At present, color printing usually uses yellow, magenta, cyan, and black four-color editions, and overprints in a certain order to start work. In theory, four-color printing can have twenty-four different printing color sequences. No matter what printing color sequence is used for the yellow, magenta, cyan, and black color plates, you should obtain satisfactory results. But in fact, the printing color sequence is different, and the color rendering effect of the printed matter is also different. Reasonable printing color sequence will make the color of the picture closer to the original, and even strengthen the atmosphere of a certain color, adjust the level of the picture, make it clear, clear or soft. In addition, it can also play a role in protecting the paper surface, increasing product gloss, and facilitating overprinting. Therefore, in color printing, especially packaging printing, more than four colors or spot colors and full version, we should pay more attention to the arrangement of printing color sequence.
In flexographic printing, the printing plates of various colors are often used in the field, and the transparency of the water-based ink used is generally not very good. Therefore, when arranging the overprinting sequence of each color printing plate, we must consider whether the color can meet the original requirements after stacking, and achieve a good overprinting effect. It directly relates to the quality of printed products. The printing color sequence is mainly based on the order selected by the original design and plate making. But according to product characteristics and technical requirements, there are often changes.
The color sequence in general flexographic screen printing is determined by the following situations.
1. Printing with strong ink hiding power. Generally, light ink is printed first, and dark ink is printed afterwards;
2. There are many overprint colors, and when dark outlines are not used as overprint rules, dark outlines should be printed first;
3. It is necessary to cover the edge of the image outline with the darkest color. When removing the outline burrs, the dark color must be overprinted last. But sometimes this dark color is the color rules of various colors. At this time, a part of the dark color can be printed first as the specification of each color register, and finally the dark contour is overprinted;
4. The main color of the picture pattern is generally arranged at the last overprint;
5. For the same color with both dots and full-field versions, in order to meet the requirements that the dots are not pasted and the full-field version is not blooming, the half-screen and full-field versions should be printed separately. In this way, the printing pressure can be adjusted separately, and different inks are used to ensure the printing quality.
When printing in three colors, the general color sequence is: cyan-magenta-yellow. Field density should be controlled at cyan 1.6, magenta 1.4, and yellow 1.2. [next]
Let's talk about a very important application area of ​​flexographic printing color sequence of plastic flexible packaging color printing:
Plastic flexible packaging printing is usually laid with white ink as the background color to set off other colors. Its advantages: First, plastic white ink has the best affinity with polyolefin films (PE, PP) and the best adhesion fastness;
The second is that white is total reflection, which makes the colors of the printed products more vivid; the third is to thicken the printing ink layer, which makes the printing layer richer and more three-dimensional.
Flexible printing plastic flexible packaging is divided into "inside printing" and "surface printing". "Inner printing" refers to a special printing method that transfers ink to the inside of a transparent film (reverse graphics and text) using a printing plate that is opposite to the image and text on the surface, thereby expressing the positive image and text on the front of the film.
The color sequence of "surface printing" and "inside printing" is exactly opposite. For example, the surface printing usually prints the background color first, while the inside printing is the final background color. The color sequence of "surface printing" color printing is generally: white-yellow-magenta-cyan-black. The color sequence of "Liyin" color printing is generally: black-cyan-magenta-yellow-white.
"Linyin" printed matter is compared with "surface-printed" printed matter, which has the characteristics of bright and beautiful, bright colors, no fading, moisture-proof and wear-resistant, firm and durable, long shelf life, no sticking, no cracking and so on. Because the ink is printed on the inside of the film (between the two films via the composite ink layer), it will not contaminate the packaged items and meet the requirements of the Commodity Hygiene Law.
The flexographic printing machine is a multi-color printing machine. The overprinting of the ink is carried out by wet stacking, at least 6 colors, generally 10 colors, and up to 12 colors. It can be used for ultraviolet and infrared glazing. The printed products are mainly decorative prints, with text, images, network cable and field, and some need to print gold, silver and glaze. Therefore, the color sequence of flexographic printing is very flexible. When deciding the printing color sequence, we cannot consider a certain factor in isolation, and we must analyze the specific requirements of the printed matter to obtain the best printing color sequence. For example, you can print the screen version first, then print the ground, then print the gold, and finally glaze. The ink color of some printed products is darker, which is limited by the amount of ink transferred by the anilox roller. If the thickness of the ink layer is not met, another printing unit can reprint the color again. The color sequence of the four-color screen cannot be changed at will. For spot color printing, the order of light to dark is generally used. Light ink is printed first, which can make dark ink superimposed and bright. For spot colors printed by the superimposed method, the color sequence of the primary color and secondary color is that the secondary color is printed first, and the primary color is printed later.
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