Thermal recording element

A process of forming a dye image comprising:

• imagewise-heating a thermal recording element by using a thermal printing head, said thermal recording element comprising a support having thereon a dye layer comprising a dye dispersed in a polymeric binder, wherein said dye layer contains
• (a) a formazan dye that absorbs at from about 400 to about 850 nm, and
• (b) a hexaarylbiimidazole which is an oxidative dimer of a 2,4,5-triarylimidazole having one of the following formulas:
• ##STR8## wherein:
• R represents an alkoxy group of from 1 to about 12 carbon atoms;
• X and X.sup.1 each independently represents oxy or imino;
• Z is an alkylene group of 1 or 2 carbon atoms;
• and
• o represents an integer of 1 or 3, with the proviso that when o is 1, then R is in the para position and when o is 3, then R is in the para and both meta positions;
• thereby forming said image.