Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

Czung-Yu Ho; Fa-Hsin Lin; Yu-Tai Tao; Jiunn-Yih Lee

doi:10.1088/1468-6996/12/6/065002

Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method

Sci Technol Adv Mater. 2011 Dec 2;12(6):065002. doi: 10.1088/1468-6996/12/6/065002. eCollection 2011 Dec.

Authors

Czung-Yu Ho¹, Fa-Hsin Lin², Yu-Tai Tao³, Jiunn-Yih Lee²

Affiliations

¹ Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan.
² Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan.
³ Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan.

Abstract

In a multicomponent nematic liquid crystal (NLC) mixture of a liquid crystal (negative-type NLC) and a photosensitive acrylic prepolymer, photopolymerization upon UV irradiation induces the separation of the LC and photosensitive acrylic prepolymer layers, thereby leading to a vertical arrangement of LC molecules. In this study, we propose a simple vertical alignment method for LC molecules, by adding a chiral smectic A (SmA∗) liquid crystal having homeotropic texture characteristics to an NLC mixture solution. Measurements of electro-optical properties revealed that the addition of the SmA∗ LC not only strengthened the anchoring force of the copolymer alignment film surface, but also significantly enhanced the contrast ratio (∼73%), response time and grayscale switching performance of the device.

Keywords: electro-optical properties; grayscale switching; homeotropic texture; liquid crystal; photosensitive; prepolymer; vertical arrangement effect.