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Silk screen refresh trend (Part 2)

3. Formation of photosensitive film

(1) direct method

this is a method that can be directly coated on stretched silk, which is now widely used. Its characteristics are: A. suitable for all kinds of silk; b. Unlimited size; c. No need to choose photosensitive emulsion; d. Any required film thickness can be processed. However, this method is time-consuming and requires training skills to obtain good quality. If you use a can coater, compared with manual coating, although turning a small bend is not very effective, the uneven thickness of the version facial mask is very few, and the unevenness of each page is very few. No proficiency is required, and anyone can paint a high-quality page. The obvious difference from the straight method is that in order to form smoothness, either use the photosensitive emulsion with low viscosity to apply it several times, or carry out post-processing such as leveling and mirror processing on the coated film surface

(2) straight method

this is a method of forming a photosensitive film on silk after the polyester film base has been coated with photosensitive emulsion and dried. The film base is stripped for use after transfer drying or just before exposure. The transfer method is water + IPA, or stick it to the wire with scraper feeder, etc. The characteristics of the straight method are as follows: a. the smoothness of the photosensitive film surface is very good; B. The film thickness of each plate is relatively uniform and the quality is stable; C. The film thickness in a plate is relatively uniform; D. Proficiency is not required; E. In order to process to the specified film thickness, if the direct method is used, the coating operation should be repeated with the material tank; If the straight method is used, the method of one-time pasting should be adopted

(3) it can be seen that connection method

this is a method of using positive image to close on the indirect method film (photosensitive emulsion), and then transferring the image formed on the film to the upper plate after exposure and development

4. Evolution of plate making technology and equipment

(1) exposure technology

in order to make a printing plate with good performance, it is often necessary to make corresponding corrections during plate making. The precondition is that the temperature and humidity during printing are the same as those during plate making. The moderate exposure time is seconds, which is convenient for operation. At present, according to the spectral sensitivity of photosensitive emulsion, most of them use ultra-high pressure mercury lamp or metal halogen lamp. Although these light sources will have irregular reflection on the reflector, they are still point light sources. The illumination around the yarn at a distance of 1m is reduced by 70% compared with the central part. In order to obtain equal ultraviolet light, some people used the exposure machine with honeycomb or annular lens and the exposure machine with A4 size film to project and magnify the 3mps version

(2) water washing developing machine

after exposing and printing the PS plate, the required image will be obtained through water development. When using manual development, use spray gun water to completely remove the unexposed part. Then wash it thoroughly with flowing water, wipe off the water with oil tanned leather or rags, or blow it away with an air gun. If the water is not wiped clean and dried, it will block the eyes and cause accidents. In order to carry out complete development, a fully automatic 100 mesh wood powder developer should be used, which is equipped with spray development and an air knife that completely squeezes hundreds of mainstream media across the country to report dry water

5. Other printing plates

the above describes the silk plate obtained according to different photosensitive emulsions (if the printing plate, which forms an image by metal, is covered, it is printed with a scraper). Below we list several printing plate structures to illustrate the development of printing plates in the 1990s and the future

(1) metal cladding

a. corrosive metal cladding: cheap and can be mass produced, and the 0.5mm pitch gap can also be adapted

metal mas: use the addition and subtraction method to form an image, and adapt to the 0.3mm gap (2). Bridge method: since the existence of buried cables

c. laser metal: cut with YAG laser, suitable for 0.25mm gap

d. metal wire: electroplate the wire and metal image parts to produce a printing plate

e. layer metal coating: use photosensitive resin on the metal coating to form an image again

f. apply polytetrafluoroethylene metal: it can prevent the north side of the welding paint from sticking dirty

g. plastic cover: change the metal plate into plastic, and the diameter can reach 50um

(2) film cutting

use a film cutting machine to cut out the image made by the desktop system without photosensitive resin and transfer it to the silk

(3) direct printing

paste the heat sensitive film resin on the polyester wire, and directly output the image made in the desktop system to the heat sensitive film resin to make a printing plate

6. Looking forward to the continued development of

printing plate technology, which is always highly praised because its printing products can meet the needs. Therefore, only by maximizing the use of comprehensive technology from image data to plate making to printing can there be development. In particular, in the 1990s, we were faced with the challenges of narrow gap and precision of electronic components, circuit boards, plasma display panels, liquid crystal displays, etc. In addition, the color printing image of CD (DVD) disc is also required to be close to the level of offset printing. In order to meet this demand, the equipment of screen printing plate making materials will continue to be innovated

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