Patent ID: 7262916

Claim:
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.