Usually, when UV printer technicians test the surface effect of patterns printed by newly developed UV inks, they will focus on the following four aspects: surface tension test, adhesion test, drying test, and ink film hardness test. Of course, according to different types of UV inks, flexibility, stretchability, viscosity, and other aspects will also be tested.
1. Surface tension test
When using a dyne pen for testing, an intermediate value should be selected as the starting point, such as 38mN/m. During the test, if the test pen wets the surface of the substrate within 2 seconds, the surface tension of the substrate is greater or just the selected value, then a larger value test pen should be selected for the second test, and so on, until the test result shrinks into water droplets (spherical) within 2 seconds, then the value before this test is regarded as the surface energy of the substrate. And use this for comparative analysis.
2. Adhesion test
This test mainly measures the adhesion between the ink and the printed material. 3M 610 tape is used as the main testing tool.
3. Dryness test
The degree of drying of the ink has a great impact on whether post-processing can be carried out. Since UV printing does not belong to surface penetration drying, if it is not completely dry, its scratch resistance and friction resistance will not be ideal. In terms of ink drying, the quality of drying will be greatly affected by the opacity of the ink, in addition to the following factors. The higher the opacity of the ink, the worse its drying.
The factors that affect drying are as follows：
(1) The thickness of UV ink.
(2) Different types of printed materials.
(3) The speed of the machine.
(4) The type of UV reflector.
(5) The intensity of the UV lamp.
4. Ink film hardness test
A certain mass (1kg load) of weight is added to the pencil as the probe. The hardness of the pencil decreases from 6H to 6B. After calibrating the level, the pencil with a flat end is at a 45° angle to the measured surface. The pencil moves at a speed of 1mm/s. Several marks are scratched on the surface of the sample. The length of each mark is about 8mm. The scratched sample is placed under a fluorescent desk lamp and observed with a 10x magnifying glass. The highest pencil hardness that does not scratch the coating is used to indicate the surface hardness of the film.