Analysis of Window Film Optical Properties
The optical properties of automotive window film mainly depend on four parameters: visible light transmittance, infrared transmittance, total solar energy absorption rate and total solar energy rejection rate. In order to analyze these four parameters, we need a professional solar transmission meter to test the window film.
The total energy rejection (Tser) of the sun reflects the total energy that is reflected off the daylight spectrum. The reflected light include visible light, far infrared rays and ultraviolet light. Higher total solar energy rejection does not necessarily mean only efficient reflection of heat, as it may also reflect visible light "effectively". Thus, the total energy of the darker window film is often better than that of the lighter film. In order to ensure a good thermal reflection performance of a window film, it is necessary to investigate its infrared transmittance (IRT) or infrared reflectance (IRR). (IRR equals 100% minus IRT
Visible Light Transmission - the higher the better
For safe driving, most countries' traffic management departments require a front windshield visible light transmission (VLT) of at least 70%. The visible light transmittance of the side windows and the rear window of the car is not less than 50%. The general professional film installation center will buy a solar transmission meter, which is specifically used to detect the visible light transmittance of the window after installing the film to determine whether it meets the statutory requirements. If the visible light transmittance is too low, it will have a greater impact on the light and affect people's field of vision.
Infra Red Transmission - the lower the better
The main part of the sun's rays that cause heat buildup is infrared (IR). Infrared light can be absorbed by the internal materials and the surface of the facility, making these materials hotter. Only the lower the infrared transmittance (IRT), the less heat that penetrates the window glass.
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