Patent ID: 7144449

Claim:
A print ink comprising: a first fluorescent coloring material that emits a fluorescence at a predetermined emission wavelength to be used for measurement or determination on excitation at a predetermined excitation wavelength; and a second fluorescent coloring material that emits a fluorescence with excitation at the predetermined excitation wavelength, wherein an excitation spectrum of the first coloring material in the ink to obtain the fluorescence at the predetermined emission wavelength has a peak wavelength range next to the predetermined fluorescence wavelength, and an emission fluorescence spectrum of the second coloring material has an emission wavelength region that includes at least the peak wavelength range, wherein the ink contains more of the second fluorescent coloring material than the first fluorescent coloring material, and wherein the first fluorescent coloring material is C.I. Acid Red 52 and the second fluorescent coloring material is the compound (A) having the following structure: