UV ink printing features

UV ink printing features

1 Instant curing UV ink can be cured in seconds after printing, which significantly improves the production efficiency; especially in the printing of iron, the use of this feature can omit the baking and drying process. Drying equipment is simple and saves space.
2 Environmental UV inks do not use solvents, do not emit pollutants when cured, and can improve the operating environment and prevent air pollution. At the same time, because there is no need for solvent treatment devices and special environmental protection devices, equipment investment can be greatly reduced.
3 Photopolymerization drying methods UV inks or UV light oils do not cure as long as they are not exposed to UV rays. In this regard, it is relatively simple to store. Moreover, photopolymerization reaction and volatile drying are not the same, and it is a kind of chemical curing. The hardness of film formation is higher than that of other ink ink films, and it is suitable for printing with higher hardness requirements of the film layer.
4 High-quality UV prints have high gloss, good rub resistance, solvent resistance, heat resistance, etc. Widely used in packaging printing.
5 Energy Saving UV curing consumes less power and saves energy.

1.UV offset printing

Offset printing can be divided into sheetfed offset printing and web offset printing according to the status of the substrate. Sheetfed offset printing is suitable for printing on paper, cardboard, plastic sheet and metal foil; web offset printing is faster, suitable for large-volume books and newspapers. , business forms and sticker printing. The use of UV inks in offset printing mainly considers the following issues: ink curing of non-absorbing substrates; ink emulsification may hinder the adhesion of inks to substrates; web presses are fast and require ink curing speed and printing speed. Matching, especially for adhesive printing and security printing using special inks, UV inks print better than resin offset inks.

Offset printing is used for printing of fine products. UV curing can reduce the loss of fine dots and increase the ink transfer rate of overprinting. When selecting the ink raw materials, the effects of each component on the UV ink must be comprehensively considered to ensure the best printing effect. Because offset ink film is generally 2 ~ 3μm, although beneficial to light curing, but the ink film is thin, the hiding power of the pigment on the printing surface will be affected, so generally to increase the pigment content in the formula; and increase the pigment content, ink film The light transmission performance will be reduced, not conducive to UV curing; and the ink film itself is thin, if the pigment wettability is not good, pigments, fillers are easily exposed to the ink film surface, affecting the ink film gloss, so choose to disperse more Good paint. The following points should also be noted when using UV offset printing.

(1) Different types of substrates should be selected for different inks. The light transmittance, the curing rate, the hiding of the ink, and the glossiness of the surface of the ink should be taken into consideration.
(2) In color printing, the ability of various pigments to absorb UV photons is different, and their transmittance is from high to low as M, Y, C, BK, so the curing degree of each color ink is also different. The transmittance directly affects the photon's excitation energy of the photoinitiator. Therefore, the printing color sequence should be ranked as BK, C, Y, and M, so that the ink with poor light transmission can absorb as many photons as possible to enhance the curing effect.
(3) The use of the alcohol dampening system can reduce the surface tension of the ink and promote the curing effect. In the printing process, the dampening area (blank portion) of the printing plate can be intensified with a fountain solution to ensure that the lipophilic area is adequate. Intimate ink, the hydrophilic area does not ink.
Improve the ink formulation and add the appropriate additives can increase the hydrophobicity of the ink, but the hydrophobicity will lead to ink shrinkage of the edge of the image, the loss of fine levels, dot boundaries are not clear, affect the quality of printed products.
(4) UV printing has high requirements on the surface strength of the paper, and the surface strength is not enough to cause pulling faults. When printing with gold or silver cardboard, the surface of such paper is smooth, and the affinity for ink is small, and the second color is easy to overprint. Pull out the first color ink. Therefore, in UV printing, papers with large surface tension should be selected, and the color sequence should be properly arranged to adjust the relevant process parameters in the printing process so as to avoid and reduce the above phenomenon.

2.UV flexo printing

Flexographic printing is a kind of printing technology that has developed rapidly in recent years. The graphic and textual parts of the printing plate are higher than the non-graphical parts, and they are flexible. They can express the subtle levels and outlines of the graphic parts. In addition, its applicable printing materials are very extensive, in addition to the traditional paper, some non-absorbable printing materials, such as plastic film, aluminum foil composite paper, glass paper, etc. can also use flexographic printing.

The use of UV ink for flexographic printing, in addition to attention should be paid to coloring, curing and adhesion problems, but also must pay attention to ink components on the ink viscosity, rheological effects in order to obtain better printability and stability.

The flexographic printing process determines that the UV ink used should not have a high viscosity. Conventional flexo printing inks are solvent-based and water-based. They require a large amount of solvent or water to adjust the viscosity. Due to the large amount of solvents used, most flexographic printing inks are similar to Newtonian fluids in terms of rheology, causing ink settling and instability. Therefore, imparting appropriate thixotropy to the flexographic printing ink can prevent the pigment flocculating from settling.
UV flexographic printing inks use reactive diluents to reduce the viscosity of the system, and therefore their viscosity may generally be higher than solvent-based flexographic printing inks. Although the viscosity of UV flexo printing inks is lower than that of screen printing and offset printing inks, the addition of pigments will increase the viscosity, especially when the wetting, dispersion, and stability of the pigments are not handled properly. In addition, the influence of pigments on the rheological properties of inks is more important, and the appropriate thixotropy is beneficial because when there is a degree of pseudo-plasticity in the cross-linking of the molecules inside the ink, there is no ink dispersion system for pigment dispersion stabilizers. The viscosity of the ink roller on high-speed operation will drastically drop, but when the ink roller enters the printing position where the ink roller enters a relatively low speed, the viscosity will quickly rise and the wetting effect on the surface of the substrate will be too poor to be suitable for printing. The ink containing a suitable dispersion stabilizer has a certain stability, and its own viscosity is not high, after a high shear, the viscosity rises slowly and the printing adaptability is better.

3.UV screen printing

The solid content of UV screen printing ink is 100%, there is no component volatilization, the ink film thickness after curing is basically the same, which is conducive to obtain a higher film thickness, printing and curing process is easy to control, can avoid blocking, spots, etc. Faults, reduce downtime.

Although the UV screen has many advantages, the determination of the photoinitiation conditions affects the curing quality of the ink layer, and the improper selection can only cure the ink film surface faster. On the other hand, UV screens have the advantage that the ink film is thick, but the lower pigment content can achieve a high hiding power, which is a favorable condition for the curing of the underlayer. Under the premise of not impeding the saturation and hiding power of the pigment, the light-transmitting filler with better refractive index is appropriately added to increase the concentration of the light-transmitting medium in the ink layer, which also helps to increase the light-absorbing amount of the underlayer initiator. Due to the thick screen printing ink film, the printing accuracy is not very high, and the pigment particle size can be larger. Therefore, under the premise of not sacrificing the dispersibility of the pigment, the pigment particle diameter can be appropriately increased, so that the actual light transmittance of the ink can be increased to facilitate the The bottom layer cures.