To the subbing solution, an organic solvent, such as alcohol or ketone, may be added, if needed. [0087] The suitable solids concentration of the subbing solution is from 0.15 to 0.75 weight % (specifically, the water-soluble resin concentration is from about 0.1 to about 0.5 weight % and the water-soluble metal salt concentration is from about 0.05 to about ???25 weight %), preferably from 0.2 to