The reason for the color difference between the printing spot inks

In order to improve the design and quality level of packaging and decoration products, printing plants in the printing of tobacco, wine, cosmetics, pharmaceuticals, daily necessities, such as trademarks, packaging, promotional materials, often use spot color ink, to ensure the color consistency of printing products, to meet customer requirements. But what are the factors that produce spot ink process color difference? Let's go on and look down.
effect of the printing process on color
1, ink thickness and ink balance
the control of ink phase in the printing process is mainly through the control of the thickness of the ink layer to achieve

. The color difference between E and 1.5 to 4.5 NBS is caused when the thickness of the ink layer changes by about 0.1 m, which obviously has a great effect. Offset ink reproduction and ink balance are closely related, in the same amount of ink, water small will affect the color of the depth. Properly grasping ink balance, paying special attention to the pH of the wetting fluid is essential. The principle of water consumption is not dirty, using the smallest possible amount of water supply.
2, printing pressure
the size of printing pressure for ink from the plate to the degree of paper has a great impact, when the printing pressure is insufficient, the transfer of ink is not sufficient, not suitable for printing; Only within the appropriate printing pressure range can you print printed prints with thick ink, clear images, rich order and good color reproduction.
3, printing speed
printing speed increase, will make the printing surface contact time is shorter, the network is virtual, ink transfer rate is reduced, printing quality is reduced. In order to ensure the full contact of the printing surface, improve the quality of printing, which requires a certain printing pressure, control the printing speed, in order to obtain a stable thickness of the ink layer.
4, dry regressing density difference
the same paper, just printed out of the sample density is higher, and after a period of time, as the drying smoothness of the ink decreased, the density value will decrease. Because the density values before and after the drying of the ink layer are different, the color of the printed image is also different. Just printed prints, ink is still in a wet state, and dry state when there is a difference. This is because the newly printed ink layer has a certain leveling, so the surface reflection to mirror reflection mainly, looks bright color, good gloss. When the ink layer is in a dry state, the surface reflection is mainly diffuse, and the color is naturally duller than when it was first printed. Therefore, the ink color of the general printing sample is slightly darker than the standard sample, but how much deep to use data control, in the sample, to determine the density values of the colors just printed down, in printing, with reference to these density values to print, can make the ink color of the two close to the same. Density meter with polarization filter can eliminate the light produced by mirror reflection on the surface of the ink layer, the measured wet color density is very close to the dry color density, and the measured density value is very small affected by the wet and dry ink layer.
The effect of surface finishing on color of printed materials
Surface finishing is the proper processing of the surface of printed materials to improve the resistance of the surface of printed materials to light, heat, water, wear, fold, chemical resistance; Packaging products mainly surface finishing methods are glossy (printing bright oil, coating cover bright oil, matte oil, UV light oil, water-based light oil, etc.), waxing, coating (bright film, matte film), bump imprint, hot gold and so on. After these surface treatments, the print will vary in color and saturation, i.e. density. These changes can be divided into physical and chemical changes. Physical changes are mainly reflected in the addition of specular and diffuse capabilities to the product surface. Generally speaking, when covered with bright light film, coated bright light oil and UV light oil, the color density increases; Chemical changes are mainly due to the organic solvents contained in coated glues, water-based light oils, and UV light oils, which combine with ink particles on the print to change the color of the ink layer.
effect of the printing material (paper) on ink color
1, paper whiteness
the factors affecting paper whiteness are:
(1) the whiteness of the slurry: the most important factor.
(2) dye: Select the dye so that it does not affect its reflectivity near the main wavelength of the measured whiteness, i.e. does not affect the whiteness of the paper.
(3) fillers: depending on their type and grade.
(4) paint: the whiteness of the paint printing paper is determined by the whiteness of the original paper, the whiteness of the coating, and the amount of coating. Different whiteness and paper with a certain color (if some paper blue the latter yellow), the color of the printed ink layer has different effects. Shanghai sticker printing for the same kind of whiteboard paper, whiteness is different, especially for colors with higher brightness values, the impact is particularly obvious, resulting in a large difference in the ratio of spot ink. Therefore, in the actual production should try to choose the same whiteness of paper printing, in order to reduce the impact of paper whiteness on the printing color.
2, the smoothness and gloss of the paper
From the impact on the quality of the printed material, the gloss of the paper and the gloss of the printed material has a very direct relationship, no matter what type of ink, the gloss of the printed material with the paper itself to improve the gloss. The gloss of the paper is directly related to the ink efficiency of the paper, and the paper with the high gloss can obtain a higher printing density when the paper is the same ink film thickness. Therefore, there is a close correlation between the gloss of the printed material and the gloss of the paper itself.
3, paper ink acceptance performance and absorption performance
ink acceptance performance refers to the paper surface in the printing process in the printing press printing moment to receive the ability to transfer ink. It is closely related to the performance of three aspects of paper: the ability of the paper surface to moisten the print ink, the ability of the paper surface to absorb certain ink parts, and the ability of the paper surface to retain and retain uniform ink film. The paper-to-ink absorption performance occurs in a longer period of time from the ink and paper contact with the full curing on the paper surface, it is related to the paper capillary hole to the ink in the absorption of low-viscosity parts and ink in some of the parts of the penetrating effect into the paper. Printing pressure, printing time, ink viscosity, paper capillary radius will affect the paper's ability to absorb ink. The same ink will have different printing densities when printed on paper with different absorption under the same conditions. The paper surface has a pore structure formed by the multi-phase complex structural elements of the opposite sex, in order to obtain good uniformity and smoothness of the paper surface, it is generally used to coat the paper surface with different thicknesses of paint. The nature and thickness of the coating determine the absorption capacity of the paper surface to the ink. Absorption capacity is different, resulting in differences in the color of the printed ink layer.
The effect of the nature of ink on color
The final effect of the printed material is closely related to the chemical and chemical properties of the ink, and the content of the ink determines the nature of the ink:
1, the size of the pigment particles and their dispersion

, pigment particles are small, well dispersed, conducive to the formation of smooth ink film, for improving the gloss of the print is also very beneficial.
2, the viscosity of the connecting material and the pigment content
According to the interface chemistry principle, capillary penetration speed is inversely related to liquid viscosity, i.e. the penetration speed decreases with the increase of viscosity. The structure of capillary network formed between ink pigment particles is an important aspect of determining the luster of printed materials. At the moment of imprinting, the ink is pressed into the paper's larger pores as a whole, and after imprinting, the connecting material begins to separate from the ink and penetrates into the paper's smaller pores. Therefore, the size of the capillary tube of the ink film determines the amount of separation of the connecting material. The capillary retains the connection material much more than the printing pressure that presses the connecting material into the paper pores.
3, drying time
the rapid drying of the ink film on the paper can reduce the amount of connecting material seeping into the paper pores, thereby improving the gloss and smoothness of the ink film. The high gloss of the ink film means that the surface is more mirror reflective, so that in most cases the human eye can see that the surface reflects much less white light than the glossy ink film, making the color more saturated. So high-gloss prints look more colorful and full. The printing ink layer of spot ink is mostly translucent or opaque, and the effect of the light transmission of the ink layer on spot color printing should also be taken into account according to the actual situation when selecting the ink formulation.More than
is for you to share the printing spot color ink color difference reasons, there are many factors that produce spot color ink printing color difference, but the main factors are: material performance, ink nature, printing conditions, printing surface finishing, these factors will affect the spot color printing process of color reproduction.
source: PANTONE Ink