Study On Structure-Activity Relationship Of Paper Coating Structure And Digital Printing Quality Of Ink Jet

Due to the advantages of variable data printing,suitable for small batch and multi batch of social demand,and lower inventory,digital inkjet printing maintain high speed growth.At the beginning,the paper analyzes various samples of printing quality defects which are produced in the process of production on Shaoxing Hucai HP T350 inkjet printer.At the same time,it also summarized the main quality defects of inkjet digital printing and proposed countermeasures.Compared with offset printing,digital printing inkjet that use a spot of pigment content and low viscosity of water-based ink lack of imprinting process,which can produce the low ink drying rate and the poor printing color reproducibility that limit the quality of inkjet digital printing and industrial development.In this study,inkjet digital printing commonly builds porous coating on surface of offset paper and coated paper.The coating has the pore size distribution and porosity,which can control the infiltration-spreading rate and the amount of infiltration-spread to solve the ink slow drying rate and poor print color reproducibility problems.The paper selects the spherical coating solution with diameter of100 nm and the uniform size.Besides,the different weights of ordinary offset paper and copperplate paper are chosen to surface coating.The results showed that: the light type of offset paper changed from macro pore to 20μm pore size,the surface porosity decreased from 50% to30%,the smoothness increased from 4s to 10 s,the glossiness increased from 1 ° to 3 °;pore size of high white offset paper changed from 10μm to 180 nm,the surface porosity decreased from 37% to 17%,smoothness increased from 35 s to 50 s,glossiness increased from 2 ° to4 °;copperplate paper surface without macro pores,which the porosityof small pores increased from 19% to 29%,the smoothness decreased from 166 s to 142 s,and the glossiness decreased from 46 ° to 30 °.After coating,there are a large number of small pore size that can form appropriate roughness on surface of offset paper,which make the offset paper from hydrophobic into hydrophilic,The water contact angle of light offset paper decreased from 120 ° to about 88 °,and the contact angle of high white offset paper decreased from 114 ° to 85 °.After coating the pore size of new distribution pore and surface roughness changed the wet state,the water contact angle of copperplate paper increased about10 ° than uncoated.Therefore,contact angle of digital printing paper surface should be controlled at between 70 ° ~ 88 °.The wetting process of the ink on the surface of the coated paper and the imbibition process of some of the binders in the capillary of the coating were analyzed with the classical wetting model and the empirical equation of the imbibition.The results show that the adhesion of ink on the surface of the paper relies mainly on free imbibition of capillary,and speed of free imbibition from fast to slow down,which can be described by the classical Lucas-Washburn imbibition model.Therefore,reducing the capillary aperture in the coating and increasing the wall roughness can increase the rate of imbibition.The wetting behavior of the ink on the coated paper surface conforms to the description of Wenzel model and the Cassie wetting condition should be minimized.In addition to the pore size distribution and porosity of the coating,the surface roughness of the coating and the roughness of the inner wall of the pores are essential to the wetting of the ink on the surface of the paper and the rate of penetration of part of the binder in the coating micro pores to the ink Important.Through the control of the imbibition rate,the lateral spreading rate and spreading amount of the ink are also controlled.The results of color reproducibility test showed that the range of lightness L * high-white offset paper coating becomes larger aftercoated;After the light offset paper coating,the M chromaticity and the K color chromaticity have a wide range of variation,which can make the corresponding M color and K color saturation larger and brightly colored.After coating,the variation of the lightness L * of the copperplate paper is small.When output yellow and black,graphics and textures on copperplate paper is bright,besides the saturation is higher.Therefore,it is helpful to improve the quality of inkjet digital printing by constructing porous coating,which can improve the permeability and permeability of ink.