Screen Making Basics - Selection, Application (in)

Characteristics Diazo-diazo Photosensitivity System Low Water Resistance - Medium Low - High Solvent Resistance Medium - High Low - High Screen Bridge Low - Medium to High Resolution - Low Middle Exposure - High Exposure Time Slow - Medium to High Exposure Tolerance Medium to High Average Low cost - China-China recommendation range Text-printing of fabrics High-quality printing in all areas (including four-color printing)

Diazo photosensitive system: that is, binary hardening, is the combination of diazo sensitization and UV hardening resin, the biggest advantage is its excellent printing effect and chemical resistance, 5-8 times faster than ordinary diazo screen system, Solid content is higher. High solid content paste can reach a certain thickness with less coating times; another advantage is wide exposure latitude, proper exposure of screens does not need to shorten the exposure time for fine lines, diazo photosensitive system has good quality, excellent performance, and price Suitable.
Wire mesh:
Wire mesh selection: According to a variety of different application requirements, the choice of wire mesh is different. The following points need to be considered in selecting wire mesh:
* Screen tension needs to be greater than 15-20 Newtons/cm.
* The thinner the screen, the better the resolution.
* The screen determines the amount of ink (printed lines greater than 300-500 microns).
* Maximum resolution: the width of the wire is not less than the opening + diameter The development of modern technology can provide high-tension screens and finer screens, so the printing quality is better.
Wire Mesh Preparation: When preparing screen materials, it is recommended to clean the screen first, which can reduce the eye of the needle and the fisheye during coating. New screens and re-used screens require degreasers for degreasing. When using the direct film system, a special grinding paste is used to increase the binding force of the screen plate and the screen; the direct photosensitive paste does not require grinding. After the degreasing treatment, humidifying agent is used to increase the wetness of the capillary film and the screen, and this step is not required for the direct photosensitive paste.
Capillary film application technology:
There are four basic methods available for capillary film. Two are used for small frames and the other two are used for large frames.
Application Method 1 (small box):
* Cut the film to the right size.
* Place the film horizontally with the photoreceptive side facing up.
* With a wet screen, one corner of the capillary film is first contacted with the screen, and then the film is gradually attached to the web. The film reacts with water.
* Use scraper to scrape excess water and dry the screen.
Application Method 2 (small box):
* Cut the film to a suitable size, place the film horizontally, with the photosensitive surface facing up.
* Put the film on the dry box.
* Wet the screen with water, and the film reacts with water.
* Scrape the water with a spatula and dry the screen.
Application Method 3 (large frame):
* The film is curled into a circular tube with the photosensitive surface facing outward.
* Wet the screen with soft water and dry the frame immediately to prevent water from flowing through the screen.
* Slowly lay the curled film on the screen.
* Use scraper to scrape off excess water and dry the screen completely.
Application Method 4 (large frame):
* This method is automatic printing instead of manual, the machine will wet the screen, the curly film will open cut. Through the combination of machines and a variety of technologies.
If the film is applied correctly and its thickness is suitable, a fine screen can be produced. If the film is too thin, it should appear serrated and edentulous. To avoid the above problems, we must follow the principle of film thickness and screen mesh.
Direct photosensitive paste application technology: Direct film can produce high-quality screens. The evaluation methods are: test screen thickness, screen and surface roughness of the substrate. (To be continued)