Discussion on the ink water balance of the hottest

Discussion on the balance of water and ink in offset printing

overprint of four inks

in color printing, the adhesion of the latter color ink on the film of the previous smaller color ink is called ink overprint, also known as ink load transfer. The color on color printing is generally presented through the dot superposition or juxtaposition of yellow, magenta, cyan, black and other colors with different area sizes. Therefore, the color reproduction effect of printed matter is not only related to the optical properties of ink. It is also related to the sequence of ink overprint and the amount of ink overprint

1. Overprint rate and its measurement

overprint rate, also known as the ink force of ink, is a physical quantity to measure the degree of ink overprint. The higher the overprint rate, the better the overprint effect. The overprint rate can be calculated by measuring the density of each color of ink and the density value of ink overprint. When studying the phenomenon of ink overprint, the overprint of the second color ink on the first color ink film is often the focus of discussion

the color of color printed matter is generally formed by overprinting two or three colors of yellow (y), magenta (m) and cyan (c) inks. When measuring the density of a monochrome ink, a color filter is installed in the densitometer by using the principle of subtraction. The color of the filter is usually complementary to the color of the measured ink. For example, blue filter is used to measure the density of yellow ink, green filter is used to measure the density of magenta ink, and red filter is used to measure the density of cyan ink

2. Ink overprint of monochrome offset press

when the ink printed first is fixed on the substrate and is close to drying, the latter ink is printed and attached to it, which is called dry printing. Ink overprint of monochrome Offset Press is carried out in a wet press dry manner, which belongs to dry printing

after the ink is attached to the substrate, the original properties of the surface are changed due to being covered by the ink, and the surface properties of the ink film become the main factor affecting ink overprint. For the ink overprint of monochrome Offset Press, if the viscosity of the first color ink is greater than that of the second color ink, the second color ink can be well attached to the first color ink film. Good overprint effect. On the contrary, if the viscosity of the second color ink is greater than that of the first color ink, the second color ink cannot adhere well to the first color ink film. And it will take away the first color ink, so overprint cannot be achieved. It can be seen that the viscosity of ink is of great significance to the overprint of ink

in dry printing, if the printing interval of the two-color oil award is improperly controlled by more than 600 industry experts, scholars, well-known entrepreneurs and investment institutions gathered at the new material capital technology summit held in Nanjing, and the ink printed first has been dried before printing one color ink, then the dry ink film has lost its viscosity, and the ink of the ink layer is difficult to adhere to it, resulting in the so-called "ink crystallization". In order to prevent the occurrence of ink crystallization, the first color ink should not be added with drying oil. Sometimes, in order to delay the drying of the ink, additives that inhibit the drying of the ink need to be added to the ink

to sum up, in actual production, in order to make the ink overprint of monochrome Offset Press proceed smoothly, the first printing ink layer must have two characteristics:

(1) maintain a certain viscosity, and the adhesion of the post printing ink is greater than the cohesion of the post printing ink

(2) maintain a certain wettability, which can be wetted by post printing ink and attached to each other

3. Multicolor offset printing machine ink overprint

when printing with a multicolor offset printing machine, the printing interval between each color is extremely short, and the ink printed in front needs to overprint new ink in a fraction of a second. The ink printed first has no time to dry, and the ink of the second color needs to overprint upward, and the ink films adhere to each other in a wet state, so it is called wet printing. Ink overprint is carried out by wet pressing

in dry printing, the ink of post printing is transferred to the ink of pre printing that has been fixed and gradually dried. The ink of post printing is separated in the middle of the ink film, that is, half of it is transferred to the ink film of the previous color, and the other half is still left on the surface of the blanket cylinder. Wet overprint is not the case. The ink of the latter color is generally split in the middle of the ink film overlapped by the two-color ink, a small part is transferred to the wet ink film of the former color, and most of it is still left on the surface of the blanket cylinder. Obviously, the ink overprint line of wet printing is drawn on the prepared sample by printing or hand (the addition of the mark line has no effect on the sample). The printing rate is lower than that of dry printing, and the ink transfer is far better than that of dry printing. In the overprint process, the phenomenon is more complex, and there are many factors affecting the ink overprint rate. Specifically, The main factors that affect the ink overprint of multi-color offset press are the viscosity, density and brightness of the ink. The following is a detailed discussion of the inks used in four-color offset printing machines, which are widely used in many industries

the viscosity of ink has a great influence on the overprint effect of wet printing. If the viscosity of the ink is large, the viscosity is also large. Therefore, the ink layer shows greater cohesion. If the viscosity of the first printing ink is lower than that of the second printing ink, the second printing ink will peel off the first printing ink according to its own cohesion, resulting in reverse overprint. In this way, wet printing cannot be carried out. Therefore, the ink used in the four-color offset press should gradually reduce the viscosity of the ink according to the order of the rollers of each unit. For yellow, magenta, cyan and black, the viscosity relationship is: Black> cyan> magenta> yellow

the density of the ink has a certain relationship with the thickness of the ink film. Generally, with the increase of the density value, the thickness of the ink film also gradually decreases. For wet printing, the ink with large ink film thickness is placed in the post color sequence printing, and the overprint effect is good