What is the printing process and its impact on the color?

Printing process is divided into three stages:

Pre-printing → refers to the work of the pre-printing, generally refers to the photography, design, production, layout, output film proofing, etc.;

Printing → refers to the work of the mid-printing, the process of printing finished products through the press;

Post-printing → refers to the work of the printing of the later stages, generally refers to the post-processing of printed materials including overgluing (laminating), over UV, oil, beer, hot stamping, embossing, laminating, binding, cutting, etc., mostly used for promotional and packaging prints.

Printing affects the color of the reasons are:

One, pressure discomfort caused by the printing of color

Printing pressure is one of the conditions of the ink transfer, due to the surface of the printing plate can not be absolutely flat, the surface of the paper is also unavoidable there are small bumps and uneven thickness, if the printing pressure is not enough or uneven, the printing ink layer is prone to uneven thickness phenomenon. Ideal printing process is in the "three flat" on the basis of the requirements of the printing plate and substrate and lining surface to achieve relatively flat conditions in order to thin ink layer through the role of balanced printing pressure, so that the prints on the role of obtaining a more uniform ink color. When the printing pressure is insufficient or uneven, the package liner body and printing plate there are poor contact conditions, it is necessary to increase the amount of ink delivery to meet the layout of the visual effect of inking, but this will not only increase the amount of ink consumption, but also prone to printing color difference and prints appear sticky dirty quality problems. Therefore, to prevent the production of printing color difference, should grasp the basic conditions of printing "three flat", and the use of uniform and constant pressure for printing. If the letterpress process (using round or flat press flat type machine) to print large-area plate products, it is best to use metal-type backing material, so that the material flatness and solidity of the material is better, the printing pressure is more stable, which is conducive to preventing pressure variations caused by the printing of chromatic aberration.

Two, the ink roller caused by poor printing color

Plain, letterpress and other printing processes, whether the print can obtain uniform ink color, the quality of the roller has a crucial role. Printing color prints on the machine, generally equipped with an ink roller, ink roller and inking roller three kinds of ink, which has a greater impact on the ink thickness is the ink roller and inking roller. The ink roller's elasticity, viscosity, roundness, hardness and surface finish how, to a large extent, determines the ink color quality of prints. If the poor elasticity of the inking roller, viscous insufficient, eccentric roller body, the gel is too hard, as well as the poor finish of the gel, etc., when the situation exists, the printing process is prone to cause uneven or unstable ink brush phenomenon, so that the printing of the printing of the ink color is not consistent. Therefore, the printing of color products should be used to better quality of the rubber roller, in order to ensure that each printing cycle coated with ink on the page to maintain the basic consistency. If the printing of bulk products, printing should be timely cleaning of the rollers, so that the paper dust retained on the rollers. Impurities can be removed to ensure the uniform origin of the ink, to prevent the production of printing color difference. On the other hand, the ink roller should be adjusted with a series of ink iron roller contact position, the general automatic printing machine is equipped with several groups of ink stringing device, in order to achieve uniform ink transmission. However, if the rubber rollers and ink rollers have poor contact, will inevitably cause the ink transfer is not sufficient, uneven, so that the ink color of the horizontal layout of the print appears uneven. In this regard, the roller should be adjusted at both ends of the axle head, so that the rubber roller and iron rollers to achieve uniform contact conditions, after adjusting the use of 5-wire steel into the rubber roller and iron rollers between the pull test, pulling the steel to the extent that there is a clear sense of resistance. In addition, it is necessary to adjust the inking roller and the contact position between the printing plate. If the inking roller is adjusted too high, the layout does not get uniform, sufficient ink coating, and easily due to the inking roller in the layout slippage and printing bar marks. If the inking roller is adjusted too low, the ink layer on the plate will be scraper printing plate drag top parts, resulting in the printing of ink color before the light after the deep color difference phenomenon, that is, the gripper parts of the ink color is light, drag the top parts of the ink color is thick. Inked roller and printing plate should be adjusted to parallel and uniform contact state, only accurate adjustment of the inked roller and plate contact position, in order to ensure uniformity of the print ink color.

Third, the inking device caused by poor printing color

When the ink bucket iron roller roundness or wear and tear deformation of the situation, the ink bucket steel plate also wear and tear deformation, as well as control of the ink bucket rollers rotating mechanism defects, so that the printing process is not stable in the amount of ink, will also cause the production of printing color difference, in this regard, should be taken to deal with the corresponding measures to prevent the production of printing color difference. In addition, attention should be paid to the reasonable bar true inking device, ink bucket in the ink to comprehensively increase or reduce the amount of delivery, there are two ways to adjust, one is through the adjustment of the ink bucket steel and ink transfer (ink) iron roller gap to realize; but by adjusting the size of the rotating arc of the ink transfer iron rod to realize. Ink in the case of thinner, should not be adjusted to the steel plate and iron rod gap is too large, in order to avoid leakage of ink caused by uneven ink color. Adjust the amount of ink, generally should be the rotation of the iron rod ink transfer arc control in its adjustable range of 1/2 between, so that the printing process of the ink concentration changes, can be flexibly adjusted to the amount of ink to ensure that the ink color of the print is uniform and consistent, to prevent the emergence of the problem of printing chromatic aberration.

Four, poor wetting factors caused by printing color

Lithographic printing process, if the wetting is not suitable, but also prone to printing color phenomenon. Such as when the water roller there is eccentricity, because of its contact with the plate is not consistent, it is easy to make the plate water supply size differences. In addition, the water roller fusion sleeve if the use of aging or adsorption of ink, impurities, will affect the water absorption of the water roller and the uniform transmission of the fountain solution. In addition, the water bucket device if there is a leakage phenomenon, will also affect the uniform delivery of water on the printing page. The existence of these adverse conditions, will destroy the layout of the ink uniformity and stability of the transfer, so that the print ink color differences. Therefore, the dampening system to maintain a good mount, should often clean the ink roller, the use of aging water roller velvet sleeve should be replaced, in order to better prevent the production of printing color difference.

Fifth, the ink caused by poor printing color

The process shows that the printing ink layer thickness and viscosity is not easy to produce printing color difference. Printing, only a moderate and uniform printing ink layer, in order to better ensure the ink color quality of the prints, and effectively prevent the printing of sticky dirty faults. If the printing ink layer is thick its viscosity increases accordingly, which is likely to cause the printing of the paper surface powder, hair phenomenon, which affects the uniformity of the ink color of the prints. However, if the printing ink layer is thin and ink viscosity is too small, the ink color of the print appears light, the visual effect of the print is poor. On the other hand, because the ink has the property of thixotropy, with the growth of the running time of the printing machine, as well as printing speed, the machine's coefficient of friction increases, the temperature of the ink will gradually increase, and its viscosity will drop accordingly, so that the printing ink color will be more and more shallow, so that before and after the batch of products, the ink color is inconsistent and the formation of chromatic aberration. Therefore, the ink adjustment must take these factors into full account, according to the climate and temperature conditions and printing machine characteristics, adjust the appropriate ink concentration, in order to reduce the chances of color differences in printing, so that the printing ink color to obtain relative stability. However, in the actual printing process, the ink viscosity drop is inevitable, often just open the print ink color is thicker, and then gradually fade, so that the ink can be properly adjusted to transfer the angle of rotation of the iron bar, and gradually increase the amount of ink, so that the ink before and after the printing of the ink color is basically the same. Mixing inter-color and multi-color ink, should try to avoid mixing ink with a large difference in specific gravity, so as not to print due to the large difference in specific gravity of the ink in the ink bucket, resulting in "layering" (i.e., precipitation and suspension) phenomenon caused by the printing of the color difference. In order to maintain continuous, uniform transmission of ink, ink knife should often be used to stir the ink in the ink bucket. In addition, the printing process due to the ink in the ink bucket significantly reduces the amount of thick, easy to make the ink bucket steel and ink transfer iron roller gap becomes small and the ink output is reduced, so that the ink color of the prints become light. In order to avoid this situation, the production should also pay attention to often add ink to the ink bucket, so that the ink bucket always maintain a certain amount of ink. In order to prevent the ink viscosity varies too much and affect the balance of the ink color of the prints, the contact between the rubber rollers and iron rollers can not be too tight, the rubber rollers are not easy to harden, in order to minimize the friction heat on the ink thixotropy effect, reduce the ink fade phenomenon.

Six, substrate material caused by poor printing color

In the daily printing process, we can find substrate material differences is also one of the reasons for printing color difference, such as substrate gloss and color differences, will produce printing color problem. To embossed aluminized paper, for example, aluminized paper paper hue differences, will cause inconsistencies in the effect of printing color. Therefore, printing color products should try to use gloss and hue of the same substrate. If, in the presence of objective factors, the same batch of products using two color and gloss of different materials, should pay attention to separate printing, and in the process by adjusting the ink hue and printing pressure, so that the two materials printing ink color is basically the same, in order to prevent the production of printing color difference.

Seven, the machine caused by poor printing color

Workers want to do a good job, it must be the first tool. Keep the machine good performance, is to improve the quality of printing ink color reliable guarantee. However, if the machine is bad, such as the embossing system is not stable, so that the pressure of each sheet is not consistent, as well as the paper delivery system is not normal, the printing of frequent empty sheets, more than one and other faults, but also the most likely to cause the emergence of the problem of printing color difference. Therefore, usually should pay attention to good maintenance and maintenance of the equipment, to pay attention to the lubrication of the vital parts of the machine, such as roller shafts and other parts to prevent wear and tear, so that the embossing mechanism to maintain good working conditions, so that the printing pressure to maintain a constant and unchanged. To adjust the Fidelity, the air pump device, so that the airway is unobstructed normal suction and delivery of printed sheets to ensure that the loss of smooth paper does not appear empty sheet phenomenon, so as to better prevent the production of printing color difference.

Eight, the printing plate caused by poor printing color

Printing plate is one of the basic elements of the quality of graphic reproduction, in the printing process, the printing plate only to maintain no deformation, no wear and tear, in order to better ensure that the layout of the amount of ink transfer stability. Printing process, if the dot layout paste or wear and deformation, lines appear to wear and expand, so that, due to changes in the amount of ink absorption layout, will inevitably make the print ink color deviation. Therefore, the printing of color products should pay attention to control the moderate printing pressure, and adjust the rubber roller, water roller contact pressure on the printing plate, to prevent excessive pressure exacerbate the wear and tear of the printing plate, so that before and after the printing of the product ink color deviation. On the other hand, should try to use a good smoothness, not easy to lose powder, hairy material for printing, which is also effective in avoiding the printing of the layout of the wear and tear deformation of one of the process measures, is conducive to better prevent the production of printing color difference.

Nine, the package lining caused by poor printing color

Package of dust is the transfer medium, the printing ink color has a great impact. If, if the package lining elasticity is too poor, with the increasing number of printing, it gradually appear sinking deformation is difficult to reset, then, it will make the print before and after the printing ink color inconsistency. On the other hand, if the printing process, the surface of the package lining adhering to a layer of ink, paper and other impurities, will also make the print ink color deviation. Therefore, the printing of color products should be selected with a certain degree of elasticity of the package liner, and timely cleaning of the rubber blanket surface of the print or confetti, in order to prevent poor lining caused by the printing of the color difference.

Ten, the characteristics of the light source and the observation angle on the identification of the difference between the color of the print

Usually identify the ink color of the print light source, mainly daylight (natural light), fluorescent lamps and incandescent lamps and other light sources. They emit different light source characteristics, the color of the light emitted also makes a difference, such as daylight for alcohol white, the observation of color is relatively accurate. Fluorescent light white with green, similar to daylight. The incandescent light is red with yellowish color, so it is difficult to accurately identify the color. Daylight and fluorescent lamps are somewhat similar, but the difference should also be considered when identifying higher quality color products. The influence of light on the identification of ink color, not only lies in the characteristics of the light source, but also with the intensity of light and the angle of irradiation has a great relationship. In the same light source, the irradiated and far away is weak. The correct angle of irradiation, should be ten angle of incidence is equal to the angle of reflection, light irradiation in the sample inevitably have part of the refraction, but the ink color does not have much effect, in the identification of the ink color of the prints, regardless of the ten daytime or nighttime should be in the light of the degree of intensity and irradiation angle are the same case. On the other hand, in identifying the ink color of prints, especially aluminized paper prints, printing midway against the color of the sample, should be correctly differentiated side by side to place the identification and overlap to place the identification of the color of the sample of the color of the existence of off-color differences, such as printing samples in the standard sample next to don't compare the color because of the difference in the angle of observation, there will be a certain degree of visual error, which can easily lead to the inky color identification is not allowed. And the printing sample of the ink color sample overlap on top of the standard sample for comparison, because of its observation angle difference is small, the identification of color is relatively accurate. This I know very well, such as the author in a trademark sample sent to the customer to confirm (the main label and the back of the same color), the customer looked at the juxtaposition of the standard samples placed side by side, that the main label and the back of the label there is a significant color difference in the background color, put forward objections. And the author through the back label stacked on top of the main label, color comparison that is to feel closer to the color, so the customer finally signed the confirmation. Process practice shows that the characteristics of the light source and observation of the difference in feet, will directly affect the accurate identification of color, so the printing of color quality requirements of high quality products, it is best to be arranged in the daytime printing, and in the comparison of color, should be used in a variety of perspectives repeated observation and comparison in order to prevent improper control of the printing process ink, resulting in the printing of products before and after the ink color is inconsistent.

In summary, the correct understanding of the printing color difference of a number of factors, through the good printing process ten and the operation of the technical level, not only can effectively avoid the production of such or such printing problems, and can better ensure the quality of color printing ink.