During printing and storage, the hue, brightness, and saturation of the printed matter often change. Whether it is a single ink or two or more colors of ink, the inner and outer inks may become darker and lighter. . High-quality print standards are: a batch of printed products before and after the darkness of the ink should be consistent, colorful to meet the proofs, dark ink and dark ink color consistent with the proofs. There are many factors that affect the color change of printed materials. There are roughly the following aspects:
First, the ink is not resistant to light caused by discoloration and fading The ink in the sunlight, the color and light will change to varying degrees, the absolute light without changing the hue of the ink is not, in the strong sunlight, all ink Colors will produce varying degrees of change. This change can be divided into two types:
1 Fading: Under the effect of sunlight and ultraviolet rays, the ink has poor light resistance, lost its original bright color, and its color becomes light gray. Especially light color inks, four-color dot printing, yellow and red colors fade faster, and vice versa, while cyan and black fade slowly.
2 Discoloration: In contrast to ink fading, under the influence of sunlight, the color changes dark, and the color also changes people to call this change color.
With the development of offset printing, there is a growing need for four-color color overlay printing inks with good lightfastness:
1 requires a beautiful color ink, graphic network full, strong.
2 Maintain a constant color for a certain period of time.
Second, the impact of emulsification on the color of the imprint printed version of the printing plate can not be separated from the blank part of the printing plate with the wetting liquid, offset printing is the first ink after the water, the water will inevitably emulsified phenomenon. After the ink is emulsified, the color will be lightened, but the water can be restored after the evaporation of water, so the greater the moisture, the greater the emulsification, it will cause discoloration. In particular, the inks with completely different degrees of emulsification are mixed together, and the discoloration phenomenon is particularly prominent.
Therefore, offset printing should use a minimum amount of water in order to reduce and control the emulsification, to achieve a balance between ink and water, and to keep the color as stable as possible.
Third, the nature of the paper and the relationship between the print copy 1 paper surface smoothness Paper surface smoothness is closely related to the copy of the print, uneven paper often requires a lot of pressure in order to make ink and it has a good contact . For example, the ink viscosity, fluidity, and thickness of the ink layer are kept constant. Increasing the pressure often increases the footprint of the imprinting. At the same time, the low-lying areas of the paper are still in poor contact. For example, the effect of the imprinting on the coated paper and the newsprint printed on the same printing plate is quite different, and the different reproduction effects can be clearly compared.
From this, it is inferred that the prints printed on rough-surfaced papers are difficult to maintain the ideal reproduction effect. Therefore, the fine print products must be printed with high-grade coated paper to ensure a good copying effect.
However, paper with high smoothness causes a decrease in capillary suction force.
2 Absorption of paper Absorbability of paper is also related to the effect of copying. Usually when printing loose paper, if the ink has high fluidity and low viscosity, the paper will absorb more ink layer binder. If the pore diameter is larger than the pigment particle diameter, even the pigment will be inhaled. This reduces the saturation of the print. Need to properly increase the thickness of the ink layer. However, increasing the thickness of the ink layer will cause "spreading" to affect the copying effect at the moment of imprinting.
The absorptive paper can make most of the ink film appear on the surface of the paper, so that the ink film layer has better saturation. Different quality papers have obvious quality effects. The printed imprints on paper with loose structure and high absorbability are not ideal. It is difficult to print high-quality products with poor paper quality, so the printability of paper is improved. For the printing company, it is necessary to select suitable paper according to the requirements of product quality.
3 Influence of Paper Penetration The permeability of the paper will make the thickness of the ink layer thinner, and the pores of the paper surface will be large, and some of the pigments will also be penetrated into the paper at the same time, so the color will have a lightening effect. For this reason, paper with rough surface texture and loose paper, and paper with large ink flowability, should be noticed for discoloration.
First, the ink is not resistant to light caused by discoloration and fading The ink in the sunlight, the color and light will change to varying degrees, the absolute light without changing the hue of the ink is not, in the strong sunlight, all ink Colors will produce varying degrees of change. This change can be divided into two types:
1 Fading: Under the effect of sunlight and ultraviolet rays, the ink has poor light resistance, lost its original bright color, and its color becomes light gray. Especially light color inks, four-color dot printing, yellow and red colors fade faster, and vice versa, while cyan and black fade slowly.
2 Discoloration: In contrast to ink fading, under the influence of sunlight, the color changes dark, and the color also changes people to call this change color.
With the development of offset printing, there is a growing need for four-color color overlay printing inks with good lightfastness:
1 requires a beautiful color ink, graphic network full, strong.
2 Maintain a constant color for a certain period of time.
Second, the impact of emulsification on the color of the imprint printed version of the printing plate can not be separated from the blank part of the printing plate with the wetting liquid, offset printing is the first ink after the water, the water will inevitably emulsified phenomenon. After the ink is emulsified, the color will be lightened, but the water can be restored after the evaporation of water, so the greater the moisture, the greater the emulsification, it will cause discoloration. In particular, the inks with completely different degrees of emulsification are mixed together, and the discoloration phenomenon is particularly prominent.
Therefore, offset printing should use a minimum amount of water in order to reduce and control the emulsification, to achieve a balance between ink and water, and to keep the color as stable as possible.
Third, the nature of the paper and the relationship between the print copy 1 paper surface smoothness Paper surface smoothness is closely related to the copy of the print, uneven paper often requires a lot of pressure in order to make ink and it has a good contact . For example, the ink viscosity, fluidity, and thickness of the ink layer are kept constant. Increasing the pressure often increases the footprint of the imprinting. At the same time, the low-lying areas of the paper are still in poor contact. For example, the effect of the imprinting on the coated paper and the newsprint printed on the same printing plate is quite different, and the different reproduction effects can be clearly compared.
From this, it is inferred that the prints printed on rough-surfaced papers are difficult to maintain the ideal reproduction effect. Therefore, the fine print products must be printed with high-grade coated paper to ensure a good copying effect.
However, paper with high smoothness causes a decrease in capillary suction force.
2 Absorption of paper Absorbability of paper is also related to the effect of copying. Usually when printing loose paper, if the ink has high fluidity and low viscosity, the paper will absorb more ink layer binder. If the pore diameter is larger than the pigment particle diameter, even the pigment will be inhaled. This reduces the saturation of the print. Need to properly increase the thickness of the ink layer. However, increasing the thickness of the ink layer will cause "spreading" to affect the copying effect at the moment of imprinting.
The absorptive paper can make most of the ink film appear on the surface of the paper, so that the ink film layer has better saturation. Different quality papers have obvious quality effects. The printed imprints on paper with loose structure and high absorbability are not ideal. It is difficult to print high-quality products with poor paper quality, so the printability of paper is improved. For the printing company, it is necessary to select suitable paper according to the requirements of product quality.
3 Influence of Paper Penetration The permeability of the paper will make the thickness of the ink layer thinner, and the pores of the paper surface will be large, and some of the pigments will also be penetrated into the paper at the same time, so the color will have a lightening effect. For this reason, paper with rough surface texture and loose paper, and paper with large ink flowability, should be noticed for discoloration.
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