| CPC G02B 6/0051 (2013.01) [G02B 6/0053 (2013.01); G02B 6/0088 (2013.01)] | 20 Claims |

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1. A backlight module, comprising:
a back plate;
a light source disposed on the back plate; and
a first optical film disposed on the back plate, wherein the first optical film includes a first upper surface and a first lower surface, and the first upper surface is farther away from the back plate than the first lower surface, and has a first prism structure,
wherein, at a first angle, a second angle and a third angle, the backlight module respectively has a first brightness value, a second brightness value and a third brightness value, which satisfy:
|[(A/C)−(B/C)]×100%|≥10%,
where A represents the first brightness value, B represents the second brightness value, C represents the third brightness value, the third brightness value is a maximum brightness value of the backlight module, and the first angle, the second angle and the third angle are different from each other.
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