Disclosed are α-oxo oxime ester compounds based on carbazole derivatives which have specific substituent groups useful as a photoinitiator, as well as photopolymerizable compositions comprising said photoinitiator and ethylenically unsaturated compounds. The photopolymerizable compositions are useful, for example, in photoresist formulations for display applications, e.g. liquid crystal display (LCD), organic light emitting diode (OLED) and touch panel.