Production and printing technology of screen printing

There are many screen-making methods, each with its own advantages and disadvantages. At present, our plate-making method mainly adopts indirect photosensitive plate-making method. It uses the chemical change of the photosensitive adhesive, that is, the photosensitive part of the photosensitive adhesive is crosslinked and hardened and firmly combined with the screen to form a plate film, and the unexposed part is washed and developed with water or other developers to form a through hole to make a screen printing plate.

First of all, you should choose a screen that matches the photo board, clean it efficiently, rinse it repeatedly with water and dry it for later use. Then brush the prepared photosensitive paste evenly on the screen, bake the screen in an oven at 60-65℃ for 10- 13 minutes, then brush the photosensitive paste evenly on the screen, and take it out for exposure after drying in the oven. If the drying time is too long or too high, it is difficult to develop and release the screen. Otherwise, the film is not firm and the exposure is not transparent.

Check the bottom plate before exposure to see whether the edge of the bottom plate is smooth, whether the handwriting is clear, whether there are scratches, dew point and other phenomena, and then expose it with a printer. When placing photo plates, they should generally be placed in the center of the screen, or they can be placed according to their actual printing requirements. In order to achieve a good plate-making edge effect, it is generally at an angle of 30 degrees with the screen wire, and the straight screen should be completely perpendicular to the screen frame, and it is also necessary to avoid stains such as holes and bubbles on the screen. Be sure to pay attention to the front and back of the original film to prevent net reflection. In the process of exposure, the most important link is to make the screen closely fit with the master to prevent the exposed picture from being false or even scrapped.

During exposure, the distance between the lamp and the diagonal of the actual plate-making diagram shall prevail (for reference), and the time is determined by the fineness of the exposed substrate. Generally, it should take 80 seconds to 100 seconds to use a printer (single lamp 2000W). The perspective glass should be carefully wiped clean. It is difficult to develop with long exposure time, and the film with short exposure time is not firm, and it is easy to fall off during development, forming a serrated edge.

Development: Immerse the exposed screen in water for one or two minutes (warm water of 30℃-40℃ is better, which can shorten the development time). Shake the unexposed parts such as the screen constantly, fully absorb water and swell, and then rinse with concentrated water. When the sun-dried pictures and texts appear, they should be developed in a short time. No matter what kind of screen, the unexposed parts must be thoroughly washed.

The control principle of development degree is: under the premise of transparent development, the shorter the time, the better. If the time is too long, the film will swell seriously, which will affect the clarity of the image and make it easy to lose and rot. If the time is too short and the development is not thorough, a mask (that is, residual glue) will appear, resulting in a waste board. Residual glue is an extremely thin photosensitive glue film, which is prone to appear highly transparent in the details of the image, difficult to distinguish, and is often mistaken for transparent, but the ink can not pass through when printing.

After development, take out the screen board, dry the running water of the screen board with absorbent paper or newspaper, and lay it flat in an oven at 60-65℃ for drying. If there are holes or unnecessary openings on the screen, screen sealant can be used for proper repair (drying time should not be too long, otherwise it will be difficult to remove the film when the screen is reused).