JPH11293165A - Aqueous pigment dispersion, its production, and utilization thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both an aqueous pigment dispersion excellent in preservation stability and water resistance and sufficiently usable as a colorant for ink jet ink by dispersing a pigment excellent in light resistance in an aqueous medium and an ink jet ink excellent in preservation stability and water resistance and to provide a method for producing the aqueous pigment dispersion. SOLUTION: This aqueous pigment dispersion is obtained by dispersing a surface treated pigment prepared by adsorbing a water-soluble resin having acidic functional groups on the pigment surface and then treating the resultant pigment with a coupling agent in an aqueous medium. The method for producing the aqueous pigment dispersion comprises dispersing the pigment and the water- soluble resin having the acidic functional groups in the aqueous medium, adsorbing the water-soluble resin on the pigment surface and then cross-linking the water-soluble resin with the coupling agent. The ink jet ink contains the aqueous pigment dispersion as the colorant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous pigment dispersion, a method for producing the same, and an ink jet ink containing the aqueous pigment dispersion as a colorant.

[0002]

2. Description of the Related Art Many conventional ink-jet inks contain a water-soluble dye as a coloring agent, and an ink containing a solution of the dye is widely used. However, although the ink containing a water-soluble dye has high stability, it has a high solubility in water, and thus has a problem that the recorded matter has poor water resistance and easily bleeds with water or the like. In order to improve such poor water resistance, attempts have been made to change the partial structure of the dye or to improve the water resistance by utilizing the reaction between recording paper and ink. Although these methods are effective for specific recording paper, they lack versatility and often do not provide sufficient water resistance. In recent years, water resistance and light resistance have been demanded for recording materials on various recording base materials. As a coloring agent, a water-insoluble and light-resistant coloring agent such as an organic pigment or carbon black is used. The aqueous pigment dispersion used has received attention.

In order to use an aqueous pigment dispersion as a colorant for an ink-jet ink, it is necessary to disperse the pigment in an aqueous medium with low viscosity, stable and fine particles.
However, the specific surface area increases as the pigment particles become finer,
During storage, viscosity increase and pigment aggregation tend to occur. Generally, a surfactant or a water-soluble resin is used as a dispersant for the aqueous pigment dispersion. The surfactant has both a hydrophobic group and a hydrophilic group, and is stabilized by the adsorption of the hydrophobic group to the pigment surface and the charge repulsion of anionic dissociable hydrophilic groups such as carboxyl, sulfone, and phosphate groups at the terminals. In many cases. Surfactants have low molecular weight and low viscosity but tend to lather.

On the other hand, a water-soluble resin has a higher molecular weight than a surfactant, and is therefore also called a polymer dispersant. Basically, it is structurally similar to a surfactant, and has a hydrophobic group adsorbed on a pigment and a dispersion stable. In many cases, it is composed of a hydrophilic group that plays a role in conversion, and is often stabilized by charge repulsion with an ion dissociable group.
Since the water-soluble resin has a higher molecular weight than the surfactant, the viscosity is high, and an ink containing an aqueous pigment dispersion using the water-soluble resin as a dispersant has good water resistance of a recorded matter. Since all of these dispersants adsorb to the pigment by physical interaction, the problem is how to maintain a stable dispersion state. In addition, the dispersing agent not adsorbed on the pigment may affect the viscosity, surface tension, foaming, and other image quality of the recorded matter in producing the ink jet ink. Has not been reached.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to disperse a pigment having excellent light fastness in an aqueous medium, to have excellent storage stability and water fastness, and to be sufficiently used as a colorant for an ink jet ink. An object of the present invention is to provide a possible aqueous pigment dispersion and a method for producing the same. The object of the present invention is
An object of the present invention is to provide an inkjet ink having excellent storage stability and water resistance.

[0006]

Means for Solving the Problems The present inventors adsorb onto a pigment surface a water-soluble resin having a hydrophobic group adsorbed on the pigment and an acidic functional group capable of stabilizing dispersion by anion dissociation and charge repulsion. After that, by treating with a coupling agent, an acid-base interaction occurs with a water-soluble resin having an acidic functional group, and at the same time, a silanol group is generated from the coupling agent, followed by dehydration condensation of the silanol group. The present inventors have found that a water-soluble resin is coated and immobilized on the pigment surface in a network by the reaction, and the present invention has been accomplished. The surface-treated pigment having the water-soluble resin immobilized on the surface can be stably dispersed in an aqueous medium. Further, the recorded matter of the inkjet ink containing the aqueous pigment dispersion as a coloring agent has good water resistance because the immobilized water-soluble resin also functions as a fixing agent.

That is, the present invention relates to an aqueous pigment dispersion obtained by adsorbing a water-soluble resin having an acidic functional group on the surface of a pigment and then treating the surface-treated pigment with a coupling agent in an aqueous medium. . Further, the present invention provides an aqueous pigment dispersion, comprising dispersing a pigment and a water-soluble resin having an acidic functional group in an aqueous medium, adsorbing the water-soluble resin on the surface of the pigment, and then crosslinking with a coupling agent. It relates to a method for producing a body. Furthermore, the present invention relates to an inkjet ink containing the above-mentioned aqueous pigment dispersion as a colorant.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. As the pigment, an organic pigment and an inorganic pigment can be used. Specific examples of the organic pigment include insoluble azo pigments such as toluidine red, toluidine maroon, hansa yellow, benzidine yellow, and pyrazolone red.
Ritol Red, Helio Bordeaux, Pigment Scarlet, Soluble azo pigments such as Permanent Red 2B, alizarin, indanthrene, pigments derived from vat dyes such as thioindigo maroon, phthalocyanine blue, phthalocyanine pigments such as phthalocyanine green, Quinacridone pigments such as quinacridone red and quinacridone magenta; perylene pigments such as perylene red and perylene scarlet; isoindolinone pigments such as isoindolinone yellow and isoindolinone orange; quinophthalone pigments; and dianthraquinonyl red. Series pigments. Specific examples of the inorganic pigment include carbon black, a titanium oxide pigment, an iron oxide pigment, a cadmium pigment, and a cobalt pigment.

When pigments are represented by color index (CI) numbers, CI pigment yellows 12, 13, 1
4, 17, 20, 24, 74, 83, 86, 93, 10
9, 110, 117, 125, 128, 137, 13
8, 147, 148, 153, 154, 166, 16
8, CI Pigment Orange 13, 16, 36, 43,
51, 55, 59, 61, CI Pigment Red 9, 4
8, 49, 52, 53, 57, 97, 122, 123,
149, 168, 177, 180, 192, 215, 2
16, 217, 220, 223, 224, 226, 22
7, 228, 238, 240, CI Pigment Violet 19, 23, 29, 30, 37, 40, 50, CI
Pigment Blue 15, 15: 1, 15: 4, 15:
6, 22, 60, 64, CI Pigment Green 7, 3
6, CI Pigment Brown 23, 25, 26, CI Pigment Black 7, CI Pigment White 6, CI
Pigment Yellow 37, CI Pigment Red 101,
CI Pigment Blue 28 and the like can be exemplified.

Of these, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments and carbon black are preferably used from the viewpoint of light resistance. As the pigment, two or more different pigments may be used in some cases. The average primary particle diameter of the pigment is 10 to 70 nm as measured by an electron microscope, and more preferably 1 to 70 nm.
It is preferably from 0 to 40 nm. When the average primary particle diameter of the pigment is smaller than 10 nm, aggregation of the pigment particles is likely to occur, resulting in poor storage stability. On the other hand, if it exceeds 70 nm, the pigment particles tend to settle due to storage of the resulting aqueous pigment dispersion. When the average primary particles of the pigment exceed 70 nm, by performing salt milling of the pigment,
It is preferable to mechanically reduce the size.

In the salt milling treatment, a water-soluble solvent is added as a lubricant to a mixture of a pigment and a water-soluble inorganic salt, and the mixture is kneaded vigorously mechanically with a kneader or the like to make the pigment finer. This treatment removes salts and water-soluble solvents. When mechanically kneading the pigment, the water-soluble inorganic salt and the water-soluble solvent, the amount of the water-soluble inorganic salt relative to the pigment is preferably 2 to 20 times by weight, more preferably 3 to 10 times by weight.
The amount of the water-soluble solvent relative to the pigment is preferably 0.5 to 3 times by weight, more preferably 0.7 to 2 times by weight. Removal of the water-soluble inorganic salt and the water-soluble solvent, the pigment and the kneaded product of the water-soluble inorganic salt and the water-soluble solvent are put into water and stirred,
After the slurry is formed, filtration and washing with water are repeated.

As the water-soluble inorganic salt, sodium chloride, potassium chloride and the like are used. Examples of the water-soluble solvent include 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether,
Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, diethylene glycol Propylene glycol monoethyl ether, liquid polypropylene glycol and the like are used.

The water-soluble resin having an acidic functional group is composed of a monomer having a hydrophobic group adsorbed on a pigment and a monomer having an acidic functional group for stabilizing dispersion, and the types, combinations and composition ratios of these monomers. Various water-soluble resins which are copolymerized by changing the above are preferably used.
The weight average molecular weight of the water-soluble resin having an acidic functional group is 1
It is preferably from 000 to 15000, more preferably from 4000 to 12000. The weight average molecular weight of the resin is 1500
If it exceeds 0, the viscosity and dispersion particle size of the obtained aqueous pigment dispersion become large, so that the ejection stability cannot be obtained when used as a colorant in an inkjet ink. On the other hand, 10
If it is less than 00, the storage stability of the aqueous pigment dispersion is not good.

The acid value of the water-soluble resin is 100 to 49.
5, more preferably 150 to 480. If the acid value is less than 100, the solubility of the water-soluble resin becomes poor, and 4
If it exceeds 95, the water resistance is undesirably reduced.
Further, it is preferable that the water-soluble resin is previously dissolved in an aqueous medium using a basic compound. Further, the glass transition point of the water-soluble resin is 20 to 160 ° C, and more preferably 30 to 1 ° C.
Preferably it is 50 ° C. If the glass transition point is less than 20 ° C., the coating film is difficult to dry, and if it exceeds 160 ° C., the coating film is brittle and the rub fixing property is not preferable.

Monomers having a hydrophobic group that functions to adsorb a water-soluble resin on the pigment surface include styrene and α.
-Aromatic vinyl monomers such as methylstyrene and vinyltoluene, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, octyl, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate 2-ethylhexyl methacrylate, lauryl methacrylate, dodecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, dibenzyl methacrylate, 2-hydroxyl methacrylate, ethyl 2-hydroxypropyl methacrylate, glycidyl methacrylate, tetrahydroxyl methacrylate , Diethylene glycol methacrylate mono (meth) ester, dipropylene glycol methacrylate mono (meth) ester, ethylene dimethacrylate Call, triethylene glycol dimethacrylate, dimethacrylate tetraethylene glycol, 1,3-butylene glycol dimethacrylate, and (meth) acrylic acid esters and the like.

The monomer having an acidic functional group has a function of stably dispersing the surface-treated pigment in an aqueous medium and a function of generating an interaction with a coupling agent.
As the monomer having an acidic functional group, a monomer having an ion-dissociable group that is stabilized by charge repulsion is preferable.Specifically, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, itaconic acid, and maleic acid And the like. Monomers having a carboxyl group such as unsaturated dicarboxylic acids such as monoalkyl esters, monoaryl esters and monoaryl alkyl esters of unsaturated dicarboxylic acids. Specific examples of the water-soluble resin having an acidic functional group include styrene-acrylic acid-based, styrene-methacrylic acid-based, and styrene-maleic acid-based resins.

The water-soluble resin having an acidic functional group is pigment 1
It is preferable to adsorb 1 to 30 parts by weight with respect to 00 parts by weight. If the amount adsorbed to 100 parts by weight of the pigment is less than 1 part by weight, it becomes difficult to stably disperse the surface-treated pigment in an aqueous medium. On the other hand, when the amount of adsorption exceeds 30 parts by weight, the obtained aqueous pigment dispersion easily aggregates,
Viscosity rises easily during storage.

In order to dissolve the water-soluble resin in the aqueous medium, a basic compound can be used. Examples of the basic compound include ammonia, alkylamine, alkanolamine, and alkylalkanolamine. These basic compounds can also be appropriately adjusted and added to the aqueous pigment dispersion as a neutralizing agent for the water-soluble resin. In this case, the pH is preferably adjusted to a desired pH of 6 to 10. The aqueous medium consists of water or a mixture of a water-soluble organic solvent and water. As the water, it is preferable to use ion-exchanged water from which metal ions and the like have been removed or distilled water. The amount of the water-soluble organic solvent is not particularly limited.
A range of 50% by weight is preferred.

Examples of the water-soluble organic solvent include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, polyethylene glycol, glycerin, tetraethylene glycol, dipropylene glycol, acetone, Diacetone alcohol, tetrahydrofuran (TH
F), dioxane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 2-pyrrolidone, 2-methylpyrrolidone, N-methyl-2-pyrrolidone, 1,2-hexanediol, , 4,6-hexanetriol, tetrafurfuryl alcohol, 4-methoxy-4-methylpentanone and the like.

Examples of the coupling agent include a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent. Among them, a silane coupling agent having an amino group at the terminal can be dissolved in an aqueous medium, and a molecule is present in the vicinity by utilizing an acid-base interaction with a water-soluble resin having an acidic functional group. It is preferably used because it is possible.

Examples of the coupling agent having an amino group at the terminal include 3- [N-allyl-N (2-aminoethyl)].
Aminopropyltrimethoxysilane, p-[(2-aminoethyl) aminomethyl] phenethyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3
-Aminopropyltrimethoxysilane, 1- (3-aminopropyl) -1,1,3,3,3-pentamethyldisiloxane, 3-aminopropyltriethoxysilane, 3
-Aminopropyltris (trimethylsiloxy) silane and the like.

The coupling agent is preferably treated with 1 to 5 parts by weight based on 100 parts by weight of the pigment. Pigment 1
If the treatment amount to less than 1 part by weight is less than 1 part by weight, the function as a cross-linking agent is lacking, hindering the fixation of the resin of the aqueous pigment dispersion, and the dispersion stability becomes insufficient. on the other hand,
When the processing amount exceeds part by weight, the reaction between the coupling agents easily proceeds, and the aqueous pigment dispersion easily aggregates, and the viscosity tends to increase during storage.

The aqueous pigment dispersion of the present invention is obtained by mixing and dispersing a pigment and a water-soluble resin having an acidic functional group in an aqueous medium with a disperser, adsorbing the water-soluble resin on the surface of the pigment, and then forming a coupling agent. Is gradually added and stirred to cross-link the water-soluble resin. The dispersing machine used is a sand mill, a dyno mill, a homogenizer, an attritor, a ball mill, a paint shaker, a fluidizer, a high-speed mixer, an ultrasonic dispersing machine, and the like, and uses glass beads, zirconia beads, stainless beads, etc. as a milling medium. It may or may not be necessary. Dispersion time is 5 minutes ~
24 hours, preferably 30 minutes to 8 hours.

In order to remove coarse particles, the step of centrifugation is performed by adsorbing a water-soluble resin on the pigment surface.
This can be performed before crosslinking with a coupling agent.
The unadsorbed water-soluble resin may be removed by ultrafiltration or the like. After addition of the coupling agent, the dispersion is 20-9
It is preferable to keep the temperature at 0 ° C. and proceed the reaction sufficiently. In addition,
The reaction is good for 2 to 4 hours per 100 ml of dispersion.
The coupling agent causes an acid-base interaction with a water-soluble resin having an acidic functional group adsorbed on the pigment in an aqueous medium, and intervenes between the water-soluble resins adsorbed on the pigment surface and the coupling agent. A silanol group is generated by a hydrolysis reaction of the alkoxy group. Next, the silanol groups are dehydrated and condensed, and as a result, the water-soluble resin having a pigment-like coating on the surface of the pigment is fixed. By-products generated by the reaction between the coupling agent and the pigment or resin may be separated by centrifugation, and the unadsorbed coupling agent may be removed by ultrafiltration or the like.

The aqueous pigment dispersion of the present invention preferably has an average dispersed particle size of 10 to 150 nm. If the average dispersed particle size is less than 10 nm, aggregation of the surface-treated pigment tends to occur, and storage stability is not good. On the other hand, when the average dispersed particle size exceeds 150 nm, sedimentation tends to occur during storage, and a stable dispersion state of the surface-treated pigment cannot be obtained. Also,
The pigment content of the aqueous pigment dispersion of the present invention is 0.1 to 5
It is preferably 0% by weight. Pigment content 0.1
When the amount is less than% by weight, the function as a colorant is lacking, and the print density becomes insufficient when used in ink. On the other hand, when the content of the pigment exceeds 50% by weight, the dispersion is likely to aggregate, and sedimentation tends to occur during storage.

Since the aqueous pigment dispersion of the present invention has excellent stability over time and good water resistance and light resistance, it can be used as a colorant as an ink jet, a plotter for information terminals, an aqueous ballpoint pen, an aqueous sign pen, a felt pen, a fountain pen. , Writing brush,
It can be used as a writing instrument for drawing pens for drafting. In particular, it is suitably used as a colorant for an inkjet ink. The ink can be produced by adding water, if necessary, a water-soluble organic solvent, additives and the like to the aqueous pigment dispersion of the present invention.

The amount of the pigment in the ink is not particularly limited, but is generally in the range of 1 to 15% by weight, preferably 1 to 10% by weight, based on the total weight of the ink. Also,
The amount of water in the ink ranges from 40 to 9 based on the total weight of the ink.
A range of 0% by weight is preferred. The water-soluble organic solvent is added to prevent drying of the ink in the nozzle portion and felt portion and the like, and to prevent solidification of the ink, and to prevent stable ink jetting and drying during writing and storage of the nozzle and felt. As the water-soluble organic solvent, the same water-soluble organic solvents as those exemplified as the medium of the aqueous pigment dispersion may be used alone or in a mixture of 1 to 50% by weight based on the total weight of the ink. it can.

Further, alcohols such as methanol, ethanol and isopropyl alcohol can be used for the purpose of speeding up the drying of the ink on paper. If the ink substrate is a permeable material such as paper, a penetrant may be added to speed up the penetration of the ink into the paper and the apparent dryness. As the penetrant, a surfactant that lowers the surface tension, for example, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium oleate, sodium dioctylsulfosuccinate, and the like can be used. These have a sufficient effect at a content of 5% by weight or less based on the total weight of the ink,
If it is larger than this, bleeding of printing and paper missing (print through) occur, which is not preferable.

To the ink of the present invention, a neutralizing agent for an aqueous resin such as ammonia, an amine or an inorganic alkali can be appropriately adjusted and added. In this case, too, the pH is adjusted to a desired pH within the range of 6 to 10. It is preferable to keep it. Further, a fungicide can be added to the ink of the present invention in a range of 0.05 to 1.0% by weight of the ink in order to prevent the generation of mold. As an antifungal agent, sodium dihydroacetate,
Sodium benzoate, sodium pyridinethione-1-oxide, zinc pyridinethione-1-oxide,
Amine salts of 1,2-benzisothiazolin-3-one, 1-benzisothiazolin-3-one and the like are used.

In order to prevent the deposition of metal at the nozzle portion and the deposition of insoluble matters in the ink, a chelating agent may be added in the range of 0.005 to 0.5% by weight of the ink. it can. The chelating agent blocks metal ions in the ink.Specifically, ethylenediaminetetraacetic acid, sodium salt of ethylenediaminetetraacetic acid, diammonium salt of ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid And the like.

Further, an antifoaming agent can be added in order to prevent the circulation and movement of the ink or the generation of bubbles during the production of the ink. Further, urea, dimethyl urea, thiourea and the like can be added as other additives.
The ink of the present invention has a pore size of 3 μm or less, preferably 1.0 μm or less.
It is preferable to filter with a filter having a size of not more than μm, more preferably not more than 0.45 μm. Prior to filtration, large particles can also be removed by centrifugation to reduce clogging in the filtration and extend the life of the filter. The ink has a viscosity of 0.8 to 15 cps (25 ° C.) and a surface tension of 25 to 50 m, depending on the type of the recording apparatus.
It is preferably adjusted as a liquid of N / m, and the average dispersed particle diameter of the ink is 10 to 10 from the viewpoint of the storage stability of the ink.
150 nm is preferred.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
In Examples, "parts and%" means "parts by weight" and "% by weight". The average primary particle diameter of the pigment used in the examples and comparative examples was measured by an electron microscope.

(Example 1) The following materials were placed in a sand mill and dispersed for 2 hours, and then 3 parts of N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane was gradually added with a dropper while stirring. . Thereafter, stirring was continued at 80 ° C. for 10 hours. After cooling to room temperature, the mixture was filtered through filter paper No. 2, then an equal amount of purified water was added through an ultrafiltration membrane, and an equal amount of the solution was discharged to obtain an aqueous pigment dispersion having a pigment concentration of 20% by weight. In addition,
In a 2 liter flask, 200 parts of a styrene maleic acid resin solution ("SMA1000" manufactured by Elfatochem, acid value 480, weight average molecular weight 5700, glass transition point 154 ° C) and 200% % Of dimethylaminoethanol dissolved in 800 parts of water, mixed and stirred, and dissolved by heating at 80 ° C. The viscosity of the aqueous resin solution was 20 to 40 cps (25 ° C.). Carbon black 100 parts (“Printex55” manufactured by Degussa, average primary particle diameter 25 nm) Styrene maleic acid resin aqueous solution (solid content 20%) 25 parts Purified water 372 parts

Example 2 The following materials were placed in a sand mill and dispersed for 2 hours. Then, 3 parts of N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane was gradually added with a dropper while stirring. An aqueous pigment dispersion having a pigment concentration of 20% by weight was obtained in the same manner as in Example 1. 100 parts of carbon black (“Printex55” manufactured by Degussa, average primary particle diameter 25 nm) Same as in Example 1 250 parts of styrene maleic acid resin aqueous solution (20% solid content) 147 parts of purified water

Example 3 The following materials were placed in a sand mill and dispersed for 2 hours. Then, 3 parts of N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane was gradually added with a dropper while stirring. An aqueous pigment dispersion having a pigment concentration of 20% by weight was obtained in the same manner as in Example 1. 100 parts of carbon black (“Printex55” manufactured by Degussa, average primary particle diameter 25 nm) Same as in Example 1 Styrene maleic acid resin aqueous solution (solid content 20%) 3 parts Purified water 394 parts

Example 4 The following materials were placed in a sand mill and dispersed for 2 hours. Then, with stirring, 0.5 part of N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane was gradually added with a dropper. An aqueous pigment dispersion having a pigment concentration of 20% by weight was obtained in the same manner as in Example 1. 100 parts of carbon black (“Printex55” manufactured by Degussa, average primary particle size 25 nm) 50 parts of an aqueous styrene maleic acid resin solution (solid content: 20%) as in Example 1 349.5 parts of purified water

(Example 5) The following materials were placed in a sand mill and dispersed for 2 hours. Then, 6 parts of N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane was gradually added with a dropper while stirring. An aqueous pigment dispersion having a pigment concentration of 20% by weight was obtained in the same manner as in Example 1. 100 parts of carbon black (“Printex55” manufactured by Degussa, average primary particle diameter 25 nm) 50 parts of an aqueous styrene maleic acid resin solution (solid content: 20%) as in Example 1 344 parts of purified water

(Example 6) [Refining treatment] 250 parts of a quinacridone-based red pigment ("Hostaperm Pink E" manufactured by Hoechst, average primary particle diameter 110 nm) was added to a stainless steel 1 gallon kneader (manufactured by Inoue Seisakusho).
2500 parts of sodium chloride and 200 parts of diethylene glycol
And kneaded for 3 hours. Next, this mixture
Pour into 2.5 liters of warm water, stir with a high-speed mixer for about 1 hour while heating to about 80 ° C to form a slurry, and then repeat the filtration and water washing 5 times to remove sodium chloride and the solvent. A dried product was obtained. The average primary particle size of the refined pigment was 20 nm.

[Preparation of Aqueous Pigment Dispersion] The following materials were placed in a sand mill and dispersed for 2 hours.
3 parts of (2-aminoethyl) -3-aminopropylmethyldimethoxysilane were gradually added with a dropper. Then 70
After stirring at 10 ° C. for 10 hours, the mixture was filtered in the same manner as in Example 1 to obtain an aqueous pigment dispersion having a pigment concentration of 20% by weight. Fine treatment pigment 100 parts Styrene maleic acid-modified resin aqueous solution (solid content 20%) 33 parts (John Krill J501, manufactured by Johnson Polymer Co., weight average molecular weight 12000, acid value 205, glass transition point 65 ° C, ammonia neutralization 120 % Solid content 29.5%) 364 parts of purified water

(Example 7) [Refining treatment] A phthalocyanine-based blue pigment ("Lionol Blue KLH-T" manufactured by Toyo Ink Mfg. Co., Ltd.) was added to a stainless steel 1 gallon kneader (manufactured by Inoue Seisakusho), average primary particle diameter.
(93 nm), 250 parts of sodium chloride and 180 parts of diethylene glycol were charged and kneaded for 3 hours. Next, the mixture was poured into 2.5 liters of warm water, stirred for about 1 hour with a high-speed mixer while heating to about 80 ° C. to form a slurry, and then filtered and washed five times to remove sodium chloride and the solvent. Except for this, a dried product of the refined pigment was obtained. The average primary particle size of the refined pigment was 60 nm.

[Preparation of Aqueous Pigment Dispersion] The following materials were placed in a sand mill and dispersed for 2 hours.
5 parts of (2-aminoethyl) -3-aminopropyltrimethoxysilane were gradually added with a dropper. Next, stirring was continued at 70 ° C. for 10 hours, followed by filtration in the same manner as in Example 1 to obtain an aqueous pigment dispersion having a pigment concentration of 20% by weight. In addition,
A styrene acrylic resin aqueous solution was placed in a 2 liter flask in a styrene acrylic resin ("Johncryl J683" manufactured by Johnson Polymer Co., Ltd., weight average molecular weight 7300, acid value 150
(200 ° C., glass transition point: 69 ° C.), and 800 parts of water in which triethanolamine was dissolved in an amount to give a neutralization ratio of 100%. The viscosity of the aqueous resin solution was 20 to 40 cps (25 ° C.). Fine treatment pigment 100 parts Styrene acrylic resin aqueous solution (solid content 20%) 150 parts Purified water 245 parts

(Example 8) [Refining treatment] A 1 gallon kneader made by stainless steel (manufactured by Inoue Seisakusho) was coated with a quinophthalone-based yellow pigment (“Pas” manufactured by BASF).
liotol Yellow K0961HD '', average primary particle diameter 200 nm) 250
Parts, 2500 parts of sodium chloride and diethylene glycol
200 parts were charged and kneaded for 3 hours. Next, the mixture was poured into 2.5 liters of warm water, stirred for about 1 hour with a high-speed mixer while heating to about 80 ° C. to form a slurry, and then filtered and washed five times to remove sodium chloride and the solvent. Except for this, a dried product of the refined pigment was obtained. The average primary particle size of the refined pigment was 40 nm.

[Preparation of Aqueous Pigment Dispersion] The following materials were placed in a sand mill and dispersed for 2 hours, and then, with stirring, 4 parts of 3-aminopropyltriethoxysilane was gradually added with a dropper. Next, stirring was continued at 70 ° C. for 10 hours, followed by filtration in the same manner as in Example 1 to obtain an aqueous pigment dispersion having a pigment concentration of 20% by weight. The styrene acrylic resin aqueous solution was placed in a 2-liter flask using a styrene acrylic resin (“Johncryl J690” manufactured by Johnson Polymer Co., Ltd.).
(Weight average molecular weight 15500, acid value 240, glass transition point 102 ° C)
A mixture was prepared by mixing and stirring 200 parts of water and 800 parts of water in which diethylaminoethanol was dissolved in an amount to give a neutralization ratio of 100%, and heated and dissolved at 80 ° C. The viscosity of the aqueous resin solution is 20-40 cp
s (25 ° C). Fine treatment pigment 100 parts Styrene acrylic resin aqueous solution (solid content 20%) 100 parts Purified water 296 parts

Comparative Example 1 A pigment was prepared in the same manner as in Example 1 except that 372 parts of purified water was changed to 375 parts, and 3 parts of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane was removed. An aqueous pigment dispersion having a concentration of 20% by weight was obtained.

(Comparative Example 2) The following materials were placed in a sand mill, dispersed for 2 hours, and then filtered through filter paper No. 2 to obtain a pigment concentration.
A 20% by weight aqueous pigment dispersion was obtained. Carbon black (Degussa "Printex55") 100 parts Sodium dodecylbenzenesulfonate 5 parts Purified water 395 parts

Comparative Example 3 An aqueous solution of a black dye ("WATER BLACK 100-L" manufactured by Orient, dye concentration 20% by weight) was used as it was.

The average dispersion particle size, viscosity and surface tension were measured as the initial physical properties of the aqueous pigment dispersions of Examples 1 to 8 and Comparative Examples 1 and 2 and the aqueous dye solution of Comparative Example 3 to evaluate the storage stability. Was. The physical property measurement methods and evaluation criteria are described below, and Table 1 shows the results. [Viscosity] Measured at 25 ° C. using a B-type viscometer. [Average dispersion particle size] The average dispersion particle size was measured by a laser diffraction type particle size distribution meter (“SALD-1100” manufactured by Shimadzu Corporation). [Surface tension] It was measured at 25 ° C using a FACE-CBVP surface tensiometer (manufactured by Kyowa Interface Science Co., Ltd.).

[Storage Stability] An aqueous pigment dispersion and 30 cc of an aqueous dye solution were placed in a screw cap bottle, left at 60 ° C. for one month, and then visually evaluated. A: No precipitate is seen. ：: No precipitate was observed, but there were slight changes in the average dispersed particle size and the viscosity. Δ: A precipitate was observed, and there was a change in average dispersed particle size and viscosity. X: A precipitate is seen, and the change in average dispersed particle size and the change in viscosity are large.

Next, inkjet inks containing the aqueous pigment dispersions of Examples 1 to 8 and Comparative Examples 1 and 2 and the aqueous dye solution of Comparative Example 3 as colorants were produced, and the initial physical properties of the obtained inkjet inks were averaged. Dispersion particle size, viscosity and surface tension are measured by the above method, printing stability, water resistance,
The light fastness and storage stability were evaluated. The evaluation methods and evaluation criteria are described below, and Table 2 shows the results. For the production of the ink, after mixing the following raw materials, a pore diameter of 1 μm,
Filtration was performed using a 90 mmφ membrane filter, followed by filtration using a 90 mmφ membrane filter with a pore size of 0.45 μm.

Aqueous pigment dispersion or dye aqueous solution (solid content: 20%) 25.0 parts Glycerin 4.0 parts Sodium dioctyl sulfosuccinate (penetrant) 1.0 part Dimethylaminoethanol 1.0 part 1,2-benzisothiazoline -3-one (fungicide) 0.3 part Sodium salt of ethylenediaminetetraacetylic acid 0.1 part Purified water 68.6 parts Total 100.0 parts

[Printing Stability] The ink was put in a cartridge of an ink jet printer (“Desktop 560” manufactured by HP) and printed on plain paper (“K” manufactured by Xerox) at room temperature. The presence or absence of ejection was visually evaluated. In addition, the same evaluation was performed after standing for 1 hour after printing. ：: No non-discharge of ink, disturbance of printing, and chipping are not observed during continuous printing. Δ: Several consecutive non-ejections of ink were observed in the solid printing portion during continuous printing. X: Non-discharge of ink at several places in a solid printing portion during continuous printing was observed.

[Water resistance] The recorded matter recorded on plain paper ("K", manufactured by Xerox Corporation) was dried, and then immersed in water for 1 minute. In addition, a filter paper was pressed against the immersion part, and ink transfer was visually evaluated. A: No ink bleeding, no run-off, and no ink transfer. ：: no ink bleeding, no run-off, but slight ink transfer was observed. Δ: Ink bleeding, slight run-off, and ink transfer were observed. ×: Ink bleeding, run-off, and ink transfer were observed.

[Light resistance] The recorded matter recorded on plain paper ("K" manufactured by Xerox Corporation) was exposed to a xenon lamp for one week, and then compared with the recorded matter immediately after recording, and the change in hue was visually evaluated. ：: Fading cannot be confirmed. X: Fading can be confirmed. [Storage stability] Put 30 cc of ink in a screw-mouth bottle,
After standing at a temperature of 1 ° C. for one month, the state of the ink was visually evaluated. A: No precipitate is seen. ：: No precipitate was observed, but there were slight changes in the average dispersed particle size and the viscosity. Δ: A precipitate was observed, and there was a change in average dispersed particle size and viscosity. X: A precipitate is seen, and the change in average dispersed particle size and the change in viscosity are large.

Next, felt pen inks containing the aqueous pigment dispersions of Examples 1 to 8 and Comparative Examples 1 and 2 and the aqueous dye solution of Comparative Example 3 as colorants were produced, and the initial physical properties of the obtained felt pen inks The viscosity was measured by the above method, and the storage stability was evaluated by the following method. Further, the obtained felt pen ink was packed in a felt pen, and writing characteristics, water resistance and light resistance were evaluated by the following methods. Table 3 shows the results.
The production of the ink was carried out by mixing the following raw materials.

Aqueous pigment dispersion (solid content: 20%) 50.0 parts Ethylene glycol 50 parts Glycerin 18.0 parts Potassium hydroxide 0.1 part Thiourea 11.1 parts Purified water 15.8 parts Total 100.0 Department

[Writing Characteristics] Writing was performed on plain paper (“K” manufactured by Xerox Corporation) using a felt pen, and the writing state was visually evaluated. ：: No fading is observed. Δ: Slight blurring is observed. ×: Blurring is observed.

[Water resistance] A recorded matter written on plain paper ("K" manufactured by Xerox Corporation) was dried, and then immersed in water for 1 minute, and the presence or absence of ink bleeding and run-off was visually evaluated. ：: no ink bleeding, no run-off Δ: Ink bleeding and run-off a little. X: Ink bleeds and runs off. [Light fastness] The recorded matter written on plain paper ("K" manufactured by Xerox Corporation) was exposed to a xenon lamp for one week, and then compared with the recorded matter immediately after recording, and the change in hue was visually evaluated. ：: Fading cannot be confirmed. X: Fading can be confirmed.

[Storage stability] 30 cc of the ink was put in a screw-bottle bottle, left at 60 ° C. for 1 month, and the ink was evaluated. A: No change in viscosity. ：: Little change in viscosity. Δ: There is a change in viscosity. X: The viscosity change is large.

[0059]

[Table 1]

[0060]

The aqueous pigment dispersion of the present invention has good water resistance and light fastness and excellent initial and storage stability, and therefore can be suitably used as a colorant for ink-jet inks and felt pen inks.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Jun Satake Toyo Ink Manufacturing Co., Ltd. 2-3-13 Kyobashi, Chuo-ku, Tokyo

Claims (9)

[Claims] An aqueous pigment dispersion obtained by adsorbing a water-soluble resin having an acidic functional group on the surface of a pigment and then treating the surface-treated pigment with a coupling agent in an aqueous medium. 2. The aqueous pigment dispersion according to claim 1, wherein 1 to 30 parts by weight of a water-soluble resin having an acidic functional group is adsorbed to 100 parts by weight of the pigment. 3. The method according to claim 1, wherein the pigment is treated with 1 to 5 parts by weight of a coupling agent per 100 parts by weight of the pigment.
Or the aqueous pigment dispersion according to item 2. 4. The aqueous pigment dispersion according to claim 1, wherein the coupling agent is a silane coupling agent having an amino group at a terminal. 5. A water-soluble resin having an acidic functional group having an acid value of 1
5. The method according to claim 1, wherein the number is from 00 to 495.
An aqueous pigment dispersion according to any one of the preceding claims. 6. The aqueous pigment dispersion according to claim 1, wherein the pigment has an average primary particle diameter of 10 to 70 nm. 7. The aqueous pigment dispersion according to claim 1, wherein the content of the pigment is 0.1 to 50% by weight. 8. An aqueous pigment dispersion characterized by dispersing a pigment and a water-soluble resin having an acidic functional group in an aqueous medium, adsorbing the water-soluble resin on the surface of the pigment, and crosslinking with a coupling agent. Manufacturing method. 9. An ink-jet ink comprising the aqueous pigment dispersion according to claim 1 as a colorant.