Application principle and prospect analysis of UV ink
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
With the continuous development of printing technology, the sheetfed offset printing market is also developing in the direction of increasing production efficiency, reducing printing costs and increasing added value. The emergence of hybrid inks is in line with the development trend of the sheetfed offset printing market. The hybrid ink is essentially a component that incorporates traditional offset inks into the formulation of UV printing inks, combining the advantages of both UV offset inks and conventional inks in terms of performance. While retaining the rapid curing characteristics of UV offset inks, it not only solves the problem of gloss loss caused by the application of UV varnish on the traditional ink, but also greatly improves the printability compared with UV offset inks.
In order to survive in the fierce market competition, printing companies must improve product quality, so they must choose the right equipment and consumables. Since UV inks give special value to prints, their use is increasing. In the field of printing, UV offset printing has become an important method for book covers, advertising posters, and decoration. Because of the good decorative effect of UV ink, it does not contain volatile harmful substances and fast fixation, and is favored by people. The application of UV technology in offset printing has shown great vitality.
First, the application principle of UV ink
The main components of the UV ink include an organic pigment, a photopolymerizable prepolymer, a photosensitive monomer, a photopolymerization initiator, and the like.
UV inks solve the drying problem in printing with their unique drying method. Its drying principle is to achieve photochemical reaction of the ink by ultraviolet radiation to the ink, thereby achieving the purpose of curing the ink. UV inks have the following two main chemical reactions during the drying process.
1. Photochemical reaction: A photopolymerization initiator contained in an ink undergoes a photochemical reaction under ultraviolet irradiation to generate a radical.
2. Chain reaction: The free radical polyfunctional prepolymer, polyfunctional prepolymer, polyfunctional crosslinking agent and reactive diluent in the ink are chained by photochemical reaction to generate free radicals capable of chain reaction. The reaction is cross-linked to each other to form a photocured product having a three-dimensional structure - a dried ink film.
Therefore, the drying of the UV ink mainly depends on the drying characteristics of the photocuring, so that the ink has different drying properties under the conditions of receiving light and being unaffected by light, that is, the ink does not receive light during printing, and maintains stable rheological properties, and has good properties. Printing state; after printing, it is irradiated by ultraviolet light and dried quickly, which can meet the post-press operation, greatly improve the production efficiency, and greatly improve the adaptability of ink drying.
Second, the advantages of UV ink
1. Volatile organics: Most UV products contain little or no organic solvents, no solvent attack and damage to the printed matter, and no pollution to the human body and the environment.
2. Suitable for non-paper substrates: can be printed on ordinary substrates, and can also be printed on non-absorbent materials such as film, synthetic paper, metal or plastic.
3. Suitable for instant post-press treatment: it can be cured quickly after being irradiated by ultraviolet light.
4. The amount of ink used is small: Since the UV ink does not contain a solvent, only the amount of ink used in the amount of 1/3 to 1/2 of the conventional ink can obtain the desired effect.
5. Strong color matching ability: Adjusting the viscosity, color tone and brightness of the ink can be rich in color. Just mix two or more basic colors to get a variety of desired colors.
6. Opacity is easy to control: pigments or pigments can be added to the extended base to achieve the desired brightness according to the standard ratio.
7. UV ink can be processed under special printing conditions such as ice, refraction, frosting and wrinkles.
Third, UV offset printing
Offset printing is a relatively mature printing process, but printing technology is constantly evolving. UV technology can improve product quality, increase production efficiency and improve the environment. Therefore, the application of UV in offset printing is still very large.
UV ink is used in offset printing. The printed matter has been solidified when it reaches the delivery part, which can avoid powder spraying, which is beneficial to the cleaning of the printing environment, protects the health of the operator, and avoids the troubles caused by the powder coating. For example, the effects of glazing and film mulching can be processed. Improve the working environment, increase production efficiency and shorten delivery time.
UV ink is cured after being irradiated by UV light source. It does not crust in the ink tank before it is irradiated, and it will not dry out on the parts and plates of the printing machine. These characteristics can prevent the occurrence of ink crust and solve the downtime of the offset printing machine. The worries of the time reduce the waste of ink.
UV offset printing inks are required for printing plates, glue sticks and blankets. Because UV inks contain reactive monomer diluents and photoinitiators, they can decompose the dots on the ordinary offset PS plate and reduce the printing durability of the printing plate. Therefore, UV offset printing must choose a special UV offset PS version. The active monomer thinner in the UV offset printing ink will infiltrate the common offset glue stick and blanket in the printing, resulting in printing failure: First, the ink is faulty, the ordinary glue stick, especially the new glue stick and blanket, on the At the beginning of the machine, the active monomer diluent in the ink was significantly reduced by the large absorption of this reactive monomer diluent. The ink polymerization cross-linking component is insufficient, and when the UV lamp is irradiated and cured, the ink film is not cured completely, and the printed product is not resistant to friction. Second, the failure of the glue stick and the blanket, the reactive monomer thinner in the UV offset ink will cause the swelling of the ordinary glue stick and the blanket, so that the printing cannot be performed normally. Therefore, UV offset printing must use a special UV glue stick and UV blanket.
At present, most of the printing companies' UV offset printing is spot color printing, so the arrangement of color sequence is also different from traditional offset printing. In the UV offset color sequence arrangement, mainly from the two aspects of the drying and quality of the printed product: 1 plus circle according to the difficulty of curing from large to small should be white, black, blue, yellow, magenta. This is because inks of different colors have different UV transmittances. For UV photons, the magenta transmittance is 50% to 60%, the yellow is 20% to 30%, the green is 8% to 20%, the black is 12%, and the white ink has the lowest transparency. Therefore, in offset printing, UV ink printing The color sequence should be W, BK, C, Y, M.2 plus circle. When performing spot color printing, small area text or line version should be printed first. The ink with deep color and small area should be printed first, and large area ink should be placed. Finally printed, this can avoid scratching a large area of the printing plate, affecting the appearance of the printed product, and can also improve the registration accuracy.
For normal offset and UV offset printing, controlling ink balance is key. The dampening solution used in UV offset printing is the same as ordinary offset printing, so the principle of less water and less ink should also be mastered. The pH of the dampening solution should be between 5.5 and 6.0, while the production is generally controlled between 5.0 and 6.5.
Fourth, the problem of UV printing
1. Ink cleaning is difficult, you need to have a special car wash water, cleaning solution.
2. UV ink storage time is not long. At present, the shelf life of UV inks is not long, because UV inks are prone to gelation and deterioration.
3. UV products can only be cured under direct UV irradiation, but the curing equipment is expensive and the investment in printing equipment is large, which increases the printing cost.
4. UV light penetrates thicker and pigment-containing coatings, which is difficult to cause ink to be incompletely cured and poorly adhered.
5. The price of raw materials is too high and the cost of printed materials increases.
6. Poor adhesion. In general, compared to conventional products, UV inks have poor adhesion to some materials, including steel sheets and aluminum sheets, and can be chemically modified to eliminate some of the problems of poor adhesion.
In short, the UV offset printing process is difficult to master. It must be carefully observed in the work, carefully summed up, combined with theory and practice in solving the process problems, and compared with the methods to solve the common offset printing process problems, to find commonalities and differences. As the development direction of ink, UV ink embodies the enhancement of human environmental awareness. UV ink has become the fastest growing green ink in the world. It is the development trend of printing in the future. It will replace water-based ink in certain fields and become the most environmentally-friendly and durable ink.