1. Field of the Invention
The present invention relates to an ink-jet printing unit having a plate-stacked type ink-jet printing head and a method of producing the same.
2. Discussion of Related Art
As an ink-jet printing head for printing, on print media such as printing sheets, images, characters, etc., by ejecting ink droplets from nozzle holes, there is conventionally known an ink-jet printing head in which are superposed a plate having a multiplicity of nozzle holes formed therethrough and arranged in rows, a plurality of plates which provide ink passages, and a piezoelectric actuator which gives vibration or oscillation for ink ejection for each nozzle hole.
Where the thus constructed printing head is mounted on a main body of a printing apparatus, the printing head is first fixed to a head holder, and the head holder is then mounted on the main body of the printing apparatus. Accordingly, the printing head needs to be fixed to the head holder with high positioning accuracy. Namely, positions of the nozzle holes with respect to the head holder influence print positions on the print media, and inclination of the nozzle holes relative to a nominal direction influences printing of the images per se. Accordingly, if the printing head can be fixed to the head holder with high positioning accuracy, it is possible to perform a high-quality printing operation.
The nozzle holes need to be formed with high accuracy. In addition, the printing head needs to be fixed to the head holder with high positioning accuracy. In the meantime, the printing head is generally formed of a metal while the head holder is generally formed of a synthetic resin. In this case, it is rather difficult to fix the printing head to the head holder with high positioning accuracy, with the printing head and the head holder butted together.
In the light of the above, it is required to first accurately position the printing head on a jig, then accurately position the head holder on the jig with the printing head accurately positioned on the jig, and finally fix the printing head to the head holder.
For the accurate positioning utilizing the jig as described above, there is known a nozzle plate having positioning holes into which positioning pins of a jig are inserted in fixing and bonding the printing head to the head holder. Such a nozzle plate is disclosed in U.S. Pat. No. 6,679,595 (corresponding to JP-A-2002-234144, in paragraphs [0022]-[0024] and FIG. 7, in particular), for instance.