| 摘要 |
PROBLEM TO BE SOLVED: To make luminance in a normal direction high and to obtain a wide visual field range by making an angle formed by the ridge line direction of a prism column formed on one surface and the ridge line direction of the prism column formed on the other surface into a specified value. SOLUTION: On both surfaces of a transparent base material 2, many prism columns 2 and 3 whose cross section is triangular are parallelly and successively provided. They are formed so that the angle (prism cross angle) formed by the ridge line directions of the prism columns 2 and 3 has in the range of 5 deg.-60 deg.. The decline of the luminance becomes large in the case that the prism cross angle is less than 5 deg. and the visual field range in a vertical direction becomes narrow when it exceeds 60 deg.. The prism cross angle is preferably in the range of 10 deg.-50 deg. and is further preferably in the range of 15 deg.-40 deg.. Thus, directional emitted light emitted from a light transmission body is deflected to the normal direction by the prism column 2 in a horizontal direction, the distribution of the light in the horizontal direction is widened by the prism column 3, and the light dispersed in the vertical direction is converged to the normal direction, thereby the luminance is improved and the visual field range in the vertical direction is widened. |
