Inkjet printing apparatus, method of printing ink using the same and method of fabricating display device

A method of printing ink, comprising:

• ejecting ink in which a plurality of particles is dispersed from an inkjet head;
• irradiating the ejected ink with a first light and a second light having different wavelengths;
• and
• calculating a concentration of the particles in the ink from the data on a first exit light and a second exit light from the ink;
• wherein the first light has a wavelength of about 500 nanometers (nm) or less, and the second light has a wavelength of about 1000 nm or more, wherein the ink is ejected from the inkjet head in a first direction,
• the first light is irradiated in a second direction perpendicular to the first direction, and
• the second light is irradiated after the first light is irradiated.

An inkjet printing apparatus comprising:

• an inkjet head which ejects ink in which a plurality of particles is dispersed;
• a first light irradiation device and a second light irradiation device which irradiate lights of different wavelength bands, respectively, to the ejected ink;
• a first sensing device on which a first exit light is incident, wherein the first exit light is obtained by scattering a first light irradiated from the first light irradiation device and incident on the ink;
• and
• a second sensing device on which a second exit light is incident, wherein the second exit light is obtained by scattering a second light irradiated from the second light irradiation device and incident on the ink;
• wherein the first light irradiated from the first light irradiation device has a wavelength of about 500 nm or less, and the second light irradiated from the second light irradiation device has a wavelength of about 1000 nm or more.