Backlight module and brightness enhancement film thereof
A backlight module includes a light source, a light guide disposed on one side of the light source, a reflector disposed under the light guide, a lower diffuser disposed on the light guide, and a brightness enhancement film, which is disposed on the lower diffuser and includes a main part and several prism structures disposed side by side on a main part plane of the main part. Each prism structure includes first to third triangular prisms. The second triangular prism is adjacent to one side of the first triangular prism, and an adjacent angle adjacent to a base angle of the first triangular prism is a right angle. The third triangular prism is adjacent to another side of the first triangular prism, and an adjacent angle adjacent to another base angle of the first triangular prism is a right angle.
1. A backlight module, comprising:
a light source;
a light guide disposed on one side of the light source;
a reflector disposed under the light guide;
a lower diffuser disposed on the light guide; and
a brightness enhancement film disposed on the lower diffuser, comprising:
a main part including a main part plane for receiving surface light guided by the light guide and diffused by the lower diffuser; and
a plurality of prism structures successively disposed side by side on the main part plane, each of the prism structures comprising:
a first triangular prism having a first plane, a second plane and a third plane, wherein the third plane overlaps with the main part plane, the third plane has a long side substantially parallel to and equal to one side of the main part plane, and the first plane and the second plane define a first angle;
a second triangular prism having a fourth plane, a fifth plane and a sixth plane, wherein the sixth plane overlaps with the main part plane, the sixth plane has a long side overlapping with the long side of the third plane, the fourth plane is perpendicular to the main part plane, and the fourth plane and the fifth plane define a second angle; and
a third triangular prism having a seventh plane, an eighth plane and a ninth plane, wherein the ninth plane overlaps with the main part plane, the ninth plane has a long side overlapping with another long side of the third plane, the seventh plane is perpendicular to the main part plane and faces the fourth plane, and the seventh plane and the eighth plane define a third angle;
wherein the first triangular prism, the second triangular prism, and the third triangular prism have different orientations;
wherein the second triangular prism of one of the prism structures is adjacent to the third triangular prism of an adjacent one of the prism structures, and the second triangular prism of the one prism structure and the third triangular prism of the adjacent one prism structure have different orientations.
2. The backlight module according to claim 1 , wherein the second triangular prism and the third triangular prism are symmetrical with respect to the first triangular prism, and the second angle equals the third angle.
3. The backlight module according to claim 2 , wherein each of the second angle and the third angle is 45 °.
4. The backlight module according to claim 1 , wherein the first angle is 90°.
5. The backlight module according to claim 4 , wherein the first triangular prism is an isosceles right triangular pillar.
6. The backlight module according to claim 1 , further comprising an upper diffuser disposed on the brightness enhancement film.
7. The backlight module according to claim 1 , further comprising a light source reflector disposed on another side of the light source.