Abstract: An optical composite substrate is disclosed and includes a substrate, a first coating layer, and a second coating layer. The substrate has a first surface and a second surface opposite to the first surface. The first coating layer is formed on the first surface; the second coating layer is formed on the second surface. Therein, the stiffness of the first coating layer is substantially equal to the stiffness of the second coating layer. When a thermal deformation of the optical composite substrate is induced by a change in temperature, the whole deformation of the optical composite substrate is reduced by the constraint effect on the substrate by the first coating layer and the second coating layer. Therefore, the optical composite substrate can keep its flatness within a certain range, so as to solve the problem in the prior art that an optical film sheet easily warps when heated.

Abstract: A hybrid optical film includes a first layer, a second layer, and a plurality of diffusion structures. The first layer has a light entering face and a first refractive index. The second layer has a second refractive index and is disposed on a face of the first layer opposite to the light entering face, wherein the second refractive index is lower than the first refractive index. The plurality of diffusion structures are disposed on the interface of the first layer and the second layer. The diffusion structure has a third refractive index, wherein the third refractive index is between the first refractive index and the second refractive index and is selectively equal to the first refractive index and the second refractive index.