Screen printing 1000 questions (1-5)

â–¼1. What is screen printing?

Screen printing belongs to stencil printing, which is called four printing methods together with plain printing, embossing, and gravure printing. Stencil printing includes stencil printing, stencil printing, spray printing, and screen printing. The principle of stencil printing is: the printing plate (the aperture of the printing plate or other printing plate can be used to make the ink through the hole) at the time of printing, the ink is transferred to the substrate (paper, ceramic, etc.) through the hole of the stencil through a certain pressure. ), forming an image or text. The stencil printing is the simplest stencil printing, beginning in the late 19th century. This type of printing is made on a special type of wax paper, and a graphic version of the wax paper is made by a typewriter or a stylus, and an ink roller is used for printing on a wax paper plate. The desired printing effect can be obtained on the substrate. In stencil printing, the most widely used is screen printing.

In screen printing, a silk fabric, a synthetic fabric, or a metal mesh is stretched over a wire frame, and a screen printing plate is produced by manually lacquering a film or photochemically making a plate. In modern screen printing technology, screen printing plates are produced by photolithography using photosensitive materials (such that the screen holes in the graphic portion of the screen plate are through holes, and the screen holes in the graphic portion are not blocked. live). During the printing, the squeegee presses the ink through the mesh part of the graphic part and transfers it to the printing material to form the same image as the original. Screen printing equipment is simple, easy to operate, printing, plate making simple and low cost, strong adaptability. Wide range of screen printing applications are common prints: color paintings, posters, business cards, binding covers, merchandising signs, and textile printing and dyeing.

â–¼2. When was screen printing invented?

Screen printing originated in China and has a history of more than 2,000 years. As early as the ancient Chinese Qin and Han Dynasties, there was a folder printing method. In the Eastern Han Dynasty, the method of batik batik was widespread, and the level of printed products also increased. To the great cause of the Sui Dynasty, people began to use the frame with a stretched net to carry out printing, so that the folder printing process developed into a screen printing. According to historical records, the exquisite costumes worn by the court during the Tang Dynasty were printed in this way. By the Song Dynasty, silk screen printing had developed and improved the oil paint originally used. It began to add starch-based rubber powder to the dye to make it a paste for screen printing, making screen printing products more colorful.

Screen printing is a major invention in China. The United States "Serigraphy" magazine has commented on China's screen printing technology: "There is evidence that the Chinese used the stables and templates two thousand years ago. The clothing of the early Ming Dynasty proved their competitive spirit and processing technology. “The invention of screen printing has promoted the development of human material civilization in the world. Today, two thousand years later, screen printing technology has been continuously developed and has become an indispensable part of human life.

â–¼3. What is the principle of screen printing?

Screen printing consists of five major elements: screen printing plates, squeegee blades, inks, printing stations, and substrates. The basic principle of screen printing is: using the screen printing plate graphics part of the network through the ink, non-graphical part of the mesh does not penetrate the basic principles of printing ink. During printing, ink is poured onto one end of the screen printing plate, and a certain pressure is applied to the ink portion of the screen printing plate by the squeegee blade while moving toward the other end of the screen plate. The ink is pushed by the squeegee from the aperture of the graphic portion onto the substrate during the movement. Due to the stickiness of the ink, the imprinting is fixed within a certain range. During the printing process, the squeegee is always in line contact with the screen plate and the substrate, and the contact line moves with the squeegee, due to the screen plate and the substrate. Keeping a certain gap between them makes the screen printing plate at the time of printing produce a reaction force against the squeegee by its own tension, and this reaction force is called resilience. Due to the effect of the resilience, the screen plate and the substrate are brought into contact with only the movable line, and the other portions of the screen plate are separated from the substrate. Causes the ink and the screen to undergo a cracking motion, which ensures the dimensional accuracy of printing and avoids soiling substrates. When the squeegee is scraped across the entire plate, it is raised and the screen plate is lifted, and the ink is scraped back to its original position. This is a printing trip.

â–¼4. What is the main difference between screen printing and other printing methods?

The main differences between screen printing and other printing methods are as follows:
1 Printing adaptability The three major printing methods of plain printing, embossing, and gravure printing can generally only print on flat substrates. Screen printing can not only be printed on a flat surface, but also printed on curved, spherical and irregular substrates. On the other hand, screen printing not only can be printed on hard objects, but can also be printed on soft objects without being limited by the texture of the substrate. In addition, in addition to direct printing, silk screen printing can also be printed by indirect printing methods as required, that is, screen printing on gelatin or silica gel plates and transfer onto substrates. Therefore, it can be said that screen printing has a strong adaptability and a wide range of applications.

2 thick ink layer, strong three-dimensional sense, texture rich offset and embossed ink layer thickness is generally 5 microns, gravure is about 12 microns, flexographic (aniline) printing ink layer thickness of 10 microns, and screen printing The thickness of the ink layer far exceeds the thickness of the above ink layer, generally up to about 30 microns. Thick screen printing for special printed circuit boards, ink layer thickness up to 1000 microns. Braille ink is printed in foamed ink. The thickness of the ink layer after foaming can reach 300 microns. The screen printing ink layer is thick, the printing quality sense is rich, the three-dimensional sense is strong, this is other the printing method cannot compare. Screen printing can not only print in a single color, but also perform color registration and screen color printing.

3 High light fastness and bright color Since the screen printing has the feature of missed printing, it can use various inks and coatings. It can not only use pastes, adhesives and various pigments, but also can use coarser pigments. In addition, the screen printing ink preparation method is simple, for example, lightfast pigments can be directly placed in the ink, which is another major feature of screen printing. Screen printing products have a great advantage of strong lightfastness. It has been shown through practice that the maximum density value range measured after a single imprint of black ink on a coated paper is compared. The offset printing is 1.4, the embossing printing is 1.6, and the gravure printing is 1.8. The screen printing maximum density value range can be Up to 2.0, so the light resistance of screen printing products is stronger than other kinds of printing products, and is more suitable for outdoor advertising and signage.

4 Large printing area At present, the size of the area printed by offset printing, embossing, and other printing methods is at most the full-sheet size, which exceeds the full-sheet size and is limited by mechanical equipment. Screen printing can be used for large-area printing. Today's screen printing products can reach a maximum of 3 meters by 4 meters or even larger.

The above four points are the difference between screen printing and other printing, but also the characteristics and advantages of screen printing. Understand the characteristics of screen printing, in the selection of printing methods, you can avoid weaknesses, highlight the advantages of screen printing, in order to achieve a more ideal printing effect.

â–¼5. What type of manuscript is suitable for screen printing?

Screen printing, like other printing, requires accurate reproduction of the original text and color tone. The original used for screen printing is not very different from the original used in other printing methods. However, in the specific plate making and printing practice, the requirements are different, which is mainly determined by the screen printing characteristics. In particular, since the screen printing ink layer is thick and bright in color, it is necessary to fully consider the special effects of screen printing when selecting originals and plate making.

In addition, the graphic lines and dot precision requirements of the manuscript used for screen printing are different from those required for ordinary printing methods. If the lines and dots of the original are very fine, it is very difficult to use screen printing. Therefore, screen printing techniques are not suitable for reproducing fine lines and dot-line originals. When selecting the printing method, various printing characteristics must be fully considered. Even in the screen printing plate making also pay attention to choose the appropriate network cable, in order to achieve the purpose of full reproduction of the original.

Silk-screen printing is more suitable for the expression of monochromatic color originals with vivid characters and lines. It is also suitable for the expression of color originals with large contrast and clear levels. Thanks to the special effects of screen printing, replicas are rich in expressiveness, and the texture and three-dimensional effect of the manuscript content are fully expressed through the rich contrast of light and shade of the thick ink layer and tone.

There are two kinds of reflective originals and transmitted originals for screen printing. Usually, reflective originals are mainly used. Color photography mostly uses transmissive originals.

Screen printing mainly uses Yang photo making screen. Different platemaking methods also have different requirements for manuscripts.

----Qi Lu Graphic Arts