Aqueous inkjet ink composition

Abstract

To provide an aqueous inkjet ink composition that is less likely to erode silicon nozzle plates and exhibits superior storage stability.SOLUTION: This aqueous inkjet ink composition contains a pigment, an alkali-soluble resin, a water-soluble organic solvent having a solubility in water at 25°C of 500 g / L or more, water, and a surfactant. The content of the water-soluble organic solvent is 20 mass% or more of the aqueous inkjet ink composition. The total amount of alkali metals is 1.5 g / L or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous inkjet ink composition. More specifically, the present invention relates to an aqueous inkjet ink composition that is less likely to corrode a silicon nozzle plate and exhibits good storage stability. [Background technology]

[0002] Conventionally, inkjet printers that eject aqueous inkjet inks containing a pigment and an alkali-soluble resin have been equipped with a nozzle plate having multiple ejection ports as the ink ejection section, and the nozzle plate has a water-repellent layer on its surface to maintain ink ejection properties.

[0003] However, when conventional aqueous inkjet inks are used on nozzle plates with silicon surfaces, there is a problem in that the water repellency of the plate is reduced due to components in the ink. To address this problem, Patent Document 1 proposes a technology to improve ejection stability by capturing polyvalent metals (Ca) in the ink with chelating resins (-H type, -Na type, -K type). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 086789 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the ink described in Patent Document 1 was prone to deterioration in storage stability.

[0006] The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an aqueous inkjet ink that is less likely to corrode a silicon nozzle plate and exhibits good storage stability. [Means for solving the problem]

[0007] The present invention, which solves the above problems, mainly comprises the following configuration.

[0008] (1) An aqueous inkjet ink composition comprising a pigment, an alkali-soluble resin, a water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, water, and a surfactant, wherein the content of the water-soluble organic solvent is 20 mass% or more in the aqueous inkjet ink composition, and the total amount of alkali metals is 1.5 g / L or less.

[0009] According to this configuration, the aqueous inkjet ink composition is less likely to corrode the silicon nozzle plate, and also exhibits good storage stability.

[0010] (2) The aqueous inkjet ink composition according to (1), wherein the alkali-soluble resin is an acrylic resin.

[0011] According to this configuration, the aqueous inkjet ink composition has the advantage that the pigment dispersibility during the production of the ink base is good and the ink composition has excellent storage stability.

[0012] (3) The aqueous inkjet ink composition according to (1) or (2), wherein the water-soluble organic solvent is an alcohol-based solvent.

[0013] According to this configuration, the aqueous inkjet ink composition has the advantage of being able to achieve both storage stability and ejection stability. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an aqueous inkjet ink that is less likely to corrode a silicon nozzle plate and exhibits good storage stability. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Aqueous inkjet ink composition> An aqueous inkjet ink composition (hereinafter also referred to as ink composition) according to one embodiment of the present invention contains a pigment, an alkali-soluble resin, a water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, water, and a surfactant. The content of the water-soluble organic solvent in the aqueous inkjet ink composition is 20 mass% or more. The total amount of alkali metals is 1.5 g / L or less. Each of these components will be described below.

[0016] (pigment) The pigment is not particularly limited. Examples of the pigment include various organic pigments and inorganic pigments. Examples of the organic pigment include dye lake pigments, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, perinone pigments, diketopyrrolopyrrole pigments, isoindolinone pigments, nitro pigments, nitroso pigments, flavanthrone pigments, quinophthalone pigments, pyranthrone pigments, and indanthrone pigments.

[0017] The inorganic pigments include carbon black, titanium oxide, zinc oxide, red iron oxide, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0018] The pigment may be surface-treated with a known surface treatment agent.

[0019] Yellow pigments include CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, 213, and the like.

[0020] Magenta pigments include CI Pigment Red 5, 7, 12, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57, 57:1, 63:1, 101, 102, 112, 122, 123, 144, 146, 149, 168, 177, 178, 179, 180, 184, 185, 190, 202, 209, 224, 242, 254, 255, 270, and CI Pigment Violet 19.

[0021] Cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, and the like.

[0022] The black pigment is carbon black (CI Pigment Black 7) or the like.

[0023] The white pigment is titanium oxide, aluminum oxide, etc. The white pigment may be surface-treated with various materials such as alumina, silica, etc.

[0024] The content of the pigment is not particularly limited. For example, the content of the pigment other than white is preferably 0.5% by mass or more, and more preferably 2% by mass or more, in the ink composition. The content of the pigment other than white is preferably 10% by mass or less, and more preferably 8% by mass or less, in the ink composition. On the other hand, the content of the white pigment is preferably 4% by mass or more, and more preferably 8% by mass or more, in the ink composition. The content of the white pigment is preferably 25% by mass or less, and more preferably 20% by mass or less, in the ink composition. By keeping the pigment content within the above range, the ink composition can achieve both good color reproducibility and good jetting properties.

[0025] (alkali-soluble resin) The alkali-soluble resin is not particularly limited. Examples of the alkali-soluble resin include a resin obtained by polymerizing a monomer having an unsaturated double bond, and a resin obtained by a reaction between functional groups.

[0026] Specifically, the alkali-soluble resin is an acrylic resin copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene or the like as the main monomer component, or various binder resins such as a styrene-acrylic resin, a styrene-maleic acid resin, a styrene-acrylic-maleic acid resin, a polyurethane resin, or a polyester resin. Of these, the alkali-soluble resin is preferably an acrylic resin. This has the advantages of providing good pigment dispersibility during ink base production and excellent storage stability for the ink composition.

[0027] These alkali-soluble resins can be dissolved in water in the presence of a basic compound and used as a water-soluble resin varnish. The basic compound is not particularly limited. Examples of basic compounds include ammonia, organic amines, and alkali metal hydroxides. Examples of organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide.

[0028] The content of the alkali-soluble resin is not particularly limited. For example, the content of the alkali-soluble resin in the ink composition is preferably 1.0% by mass or more, and more preferably 1.3% by mass or more. Furthermore, the content of the alkali-soluble resin in the ink composition is preferably 3.3% by mass or less, and more preferably 3.0% by mass or less. By keeping the content of the alkali-soluble resin within the above range, the ink composition can achieve both storage stability and ejection stability.

[0029] (Water-soluble organic solvent) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25° C. There are no particular limitations on such water-soluble organic solvent. For example, the water-soluble organic solvent is preferably an alcohol or polyhydric alcohol solvent, and more preferably methanol, ethanol, propanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, glycerin, or the like.

[0030] The content of the water-soluble organic solvent in the ink composition is sufficient as long as it is 20% by mass or more, and preferably 25% by mass or more. The content of the water-soluble organic solvent in the ink composition is preferably 50% by mass or less, and more preferably 45% by mass or less. If the content of the water-soluble organic solvent is less than 20% by mass, the ink composition may have a problem of poor ejection stability.

[0031] In addition to the water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, the ink composition of this embodiment may also contain a water-soluble organic solvent having a water solubility of less than 500 g / L at 25°C (also referred to as other water-soluble organic solvent). Examples of such other water-soluble organic solvents include hexanol, ethylene glycol monooctyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, and dibutyl glycol. The ink composition of this embodiment contains 20% by mass or more of the water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, distinguishing it from other water-soluble organic solvents. This provides the ink composition of this embodiment with the advantage of improved storage stability.

[0032] (water) Water is added to impart fluidity to the ink composition.

[0033] The water content is not particularly limited. For example, the water content in the ink composition is preferably 10% by mass or more, and more preferably 30% by mass or more. The water content in the ink composition is preferably 70% by mass or less, and more preferably 60% by mass or less. When the water content is within the above range, the ink composition can exhibit appropriate fluidity.

[0034] (surfactant) The surfactant is not particularly limited, and examples thereof include acetylene-based surfactants and silicone-based surfactants.

[0035] Commercially available acetylene surfactants include "Dynol 607," "Dynol 609," "Olfine E-1004," "Olfine E-1010," "Olfine E-1020," "Olfine PD-001," "Olfine PD-002W," "Olfine PD-004," "Olfine PD-005," "Olfine EXP. 4001," "Olfine EXP. 4200," "Olfine EXP. 4123," and "Olfine EXP. 4300" (all manufactured by Nissin Chemical Industry Co., Ltd.); "Surfynol 104E," "Surfynol 104H," "Surfynol 104A," "Surfynol 104BC," "Surfynol 104DPM," "Surfynol 104PA," "Surfynol 104PG-50," "Surfynol 420," "Surfynol 440," and "Surfynol 465" (all manufactured by EVONIK).

[0036] Commercially available silicone surfactants include "BYK-307," "BYK-333," "BYK-347," "BYK-348," "BYK-349," "BYK-345," "BYK-378," and "BYK-3455" (all manufactured by BYK-Chemie).

[0037] The content of the surfactant is not particularly limited. For example, the content of the surfactant in the ink composition is preferably 0.1% by mass or more, and more preferably 0.3% by mass or more. Furthermore, the content of the surfactant in the ink composition is preferably 10.0% by mass or less, and more preferably 6.0% by mass or less. Having the surfactant content within the above range has the advantage of improving the image quality of the printed matter.

[0038] (optional ingredient) The ink composition of this embodiment may be blended with various additives as appropriate, such as extender pigments such as calcium carbonate, kaolin, barium sulfate, aluminum hydroxide, clay, and talc, inorganic fine particles and adhesive resins (acrylic resins, vinyl acetate resins) to impart anti-slip properties, leveling agents to improve leveling properties, antifoaming agents to impart antifoaming properties, basic compounds such as caustic soda to impart resolubility, film-forming emulsions, preservatives, rust inhibitors, and crosslinking agents.

[0039] The ink composition of this embodiment is characterized in that the total amount of alkali metals is 1.5 g / L or less. The total amount of alkali metals may be 1.5 g / L or less, and preferably 1.4 g / L or less. The total amount of alkali metals is preferably 0.5 g / L or more, and more preferably 0.9 g / L or more. By having the total amount of alkali metals within the above range, the ink composition is likely to maintain its storage stability and water repellency on the nozzle plate for a long period of time. The total amount of alkali metals can be measured by quantifying Na and K using a calibration curve method using an atomic absorption spectrophotometer (model number: ZA3300, sold by Hitachi High-Tech Science Corporation).

[0040] The ink composition of this embodiment can be prepared by stirring and mixing a pigment, an alkali-soluble resin, a water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, water, a surfactant, and various optional components, grinding the mixture using various grinding machines such as a bead mill, ball mill, sand mill, attritor, roll mill, or pearl mill, and then performing a process to reduce the total amount of alkali metals.

[0041] That is, if the above-described ink composition manufacturing method does not include a treatment to reduce the total amount of alkali metals, the total amount of alkali metals in the resulting ink composition will exceed 1.5 g / L. Therefore, the ink composition of this embodiment is adjusted to have a total amount of alkali metals of 1.5 g / L or less by incorporating a treatment step to reduce the total amount of alkali metals.

[0042] Such a treatment step is not particularly limited, and an example of the treatment step is a step of treating the ink composition with an ion exchange resin or a chelating resin.

[0043] The ion exchange resin is not particularly limited. Examples of the ion exchange resin include acrylic acid type, methacrylic acid type, sulfonic acid type, trimethylammonium type, dimethylethanolammonium type, and polyamine type. Among these, the ion exchange resin is preferably a methacrylic acid type or a sulfonic acid type.

[0044] The chelating resin is not particularly limited. Examples of the chelating resin include iminodiacetic acid type, polyamine type, primary amine type, methylglucamine type, amidoxime type, isothiouronium type, thiol type, sulfonic acid type, phosphonic acid type, aminophosphoric acid type, bispicolylamine type, and semithiocarbamic acid type. Among these, the chelating resin is preferably iminodiacetic acid type.

[0045] In the treatment step, the mixture of various raw materials is mixed with the ion exchange resin or chelating resin to remove the alkali metals. As a result, the total amount of alkali metals in the resulting ink composition can be adjusted to 1.5 g / L or less. The ion exchange resin and chelating resin can be removed using, for example, a 250 mesh sieve. [Example]

[0046] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0047] The raw materials and preparation methods used are shown below. <Water-based resin varnish> 20 parts by mass of an acrylic acid / n-butyl acrylate / benzyl methacrylate / styrene copolymer having a glass transition temperature of 40°C, a weight average molecular weight of 30,000, and an acid value of 185 mgKOH / g was dissolved in a mixed solution of 2.5 parts by mass of potassium hydroxide and 77.5 parts by mass of water to obtain an aqueous resin varnish with a solids content of 20%.

[0048] <Preparation of Water-Based Black Ink Base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of carbon black (trade name: Printex 90, manufactured by Degussa) was added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous black ink base. <Preparation of Water-Based Yellow Ink Base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of a yellow pigment (product name: Novapalm Yellow 4G01, manufactured by Clariant) was added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous yellow ink base. <Preparation of Water-Based Magenta Ink Base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of magenta pigment (product name: Inkjet Magenta E5B02, manufactured by Clariant) was added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous magenta ink base. <Preparation of aqueous cyan ink base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of a cyan pigment (product name: Heliogen Blue L7101F, manufactured by BASF) was added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous cyan ink base.

[0049] Example 1 (Production of aqueous inkjet ink composition) Each ink base was mixed with various raw materials so as to obtain the formulation shown in Table 1 below, to produce an aqueous inkjet ink composition.

[0050] [Table 1]

[0051] (Treatment process using ion exchange resin and chelating resin) 100 g of the aqueous inkjet ink composition and 1.0 g of the following ion exchange resin 1 were mixed and stirred for 30 minutes. The ion exchange resin was then removed using a 250 mesh sieve, thereby obtaining the aqueous inkjet ink composition of Example 1.

[0052] <Ion exchange resins / chelating resins> Ion exchange resin 1: acrylic acid type ion exchange resin, Amberlite IRC76 (manufactured by Organo Corporation) Ion exchange resin 2: sulfonic acid type ion exchange resin, Amberlite HPR1024 H (manufactured by Organo Corporation) Chelate resin 1: Iminodiacetic acid type chelating resin, terminal carboxyl group is not neutralized

[0053] <Examples 2 to 8, Comparative Examples 1 and 2> Aqueous inkjet ink compositions were prepared in the same manner as in Example 1, except for the formulation changes shown in Table 1. The ink composition of Comparative Example 1 is the same ink composition as the ink composition of Example 2 before the treatment with the ion exchange resin / chelating resin.

[0054] The alkali metal content of each aqueous inkjet ink composition was measured before and after the treatment process. Furthermore, the storage stability and the change in water repellency over time on the nozzle plate were evaluated for each aqueous inkjet ink composition. The results are shown in Table 1.

[0055] <Determination of alkali metals> The aqueous inkjet ink composition was diluted 3000 times with ion-exchanged water, and Na and K were quantified by the calibration curve method using an atomic absorption spectrophotometer (model number: ZA3300, sold by Hitachi High-Tech Science Corporation).

[0056] <Storage stability> The aqueous inkjet ink composition was placed in a glass bottle, and the viscosity at 25°C was measured using a viscometer (RE100L model, manufactured by Toki Sangyo Co., Ltd.). The bottle was then sealed and stored at 60°C for one month, and the viscosity (25°C) after storage was measured using the viscometer. The stability over time was evaluated as the rate of viscosity change (viscosity after one month at 60°C - viscosity before storage / viscosity before storage). (Evaluation criteria) ○: The viscosity change rate was less than 5%. △: The viscosity change rate was 5% or more and less than 10%. ×: The viscosity change rate was 10% or more and less than 30%.

[0057] <Changes in water repellency over time on nozzle plate> A 2 cm x 2 cm silicon nozzle plate was immersed in the aqueous inkjet ink composition and stored at 60°C for one month, and the water repellency of the nozzle plate after storage was evaluated by the contact angle of water. (Evaluation criteria) ○: The contact angle of water was 90° or more. △: The contact angle of water was 80° or more and less than 90° ×: The contact angle of water was less than 80°.

[0058] As shown in Table 1, the aqueous inkjet ink composition of the present invention was less likely to corrode the silicon nozzle plate and exhibited good storage stability.

Claims

1. The ink contains a pigment, an alkali-soluble resin, a water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, water, and a surfactant, the content of the water-soluble organic solvent in the aqueous inkjet ink composition is 20% by mass or more, The aqueous inkjet ink composition has a total amount of alkali metals of 0.9 to 1.5 g / L.

2. The aqueous ink-jet ink composition according to claim 1 , wherein the alkali-soluble resin is an acrylic resin.

3. 3. The aqueous ink-jet ink composition according to claim 1, wherein the water-soluble organic solvent is an alcohol-based solvent.

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