Printing, as a kind of image and character reproduction technology, its social significance lies in that it records and spreads the corresponding history and culture while reproducing words and images. Therefore, the country where printing technology appears must be the ancient country of human civilization. As a practical technology for reproduction, printing was invented by the Chinese people, and the well-known seal is its early prototype. What factors affect the color difference of spot color printing? Let's talk about it today.
1. The influence of paper on color
Glossiness and smoothness: the glossiness of printed matter depends on the glossiness and smoothness of paper. The surface of printing paper belongs to semi gloss surface, especially coated paper.
On color printed matter, when the light rays irradiate the paper surface at an incidence angle of 45 degrees, about 4% of the light will be reflected, which is the reflected light from the first layer surface. And the rest of the incident light through the ink layer, after the selective absorption of the ink, and then through the ink layer reflection, into the human eye, perceived by the human eye, this is the color we observed. If the glossiness and smoothness of the paper is high, the light reflected from the surface of the first layer is specular reflection, which is not easy to enter the human eye. At this time, the color observed is basically the color reflected through the ink layer.
2. The effect of diluent on color
Diluent is a kind of colorless transparent substance in the form of oil paste, which mainly plays the role of diluting color in spot color printing. The effect of diluent on hue is different, especially blue.
In the process of preparing spot color ink, the shearing force and pressure produced by homogenizer and spreader are smaller than those on the printing press.
There is no need to add diluting agent in album printing, but only adding diluting agent in matching ink to make color card can produce uniform spot color ink display card. In the case of the same color density, there is a color difference between the color card and the printed matter. This is because the addition of diluent changes the distribution of pigment in the ink, and changes the absorption, refraction and reflection of light in the ink, resulting in the color difference, which is caused by the difference of the system.
The above factors affect spot color printing color difference, in addition, just printed, ink is still in wet state, and dry state when there is a density difference. The phenomenon that wet color density is greater than dry color density is called dry density phenomenon. This is because the newly printed ink layer has a certain leveling, so the surface reflection is mainly specular reflection, which looks bright and glossy.
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