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

The present invention relates to an aqueous ink composition that improves the fastness properties of images obtained by ink jet recording. The invention addresses the problem of polymer seeping out of the ink and causing ejection characteristics deterioration. The invention proposes an aqueous ink composition comprising a polymer having hydroxyl groups and a pigment dispersed therein, wherein the content of the polymer that is not adsorbed on the pigment is at least 2.0 mass % based on the total mass of the ink. The invention also provides an ink cartridge, a recording unit, and an ink jet recording method using this aqueous ink composition. The technical effects of the invention are improved scratch resistance, highlighter resistance, and inhibition of seeping out of the polymer and deterioration of ejection characteristics even after long-term storage.

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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