Printing new technology refracting screen printing technology
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The refraction screen printing technology that has emerged in recent years is a new star in the packaging screen printing family. The traditional refraction effect is generally to first produce a copper-zinc plate with a refractive texture, and use a round-pressed or round-pressed letterpress printing machine to press lines of different angles on gold and silver cardboard to produce a refractive texture effect. The disadvantage of the method is that the plate making cost is high and the effect is not ideal. The screen printing can easily print ultra-fine concave and convex lines on the mirror gold and silver cardboard. After the light is irradiated, a colorful refraction effect will be produced, which makes the screen printing package more noble and gorgeous.
The process of refraction screen printing process is: refraction original design; stretch net; cleaning rough screen version; coating photosensitive glue; exposure; development; revision; double exposure;
1. Refractive original design
The design points of the refraction original are as follows: the part of the image that needs to be refraction point is drawn into a millimeter aliquot, and the length per mm is divided into 5~8 bisectors, and each aliquot is divided into black and white 10~16, etc. For example, 16 can be designed as black 4 white 12 or black 8 white 8. The lines are divided into three types: straight line, arc, and ellipse. The lines and arcs are kissed with each other.
The refraction pattern is fine and complex in appearance, and it cannot be seen through the internal structure with the naked eye. Under the microscope of 40 times or more, it can be seen at a glance that the refraction map is composed of several segments or tens of segments equidistantly arranged but with different angles and curvatures. The thickness of the folded light bar should be 0.10~0.15μm, which can be produced by a high resolution laser phototyper.
2. Making a refraction screen
(1) Selection of mesh and stretcher. To make a reticulated screen, it is necessary to select a suitable screen. The screen is required to have good elasticity, and it is resistant to friction. The expansion ratio is very small, the mesh is large, and the ink layer is printed. Thick. Polyester screen is an ideal choice, the general choice of mesh is 390 ~ 420 mesh / inch.
When the net is stretched, the angle of 22.5° is selected, and the tension of the screen is required.
18~22N/cm. For the new stretched screen version, it must be cleaned and roughened, which has a very important influence on the quality of the screen.
(2) Coating photosensitive adhesive. Whether using automatic gluing or manual gluing, it is necessary to ensure that the gluing is even and even. The number of gluing of the reticulated screen depends on the consistency of the photosensitive adhesive, generally 4 times. When the first time is applied, the glue applicator should be evenly scraped on both sides of the screen, so that the photoresist is evenly filled in the mesh, and then dried in a drying oven at 40 ° C. 2nd, 3rd Only the printing surface can be glued and dried, and the fourth time is glued and dried on the scraping surface.
(3) Exposure. Folding light strips are more delicate, more dense. In order to ensure the quality of the printing plate, it is necessary to use a printing machine with a vacuum adsorption device to print the plate. When printing, the film should be closely attached to the surface of the screen. The printing time should be appropriate. If it is too long, the development will be difficult. If it is too short, it will affect the printing durability of the screen. The folding light will also become thicker. It can be measured with the test strip. The exact exposure time required.
(4) Development. Put the dried screen into the shaded pool, the water depth in the pool is 20~30cm, the screen should be soaked in water for 1 minute, then the screen is repeatedly pressed into the water, and the image is pressed with water pressure. Part of the photosensitive adhesive is extruded and cleaned. In order to ensure uniformity of the refractive index screen, it needs to be washed with a low pressure water gun during development. After sufficient development, it is dried.
(5) Revision. Check the layout for pinholes, air bubbles, etc., and repair them.
(6) Double exposure. After the screen is dried, a double exposure is also required to completely cure the photosensitive film of the layout to improve the printing durability of the screen.
3.UV refractive ink
UV-refractive inks produce a unique refraction effect only when printed on the surface of a mirrored substrate. When printing, it can be diluted by adding an appropriate amount of diluent as needed.
4. Refraction screen printing
If the area of the refraction printed image is large, in order to ensure the quality, it must be completed with a high-precision screen printing machine, and a small area can be manually printed. Refractive screen printing requires the operator to understand the quality of the screen, the hardness, angle and pressure of the squeegee, and the performance of the UV refracting ink, so that it can be used to deal with various problems 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 must be tested first to determine the quality is stable and reliable before mass production.
2. The ink must be thoroughly stirred before use. Especially when mixing several patterns of ice-cream ink, it is best to use bamboo plate to stir. When using in large quantities, it is best to stir with a wide-leaf mixer.
3. Pay attention to check the curing of the ink to avoid affecting the hardness and adhesion fastness of the ink layer due to incomplete curing.
4. The temperature change will change the viscosity of the ink, which will cause the difference in printing effect. Therefore, the ink should be placed in the printing workshop in advance to adapt to the temperature of the workshop to ensure the stability of the quality.
5. UV ink is irritating to the skin. Be careful when taking it, avoid contact with the skin. If the skin is stained with ink, rinse it immediately with soapy water.
6. The ink should be sealed and stored at low temperature (2~18°C), protected from light and heat, and the storage period is generally 6 months to avoid changes in ink performance.