A heat sinking element and a method of treating a heat sinking element are provided. The heat sinking element includes a metal body. The metal body is mainly composed of aluminum. A surface of the metal body has a plurality of micron-nano holes and a diameter of the micron-nano hole is smaller than 300 nano meter. The method of treating a heat sinking element includes performing an oxidation process and an etching process so as to form a plurality of micron-nano holes.

The present invention provides a composite optical film including a brightness enhancement film, a high refractive-index layer, and an intermediate layer. The brightness enhancement film has a plurality of brightness enhancement structure parallel to each other, and a top surface and a bottom surface opposite to each other. The brightness structure is disposed on the top surface. The high refractive-index layer is disposed on the bottom surface, and includes a film and a plurality of inorganic nano-particle disposed within the film. The intermediate layer is disposed between the brightness enhancement film and the high refractive-index layer.