UV ink, is refers to the UV light irradiation instant cure ink. The main components of UV ink include pigments, oligomers, monomers (active diluent), light initiator and various additives, etc.. The resin and reactive diluent plays a pigment fixation and to provide the role of membrane properties; pigments give ink moderate color and on the substrate covering power; photo induced agents require in pigment interference still can absorb the photon initiated polymerization. 

From the printing process, UV ink fixing speed, conjunctival performance good, for all kinds of printing material has good adhesion and scratch resistance, wear resistance, acid and alkali properties as compared with ordinary ink. Therefore, although the price than ordinary ink is much more expensive, but was widely used. 

At present, the use of UV ink printing area has the following categories: 

1 non absorbent material printing 

Such as polyethlene (PE) film, polyvinyl chloride (PVC) film, polypropylene (PP) film, metal foil and non absorbent materials such as special. If we use common solvent based inks for printing in the printing material, drying time, usually requires the use of dusting, drying rack device or in the ink adding other additives, and UV ink no such problems. 

2 metal materials printing 

On the surface of the metal material using UV ink printing, can shorten the curing process and simplify the original curing device. At the same time, UV ink surface good curing and conjunctivitis can not only improve the finishing characteristics, but also improve the appearance of the product quality. 

3 commercial paper printing 

The use of commercial paper printing printing material and ink is more special, such as non carbon copy paper, thermal paper, magnetic ink, anti-counterfeit ink and ink has a certain resistance to discoloration resistance, heat resistance and stability, it is best to use the UV ink or UV light oil. At the same time, due to the speed of printing equipment, printing ink, ink dosage, but also with the use of UV printing ink favorable conditions. 

Process adaptability of UV printing 

1.UV printing (offset) 

Offset according to the state of the substrate can be divided into sheet fed offset printing and web offset, sheet fed offset printing is suitable for paper, cardboard, plastic sheet and foil printing; rotary offset printing speed faster, suitable for large quantities of books, newspapers, business forms and printing self-adhesive. In offset printing using UV ink, the main consideration from the following several aspects: non absorption of printer materials of ink curing; ink emulsification may will hinder the attachment of ink and substrate; rotary printing machine speed and phase matching ink curing speed and the printing speed, especially using self-adhesive printing and special printing ink security printing, UV ink printing effect better in the resin type printing ink. 

Used for offset printing fine products, UV curing can reduce the tiny dot loss, improved color overprint of ink transfer rate. In the selection of ink materials, to consider the effects of the components on the UV ink, to ensure the best printing effect. Since offset printing ink film is generally 2 ~ 3 m, although beneficial to light cured, but thin film of ink, pigment on the substrate surface hiding power will be subject to certain impact, it is generally to improve the pigment content in the formula; with increasing the content of pigment, the light transmittance of a film of ink will be reduced, is not conducive to the UV curing; and ink film itself is thin, if pigment wetting is not good, pigment, filler easily exposed in the monlchamus membrane surface, affect the ink film gloss, so to choose good pigment dispersion. When using UV offset printing should also pay attention to the following points. 

(1) the different nature of the substrate should choose a different ink, to consider the transparency of the ink, curing rate, the cover of the ink and printing surface gloss, etc.. 

(2) in color printing, the ability of various pigments to absorb UV photons is different, the transmission rate from high to low is M, Y, C, BK, so the degree of curing of different colors of ink is also different. The transmission rate directly influences the excitation energy of the photon to the light initiator, so the printing color sequence is suitable for BK, C, Y and M, so that the ink with poor transparency can absorb photons as much as possible, and the curing effect can be enhanced. 

(3) use of alcohol dampening system can reduce the surface tension of the ink, accelerates the curing effect, and in the printing process, the fountain solution strengthening treatment on the printing plate oleophobic region (blank), to ensure that the lipophilic region sufficiently Pro ink and hydrophilic regions not dwell. 

Improving the ink formula and adding the corresponding additives can increase the hydrophobicity of the ink, but it will lead to shrinkage of the edge of the image, the fine level is lost, the dot boundary is not clear, etc.. 

(4) UV printing on paper surface strength high, surface strength is easy to occur galling failure, with gold, silver cardboard printing, due to the paper surface smooth, less affinity for ink, the second color overprint easy to out the color Mexican rabbit. Therefore, in the UV printing, should choose the surface tension larger paper, and reasonable arrangement of color sequence, adjust the printing process related process parameters, in order to avoid and reduce the occurrence of the above phenomenon. 

2.UV printing (flexible version) 

Flexo printing is a rapid development in recent years, a type of printing process, printing plate picture and text part is higher than the non graphic part, and has the flexibility to be able to better express the graphic part of the fine level and profile. In addition, its application of printer materials is very extensive, in addition to the traditional paper, some non absorption of printer materials, such as plastic film, aluminum foil composite paper, glass paper can also use of flexo printing. 

Flexo printing using UV ink, in addition to coloring, curing and adhesion problems that should be paid attention to in, but also must pay attention to ink components of ink viscosity, rheological property in order to obtain good printability and stability. 

Flexible version of the printing process determines that the use of UV ink should not have a higher viscosity. Traditional flexographic printing ink, there are two kinds of solvent and water, needed a large amount of solvent or water to adjust the viscosity of. Due to the use of a large number of solvent, most flexible printing ink in rheology approximation to Newton fluid, will cause the ink deposition, unstable, so given the flexo printing ink proper thixotropy can prevent pigment flocculation and sedimentation. 

UV flexo printing ink is to reduce the viscosity of the system viscosity, and therefore, the overall viscosity may be higher than the solvent based flexo printing ink. Although the UV flexo printing ink viscosity than screen printing, offset printing ink low, but the addition of pigment will increase the viscosity, especially in the pigment wetting, dispersion, stability and stability of the processing does not HERSHEY'S. In addition, pigment ink flow affect the denaturation is more important, proper thixotropy is beneficial. This is because when internal ink molecules cross-linked to a certain extent and pseudoplastic when no pigment dispersion stabilizer of ink system, in the high-speed operation of the roller, its viscosity will plummet, but from the roller into the rate relatively low printing part, the viscosity will rise rapidly, for the substrate surface wettability is poor and not suitable for printing. The ink containing the appropriate dispersion stabilizer has a certain stability, and its viscosity is not high, after high shear, the viscosity recovery is relatively slow, good printing adaptability. 3.UV printing (screen) 

Screen printing UV ink solid content was 100%, there is no volatile, after curing ink film thickness was almost constant, is conducive to obtaining high film thickness, printing and curing process is easy to control can avoid blocking version, spots and fault, reduce downtime. 

Although UV screen printed with many advantages, but light initiation determined, effects of ink layer curing quality, improper selection and only in the monlchamus membrane surface curing fast. On the other hand, UV net printed with its advantages, although the thick Jimo film, but the lower pigment content can reach a high hiding power, which is favorable for the underlying curing conditions. Under the premises does not prevent pigment saturation and hiding power, appropriate to add well refraction of light filler, increased ink layer transparent medium concentration, also help to improve the underlying triggered to light absorption agent. Due to the screen printing ink film thickness, the printing precision is not very high, pigment particle diameter can be larger, so under the premise without sacrificing the pigment dispersion, an appropriate increase in pigment particle size, increase the actual pervious to light the ink, in order to facilitate the underlying curing.