JP2000063723A - Ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink composition usable for printing a paper in general use in a thick ink without causing any blur of characters and images and for presenting a printed matter for printing good in dryability and free from any tails by including a coloring component in a resin insoluble in the dispersion medium. SOLUTION: This composition comprises (A) a coloring matter (e.g. basic azo dyes) and (B) a dispersion medium dispersedly holding the component A, wherein the component A is contained in a resin insoluble in the component B and the resin is dispersed in the dispersion medium in the form of particulates. Preferably, the composition further comprises (C) a dispersant and the component B is made of an organic solvent of e.g. a normal paraffin-based hydrocarbon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink used in an ink jet recording apparatus for ejecting ink droplets to form characters and images on a recording medium such as paper.

[0002]

2. Description of the Related Art Conventionally, ink jet recording methods can be broadly classified into two types: continuous type and on-demand type. As the ink used in such an inkjet system, a dissolution type water-based ink composition in which a dye is dissolved in water is predominant.

As the water-based ink, those in which various water-soluble dyes are dissolved in water or a mixed solvent of water and a water-soluble organic solvent, and various additives are added if necessary, are mainly used at present. The advantages of these ink jet recordings are that they are direct recording, the process is simple, they are noiseless because they are not impact methods, they are easy to colorize, they are capable of high speed recording, and plain paper can be used. It has excellent features such as low running cost and high resolution recording because it ejects minute ink droplets.
Its potential is drawing attention.

However, in the above-mentioned prior art, although there are some differences depending on the method, the common technical problems to be solved are: (1) Ink bleeds on the transfer paper and a high-quality recorded image cannot be obtained. (2) The drying speed of the ink on the transfer-receiving paper is slow, causing tailing. (3) The nozzle and the ink supply path are clogged, and the ink ejection is not stable.

Attempts have also been made to solve the above-mentioned problems, for example, in JP-A-55-29546, a specific surfactant is added to lower the surface tension and to cover the ink. It has been proposed to improve the absorbability of transfer paper. In Japanese Patent Laid-Open No. 56-57862, a strongly basic substance is added to raise the pH, and a sizing agent and a pulp agent, which are water-proof treatment agents for plain paper, are chemically dissolved to control the spread and absorption of dots. How to do is reported. In addition, JP-A-5
Japanese Patent Laid-Open No. 8-13675 proposes a method of controlling the spread of dots and the absorptivity to transfer paper by adding polyvinylpyrrolidone having a molecular weight of 40,000 or more to the ink. According to the knowledge of the present inventor, it is considered that these attempts only partially solve the above-mentioned problems, and are not a measure to harmoniously solve all the problems.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve such a problem, and is an ink jet in which minute droplet ink is ejected from a recording head and the ink is adhered onto a transfer paper to perform printing. An object of the present invention is to provide an ink composition for an inkjet printer, which enables high-concentration printing on a plain paper without blurring of characters or images on plain paper.

A second object of the present invention is to provide an ink composition for an ink jet printer, which has a good drying property and enables recording without tail trailing.

A third object of the present invention is to provide an ink composition for an ink jet printer which is free from clogging in the nozzle and in the ink supply path and which is excellent in ejection stability.

[0009]

The ink composition according to the present invention is an ink composition containing a coloring component and a dispersion medium for uniformly dispersing and holding the coloring component, wherein the coloring component is the dispersion medium. Contained in a resin that is insoluble to
In addition, the resin is characterized by being dispersed in a dispersion medium in the form of fine particles.

Conventionally, in a general ink composition, the separation of a coloring component and a solvent (vehicle) on a recording material is considered to be an unfavorable phenomenon and a property which should be avoided as an ink. Was there. The present inventor has found that, by reversing the conventional wisdom about such conventional inks and using them in an advantageous manner, the characteristics required for ink jet recording can be extremely effectively adapted. The present invention has been completed based on this finding.

When printing is performed on ordinary paper using the ink of the present invention, the coloring component in the ink attached to the paper is fixed at the position where the ink is attached, and only the dispersion medium is used. It spreads along the fibers to increase the surface area and dries quickly. In this way, at the moment when the ink adheres to the paper, the coloring component and the dispersion medium are separated very quickly, so that the coloring component and the dispersion medium do not move along the fiber. That is, bleeding is prevented.

As described above, the reason why the coloring component in the ink and the dispersion medium can be quickly separated after adhering to the paper to effectively prevent the bleeding is not clear, but the surface of the dispersion medium in the ink component is not clear. Due to the low tension, the moving speed of the dispersion medium utilizing the capillarity caused by the fibers of the paper becomes extremely high, the cohesive force between the colored components in the dispersed state, and the relatively high strength between the colored components and the paper. It is considered that the main factor is that the high cohesive force prevents migration of the coloring component after attachment. The ink of the present invention is excellent not only in good printing quality but also in the effect of improving scratch resistance due to the above separation phenomenon.

The above-mentioned phenomenon is illustrated in FIG. In FIG. 1, 1 is a circle, and 2 is a boundary line is called a contour. In the circle of 1, the dispersion medium, which is a constituent component of the ink for an ink jet printer of the present invention, permeates (O
It is formed by diffusion on an HP sheet or the like), and evaporates to dryness over time and disappears. Also,
FIG. 2 is a diagram showing a state of ink dots on a printing object when printing is performed using a conventional ink for an inkjet printer, and FIGS. 1 and 2 are formed by the same amount of ink droplets. The state of ink dots is shown at the same scale.
As can be seen from these two figures, the ink for conventional ink jet printers absorbs and diffuses along the fibers of the print-receiving paper, causing bleeding as shown by 3, the print density is low, and the dot shape is circular. It is far from, and is the biggest factor of print quality deterioration. On the other hand, the ink for an inkjet printer of the present invention does not penetrate along fibers and forms a circle with a sharp contour, so that the printing density is high, the printing quality is good, and it is also compatible with high resolution recording. Is.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The constituent components of the ink composition of the present invention will be specifically described below.

In the ink composition of the present invention, the coloring component is dispersed in the dispersion medium in the state of emulsion. As such a dispersion system, for example, a dispersoid can be formed by incorporating a dye into a resin (hereinafter, also referred to as a fixing agent) insoluble in the dispersion medium. In such an embodiment, for example, the ink composition contains a dye, a high-boiling point / low-volatile solvent and a fixing agent, the fixing agent contains the dye, and a colloidal fluid dispersed as fine particles in a dispersion medium is used. Constitute.

The present inventor has developed various liquid inks capable of achieving high print quality on any transfer medium, having water resistance, and having excellent recording stability and storage stability without clogging. An ink composed of a combination of a dye, an organic solvent and a fixing agent was prepared, and as a result of experiments, resin particles uniformly dispersed in a dispersion medium were impregnated with, adsorbed on, or carried a dye, which is a colorant, Only the colored component is fixed on the transferred material, and the solvent is allowed to permeate / diffuse or flow out of the transferred material to quickly separate the colored component and the solvent, and a dot shape with a sharp outline is formed as shown in FIG. It has been found that a retained film is formed and solidified and fixed. Further, the drying property is also good, and there is no set-off or tailing due to the surface film of the fixing agent due to separation and evaporation of the solvent.

Further, by using an organic solvent having a high boiling point and a low volatility as a dispersion medium for dispersing the colored fine particles,
It is possible to prevent clogging.

In the present invention, 21 in FIG. 4 is looped around, and the boundary line portion of 22 is called a contour. The modes of separation are shown in FIG. 5 (separation by surface only) and FIG. When it penetrates inside), it also includes such phenomena. Also,
24 in FIG. 4 is called bleeding. In the present invention, such bleeding of the coloring component along the fiber is prevented.

The colorant used in the above-mentioned emulsion type ink is a water-soluble dye or oil-soluble dye used in conventional inks, and the addition of other ink components causes a change in color tone and a precipitate. Any dye can be used as long as it does not generate

For example, basic azo dyes, acidic azo dyes,
Direct dyes, anthraquinone dyes, carbonium dyes, rhodamine dyes, quinoneimine dyes and the like can be mentioned. These dyes are uniformly dispersed in a dispersion medium as a coloring component in a state of being impregnated, chemically bonded and supported in resin / wax particles.

As the material to be colored (that is, the fixing agent),
A vinyl ester-based, acrylic ester-based, methacrylic ester-based, styrene-based, or olefin-based monomer homopolymerization or copolymerization resin emulsion, wax emulsion, or the like can be used.

In order to hold the colored particles uniformly in the dispersion medium, various kinds of surfactants, dispersing agents, surface treatment, graft polymerization and the like are used.

Further, a solubilizer for impregnating a dye for coloring emulsion particles is added, a dye is added at the time of emulsion polymerization for producing an emulsion, and a resin / wax that is not dissolved in a dispersion medium is heated and melted to obtain a dye. Can also be dissolved and mechanically dispersed using a dispersant.

In the emulsion system as described above, if the amount of the dye added is less than 0.5% by weight, desired color tone and density cannot be obtained, and if it exceeds 20% by weight, clogging occurs.
The amount is preferably 0.5 to 20% by weight because it may affect storage stability.

Examples of the preferable organic solvent in this case include normal paraffin hydrocarbons, isoparaffin hydrocarbons, aliphatic hydrocarbons, and halogenated aliphatic hydrocarbons. From the viewpoint of odor, safety and dryness, a paraffinic or alicyclic hydrocarbon having a boiling point of 150 to 250 ° C. is preferable, and examples thereof include Isopar G, H, K and L.
And L (manufactured by Exxon Chemical), IP Solvent (manufactured by Idemitsu Petroleum), Shelsol 71 (manufactured by Shell Chemical) and the like can be preferably used.

Preferred organic solvent-soluble resins include rosin resins, terpene resins, petroleum resins, coumarone-indene resins, styrene resins, phenol resins, xylene resins, acrylic resins and the like.

In the present invention, the surface tension (at 25 ° C.) of the above dispersion medium is preferably limited to 50 dyn / cm or less, more preferably 35 dyn / cm or less.
When the surface tension exceeds 50 dyn / cm, the separation speed between the coloring component and the dispersion medium tends to be low.

Further, the control of the surface tension of the dispersion medium can be adjusted to an optimum value by adding a surfactant having compatibility with the organic solvent.

The basic structure of the present invention is as described above,
Conventionally known dispersants, surfactants, emulsifiers, viscosity modifiers,
A specific resistance adjusting agent, an antifungal agent and the like can be added if necessary.

As the physical properties of the ink, the temperature during operation is 0 ° C.
The ink viscosity in the case of being set to ˜50 ° C. is preferably 30 mpa · s or less in the vicinity of the ejection nozzle in consideration of the stability of the ink supply under the high speed response of the head and the stability of ink droplet flight. 2.0 to 15.0 mPa · s is more preferable for realizing high-speed response.

As a method for preparing an ink, the respective components are blended and treated with a dispersion mill such as a ball mill, an attritor or a sand mill to obtain a uniform dispersion, and if necessary, giant particles,
It can also be filtered through a filter to remove dust.

Means for uniformly dispersing the coloring component in the dispersion medium include the action of the electric double layer, the action of protecting the adsorption layer formed by the surfactant or the polymer protective colloid, and the reactive group soluble in the dispersion medium. It can be used as a method of chemically bonding the polymer having a functional group to the surface of the coloring component, a method of chemically bonding the above-mentioned coupling agent to the surface of the coloring component, an emulsion polymerization and the like.

If necessary, it is necessary to perform pressure reduction / pressurization through a filter or the like in order to remove large particles, dust, contamination, etc., and stirring / mixing / preparation to obtain a final ink form. .

The use of the ink composition of the present invention enables clear printing with high density without causing bleeding on plain paper, which has been a problem in the past, and does not cause clogging. The dispersed material can be printed on an OHP sheet or the like, has the effect of having abrasion resistance and good storability.

Further, the use of the pigment also has a special effect that the light resistance is improved as compared with the conventional ink.

The ink composition for ink jet recording according to the present invention can be widely used as an ink for an ink jet recording apparatus which ejects ink droplets to print on a recording medium.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a state in which an ink according to the present invention is attached to an object to be printed (paper).

FIG. 2 is a conceptual diagram showing a state in which conventional ink adheres to an object to be printed (paper),

FIG. 3 is a conceptual diagram showing a state in which the ink according to the present invention is attached to an object to be printed (paper).

FIG. 4 is a conceptual cross-sectional view showing a state in which the ink according to the present invention is attached to an object to be printed (paper).

FIG. 5 is a conceptual diagram of a cross section showing a state in which the ink according to the present invention is attached to an object to be printed (paper).

FIG. 6 is a conceptual diagram showing a state in which conventional ink adheres to an object to be printed (paper),

FIG. 7 is a conceptual diagram showing a state in which the ink according to the present invention is attached to an object to be printed (paper).

FIG. 8 is a conceptual diagram showing a state in which conventional ink adheres to an object to be printed (paper),

   ─────────────────────────────────────────────────── ─── Continued front page    (31) Priority claim number Japanese Patent Application No. 2-29214 (32) Priority date February 8, 1990 (February 8, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-29215 (32) Priority date February 8, 1990 (February 8, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-29216 (32) Priority date February 8, 1990 (February 8, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-127431 (32) Priority date May 17, 1990 (May 17, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-127435 (32) Priority date May 17, 1990 (May 17, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-128774 (32) Priority date May 18, 1990 (May 18, 1990) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-130789 (32) Priority date May 21, 1990 (May 21, 1990) (33) Priority claiming country Japan (JP) (72) Inventor Kenichi Hayashi             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation (72) Inventor Yaeko Maruyama             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation (72) Inventor Noriko Oyama             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation (72) Inventor Hiroyuki Onishi             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation

Claims (3)

[Claims] 1. An ink composition containing a coloring component and a dispersion medium for uniformly holding the coloring component, wherein the coloring component is contained in a resin insoluble in the dispersion medium. And an ink composition comprising the resin dispersed in a dispersion medium in the form of fine particles. 2. The ink composition according to claim 1, wherein the ink composition further contains a dispersant. 3. The ink composition according to claim 1, wherein the dispersion medium comprises an organic solvent.