Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-06-18
2003-04-15
Vo, Anh T. N. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S096000
Reexamination Certificate
active
06547381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink, an image recording process, an ink cartridge, a recording unit, an ink set and an image forming apparatus.
2. Related Background Art
Inks with greatly various manners of being composed have heretofore been reported for writing utensils (fountain pens, marking pens, aqueous ball point pens, etc.) and ink-jet recording. In particular, in recent years, detailed research has been conducted regarding such issues as composition and physical properties of carbon black itself, and compositions and physical properties of inks containing such carbon black, whereby good recording can be conducted even on plain paper such as paper for copying, paper for reporting, notepaper, letter paper, bond paper and continuous business forms which are commonly used in offices.
For example, Japanese Patent Application Laid-Open No. 3-210373 describes water-based ink-jet inks comprising acid carbon black and an alkali-soluble polymer as a dispersing agent for the carbon black. Japanese Patent Application Laid-Open No. 3-134073 describes ink-jet inks comprising neutral or basic carbon black and a water-soluble resin as a dispersing agent for the carbon black, which are easy to be provided as dispersions excellent in shelf stability and ejection stability in bubble-jet recording apparatus.
Japanese Patent Application Laid-Open No. 8-3498 has offered a technical problem that when an ink comprising carbon black together with a dispersing agent is used as an ink for ink-jet recording, ejection becomes unstable, or sufficient optical density is not achieved, and discloses inks using self-dispersing carbon black capable of being dispersed in a solvent without using any dispersing agent as inks capable of solving such a problem. WO-A-No. 96/18695 (Japanese Patent Application Laid-Open No. 10-510862 through PCT route) and U.S. Pat. No. 5,746,818 (Japanese Patent Application Laid-Open No. 10-95941) also disclose ink-jet inks comprising self-dispersing carbon black and describe them as creating high-quality images.
The present inventors disclosed, in EP-A-No. 943,666, a technical means that a salt is added in addition to the above-described self-dispersing carbon black upon use of the self-dispersing carbon black as an ink-jet ink for the purpose of improving dependency of image density on the kind of paper and reducing bleeding at boundaries between a black ink and color inks.
By the way, as factors for considering the nature of an ink for ink-jet, there are the intermittent ejection stability and crusting property of the ink. Specifically, the intermittent ejection stability of the ink means the following property. Namely, when an ink is ejected from a predetermined nozzle of an ink-jet recording head, the ejection of the ink from the nozzle is stopped for a considerably long period of time (for example, about 12 hours) and the ink is then ejected again from the nozzle, the resumption of ejection of the ink may not be stably conducted in some cases to disorder printing. As described above, the operation that the ink is ejected from the predetermined nozzle, the ejection of the ink from the nozzle is stopped for the predetermined period of time and the ink is then ejected again from the nozzle is referred to as “intermittent ejection of ink”, and unstable resumption of ejection of the ink is referred to as “poor intermittent ejection”.
The crusting property of the ink means the following property. Namely, when ejection of an ink from a nozzle is stopped for a long period of time (for example, several days or longer) and the ink is then ejected again from the nozzle, a recovery operation for removing an ink which has undergone an increase in viscosity or solidification within the nozzle may be required in some cases. A state that the resumption of ejection of the ink is not stably conducted due to the viscosity increase or solidification of the ink within the nozzle is referred to as “crusting of ink”, and an ink of which a great number of recovery operations is required for achieving stable resumption of ejection is referred to as “ink poor in crusting property”.
Ink-jet inks have been required to have extremely high properties with the formation of ultrahigh-quality images by ink-jet recording in recent years.
SUMMARY OF THE INVENTION
However, it may not be said that technical findings for providing images having high optical density (OD) and sharp edge and achieving ink-jet ejection properties such as intermittent ejection stability and crusting property as to pigment inks comprising the above-described self-dispersing carbon black as a coloring material, particularly black pigment inks are sufficiently accumulated, and so their behavior as inks for ink-jet recording is not completely clarified.
For example, the ink comprising the self-dispersing carbon black and a salt proposed by the present inventors is extremely useful for lessening the dependency of image density on the kind of paper and the bleeding at boundaries between a black ink and color ink(s), which are the original objects. However, the present inventors have carried out a further investigation with a view toward establishing far excellent ink-jet recording techniques. As a result, it has been found that the intermittent ejection stability and crusting property of the inks greatly vary according to the structure of a recording head used.
The structures of a recording head is expected to be diversified with the wide product development of ink-jet printers and spread of application fields of ink-jet recording techniques, which has given us recognition that technical development is required as to inks which exhibit good and stable ink-jet properties against the diversification of recording heads while making the best use of the excellent properties of the inks comprising self-dispersing carbon black.
It is accordingly an object of the present invention to provide an ink comprising a pigment, particularly self-dispersing carbon black as a coloring material and having excellent ink-jet recording properties.
Another object of the present invention is to provide an image recording process capable of stably forming high-quality ink-jet recorded images.
A further object of the present invention is to provide a method of improving crusting property in ink-jet recording using a head having, in an ink flow path, a site where the flow resistance of the ink is greatly changed.
A still further object of the present invention is to provide an image recording process and an image forming apparatus which can stably provide high-quality prints, and an ink cartridge and a recording unit used therein.
A yet still further object of the present invention is to provide a method of lessening crusting on an ink-jet recording head.
A yet still further object of the present invention is to provide a method of improving intermittent ejection stability in an ink-jet recording process comprising the step of ejecting an ink plural times at a prescribed time interval, and particularly a method of improving intermittent ejection stability at the time when a recording head of the so-called side shooter type that a liquid is ejected in a direction opposite to an ink ejecting pressure-generating element is used.
The above objects can be achieved by the present invention described below.
According to an aspect of the present invention, there is provided an ink comprising a coloring material and an aqueous medium wherein the coloring material contains a self-dispersing type carbon black, the self-dispersing carbon black having a hydrophilic group bound to the surface thereof directly or through another atomic group, and wherein the ink contains potassium ion in an amount of 0.6 wt % or more of the weight of the carbon black.
According to an embodiment of the present invention, there is thus provided an ink comprising a coloring material at least containing self-dispersing carbon black having at least one hydrophilic group bound directly or through another atomic group to the surface thereof,
Mishina Shinya
Osumi Koichi
Watanabe Tomonari
Shah Manish S
Vo Anh T. N.
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