Color printing is now used by many products, such as newspapers, books, magazines, advertising, and various types of packaging. In spite of this, rare color prints that really qualify as fine prints are rare. Of course, this is related to many factors, such as printing equipment, printing materials, printing technology, etc. However, among many factors, the balance of colors and the arrangement of color sequences play a relatively important role in the quality of printed products. In the following, the author will talk about the color balance brown sequence in the color printing of general books and newspapers, and share the reference.
Color balance problem
1. Dot increase
Dot gains between different colors can cause problems with the overall color balance. If the difference between the increase value of each outlet and the normal (recommended) value is too large, the relationship between various colors will be seriously affected and surplus colors will be produced on the printed sheets. In actual printing, the balance of colors is usually evaluated in a 50% tone. Although at 50% dots, the allowable error for dot gain for each color is ±4%, the dot gain difference between the two colors cannot exceed 4%. Otherwise, the balance of printing colors will be seriously affected.
2. Printing contrast
Print contrast is an objective method of describing the openness of the dark portion of a printed image to indicate the ability to maintain the dark details of the print. If the print density conforms to the SNAP rule, a higher print contrast indicates a higher ability to maintain the dark detail of the print. The contrast can be calculated by the formula.
Contrast = (is the density at low density - 75% tone) X 100% / field density
If the density is in line with the SNAP (Printing Newsprint Advertising Parameter Description) rule, the result of the formula is as shown in the table. If density does not comply with SNAP rules. You need to make appropriate adjustments according to the SNAP parameters to get the correct printing results.
3. Image registration and registration problems on printing presses
Accurate positioning and registration of four colors is an important task for four-color printing. To perform positioning and registration, first of all, we must carefully arrange the color sequence so that each color can be printed at a precise position. If the positioning of the graphics is incorrect, the copied colors appear blurred, the image is distorted, and the image is not clear. In actual printing, care should be taken to ensure that any color and black registration error in each direction cannot exceed 0.012 inches, including both axial and diagonal directions.
Printing sequence problem
1. Color printing sequence of general color offset printing products
The so-called general color offset printing products refer to color prints printed on a single-sheet or multi-color offset printing machine.
(1) Printing color arrangement of sheet-fed single-color offset printing press
When a single-color offset press prints, the ink is superimposed by wet-dry dry printing. The interval between the two inks is longer, and the shorter one is several tens of hours. When the ink is overprinted, if it is the same color The adhesiveness of the ink is greater than the adhesiveness of the ink of the latter color, then the ink of the latter color can be well attached to the ink film of the previous color ink, and the overprinting effect of the ink film of the previous color ink will be good, and vice versa. One-color ink not only does not adhere well to the ink film of the previous color ink, but also removes part of the previous color ink film. The overprint effect is naturally not good, and even color reproduction is not possible. Visible, the adhesiveness of the ink Ink overprinting is very important.
Drying methods of printing inks for sheetfed offset printing machines are mainly based on oxidative polymerization drying and supplemented by osmotic drying. In the ink drying process, the adhesiveness of the ink will also change, the reality will increase, and then decrease, and the ink formed when the ink is completely dry will lose its adhesiveness. According to the law of ink adhesion with drying time, as long as the time interval between printing of two inks is well mastered, the adhesion of the ink of the previous color is large, and the printing of the ink of the latter color is small, and a good overprint effect can be obtained. However, due to the long time required for the offset printing ink to dry completely, it is generally not allowed to cause “overprinting†or “ink crystallization†failures in the color sequence. Therefore, the use of a single color offset press for printing color prints is more flexible in the selection of the print color sequence, and is generally considered in terms of the accuracy of overprinting, the degree of operation change, and the cost of printing. For example, considering that the heavy deformation of the paper during the printing process will gradually become stable, it may be first printed on the yellow ink required for overprinting precision, or the smaller ink color of the first printed image, so that the printing color sequence can be arranged, and the post-printing can be reduced. The degree of ink overprinting is inaccurate; if the printing color sequence is arranged from light to dark, it is easier to replace the ink; if the low-cost opaque chrome yellow ink room is printed in the first color, printing can be reduced. cost.
(2) Multi-color offset printing press color arrangement
Multi-color offset printing is used. If a four-color offset printing press is used, the color printing will be printed out once. When printing with a multi-color offset printing press, the printing interval between colors is very short. The first printing ink has just been printed for a fraction of a second, and the ink of the one-color ink is to be overprinted. The ink transfer printing is a wet-wet wet printing process. Since the wet printing is always carried out in the wet and wet manner at the moment of overprinting, the adhesiveness of the previous color ink has not yet increased with the drying time, so in order to ensure the normal operation of the overprinting, the adhesiveness of the various inks is ensured. It must be gradually reduced from the front to the back in the printing unit.
Printing with a multi-color offset press has a low trap rate because in the dry printing, the post-printing ink is transferred to the pre-printed ink that has been fixed and gradually dried, and the post-printing ink is split in the middle of its own ink film. It is transferred to the ink film of the preprinted ink, and the other part remains on the surface of the plate. However, wet printing is not the case. The latter color ink is generally split between the two ink inks, and only a small part of the ink is transferred to the previous color wet ink film. Most of the ink still remains on the printing plate.
The density of the ink has a certain relationship with the thickness of the ink film. Generally, as the ink density value increases, the thickness of the ink film also gradually increases. According to China's printing industry standard CY/T5-99, the field density of fine prints is: 0.85 to 1.10 for yellow, 1.25 to 1.50 for magenta, 1.30 to 1.55 for cyan, and 1.40 to 1.75 for black. If calculated according to the upper limit of the standard range, the actual results show that the ink film thickness at the yellow ink density of 1.10 is approximately 1.43 μm, the ink film thickness at the magenta ink density of 1.50 is approximately 0.96 μm, and the density of the cyan ink is 1.55. The thickness of the ink film is about 0.82 μm, and the thickness of the ink film when the ink of the black ink is 1.75 is about 0.75 μm. If the ink of the above density is used, the printing is performed in the order of black, cyan, magenta, and yellow, and the overprinting effect is good; if the printing sequence is changed to black, cyan, magenta, the ink film thickness becomes 0.73 μm at a time. 0.82 μm, 1.43 μM, and 0.96 μm, apparently the superimposition of magenta ink is not good. Even if the amount of magenta ink is increased in order to increase the overprinting effect of the magenta ink, color misalignment, damage to the gray balance of the printed matter, exacerbation of the dot gain, and the like will occur.
Brightness is an important indicator of ink performance. Among yellow, magenta, cyan and black four-color inks, the yellow ink has the highest lightness, and the black ink has the lowest lightness. The high brightness of the ink on the last color printing, can make the printing screen more beautiful, and the darkest, dark color ink should be the first printing.
From the above analysis, it can be seen that the factors that restrict the normal printing of the wet printing ink are far more than the dry printing, so the butterfly silver sequence of the multi-color offset printing machine is also relatively fixed. At present, the recommended printing color sequence is: black, cyan, magenta, and yellow. It is to take into consideration factors such as the prepress processing, printing process, ink coloring properties, etc. of general color prints (prints not including the under color removal process). definite. Production practice has proved that the use of this printing color sequence is advantageous for improving the ink overprinting effect of a sheet-fed multicolor offset printing press. Some ink manufacturers produce four-color offset printing inks, whose adhesiveness is black, cyan, magenta, and yellow in the order from small to large, and is also adapted to the sequence of wet printing ink overprinting.
2. Printing color sequence of color newspapers
The color newspaper is made by printing yellow, magenta, cyan, and black inks on an offset printing press. The effect of color reproduction is the most important indicator for evaluating color newspaper printing. In order to improve the printing quality of color newspapers, in addition to focusing on prepress processing, printing equipment, paper, ink, etc., we must also select the printing color sequence rationally based on the performance of the printing press, paper, and ink.
In order to pursue higher and higher newspaper effectiveness, printers often have to complete the entire 90,000 contract manufacturing process within a few hours. The increase of the printing speed makes the time of ink overprinting shorter than the multi-color printing of the single sheet. From the structure of the printing press and the time interval of ink overprinting, the ink of the color newspaper is superimposed on wet and wet wet printing. The color order of printing is in accordance with the black, cyan, magenta, and yellow colors of the multi-color offset printing press. reasonable.
Except for a few fine newspapers printed on copperplate paper, the vast majority of color newspapers, like black-and-white newspapers, use newsprint with a rough surface, porous, ink-absorptive, and good flexibility, and are mainly based on osmotic drying and oxidative polymerization and drying. Roll web offset printing inks. Under the effect of compressive stress, the ink penetrates quickly into the micropores of newsprint. The fixation and drying of the ink are carried out almost at the same time. The ink after printing is preprinted and superimposed on the fast-drying ink layer. From the drying perspective of the ink, the ink overlay of the color paper also has wet-dry dry printing, and the color-sequencing arrangement is the same as that of the single-color offset printing machine, and has greater flexibility.
Colorful newspapers use porous, easily deformable, and low-white newsprint paper. It is difficult to register on high-speed web offset presses, and the color reproducibility is worse than that of offset papers. Solid color newspapers are printed products. More national standards "Quality requirements and test methods for newspaper prints", the quality of color pictures in newspapers basically meet the natural tone, four-color overprint accuracy. Therefore, in addition to considering the overprinting effect of ink, the printing color sequence of color newspapers must also meet the requirements for color registration and color reproduction of color newspapers in the national standard. The following example gives an analysis of the color of newspapers.
For example, a newspaper printing company uses Canadian newsprint and Tiens high speed web offset printing ink. The tack values ​​of the black, cyan, magenta, and yellow inks are: 197, 148, 155, and 219, respectively. In accordance with the wet printing printing color imaginary should be yellow, black, magenta, green, but the factory uses Gaussian rotary offset press for the side-by-side unit type, a long paper path, overprinting accuracy is relatively difficult to control. From the point of view of printing overprinting, black ink is less adhesive than yellow ink, and the overprint effect is poor. However, when the penetrating dry black ink and the ink-absorbing newsprint are in contact with each other, the ink will be fixed and dry, and the adhesiveness will rise sharply. When the yellow ink is overprinted, the “anti-stripping†failure of the ink will not occur. Therefore, the color sequence used in actual production is black, yellow, magenta, and cyan.
For another example, the adhesion Tack values ​​of black, cyan, magenta, and yellow inks of Gao's Rolls-Royal offset printing ink in Shanxi are: 192, 186, 195, and 198, respectively. The difference between the adhesiveness of each color ink is small, and the color sequence is not greatly influenced by the adhesiveness. When printing using this ink, the printing color sequence is mainly selected based on the structure of the printing machine and the color reproduction. If a Gaussian full-web offset press is used, the path of the paper is short, and the registration is easy. The sequence of cyan, magenta, yellow, and black is used, which is conducive to print registration and will not use black with a large amount of ink. Ink failure occurred in the ink and the color reproducibility was good.
For the printing of copper plate, because the surface of the copper plate paper has a dense coating layer, the permeability is smaller than that of the newsprint paper, and the dry and dry web offset printing ink is used for printing. The drying speed is much slower than that of the newsprint paper, so the printing color sequence Follow the rule of wet printing ink overprinting rate. Once there was a newspaper company printing plant that used Goss full-satellite web offset presses and 85g/m2 copperplate paper to print color newspapers. The print sequence colors used were cyan, magenta, black, and yellow. As a result, there was a yellow paste on the printing process. Black ink, but yellow ink is not transferred to the paper on the fault. In order to find out the reasons for their adhesion to four-color inks, a domestic YQM-IB stickiness meter was used. The Tack values ​​of yellow, cyan, magenta, and black inks were: 6.05, 6.75, 7.85, and 4.37, respectively. Later, when the printing color sequence was changed to cyan, magenta, yellow, and black, the ink transfer was normal, and the overprinting effect was good. It appears that when printed with copper plate paper, color ink should pay special attention to the effect of ink adhesion.
Color balance problem
1. Dot increase
Dot gains between different colors can cause problems with the overall color balance. If the difference between the increase value of each outlet and the normal (recommended) value is too large, the relationship between various colors will be seriously affected and surplus colors will be produced on the printed sheets. In actual printing, the balance of colors is usually evaluated in a 50% tone. Although at 50% dots, the allowable error for dot gain for each color is ±4%, the dot gain difference between the two colors cannot exceed 4%. Otherwise, the balance of printing colors will be seriously affected.
2. Printing contrast
Print contrast is an objective method of describing the openness of the dark portion of a printed image to indicate the ability to maintain the dark details of the print. If the print density conforms to the SNAP rule, a higher print contrast indicates a higher ability to maintain the dark detail of the print. The contrast can be calculated by the formula.
Contrast = (is the density at low density - 75% tone) X 100% / field density
If the density is in line with the SNAP (Printing Newsprint Advertising Parameter Description) rule, the result of the formula is as shown in the table. If density does not comply with SNAP rules. You need to make appropriate adjustments according to the SNAP parameters to get the correct printing results.
3. Image registration and registration problems on printing presses
Accurate positioning and registration of four colors is an important task for four-color printing. To perform positioning and registration, first of all, we must carefully arrange the color sequence so that each color can be printed at a precise position. If the positioning of the graphics is incorrect, the copied colors appear blurred, the image is distorted, and the image is not clear. In actual printing, care should be taken to ensure that any color and black registration error in each direction cannot exceed 0.012 inches, including both axial and diagonal directions.
Printing sequence problem
1. Color printing sequence of general color offset printing products
The so-called general color offset printing products refer to color prints printed on a single-sheet or multi-color offset printing machine.
(1) Printing color arrangement of sheet-fed single-color offset printing press
When a single-color offset press prints, the ink is superimposed by wet-dry dry printing. The interval between the two inks is longer, and the shorter one is several tens of hours. When the ink is overprinted, if it is the same color The adhesiveness of the ink is greater than the adhesiveness of the ink of the latter color, then the ink of the latter color can be well attached to the ink film of the previous color ink, and the overprinting effect of the ink film of the previous color ink will be good, and vice versa. One-color ink not only does not adhere well to the ink film of the previous color ink, but also removes part of the previous color ink film. The overprint effect is naturally not good, and even color reproduction is not possible. Visible, the adhesiveness of the ink Ink overprinting is very important.
Drying methods of printing inks for sheetfed offset printing machines are mainly based on oxidative polymerization drying and supplemented by osmotic drying. In the ink drying process, the adhesiveness of the ink will also change, the reality will increase, and then decrease, and the ink formed when the ink is completely dry will lose its adhesiveness. According to the law of ink adhesion with drying time, as long as the time interval between printing of two inks is well mastered, the adhesion of the ink of the previous color is large, and the printing of the ink of the latter color is small, and a good overprint effect can be obtained. However, due to the long time required for the offset printing ink to dry completely, it is generally not allowed to cause “overprinting†or “ink crystallization†failures in the color sequence. Therefore, the use of a single color offset press for printing color prints is more flexible in the selection of the print color sequence, and is generally considered in terms of the accuracy of overprinting, the degree of operation change, and the cost of printing. For example, considering that the heavy deformation of the paper during the printing process will gradually become stable, it may be first printed on the yellow ink required for overprinting precision, or the smaller ink color of the first printed image, so that the printing color sequence can be arranged, and the post-printing can be reduced. The degree of ink overprinting is inaccurate; if the printing color sequence is arranged from light to dark, it is easier to replace the ink; if the low-cost opaque chrome yellow ink room is printed in the first color, printing can be reduced. cost.
(2) Multi-color offset printing press color arrangement
Multi-color offset printing is used. If a four-color offset printing press is used, the color printing will be printed out once. When printing with a multi-color offset printing press, the printing interval between colors is very short. The first printing ink has just been printed for a fraction of a second, and the ink of the one-color ink is to be overprinted. The ink transfer printing is a wet-wet wet printing process. Since the wet printing is always carried out in the wet and wet manner at the moment of overprinting, the adhesiveness of the previous color ink has not yet increased with the drying time, so in order to ensure the normal operation of the overprinting, the adhesiveness of the various inks is ensured. It must be gradually reduced from the front to the back in the printing unit.
Printing with a multi-color offset press has a low trap rate because in the dry printing, the post-printing ink is transferred to the pre-printed ink that has been fixed and gradually dried, and the post-printing ink is split in the middle of its own ink film. It is transferred to the ink film of the preprinted ink, and the other part remains on the surface of the plate. However, wet printing is not the case. The latter color ink is generally split between the two ink inks, and only a small part of the ink is transferred to the previous color wet ink film. Most of the ink still remains on the printing plate.
The density of the ink has a certain relationship with the thickness of the ink film. Generally, as the ink density value increases, the thickness of the ink film also gradually increases. According to China's printing industry standard CY/T5-99, the field density of fine prints is: 0.85 to 1.10 for yellow, 1.25 to 1.50 for magenta, 1.30 to 1.55 for cyan, and 1.40 to 1.75 for black. If calculated according to the upper limit of the standard range, the actual results show that the ink film thickness at the yellow ink density of 1.10 is approximately 1.43 μm, the ink film thickness at the magenta ink density of 1.50 is approximately 0.96 μm, and the density of the cyan ink is 1.55. The thickness of the ink film is about 0.82 μm, and the thickness of the ink film when the ink of the black ink is 1.75 is about 0.75 μm. If the ink of the above density is used, the printing is performed in the order of black, cyan, magenta, and yellow, and the overprinting effect is good; if the printing sequence is changed to black, cyan, magenta, the ink film thickness becomes 0.73 μm at a time. 0.82 μm, 1.43 μM, and 0.96 μm, apparently the superimposition of magenta ink is not good. Even if the amount of magenta ink is increased in order to increase the overprinting effect of the magenta ink, color misalignment, damage to the gray balance of the printed matter, exacerbation of the dot gain, and the like will occur.
Brightness is an important indicator of ink performance. Among yellow, magenta, cyan and black four-color inks, the yellow ink has the highest lightness, and the black ink has the lowest lightness. The high brightness of the ink on the last color printing, can make the printing screen more beautiful, and the darkest, dark color ink should be the first printing.
From the above analysis, it can be seen that the factors that restrict the normal printing of the wet printing ink are far more than the dry printing, so the butterfly silver sequence of the multi-color offset printing machine is also relatively fixed. At present, the recommended printing color sequence is: black, cyan, magenta, and yellow. It is to take into consideration factors such as the prepress processing, printing process, ink coloring properties, etc. of general color prints (prints not including the under color removal process). definite. Production practice has proved that the use of this printing color sequence is advantageous for improving the ink overprinting effect of a sheet-fed multicolor offset printing press. Some ink manufacturers produce four-color offset printing inks, whose adhesiveness is black, cyan, magenta, and yellow in the order from small to large, and is also adapted to the sequence of wet printing ink overprinting.
2. Printing color sequence of color newspapers
The color newspaper is made by printing yellow, magenta, cyan, and black inks on an offset printing press. The effect of color reproduction is the most important indicator for evaluating color newspaper printing. In order to improve the printing quality of color newspapers, in addition to focusing on prepress processing, printing equipment, paper, ink, etc., we must also select the printing color sequence rationally based on the performance of the printing press, paper, and ink.
In order to pursue higher and higher newspaper effectiveness, printers often have to complete the entire 90,000 contract manufacturing process within a few hours. The increase of the printing speed makes the time of ink overprinting shorter than the multi-color printing of the single sheet. From the structure of the printing press and the time interval of ink overprinting, the ink of the color newspaper is superimposed on wet and wet wet printing. The color order of printing is in accordance with the black, cyan, magenta, and yellow colors of the multi-color offset printing press. reasonable.
Except for a few fine newspapers printed on copperplate paper, the vast majority of color newspapers, like black-and-white newspapers, use newsprint with a rough surface, porous, ink-absorptive, and good flexibility, and are mainly based on osmotic drying and oxidative polymerization and drying. Roll web offset printing inks. Under the effect of compressive stress, the ink penetrates quickly into the micropores of newsprint. The fixation and drying of the ink are carried out almost at the same time. The ink after printing is preprinted and superimposed on the fast-drying ink layer. From the drying perspective of the ink, the ink overlay of the color paper also has wet-dry dry printing, and the color-sequencing arrangement is the same as that of the single-color offset printing machine, and has greater flexibility.
Colorful newspapers use porous, easily deformable, and low-white newsprint paper. It is difficult to register on high-speed web offset presses, and the color reproducibility is worse than that of offset papers. Solid color newspapers are printed products. More national standards "Quality requirements and test methods for newspaper prints", the quality of color pictures in newspapers basically meet the natural tone, four-color overprint accuracy. Therefore, in addition to considering the overprinting effect of ink, the printing color sequence of color newspapers must also meet the requirements for color registration and color reproduction of color newspapers in the national standard. The following example gives an analysis of the color of newspapers.
For example, a newspaper printing company uses Canadian newsprint and Tiens high speed web offset printing ink. The tack values ​​of the black, cyan, magenta, and yellow inks are: 197, 148, 155, and 219, respectively. In accordance with the wet printing printing color imaginary should be yellow, black, magenta, green, but the factory uses Gaussian rotary offset press for the side-by-side unit type, a long paper path, overprinting accuracy is relatively difficult to control. From the point of view of printing overprinting, black ink is less adhesive than yellow ink, and the overprint effect is poor. However, when the penetrating dry black ink and the ink-absorbing newsprint are in contact with each other, the ink will be fixed and dry, and the adhesiveness will rise sharply. When the yellow ink is overprinted, the “anti-stripping†failure of the ink will not occur. Therefore, the color sequence used in actual production is black, yellow, magenta, and cyan.
For another example, the adhesion Tack values ​​of black, cyan, magenta, and yellow inks of Gao's Rolls-Royal offset printing ink in Shanxi are: 192, 186, 195, and 198, respectively. The difference between the adhesiveness of each color ink is small, and the color sequence is not greatly influenced by the adhesiveness. When printing using this ink, the printing color sequence is mainly selected based on the structure of the printing machine and the color reproduction. If a Gaussian full-web offset press is used, the path of the paper is short, and the registration is easy. The sequence of cyan, magenta, yellow, and black is used, which is conducive to print registration and will not use black with a large amount of ink. Ink failure occurred in the ink and the color reproducibility was good.
For the printing of copper plate, because the surface of the copper plate paper has a dense coating layer, the permeability is smaller than that of the newsprint paper, and the dry and dry web offset printing ink is used for printing. The drying speed is much slower than that of the newsprint paper, so the printing color sequence Follow the rule of wet printing ink overprinting rate. Once there was a newspaper company printing plant that used Goss full-satellite web offset presses and 85g/m2 copperplate paper to print color newspapers. The print sequence colors used were cyan, magenta, black, and yellow. As a result, there was a yellow paste on the printing process. Black ink, but yellow ink is not transferred to the paper on the fault. In order to find out the reasons for their adhesion to four-color inks, a domestic YQM-IB stickiness meter was used. The Tack values ​​of yellow, cyan, magenta, and black inks were: 6.05, 6.75, 7.85, and 4.37, respectively. Later, when the printing color sequence was changed to cyan, magenta, yellow, and black, the ink transfer was normal, and the overprinting effect was good. It appears that when printed with copper plate paper, color ink should pay special attention to the effect of ink adhesion.
Promotional Lipstick Tub,Metal Lipstick Container,Spring Lipstick Tube
Huasheng Plastic Co., Ltd. , http://www.stcosmeticscase.com