The final effect of the print is closely related to the physical and chemical properties of the ink. The composition of the ink determines the properties of the ink:
1. The size of the pigment particles and the degree of dispersion
Although the role of the ink film capillary is an important factor in forming the gloss of the print, the apparent size of the pigment particles in the dispersed state is more important, which directly determines the state of the capillary of the ink film. Therefore, the pigment particles are small and well dispersed, which is advantageous for forming a smooth ink film, and is also very advantageous for improving the gloss of the printed matter.
2. The viscosity of the binder and the content of the pigment
According to the interface chemistry, the capillary permeation rate is inversely related to the viscosity of the liquid, that is, the permeation rate decreases as the viscosity increases. The capillary network structure formed between the ink pigment particles is an important aspect that determines the gloss of the print. At the moment of imprinting, the ink is integrally pressed into the larger pores of the paper; after imprinting, the binder begins to separate from the ink and penetrate into the smaller pores of the paper. Therefore, the size of the ink film capillary determines the amount of separation of the binder. Capillary retention of the binder is much more effective than printing pressure to press the binder into the pores of the paper.
3. Drying time
The rapid drying of the ink film on the paper surface can reduce the amount of the binder which penetrates into the paper pores, thereby improving the gloss and smoothness of the ink film. The high gloss of the ink film means that the specular reflection of the surface is relatively high so that the human eye can see that the white light reflected by the surface is much less than the ink film with low glossiness in most cases so that the saturation of the color is higher. Therefore, the print with high gloss looks more vivid and full. The printing ink layer of the spot color ink is mostly translucent or opaque. When selecting the ink formula, the influence of the light transmittance of the ink layer on the spot color printing should be considered according to the actual situation.