As the solvent used in the charge transport layer coating solution, usable are ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dimethoxymethane, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and hydrocarbons substituted with a halogen atom, such as chlorobenzene, chloroform and carbon tetrachloride.