To achieve screen printing, the screen-printing sensitizer (or coating) must be attached to a special cloth or screen to produce the images needed for screen printing. To get good screen printing quality, the choice of screen is very important. It depends on printing requirements, print quality, type of template or media, how much detail is printed, and the surface condition of the substrate. But no matter what kind of wire mesh material, it must have a certain degree of elasticity and strength, can withstand dragging back and forth without being torn; it must have a clearly visible mesh; mesh and opening must be the same size; wire The network cable must not run. The screen must be resistant to pigments, inks, solvents, resistance to cleaning, resistance to media, resistance to pull, resistance to rubber, adapt to storage conditions, resistance to vibration and extrusion of the printing press, and suitability for printing. Other conditions. In short, the conditions of the screen are very demanding.
In foreign countries, such as the United States and other countries, the materials used for screens are mainly silk (mesh), nylon (nylon mesh), polyester (polyester mesh), metal-treated polyester (nickel-plated polyester mesh), and stainless steel (stainless steel mesh), phosphor bronze, thin cotton, cotton and some cheesecloth. The wire used as a mesh may be made of animal materials, or may be made of plants, minerals, synthetic materials, and combinations thereof. The following describes the advantages and disadvantages of different screen meshes by illustrating the printing characteristics, usage, and practicality of various screen materials.
Development and progress <br> <br> silk screen, especially since 1945, have tended to meet the complex application of screen printing, such as the very fine print, the printed circuit and so on. At the same time, it also tends to produce sophisticated, high-end screen printing products.
Screen printers conducted various production experiments on wire mesh materials and found that silk is the most satisfactory wire mesh material in general use. This is mainly due to the chemical and physical properties of silk, as well as its multi-filament characteristics, which make it advantageous for the best adhesion of screen printing films and emulsion layers. In spite of this, nylon and polyester meshes can be finely woven, and finer details can be obtained in printing. Therefore, the current use of silk fabrics is not as much as nylon and polyester. However, silk screens are undoubtedly the earliest in terms of the silk screen family rankings, and it is precisely because of this that the name “silk screen printing†is used as a generic term for all screen printing. In the 19th century, the Netherlands, Switzerland and France initially used silk to filter flour, which was the earliest analogue of screen printing. Silk is the strongest of natural fibers, and the maximum number of screens it can produce can reach 25,000 impressions. Wire mesh can be categorized in the following ways: (a) woven structure; (b) number of threads, ie, how many meshes per inch or cm; (c) quality.
There are two basic methods of weaving in a woven structure: the weaving method and the weaving method. The braided wire mesh is thick and strong. The weaving method uses two warps to twist on the weft. It can prevent slippage of the weft and better maintain the consistency of the mesh. On the screen cloth, the warp direction is the length direction, and the weft direction forms a cross intersection with it. In addition, the two directions must be the same in length and thickness. It is mostly used for large area thick ink printing.
The leno weaving method was changed from the weaving method and was made on a leno weaving machine. Yarn weaving and leno weaving have better product strength.
Flat weave, sometimes called plain weave. Plain weave mesh is the use of this weave. The weaving method of plain weave has the densest weft and warp, the best strength, the uniform mesh, and the imprinting is clearer than other weaves. Plain weave is used for screens up to 305 mesh/inch.
For the classification of the number of lines, the standard burrs are NO.0000 to NO.25, NO.0000 is the roughest, and NO.25 is the finest. The higher the number of lines, the smaller the opening of the screen and the finer it is. For example, the roughest NO.2 used in the screen is 53 lines/inch; NO.25 is 200 lines/inch. NO.10, 12, 14 and 16 are the most commonly used screen printing. Among them, NO.12 is most applicable. The stencil cloth does not use the number of lines to classify, but it also needs to provide the corresponding wire data information in the screen industry.
When marking the quality, the numbers on the silk fabric end with "X," "XX," or "XXX,". These signs indicate the strength of the screen. In the market, the screen quality may have only numbers (NO.12, NO.14, etc.); there are one with X (NO.12X, NO.14X, etc.); there are two with X (NO. 12XX , NO.14XX, etc.); with three X (NO.12XXX, NO.14XXX, etc.). With two X is commonly used in screen printing, with three X screen can be used for thicker network conditions. However, in some cases it is also replaced by a double X multi-fibre polyester, such as thicker inks and higher pressures. The width of the screen can be up to 60 inches (152 cm) in length.
Plain screens are available in sizes ranging from NO.6XX (74 lines/inch or 29 lines/cm) to NO.16XX (157 lines/inch or 62 lines/cm) up to 60 inches (152 cm) in width.
The finer the printing, the higher the number of screens. However, if the screen is too thin, it may cause the ink to pass through the mesh or even block the mesh. In the case where the screen satisfies printing requirements, screen printers use rough screens as much as possible. Table 1 shows the number of different screens used in a given number of screens, the screen aperture (or opening), the number of screens, and the type of stencil.
Artificial silk cloth
Artificial silk cloth is a synthetic cloth. The most commonly used are nylon and polyester. These materials have high abrasion resistance, high elastic strength, and high elasticity, so they are very suitable for making wire mesh. The uniform mesh of the artificial cloth, especially the single fiber thread, can form a square mesh on the screen cloth. Silk and polyester meshes can only be obtained from multi-fiber threads, but nylon, polyester and metal meshes can be obtained from monofilament threads, ie, each thread contains only one fiber.
Screen suppliers sell polyester screens from NO. 6XX to NO. 21XX (multi-fiber), approximately between 65 lines/inch and 300 lines/inch. Nylon and silk screens are sold between about NO.6XX and NO.25XX, with 30 lines/inch to 460 lines/inch. The width can reach 120 inches.
Cotton fabric
Cotton fabrics are woven from cotton and have many grades. It is mostly used for short live, because it is not as durable as silk. Knife stencils and photo plates can be used for this material. Since it will scratch the cable during cleaning, it is generally best not to reuse it. In addition, the use of such screens wastes ink compared to other screens and can become slack after repeated use. The screen width is between 37 inches and 60 inches. There are domestic and imported.
Cotton yarn
Cotton yarn (or cotton) is woven from cotton or linen. It is rough, about the equivalent of NO.4 or NO.5 silk. It can be used to print the surface of the stencil that is in contact with the cloth, and can be used for long-lived printing from 5,000 to 10,000 prints. It is cheaper than silk and has the same width.
chiffon
Tulle is a cloth used for roller printing in the wire mesh industry. Although it is mainly used abroad, it is also necessary to understand it. There are some grades of this cloth in cotton and silk. It is the cheapest cloth and cannot be reused. It is equivalent to NO.20 wire mesh and is the only kind of wire mesh with a paper stencil.
Before the tulle sticks under the frame, it should first be immersed in water and squeezed out of the water before it sticks to the frame. So it can stick more firmly. The ink used is a thin standard ink, or other less expensive ink. The ink passes through the screen under the pressure of the printing roller and is printed on paper or cardboard. Be careful not to use a squeegee, only print rollers, because the squeegee is easy to scratch the thin gauze screen.
There are other materials that can be used for screen cloths, but they must be practiced many times under normal printing conditions before being promoted for industrial use.
Since it is difficult to distinguish between two different numbers of screens by ordinary observation, the screen number should be marked on the edge of the screen. Some screen printers use different colors to distinguish different screens with different colors. And the printer must always know which screens are rough and which screens are fine, and choose the screen that best suits them.
In a word, there are many kinds of screen materials, so we must know more about the screen before we can choose which ones we can clearly know which material is best suited to our production needs.