Aqueous ink, aqueous ink set, ink cartridge, ink-jet recording apparatus, ink-jet recording method, and image-forming method

Abstract

An aqueous ink comprises water, a water-insoluble coloring material, and plurality of water-soluble organic solvents and the plurality of water-soluble organic solvents including a good medium or good mediums for the water-insoluble coloring material and a poor medium or poor mediums for the water-insoluble coloring material. The ratio of the content of the poor medium and the content of the good medium is in a specific range. A water-soluble organic solvent showing the maximum Ka value out of respective Ka values of the plurality of water-soluble organic solvents is the poor medium. When the aqueous ink is in contact with a specific reaction liquid, the dissolution state or dispersed state of the water-insoluble coloring material in the ink is made unstable. As a result, an image which has a sufficiently large area factor even with a small amount of ink droplets and is excellent in image density, bleeding resistance, and fixability can be obtained. In addition, the aqueous ink is excellent in storage stability.

Description

[0001] This application is a continuation of International Application No. PCT / JP2005 / 012277, filed Jun. 28, 2005, which claims the benefit of Japanese Patent Application Nos. 2004-190555 filed Jun. 28, 2004, and 2004-190573 filed Jun. 28, 2004. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an aqueous ink and an aqueous ink set each containing a water-insoluble coloring material. More specifically, the present invention relates to a recording method and a recording apparatus each using an ink-jet recording system; and an aqueous ink suitable for an image-forming method. [0004] 2. Related Background Art [0005] Ink containing, as a coloring agent, a water-insoluble coloring material such as a pigment (pigment ink) has been conventionally known to provide an image excellent in fastness properties such as water resistance and light resistance. Various techniques have been recently proposed for the purpose of increasing the image den...

AI Technical Summary

Benefits of technology

[0012] In view of the above problems, the inventors of the present invention have made various studies on ink capable of effectively suppressing color mixing (bleeding) at a boundary between regions of respective colors when a color image having a high image density and regions, which are different from each other in color, adjacent to each other is recorded on plain paper such as copy paper or recycled paper to be used as a recording medium. As a result, they have found that the above problems can be solved by utilizing the properties of a water-insoluble coloring material and a water-soluble organic solvent in ink.

[0026] According to the present invention, there can be provided an aqueous ink to be used for an image-forming method including the step of applying a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with an aqueous ink comprising a water-insoluble coloring material (two-liquid system), the aqueous ink having a sufficiently large area factor even with a small amount of ink droplets, being capable of providing an image excellent in image density; and having excellent storage stability. According to another embodiment of the present invention, there can be provided an aqueous ink set which can achieve both performance requested when plain paper is used as a recording medium (such as bleeding resistance or a high image density) and performance requested when a recording medium having surface gloss is used (such as gloss) by selecting aqueous ink to be used for forming an image in accordance with a kind of recording medium. According to another embodiment of the present invention, there can be provided an ink-jet recording method, an ink cartridge, and an ink-jet recording apparatus each using the aqueous ink or aqueous ink set having the above constitution. According to another embodiment of the present invention, there can be provided an image-forming method capable of effectively suppressing color mixing (bleeding) at a boundary between images of different colors when a color image having regions, which are different from each other in color, adjacent to each other is recorded on plain paper.

Problems solved by technology

This finding means that each of the above techniques requires an increased amount of ink to be applied as compared to that of conventional pigment ink obtained by dispersing a pigment by means of a polymer dispersant or the like for obtaining the same image density, and each of the above techniques is susceptible to improvement in this respect.

However, when the permeability of ink is improved, the ink permeates into not only the surface of a recording medium but also the depth direction of the recording medium, so a sufficient image density may not be obtained.

As a result, they have revealed that, when a coloring material is present in ink in a high concentration, a large amount of excessive coloring material is present on the surface of a recording medium, or dots having visually different shapes are formed, and that a waste coloring material not involved in color development is present in the recording medium.

(1) A problem in which, when a pigment present in ink in a dispersed state is forcedly flocculated at the surface of a recording medium, an area by which the surface of the recording medium can be covered with a coloring material as compared to the volume of an ink droplet (so-called an area factor) may not be sufficient, so the amount of ink to be applied necessary for obtaining the same image density increases.

(2) A problem in which, when the permeability of ink is improved, the ink permeates into not only the surface of a recording medium but also the depth direction of the recording medium, so a coloring material cannot be distributed in a high concentration near the surface of the recording medium, and hence a high image density cannot be achieved.

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