US Patent 7594715 Inkjet recording system

An inkjet recording system that discharges pigment ink from a liquid droplet discharge head in which a part of wall surface of pressure chamber is formed of a piezoelectric element, wherein average surface inclination Δa (mrad) of surface of the piezoelectric element forming a part of wall surface of the pressure chamber satisfies Δa≦1050, and average volumetric particle diameter D (nm) of pigment contained in the ink satisfies 80≦D≦200. Preferably, the arithmetic average surface inclination Δa and the average volumetric particle diameter D of the pigment satisfy the following formula (1):(1/D)×cos2(Δa/1000)>0.003  (1).