(1) Positive hole transport material in Japanese Laid-Open Patent Applications Nos. 55-154955 and 55-156954 ##STR101## wherein R21 is methyl group, ethyl group, 2-hydroxyethyl group or 2-chloroethyl group; R22 is methyl group, ethyl group, benzyl group or phenyl group; and R23 is a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1