Physical and chemical properties and technical indicators of paper, including physical performance indicators, optical performance indicators, printing performance indicators, and chemical performance indicators.
Among them offset printing is closely related to:
Compactness, tensile strength, elasticity, whiteness, absorbability, smoothness, glossiness, pH value, etc.
Paper compactness and anti-pull strength value, a printing process in compression separation, ink viscosity, and rubber blanket surface moisture produced by the adhesive force, will produce hair, and powder phenomenon, resulting in burrs on the printed matter spot or field white failure.
The flexibility of the paper with the direction of the fiber arrangement, filament (along the wire) direction of the expansion rate is less than the fiber arrangement on both sides of the direction of the expansion rate, so offset printing in the direction of the filament with the drum axis parallel to the paper for printing, in order to minimize the wet elongation of the paper caused by the image overprint.
The whiteness and smoothness of the paper, related to the printed image of the degree of color and saturation, high whiteness of the paper printed with color ink, the light projected on the paper is less absorbed by the paper, more reflection, so it can better present the original appearance of ink color.
The whiteness of the paper has ash, absorption projection light more, less reflected light, and print image gray. Poor smoothness of the paper surface rough, oil absorption, print dry after luster, projected light is absorbed more and reflected light diffuse reflection, the print visual effect is poor, color gray not bright.
Oil-absorbing paper before the impression has not dried conjunctiva, a lot of ink in the absorption of ink linker, resulting in the impression surface conjunctiva rough, the product is not. In severe cases, there will be blotting failure.
General paper pH value, in 5 above, is slightly acidic, when the pH value falls below 5, the paper acidity increases, this paper can destroy the drying of the ink, imprinting non-failure.