Figure 11 also shows the phosphor formation process by photolithographic method. Photosensitive phosphor paste is
made of photo resists in which phosphor particle of specified colors are evenly dispersed. The prepared paste is coated to
the entire surface of a rear substrate with barrier ribs. This substrate is then dried to evaporate the solvents in the paste at
100-120 'C. Any remaining paste on top of the barrier ribs does not cause any problems. Next, the dried film is exposed by
UV light through a photo mask. The exposure and development of this paste produces a phosphor paste layers for the three
primary colors. Finally, the substrate is fired to bum out all organic ingredients remaining in the phosphor paste layers and
ensure that the phosphor layers consist of only phosphor particles. The primary issue of using this method this method is on
the recycling of removed phosphor material. Figure 12 shows SEM images of phosphor layers made using screen printing
method and photolithographic method.