Design Of Viewing Angle Deflecting Film For LED Backlight

The main viewing angle of an LCD commonly used in daily life is the normal direction.However,in some special occasions,such as in the cockpit of airplanes,trains,and automobiles,due to the limitation of the installation space and angle of the display,there exists the difference between the main viewing angle of a display and observers,which leads to poor viewing effect and also cause a waste of light energy.In order to solve this problem,this paper proposes a method for designing the surface microstructure of the viewing angle deflection film based on extended light source.The several kinds of viewing angle deflection films with different deflection angles are designed to fulfill the various requirements on the viewing angle deflection in different applications.First,a design method based on extended light source discretization and segmented-weighted superposition is proposed,which could avoid the tedious optimization in the traditional point light source-based design process.Several kinds of the viewing angle deflection are designed and prepared to verify the the feasibility and effect of the method.In order to further increase the light transmittance of the viewing angle deflection film,an optimized design method based on compressed viewing angle is proposed.The simulation results show that the optimized viewing angle deflection film has a significant increase in light transmittance compared with the non-optimized.Aiming at the problem of large deflection angles,this paper adopts the stacking method of double-layer viewing angle deflection films and redesigns the surface microstructure of the upper deflection film to obtain with the large deflection angles of 35° and 40°.Verified by simulation,these two double-layer viewing angle deflection films can deflect the main viewing angle of the LED backlight to the target angle.Two samples of viewing angle deflection film are prepared using maskless direct writing lithography equipment.The viewing angle test is carried out.The test results show that after adding a 20° viewing angle deflection film,the vertical main viewing angle of the LED backlight deflectes from 0° to 21°,the half-brightness angle is changed from(-22.5°,25.5°)to(-11°,49°),and the light transmittance is 81.1%.After adding a 40° double-layer viewing angle deflection film,the main viewing angle is deviated from 0° to 39°,the half-brightness angle becomes(18°,60°),and the light transmittance is 66.3%,which meets the design requirements.