Water-based UV screen printing ink characteristics and use

UV ink is a kind of chemical reaction ink. It is a specific application of UV light curing technology in the ink field. It consists of resin with unsaturated functional groups, reactive diluents and initiators, and pigments and auxiliaries. After printing on the substrate When exposed to ultraviolet light, the initiators cleave to produce living radicals or cations, which cause the polymerization of unsaturated functional groups to complete the drying process. During this process, no organic substances are volatilized.

UV ink does not contain organic solvents, and its TVOC value is very low. It will not cause pollution to the atmosphere during production and use; because no heating device is required, energy conservation is significant. A hot air drying tunnel generally 10 ~ 20m long, power consumption 80KW, low thermal efficiency; and UV dryers are generally 3m long, power 20 ~ 30KW, under normal conditions leaving the dryer can print the next process or stacking packaging It's the goal that all printers dream of.

UV inks are very stable in use, in particular, they can overcome problems such as dot enlargement, pattern distortion, crusting, jamming, and inconsistent print colors of solvent inks that often appear in the printing process.

Based on the UV ink technology, the UV water-based ink combines the characteristics of the water-based ink, making the product more excellent in printability, dimensional stability, screen cleaning than 100% UV ink, especially suitable for large format screen printing. application. During the ink drying process, heat of polymerization is released, and heat dissipation is important for the dimensional stability of the substrate. For screen printing, the ink coating layer is relatively thick, generally 6 ~ 10μ, heat dissipation is slow, the accumulated heat easily make the ink site temperature is too high, causing deformation of the substrate, overprinting is not allowed, even more prominent in large-format printing . The introduction of water absorbs a large amount of heat energy and transfers heat as the convective air volatilizes, reducing the possibility of deformation. Although it is an aqueous ink, the dry ink has good water resistance due to the fact that the film layer forms a network-like cross-linked structure during polymerization drying to become hydrophobic.

IH series water-based UV inks are specially designed for outdoor advertising printing. The pigments used are selected from the best products of international famous brands and have excellent outdoor light performance. It is used for light box advertisements with bright colors, sharp spots, and clear images. Unlike the use of ordinary ink must be "first four after three," save time and materials, greatly reducing the cost of printing. In the multi-color dot printing business, if solvent inks are used to overprint the second, third, and fourth colors, the dissolution of the solvent before volatilization and the dispersion and thinning of the former color ink film cause dot gain and pattern distortion. The use of UV water-based inks does not present the above problems. Because the moisture content is small, the weight loss of the ink layer after curing is low, and the utilization rate is high. The printing ink area of ​​the solvent ink is 35-40 M2 per kilogram, and the water-based UV ink can print 70-80 M2. Regarding the stability of the ink on the screen, the performance of the water-based UV ink is even better. Without UV irradiation, it will not be solidified. There will be no persistent problems in the printing industry such as the crust of the solvent ink, blocking mesh, and frozen plates. Good color consistency and high yield.

Water-based UV screen printing ink features

·Without the addition of organic solvents, minimal VOC emissions, no odors, and no flammable or explosive hazards, the environmental and sanitation conditions of ink production and printing production sites have been fundamentally improved. Can meet the most stringent requirements of the environmental protection management department for the industry.
·There is no organic solvent residue in the print ink layer; no or very low detection of heavy metals, can meet the stringent food, drug packaging and use requirements on children's toys.
·Good storage stability, low temperature -20°C and high temperature 60°C for 48 hours to restore normal temperature, ink flow change no more than 15%, ink printability and curing drying speed does not change.
· It has excellent stability in use, that is, the use of high-mesh net cloth is also not frozen, does not block the network, the print color is the same, and the yield is high.
· High solid content, less ink layer thinning, no dispersion before curing, clear pattern after printing, strong dot network performance, bright color, no need to print back three colors.
·Using UV light source for drying process, high energy utilization, fast drying, saving time, occupying less space, high production efficiency, and suitable for fast-paced orders.
Adhesion is strong, suitable for a variety of synthetic paper, light box cloth, KT board substrate · Resistant to sunlight, abrasion resistance, water resistance, suitable for printed materials used in outdoor places. Many kinds of advertising prints produced by printers have been published in Beijing, Shanghai, Guangzhou and other cities.

· Screen cleaning using ordinary detergents and tap water, no organic solvents, cost savings, safe operation and no harm.

Use of water-based UV screen printing inks

(1) Product use process

(2) How to use the product

• Storage room temperature 5 ~ 30 °C, the use of ambient temperature to 20 ~ 30 °C is appropriate, too low temperature will make the ink viscosity becomes larger or smaller. The room temperature is stable, the printing operation conditions can be guaranteed, and the quality of the printed matter is stable. Note that changes in the spring, summer, autumn and winter seasons, and temperature changes in the morning, evening and evening may cause different operating temperatures. It is necessary to put a temperature and humidity table next to the printing press.

· The thixotropy of this product is large, the viscosity will be reduced to some extent after fully stirring, and the stirring time before use is not less than 5 minutes. When it is necessary to reduce the viscosity, please use the supporting diluent and mix it while stirring. The amount should not exceed 8%. Do not mix with other inks.

Use 350-450 mesh high-tensile PET monofilament mesh (even after coping treatment) and use aluminum alloy mesh frame stretch net, so that the tension reaches 18 to 24 Newton; Water and oil dual-use water resistance can be film release photosensitive adhesive plate. The thickness of the ink wet film is mainly determined by the mesh number of the screen and the thickness of the paste. The adhesive layer is required to be 4 to 5 μm, and the ink film is guaranteed to be 6 to 8 μm. The ink layer having a thickness of more than 10 μm has a slow drying speed, and the adhesion and bending resistance are affected.

• Use a special 80oUV polyurethane blade, because some of the resin material in the ink has a swell effect on the blade. When the blade is not suitable for printing, it is necessary to rotate, grind, and reverse until it is replaced.

· This product is best suited for printing on PVC, KT board, Andy board and plain paper coated PI synthetic paper from Taiwan South Asia. The printability of other substrates should be based on trial and print evaluation.

· A new print and a new substrate should be prepared for preliminary testing and a comprehensive evaluation of the process capabilities and the printing of various indicators such as: adhesion, bending resistance, etc., master and determine the parameters. At the same time, it is also necessary to convey related knowledge and operating techniques to relevant personnel.

· It is not a simple matter to select and purchase a better curing machine. High and stable unit power and low calorific value are the most important performances. High pressure mercury lamps or metal halides with unit power above 120 W/cm must be equipped. Lights and effective heat dissipation mechanism. After the lamp is used for a period of time, the light intensity will drop, and the change of the light intensity should be regularly detected in order to perform the necessary adjustment or replacement. The heat generated by the lamp should have an effective cooling method, adjust the appropriate lamp distance and belt speed, so as to avoid thermal deformation of the printed material caused by overprinting is not allowed or even scrapped.

· There are differences in the curing conditions of different colors of ink. Generally, the order from easy to difficult is red, yellow, black and black. The mixed color of the printer's own blend must be tested to know the exact curing conditions. The ink layer after the light irradiation does not reach the optimal degree of curing immediately, and the stable adhesion can be achieved in 24 hours.

• When multicolor printing is performed in different colors, the front color cannot be cured excessively, and the first color must be used with a suitably fast tape speed, because excessive surface curing reduces the surface energy and affects the adhesion of the latter color. The specific control method acquires data during the preliminary test.

• Insufficient adhesion often results from insufficient curing, and this problem is mainly concentrated on the use of black ink. The black ink has a large absorption capacity for light, so that the light energy received by the photoinitiator is reduced, the curing is slow, and the gap between the printing plate and the substrate is appropriately enlarged during printing to form a thin ink layer as much as possible.

· When it is necessary to reduce the color density, use a colorless ink; when a high gloss effect is required, cover the bright oil, and you can also choose to use the high-light series ink.

· Uncleaned screens should not be placed in places with light; when cleaning screens, they can be scrubbed with industrial alcohol, then washed with detergent solution, washed once with 783, and then removed and ghosted. Rinse with clean water and dry completely.

• The ink is valid for 6 months from the date of production. Products that have passed the valid period can still be used normally after they have been inspected and tested for effective use. When the ink is not used, the lid must be tightly closed and stored in a cool, shady and cool environment. Recycling inks are packed in empty buckets to avoid contamination of new ink.

• If a printer using solvent-based inks for many years prepares to switch to UV-based water-based inks, there is a need for comprehensive new knowledge and new skills training from managers to producers, as ink suppliers are very willing to provide help within their capabilities.

Reprinted from: Yingli Technology

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