Keio Photonics Research Institute, Keio University, Shin-Kawasaki Town Campus E-building, 7-1 Shin-kawasaki Saiwai-ku, Kawasaki-shi, Kanagawa 212-0032, Japan
Satoshi Yanai
Keio Photonics Research Institute, Keio University, Shin-Kawasaki Town Campus E-building, 7-1 Shin-kawasaki Saiwai-ku, Kawasaki-shi, Kanagawa 212-0032, Japan
Sumihisa Oda
Saiden Chemical Industry Co., Ltd., 3-4-7, Honcho, Nihonbashi, Chuo-ku, Tokyo 103-0023, Japan
Akihiro Tagaya
Keio Photonics Research Institute, Keio University, Shin-Kawasaki Town Campus E-building, 7-1 Shin-kawasaki Saiwai-ku, Kawasaki-shi, Kanagawa 212-0032, Japan
Yasuhiro Koike
Keio Photonics Research Institute, Keio University, Shin-Kawasaki Town Campus E-building, 7-1 Shin-kawasaki Saiwai-ku, Kawasaki-shi, Kanagawa 212-0032, Japan
We have developed zero-birefringence pressure-sensitive adhesives (PSAs) that exhibit almost no birefringence at any orientation of polymer chains. To evaluate the birefringence of PSAs quantitatively, we report a novel birefringence-measurement method utilizing zero–zero-birefringence polymers that exhibit no birefringence at any orientation of polymer chains and in elastic deformation. By employing this method, we designed and synthesized poly(butyl acrylate/phenoxyethyl acrylate/acrylic acid/hydroxyethyl acrylate) = 80.0:20.0:1.5:1.0 (by weight) that contains 1.8 wt% isocyanate-type crosslinker that exhibited almost zero birefringence. Furthermore, we demonstrated that after the accelerated aging test by applying heat, this zero-birefringence PSA almost completely prevented light leakage through crossed polarizers.
