JPH0525414A - Ink for ink-jet printer - Google Patents

Abstract

PURPOSE:To improve printed image quality, rubbing resistance, and dispersion stability by incorporating, into a nonpolar insulating solvent, a pigment, resin particles insoluble in the solvent, and a dispersant. CONSTITUTION:A dispersant is dissolved in a nonpolar insulating solvent and a pigment is then dispersed in the solution. This dispersion is filtered to obtain a liquid A. To this liquid A is gradually added a liquid B which is a dispersion in a nonpolar insulating solvent of resin particles insoluble therein. Thus, an ink for use in an ink-jet printer is obtained which has a viscosity of 30muPa.s or lower at 0-50 deg.C around the delivery nozzle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for ejecting ink droplets from fine ejection openings provided in a recording head and forming characters or images on a transfer medium such as recording paper by the ink droplets. The present invention relates to a suitable ink for inkjet printers.

[0002]

2. Description of the Related Art The mainstream of ink applied to an ink jet system is composed of a water-soluble dye and its solvent. When actual printing is performed mainly with ink containing a water-soluble dye, ink bleeds on the transfer medium and high-quality printing cannot be obtained, and the color tone of the formed recorded image is unclear and the density is low. The recorded image thus obtained has drawbacks such as poor water resistance and light resistance. Therefore, recently, in order to improve the water resistance and light resistance of a recorded image, which is one of the problems of the ink containing mainly the water-soluble dye, an attempt has been made to apply a pigment-based ink to an inkjet recording method.

[0003]

However, there is a problem that the dispersion stability is poor because the pigment is insoluble in the ink medium. Further, the above-described conventional pigment-based ink has a problem that the ink still bleeds on the transfer medium, and further has a defect that the ink fixing strength is low.

Therefore, the present invention solves the above-mentioned problems, and an object of the present invention is to make it possible to perform printing without blurring of characters or images, and to improve the scratch resistance and dispersion stability. It's about providing high ink.

[0005]

The ink for an ink jet printer of the present invention comprises a non-polar insulating solvent, a pigment, and
Insoluble resin particles and a dispersant are added.

[0006]

The present invention will be specifically described below with reference to examples, but the invention is not limited thereto.

In the method for producing an ink for an ink jet printer of the present invention, a dispersant is added to and dissolved in a polar insulating solvent, then a pigment is added and treated with a disperser such as a ball mill, attritor or sand mill to obtain a uniform dispersion. As a dispersion system, a liquid A is obtained by filtering through a filter or the like to remove huge particles, dust, etc., if necessary. Next, a solution B in which insoluble resin particles are dispersed in a nonpolar insulating solvent is separately prepared, and the solution B is added to the solution A.
The liquid is added with gradual stirring to obtain the desired inkjet printer ink. If necessary, it can be further filtered.

The components of the ink will be specifically illustrated below.

(Pigment) As the pigment that can be used in the ink for an ink jet printer of the present invention, various organic or inorganic pigments including conventionally known ones can be used. Examples include carbon black, insoluble azo pigments, phthalocyanine pigments, isoindolinone pigments, quinacridone pigments, perinone / perylene pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments. Examples thereof include pigments and metal oxides (iron oxide, titanium oxide, cadmium oxide, chromium oxide, etc.). In some cases, two or more of these may be mixed and used.

(Insoluble Resin Particles) Examples of the insoluble resin particles that can be used in the ink for an ink jet printer of the present invention include polyvinyl acetate resin particles, vinyl acetate copolymer resin particles (for example, vinyl acetate acrylate, vinyl maleate). Dibutyl acid, vinyl acetate, vinyl acetate), acrylic ester copolymer resin particles (eg, acrylic ester methyl methacrylate, acrylic ester styrene), other thermoplastic resin particles (eg, vinylidene chloride copolymer, vinyl chloride) -Copolymer, polyethylene), thermosetting resin particles (for example, epoxy resin), synthetic resin particles (for example, butadiene styrene, butadiene acrylonitrile), and the like. These insoluble resin particles may be used in combination of two or more kinds depending on the case.
The dispersion medium in which the insoluble resin particles are dispersed is preferably the same solvent as the nonpolar insulating solvent that is the main component of the ink.

(Solvent) As the non-polar insulating solvent that can be used in the ink jet printer of the present invention, an aliphatic hydrocarbon solvent, specifically, Isopar manufactured by Exxon Co., Soltor manufactured by Phillips Oil Co., Ltd., Idemitsu Petrochemical Co., Ltd. The company's IP solvent, Petroleum Naphtha, Shell Petrochemical Co., Ltd. B. R. , Shelsol, Pegasol of Mobil Oil Co., and the like. The properties required for the insulating solvent are that the above-mentioned insoluble resin particles are not aggregated, that they are less toxic, that they are less flammable, and that they have less odor. Moreover, these can also be used in mixture of 2 or more types depending on the case.

(Dispersant) As a dispersant which is appropriately added to the ink for an ink jet printer of the present invention in order to disperse a pigment in a non-polar insulating solvent, a dispersant which is compatible with the above solvent or stable As long as it can disperse fine particles, specific examples thereof include sorbitan fatty acid ester (sorbitan monooleate, sorbitan monolaurate, sorbitan sesquioleate, sorbitan trioleate, etc.), polyoxyethylene sorbitan fatty acid ester ( Polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, etc.), polyethylene glycol fatty acid ester (polyoxyethylene monostearate, polyethylene bricol diisostearate, etc.), polyoxyethylene alkylphenyl ether Le (polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, etc.), etc. are preferable. In addition to these, an anionic activator, a cationic activator or a nonionic activator can be used. Moreover, these can be used in mixture of 2 or more types depending on the case.

(Physical properties preferred as ink) As for the physical properties of ink, the ink viscosity when the operating temperature is set to 0 to 50 ° C. is the stability of ink supply and the stability of ink droplet flight under high speed response of the head. 30mPa · s or less is required near the nozzle when discharging,
2.0 to 15.0 mP to achieve even faster response
a · s is more preferable.

The components of the ink for the ink jet printer of the present invention will be specifically illustrated below by using the above-mentioned materials, but the components are not limited thereto.

Table 1 shows the ink compositions of Examples and Comparative Examples of the present invention.

[0016]

[Table 1]

Examples 1 to 7 of the ink for an ink-jet printer of the present invention in which a known ink-on-demand type ink jet printer contains an insoluble resin in a non-polar insulating solvent, and an insoluble resin in a non-polar insulating solvent. Comparative examples 1 and 2, which are conventional inks for inkjet printers containing no ink, were printed, the print quality was printed with a character pattern, and the bleeding condition was evaluated. The bleeding was confirmed visually, and the bleeding was visually confirmed. Regarding the scratch resistance test, after printing a full solid pattern and completely drying the printed material, rubbing the solid part with a finger and visually observing no background stain on the recording medium ○ 〃 was confirmed × It was classified according to the judgment criteria. Further, regarding the dispersion stability, the aggregation state of the ink was observed, and it was classified according to the criterion of “no aggregation occurred at 70 ° C. for 3 months, ◯” occurred. Table 2 shows each evaluation result.
Shown in.

[0018]

[Table 2]

As shown in Table 2, the inks of Examples 1 to 7 of the ink for an ink jet printer of the present invention containing an insoluble resin in a non-polar insulating solvent are different in terms of print bleeding and scratch resistance. Is also good, but in Comparative Examples 1 and 2 which are conventional inks for inkjet printers that do not contain an insoluble resin in a non-polar insulating solvent, scuff resistance is scumming, and print quality is print bleeding. Each was clearly visible. In the dispersion stability evaluation test, all of the examples are good, but the examples are not suitable for the comparative example 1, and the pigment is not added for the comparative example 2, so the aggregation is not confirmed. It was not suitable because it precipitated in the inside.

[0020]

As described above, when the ink for an ink jet printer of the present invention is used, printing blur and scratch resistance are improved when actual printing is performed on a transfer medium.
It also has the effect of being excellent in dispersion stability.

Claims (1)

Claim: What is claimed is: 1. An ink for an ink jet printer comprising a non-polar insulating solvent, a pigment, insoluble resin particles and a dispersant.