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To date, the orientational birefringence and the photoelastic birefringence of alternating copolymers have not been studied in detail. We focused on N-substituted maleimide (RMI) and styrene (St) as alternating copolymers and analyzed the birefringence, refractive index, and glass transition temperature (Tg) of the alternating copolymers. It was found that the photoelastic coefficient and Tg exhibit a nonlinear relationship with the composition ratio of RMI and St. It is considered that the alternating copolymerization of RMI and St confirms that the conformation is inhibited by interacting with each other. A zero–zero-birefringence polymer that exhibits no birefringence was obtained by using N-ethylmaleimide and St and adjusting the composition ratio. This polymer showed a high Tg, low haze, and a low temperature dependence of birefringence. [ABSTRACT FROM AUTHOR]

The random depolarization film (RDF), a polymer film doped with birefringent particles, converts linearly polarized light to randomly polarized light. This paper shows that a novel RDF with controlled birefringence resolves polarization problems of the display such as blackout, color change, and color mura problems. Furthermore, the novel RDF achieved a higher contrast ratio and a sharper image than a conventional RDF doped with calcite particles. [ABSTRACT FROM AUTHOR]

The intrinsic birefringence [DELTA][n.sup.0] and photoelastic coefficient C of poly(methyl methacrylate), poly(2,2,2-trifluroethyl methacrylate), poly(phenyl methacrylate), and poly(2,2,3,3,3-pentafluorophenyl methacrylate) were determined. We categorized these methacrylate polymers into four birefringence-types, even though their molecular structures differed only by the substituents on the side chains. Based on the results of [DELTA][n.sup.0] and C, novel polymers that exhibit neither orientational nor photoelastic birefringence, i.e., zero-zero-birefringence polymers, were designed and synthesized by quaternary copolymerization system. Furthermore, we confirmed that the mechanisms of orientational birefringence and photoelastic birefringence generation were different in these methacrylate polymers. The conformation of the repeat unit of the polymers was nearly constant during the generation of orientational birefringence. In contrast, the conformation of the repeat unit of the polymers changed during the generation of photoelastic birefringence in the glassy state. These findings demonstrated the reasonability of evaluating orientational and photoelastic birefringence separately, as well as the adequacy of the classification of polymers into four birefringence-types. Given these results and the fact that zero-zero-birefringence polymers could be prepared successfully by four-birefringence type monomers, we demonstrated the reasonability of the method for designing the zero-zero-birefringence polymers., INTRODUCTION Optical polymers have been used as key materials in various devices such as optical disks, lenses, and functional films for liquid crystal displays (LCDs) because of their light weight, [...]