Relation between Wavelength Dispersion of Refractive Index and Birefringence of Polymers Estimated by Quantum Chemical Calculation and Chemical Structure

Recently, optical polymers come to be used for various optical applications such as pick-up lenses in optical disk drives, retardation films used in color liquid crystal displays, and so on. Therefore, not only the value of refractive index and birefringence at one wavelength of light but also the dispersion of them has to be controlled. In this study, the wavelength dispersion of the refractive index and birefringence of several polymers are estimated by using quantum chemical calculations. Moreover, benzene, cyclohexane and n-hexane are used as model compounds of the polymers to establish a relation between chemical structure and dispersion. As a result, it was found that the wavelength dispersion of birefringence took a larger or equal value than that of the refractive index because birefringence is the difference of refractive indices in two orthogonal directions. Therefore, when the polarization anisotropy of a molecule is big, the birefringence dispersion also becomes big.