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

Abstract

An ink jet ink contains at least a coloring material and a specific water-soluble organic solvent and has both excellent color developability and excellent humidity resistance. The coloring material exhibits a small (9 or less) color difference ΔE value which is determined by a method including a series of specific steps and is represented as the square root of (L1-L2)2+(a1-a2)2+(b1-b2)2. The specific water-soluble organic solvent has an evaporation rate X smaller than that of water and a moisture absorptivity Y, the values of X and Y satisfying the relation of Y≦2.8X+10. The content of the specific water-soluble organic solvent is 50 mass % or more of the total amount of water-soluble organic solvents contained in the ink.

Description

[0001] This application is a continuation of International Application No. PCT / JP2005 / 012701, filed Jul. 4, 2005, which claims the benefit of Japanese Patent Application Nos. 2004-196446 filed Jul. 2, 2004, 2004-196449 filed Jul. 2, 2004 and 2005-193806 filed Jul. 1, 2005.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an ink jet ink having good color developability, good humidity resistance, and high reliability as ink jet ink; an ink jet recording method; a recording unit; an ink cartridge; and an ink jet recording apparatus. [0004] 2. Related Background Art [0005] An ink jet recording method is a recording method involving applying a small ink droplet to any one of recording media such as plain paper and glossy media to form an image, and has become rapidly widespread owing to a reduction in its cost and an improvement in its recording rate. With the rapid spread of a digital camera in addition to an improvement in quality of a...

AI Technical Summary

Benefits of technology

[0014] The inventors of the present invention have found that a coloring material used in a conventional yellow ink for ink jet recording tends to be poor in humidity resistance when the coloring material has good color developability, while the coloring material tends to be poor in color developability when the coloring material has good humidity resistance. Such tendency is also in correlation with the molecular weight of the coloring material. In general, a coloring material having a large molecular weight hardly moves in a recording medium when the coloring material is brought into contact with excessive humidity after the coloring material has been fixed to the recording medium. As a result, humidity resistance can be improved. Meanwhile, the coloring material having a large molecular weight has a structure in which a part not contributing to coloring is relatively large, so coloring efficiency per unit mass reduces. Therefore, when a coloring material having a large molecular weight and good humidity resistance is to be used, color developability must be sacrificed. In other words, compatibility between color developability and humidity resistance in an ink containing a yellow coloring material must be achieved in order to increase the image storage stability of an ink jet recorded article to the level of silver halide photograph or higher.

[0018] Therefore, a major object of the present invention is to provide a novel technique for suppressing a change in color tone due to migration by paying attention to the amount of a water-soluble organic solvent present in a recorded article on the basis of the foregoing finding.

[0019] Another object of the present invention is to provide an ink excellent in humidity resistance and properties as an ink jet ink such as start up ejection stability.

[0020] Another object of the present invention is to provide an ink excellent in humidity resistance, start up ejection stability, image density, and color tone.

[0031] According to the present invention, there can be provided: an ink jet yellow ink which satisfies color developability requested for ink jet ink and has high humidity resistance even when letters are printed by means of the ink on various recording media; and an ink jet recording method, a recording unit, an ink cartridge, and an ink jet recording apparatus each using the ink.

Problems solved by technology

Meanwhile, the coloring material having a large molecular weight has a structure in which a part not contributing to coloring is relatively large, so coloring efficiency per unit mass reduces.

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