Research On Optimization And Evaluation Of Ink - Jet Printing Paper

As the information reproduction carrier, the ink-jet printing paper is crucial for the imaging quality. In the ink-jet printing adopting water-based ink, how to control the permeation and diffusion degree of ink in the paper and guaranteeing the drying rate of ink droplet and image resolution are becoming hot spots of research and modification of ink-jet printing paper coating.In this paper, paper printability requirements of ink-jet printing, interaction mechanism of coating and ink, coating characteristic and influence of coating parameters on the coating and printing quality are discussed in theory, influence of pigment particle size, adhesive compounding method, category of fixing agent and its consumption on the coating quality, image quality and printability of ink-jet printing paper is studied through systematic analysis of properties of pigment, adhesive and fixing agent in the coating component of ink-jet printing paper and its printability, and the action mechanism of pore volume and hydrophilicity of coating on ink permeation and diffusion is summarized.In the engineering, the process of filling the coating surface with pigment particles is simulated by the computer simulation technology, and the screening and optimization model and method of pigment particle size proportion are established. Comprehensive assessment of performance indexes including the compounding proportion of adhesive and consumption of fixing agent is optimized by the principal component analysis and cluster analysis methods, the type, proportion, consumption, coating parameters and calendering process parameters of each component conforming to the requirements of ink-jet printability are screened out, and the optimum process conditions of ink-jet printing paper are obtained through the multi-index orthogonal experiment method.In this paper, the printability evaluation system based on the image quality is established according to the Engelfrum quality circle and image quality domain, including the color evaluation combining the density and chromaticity with the spectrum, tone evaluation based on the brightness, clarity evaluation based on the micro image and uniformity evaluation based on the frequency domain, and the printability and imaging quality of paper obtained by the orthogonal experiment optimization are verified and assessed by the evaluation system.Main research achievements and conclusions of this paper are as follows:1. Diffusion and permeation of ink on the coating determines the quality of ink-jet printing image. Diffusion and permeation are affected by physical and chemical action between the ink and coating. Physical action includes wetting phenomenon, capillarity and electrostatic adsorption, and chemical action mainly refers to ionic reaction occurring between the coating component and color generation agent of ink. Occurrence of these phenomena has great relationship with the pore volume, pore size distribution and hydrophilic property of coating and quantity of electric charge of coating component, while these three properties are determined by the pigment, adhesive and fixing agent in the coating separately.2. The coating porosity condition is mainly determined by the distribution of pigment particle size. If the pigment particle size is too large, many large pores are formed on the coating surface, and ink permeate quickly due to the action of gravity, which can easily cause dim image color; while if the pigment particle size is too small, the coating pore volume will be increased and average pore size will be reduced, and ink is absorbed under the capillary action, which can easily cause light color due to fewer pigment on the surface. Besides, too small particle size can also result in high coatings viscosity and poor dispersing property.3. Suitable particle size distribution is the key to balance the diffusion and permeation. Application of computer simulation can not only effectively simulate the pigment accumulation state, but also optimize the proportion of screened pigment particle so as to optimize the coating particle and reduce the cost.4. Two kinds of adhesives, namely polyvinyl alcohol and ethylene-vinyl acetate latex have good complementarity in terms of molecular shape, molecular size and hydrophilic property. When they are used separately, the paper printability is poorer, but when they are compounded at certain proportion, they will complement each other’s advantages so as to optimize the coating stability, paper surface strength and ink receptivity of paper and obtain better image quality.5. The fixing agent generates insoluble salt with the color generation agent through the chemical reaction or makes the color generation agent set through the attraction action of electric charge, and it has obvious chromatography action on the diffusion and permeation of ink, can slow down or prevent the diffusion and permeation degree of color generation agent along with the solvent, make more pigments or dyes gather on the coating surface, and further increase the color density and its saturation degree. Meanwhile, the fixing agent is a kind of excellent flocculant, so if too many fixing agents are used, the coating viscosity will be increased, the coating structure will change, and the coating component cannot distribute uniformly.6. Using principal component analysis and cluster analysis methods together can not only screen out the optimum result scientifically and comprehensively, but also obtain optimum category in the object classification so that single-factor experiment at the earlier stage can provide better technical support for multi-index orthogonal experiment at the later stage.