Cleaning method for nozzle plate of an ink jet print head

#This invention relates to a cleaning method for a nozzle plate of an ink jet print head to remove contaminants from the surface thereof.

#Ink jet printers are well known in the printing industry. Ink jet printers are just one of many different types of printing systems that have been developed which include laser electrophotographic printers, LED electrophotographic printers, dot matrix impact printers, thermal paper printers, film recorders, thermal wax printers and dye diffusion thermal transfer printers. Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing industry because of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfers and fixing.

#There is a problem with ink jet printers in that dirt or other contaminants from paper or the atmosphere clog the nozzles of the nozzle plate causing misdirected ink drops or malfunctioning nozzles, which adversely affect the image quality of the printed image.

#The drawing in FIG. 1 illustrates a cross section of a nozzle plate 10, for an ink jet print head containing contaminants and adhesive material.

#FIG. 2 illustrates the adhesive in contact with the nozzle plate.

#FIG. 3 illustrates heat being applied and

#A nozzle plate for an ink jet print head preferably comprises silicon having an array of orifices through which ink is ejected. The orifices may be prepared by conventional etching techniques. The nozzle plate may also have a metallic oxide or nitride coating. It should be appreciated that other materials besides silicon, such as electro-formed nickel or polyimide, may be used to prepare the underlying nozzle plate as is known in the art. Further, other metals such as gold, silver, palladium and copper may be used to coat the underlying nozzle plate material. As noted above, the ink jet print head employed has multiple nozzles on the nozzle plate.

#The heat-activatable adhesive material which may be used in the invention may be a hot-melt adhesive, such as a butyl rubber, nitrile rubber, styrene butadiene rubber adhesive, styrene-isoprene-styrene copolymer, ethylene acrylate copolymer, acrylic adhesive, polyolefin, poly(ethyl vinyl acetate), polyethylene adipate, a polyester or a polyamide and other related adhesives. Other materials that may be used include a thermal-curable or photo-curable material, such as epoxy formulations, isocyanate/bisphenol and isocyanate/bisamine formulations, polyimides or Novalac® resins; or a thermally reversible polymer gel, such as N-alkyl-substituted acrylamide polymers and copolymers or graft copolymers of N-alkyl-substituted acrylamides. Such materials can be combined with known tackifier and plasticizer materials to obtain the desired level of adhesion and cohesion.

#In preferred embodiment of the invention, the heat-activatable adhesive material is a thermally reversible polymer gel comprising tri-block copolymers of poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) (PMMA-PBA-PMMA). It may be employed at a concentration of 3%-40% in a suitable solvent, such as ethanol, propanol, iso-propanol, n-butanol or 2-ethylhexanol. A thermally reversible polymer formulation forms a polymer gel at room temperature with a Young's modulus as low as 2.5×103 Pa (Mowery, C. L. et. al. “Adhesion of Thermally Reversible Gels to Solid Surfaces”, Langmuir, 1997, 13, 6101). At an elevated temperature, e.g., 70° C., the gel melts and the material behaves as a viscous liquid with a typical complex viscosity of about 10 Pa·s at 1 Hz. When the material at the elevated temperature is cooled, gelation occurs very rapidly, forming a gel again. The adhesive characteristics of the gel are disclosed in the reference provided above.