Pretilt angle of liquid crystals on polyimide films photo-aligned by single oblique angle irradiation with un-polarized light

Kenji Sakamoto, Kiyoaki Usami, Toru Sasaki, Yoichi Uehara, Sukekatsu Ushioda

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We have investigated the pretilt angle of liquid crystal (LC) molecules induced by photo-aligned films of polyimide containing azobenzene in the backbone structure (Azo-PI). The photo-alignment treatment was single oblique-angle irradiation with un-polarized light (UP-L) at an incidence angle of 45°. It was performed on films of polyamic acid (Azo-PAA) using a light source of wavelength 340-500 nm. The photo-treated films of Azo-PAA were converted into Azo-PI by thermal imidization. The pretilt angle of LC molecules was determined by a crystal rotation method. The pretilt angle increased with the UP-L exposure, reaching ∼3° at 880J/cm2. For UP-L exposures above 440J/cm2 the LC alignment was uniform and defect-free, while marbled textures were observed below 220J/cm2, This is due to the small in-plane anisotropy of the photo-aligned Azo-PI films.

Original languageEnglish
Pages (from-to)2705-2707
Number of pages3
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume45
Issue number4 A
DOIs
Publication statusPublished - 2006 Apr 7

Keywords

  • Alignment films
  • Azobenzene
  • Liquid crystals
  • Photo-alignment
  • Photo-isomerization
  • Polyimide
  • Pretilt angle

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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