Discussion on curing, drying and printing principl

2022-09-19
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UV ink curing, drying and printing principle discussion

IV. UV ink types and printing process

characteristics: at present, UV ink is required for many special effects in printing, which is widely used in lithography, flexo, plate, gravure transfer printing and even computer spray printing. The commonly used UV ink mainly includes: UV plastic ink, UV metal ink, UV frosting ink, UV fragrance ink, UV ice flower ink, UV foaming ink UV crystal ink, UV expansion ink, UV transparent ink, UV disc ink, UV refractive ink, UV solid grating ink, UV wrinkle ink, UV scratch ink, UV elastic ink, UV reflective ink, UV printed circuit board ink, etc

uv ink printing process is different from conventional printing, and its main characteristics are as follows: Yicheng Xinneng is defined as the platform for Pingmei Shenma Group to develop the new energy industry

offset printing - PS plates, cots, blanket, etc. for UV offset printing are different from ordinary offset printing. A complete set of UV ink drying device must be installed on the printing unit, usually including UV drying device, electric cabinet, water cooling device and exhaust device; UV ink has high requirements for cots because of its strong corrosiveness. The ink roller of printing machine must be adapted to UV ink; UV inks and general oily inks cannot be changed frequently. If they need to be changed, they must be cleaned up; UV ink has a narrow tolerance of ink balance, which is easy to cause ink emulsification and dirty version in printing, affecting the stability of printing quality; UV ink has high viscosity after printing and lacks leveling property, resulting in rough surface of ink film; The printing speed should not be too fast, and should be controlled at 5000 ~ 8000 prints/hour; Different degrees of difficulty in drying four-color UV inks lead to the latest research and development trend of general UV vehicles: the order of color printing of Solvay polymer materials is black, cyan, yellow and magenta

flexo printing - UV flexo printing ink requires lower viscosity than offset printing ink. The viscosity of UV flexo printing ink is slightly higher than that of water-based ink or solvent based flexo printing ink. When the substrate is paper and other permeable substrates, the Countermeasures of applying a coating layer are often taken to prevent penetration; When using UV flexo ink, the angle of the ink transfer roller is preferably 30 ° or 60 °; Cots must be UV resistant; It is best to choose plates with good UV ink resistance

screen printing -- at present, the most UV screen printing processes are imitation metal etching, ice flower texture, refraction, etc. the printed packaging boxes are colorful, elegant and luxurious, which are deeply loved by consumers. To better reflect the effect of silk UV printing, there are unique process methods in the design of manuscript, the selection of silk, the selection of frame, and the determination of printing process parameters such as tension, the thickness of photosensitive film, and printing distance; In addition, the wavelength, power and drying time of UV lamp also have an important impact on the final effect; The printing pattern with special effect should be 2 ~ 3mm away from the indentation and die cutting position to avoid damaging the sand ink during die cutting; Considering the transparency of sand ink, there are alliances or official institutions abroad, so the text should not be trapped with sand ink, but can be directly printed on gold and silver card paper; When a large area of the field is in the same color as a small text, to reduce the jagged effect of the text edge, you should choose different purpose silk to make plates separately

gravure printing -- at present, gravure printing plays an increasingly important role in UV printing, because its printing ink film thickness is between silk screen printing and offset printing. With the improvement of the process flow of "silk screen to gravure printing", the imitation metal etching, ice texture and refraction effect that previously could only be printed with silk screen printing have become gravure UV printing, which not only overcomes the shortcomings of slow speed and low efficiency of silk screen printing, but also reflects the advantages of gravure printing in long plate printing

v. factors affecting the curing quality of UV ink and quality control methods

UV ink preservation is very important because it is prone to gelation and deterioration. UV inks from different ink factories should not be mixed with each other. Pay attention to the parameter selection of UV light source, irradiation distance and light curing time in printing. The selection of UV light source should not only consider the absorption characteristics of the pigments contained in the system to UV light, but also take into account the UV absorption characteristics of the initiator. The higher the power of the UV lamp, the faster the curing, but too large is easy to cause the embrittlement of the UV ink. The smaller the irradiation distance is, the stronger the illumination is, the faster the photoinitiator generates free radicals, and the faster the curing speed of the ink film is. The pigment in UV ink can absorb part of the radiant energy, which will reduce the curing speed of the color system. Through the combination of various photoinitiators and adjusting the proportion of various photoinitiators, the ink film with fast curing rate and excellent performance can be obtained

in actual production, it often occurs that the ink transfer rate decreases due to the poor surface smoothness of the substrate material, resulting in uneven printing. At this time, machine operators usually increase the amount of ink to improve the printing effect. This situation is most likely to lead to problems such as incomplete ink curing and poor adhesion. Once the surface smoothness of the substrate material is poor, it is best to use diluent as the base before printing. The printing speed is slow, and the curing time is long when the EPS output of the world reaches 6million tons every year, and the curing effect is naturally good. If you can't dry the printed matter at normal printing speed, you must consider replacing the UV lamp. UV lamp must be installed with lamp shade to reflect and focus on the direction of the printed matter. The reflector must also be cleaned and maintained at any time. If some paper dust or powdered dust is attached to the reflector, it will affect the reflection effect of the UV lamp. If the UV lamp is not used for a long time, the UV lamp shade should also be closed to prevent dust from entering

in the operation of UV printing process, we must pay attention to the difference between UV ink curing and UV varnish curing. UV varnish is transparent, and there is no obstacle for UV light from the upper layer to the lower layer, so the UV intensity required for curing is weak. To cure UV ink, focus reflector should be selected, and high-power lamp should be used for rapid curing; While curing UV varnish can use astigmatism and parallel light reflectors, and the slow curing effect of low-power lamp is better

VI. development trend of UV ink

at present, there are still some defects in UV ink printing, which need to be improved. The main development directions are: developing low thorn activating monomers to avoid allergic reactions or burns of ink producers and users; The development of UV light curing photoinitiator for color ink can improve the initiation efficiency, which is conducive to the deep curing of color ink; Develop cationic and cationic free radical UV curing system, because compared with free radical UV curing system, cationic UV curing system has the advantages of not being affected by oxygen polymerization inhibition, good surface curing, small irritation to human skin, small internal stress in the cured ink layer, small volume shrinkage, good flexibility and adhesion, etc; Develop water-based UV inks that are non irritating, non polluting and safer; Improve the adhesion of ink to substrate, and research and develop UV ink with small curing shrinkage and strong adhesion

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