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 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,
• wherein 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,
• 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, and
• 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 reached the second light exit surface,
• wherein when a point of intersection of the first light exit surface and the optical axis is denoted as C, a point on a boundary between the transmissive region and the total reflection region is denoted as P, a distance between the point C and the starting point is denoted as d, an angle between the optical axis and a line connecting the point P and the starting point is denoted as θp, and a length of a straight line connecting the point C and the point P is denoted as a, the following inequality is satisfied:
• 1.10<a/(d×tan θp)<1.30.

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 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,
• wherein 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,
• the first light exit surface has a transmissive region located in the center of the first light exit surface and a specular 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 specular reflection region being covered with a reflective layer capable of specularly 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, and
• 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 reached the second light exit surface.