In addition, the uneven surface structure needs to have an enough thickness to generate an uneven surface with sufficiently large unevenness. As described above, for example, the unevenness on the surface of the uneven surface structure may be controlled to be greater than 10 nm and smaller than twice the total thickness of the OLED film, for example, smaller than 0.5 microns.

In one embodiment, the vertical projections of the uneven surface structures or the porous structure in the preceding embodiments may be set to be in a grid shape, so that each OLED lighting element is surrounded by the uneven surface structure or the porous structure. This arrangement requires a simplest manufacturing process when the uneven surface structure or the porous structure is etched. In addition, the uneven surface structure or the porous structure may be connected with an external voltage source or float if the uneven surface structure or the porous structure is made of a conductive material. The whole uneven surface structure or porous structure is connected together in the grid shape, which can prevent electrostatic charges from being accumulated in a local region and facilitate the export of electrostatic charges accumulated in the display apparatus due to static electricity, or prevent the electrostatic charge from being accumulated in the local region.