Screen printing refers to the screen printing plate with pictures and texts, which is based on the screen and made by the photosensitive plate making method. Screen printing consists of five elements: screen printing plate, scraper, ink, printing table and substrate. Using the basic principle of screen printing that part of the mesh of image and text can pass through the ink and part of the mesh of non image and text can’t pass through the ink. During printing, ink is poured into one end of the screen plate, and a scraper is used to exert certain pressure on the ink part of the screen plate. Meanwhile, the ink moves towards the other end of the screen plate at a constant speed. During the movement, the scraper squeezes the ink from the mesh of the graphic part to the substrate.
Silk screen printing is to make silk screen printing plate with silk fabric, synthetic fiber fabric or metal wire mesh stretched on the screen frame and by hand carved paint film or photochemical plate making method. Modern screen printing technology is to use sensitive materials to make a screen plate by means of photoplate making (making the screen hole of the graphic part of the screen plate as a through hole instead of the screen hole of the graphic part blocked). Oil painting, print, poster, business card, binding cover, commodity packaging, commodity label, printing and dyeing textiles, glass and metal plane carriers, etc.
Working principle
Screen printing consists of five elements: screen plate, scraper, ink, printing table and substrate. The basic principle of screen printing is to use the basic principle of screen printing that the part of image and text is ink permeable and the part of non image and text is ink impermeable. When printing, pour ink into one end of the screen printing plate, apply certain pressure on the ink part of the screen printing plate with the scraper, and move towards the other end of the screen printing plate at the same time. The ink is pressed to the substrate by the scraper from the mesh of the graphic part during the movement. Due to the stickiness of the ink, the imprint is fixed within a certain range. In the printing process, the scraper is always in line contact with the screen printing plate and substrate, and the contact line moves with the scraper movement. Because there is a certain gap between the screen printing plate and substrate, the silk screen printing plate will produce a reaction force on the scraper through its own tension. This reaction force is called back force Elastic force. As a result of the effect of resilience, the screen printing plate and substrate are only in mobile line contact, while other parts of the screen printing plate are out of contact with substrate. So that the ink and screen fracture movement, ensure the printing size accuracy and avoid rubbing dirty substrate. When the scraper scrapes across the whole page, it lifts up the screen printing plate, and scrapes the ink back to its original position. This is a printing trip.
Advantage
Advantages of screen printing:
(1) Not limited by substrate size and shape
Generally, printing can only be carried out on a plane, while screen printing can not only be carried out on a plane, but also on a special shaped shaped object such as a spherical surface, and anything with shape can be carried out by screen printing.
(2) Soft printing
The screen is soft and elastic.
(3) Strong ink coverage
It can be printed in pure white on all black paper with strong stereoscopic sense.
(4) Suitable for all kinds of ink
(5) Strong optical rotation resistance
It can keep the luster of the printed matter unchanged. (no effect of temperature and sunlight). This makes printing some adhesive, without additional lamination and other processes.
(6) Flexible printing methods
(7) Convenient plate making, low price and easy to master technology
(8) Strong adhesion
(9) It can be printed by hand or by machine
(10) It is suitable for long-term display, and the outdoor advertisements are expressive
Distinguishing characteristics
Strong printing adaptability
In general, the three printing methods of lithography, embossing and gravure can only be printed on the flat substrate. Screen printing can be used not only on the plane, but also on the substrate of curved surface, spherical surface and concave convex surface. On the other hand, screen printing not only can be printed on hard materials, but also on soft materials, not limited by the texture of substrate. In addition, in addition to direct printing, screen printing can also be used as required by indirect printing method, that is, first screen printing on gelatin or silica gel plate, and then transfer to substrate. Therefore, it can be said that screen printing has a strong adaptability and a wide range of applications.
Stereoscopic perception
The thickness of ink layer of offset and embossing with rich texture is generally 5 microns, that of gravure printing is about 12 microns, and that of flexographic (aniline) printing is 10 microns. The thickness of ink layer of screen printing is far greater than that of the above ink layer, generally up to about 30 microns. Special printed circuit board with thick screen printing, ink layer thickness up to 1000 microns. Braille braille is printed with foaming ink, and the thickness of the ink layer after foaming can reach 1300 microns. The screen printing ink layer is thick, the printing quality is rich, and the stereoscopic sense is strong, which can not be compared with other printing methods. Screen printing not only can be monochromatic printing, but also can be used for chromatic overprinting and screen printing.
Light fastness
Because screen printing has the characteristics of missing printing, it can use all kinds of ink and coating, not only can use slurry, adhesive and all kinds of pigments, but also can use pigment with coarser particles. In addition, screen printing ink is easy to deploy, for example, the light resistant pigment can be directly placed in the ink, which is another feature of screen printing. Screen printing products have a great advantage of light resistance. The practice shows that compared with the maximum density range measured after one time of using black ink on copper plate paper, offset printing is 1.4, convex printing is 1.6, gravure printing is 1.8, and the maximum density range of screen printing is 2.0. Therefore, the light resistance of screen printing products is stronger than that of other kinds of printing products, which is more suitable for outdoor advertising and sign.
Large printing area
In general, the area size printed by offset printing, embossing and other printing methods is the maximum full size. If the area size exceeds the full size, it is limited by mechanical equipment. However, screen printing can be used for large-area printing. Nowadays, the maximum range of screen printing products can reach 3M × 4m, or even larger.
The above four points are the differences between screen printing and other printing, as well as the characteristics and advantages of screen printing. Understanding the characteristics of screen printing, in the selection of printing methods, we can develop advantages and avoid disadvantages, highlight the advantages of screen printing, so as to achieve a more ideal printing effect.
main features
The characteristics of screen printing are summarized as follows:
① There are many types of inks that can be used for screen printing. Namely: oil, water, synthetic resin emulsion, powder and other types of ink.
② The layout is soft. Screen printing is not only suitable for printing on soft articles such as paper and cloth, but also suitable for printing on hard articles such as glass and ceramics.
③ Screen printing has a small imprinting force. Due to the small pressure used in printing, it is also suitable for printing on fragile objects.
④ Thick ink layer, strong coverage.
⑤ It is not limited by the surface shape and area of substrate. It can be seen from the above that screen printing can not only be printed on the plane, but also on the curved surface or spherical surface; it is not only suitable for printing on small objects, but also suitable for printing on large objects. This printing method has great flexibility and wide applicability.
Printing method
There are two kinds of screen printing: manual printing and mechanical printing.
Manual printing refers to the up and down movement of the printing plate from paper renewal to paper receipt, and the scraping and scraping are all manual operations.
Mechanical printing refers to the printing process completed by mechanical action. It is also 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; full-automatic means that the whole printing process is done by machinery.
There is also a quick and easy curved screen printing method, movable screen printing, that is, the screen is removed and printed directly on the substrate surface. With live screen printing method, a large number of printed products can be printed, such as latex plastic bucket, pure water bucket, washbasin, thermos bottle, cup, bowl, plate and other products. At the same time, the method can be used to print the signboard on the automobile and the special plane.
Production of the screen plate: first, dry and repair the sensitive text plate, then remove it and cut it according to the size. And at both ends of the screen plate with wood or aluminum as the skeleton with adhesive tape, can also be used to directly glue, so that can be made into the required live surface screen version. Operation method of movable surface screen: different printing materials are selected according to the substrate for mixing: first, select a flat plate and a plate to mix the ink, then, one person holds the movable surface screen plate with both hands to tightly stick the printed part on the substrate surface, the other person uses a scraper to evenly dip the ink on the upper surface of the scraper, and then place the scraper on the inking plate evenly Print evenly on the layout.
If the printed graphic area is too large, the ink can be poured on the layout according to the situation, but do not let the ink flow out of the substrate. Pay attention to the deployment of ink not too thin, not too dry, moderate humidity is good. Small area printing and painting can be operated by one person. One end of the movable surface plate is pasted on the required position of the substrate machine with packaging tape, and then the plate is tightened tightly on the substrate with the other hand to print. Attention to plate starting: the plate starting must be lighter according to the direction of one end of the adhesive tape. If two people operate the plate starting advertisement, the same is true. This method of printing has the advantages of convenient operation, flexible requirements for substrate, large capacity, small quantity, low cost and energy saving.
Printing classification editor
Screen printing not only adapts to general paper printing, but also has a wide range of adaptability. For example: ceramics, glass, printed circuit board, etc. According to the different texture of the substrate, the printing time is different. Although each series has an inseparable internal relationship, they have their own particularity due to the different substrate (i.e. 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. In this way, a relatively independent printing system is formed.
Main application
Screen printing is widely used. Any object other than water and air (including other liquids and gases) can be used as substrate. It has been said in the evaluation of screen printing that if you want to find the ideal printing method on the earth to achieve the printing purpose, it is likely to be screen printing.
Specifically, screen printing is mainly used in the following aspects:
① Paper printing art printing — advertising, pictorial, calendar, lantern paper, etc.
Trademark printing
Transfer printing
Packaging printing
Building materials printing – wall paper pasting, etc
② Plastic printed plastic film — Vinyl toys, schoolbags, plastic bags, etc.
Plastic standard plate – false metal composite material and various standard plates.
Production parts – instrument parts.
③ Wood printing crafts — lacquerware, wood crafts, toys.
Processing semi-finished products — sporting goods, wooden boards, ceilings, road signs, signboards, fake metal wrenches, billboards, etc.
④ Metal products printing metal cylinder, metal ware, metal products.
⑤ Glass, ceramic printing glass — mirror, glass plate, cup, bottle, etc.
Ceramics — utensils and crafts.
⑥ Sign text description board, dial, shaped items.
⑦ PCB printed circuit board, base plate for civil or industrial use, thick film integrated circuit board, cold light sheet.
⑧ Printing and dyeing — flags, fabrics, towels, handkerchiefs, shirts, vests, knitwear, etc.
Other printing — pocket, shoes, number cloth and all kinds of bags, backpacks, handbags, schoolbags, etc.
⑨ Leather printing