Packaging print color

Due to the requirements of human vision, there are color issues in many industries around us. Such as the color of the degree of color, color accuracy, color persistence and so on. These industries include printing (surfaces of paper, plastics, metals, etc.), textiles, pigment inks, paint coatings, furniture decoration, etc., involving all aspects of people's lives. And contact with the daily life of our consumers most often the most frequently printed packaging. The color detection, control and management of packaging printing has become one of the major issues that many consumer product manufacturers and packaging printing manufacturers have been concerned about.
The main factors affecting the quality of color print reproduction The main factors affecting the quality of color print reproduction are the following:
1. Ink Hue and Solid Density: The inks used in printing production have different degrees of color shift, resulting in color cast images, and the color inks with less color shift should be used for color printing. The density of solid ink on the surface of the printed image determines the reproduction range of the tone and tone of the printed image.
2. Dot enlargement: In the printing, there will always be dot gains. The dot enlargement will reduce the contrast of the image and make the whole image darker. The darker dot will become blurred. If the dots of the various colors are enlarged at the same time, the overall image will darken. When one of the dots is enlarged, the image will have a color cast.
3. Printing color sequence and overprint: Color printing inks are superimposed on one color, and overprinting requires precise registration. Misregistration can produce color deviations, color mixing, and gradation disorders. Printing color sequence has a great influence on the overprinting effect. For multi-color printing presses, the interval between printing inks of various colors is very short. When the front ink is not dry, the ink on the back has already been superimposed, and it belongs to the printing state of “wet and wet”. As long as the printing sequence of the ink is changed, the hue, brightness, and saturation after overprinting will change.
4. Ink temperature and viscosity: In printing replication, ink viscosity is a very important parameter. Studies have shown that after the printing press is turned on, the printing image produces a color deviation, and 60% is caused by the temperature change of the ink roller.
5. Offset ink balance: For offset printing, ink balance will directly affect the image copy quality. The small amount of water will make the plate dirty, paste version; water ambassador ink emulsification, so that the color saturation of the printed image is reduced.
Because of the above reasons, various problems can arise, so we must be able to find the problem in time. The quality inspection of printed matter is a necessary part.
The color detection method of printed matter is a part of the color management process. Color detection is an indispensable step, and it is also the first step of color management to perform calibration. The calibration is performed with the instrument and the data is digitized. This data must be guaranteed to be in the same measurement state. The parameter settings for measuring different colors are also the same, so that they are comparable. There are two methods for color detection:
1. Densitometer Measurement: The Densitometer is an instrument with three broadband filters. By reading the reflectance of R, G, and B in the color, the density value of C, M, and Y is calculated. Densitometer measurements cannot be used for color management, but it helps with the basic linearity of digital proofing.
2. Spectrophotometer Colorimetry: Measures the reflectance of light at each wavelength of visible light on the color surface. Visible light was irradiated on the color surface at a certain step distance (5 nm, 10 nm, 20 nm), and the reflectance was measured point by point. The spectrophotometer is a kind of flexible and ideal color measuring instrument. At present, the color measuring instruments used for printing color quality inspection in some foreign printers use the spectrophotometer.
At present, many companies that have focused on printing quality have used various types of densitometers and spectrophotometers to detect the quality of films and prints and have received very good results. Like Tetra Pak in Kunshan, although there is only one printing line, there are three Swiss GretagMacbeth density and colorimeters. With instrument detection, it is possible to avoid the effects of human eye fatigue, visual persistence, visual memory, etc. on the observation of color, so that the quality inspection can be performed objectively and accurately, which brings about the improvement of production efficiency and the improvement of production quality. The economic benefits are also very considerable. Several problems to be considered by the instrument For books and other four-color prints, GretagMacbeth's D118C Chinese display densitometer is available at a price of approximately RMB 30,000. For packaged printed products, since spot colors are often used, and the substrates are often plastics, metals, or other specialty materials, the above products are not suitable. SpectroEye or ColorEye 7000A spectrophotometers should be selected at a price of RMB 50,000. about. Large-scale full-page printing quality control systems such as Heidelberg's CPC24, CP2000, etc. are also used by many users (such as Leo packaging in Guangdong), but the price is relatively expensive, in the RMB 80-100 million. GretagMacbeth's "SpectroMat", although not on-line, is more suitable for controlling multiple presses in a large shop, and the price is only around RMB 300,000. It can detect the control strips, spot colors, and any important areas of the full-page print, and provides advice on ink volume control.
Although these tools are of great help to the control of print quality, they can help prevent the delivery of unqualified products, but they cannot solve the problem of printing color deviations at the source. How to make the printed products close to the proofs even before they are tested, so as to minimize waste loss and increase production efficiency? This is the biggest exciting challenge faced by color management. This requires the implementation of color management and control throughout the entire process from input, prepress, platemaking, and printing, prior to the detection of the color of printed matter.