Abstract: An inkjet ink set comprising at least two inks, wherein at least one ink contains a betaine compound and at least one other ink contains a nonionic surfactant.

Abstract: The invention provides an improved thermal head having a protective film of a heater which comprises a carbon-based protective layer having a hardness difference in its thickness direction. The invention also provides an improved method of manufacturing the thermal head. A thermal head is thus obtained having a protective layer which is significantly protected from corrosion and wear, also from cracks and peeling-off due to heat and mechanical impact, and which allows the thermal head to have a sufficient durability to exhibit a high reliability over an extended period of time, thereby ensuring that the thermal recording of high-quality images is performed consistently over an extended period of operation.