Back cover network version of the seal at the bottom of the role, generally can be summarized as fill area, smooth out the ink layer, fixed hue, enhance the resistance of light and so on. Due to the effect of back cover, choice of screen production should be treated differently according to specific situation. When sealing the bottom to fill the area, the main function of the filled area is the impression of the key body and is a large area of the panel background, in order to prevent the base exposed the shape of the switching circuit is too thin, or develop the disadvantages of non-uniform background ink layer, should consider to choose at this time is a bit thick screen film layer; When the main function is to seal the bottom has been all the way on the back of the ink layer for a full flat and coverage, on the one hand, make the inky especially in front of the directly by the three color printing ink layer of color is more bright-coloured, accurate, on the other hand increases the ink layer thickness (especially the key body of ink layer thickness), reach the role of wear-resisting, blocking light, used as a secondary thickening of the screen should be adopted for thin film layer, and ink appropriate USES does not change other white or pale color ink layer hue. A thick screen of large amount of ink, ink solvent content in the corresponding increase in the number of large ink layer in the evaporation of the solvent is likely to make the printing ink layer cracks, outsmart oneself instead. Above is for back cover thickness selection screen. The choice of mode of plate making, we learned that it is not from the role of the back cover as demanding as text and line, therefore, are considered in the choice of mode of screen economic, convenient, its range is wide.