PURPOSE: To provide a novel compd. which imparts an increased photosetting rate in a planographic printing plate, imparts increased deep part hardness in a screen printing method and is useful for photoinitiator, etc.

CONSTITUTION: This compd. is represented by the formula (R1 is halogen, 1-10C alkoxy; R2, R4 are each H, halogen, 1-6C alkyl; X is O, S; R3 is substd. 1-6C alkyl, substd. 1-10C alkenyl, 3-6C cycloalkyl, etc.), for example, 1-chlor-4-n- propoxythioxanthone. The compd. of formula is obtd. by bringing 2,2'- dithiobisbenzoic acid or 2-mercaptobenzoic acid or its deriv. into reaction with a substd. phenol or thiophenol to form a substd. hydroxy or thio-thioxanthone compd., then bringing the hydroxy compd. or thio compd. into reaction with a compd. for alkylation or a compd. for acylation.