▼1. What is screen printing?
Screen printing belongs to stencil printing. It is called the four major printing methods together with offset printing, embossed printing and gravure printing. Hole printing includes transcription plates, perforated plates, spray printing and screen printing. The principle of stencil printing is: when the printing plate (a paper plate or other plate base is made with holes through which ink can pass), a certain amount of pressure is used to transfer the ink to the substrate (paper, ceramics, etc.) through the holes of the stencil. ) to form an image or text. Transcription printing is the simplest type of hole printing and began in the late 19th century. This kind of printing is done on special wax paper, using a typewriter or stylus to make a wax paper graphic plate. An ink roller is used to print on the wax paper plate, and the ideal printing effect can be obtained on the substrate. In stencil printing, the most widely used one is screen printing
Screen printing is to stretch silk fabric, synthetic fiber fabric or metal mesh on the screen frame, and use hand-engraved paint film or photochemical plate making. How to make a screen printing plate. Modern screen printing technology uses photosensitive materials to make screen printing plates through photographic plate making (so that the screen holes in the graphic and text parts of the screen printing plate are through holes, while the screen holes in the non-graphic and text parts are blocked. live). During printing, the ink is transferred to the substrate through the mesh of the graphic part through the squeezing of the scraper, forming the same graphic and text as the original. Screen printing equipment is simple, easy to operate, easy to print and plate making, low in cost, and has strong adaptability. Screen printing has a wide range of applications. Common printed materials include: color oil paintings, posters, business cards, binding covers, product signs, and printed and dyed textiles.
[Edit this paragraph]▼2. When was screen printing invented?
Screen printing first originated in China and has a history of more than 2,000 years. As early as the Qin and Han Dynasties in ancient my country, the clip printing method appeared. By the Eastern Han Dynasty, the Jiajie batik method had become widely popular, and the level of printed products had also improved. During the Daye period of the Sui Dynasty, people began to use frames stretched with silk net for printing, and the clip printing process developed into screen printing. According to historical records, the exquisite costumes worn in the palace during the Tang Dynasty were printed using this method. In the Song Dynasty, screen printing developed again, and the original oil-based paint was improved, and starch powder was added to the dye to turn it into a slurry for screen printing, making the screen printing products more colorful.
Screen printing is a great invention in China. The American "Screen Printing" magazine once commented on China's screen printing technology: "There is evidence that the Chinese used horsehair and templates two thousand years ago. The clothing of the early Ming Dynasty proves their competitive spirit and processing technology?" quot;The invention of screen printing promoted the development of human material civilization in the world. Today, two thousand years later, screen printing technology continues to develop and improve, and has now become an indispensable part of human life.
[Edit this paragraph]▼3. What is the principle of screen printing?
Screen printing consists of five major 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 the screen printing plate is transparent to the ink, and the mesh of the non-graphic part is impermeable to the ink. When printing, pour the ink on one end of the screen printing plate. The scraper exerts a certain pressure on the ink part of the screen printing plate and moves toward the other end of the screen printing plate. The ink is squeezed from the mesh of the graphic part onto the substrate during the movement. The viscosity of the ink causes the imprint to be fixed within a certain range. During the printing process, the scraper is always in line contact with the screen printing plate and the substrate. The contact line moves with the movement of the scraper. Due to the relationship between the screen printing plate and the substrate, There is a certain gap between them, so that the screen printing plate generates a reaction force on the scraper through its own tension during printing. This reaction force is called rebound force, so that the screen printing plate and the substrate are only in contact with each other. There is a moving line contact, while the other parts of the screen printing plate are separated from the substrate, causing the ink and the screen to break, ensuring the printing dimensional accuracy and preventing the substrate from being smeared when the scraper scrapes across the entire page. At the same time, the screen printing plate is also lifted up, and the ink is gently scraped back to the original position. This is a printing stroke.
[Edit this paragraph]▼4. The difference between screen printing and other printing methods
Compared with other printing methods, the main differences between screen printing and other printing methods are as follows:
①Strong printing adaptability: plain printing, embossed printing, The three major printing methods of gravure printing can generally only print on flat substrates. Screen printing can not only print on flat surfaces, but also on curved, spherical and concave-convex surfaces. On the other hand, screen printing can not only print on hard objects, but also print on soft objects, and is not limited by the texture of the substrate. In addition, in addition to direct printing, screen printing can also be printed using indirect printing methods as needed, that is, screen printing is first printed on a gelatin or silicone plate, and then transferred to the substrate. Therefore, it can be said that screen printing has strong adaptability and a wide range of applications.
② The ink layer is thick, three-dimensional and rich in texture. The ink layer thickness for offset printing and embossed printing is generally 5 microns, for gravure printing it is about 12 microns, and for flexographic (aniline) printing it is 10 microns. Microns, and the thickness of the ink layer for screen printing far exceeds the thickness of the above ink layer, generally up to about 30 microns. Specially used for thick screen printing of printed circuit boards, the thickness of the ink layer can be up to 1000 microns. Use foaming ink to print Braille dots, and the thickness of the ink layer after foaming can reach 1,300 microns. Screen printing has a thick ink layer, rich printing quality and strong three-dimensional effect, which is unmatched by other printing methods. Silk screen printing can not only print in single color, but also can print in color and screen color.
③ Strong light resistance and bright color. Since screen printing has the characteristics of leakage, it can use various inks and coatings. Not only slurries, adhesives and various pigments can be used, but also Use coarser grained pigments. In addition, the preparation method of screen printing ink is simple. For example, the light-fast pigment can be directly put into the ink for preparation, which is another major feature of screen printing. Screen printing products have the great advantage of strong light resistance. Practice has shown that, based on the maximum density value range measured after one imprint on coated paper using black ink, offset printing is 1.4, embossing printing is 1.6, and gravure printing is 1.8, while the maximum density value range of screen printing can be It reaches 2.0, so the light fastness of screen printing products is stronger than that of other types of printing products, and it is more suitable for outdoor advertising and signage.
④Large printing area. At present, the maximum area printed by offset printing, embossed printing and other printing methods is the full sheet size. If it exceeds the full sheet size, it is limited by mechanical equipment. Screen printing can print on a large area. Today's screen printing products can reach a maximum size of 3 meters × 4 meters or even larger.
The above four points are the differences between screen printing and other printing, and they are also the characteristics and advantages of screen printing. After understanding the characteristics of screen printing, you can maximize your strengths and avoid weaknesses when choosing a printing method, highlighting the advantages of screen printing to achieve a more ideal printing effect.
[Edit this paragraph]▼5. What type of original is suitable for screen printing?
Silk screen printing, like other printing, needs to accurately reproduce the image, text and tone of the original. In principle, the manuscripts used in screen printing are not very different from the manuscripts used in other printing methods, but in specific plate making and printing practices, the requirements are different, which is mainly determined by the characteristics of screen printing. Especially because the screen printing ink layer is thick and the color is bright, the special effects of screen printing should be fully considered when selecting original manuscripts and plate making.
In addition, the requirements for the graphic and text lines and dot accuracy of the manuscript used for screen printing are also different from the requirements for the manuscript used for ordinary printing methods. If the lines and dots of the original are very fine, it will be very difficult to use screen printing to make plates. Therefore, screen printing technology is not suitable for reproducing original manuscripts with fine lines and dots. When selecting printing methods, the characteristics of various printings should be fully considered. Even when making screen printing plates, attention must be paid to selecting appropriate screen cables in order to fully reproduce the original manuscript.
Screen printing is more suitable for monochrome complete color manuscripts that express text and bright lines. It is also suitable for color manuscripts with large contrast and clear layers.
Through the special effects of screen printing, the reproduction has rich expressive power. Through the rich and thick ink layer and the contrast of light and dark tones, the texture and three-dimensional effect of the original content are fully expressed.
There are two types of screen printing photographic plate-making originals: reflective originals and transmission originals. Reflective originals are usually mainly used. Color photography mostly uses transmission originals.
Screen printing mainly uses positive images to make screens. Different plate making methods have different requirements for the original manuscript.
[Edit this paragraph]▼6. What are the main characteristics of screen printing?
The characteristics of screen printing can be summarized in the following aspects:
① Screen printing can use many types of inks. Namely: oil-based, water-based, synthetic resin emulsion type, powder and other types of ink.
②The layout is soft. The screen printing layout is soft and has a certain degree of elasticity. It is not only suitable for printing on soft items such as paper and cloth, but also suitable for printing on hard items such as glass, ceramics, etc.
③The printing force of screen printing is small. Since the pressure used during printing is small, it is also suitable for printing on fragile shopping objects.
④The ink layer is thick and has strong coverage.
⑤ It is not limited by the surface shape and area size of the substrate. As can be seen from the above, screen printing can not only print on flat surfaces, but also on curved or spherical surfaces; 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.
[Edit this paragraph]▼7. How many methods are there for screen printing?
There are usually two types of screen printing, namely manual printing and mechanical printing.
Manual printing means that from paper feeding to paper delivery, the up and down movement of the printing plate, and scraping and scraping are all manual operations.
Mechanical printing means that the printing process is completed by mechanical action. It is divided into semi-automatic and fully-automatic printing. Semi-automatic means that the placing and taking out of the substrate is manually operated, and printing is completed by machinery; fully-automatic means that the entire printing process is completed by machinery.
There is also a quick and easy method of curved screen printing, movable surface screen printing, which involves removing the screen layout and directly attaching it to the surface of the substrate for printing. Using the removable surface screen printing method, a large number of processed printed products can be printed, such as latex plastic buckets, pure water buckets, washbasins, thermos bottles, cups, bowls, plates and other products. At the same time, this method can be used to print signboards on cars and also on special-shaped flat surfaces.
Preparation of movable screen plate:
First dry and repair the photosensitive text and picture plate, then take it off and cut it according to size. And use wood chips or aluminum sheets as the skeleton at both ends of the screen, and use adhesive tape to firmly fix it. You can also use adhesive to directly fix it, so that the required removable screen version can be made.
How to operate the movable mesh:
Select different printing materials according to the substrate: first, use a flat plate and a plate to mix the ink, and then, one person holds the movable mesh with both hands. Face the screen plate and place the printed part tightly on the surface of the substrate. Another person uses a scraper to evenly dip the ink on the upper surface of the scraper on the ink adjusting plate. Then, place the scraper evenly on the ink adjusting plate. Scrape evenly across the surface.
If the printed graphics area is too large, you can pour ink on the layout according to the situation, but do not let the ink flow out of the substrate. Be careful not to make the ink too thin or too dry. It is better to have a moderate amount of dryness and wetness. Small-area printing and painting can be operated by one person. The method is to use packaging tape to affix one end of the movable plate to the desired position on the substrate machine, and then use the other hand to tighten the printing plate against the substrate. for printing. Note for starting the plate: Be sure to lift the plate lightly in the direction of the end of the tape. This is also true if two people operate the plate for advertising. Printing using this method is easy to operate and has flexible requirements for substrates. It can be large or small, and the quantity It can be more or less, and has the advantages of low cost and energy saving.
[Edit this paragraph]▼8. How is screen printing classified?
Screen printing is not only suitable for general paper printing, but also has a very wide range of adaptability. For example: ceramics, glass, printed circuit boards, etc.
Depending on the texture of the substrate, printing will be different. Although there is an inseparable internal connection between each series, each has its own particularity due to the different textures of the substrate (that is, different chemical and physical properties). Therefore, people usually divide them into several categories according to different substrates: paper printing, plastic printing, ceramic printing, glass printing, circuit board printing, metal printing, textile printing and so on. In this way, each relatively independent printing system is formed.
[Edit this paragraph]▼9. What are the main applications of screen printing?
The application scope of screen printing is very wide. Except for water and air (including other liquids and gases), any object can be used as a printing substrate. Someone once said this when evaluating screen printing: If you want to find the ideal printing method on earth to achieve the purpose of printing, it is probably the screen printing method.
Specifically, screen printing is mainly used in the following areas:
①Paper printing
Art printing - advertisements, illustrated magazines, calendars, lanterns paper etc.
Trademark printing
Transfer printing
Packaging printing
Building materials printing - wallpaper, etc.
②Plastic printing
Plastic film - vinyl toys, school bags, plastic bags, etc.
Plastic dials - fake metal composite materials and various dials.
Production of parts - instrument parts.
③Wood product printing
Crafts - lacquerware, wooden crafts, toys.
Processing of semi-finished products - sporting goods, wooden boards, ceilings, road signs, signs, fake metal levers, billboards, etc.
④Metal product printing
Metal cylinders, metal utensils, and metal products.
⑤Printing of glass and ceramic products
Glass - mirrors, glass plates, cups, bottles, etc.
Ceramics - utensils, handicrafts.
⑥Signs
Text instruction boards, dials, and formed objects.
⑦Circuit board printing
Printed circuit boards, civil or industrial substrates, thick film integrated circuit boards.
⑧Printing and dyeing
Printing and dyeing--flags, cloth, towels, handkerchiefs, shirts, vests, knitwear, etc. '
Other printing - pockets, shoes, bib numbers and various bags, backpacks, handbags, schoolbags, etc.
⑨Leather product printing
[Edit this paragraph]▼10. Detailed explanation of several types of screen printing and their application methods
Screen printing is a kind of printing with a wide range of applications. According to different printing materials, it can be divided into: fabric printing, plastic printing, metal printing, Ceramic printing, glass printing, electronic product printing, lottery screen printing, electronic decorative advertising board screen printing, metal advertising board screen printing, stainless steel product screen printing, light reflector screen printing, screen transfer anodized aluminum, screen printing and lacquer screen printing, etc.
Fabric printing
Fabric printing refers to the process of forming patterns on fabrics by printing. Printing methods include: pattern printing, screen printing, drum screen printing, transfer printing and multi-color shower printing. Screen printing is derived from pattern printing (including pattern paper and zinc plates). From manual operation, it gradually moved towards semi-automation, complete automation, and later developed from the flat mesh type to the rotary mesh type.
There are generally several printing methods for fabric printing:
1. Direct printing with paint
Direct printing with paint is to print the prepared printing paste directly on the fabric. This is the simplest and most commonly used process in the printing process. The paint direct printing process generally refers to printing on white or light-colored fabrics. It is easy to match colors and has a simple process. It can be baked after printing and is suitable for textiles of various fibers. The paint direct printing process can be divided into Acramin F-type adhesives according to the adhesives commonly used at present. There are three direct printing processes: acrylic adhesive, styrene-butadiene emulsion and chitin adhesive.
2. Silk printing
The main methods of silk printing include direct printing, discharge printing and resist printing. The direct printing method has been introduced before. The discharge printing method, transfer printing method, penetration printing method, etc. will be introduced separately in the relevant sections below. Here we mainly introduce the resist printing method.
3． Knitted underwear printing
Knitted underwear printing mainly uses the paint direct printing process. After printing, the fabric can be doubled or dried naturally, which avoids problems such as easy deformation of knitted fabrics during wet processing and difficulty in wet processing of agricultural films. The printing method is mainly flat screen screen printing, which is divided into two methods: manual scraping printing and machine operation. This printing method can adapt to various patterns and organizational structures, and is suitable for the production needs of small batches and multiple colors.
4. Discharge printing
Discharge printing is also called carving printing, which refers to a printing method that uses a discharge agent to print on colored fabrics to destroy the dyed pigments, thereby obtaining various patterns and patterns. Dye discharge agent is a chemical that can make dye base lose color. Diaobaijue, stannous chloride, etc. This method can be divided into two types: the pattern is white (discharge printing) and the pattern is colored (discharge printing). The latter dyeing method makes the fabric pattern fine, but the process is complicated and the cost is high.
5. Silk screen burnout
The burnout system uses two fiber blended fabrics with different acid resistance. After acid burnout printing and chemical processing, the natural fibers that are not acid-resistant are partially rotted away, revealing the acid-resistant fabric. The chemical fiber part forms a crystal-clear flower pattern, and its special style gives the burnt-out product a high-end and gorgeous feel. Burnt-out products not only have a gorgeous appearance, but also have excellent internal quality. They are wear-resistant, high-strength, easy to wash, quick-drying, and non-ironing, and are welcomed by domestic and foreign markets. The research and application of burnout technology has become popular in the textile printing and dyeing industry in recent years.
6. Wool fabric printing
At present, printed wool fabrics are mainly thin plain weave fabrics or gauze fabrics, which are mostly used to make women's shirts, dresses, quilts and skirts. In addition to direct printing, wool fabric printing also includes discharge printing, anti-printing and transfer printing. Wool blended fabric printing also occupies a certain proportion. At present, relief finishing of wool fabrics is also quite popular, mainly used for woolen sweaters.
7. Velveteen printing
Diamond printing takes advantage of the characteristics of silk screen printing to print on velvet, which can obtain a special flash effect, emitting the light of natural diamonds under sunlight. .
8. Foam printing
There are many varieties of special fabric printing, and foam printing is one of them. The characteristics of foam printing are: strong three-dimensional effect, similar to artificial embroidery, soft hand feel, wear-resistant, washable, good fastness, elastic, and can be widely used in tablecloths, curtains, tea towels, handkerchiefs, pillow covers, clothing, and travel Souvenirs, etc. It can be used not only on natural fiber fabrics such as cotton, linen, and silk, but also on man-made fiber fabrics.
9． Flocking printing
Electrostatic flocking is a new technology that is currently emerging in the textile industry. It is a product that uses high-voltage electrostatic fields to plant short fibers on gray fabrics. Flocking products have simple technology, strong three-dimensional effect and low cost. Therefore, they are widely used in rubber, plastics, artificial leather, and decorative products. Especially for small batches of tourism products, it shows its incomparable superiority. Using flocking patterns to decorate shoes, hats, children's clothing, trademarks, and clothing will make them unique.
10 Transfer printing Transfer printing is a printing process that relies on the sublimation of dyes and the diffusion and affinity of dye vapor to fibers to complete the coloring effect. Transfer printing is a printing and dyeing production method with practical significance in waterless processing. In addition to not using water, another major feature is that the paper deforms very little, so it can print fine multi-layered patterns and photographic images. Really transfer the pattern image to the cloth. The effect is sometimes better than ordinary anti-dye and discharge printing.
In addition to the above ten common printing methods, there are also some special printing methods, such as: electrochemical aluminum transfer printing, photoluminescence printing, fluorescent printing, gold and silver powder printing, paint foam printing, color changing printing , Fragrance printing, diamond printing and pearlescent printing, etc., printing methods.
[Edit this paragraph] Screen printing on glass
Based on the principle of screen printing, ink is printed on the surface of flat glass, and then the ink is cured to make the pattern strong and durable. The process is as follows:
Stretching → Sizing → Drying → Printing → Developing → Drying
↓
Flat glass → Cutting → Edge grinding → Cleaning Drying → Printing
↓
Sintering
Suitable for printing glass
Cut the glass according to user requirements, which can be regular shapes or It can be of irregular shape, then chamfered and ground, then cleaned, dried and ready for use. Special attention should be paid here that there should be no water marks on the surface of flat glass.
Selection of screen
The screen printing plate used for flat glass printing is the same as the general screen printing plate. The glass screen printing plate can be made of synthetic fiber screen, stainless steel screen, natural screen. Fiber screen. When printing general color materials, any of the above-mentioned screens can be used, and generally cheap synthetic fiber screens are used; when used for gold and silver decoration, stainless steel screens cannot be selected. The specifications of the wire mesh are generally 270 to 300 mesh.
Selection of screen frame
At present, the more formal screen frame with less deformation is the aluminum alloy screen frame. Its size should be larger than the pattern, and the specific size should be the outer edge distance of the pattern. The screen frame should be between 70 and 100mm. In addition, when choosing a screen frame, its strength is very important. The key is to have enough rigidity in the horizontal direction.
Stretch net
Choose mesh silk and net frame, combine the two, this is stretch net. There are many ways to stretch the screen, including manual, motorized, and pneumatic methods. The most advanced one at present, which can stretch high-quality screens, is the pneumatic stretcher. The requirements for stretching the mesh are that the tension is uniform, the warp and weft lines of the mesh should be kept vertical, and the mesh glue should be firm and not loose.
Choose photosensitive glue
Currently commercially available photosensitive glues include dichromate series, diazonium salt series, and iron salt series. The requirements for photosensitive adhesive for screen printing plate making are: good plate making performance and easy coating. The photosensitive spectrum range is 340~440nm, with good developing performance, high resolution, good stability, easy to store, economical and hygienic, non-toxic and non-polluting. The requirements for photosensitive materials in printing are: the plate film formed by the photosensitive materials can adapt to the performance requirements of different types of inks. It has considerable printing resistance and can withstand a considerable number of scrapings by the squeegee; it has good bonding force with the screen and does not cause release problems during printing; it is easy to peel off, which is conducive to the recycling of screen plates.
Drying the plate
After selecting the above materials, apply photosensitive glue in the darkroom; it must be uniform and then dry. Generally, it is required to apply it twice. Printing requires exposure on a cold light source printing machine. The exposure time should be determined according to the pattern, usually between 12 and 30 minutes. After exposure and development, the screen printing screen is produced.
Printing
Flat glass printing machines include manual, semi-automatic, and fully automatic types. Manual printing machines are suitable for small batches and small specifications of flat glass. Semi-automatic and fully-automatic printing machines are suitable for large-volume, large-size, multi-color printing, and have the advantage of accuracy and speed. The largest semi-automatic printing machine can print glass with a size of 2000×1500mm. Fully automatic printing machines are generally used for printing car windshields, and several foreign companies can provide such equipment.
Ink
Flat glass decorative ink is divided into two types: organic ink and inorganic ink. The colorants and connecting materials of organic ink are all organic substances. This kind of ink has a good effect in decorating flat glass, but the film is not strong enough and the chemical stability is not good. It is a short-life decoration method. Inorganic ink is composed of colorants, fluxes, and connecting agents. The colorants are inorganic colorants such as chromium oxide, cobalt oxide, etc. The flux is low melting point glass, common ones include lead oxide and borosilicate glass. The most important thing about the performance of the flux is that it is not too different from the thermal expansion coefficient of the printed glass.
Typical flux components: SiO2 19182, As2O3 2113, MgO 0146, PbO 62110, CaO 0127, K2O 1183, B2O3 10175, Al2O3 1163, Na2O 1176. The connecting agent in inorganic ink - scraper oil is an organic substance that is completely burned during the sintering process, but has no effect on the decorative effect.
The composition of scraper oil is: 3g ethyl cellulose, 100ml terpineol, 10ml turpentine, 5ml alkyd resin. The ratio of pigment and connector of inorganic ink is 10g:8ml, which can be obtained by stirring and grinding.
Sintered
Glass is an amorphous inorganic material that softens as the temperature increases. When heated to the softening temperature of the glass, the glass will deform. Glass glaze is decorated on the surface of flat glass through silk screen printing and needs to be solidified on the glass surface through high-temperature sintering. However, the sintering temperature must be lower than the softening temperature of the decorated glass to ensure that the decorative glass does not deform. Generally, the sintering temperature of glass glaze is not higher than 520°C, and is usually controlled between 480 and 520°C.
Low-temperature glass glazes are produced by several manufacturers in China, and the prices are relatively low. There are several international companies that can provide similar products, but the price is ten or twenty times different from domestic products. Domestic consumption levels have not yet reached the level of using this type of glaze, but the glazes provided abroad are indeed much better in color and layer than domestic ones. To improve the quality of decorative glass, it is inevitable to improve the grade of glaze. Sintering equipment includes flame furnaces and resistance furnaces. Resistance furnaces are divided into vertical hanging type and horizontal roller type according to the hanging method of glass.
The vertical hanging sintering furnace has the advantages of small sintering deformation and a yield of more than 95%, but the equipment is complicated. If the horizontal roller type is not properly adjusted, it is prone to large deformation and low yield. In addition, it is also feasible to use a horizontal tempering furnace to produce decorative glass. The grade of the product is improved and the safety is guaranteed. It is an ideal sintering method.
[Edit this paragraph]▼11. The development direction of screen printing technology
There is no doubt that if a rotary screen printing machine using water-based ink can be developed, if the screen printing machine is more efficient, if parameters such as scraper pressure, speed and angle can be read If program control can be obtained and implemented, if the production can be repeated according to the program when printing repeated prints, and if the production data can be used correctly in the entire process from pre-press preparation to printing, screen printing will definitely develop further. my country's screen printing will develop in depth and breadth in the future. "Deep" means developing to a higher level. The international screen printing industry has already widely used computer design, plate making, electronic engraving and other advanced technologies, but our country is still in the research and trial stage of these new technologies; "wide" means developing new ones. Screen printing products, such as outdoor large screen printing advertisements, etc. Therefore, my country's packaging and printing will make a leap forward in terms of equipment, technology and scale.