Dual-Functional Transparent Projection Film with Privacy Protection via Cholesteric Liquid Crystal Polymer Networks

Transparent projection screens are widely used across various industries for applications that require overlaying digital content onto real-world environments while maintaining high transparency. However, existing technologies face challenges in balancing transparency, projection quality, and privacy protection. In this work, a novel transparent projection screen is  based on cholesteric liquid crystal (CLC) polymer networks is developed. The CLC networks are designed and fabricated to have a small birefringence to achieve a narrow bandwidth. This allows a selective reflection of designed colors for full-color projection, while allowing other light to transmit. The CLC films, designed with multi-layer CLC networks, selectively reflect red, green, and blue light to achieve high-quality full-color projection while maintaining transparency. The tri-layer CLC film demonstrates an average transparency of 70.2% and a color gamut covering 112% of the sRGB standard, ensuring vibrant and accurate color reproduction. To incorporate privacy protection, a hexa-layer CLC structure is developed, reflecting ≈100% of RGB light and preventing interior light from escaping, while still allowing ambient outdoor light to pass through. This dual functionality highlights the potential of CLC-based transparent projection films for applications in secure communication, immersive displays, and advanced visual technologies where both transparency and privacy are essential.