The ink factor that affects the gloss of the print is mainly the smoothness of the ink film, which is determined by the nature and quantity of the link material. The ink should contain finely dispersed fine pigments, and have sufficient viscosity and faster drying speed to avoid excessive penetration of the binder into the paper pores. In addition, the ink should also have good fluidity in order to form a smooth ink film after printing.
1) Effect of Ink Film Thickness on Print Gloss
After the paper absorbs the ink binder to the maximum extent, the remaining binder remains in the ink film, which can effectively improve the gloss of the print. The thicker the ink film, the more the remaining linking material, the more conducive to improving the gloss of the print. The gloss increases with the thickness of the ink film. Although the ink is the same, the gloss of the print formed by different papers varies with the ink film thickness. When the ink film is thin, the luster of the high-gloss coating paper decreases as the thickness of the ink film increases. This is because the ink film masks the original higher gloss of the paper itself, and the gloss of the ink film itself is absorbed by the paper. With the gradual increase of the thickness of the ink film, after the absorption of the link material on the paper is substantially saturated, the surface retains the linking material and the glossiness also increases. The gloss of coated cardboard prints increases rapidly with the increase of ink film thickness. After the ink film thickness increases to 3.8 μm, the gloss no longer increases with the increase of ink film thickness.
2) Ink flow
The fluidity of the ink is too large, the dots are enlarged, the size of the print is enlarged, the ink layer is thinned, and the glossiness of the printing is poor; the fluidity of the ink is too small, the glossiness is high, the ink is not easy to transfer, and is also not conducive to printing. Therefore, in order to obtain better gloss, the fluidity of the ink should be controlled, not too large or too small.
3) Leveling of ink
In the printing process, the leveling property of the ink is good, then the glossiness is good; the leveling property is poor, and the drawing is easy, then the glossiness is poor.
4) The content of pigment in ink
The pigment content of the ink is high, and a large number of fine capillaries can be formed in the ink film. The ability of these large, small capillaries to retain the web material is much greater than the ability of the fiber surface to absorb the web material. Therefore, compared with inks with low pigment content, inks with high pigment content can make the ink film retain more linking material. A print using an ink having a high pigment content has a higher glossiness than a print having an ink having a lower gloss level than a pigment. Therefore, the capillary network structure formed between the ink pigment particles is the main factor affecting the gloss of the printed matter.
In the actual printing, the method of adding gloss oil to increase the gloss of the print is completely different from the method of increasing the pigment content of the ink. The two methods for increasing the gloss of printed materials are selected according to the composition of the ink and the thickness of the printed ink film. Due to the need for color printing in color printing, the method of increasing the pigment content is limited. Small-particle pigmented inks, when the pigment content is reduced, the gloss of the printed matter decreases, and only when the ink film is relatively thick can a high gloss be produced. Therefore, for this case, the method of increasing the content of the pigment can be used to increase the gloss of printed matters. However, the amount of pigment can only be increased to a certain limit. Otherwise, the pigment particles cannot be completely covered by the binder, and the phenomenon of light scattering on the surface of the ink film is intensified, resulting in a decrease in gloss of the printed matter.
5) Size and dispersion of pigment particles
The size of the pigment particles in the dispersed state directly determines the state of the capillary of the ink film, and if the ink particles are urine, more small capillary tubes can be formed. Increase the ability of the ink film to retain the binder and improve the gloss of the print. At the same time, if the pigment particles are well dispersed, it also helps to form a smooth ink film, which can improve the gloss of prints. The factors that affect the dispersion of pigment particles are the pH of the pigment particles and the content of volatile substances in the ink. The low pH of the pigment, the high content of volatile substances in the ink, and the dispersion of the pigment particles.
6) Ink transparency
After the ink with high transparency forms an ink film, part of the incident light is reflected by the surface of the ink film, and the other part reaches the surface of the paper, and is reflected again to form two filter colors. This complex reflection enriches the effect of color and luster; opaque pigment forms Ink film, its gloss is only reflected from the surface, the gloss effect is certainly not as good as transparent ink.
7) Gloss of the binder
The glossiness of the linking material is the main factor for the glossiness of the ink blotting. The early ink linking materials mainly consisted of linseed oil, tung oil, eucalyptus oil, and other vegetable oils. The smoothness of the conjunctiva surface is not high and can only exhibit fatness. Membrane surface, diffuse reflection of incident light, the gloss of the print is poor. Nowadays, the binder of the ink is mainly composed of resin. After the conjunctiva has been blotted, the surface smoothness is high, and the diffuse reflection of the incident light is reduced. Therefore, the gloss of the print is several times higher than that of the early ink.
8) Solvent penetration rate
At the end of printing, since the drying and fixing of the ink has not been fully completed, the glossiness of the printing surface is very high, such as coated paper, and the glossiness of the printed surface of the printing surface is often 15-20 degrees higher than that of the white paper surface. , And the surface is still moist and shiny. However, as the ink is further dried and fixed, the gloss will slowly decrease. When the solvent in the ink still remains on the paper, the ink maintains a certain degree of fluidity and has a high degree of smoothness. However, as the solvent penetrates into the paper, the smoothness of the surface is determined by the pigment particles. At this time, the pigment particles are much larger than the molecules of the solvent. Therefore, the smoothness of the printing surface is consistent with the solvent. Permeate and have to drop. In this process, the solvent penetration rate directly affects the smoothness and gloss of the printed surface. If the permeation proceeds slowly, and the oxidative polymerization of the resin proceeds at a suitable rate, the ink surface can be hardened by film formation while maintaining a relatively high level of smoothness. This print gloss can be maintained to a high degree. On the contrary, if the permeation of the solvent proceeds rapidly, the polymerization hardening of the resin can be completed only when the smoothness of the printed surface has been greatly reduced, so that the gloss of the printed matter is significantly reduced.
Therefore, in the case of the same paper gloss, the slower the ink permeation speed, the higher the print gloss. Even in the case where the glossiness of the white paper and the ink permeation speed are the same, the print glossiness differs depending on the state of ink permeation on the paper surface. In general, a dense and subtle infiltration state is more conducive to the improvement of printing glossiness than a sparse and coarse infiltration state at the same penetration speed. However, reducing ink penetration and conjunctival speed to increase printing gloss can cause backside sticking ink failure. Therefore, the improvement of papermaking technology alone cannot achieve the goal of both improving the printing glossiness and preventing sticking ink failures. This problem needs to be solved by the improvement of ink manufacturing technology.
9) Dry form of ink.
The same amount of ink used in different dry forms, its gloss is not the same, the general oxidative conjunctiva drying than the osmotic gloss is high, because the oxidized conjunctiva dry ink in the film-forming binder more.