Finger-Temperature-Detecting Liquid Crystal Composite Film for Anti-Counterfeiting Labels

• Main Authors: Yanzi Gao, Ke Feng, Jin Zhang, Lanying Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Molecules
• Subjects: liquid crystal; anti-fake; cholesteric phase; side-chain liquid crystal polymers
• Online Access: https://www.mdpi.com/1420-3049/25/3/521

The development of the economy has increased the demand for anti-counterfeiting technologies, and with the traditional ones becoming known to the public, new and more effective ones are needed. In this study, a series of liquid crystal mixtures containing side-chain liquid crystal polymers and small-molecular-weight liquid crystals (LCs) were designed and prepared. The phase transition behavior and self-assembling structures of the LC mixtures were investigated by a combination of differential scanning calorimetry, polarized optical microscopy, and small-angle X-ray diffraction. The optical properties of the mixture film were characterized with a UV/VIS/IR spectrum study. The results reveal that the obtained film exhibited different optical modes between transparent, scattering, and selective reflection under finger-temperature control. Therefore, by the introduction of a coexisting thermal- or optical-polymer-dispersed network, a liquid crystal composite film with an integration of apparent optical switching modes and enhanced strength and toughness was successfully demonstrated. This research provides a versatile strategy for the design and preparation of liquid crystal anti-counterfeiting materials for practical use. In this study, a prototype finger-temperature-detecting anti-counterfeiting label was prepared, and its temperature-response property was demonstrated.