To provide a highly bonding tile in which bonding property to a hydraulic binder is improved, a highly bonding substrate structure, their manufacturing methods and a coating liquid for forming a highly bonding hydrophilic layer for improving bonding property.

The coating liquid containing hydrophilic inorganic fine particles such as silica and preferably siliceous substance for binding and having 18 to 93 molar ratio of SiO2/alkali, is uniformly applied to a tile rear surface or a substrate structure surface, then is subjected to heat treatment or drying to form a hydrophilic layer in which the silica fine particles are bound by a siliceous binder. Preferably the hydrophilic layer is formed by heat treating the tile on which the coating liquid is applied at 300 to 700°C.