The Correlation Analysis of the Interrelation between the Surface Optical Characteristics of Protected Paper and Characteristics of Imprints

Abstract

Done correlation analysis of interconnection between the characteristics of protected against forgery paper (roughness parameters and fractal dimension) and optical characteristics of imprints (optical density, color difference), which enabled the prediction of the optical characteristics of impressions and taking into account the differences of optical characteristics in watermark areas and outside them. In this work experimental data of researches physical and technical characteristics, parameters of roughness and fractal dimension of samples of a banknote paper, and also characteristics of the protected paper with water signs are used. The relationship between the characteristics of the surface of the paper and the quality of the optical characteristics of the imprints is best observed when constructing graphical relationships between the relevant indicators. Dependence is established for each banknote paper sample. The calculation of quadratic deviations of experimental data showed a correlation between the characteristics of the surface of the paper and the parameters of optical density (D). Graphic dependencies are approximated by regressive equations with the definition of correlation coefficients. On the basis of the analysis of the obtained results and regression equations, interconnection of the characteristics of the surface of the banknote paper, the ink, the amount of ink on the imprint, which correlates with the optical characteristics, allows us to establish control and quality control. It was found that with increasing values of Ra there is a decrease in the optical density of the imprint and an increase in the optical density of its back (ie, interlacing). With an increase in the optical density of the paper to the lumen, an increase in the optical density of the imprint and a decrease in the optical density of the back of the imprint is observed. There is a tendency to increase the optical density of the imprint and decrease the optical density of the back of the imprint with the increase in the thickness of the paper. The obtained experimental data confirmed theoretical calculations. The error between the experimental data and theoretical calculations is 5–10 %. The advantage of this work is that, under the conditions of multi-series production of banknote products, it is possible to control the quality indices of the imprints for a larger number of materials, compared with the regulated standards.

Keywords

• кореляційний аналіз
• банкнотний папір
• водяний знак
• шорсткість паперу
• оптична густина