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Label printing covers several major printing methods, in the plate making stage. Depending on the nature of the product, different printing methods are selected. For different printing methods, the platemaking process is also different. This article briefly introduces the flexible plate making process as an example.
The process of flexographic plate-making is as follows: manuscript-film (exposed film) -exposure-rinsing-drying-post-processing.
1. Original. The manuscript design suitable for flexible printing should have the following characteristics: many color numbers. However, there are few in mould labels; it is not required to reproduce particularly small details; the network cable is not too high, but it can obtain color printing effects; it can be used for packaging processing online.
2. Film (overcast). It meets the needs of plate making, with clear graphics and accurate size specifications; using frosted film, the density of the four corners of the film must be consistent; using the film orthography; using a transmission density meter to measure, the white density is less than 0.06;
3. Exposure includes back exposure and main exposure.
① Back exposure. The support film of the photosensitive resin plate faces upward and the protective film faces down in the exposure drawer to receive exposure. Ultraviolet light passes through the support film to cure the photosensitive adhesive layer. In order to establish a stable base, the depth of the washing plate can also be controlled, and the binding force between the supporting film and the photosensitive resin layer can be strengthened. The back exposure time is determined by the required substrate thickness.
② The main exposure. Also known as front exposure, the support plate of the photosensitive resin plate faces down and the protective film faces up. Tile in the exposure drawer. Tear off the protective film one at a time, and then affix the film film surface to the photosensitive resin plate. Cover the vacuum film flat female 1 with high yield * female A inspection method cover the film (the non-medicine film is evacuated to make the film and the photosensitive resin layer adhere tightly. Ultraviolet light passes through the vacuum film and the film transparent part to make the plate light sensitive Partial polymerization curing. The length of the main exposure time is determined by the version of the plate and the intensity of the light source. If the exposure time is too short, the slope of the graphic will be too straight, the lines will be bent, and the small characters and small dots will be washed away. The handwriting is blurred. If there are large, small, thick, and thin lines on the same printing plate. Depending on the situation, a black film can be used to cover the exposure. Small portions will not be lost due to processing to ensure the quality of the printing plate.
4. rinse. Wash and dissolve the non-photosensitive parts to retain the photopolymerized relief. 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, unsensitized 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 the fine parts to deform or Fall off.
5. drying. Remove the plate washing solvent to restore the plate to its original size and thickness. The baking temperature is between 50-60 ° C. The baking time is determined by the thickness of the plate and the length of the plate washing time. Generally, the thick plate is two hours and the thin plate is one hour. The baking time is too long, and the baking temperature is too high, which will make the printing plate 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 phenomenon of rotten printing will occur during printing.
6. Post-processing. Detackification and post-exposure. The photosensitive resin is completely hardened (polymerized) to achieve the desired hardness index, and the viscosity of the printing plate is eliminated to facilitate ink transfer. The post-treatment time is obtained by testing, and the purpose is not to crack or stick.