Mitsuru Ishibashi

Analysis of rubbed polyimide films by polarized infrared spectroscopy : Effects of immersion in organic solvents

We applied polarized infrared (IR) spectroscopy to the analysis of rubbed polyimide (PI) films and evaluated the PI orientation induced by rubbing by measuring the dichroic difference. The IR dichroic difference and liquid crystal (LC) alignment were analyzed for rubbed PI films that were immersed in various organic solvents. The solvents which reduced the dichroic difference and pretilt angle of LC molecules could be characterized in terms of their solubility parameters. When the dichroic difference of the PI films was greatly reduced by the immersion in the solvents, a correlation between the LC pretilt angle and the dichroic difference (i.e. the in-plane orientation of the PI molecules) was observed.

Two-Dimensional Infrared Spectroscopy of Electric-Field-Induced Reorientation Dynamics of a Mixed Nematic Liquid Crystal

A two-dimensional infrared (2D IR) spectrometer has been modified by the following methods to solve several problems on the 2D IR spectroscopy of electric-field-induced reorientation dynamics of a mixed nematic liquid crystal: (1) The response of the liquid crystal (LC) to an electric field was stabilized by an amplitude-modulated ac electric field. (2) Formulation of an anti-reflection coating (ARC) has been proposed to suppress the interference caused by multiple reflections between IR liquid crystal cell windows. (3) The Fourier transform procedure has been modified to correct the phase of the dynamic difference interferograms without spectral anomalies. These modifications can provide a better signal-to-noise ratio and reproducible 2D IR spectrum of a mixed nematic liquid crystal.

Analysis of Rubbed Polyimide Films by Polarized Infrared Spectroscopy

Abstract Polarized infrared spectroscopy was applied to the analysis of rubbed polyimide films. N2 purge of a sample chamber and increased substrate thickness enhanced the detection sensitivity. Dichroic differences were measured for the rubbed polyimide films at varied translating speed of the rubbing roller and at varied substrate temperature. The results suggest that the orientation of the polyimide was enhanced by increased polyimide surface temperature brought about by the heat of friction or the external heat. Moreover, a correlation between the LC alignment and the orientation of the polyimide chains was revealed by the analysis of the dichroic difference of the rubbed polyimide films immersed in organic solvents and the LC alignment on the films.

Photocurable Inkjet Ink for Printing on Metallic and Plastic Substrates

A novel vinyl ether monomer was employed to improve curing properties of photocurable inkjet ink. A cationic polymerization system was used and the improved curing properties using a novel hybrid vinyl ether monomer with cyclic ether compounds were demonstrated. The cured UV ink film showed good adhesion on metallic substrates such as stainless steel, copper, aluminum and also plastic substrates. The stability of pigment dispersion in the ink was improved by controlling zeta-potential of the ink. The higher zeta-potential value resulted in stable particle size of the pigment and viscosity of the ink.