How to print non-absorbent materials such as plastics with ordinary offset printing machines
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With the development of society, people's demand for fine prints is getting higher and higher, and the printing materials of lithographic offset printing are becoming more and more diversified from single paper, PVC, PE, PP, PET, synthetic paper, gold and silver cards, etc. Non-absorbent materials are also increasing as substrates. In recent years, the rapid development of UV offset printing technology has largely met this demand, but UV offset printing currently has certain limitations: UV offset printing machinery and equipment investment is relatively high; ink and consumables cost higher; production Management, process technology, technical personnel and related supporting warehousing and production conditions are relatively high. Offset film inks are based on the drying of oxidized conjunctiva, and the printing of non-absorbent substrates such as plastic film and gold and silver cardboard is completed on ordinary offset printing machines. This solves many printing companies without UV offset printing equipment and cannot engage in plastic film. The printing of printing materials such as gold and silver cardboard has greatly facilitated the printing industry and expanded the scope of the printing business.
The characteristics of offset printing film inks are: inks rely on oxidized conjunctiva to dry, no need to pass UV or IR on non-absorbent substrates; post-printing surface drying and fixing time is faster than general offset printing inks, printing is not easy to stick flowers; good for substrates The adhesion is bright and colorful; compared with UV offset inks, the ink layer of the film ink is relatively thin and the dots are fine.
Offset film inks should pay attention to the following matters during use: PVC, PE, PP, PET and other plastic film should be corona treated before printing, in line with printing requirements; the pH value of dampening solution should be controlled at around 6, not too sour Otherwise, it will affect the drying of the ink; the amount of alcohol in the dampening solution can be appropriately increased, and can be controlled at about 15%. The printing water supply should be minimized during printing. If the amount of water in the plate is too large, the ink will be excessively emulsified, which will cause the ink to be slow. Dry or not dry; to use dusting, each stack should not be too high, so as not to cause sticky flowers, the printed post should be placed in a place with relative humidity below 60% to facilitate ink drying; ink should be cleaned immediately after printing And an ink roller to prevent the ink from drying on the ink roller.
In addition to the basic four-color and bottom-bottom white, the offset film inks are available in a variety of spot colors, which are good for printing non-absorbent substrates such as plastic film and gold and silver cards with ordinary offset presses. However, film inks also have shortcomings, mainly as follows: the post-printing inks are dried on non-absorbent substrates for a long time, and the inks are completely dry, generally take 5 to 6 hours or even longer, and the printed products are easy to scratch before the ink is dried. Sticky dirt, it is easy to produce defective products in production operations. In response to this situation, the printing industry personnel have successfully researched and launched the water-based varnish-film water oil specially used for non-absorbent printing materials such as plastic film, which greatly facilitates the printing production operation, improves and Improve the quality of production.
According to different coating methods, film water oil is divided into two types: film water oil for connecting optical machines and film water and oil for independent glazing machines. The optical film water oil on the line can be coated on the printing machine with the optical unit on the line, and the printing and glazing are completed once. After the film water oil is dried by infrared, it reaches the initial dry state of the surface, and the ink on the surface of the printed sheet is lightly pressed by hand, and the varnish does not stick to the hand, so that the powder can be dispensed with, and the printed matter can be prevented from being scratched and sticked. Film water oil is different from ordinary water oil used in paper. It has gas permeability after drying into film, which is beneficial to the contact of ink with air, and does not affect the drying basis of film ink oxidized film. Film water oil can effectively improve the adhesion of film ink on the substrate, protect the printing ink layer from scratching and improve all aspects of resistance. In addition, the film water oil can not only be fully coated on the optical machine, but also can be partially coated with a glazing resin plate to make the printed matter achieve a rather beautiful effect. For some films, after the printing ink is dried, the wear resistance and scratch resistance of the substrate are poor. The independent glazing film water oil can enhance the wear resistance and scratch resistance of the ink, achieve good adhesion effect, and use Convenient, ordinary infrared or hot air drying independent oil machine can be applied.
Film inks are used in combination with film water and oil to print non-absorbent materials such as plastic film on ordinary offset presses, especially for presses with optical units on the line. It is also an ideal choice for printing companies without UV offset printing equipment. A backup solution for printing companies with UV printing equipment.