When purchasing UV ink by observing the color of ink, we should "look at the colour and look at the colour". UV ink is sensitive to ultraviolet light. If the constructed UV ink continues to be exposed to ultraviolet light (such as sunlight and fluorescent lamp), the UV ink will continue to react and turn yellow, which is the inherent defect of the UV ink. For conventional UV ink, it can not be fundamentally improved for the time being, but the degree of yellowing of UV ink from different suppliers is different unless specific non-yellowing or ultra-white UV ink is used. For UV ink discoloration after polishing, the main reason is the ink problem. In the ink, there is