Although CTP has been used for a long time and has begun to spread in China, some printing companies are still using PS plates. PS plate is still the printing plate with the largest proportion of domestic use at this stage. Let me introduce you to the two important conditions that determine the quality of PS plates: the quality of the original plate and the quality of the plate. In offset printing, plate making is the guarantee of printing quality. Only by guaranteeing the quality of PS plate making can the quality of printed matter be ensured. So, what are the main points of a good quality printing plate? Let us explain in detail from the two aspects of original plate quality and plate quality. 1. Original quality The original version refers to the film or sulfuric acid paper output from the pre-press. Its quality directly affects the plate-making effect of the PS version. There are two important indicators of original quality: (1) Dot density When printing a positive image, the dots must have sufficient density. The density of a single dot is above 3.0, the solid density is above 3.5, and the transmission density of the blank area of ​​the film should be less than 0.05. (2) Bright dots The density of the dot center and the density of the edge are the same, so that the tolerance of the exposure time can be expanded. The original version is clean and free of dirt. It is best to use a complete film without a knife edge and collage tape to ensure that the film is tightly combined with the PS version to avoid virtual dots caused by light scattering. 2. Plate quality (1) Edition base The base should be clean, uniform in thickness and uniform in distribution, with moderate thickness and moderate depth. The photosensitive liquid is coated evenly, without bubbles and scratches. Generally, the average depth of sand mesh (RZ) is 5 to 7.5 μm, and the average roughness (Ra) is about 0.6 μm. (2) Photosensitive adhesive layer The photosensitive coating is uniform and the thickness is moderate, which completely covers the peaks of the sand mesh, but not too thick, which affects the resolution of the printing plate. Generally, the thickness of the coating layer of the PS plate is about 1.8 g / m2. MIANYANG BIGANT TECHNOLOGY CO LTD , https://www.bigantech.com