Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-02-16
2001-12-25
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031750, C106S031860
Reexamination Certificate
active
06332919
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink, an ink set, an ink cartridge, a recording unit, an image recording apparatus and an image recording method.
2. Related Background Art
Hitherto, as a black ink for writing implements such as fountain pen, sign pen or ball-point pen and a black ink for an ink-jet printer, an ink using carbon black, a black colorant, high in optical density of image and excellent in fastness has been proposed. Especially in recent years, a detailed research and development has been made from diverse aspects such as composition and property of the ink, so as to perform a good recording even on plain paper such as copy paper used generally in offices, report paper, notebook paper, letter paper, bond paper and serial slip paper. For example, Japanese Patent Application Laid-Open Nos. 63-152681 and 64-6074 disclose a water-based pigment ink containing carbon black and a dispersant. Besides, Japanese Patent Application Laid-Open No. 8-3498 mentions technical problems that ejection becomes unstable and no sufficient printing density cannot be obtained when an ink containing carbon black together with a dispersant is used as ink for ink-jet printer, and it discloses a water-based pigment ink comprising a self dispersible carbon black using no dispersant as an ink capable of solving such problems.
SUMMARY OF THE INVENTION
The present inventors have made various examinations on cases of using a black ink containing the above self dispersible carbon black as a black pigment for ink-jet recording. As a result, it has been found a case that insufficient character quality or insufficient image density is obtained depending on types of recording media such as paper and the like.
Besides, in printing color images by using such a black ink as mentioned above together with other color ink such as at least one color ink selected from magenta ink, cyan ink, yellow ink, red ink, green ink and blue ink, there has been recognized a phenomenon that an image quality is lowered by blotting of ink at the boundary between the black image portion and the color image portion on a recording medium and by non-uniform mix of ink (hereinafter, referred to as “bleeding”).
In order to prevent or reduce such bleeding, an idea of promoting the permeability of ink into recording media by addition of a so-called surfactant (such as, e.g. Japanese Patent Application Laid-Open No. 55-65269) or an idea of mainly employing volatile solvent as a solvent of ink (such as, e.g. Japanese Patent Application Laid-Open No. 55-66976) has been proposed. Also with these background techniques, however, a decrease in optical density of image and a decrease in ejection stability were brought about in some cases. In consideration of such background techniques, the present inventors have found that it is necessary to develop a black ink hardly changing in image quality even when types of recording media may be varied, in a case using the ink singly or a combination thereof with other color ink, with respect to an ink comprising a self dispersible carbon black as black pigment.
It is one object of the present invention to provide a black ink capable of mitigating an influence of recording media to an image quality and providing a black ink which can provide a high quality image stably.
It is one object of the present invention to provide a black ink capable of mitigating an influence of recording media to an image quality and providing a black ink which can provide a high quality image stably and is excellent in ink-jet ejection characteristics.
It is another object of the present invention to provide an ink set capable of effectively inhibiting the bleeding. Especially, because a black ink is often used for outputting characters or the like, a high OD (optical density) and a large difference in sharpness of characters are strongly required. Thus, in a technical skill for preventing the bleeding by using highly permeable ink as mentioned above, both character quality grade and OD have not yet been satisfied at a high level. It is also an object of the present invention to satisfy both character quality grade and OD at a higher level.
Furthermore, it is a further object of the present invention to provide an image recording apparatus and an image recording method, capable of mitigating an influence of recording media to an image quality and providing a high quality image stably, and moreover an ink cartridge and a recording unit used for them.
The above objects can be achieved by the present invention described below.
According to a first aspect of the present invention, there is provided an aqueous ink comprising at least one salt selected from the group consisting of (M1)
2
SO
4
, CH
3
COO(M1), Ph—COO(M1), (M1)NO
3
, (M1)Cl, (M1)Br, (M1)I, (M1)
2
SO
3
and (M1)
2
CO
3
, where M1 is an alkali metal, ammonium or organo-ammonium and Ph means a phenyl group, and a self dispersible carbon black.
According to this embodiment, a high grade image can be formed even in the character printing on highly permeable paper which may cause damaging an image grade, such as sharpness of characters, or lowering the image density. Incidentally, the reason why such an effect is obtained according to this embodiment is obscure, but is attributable to a rapid occurrence of solid-liquid separation after deposited to the paper surface in contrast to the stable dispersion of pigments in ink, for example when the ink is ejected and deposited to paper surface by the ink jet method. In other words, a slow solid-liquid separation allows ink to diffuse all over the paper for paper having a high permeability. As a result, a decrease in optical density of image as well as damages on the sharpness of characters (character quality grade) is naturally derived from a permeation of ink into the depth of paper. Since a solid-liquid separation occurs rapidly in paper according to this embodiment, however, the above phenomenon is considered to become difficult to occur for paper relatively high in permeability. In brief, it is considered to become insusceptible to factors such as degree of permeability dependent on the type of paper. And such an effect seems to be best obtained for 0.05 to 10% by weight of salts relative to the whole weight of ink. Furthermore, sulfates such as potassium sulfate or benzoates such as ammonium benzoate slightly affect the characteristics of the above ink, e.g. in use for ink-jet printing.
Besides, as another example of ink according to this embodiment, an ink comprising a self dispersible carbon black, on the surface of which at least one selected from —COO(M2), —SO
3
(M2)
2
and —PO
3
H(M2) is bonded directly or via other atomic groups, and a salt in which M1 and M2 are identical is mentioned. On account of its still better stability, this is one of the preferred embodiments. With M2 of ammonium (NH
4
), for example, addition of an ammonium salt, e.g. ammonium benzoate, as a salt to ink can further improve the water fastness or the like of ink-jet recording images obtained.
Besides, as another embodiment of the above ink, ink the pH of which is set to 9 to 12 can be mentioned, and the ink is also employed appropriately in stably obtaining a high grade image. Namely, a knowledge about the above ink that a long-period preservation brings about an acidic shift of pH, leading to various changes in characteristics such as an increase in viscosity of ink, has been obtained. And, a further examination on this point revealed a new knowledge that a change in characteristics of ink becomes extremely slow when the pH of ink is set within the above range and a change in characteristics accompanying the ink pH change during the preservation becomes as slight as substantially negligible. And, the above invention is based on such the knowledge.
And as a still another embodiment of the above ink, those coexistent with an stabilizer selected from anionic surfactant, cationic surfactant and the like, for example, can be mentioned. Such a composition permits a change in the characterist
Hattori Yoshifumi
Mishina Shinya
Osumi Koichi
Sanada Mikio
Takizawa Yoshihisa
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Klemanski Helene
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