UV ink is a kind of ink without solvent, fast drying speed, good gloss, colorful, water resistance, solvent resistance and abrasion resistance. At present, UV ink has become a more mature ink technology, and its pollutant emissions are almost zero. UV (ultraviolet light curing) ink refers to the use of UV light of different wavelengths and energies to polymerize the monomers in the ink binder to form a polymer, and the ink is formed into a film and dried. UV inks also belong to inks. As inks, they must have bright colors (except for special cases), good printability, and appropriate curing and drying rates.
In addition, UV inks also have the following characteristics: ink curing of non-absorbing substrates; ink emulsification may hinder the adhesion of inks to substrates; web presses are fast and require the ink's curing speed to match the printing speed, especially if it is not Adhesive printing and the use of special ink securities printing, UV ink printing effect is better than the resin offset ink. Taking into account the above properties, printing companies generally use UV inks in offset printing.
However, the printing industry should also pay attention to the following points 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.
According to the survey, UV curing technology was applied to industrial production in the early 1960s, but it was not until the 1970s that it was used by the printing industry in a limited range. With the development of modern science and technology, UV inks and their curing and drying technologies have become increasingly sophisticated. In the late 1990s, UV technology was widely used in offset printing. In recent years, UV offset printing has been developing very rapidly, with an annual growth rate of over 10%. In the European and American packaging and printing industry, UV inks account for about 65% of the entire offset ink sales.
UV inks are usually composed of pigments, prepolymers, reactive diluents, photoinitiators, and additives. They do not contain solvents. The solid content of the ink after curing is close to 100%, and almost no VOC (organic volatiles). The process will not cause more harmful environmental pollution, no need to invest in environmental treatment facilities and security protection equipment, making UV inks as "the most appropriate environmental protection material." Since organic solvents are not required for UV inks or varnish, it can effectively save oil resources, at the same time, it can reduce the damage to the living environment, save costs due to air purification, and improve the work environment and health problems. Therefore, UV offset printing technology has many obvious low-carbon printing features compared to conventional offset printing technology.
The green characteristics of UV offset printing, such as VOC-free emission, low energy consumption, and low production cost, will make it a very important position in offset printing for low-carbon and green roads. Because, with the development of social economy and people's awareness of environmental protection, the low carbonization and green of printing is the only way for the printing industry. This shows that the offset printing market is vast, and the offset printing market will certainly drive the development of the UV ink market.
In addition, UV inks also have the following characteristics: ink curing of non-absorbing substrates; ink emulsification may hinder the adhesion of inks to substrates; web presses are fast and require the ink's curing speed to match the printing speed, especially if it is not Adhesive printing and the use of special ink securities printing, UV ink printing effect is better than the resin offset ink. Taking into account the above properties, printing companies generally use UV inks in offset printing.
However, the printing industry should also pay attention to the following points 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.
According to the survey, UV curing technology was applied to industrial production in the early 1960s, but it was not until the 1970s that it was used by the printing industry in a limited range. With the development of modern science and technology, UV inks and their curing and drying technologies have become increasingly sophisticated. In the late 1990s, UV technology was widely used in offset printing. In recent years, UV offset printing has been developing very rapidly, with an annual growth rate of over 10%. In the European and American packaging and printing industry, UV inks account for about 65% of the entire offset ink sales.
UV inks are usually composed of pigments, prepolymers, reactive diluents, photoinitiators, and additives. They do not contain solvents. The solid content of the ink after curing is close to 100%, and almost no VOC (organic volatiles). The process will not cause more harmful environmental pollution, no need to invest in environmental treatment facilities and security protection equipment, making UV inks as "the most appropriate environmental protection material." Since organic solvents are not required for UV inks or varnish, it can effectively save oil resources, at the same time, it can reduce the damage to the living environment, save costs due to air purification, and improve the work environment and health problems. Therefore, UV offset printing technology has many obvious low-carbon printing features compared to conventional offset printing technology.
The green characteristics of UV offset printing, such as VOC-free emission, low energy consumption, and low production cost, will make it a very important position in offset printing for low-carbon and green roads. Because, with the development of social economy and people's awareness of environmental protection, the low carbonization and green of printing is the only way for the printing industry. This shows that the offset printing market is vast, and the offset printing market will certainly drive the development of the UV ink market.
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