Aqueous ink, ink jet recording method, ink cartridge, recording unit and ink jet recording apparatus

Abstract

The invention provides an aqueous ink comprising a polymer having hydroxyl groups and a pigment, which can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of storage stability and ejection characteristics even when it is stored for a long period of time. The aqueous ink comprises a polymer having hydroxyl groups and a pigment, wherein a proportion of a content of a polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups to the content of the pigment in the ink is 2.0 mass % or more, and a content (mass %) of the polymer that is not adsorbed on the pigment out of the polymer having hydroxyl groups is 0.20 mass % or less based on the total mass of the ink.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an aqueous ink comprising a polymer and a pigment. [0003] 2. Description of the Related Art [0004] It has been known to use a pigment as a coloring material of an ink in order to make excellent the fastness properties, such as light fastness, gas fastness and water fastness, of an image obtained by an ink jet recording method. It has also been known to use in an ink a resin dispersion pigment that is dispersed with a polymer as a dispersant, or a self-dispersible pigment to the surface of which an hydrophilic group is bonded and a water-soluble polymer in order to improve the scratch resistance and highlighter resistance of an image (Japanese Patent Application Laid-Open No. H05-179183). SUMMARY OF THE INVENTION [0005] The present inventors have carried out a detailed investigation as to inks comprising a resin dispersion pigment with a view toward improving the fastness properties, ...

AI Technical Summary

Benefits of technology

[0006] Thus, the present inventors have carried out a further detailed investigation as to polymers used as dispersants for the purpose of making excellent the fastness properties, scratch resistance and highlighter resistance of images as well as the ejection characteristics of inks. As a result, it has been found that an ink in which a pigment is dispersed with a polymer having hydroxyl groups can solve the above-described problems.

[0008] Accordingly, it is an object of the present invention to provide an aqueous ink (hereinafter may also be referred to as “ink”) capable of solving the following problems when the aqueous ink comprising a resin dispersion pigment that is dispersed with a polymer having hydroxyl groups as a dispersant. In other words, the object is to provide an aqueous ink that can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of ejection characteristics even when it is stored for a long period of time.

[0015] According to the present invention, there can be provided an aqueous ink capable of solving the following problems when using the aqueous ink comprising a resin dispersion pigment that is dispersed with a polymer having hydroxyl groups as a dispersant. In other words, there can be provided an aqueous ink that can provide images excellent in scratch resistance and highlighter resistance and can inhibit the seeping out phenomenon of the polymer and the deterioration of storage stability and ejection characteristics even when it is stored for a long period of time.

Problems solved by technology

However, it has been found that when an ink cartridge stored therein with an ink in which a pigment is dispersed with a polymer having hydroxyl groups is installed in an ink jet recording apparatus and then is left to stand for a long period of time without ejecting the ink, the following new technical problem is raised.

Namely, it has been found that the polymer in the ink seeps out through ejection orifices of a recording head, adheres in the vicinity of the ejection orifices and then sticks there, thereby the ejection characteristics are deteriorated.

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