At present, there are mainly two methods to detect the printing quality of packaging box: density method and chroma method.
In the middle, density mode is a process control mode, which controls the key steps of the printing production process according to the ink layer thickness. Chroma mode is a high-precision system control mode, which controls the color according to the direct measurement of chroma or spectroscopic spectrum, but it is necessary to consider the printing data, application environment and test purpose comprehensively. In the way of realization, we can use either the off-line way of manual sampling or the on-line way of automatic detection.
In the gift box packaging, the use of special materials and new materials is a trend, such as the development of cigarette package from paper soft package, cardboard hard package to aluminum foil gold and silver cardboard hard package. These composite or coating materials with high gloss surface have metallic luster and refraction surface. After printing delicate pictures of various colors, they give people a feeling of high-grade elegance and can greatly promote the value-added space of commodities. They are widely used in high-grade color boxes.
This kind of material with high gloss surface has a strong metallic luster due to its steep surface coating. When the incident light shines, it will have a strong specular reflection. Therefore, the color surface of the object surface will change with the change of the investigation point of view, which makes the color in the printing production process difficult to control, so that the printing factory is faced with the common quality control problem of ensuring the same batch of prints, or even different batches of prints, and the request for special detection skills.
Except for the four-color color printing, there are many spot color and anti-counterfeiting technologies for the color box printed with special materials. The detection content includes density, dot expansion, registration and gloss. Because of the restriction of the surface gloss of the special material, it is necessary to use the measuring instrument of D / 0 to measure the optical conditions in the measurement of density and dot. The best choice is to divide the visible light band of 400-700nm into 31 measuring distances and measure the spectral reflectance of the object's color according to the principle of light splitting. Then we can get the color CIELAB value and the color difference spectrometer, such as the SP series of X-Rite. Then, ensure the accuracy and reliability of the measurement data of high gloss surface materials. Several measuring instruments, such as X-Rite 900 series, which are used in 0 / 45 of general materials, are unable to achieve common and accurate functions.