The screen version is one of the important factors determining the quality of screen printing. Many screen printing quality problems are directly or indirectly related to the materials used in the screen making process and plate making. Therefore, in order to ensure good screen printing quality, it is necessary to strictly select the plate-making materials according to the requirements of the screen-making process, and at the same time correctly master the screen-making technology and rationally select the plate-making equipment. Choice of mesh and net frame 1. Choice of mesh The screen version has the following basic requirements for the selected mesh. (1) The tensile strength is large. The screen has the ability to resist damage (fracture) when subjected to a certain tensile force. In addition, the change in strength after moisture absorption of the screen should be small. (2) The elongation at break is small. Elongation at break is the ratio of the elongation of the screen to the original length when broken under a certain tension, expressed as a percentage. When the elongation at break is large, the planar stability of the screen is poor. In addition, the screen is also required to have sufficient elasticity under a certain tension (about 3%). (3) Good resilience. Resilience refers to the recovery ability after the wire is stretched for a certain length and the external force is released. The better the rebound resilience, The sharper the printed edge. In addition, the screen is required to have good temperature and humidity change stability, good ink penetration performance, and good chemical resistance. Comprehensive comparison, nylon mesh and polyester mesh basically meet the above requirements. In order to ensure the accuracy of screen printing, monofilament polyester mesh should be used as much as possible, and it is better to have a mesh with a higher mesh size, a smaller wire diameter and a smaller mesh. The color of the screen is preferably yellow or brownish yellow to prevent vignetting. 2. Selection of the frame The frame is generally made of hard alloy aluminum (square tube type) such as LY12 and LF2, because the metal frame has high precision and relatively stable size. The four corners of the frame are made of argon arc welding or riveting. Stretching requirements In general screen printing, there are three types of stretching methods: manual, mechanical and pneumatic. When the printing quality requirements are high, it is best to use a pneumatic stretching net, which is characterized by uniform pulling force and convenient use, and is particularly suitable for high-precision printing. In the process of stretching the net, there are several requirements. (1) When using the pneumatic stretching machine, after the tension reaches the requirement, it must be allowed to stand for 3 to 6 hours before applying the stretch net glue. (2) The stretched net should be placed for at least 24 hours to ensure the stress balance at each point and prevent deformation. The higher the net version of the mesh, the longer it is required to be placed, generally 2 to 3 days is appropriate. (3) The warp and weft wire is kept vertical to prevent slackening of the wire. Requirements for photosensitive materials 1. Screen printing requirements for photosensitive materials The screen requires that the photosensitive material has good plate-making performance and is easy to apply. It has a suitable range of sensitometric spectrum. Generally, the photosensitive wavelength should be 340-440 μm. Because the plate-making operation and plate storage require strict darkroom conditions, if the photosensitive wavelength is too short, the light source The choice, the protection of personnel will become more difficult. The photosensitive material has high sensitivity and can achieve the purpose of energy saving and rapid plate making; the better the developability of the photosensitive material, the better the stability of the screen, and the convenient storage and waste. 2. Screen printing requirements for photosensitive materials The plate formed by the photosensitive material should meet the performance requirements of different kinds of inks, and has a certain printing durability, can withstand the blade pressure; requires the bonding ability of the photosensitive material and the mesh to be strong, does not produce release film during printing; Producing "ghosts" is conducive to the reuse of the screen. Selection of light source Proper selection and use of the light source is of great significance for improving the quality of screen printing, saving energy, simplifying operations, maintaining the health of operators, and reducing costs. Since the energy of light varies with wavelength frequencies, the shorter the wavelength, the higher the frequency and the greater the light energy. When light is absorbed by a substance during radiation, since the photon has a certain amount of energy, it causes physical and chemical changes in the substance. The so-called photochemical matching means that the spectral output distribution of the selected light source should match the spectral color sensitivity of the photosensitive material, that is, the wavelength range in which the photosensitive material absorbs light photochemical reaction is exactly the output range of the light source luminescence spectrum, and the maximum photographic material. The absorption peak is exactly at the output peak of the light source. Such a light source is maximally absorbed by the photosensitive material to cause a photochemical reaction. Therefore, according to the selected photosensitive material, the selected light source should be selected. At present, the photosensitive wavelengths of various photosensitive materials used in the industry are mostly distributed between 250 and 510 μm. In theory, any light source with a peak wavelength between 250 and 510 μm on the emission curve of the luminescence spectrum can be used for screen printing. In addition, in the printing plate, the size of the screen, the output power of the light source, the distance between the screen and the light source should be fully studied to improve the quality of the printing plate. Precautions when choosing a light source 1. Requires high luminous efficiency and high intensity of the light source Under other conditions, the greater the power and luminous efficiency of the light source, the greater the luminous intensity or brightness, the greater the illumination of the exposed surface, and the time required for the photosensitive material to achieve the same exposure. The shorter it is. 2. The heat radiation of the light source is small The thermal radiation should be as small as possible while ensuring that the light source has sufficient luminous intensity or brightness. When using a high-power strong light source, it is necessary to take forced cooling measures (such as air cooling, water cooling, etc.), and measures should be taken to keep the temperature of the photosensitive material below 32 °C. Eyeshadow Stick,Eyeshadow Pencil,Eye Shadow Pen,Eyeshadow Palette Guangzhou Bijiang Cosmetics Co., Ltd. , https://www.bijiangcosmetics.com
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