Patent ID: 7407263

Claim:
A head unit for use in a droplet ejection apparatus, the head unit being provided with a plurality of droplet ejection heads for ejecting a liquid material of a predetermined color onto a base in the form of droplets, wherein the plurality of droplet ejection heads comprises at least a first droplet ejection head, a second droplet ejection head, a third droplet ejection head and a fourth droplet ejection head for ejecting the liquid material of the predetermined same color, each of the droplet ejection heads including at least one nozzle array having a plurality of nozzles linearly aligned, the liquid material being adapted to be ejected through the plurality of nozzles of each of the droplet ejection heads in the form of droplets, wherein the first droplet ejection head and the second droplet ejection head constitute a first set, and the third droplet ejection head and the fourth droplet ejection head constitute a second set, and the first set and the second set partially overlap each other, wherein in the first set the first droplet ejection head and the second droplet ejection head are arranged along a first direction parallel to each of the nozzle arrays so that the nozzles of the nozzle array of the first droplet ejection head and the nozzles of the nozzle array of the second droplet ejection head are consecutive via a seam between the first droplet ejection head and the second droplet ejection head when viewed from a second direction perpendicular to the first direction, and in the second set the third droplet ejection head and the fourth droplet ejection head are arranged along the first direction so that the nozzles of the nozzle array of the third droplet ejection head and the nozzles of the nozzle array of the fourth droplet ejection head are consecutive via a seam between the third droplet ejection head and the fourth droplet ejection head when viewed from the second direction, wherein the second droplet ejection head is arranged between the third droplet ejection head and the fourth droplet ejection head when viewed from the first direction, and the third droplet ejection head is arranged between the first droplet ejection head and the second droplet ejection head when viewed from the first direction, wherein the droplet ejection heads are arranged so that all the seams thereof are shifted with respect to each other in the first direction when viewed from the second direction.