▎ 摘　　要

NOVELTY - Solid state thermochromic polymer film (100) comprises at least two separated solid phases, where the separated solid phases are transparent and comprise at least one phase which undergoes a crystal melting and has a reduced refractive index above a threshold temperature, becomes opaque when its temperature rises above the threshold temperature and reverts to being transparent when its temperature lowers to an ambient temperature below the threshold temperature. USE - The film is useful in a smart window (claimed). ADVANTAGE - The film: reduces the opacity; shows good modulation ability of sunlight; and is economical. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a smart window comprising the film and a transparent heater comprising a transparent conductive layer in thermal contact with the film so as to heat the film when desired, where the transparent conductive layer has a transmittance of at least 70% for at least one wavelengths lambda or all the wavelengths lambda 400-1400 nm. DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the film. Film (100) Second phase (102) First phase (104)