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.
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.
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