JP2023101323A - Ink, ink set, inkjet printer, and inkjet printing method - Google Patents

Abstract

To provide an ink having excellent image density on a plain paper medium and also having excellent curling resistance.SOLUTION: An ink is for use in an inkjet printer having an inkjet head that has a nozzle for discharging ink and further having a nozzle plate with an ink-repelling layer containing silicon resin or fluororesin at least on an ink discharge side surface. An ink contains a colorant, a water-soluble organic solvent, naphthalenesulfonic acid-formaldehyde condensate or the like, or polyoxyethylene-β-naphthyl ether or the like, and water. The product of a viscosity η [mPa s] at 25°C with a rotational viscometer and a surface tension σ [mN/m] with a bubble life time of 150 ms at 25°C by the maximum bubble pressure method is 100 or more and 130 or less.SELECTED DRAWING: None

Description

The present invention relates to inks, ink sets, inkjet printing devices, and inkjet printing methods.

Japanese Patent Application Laid-Open No. 2003-100002 describes a double-sided printing method in which a sheet is transported within three seconds from the start of front side printing to the start of back side printing.
Patent Document 2 describes an ink containing two or more polysiloxane-based surfactants with different HLBs.
Patent Document 3 describes an ink containing carbon black having a hydrophilic group and carbon black dispersed with sodium naphthalenesulfonate formalin condensate.

An object of the present invention is to provide an ink that exhibits good image density and curl resistance and has good storage stability, especially when applied to plain paper media.

（一般式（１）中、ｍは１～４の整数を表す。）

（一般式（２）中、Ｒ^１は炭素数１～２０のアルキル基、炭素数７～８のアラルキル基、またはアリル基を表し、ｌは０～７の整数を表し、ｎは２０～２００の整数を表す。） The present invention for solving the above problems relates to an ink as described in (1) below.
(1) An ink for use in an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface. hand,
The ink contains a coloring material, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water,
The product of the viscosity η [mPa s] measured by a rotational viscometer at 25°C and the surface tension σ [mN/m] at a bubble life time of 150 ms measured by the maximum bubble pressure method at 25°C is 100 or more and 130 or less. An ink characterized by:

(In general formula (1), m represents an integer of 1 to 4.)

(In general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents 20 to 200 represents an integer of

The ink of the present invention exhibits good image density and curl resistance when applied to plain paper media, and has good storage stability.

FIG. 1 is a perspective view showing an example of an inkjet printer of the present invention. FIG. 2 is a cross-sectional view showing an example of the overall configuration of the inkjet printing apparatus of the present invention. FIG. 3 is an explanatory plan view showing an example of a nozzle plate in the inkjet printing apparatus of the present invention. FIG. 4 is an enlarged cross-sectional explanatory view of the nozzle portion of the nozzle plate in the inkjet printing apparatus of the present invention. FIG. 5 is a diagram showing a state in which silicone resin is applied by application using a dispenser to form an ink-repellent layer.

In general, the degree of ink penetration into plain paper media is determined by the viscosity and surface tension of the ink. When both values are large, the ink is difficult to penetrate, and conversely, when the values are small, the ink is easy to penetrate.
If the ink does not easily permeate, the coloring material remains on the surface of the medium, and although a high density can be expected, the fixability deteriorates, and the medium surface curls greatly due to the slow permeation.
On the other hand, if the ink permeates easily, the fixability can be expected to be improved, but the image density is lowered and the permeation is rapid, resulting in large curling of the back surface of the medium.

The degree of ink penetration into the media is affected by both viscosity and surface tension. If either value is extremely small, the ink will easily penetrate. makes it difficult for ink to penetrate. If the viscosity and surface tension of the ink are specified separately, it is considered impossible to achieve both good image density and curl resistance.
In the ink of the present invention, the permeability is controlled by specifying the value (η × σ) of the product of the viscosity η [mPa s] and the surface tension σ [mN/m]. , exhibits good image density and curl resistance, and has good storage stability.

The ink of the present invention contains a coloring material, a water-soluble organic solvent, the compound represented by the general formula (1) or the general formula (2), and water, and has a viscosity η [mPa ·s] and the surface tension σ [mN/m] at a bubble life time of 150 ms in the maximum bubble pressure method at 25°C is 100 or more and 130 or less.
The ink of the present invention is an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface side. used for
By using the ink of the present invention in the ink jet printing apparatus, excellent ejection stability can be obtained, and in particular, both image density and curl resistance on plain paper media can be achieved.
The components of the ink of the present invention are described below.

<Ink>
Organic solvents, water, coloring materials, resins, additives, and the like used in the ink are described below.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples thereof include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.
Specific examples of water-soluble organic solvents include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol , 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl- Polyhydric alcohols such as 1,3-pentanediol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl Polyhydric alcohol alkyl ethers such as ethers, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone , 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, nitrogen-containing heterocyclic compounds such as γ-butyrolactone, formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N- Amides such as dimethylpropionamide and 3-butoxy-N,N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine, triethylamine and trimethylglycine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate , ethylene carbonate and the like.

Among the organic solvents, one or more organic solvents having a boiling point of 200° C. or higher and a saturated water content of 50% or higher at a temperature of 25° C. and humidity of 50% RH can be selected from the viewpoint of media permeability and drying characteristics. preferable. Specific examples of the organic solvent include, for example, trimethylglycine, and it is preferable that these organic solvents be 5% by mass or more of the total amount of the organic solvent contained in the ink.

From the viewpoint of the storage stability of the ink, the mixed solvent SP value (solubility parameter) of the organic solvent in the ink is preferably 14.3 (cal/cm ³ ) ^0.5 or more.
In addition, when the organic solvent in the ink is a mixed solvent composed of a mixture of a plurality of organic solvents, the SP value of the mixed solvent is preferably 14.3 (cal/cm ³ ) ^0.5 or more.
When the mixed solvent consists of n kinds of organic solvents, the SP value of the mixed solvent can be specifically calculated by the following formula.
Mixed solvent SP value of organic solvent in ink (cal/cm ³ ) ^0.5
= [SP value of organic solvent _S1 x volume fraction of organic solvent _S1 ] +
+ [SP value of organic solvent _Sn x volume fraction of organic solvent _Sn ]

Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Specific examples of glycol ether compounds include polyhydric alcohol alkyls such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Ethers; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like.

A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve ink permeability when paper is used as a recording medium.

The content of the organic solvent in the ink is not particularly limited and can be appropriately selected according to the purpose. 20% by mass or more and 60% by mass or less is more preferable.

<Water>
The content of water in the ink is not particularly limited and can be appropriately selected according to the purpose. % to 60% by mass is more preferred.

<Color material>
The coloring material is not particularly limited, and pigments and dyes can be used.
An inorganic pigment or an organic pigment can be used as the pigment. These may be used individually by 1 type, and may use 2 or more types together. Mixed crystals may also be used.
Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy color pigments such as gold and silver, and metallic pigments.
As inorganic pigments, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as contact method, furnace method, thermal method, etc. can be used.
Organic pigments include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.). , dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
Specific examples of pigments for black include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black and channel black, or copper and iron (C.I. Pigment Black 11). , metals such as titanium oxide, and organic pigments such as aniline black (C.I. Pigment Black 1).
Further, for color, C.I. I. Pigment yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52: 2, 53:1, 57:1 (brilliant carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (red iron oxide), 104, 105, 106, 108 ( cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. Pigment Violet 1 (rhodamine lake), 3, 5:1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3, 15:4 (phthalocyanine blue), 16, 17:1, 56, 60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.
Dyes are not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and may be used singly or in combination of two or more.
Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9,45,249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Direct Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. and Reactive Black 3,4,35.

The black ink colorant is carbon black, the cyan ink colorant is Pigment Blue 15:3, the magenta ink colorant is Pigment Red 122 or 269, and the yellow ink colorant is Pigment Yellow 74. This is preferable because the effects of storage stability and color gamut expansion can be obtained.

In order to disperse the pigment and obtain an ink, there are a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of coating the surface of the pigment with a resin for dispersion, and a method of dispersing using a dispersant. method, etc.
As a method of making a self-dispersing pigment by introducing a hydrophilic functional group into a pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (for example, carbon) to make it dispersible in water. is mentioned.
As a method of coating the surface of a pigment with a resin and dispersing it, there is a method of encapsulating the pigment in microcapsules to make it dispersible in water. This can be rephrased as a resin-coated pigment. In this case, all the pigments mixed in the ink need not be coated with a resin, and uncoated pigments or partially coated pigments may be dispersed in the ink as long as the effects of the present invention are not impaired. may be
Examples of the method of dispersing using a dispersant include a method of dispersing using a known low-molecular-weight dispersant and high-molecular-weight dispersant typified by surfactants.

As the dispersant, a compound represented by the following general formula (1) or (2) is used. By using the dispersant, a water-based pigment dispersion and a water-based ink having a small average particle size and excellent storage stability can be obtained.
The content of the dispersant represented by the general formula (1) or (2) is preferably 0.01 to 0.5, more preferably 0.1 to 0.4, based on the mass ratio of 1 to 1 pigment in the ink. . When the content is within this range, an ink having a small volume-average particle size can be obtained, the dispersibility of the pigment can be improved, and the viscosity of the ink can be made appropriate, which is preferable.

（一般式（１）中、ｍは１～４の整数を表す。）

（一般式（２）中、Ｒ^１は炭素数１～２０のアルキル基、炭素数７～８のアラルキル基、またはアリル基を表し、ｌは０～７の整数を表し、ｎは２０～２００の整数を表す。）

(In general formula (1), m represents an integer of 1 to 4.)

(In general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents 20 to 200 represents an integer of

Good dispersibility by using a naphthalenesulfonic acid formalin condensate as the compound represented by the general formula (1) and using polyoxyethylene-β-naphthyl ether as the compound represented by the general formula (2) is obtained and is preferable.

<Fluorescent brightener>
Fluorescent brightening agents absorb invisible short-wavelength ultraviolet rays and convert them into visible violet to blue light, and are also called fluorescent dyes. A fluorescent whitening agent may also be used.
Examples of fluorescent brightening agents to be used include those having a structural unit represented by the following structural formula (1) or (2).

Those having a structural unit represented by the structural formula (1) are benzoxazole or derivatives thereof; those having a structural unit represented by the structural formula (2) are coumarin or derivatives thereof; Any hydrophobicity may be used.

The content of the fluorescent brightening agent in the ink is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.005% by mass or more and 0.2% by mass or less. By setting the content of the fluorescent brightening agent to 0.001% by mass or more, it is possible to visually express a high concentration. On the other hand, by setting the content of the fluorescent brightening agent to 1% by mass or less, it is possible to suppress the phenomenon of concentration quenching, in which the incident light is immediately absorbed or the fluorescence intensity decreases due to collisions between molecules.
Examples of fluorescent brighteners include commercial products such as TINOPAL OB (manufactured by BASF), Nikkafluor OB, Nikkabright PAW-L, and Nikkafluor MCT (manufactured by Nippon Kagaku Kogyosho Co., Ltd.).

<Fluorescent whitening enhancer>
In the present invention, a fluorescent brightening enhancer may be used to improve the effect of the fluorescent brightening agent. The fluorescent whitening enhancer improves the dispersibility of the fluorescent whitening agent and improves the effect of the fluorescent whitening agent by migrating to the surface, and is specifically a polyether polyol.
The content of the fluorescent brightening enhancer in the ink is preferably 0.2% by mass or more and 2% by mass or less, more preferably 0.5% by mass or more and 2% by mass or less, relative to the content of the coloring material. By setting the content of the fluorescent brightening enhancer to 0.2% by mass or more based on the content of the colorant, it is possible to visually express a high density. On the other hand, by setting the content of the fluorescent brightening enhancer to 2% by mass or less with respect to the content of the coloring material, it is possible to improve ejection stability.
Examples of the fluorescent brightening enhancer include commercially available products such as Optiact I-10 manufactured by San Nopco Co., Ltd.

<Pigment dispersion>
Inks can be obtained by mixing materials such as water and organic solvents with pigments. Ink can also be produced by mixing a pigment with water, a dispersant, and the like to form a pigment dispersion, and then mixing materials such as water and an organic solvent.
The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and optionally other components, and adjusting the particle size. Dispersion should be carried out using a disperser.
The particle diameter of the pigment in the pigment dispersion is not particularly limited, but the dispersion stability of the pigment is improved, and the image quality such as ejection stability and image density is improved. 500 nm or less is preferable, and 20 nm or more and 150 nm or less is more preferable. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected according to the purpose. % or more and 50 mass % or less is preferable, and 0.1 mass % or more and 30 mass % or less is more preferable.
The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator, or the like, if necessary.

<Resin>
In the present invention, the ink contains a polyether-based urethane resin represented by the following general formula (7). By including the polyether-based urethane resin represented by the general formula (7), the dispersion of the pigment is stabilized, and the storage stability is particularly excellent. The resin represented by general formula (7) can be identified by using GC-MS and NMR, for example.

The acid value of the polyether-based urethane resin is preferably 48 (KOHmg/g) or more and 80 (KOHmg/g) or less. When the acid value is 48 (mg KOH/g) or less or 80 (mg KOH/g) or more, the pigment dispersion becomes unstable, resulting in poor storage stability. The acid value is measured by dissolving the measurement sample in an ethanol/ether mixed solution, adding a phenolphthalein solution as an indicator, and then titrating with a 0.1 mol/l potassium hydroxide solution. It can be calculated from the required 0.1 mol/l potassium hydroxide solution.

Polyether-based urethane resin particles may be used as the polyether-based urethane resin.
As the resin particles, appropriately synthesized ones may be used, or commercially available products may be used. Examples of commercially available products include Takelac W5661 and W932 manufactured by Mitsui Chemicals, Inc. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types of resin particles.

The ink may contain other resins. The type of resin contained in the ink is not particularly limited and can be appropriately selected according to the purpose. resins, styrene-butadiene-based resins, vinyl chloride-based resins, acrylic-styrene-based resins, acrylic-silicone-based resins, and the like.
Resin particles made of these resins may also be used. Ink can be obtained by mixing resin particles in a resin emulsion state in which water is dispersed as a dispersion medium with a material such as a coloring material or an organic solvent.

The volume-average particle diameter of the resin particles is not particularly limited and can be appropriately selected according to the intended purpose. 200 nm or less is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
The volume average particle diameter can be measured, for example, using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the resin is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoint of fixability and storage stability of the ink, the content is 1% by mass or more and 30% by mass or less based on the total amount of the ink. is preferable, and 5% by mass or more and 20% by mass or less is more preferable.

The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose. is preferably 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

In order to improve image density and fixability, the ratio (R/P) of the amount of coloring material (P) to the total amount of resin (R) is preferably 0.05 or more and 0.35 or less. The total amount of resin means all resins contained in the ink, and includes the resin used for coating the coloring material and the resin contained in the ink as a binder resin. A resin represents an organic substance having a weight average molecular weight of 5,000 or more.

<Additive>
Surfactants, antifoaming agents, antiseptic antifungal agents, anticorrosive agents, pH adjusters, etc. may be added to the ink as necessary.

<Surfactant>
Silicon-based compounds, acetylene-based compounds, and polyoxyethylene alkyl ether-based compounds can be suitably used as surfactants in the ink of the present invention.
A surfactant is added to improve penetration or wettability into a substrate, and generally a surfactant with a low HLB (Hydrophilic Lipophilic Balance) is used. However, those with low HLB generally have low solubility in vehicles containing water, and cause problems such as deterioration of storage stability and separation.
In order to solve the above problems in the present invention, a silicon-based compound represented by the following general formula (3) or the following general formula (4), an acetylene-based compound represented by the following general formula (5), and the following general formula ( Any one of the polyoxyethylene alkyl ether compounds represented by 6) is included. The compounds of the following general formulas (3) to (6) can be identified by using GC-MS and NMR, for example.

（一般式（３）中、ａは０～２３の整数、ｂは１～１０の整数、ｃは１～２３の整数、ｄは０～２３の整数、Ｒは水素原子または炭素数１～４のアルキル基を示す。）

(In the general formula (3), a is an integer of 0 to 23, b is an integer of 1 to 10, c is an integer of 1 to 23, d is an integer of 0 to 23, R is a hydrogen atom or 1 to 4 carbon atoms indicates the alkyl group of.)

（一般式（４）中、ａは１～８の整数、Ｒは水素原子または炭素数１～４のアルキル基を示す。）

(In general formula (4), a is an integer of 1 to 8, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

（一般式（５）中、Ｒ_１～Ｒ_４はアルキル基、ｍ＋ｎは１～２０の整数、Ｙはアセチレン基を示す。）

(In general formula (5), R ₁ to R ₄ are alkyl groups, m+n is an integer of 1 to 20, and Y is an acetylene group.)

In the present invention, it is preferable to use a polysiloxane compound represented by the general formula (3) having a low HLB and a polysiloxane compound represented by the general formula (4) having a high HLB. may be used or may be used together. Especially when used in combination, a polysiloxane compound with a low HLB can be compatible with a polysiloxane compound with a high HLB, so separation over time can be suppressed while maintaining the wettability to the substrate.

The content of the silicon-based compound is preferably 0.001% by mass or more and 3% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less, relative to the total amount of the ink.
As the silicon-based compound, an appropriately synthesized one may be used, or a commercially available product may be used. Examples of commercially available products include KF-6028, KF-6038 (manufactured by Shin-Etsu Chemical Co., Ltd.), SAG002, SAG503A (manufactured by Nisshin Chemical Co., Ltd.), etc. Among these, from the viewpoint of storage stability, KF6028 and SAG503A are particularly preferred.

In the present invention, it is preferable to use an acetylenic compound represented by the general formula (5) and having an HLB of 8 or more and 13 or less.
When the HLB is 8 or more, the storage stability is improved without becoming difficult to dissolve in a vehicle containing water. Moreover, since the HLB is 13 or less, the antifoaming property does not deteriorate.
The content of the acetylene-based compound is preferably 0.1% by mass or more and 3.0% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less, relative to the total amount of the ink.
As the acetylene-based compound, an appropriately synthesized one may be used, or a commercially available product may be used. Commercially available products include, for example, Surfynol 104 series, Surfynol 420, 440, 465, 485, Olphine PD-002W, EXP. 4001, EXP. 4200, EXP. 4123 (manufactured by Nissin Chemical Industry Co., Ltd.), acetinol E60, E100, E200 (manufactured by Kawaken Fine Chemicals Co., Ltd.), etc., and among these, Nissin Chemical Industry Co., Ltd. from the viewpoint of antifoaming and storage stability. Surfynol 440, 465, Olfine PD-002W, EXP. 4001, EXP. 4200, EXP. 4123 is particularly preferred. These may be used individually by 1 type, or may use 2 or more types together.

In the present invention, it is preferable to use the polyoxyethylene alkyl ether compound represented by the general formula (6).
The content of the polyoxyethylene alkyl ether compound is preferably 0.1% by mass or more and 2.0% by mass or less, more preferably 0.5% by mass or more and 1.0% by mass or less, relative to the total amount of the ink. When the amount of the compound represented by the general formula (6) is 0.1% by mass or more relative to the total amount of the ink, the target image density can be obtained without spreading the dots after the ink lands on the recording medium. . On the other hand, when the content is 2.0% by mass or less, the surface tension does not decrease, and the time for the ink overflowing from the nozzle to return to the nozzle after ejection from an ink ejection means such as an inkjet head does not become long. , there is no risk of frequent discharge bending.

As the polyoxyethylene alkyl ether-based compound, an appropriately synthesized one may be used, or a commercially available product may be used. Commercially available products include, for example, TRITON (registered trademark) HW-1000, TMN-3, TMN-6, TMN-100X, TMN-10 (manufactured by Dow Chemical Company). ) HW-1000 and TMN-6 are particularly preferred. These may be used individually by 1 type, or may use 2 or more types together.

In addition, the above surfactants may be used in combination with other surfactants. For example, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can all be used. .
The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among them, those that do not decompose even at high pH are preferable. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as water-based surfactants. As the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.
Examples of fluorine-based surfactants include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups in side chains. Polyoxyalkylene ether polymer compounds are particularly preferred due to their low foaming properties. Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate. Examples of the perfluoroalkylcarboxylic acid compounds include perfluoroalkylcarboxylic acids and perfluoroalkylcarboxylic acid salts. As the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, and a perfluoroalkyl ether group in a side chain Examples thereof include salts of polyoxyalkylene ether polymers. Counter ions _of salts _in these fluorosurfactants include Li, Na, _K , _NH4 , _NH3CH2CH2OH , _NH2 ( _CH2CH2OH ) _{2 ,} and NH( _CH2CH2OH ). ₃ and the like.
Examples of amphoteric surfactants include laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxyethylbetaine and the like.
Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of anionic surfactants include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like.
These may be used individually by 1 type, or may use 2 or more types together.

<Antifoaming agent>
The antifoaming agent is not particularly limited, and examples thereof include silicone antifoaming agents, polyether antifoaming agents, fatty acid ester antifoaming agents, and acetylene compounds.

As the acetylene-based compound, an appropriately synthesized one may be used, or a commercially available product may be used. Examples of commercially available products include Surfynol DF1100, Olphine D-10A, D-10PG (manufactured by Nissin Chemical Industry Co., Ltd.), Acetinol E13T, E40 (manufactured by Kawaken Fine Chemicals Co., Ltd.).
In addition, in the present invention, Surfynol AD01 (2,4,7,9-tetramethyldecane-4,7-diol_manufactured by Nissin Chemical Industry Co., Ltd.) may be used in addition to the acetylenic compound as an antifoaming agent. good.
Among antifoaming agents, from the viewpoint of antifoaming properties and storage stability, acetylenic compounds such as Olfin D-10PG manufactured by Nissin Chemical Industry Co., Ltd. and Acetynol E40 manufactured by Kawaken Fine Chemicals Co., Ltd. are particularly preferable. Surfynol AD01 manufactured by Nissin Chemical Industry Co., Ltd. is particularly preferred. These may be used individually by 1 type, or may use 2 or more types together.

<Preservative and antifungal agent>
The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

<Antirust agent>
The rust inhibitor is not particularly limited, and examples thereof include acidic sulfites and sodium thiosulfate.

<pH adjuster>
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical properties of the ink are not particularly limited and can be appropriately selected depending on the intended purpose. For example, viscosity, surface tension, pH and the like are preferably within the following ranges.
The viscosity of the ink at 25° C. is preferably 5 mPa·s or more and 30 mPa·s or less, more preferably 5 mPa·s or more and 25 mPa·s or less, from the viewpoint of improving the print density and character quality and obtaining good ejection properties. more preferred. Here, for viscosity, for example, a rotational viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. Measurement conditions are 25° C., standard cone rotor (1°34′×R24), sample liquid volume 1.2 mL, rotation speed 50 rpm, 3 minutes.
The surface tension of the ink is preferably 35 mN/m or less, more preferably 32 mN/m or less at 25° C., from the viewpoint that the ink is appropriately leveled on the recording medium and the drying time of the ink is shortened. In order to suppress color mixture (bleed) between ink colors, the surface tension of cyan ink, magenta ink, and yellow ink is lower than that of black ink, and the difference is preferably 3.0 mN/m or more. , 3.0 mN/m or more and 7.0 mN/m or less.
The pH of the ink is preferably from 7 to 12, more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members in contact with the liquid.

<Pretreatment liquid>
The pretreatment liquid contains a flocculant, an organic solvent, and water, and may optionally contain a surfactant, an antifoaming agent, a pH adjuster, an antiseptic agent, an antirust agent, and the like.
Organic solvents, surfactants, antifoaming agents, pH adjusters, antiseptic antifungal agents, and antirust agents can be the same materials as used for inks, and other materials used for known treatment liquids can be used. .
The type of flocculant is not particularly limited, and examples thereof include water-soluble cationic polymers, acids, polyvalent metal salts, and the like.

<Post-treatment liquid>
The post-treatment liquid is not particularly limited as long as it can form a transparent layer. The post-treatment liquid is obtained by selecting and mixing organic solvents, water, resins, surfactants, antifoaming agents, pH adjusters, antiseptic antifungal agents, anticorrosive agents, etc., as necessary. Further, the post-treatment liquid may be applied to the entire recording area formed on the recording medium, or may be applied only to the area where the ink image is formed.

<Recording medium>
The recording medium used for recording is not particularly limited, but includes plain paper, glossy paper, special paper, cloth, film, OHP sheet, general-purpose printing paper, and the like.

<Records>
The ink recorded matter of the present invention has an image formed on a recording medium using the ink of the present invention.
A recorded matter can be obtained by recording with an inkjet recording apparatus and an inkjet recording method.

<Recording device>
As shown in FIG. 1, the ink jet recording apparatus used in the present invention comprises an apparatus main body 101, a paper feed tray 102 for loading paper attached to the apparatus main body 101, and an image recording apparatus attached to the apparatus main body 101. A paper discharge tray 103 for stocking paper is provided. The upper surface of the upper cover 111 of the apparatus main body 101 is flat, and the front surface 112 of the front cover of the apparatus main body 101 is inclined downward and rearward with respect to the upper surface. In the front, there are a discharge tray 103 and a paper feed tray 102 protruding forward (front side).
Further, at one end of the front surface 112, there is an ink cartridge loading section 104 which protrudes forward from the front surface 112 and is lower than the upper cover 111. An ink cartridge is attached to and detached from the ink cartridge loading section 104. It has a front cover 115 that can be opened and closed.

As shown in FIG. 2, inside the apparatus main body 101, a carriage 133 is slidably held in the main scanning direction by a guide rod 131 and a stay 132, which are guide members horizontally mounted on left and right side plates. Move by scanning.
The carriage 133 is provided with a plurality of ink ejection openings for a recording head 134 comprising four inkjet heads for ejecting ink droplets of respective colors of yellow (Y), cyan (C), magenta (M), and black (K). They are arranged in a direction intersecting the main scanning direction, and mounted with the ink droplet ejection direction directed downward.

The ink jet head constituting the recording head 134 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator utilizing a phase change due to film boiling of a liquid using an electrothermal conversion element such as a heating resistor, and a metal phase change due to a temperature change. A shape memory alloy actuator, an electrostatic actuator using static electricity, or the like provided as an energy generating means for ejecting ink can be used.

Further, the carriage 133 is equipped with sub-tanks 135 of respective colors for supplying inks of respective colors to the recording head 134 . Ink is replenished from the ink cartridge according to the present invention loaded in the ink cartridge loading section 104 to the sub-tank 135 through the ink supply tube.

On the other hand, as a paper feed unit for feeding the paper 142 stacked on the paper stacking unit 141 of the paper feed tray 103, a half-moon roller (paper feed roller) separates and feeds the paper 142 one by one from the paper stacking unit 141. A separation pad 144 made of a material having a large coefficient of friction is provided facing the paper feed roller 143 and the paper feed roller 143 , and the separation pad 144 is biased toward the paper feed roller 143 .

On the other hand, as a transport unit for transporting the paper 142 fed from the paper feed unit below the recording head 134, a transport belt 151 for electrostatically attracting the paper 142 and transporting it, and A counter roller 152 for sandwiching and conveying the paper 142 sent via the guide 145 with the conveying belt 151, and turning the direction of the paper 142 sent vertically upward by 90° to make it follow the conveying belt 151. and a leading end pressure roller 155 urged toward the transport belt 151 by a pressing member 154 . Further, a charging roller 156 as a charging means is provided to charge the surface of the conveying belt 151 .

Here, the conveying belt 151 is an endless belt, which is stretched between a conveying roller 157 and a tension roller 158 so as to rotate in the belt conveying direction. The conveying belt 151 has, for example, a surface layer formed of a pure resin material having a thickness of about 40 μm without resistance control, such as an ETFE pure material, which serves as a sheet attracting surface, and a surface layer made of the same material as the surface layer for resistance control using carbon. It has a back layer (ground layer) that has been carried out.
A guide member 161 is arranged on the back side of the conveying belt 151 so as to correspond to the printing area of the recording head 134 .
Furthermore, as a paper discharge section for discharging the paper 142 recorded by the recording head 134, a separation claw 171 for separating the paper 142 from the conveying belt 151, a paper discharge roller 172 and a paper discharge roller 173 are provided. , the paper discharge tray 103 is provided below the paper discharge rollers 172 .

The recording paper attracted to the conveying belt is ejected while being pressed by the ejection roller from above. Basically, recording paper is conveyed by a conveying belt and conveying rollers, and the discharge rollers in actual printers play an auxiliary role such as suppressing floating of the paper. Therefore, it is possible to reduce the number of rollers remarkably compared with the conventional ink jet printer, and it is possible to reduce stains and scratches on the recorded image.
A double-sided sheet feeding unit 181 is detachably attached to the rear portion of the apparatus main body 101 . This double-sided paper feeding unit 181 takes in the paper 142 returned by the reverse rotation of the transport belt 151 , reverses it, and feeds the paper 142 again between the counter roller 152 and the transport belt 151 . Further, a manual paper feeding unit 182 is provided on the upper surface of the double-sided paper feeding unit 181 .

When double-sided printing is performed, the paper is transported to the double-sided paper feed unit and reversed immediately after printing on the front side without waiting. The ink of the present invention has a high permeability to paper and a low water content, so that it evaporates quickly and can be reversed without staining the printed image without providing a drying time or a drying means such as a heater.
In the ink jet recording apparatus configured as described above, the paper 142 is separated and fed one by one from the paper feeding unit, and the paper 142 fed vertically upward is guided by the guide 145, and is guided by the conveying belt 151 and the counter roller 152. Further, the leading edge of the sheet is guided by a conveying guide 153 and pressed against the conveying belt 151 by a leading edge pressing roller 155, so that the conveying direction is changed by 90°.
At this time, the conveying belt 157 is charged by the charging roller 156, and the paper 142 is electrostatically attracted to the conveying belt 151 and conveyed. Therefore, by driving the recording head 134 according to the image signal while moving the carriage 133, ink droplets are ejected onto the stationary paper 142 to record one line. Make a record of the line of Upon receiving a recording end signal or a signal indicating that the trailing edge of the paper 142 has reached the recording area, the recording operation is terminated and the paper 142 is discharged to the paper discharge tray 103 .

An AC bias is applied to the charging belt, positive and negative charges are alternately charged at a constant pitch, and the recording paper is attracted to the conveyor belt by electrostatic force generated by intermittently generated minute electric fields. A preferred range of AC bias to be applied is ±1.2 kV to ±2.6 kV, more preferably ±1.6 kV to ±2.4 kV. If the AC bias value is below the lower limit, sufficient attracting force cannot be obtained, and if it is above the upper limit, minute droplets generated when ink is ejected from the nozzles will be affected by the electric charge and will not land on the paper and reach the head. It will come back and make the area around the head dirty. The electrical properties of the ink are involved in the effect of the charge on the minute droplets. In other words, the greater the electric conductivity of the ink, the more easily the ejected droplets are affected by electric charge. Therefore, it is necessary to suppress the electric conductivity of the ink.
Then, when the near-end of the remaining amount of ink in the sub-tank 135 is detected, the sub-tank 135 is replenished with a predetermined amount of ink from the ink cartridge.

FIG. 3 is an explanatory plan view showing an example of a nozzle plate in the inkjet printing apparatus of the present invention.
Here, the nozzle plate used in the inkjet printing apparatus of the present invention will be described with reference to FIGS. 3 and 4. FIG.
FIG. 3 is an explanatory plan view of the nozzle plate, and FIG. 4 is an enlarged sectional explanatory view of one nozzle portion.

The nozzle plate 10 includes a nozzle base 20 formed with holes (hereinafter also referred to as “nozzles”) 21 that serve as nozzles 11 for ejecting liquid, and an intermediate layer 30 formed on the surface of the nozzle base 20. and an ink-repellent layer 40 formed on the liquid ejection surface side.
The nozzle base material 20 is, for example, a flat metal member. Although a stainless steel flat metal member is used as the nozzle base material 20, it is not limited to this.
The nozzle 11 has a cylindrical portion 21a on the side of the liquid ejection surface, and a truncated cone portion 21b on the side opposite to the liquid ejection surface.

The intermediate layer 30 is composed of one or a plurality of layers such as a SiO ₂ layer and a silane coupling agent layer, which serve as base layers. This intermediate layer 30 may not be provided.

The ink repellent layer 40 is a layer containing silicon resin.
The ink-repellent layer 40 has an inclined surface area 41 in which an inclined surface 41 a is formed in the outer peripheral portion of the nozzle 11 so that the film thickness decreases toward the edge 11 a side of the nozzle 11 . A region 42 other than the slope region 41 of the ink-repellent layer 40 has a substantially uniform film thickness and is flat. In addition, the slope 41a of the slope region 41 may be linearly slanted in cross-section, or may be curvedly slanted.
The average film thickness of the surface of the ink-repellent layer 40 on the side of the ink ejection surface is preferably 1 μm or more and 3 μm or less.
In the intermediate layer 30, it is preferable that the layer forming the base of the ink repellent layer 40 is a silane coupling agent layer having an amino group. As a result, the amino group interacts with the liquid-repellent film material to obtain high adhesion.

(Manufacturing method for nozzle member of inkjet head)
FIG. 5 is a diagram showing a configuration for forming the ink-repellent layer 31 on the surface of the nozzle plate 32 by applying silicone resin by applying using the dispenser 34 according to the present embodiment.
A dispenser 34 for applying a silicone solution is arranged on the ink ejection surface side of the nozzle plate 32 formed by Ni electroforming, and the nozzle plate 32 and the tip of the needle 35 are kept at a predetermined constant distance. By scanning the dispenser 34 while ejecting the silicone resin from the tip of the needle 35, a silicone resin film is selectively formed on the ink ejection surface of the nozzle plate 32. As shown in FIG.

In this embodiment, room-temperature curing silicone resin SR2411 (manufactured by Dow Corning Toray Co., Ltd.) is used as the silicone resin. However, a small amount of silicon was found to flow around the nozzle holes and the back surface of the nozzle plate. The thickness of the silicone resin film thus selectively formed was 1.2 μm, and the surface roughness (Ra) was 0.18 μm.

Any material that repels ink can be used as the material of the ink-repellent layer, and a specific example is a silicon-based water-repellent material.
Examples of the silicone-based water-repellent material include room-temperature-curing liquid silicone resins or elastomers, which are applied to the surface of the substrate and allowed to stand in the atmosphere at room temperature to polymerize and cure to form an ink-repellent film. is preferred.

The silicone-based water-repellent material described above is a heat-curable liquid silicone resin or elastomer, which may be applied to the substrate surface and cured by heat treatment to form an ink-repellent film.
The silicone-based water-repellent material is an ultraviolet curable liquid silicone resin or elastomer, which may be applied to the substrate surface and cured by irradiation with ultraviolet rays to form an ink-repellent film.
It is preferable that the silicone-based water-repellent material has a viscosity of 1000 cp or less.

The critical surface tension of the ink-repellent layer is preferably from 5 mN/m to 40 mN/m, more preferably from 5 mN/m to 30 mN/m. If the critical surface tension exceeds 30 mN/m, the nozzle plate will become too wet with ink during long-term use, which may result in ink discharge bending and particle formation abnormalities during repeated printing. .
On the other hand, if it exceeds 40 mN/m, the phenomenon that the ink is too wet on the nozzle plate from the initial stage may occur, which may result in ejection bending or abnormal particle formation of the ink from the initial stage.

In the present invention, the terms image formation, recording, printing, and printing are all synonymous.

The terms recording medium, medium, and printed material are all synonymous.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. "Parts" and "%" in the examples are "mass parts" and "mass%" unless otherwise specified.
Unless otherwise specified, preparation, evaluation, etc. were performed under the conditions of 23° C. and 50% humidity.

(Preparation of pigment dispersion)
<Preparation of black pigment dispersion>
A mixed slurry was obtained by premixing 250 parts of carbon black (manufactured by Degussa), 50 parts of the compound represented by the general formula (1) (Takesurf A-45-K_manufactured by Takemoto Yushi Co., Ltd.), and 700 parts of distilled water. . Next, with a disc-type media mill (UMA type_Kotobuki Kogyo Co., Ltd.), using 0.015 mm zirconia beads (filling rate 70%), a volume average of around 100 nm at a peripheral speed of 6 m / s and a liquid temperature of 10 ° C. It was circulated and dispersed until the particle size was reached. Next, coarse particles are separated with a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.), and filtered through a filter with a pore size of 1.2 μm. A black pigment dispersion with a concentration of 15% was obtained.

<Preparation of blue pigment dispersion>
Pigment Blue 15:3 (manufactured by Dainichiseika Kogyo Co., Ltd.) 250 parts, the compound represented by the general formula (2) (Pionin D-7240_Takemoto Oil Co., Ltd.) 50 parts, distilled water 700 parts premixed A mixed slurry was obtained. Next, with a disc-type media mill (UMA type_Kotobuki Kogyo Co., Ltd.), using 0.015 mm zirconia beads (filling rate 70%), a volume average of around 100 nm at a peripheral speed of 6 m / s and a liquid temperature of 10 ° C. It was circulated and dispersed until the particle size was reached. Next, coarse particles are separated with a centrifuge (Model-7700, manufactured by Kubota Shoji Co., Ltd.), and filtered through a filter with a pore size of 1.2 μm. A blue pigment dispersion with a concentration of 15% was obtained.

<Preparation of red pigment dispersion>
In the preparation of the blue pigment dispersion, except that Pigment Blue 15:3 was changed to Pigment Red 122 (manufactured by Dainichiseika Kogyo Co., Ltd.), a red pigment having a pigment concentration of 15% was prepared in the same manner as in the preparation of the blue pigment dispersion. A dispersion was obtained.

<Preparation of yellow pigment dispersion>
In the preparation of the blue pigment dispersion, except that Pigment Blue 15:3 was changed to Pigment Yellow 74 (manufactured by Dainichiseika Kogyo Co., Ltd.), a yellow pigment with a pigment concentration of 15% in the same manner as in the preparation of the blue pigment dispersion. A dispersion was obtained.

(Preparation of styrene-acrylic resin-coated pigment dispersion)
<Preparation of resin-coated black pigment dispersion>
11.2 g of styrene, 2.8 g of acrylic acid, 12 g of lauryl methacrylate, 4 g of polyethylene glycol methacrylate, 4 g of styrene macromer and 0.4 g of mercaptoethanol were mixed and heated to 65°C. Then 100.8 g styrene, 25.2 g acrylic acid, 108 g lauryl methacrylate, 36.2 g polyethylene glycol methacrylate, 60 g hydroxyethyl methacrylate, 36 g styrene macromer, 3.6 g mercaptoethanol, 2.4 g azobismethylvaleronitrile, and methyl ethyl ketone. 18 g of the mixed solution was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65° C. for 1 hour, 0.8 g of azobismethylvaleronitrile was added and further aged for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a solid concentration of 50%.

Then, 25 g of the polymer solution, 50 g of carbon black (manufactured by Cabot Corporation), 13.6 g of 1 mol/l potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of water were sufficiently stirred and kneaded by a roll mill. After the obtained paste was put into 200 g of pure water and sufficiently stirred, the methyl ethyl ketone was removed with an evaporator, and after pressure filtration with a polyvinylidene fluoride membrane filter with an average pore size of 5 μm, the solid content concentration was adjusted to 20%. A styrene-acrylic resin-coated black pigment dispersion having a solid concentration of 20% (pigment concentration of 15%, coating resin concentration of 5%) was obtained.

<Preparation of resin-coated blue pigment dispersion>
In the preparation of the resin-coated black pigment dispersion, in the same manner as in the preparation of the resin-coated black pigment dispersion, except that the carbon black was changed to Pigment Blue 15:3 (manufactured by Dainichiseika Kogyo Co., Ltd.), the solid content concentration A 20% (pigment concentration: 15%, coating resin concentration: 5%) styrene-acrylic resin-coated blue pigment dispersion was obtained.

<Preparation of resin-coated red pigment dispersion>
In the preparation of the resin-coated black pigment dispersion, in the same manner as in the preparation of the resin-coated black pigment dispersion, except that the carbon black was changed to Pigment Red 122 (manufactured by Dainichiseika Kogyo Co., Ltd.), solid content concentration 20% A styrene-acrylic resin-coated red pigment dispersion having a pigment concentration of 15% and a coating resin concentration of 5% was obtained.

<Preparation of resin-coated yellow pigment dispersion>
In the preparation of the resin-coated black pigment dispersion, in the same manner as in the preparation of the resin-coated black pigment dispersion, except that the carbon black was changed to Pigment Yellow 74 (manufactured by Dainichiseika Kogyo Co., Ltd.), solid content concentration 20% A styrene-acrylic resin-coated yellow pigment dispersion having a pigment concentration of 15% and a coating resin concentration of 5% was obtained.

<Synthesis of aqueous dispersion of water-based polyurethane resin>
119.70 g of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate was added as a polyisocyanate component to a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, and active hydrogen. As components, 60.90 g of dimethylolpropionic acid, 60.40 g of bisphenoxyethanol fluorene (manufactured by Osaka Gas Chemicals Co., Ltd.), 13.37 g of polytetramethylene glycol having a number average molecular weight of 2,000, and 300.00 g of methyl ethyl ketone as a solvent were added. The mixture was heated to 80° C. under a nitrogen atmosphere and stirred for 12 hours.

After confirming that the isocyanate absorption band disappeared by infrared absorption spectrum, the temperature was lowered to 40° C., 45.99 g of triethylamine was added for neutralization, and then 700.00 g of water was added and dispersed using a homodisper. After that, methyl ethyl ketone is distilled off under reduced pressure of 6.66 kPa at 50° C., resulting in a fluorene skeleton content of 20% by mass, an acid value of 85 KOHmg/g, a solid concentration of 30% by mass, and a viscosity of 200 mPa, which does not substantially contain a solvent.・An aqueous dispersion of an aqueous polyurethane resin of s was obtained.

The following were used as other ink components.

<Organic solvent>
・ Organic solvent A (manufactured by Asahi Kasei Finechem Co., Ltd. _ trimethylglycine: saturated water content = 52%)
・ Organic solvent B (Glycerin manufactured by Sakamoto Chemical Industry Co., Ltd.: saturated water content = 26%)
・ Organic solvent C (manufactured by Tokyo Chemical Industry Co., Ltd. _ 1,3-butylene glycol: saturated water content = 15%)

<Resin particles>
- Polyether-based urethane resin particles A (Takelac W5661 manufactured by Mitsui Chemicals, Inc.: acid value = 48 KOHmg/g)
* Compound of general formula (7) Polyether-based urethane resin particles B (Takelac W932 manufactured by Mitsui Chemicals, Inc.: acid value = 80 KOHmg / g)
* Compound of general formula (7) Urethane resin particles (synthetic product: acid value = 85 KOHmg / g)

<Surfactant>
・ Silicon surfactant A (KF-6028 manufactured by Shin-Etsu Chemical Co., Ltd.)
* Compound of general formula (3) Silicon surfactant B (manufactured by Nissin Chemical Industry Co., Ltd._SAG503A)
* Compound of general formula (4) Acetylene surfactant (Nissin Chemical Industry Co., Ltd._Surfinol 440)
* Compound of general formula (5) Polyoxyethylene alkyl ether surfactant (_TRITON HW-1000 manufactured by Dow Chemical Co.)
* Compound of general formula (6) Fluorosurfactant (_PF656 manufactured by OMNOVA)

<Antifoaming agent>
・2,4,7,9-Tetramethyldecane-4,7-diol (Surfinol AD01 manufactured by Nissin Chemical Industry Co., Ltd.)

<pH adjuster>
・ 2-amino-2-ethyl-1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.)

<Preservative and antifungal agent>
・LV (S) (manufactured by Avecia)

(Ink preparation)
<Examples 1 to 21, Comparative Examples 1 to 5>
Tables 1 to 3 show formulations of the inks of Examples and Comparative Examples.
First, for each example and comparative example, water-soluble organic solvents, surfactants, other additives (antifoaming agents, pH adjusters, antibacterial agents, etc.) shown in Tables 1 to 3, and ion-exchanged water were mixed. Stirred for hours.
Next, the resin particles were added and stirred for an additional hour to mix uniformly. After that, various pigment dispersions were added, and the mixture was further stirred for 1 hour to be uniformly mixed. This mixture was pressure-filtered through a polyvinylidene fluoride membrane filter having an average pore size of 0.8 μm to remove coarse particles and dust to obtain inks of Examples 1-21 and Comparative Examples 1-5.

<Curl resistance evaluation method>
The black, cyan, magenta, and yellow inks in Tables 1 to 3 are silicone resin (room temperature curing silicone resin SR2411 manufactured by Dow Corning Toray Co., Ltd.) or fluorine resin (fluorine coating agent L-8030 manufactured by DuPont Toray Co., Ltd.). ) with an image forming apparatus (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.) having a nozzle plate with an ink-repellent layer made by ) onto a recording medium (My Paper manufactured by NBS Ricoh Co., Ltd.) at a printing resolution of 600 × 600 dpi, and the print sample is horizontally printed. After placing the paper on a flat stand, the amount of curl at the edges (4 points) of the paper was measured, and the average value was used. The measurement was performed 10 seconds after printing and 12 hours after printing. If the difference in curl amount between 10 seconds after printing and 12 hours after printing is 50 mm or less, it is at a practically usable level.

<Print method>
Black, cyan, magenta, and yellow inks in Table 1 are based on silicone resin (room temperature curing silicone resin SR2411 manufactured by Dow Corning Toray Co., Ltd.) or fluorine resin (fluorine coating agent L-8030 manufactured by DuPont Toray Co., Ltd.). An image forming apparatus (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.) having a nozzle plate with an ink-repellent layer is used to print on a recording medium (My Paper manufactured by NBS Ricoh Co., Ltd.) at a printing resolution of 600 x 600 dpi, and dried overnight at room temperature. A printed sample was obtained. As the printing chart, a 2 cm square solid image and an image in which a black solid image and a color solid image are adjacent to each other were used.

<Image density evaluation>
The image density in the solid image was measured from the solid image of the print sample using an image measuring device (Exact manufactured by X-Rite). The practically usable image densities of color images are as follows.
Black: 1.15 or more Cyan: 0.95 or more Magenta: 0.90 or more Yellow: 0.75 or more

<Fixability evaluation>
The solid image in the printed sample was rubbed back and forth five times with a rubbing device (Crockmeter, manufactured by Daiei Kagaku Seiki Co., Ltd.) with a cotton cloth attached, and the density of the ink transferred to the cotton cloth was measured by an image measuring device (Exact, manufactured by X-Rite). was measured, and judgment was carried out according to the following evaluation standards. Incidentally, if the evaluation value is less than 0.10, it is at a practically usable level.
(Evaluation criteria)
○: less than 0.05 △: 0.05 or more and less than 0.10 ×: 0.10 or more

<Bleeding evaluation>
Bleeding at the boundary between the solid black image and the solid color image was determined visually. As the black ink, the ink of Example 10, which has the lowest surface tension among the examples, was used.
(Evaluation criteria)
〇: No bleeding △: Bleeding is observed, but at a level that does not pose a problem in actual use ×: Bleeding

<Storage stability evaluation>
The ink was placed in a sealed container (_IBOY manufactured by AS ONE Corporation) and stored in a constant temperature bath (_PR-3J manufactured by ESPEC) at 70° C. for 14 days. The viscosity before and after storage was measured with a viscometer (RE-85L manufactured by Toki Sangyo Co., Ltd.) and judged according to the following evaluation criteria. If the change rate of viscosity is less than ±10% of the initial viscosity, it is at a practically usable level.
(Evaluation criteria)
○: Viscosity change rate: 0 to less than ±5% △: Viscosity change rate: ±5% or more to less than ±10% ×: Viscosity change rate: ±10% or more

<Evaluation of viscosity during water evaporation>
5 g of ink was weighed into a glass petri dish (manufactured by AS ONE Corporation) having a diameter of 33 mm and left in a constant temperature bath (_PR-3J manufactured by ESPEC) at 23° C. and 10% for 5 hours. The viscosity after standing was measured with a viscometer (RE-85L manufactured by Toki Sangyo Co., Ltd.) and judged according to the following evaluation criteria. In addition, if the viscosity after standing is less than 1,000 mPa·s, it is at a practically usable level.
(Evaluation criteria)
○: Less than 500 mPa s △: 500 mPa s or more and less than 1,000 mPa s ×: 1,000 mPa s or more

<Ink viscosity measurement>
The viscosity of the ink was measured using a viscometer (RE-85L manufactured by Toki Sangyo Co., Ltd.).

<Ink surface tension measurement (150 ms)>
The surface tension of the ink was measured using a dynamic surface tensiometer (Dynotester manufactured by SITA) at a bubble life time of 150 ms in the maximum bubble pressure method.

The evaluation results are shown in Tables 1-3.

（一般式（１）中、ｍは１～４の整数を表す。）

（一般式（２）中、Ｒ^１は炭素数１～２０のアルキル基、炭素数７～８のアラルキル基、またはアリル基を表し、ｌは０～７の整数を表し、ｎは２０～２００の整数を表す。）
（２）前記水溶性有機溶剤が、２５℃５０％ＲＨ下における飽和水分量が５０％以上のものを１種以上含む、上記（１）に記載のインク。
（３）更に下記一般式（３）又は下記一般式（４）で表されるシリコン系化合物、下記一般式（５）で表されるアセチレン系化合物、下記一般式（６）で表されるポリオキシエチレンアルキルエーテル系化合物のいずれか１種を含む、上記（１）又は（２）に記載のインク。

（一般式（３）中、ａは０～２３の整数、ｂは１～１０の整数、ｃは１～２３の整数、ｄは０～２３の整数、Ｒは水素原子または炭素数１～４のアルキル基を示す。）

（一般式（４）中、ａは１～８の整数、Ｒは水素原子または炭素数１～４のアルキル基を示す。）

（一般式（５）中、Ｒ_１～Ｒ_４はアルキル基、ｍ＋ｎは１～２０の整数、Ｙはアセチレン基を示す。）

（４）更に２，４，７，９－テトラメチルデカン－４，７－ジオールを含む、上記（１）乃至（３）のいずれか１項に記載のインク。
（５）更に下記一般式（７）で表されるポリエーテル系ウレタン樹脂を含む、上記（１）乃至（４）のいずれか１項に記載のインク。

（６）前記ポリエーテル系ウレタン樹脂の酸価が４８（ＫＯＨｍｇ／ｇ）以上８０（ＫＯＨｍｇ／ｇ）以下である、上記（５）に記載のインク。
（７）色材として、その表面の一部または全てがスチレンアクリル樹脂で覆われた顔料を含む、上記（１）乃至（６）のいずれか１項に記載のインク。
（８）インク中における色材量（Ｐ）と全樹脂量（Ｒ）との質量比率（Ｒ／Ｐ）が０．０５以上０．３５以下である、上記（１）乃至（７）のいずれか１項に記載のインク。
（９）インクを吐出するノズルを有し、更に少なくともインク吐出面側表面にシリコン樹脂またはフッ素樹脂を含有する撥インク層を有するノズルプレートを備えたインクジェットヘッドを有するインクジェット印刷装置において用いる、ブラックインク、シアンインク、マゼンタインク、及びイエローインクを含むインクセットであって、
前記各インクが色材、水溶性有機溶剤、下記一般式（１）または下記一般式（２）で表される化合物、及び水を含み、
前記ブラックインクの色材がカーボンブラックであり、前記シアンインクの色材がＰｉｇｍｅｎｔ Ｂｌｕｅ １５：３であり、前記マゼンタインクの色材がＰｉｇｍｅｎｔ Ｒｅｄ １２２または２６９であり、前記イエローインクの色材がＰｉｇｍｅｎｔ Ｙｅｌｌｏｗ ７４であり、
２５℃における回転粘度計での粘度η［ｍＰａ・ｓ］と、２５℃における最大泡圧法でのｂｕｂｂｌｅ ｌｉｆｅ ｔｉｍｅが１５０ｍｓ時の表面張力σ［ｍＮ／ｍ］との積の値が１００以上１３０以下であることを特徴とするインクセット。

（一般式（１）中、ｍは１～４の整数を表す。）

（一般式（２）中、Ｒ^１は炭素数１～２０のアルキル基、炭素数７～８のアラルキル基、又はアリル基を表し、ｌは０～７の整数を表し、ｎは２０～２００の整数を表す。）
（１０）前記シアンインク、前記マゼンタインク、前記イエローインクのそれぞれの表面張力の値が、前記ブラックインクの表面張力の値よりも３ｍＮ／ｍ以上低い、上記（９）に記載のインクセット。
（１１）インクを吐出するノズルを有するインクジェットヘッドと、インクとを有するインクジェット印刷装置であって、
前記インクジェットヘッドは、少なくともインク吐出面側表面に撥インク層を有するノズルプレートを備えたインクジェットヘッドであり、前記撥インク層がシリコン樹脂またはフッ素樹脂を含有し、
前記インクが上記（１）乃至（８）のいずれか１項に記載のインクであることを特徴とするインクジェット印刷装置。
（１２）被印刷物に、インクを吐出するノズルを有するインクジェットヘッドを用いてインクを付与する工程を有するインクジェット印刷方法であって、
前記インクジェットヘッドとして、少なくともインク吐出面側表面に撥インク層を有するノズルプレートを備えたインクジェットヘッドを用い、
前記インクとして上記（１）乃至（８）のいずれか１項に記載のインクを用いることを特徴とするインクジェット印刷方法。 The present invention relates to the ink of (1) below, and includes the following (2) to (12) as embodiments.
(1) An ink for use in an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface. There is
The ink contains a coloring material, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water,
The product of the viscosity η [mPa s] measured by a rotational viscometer at 25°C and the surface tension σ [mN/m] at a bubble life time of 150 ms measured by the maximum bubble pressure method at 25°C is 100 or more and 130 or less. An ink characterized by:

(In general formula (1), m represents an integer of 1 to 4.)

(In general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents 20 to 200 represents an integer of
(2) The ink according to (1) above, wherein the water-soluble organic solvent contains at least one solvent having a saturated water content of 50% or more at 25° C. and 50% RH.
(3) Furthermore, silicon-based compounds represented by the following general formula (3) or the following general formula (4), acetylene-based compounds represented by the following general formula (5), polysilicon compounds represented by the following general formula (6) The ink according to (1) or (2) above, containing any one of oxyethylene alkyl ether compounds.

(In the general formula (3), a is an integer of 0 to 23, b is an integer of 1 to 10, c is an integer of 1 to 23, d is an integer of 0 to 23, R is a hydrogen atom or 1 to 4 carbon atoms indicates the alkyl group of.)

(In general formula (4), a is an integer of 1 to 8, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

(In general formula (5), R ₁ to R ₄ are alkyl groups, m+n is an integer of 1 to 20, and Y is an acetylene group.)

(4) The ink according to any one of (1) to (3) above, further comprising 2,4,7,9-tetramethyldecane-4,7-diol.
(5) The ink according to any one of (1) to (4) above, further comprising a polyether-based urethane resin represented by the following general formula (7).

(6) The ink according to (5) above, wherein the polyether-based urethane resin has an acid value of 48 (mg KOH/g) or more and 80 (mg KOH/g) or less.
(7) The ink according to any one of (1) to (6) above, which contains, as a colorant, a pigment partially or entirely covered with a styrene-acrylic resin.
(8) Any one of the above (1) to (7), wherein the mass ratio (R/P) of the amount of coloring material (P) and the amount of total resin (R) in the ink is 0.05 or more and 0.35 or less. or the ink according to item 1.
(9) Black ink used in an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface side. , a cyan ink, a magenta ink, and a yellow ink, wherein
each of the inks contains a coloring material, a water-soluble organic solvent, a compound represented by the following general formula (1) or (2), and water;
The colorant of the black ink is carbon black, the colorant of the cyan ink is Pigment Blue 15:3, the colorant of the magenta ink is Pigment Red 122 or 269, and the colorant of the yellow ink is Pigment. Yellow 74,
The product of the viscosity η [mPa s] measured by a rotational viscometer at 25°C and the surface tension σ [mN/m] at a bubble life time of 150 ms measured by the maximum bubble pressure method at 25°C is 100 or more and 130 or less. An ink set characterized by:

(In general formula (1), m represents an integer of 1 to 4.)

(In the general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group; l represents an integer of 0 to 7; n represents 20 to 200; represents an integer of
(10) The ink set according to (9) above, wherein each of the cyan ink, the magenta ink, and the yellow ink has a surface tension value lower than that of the black ink by 3 mN/m or more.
(11) An inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and ink,
The inkjet head is an inkjet head provided with a nozzle plate having an ink-repellent layer on at least the ink ejection surface side surface, the ink-repellent layer containing a silicone resin or a fluororesin,
An inkjet printing apparatus, wherein the ink is the ink according to any one of (1) to (8) above.
(12) An inkjet printing method comprising a step of applying ink to a material to be printed using an inkjet head having nozzles for ejecting ink,
As the inkjet head, an inkjet head having a nozzle plate having an ink-repellent layer at least on the ink ejection surface side is used,
An inkjet printing method, wherein the ink described in any one of (1) to (8) above is used as the ink.

10, 32 Nozzle plate 11 Nozzle 11a Edge 20 Nozzle base material 21 Hole, Nozzle 21a Cylindrical portion 21b Conical frustoconical portion 30 Intermediate layer 31, 40 Ink-repellent layer 34 Dispenser 35 Needle 41 Slope region 41a Slope 101 Device body 102 Paper feed Tray 103 Paper output tray 104 Ink cartridge loading unit 105 Operation unit 111 Upper cover 112 Front cover 115 Front cover 131 Guide rod 132 Stay 133 Carriage 134 Recording head 135 Sub tank 141 Paper stacking unit 142 Paper 143 Paper feed roller 144 Separation pad 145 Guide 151 Conveyor Belt 152 Counter Roller 153 Conveyor Guide 154 Pressing Member 155 Leading Edge Pressure Roller 156 Charging Roller 157 Conveyor Roller 158 Tension Roller 161 Guide Member 171 Separation Claw 172 Paper Ejection Roller 173 Paper Ejection Roller 181 Duplex Paper Feed Unit 182 Manual Paper Feed Department

Japanese Patent No. 6582615 Japanese Patent No. 4138593 Japanese Patent No. 5958788

Claims (12)

An ink for use in an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface,
The ink contains a coloring material, a water-soluble organic solvent, a compound represented by the following general formula (1) or the following general formula (2), and water,
The product of the viscosity η [mPa s] measured by a rotational viscometer at 25°C and the surface tension σ [mN/m] at a bubble life time of 150 ms measured by the maximum bubble pressure method at 25°C is 100 or more and 130 or less. An ink characterized by:

(In general formula (1), m represents an integer of 1 to 4.)

(In general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group, l represents an integer of 0 to 7, and n represents 20 to 200 represents an integer of 2. The ink according to claim 1, wherein the water-soluble organic solvent contains at least one solvent having a saturated water content of 50% or more at 25° C. and 50% RH. Furthermore, silicon-based compounds represented by the following general formula (3) or the following general formula (4), acetylene-based compounds represented by the following general formula (5), and polyoxyethylene alkyls represented by the following general formula (6) 3. The ink according to claim 1, comprising any one of ether compounds.

(In the general formula (3), a is an integer of 0 to 23, b is an integer of 1 to 10, c is an integer of 1 to 23, d is an integer of 0 to 23, R is a hydrogen atom or 1 to 4 carbon atoms indicates the alkyl group of.)

(In general formula (4), a is an integer of 1 to 8, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

(In general formula (5), R ₁ to R ₄ are alkyl groups, m+n is an integer of 1 to 20, and Y is an acetylene group.)

4. The ink of any one of claims 1 to 3, further comprising 2,4,7,9-tetramethyldecane-4,7-diol. 5. The ink according to any one of claims 1 to 4, further comprising a polyether-based urethane resin represented by the following general formula (7).

6. The ink according to claim 5, wherein the polyether-based urethane resin has an acid value of 48 (mg KOH/g) or more and 80 (mg KOH/g) or less. 7. The ink according to any one of claims 1 to 6, which contains, as a coloring material, a pigment whose surface is partially or wholly covered with a styrene-acrylic resin. 8. The ink according to any one of claims 1 to 7, wherein the mass ratio (R/P) of the colorant amount (P) and the total resin amount (R) in the ink is 0.05 or more and 0.35 or less. ink. Black ink and cyan ink for use in an inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and a nozzle plate having an ink-repellent layer containing silicone resin or fluororesin on at least the surface of the ink ejection surface side. , a magenta ink, and a yellow ink,
each of the inks contains a coloring material, a water-soluble organic solvent, a compound represented by the following general formula (1) or (2), and water;
The colorant of the black ink is carbon black, the colorant of the cyan ink is Pigment Blue 15:3, the colorant of the magenta ink is Pigment Red 122 or 269, and the colorant of the yellow ink is Pigment. Yellow 74,
The product of the viscosity η [mPa s] measured by a rotational viscometer at 25°C and the surface tension σ [mN/m] at a bubble life time of 150 ms measured by the maximum bubble pressure method at 25°C is 100 or more and 130 or less. An ink set characterized by:

(In general formula (1), m represents an integer of 1 to 4.)

(In the general formula (2), R ¹ represents an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, or an allyl group; l represents an integer of 0 to 7; n represents 20 to 200; represents an integer of 10. The ink set according to claim 9, wherein each of the cyan ink, the magenta ink, and the yellow ink has a surface tension value lower than that of the black ink by 3 mN/m or more. An inkjet printing apparatus having an inkjet head having nozzles for ejecting ink and ink,
The inkjet head is an inkjet head provided with a nozzle plate having an ink-repellent layer on at least the ink ejection surface side surface, the ink-repellent layer containing a silicone resin or a fluororesin,
An inkjet printing apparatus, wherein the ink is the ink according to any one of claims 1 to 8. An inkjet printing method comprising a step of applying ink to an object to be printed using an inkjet head having nozzles for ejecting ink,
As the inkjet head, an inkjet head having a nozzle plate having an ink-repellent layer at least on the ink ejection surface side is used,
An inkjet printing method, wherein the ink according to any one of claims 1 to 8 is used as the ink.

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