1. The light fastness of screen printing ink
Light fastness refers to a property of the color stability of ink printing under sunlight. It depends on the light resistance of the pigment, the thickness of the ink layer, the properties of the binder and the filler, etc. Packaging printing and outdoor advertisements have very high requirements on the light fastness of inks. Outdoor advertisements usually require 3~5a (years) without significant change in the color of the printed product. Exposure to light causes chemical (such as oxidation or reduction) reactions and physical (crystalline) changes in the pigment, causing the pigment to darken, lighten or even fade away completely.
Second, the chemical resistance of screen printing ink
The ink's ability to resist water, acid, alkali and solvents is collectively referred to as chemical resistance. Its measurement standards and methods should start from the application target. Soaking method and wet wiping method are commonly used in the past.
The soaking method is to soak the dried printed matter in selected water, acid, alkali and solvent, take it out after a certain period of time, and compare the change degree of the printed matter before and after soaking.
The wet wiping method is to soak the selected cloth with the solution, and then wipe the dried printed matter back and forth several times (50-100 times), and then compare the difference between the printed matter before and after wet wiping.
