Oil based ink composition for inkjet printer

Abstract

An oil based ink composition for inkjet printer comprising colored resin particles obtained by dispersion polymerization of a monofunctional polymerizable monomer (A) and a macromonomer (M) copolymerizable with the monomer (A) with coloring component fine particles comprising a surface-treated coloring agent, which are dispersed in a non-aqueous solvent having a dielectric constant of from 1.5 to 20 and a surface tension of from 15 to 60 mN/m at 25° C., as seed particles, in the presence of a dispersion stabilizer (P) soluble in the non-aqueous solvent and a polymerization initiator.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an oil based ink for use in inkjet recording device, which ejects ink to form letters or images on an ink receiving medium such as recording paper. In particular, the invention relates to an oil based ink comprising a colored resin particle in which a coloring component particle of surface-treated coloring agent is further coated with a polymer, an electrophotographic developer, and a process of producing the colored resin particle. BACKGROUND OF THE INVENTION [0002] Hitherto, there have been known various inkjet recording systems including on-demand ejection systems and continuous ejection systems, as described, for example, in Takeshi Agui, et al., Real Color Hard Copy, Sangyo Tosho Co., Ltd. (1993), Shin Ohno, Non-impact Printing—Technologies and Materials-, CMC Publishing Co., Ltd. (1986), and Takeshi Amari, Inkjet Printers—Technologies and Materials-, published by CMC Publishing Co., Ltd. (1998). Further, the contin...

AI Technical Summary

Benefits of technology

[0013] Therefore, an object of the invention is to provide an oil based ink for inkjet printer in which a pigment is uniformly dispersed in the state of fine particle and dispersion stability of the pigment dispersion is excellent, and which has high discharge stability free from the occurrence of clogging in a nozzle section.

Problems solved by technology

However, in the case where printing is practically carried out using the aqueous dye ink, many drawbacks are encountered in that the ink blurs on recording paper depending on the kind of paper, whereby high-quality print can not be obtained, in that a formed recorded image is poor in water resistance and light fastness, in that drying of ink on recording paper is so slow that streaks occur, and in that a recorded image is deteriorated due to color mixing (color turbidity or color unevenness occurred on the interface when dots having different colors are printed adjacent to each other).

However, there is a problem in that since the pigment is insoluble in the medium, dispersion stability of the ink is ordinarily poor to likely cause clogging in a nozzle section.

However, such inks still have a problem in that clogging of ink in a nozzle section is liable to occur, because it is not sufficient to uniformly disperse the pigment particles in the state of fine particles in the non-polar insulating solvent and the dispersion stability thereof is inferior.

In addition, there is a large defect in that the ink is poor in scratch resistance because the pigment itself does not have a fixing ability on recording paper.

However, the proposed resin is still insufficient with respect to dispersion stability of pigment and is questionable in reliability as ink.

Moreover, since the resin is dissolved in the non-polar solvent, the resin does not remain in an amount sufficient for completely fixing the pigment on recording paper, so that water resistance and scratch resistance are not sufficient.

However, since it is difficult to uniformly disperse the pigment-included resin particles in the state of fine particle and dispersion stability thereof is not sufficient, there is a problem in reliability as ink.

As a result, a problem occurs in that storage stability of the pulverized pigment dispersion is damaged.

However, high-level techniques are required for dispersing pigment in the state of fine particle, and it is very difficult to increase the dispersion stability thereof.

Therefore, it is the actual situation that oil based pigment ink capable of meeting the above-described requirements is hardly available.

However, since it is very difficult to control the polarity on the pigment surface, it is the actual situation that oil based pigment ink capable of meeting the above-described requirements is hardly available.

However, the method of using a dye as the coloring agent has defects in that preparation of a black liquid developer is difficult, in that an image density is low because of the dye system, and in that light fading occurs.

Although the effect for improving dispersion stability of coloring agent is found, the electrophotographic liquid developer is still insufficient in the dispersion stability.

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