Screen printing belongs to orifice printing. In the modern printing industry, letterpress printing, gravure printing, lithographic printing and screen printing have become the four major printing methods. The printed graphics and text can be printed on paper or other printed materials through ink. Screen printing is the most widely used in the printing industry. It is widely used in decoration, printing and dyeing, electronic instruments, printed circuits, advertising and other industries on various materials such as plastic, paper, metal, rubber, glass, knitted fabrics, etc. Relevant experts believe that screen printing can be printed on all materials except air and water. Equipped with universal printing. With the continuous emergence of new processes, new materials and new technologies, screen printing products tend to be high-end. Screen printing is a very promising industry both at home and abroad. Photographic platemaking uses the photochemical changes of the photoresist. That is, the light-receiving part of the photoresist is cross-linked, and it is firmly combined with the screen. The non-photosensitive part is washed with water to form a transparent part on the screen, which can pass the ink when printing. Process flow: Manuscript Making-> Screen Selection-> Stretching Screen-> Cleaning-> Blow Drying-> Formulated Photosensitive Adhesive-> Coated Photosensitive Adhesive-> Blow Drying and Exposure Printing-> Development-> Water Absorption and Blow Drying-> Check Revision-> 2 Exposure-> Edge band printing 1. Production of manuscript The manuscript requires greater contrast as possible, that is, the darker the picture and text, the better the transparency. The original is divided into rubber, sulfuric acid paper and paper. Film is the best manuscript in the original, followed by sulfuric acid paper, both of which can be directly made. The paper manuscript is coated with vegetable oil (peanut oil, soybean oil, etc.) on the reverse side of the manuscript to make the manuscript transparent, and then wipe off the excess vegetable oil to make the plate. 1. Use computer to type, copy manuscript (copier can zoom in and out), hand-painted manuscript. In order to ensure accurate overprinting, each manuscript can be set with crosshairs aligned. Second, the choice of wire mesh Screen is one of the main materials for making screen. It is the carrier of the photosensitive film image. It forms a screen printing plate together with the photosensitive film and silk frame. The most commonly used wire mesh varieties are nylon (also known as nylon) and polyester (also known as polyester). It is divided into plain weave, semi-interweave, and full interweave from the preparation method. Plain weave wire mesh is the thinnest and the interweave is the thickest. Generally we use plain weave wire mesh. When the ink layer is required to be extra thick, full twisted woven can be used. Nylon (cotton) wire mesh: has good elasticity and ink-passing performance; can withstand a certain degree of alkali solution; good abrasion resistance and tensile resistance. It is not acid-resistant, has a large extension, and is not suitable for large-area color screen printing; it will become brittle and affect the strength when exposed to sunlight for a long time. Polyester wire mesh: It has lower extensibility than nylon wire mesh, and has excellent dimensional stability. It is appropriate to make color printing plates; it has good chemical resistance, abrasion resistance and tensile resistance. Its binding performance with photosensitive materials is not as good as nylon wire mesh and must be surface roughened. The through-hole rate is slightly smaller than nylon wire mesh. The intensity of exposure to sunlight for a long time decreased slightly. Wire mesh specifications are used to describe the number of meshes per unit area of ​​wire mesh is the number of wire mesh. At present, domestic wire mesh product specifications are expressed in terms of the number of holes per unit length (cm), ie mesh / cm. Imported products are also expressed in English units of measurement, both headings / ln. The number indicates the density of the wire mesh. The higher the mesh, the denser the wire mesh and the smaller the mesh. In screen printing, there are many kinds of printing materials, and the materials have their own characteristics. Usually the choice of screen can be selected according to the printing material and the accuracy of printing. For example: posters, hard fiber prints, rough panels, foils on coarse grain surfaces, 200-mesh screens are optional. For printing fine graphics, you can choose a screen with a mesh size of more than 300 meshes, and a 350 mesh screen for monochromatic screen prints, trademarks, dials, etc. Print extremely fine graphics and texts, and choose a screen with a mesh size of more than 420 mesh. Generally speaking, the higher the screen mesh of the same type, the more suitable for making fine screens. For textiles; 150-200 mesh screens are used for printed cotton, and 250-300 mesh screens are indeed good. The silk uses 300-350 mesh screen. Foam printing is generally 80 mesh ~ 150 mesh screen. Here, about 120 mesh is selected for the printing paint screen. 3. Screen and screen mesh 1. The screen frame is the carrier of the screen used for screen printing. The requirements of the screen for the screen frame: the screen frame must have the strength to resist the tension required by the screen stretched net. After the net stretched, it must be strong, durable, stable in performance, and long-term use without deformation. There are also materials that are resistant to water, solvents, acids, and other chemical materials. It should also be light and cheap. Commonly used wire mesh frame materials are: wood, aluminum frame. (1) Wooden mesh frame-it has the characteristics of simple production, light weight, low price, easy operation and use, and simple and reliable way of fixing the net. Suitable for manual operation by small-scale manufacturers. However, due to its poor water resistance, the frame surface is easily deformed and the stability is difficult to last. To prevent deformation, L-shaped hardware accessories can be installed around the frame. (If the printing quality requirements are high, it is best to use aluminum frame). (2) Aluminum frame-good strength, stable performance, light operation, and not easy to deform. Does not rust. Although the investment is large at one time, it can be used repeatedly for a long time. Therefore, the aluminum frame can be used when the printing accuracy is higher or the product is overprinted. The area is larger than the actual printing area, usually to ensure the left and right 4cm ~ 6cm, up and down 6cm ~ 8cm vacant space. NMT-1 type stretching machine can be used to stretch the net more quickly and conveniently. 2. Stretching the net is the process of tightening the wire net and making it firmly combined with the net frame. (1) Hand-stretched net (wooden frame): First tear the screen according to the required size. Wash with detergent, rinse with water, and stretch the wire mesh on the frame. First, use a lath (made of plywood, the same length as the inner frame of the net frame) to wrap the wire mesh on one side, nail it to one side of the frame, and then use a wooden strip to curl the opposite side, tighten it tightly, and nail it with nails . The other two sides are nailed in sequence. Rinse the water and dry it with a hairdryer. The screen version is generally stretched well in advance, and strives to be smooth and tight. (2) Stretching machine (wooden frame, aluminum frame): put the net frame on the adjustment plate fixed by the stretcher machine, then put the wire mesh on the stand of the stretcher machine, and put the fixed dogma on the edge To fix the net. Adjust the four handles. When adjusting, you need to apply gentle force. Slowly stretch the wire mesh, level it, and tighten it until it is the tightest. Then adjust the tension bar below to make the frame and the wire mesh fit tightly, and then apply the glue. After the glue adhesive is dry, cut it off along the outer edge of the frame with a blade. [next] Fourth, with coated photosensitive adhesive 1. The NMT-1 microcomputer multi-functional plate-making machine is suitable for all kinds of photosensitive adhesives. Our commonly used diazo photosensitive adhesive has the characteristics of slow dark reaction and long storage period. It only needs a semi-dark room when preparing, and can be red or black during the day Just close the curtains. The screen version can be reused to reduce costs. The plate-making precision is high, and it is non-toxic and pollution-free. The diazo photosensitive adhesive is divided into water-resistant and oil-resistant types. The water-resistant photosensitive adhesive is used to make plate for printing water-soluble printing materials; the oil-resistant photosensitive adhesive is used for making plate for printing solvent-based printing materials. In a semi-dark room, fully dissolve the photosensitizer with 50 ml of distilled water or purified water. Add 950 grams of glue and stir well. After standing for 4 hours, the bubbles disappear before use. Do not use metal products to stir, so as not to affect stability. The storage temperature of the prepared glue solution is preferably between 5-20 ℃ and placed in the fresh-keeping layer of the refrigerator. Shelf life is 1-2 months. (1) Preparation: A. Coating tool: It is best to use a sizing device made of stainless steel. The upper mouth of the sizing device is wide and narrow, and the upper mouth is smooth. (2), coated photosensitive adhesive Scraping: Pour the prepared photosensitive glue into the sizing device, hold the screen frame with one hand, and push the front edge of the sizing device to the screen board with the other hand, the sizing device and the screen board are at 60 degrees to 70 degrees angle. After the sizing device and the screen are all in contact with the glue, gently pull it from the bottom up with a slight force, without stopping in the middle, so that the photosensitive glue is evenly coated on the screen. Generally, apply photosensitive glue 7 to 8 times on the reverse side of the screen. Then air scrape (the glue is not in contact with the screen) 1-2 times, blow dry at low temperature, and then you can print the plate. After the above process is completed, you can scrape the glue on the side of the screen that contacts the substrate and blow dry, but the film should not be too thick, otherwise it is not suitable for development, and the adhesion of the glue to the screen will also be relatively reduced. Five, drying board Printing is the use of the chemical reaction of photosensitive glue, which means that the part of the glue that is irradiated by light of a certain spectral wavelength produces a glue-linking reaction and solidifies, while the other parts do not produce glue-linking and do not cure. Rinse and develop with water to form a transparent part of the text and pass the ink. Form a screen for printing. This process is the key process to make a leap from quantitative to qualitative changes. The manuscript should be further inspected before printing. The more opaque the graphic part is, the better the transparency is. When printing, first place the manuscript on the glass of the NMT-1 microcomputer multi-functional plate-making machine (in order to make the manuscript compact on the screen, you can first place a glass on the device that is smaller than the inner frame of the screen, and then Put the manuscript on top) Then put the screen on the manuscript, cover it with black velvet cloth, put a piece of glass smaller than the inner frame of the screen, and press it with a physical object to keep the manuscript and the screen close Turn on the switch of the device, press the power button, turn on the power, set the time, press the printing button to start printing, and after the printing is completed, it will automatically stop and develop. Reference time for printing version NMT-1: Water-resistant photoresist 3 minutes in summer to 5 minutes in winter 8 minutes to 13 minutes in spring 5 minutes to 10 minutes Oil-resistant photosensitive adhesive 5 minutes to 10 minutes in summer 10 minutes to 20 minutes in winter 8 minutes to 15 minutes in spring The above time uses 300 mesh screen, XS series photosensitive adhesive as an example, for reference only. The correctness of the printing time directly affects the quality of the printing plate. Its measurement habitually depends on the operator's experience, and can also be measured with the help of some tools or a combination of both. [next] 6. Development: The silk screen can be developed after it has been printed. The development is to dissolve the unexposed photosensitive glue with a developing solution, so that the mesh holes on the screen that need to be over-permeated are completely transparent. Generally use cold or warm water to develop. Put a certain amount of clean water in the developing tank, soak the screen in water for 1-2 minutes. When the screen is immersed in water, the screen must be lifted up and down. Use the impulse of water to display the pattern. After most of the pattern is displayed, rinse it with slightly pressured water (preferably a pressure water gun, such as a waterless gun, can be connected to the faucet with a rubber tube, and squeeze the hose firmly to make the water flow There is a certain pressure to wash the screen. But it is not appropriate to use too much water to avoid damaging the film). After the graphics are wet, rinse it once with water, shake off the water beads, and blow dry. Before drying, it is best to use a sponge or newspaper to wash off the moisture on the surface of the screen, so as to prevent the moisture from flowing down on the surface of the screen to produce residual glue, which affects the clarity of the edge of the line. Seven, check revision: After the screen plate is dry, you can turn on the light source on the microcomputer multi-function plate-making machine to check whether there are air holes and trachoma, which can be repaired with photosensitive adhesive. 8. Second exposure: In order to enhance the printing durability of the template, the trimmed screen can be placed on the microcomputer multi-function plate-making printing machine and then printed for 10 minutes to 20 minutes. After the screen is exposed again, the film is stronger. Nine, edge banding printing: Screen inspection is the final process in the entire plate-making work. Small defects exposed after development can be corrected by revision. If a major defect occurs, the plate must be remade. After the screen printing is completed, seal the four sides of the screen frame with adhesive tape (the edge sealing is to prevent ink leakage) to print. INCHEE FURNITURE CO.,LTD , https://www.incheehome.com
2. If the original is multi-color (color block), the original version will be divided into several colors accordingly.
B. Drying temperature: After coating the photosensitive glue, it should be dried at the ground temperature, and the temperature should be controlled below 40 ℃. Should not be too high, it can be dried with a hair dryer at low temperature.
C. Studio requirements: The plate-making room is a semi-dark room, so red can be used as the lighting source, so it is better to see the objects clearly. In actual work, the ordinary room can be closed with curtains.
D. Manuscript checking: The manuscript must be further checked before making a plate. The content includes the blackness of the manuscript, lack of lines, and graphic errors.
The function of the screen sealing glue is to seal the leaking parts other than the screen graphics when the solvent-based ink is printed to prevent the printing material from leaking. It can also be used to seal temporarily unprinted parts. If you print this part again, you can clean the ink on the screen and flush it with water.
Liquid wallpaper printing plate-making technology