Research On The Color Measurement And Evaluation Methods Of The Printed Paper Of Aluminized

Two key points of printing quality control are color measurement and evaluation of color difference.Due to the metallic coatings of the aluminized cardboard,the appearance of printed products changes with the illumination and observation condition.It leads to uncertainty in color measurement,chromaticity evaluation and instability in the quality control of printed products.Therefore,it is very urgent and necessary to study the color measurement and color difference evaluation method of aluminum coatings under different geometric conditions for industrial production and application.In this paper,the correlation and difference of the measurement results of specular reflectors,diffuse reflectors and ordinary reflectors are analyzed under different geometric conditions.Four kinds of geometrical conditions(0°/45°,45°/0°,d/8°(SCI)and d/80(SCE))are chosen and the aluminized cardboard is used as the experimental sample substrate.Color-measuring instrument repeatability and the substrate uniformity are analyzed and evaluated,and then the relationship between different geometric conditions,reflectance data and basic color data is analyzed.The result shows that the descent order of the reflectance of the same sheet of aluminized cardboard is:SCI>SCE>45°/0°>0°/45°,and that 0°/45°,45°/0° and SCE is infeasible as the measurement condition of aluminized cardboard in computer color matching,moreover the small color difference of color sample pairs measured in different geometric conditions is very similar.On the basis of the above research,the main focus of this paper is the Color discrimination properties of aluminized cardboard under different geometric conditions.The four color centers of C?M?Y and Grey are chosen and different color samples in six color directions around the color centers are designed in the color discrimination threshold experiment.Color discrimination threshold experiment is conducted under the international standardized geometric condition for printing quality evaluation(D50,0°/45°).Relations are explored between the measurements under different geometric conditions and subjective experiment results,and the corresponding values of color discrimination thresholds are given.Meanwhile,under different geometric conditions,the comparison is made of the performance evaluation of four formulas,including CIE LAB,CIE 94,CIE DE2000 and CMC(1:1),the experiment demonstrates that the CIE LAB formula has the best performance,and its color discrimination thresholds under 0°/45°,45°/0°,d/8°(SCE)and d/8°(SCI)respectively are 1.32?1.34?1.44 and 1.24 CIE LAB units.Hopefully,these conclusions will provide helpful guidance for production.