[China Packaging Network News] Color box packaging products often appear in the production of color recovery issues, such as neutral gray cast color, and then affect product quality, which in addition to the equipment itself, production personnel skill level problems, the key One problem is that companies have not been able to implement effective color management and reasonable use of ink.
Color management is to manage people's perception of color. The purpose is to make the conversion between different colors in the entire process of image copying to ensure that the appearance of the image color can be matched from the input display to the appearance displayed in the output. Color and consistency with the replica.
Image copying requires multiple stages of image acquisition, processing, color separation, printing, etc. At each stage, the color information will be displayed according to the color rendering and color description features of the device used at that time. Unusual scanning and display devices may have a different color display for a single original. In addition, the color expression between the RGB three-color display screen and the four-color printing ink is different. The lack of consistency in the conversion of RGB data into CMYK, and the use of different paper and ink The prints are not the same. Therefore, it is necessary to control color recovery on various types of devices and media in the production system through color management.
Color management content
Setting up the device's color description file (Profile) is the middle of color management. The description file has the representative color features of each device, such as the chromaticity characterization curve, the transmission color gamut characteristic curve, etc. The color management system uses these to have The representative color features complete the matching and conversion of the color space of each device.
To conduct color management, it is necessary to follow a series of courtesy procedures to achieve the expected results. Color management is divided into three methods on the matter of affairs, abbreviated as "3C", namely, Calibration, Characterization, and Conversion.
Calibration: In order to guarantee the invariability, reliability, and sustainability of the color information transfer process, the input, display, and output devices are required to be calibrated to guarantee that they are in the standard duty profile. Enter the brightness, contrast, and correction of the noise field in the correction scanner. To guarantee that there is a consistent copy of the manuscript, you should be able to obtain the same image data regardless of the time of the scan.
By setting the display's brightness, contrast, color temperature, and the gamma value of the entire display system, it can accurately display colors. The output correction collects the corrections of printers, imagesetters, printers, and proofers, and corrects the characteristics of the printers, so that the device can be output according to the factory-standard characteristics.
Characterization: Recording the corrected features of all devices is the process of characterization. These feature description files are bridges from device color space to standard device-independent color space (PCS).
Conversion: Based on the calibration of the system equipment, the equipment is used to describe the files, and the standard equipment-independent color space is used as the preamble to complete the accurate conversion between the equipment's color spaces. Since the color gamut of the output device is narrower than the color gamut of the original document, scanner, and display, the color gamut needs to be shortened during color conversion, and the color gamut is shortened. In the ICC negotiation, there are absolute colorimetry, relative colorimetry, There are four methods of convex saturation and sensory methods.
Implementation of color management
Shallowly speaking, about a packaging and printing company to do a good job in color management, the need for a standard situation light source; high-quality color profile generation; improve the older generation of color management systems; standard measuring instruments and test equipment; standard colors Color target; standard print management; standard remote digital color management; standard scan recovery, digital camera color management; standard monitor correction and screen soft proofing. In the specific implementation process of color management, we should do the following aspects: We must do a good job in the standardization, standardization, and data production management of the various processes throughout the printing process. This is the premise and basis for the use of ICC color management.
Enterprises should rigorously formulate quality standards for fine products, standards for raw and auxiliary materials and equipment such as paper and ink, standards for measuring equipment and light sources, and formulate standardized management documents, and require everyone to strictly implement the standards. Monitors, soft proofing, printer ICC files, printer parameters, etc., must be standardized, and quantified within standards and specifications. All data that can be expressed locally, through testing methods, summarize the data that can guarantee quality. The three are in the opposite, interdependent, and then guarantee the same high-quality, high-efficiency production.
Prepress image processing skills is the basis and key link of print copy quality. The monitor must be professional, the scanning of originals and the handling of digital manuscripts should be consistent with the four basic standards of copy quality (gray balance, tone reproduction, color correction, sharpness enhancement) to indicate the obligation and pass the parameters of the four standards of the implementation specification. . After the completion of the scanning of documents, adjustments and artistic processing of non-compliant manuscript defects should be made, so that the printing product level will become even richer, and the consequences will be better than that of the manuscript. With regard to remotely-printed companies, the management of Profile files for remote digital proofing ensures that the digital proofs in both locations are the same color.
The choice of color management system
At that time, there were many color management systems on the market, such as Adobe's Photoshop color management system, Apple's ColorSync color management system, and Kodak's color management system. Different color management systems have different types of color management capabilities for the device and all have their own areas of expertise. Therefore, companies must first determine which devices require consistent colors in order to make selections.
Second, we must determine the self-description files in the color management system, and whether it can support the tree to draw files in the open system immediately. If it is a blockade system, we must draw the files from the factory tree immediately. How much needs to be determined can withstand the tree? The cost of drawing a file immediately. Should be based on the company's own situation, the system's compatibility, equipment support capabilities, scalability, compatibility and ease of use and other functions to compare and test, testing can be used when consistent colorful manuscripts, observe which system is in the specific Under the operating conditions, the most consistent results with the manuscript can be obtained.
Effective color management is a guarantee of the quality of the entire copy, but the final product is obtained via ink. As one of the five printing elements, ink has the most important influence on the printing process and quality. Accurate and reasonable use and distribution of ink is the key to guarantee accurate recovery of color. The use of ink.
Ink Composition and Function: Water-based inks are made from water-soluble resins, high-grade pigments, solvents and additives. The hue depends on the nature of the pigment. The coarseness of the pigment requires the pigment to have brilliant luster, robust coloring power and concealment, superior resistance and high turbulence. In order to obtain the superior printability of the ink, it is often necessary to adjust the ink's motility, monotonicity, and stickiness with various types of ink additives according to different conditions. There are many factors in choosing the quality of ink and ink, and if it is not properly used, it will bring a series of quality problems. During purchase and application, attention should be paid to analysis to determine the shape of its quarrel, and adjustments should be made according to the situation to guarantee its excellent printability. .
In printing, the ink ink has a certain viscosity, which is the prerequisite for the stalemate to transfer and transfer ink. Therefore, the viscosity of the high-grade ink is controlled to be about 20±5 seconds, and the difference in the viscosity will constitute the depth of printing color. In the theoretical production process, the PH value of the ink on the machine can be adjusted or controlled between 8.0 and 9.5 depending on the difference between the product and the temperature.
Ink distribution: The ink assignment first hypothesis refers to the color of the ink. In the printing of packaging products, the color used in ink painting is mainly flat spot painting of spot color, and it reaches the dual effects of sight and anti-counterfeiting.
These unsuitable spot colors cannot be overprinted by the four colors of blue, yellow, black, and black, and they can not be directly applied to the original ink. They must be acquired by disproportionate distribution of the original ink according to the production status by skilled personnel. .
The color distribution of the ink is based on subtractive color theory. That is, any color can be assigned using the disproportionate noisy colors of the three primary colors, and consider the three basic attributes of hue, lightness, and saturation. In the color matching process, the ink used should be selected according to the theoretical printing process, the ink layer thickness, the printing substrate, and other factors, and the hue, gloss, coloring power, and concealment power of the ink itself should be considered.
Color matching process
Analysis of the original color: Toning is performed on the color sample of the original. In order to increase the blindness of the color, it is necessary to first analyze the color of the original to determine the hue and proportion of the original color ink. The first hypothesis of the analysis manuscript is based on the method of instrument colorimetry and human eye colorimetry. The use of printing chromatography to determine the proportion of three primary inks is relatively simple, and the three primary color inks and white ink content can be calculated based on the percentage of the primary dot area marked in the chromatogram.
Color Matching: According to the calculated ratio, a small amount of primary color ink is assigned first. Keep an eye out for the contrast between ink and the original color. When the colors are close, it is desirable to adjust the ink to draw a contrast on the scratch paper, and then repeat until the two colors are exactly the same. When colorimetric, the ink should be made evenly, and the thinner the ink layer, the better. In order to guarantee the accuracy of hue hue, the paper should be the same as the paper used for printing. The adjustment of brightness and saturation is done by adding white ink and black ink. When demand involves white and black ink, it should pay special attention to the accuracy of weighing.
After the ink to be dispensed arrives at the original request, batch ink dispensing may be performed in proportion. The assigned amount of ink used in a batch of jobs is determined by the type of paper, image area, number of prints, and amount of wear.
Record: After the preparation is complete, the ratio of various inks used in the ink transfer, ink transfer, dry oil, ink type, quantity, and manufacturer information will be published in detail. It will be used as a reference when backing ink is used.
Other hardships: When analyzing originals and color comparisons, it is best to use a standard light source or a light source that is close to daylight. Also, wait until the ink film is monotonous before performing colorimetry to add visual errors. Try to use color inks that are close to the original color ink or other single color inks. The color matching uses too much color ink, and the worse the brightness and saturation, then affect the printing results. Therefore, the fewer the number of inks in the color matching, the better. It is best to select the ink products of the same manufacturer.
When coloring, we must fully inquire about the daily printing speed and printing pressure of our equipment, and control the ink viscosity. Different printing speeds and pressures will have different shades of printed matter, so assigning good ink at low speeds will require printing speed to open to the normal speed and checking with the original again to avoid chromatic aberration. .
After the ink is drawn out, it is assumed that there is an error in the color sample and the original printed on the machine. The ink fountain and the ink roller should be cleaned when replacing the color to prevent the cleaning from being unclean and causing color cast. The remaining spot-color ink after printing can still be assigned according to the hue of the new manuscript, but often the saturation is grayish. Especially the residual ink that is retrieved from the ink fountain can be emulsified or printed. change.