JP2000053900A - Aqueous ink for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aq. ink for ink jet recording which is free of defective delivery and has been improved in arrival position of ink drops and in setting density by adding two specific compds. to a polymer emulsion obtd. by impregnating fine vinyl polymer particles with a colorant. SOLUTION: A neutralizing agent and optionally a surfactant are added to a soln. or dispersion which is obtd. by adding a colorant and a vinyl polymer formed from a (meth)acrylamide monomer, a monomer having a salt-forming group, and a monomer copolymerizable with the foregoing monomers to an org. solvent, ionizing the salt-forming groups. The soln. or dispersion is then emulsified with water and is freed of the org. solvent by distillation, thus giving an aq. emulsion contg. fine vinyl polymer particles impregnated with a colorant. This aq. emulsion is compounded with at least one compd. selected from among urea, alkylglycines, and glycinebetaine and a compd. of formula I and/or formula II. In the formula, R1 and R2 are each a linear, branched, or cyclic alkyl group; and M is an alkali metal ion or a quaternary ammonium ion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording ink in which defective ink ejection is prevented and the accuracy of the landing position of ink droplets and the print density are improved.

[0002]

2. Description of the Related Art Ink jet recording inks having improved water resistance include inks containing latex (JP-A-55-18412).
Containing a polymer or colored polymer latex (JP-A-5
JP-A-9-30873).

[0003] However, ink containing latex causes nozzle clogging. In addition, when printing is performed by a printer of a thermal jet system, the ejection is not stabilized, and the accuracy of the landing position of the ink droplet is reduced. Further, the print density does not become sufficiently high. In addition, even when the amount of the coloring material introduced is sufficient, there is a problem that stripes and blurring occur on the printed matter due to a decrease in the landing position accuracy, and the printing density is not sufficiently increased.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet recording ink in which ink ejection failure is prevented and the accuracy of the landing position of ink droplets and the print density are improved.

[0005]

According to the present invention, the above object has been attained by incorporating a specific compound in a water-based ink comprising an emulsion of a specific polymer.

[0006] That is, the present invention comprises a polymer emulsion obtained by impregnating polymer fine particles with a coloring material, comprising urea,
At least one compound A selected from the group consisting of alkyl glycine and glycine betaine, and the following compound (I)
And at least one compound B selected from the group consisting of (II) and (II), and wherein the polymer is a vinyl polymer.

[0007]

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[0008]

DETAILED DESCRIPTION OF THE INVENTION The aqueous ink for ink-jet recording of the present invention (hereinafter simply referred to as "aqueous ink") comprises at least one compound A selected from the group consisting of urea, alkylglycine and glycinebetaine, A combination with at least one compound B selected from the group consisting of compounds (I) and (II) is used.

Among the compounds A, those having the general formula of R ₃ R ₄ NCH ₂ COOM are used as the alkylglycine,
The general formula, as R ₃ and R ₄ the same or different hydrogen atom or an alkyl group having 1 to 5 carbon atoms are preferably used (however, R ₃ and R ₄ are not hydrogen atoms at the same time).
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and an isopropyl group. As M, a hydrogen atom, an alkali metal atom or an alkaline earth metal atom is used, and a hydrogen atom or an alkali metal atom is preferably used. Specific examples of the alkylglycine include N-methylglycine, N, N-dimethylglycine and N-methylglycine.
-Ethylglycine and the like.

As the compound A, one or more compounds can be used. Particularly preferably used are urea, N-methylglycine, N, N, N-trimethylglycine and glycylbetaine. Compound A is preferably contained in the aqueous ink of the present invention in an amount of 1 to 50% by weight, more preferably 2 to 35% by weight, and even more preferably 5 to 25% by weight. If the content of the compound A is less than 1% by weight, the emulsion is liable to be scorched on the head, so that the landing position accuracy of ink droplets may be reduced. Dischargeability is apt to decrease, so the printing quality on recording paper deteriorates,
The abrasion resistance may be reduced.

The above compound used as compound B
In (I) and (II), R ₁ and R ₂ are preferably the same or different n-hexyl group, 1-methylpentyl group, 2-ethylhexyl group, n-octyl group, n-amyl group, cyclohexyl Group, isobutyl group, isotridecyl group, isoamyl group, n-butyl group, n-heptyl group,
n-nonyl group, n-decyl group, n-dodecyl group, n-tridecyl group, 1-methylbutyl group, 2-methylbutyl group, 1,3-dimethylbutyl group, 1-methylbutyl group,
Dimethylbutyl group, 1-methylhexyl group, 1-methylheptyl group, 1-propylbutyl group, 1-butylamyl group, 1-methyl-4ethylhexyl group, 1-methyl-4
An ethyl octyl group or the like is used. In particular, R ₁ and R ₂ are preferably the same group. Examples of M include alkali metal atoms such as Na and K, and quaternary ammonium ions such as NH ₄ ⁺ and N (CH ₂ CH ₂ OH) ₄ ⁺ . Preferred examples of the compound (I) include compounds represented by the following formulas (Ia) to (Ic). On the other hand, the following formula a COONa group was replaced by OPO ₃ Na ₂ group in the compound represented by the following formula Examples of preferred as the compound (II) (Ia) ~ ( Ic) (IIa) ~
And the compound represented by (IIc).

[0012]

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[0013]

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As compound B, either one of compounds (I) and (II) or a combination of both can be used. Compound B is preferably present in the aqueous ink of the present invention in an amount of 0.001 to 0.001.
To 2% by weight, more preferably 0.005 to 2% by weight, and even more preferably 0.01 to 1% by weight. Compound B
If the content is less than 0.001% by weight, the emulsion easily sticks to the head, the ejection is not stable, and the accuracy of the ink droplet landing position may decrease. Is preferably within the above-mentioned range because the penetration force of the toner is promoted and a sufficient print density may not be obtained (in particular, remarkable with plain paper).

Compounds (I) and (II) can be obtained by known synthetic methods. For example, compound (I) is
The maleic diester obtained by the esterification reaction between alcohol and maleic anhydride was hydroborated with B ₂ H ₆ and oxidized with hydrogen peroxide and OH ^- ion.
A hydroxyl group is introduced by a reverse Markovnikov hydration reaction, which is a combination with a hydrolysis reaction, and the hydroxyl group is oxidized with nitric acid to be converted into a carboxyl group, followed by neutralization with an alkali. Compound (I
I) is to react a phosphoric anhydride with a maleic diester in which a hydroxyl group has been introduced to obtain a phosphoric acid monoester and a phosphoric acid diester, and neutralize the phosphoric acid monoester with an alkali. Is obtained by

The aqueous ink of the present invention is an aqueous dispersion containing the compound A and the compound B in a polymer emulsion. As the polymer emulsion, an emulsion of colored polymer fine particles colored with a coloring material is used, and particularly, an emulsion of polymer fine particles impregnated with a water-insoluble or poorly water-soluble coloring material is preferably used. In the present specification, "impregnated with a coloring material"
The expression means one or both of a state in which the coloring material is sealed in the polymer fine particles and a state in which the coloring material is adsorbed on the surface of the polymer fine particles. In this case, it is not necessary that all the coloring materials incorporated in the aqueous ink of the present invention be encapsulated or adsorbed in the polymer fine particles, and the coloring materials are dispersed in the emulsion as long as the effects of the present invention are not impaired. You may. In a preferred embodiment of the present invention, the water-based ink comprises an emulsion of polymer fine particles impregnated with a water-insoluble or poorly water-soluble colorant, and the compound A
And compound B.

The coloring material is not particularly limited as long as it is a water-insoluble or hardly water-soluble coloring material and can be adsorbed by the polymer. In this specification,
The term “water-insoluble or poorly water-soluble” means that at least 10 parts by weight of a coloring material does not dissolve in 100 parts by weight of water at 20 ° C. It is not allowed. Examples of the coloring material include dyes such as oil-soluble dyes and disperse dyes, and pigments. In particular, oil-soluble dyes and disperse dyes are preferred from the viewpoint of good adsorption and encapsulation properties.

Each of the dyes used in the present invention is preferably an organic solvent,
For example, it is preferably dissolved in a ketone-based solvent at 2 g / L or more, more preferably 20 to 600 g / L.

The above coloring material is contained in the water-based ink of the present invention in an amount of 1 to 1.
Preferably, it is blended at 30% by weight, more preferably 1.5 to 25% by weight. If the amount of the coloring material is less than 1% by weight, the print density may not be sufficient. If the amount is more than 30% by weight, the stability of the polymer fine particles with time is reduced, and the particle size increases. The dispersion stability of the emulsion itself tends to decrease. In addition, the amount of the coloring material is, in relation to the amount of the polymer,
It is preferably about 10 to 200% by weight, especially about 25 to 150% by weight, based on the weight of the polymer.

As the polymer constituting the polymer emulsion, various vinyl polymers are used. In particular, an acrylamide-based or methacrylamide-based monomer (a) (excluding those having a salt-forming group), a polymerizable monomer (b) having a salt-forming group, and a monomer copolymerizable with these monomers (c ) Is used. In such a polymer emulsion,
By containing the compound A and the compound B in combination, the face of the print head is prevented from being stained, the accuracy of the landing position of the ink droplet is improved, and the print density on plain paper is improved.

The acrylamide-based or methacrylamide-based monomer (a) includes, for example, JP-A-9-28
No. 6,939, column 5, line 40 to column 7, line 22.

The above polymerizable monomer (b) having a salt-forming group
For example, Japanese Patent Application Laid-Open No. 9-286939
Column 23, line 8 to column 8, line 29 include monomers.

Examples of the monomer (c) copolymerizable with the above monomers (a) and (b) include, for example, JP-A-9-28693.
The monomers described in column 8, line 30 to column 9, line 1 of JP-A-9 are mentioned. Among these, it is particularly preferable to use methyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate, 2-methylstyrene, and 2-hydroxyethyl methacrylate.

A monomer (c) copolymerizable with the above monomer
Is not limited to the above, and a commercially available radical copolymerizable monomer can also be used. In particular, the following formula (1-1)
Using one or more monomers represented by (1-4),
It is preferable from the viewpoint of storage stability of the emulsion.

[0025]

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Commercially available monomers (c) include styrene and / or acrylonitrile copolymer macromers having a methacryloyloxy group at one end [AN-6, AS-6 (trade name) manufactured by Toagosei Co., Ltd.] ], A methyl methacrylate polymer macromer having a methacryloyloxy group at one end [manufactured by Toagosei Co., Ltd., AA-6 (trade name)], a polyoxyethylene macromer having a methacryloyloxy group at one end [Shin Nakamura Chemical ( Co., Ltd., NK ester M-90Gne
w, M-40Gnew and M-20Gnew (trade name)], polyester macromers having a methacryloyloxy group at one end [FM4DX (trade name) manufactured by Daicel Chemical Industries, Ltd.] and the like.

When synthesizing the vinyl polymer, the monomer (a) is used in an amount of 1 to 40 with respect to the total amount of the monomers.
% By weight of the above monomer (b),
The copolymerization is preferably carried out using 25% by weight of the monomer (c) in a proportion of 35 to 96% by weight based on the total amount of the monomers.

In synthesizing the vinyl polymer, it is preferable to use a silicon macromer represented by the following formula (2) as a copolymer component.

[0029]

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In the silicone macromer represented by the above formula (2), X represents a polymerizable unsaturated group, and specifically, groups such as CH ₂ ＣＨCH— and CH ₂ ＣC (CH ₃ ) — No. Y represents a divalent linking group, specifically -C
_{OO -, - COOC b H 2b} - ( wherein b is a number of 1 to 5) and phenylene group and the like, -COOC ₃ H
_6- is preferred. R ₅ represents a hydrogen atom; a lower alkyl group such as a methyl group or an ethyl group; an aryl group such as a phenyl group; an alkoxy group such as a methoxy group, and is preferably a methyl group. Z is a number average molecular weight of at least about 500 [gel permeation chromatography (hereinafter GPC)
To convert to polystyrene. same as below. And preferably a monovalent dimethyl siloxane polymer having a number average molecular weight of 800 to 5,000. n is 0 or 1, and preferably 1. m is an integer of 1 to 3, and is preferably 1.

As the silicone macromer, the following formula (2)
-1) to (2-4). Among them, those represented by the formula (2-1) are preferable, and particularly, those represented by the following formula (2)
-1-1) Those represented by [FM-0711 (trade name) manufactured by Chisso Corporation] are preferable.

[0032]

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[0033]

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The above vinyl polymer is disclosed in JP-A-9-28.
No. 6,939, column 9, lines 10 to 23, and is particularly preferably produced by a solution polymerization method.

In the copolymerization, a radical polymerization initiator is used, and examples thereof include those described in JP-A-9-286939, column 9, lines 24 to 36. Among these, it is particularly preferable to use an azo compound.
These radical polymerization initiators are added to the total amount of the monomers.
It is preferable to use 0.001 to 2.0 mol%, particularly 0.01 to 1.0 mol%.

At the time of copolymerization, a polymerization chain transfer agent may be further added. A specific example thereof is disclosed in
No. 939, column 9, line 37 to column 10, line 10. Among them, mercaptoethanol, n-dodecylmercaptan, t-dodecylmercaptan, dimethylxanthogen disulfide, tetramethylthiuram disulfide, carbon tetrachloride, pentaphenylethane, acrolein, methacrolein, allyl alcohol, α-methylstyrene dimer (2, 4-Diphenyl-4-methyl-1-pentene is preferably 50% by weight or more), xanthene, and 2,5-dihydrofuran.

A specific copolymerization method is described in, for example,
No. 286939, column 10, lines 11-19. The weight average molecular weight of the vinyl polymer obtained by copolymerization (in terms of polystyrene by GPC; the same applies hereinafter) is preferably from 3,000 to 50,000.

The vinyl-based polymer of the present invention is used in order to ensure a sufficient print density and to prevent clogging of the printer head due to thickening of the ink due to ink evaporation and aggregation of polymer fine particles. It is preferable that 1 to 30% by weight, particularly 2 to 20% by weight as a solid content is incorporated therein.

The content of the vinyl-based polymer in the water-based ink of the present invention is such that the weight ratio (former / latter) of the polymer to the compound A is 1 / about the content of the compound A and the compound B. 5-5 / 1, especially 1 / 3-3 /
1, and the weight ratio of the polymer to the compound B (former / latter) is 5/1 to 2000/1, particularly 10
/ 1 to 1000/1.

The above-mentioned vinyl polymer preferably has a glass transition point (hereinafter, referred to as Tg) of 20 ° C. or higher.
50-150 ° C is preferred. The temperature is preferably 20 ° C. or higher for an ink jet system using a piezoelectric element, and 30 ° C. or higher for an ink jet recording system using thermal energy.
Outside of these preferred ranges, the vinyl polymer tends to solidify at the nozzle of the printer, and the nozzle may be clogged. In addition, when the printed papers are overlapped, paper reflection of the ink may occur. In addition, Tg is measured by a differential scanning calorimeter (hereinafter, referred to as DSC).

The aqueous ink of the present invention is an aqueous emulsion using water (preferably ion-exchanged water) as a medium. The amount of water is preferably 50 to 98% by weight, more preferably 55 to 95% by weight, and still more preferably 60 to 90% by weight.
It is.

The water-based ink of the present invention may further contain a wetting agent such as a polyhydric alcohol within a range not exceeding the preferable viscosity as the ink for ink jet recording. The preferred compounding amount is 0.1 to 50% by weight, particularly 1 to 30% by weight in the aqueous ink of the present invention.

In addition to the above-mentioned components, the water-based ink of the present invention contains a dispersant such as a cationic, anionic or nonionic surfactant, a defoaming agent such as a silicone, and the above-mentioned various surfactants. Conventionally known various types such as surface tension regulators, ultraviolet absorbers such as benzotriazole, benzophenone, salicylic acid ester and cyanoacrylate, fungicides such as chloromethylphenol, chelating agents such as EDTA, and oxygen absorbers such as sulfites. Additives may be blended.

From the viewpoints of reducing the particle size of the polymer fine particles and the stability of the emulsion, it is desirable that the above dispersant is generally incorporated in the aqueous ink of the present invention in an amount of 0.01 to 10% by weight, preferably 0.05 to 10% by weight. -5% by weight, more preferably 0.1-1% by weight.

The antifoaming agent is contained in the aqueous ink of the present invention in an amount of 0%.
To 2% by weight, in particular 0.001 to 2% by weight, in particular 0.
It is preferable that 005 to 0.5% by weight be blended. When the amount of the defoaming agent exceeds 2% by weight, the generation of bubbles is suppressed, but at the time of printing, repelling occurs in the ink and the printing quality may deteriorate.

As the surface tension adjusting agent, the above-mentioned silicone-based antifoaming agents and various surfactants of cationic, anionic or nonionic type can be used. In particular, the use of a silicone-based antifoaming agent, an ethylene oxide compound of an alkyl phenol, or an ethylene oxide adduct of acetylene glycol suppresses the generation of bubbles, facilitates adjustment of the surface tension of the ink, and causes ink ejection and bleeding. This is preferable in that there is little unevenness in print density.

When using the surface tension modifier, one or more of these compounds can be used. The mixing amount of these surface tension adjusters is 0.005 to 1 in the aqueous ink of the present invention from the viewpoint of print quality and ink stability.
Desirably, it is 5% by weight.

The water-based ink of the present invention has a temperature of 20 ° C.
The surface tension at the point of 2
It is preferably from 5 to 65 mN / m, more preferably from 25 to 55 mN / m, and still more preferably from 28 to 50 mN / m.
/ M. If the surface tension is less than 25 mN / m, bleeding of ink and deterioration of printing quality may occur, and ink leakage may occur from a print head nozzle of an inkjet printer. The surface tension is measured using an automatic surface tensiometer (CBVP-Z type) manufactured by Kyowa Interface Science Co., Ltd.
Can be measured.

From the viewpoint of ejection stability, the aqueous ink of the present invention has a viscosity at 20 ° C. of 0.5 to 8 mPa · s.
sec, more preferably 0.5 to
5 mPa · sec, more preferably 1 to 5 mPa · sec
c, and still more preferably 1 to 3 mPa · sec.
If the viscosity is less than 0.5 mPa · sec, bleeding of the ink becomes remarkable, and ink may leak from the print head nozzles of the ink jet printer. On the other hand, when the viscosity exceeds 8 mPa · sec, the viscosity of the ink for inkjet becomes too high, and the ink is not supplied to the print head. . The above viscosity was measured using an E-type viscometer (VISCONIC ELD) manufactured by Tokyo Keiki Co., Ltd., or a rotational vibration type viscometer (Viscomate VM-V) manufactured by Nikkato Tokyo Branch.
100).

In the production of the aqueous ink of the present invention, first, the above-mentioned polymer emulsion is prepared. That is, the vinyl polymer and the coloring material are added to the organic solvent,
Next, a neutralizing agent and, if necessary, a surfactant are added to the obtained solution or dispersion to ionize the salt-forming groups in the vinyl polymer. Next, when water is added to the obtained mixture, the mixture is emulsified by a known emulsification method, for example, a phase inversion emulsification method or a forced emulsification method. In view of the stability of the emulsion, the forced emulsification method is preferred. Thereafter, the organic solvent is distilled off from the emulsion by heating the system under reduced pressure. As a result, an aqueous emulsion of polymer fine particles impregnated with the coloring material is obtained.

By dissolving various hydrophobic stabilizers together with the coloring material in the water-insoluble organic solvent at the time of preparing the emulsion, the stabilizers can be encapsulated in the polymer. Examples of the stabilizer include ultraviolet absorbers such as benzotriazole, benzophenone, salicylate and cyanoacrylate described above; primary antioxidants such as hindered phenols and amines;
Preferred are secondary antioxidants such as sulfur type and ultraviolet stabilizers such as hindered amine type.

After obtaining an aqueous emulsion of polymer fine particles impregnated with a coloring material in this way, the above-mentioned compound A and compound B and, if necessary, other components are added to the emulsion. The water-based ink of the present invention is obtained.

In preparing the water-based ink of the present invention, it is preferable to remove coarse particles in the ink. For example,
The prepared ink is filtered under pressure with a filter or treated with a centrifuge to remove particles having a size of preferably 2,000 nm or more, more preferably 1,000 nm or more, and more preferably 500 nm or more. Is obtained.

The pH of the polymer emulsion thus obtained and the final aqueous ink are adjusted to pH = 5 to 12, preferably 5, to ensure the stability of the emulsion.
It is preferable to adjust so as to be 5 to 10. For example, by adding sodium hydroxide to the emulsification step of the polymer emulsion or the final aqueous ink to neutralize it,
adjust.

The ink-jet recording ink of the present invention comprises:
It is mainly used for ink-jet recording, but can also be used as ink for writing implements such as general fountain pens, ball-point pens, and felt-tip pens.

[0056]

Embodiments will be described below. In addition, "%" in the example
And "parts" are by weight unless otherwise specified.

[Production Example 1] Into a reactor were charged 20 parts of methyl ethyl ketone as a polymerization solvent, and monomers and polymerization chain transfer agents listed in the column of initial charged monomers in Table 1 as polymerizable unsaturated monomers. Substitution was sufficiently performed. Under a nitrogen atmosphere, the temperature of the mixture in the reaction vessel was raised to 65 ° C. while stirring. Separately, the monomers and polymerization chain transfer agents described in the column of dropped monomers in Table 1, 60 parts of methyl ethyl ketone, and 0.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) were used. The mixed solution obtained by mixing and sufficiently replacing with nitrogen was gradually dropped into the reaction vessel over 3 hours. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 0.1 part of 2,2′-azobis (2,4-dimethylvaleronitrile) in 5 parts of methyl ethyl ketone was added, and further added at 65 ° C. for 2 hours and at 70 ° C. for 2 hours. After aging for a time, a vinyl polymer solution was obtained.

A part of the obtained vinyl polymer solution was
It was dried at 105 ° C. under reduced pressure for 2 hours and isolated by completely removing the solvent. The weight-average molecular weight of this vinyl polymer by GPC using tetrahydrofuran as a solvent is about 10,000 and the Tg by DSC
Was 180 ° C.

The vinyl polymer solution obtained above was dried under reduced pressure, and 5 g of the vinyl polymer obtained was mixed with 25 g of toluene and Vail Fast Bl (trade name) which is a hydrophobic dye.
5ue of 2ue [manufactured by Orient Chemical Co., Ltd.] was added and completely dissolved, and 2 g of an aqueous sodium hydroxide solution was added to partially neutralize the salt-forming groups of the vinyl polymer. Next, 300 g of ion-exchanged water was added and stirred, and then emulsified for 30 minutes using a microfluidizer (trade name, manufactured by Microfluidizer), which is an emulsifying apparatus. The obtained emulsion was completely removed by removing toluene at 60 ° C. under reduced pressure, and further concentrated by removing a part of water to obtain an emulsion of vinyl polymer fine particles impregnated with a hydrophobic dye (average particle size: 98 nm). , Solid content: 10%).

[0060]

[Table 1]

Example 1 Emulsions of polymer fine particles obtained in Production Example 1 were mixed with the following components in the following composition, and the obtained dispersion was filtered through a 0.2 μm filter to remove dust and coarse particles. Thus, an aqueous ink was obtained. Using this ink, printing was performed with a commercially available Canon Color Bubble Jet Printer (Model No. BJC-420J), and the dirt on the face of the print head, the accuracy of the landing position of the ink droplet, and the print density were evaluated by the following methods. did. Table 2 shows the results.

-60 g of the emulsion obtained in Production Example 1-5 g of urea (compound A)-0.1 g of the above compound (Ia) (compound B)-5 g of ethylene glycol-5 g of glycerin-24.9 g of ion-exchanged water

<Evaluation of Stains on the Face Surface of the Print Head and Accuracy of the Impact Position of Ink Droplets>
The accuracy of the ink landing position when 3,000 prints were made on zero sheets and character printing, and stains on the face surface of the print head after printing were observed, were evaluated according to the following criteria. <Ink landing position> A: Both solid and character printing are normal. ；: The landing position in character printing is normal, and in solid printing, streaks are seen due to the deviation of the landing position. Δ: Disturbance is observed in the landing position in both solid and character printing. X: Printing blur occurs during printing. Character cannot be identified. <Stain on the face> A: There is no stain on the face for both solid and character printing. ；: There is no dirt on the face surface in character printing, but dirt is seen on the face surface in solid printing. However, the nozzle is not closed. Δ: Stain is seen on the face surface in both solid and character printing. However, the nozzle is not closed. ×: Nozzle clogged during printing.

<Print Density> Solid printing was performed on recycled paper for PPC [manufactured by Nippon Kaishi Paper Co., Ltd.], and after natural drying in a room for 24 hours, the optical density was measured using a Macbeth densitometer RD9.
18 (manufactured by Macbeth). Note that there is no quality problem if the print density is 1.40 or more.

Examples 2 to 6 Water-based inks were produced in the same manner as in Example 1 except that the compounds shown in Table 2 were used instead of the compounds A and B used in Example 1. The obtained water-based ink was evaluated in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 1 An aqueous ink was produced in the same manner as in Example 1 except that urea was not used. The obtained water-based ink was evaluated in the same manner as in Example 1. Table 2 shows the results.

[0067]

[Table 2]

As is evident from the results shown in Table 2, the water-based ink of the embodiment comprising an emulsion of fine polymer particles impregnated with a coloring material and containing a specific compound can prevent the face of the print head from being stained. It can be seen that the accuracy of the landing position of the ink droplet is high and that the ink droplet has a sufficient print density. Further, although not shown in the table, the aqueous inks of the examples had high liquid stability, and were excellent in water resistance and scratch resistance.

[0069]

According to the water-based ink of the present invention, it is possible to prevent ink ejection failure due to contamination of the face surface of the print head, improve the accuracy of the landing position of ink droplets, and improve the print density on plain paper. Is improved. Further, the aqueous ink of the present invention has high liquid stability, and is excellent in water resistance and scratch resistance.

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Claims (4)

[Claims] 1. A polymer emulsion obtained by impregnating polymer fine particles with a coloring material, comprising at least one compound A selected from the group consisting of urea, alkyl glycine and glycine betaine, and the following compounds (I) and (II): A water-based ink for inkjet recording, comprising at least one compound B selected from the group consisting of: and the polymer is a vinyl polymer. Embedded image 2. The aqueous ink for ink-jet recording according to claim 1, wherein the compound A is contained in an amount of 1 to 50% by weight and the compound B is contained in an amount of 0.001 to 2% by weight. 3. The aqueous ink for ink-jet recording according to claim 1, wherein the polymer is contained in an amount of 1 to 30% by weight as a solid content. 4. The weight ratio of the polymer to the compound A (former / latter) is 1/5 to 5/1, and the weight ratio of the polymer to the compound B (former / latter) is 5/1. ~ 20
The aqueous ink for inkjet recording according to any one of claims 1 to 3, wherein the ratio is 00/1.