Abstract: A back light module is provided. The back light module includes a first light emitting module, a second light emitting module and an attenuator. The first light emitting module has a light output surface. The second light emitting module is disposed on one side of the first light emitting module opposite to the light output surface. The attenuator is disposed between the first light emitting module and the second light emitting module, and includes a first polarizer having a first absorption axis.

Abstract: An optical multi-layer structure for a flat panel display device is provided. The optical multi-layer structure includes a first optical layer, a second optical layer, a surface strengthening layer, and an adhesive layer. The first optical layer converts a light into a first polarized light. The second optical layer is disposed on the first optical layer and converts the first polarized light into a second polarized light. The surface strengthening layer is disposed on the second optical layer. The adhesive layer is disposed between the second optical layer and the surface strengthening layer, and is in direct contact with the second optical layer and the surface strengthening layer. A flat panel display device having the optical multi-layer structure is also disclosed.