Diffraction grating in a holographic polymer dispersed liquid crystal based on polyurethane acrylate

Abstract

Diffraction modes of holographic grating were fabricated with polyurethane acrylates of various monomers, and with various film compositions, irradiation intensities, cell gaps and reading angles. An optimum monomer composition, LC content and irradiation intensity were obtained in terms of diffraction efficiency. Of the two types of multifunctional acrylate examined, dipentaerythritol penta‐/hexa‐acylate (DPHPA) gave better diffraction efficiency than the trimethylolpropane triacrylate (TMPTA) throughout the monomer compositions tested. This was interpreted in terms of high elasticity of the high functionality monomer. The existence of an optimum irradiation intensity at fixed resin composition was interpreted in terms of optimum rate of cure. A monotonic increases of diffraction efficiency with cell gap and interbeam angle were also noted, implying that the grating was formed uniformly as visualized by scanning electron microscopy.

Acknowledgements

This research was supported by the Korea Ministry of Science and Technology (MOST) and Ministry of Information and Communication (MIC) via IMT2000.