Zhen-Xin Zhong

Liquid crystal photoalignment material based on chloromethylated polyimide

We report a liquid crystal photoalignment material with high photosensitivity and excellent thermal stability. The chloromethylated aromatic polyimide exhibited defect-free homogeneous alignment of liquid crystals upon irradiation of polarized deep ultraviolet (UV) for 50s. The aligning ability of the film was retained up to 210°C, and the cell containing liquid crystals could be stored at 85°C for more than 14 days without any deterioration. FT-IR and UV–vis spectra confirmed that the alignment was induced by photodecomposition of polyimide, drastically accelerated by the introduction of chloromethyl side group.

Liquid crystal photoalignment using soluble photosensitive polyimide

A novel soluble fluorinated polyimide containing a photosensitive chalcone unit in the main chain was investigated as a thermally stable photoalignment material for liquid crystals. A defect-free homogeneous alignment of liquid crystals was induced on the surface of a polymer film after exposure to linearly polarized UV light at an exposure energy of 7200 mJ/cm2. Spectroscopic analyses revealed that [2+2] cycloadditon between the chalcone moieties generated the surface anisotropy needed to induce an efficient alignment of liquid crystals.

Liquid-crystal photoalignment by photosensitive fluorinated poly(arylene ether)

We report a liquid-crystal (LC) photoalignment material with a high photosensitivity based on the fluorinated poly(arylene ether) containing a chalcone unit in the main chain. The fluorinated poly(arylene ether) exhibited defect-free homogeneous alignment of LCs upon irradiation of linearly polarized UV light for 10s. Spectroscopic analyses revealed that [2+2] cycloaddition between the chalcone moieties generated the surface anisotropy to induce an efficient alignment of LCs.

Novel Liquid Crystal Photoalignment System Based on New Soluble Polyimide

Novel liquid crystals(LCs)photoalignment system, which exhibits outstanding photosensitivity and excellent thermal stability, has been developed based on new soluble polyimide. Homogeneous alignment of liquid crystals(LCs)was induced by soluble polyimide(CMPI)having chloromethyl side groups upon irradiation of linearly polarized UV light(LPUVL)with short irradiation time. The photoaligned film was thermally stable without destroying LC alignment when LC cell was stored at 85°C for 14 days. The pretilt angle of LC decreased with irradiation time, which is contributed by the increased polar surface energy of CMPI film after irradiation of LPUVL. FT-IR spectra confirmed that the photosensitivity of polyimide was improved greatly by introducing chloromethyl group and the alignment of LC was contribute by the photo-decomposition of polyimide main chain upon irradiation.

Zero-birefringence photosensitive poly(arylene ether) for optical waveguides

Novel photosensitive fluorinated poly(arylene ether) containing chalcone unit (F-PAECh) in the main chain was synthesized from decafluorinated chalcone and fluorinated bisphenol at low temperature for polymer optical waveguide application. Upon UV irradiation on the resulting polymer film, [2+2] cycloaddition of chalocone moiety induced the anisotropic decrease of the refractive indices (nTE and nTM) accompanied with crosslinking of polymer film. The decrease was more significant in in-plane direction than out-of-plane direction, and consequently, zero birefringence was obtained with 4.5 min of exposure. Zero-birefringence as well as its excellent optical properties of F-PAECh makes it a promising candidate material for use in high-performance wavelength division multiplexing components such as polarization-independent arrayed waveguide gratings and Bragg wavelength filters.

A Study on Electro-optical Characteristics Dependent on Surface Anchoring Energy in the Fringe-field Switching Mode

Liquid crystal (LC) alignment using a photoalignment method by irradiation of polarized ultraviolet (UV) on an alignment layer has been investigated. Photoalignment method exhibits weaker anchoring energy than rubbing method so that we have studied electro-optic characteristics of fringe-field switching (FFS) mode with alignment layers using the photo and rubbing alignment methods. The cell using photo alignment layer shows lower threshold and operation voltage than those using rubbed alignment layer. Also, the former method shows higher transmittance than that of the latter.

40.4: New Photoalignment Polymeric Materials with Excellent Photosensitivity and Stability

Novel soluble photoalignment materials with high photosensitivity and good thermal stability were synthesized by chloromethylation of 6FDA-ODA polyimide, and their photoalignment properties were investigated. The photosensitivity of 6FDA-ODA polyimide was improved greatly by the introduction of chloromethyl side group. The ECB LC cell made with photoaligned films could be stored at 85°C. for at least 14 days without deteriorating LC alignment. The irradiation of polarized UV light on the polymer surface induced thermally stable alignment of LC due to the surface anisotropy caused by photodecomposition of polyimide main chain.