투명 전극용 나노 실버 페이스트의 물성 연구

Abstract

Touch screen panel(TSP) is expanding its market from small size smart phone/tablet PC to notebook PC and large size electronic blackboard. Conventional transparent conducting electrode(TCE), ITO (Indium tin oxide), can not be used in the medium to large size TSP due to increased electrical resistance and consequent slow response time to touch. Therefore various TCE materials have been developed including metal thin film deposition combined with photolithographic patterning, graphene, and conducting polymers. Metal mesh TCE, however, is becoming the practical solution from the viewpoint of industrial production of medium to large size TSPs. Metal mesh TCE film is fabricated by a series of processes such as UV imprinting of transparent trench pattern (width 2~5μm) layer onto PET film, filling of silver paste and wiping of the surface, and heat curing of the silver paste. In this work nano-size(40~50nm) silver particles were synthesized and mixed with submicron(250~300nm) size silver particles to make silver pastes for the fabrication of metal mesh type TCE films. The filling of these silver pastes into the patterned trench layer was examined by using a specially designed filling machine and rheological testing of the silver pastes. The wiping of the trench layer surface to remove any residual silver paste or particles was tested with various mixture solvents from which ethyl cellosolve acetate(ECA) : H2O = 90 : 10 wt% was found to give best result. The silver paste with 40~50nm Ag : 250~300nm, Ag = 10 : 90 wt% mixture gave highest electrical conductance. The optical quality of the metal mesh TCE film obtained with this silver paste under optimized process exhibited light transmittance of 90.4% and haze at 1.2%, suitable for TSP application.