How to prevent color deviation of printed matter

How to prevent color deviation of printed matter

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Any kind of color print is completed by a certain coloring process of yellow, magenta, cyan, and black according to a certain plate making process and printing color sequence. How to prevent color deviation of printed matter and accurately reproduce color and level is a problem worthy of attention in the printing process. If these aspects are neglected, it will affect the quality of printed matter and make the color and level of printed matter appear biased.

Color shift: refers to the difference in color when printed products are compared with originals or proofs.

The prevention of color shift should pay attention to two reasons in the process technology. (1) Arrangement of the angle of the plate making network. (2) Arrangement of printing color sequence.

One: Arrangement of the angle of the network cable in the process of color plate making

In the process of color plate making, if the arrangement angle of the cable is not correct, it will affect the printing color effect, and in the case of serious, it will produce moiré.

The current four-color plate printing is mainly composed of yellow, magenta and cyan, and the color of the picture is ever-changing. The black version only emphasizes the dark part and plays the role of skeleton. From the color rendering performance: among the four colors of yellow, magenta, cyan and black, the visual perception of yellow is the weakest, the magenta and cyan are the second, and the black is the strongest. Since the line of sight of a person is particularly sensitive to a dot at a 45° angle, the dot at 0 or 90 degrees feels poor, and the angle of the dot at 15 or 75 degrees is generally perceived by the human eye.

In view of the above factors, the angle of the screen of each color version should be determined according to the main color of the original when making the plate. Therefore, the main color printing plate of the original should be made into 45° other colors to make 15°, 75°, and 90°.

 For monochrome mesh prints, we should use 45 degree dots.

However, multi-color mesh prints, the angles of the dots of each color must be staggered, and the angles of the commonly used color network cables are as follows:

1. For two-color printing, the main color version or the dark version uses a 45° screen angle, and the secondary color version or the light color version uses a 15° screen angle.

2. For three-color printing, the main color version or the dark version uses a 45° screen angle, and the other two color versions use a 15° and 75° screen angle.

3. For four-color printing, the main color version uses a 45° screen angle, the yellow version uses a 90° screen angle, and the other two colors use 15° and 75° screen angles respectively.

According to the main color tone of the screen, the network cable angle is as follows:

 (1) If the main color of the screen is a warm red color, it can be set to: magenta plate 45°, black plate 15°, cyan plate 75°, yellow plate 90°.

(2) If the main color of the screen is a cool blue color, then: blue 45°, black 75°, magenta 15°, yellow 90°.

 (3) If the main color of the picture is black Chinese painting, then: black version 45°, green version 75°, magenta version 15°, yellow version 90°.

 In the case of normal printing, the angle of the network cable is arranged according to the above method, and then the color sequence is correctly arranged, which can effectively prevent the color shift of the printed matter. Make the prints bright and clear.

Second: the arrangement of the printing color sequence.

 Color printing, whether it is a monochrome machine or a multi-color machine, no matter what type of ink is used, it will face a color sequence problem. Only by properly arranging the printing color sequence can the gray balance be achieved, and the color and level of the original can be fully reproduced to achieve the desired printing effect.

In multi-color printing, the order in which the color separation plates are sequentially overprinted on the substrate in a certain color order is called a printing color sequence.

Printing color sequence arrangement is very important, its main role has three aspects:

(1) Correct color cast

Yellow, magenta, and cyan primary printing inks have certain gray components regardless of the brand, and more or less have some color cast. The whiteness of the paper we use, the accuracy of the press, and the process operation also have some shortcomings. This will result in a color shift. Choosing a reasonable printing color sequence can make up for these deficiencies to a certain extent and play a role in correcting the color shift.

(2) Display color correctly

The three primary colors of ink are combined in different proportions and will display thousands of new colors. Different print color sequences will show different color effects. If the same plate is used, the same process can be used to superimpose magenta on yellow or yellow on magenta, and the color effects are different. In the four-color screen printing, the dot of the dark tone portion is overprinted on the dot, and the dot of the high light tone portion is printed on the blank portion of the paper. The effect of the displayed color is different due to the difference of the ink cover and the thickness of the ink layer. .

In four-color printing, yellow, magenta, cyan, and black can have 24 different printing color sequences according to the arrangement. That kind of printing color order is good, there is no specific regulations, and appropriate arrangements must be made according to the specific circumstances.

(3) Reflecting the overprint status

 If the selected printing color sequence does not match the ink performance, there will be problems such as color mixing, ghosting, and printing.

It can be seen that choosing the correct printing color sequence is one of the important measures to ensure normal printing and obtain the best printing effect.

The choice of printing color sequence generally follows the following principles: 1. According to the brightness of the three primary colors, the color sequence is arranged: the brightness of the three primary color inks is reflected on the spectrophotometric curve of the three primary color inks, and the higher the reflectivity, the higher the brightness of the ink. Therefore, the brightness of the three primary colors ink is yellow > green > magenta > black. The first print with a small brightness and the back print with a large brightness.

2. Arrange the color sequence according to the transparency and hiding power of the three primary color inks: the transparency and hiding power of the ink depend on the difference between the refractive index of the pigment and the binder. The ink with strong opacity has a great influence on the color after the color combination, and it is not easy to display the correct color as the post-printing overprint, and the good color mixing effect is not achieved. Therefore, the ink with poor transparency is printed first, and the ink with strong transparency is printed.

3. Arrange the color sequence according to the size of the dot area: in general, the area of the dot is small, and the area of the dot is large.

4. Arrange color sequence according to the characteristics of the original: Each original has different characteristics, some are warm colors, and some are cool colors. In the color sequence arrangement, the color sequence mainly composed of warm color is black, cyan, magenta, and yellow; the color sequence mainly composed of cool color is black, magenta, cyan, and yellow.

5. According to the different printing equipment, color order

(1) Monochrome color sequence: When a monochrome machine prints a multi-color product, the ink transfer is wet and dry, and when the color sequence is considered, the ink viscosity can be placed in a lesser position.

Under the condition that the quality of paper and ink is good, the general printing color sequence is black, cyan, magenta and yellow. When the paper quality is poor, the surface is rough, the tightness is low, and the ink absorption is strong, the color sequence can be selected to be yellow, magenta, cyan, and black. Due to the large size of the yellow plate, it can make up for the defects of the paper. Make the printing effect better. In addition, yellow, magenta, cyan, and black sequences are used to facilitate color change, and it is easy to clean the ink roller and ink tank. Another reason for the monochrome printing machine to print the yellow version is that the human vision is not sensitive to the yellow dot, and when the yellow color is printed, even if there is a slight overprinting phenomenon, the naked eye is not easy to observe, thus Conducive to the effect of four-color overprinting.

(2) In the printing of the two-color machine, the second color and the third color are wet-stacked overprinting. The printing of 1-2 colors and 3 4 colors is wet-stack overprinting. The printing color sequence of the two-color machine is alternated between bright and dark colors, and the ink amount is large in the second color group, so the following is generally used in printing. Printing color sequence: 1-2 color magenta - blue or cyan - magenta; 3-4 color black - yellow or yellow - black, but also as needed. To highlight a certain color, such as green, it should be printed in the order of magenta-yellow, cyan-black, in order to obtain a better printing effect. It is also possible to use a color sequence of black-yellow, magenta-cyan, which is easier to control. (3) Four-color machine printing is a wet-wet printing method. In order to make the latter color ink transfer to the ink layer of the previous color substrate, the adhesion of the ink along the printing color sequence should be reduced sequentially, otherwise a reverse stack will occur. Printing phenomenon. Generally, the ink is printed with a dark color with a large viscosity, and the ink with a small viscosity is printed with a small color. Common color sequences are black, cyan, magenta, yellow, or black, magenta, cyan, and yellow. While changing the color sequence, the viscosity of the ink should also be adjusted accordingly.

 In the four-color machine printing, the yellow ink is discharged to the last color printing, which has three main advantages. (1) Since the yellow ink has good transparency, the last color is favorable for a sufficient amount of light to enter the upper and lower ink layers, so that the printed matter is more vivid. (2) The drying performance of yellow ink is faster and the printing area is larger. Arranging the yellow ink to the last color not only prevents the crystallization caused by the excessive drying speed of the yellow ink, but also utilizes the characteristics that the printing area is large and the conjunctiva is quickly oxidized, and the cover is covered on the surface of other ink layers. Improve the gloss of printed matter. (3) The yellow color is arranged in the last color, which is convenient for controlling the amount of ink used in yellow, and can be adjusted at any time according to the sample.

6. Arrange the color sequence according to the nature of the paper: the smoothness, whiteness, tightness and surface strength of the paper are different. The flat and tight paper is printed first with dark color and then printed with bright color; the thick and loose paper is printed with bright yellow. Ink, after printing dark, because yellow ink can cover paper defects such as paper hair and powder.

7. Arrange the color sequence according to the drying performance of the ink: It has been proved that the drying speed of yellow ink is nearly twice that of magenta ink, the magenta ink is twice as fast as the green ink, and the black ink is the slowest. Ink with slow drying performance should be printed first, and ink with fast drying performance should be printed. The monochromator machine crystallizes the anti-ink surface, and generally prints yellow at the end to facilitate rapid conjunctival drying.

8. Arrange the color sequence according to the flat net and the field: When the print has a flat net and the ground, in order to obtain a good print quality, the print on the ground is flat, the ink color is thick, and the color is bright. Generally, the flat net graphic is printed first, and then printed on the ground.

9. According to the light color and dark color arrangement: in order to make the print has a certain gloss and print a light color, first printed dark, then printed light.

10. Products based on text and black version generally adopt cyan, magenta, yellow, and black sequences, but black text and patterns cannot be printed on yellow solids. Otherwise, due to the small viscosity of yellow ink and large black viscosity, reverse overprinting occurs. Causes black to be printed or untrue.

11. For a picture with a small color overprinting area, the color registration sequence can generally adopt the principle of large color printing after printing.

12. Gold, silver products, because the adhesion of gold ink, silver ink is very small, gold, silver ink should be placed in the last color as much as possible, under normal circumstances should not use three stacks of ink printing.

13. The color sequence of printing should be as consistent as possible with the color sequence when proofing, otherwise it will not catch up with the effect of proofing.

14. When printing, the angles of the adjacent two color sequences should be 30° apart. If black, cyan, magenta, and yellow are used, the corresponding angles of the screen are black 75°, green 15°, magenta 45°, and yellow 90°. In summary, in the actual printing production, according to the quality requirements of the printed matter, the performance of the paper, the ink, the precision of the printing machine, etc., the printing color sequence can be flexibly arranged to achieve the best printing effect.