Effect of light-changing ink factors on the gloss of printed matter

Effect of light-changing ink factors on the gloss of printed matter

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 binder. The ink should contain finely dispersed fine pigments with sufficient viscosity and fast 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. Influence of ink film thickness on print gloss

After the paper absorbs the ink material to the maximum extent, the remaining binder remains in the ink film, which can effectively improve the gloss of the printed matter. The thicker the ink film, the more the remaining binder, the more beneficial it is to improve the gloss of the print. The gloss increases with the increase in the thickness of the ink film, and although the inks are the same, the gloss of the print formed by the different papers varies with the thickness of the ink film. When the ink film 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 covers the original high gloss of the paper itself, and the gloss formed by the ink film itself is absorbed by the paper. Lowering; as the thickness of the ink film is gradually increased, after the absorption of the binder by the paper is substantially saturated, the surface retains the binder and the gloss is continuously increased. The gloss of the coated paperboard print increases rapidly with the increase of the thickness of the ink film. After the thickness of the ink film is increased to 3.8 μm, the gloss no longer increases with the increase of the thickness of the ink film.

2, ink mobility

The fluidity of the ink is too large, the dot size is increased, the size of the blot is enlarged, the ink layer is thinned, and the printing gloss is poor; the ink fluidity is too small, the gloss is high, the ink is not easily transferred, and the printing is not favorable. Therefore, in order to obtain a good gloss, the fluidity of the ink should be controlled, and it should not be too large or too small.

3, ink leveling

In the printing process, the ink has good leveling property, and the gloss is good; the leveling property is poor, and the drawing is easy, and the gloss is poor.

4, the content of pigment in the ink

The ink has a high pigment content, and a large number of fine capillaries can be formed in the ink film. The ability of these large number of fine capillaries to retain the binder is much greater than the ability of the fiber gap to absorb the binder on the surface of the paper. Therefore, an ink having a high pigment content enables the ink film to retain more binder than an ink having a lower pigment content. A print using an ink having a high pigment content has a higher gloss than a print of an ink having a lower pigment content. Therefore, the capillary network structure formed between the ink pigment particles is a major factor affecting the gloss of the print.

In the actual printing, the method of using a bright varnish to increase the gloss of the printed matter is completely different from the method of increasing the pigment content of the ink. These two methods of increasing the gloss of the print are selected according to the composition of the ink and the thickness of the printed ink film. The method of increasing the pigment content is limited due to the need for color printing color reduction. Inks formulated with small particle pigments, when the pigment content is reduced, the gloss of the print is reduced, and a higher gloss can be produced only when the ink film is relatively thick. Therefore, in this case, a method of increasing the pigment content can be employed to improve the gloss of the print. However, the amount of pigment can only be increased to a certain limit, otherwise the pigment particles can not be completely covered by the binder, which causes the light scattering phenomenon on the surface of the ink film to be aggravated, which in turn causes the gloss of the print to decrease.

5, the size of the pigment particles and its degree of dispersion

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 small, more small capillaries can be formed. Increase the ability of the ink film to retain the binder and increase the gloss of the print. At the same time, if the pigment particles are well dispersed, it also contributes to the formation of a smooth ink film, which can improve the gloss of the printed matter. The limiting factors affecting the degree of dispersion of the pigment particles are the pH of the pigment particles and the content of volatile substances in the ink. The pigment has a low pH value, a high volatile content in the ink, and a good dispersion of the pigment particles.

6, the transparency of the ink

After the ink with high transparency forms the 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 then reflects out to form two color filters. This complex reflection enriches the color effect; the opaque pigment is formed. Ink film, its gloss is only reflected from the surface, the gloss effect is certainly not as good as the transparent ink.

7, the gloss of the binder

The gloss of the binder is the main factor for the gloss of the ink imprint. The early ink binders are mainly vegetable oils such as linseed oil, tung oil and emu oil. The smoothness of the surface after conjunctiva is not high and can only be fatty. The film surface forms a diffuse reflection on the incident light, and the gloss of the imprint is poor. Nowadays, the binder of the ink is mainly composed of resin, the smoothness of the surface after the imprinting of the conjunctiva is high, and the diffuse reflection of the incident light is reduced, so that the gloss of the imprint 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 have not been completely completed, the gloss of the printed surface is very high. For example, coated paper, the gloss of the printed surface is often 15-20 degrees higher than that of the white paper. And the surface is still moist and shiny. However, as the ink is further dried and fixed, the gloss will gradually decrease. When the solvent in the ink is still on the paper surface, the ink maintains a certain degree of fluidity and has high smoothness. However, as the solvent penetrates into the paper, the smoothness of the surface is determined by the particles of the pigment, and at this time the pigment particles are much larger than the molecules of the solvent, so the smoothness of the printed surface is with the solvent. Infiltration has to be reduced. During 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 is also carried out at a suitable rate, the surface of the ink can be hardened by film formation while maintaining a relatively high smoothness. This print gloss can be kept to a high degree. On the contrary, if the penetration of the solvent is rapid, the polymerization hardening of the resin can be completed only when the smoothness of the printing surface is greatly reduced, so that the gloss of the print is remarkably lowered.

Therefore, in the case where the gloss of the paper is the same, the slower the penetration speed of the ink, the higher the printing gloss. Even in the case where the white paper gloss and the ink penetration speed are the same, the printing gloss differs depending on the state of penetration of the ink on the paper surface. In general, at the same permeation rate, a dense and finely permeable state is more favorable for an increase in printing gloss than a sparse and coarse osmotic state. However, reducing the penetration of the ink and the speed of the conjunctiva to increase the gloss of the print can cause backside sticking failure. Therefore, the improvement of the papermaking technology alone cannot achieve the purpose of improving the printing gloss and preventing the sticking of the ink sticking, and the solution to this problem has yet to be improved by the ink manufacturing technology.

9, the dry form of the ink

The same amount of ink is in different dry forms, and the gloss is different. Generally, the oxidized conjunctiva is dried more than the osmotic dryness, because the oxidized conjunctiva is dried in the ink.