Broadband reflection and infrared shielding characterisation of cholesteric liquid crystals doped with UV–absorbing layer

Cholesteric liquid crystals (CLCs) are widely used in the field of infrared (IR) modulation as a chiral photonic material with wavelength and polarisation selective reflection. However, there is ongoing interest in discovering a simpler method to harness liquid crystal materials for IR shielding. In this study, a CLC-based IR reflector was prepared. Broadband reflection of CLC was achieved by spin-coating a layer of PMMA-UV8080 to generate a vertical intensity gradient of UV light. By optimising the concentration of the UV absorber, UV intensity, and temperature during the polymerisation process, the reflective bandwidth in the NIR band at 1656 nm is 554 nm. It was found that the temperature difference between the CLC reflector covered with 3% R811 and covered with a blank liquid crystal cassette under IR light irradiation was 5.7 °C. Additionally, the temperature difference between the surface of the blank liquid crystal cell and the CLC reflector under IR thermography after irradiation for 40 min under an IR therapeutic apparatus was 3 °C. Furthermore, the UV shielding efficiency of the prepared CLC reflector reached 99.2%. Both these findings, coupled with the simplicity of the preparation, suggest that the prepared CLC reflectors hold great promise for future applications.