The so-called series of printed matter refers to the same kind of product internal and external packaging specifications are different or complete sets of products using printing materials are not the same, but the graphic layout structure or color is the same or similar. Due to differences in material characteristics or printing layout specifications, the adaptability of the printing process is also very different. For example, the outer packaging of corrugated boxes, color box surface layer printing materials are whiteboard paper, cow truck or box board paper, etc., carton packaging materials are whiteboard paper, cow truck, white card, glass card, copper plate card, PE coated paper, etc., flexible packaging plastic film, cellophane, tissue paper, glossy paper, copy paper, offset paper, vacuum aluminized paper, laser paper, etc. Corrugated cardboard thickness, surface flatness characteristics, as well as PE coated paper, plastic film, cellophane, tissue paper, vacuum aluminized paper printing process, from the characteristics of the material and product packaging safety, health and quality considerations, suitable for flexographic printing with water-based ink, can better ensure the quality of products. For the pre-printing process of color box face paper, color box printing whiteboard paper, cattle pickup; Vacuum aluminized paper, laser paper and other materials, a large number of gravure or flexographic process can be used, which can make the printing quality and production costs are better balanced. For the number of about 100,000 prints of white board paper, cow pickup, white card, glass card, copper plate card products, as well as glossy paper, copy paper, offset paper, vacuum aluminized paper, laser paper can be used offset printing process is more suitable. Among them, the quantity of glossy paper and copy paper is low, which is not suitable for high-speed automatic paper feed, and the low-speed 01 offset press can be used for printing in order to better ensure the overprinting quality of the product.
Now many printed materials are designed and produced by customers or advertising companies, because they do not fully understand the printing process, often resulting in the production of manuscripts, can not adapt to the requirements of the printing process. Taking the series of prints with the same mesh structure as an example, due to the different printing materials used, there will be a large difference in printing color. It is the same offset printing process printed paper plate (white board paper material) and paper cup (single-sided PE coated paper) these two products, due to the good surface smoothness of the white board paper material, the ink absorption is less, and the surface of the single-sided PE coated paper is relatively rough, the ink absorption is larger, with these two materials printing the same structure of the plate, the color will be larger. Generally, the printing color of single-sided PE coated paper is obviously lighter than that of whiteboard paper, and the color difference caused by the difference in the printing performance of materials can not be overcome by the adjustment of ink volume and pressure. Generally, it is necessary to adjust the main color dot area of the printed single-sided PE coated paper appropriately through the plate design to make the printing color close. Therefore, when receiving a series of prints with the same layout structure and different substrate materials, we must first carefully analyze the layout structure and substrate material characteristics of the original manuscript, and then determine a reasonable plate-making design scheme, that is, according to the material gloss and printing ink absorption performance, reasonably adjust the dot area of a certain product layout. To ensure that the colors printed by different materials are similar.
Multi-plate structure of printed matter, a sheet usually spits out several different varieties of pages, if not taking into account the difference in printing color of different varieties, and the color difference of different varieties in the same vertical, then, once one of the vertical layout of one of the printing color is shallow or deep, it is difficult to locally adjust the ink output through the ink hopper. To achieve the corresponding vertical layout of a variety of layout ink control, ink adjustment often appear to ignore the situation, can not take into account the printing color of the overall vertical layout. Therefore, for multi-plate paper plates, paper cups, trademarks and other products, each longitudinal position is best to fight the same variety or fight the color of the same variety, in order to facilitate the effective adjustment of the amount of ink coating. Do not spell several products with large color contrast in the same longitudinal orientation, because this is the most easy to produce color difference, even if the printing color can be controlled through the adjustment of the ink coating amount, but it is easy to produce chain printing quality problems, such as paper wool, paste plate, dirty plate and other bad conditions.
The main characteristics of the series of prints are generally the same graphics, but the size difference, and the substrate material characteristics are completely different. If the structure of the film mesh has been made is the same, it can be considered in the printing process technology, according to the gloss and ink absorption of the substrate layout, the exposure time of the main color plate of a certain product can be properly controlled to achieve the adjustment of the dot size. For example, the substrate of a series of products has two kinds of glass card and offset paper. The offset paper layout is relatively rough and the ink absorption is large, and the exposure time of the main color plate can be appropriately shortened to achieve the purpose of increasing the dot area, so that the ink color of the printed offset paper print layout can be close to the ink color of the glass card print layout, and it is not easy to paste the plate. However, it must be pointed out that there is a limit to the size of the network adjusted by the printing link, and it can only be a small amount of adjustment. If the exposure time is too short, the layout darkening and white spots are prone to paste death, and the layout hierarchy is poor. Therefore, the exposure time adjustment should master a suitable degree, such as the original normal exposure should be 140S. The shortened exposure time should be controlled between 110-120S.
Printing pressure is the printing transfer medium, the size of the printing pressure directly reflects the depth of the printing ink, especially the relief printing process, the size of the pressure on the printing ink depth of the influence is greater, when the printing pressure increases, the printing color will deepen the phenomenon, on the contrary, reduce the printing pressure, the printing color will appear shallow. For series of prints with different substrates, when the surface of the printing material is rough, the printing pressure can be appropriately increased to deepen the printing color, so that the color of the printed matter of different materials is close. However, the printing pressure adjustment should also control a suitable degree, too much pressure adjustment is easy to speed up plate wear, and easy to produce paste plate, printing plate stretching deformation and other chain quality problems, which is the problem to pay attention to when printing process operation. General relief printing pressure increase adjustment, do not exceed 30 wires, otherwise, printing deformation will directly affect the overprint quality of the product.
6. Control the printing color by adjusting the ink hue
Four-color prints are printed with standard four-color inks in accordance with the conventional process, but when there is an obvious difference in the color of a certain color, the color requirements cannot be reached through the adjustment of the ink amount, and the appropriate adjustment of the ink hue of a certain color can be considered to make the ink color of the printed product meet the requirements of the original color. For example, when we print a four-color trademark, after overprinting, the light orange page color has a clear red phase, the yellow color has a significant lack of feeling, and the color of the original color is significantly different from the original color, and the reduction of the amount of M ink and the increase of Y color adjustment are limited, and can not be adjusted to the original ink color consistent requirements, in this case, It seems that only by appropriately reducing the dot area of the M version and increasing the dot area of the Y version can the effect of effective color adjustment be achieved, but this is very time-consuming and will increase the economic cost, which is not desirable. Through careful analysis and research of the printing sample, the author found that in addition to the overprinting relationship between the Y-color part of the flat screen and the M-color plate of the flat screen, the M-color plate did not have a single monochromatic color printing result. Therefore, the author germinated the ink of "four-color red" and added some ink of "four-color yellow" to form a special spot color red ink for overprinting. After this treatment, the printing color of the light orange overprint layout immediately achieves the effect similar to the color of the sample, so that the printing color of the product finally meets the requirements of customers. In the same way, in the printing of a series of prints of different materials, often because of the difference in material and the hue of a certain main color is obviously shallow, in this regard, you can consider using the appropriate adjustment of the ink hue of a color to achieve the correction of the printing ink color, which is also the easiest and fastest way.
Due to the differences in the printing process, the thickness of the printing ink layer is also significantly different, and the series of printed matter with large material differences, according to the print layout color and the adaptability of the material to the printing process, the selection of the appropriate process for printing is also an effective way to control the printing color. The thickness of the ink layer of various printing processes is about: offset printing 3μm; Letterpress 8μm; Flexo printing 10μm; Gravure 12μm; Screen printing 30μm, according to the basic performance of the substrate, surface gloss, ink absorption, and the structure of the layout pattern, as appropriate, consider selecting the printing process suitable for the ink absorption characteristics of the substrate material. The offset printing process is limited by the ink balance, and the ink coating amount adjustment is small, which is more suitable for printing substrates with relatively good gloss, such as coated paper, glass card, white card, offset paper, white board paper, cattle pickup and so on. The tissue paper soft texture, ink absorption, poor tensile strength, easy to stretch deformation, it is more suitable for the use of low viscosity liquid water-based ink printing, in order to obtain the ideal printing color, and water-based ink has a huge advantage on environmental protection, so the use of flexographic process printing napkins is the best choice. The selection of printing process should not only consider the impact of the printing characteristics of the substrate on the printing color, but also consider the printing production cost, such as the high cost of gravure and flexographic process, which is more suitable for printing long-term products.
Due to the limitations of the production scale of the printing plant, such as some factories only have a single flexo printing process, and some factories are single offset printing process or gravure printing process, many series of prints, customers often have to be sent to several factories for printing. Due to the consideration of production costs, some customers do not use the proofing process, often first printed a certain material of the printing sample, as another material of the color reference sample, such as the use of pre-printed flexible printing napkins as offset white board paper plate or coated paper cup printing color, to the printing color control brings a certain difficulty, Offset printing is often difficult to keep up with the ink color of flexo printing. Because the flexographic ink layer is thick, and the offset ink layer can be adjusted relatively less than the flexographic process. Therefore, with different processes to print series of prints, it is appropriate to arrange the use of offset printing process of the product first printing, the use of flexo printing, gravure or screen printing after printing, so as to facilitate the control of the color of the series of prints. If the same offset printing process is used to print products of different materials, it should be considered that the material with good gloss should be printed first, and the material with poor gloss should be arranged for post-printing. Because of the good gloss material, the size control of the printing ink amount is relatively accurate, which can reduce the chance of large deviations in the printing color. It is worth mentioning that the use of printed manuscript as the printing color of the same, we should pay attention to the impact of the light transmission performance of the sample material on the identification of color vision, such as thin film printed matter, napkin printed matter transparency is high, should be placed on the standard sample table with the printing sample for identification.
