China's printing industry and ink industry belong to different departments, so the relationship is alienated. Ink printers and printers rarely explain the nature of the ink in detail. As a result, many printability problems cannot be well studied. Now briefly introduce the composition of ink, and then discuss the relationship between the various properties of ink and printing.
First, the composition of the ink
The pigments (colorants), fillers, binders, and adjuvants are mixed and ground to uniformly distribute the pigments, fillers, and adjuvants in the binder, forming a colloidal dispersion system with a uniform and delicate appearance. Or paste, this is the ink.
Due to the different printing processes, inks are required to have different properties. If the gravure ink is thin, the adhesiveness is also very small, otherwise it can not be filled into the plate. Can not be scraped clean by the scraper. The ink is mostly used for letterpress printing presses. The printing speed is up to 10,000 printing/hours. The paper used is good newsprint. Therefore, the ink is only slightly thicker than gravure ink. , And the penetration and drying are very good. Otherwise, it will not meet the requirements of high-speed printing and rapid drying. The letterpress rotary printing machine of the book is slower, and the used paper is more solid and less absorbent. Therefore, the ink in the printed book is thicker and stickier than the ink, and the permeation and drying properties are slightly slower. Some of them even have the property of a part of the oxidized aggregate film drying. The writing of the books and magazines can be printed more clearly and it is not easy to erase them after drying. Color letterpress printing is mostly used for printing logos, packaging, and other prints, and the printing speed is slower. The paper used is from relief paper, offset paper, coated paper, and glass powder-coated paper. The printed matter is required to have vivid colors and clear graphics, solid general letterpress inks, or color lead inks, and other inks (including copper and zinc inks). The inks are much thicker and more sticky than the inks. Otherwise, dot prints are not clear. Because the printing speed is slower and the paper absorbs poorly, the solid-oxidation-polymerized conjunctiva is dried. In addition, it must be colorful and have a certain degree of luster. As for printed copper plated paper, coated paper and other printed materials, offset printing inks with higher color density are generally used, and even bright light fixes the offset printing inks in order to obtain bright colors and excellent gloss. Offset printing uses the oil-water mutual exclusion principle to print, so the offset ink must have a certain water resistance and should not be heavily emulsified on the printer and bleed in the solution. Because the offset printing speed is now faster than embossing, and after rubber transfer, the viscosity of the ink must not be too high, so its thickness is less than that of colored lead ink and its viscosity is also small. All the papers used are offset papers and coated papers, so they are also dry for oxidative polymerization. Some require that the back surface is not stained, so it is necessary to fasten the ink. If you want good gloss, you need to fix the ink with bright light.
The nature of the ink is actually determined by its composition, such as the color, tinting strength, light resistance, acid resistance, alkali resistance, soap resistance, heat resistance, resistance to various solvents and water resistance of the ink, and is mainly determined by the pigment. The properties of the ink such as drying property, fast fixing property, glossiness, friction resistance, flex resistance, etc. mainly depend on the binder. The viscosity, viscosity, fluidity and other properties of the ink are largely related to the binder but are also related to the nature and amount of the pigment and filler used. Therefore, the ink worker should understand the characteristics of the printing process and the substrate before designing to design and manufacture the ink that meets the requirements. The printers should also have a certain degree of understanding of the nature of the ink in order to use the ink properly.
Second, the relationship between various properties of ink and printing
1. Color tinting strength and transparency
The color of the ink, especially the color of the ink of the three primary colors, is often measured in terms of density, color difference, grayscale, and actual color efficiency in printing, and is generally measured and calculated by a color density meter in a solid or color part of a printed matter or proof. Got it. However, to measure the quality of ink, a certain amount of ink must be taken in accordance with the international standard method, and printed on the specified coated paper with a certain pressure and printing area into color blocks using an IGT fitness tester, and then a color densitometer is used. Make measurements and calculations. Otherwise, these valid data are not standard and comparative.
For trichromatic inks, the color density should be within a certain range, usually yellow 1.00 ± 0.05, magenta 1.45 ± 0.05, blue 1.55 ± 0.05. However, due to the different requirements of the original color tone, it may be slightly different. When the density of the three primary colors is within the above range, the gray balance can generally be achieved, and the color difference, grayscale, and actual color efficiency thus calculated are also of practical significance. The standard color ink that meets the ideals of the three primary colors in the world does not exist. However, the smaller the color difference should be, the better the gray balance and the reproduction of the original color are. When the grayscale is small, that is, the brightness is high, when the color of the original is very vivid, the three primary colors having a large grayscale cannot reproduce the bright original color. As for the drawing or some of the original tones that are relatively dark, the gray scale of the three primary colors is not necessarily required at the time of printing, and sometimes the grayscale or the underprint or spot color is increased. The actual color efficiency refers to the purity of the main color tone, and the higher the color efficiency, the larger the range of the solid color matching with the other two three-primary inks. In general, inks with small color casts and small gray scales have greater actual color efficiencies. To measure the color quality of the three primary color inks, it should generally be small in color, small in gray scale, and the actual color efficiency is better.