At present, the detection technology of color box printing quality mainly has two kinds of density mode and color mode . Among them, the density mode is a process control mode that controls the key aspects of the printing production process according to the thickness of the ink layer. The chromaticity mode is a high-precision system control mode that performs color control based on visual measurements of chromaticity or spectroscopic spectroscopy, but requires a combination of printed materials, application environments, and testing purposes. In the implementation manner, either the manual sampling offline mode or the automatic detection online mode may be adopted.
1. Detection and control of printing quality of special materials
In the color box packaging, the application and innovation of special materials and new materials is a trend, such as the development of cigarette packets from paper soft packs and cardboard hard packs to aluminum foil gold and silver cardboard hard packs. These high-gloss surface composite or coating materials have metallic luster and refractive surface. After printing beautiful patterns of various colors, they give people a sense of high-grade elegance, which can greatly enhance the product value-added space, and are widely used in high-end color boxes.
Such high-gloss surface materials have a strong metallic luster due to the flat coating of the surface, and strong specular reflection occurs when the incident light is irradiated. Therefore, the color appearance of the surface of the object changes with the change of the viewing angle, which leads to the color control in the printing production process is not easy to control, so that the printing factory faces the same ink color of the same batch of printed products and even different batches of printed products. Quality control problems and their special testing technical requirements.
In addition to the four-color printing color map, the color box printed by special materials has many spot colors and anti-counterfeiting techniques, and its detection contents include density, dot enlargement, registration and gloss. Due to the restriction of the surface gloss of special materials, in the measurement of density and dot, it is necessary to use the test instrument that uses d/0 to measure the optical geometry. It is best to divide the visible light 400-700 nm band into 31 measurement intervals according to the principle of splitting, and measure the object. The spectral reflectance of the color spectrum, which in turn leads to a spectroscopic spectrometer with color CIELab values and chromatic aberrations, such as the SP series of X-Rite. Thereby, the accuracy and reliability of the measurement data of the high gloss surface material are ensured. Measuring instruments used in the geometrical conditions of ordinary materials 0/45, such as the X-Rite 900 series, are unable to achieve consistent and accurate results.
2. Detection and control of spot color printing quality
In the printing of color box packaging products, because the spot color printing has a large area of solid color blocks, the color is dazzling, the shelf display effect is good; the color difference caused by the dot overprinting and the dot deformation is reduced, the color is stable, and the identification is easy, so a large number of special Color printing is its basic feature. At present, domestic color box printing enterprises are relatively backward in the measurement and control of spot colors, and most of them are still in the stage of relying on the experience of workers to deploy spot color inks. The ratio of spot color inks is not accurate enough, the allocation time is long, and subjective factors have a great influence. Disadvantages. Therefore, the use of color matching system is the best solution, and it is also the mainstream technology and development direction of international color box quality control and detection.
The spot color ink system is a system consisting of a computer, color matching software, spectrophotometer, analytical balance, ink level meter, ink stick meter and printability meter. The spot color ink distribution system can store the parameters of the printing material, ink and color matching data of the color box printing enterprise in the system database through testing and experiment. The color matching software can perform spectrophotometric measurement according to the spot color color sample provided by the customer, and the application computer automatically Perform color matching analysis and color matching operation, control the color matching conditions according to the CIELab value, density value, and △E of the customer sample and the color matching sample, and provide printing control parameters, so that the data of the spot color ink can be realized. For example, the Swiss GretagMacbeth ink formulation system including the hardware spectrophotometer SpectroEye and InkFormulation, the SpectroEye can not only measure the print dot, density value, but also the Hue, Saturation and Luminosity; InkFormulation only needs A precise database can be created with a small concentration of scales. Color matching data can be used for offset printing, flexo, gravure and screen printing, and can provide a variety of ink formulation sorting methods, such as hue similarity, metamerism value, spot color ink unit price, ink usage, Ink layer thickness, etc. Therefore, the application of the number has fundamentally broken through the constraints of experience color matching, to meet the development requirements of higher quality, shorter cycle and lower cost in the color box printing industry.
