UV ink helps packaging and printing enterprises to achieve green production

Guide: With the advancement of green printing, environmentally friendly inks have become more and more concerned. Among them, UV inks with environmentally friendly characteristics are widely used.

What is UV ink?

UV ink refers to an ink that is cured by UV light. The main components of the UV ink include pigments, oligomers, monomers (reactive diluents), photoinitiators, and various auxiliaries. Among them, the resin and the reactive diluent act to fix the pigment and provide film-forming properties; the pigment imparts a moderate color to the ink and the hiding power to the substrate; and the photoinitiator requires absorption of the photon-initiated polymerization under the interference of the pigment.

From the printing process, UV ink has fast fixing speed, good conjunctival performance, good adhesion to all kinds of printing materials, and scratch resistance, abrasion resistance, acid resistance, alkalinity and other properties are better than ordinary inks. It is solvent-free, non-flammable, and does not pollute the environment. Therefore, although its price is much more expensive than ordinary ink, it is widely used.

What are the characteristics of UV inks?

1. The curing process of UV ink is a photochemical reaction process, which is a process from linear structure to mesh structure. Therefore, the printing ink layer has many advantages such as water resistance, alcohol resistance, wear resistance, anti-aging, etc. Not too late. The scratch resistance and chemical resistance of UV inks is one of the main requirements for label combination printing. The curing principle of UV inks also determines that it is ideal for printing non-absorbent substrates.

2. No solvent volatilization, high solid content of imprinting, small amount of ink used, and low comprehensive cost. For the same flexographic product, the amount of UV ink is less than 50% of the ink. However, due to the high ink concentration, it is necessary to use a closed type ink tank, and at the same time, to increase the temperature adjustment system for adjusting the viscosity of the ink, in order to prevent heat shrinkage of the substrate, a UV lamp cooling system is also required.

3, UV ink particles are fine, high concentration, no change in physical properties during printing, no solvent volatilization, stable viscosity, so printability is good, printing quality is high, not easy to paste, stack, high viscosity printing, and ink The layer is firmly attached, the dot density is high, the price tone is reproducible, the ink color is bright and bright, and the UV ink of a certain color is adjusted. Only a small adjustment and preparation time is required before printing, which is especially suitable for spot colors and large areas. Field printing.

4. Although UV ink has good stability, it will change under high temperature and high humidity environment, and should be stored in the environment below 20 °C.

5. UV inks cannot be mixed with general inks. Thinners and cleaning agents must also be used exclusively or in combination.

6. The specific UV ink of a certain type is not commonly used for all printing materials. It depends on different substrates and models during printing, and is selected correctly through testing.

Which printing areas are UV inks used in?

1. Non-absorbent materials such as polyethylene (PE) film, polyvinyl chloride (PVC (5045, 5.00, 0.10%)) film, polypropylene (PP) film, metal foil and non-absorbent special materials. If these printing materials are printed by ordinary solvent-based inks, a certain drying time is required, and it is usually necessary to use a dusting, a drying device or other additives in the ink, and the UV ink has no such trouble.

2. When the metal material is printed on the surface of the metal material with UV ink, the curing process can be shortened and the original curing device can be simplified. At the same time, the good curability and conjunctival properties of the UV ink surface not only improve the post-press processing characteristics, but also improve the appearance quality of the product.

3. Commercial paper printing Commercial paper printing uses special printing materials and inks, such as carbonless copy paper, thermal paper, magnetic ink, anti-counterfeiting ink, etc., and requires ink to have certain resistance to discoloration, heat resistance and stability. Therefore, it is easy to use UV ink or UV varnish. At the same time, due to the high speed of the printing equipment and the low ink consumption, it also has the favorable conditions for printing with UV ink.

UV inks and various materials matching problems Compared with other inks, UV inks have great advantages in both printing process and printing quality, and can obtain printing effects that other inks cannot obtain. However, when using UV inks, attention should be paid to the matching problems with various materials.

1. The number of UV lamps in the UV lamp curing device and the radiation intensity must depend on the printing speed, the thickness of the ink film and the brightness of the ink color. Take BASF's UV ink and UV varnish as an example. If the standard ink film thickness of color (such as cyan) is 1.20-1.40g/m2 and the printing speed is 100m/min, then two 120W/cm medium pressure mercury lamps should be used; if the ink density is high and dark, the ink is printed. On one or two overlays, the overall cure is more difficult, because the UV light is quickly absorbed by the deeper ink.

The curing difficulty of standard four-color UV inks is magenta, yellow, cyan and black from small to large. Therefore, the color sequence of UV multi-color printing should be black, cyan, yellow and magenta. Some spot colors are also difficult to cure, such as green; opaque colors are also difficult to cure because it reflects UV light back; gold and silver inks have the same problem.

The life of UV lamps is limited, and aging lamps cannot be cured by UV ink or UV varnish. Most of the instructions in the instruction manual indicate that the UV lamp must be replaced after about 1000 hours of use. In fact, if the print does not cure at the normal printing speed, it is necessary to consider replacing the UV lamp so as not to affect the overall printing operation.

2. Reflector If no reflector is installed, about 80% of the UV light will not illuminate the substrate due to scattering. Therefore, the UV curing device must be equipped with a lamp cover to reflect the UV light on the substrate. The reflector must be kept clean, and dust or dust can adhere to the reflector, which can affect the reflection. Normally, when the UV lamp is not in use, the UV lamp cover should be closed to prevent dust from falling.

Summary: The printing industry or the packaging industry is worth mentioning. To achieve sustainable development, environmentally friendly green production is inevitable. In practice, it is important to achieve greening from the production chain. As an important consumable in printing production, inks are also the trend of the environment. The promotion and application of UV ink will once again promote the improvement of the quality of printing products and the development of printing technology.

(Information from Flexo House, Business Association)

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