Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-12-28
2003-05-13
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Controller
C347S043000
Reexamination Certificate
active
06561608
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming method and apparatus for producing a fluid having a predetermined density and/or a predetermined color by changing a proportion or 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. Further, the present invention relates to a recording head for use in this image forming apparatus.
2. Description of the Prior Art
U.S. Pat. No. 4,109,282 (which will be referred to as a prior art reference 1, hereinafter) discloses a printer having a structure such that a valve called a flap valve is provided 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 the 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 provided on a surface opposed to the flap valve and the valve itself is mechanically deformed by the electrostatic attracting force to cause displacement of the valve. Further, the ink is absorbed in paper by a capillary phenomenon between fibers of the print paper.
U.S. Pat. No. 4,614,953 (which will be referred to as a prior art reference 2, hereinafter) 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 a desired amount of ink and a pressure pulse obtained by driving this piezoelectric device is utilized.
Unexamined Japanese Patent Publication (KOKAI) No. 201024/1993 (which will be referred to as a prior art reference 3, hereinafter) discloses an ink jet print head including: a liquid chamber in which a carrier liquid is filled; ink jet driving means provided 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 for adjusting an amount of mixture of ink to a desired value is provided.
Similarly, Unexamined Japanese Patent Publication (KOKAI) No. 125259/1995 (which will be referred to as a prior art reference 4, hereinafter) discloses an ink jet recording head including: first and second supplying means for supplying inks having first and second densities, respectively; and controlling means which controls 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 the nucleate boiling caused due to the heat energy is used to drive, e.g., a piston-type valve or a cantilever-like valve. Further, this reference 4 describes that an inflow of ink can be effectively controlled in an area where the inflow is particularly small by adopting an actuator consisting of shape memory alloy to this valve.
Unexamined Japanese Patent Publication (KAKAI) No. 207664/1991 (which will be referred to as a prior art reference 5, hereinafter) 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 (which will be referred to as a prior art reference 6, hereinafter) 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 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.
Unexamined Japanese Patent Publication (KOKAI) No. 264372/1998 (which will be referred to as a prior art reference 7, hereinafter) discloses employment of a plurality of line heads in which ink ejection nozzles are linearly aligned. In this example, when the respective line heads are biased and arranged in a direction for feeding print paper and positions of nozzles in the respective line heads are biased relatively to a direction of the width of the print paper, the pixel density can be enhanced. Further, ink having a single color is ejected from each nozzle, and ink droplets having different colors are combined by ejecting ink having different colors in accordance with the line heads, thereby representing predetermined colors on the print paper.
In the respective prior arts disclosed in the prior art references 1 to 6, the different types of ink are mixed in advance to be then ejected, and an amount of supply of at least one type of ink among the multiple types of ink to be mixed is controlled. Therefore, a quantity of flow of ink having a desired density after mixed, i.e., a volume flow rate per unit time varies in accordance with a change in density or color. It has been revealed that, when the volume flow rate (which is also referred to as a flow rate hereinafter) per unit time of the ink fluid after mixing fluctuates in accordance with a change in ratio of mixture due to density or color in this manner, the quality of a finally-formed image is prominently deteriorated.
That is, in the image forming technique adopting the conventional ink jet mode described above, a volume of droplets formed by one ejecting operation (the ejection volume) is substantially constant, whereas a liquid flow rate of the mixed ink which is newly sequentially supplied to an ejection port (a jet generating portion) fluctuates. For example, when a supplied flow rate of the mixed ink is large, the supplied amount of the ink exceeds a quantity of droplets which can be ejected by one ejection operation, and the liquid remaining in the ejection port is mixed in the droplets for the next pixel. Further, when a supplied flow rate of the mixed ink is small, a part of the droplets for the next pixel is disadvantageously fetched. This adversely affects the image quality.
The applicants has been examining a mode for continuously transporting the ink liquid to an image receiving medium as a continuous flow without making droplets of the ink liquid (which will be referred to as a continuous coating mode hereinafter) in place of the ink jet mode. It has revealed that a fluctuation of an amount of supply of the mixed ink results in various problems as described above in this mode too. For example, when an amount of supply of the mixed ink liquid changes, a flow of the liquid may be disordered.
In the continuous coating mode, it is desirable that this liquid is transported to an image receiving medium as a steady flow. If there is an occurrence of a disorder or a whirlpool in this flow, the image quality is deteriorated. In addition, a fluctuation of an amount of supply of the liquid leads to coating layers having different thicknesses formed on the image receiving medium, but it is very difficult to stably form the coating layers having different thicknesses depending on the structure of a liquid ejection port. Even if formation of such coating layers is possible, irregularity is generated on the surface of the
Ishizaka Hideo
Matsumoto Nobuo
Yamamoto Ryoichi
Birch & Stewart Kolasch & Birch, LLP
Feggins K.
Fuji Photo Film Co. , Ltd.
Nguyen Lamson
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