Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-07-27
2003-06-24
Barlow, John (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S103000, C347S043000
Reexamination Certificate
active
06582054
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for generating a recording fluid having a predetermined density and/or a predetermined color by changing a mixing ratio of a plurality of inks based on an image signal and leading the thus obtained fluid to an image receiving medium to form an image.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,109,282 (hereinafter referred to as a prior art reference 1) discloses a printer having a structure such that a valve called a flap valve is disposed in a flow channel for leading two types of liquid, i.e., clear ink and black ink onto a substrate for forming an image. The flow channel for each ink is opened/closed by displacing this valve so that the two types of liquid are mixed in a desired density to be transferred onto the substrate. This enables printout of an image having gray scale information which is the same as that of the image information displayed on a TV screen. In this reference is disclosed that a voltage is applied between the flap valve and an electrode disposed on a surface opposite to the flap valve and the valve itself is mechanically deformed by an electrostatic attracting force to cause displacement of the valve. Furthermore, the ink is absorbed in paper by a capillary phenomenon between fibers of the print paper.
U.S. Pat. No. 4,614,953 (hereinafter referred to as a prior art reference 2) discloses a printer head apparatus by which only a desired amount of multiple types of ink having different colors and solvent is led to a third chamber to be mixed therein. In this reference is disclosed that a chamber and a diaphragm-type piezoelectric effect device attached to this chamber are used as means for check-weighing the desired amount of ink and a pressure pulse obtained by driving this piezoelectric device is utilized.
Unexamined Japanese Patent Publication (KOKAI) No. 201024/1993 (hereinafter referred to as a prior art reference 3) discloses an ink jet print head including: a liquid chamber filled with a carrier liquid; ink jet driving means disposed in the liquid chamber; a nozzle communicating with the liquid chamber; and a mixing portion for mixing ink to the carrier liquid in this nozzle. In this reference is also disclosed that adjusting means having a check valve structure for adjusting an amount of mixture of ink to a desired value is provided.
Similarly, Unexamined Japanese Patent Publication (KOKAI) No. 125259/1995 (hereinafter referred to as a prior art reference 4) discloses an ink jet recording head including: first and second supplying means for supplying inks having first and second densities, respectively; and controlling means for controlling an amount of supply of the second ink by the second supplying means so that a desired ink density can be obtained.
In this reference 4, employment of a micro-pump which has an exclusive heating device and is driven by its heat energy is disclosed. As this micro-pump, there is disclosed an example such that the heat energy is generated by the heating device and a pressure obtained by nucleate boiling caused by the heat energy is used to drive, for example, a piston-type valve or a cantilever-like valve. Furthermore, this reference 4 describes that an inflow of ink can effectively be controlled in an area where the inflow is particularly small by adopting an actuator consisting of a shape memory alloy to this valve.
Unexamined Japanese Patent Publication (KOKAI) No. 207664/1991 (hereinafter referred to as a prior art reference 5) discloses a structure which is similar to that in the prior art reference 2 but does not use a third chamber for mixing a plurality of types of ink.
Unexamined Japanese Patent Publication (KOKAI) No. 156131/1997 (hereinafter referred to as a prior art reference 6) discloses an ink jet printer comprising a plurality of printer heads for forming an image having multiple colors based on image data. Ink and diluent are mixed at a predetermined ratio to obtain diluted ink which is jetted from a nozzle so that a recording image is formed on a recording medium. The ink jet printer ejects the diluent from at least one printer head out of the multiple printer heads when all-white image data, that is, data representing that amount of mixture of ink is too small to realize a clear printing density, is input. As a result, a rapid change in tone (a tone jump) is prevented and the additional consumption of the diluent is suppressed to improve drying characteristics.
In the prior art disclosed in the prior art reference 1, the ejection ports for two types of liquid are separately open directly to the print paper, and the respective types of liquid are separately attracted on the print paper by the capillary phenomenon immediately after ejection. Therefore, a quantity of attraction of each liquid on the paper readily fluctuates under influence of a paper quality of the print paper, which results in the unstable image quality or difficulty of formation of an image having high fidelity to the image signal.
In any of the prior art references 2 to 6, a plurality of inks are mixed beforehand or caused to be confluent, and thereafter the mixed liquid (including the confluent liquid) is led onto the print paper. However, when a mixing ratio of one ink is remarkably small (ejection amount is remarkably small), the ink cannot smoothly be confluent with other ink. That is, when the ejection amount of the ink is small, an amount (ingress amount) of the ink advancing to the mixing portion (or a confluence portion) for mixing with the other ink becomes small. Therefore, a leading end of the ink cannot cut in a flow of the other ink by a surface tension of the ink. Therefore, the density of a mixed liquid (confluent liquid) cannot follow the image signal with fidelity, and a problem that an image quality is deteriorated occurs.
Furthermore, in any of the prior arts disclosed in the prior art references 2 to 6, a plurality of inks are brought into contact with one another in the mixing section (the confluence portion), and each ink is ejected by a predetermined amount to be mixed. That is, the ejection port for each ink is formed and assembled in the mixing section. Each ink cannot therefore be prevented from being naturally diffused from one another.
For example, even if a given ink is not ejected into a mixing chamber in accordance with the image signal, this ink is naturally diffused in the mixing chamber. Thus, the density and/or color of the finally mixed ink liquid differs from the image signal, and an image which has fidelity to the image signal cannot be formed. Even if the natural diffusion of the ink is small, distortion of a contact interface occurs due to a vibration in the mixing portion or any other disturbance, and therefore the undesired mixing of ink is facilitated and the above-described problem becomes more prominent.
Additionally, the prior art reference 3 discloses that adjusting means functioning as a check valve is disposed in the vicinity of the opening of the ink channel formed in the mixing portion in order to mainly prevent the inks from being naturally diffused from one another. However, the adjusting means having the check valve structure complicates a print head configuration and leads to problems such as difficulty in manufacturing, reduction of productivity or increase of a manufacturing cost.
Furthermore, the prior art reference 6 discloses that a colorless diluent continues to flow in case of all-white image data in order to avoid a rapid change in tone (tone jump), but the ink which is not colorless and transparent is continuously diffused in this diluent in this case, and hence the above-mentioned problems can not be prevented.
To solve the problem, the present applicant has considered that the small amount of image forming ink is constantly and continuously supplied to the other ink such as a transparent liquid (image non-forming ink) (e.g., Unexamined Japanese Patent Publication (KOKAI) No. 246920/2000 corresponding to EP 101653A2 and U.S. patent application Ser. No. 09/472,970). For example, when
Matsumoto Nobuo
Yamamoto Ryoichi
Barlow John
Fuji Photo Film Co. , Ltd.
Nguyen Lam
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