The indirect method of photosensitive plate making is mainly used in silk printing. It uses the chemical change of the photosensitive paste, that is, the photosensitive paste produces cross-linking hardening locally and solidifies and separates with the screen to form a film, and the non-photosensitive part develops with water or other developing solution to form a through hole to make a screen printing plate.
First of all, the screen matching the photo should be wiped, cleaned with high efficiency, rinsed repeatedly with water, and dried to be used. Then, the distributing paste is brushed on the screen evenly, and the screen plate is placed in the oven at 60-65 C for 10-13 minutes, then the paste is brushed and painted equally. After drying in the oven, the paste is taken out to be exposed. If the drying time is too long or too high, it will be difficult to develop and remove the screen. On the contrary, the film is not firm and the exposure is not transparent.
Before exposure, we should check the bottom plate to see if the edge of the bottom plate can be lubricated, whether the handwriting can be distinguished, whether there are scratches, dew points and other phenomena, and then stop the exposure with the plate dryer. When placing a photographic plate, it should be placed in the central part of the net, or according to its own practical printing request. In the process of exposure, the most important step is to make the screen and the bottom plate adhere closely, so as to avoid the falseness of the sunburnt pictures and even scrap them.
Developing: It is better to immerse the exposed screen in water for one or two minutes (30-40 C warm water can shorten the developing time), shake the screen and other non-sensitive parts to absorb enough water to swell, then rinse with strong water, and so on. The developing should be completed in a short time. No matter what kind of screen version, it is necessary to wash the parts that are not sensitive to light completely.
The control criterion of development level is that the shorter the time, the better under the premise of development and development. Over time, the wet shrinkage of the film is serious, which affects the clarity of the image, and is easy to lose, and the film rots easily; over time, the development is not complete will leave a mat (i.e. residual glue) to form a scrap version. Residual glue is a very thin residual film of photosensitive glue. It is easy to show high transparency in image details and difficult to distinguish. It is often mistaken for transparency, but ink cannot pass through when printing with dry glue.
2. Because of the existence of static electricity, the consumption difficulties caused by static electricity in printing are as follows:
1. After screen printing, the ink on the screen is pulled up in a fluffy shape along with the screen plate. The phenomenon that the "flying wool" ink filament has just broken off after the workpiece is taken out.
2. When overprinting, the edges of the former and the latter inks squeeze out each other, so that the ink can not be printed between the two inks.
3. In screen printing, the workpiece is glued to the screen, especially to the screen position where the scraper moves to the end.
4. Printing materials can not be separated from each other
Because of the existence of static electricity in screen printing, many quality problems can be formed, so that printing can not continue, then how to prevent and eliminate static electricity in screen printing?
1. The workpiece itself is electrified. At this time, the electrostatic device can be used to stop the electrostatic disposal of its appearance before silk printing. The method is very simple; it can eliminate the static electricity on the surface of the workpiece by using the equipment except static electricity, and it can be printed after disposal.
2. Screen printing plastic workpiece with static electricity. Antistatic agents can be added to the plastics formulation beforehand, which requires the supplier of consumable plastics raw materials to complete.
3. An antistatic coating can also be added to the surface of the workpiece with static electricity to eliminate static electricity.
4. Reasonable use of ink solvent. Even though the ink solvent mixing performance is good, the solvent with good conductivity distributes the ink viscosity.
5. Grounding of workpiece is added to screen printing equipment to release its charge and eliminate static electricity.
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