Diisopropyl biphenyl is a colorless and odorless transparent liquid that is the new carbonless copy paper dye solvent, which has advantages of proper viscosity, strong solvent power and low cost. Diisopropyl biphenyl is used to produce carbonless copy paper and pressure-sensitive carbon materials which have clear and tight prints. It is also the raw material of manufacturing high temperature heat transfer fluid, vacuum pump oil, lubricating oil and electric insulating oil, dye mordant, surface active material, synthetic fiber and plastics.