Refractive screen printing technology, which has emerged in recent years, is a new star in the packaging screen printing family. The traditional refraction effect is generally to first make a copper-zinc plate with a refraction texture, and use a round press or a flat press letterpress to press lines of different angles on gold and silver cardboard to produce a refraction texture effect. The disadvantage of this method is that the plate-making cost is high and the effect is not ideal. The screen printing can easily print ultra-thin concave and convex lines on the mirror gold and silver cardboard. After the light is irradiated, it will produce a colorful refraction effect, making the screen printing box more noble and gorgeous. The process flow of refraction screen printing is: refraction manuscript design → stretching screen → cleaning and roughening screen plate → coating photosensitive adhesive → exposure → development → repairing plate → secondary exposure → printing. 1. Refractive original design The main points of the design of the refracted manuscript are as follows: draw the part of the image that needs to be refracted to a millimeter bisector, divide the length of each millimeter into 5-8 bisectors, and each bisector is divided into black and white 10-16 Taking 16 as an example, it can be designed as black 4 white 12 or black 8 white 8. There are three types of lines: straight line, arc, and ellipse, and the line and the arc are connected with each other as the image changes. The appearance of the refraction pattern is fine and complex, and its internal structure cannot be seen through the naked eye. Under a microscope of more than 40 times, you can see at a glance that the refracted graph is composed of several or dozens of lines arranged at equal distances but with different angles and radians. The thickness of the refraction bar should be 0.10 ～ 0.15μm, and the film can be produced with a high-resolution laser phototypesetting machine. 2. Make a refraction screen (1) Selection of wire mesh and stretching. To make a refractive screen, a suitable screen must be selected. The screen must have good elasticity, be resistant to friction, have a very small expansion rate, have a large mesh opening, and have a thick printing ink layer. Polyester wire mesh is an ideal choice. Generally, the mesh size is 390 ～ 420 mesh / inch. When stretching the net, choose an oblique stretch net with an angle of 22.5 °. 18 ～ 22N / cm. The newly stretched silk screen must be cleaned and roughened, which has a very important effect on the quality of the screen. (2) Apply photosensitive glue. Regardless of whether automatic gluing or manual gluing is used, the glue must be applied evenly and evenly. The number of times that the refractive screen is glued depends on the thinness of the photoresist, and it usually takes 4 times. During the first glue application, the glue applicator should be scraped on both sides of the screen repeatedly and evenly to make the photosensitive glue fill the mesh holes evenly, and then dried in a drying oven at 40 ℃. In the second and third times, only the adhesive on the printing surface should be dried, and in the fourth time, the adhesive should be dried on the ink scraping surface. (3) Exposure. Refractive rays are finer and denser. In order to ensure the quality of printing, it is necessary to use the printing machine with vacuum adsorption device to print. When printing, the film should be closely attached to the photosensitive film surface of the screen, and the printing time should be appropriate. If it is too long, it will be difficult to develop. If it is too short, it will affect the durability of the screen, and the refractive bar will also become thicker. You can use the test strip to measure the exact exposure time required. (4) Development. Put the stencils in the shaded pool with a water depth of 20-30cm. The stencils should be immersed in water for 1 minute, then press the stencils repeatedly into the water, and use the water pressure to squeeze the photosensitive adhesive of the image part Press it out and clean it. In order to ensure the uniformity of the photosensitive film of the refractive screen, it needs to be rinsed with a low-pressure water gun during development. Dry after sufficient development. (5) Revision. Check the layout for pinholes, air bubbles and other defects, and make repairs. (6) Double exposure. After the screen is dried, a second exposure is required to completely cure the photosensitive film on the screen surface and improve the printing durability of the screen. [next] 3.UV refractive ink UV refractive ink can produce unique refractive effect only when it is printed on the surface of mirror substrate. When printing, you can add an appropriate amount of thinner for dilution. 4. Refractive screen printing If the area of ​​refraction printing is large, in order to ensure the quality, it must be completed with a high-precision screen printing machine. For small areas, manual printing can be used. Refractive screen printing requires operators to have an understanding of the production of high-quality screens, the hardness, angle and pressure of the squeegee, and the performance of UV refractive ink, so that they can take corresponding measures for various problems that occur in the production process. Countermeasures. Precautions 1. The same type of screen printing ink produced by different manufacturers has certain differences in quality and performance. Generally, it is necessary to go through trial printing first, and then ensure that the quality is stable and reliable before mass production. 2. The ink must be fully stirred before use, especially when mixing several patterns of ice flower ink, it is best to use a bamboo board to stir, when a large number of use is best to use a wide leaf mixer. 3. Pay attention to check the curing of the ink, so as not to affect the hardness and adhesion fastness of the ink layer due to incomplete curing. 4. Temperature changes will change the viscosity of the ink, resulting in differences in printing results, so the ink should be put into the printing workshop in advance to adapt to the workshop temperature to ensure the stability of quality. 5. UV ink is irritating to the skin. Be careful when taking it to avoid contact with the skin. If the skin is stained with ink, it should be rinsed with soapy water immediately. 6. The ink should be sealed and stored at low temperature (2 ～ 18 ℃), protected from light and heat. The storage period is generally 6 months to avoid changes in the performance of the ink. 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