JPH11315229A - Water-base ink for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink reduced in attack against a head member without detriment to storage stability and realizing a high water resistance and high print quality by incorporating water, a water-soluble colorant, a cationic water- soluble polymer, and a carboxyl-containing organic acid or a salt thereof into the ink. SOLUTION: This ink comprises deionized water; 0.5-20 wt.% water-soluble colorant selected from among alkali-soluble colored substances such as dyes and pigments; 0.1-20 wt.% cationic water-soluble polymer such as e.g. a homo- or co-polymer of e.g. polyethyleneimide having a structure selected among ethyleneimine, allylamine, diallylamine, etc., and 0.01-10 wt.% carboxyl-containing organic acid (salt) such as an organic acid such as acetic acid, benzoic acid, or the like or a sodium salt thereof. This ink additionally contains a pH modifier such as sodium hydroxide, 5-50 wt.% humectant comprising an aqueous organic solvent such as ethylene glycol or sorbitol, and a penetration accelerator such as a lower alcohol, a cellosolve, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-resistant water-based ink for ink-jet recording.

[0002]

2. Description of the Related Art In an ink jet recording system, recording is performed by ejecting ink as small droplets and attaching the ink to a recording medium such as paper. This method is characterized in that it is possible to increase the resolution of an image and to increase the recording speed with a relatively inexpensive apparatus, and it is easy to obtain a clear and high-quality recorded image in colorization.

[0003] Among the inks used in the ink jet recording system, aqueous inks using aqueous dyes are excellent in safety, color image forming properties, etc., because the main solvent is water, and therefore they are used for ink jet recording. It has become the mainstream of ink.

In recent years, there has been a demand for improvement in water resistance on recording paper in ink jet recording, and various combinations of a water-soluble basic resin and an anionic dye have been studied as aqueous inks for ink jet recording having water resistance. Have been.

As a method for imparting water resistance by adding a basic resin to an ink, Japanese Patent Application Laid-Open No. Sho 62-119280 discloses an ink comprising a hydroxyethylated polyethyleneimine polymer and a dye component. Water resistance is exhibited directly in combination with polyethyleneimine or with an acidic or reactive dye.

JP-A-2-255876, JP-A-2-2-2
96878 and JP-A-3-188174 disclose an ink composition comprising a polyamine having a primary amino group having a molecular weight of 300 or more, an anionic dye, and a stabilizing agent such as urea or thiourea. ing. here,
Water resistance is exhibited by a combination of a primary amine and an anionic dye.

Japanese Patent Application Laid-Open No. 7-305011 discloses an aqueous ink comprising a basic water-soluble polymer, an anionic dye having a volatile base as a counter ion, and a buffer having a volatile base as a counter ion. I have. The volatile base suppresses the dissociation of the polymer in the ink, and on the paper, the volatile base is evaporated to promote a salt-forming reaction between the polymer and the dye, thereby obtaining water resistance.

[0008]

In the method of imparting water resistance by adding a basic resin to an ink containing an anionic dye, it is considered that the water resistance is exhibited by the reaction between the dye anion and the resin cation on the recording medium. Can be This is because each of the inks is in a dissolved state in a state of a sufficient amount of water, and when the ink is dried to some extent after printing to reduce the amount of water, the two are insolubilized and precipitated to become water resistant.

[0009] However, such a water-resistant ink has a sufficient water content depending on the pH of the ink.
Since the resin and the dye may interact with each other to cause precipitation, it is necessary to increase the pH as much as possible to maintain the stability of the ink. However, if the pH of the ink is high, it has an adverse effect such as dissolving, deforming and coloring the head member, which also shortens the life of the head member. In addition, this water-resistant ink is easily affected by the pH of the recording medium surface, and is particularly suitable for printing on a special recording medium (glossy paper, glossy film sheet, etc.) requiring a high-quality recording image equal to or higher than a color photograph. In this case, a new problem that a sufficient recorded image cannot be obtained in some cases (loss of glossiness, reduction of coloring property, reduction of ink permeability, etc.) has newly occurred.

Accordingly, the present invention solves these problems. Ink-jet recording capable of alleviating the attack on the head member while maintaining the storage stability of the ink, and realizing water resistance and high printing quality. The purpose of the present invention is to provide a water-based ink.

[0011]

The aqueous ink for ink-jet recording of the present invention comprises at least water, a water-soluble colorant,
It is characterized by comprising a cationic water-soluble polymer and an organic acid having a carboxyl group or a salt thereof.

The aqueous ink for ink jet recording of the present invention is characterized in that the organic acid or a salt thereof is contained in the ink in an ionized state.

The aqueous ink for ink jet recording of the present invention is characterized in that the colorant is alkali-soluble and is selected from organic dyes and pigments.

In the water-based ink for ink-jet recording of the present invention, the colorant is contained in an amount of 0.5 to 20 wt% based on the ink.
It is characterized by being included in the range.

In the water-based ink for ink-jet recording of the present invention, the cationic water-soluble polymer contains at least ethyleneimine, allylamine, diallylamine in the molecule.
It has a structure selected from dimethylallylamine.

The aqueous ink jet recording ink of the present invention is characterized in that the cationic water-soluble polymer is contained in the range of 0.1 to 20% by weight of the ink.

In the aqueous ink jet recording ink of the present invention, the organic acid or a salt thereof is added to the ink in an amount of 0.01%.
-10 wt%.

The aqueous ink for ink-jet recording of the present invention is characterized in that the pH of the ink is 10 or less.

The aqueous ink jet recording ink of the present invention is characterized in that the ink further contains a humectant selected from a water-soluble organic solvent and / or a saccharide having a vapor pressure lower than that of pure water.

The aqueous ink jet recording ink of the present invention is characterized in that the ink further contains a penetration enhancer selected from the group consisting of lower alcohols, cellosolves, carbitols and nonionic surfactants. .

[0021]

DETAILED DESCRIPTION OF THE INVENTION The aqueous ink for ink-jet recording according to the present invention comprises at least water, a water-soluble coloring agent, a cationic water-soluble polymer, and an organic acid having a carboxyl group or a salt thereof. Here, the water serves as a medium for the aqueous ink, and dissolves and holds the colorant, the cationic water-soluble polymer, the organic acid or its salt, the humectant, and the penetration enhancer.

As the water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. Further, it is preferable to use water sterilized by ultraviolet irradiation, hydrogen peroxide addition, or the like, since mold and bacteria can be prevented from occurring when the ink composition is stored for a long period of time.

The colorant dissolves in the aqueous ink and gives a printed material a large number of colors on a recording medium after printing with an ink jet recording apparatus. Further, the colorant is selected from colored substances of organic dyes or pigments which are soluble in alkali. These are suitable for use in inks because of their high color density per weight and vivid color.

Here, the term "alkali-soluble" refers to a colored substance that dissolves in an alkaline medium, wherein the water-soluble group contained in the molecule is an acidic or basic dissociable group, or a non-dissociable functional group. Further, a plurality of them may be included. Further, a colored substance that is soluble in an acidic solution may be used as long as it is soluble in an alkali.

The colorant has an affinity for the cationic water-soluble polymer by being dissolved in an alkali. on the other hand,
Since this polymer also has a high affinity for paper fibers, after printing, the polymer is fixed to the paper fibers, and the colorant and polymer are fixed to the paper as a water-insoluble salt to obtain water resistance. Presumed.

The colorant is desirably added in the range of 0.5 to 20% by weight based on the total weight of the ink composition.
When the content is 0.5% by weight or more, the printed matter printed by the inkjet recording method can exhibit a sufficient optical density. When the content is 20% by weight or less, it is easy to adjust the viscosity to a value suitable for the ink jet recording method.

Among the coloring agents, dyes are organic colored substances that dissolve in water, and those that are classified into acid dyes, direct dyes, reactive dyes, soluble vat dyes, and food coloring in the color index are useful. It is. In addition, colorants classified as oil-soluble dyes and basic dyes in the color index can be used as long as they are insoluble in neutral water but soluble in alkaline water.

The pigment is selected from pigments classified in the color index. The pigment is generally an organic colored substance that is insoluble in water, but some of them are alkali-soluble and are selected from them.

Dyes and pigments include, for example, C.I. I. Acid Yellow 1, 3, 11, 17, 1
9,23,25,29,36,38,40,42,4
4, 49, 59, 61, 70, 72, 75, 76, 7
8, 79, 98, 99, 110, 111, 127, 13
1, 135, 142, 162, 164, 165, C.I.
I. Direct Yellow 1, 8, 11, 12, 24, 2
6, 27, 33, 39, 44, 50, 55, 58, 8
5, 86, 87, 88, 89, 98, 110, 132,
142, 144, C.I. I. Reactive Yellow 1,
2, 3, 4, 6, 7, 11, 12, 13, 14, 15,
16, 17, 18, 22, 23, 24, 25, 26, 2,
7, 37, 42, C.I. I. Food yellow 3, 4, C.I.
I. Solvent Yellow 15, 19, 21, 30, 10
9, C.I. I. Pigment Yellow 23 and the like.

Further, as the red type, C.I. I. Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 2
7, 32, 35, 37, 42, 51, 52, 57, 7
5, 77, 80, 82, 85, 87, 88, 89, 9
2, 94, 97, 106, 111, 114, 115, 1
17, 118, 119, 129, 130, 131, 13
3, 134, 138, 143, 145, 154, 15
5, 158, 168, 180, 183, 184, 18
6, 194, 198, 209, 211, 215, 21
9, 249, 252, 254, 262, 265, 27
4, 282, 289, 303, 317, 320, 32
1, 322, C.I. I. Direct Red 1, 2, 4,
9, 11, 13, 17, 20, 23, 24, 28, 3
1, 33, 37, 39, 44, 46, 62, 63, 7
5, 79, 80, 81, 83, 84, 89, 95, 9
9, 113, 197, 201, 218, 220, 22
4, 225, 226, 227228, 229, 230,
231, C.I. I. Reactive Red 1, 2, 3, 4,
5, 6, 7, 8, 11, 12, 13, 15, 16, 1
7, 19, 20, 21, 22, 23, 24, 28, 2
9, 31, 32, 33, 34, 35, 36, 37, 3
8, 39, 40, 41, 42, 43, 45, 46, 4
9, 50, 58, 59, 63, 64, C.I. I. Sorbilize Red 1, C.I. I. Food Red 7, 9, 14,
C. I. Pigment Red 41, 48, 54, 57, 5
7, 58, 63, 68, 81 and the like.

As the blue color, C.I. I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 2
9, 40, 41, 43, 45, 54, 59, 60, 6
2, 72, 74, 78, 80, 82, 83, 90, 9
2, 93, 100, 102, 103, 104, 112,
113, 117, 120, 126, 127, 129, 1
30, 131, 138, 140, 142, 143, 15
1, 154, 158, 161, 166, 167, 16
8, 170, 171, 182, 183, 184, 18
7, 192, 199, 203, 204, 205, 22
9, 234, 236, 249, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76,
77, 78, 80, 86, 87, 90, 98, 106,
108, 120, 123, 158, 160, 163, 1
65, 168, 192, 193, 194, 195, 19
6, 199, 200, 201, 202, 203, 20
7, 225, 226, 236, 237, 246, 24
8, 249, C.I. I. Reactive Blue 1, 2, 3,
4, 5, 7, 8, 9, 13, 14, 15, 17, 18,
19, 20, 21, 25, 26, 27, 28, 29, 3
1, 32, 33, 34, 37, 38, 39, 40, 4
1, 43, 44, 46, C.I. I. Solubiliz Bat Blue 1, 5, 41, C.I. I. Bat blue 29, C.I.
I. Food blue 1, 2, C.I. I. Basic Blue 9, 25, 28, 29, 44, C.I. I. Pigment Blue 1, 17 and the like.

Further, as the black type, C.I. I. Acid Black 1, 2, 7, 24, 26, 29, 31, 48,
50, 51, 52, 58, 60, 62, 63, 64, 6
7, 72, 76, 77, 94, 107, 108, 09,
110, 112, 115, 118, 119, 121, 1
22, 131, 132, 139, 140, 155, 15
6, 157, 158, 159, 191; I. Direct black 17, 19, 22, 32, 35, 38, 5
1,56,62,71,74,75,77,94,10
5, 106, 107, 108, 112, 113, 11
7, 118, 132, 133, 146, 154, 16
8, 171, 195, C.I. I. Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 1
4, 18, C.I. I. Sorbilize Butt Black 1C.
I. Food Black 2 and the like.

These colorants can be used alone or in combination of two or more. The coloring agent that can be used in the present invention is not limited to those described here, and any coloring agent that meets the requirements can be used.

The cationic water-soluble polymer is dissolved in the aqueous ink, and after printing with an ink jet recording apparatus, a colorant is fixed on a recording medium to give water resistance.

Any cationic water-soluble polymer can be used as long as it meets the requirements. Further, those having a structure selected from ethyleneimine, allylamine, diallylamine and dimethylallylamine in the molecule are more desirable. It is presumed that since the molecule has a cationic structure, it can interact with an alkali-soluble coloring agent and can exhibit water resistance after printing. As the cationic water-soluble polymer, any homopolymer of polyethyleneimine, polyallylamine, polydiallylamine and polydimethylallylamine having only the above-mentioned structure can be used. Further, not only primary but also secondary, tertiary and quaternary amine polymers may be used. Further, even a copolymer containing at least the above-mentioned structure can be used. For example, a copolymer obtained by copolymerizing methacrylic acid hydroxyester such as acrylamide or hydroxyethyl methacrylate, vinylpyrrolidone, vinyl acetate, acrylic acid, maleic acid, sulfur dioxide, or the like can be used.

Specific examples of the cationic water-soluble resin polymer include PAS-J-81 (trade name, manufactured by Nitto Boseki Co., Ltd.), PCQ-1, PAL-2, and PCL-2 (all of which are trade names, Senka Co., Ltd.), Polyfix 601
(Trade name, manufactured by Showa Polymer Co., Ltd.), Himax SC
-700 (trade name, manufactured by Hymo Co., Ltd.), Epomin SP-003, SP-00 as polyethyleneimine derivatives
6, SP-012, SP-018, SP-103, SP
-110, SP-200, P-1000 (all of which are trade names, manufactured by Nippon Shokubai Co., Ltd.), PAA-L, PAA-HCl-L, PAA-10 as polyallylamine derivatives
_{C, PAA-CH 3 COOH-} S, PAA-D11-H
PA and PAS-A- as polydiallylamine derivatives
1, PAS-A-5, PAS-H-5L, PAS-J-
81, PAS-880, PAS-92, PAS-M-
1, PAS-410, as a polyallylamine hydrochloride derivative, DAMFIX 723, DAMFIX 202, DAMFIX 303, DAMFIX NK, DAMFIX F, DAMFIX 707, DAMFIX 80
8, Danfix T, Danfix 505RE, Danfix 5000, Danfix 7000, Danfix PAA, Danfix HC (all are trade names, manufactured by Nitto Boseki Co., Ltd.), dimethyl of the polyallylamine derivative as a polydimethylallylamine derivative Or by subjecting a polyallylamine hydrochloride derivative to dimethylation after desalting treatment.

These cationic water-soluble polymers can be used alone or in combination of two or more, but it is desirable to add them in the range of 0.1 to 20% by weight based on the total amount of the ink composition. When the content is 0.1% by weight or more, the printed matter printed by the inkjet recording method can have water resistance. When the content is 20% by weight or less, it is easy to adjust the viscosity to a value suitable for the ink jet recording method.

An organic acid having a carboxyl group or a salt thereof has an effect of lowering the pH of the ink. In addition, when printing on special recording media (glossy paper, glossy film sheet, etc.), it suppresses precipitation due to rapid interaction between the cationic water-soluble polymer and the colorant, and is excellent in gloss, color development, and permeability. The effect of forming an image is also shown. For this purpose, the organic acid having a carboxyl group or its salt is ionized in the ink, and 0.01 to 10 wt.
% Is preferable.

Specifically, organic acids include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, benzoic acid, phthalic acid,
Salicylic acid and the like can be mentioned. Organic salts include disodium adipate, sodium L-ascorbate, sodium benzoate, sodium formate, and citric acid 3
Sodium, tripotassium citrate, sodium acetate, potassium acetate, ammonium acetate, sodium salicylate, disodium oxalate, potassium oxalate, potassium hydrogen oxalate, disodium tartrate, dipotassium tartrate, sodium potassium tartrate, ammonium tartrate,
Sodium stearate, sodium lactate, phthalic acid 2
Sodium, disodium maleate, potassium laurate and the like can be mentioned.

In the organic acid salt having a carboxyl group, a cation and an anion may be separately added to the ink. For example, when benzoic acid and sodium hydroxide are separately added to the ink and prepared, the same effect as when sodium benzoate is added can be obtained. Hydroxides of metal ions, organic amines, and the like can be used as such additives. For example, hydroxides of metal ions include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the organic amine include ethylamine, diethylamine, triethylamine, 2-aminoethanol, 2- (diethylamino) ethanol, and the like.

As the pH adjuster, sodium hydroxide,
Potassium hydroxide, lithium hydroxide, inorganic bases such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, diisopropylamine, tert-butylamine, dibusylamine,
Mono-, di- or tri-lower alkylamines such as diisobutylamine, isopropylamine, sec-butylamine and pentylamine; lower alkyl lower hydroxyalkoxyamines such as 3-ethoxypropylamine or 3-methoxypropylamine; -Lower alkyl lower alkoxyamines such as ethoxypropylamine or 3-methoxypropylamine, 2-aminoethanol, 2- (dimethylamino) ethanol, 2- (diethylamino) ethanol, diethanolamine, N-butyldiethanolamine, triethanolamine Mono-, di- or tri-lower hydroxyalkylamines such as aminomethylpropanol or triisopropanolamine, iminobispropylamine, 3-diethylaminopropyl Min, dibutyl aminopropyl amine, methylaminopropylamine, dimethylamino propane diamine, to use an organic amine such as methyl iminobispropylamine preferred.

These pH adjusters can also be used as hydrates and organic amines of the above-mentioned metal ions as cations for the organic acid having a carboxyl group.

These organic acids or salts thereof can be used alone or in combination of two or more. In addition, the organic acid or its salt which can be used in the present invention is not limited to those described herein, and any organic acid or salt thereof can be used as long as it meets the requirements.

The present invention can further include a humectant selected from water-soluble organic solvents and / or saccharides having a vapor pressure lower than that of pure water.

By including a humectant, the ink can be kept moist by suppressing evaporation of water in the ink jet recording system. In addition, with a water-soluble organic solvent, the viscosity can be easily changed without improving the ejection stability or changing the ink characteristics.

The water-soluble organic solvent refers to a medium capable of dissolving a solute, and is selected from water-soluble organic solvents having a vapor pressure lower than that of water. Specifically, ethylene glycol, propylene glycol, butanediol, pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, glycerin, 1,2,2
Polyhydric alcohols such as 6-hexanetriol, diethylene glycol, dipropylene glycol, ketones such as acetonylacetone, esters such as γ-butyrolactone, triethyl phosphate, furfuryl alcohol, tetrahydrofurfuryl alcohol, thiodiglycol, etc. Is desirable.

The saccharide is preferably maltitol, sorbitol, gluconolactone, maltose or the like.

The humectant is 5 to 50% of the total amount of the ink.
It is more preferable to add them in the range. If it is 5% or more, moisture retention can be obtained. If it is 50% or less, it is easy to adjust the viscosity to be used for ink jet recording.

In the present invention, the ink may further contain a penetration enhancer selected from lower alcohols, cellosolves, carbitols, and nonionic surfactants. The penetration enhancer is used to lower the surface tension of the ink to promote the penetration of the ink into the recording medium and to shorten the ink drying time. As a lower alcohol, ethanol, isopropanol, butanol, pentanol are used. Cellosolves such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; carbitols such as diethylene glycol monobutyl ether and triethylene glycol monobutyl ether glycol ether; and Surfinol 61, 82, 104 and 4 as nonionic surfactants.
40, 465, 485 (all of which are trade names, manufactured by Air Products and Chemicals), Nissan Nonion K-211, K-220, P-213, E-215,
E-220, S-215, S-220, HS-220,
NS-212 and NS-220 (both are trade names, manufactured by NOF CORPORATION) are preferred.

If necessary, an auxiliary agent generally used for aqueous inks for ink-jet recording can be added to the ink.

Examples of the auxiliary agent added as needed include a hydrotrope agent, a pH adjuster, a fungicide, a chelating agent, a preservative, and a rust preventive.

As the hydrotroping agent which can be added as required, urea, alkyl urea, ethylene urea, propylene urea, thiourea, guanidate, tetraalkyl ammonium halide and the like can be added.

[0053]

The aqueous ink for ink-jet recording according to the present invention is capable of maintaining the stability of ink storage and the reliability of head members while ensuring the ejection stability of ink and the water resistance of printed matter.
In addition, when printing on special recording media (glossy paper, glossy film sheet, etc.), recording images of sufficient quality (glossy,
The reason why it is possible to obtain an image having excellent coloring and penetrability) is not always clear at present, but it can be estimated as follows (although the present invention is limited by the following inferences). Not something).

That is, it is considered that the water resistance of such a water-based ink is developed by the reaction of the colorant anion and the polymer cation to make them insoluble in water. Because of this,
Especially in printing on special recording media, etc., before the ink sufficiently penetrates into the recording medium, the insolubilization reaction between the colorant and the polymer occurs rapidly due to the influence of pH, etc., and the reactants accumulate on the recording medium surface. Therefore, it is considered that a decrease in image quality (loss of glossiness, decrease in color development, etc.) occurs. On the other hand, as shown in the present invention, when an organic acid having a carboxyl group or a salt thereof is present in the ink, a pH buffering action is caused by the carboxylic acid, and the reaction between such a colorant anion and a polymer cation is moderated. Is presumed to be in a state where it hardly appears until it has permeated the recording medium and has been sufficiently reduced. For the same reason, it is presumed that these inks are also effective in preventing dry clogging due to the reaction between the colorant and the polymer at the tip of the inkjet head.

When an organic acid having a carboxyl group or a salt thereof is added, a pH buffering action also works in the ink to lower the pH of the ink. At the same time, to suppress the interaction between the colorant anion and the polymer cation,
It is presumed that the stability of the ink can be maintained without causing precipitation even if the ink pH decreases. As the ink pH decreases, the attack property of the head member is reduced, and the reliability can be maintained for a longer time.

The reason that such ink can ensure the water resistance is that after printing and drying, the polymer and the colorant are fixed near the surface of the recording medium and become insoluble in water, but the organic acid having a carboxyl group or its salt is colored. Compared to agents and polymers,
Since it is small enough and quickly penetrates deep into the recording medium, it is presumed that it does not affect the reduction in the water resistance of the printed matter.

[0057]

EXAMPLES <Preparation of Cationic Water-Soluble Polymer> (Synthesis Example 1) Synthesis of polyallylamine 286 g of monoallylamine was dropped into 550 g of 35% hydrochloric acid while stirring at 5 to 10 ° C. under ice cooling. After the dropwise addition, water and hydrogen chloride were removed at 60 ° C. under reduced pressure using a rotary evaporator to obtain white crystals. The crystals were dried at 80 ° C. under reduced pressure to give monoallylamine hydrochloride 48.
5 g were obtained. This monoallylamine hydrochloride was adjusted to a 70% aqueous solution, and 50 g of the aqueous solution was added to the radical initiator 2,
0.01 mol of 2'-azobis (2-aminopropane) dihydrochloride was dissolved, and 25 g of 35% hydrochloric acid was added.
Thereafter, polymerization was allowed to stand at 60 ° C. for 40 hours. After the polymerization was completed, the system was poured into a mixed solution of 1900 g of acetone / 100 g of methanol, and the resulting precipitate was filtered to obtain polyallylamine hydrochloride.

This polyallylamine hydrochloride was dissolved in ultrapure water to prepare a 10% aqueous solution, and an ion exchange resin IRA900 previously ion-exchanged with sodium hydroxide.
Hydrochloric acid was removed using (trade name, manufactured by Organo) to obtain polyallylamine having a molecular weight of 2,000.

(Synthesis Example 2) 2,2′-
It was prepared in a similar manner except that azobis- (2-amidinopropane) dihydrochloride was doubled. The molecular weight of the obtained polyallylamine was 1,500.

(Synthesis Example 3) Synthesis of poly- (N, N-dimethylallylamine) While maintaining a 25% aqueous solution of polyallylamine having a molecular weight of 1,500 prepared in Synthesis Example 2 at 40 ° C., % Formalin was added dropwise in sequence. After dropping,
The system was gradually heated to 90 ° C. After confirming the generation of carbon dioxide, the mixture was allowed to stand for 6 hours. After confirming that the generation of gas had ceased, the reaction solution was poured into acetone to precipitate a reaction product. By filtration and drying, poly- (N, N
-Dimethylallylamine).

<Evaluation method> (Water resistance) MJ-5000C (trade name, manufactured by Seiko Epson Corporation) was filled with ink as a printer of an ink jet recording system, and Xerox-P (trade name, Fuji) was used as neutral plain paper. Xerox Co., Ltd.), EPP (trade name, manufactured by Seiko Epson Corporation) as acidic plain paper, and Xerox-R (trade name, manufactured by Fuji Xerox Co., Ltd.) as recycled paper. After standing for 1 hour, the water resistance was evaluated by a JISL0853 water drop test. The criteria are as shown in Table 1.

[0062]

[Table 1]

(Storage Stability of Ink) The inks prepared in Examples and Comparative Examples were placed in glass sample bottles, and left at 60 ° C. for 1 week and at −30 ° C. for 1 week, respectively.
The presence or absence of a precipitate in the ink was observed. Precipitates were determined by passing 2 cc of the ink through a filter having a diameter of 1 mm and a pore size of 10 μm, and observing with a microscope at a magnification of 50 times from the number of residues on the filter. The criteria are as shown in Table 1.

(Glossiness of Recorded Image) MJ-5000C (trade name, manufactured by Seiko Epson Corporation) was filled with ink as an ink jet recording system printer, and special glossy paper (trade name, manufactured by Seiko Epson Corporation) was used. Dedicated glossy film (product name, manufactured by Seiko Epson Corporation)
And the glossiness of the recorded image was evaluated. The criteria are as shown in Table 1.

(Reliability of Head Member) The inks prepared in Examples and Comparative Examples and the head component members were individually placed in a Petri dish, left at 70 ° C. for one week, and the state of the supplied head members was observed. Changes in the state of the sample, such as dissolution, deformation, and coloring, were compared with those of the initial members and judged. The criteria are as shown in Table 1.

<Preparation of Ink> (Example 1) 5 g of Direct Fast Black AB (trade name, CI Direct Black 32, manufactured by Sumitomo Chemical Co., Ltd.) as a colorant was dissolved in 50 g of ultrapure water. A dye solution was prepared. 1.5 g of polyallylamine having a molecular weight of 2,000 synthesized in Synthesis Example 1 as a cationic water-soluble polymer and 0.5 g of acetic acid as an organic acid are added to the stirring dye solution, and the total amount of ultrapure water becomes 100 g. Addition and stirring were carried out. Subsequently, the mixture was filtered through a metal mesh filter having a pore size of about 5 μm to prepare an aqueous ink for inkjet recording. The prepared ink pH was 9.7.

Example 2 In 50 g of ultrapure water, Direct Fast Yellow R (trade name, CI Direct Yellow 50, manufactured by Sumitomo Chemical Co., Ltd.) was used as a colorant.
5 g was dissolved to prepare a dye solution. To the stirring dye solution, 1.5 wt% of PAA-10C (trade name, manufactured by Nitto Boseki Co., Ltd.) as a cationic water-soluble polymer in terms of solid content, and 0.3 g of sodium formate as an organic acid salt were added. Add ultrapure water to total amount of 100g
The mixture was added and stirred until the mixture became. Subsequently, the mixture was filtered through a metal mesh filter having a pore size of about 5 μm to prepare an aqueous ink for inkjet recording. The prepared ink pH was 10.3
was.

Example 3 A dye solution was prepared by dissolving 2 g of Nippon Fast Red BB (trade name, CI Direct Red 31 manufactured by Sumitomo Chemical Co., Ltd.) as a colorant in 50 g of ultrapure water. did. 2 g of SP-012 (trade name, manufactured by Nippon Shokubai Co., Ltd.) which is polyethyleneimine as a cationic water-soluble polymer is added to the stirring dye solution.
, Then 0.5 g of lactic acid, 0.1 g of sodium hydroxide
g was added, and ultrapure water was added and stirred until the total amount became 100 g. Subsequently, the mixture was filtered through a metal mesh filter having a pore size of about 5 μm to prepare an aqueous ink for inkjet recording. The prepared ink pH was 10.7.

Example 4 A dye solution was prepared by dissolving 4 g of Kayalar Star Koiz Blue GL (trade name, Nippon Kayaku Co., Ltd., CI Direct Blue 86) as a colorant in 50 g of ultrapure water. did. Poly- (N, N-dimethylallylamine) having a molecular weight of 2,200 synthesized in Synthesis Example 3 as a cationic water-soluble polymer in a stirring dye solution.
3 g and 0.48 g of ammonium tartrate were added, and ultrapure water was added and stirred until the total amount became 100 g. Subsequently, the mixture was filtered through a metal mesh filter having a pore size of about 5 μm to prepare an aqueous ink for inkjet recording. The prepared ink pH was 9.9.

The inks of Examples 1 to 4 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. The results are summarized in Table 2.

[0071]

[Table 2]

Example 5 In contrast to Example 1, the coloring agent was Nigrosine NB (trade name, manufactured by Sumitomo Chemical Co., Ltd.).
C. I. Acid Black 2) 3 g, PAS-A-1 which is a copolymer of diallylamine and sulfur dioxide as a cationic water-soluble polymer (trade name, manufactured by Nitto Boseki Co., Ltd.)
Was changed to 2.5% by weight in terms of solid content, 0.3 g of acetic acid was added, and 0.6 g of potassium hydroxide was further added to prepare a water-based ink for ink jet recording.
The prepared ink pH was 10.2.

(Example 6) In comparison with Example 1, 3.5 g of Mike Slen Solble Blue O (trade name, CI Solbilize Bat Blue 1 manufactured by Mitsui Toatsu Chemicals, Inc.) was used as a coloring agent. And a molecular weight of about 2,200 synthesized in Synthesis Example 3.
1.5 g of poly- (N, N-dimethylallylamine)
A water-based ink for ink-jet recording was prepared in the same manner except that the above was changed. The prepared ink pH was 9.7.

(Example 7) In contrast to Example 1, the coloring agent was Sumifix Brilliant Blue R (trade name, CI Reactive Blue 19, manufactured by Sumitomo Chemical Co., Ltd.).
2 g, a water-based ink for ink-jet recording is prepared in the same manner except that PAA-L (trade name, manufactured by Nitto Boseki Co., Ltd.), which is a polyallylamine as a cationic water-soluble polymer, is changed to 2.5 wt% in terms of solid content. did. The pH of the prepared ink was 10.8.

Example 8 In contrast to Example 1, the coloring agent was changed to Food Yellow No. 5 (trade name, manufactured by Hodogaya Chemical Industry Co., Ltd.).
C. I. Food Yellow 3) A water-based ink for inkjet recording was prepared in the same manner except that 2.5 g of poly- (N, N-dimethylallylamine) having a molecular weight of about 2,200 synthesized in Synthesis Example 3 was changed to 3 g. The prepared ink pH was 9.8.

Example 9 In contrast to Example 1, 2 g of Eizemethylene Blue FZ (trade name, CI Basic Blue 9 manufactured by Hodogaya Chemical Industry Co., Ltd.) was used as a coloring agent, and polycation was used as a cationic water-soluble polymer. P which is allylamine
AA-10C (trade name, manufactured by Nitto Boseki Co., Ltd.) was 2% by weight in terms of solid content, and sodium lactate was 0.5 as an organic acid salt.
A water-based ink for inkjet recording was prepared in the same manner except that g was changed to g. The prepared ink pH was 9.7.

(Example 10) In contrast to Example 1, 2.5 g of Zapon Fast Yellow CGG (trade name, CI Solvent Yellow 15 manufactured by BASF) was used, and diallyl was used as a cationic water-soluble polymer. PAS-J-81 (trade name, manufactured by Nitto Boseki Co., Ltd.), which is a copolymer of dimethylamine and acrylamide, is 1.5 wt.
%, Formic acid was changed to 0.2 g as an organic acid, and 0.25 g of potassium hydroxide was further added to prepare a water-based ink for inkjet recording in the same manner. The pH of the prepared ink was 10.5.

(Example 11) In contrast to Example 1, the colorant was pink 6G (trade name, manufactured by Noma Chemical Industry Co., Ltd., C.I.
I. Pigment Red 81) 2.5 g, PAA-10C of polyallylamine as a cationic water-soluble polymer
(Trade name, manufactured by Nitto Boseki Co., Ltd.) 2 wt.
%, A water-based ink for ink-jet recording was prepared in the same manner except that the amount was changed to%. The prepared ink pH was 9.7.

The inks of Examples 5 to 11 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. Therefore, the coloring agent is not only a water-soluble acid dye, a direct dye, a reactive dye, a soluble vat dye, a food dye, a basic dye, but also a water-insoluble oil if soluble in alkali. Soluble dye,
Even pigments can prepare inks that are suitable for the requirements of the ink of the present invention. The results are summarized in Table 3.

[0080]

[Table 3]

(Example 12) In comparison with Example 1, 0.5 g of Direct Fast Black AB and a molecular weight of 2,200 synthesized in Synthesis Example 3 as a cationic water-soluble polymer.
0.5 g of poly- (N, N-dimethylallylamine)
A water-based ink for ink-jet recording was prepared in the same manner except that the above was changed. The pH of the prepared ink was 9.6.

(Example 13) In comparison with Example 1, 10 g of Direct Fast Black AB and polyethylene imine SP-012 (trade name, cationic water-soluble polymer) were used.
A water-based ink for ink-jet recording was prepared in the same manner except that 10 g of salicylic acid and 1.0 g of salicylic acid were added, and 0.13 g of potassium hydroxide was further added. The prepared ink pH was 10.6.

Example 14 To Example 1, 20 g of Direct Fast Black AB and poly- (N, N-dimethylallylamine) having a molecular weight of 2,200 and synthesized in Synthesis Example 3 as a cationic water-soluble polymer were used. An aqueous ink for inkjet recording was prepared in the same manner except that the amount was changed to 15 g and 1.0 g of propylamine, and 0.06 g of sodium hydroxide was added. The pH of the prepared ink is 1
It was 0.7.

The inks of Examples 12 to 14 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of the head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. Therefore, if the colorant is contained in the range of 0.5 to 20 wt% with respect to the ink, an ink suitable for the requirements of the ink of the present invention can be prepared. The results are summarized in Table 4.

[0085]

[Table 4]

(Example 15) In contrast to Example 1, the cationic water-soluble polymer was replaced with polyethyleneimine SP-012.
(Trade name, manufactured by Nippon Shokubai Co., Ltd.) An aqueous ink for inkjet recording was prepared in the same manner except that the amount was changed to 2.5 g and further 0.02 g of potassium hydroxide was added. The prepared ink pH was 9.2.

(Example 16) In contrast to Example 1, poly- (N, N-dimethylallylamine) having a molecular weight of 2,200 and synthesized in Synthesis Example 3 as a cationic water-soluble polymer.
Was changed to 2.0 g to prepare an aqueous ink jet recording ink in the same manner. The prepared ink pH was 9.7.

Example 17 In contrast to Example 1, PAS-J-81 (trade name, manufactured by Nitto Boseki Co., Ltd.), which is a copolymer of diallyldimethylamine and acrylamide, was used as a cationic water-soluble polymer. A water-based ink for ink-jet recording was prepared in the same manner except that the amount was changed to 2% by weight, 0.3 g of ammonium tartrate, and 0.17 g of sodium hydroxide was further added. At this time, the pH of the ink was 8.6.

Example 18 In comparison with Example 1, 3% by weight of solid content-converted DAMFIX 723 (trade name, manufactured by Nitto Boseki Co., Ltd.), which is a cationic water-soluble polymer polyallylamine hydrochloride, was added. .21 g, and an aqueous ink for inkjet recording was prepared in the same manner except that 0.23 g of potassium hydroxide was further added. The pH of the prepared ink was 8.1.

(Example 19) In contrast to Example 1, PA which is polyallylamine as a cationic water-soluble polymer was used.
A water-based ink for ink jet recording was prepared in the same manner except that AL (trade name, manufactured by Nitto Boseki Co., Ltd.) was changed to 2 wt% in terms of solid content. The prepared ink pH was 9.7.

The inks of Examples 15 to 19 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. Therefore, as long as the cationic water-soluble polymer has at least a structure selected from ethyleneimine, dimethylallylamine, allylamine and diallylamine in the molecule, not only a homopolymer but also a copolymer, the requirements of the ink of the present invention Can be prepared. The results are summarized in Table 5.

[0092]

[Table 5]

(Example 20) In comparison with Example 1, 0.5 g of Direct Fast Black AB was used, and PAS-H which was polydiallylamine as a cationic water-soluble polymer was used.
-5 L (trade name, manufactured by Nitto Boseki Co., Ltd.) is changed to 0.1 wt% in terms of solid content, 0.07 g of lactic acid, and then 0.25 g of sodium hydroxide is added, and the aqueous ink for inkjet recording is produced in the same manner. Was prepared. The prepared ink pH was 8.3.

(Example 21) In comparison with Example 1, 30 g of ultrapure water to be initially charged and Direct Fast Black A
B, 3 g of polyallylamine PAA-10C (trade name, manufactured by Nitto Boseki Co., Ltd.) as a cationic water-soluble polymer was changed to 10 wt% in terms of solid content and 1.0 g of benzoic acid, and 0.05 g of potassium hydroxide was further added. A water-based ink for ink-jet recording was prepared in the same manner except that was added. At this time, the pH of the ink was 10.1.

(Example 22) In comparison with Example 1, 30 g of ultrapure water to be initially charged and Direct Fast Black A
B was changed to 5 g, 20 g of Epomin SP-003 (trade name, manufactured by Nippon Shokubai Co., Ltd.), which is polyethyleneimine as a cationic water-soluble polymer, and 2.0 g of sodium acetate, and 2 g of 2- (dimethylamino) ethanol was added. Prepared a water-based ink for ink-jet recording by the same method. The prepared ink pH was 10.6.

The inks of Examples 20 to 22 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. Therefore, the amount of the cationic water-soluble polymer is 0.1 to 20 wt.
%, It is possible to prepare an ink suitable for the requirements of the ink of the present invention. The results are summarized in Table 6.

[0097]

[Table 6]

(Example 23) In comparison with Example 1, the colorant was added to 1.0 g of Kayalar Star Coize Blue GL (trade name, Nippon Kayaku Co., Ltd., CI Direct Blue 86) and 0.01 g of acetic acid. A water-based ink for ink-jet recording was prepared in the same manner except for the change. Prepared ink pH
Was 10.1.

(Example 24) In comparison with Example 1, the colorants were 4.0 g of Kayalar Star Coize Blue GL (trade name, Nippon Kayaku Co., Ltd., CI Direct Blue 86) and 3.0 g of propionic acid. And aqueous ink for inkjet recording was prepared in the same manner except that 0.13 g of potassium hydroxide was further added. The prepared ink pH was 9.8.

(Example 25) In comparison with Example 1, the coloring agent was 6.0 g of Kayalar Star Coize Blue GL (trade name, Nippon Kayaku Co., Ltd., CI Direct Blue 86) and 10.0 g of stearic acid. And aqueous ink for inkjet recording was prepared in the same manner except that 0.86 g of potassium hydroxide was further added. The pH of the prepared ink was 8.8.

The inks of Examples 23 to 25 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good or good. Therefore, if the organic acid and the organic acid salt are contained in the ink in the range of 0.01 to 10% by weight, a preferable ink for the requirements of the ink of the present invention can be prepared. The results are summarized in Table 7.

[0102]

[Table 7]

Examples 1, 4, 6, 8, 9, 11,
From the results of 15, 18, 24 to 28, 31, the ink pH
Was adjusted to 10 or less, the reliability of the head component was good, and the glossiness of the recorded image was particularly good.

Example 26 An aqueous ink for inkjet recording was prepared in the same manner as in Example 1, except that 10 g of glycerin was further added as a humectant. The prepared ink pH was 9.7.

Example 27 An aqueous ink jet recording ink was prepared in the same manner as in Example 1 except that 10 g of maltitol was further added as a humectant. The pH of the prepared ink was 9.6.

Example 28 An aqueous ink for inkjet recording was prepared in the same manner as in Example 1, except that 10 g of thiodiglycol was further added as a humectant. The prepared ink pH was 9.8.

The inks of Examples 26 to 28 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, all the inks had good water resistance, storage stability of the ink, and reliability of the head member. The glossiness of the recorded image was particularly good. Therefore, even if a humectant is further added to the ink of the present invention, a preferable ink for the requirements of the present invention can be prepared. The results are summarized in Table 8.

[0108]

[Table 8]

(Example 29) In comparison with Example 1, 4 g of Direct Fast Black AB and PAA-10C of polyallylamine (trade name, manufactured by Nitto Boseki Co., Ltd.) as a cationic water-soluble polymer were converted into 1 solid content. 0.3wt
%, 2- (dimethylamino) ethanol 5 g, and diethylene glycol monobutyl ether 10 g as a penetration enhancer were prepared in the same manner to prepare an aqueous ink jet recording ink. The pH of the prepared ink is 1
It was 0.6.

(Example 30) In comparison with Example 1, 4 g of direct fast black AB and PAS-A-1 which is a copolymer of diallylamine and sulfur dioxide as a cationic water-soluble polymer (trade name, Nitto Boseki Co., Ltd.) Was changed to 3.5 wt% in terms of solid content, and 4 g of 2- (dimethylamino) ethanol was further added. Surfynol 465 (trade name, Air Products and Products Co., Ltd.) as a nonionic surfactant was used as a penetration enhancer. Chemicals) 0.8g,
An aqueous ink jet recording ink was prepared in the same manner except that 0.4 g of potassium hydroxide was added. The pH of the prepared ink was 9.6.

(Example 31) In comparison with Example 1, 6 g of direct fast black AB, 10 g of glycerin as a humectant, 10 g of diethylene glycol monobutyl ether as a penetration enhancer and Surfynol 465 as a nonionic surfactant (trade name, A water-based ink for inkjet recording was prepared in the same manner except that 0.8 g of Air Products and Chemicals was added. The pH of the prepared ink was 8.7.

The inks of Examples 29 to 31 were evaluated for water resistance, storage stability of the ink, glossiness of a recorded image, and reliability of a head member. As a result, the water resistance, the storage stability of the ink and the reliability of the head member were good or within the limits for all the inks. The glossiness of the recorded image was particularly good. Therefore, even if a penetration enhancer is further added to the ink of the present invention, an ink suitable for the requirements of the present invention can be prepared. The results are summarized in Table 9.

[0113]

[Table 9]

Further, the inks of Examples 29 to 31 to which a penetration enhancer was added were neutral plain paper Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) and acidic plain paper EPP.
When solid printing is performed on recycled paper (trade name, manufactured by Seiko Epson Corporation) and recycled paper Xerox-R (trade name, manufactured by Fuji Xerox Co., Ltd.), the drying time during which the ink liquid penetrates from the paper surface to the inside of the paper disappears. Was less than 2 seconds, and a quick-drying, super-permeable ink was obtained.

<Comparative Example> (Comparative Example 1) A water-based ink for ink-jet recording was prepared in the same manner as in Example 1, except that acetic acid as an organic acid was not added. The pH of the prepared ink was 12.2.

Comparative Example 2 C.I. I. Dissolve 3.5 g of Direct Blue 199,
A dye solution was prepared. Here, 1.5 g of polyallylamine having a molecular weight of 1,500 synthesized in Synthesis Example 2 as a cationic water-soluble polymer, 10 g of glycerin and 10 g of diethylene glycol as humectants, 10 g of diethylene glycol monobutyl ether as humectants, nonionic interface 0.8 g of Surfynol 465 as activator
added. Further, an appropriate amount of 1N HCl was added to adjust the pH, and ultrapure water was added so that the total amount became 100 g, followed by stirring and mixing. Subsequently, the mixture was filtered through a metal mesh filter having a pore size of about 5 μm to prepare an aqueous ink for inkjet recording. No organic acid having a carboxylic acid was added to this ink. The prepared ink pH was 11.4.

For the inks of Comparative Examples 1 and 2, water resistance and
The storage stability of the ink, the glossiness of the recorded image, and the reliability of the head member were evaluated. As a result, the water resistance and the storage stability of the ink were good, but the glossiness of the recorded image and the reliability of the head were impossible. The results are summarized in Table 10.

[0118]

[Table 10]

(Comparative Example 3) A procedure was carried out in the same manner as in Example 1 except that polyallylamine was changed to ultrapure water. The pH of the prepared ink was 8.8.

The ink of Comparative Example 3 was an ink containing no dye-based water-soluble polymer, a dye, a water-soluble organic solvent, an organic acid, and water. About this ink,
The water resistance, the storage stability of the ink, the glossiness of the recorded image, and the reliability of the head member were evaluated. The results showed that the storage stability of the ink, the glossiness of the recorded image, and the reliability of the head were good to within limits but water resistance was not obtained. Table 10 shows the results.

[0121]

As described above, according to the present invention, the ink comprises at least water, a water-soluble colorant, a cationic water-soluble polymer, an organic acid having a carboxyl group or a salt thereof. It has become possible to provide a recording water-based ink that can realize the water resistance of a printed matter and a high-quality recorded image on a special recording medium while maintaining the storage stability of the recording medium and the reliability of the head member.

Claims (10)

[Claims] 1. An aqueous ink jet recording ink comprising at least water, a water-soluble colorant, a cationic water-soluble polymer, and an organic acid having a carboxyl group or a salt thereof. 2. The aqueous ink for ink-jet recording according to claim 1, wherein the organic acid or a salt thereof is contained in the ink in an ionized state. 3. The colorant is alkali-soluble,
The aqueous ink for inkjet recording according to any one of claims 1 to 2, wherein the aqueous ink is selected from organic dyes and pigments. 4. The method according to claim 1, wherein the colorant is 0.5 to
2. The composition according to claim 1, wherein the content is in the range of 20 wt%.
The aqueous ink for inkjet recording according to any one of claims 1 to 3. 5. The cationic water-soluble polymer according to claim 1, wherein the molecule has at least a structure selected from ethyleneimine, allylamine, diallylamine, and dimethylallylamine. 3. The aqueous ink for inkjet recording according to item 1. 6. The aqueous solution for ink-jet recording according to claim 1, wherein the cationic water-soluble polymer is contained in an amount of 0.1 to 20% by weight based on the ink. ink. 7. The aqueous ink for inkjet recording according to claim 1, wherein the organic acid or a salt thereof is contained in an amount of 0.01 to 10% by weight based on the ink. 8. The aqueous ink for ink-jet recording according to claim 1, wherein the pH of the ink is 10 or less. 9. The ink according to claim 1, wherein the ink further contains a humectant selected from a water-soluble organic solvent and / or a saccharide having a vapor pressure lower than that of pure water. Water-based ink for inkjet recording. 10. The ink according to claim 1, further comprising a permeation enhancer selected from the group consisting of lower alcohols, cellosolves, carbitols, and nonionic surfactants. The aqueous ink for inkjet recording according to claim 1.