In color printing, how to reasonably arrange the color overprinting sequence is an important subject studied by process technicians. An important role of printing is to copy manuscripts artistically, which requires the printing workers to have a certain degree of artistic appreciation and master the ability to express color changes. Improper color sequence arrangement may cause the color deviation, color mixing and reverse overprinting of the printed matter; scientific color sequence arrangement will make the color of the printed matter more close to the original, and even strengthen a certain color atmosphere to make the level clear, the dots clear, and the overprint accurate. The colors are real, natural and harmonious.
There are three reasons why the color sequence needs to be arranged: the effect of ink overprinting and the shortcomings of the ink color itself, the quality of the paper, and the human's ability to recognize colors. The most fundamental reason is the incomplete transparency of the printing ink itself, that is, the hiding power of the ink itself. The post-printing ink has a certain covering effect on the first-printed ink layer, so that the color displayed by the printed matter always focuses on the latter color, or on the mixed color of the back color and the front color. The starting point for choosing the color sequence is to flexibly arrange the color sequence according to the specific conditions of the original and the current process conditions, taking care of the main aspects (such as tone reproduction, color reproduction, graphic clarity, printing uniformity and printing repetition rate, etc.) .
1. Due to the good transparency of yellow ink, the last color is good for enough white light to enter the upper and lower ink layers to obtain bright and bright colors.
2. Yellow ink has faster drying performance and larger printing area. Putting yellow ink to the last color can not only prevent the vitrification caused by the yellow ink drying too fast, but also use its large printing area and can quickly oxidize the conjunctiva. It covers the surface of other ink layers to make The printed matter has a certain glossiness.
3. Yellow is ranked in the last color, which is convenient for controlling the amount of yellow ink, which can be adjusted at any time.
4. Yellow ink is expensive, and arranging it in the last color can save the amount of yellow ink and reduce costs.
Color printing is a combination of technology and art. When we arrange the printing color sequence, we should properly consider it from an artistic perspective, which can make the printed matter more artistically appealing and meet the needs of readers.
There is a period of time between the first color and the second color printing of the offset monochrome machine. During this time, the binder in the oil foam gradually penetrates into the paper, and the ink surface layer gradually oxidizes the conjunctiva. When printing the second color, the ink is printed on the conjunctival ink layer, which is called wet pressing and drying. When the multi-color machine is printing, the inks of the various color plates are overprinted in less than a few seconds, and the interval between the colors is extremely short. It is impossible for the post-printing color to be printed on the ink layer of the oxidized conjunctiva. Wet wet.
In the process of "wet pressing wet" in multi-color machine, white paper is the most acceptable for the first set of inks. Black is the most obvious, followed by cyan and magenta, known as the three strong colors. Human vision reflects the most dull yellow, so it is placed last. The ink of the first color group should be thicker. In the future, the density of each color ink will decrease from machine to machine. The black is placed in the first color for easy overprinting. This is why multicolor machines generally use black, cyan, magenta, and yellow as the main color sequence. (Generally, the viscosity relationship of 4-color ink: T black ≥ T blue = T red> T yellow. T represents the ink viscosity value)
Overprinting of multi-color machine inks is carried out under the condition of "wet to wet". In terms of the relationship between ink viscosity and overprinting, the viscosity value of the latter color ink cannot be more than that of the previous color ink, otherwise it will be just printed The ink of the previous color sticks down and is transferred to the printing plate by the rubber roller, which not only causes "color mixing" of the ink, but also causes the ink to not be printed, and the ink color of the printed part is very light and unspiritual. Found that this situation can be remedied by adjusting the viscosity relationship of the four-color ink or changing the color sequence of the ink. (Adjust the viscosity of the ink by adding a viscosity-reducing agent such as mineral oil or adding some viscosity-increasing agents such as No. 0 ink.)
The method of arranging color sequence should follow the principle of highlighting the main color of the picture to prevent the main color from being covered to determine the color sequence. Generally speaking, the arrangement of the color sequence is based on the picture area and the dominant colors.
Therefore, after accepting the product printing order, we must analyze the focus of a certain color of the proofing screen, change the color sequence appropriately to meet the original, to fully express the original, and better reproduce its tone and color.
The portrait-oriented calendar (warm tone) of general portrait calendars is mainly black, blue, red, and yellow. Generally, the large-scale landscape-dominated pictures (cold tone) are mainly black, red, blue and yellow. Large-area 4-color spot colors should be dominated by dominant colors, including large-area black, and the possibility of the final printing color sequence is not ruled out. For a part of the main color plate with different shades, it is possible to adopt the method of two-layer fold plate printing or multi-exposure PS plate printing method when the difference between printing and proofing is relatively difficult. In short, the main color should be restored. Be courageous and scientific. It is necessary to fully understand that plate making proofing is round flattening, and printing is round flattening. The fact that the dot expansion value printing is greater than proofing.
In summary, the arrangement of the color sequence of the multi-color machine is closely related to the quality of the printing quality. How to arrange the color sequence scientifically and reasonably is still a subject in the process technology research.
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