Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-11-17
2003-05-13
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S046000
Reexamination Certificate
active
06561624
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of processing a nozzle plate, a method of manufacturing a nozzle plate, a nozzle plate, an ink jet head, and image forming apparatus.
In an ink jet printer, the ink chamber of the ink jet head is filled with ink and it is jetted from a nozzle by the application of pressure to the ink chamber. After jetting, the ink meniscus, the surface of the ink, is withdrawn into the nozzle. After that, the ink chamber is refilled with ink from the ink tank, to be ready for the next jetting of ink.
However, because the pressure, which is applied for jetting ink, remains and fluctuates after the jetting of ink owing to the delay of the ink following the pressure applied, the ink meniscus vibrates. Owing to the remaining pressure fluctuation, sometimes the ink in the nozzle overflows the outlet for jetting to the outside. The ink, which has overflowed onto the surface of the nozzle plate, is next withdrawn into the nozzle by being brought into negative pressure, but the surface of the nozzle plate is smudged by the ink which has overflowed. If the ink droplet which is jetted next comes in contact with this smudge, the direction of jetting is deviated, or jetting is often made impossible; thus, the smudge of the nozzle plate makes one of big causes of the deterioration of image quality.
In order to prevent the smudge of the nozzle plate with ink, it has been put into practice that an ink-repellent processing is applied to the surface of the nozzle plate. If the surface of the nozzle plate is subjected to an ink-repellent processing, when ink meniscus comes outside the jetting outlet, it can be prevented that the ink overflows onto the surface of the nozzle plate, or spreads out by wetting the surface.
On top of the nozzle plate, if the inside of the nozzle hole is processed for repelling ink, the nozzle plate is made more scarcely to be smudged and jetting is stabilized. Because the ink meniscus is formed at the border of the portion subjected to the processing for repelling ink and the portion not subjected to the ink-repellent processing, if this border is located at a position retracting into the nozzle hole for a certain length, jetting is stabilized and the flying direction of the ink droplet is also stabilized. Further, even though the meniscus vibrates, the surface of the nozzle plate is hardly smudged, because ink is difficult to come out onto the surface of the nozzle plate.
If the entering length of the portion processed for repelling ink is too long, the resistance for jetting ink becomes large, to reduce the amount of ink jetting. Further, an air bubble is easy to be sucked into the ink chamber. On the contrary, if the entering length is too short, the surface of the nozzle plate is easy to be smudged, and the direction of the ink droplet is easy to deviate, to cause the jet-stabilizing effect to be lost. Because there are several tens to several hundreds of nozzle holes in one nozzle plate, it is especially important to apply the ink-repellent processing to the outlet portion of every nozzle hole for a constant length and uniformly. If the length of the processed portion varies from one nozzle to another nozzle, the amount of jetted ink droplet and the flying direction also vary from one to another, to reduce image quality to a large extent.
Further, on the other hand, at the ink inlet side in the nozzle hole, a film having familiarity for ink (hereinafter a coined word “ink-familiar” will be used for the phrase “having familiarity for ink”) is formed in order that ink may flow smoothly into the nozzle. It is desired that the portion of this ink-familiar film also enters into every nozzle uniformly, because it influences the amount of ink droplet to be jetted and the flying direction.
It is noted in the publications of the unexamined patent applications S48-37030 and S57-107848 etc. that the surface of the nozzle plate and the inside of the nozzle holes for a certain depth are coated with an ink-repellent material by sputtering after the nozzle holes have been formed in the nozzle plate. However, it is very difficult to apply by sputtering an ink-repellent processing to the portion near the outlet inside the nozzle holes for a constant length.
In the publication of the unexamined patent application S64-87359, it is noted that the nozzle holes are filled with a natural wax and the wax attached to the end surface of the holes is wiped off, then the surface of the nozzle plate and an ink-repellent film is formed at the portion near the jetting outlet of the nozzle holes by coating with tetrafluoroethylene using the plasma polymerization method, and after that, the wax is solved and removed.
In the publication of the unexamined patent application H10-157106, it is noted that an ink-familiar film is provided at the ink inlet side by electrodeposition coating with the ink outlet side of the nozzle plate protected by a protective sheet, then the protective sheet is removed and an ink-repellent film is provided at the ink outlet side of the nozzles by electrodeposition coating.
In the publication of the unexamined patent application H7-125220, it is noted that a resin film is laminated and inserted from the rear side of the nozzle plate made of a stainless steel, and the surface of the nozzle plate and the outlet portion of the nozzle holes are processed for repelling ink, to make the ink-repellent processing get into the inside of the nozzle holes for a certain length from the surface, without being limited to the surface.
In any one of the former examples, the ink-repellent processing is carried out after the formation of the holes. At that time, if the inside of the nozzle holes and the rear surface is subjected to the ink-repellent processing, air bubbles stagnate there, or the nozzle plate can not be bonded to the main body. For that reason, it has been put into practice that first the rear surface and the inside of the nozzle holes are masked, then an ink-repellent processing is carried out, and the masking material is removed. For example, as the representative method of masking, a method as described in the publication of the unexamined patent application S64-87359 such that the nozzle holes are filled with a resin material and the rear surface of the nozzle plate is covered with the resin material, and a method as described in the publication of the unexamined patent application H10-157106 such that the rear surface of the nozzle plate is laminated with a resin film can be cited; many are methods such that the resin material overflowing onto the front surface is removed and an ink-repellent processing is applied only to the front surface.
However, it is difficult to control the method in which the nozzle holes are filled with a resin material with a high precision to determine the entering length of the portion subjected to the ink-repellent processing, its cost comes to a high value, and mass production can not be expected. Further, it is difficult to remove the resin material from the nozzle holes completely after processing. Because the processing is troublesome, the fluctuation of the length among the nozzles is large, and the jet stabilization of ink droplets is sometimes made worse on the contrary.
Generally speaking, several tens to several hundreds of nozzles having a hole diameter of 20 to 60 &mgr;m are formed in the nozzle plate, therefore, it is extremely difficult to fill each of the nozzles with a photosensitive resin material uniformly with a precision in the order of &mgr;m. If the entering length of the ink-repellent film have a fluctuation among the nozzles, the amount of ink jetted from each of the nozzles varies from one nozzle to another, to make a cause to lower image quality by a great deal. Further, it is also difficult to remove completely the resin material which has been crosslinked after processing from the nozzle holes having a diameter of 20 to 60 &mgr;m. If the crosslinked resin material is removed in a severe condition, sometimes the ink-repellent film coated by electrodeposition is pee
Kikugawa Shozo
Namiki Takemasa
Frishauf Holtz Goodman & Chick P.C.
Konica Corporation
Vo Anh T. N.
LandOfFree
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