Improvement of Blister Resistance for Optically Clear Pressure-Sensitive Adhesive by Surface Segregation of Tackifier

Abstract

The blister resistance under heat and humidity has been improved through the addition of tackifier (TF) to pressure sensitive adhesive (PSA) for touch screen (Qptically Qlear pressure sensitive Adhe_ sive: OCA). The blister resistance tests were conducted for PSAs containing several TFs which have various miscibilities with the base polymer (BP). The TF which shows proper miscibility with BP significantly improved the blister resistance. Moreover the blister resistances related to the adhesions under high temperature. The surface composition of the PSA containing TF was measured by X-ray photoelectron spectroscopy. The surface weight fraction of the TF prevented the blistering was almost 100%, indicatingthat the TF segregated onto the surface of the PSA. Moreover the surface segregation of TF didn't influence the viscoelasticity behavior measured by dynamic mechanical analysis. It was assumed that the improvement of the adhesion properties under high temperature related to the high Tg region near the surface of the PSA formed by the surface segregation of TF.