PRISM SHEET AND BACK LIGHT

摘要

PROBLEM TO BE SOLVED: To provide a prism sheet and a back light in which loss of light in the prism sheet itself is decreased to improve its optical efficiency and high luminance is obtained as a liquid crystal display device. SOLUTION: The prism sheet has a many lines of prisms formed in parallel made of active ray-hardening resin on one surface of a transparent substrate. The pitch of the prism lines is 30 to 500 μm. When almost parallel rays are made to enter from the flat face opposing the prism face of the prism sheet along the direction having a specified angle from the normal line of the flat face to the parallel direction to the prism lines, the quantity of light transmitting the prism sheet and exiting from the prism face is <=15% of the quantity of the incident light.