The influence of ink on the glossiness of printed matter

The influence of ink on Glossiness of printed matter is mainly due to the smoothness of ink film, which is determined by the nature and quantity of binder The ink shall contain fine pigments with uniform dispersion, sufficient viscosity and fast drying speed to avoid excessive penetration of binder into the paper pores In addition, the ink should also have good fluidity, so as to form a smooth ink film after printing 1) The influence of ink film thickness on the gloss of printed matter after the paper Zui absorbs the binder of ink to a large extent, the remaining binder remains in the ink film, which can effectively improve the gloss of printed matter The thicker the ink film is, the more binders are left, which is more conducive to improving the gloss of the printed matter The gloss increases with the increase of ink film thickness Although the ink is the same, the gloss of printed matter formed by different paper varies with the thickness of ink film When the ink film of high gloss coated paper is thin, the gloss of the printed matter decreases with the increase of the thickness of the ink film This is because the ink film masks the original high gloss of the paper itself, and the gloss formed by the ink film itself decreases with the absorption of the paper With the gradual increase of the thickness of the ink film, after the absorption of the paper to the binder is basically saturated, the surface retained binder increases, and the glossiness is not the same Break up The glossiness of Coated Paperboard Printing increases rapidly with the increase of ink film thickness When the ink film thickness increases to 3.8 μ m, the glossiness will not increase with the increase of ink film thickness 2) The fluidity of ink the fluidity of ink is too large, the dot is enlarged, the imprint size is enlarged, the ink layer is thinned, and the printing glossiness is poor; the fluidity of ink is too small, the glossiness is high, the ink is not easy to transfer, and it is not conducive to printing Therefore, in order to get a better glossiness, we should control the flow of ink, not too big or too small 3) Ink leveling in the printing process, ink leveling is good, the glossiness is good; leveling is poor, easy to draw, the glossiness is poor 4) Ink pigment content ink pigment content is high, in the ink film can form a large number of small capillary However, the capacity of these small capillaries to retain the binder is much greater than that of the fiber gap on the paper surface Therefore, compared with the ink with low pigment content, the ink with high pigment content can make the ink film retain more binders The glossiness of printing products with high pigment content is higher than that of printing products with low pigment content Therefore, the capillary network structure formed between ink and pigment particles is the main factor affecting the gloss of the printed matter In the actual printing, the method of brightening oil is used to increase the gloss of the printed matter, which is totally different from the method of increasing the pigment content of the ink The two methods to increase the gloss of printed matter should be selected according to the composition of ink and the thickness of printing ink film Due to the need of color reduction in color printing, the method of increasing pigment content is limited When the pigment content is reduced, the gloss of printed matter will be reduced Only when the ink film is quite thick, can it produce high gloss Therefore, the method of increasing pigment content can be used to improve the gloss of printed matter However, the amount of pigment can only be increased to a certain limit, otherwise, because the pigment particles can not be completely covered by the binder, the light scattering phenomenon on the surface of the ink film will be intensified and the gloss of the printed matter will be reduced 5) The size and dispersion of pigment particles directly determine the state of ink film capillary If the ink particles urinate, more small capillaries can be formed Increase the ability of ink film to retain binder and improve the gloss of printed matter At the same time, if the pigment particles are well dispersed, it also helps to form a smooth ink film, which can improve the luster of the printed matter The factors that affect the dispersion of pigment particles are the pH value of pigment particles and the content of volatile matter in ink The pH value of pigment is low, the volatile matter content of ink is high, and the dispersion of pigment particles is good 6) Transparency of ink After the ink film with high transparency is formed, one part of the incident light is reflected by the surface of the ink film, the other part reaches the paper surface, and then reflected out, forming two filter colors This complex reflection enriches the color effect; while the luster of the ink film formed by the opaque pigment is only reflected by the surface, and the luster effect is certainly not as good as that of the transparent ink 7) The luster of binders is the main factor of whether ink imprinting can produce luster The early ink binders are mainly linseed oil, tung oil, catalpa oil and other vegetable oil The surface smoothness after conjunctiva is not high, only showing fatty film surface, diffuse reflection of incident light, and the gloss of imprinting is poor Now the ink binder is mainly composed of resin After imprinting the conjunctiva, the surface smoothness is high, and the diffuse reflection of incident light is reduced, so the gloss of imprinting is several times higher than that of early ink 8) At the end of solvent penetration printing, due to the incomplete drying and fixation of the ink, the glossiness of the printing surface is very high For example, the glossiness of the field part of the printing surface of coated paper is often 15-20 degrees higher than that of white paper, and the surface is still wet and shiny However, with the further drying and fixation of the ink, the gloss will slowly decline When the solvent in the ink is still on the paper, the ink maintains a certain degree of fluidity and has a high smoothness However, with the penetration of solvent into the paper, the smoothness of the surface is determined by the pigment particles, which are much larger than the solvent molecules Therefore, the smoothness of the printing surface has to decline with the penetration of solvent In this process, the speed of solvent penetration directly affects the smoothness and glossiness of the printing surface If the penetration is slow, and the oxidation polymerization of the resin is carried out at a suitable speed, the ink surface can become hard under the condition of maintaining a high smoothness In this way, the printing glossiness can be kept at a high level On the contrary, if the penetration of solvent is rapid, then the polymerization hardening of resin can be completed only when the smoothness of the printing surface has been greatly reduced, so the glossiness of the printed matter will be significantly reduced Therefore, in the case of the same glossiness of paper, the slower the penetration speed of ink, the higher the glossiness of printing Even if the glossiness of white paper and the penetration speed of ink are the same, the printing glossiness will vary according to the penetration state of ink on paper Generally speaking, at the same penetration rate, the dense and fine penetration state is more conducive to the improvement of printing glossiness than the sparse and coarse penetration state However, reducing the ink penetration and conjunctival speed to improve the printing glossiness will cause the back ink sticking failure Therefore, the improvement of paper-making technology alone can not achieve the goal of not only improving the printing glossiness but also preventing ink sticking failure The solution to this problem still needs the improvement of ink manufacturing technology 9) Drying form of ink The same ink amount adopts different drying forms, and its glossiness is also different Generally, the glossiness of oxidized conjunctiva drying is higher than that of osmotic drying, because there are more film-forming binders in oxidized conjunctiva drying ink The glossiness of printing ink can be tested by glossiness meter, which has been certified by national metrology products and compared with international standards, and is widely used in the rapid and accurate measurement of mirror glossiness of paint, ink, paint, paper, printing, plastic and other flat surfaces