| 摘要 |
PROBLEM TO BE SOLVED: To make luminance in a normal direction relatively high and to obtain a wide visual field range by parallelly forming many prism columns and making the respective vertexes of the prism columns formed on one surface and the other surface have a specified angle. SOLUTION: On both surfaces of a transparent base material 2, many prism columns 2 and 3 whose section is triangular are parallelly and successively provided. The vertical angle of the prism column 2 is 50 deg.-75 deg. and thus, the direction of light is controlled to the vicinity of the normal direction. The vertical angle of the prism column 3 is in the range of 110 deg.-150 deg. and thus, the visual field range is widened while suppressing luminance decline in the normal direction. The vertical angle of the prism column 2 is preferably in the range of 55 deg.-70 deg. and the vertical angle of the prism column 3 is preferably in the range of 113 deg.-145 deg., further preferably in the range of 120 deg.-140 deg.. It is preferable to form them so as to make the ridge line directions of the prism columns 2 and 3 difference from each other and thus, the direction control and distribution control of light are performed between two directions and the balance of the luminance and the visual field range is improved.
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