The refractive 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 produce a copper-zinc plate with a refractive texture first, and press a line with different angles on a gold or silver card paper with a round press or a round press-type letterpress printing machine to produce a refractive light 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 card paper. After the light irradiation, it will produce colorful refraction effect, making the screen printing box more noble and gorgeous.
Refractive screen printing process flow is: refraction manuscript design → stretch net → cleaning coarse screen version → coating photosensitive adhesive → exposure → development → revision → double exposure → printing.
1. Refraction manuscript design
The main points of the design of the refraction manuscript are as follows: The part of the image where the refraction point is required is drawn as a millimeter digraph, and the length of each millimeter is divided into 5 to 8 bisectors, and each bisector is further divided into white and white 10 to 16 and so on. Points, taking 16 as an example, can be designed as black 4 white 12, or black 8 white 8. The lines are divided into three types: straight lines, arcs, and ellipses. Lines and arcs are kiss-connected with image changes.
The refractive pattern is fine and complex in appearance, and its internal structure cannot be seen with the naked eye. Under the microscope with more than 40 times, it can be seen at a glance that the reticle map is composed of several segments or several tens of segments arranged at equal distances but with different angles and arcs. The thickness of the broken light bar should be 0.10 to 0.15 μm, which can be produced with a high-resolution laser imagesetter.
2. Making a refractive screen
(1) Screen selection and stretching. The production of refractive index screens must use suitable screens. The screens are required to have good elasticity and friction resistance. The retractility rate should be very small, the mesh opening should be large, and the printing ink layer should be thick. Polyester wire mesh is an ideal choice, the general choice of mesh is 390-420 mesh/inch.
When the net is stretched, a diagonal stretching netting of 22.5° is selected, and the tension of the screen is required.
18-22N/cm. For the new stencil screen plate must be cleaned and roughened, which has a very important impact on the quality of the screen.
(2) Coated photoresist. Whether it is using automatic gluing or manual gluing, it must be ensured that the coating is even and smooth. The number of refraction screen sizing depends on the thin consistency of the sensitized adhesive, which usually takes 4 times. During the first gluing, the squeegee should be evenly scraped on both sides of the screen, so that the sensitized adhesive fills the mesh evenly, and then it is dried in a drying oven at 40°C. On the 2nd and 3rd times, only the glue on the printing surface can be dried, and on the 4th time, the glue on the squeegee surface is dried.
(3) Exposure. The broken light bar is more detailed, 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. When printing, the film should be closely attached to the screen photosensitive film surface, 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 screen printing resistance and the folded light stripe will also become thicker. The test strip can be used to measure the exact exposure time required.
(4) Development. Put the dried screen plate into the shaded pool. The depth of the tank is 20~30cm. The screen plate should be soaked in water for 1 minute. Afterwards, the screen plate is repeatedly pressed into the water, and the photosensitive part of the image part is squeezed by water pressure. Press it out and clean it. In order to ensure that the refractive index of the refraction screen is uniform, it is necessary to use a low-pressure water gun for developing. After sufficient development, dry it.
(5) Revised edition. Check the layout for defects such as pinholes and air bubbles, and perform repairs.
(6) Double exposure. After the screen drying, the second exposure is performed to completely cure the photosensitive film of the screen and improve the resistance of the screen.
3.UV refraction ink
UV-reflecting inks produce unique refractive effects only when printed on the surface of a mirror-printing material. During printing, an appropriate amount of thinner can be added for dilution.
4. Refractive screen printing
If the area of ​​the refraction printing graphic is large, it must be completed with a high-precision screen printer in order to ensure the quality. A small area can be printed by hand. Refractive laser screen printing requires operators to understand the production of high-quality screens, the hardness, angle and pressure of the squeegees, and the performance of UV-refraction inks, so that they can take corresponding actions in response to various problems in the production process. Countermeasures.
Precautions
1. The screen printing inks of the same type produced by different manufacturers also have certain differences in quality and performance. Generally, they must be tested and printed first, and then the mass production should be carried out after determining the quality is stable and reliable.
2. The ink must be fully stirred before use, especially in the mixed use of several patterns of ice flower ink, it is best to use a bamboo plate to stir, when used in large quantities is best to use a wide-blade stirrer.
3. Carefully check the curing of the ink so as not to affect the hardness and adhesion of the ink layer due to incomplete curing.
4. Temperature changes will change the viscosity of the ink, resulting in differences in the printing effect, so the ink should be put into the printing shop in advance to make it adapt to the workshop temperature and ensure the stability of the quality.
5.UV ink is irritating to the skin. Take care when using it to avoid contact with the skin. If the skin is stained with ink, wash it with soapy water immediately.
6. The ink should be stored under low temperature (2～18°C), protected from heat and light, and the storage period is generally 6 months so as not to change the ink performance.
Refractive screen printing technology standard for packaging printing products
May 28 10:05:31, 2024
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