Analysis of the most popular factors affecting the

2022-08-16
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Analysis of factors affecting the color change of printed matter

during printing and storage, the hue, lightness and saturation of printed matter will change. Whether monochrome ink or two or more color inks, the color may become darker or lighter under internal and external effects. The standard of high-quality printed matter is: the ink color of a batch of products is the same in depth and lightness, and the color is bright, which conforms to the ink hue and lightness of the sample. There are many factors that affect the color change of printed matter, including the following aspects

discoloration and discoloration of ink that is not resistant to light. Key points for operation of hydraulic universal testing machine

under the irradiation of sunlight, the color and brightness of ink will change to varying degrees, which can be divided into two types

1. Fading: under the action of ultraviolet light, the ink has poor light resistance, loses its original bright color, and turns pale into gray white. Especially for light color ink and four-color overprint, yellow and red fade faster, while cyan and ink fade slower

2. discoloration: in contrast to the fading of black printing ink, the color darkens under the action of sunlight

influence of emulsification on imprinting color

offset printing plates cannot be separated from wetting liquid. HPM hopes that in the near future, more companies will use tepex materials for inking in more applications, which will inevitably lead to emulsification. The color of the ink will fade after emulsification, but it will return to its original color after water evaporation. The greater the water content, the greater the emulsification amount. In particular, the color change phenomenon is particularly prominent when the color inks with completely different emulsification degrees are mixed together

relationship between paper properties and imprinting replication

1. Surface smoothness of paper. There is a close relationship between the smoothness of paper surface and imprinting reproduction, and the uneven paper surface often needs greater pressure. For example, the ink viscosity, fluidity and ink layer thickness are maintained at a certain amount, and increasing the pressure increases the spreading area of the imprint. At the same time, the low concave parts of the paper are still in poor contact, for example, the imprinting effect of coated paper and paper printed on the same printing plate is quite different

2. Paper absorption. The absorbency of paper is also directly related to the reproduction effect. If printing paper with loose texture has high ink fluidity and low viscosity, the paper will absorb more ink layer connecting materials. If the pores are larger than the diameter of complex particles involved in the process of making refil regenerated 3D printing wire, even the pigment will be sucked in, reducing the saturation of the imprint, and it is necessary to appropriately increase the thickness of the ink layer. However, increasing the thickness of the ink layer will cause "spreading" and affect the effect of imprinting replication. For paper with small absorption, most of the ink film appears on the paper surface, so that the imprinted ink layer has better saturation

the influence of paper permeability on color

paper permeability is large, which reduces the thickness of the ink layer, increases the pores on the paper surface, and also makes some pigment particles penetrate into the paper. Therefore, when using paper with rough surface, loose texture and high ink fluidity, pay attention to color change

influence of heat resistance of pigments

in the drying process of ink, bright and fast drying adhesive printing ink is mainly oxidized conjunctival drying. There is a fixed stage before the offset printing ink is dried. Too fast drying will release a lot of heat. If the heat is dissipated slowly, the heat-resistant pigment will change color. For example, the golden ink darkens and loses its original luster

when printing, the printing sheets are stacked in stacks on the paper receiving table. Due to excessive stacking, the printing ink in the middle part is oxidized, polymerized and exothermic reaction, so the heat is not easy to be dissipated. If the temperature is too high, the color changes more in the middle part

the influence of dry oil on the discoloration of imprints

light color inks belong to cold tones. Intermediate inks such as light yellow, emerald green and lake blue should not be used, because red dry oil itself has a deep purplish red, which will affect the color of light color inks

the white drying oil looks white, but it turns light brown after oxidizing the conjunctiva. If the amount of white drying oil is large, the imprint may be yellowish brown, while the color of dark color inks such as blue, black and purple will not be greatly affected by the red drying oil

influence of ink alkali intolerance on imprinting color

pH value of printed paper =7, neutral paper is the best, ink made of inorganic pigments has poor acid and alkali resistance, organic pigments have good acid and alkali resistance, especially medium blue and dark blue inks will fade when exposed to alkali. The color of medium yellow will turn red when encountering alkali, and the anodized aluminum foil and printing gold will turn antique yellow when encountering alkali, without gloss. Zhang Pian is weak and more alkaline. In the later stage of printing, when binding and production encounter alkaline adhesives, if the packaging and decoration printing products are packaging alkaline substances such as soap, soap, washing powder and so on, we should consider the alkali resistance and saponification resistance of the ink

discoloration factors in the storage and use of printed materials

most printed products will inevitably appear yellow after long-term storage, for the following reasons

1. the fibers in the paper contain more lignin and change color. For example, paper printed newspapers are most likely to turn yellow and brittle

2. The color printing products of offset four-color dot overprint, most of which are exposed to sunlight for a long time, wind and rain, outdoor high temperature erosion, etc., change color or fade because the pigment is not resistant to light and heat

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