Assistant light source and front-light

摘要

To provide an assistant light source and a front-light emitting light to the light guide plate efficiently. A sectional shape of prism 14 a in the center of light stick is isosceles triangle having a tip angle (T°) of 100° and a tilt angle (a₁) of 40°. The depth of the prism 14 a is D₁ mum. A sectional shape of prism 14 b in a ¼ position from an end of light stick is triangle having a tip angle (T°) of 100° and a tilt angle (a₂) of 34.8°. The depth of the prism 14 b is D₂ mum. A sectional shape of prism 14 c in an end of light stick is triangle having a tip angle (T°) of 100° and a tilt angle (a₃) of 24.05°. The depth of the prism 14 c is D₃ mum.