JP2007224210A - Pigment dispersion for ink jet, method for producing the same and ink for ink jet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment dispersion for ink jet, excellent in disperse stability and storage stability and free from change of characteristics, particularly in high-temperature storage and to provide a method for producing the dispersion and to provide a pigment-based ink for ink jet using the pigment dispersion. <P>SOLUTION: In the method for producing the pigment dispersion for ink jet by dispersing a mixture containing at least the pigment, dispersion and water, the disperse is carried out by using an alkali ion water as the water. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet pigment dispersion, a method for producing the same, and an inkjet ink, and more specifically, an inkjet pigment dispersion having excellent saturation, ejection stability, and liquid stability, a method for producing the same, and the same. The present invention relates to a pigment-based ink-jet ink using.

  The inkjet recording method is easy to make full color because the process is simpler than other recording methods, and there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration. As ink-jet inks, dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used. Dye-based inks have excellent color tone, but are resistant to light. There was a disadvantage that was inferior in nature. On the other hand, pigment-based inks in which carbon black and various organic pigments are dispersed are actively studied because they are superior in light resistance compared to dye-based inks.

  For inks using organic pigments or carbon black, a method is employed in which these pigments are mechanically pulverized and dispersed using a media-type disperser such as a sand mill with the aid of a dispersant until a predetermined particle diameter is obtained. ing. On the other hand, in recent years, it has been desired to reduce the particle diameter of the pigment in order to improve the fineness of the image, and various dispersion methods and dispersion process conditions have been proposed to reduce the particle diameter. Unless carbon black is made very fine and stably dispersed in the medium, good transparency, fineness and color developability cannot be obtained, and ink jet ink causes nozzle clogging. However, in general, the degree of atomization by mechanical pulverization / dispersion of the pigment is practically limited, and the atomized pigment ink tends to cause problems such as secondary aggregation and storage stability.

In order to improve nozzle clogging and good color developability, it is necessary to reduce the average particle diameter of the pigment, but styrene-acrylic acid copolymers (see, for example, Patent Document 1), which are currently widely used, Ink using a polymer dispersant such as styrene-maleic acid copolymer (for example, see Patent Document 2), sodium naphthalene sulfonate formalin condensate (for example, see Patent Document 2), polyethylene glycol having propenyl group Interfaces such as alkyl phenyl ethers (for example, see Patent Document 3), polyethylene glycol alkyl phenyl ether sulfates (for example, see Patent Document 4), polyethylene glycol alkyl phenyl ether phosphates (for example, see Patent Document 4), etc. In any of the inks using the activator, the average particle size of the pigment is large, For the stability of the poor, it was inferior in discharge stability and liquid stability.
Also contains water-based pigment-based ink for ink jet (Patent Document 5) in which carbon black added with humic acid is dispersed in a liquid medium containing alkaline ionized water as a main component, pigment having a specific particle size distribution, dispersant and water Ink jet ink (Patent Document 6) using polyethylene oxide β-naphthyl ether as the dispersant has also been proposed.
However, an ink containing a pigment dispersion obtained by using the above dispersant is a high molecular weight resin or a surfactant, and therefore is ejected from a fine nozzle hole of a recording head for a long time. Dispersion adheres to the periphery of the nozzle hole, impairing ejection stability.

JP 2004-263035 A JP-A-56-147863 JP-A-10-168367 Japanese Patent Laid-Open No. 10-88050 Japanese Patent No. 30695550 JP 2004-2715 A

The present invention has been made in view of the above problems, and is an inkjet pigment dispersion that has excellent ejection stability, excellent storage stability, and has no change in properties particularly during high-temperature storage, and a pigment using the same It is an object of the present invention to provide a technique related to a method for producing an inkjet ink.
That is, an object is to provide an inkjet pigment dispersion excellent in ejection stability and storage stability, a method for producing the same, and a pigment-based inkjet ink using the same.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by dispersing the water contained in the dispersion liquid using alkaline ion water when the pigment is dispersed.
That is, the said subject is solved by following (1)-(10) of this invention.
(1) “A method for producing an inkjet pigment dispersion in which a mixture containing at least a pigment, a dispersant, and water is dispersed, wherein the pigment is dispersed using alkaline ionized water as the water” Method for producing dispersion ";
(2) “The method for producing an inkjet pigment dispersion according to (1) above, wherein the pigment particles in the pigment dispersion are dispersed until an average particle diameter (D ₅₀ ) is 100 nm or less” ;
(3) “The method for producing an inkjet pigment dispersion according to (1) or (2) above, wherein electrolytic alkaline ionized water having a pH of 10 or more is used as the alkaline ionized water”;
(4) The inkjet pigment dispersion according to any one of (1) to (3) above, wherein the dispersant is used in a ratio of 0.05 to 5 with respect to the pigment 1 on a weight basis. Production method";
(5) “The method for producing an inkjet pigment dispersion according to any one of (1) to (4) above, wherein a polymer dispersant or a surfactant is used as the dispersant”;
(6) “The polymer dispersant is at least one selected from a styrene-acrylic acid copolymer, a styrene-maleic acid copolymer, and a sodium naphthalene sulfonate formalin condensate (5 A method for producing a pigment dispersion for inkjet according to claim 1];
(7) “The method for producing an inkjet pigment dispersion as described in (5) above, wherein at least one compound represented by the following general formula (1) is used as the surfactant.

（式中、Ｒ_１は炭素数８〜２２のアルキル基またはアルキルフェニル基を表わし、Ｍは、アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、及びアルカノールアミンから選らばれるいずれかを表わし、ｎは４〜２１の整数を表わす。）」；
（８）「前記界面活性剤として、下記一般式（２）で示される化合物の少なくとも一種を用いることを特徴とする前記（５）に記載のインクジェット用顔料分散液の製造方法。

(In the formula, R ₁ represents an alkyl group having 8 to 22 carbon atoms or an alkylphenyl group, M represents any one selected from alkali metal ions, quaternary ammonium, quaternary phosphonium, and alkanolamine; n represents an integer of 4 to 21) ";
(8) “The method for producing an inkjet pigment dispersion according to (5) above, wherein at least one compound represented by the following general formula (2) is used as the surfactant.

（式中、ｎは２０〜１００の整数である）」；
（９）「前記（１）乃至（８）の何れかに記載の製造方法により製造されたことを特徴とするインクジェット用顔料分散液」；
（１０）「前記（９）に記載のインクジェット用顔料分散液を用いたことを特徴とするインクジェット用インク」。

(Where n is an integer from 20 to 100) ";
(9) “Inkjet pigment dispersion characterized by being produced by the production method according to any one of (1) to (8)”;
(10) “Ink jet ink using the ink jet pigment dispersion liquid according to (9)”.

  ADVANTAGE OF THE INVENTION According to this invention, the pigment dispersion liquid for inkjets excellent in saturation, discharge stability, and liquid stability, its manufacturing method, and pigment-type inkjet ink can be provided.

Hereinafter, the present invention will be described in more detail.
A feature of the present invention is a method for producing a pigment dispersion for inkjet, in which a mixture containing at least a pigment, a dispersant, and water is dispersed, wherein the dispersion contains alkali ion water as the contained water. Is. Alkaline ion water is alkaline water that is generated on the cathode side when water is electrolyzed, and usually water having a pH of 8.5 or higher is called alkali ion water. The pH upper limit value of the alkaline ionized water is about 13, although it depends on the ability of the alkaline ionized water production apparatus to be used.

  Here, the alkaline ionized water used in the present invention is preferably electrolytic alkaline ionized water having a pH of 10 or more, and the electrolytic alkaline ionized water referred to in the present invention is the alkaline water generated on the cathode side when water is electrolyzed. This means that it is distinguished from an alkaline aqueous solution obtained by adding an alkali such as NaOH or ammonia. The electrolytic alkaline ionized water used in the present invention may contain a buffer, and therefore sodium ions, potassium ions, phosphate ions, silicate ions, lactate ions, pyrophosphate ions derived from the buffer agents, It may contain ions such as fluorine ions and chlorine ions. By adding a buffering agent, the characteristics as alkaline ionized water can be maintained for a long time. Further, the electrolytic alkaline ionized water may be obtained by diluting the stock solution with ion exchange water or ultrapure water 1 to several times for pH adjustment or the like.

  If electrolytic alkaline ionized water has a pH of 10 or more, electrolysis of water may be performed, and the alkaline water produced on the cathode side may be recovered and used, or EKO- manufactured by JEOL Active Co., Ltd. Commercial products such as 13 (pH about 12) may be used. Moreover, as long as pH is 10 or more, the electrolytic alkaline ionized water may be a solution obtained by diluting the stock solution with pure water or ion-exchanged water, or may further contain a buffering agent or the like. . The electrolytic alkaline ionized water has an excellent osmotic action. Particularly, electrolytic alkaline ionized water having a pH of 10 or higher has high osmotic characteristics.

  An example of using simple alkaline ionized water for ink-jet ink is described in Japanese Patent Application Laid-Open No. 2000-119571, and there is a description that inclusion in the ink improves the head cleaning properties. Ionized water is used when the pigment is pulverized and dispersed, and is characterized in that the pigment and the dispersion medium become familiar and efficiently dispersed.

  The surface of the organic pigment for coloring, carbon black, is inherently new oily, and is well adapted to oil, but has no affinity for water, and as a result, it easily repels water. For this reason, even if an attempt is made to mix and disperse the pigment in the aqueous solution in which the dispersant is dissolved, the pigment surface is not easily wetted with the aqueous solution, and the dispersion efficiency is poor. Miniaturization is the disintegration of pigment aggregates into primary particles or a state close to primary particles and the grinding of primary particles. Therefore, in the present invention, by using alkaline ionized water as the dispersion medium water, the dispersing agent is adsorbed on the pigment surface by the excellent penetrating action that is a characteristic of the dispersion medium, and the dispersion can proceed efficiently.

In the method for producing a pigment dispersion for inkjet according to the present invention, the dispersion treatment is preferably carried out until the average particle diameter (D ₅₀ ) of the pigment particles is 100 nm or less. According to the document “Coloring Material 69 [12], 855-866 (1996)”, the level of atomization required by an inkjet apparatus is as follows: (1) fluid characteristics required by the device, and (2) the market period of ink products. In consideration of stability, there is a description that the average particle size is 80 to 250 nm and the maximum particle size is about 300 nm. In the present invention, an average particle diameter (D ₅₀ ) of pigment particles is 100 nm or less in order to produce a pigment dispersion excellent in saturation, ejection stability, and liquid stability and a pigment-based inkjet ink using the same. Dispersion treatment is preferably performed until

In general, as the dispersion is advanced, the spread of the particle size distribution increases. However, in the present invention, in order to solve the above problems, the average particle size (D ₅₀ ) of the pigment particles is 100 nm or less and the particle size distribution of the pigment particles is It is preferable to produce a pigment dispersion having a particle size standard deviation smaller than the average particle size (D ₅₀ ). To that end, the present invention can be achieved by using alkaline ionized water as the dispersion medium water.

The average particle diameter (D ₅₀ ) of the pigment particles is more preferably 80 nm or less. When the average particle diameter (D ₅₀ ) exceeds 100 nm, the saturation, ejection stability, and liquid stability deteriorate.
Incidentally, in average particle diameter (D ₅₀₎ of the present invention it is possible to measure by a conventional method, it can be measured, for example using a particle size analyzer Microtrac UPA 150. In addition, the standard deviation of the particle diameter referred to in the present invention can be measured by a conventional method, but this also employs a measured value sd obtained by measuring using, for example, a particle size analyzer UPA150 manufactured by Nikkiso Co., Ltd. be able to.
The measurement of the average particle diameter (D ₅₀ ) and particle diameter standard deviation of the pigment particles will be described in detail below.
The average particle diameter (D ₅₀ ) and particle diameter standard deviation of the present invention were measured using a particle size analyzer Microtrac UPA150. The dispersion was placed in a measurement cell and was measured according to the measurement procedure attached to the title measuring instrument. As parameters input at the time of measurement, the viscosity of the dispersion was input as the viscosity, and the density of the pigment was input as the density of the dispersed particles. This measuring apparatus measures the particle diameter by utilizing the Brownian motion of the dispersion, and measures the particle diameter by irradiating the solution with laser light and detecting the scattered light. The average particle diameter D _50, when calculated cumulative curve of the particle size distribution of the dispersion on the total volume of the dispersion as 100%, expressed as D ₅₀ value points of 50 percent of the cumulative curve is 50% diameter, Usually, it is defined as a cumulative average diameter (center diameter: Median diameter). The particle size standard deviation is obtained by dividing the difference between the particle size (D ₈₄ ) where the cumulative curve of the measured particle size distribution is 84% and the particle size (D ₁₆ ) where the cumulative curve is 16% by 2. With the value, the particle size analyzer Microtrac UPA150 automatically displays the value as a measured value.

  In the present invention, a dispersion apparatus for producing an inkjet pigment dispersion can be a commonly used dispersion apparatus. When the dispersion means is roughly classified by energy form, (1) compression, (2) grinding, It is divided into (3) shear and (4) impact. Rolls, kneaders, and attritors are used to disperse high-viscosity products such as ink, but beads (media) that enable efficient dispersion of fine particles for the dispersion of low-viscosity liquids such as ink for inkjet. A horizontal bead mill is preferable in order to perform fine particle dispersion with a narrow particle size distribution. In addition, beads (dispersion media) include glass, alumina, zirconia, and modified zirconia, and various types of media. In terms of fine dispersion of pigment particles, sharpening of particle size distribution, and efficiency, zirconia or modified zirconia materials are also available. Media is preferred.

  The average particle size (D50) and particle size standard deviation can be controlled by the peripheral speed of the rotating part of the disperser, the dispersion time, the dispersion flow rate, and the dispersion temperature when the pigment is dispersed using a disperser.

Further, in this case, in order for the average particle diameter (D ₅₀ ) of the pigment particles to be 100 nm or less and the particle diameter standard deviation in the particle size distribution of the pigment particles to be smaller than the average particle diameter (D ₅₀ ), the disperser rotates. If the partial peripheral speed is too high, the pigment dispersion tends to aggregate, and if it is too low, the dispersion efficiency is poor and the productivity is lowered, so that it is preferably 6 to 13 m / s.

  Further, the dispersion flow rate is preferably 300 ml / min or more, and if it is less than 300 ml / min, the dispersion temperature rises, which is not preferable for dispersion stability. Further, the circulation type dispersion is not preferable because the standard deviation of the particle diameter tends to increase in the short-time dispersion. Further, the dispersion temperature is preferably less than 10 ° C. during dispersion, and more preferably 4 to 8 ° C. has good dispersion stability.

In addition, when the above-described disperser and dispersion medium are used, the average particle size can be controlled by adjusting the size of the dispersion medium (beads). In this case, in order to make the average particle diameter (D ₅₀ ) 100 nm or less, it is preferable to make the beads about 0.1 to 1.0 mm, and more preferably 0.1 to 0.5 mm. Also it is smaller than the average particle size particle size standard deviation (D ₅₀₎ in the present invention by this method.

Moreover, in the manufacturing method of the pigment dispersion for inkjets of this invention, it is preferable to use a dispersing agent in the ratio of 0.05-5 with respect to the pigment 1 on the basis of weight. The ratio relative to the pigment 1 is more preferably 0.1 to 3, and further preferably 0.3 to 2. By using alkaline ionized water as a dispersion medium during the production of the pigment dispersion and adopting the amount of such a dispersant used, the average particle diameter (D ₅₀ ) can be reduced and the particle diameter standard deviation can be reduced. In this way, it is possible to provide an inkjet pigment dispersion that is further excellent in saturation, ejection stability, and liquid stability.

  Note that when the amount of the dispersant used is less than 0.05, the above effect is difficult to achieve, and the storage stability of the pigment dispersion and the ink is poor, and as a result, nozzle clogging tends to occur. If it is greater than 5, the viscosity of the pigment dispersion and ink tends to be too high, and printing by the ink jet method tends to be difficult.

  The dispersant used in the method for producing an inkjet pigment dispersion of the present invention is not particularly limited, but the dispersant includes a polymer dispersant and a surfactant, and the polymer dispersant is mainly alkaline. Soluble polymer compounds are used. Since the polymer dispersant is irreversibly adsorbed to the pigment, the dispersion stability can be improved. Generally, it is a water-soluble resin having a soluble group of (meth) acrylic acid and maleic acid. Specific examples include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid. Copolymers, sodium naphthalene sulfonate formalin condensate, etc., preferably styrene-acrylic acid copolymer, styrene-maleic acid copolymer, sodium naphthalene sulfonate formalin condensate.

  In addition, the use of a surfactant as a dispersant has an advantage that the viscosity tends to be low even when the pigment concentration is high. For example, a functional group such as a hydroxyl group, a sulfonic acid group, or a phosphoric acid group is present at the molecular end. Nonionic and anionic surfactants with a hydrophobicity and adsorption to the pigment surface and affinity to aqueous media by hydrophobic groups and polyethylene glycol chains, and stabilization by functional ion repulsion. As specific examples, surfactants such as polyethylene glycol alkyl ether, polyethylene glycol alkyl phenyl ether, polyethylene glycol alkyl phenyl ether sulfate, and polyethylene glycol alkyl phenyl ether phosphate can be used.

  The surfactant preferably used as a dispersant in the present invention is a surfactant represented by the following general formula (1).

（式中、Ｒ_１は炭素数８〜２２のアルキル基またはアルキルフェニル基を表わし、Ｍは、アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、及びアルカノールアミンから選択されるいずれかを表わし、第４級アンモニウムが好ましい。ｎは４〜２１の整数を表わす。）

(In the formula, R ₁ represents an alkyl group having 8 to 22 carbon atoms or an alkylphenyl group, and M represents one selected from alkali metal ions, quaternary ammonium, quaternary phosphonium, and alkanolamine. And quaternary ammonium is preferred, and n represents an integer of 4 to 21.)

[Surfactant Component Represented by General Formula (I)]
In the surfactant component represented by the general formula (I), when R ₁ is an alkyl group, the following are preferable.

前記Ｒ_１がアルキルフェニル基の場合以下のものが好適である。

When R ₁ is an alkylphenyl group, the following are preferable.

  As a specific example of the component represented by the general formula (I), a commercially available product can be used, Daiten Kogyo Seiyaku Co., Ltd. Hightenol N-07, Hightenol N-08, Hightenol N-17, Hightenol NE-05, Hightenol NE-15, Hightenol NF-13, Hightenol 08E, Hightenol 12, and Hightenol 18E fall under these, but are not limited thereto. Moreover, these may be used independently or may be used in mixture of multiple things.

  In the present invention, it is preferable to use at least one surfactant represented by the following general formula (2) as a dispersant.

一般式（２）において、ｎは好ましくは２０〜１００、更に好ましくは３０〜５０である。ｎが２０未満では分散安定性が低下する傾向があり、ｎが１００より大きいと分散液及びインクの粘度が高くなる傾向がある。中でもｎが４０である、ＰＯＥ（ｎ＝４０）βナフチルエーテルが更に好ましい。

In the general formula (2), n is preferably 20 to 100, more preferably 30 to 50. When n is less than 20, the dispersion stability tends to decrease, and when n is greater than 100, the viscosity of the dispersion and ink tends to increase. Among them, POE (n = 40) β naphthyl ether in which n is 40 is more preferable.

  Examples of the pigment used in the method for producing an inkjet pigment dispersion of the present invention include, for example, carbon black produced by a furnace method or a channel method as a black pigment.

  Examples of the yellow pigment include Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 155, Pigment Yellow 180, etc. It is below.

  Examples of magenta pigments include Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57 (Ca), Pigment Red 57: 1, Pigment Red 112, Pigment. Red 122, pigment red 123, pigment red 168, pigment red 184, pigment red 202, pigment violet 19, and the like.

  Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Bat Blue 4, Examples include Bat Blue 60.

  Among these, by using Pigment Yellow 138 as a yellow pigment, Pigment Red 122 as a magenta pigment, and Pigment Blue 15: 3 as a cyan pigment, an ink for ink-jet ink having excellent color tone and light resistance can be obtained.

  In the pigment dispersion of the present invention, the pigment concentration is preferably 5 to 30% by weight. If it is less than 5% by weight, the productivity is inferior, and if it is more than 30% by weight, the viscosity of the pigment dispersion tends to be too high and dispersion tends to be difficult.

  Moreover, various additives other than water can be mix | blended with the pigment dispersion liquid of this invention. For example, as a water-soluble organic medium, alcohols such as methanol, ethanol, 1-propanol and 2-propanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerin, N-methylpyrrolidone, 2-pyrrolidone and the like Pyrrolidone derivatives, ketones such as acetone and methyl ethyl ketone, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and nonionic, anionic, cationic, amphoteric surfactants and preservatives.

  The inkjet pigment dispersion of the present invention is dispersed by the above-described production method. However, in order to uniformly mix the pigment and the dispersion medium before the main dispersion, preliminary dispersion may be performed. As the preliminary dispersion method, a high-speed dissolver, a homomixer, or the like is preferable, and a continuous homomixer such as a TK homomic line mill (manufactured by Tokushu Kika Kogyo Co., Ltd.) can be preferably used. Further, there may be some coarse particles after dispersion, and a centrifugal separation process or a filtration process using a membrane filter or the like may be performed to remove them.

The pigment dispersion of the present invention thus obtained can be suitably used particularly as a pigment-based inkjet ink.
The pigment-based ink-jet ink uses a known method, for example, the pigment dispersion of the present invention, and this is mixed with water, a water-soluble organic solvent, a surfactant and the like, and coarse particles are filtered and degassed with a filter or the like. Can be obtained.

Examples of water-soluble organic solvents include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, and 2,3-butanediol. 1,4-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 1,2,4- Polyhydric alcohols such as butanetriol, 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol Polyhydric alcohol alkyl ethers such as coal monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2 Nitrogen-containing heterocyclic compounds such as pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; formamide, N-methyl Amides such as formamide and N, N-dimethylformamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, trie Amines such as triethanolamine, dimethyl sulfoxide, sulfolane, thiodiethanol, sulfur-containing compounds such as thiodiglycol, propylene carbonate, ethylene and the like carbonates. These solvents are used alone or in combination with water.
The amount of the water-soluble organic solvent used is preferably about 5 to 50% by weight of the ink composition, more preferably about 10 to 40% by weight.

  Examples of the surfactant that can be used include various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and the like, preferably anionic surfactants, It is a nonionic surfactant.

  The anionic surfactant preferably contains a polyoxyalkylene alkyl ether carboxylate surfactant, a polyoxyalkylene alkyl ether sulfonate salt, or a polyoxyalkylene aryl ether sulfonate surfactant. Examples of the polyoxyalkylene alkyl ether carboxylate surfactant include ECT-3NEX, ECTD-3NEX, ECTD-6NEX, ECT-3, ECT-7, AKYPO RLM 45NV (CHEM-Y) manufactured by Nikko Chemicals, AKYPO RLM45 (CHEM-Y), AKYPO RLM100NV (CHEM-Y), AKYPO RLM100 (CHEM-Y), etc. can be used, and polyoxyalkylene alkyl ether sulfonate or polyoxyalkylene aryl ether sulfonate surface activity Examples of the agent include NICOL SBL-4T manufactured by Nikko Chemicals, Hightenol N-07, Hightenol N-08, Hightenol N-17, Hightenol NE-05, and Hightenol NE manufactured by Daiichi Kogyo Seiyaku. − 5, Hitenol NF-13, Hitenol 08E, Hitenol 12, or the like can be used Hitenol 18E. In particular, when ECTD-3NEX, ECTD-6NEX, NICOL SBL-4T, Haitenol 08E, or Haitenol 18E is used, good recording quality is exhibited.

  Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, Ethers such as polyoxyethylene alkyl ether and polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, Esters such as sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate, Fluoroalkyl ester, and the like fluorine-containing surfactants such as perfluoroalkyl carboxylates.

The addition amount of these surfactants is preferably about 0.01 to 2.0% by weight, more preferably about 0.1 to 1.5% by weight of the ink composition.
The pigment concentration of the ink is preferably 1 to 7% by weight. If the amount is less than 1% by weight, the image density is low and the printed image is not clear. If the amount is more than 7% by weight, not only the viscosity of the ink tends to be high but also nozzle clogging tends to occur. Further, the ink can be blended with a material equivalent to the material described as an additive to the pigment dispersion as required.

  The pigment-based inkjet ink of the present invention thus obtained contains, for example, an inkjet recording ink set that forms an image on an image support by superimposing a plurality of different hue inks in order to form a color image. The ink cartridge can be suitably used.

  In addition, the pigment-based inkjet ink of the present invention is a printing method capable of forming an image by an inkjet printing apparatus that forms an image by ejecting the ink on an image support such as paper and recording (printing). May be a continuous injection type or an on-demand type. Examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not limited to these examples. In the examples, parts and% are based on weight.

Example 1
(Prescription 1)
150 parts of Pigment Red 122 (FASTOGEN SUPER MAGENTA RG manufactured by Dainippon Ink, Inc.)
Styrene-acrylic acid copolymer aqueous solution (solid content concentration: 30%) 100 parts (John Crill 70 MW 16,500, manufactured by Johnson Polymer Co., Ltd.)
325 parts of alkaline ionized water (PH: about 12) (EKO-13 manufactured by JEOL Active Ltd.)
325 parts of ion-exchanged water Premixed and then dispersed in a disk-type bead mill (Shinmaru Enterprises KDL type) using 0.3 mm zirconia beads at a peripheral speed of 10 m / s and a liquid temperature of 10 ° C. for 1.5 hours As a result, an inkjet pigment dispersion (A) was obtained.

Example 2
(Prescription 2)
Pigment Blue 15: 3 150 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.)
150 parts of styrene-maleic anhydride copolymer aqueous solution (20% solution obtained by neutralizing SMA-1000 manufactured by Sartomer Co. with ammonia water)
300 parts of alkaline ionized water (JEOL Active Co., Ltd. EKO-13)
300 parts of ion-exchanged water was dispersed by the same operation as in Example 1 to obtain an inkjet pigment dispersion (B).

Example 3
(Prescription 3)
150 parts of Pigment Yellow 138 (LIONOGEN YELLOW 1010 manufactured by Toyo Ink)
Sodium naphthalene sulfonate formalin condensate 20 parts (Labelin WP, manufactured by Daiichi Kogyo Seiyaku)
365 parts of alkaline ionized water (EKO-13 manufactured by JEOL Active Ltd.)
365 parts of ion-exchanged water Dispersed in the same manner as in Example 1 to obtain an inkjet pigment dispersion (C).

Example 4
(Prescription 4)
150 parts of Pigment Red 122 (FASTOGEN SUPER MAGENTA RG manufactured by Dainippon Ink, Inc.)
25 parts of surfactant of the above formula (1-7) 365 parts of alkaline ionized water (EKO-13 manufactured by JEOL Active Ltd.)
360 parts of ion-exchanged water was dispersed by the same operation as in Example 1 to obtain an inkjet pigment dispersion (D).

Example 5
(Prescription 5)
Pigment Blue 15: 3 150 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.)
25 parts of surfactant of formula (1-11) 365 parts alkaline ionized water (EKO-13 manufactured by JEOL Active Ltd.)
Ion-exchanged water 360 parts Dispersed in the same manner as in Example 1 to obtain an inkjet pigment dispersion (E).

Example 6
(Prescription 6)
150 parts of Pigment Yellow 138 (LIONOGEN YELLOW 1010 manufactured by Toyo Ink)
Compound of general formula (2) (n = 40) 100 parts Alkaline ion water 325 parts (EKO-13 manufactured by JEOL Active Ltd.)
325 parts of ion-exchanged water Dispersed in the same manner as in Example 1 to obtain an inkjet pigment dispersion (F).

Example 7
(Prescription 7)
Pigment Blue 15: 3 150 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.)
25 parts of polyethylene glycol lauryl ether phosphate (Phosphanol RD-510Y manufactured by Toho Chemical Industry)
365 parts of alkaline ionized water (JEOL Active Co., Ltd. EKO-13)
360 parts of ion-exchanged water was dispersed by the same operation as in Example 1 to obtain an inkjet pigment dispersion (G).

Example 8
(Prescription 8)
Pigment Blue 15: 3 150 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.)
20 parts of polyethylene glycol olein ether (Pegnol O-6 manufactured by Toho Chemical Industries)
365 parts of alkaline ionized water (JEOL Active Co., Ltd. EKO-13)
365 parts of ion exchange water Dispersed in the same manner as in Example 1 to obtain a pigment dispersion (H) for inkjet.

Example 9
An inkjet pigment dispersion (I) was obtained in the same manner as in Example 1 except that the alkali ion water was changed to the alkali ion water produced by the following method.
Alkaline ion water produced by adjusting water in mode “alkali 3” using a national alkali ion water conditioner TK7405 was used. The pH of the conditioned alkaline ionized water was 9.5.

Comparative Example 1
An inkjet pigment dispersion (a) was obtained in the same manner as in Example 1 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 2
An inkjet pigment dispersion (b) was obtained in the same manner as in Example 2 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 3
An inkjet pigment dispersion (c) was obtained in the same manner as in Example 3 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 4
An inkjet pigment dispersion (d) was obtained in the same manner as in Example 4 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 5
An inkjet pigment dispersion (e) was obtained in the same manner as in Example 5 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 6
An inkjet pigment dispersion (f) was obtained in the same manner as in Example 1 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 7
An inkjet pigment dispersion (g) was obtained in the same manner as in Example 7 except that the alkaline ionized water was changed to ion exchanged water.

Comparative Example 8
An inkjet pigment dispersion (h) was obtained in the same manner as in Example 1 except that the alkaline ionized water was changed to ion exchanged water.

  Using the pigment dispersions (A), (B), (C), (D), (E), (F), (G), (H), and (I) obtained by the above method, the following inks are used: An ink liquid was prepared according to Formula 1 or Formula 2, stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum degassed to obtain ink liquids containing the pigment dispersions of Examples 1-9. Similarly, an ink liquid was prepared according to ink formulation 1 or formulation 2 using pigment dispersions (a) to (h), stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated. An ink liquid containing ˜8 pigment dispersions was obtained.

Ink formula (1)
Pigment dispersion (pigment concentration 15% by weight) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-ethyl-1,3-hexanediol 3.0 parts 2-pyrrolidone 3.0 parts Polyoxyethylene (3 ) Sodium alkyl acetate (C13) ether acetate 0.45 parts Distilled water 73.55 parts

Ink formula (2)
Pigment dispersion (pigment concentration 15% by weight) 30.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-ethyl-1,3-hexanediol 3.0 parts 2-pyrrolidone 3.0 parts Polyoxyethylene (3 ) Alkyl (C13) ether sodium acetate 0.45 parts distilled water 83.55 parts

Further, the average particle size (D ₅₀ ) of the pigment particles contained in the pigment dispersions (A) to (I) and (a) to (h) and the particle size standard deviation (sd) in the particle size distribution of the pigment particles are expressed as follows. It was measured. The average particle size (D ₅₀ ) was measured using a particle size analyzer Microtrac UPA150 manufactured by Nikkiso Co., Ltd. The particle size standard deviation was also measured using a microtrack particle size analyzer UPA150 manufactured by Nikkiso Co., Ltd. And measured. Further, printing was performed on plain paper (Xerox 4024) using an inkjet printer EM-930C manufactured by EPSON, and the ejection stability and the printed image were evaluated with an X-Rite densitometer. The results are shown in Table 1.

In Table 1, each evaluation method and evaluation criteria are as follows.
As for the image density, the density of the solid image portion was measured using X-Rite 938 manufactured by Amtec Corporation. In the measurement method, the measurement unit of the X-Rite 938 is pressed against the image unit, and the DEN value measured at that time is the m1 value for magenta, the c1 value for cyan, and the y1 for yellow. The value was measured by reading.

The sharpness (saturation) of an image is obtained by measuring the solid image of an image sample with an X-Rite densitometer and reading the L ^* value, a ^* value, and b ^* value measured in the same manner as the image density. The points of a ^* value and b ^* value are plotted on the chromaticity diagram, and the distance from the origin on the chromaticity diagram is said. For more details about the a ^* value and b ^* value on the chromaticity diagram

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As for ejection stability, after printing the printed matter, the printer was left in a 40 ° C. environment for one month with the printer head capped. Whether the discharge state of the printer after being left is restored to the initial discharge state was evaluated by the following number of cleaning operations.
○: Recovered by one operation.
Δ: Recovered by 2 to 3 operations.
X: No recovery was observed even after three or more operations.

The ink storability was evaluated by measuring the particle diameter, surface tension, and viscosity after each ink was sealed in a polyethylene container and stored at 70 ° C. for 3 weeks, and evaluated according to the rate of change from the initial physical properties as follows.
○: Within 10% △: Within 30% ×: Over 30%

As is apparent from Table 1, the ink-jet ink using the pigment dispersion of the present invention has excellent pigment dispersibility, excellent image saturation and density, and ink ejection stability and storage stability. Are better.

Claims (10)

  A method for producing an inkjet pigment dispersion in which a mixture containing at least a pigment, a dispersant, and water is dispersed, wherein the dispersion is dispersed using alkaline ionized water as the water. Method. The method for producing an inkjet pigment dispersion according to claim 1, wherein the pigment particles in the pigment dispersion are dispersed until an average particle diameter (D ₅₀ ) is 100 nm or less.   3. The method for producing an inkjet pigment dispersion according to claim 1, wherein electrolytic alkaline ionized water having a pH of 10 or more is used as the alkaline ionized water.   The method for producing an inkjet pigment dispersion according to any one of claims 1 to 3, wherein the dispersant is used at a ratio of 0.05 to 5 with respect to the pigment 1 on a weight basis.   The method for producing an inkjet pigment dispersion according to any one of claims 1 to 4, wherein a polymer dispersant or a surfactant is used as the dispersant.   The inkjet according to claim 5, wherein at least one selected from a styrene-acrylic acid copolymer, a styrene-maleic acid copolymer, and a sodium naphthalene sulfonate formalin condensate is used as the polymer dispersant. For producing a pigment dispersion for use. The method for producing an inkjet pigment dispersion according to claim 5, wherein at least one compound represented by the following general formula (1) is used as the surfactant.

(In the formula, R ₁ represents an alkyl group having 8 to 22 carbon atoms or an alkylphenyl group, M represents any one selected from alkali metal ions, quaternary ammonium, quaternary phosphonium, and alkanolamine; n represents an integer of 4 to 21.) 6. The method for producing an inkjet pigment dispersion according to claim 5, wherein at least one compound represented by the following general formula (2) is used as the surfactant.

(In the formula, n is an integer of 20 to 100)   An inkjet pigment dispersion produced by the production method according to claim 1. An ink-jet ink comprising the ink-jet pigment dispersion according to claim 9.