| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface light source device and a transparent type display device, capable of obtaining an appropriately narrow view angle, preferable for personal use, with a relatively simple shaped columnar unit prism.SOLUTION: A surface light source device 100 includes a light guide member 10, two light source parts 20 disposed at light incident surfaces 10a, which are opposing side ends of the light guide member, and a prism sheet 30 having a prism surface 31p faced to a light guide member side. A plurality of columnar unit prisms 31 are disposed so as to, with their longitudinal directions orthogonal to a light guide direction Dg of the light guide member, collimate their disposing directions to the light guide direction, and neighbor each other. Each of the columnar unit prisms 31 has a cross-sectional shape of a symmetric pentagon, having a steep slope surface 31a at a bottom side and a gentle slope surface 31b, and has two peaks on the light distribution characteristic in the light guide direction. A transparent type display device 200 employs the surface light source device as a back light source. |
