At present, the color inkjet paper ink coating is basically divided into resins and pigments. Resin ink coating is mainly composed of some polymer swelling which has strong ability of absorbing ink; pigment ink coating containing special pigment, a large number of micropores in the coating, so as to realize the rapid absorption of the ink and color.
(1) selection of pigments
The specific surface area, pigment ink suction and liquid transfer amount will impact the size of the coating ink absorbency and image dot roundness, absorption coefficient and scattering coefficient of pigment will affect the optical density and bright image, so in order to meet the characteristics of color inkjet printing paper, a selection of large surface area, a large quantity of ink absorption, liquid transfer capacity, absorption coefficient and scattering coefficient of small coating pigments.
Under the same conditions, the main pigment liquid transfer amount of the order is: > > silica synthetic silicate precipitated calcium carbonate > clay, wherein the liquid silica in 0.01s transfer within the maximum amount of up to about 15mL/m2; silica, calcium carbonate, titanium dioxide is the size of the light scattering coefficient of the order is: silica calcium carbonate. < titanium dioxide; absorption coefficient of the size of the order is: > > titania silica calcium carbonate. Therefore, the comprehensive comparison, small particle size, large specific surface area, high oil absorption of silica is a more appropriate pigment.
(2) selection of adhesive
The main function of adhesive in pigment coating in addition to pigment coating substrate bonding on the outside, but also on the paint viscosity, rheology, release plays an important role in water and curing time of coating adhesive properties, the content and distribution of optical properties of color inkjet paper and ink absorption effect on the great.
At present, color inkjet printing paper adhesive commonly used with starch, polyvinyl alcohol (PVA), ethylene vinyl acetate copolymer (EVA), carboxymethyl cellulose (CMC) and styrene butadiene latex, acrylate latex, polyvinyl pyrrolidone (PVP) etc.. The PVA has the advantages of strong adhesive force, high transparency, crosslinked water resistance, good compatibility, but also can be used as a carrier coating stabilizer, fluorescent whitening agent, in the modulation of inkjet paper coating is preferred. In addition, in the actual production, in order to avoid due to the increase of solid content coating caused by paint viscosity increased sharply, influence of coating rheology, should use can be partially hydrolyzed (degree of hydrolysis was 87% ~ 89%), the relative molecular mass is low, low or moderate levels of PVA.
(3) selection of adjuvant
In order to further improve the printing performance and other physical properties of color inkjet printing paper, some auxiliary agents should be added to the coating. The common auxiliary agents are dispersing agent, defoaming agent, water proofing agent, ultraviolet absorbent and anti-aging agent.