Conventional antireflection coating by thin films of quarter-wavelength thickness is limited by material selections and these films' refractive indices. The optimal design by non-quarter-wavelength thickness is presented in this study. A multilayer thin-film model is developed by the admittance loci to show that the two-layer thin film of SiNx/SiOy at 124/87 nm and three layer of SiNx/SiNy/SiOz at 58/84/83 nm can achieve average transmittances of 94.4% and 94.9%, respectively, on polymer, glass, and silicon substrates. The optimal design is validated by plasma enhanced chemical vapor deposition of N2O/SiH4 and NH3/SiH4 to achieve the desired optical constants. Application of the antireflection coating to a 4 in. liquid crystal display demonstrates that the transmittance is over 94%, the mean luminance can be increased by 25%, and the total reflection angle increased from 41 degrees to 58 degrees.