Concentric dot is a new shape of ink dot, which subdivides dot of AM screening into ring and space. Concentric dot has morphological characteristics and reproduction characteristics of AM dots and FM dots, also has excellent color reproduction characteristics. Compared with traditional solid dot, high saturation of concentric dot has been proven. However, the mechanism of this phenomenon is rarely reported. Taking AM dots as reference, this paper try to explain the high saturation of concentric dot theoretically from several aspects, and aims to reveal the mechanism of the color reproduction characteristics of concentric dots. Due to the low amount of ink, the surface of concentric dots is smoother, and achieves better reproduction of color. The distribution characteristics of ring and space result in dot gain both inside and outside of concentric dots, which have a positive impact on the color reproduction. Establishing the relationship of optical dot area and saturation, the difference of color reproduction characteristics between concentric dots and AM dots can be analyzed as the result of the different microstructure of two dots. Using the improved Clapper-Yule model and the law of Lambert-Beer, the conclusion above can be analyzed theoretically. On this basis, experiments are designed and carried out to prove the correctness of theoretical analysis. According to the research, several conclusions are made. The conclusions can be list as follow: different saturations of concentric dots and AM dots lead to different color reproduction, when optical dot area stays the same; different saturations of concentric dots and AM dots is mainly caused by the microstructures of the tow dots; Under the same condition of incident light, concentric dots of monochrome ink reflect more of the visible spectrum than AM dots after absorption, which reasonably explains the high saturation of concentric dots. The study is to reveal the principle of color reproduction of concentric dots with high saturation, providing a theoretical basis for the application of concentric screening technology.
“Water-in-water” emulsions of hydrophobically associating cationic polyacrylamide (HACPAM) with both cationic groups (methacrylatoethyl trimethyl ammonium chloride, DMC) and hydrophobic groups (n-butyl acrylate, BA) were synthesized by dispersion polymerization. The structure of the copolymer was confirmed by FTIR and 1HNMR. The prepared “water-in-water” emulsions possessed high solid content, low viscosity, good stability and solubility. An image analyzer photographed the size of the emulsion particles. The polymerization behaviors with varying concentrations of acrylamide, DMC, BA, stabilizer and reaction time were investigated. Appropriate concentrations of monomer, BA and DMC for stable dispersion system were in the scope of 10~15 wt%, 0.025 ~ 0.15 wt% and 1~ 4 wt%, respectively. The dynamic drainage experiment results show that the HACPAM “water-in-water” emulsions can be directly used as retention aid and obviously improve the retention efficiency of bleached broad-leaved pulp.
Concentric dot is formed by dividing round AM dot into thin concentric rings, which has not only the shape characteristic of AM and FM dots, but also the features and advantages of the two dots. The Concentric Screening is a new halftone screening technology which breaks through the traditional model of reproduction image information by solid dot. To use concentric screening technology in offset printing, the first step is running single color print test to determine concentric screening parameters for the given printing condition. which is unique to concentric screening compare with solid dot printing. Through analyzing and evaluating the printing characteristics of single color print test, the paper provides the method to determine screening parameters such as screening rulings、CTP precision、the width of Ring and Space; Designing and running the four color test based on the first step is aimed to study the reproduction characteristic of concentric dot about gamut、definition、chroma, tone, compared with solid dot. The research shows that the parameters of concentric screening should be determined according to the specific production condition in offset printing. Concentric screening can obtain high saturation and present large color gamut. Also, concentric screening is suitable for high-quality products, which can accept high screen rulings and high-definition. This paper contains experimental study on the correlation between concentric screening parameters and color reproduction. The basis for evaluating concentric screening parameters is offered, and a comprehensive evaluation of its reproduction characteristics is done. This study provides a theoretical basis for the application of the concentric screening technology in offset printing.
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