Effect of chemical structure of acrylic pressure‐sensitive adhesives for polarizing film on light leakage phenomenon in TFT‐LCDs

Increasing image quality in thin‐film transistor liquid crystal displays (TFT‐LCD) is a recognized challenge for electronic companies and specialists working in this area. One of the main problems in TFT‐LCDs is a phenomenon called “light leakage”, affecting black–white contrast and color brightness. It occurs because of a heat‐induced shrinkage and disorientation of the polarizing film of TFT‐LCD, which controls the intensity of the light from the backlight unit. Improvement of the light leakage can be achieved through using a pressure‐sensitive adhesive (PSA) used for assembling the polarizing film onto the TFT‐LCD panel. In this paper, eight acrylic/methacrylic monomers with high glass transition temperature (Tg) were employed for synthesis of the polymers for the adhesive. Effect of structure, Tg, and elasticity modulus of the synthesized polymers on the light leakage was investigated simultaneously for 2.5‐ and 7.0‐in. size samples. We demonstrated that the light leakage can be minimized through two different mechanisms—high stress relaxation of the polymers with low Tg and low modulus and high shrinkage resistance of the polymers with high Tg and high modulus. The results of this work indicate a possibility to develop a universal PSA for polarizing film in TFT‐LCDs of different sizes that will have a positive effect on manufacturing productivity and lowering prices of digital devices. Copyright © 2011 John Wiley & Sons, Ltd.