This study utilizes a tweeter to provide a source of harmonic vibration for use in the noncontact excitation method. Sound is transmitted through air to generate a resonance mode shape in optical diffuser films. The amplitude fluctuation electronic pattern speckle interferometry is adopted to capture the image of resonance mode shapes and corresponding natural frequencies of the optical diffuser films. Furthermore, the density of the optical diffuser films is measured using a pycnometer, and the Young's modulus of the films is determined using a micro-tension and a compression testing system. The Poisson's ratio of the optical diffuser film is thereby determined from the data on the first six natural frequencies of the diffuser film, its density, and its Young's modulus. The finite element method is employed to compare the experimental data on the natural frequencies of the films. Finally, optical diffuser film is measured in a high temperature, high humidity environment to elucidate this environment's effects on the mechanical properties of the films. Experimental results reveal that the Young's modulus of the optical diffuser films declines as the temperature increases accompanying warps and winkles. The optical diffuser films under high humidity and develop more air bubbles inside the films. The detection of luminance of diffuser films is discussed. Applications of these combined methods to experimental data are demonstrated.
The optical diffuser films have the excellently optical properties, but the mechanical properties are very important information. Especially, the more lamps used to enhance brightness in direct type backlight unit let more heating to be created. This side thermal effect makes optical diffuser films to occur warps and wrinkles via thermal stress and it leads to poor uniform performance in brightness. Therefore, the mechanical properties of optical diffuser films are the significant parameters for design. advantages on the mechanical properties are determined by evaluation the optical diffuser films.
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