In a structure of an ink tank having a deformable sheet that constitutes the tank and a spring for imparting a negative pressure, unstableness of the negative pressure attributable to the deformation of the sheet as a result of ink consumption is prevented. The formula compound is particularly suitable for using as a component in a black dye composition for ink-jet printing ink, and inkjet printing inks with good light-fastness are obtained. Further, grooves are formed in the circuit board, the sensor holder, and the busbar, wherein fitting a jig to these grooves enables high-precision assembly of these components.