As far as environmental protection is concerned, screen printing is a pollution process. First of all, the plate-making process produces developer, the ink used produces ink barrels, and cleaning wastewater or waste rags are produced during cleaning.
1. What is screen printing?
Screen printing belongs to stencil printing, and it is called four printing methods together with lithography, gravure printing and gravure printing. Stencil printing includes copying stencil, engraving stencil, stencil printing and screen printing. The principle of stencil printing is that when printing, the ink is transferred to the substrate (paper, ceramics, etc.). ) pass through the perforation of the template with a certain pressure to form an image or text. Transcription printing is the simplest stencil printing, which started at the end of19th century. This kind of printing is made of special wax paper with typewriter or iron pen, and printed on the wax paper with ink roller, and the ideal printing effect can be obtained on the substrate. Screen printing is widely used in stencil printing.
Screen printing is to stretch silk fabric, synthetic fiber fabric or metal screen on a screen frame, and make a screen printing plate by hand carving paint film or photochemical plate making. Modern screen printing technology is to make a screen printing plate by photographic plate making with photosensitive materials (making the screen holes in the graphic part of the screen printing plate as through holes, but not blocking the screen holes in the graphic part). When printing, the ink is squeezed by the scraper and transferred to the substrate through the mesh of the graphic part to form the same graphic as the original. Screen printing equipment is simple, easy to operate, simple in printing and plate making, low in cost and strong in adaptability. Screen printing is widely used. Common printed matter includes: color oil paintings, posters, business cards, binding covers, commodity signs and printed textiles.
▼ 2. When was screen printing invented?
Screen printing originated in China and has a history of more than two thousand years. As early as the Qin and Han Dynasties in ancient China, the method of sandwiched printing appeared. By the Eastern Han Dynasty, batik printing was popular, and the level of printed products also improved. During the great cause of the Sui Dynasty (605-618), people began to use silk screen to stretch the frame, which made the clip printing process develop into screen printing. According to historical records, the fine clothes worn in the court of the Tang Dynasty were printed in this way. In the Song Dynasty, screen printing developed again, and the original oil painting was improved. Starch rubber powder is added to the dye to make it become the size of screen printing, which makes the screen printing products more colorful.
Screen printing is a great invention of China. American Screen Printing magazine once commented on China's screen printing technology: "There is evidence that people in China used horse bristles and templates two thousand years ago. The clothes in the early Ming Dynasty proved their competitive spirit and processing technology. The invention of screen printing promoted the development of human material civilization in the world. Today, two thousand years later, screen printing technology has been continuously developed and perfected, and now it has become an indispensable part of human life.
▼ 3. What is the principle of screen printing?
Screen printing consists of five elements, namely screen printing plate, scraper, ink, printing table and substrate. The basic principle of screen printing is to use the basic principle that the mesh of graphic part of screen printing plate is permeable to ink and the mesh of non-graphic part is not permeable to ink. When printing, the ink is poured into one end of the screen printing plate, and the ink part of the screen printing plate is pressed with a scraper, while moving to the other end of the screen printing plate. During the movement, the scraper squeezes the ink from the grid of the graphic part onto the substrate. Because of the viscosity of ink, the imprint is fixed in a certain range. In the printing process, the scraper always contacts the screen printing plate and the substrate line, and the contact line moves with the movement of the scraper. Because there is a certain gap between the screen printing plate and the substrate, the screen printing plate generates a reaction force on the scraper through its own tension, which is called resilience. Due to the resilience, the screen printing plate is only in movable line contact with the substrate, while other parts of the screen printing plate are not in contact with the substrate. Make the ink and screen break, ensure the printing size accuracy and avoid rubbing the substrate. When the scraper is lifted after scraping the whole page, the screen printing plate is also lifted, and the ink is gently scraped back to the original position. This is a printed stroke.
▼ 4. What is the main difference between screen printing and other printing methods?
Compared with other printing methods, screen printing has the following main differences:
① Strong printing adaptability: Lithographic printing, letterpress printing and gravure printing can only be printed on a flat substrate. Screen printing can be printed not only on the plane, but also on the substrate with curved surface, spherical surface and concave-convex surface. On the other hand, screen printing can be printed not only on hard objects, but also on soft objects, which is not limited by the texture of the substrate. In addition, in addition to direct printing, screen printing can also be printed by indirect printing as needed, that is, screen printing is carried out on gelatin or silica gel board first, and then transferred to the substrate. Therefore, it can be said that screen printing has strong adaptability and wide application range.
(2) Thick ink layer, strong stereoscopic impression and rich texture. The ink thickness of offset printing and relief printing is generally 5 microns, gravure printing is about 12 microns, and flexographic printing is about 10 microns. The ink thickness of screen printing far exceeds the above ink thickness, generally reaching about 30 microns. Used for thick screen printing of printed circuit boards, the thickness of ink layer can reach 1000 micron. Braille dots are printed with foam ink, and the thickness of the foam ink layer can reach 300 microns. Screen printing has thick ink layer, rich texture and strong three-dimensional sense, which is incomparable to other printing methods. Screen printing can be not only monochrome printing, but also color printing and screen printing.
(3) Strong light resistance and bright color. Because screen printing has the characteristic of missing printing, various inks and coatings can be used, not only pastes, adhesives and pigments, but also coarse-grained pigments. In addition, the preparation method of screen printing ink is simple, for example, light-resistant pigments can be directly put into the ink for preparation, which is another major feature of screen printing. Silk screen printing products have great advantages, that is, strong light resistance. Practice shows that the maximum density range of screen printing is offset printing 1.4, relief printing 1.6 and gravure printing 1.8, while the maximum density range of screen printing can reach 2.0. Therefore, screen printing products have stronger light resistance than other types of printing products and are more suitable for outdoor use.
(4) Large printing area. At present, the area size printed by general offset printing, relief printing and other printing methods is full size. If it exceeds the full size, it will be limited by mechanical equipment. Screen printing can be used for large-area printing, and the maximum range of screen printing products today can reach 3 meters ×4 meters, or even more.
The above four points are the differences between screen printing and other printing, and also the characteristics and advantages of screen printing. Knowing the characteristics of screen printing, we can develop our strengths and avoid weaknesses when choosing printing methods, and highlight the advantages of screen printing, thus achieving more ideal printing results.
▼ 5. What kind of manuscript is screen printing suitable for?
Screen printing, like other printing, needs to accurately reproduce the text and tone of the original. In principle, the manuscript used in screen printing is not much different from that used in other printing methods, but in the specific plate-making printing practice, its requirements are different, which is mainly determined by the characteristics of screen printing. In particular, due to the thick ink layer and bright colors of screen printing, the special effects of screen printing should be fully considered when selecting manuscripts for plate making.
In addition, the accuracy requirements of the original lines and dots used in screen printing are different from those used in ordinary printing methods. If the lines and dots of the manuscript are very fine, it is very difficult to make a plate by screen printing. Therefore, screen printing technology is not suitable for copying manuscripts with fine lines and dots. When choosing printing methods, we should fully consider the characteristics of various printing. Even in screen printing, attention should be paid to selecting the appropriate number of screen lines in order to fully reproduce the manuscript.
Screen printing is more suitable for monochrome full-color manuscripts with bright lines, and also for color manuscripts with large contrast and clear layers. Through the special effect of screen printing, the replica has rich expressive force, and through the rich and thick ink layer and the contrast between light and shade of tone, the texture and three-dimensional sense of the original content are fully expressed.
There are two kinds of screen printing photographic plate-making manuscripts: reflective manuscripts and transmissive manuscripts. It is usually based on reflective manuscripts. Color photography mostly uses transmission manuscripts.
Screen printing mainly uses positive images to make screen plates. Different plate-making methods have different requirements for manuscripts.
▼ 6. What are the main features of screen printing?
The characteristics of screen printing can be summarized as follows:
① Screen printing can use many types of inks. Namely: oily, water-based, synthetic resin emulsion, powder and other inks.
② The layout is soft. Screen printing is soft and elastic, which is not only suitable for printing on soft objects such as paper and cloth, but also suitable for printing on hard objects such as glass and ceramics.
③ Screen printing has small impression force. Because the pressure used in printing is small, it is also suitable for printing on fragile objects.
④ Thick ink layer and strong coverage.
⑤ Not limited by the surface shape and area of the substrate. As can be seen from the above, screen printing can be printed not only on a plane, but also on a curved surface or a spherical surface; It is not only suitable for printing on small objects, but also suitable for printing on larger objects. This printing method has great flexibility and wide applicability.
▼ 7. How many methods are there for screen printing?
There are usually two kinds of screen printing, namely manual printing and mechanical printing.
Manual printing refers to the manual operation from paper receiving to paper delivery, printing plate moving up and down and scraping printing.
Mechanical printing means that the printing process is completed by mechanical action. Among them, it is divided into semi-automatic and full-automatic printing. Semi-automatic means that the substrate is put in and taken out by manual operation, and printing is done by machinery. Fully automatic means that the whole printing process is completed by machinery.
▼ 8. How is screen printing classified?
Screen printing not only adapts to ordinary paper printing, but also has wide adaptability. For example: ceramics, glass, printed circuit boards, etc. Printing is different according to the texture of the substrate. Although there is an inseparable internal relationship between the series, each series has its own particularity because of the different texture of the matrix (that is, different chemical and physical properties). Therefore, people usually divide it into paper printing, plastic printing, ceramic printing, glass printing, circuit board printing, metal printing, textile printing and so on according to the different substrates. In this way, a relatively independent printing system is formed.
▼ 9. What are the main applications of screen printing?
Screen printing is widely used. Any object can be used as a substrate except water and air (including other liquids and gases). Someone once said when evaluating screen printing: If you want to find an ideal printing method on the earth and achieve the printing purpose, it is probably screen printing.
Specifically, screen printing is mainly used in the following aspects:
① Paper printing
Art printing-advertising, pictorial, calendar, lantern paper, etc.
Label printing
Transfer printing
Packaging and printing
Building materials printing-wallpaper pasting, etc.
② Plastic printing
Plastic film-vinyl toys, schoolbags, plastic bags, etc.
Plastic target-pseudometal composite material and various targets.
Production parts-instrument parts.
③ Woodworking printing
Crafts-lacquerware, wooden crafts, toys.
Processing semi-finished products-sporting goods, plates, ceilings, road signs, signboards, fake metal wrenches, billboards, etc.
④ Printing of metal products.
Metal cylinder, metal container, metal product.
⑤ Printing of glass and ceramic products.
Glass mirror, glass plate, cup, bottle, etc.
Ceramics-utensils, handicrafts.
6 signs
Word board, dial, special-shaped article.
⑦ circuit board printing
Printed circuit board, civil or industrial substrate, thick film integrated circuit board.
8 printing and dyeing
Printing and dyeing-flags, fabrics, towels, handkerchiefs, shirts, vests, knitwear, etc.
Other printing-pockets, shoes, numbered cloth and various bags, backpacks, handbags, schoolbags, etc.
Pet-name ruby leather products printing
▼ 10. What is the main process of screen printing? Is the process a needle?
The main processes of screen printing are: making original manuscript, making screen printing plate, printing, ink drying and so on.
▼ 1 1. What is a tensiometer?
Tension meter is an instrument to measure the mutual traction between the inner side of the screen and the fixed screen contact when the screen is under tension. There are two kinds of tensiometers, mechanical and electronic, and the unit for measuring tension is expressed in Newton/cm. Tension can also be expressed in terms of relative values. The centimeter tensiometer is a kind of tension expressed by relative value, which is calculated by the value (mm) of screen sinking depth caused by self-weight. Tension values can be obtained directly from the indicator panel or indirectly from the control panel. There are two kinds of tensiometers: manual and mechanical. Tension meter is an important testing instrument to test the quality of screen printing plates. In order to ensure the tension required for plate making, a tensiometer should be used to measure during or after screen stretching.
▼ 12. What is a grid ruler? What is its purpose?
Mesh ruler is also called latitude and longitude densimeter. It is mainly used to measure the mesh number of various screens. There are two kinds of mesh rulers: glass plate and plastic plate. The measurement method is as follows: when measuring, first make the screen transparent or put it on the reading table, put the mesh ruler on the screen, and then slowly move the mesh ruler on the screen so that the vertical line on the mesh ruler is parallel to the warp or weft of the screen. At this time, due to the overlapping between the latitude and longitude lines of the screen and the vertical lines on the grid ruler, a prismatic pattern is formed on the grid ruler, and the corresponding scale number on the grid ruler pointed by the transverse diagonal of the pattern is the mesh number of the screen to be tested.
Mesh ruler is a common tool for measuring mesh number of screen. Usually, in order to maintain the accuracy of measuring instruments and the accuracy of measuring data, it is necessary to keep the mesh ruler clean and prevent scratches and scratches on the mesh ruler. After use, the instrument should be wiped clean and properly kept.
▼ 13. What is a densimeter? What is the purpose of densimeter?
Densitometer is a common instrument for measuring manuscripts in printing plants. It is a photoelectric measuring instrument for measuring the gray value of black and white manuscripts and measuring the continuous tone or dot value. Densitometers are divided into transmission densimeter and reflection densimeter. Transmission densitometer is suitable for measuring transparent manuscripts, and reflection densitometer is suitable for measuring field manuscripts. The measuring range of densitometer is 0 ~ 2.5, and the larger the number, the higher the blackness. The basic principle of measurement is to measure the blackening degree of photosensitive materials after exposure and development. In plate making, the silver bromide on the photosensitive material is exposed, and after development, it is reduced to metallic silver, forming a certain opacity. Black, high density; Low blackness and low density. Instruments with filters can also measure the color density of color manuscripts. Its measuring principle is similar to the above basic principle.
▼ 14. What is a colorimeter? What is its purpose?
Colorimeter is also called colorimeter. It is an instrument for measuring the color characteristics of materials. The main purpose of colorimeter is to measure and analyze the color, hue and color value of the measured substance. If the colorimeter is connected with the computer, the ability of color analysis and processing can be improved. Users can search and call all kinds of data from the color storage library of the microcomputer and match colors as needed.
▼ 15. What is a hardness tester? What is its purpose?
Hardness tester is an instrument for measuring the hardness of objects, which can be divided into simple hardness tester and complex hardness tester according to the complexity. Hardness tester is widely used in rubber industry. In the process of screen printing, the hardness tester is mainly used to detect the hardness of scraper materials.
Pad printing is based on the principle of gravure printing. Tools include silicone rubber head, pattern printing board (steel or fiber) and ink, which can print all kinds of thin lines, fonts and patterns, and even four-color screen images. No matter whether the surface of printed matter is concave, convex or irregular, it can still achieve the ideal effect. For example, printing four-color trademarks on golf balls is one of the strengths of pad printing machines.
Pad printing technology is a special printing technology just introduced into China in 1980s. Because it has obvious advantages in products with small printing area and uneven surface, it makes up for the shortage of screen printing technology, so it has developed rapidly in recent years In the early 1990s, with the further opening of the China market, a large number of foreign-funded enterprises mainly engaged in traditional industries such as electronics, plastics, gifts and toys entered the China market in succession. As the main decorative methods, pad printing technology and screen printing technology have made extraordinary development. According to incomplete statistics, the application of pad printing technology and screen printing technology in the above industries reached 27%, 64%, 565, 438+0% and 66% respectively. Pad printing refers to the way that the substrate is an irregular and specially shaped surface (such as instruments, electrical parts, toys, etc.). ), copper or steel intaglio is used, and the hemispherical pad is cast by silicone rubber, so that the ink is transferred to the substrate by pressing the layout to complete the transfer printing.
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