In most display devices such as liquid crystal display devices, plasma display devices, and organic EL display devices, a display panel is thermo-compression bonded to a flexible circuit board through an anisotropic conductive film to establish anisotropic conductive connection therebetween. Conventionally, a film formed from a dispersion of conductive particles in a binder composition containing, as main components, a thermoplastic resin, an epoxy-based resin, and an amine-based curing agent is used as such an anisotropic conductive film. The conditions for thermo-compression bonding are normally 180° C. for 7 seconds.
In recent years, the screen size of display panels is increasing. Therefore, the influence of thermal stress generated in such a display panel during thermo-compression bonding using an anisotropic conductive film is not negligible. To minimize the influence, the conditions for thermo-compression bonding need to be changed from 180° C. for 7 seconds to 160° C. ±20° C. for 4 seconds. To meet this demand, as an anisotropic conductive film capable of compression bonding at relatively low temperatures, a radical-polymerizable anisotropic conductive film formed from a dispersion of conductive particles in a binder containing, as main components, a thermoplastic resin, a polyfunctional acrylate, and a peroxide is used. However, in a thermal curing process of such a radical-polymerizable anisotropic conductive film, the formation of hydroxyl groups that improve adhesion properties to display panels and flexible circuit boards is not expected. Therefore, to improve the adhesion properties, a urethane acrylate having in its molecule at least two highly polar urethane bonds having affinity for polyimides and metal surfaces is added to the binder (Patent Document 1).    [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-257208.
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