NEW MATERIAL:A phenolic compound shown by formula I (R1-R3 are alkyl or aryl).

EXAMPLE: 5', 5"-Di-tert-butyl-4',6'-hydroxy [1,1':3',1'':3",1''']-quaterphenyl.

USE: An image preservation improver for heat-sensitive recording material.

PREPARATION: For example, a p-phenylphenol derivative shown by formula II is reacted with an aqueous solution of H2O2 in a water solvent in the presence of NaOH and neutralized with hydrochloric acid to give a compound shown by formula I.