1. Back exposure. The support film of the photosensitive resin plate upwards and the protective film downwards are laid flat in the exposure drawer to receive exposure. Ultraviolet light penetrates the support film to cure the photosensitive adhesive layer. In order to establish a stable base, the washing depth can also be controlled, and the bonding force between the support film and the photosensitive resin layer can be strengthened. The back exposure time is determined according to the required substrate thickness.
2.The main exposure. Also known as front exposure, the photosensitive resin plate supporting film faces down and the protective film faces up. Tiled in the exposure drawer. Tear off the protective film once in a row, and then stick the film surface on the photosensitive resin plate. Place the vacuum film flat on the film (non-medicated film surface) and apply a vacuum to make the film closely adhere to the photosensitive resin layer. Ultraviolet rays pass through the vacuum film and the transparent part of the film to polymerize and cure the photosensitive part of the plate. The length of the main exposure time is determined by the plate model and the intensity of the light source. If the exposure time is too short, the slope of the picture and text will be too straight, the lines will be bent, and the small characters and dots will be washed away. On the contrary, the exposure time will be too long and the handwriting will be blurred. If there are big, small, thick and thin lines on the same printing plate. Cover with black film depending on the situation and expose separately. Small parts will not be lost due to washing to ensure the quality of the printing plate. The main points of the main exposure operation are shown in Table 1.
3. rinse. The non-sensitized part is washed and dissolved, and the photopolymerized relief is retained. The length of the plate-washing time is determined by the thickness of the printing plate and the depth of the print. If the plate-washing time is too short, non-sensitized resin will be left on the plate and affect the plate-making depth. If the plate-washing time is too long, the plate will swell, causing deformation or fine parts Fall off.
4. drying. Remove the washing solvent to restore the original size and thickness of the printing plate. The baking temperature is between 50-60℃. The baking time is determined by the thickness of the plate and the length of the washing time, generally two hours for thick plates and one hour for thin plates. If the baking time is too long and the baking temperature is too high, the printing plate will become brittle and affect the printing life. If the baking temperature is too low, the drying time will be prolonged. If the baking time is too short, the plate will be rotten during printing.
5. Post-processing. That is, debonding and post-exposure. The photosensitive resin is completely hardened (polymerized) to reach the required hardness index, and the viscosity of the printing plate is eliminated to facilitate the transfer of ink. The post-treatment time is obtained from the test, and the purpose is not to crack or stick.