Ink drop problem in printing label printing
In the label printing process of film materials, the problem of printing off the ink on the surface layer is easy to occur, which greatly affects the quality of the printed matter and even delays the delivery date. The following is a summary of the reasons for the common ink drop and improvement methods from the daily printing experience, for the industry to discuss together to find the best solution. Problem 1: Coating defects Conventional films are divided into coated and uncoated, and the cause of film coating defects leading to ink drop is divided into two cases: for coated film materials, if the surface coating is poorly cured , the ink adhesion will be poor; and the uncoated film material often has poor adhesion to the surface layer and the ink, causing the ink to drop ink. The ink drop caused by the coating defect can be solved by the following method: taking the surface varnish printing treatment to protect the ink surface layer to prevent the ink from being lost; the surface layer is treated with corona, the surface of the material is corona The dyne value should be no less than 38mm/m, and the dyne value below 36mm/m will directly affect the printing ink firmness; the top layer primer or the strong adhesion of the ink can also improve the film surface. The inking power of the layer; some subsurface synthetic paper materials are not suitable for inspection with 3M tape because of the paper coating properties of the surface coating. Question 2: Tension For film materials with a corona-treated surface, in order to achieve good ink wetting, the dyne value usually needs to be more than 38mm/m. Below 36mm/m, the problem of ink drop is easy to occur; at the same time, the dyne value of this material Will gradually fade over time, there will be printing problems. The essence of this problem is the tension problem. For the ink drop caused by this situation, there are several solutions: using a satellite corrugator with an on-line corona function, performing on-line corona treatment to improve the surface energy of the film material; and using a batch printer to perform surface primer coating Treatment to improve the surface printing adhesion; when the dyne value disappears, the corona needs to be processed during printing, but the size of the dyne does not fully represent the adhesion between the ink and the face material, generally Dyne The value of the regression period is 3 months to 6 months, so it is recommended to minimize the long-term storage of stock materials. Finally, it is recommended to use a higher adhesion ink, it is recommended to consult the ink supplier. Question 3: Ink drying and tension In the printing process, ink drying and tension may also cause ink to be lost. Specifically, it is divided into: the printing ink layer is too thick to make the drying incomplete; the UV lamp energy is insufficient, the lamp tube is aging, the lamp tube reflector is aging, the UV lamp drying and curing is insufficient, the ink layer is not dried; the ink is excessively dried, resulting in material deformation and formation. The ink layer is peeled off. This problem of ink loss can be solved in the following three ways: First, the use of deep ink thin printing, is commonly known as reducing the amount of ink, such as spot color ink, can be equipped with a deeper, less ink in the official printing, to achieve the sample effect, while increasing the UV lamp output power , reduce the printing speed, increase the exposure time of the UV lamp, and achieve the drying effect. This solution is suitable for old intermittent or satellite rotary machines and old UV lamp solutions. Second, check the UV lamp for aging and clean the reflector. Usually, the domestic UV lamp has a service life of 500-1000 hours, and the imported lamp life is about 1000-2500 hours. For details, please refer to the actual use. It is recommended that the printing factory carry out the cleaning of the UV lamp every six months or so to ensure normal use. Third, reduce the output power of the UV lamp. The specific operation is the general printing work of the printing factory. The color of the first few groups of the color sequence is mostly the standard or small characters. The required illumination is limited, and the UV lamp can be turned on and the light can be dried. High-grade over-irradiation is not allowed, because the absorption energy of the film material is limited, and the excessive irradiation will cause the film material to curl and become brittle, and the adhesion of the ink will decrease, and the principle of using the high-grade UV lamp after the low-grade first can be followed. Question 4: Matching inks and materials Finally, the degree of matching of the ink to the material will also cause ink to some extent. For example, the use of ink molecules is too strong to form a uniform ink layer on the surface of the substrate material; or the use of ink models that exceed the shelf life or inferior domestic brand inks can cause ink to be printed off. In the above situation, you can switch to inks that match the printing materials, such as film-specific inks and light-fast and light-resistant inks. For expired inks, you need to do printing tests before printing, or print some simple ones. Text or small logo design, as well as some low-end products; printing large-area solid and full-screen dot network cable patterns, it is recommended to use good brand, high adhesion ink. Summary of factors affecting ink ink loss Through the above analysis, we can summarize the eight reasons for ink drop: 1. The coated film material has poor surface coating fastness; 2, uncoated film material, resulting in poor adhesion to the ink after printing; 3. The Dyne value is low. For a corona-treated film material with a printed surface, good ink wetting is required, and the dyne value usually needs to be 38 mm/m or more; 4. The dyne value subsides and the printed surface is corona treated film material, and the dyne value may gradually disappear with time, and the regression period is 3-6 months; 5. The ink layer is too thick and the power of the UV lamp is insufficient, which causes the ink layer to be insufficiently cured; 6. 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