4-Arylbenzoyl benzoic acid esters, such as the ethylhexyl esters and amyl esters of 4-phenylbenzoyl benzoic acid, are described, which are liquid and show excellent solubility in acrylic or methacrylic monomers. Compounds of Formula 1, wherein R1, R2, and A are as defined herein, are disclosed. They are suitable as components for radical photoinitiator systems for UV-curable compositions.