Screen printing began in the late 19th century and is one of the four common printing methods. During printing, through the extrusion of the squeegee, the ink is 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, easy to print and plate making, low cost, and strong adaptability. Different from the other three methods, it can not only print on the plane, but also because the screen can partially wrap the three-dimensional object, so this enables screen printing to print images and texts on the already made molded products. . In recent years, screen printing has developed rapidly and is called “the king of decoration printing”.
Screen printing belongs to stencil printing, and it is called the four major printing methods together with lithographic printing, letterpress printing, and gravure printing. Stencil printing includes transcription, perforated pattern, spray pattern and screen printing. The principle of stencil printing is: during printing, the printing plate (paper film plate or other plate base with holes through which the ink can pass) transfers the ink through the holes of the stencil to the substrate (paper, ceramics, etc.) through a certain pressure. ) to form images or text.
During printing, through the extrusion of the squeegee, the ink is 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, easy to print and plate making, low cost, and strong adaptability. Common applications of screen printing are: color oil paintings, posters, business cards, binding covers, commodity signs, signage, and printing and dyeing textiles.
Screen printing consists of five elements, namely screen printing plate, squeegee, ink, printing table and substrate.
The basic principle of screen printing is to use the basic principle that the mesh of the graphic part 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 ink on one end of the screen printing plate, apply a certain pressure to the ink part of the screen printing plate with a scraper, and move to the other end of the screen printing plate at the same time. The ink is squeezed onto the substrate by the scraper from the mesh of the graphic part during the movement. Due to the viscosity of the ink, the imprint is fixed within a certain range. During the printing process, the squeegee is always in line contact with the screen printing plate and the substrate, and the contact line moves with the movement of the squeegee. Since a certain gap is maintained between the screen printing plate and the substrate, the screen printing plate during printing generates a reaction force on the scraper through its own tension, and this reaction force is called rebound force. Due to the effect of resilience, the screen printing plate and the substrate are only in moving line contact, and the screen printing plate is in a state of separation from the curled penny and the fog, which causes the ink and the screen to break and move to ensure the printing. Dimensional accuracy and avoid smearing gold dirty substrates. When the squeegee scrapes the entire layout and lifts, the screen printing plate is also lifted, and the ink is gently scraped back to the original position. So far it’s a printing trip
①The printing adaptability is strong. The three major printing methods of lithography, gravure and embossing can generally only be printed on flat substrates, while screen printing can not only print on flat surfaces, but also print on curved, spherical and concave-convex substrates. On the other hand, because the screen printing plate is soft and has a certain elasticity, and the printing pressure is small, screen printing can not only print on hard materials, but also print on soft materials and fragile objects. Not limited by the texture of the substrate. In addition, in addition to direct printing, screen printing can also be printed by indirect printing method as needed, that is, screen printing on gelatin or silicone plate first, and then transfer to the substrate. Therefore, screen printing is highly adaptable and has a wide range of applications.
②The ink layer is thick and the three-dimensional effect is strong. The thickness of the ink layer on the substrate is different for different printing methods. The thickness of the ink layer of offset printing and embossing is generally about 5 μm, that of gravure printing is about 12 μm, that of flexographic printing is about 12 μm, and the thickness of the ink layer of screen printing is about 12 μm. It far exceeds the thickness of the above-mentioned ink layer, generally up to about 30 μm. Special thick film screen printing for printed circuit boards, the thickness of the ink layer can reach 1000μm, Braille characters are printed with foaming ink, and the thickness of the ink layer after foaming can reach 300μm. The screen printing ink layer is thick and the three-dimensional effect is strong, which is incomparable with other printing methods.
Screen printing can not only print in monochrome, but also register and screen color printing.
③ Strong light resistance and bright colors. Because screen printing has the characteristics of missing printing, it can use various inks and coatings, not only pastes, binders and various pigments, but also coatings with coarser particles. besides. Screen printing ink formulation method is simple, eg. Putting the light-fast pigment directly into the ink can make the screen printing products have strong light-fastness, which is more suitable for outdoor advertising and signage.
④The printing format is large. Generally, the printing format of convex case, offset printing and other printing methods is the largest full sheet or double full sheet. If this size is exceeded, it is limited by mechanical equipment. And screen printing can be used for large-area printing. Today’s screen-printed products have a maximum size of 3 × 4 square meters, or even larger. Screen printing can also print on ultra-small, ultra-high-precision specialty items. This characteristic makes screen printing great flexibility and wide applicability.
Compared to lithographic offset printing, the limitation of screen printing is the smaller range of layer reproduction. The color stability of color printing is difficult to control, and the overprint error is also large, and it is difficult to print fine products.
The range of screen printing applications is very broad. In addition to water and air (including other liquids and gases), any kind of object can be used as a 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 likely to be the screen printing method. Specifically, screen printing is mainly used in the following aspects:
Paper printing: art printing (advertising, pictorial, calendar, lantern paper), trademark printing, transfer printing, packaging printing, building materials printing (paste wallpaper):
Plastic printing: plastic film (vinyl toys, school bags, plastic bags), plastic scales (fake metal composite materials and various scales), production parts (instrument parts);
Printing of wood products: handicrafts (lacquerware, wooden handicrafts, toys), semi-finished products (sports goods, wooden boards, ceilings, road signs, signs, fake metal plates, billboards);
Metal product printing: metal slips, metal utensils, metal products;
Glass, ceramic products printing: glass (mirrors, glass plates, cups, bottles), ceramics (utensils, handicrafts);
Signs: text boards, dials, shaped items;
Circuit board printing: printed circuit boards, civil or industrial substrates, thick film integrated circuit boards:
Printing and dyeing: printing and dyeing (flags, cloth, towels, handkerchiefs, shirts, vests, knitwear), other printing (pockets, shoes, bibs and various bags, backpacks, handbags, school bags);
Leather goods printing: clothing (clothes, shoes, belts, bags, wallets).