| 摘要 |
PROBLEM TO BE SOLVED: To obtain a diffusion plate which gives rise to great unsharpness with uniform brightness and can brighten a screen. SOLUTION: The diffusion surface is constituted by arranging a multiplicity of one or plural kinds of random pattern structures. The random pattern structures consist of plural micro-rectangular elements (E1 to E4) having four kinds of heights. The rectangular elements (E1 to E4) are irregularly arranged so as to constitute plural kinds of diffraction gratings varying in grating pitch. The top end faces of the respective rectangular elements (E1 to E4) constitute a projecting shape.
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