Research on Color Management of Plastic Flexible Packaging Printing
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First, the importance of color management
Color is a sensation that occupies 90% of the visual appearance, and consumers use color as a major factor in buying a particular product. Color in the market circulation, increased brand recognition by 80%. Due to the increasing internationalization of world-renowned brands, which affects and drives the corresponding packaging design and packaging printing services, the localization demand for packaging printing is stronger than packaging design. Many of our large and medium-sized packaging and printing companies in China have a considerable proportion of their business from these global brands.
Due to the uniform requirements of brand image, brand owners are paying more and more attention to the management of visual identity systems such as their brand identity colors. This has also spawned a new service industry: color management services. Global brand owners have begun to hire professional color management service companies to provide color management services for their brands worldwide. Based on the brand owner's requirements for the management and color control of the supply chain, correct color reproduction is one of the most important and important contents of plastic flexible packaging printing. PantoneLIVE, a cloud-based color management communication standard platform, has taken into account different substrates and printing methods, overcoming the color differences caused by different supply chains and different processes, and achieving color consistency from design to printing. This platform greatly reduces the cost of brand color communication on a global scale and is the contact tool for the entire brand and packaging printing supply chain.
Second, the definition of plastic flexible packaging printing and market demand
In the general terminology of national packaging (GB4122-83), a flexible package is defined as a package in which the shape of the container can be changed after filling or removing the contents. Various bags, boxes, sleeves, envelopes, etc. made of paper, aluminum foil, fiber, plastic film and composites thereof are all soft-packed. It is important in flexible packaging printing based on plastic film. Plastic flexible packaging printing refers to special printing with plastic film or plastic products as the printing material. It is named after the substrate and is a printing method that involves a wide range of processes, complex processes, and special styles. Printing materials range from film and composite materials for flexible packaging to various types of paper (wine labels, tipping paper, decorative paper, cigarette packets, carton printing, etc.). The plastic film or plastic product used for plastic packaging printing has a polar gene in its molecular structure, has good chemical stability, is resistant to most acid and alkali corrosion, and is insoluble in a common solvent at normal temperature. Due to the addition of antioxidants and stabilizers in the plastics production process, the affinity between the plastic and the ink is poor, and the ink is not easy to dry after printing. Therefore, the plastic substrate must be processed before printing to make it good for the ink. And, the ink is well adsorbed during printing, and the ink layer is not separated from the substrate after printing.
In recent years, as the output of food, beverages, dairy products, cosmetics, detergents, beer, and condiments has increased, the flexible packaging of plastic and plastic composite materials has become more and more demanding. From the pursuit of development speed to the development of circular economy and green packaging development centering on improving quality, creating brands, saving energy and reducing consumption, the flexible packaging printing industry has developed rapidly.
Third, the characteristics of plastic printing color management
The color deviation between the printed image and the sample and the color change during the printing process are one of the most common manifestations of print quality defects. How to truly evaluate the color objectively, the objectively measured variables and the appropriate measurement methods are very necessary. Due to the unique plate and printing process, the color management of plastic printing is different from the common substrate-printing method, which is mainly reflected in the following aspects.
1. Dot-growth characteristics: Plastic printing is different from offset printing, and the thickness of the ink layer of offset printing is difficult to control. However, the size of the dot can be controlled within the specified range by the pre-press dot compensation curve, so the consistency of the solid color of the offset printing is poor, and the reduction of the dot area is good, and the printing of the plastic flexible packaging is soft due to the printing plate material. The dot size increases and is severe under printing pressure. A small change in printing pressure will cause a significant change in the entire printed image; when the density of the ink in the field increases, the dot gain will increase, which has a great influence on the color of the image in the image.
2. Tonal reproduction characteristics: The tone reproduction ability of plastic printing is not as good as offset printing. The minimum 3% of online shop reproducible on the plate will generally expand to more than 10%, and the dot will be paste at about 90%. Less than 10% of the outlets are easy to lose, making plastic flexible packaging printing is very limited at the level of the tone, but its solid color consistency is better, suitable for spot color printing. The relative contrast, also called print contrast, referred to as the K value, is an important parameter for controlling the tone of the image.
3. Plastic Ink: In the reproduction of printed images, ink viscosity is a very important parameter. General plastic printing uses water-based inks, the least viscous, spray-like paint, contains many solvents, and has good fluidity and transferability of colloidal fluid. Offset and embossing generally use viscous inks, which are very viscous. The viscosity of the plastic ink is small, and there is no ink distribution and ink squeezing mechanism in the inking device. The amount of ink transmitted to the surface of the paper is reduced by the movement of the ink roller, resulting in a change in the tone and tone of the printed image, insufficient color saturation, and printing. Visual effects are often not bright enough.
4. Anilox roller transfer: The anilox roller needs to be cleaned in time, and its ink transfer performance is stable, which is convenient for conveying ink volume control.
5. Printing suitability of the substrate: plastic printing, the surface tension of the substrate is the first factor to consider. Untreated plastic films have extremely low surface tension and generally require corona treatment to increase the surface tension of the plastic substrate. The printing suitability of plastic printing lies in the plastic surface. The plastic surface is smooth, chemically inert, non-hydrophilic, and not easily wetted by ink and solvent. The lower the surface energy of the polymer, the smaller the surface tension, the more difficult it is to be The liquid is infiltrated. The surface energy also affects the adhesion of the ink to the substrate and the degree of spreading of the ink on the surface of the plastic film, thereby affecting the color reproduction.
Fourth, the implementation of plastic printing color management
Color management is consistent with the color of the entire process from device input to product printing, correctly reproducing the tone and color of the original, and truly achieving the WYSIWYG effect. Based on the plastic printing color management of these features, the main points of implementation are as follows.
1. The problem of increasing the value of the dot. The RIP process can be appropriately compensated for by the appropriate dot gain expansion compensation curve in the prepress process, so that the final expansion from the plate making to printing is within a reasonable range. The production of the dot gain compensation curve can be done in a variety of ways, either by hand or by software. There is a mature curve making software on the market. The Alwan ColorHub color hub uses a fully automatic color conversion server to help different printing processes improve color matching, print quality and production efficiency. Its powerful automated plate curve making software requires only simple numerical settings, and can quickly and easily output the dot gain expansion curve of most RIP software on the market.
2. For the tone copy problem.
(1) Perform reasonable pre-press compensation for image files during pre-press design, and adjust the tone for highlights or shadows.
(2) Using two different screening technologies in combination, the amplitude modulation network is used for the part of the tone range of 10% to 90%, and the other part can be adjusted by the frequency modulation network point, so that the small network point is restored and reproduced, and the dark adjustment area is pulled up. The tone level enhances the print contrast.
(3) Pre-press design requires prediction of small dot areas that are easy to lose, and improves color predictability. Using design software such as Photoshop plug-in function, such as GMGColorplugin software, you can freely set the starting point of the lost network, predicting the lost network effect after printing.
3. For the problem of insufficient ink color saturation. The display uses RGB three-color color and light addition, and the printing machine uses the CMYK four-color subtraction color forming principle. The color gamut space that the display can display is generally larger than the color space that can be printed, that is, what is seen. Many designers like to use high-saturation colors, which are bright and beautiful on the display, but the prints are grayed out, which is not ideal. Therefore, in color design, designers can use standard color cards and color optimization software such as PANTONE to complete the standard to non-standard, standard to standard, standard to custom conversion, the software itself has many integrated functions, such as Gao Bao True color separation, spot color reproduction, ink optimization and other functions, for process printing, can greatly improve the true reproduction of color and improve the consistency of expected results.
4. For the problem of ink transfer on the anilox roller. Since the current production color of the brand is ultimately presented to the consumer through the brand packaging, the final print is the basis for the entire color management process. Whether it is a pre-display, or an intermediate printing device or printing device, the final print is used as the color basis. Therefore, the color stability of the printed matter as the basis of the entire process color is very important. In order to achieve stable color printing, the core is standardized printing process management, and the strategy is full process thinking and step-by-step implementation. In the process of controlling the ink, the premise is to ensure the stability and consistency of different batches of ink.
5. For a variety of different substrates, set up a packet, including specific parameter information, such as metal color, matte effect, embossing and other printing capability range information, ink selection, printing contrast, ICC color, color Information on objectives and materials. Understanding the printing process is very significant, it can make the results of the printed products closer to "what you see is what you get", reduce the production cost of the enterprise, and improve the production efficiency of the printing workshop.
The choice of materials is an important factor affecting color. Printing is often a sample of soft proofing from the screen, and this does not reflect the choice of substrate. The emergence of the latest Pantone Live has just solved this bottleneck. Pantone Live is a cloud-based color service that stores the entire spectrum of data in a "cloud" based on security, providing even access to the brand's color standards. The brand color standard is a major part of Pantone Live. These color standards are derived from real inks on real substrates using a real printing process. This allows brand owners to predict how the company's proprietary colors will be reproduced on a wide variety of substrates and share them with the global packaging design and printing supply chain.