| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical sheet excellent in contrast and a display device having the optical sheet. SOLUTION: The optical sheet is placed in an observer's side of an image light source 2 and has a plurality of layers that control the light from the image light source to exit to the observer's side. At least one layer in the plurality of layers is an optical functional sheet layer 11 comprising: prism portions 12, 12, ..., arranged along the sheet face as transmissive for light, each cross-sectional feature of which in the thickness direction is a trapezoid having a short upper bottom in one sheet face side and a long lower bottom in the other sheet face side; and light-absorbing portions 13, 13, ..., arranged as absorptive for light between the prism portions, each cross-sectional form of which in the thickness direction has a side line extending in the sheet thickness direction to have an inclinationθ<SB>h</SB>with respect to the normal line of the sheet surface. The prism portion is made of a material having a refractive index of N<SB>p</SB>, satisfying z≥x/(tan(sin<SP>-1</SP>(N<SB>p</SB>×2<SP>(1/2)</SP>)<SP>-1</SP>)-tanθ<SB>h</SB>), wherein x represents the length of the short upper bottom and z represents the distance of the light-absorbing portion in the direction of the normal line of the sheet surface. COPYRIGHT: (C)2009,JPO&INPIT
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