As we all know, the so-called uv matte film varnishes, that is, ultraviolet curable inks, after printing, the ink layer transferred to the substrate immediately after curing by ultraviolet rays to form ink ink film, based on its special drying principle, decided Its connection material additives, printing equipment and methods of use are different from common oil and resin inks, and also determine the advantages of uv matte film gloss oils that are not as good as general oily inks. A brief analysis of its characteristics:
(1) The drying speed is fast. Generally, no back sticking or adhesion will occur during the printing process. No additional dusting is needed to prevent sticky adhesion and purify the working environment.
(2) Because the drying speed is fast, the production cycle is shortened, especially for the products with post-press processing, while also reducing the product storage space and site;
(3) excellent adhesion and abrasion resistance, and excellent water resistance, especially suitable for non-absorbent substrates such as PE paper and aluminum foil;
(4) In the process of ink drying, the amount of volatile solvent gas is low, and it is non-toxic after drying. It is suitable for food or pharmaceutical packaging.
Because uv matte film oil is stored in different drying principles and chemical compositions than ordinary inks, there are many areas that need attention during use. Such as the use of printing plates, printing rollers, ink drying, ink cleaning and security protection, ink storage, the following brief description of these aspects:
First, UV offset printing plate
The PS plate can be divided into positive plate and negative plate according to the principle of its exposure and imaging. Because the positive part of the positive plate is the photo-curing photosensitive layer, and the blank part, ie the unexposed part, is dissolved away. In the process of cleaning the printing plate, special cleaning agents are used to clean the printing plates. The cleaning power of these cleaning agents is very strong. During the cleaning, the photosensitive layer on the graphic part of the plate may be dissolved to make it fall off. In order to prevent this problem from happening when the printing plate is lowered or scrapped in the ability to transfer ink, when using the PS positive plate, it is necessary to make baking plate processing or use a special PS plate for UV. The method of baking the plate is to place the plate in a baking box. About 250 Â°C temperature, baking time 6-8 minutes. In this way, the interior of the photosensitive layer of the PS plate can be sufficiently hardened, and at the same time, its abrasion resistance and solvent resistance can be improved.
For the UV printing PS negative version is basically not used, and baking version has no effect.
Second, the printing roller
Because uv matte film varnish contains chemical components such as acrylic resin monomer and photopolymerization inducer in the connection material, these components have strong penetration or even dissolution capacity for rubber, which causes the rubber roller to swell or deform. The change of its transfer ink properties, resulting in a lot of printing failures, so the ordinary offset printing ink roller is not suitable for printing uv matte film Varnish, and printing uv matte film UV oil is best to use special UV roller, sometimes even if the use of UV glue There are also various problems with the rollers. For example, a new roller that has just been activated can be used to pre-treat the rollers in order to prevent malfunctions when the common ink and the uv matte film are alternately used. For example, it is pre-coated with uv matte film varnish thinner for 24 hours before printing, cleaned before printing, coated with uv matte film lacquer for about 1 hour, and then washed with detergent and then inked.
Third, uv matte film drying
The drying method and principle of uv matte film varnish is different from common inks. It causes photopolymerization of the ink's internal components to instantly solidify and dry by ultraviolet light irradiation. Its drying is different from that of common inks such as volatization, oxidation and penetration drying. There are many places to pay attention to:
(1) It must be confirmed whether the ink layer is really dry
For various reasons, such as the ink layer is too thick, dark color poor transparency of the ink, light intensity is not enough, the speed is too fast and other reasons, will make uv matte film ink layer to produce a false dry, see the surface seems to have dried, The interior of the ink layer is not completely dry, this false drying will cause the product to stick for a period of time after the adhesion, the use of a large odor, poor packaging fitness and poor abrasion and other issues occur, and sometimes even make the product Lots of scrapped, huge losses, so pay special attention to this issue, there are several specific methods: The first is to use a transparent tape to peel test, stick the tape paper to the ink layer and hand smooth the tape again Pull down to see if the ink layer will be stuck down, if it is not completely dry, otherwise it means that the dry is good, the second method can use a friction tester for the friction test, if the deink is serious, it is not completely dry; .
2) uv matte film drying oil source
Ultraviolet light for uv matte film drying is emitted by UV lamp. The ultraviolet lamp used now separates the pressure mercury lamp and metal halogen lamp. The two lamps have different light waves due to their different filling media. The mercury lamp has a wavelength of 200-400 MM, and the metal halide lamp has a wavelength of 250-450 MM. Since the light wave is different, the effect is also different. If you want to strengthen the surface drying, then use a high-pressure mercury lamp is better, such as a colorless ink or printing better light; if you print a dark ink series or poor transparency, you need to strengthen the internal drying of the metal halogen The light is better.
Comprehensive advantages and disadvantages of these two kinds of lamp tubes are generally mixed and used when used, which not only enhances the surface hardening but also strengthens the internal drying. However, when used together, the UV power supply specifications of the equipment configuration should be fully considered to be compatible with the lamp tube.
(3) Use of uv matte film varnish additives and cleaning, safety precautions
The use of uv matte film auxiliaries must be dedicated, supporting, can not use ordinary ink diluents and other additives, otherwise it will have adverse consequences such as poor drying, poor delivery, additives must be limited before use, can not be In general, inks that are generally controlled within 5% and produced by different manufacturers have different compositions of auxiliary components. It is best to use the ink manufacturers' or recommend them to use, and the inks of different manufacturers cannot be mixed.
The uv matte film is cleaned with its special cleaning agent and cannot be cleaned with gasoline, kerosene or alcohol. Because uv matte film polish remover has strong dissolving power, if you accidentally touch the skin or splash your eyes, it will cause skin irritation or burns, so you should pay attention during use, wear protective gloves during cleaning, and wear protective glasses when necessary. To prevent eye burns, in addition, if the uv matte film is inadvertently adhered to the device, the non-UV paint surface protective coating cannot be wiped with a UV cleaner, otherwise the surface will be dissolved and rubbed off.
Fourth, uv matte film storage precautions
Because of its special drying principle and chemical composition, uv matte film should pay special attention to light and heat insulation during storage.
Because the solar spectrum contains a large amount of ultraviolet rays, when sunlight directly or indirectly irradiates the surface of the ink, uv matte film varnish will harden and crust, resulting in waste and printing failures. At the same time, long-term fluorescent lamp irradiation may also be caused by ultraviolet rays. The ink is hardened, so it is best to use isolated fluorescent lamps, especially the lighting source on the printer ink fountain, so uv matte film should be protected from light.
At the same time when the ink temperature exceeds 30Â°C, the ink will produce a chemical reaction, one of the consequences is hardening and drying; the other is to produce gelation to increase the viscosity, and printability is reduced, especially the used residual ink. Therefore, uv matte film should be stored in a cool place as much as possible.
Fifth, the color arrangement of the printing process
Because different colors and types of inks affect the drying and curing speeds due to the different absorption and transmission of ultraviolet rays, they should be fully considered in arranging the printing color sequence. High concentration of white and dark colors, such as black and blue and some spot colors and gold and silver inks, are particularly strong in the reflection and absorption of ultraviolet rays, and poor in the transmission of ultraviolet rays, so the drying and curing speed is slower and the color sequence is arranged. When it is allowed, it should be printed in advance so as to increase the number of times of irradiation to enhance drying. Yellow, magenta, and other colors with good drying properties can be post-printed. When adjusting the ink with slower ink drying speed, the photocuring initiator can be appropriately added to accelerate the drying and curing, but excessive addition will hinder the curing speed. Therefore, the addition amount should be controlled within 4%, affecting the uv matte film varnish. Another factor of dry curing is the thickness of the ink layer. The thicker the ink layer, the slower the curing speed; otherwise, the better.
In summary, it can be seen that, in use, uv matte film oil is not the same as other inks. There are more factors affecting the final printing effect. Any mistakes in any one link will have different degrees of consequences. Therefore, only A comprehensive understanding of the composition and use of uv matte film varnish can give full play to the advantages of uv matte film varnish to create the ideal high quality product.
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