capable of totally reflecting light that has been emitted from the starting point at a relatively large angle with respect to the optical axis and then reached the first light exit surface,
• the second light exit surface has a shape capable of transmitting approximately the entire amount of light that has been emitted from the starting point and then directly reached the second light exit surface, and of totally reflecting approximately the entire amount of the light that has been totally reflected at the total reflection region and then reached the second light exit surface,
• the ring portion has a front surface extending outwardly from a periphery of the light exit surface, a back surface extending outwardly from a periphery of the light entrance surface, and an end surface connecting an outer edge of the front surface and an outer edge of the back surface,
• the back surface has a shape such that light that has been emitted from the light source, totally reflected repeatedly at the light exit surface, and then entered the ring portion is guided to the end surface by total reflection, and
• the end surface has a shape such that light that has been totally reflected at the back surface and reached the end surface is refracted to reach the surface to be irradiated.