1. Discoloration of ink drying process In the printing process, the ink color of the newly printed ink is compared with the ink color of the dried ink. The ink color of the newly printed ink is darker. After a period of time, the ink color will become lighter after the blot is dried; this is not that the ink is not lightfast The problem of fading and discoloration is mainly due to the discoloration caused by the penetration and oxidation of the conjunctiva during the drying process. Relief ink is mainly permeated to dryness, the product just printed from the printing machine table, the ink layer is relatively thick, at this time, it takes some time to penetrate and oxidize the conjunctival dry blank. Then, a large part of the connecting material in the oil storm will penetrate into the inside of the paper fibers, and the ink layer after the oxidized conjunctiva becomes thinner and the color will become lighter, which is an inevitable phenomenon that is often seen. When printing, the ink color should be controlled to be slightly darker than the original printed sample ink color. When the ink is dry, it will meet the requirements of the sample ink color. 2. The ink itself fades without light resistance It is inevitable that the ink fades and changes color when exposed to light. All inks will fade and change color to varying degrees after exposure to light. The light-colored ink fades after long exposure to light, and the discoloration is very serious. Yellow, crystal red, and green fade fast, and blue, blue, and black fade slowly. In actual work, when adjusting ink, you should try to choose inks with good light resistance. When adjusting light and light colors, you should pay attention to the light resistance of the ink after diluting. When mixing inks, you should also consider the light resistance between several colors of ink— Consistency. Since outdoor advertising posters easily fade when exposed to sunlight, the lightfastness of the ink must be considered. The same blue ink, phthalocyanine blue is lightfast than light lake blue and peacock blue, and it is not easy to change color. Gray can add black ink and phthalocyanine ink to white ink; emerald green can use monochromatic phthalocyanine green; if it is not yellow enough, light resin yellow ink can be added. If you add a little more white ink, the color will be more vivid. If you use peacock blue with chrome yellow ink, it will easily fade, change color and yellow. 3. The acidity and alkalinity of paper fade the ink. Effect of discoloration In general, paper is weakly alkaline. The ideal paper PH value is 7, which is neutral. Due to the need to add caustic soda (NaOH), sulfide, chlorine and other chemicals during the papermaking process, improper handling in the pulping and papermaking process may cause paper It is acidic or alkaline. There are certain residual chlorine and organic acids in the pulp. If the paper is not properly processed, the paper produced will be acidic; if alkaline fillers and colorants are used in the papermaking process, there will be Residual alkali solution, without the necessary treatment, the paper made in this way is alkaline. ①The acidity and alkalinity of paper have a great influence on the printing process and the color durability of the printed matter. The acidity and alkalinity of the paper have a direct effect on the drying of the oxidized conjunctiva of the blot. The drying of the paper with a large acidity is particularly slow. This is because the acidic substance can inhibit the drying of the oxidized conjunctiva of the blot. ② The acidity and alkalinity of the paper can also cause ink fading and discoloration. The pH value of the raw material paper is acidic when it is less than 7, and it is alkaline when it is greater than 7. Paper with strong acidity and due to the weak acidity of the water bucket solution will affect the ink and cause it to change color, such as malachite blue turns green after being acidic. . ③ The oil halo is more resistant to alkalis. Basically, all inks will fade or change color when they meet alkali. The chrome yellow ink turns red when it meets alkali, and the medium blue discolors when it meets alkali. Especially gold ink, silver ink and anodized aluminum foil bronzing will lose their original luster when they encounter alkaline substances. The golden color becomes pale yellow, the silver becomes black and dull, and the adhesion declines, which often results in scrapped prints. The alkalinity of the paper comes from the papermaking process itself, and some are caused by the binders containing alkaline substances used in the subsequent bookbinding production. If bubble base and other alkaline adhesives are used, the alkaline substance will penetrate into the paper fibers and react with the ink pigment particles on the surface of the paper to make it fade and change color. When selecting raw materials and bonding agents, first analyze the binder, the physical and chemical properties of the paper, and the effect of acid and alkali on the ink, paper, anodized aluminum foil, gold powder, silver powder and film. 4. Discoloration and discoloration caused by temperature Some packaging and decoration trademarks are posted on rice cookers. On high pressure cookers, electronic ignition stoves, kitchen utensils, the ink quickly fades and changes color at high temperatures. The heat resistance of the ink is around 120 degrees Celsius. Offset presses and other printing machinery are not prepared to run at high speed during operation. The ink and the ink roller, the ink and the plate surface friction heat, and the ink will also generate heat at this time. Especially when red and white dry oils are added to the ink, it will generate heat during the ink drying process, requiring the ink to have better heat resistance and gold printing. The products printed with silver should be careful not to accumulate too much printed goods on the delivery table. Otherwise, the printed matter will fade or change color due to heat. Solution: Use cardboard to layer the paper when collecting paper, and stack it thinner. Reduce fever, 5. Fading and discoloration caused by improper color sequence of printing The common color sequence of Shan Yudian's four-color version of monochromatic machine is: Y, M, C, BK, and the four-color machine is the inverted color sequence: BK, c, M, Y. What is printed afterwards will affect the fading and discoloration of the printing ink, especially the advertising posters. Propaganda pictures, New Year pictures, couplets, and small commercial advertisements. In actual production, these products are outdoor advertisements, so the light resistance and heat resistance of the printed matter will be considered when printing. Because these products are directly exposed to the sun's ultraviolet rays when they are posted outdoors, the wind and rain will make the bright colors on the printed matter easily fade and change color. Only long-term exposure to outdoor prints c, BK two dark colors of ink still partly remain, Y, M two colors have been removed, which shows that c, BK two inks have better light and heat resistance. Therefore, advertising pictures, New Year pictures. Propaganda posters, couplets, and other printed materials posted outdoors, in order to reduce the sun and ultraviolet light fade after fading. It is best to print Y and M colors first, and C and Bk inks to be printed at the end, which can reduce the problem of fading of printed products. When arranging the printing color sequence, the light color and the ink that easily fades and changes color are printed first. After dark ink printing, it can prevent fading and discoloration 6. Fading and discoloration caused by improper amount of dry oil The amount of red dry oil and white dry oil added to the ink does not exceed 5% of the amount of ink, about 3%. The dry oil has a strong catalytic effect in the ink layer, and it generates heat. , It will make the ink fade and change color. Attention should be paid when using desiccant: ①Separated from the air. Use now to avoid conjunctiva; (2) The content of the desiccant in the ink is 3%, do not overdose, otherwise it will be easy to appear crystallization and fading, discoloration; ③ The second color is more dots than the first color; ④The weather is cold and the temperature is low in winter. It should be put more-points; in summer it should be less. The red dry oil itself has a deep purple color, which will have a slight effect on the color of the ink when used in the preparation of light-colored inks. The red dry oil is used for the preparation of darker colors; The conjunctiva is light brown after drying. When blending light color ink, if too much white dry oil is added, it will appear light brown. Nylon Raincoat, Ladies Nylon Raincoats, Mens Nylon Raincoat, Womens Nylon Raincoat
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The color rendering mechanism of printed matter is carried out by subtractive color method. Sunlight, fluorescent lamps, incandescent lamps and other light particles are irradiated by the light source light on the fine particles of ink pigments. The colored light reflected by the selective absorption of light by the pigments can show beautiful colors. The deeper the light penetrates the ink film, The reflected light becomes more saturated, so the thicker the ink layer, the darker the color; the transparency of the ink is good, the color is brighter.
Books, periodicals, newspapers, advertising posters, new year pictures and other printed products, under the illumination of sunlight, fluorescent lamps, incandescent lamps and other light sources, can be selectively absorbed and reflected by ink pigments to display colorful and magenta colors. There are many factors that cause discoloration and discoloration of the printed matter. The light resistance of the ink, the acidity and alkalinity of the paper, the temperature, and the arrangement of the printing color sequence are all causes of the discoloration and discoloration of the printed matter.