Effects of soft segment mixtures with different molecular weight on the properties and reliability of UV curable adhesives for electrodes protection of plasma display panel (PDP)

A series of urethane acrylate oligomers has been synthesized from isophorone diisocyanate (IPDI), mixture of soft segments with different Mw, i.e., poly(ethylene-co-1,2-butylene)diol (PEBD, Mw = 2400) and 2-butyl-2-ethyl-1,3-propanediol (BEPD, Mw = 160) and 2-hydroxyethyl methacrylate (HEMA) using dibutyl tin dilaurate (DBTL) as a catalyst. Subsequently, the UV curable adhesives were fabricated by mixing the prepared oligomers, reactive diluents (Isobonyl acrylate and 4-hydroxybutyl acrylate) and photo initiator (1-hydroxy-cyclohexyl-phenyl-ketone). The physical and mechanical properties of UV cured adhesives such as coefficient of thermal expansion (CTE), elastic modulus (E′), glass transition temperature (Tg), adhesion strength and water vapor transmission rate (WVTR) were measured. And electrochemical migration of Ag electrodes, which brings on the degradation of surface insulation resistance, was also investigated by monitoring insulation resistance during 100 h of 50 °C, 90%RH storage test.