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Proceedings Paper

Design of temperature-independent zero-birefringence pressure sensitive adhesives (Conference Presentation)
Author(s): Kaoru Kosaka; Houran Shafiee; Hiroyuki Ogawa; Sumihisa Oda; Akihiro Tagaya; Yasuhiro Koike

Paper Abstract

Liquid crystal displays (LCDs) are composed of two glass substrates, two polarizers and some optical films. These components are laminated by pressure sensitive adhesives (PSAs). When a polarizer shrinks by humidity or the heat from a backlight of LCDs, stress appears and deforms PSAs. PSAs tend to exhibit birefringence due to applied stress and temperature change, which causes light leakage degrading image quality of LCDs. PSAs are consisted of main chain polymers and cross-linkers. To evaluate birefringence of PSAs at room temperature is difficult because PSAs easily plastically deform at the temperature. The purpose of this article is to design temperature-independent zero-birefringence PSAs (TIZBPSAs) exhibiting almost no birefringence even during stress-induced deformation over a wide temperature range. Butyl acrylate (BA) and phenoxyethyl acrylate (PHEA) were selected as the monomers of main chain polymers and an isocyanate-type cross-linker was added. Trilaminar films were prepared in which PSAs were sandwiched between two supporting films. We successfully evaluated birefringence and temperature dependence of birefringence of PSAs for the first time by using temperature-independent zero-birefringence polymers (TIZBPs) as the supporting films. TIZBPs, designed in our group, show almost no orientational birefringence even when the polymer main chain is in an oriented state and almost no temperature dependence of orientational birefringence over a wide temperature range. We have proposed a novel method to design PSAs having desirable the birefringence properties by determining the contributions of BA, PHEA and the cross-linker to birefringence and temperature dependence of PSAs quantitatively. Furthermore, we have designed TIZBPSAs by the proposed method.

Paper Details

Date Published: 21 April 2017
PDF: 1 pages
Proc. SPIE 10125, Emerging Liquid Crystal Technologies XII, 101250Q (21 April 2017); doi: 10.1117/12.2250682
Show Author Affiliations
Kaoru Kosaka, Keio Univ. (Japan)
Houran Shafiee, Keio Univ. (Japan)
Hiroyuki Ogawa, Saiden Chemical Industry Co., Ltd. (Japan)
Sumihisa Oda, Saiden Chemical Industry Co., Ltd. (Japan)
Akihiro Tagaya, Keio Univ. (Japan)
Yasuhiro Koike, Keio Univ. (Japan)

Published in SPIE Proceedings Vol. 10125:
Emerging Liquid Crystal Technologies XII
Liang-Chy Chien, Editor(s)

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