It has been reported that yellow tungsten oxide film (It is more often known as tungsten trioxide film or WO3 film.) may be used as the basic material for package security label. This is mainly a package security label made by combining the characteristics of WO3 film under ultraviolet (sunlight) radiation with other technologies.
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When a consumer places such a label under sunlight, the label will change, that is, it will turn blue to verify the authenticity of the product. This is because yellow tungsten oxide film is an excellent wide band gap metal oxide semiconductor, which has special color-changing characteristics, such as electrochromic characteristics, photochromic characteristics, and gasochromic characteristics. Wherein, this package security label uses the photochromic properties of WO3. As the most studied transition material oxide for photochromism, WO3 has received much attention. It means that WO3 is popular.
