Ink Printing Common Failure Analysis - Dirty

Dirty

In the printing process, dirtiness and stickiness are two different concepts. Dirty generally refers to dirtiness in non-graphic areas, including blurred imprints, and even dot joints. Dirty can be divided into floating and dirty oils.

Float dirty

Dirty refers to the appearance of light-colored stains in the non-graphical area or the graphic and text blurring in the graphic area, and it is easier to wipe off dirt.

1) Cause

1Because the ink is soft and the water resistance is not strong, some of the ink will be emulsified after being affected by the fountain solution, and enter the fountain solution through the circulation system to form an oil-in-water emulsion; 2 Chemicals and wetting agents in the paper Encourage the ink emulsification; 3 some fountain solution contains soaps, detergents and other substances, but also cause ink emulsification.

2) Solution

1 Replace with a slightly higher viscosity, good water resistance, difficult to emulsify the ink; or in the original ink to add high viscosity varnish; 2 replace the paper used; 3 adjust the amount of fountain solution to ensure the appropriate conductivity and pH value.

2. Dirty oil

Dirty oil means that the non-graphic area of ​​the printing plate has a fat-sensitive property, which causes the blank area of ​​the printing plate to become inked and stains the printed matter.

1) Cause

1The ink is too thin and soft; 2The ink is supplied for a long time during printing, and the amount of ink is too large; 3The free fatty acids and surfactants with higher concentration exist in the ink; 4The influence of the treatment agent in the pigment; And the pressure of the blanket is too large or the ageing of the printing roller and the blanket deteriorates the surface structure of the printing plate; 6 Dissolve the fat-sensitive substance from the paper coating.

2) Solution

1 Replace the ink or add high viscosity resin oil to the original ink to make the ink have better viscoelasticity; 2 control the amount of ink to be printed; 3 control the amount of fountain solution; 4 adjust the pressure of the rubber roller and rubber blanket, Or replace the rubber roller, blanket; 5 replace the paper.