Ink-jet recording ink, ink cartridge and recording device using such ink

FIG. 5

Ultraviolet-ray

absorbing agent ... ( absorbing agent

HO

nu AH0

f Organic Organic

/ silicon silicon

Ultraviolet-ray compound compound

absorbing agent

INK-JET RECORDING INK, INK CARTRIDGE AND RECORDING DEVICE USING SUCH INK

[0001] BACKGROUND OF THE INVENTION

[0002] The present invention relates to an ink-jet recording ink that is suitably applied to ink-jet recording, an ink cartridge and a recording device using such an ink.

[0003] Conventionally, with respect to the ink used for ink-jet recording of this type, an ink containing a dye serving as a color material, a moisture-retaining agent, a penetrating agent and water has been well known. When an image is formed on a recording medium such as recording paper and the like by using an ink containing a dye, a problem is raised in the water-resisting property of the image, that is, in that the dye oozes into water when the image gets wet with water. In particular, when plain paper (commonly-used commercial paper, more specifically, paper which is used in a copying machine in an electrophotographic system, and is not intended to provide optimal structure, composition, characteristics and the like for use in ink-jet recording) is used for the recording, the water-resisting property deteriorates seriously.

[0004] Therefore, as described in patent gazettes, for example, Japanese Patent Applications Laid-Open Nos. 10-212439, 11-293167, 11-315231 and 2000-178494, an ink-jet recording ink has been proposed in which a hydrolytic silane compound (organic silicon compound) is contained so as to improve the water-resisting property in an image on a recording medium. In other words, when ink droplets adhere to the recording medium and moisture (solvent) evaporates or permeates into the recording medium, the above-mentioned silane compound remaining on the recording medium is subjected to a condensation polymerizing reaction so that the resulting silane compound of the condensation polymerizing reaction surrounds the dye; thus, even when the image on the recording medium such as recording paper gets well with water, it is possible to prevent the dye from oozing into water, and consequently to improve the water-resisting property of the image.

[0005] However, although the above-mentioned conventional arrangement provides sufficient effects to improve the water-resisting property, it fails to provide a sufficient light resistance to the image, and the resulting problem is that, after an image formed in this method has been stored for a long period, fading occurs in the image. In other words, when an image such as a printed matter formed on a recording medium such as recording paper by using this waterproof ink is subjected to irradiation with light (ultraviolet rays) such as sun light and light from a fluorescent lamp, the organic silicon compound contained in the waterproof ink attacks the color material due to the light energy to decompose the color material structure to cause a change in hues and degradation in image density, resulting in fading in the image.

[0006] The mechanism of this color material decomposition is explained as follows: as shown in FIG. 7, when ultraviolet rays are directed to a conventional waterproof ink containing an organic silicon compound and a color material, an amino group (—NH2) contained in the organic silicon compound in the ink attacks an azo group (—N=N—) of the color material through the light energy thereof, and changes the double bond of the azo group to a

single bond, as shown in FIG. 8A, or causes a cleavage in the double bond as shown in FIG. 8B; consequently, it is considered that these cause a decomposition in the color material structure, and result in a change in hues and a reduction in the image density.

[0007] The objective of the present invention is to provide an inkjet recording ink containing a water soluble substance that is subjected to a condensation polymerizing reaction without water by preventing a color material from denaturing due to an organic silicon compound added to the ink so as to apply a water-resisting property to the ink, and also to improve the water resistance of an image on a recording medium (in particular, plain paper) formed by using the ink-jet recording ink, while improving the light-resisting property of the image.

SUMMARY OF THE INVENTION

[0008] In order to achieve the above-mentioned objective, the present invention allows an ink to contain an organic silicon compound and an ultraviolet-ray absorbing agent at a predetermined concentration ratio with respect to the entire ink.

[0009] More specifically, in accordance with the present invention, an ink-jet recording ink, which contains a color material, water, a moisture-retaining agent, an organic silicon compound and a ultraviolet-ray absorbing agent, is designed so that the above-mentioned organic silicon compound is set to 0.1 parts by weight to 50 parts by weight, with the above-mentioned ultraviolet-ray absorbing agent being set to 0.1 parts by weight to 10 parts by weight, with respect to 100 parts by weight of the ink.

[0010] Moreover, in accordance with the present invention, preferably, the above-mentioned ultraviolet-ray absorbing agent is at least one member selected from the group consisting of benzophenone-based, benzotriazole-based, cyano-acrylate-based and oxalic acid anilide-based compounds.

[0011] Furthermore, in accordance with the present invention, preferably, the ink further contains a penetrating agent. With this arrangement, the ink solvent, composed of the moisture-retaining agent, the penetrating agent and water, is allowed to permeate into the recording medium quickly after the ink has adhered to the recording medium (for example, paper). With this arrangement, the condensation polymerizing reaction of the water soluble substance is quickly carried out so as to positively surround the color material (and ultraviolet-ray absorbing agent). Consequently, it becomes possible to further improve the water-resisting property of the image.

[0012] With the above-mentioned arrangement, since the organic silicon compound for improving the water-resisting property is contained in the ink, it becomes possible to improve the water-resisting property of the image formed by the ink on a recording medium such as recording paper. Moreover, the ultraviolet-ray absorbing agent having a predetermined concentration is contained in the ink; therefore, even when, upon irradiation with ultraviolet rays, the amino group of the above-mentioned organic silicon compound tries to attach the azo group of the color material, the light energy of the ultraviolet rays is converted to kinetic energy, heat energy and the like by the ultraviolet-ray absorbing