There are many screen making methods. Currently, the most commonly used plate making method mainly uses the photosensitive plate making method. It uses the chemical change of the photoresist, that is, the light-receiving part of the photoresist is crosslinked and hardened and is firmly combined with the screen to form a plate film. The unphotosensitive part is washed and developed by water or other developing solution to form through holes to form a screen. Printing plate.
First, clean both sides of the stretched blank screen, then brush the prepared photosensitive glue evenly on both sides of the screen. Place the screen in an oven at 60-65 ° C, bake for 10 minutes, and then wipe the photosensitive glue. Brush evenly, dry it in the oven, and then take it out for exposure. If the drying time is too long or too high, it will cause difficulty in development and off the screen. Otherwise, the plate film is not strong and the exposure is not transparent. Before the exposure, the printed film or sulfuric acid paper should be inspected once to see whether the edges of the base plate are smooth, whether the writing is clear, and whether there are scratches, dew points, etc., and then use a plate exposure machine to perform exposure.
When placing film, it should generally be placed in the center of the screen, or it can be placed according to its actual printing requirements. In order to achieve a good plate edge effect, the angle is generally 30 degrees with the mesh. The straight stretch net should be completely perpendicular to the screen frame. It must avoid the holes and bubbles on the screen. Attention must be paid to the front and back of the manuscript film to prevent the screen from being reversed. The most important link in the exposure process is to closely attach the screen to the base plate to prevent the sun-dried pictures from becoming false or even scrapped.
When exposing, the distance of the lamp should be based on the diagonal of the actual drawing of the plate (for reference), and the time is determined by the fineness of the exposed plate. The plate exposure machine (single lamp 2000W) should generally be in the range of 80 seconds to 100 seconds. Wipe the see-through glass carefully. Long exposure time is difficult to develop, short time version of the film is not strong, easy to fall off during development and easy to form jagged edges.
Development: immerse the exposed screen in water for one or two minutes (30 ° C-40 ° C warm water is more effective and can shorten the development time). After shaking the screen plate and other non-photosensitive parts to fully absorb water and swell, Rinse with strong water, and wait for the pictures and texts to be displayed. The development should be completed in a short time. Regardless of the screen, the unsensitized part must be completely washed. The control principle of the degree of development is: on the premise of transparence and development, the shorter the time, the better. If the time is too long, the wet expansion of the film layer is severe, which affects the sharpness of the image, and is easy to lose, and the plate film is easy to rot. Residual glue is a very thin residual film of photosensitive adhesive. It is easy to appear highly transparent in the details of the image, and it is difficult to distinguish. It is often mistakenly considered transparent, and the ink cannot pass through during printing.
After development, take the screen out of the screen and absorb the running water from the screen, and dry it out in an oven at 60-65 ° C. If there are holes or parts that should not be opened on the plate, you can use the screen sealant for proper repair (the drying time should not be too long, otherwise it will cause difficulty in removing the film when the screen is reused).
