Vacuum coating due to radiation-curable coatings green and high efficiency, makes the technology in the world gained widespread attention and rapid growth, its applications more widely. UV coating layer having excellent surface smoothness, is suitable as a primer for the vacuum metal coating technology, available very bright metal appearance on the plastic substrate.
With the development of the automobile industry, many metal replacement technology has been applied, the current car headlight reflector applications, has been fully adopted in the PC, BMC and other plastic surface by vacuum metallized to increase the reflection effect for this area the UV coating requires a good leveling, high temperature resistance (for PC substrates require more than 120 ℃, BMC substrates up to 180 ℃)....
In the design of PC reflector headlights when using UV primer, pay attention to increase the crosslink density coating the coating to ensure a good closure, by adjusting the ratio of reactive diluent formulations to the coating and the substrate, adhesion between the coating and the coating to achieve the best, the complex structure of the workpiece, pay special attention to ensure that the site is not sufficient UV radiation can be completely cured. The main reason for the vacuum coating UV primer requirements before vacuum coating to a plastic substrate surface UV coating has the following two points:
First, when the base is closed by UV coating, vacuum coating, or prevent the use of the escape of volatile impurities in the substrate workpiece, affect coating quality. Like when the lamp reflector applications, due to the use of the process temperature rises above 100 ℃, if volatile impurities in the substrate will release the aluminum layer hair color, color, affect the reflection effect. Figure 1 (omitted) for the DSC curve PC plastic, this figure shows the PC when the substrate has a temperature of about 90 ℃ significant heat flux, may be considered material to release a glass transition temperature Tg of about 140 ℃, the material use temperature should be below this temperature.
Second, to improve the flatness of the substrate surface, ensure the coating mirror effect. Generally plastic surface roughness 0.51nn around itself, vacuum coating thickness does not exceed 0.2μm, was unable to fill the uneven surface of the substrate, are not ideal mirror effect, UV coating thickness of 10-20μm, surface flatness 0.1μm or less, you can fill the substrate coating defects and get the desired effect. For PC material headlight reflector of UV coating must have the following basic characteristics:
(1) leveling state is good, bright paint film, so you can make sure that there is a complete vacuum coating of reflective film.
(2) coating with seal action, ensures the escape of PC substrate does not affect the coating composition at 120 ℃ time.
(3) the coating itself has a certain heat resistance, 120 ℃ will not have material effect on the decomposition release coating.
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