The 3D patterns of thermosetting ink screen printing are now widely used in clothing, especially the logos on many sports brand clothing, which use thick version screen printing technology to replace the traditional computer embroidery technology, making the brand clothing a new level. Screen printing fine 3D patterns have strict requirements on all aspects of film production, ink use, printing method, printing method and thermosetting treatment. The standard of a high-quality 3D printed product is: clear imprint and strong three-dimensional impression. There are two concepts involved here: a clear imprint. From the point of view of screen printing, the edges of the printed product should be uniform, the angle of the right-angle type should be sharp, the edge and the face should be 90 °, the surface should be flat, the corner of the rounded type should be rounded, and the surface Bright; followed by strong three-dimensional sense, three-dimensional sense means that the printed matter reaches a certain ink layer height, the higher the height, the stronger the three-dimensional sense. The above quality standards are relatively easy for printing large patterns, but if it is a very small pattern, it will increase many technical difficulties. We take the printing of cylindrical dots with a diameter of 1mm and a height of 1.5mm as an example to explain each production link and technical issues. Plate-making film: prepare two films, one for the positive picture and the other for the mirror picture. Screen version: Prepare two versions, one with a 100-mesh screen for the thick version and the other with a 180-mesh screen for the overlay. The tension of the two versions must reach 20N / cm. Thick version photoresist coating: Use a large round mouth sizing device to coat the screen scraping surface twice, then apply the screen printing surface (contact surface with the substrate) 4 to 5 times, and continue to coat the printing surface after drying gum. Finally, the thickness of the printed surface adhesive reaches 0.2mm ~ 0.3mm. Two-sided printing method: first stick two plate-making films to the two sides of the screen with double-sided tape, and align the "ten" word positioning line, the exposure time is one-third of the normal single-sided exposure, such as total exposure needs Use 3min, then expose the scraped surface for 1min, and then expose for 2min according to the conventional method. Why use two films to expose on both sides? We can find the difference between the single-sided exposure and the two-sided exposure of the thick version. Single-sided exposure. In the process of light irradiation, due to the certain thickness of the photoresist, the light is irradiated upward through different angles, so that the actual covering part of the top of the photoresist is smaller than the actual size of the film, and the stencil that is exposed is conical. The dots printed with this thick plate must also be conical. The upper and lower sides are exposed, and the resulting mask is cylindrical. Ink use: There are two methods, one is to use transparent thermosetting ink as the base and then overprint with colored ink, the other method is to use thick printing with transparent ink, and when the desired height is reached, use thin printing with colored ink to cover . The ink must be fully stirred before use. Squeegee: Hardness 70 ～ 75, sharp blade, right angle. Screen pitch: The screen pitch should be determined according to the printing result. For example, if the screen cannot be quickly popped up after printing, the screen pitch is too small. For example, there are many pinholes on the imprinted surface and the viscosity of the ink is not too large, indicating that the screen pitch is too large. The ink of the hole is not completely adhered to the substrate after being cut, and then it is taken up by the silk screen and stored in the mesh hole. Printing and loose drying: There are two forms of printing, one is mechanical printing, large area 3D patterns are suitable for automatic garment printing machine operation, small area fine 3D patterns are suitable for manual platen printing, because the height of 3D printing is through screen The thickness and the number of printing are completed. The thicker the version, the fewer the number of printing. However, the small area 3D version cannot be made too thick, so more printing times will inevitably increase costs and work efficiency is not high. The surface of the substrate must be leveled before printing, especially the cotton knitted fabric, the surface of the yarn support is not smooth, and there is a layer of wool fiber on the back surface of the cloth. Due to the small coloring area of ​​the ink, if it adheres to the floating wool There is no fastness on the fiber. Usually the leveling method is to stick a piece of screen paper to the printing area, and use a scraper to scrape the pressure on the top to make the back of the screen squeeze the substrate. This method is not very effective. The author has designed a squeezing device (introduced in another article) that can be used on both fully automatic machines and manual operations, and the effect is relatively good. The key part of printing 3D is the first pass of the primer. The first pass is printed well, the quality is guaranteed, and the number of prints will also be reduced. The first pass fills the screen with ink, and the height of the print is the thickness of the screen plus the photoresist. If the hollow part of the screen is filled up for the first time, it can effectively reduce the number of printing and ensure the quality of the subsequent overprint, because the height of the subsequent overprint is also the thickness of the screen. If it is hand-printed, the power of scraping ink should be greater during the first pass, so that the ink can fully contact with the printed matter to improve the adhesion fastness. When filling the mesh, the ink should be collected gently to make the ink layer as high as possible. a little. After each printing, there should be bulk drying. There are two methods for bulk drying, one is the bulk oven, and the other is blowing with a musket. The temperature and speed of loose baking should be controlled so that the ink surface just sticks to the ink. The curing temperature of the surface of the thermosetting ink is about 100 ℃. If the temperature of the loose baking is too high, the ink layer will become thinner, thereby increasing the number of printing times. After heat curing, the curing temperature of the thermosetting ink is about 160 ℃, and the baking time can be appropriately extended to make the ink fully cured and firmly adhere to the substrate. The method of checking the fastness is to stick the printed material with adhesive tape, and then pull it apart firmly. If there is no deinking, it means good fastness. Zhejiang Lamon Technology Inc. , https://www.babychaires.com
Screen printing of fine 3D patterns