Liquid crystal display cells fabricated on plastic substrate driven by low-voltage organic thin-film transistor with improved gate insulator and passivation layer

Yoshihide Fujisaki, Hiroto Sato, Hideo Fujikake, Youji Inoue, Shizuo Tokito, Taiichiro Kurita

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Organic thin-film transistor (OTFT)-driven 5 × 5 polymer-dispersed liquid crystal (PDLC) display cells on a flexible plastic substrate have been developed. It is necessary to increase the maximum usable gate voltage of OTFT to obtain a high contrast ratio. We propose a stacked gate insulator that consists of polyvinylphenol and anodized Ta2O5 for decreasing the gate leakage current and increase the maximum voltage. The OTFT with the insulator showed a field-effect mobility of 0.4 cm2 / (V s), a current on/off ratio of 105, a low threshold voltage of 1.1 V, and a subthreshold slope of 0.2V/decade. Leakage current was successively decreased up to a gate voltage of 15 V, maintaining a low-voltage operation of OTFT. Double passivation layers using polyvinylalcohol and photosensitive acrylic material are also proposed to prevent the degradation of OTFT by liquid crystal. The bending characteristics of OTFT on plastic substrates were also measured for various radiuses of curvature. The OTFT can operate at a radius of curvature exceeding 20 mm. On the fabricated display cells, we confirmed a good display operation with a contrast ratio of 10 : 1 with a low driving voltage of 12-13 V.

Original languageEnglish
Pages (from-to)3728-3732
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume44
Issue number6 A
DOIs
Publication statusPublished - 2005 Jun 1
Externally publishedYes

Keywords

  • Active matrix
  • Flexible display
  • Gate insulator
  • Organic TFT
  • PDLC
  • Passivation layer

ASJC Scopus subject areas

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

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