Inkjet ink composition

Abstract

To provide an inkjet ink composition and the like that achieve favorable discharge stability while also enabling favorable recovery from clogging.SOLUTION: An inkjet ink composition comprises a colorant, an acetylene glycol surfactant having an HLB value of 6 or less, and an organic solvent represented by formula (1), wherein, with respect to the total amount of the inkjet ink composition, the content A of the acetylene glycol surfactant having an HLB value of 6 or less and the content B of the organic solvent represented by formula (1) satisfy a content ratio A / B of 1.00 or less, and a total content A+B of 15 mass% or less (where n is an integer of 4 to 8, and R is an alkyl group having 5 to 7 carbon atoms, which may have a substituent).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to ink-jet ink compositions. [Background technology]

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment and have been rapidly developing in various fields. For example, Patent Document 1 discloses an aqueous inkjet ink composition containing pigment particles, inorganic oxide particles, and a lactam solvent for the purpose of improving the color development of the ink, in which the pigment particles have a volume average particle size within a specific range and the content of the inorganic oxide particles is 5.0% by mass or more and 10.0% by mass or less with respect to the total mass of the ink composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-176235 Summary of the Invention [Problem to be solved by the invention]

[0004] The inkjet ink composition described in Patent Document 1 achieves high color development by using a pigment having a specific particle diameter relationship and inorganic oxide particles. However, Patent Document 1 does not consider ejection stability from the perspective of landing ink droplets at targeted positions when ejecting the inkjet ink composition from an inkjet head, or clogging recovery when the ink is sufficiently dried in the nozzle. [Means for solving the problem]

[0005] The present invention provides an inkjet ink composition comprising a colorant, an acetylene glycol surfactant having an HLB value of 6 or less, and an organic solvent represented by the following formula (1), wherein the content A of the acetylene glycol surfactant having an HLB value of 6 or less relative to the total amount of the inkjet ink composition and the content B of the organic solvent represented by the above formula (1) relative to the total amount of the inkjet ink composition are such that the content ratio A / B is 1.00 or less, and the total content A+B is 15 mass% or less.

[0006] [ka]

[0007] Here, n is an integer of 4 to 8, and R is an alkyl group having 5 to 7 carbon atoms which may have a substituent. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram of a recording apparatus used in the present embodiment. [Figure 2] FIG. 2 is a schematic diagram of a recording apparatus used in the present embodiment. [Figure 3] 1 is a table showing the results of examples. [Figure 4] 1 is a table showing the results of examples. [Figure 5] 1 is a table showing the results of examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0010] 1. Inkjet ink composition The inkjet ink composition of this embodiment contains a colorant, an acetylene glycol surfactant having an HLB value of 6 or less, and an organic solvent represented by the following formula (1), wherein the content A of the acetylene glycol surfactant having an HLB value of 6 or less relative to the total amount of the inkjet ink composition and the content B of the organic solvent represented by the following formula (1) relative to the total amount of the inkjet ink composition are such that the content ratio A / B is 1.00 or less, and the total content A+B is 15 mass% or less.

[0011] [ka]

[0012] (wherein n is an integer of 4 to 8, and R is an alkyl group having 5 to 7 carbon atoms which may have a substituent.)

[0013] Recording methods using inkjet printers require high-speed printing, and in these recording methods, it is necessary to ensure that the ink lands at the desired position on the recording medium without causing deviation in the ink flight path after being ejected from the inkjet head. In other words, it is important to improve the ink ejection stability. In particular, for business inkjet printers, there is a great need for continuous high-speed printing, so improving the ink ejection stability is particularly important.

[0014] Therefore, we have found that including an acetylene glycol-based surfactant with a low HLB value in an inkjet ink composition improves the ejection stability of the inkjet ink composition from an inkjet head. This is thought to be because the surfactant reduces the surface tension of the inkjet ink composition, enabling the formation of smaller ink droplets during ejection, reducing the likelihood of ink deflection. On the other hand, acetylene glycol-based surfactants with a low HLB value have low solubility in solvents such as water, making them prone to phase separation in inkjet ink compositions containing such surfactants. This phase separation is particularly likely to occur when the inkjet ink composition dries in the nozzles of an inkjet head and the amount of solvent, such as water, decreases, or when the inkjet ink composition is stored without immediate use. As a result, we have found that the inkjet head tends to clog during recording, and that the clogged nozzles are difficult to recover from, even after head cleaning, i.e., the clogging recovery ability tends to deteriorate. Furthermore, we have found that ejection stability is likely to deteriorate after the surfactant phase separates.

[0015] In this regard, the inkjet ink composition of this embodiment contains an organic solvent represented by the above formula (1) in addition to an acetylene glycol surfactant having an HLB value of 6 or less. The organic solvent tends to improve the solubility of the surfactant in solvents such as water. Therefore, the inkjet ink composition of this embodiment can achieve both good ejection stability due to the inclusion of the surfactant and good clogging recovery properties.

[0016] Each component of the inkjet ink composition of this embodiment will be described in detail below. Note that, hereinafter, the inkjet ink composition of this embodiment will also be simply referred to as the "ink composition."

[0017] 1.1.Colorants The ink composition of this embodiment contains a colorant. Examples of the colorant include dyes and pigments. The content of the colorant relative to the total amount of the ink composition is not particularly limited, but is, for example, 1 to 10 mass %. The colorant may be used alone or in combination of two or more types.

[0018] 1.1.1.Pigments By using a pigment as the coloring material, the light resistance of the ink composition of this embodiment can be improved. Both inorganic pigments and organic pigments can be used as the pigment.

[0019] As inorganic pigments, carbon blacks (CI (Colour Index Generic Name) Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide can be used.

[0020] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates (for example, basic dye chelates, acid dye chelates, etc.); dye lakes (basic dye lakes, acid dye lakes), nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments.

[0021] In addition, examples of pigments include resin-dispersed pigments and self-dispersed pigments, and either can be used. Resin-dispersed pigments are pigments that can be dispersed in a solvent such as water by a resin. The resin in the resin-dispersed pigment can be a dispersant, as described below.

[0022] A self-dispersing pigment is a pigment that can be dispersed in a solvent such as water without relying on a resin, and more specifically, refers to a pigment whose surface has been modified by directly or indirectly bonding to its surface functional groups such as carbonyl groups, carboxyl groups, aldehyde groups, hydroxyl groups, sulfone groups, ammonium groups, and salts thereof.

[0023] The self-dispersing pigment may be a commercially available product or a preparation prepared by a known method, such as "Microjet CW1" and "Microjet CW2" manufactured by Orient Chemical Industry Co., Ltd., or "CAB-O-JET 200" and "CAB-O-JET 300" manufactured by Cabot Corporation.

[0024] The content of the pigment relative to the total amount of the ink composition is not particularly limited, but is, for example, 1 to 10 mass %, 2 to 9 mass %, or 3 to 8 mass %.

[0025] Dispersants When the ink composition of this embodiment contains a pigment, it may contain a dispersant to improve the dispersibility of the pigment. Note that in this embodiment, the dispersant for dispersing the pigment is not included in the resin described below. The dispersant may be used alone, or two or more types may be used in combination.

[0026] The dispersant is not particularly limited, but examples thereof include dispersants commonly used in preparing pigment dispersions, such as polymer dispersants, and specific examples thereof include those containing one or more of polyoxyalkylene polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicon-containing polymers, sulfur-containing polymers, fluorine-containing polymers, and epoxy resins as the main component.

[0027] Commercially available polymer dispersants include the Ajisper series manufactured by Ajinomoto Fine-Techno Co., Ltd., the Solsperse series (Solsperse 36000, etc.) available from Avecia and Noveon, the Disperbic series manufactured by BYK Additives & Instruments, and the Disparlon series manufactured by Kusumoto Chemicals Co., Ltd.

[0028] The content of the dispersant relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 5.0% by mass.

[0029] 1.1.3.Dye The dye is not particularly limited, and examples thereof include acid dyes, direct dyes, reactive dyes, and basic dyes. The dye is not particularly limited, and examples thereof include CI Acid Yellow 17, 23, 42, 44, 79, 142, CI Acid Red 52, 80, 82, 249, 254, 289, CI Acid Blue 9, 45, 249, CI Acid Black 1, 2, 24, 94, CI Food Black 1, 2, CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 14 2, 144, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, CI Reactive Black 3, 4, 35.

[0030] The content of the dye relative to the total amount of the ink composition is not particularly limited, but is, for example, 1 to 10 mass %, 2 to 9 mass %, or 3 to 8 mass %.

[0031] 1.2.Resin The ink composition of this embodiment may contain a resin. Examples of the resin include resin particles and water-soluble resins. By using the above-mentioned resin particles or water-soluble resin, the fixability of the ink composition to a recording medium tends to be improved. The resin may be in the form of a dispersion, particles, an emulsion, or a solution in a solvent.

[0032] The resin is not particularly limited, but examples thereof include resin particles made of urethane-based resins, acrylic-based resins, fluorene-based resins, polyolefin-based resins, rosin-modified resins, terpene-based resins, polyester-based resins, polyamide-based resins, epoxy-based resins, vinyl chloride-based resins, ethylene vinyl acetate-based resins, etc.; and water-soluble resins such as water-soluble urethane-based resins and water-soluble acrylic-based resins. The resins may be used alone or in combination of two or more.

[0033] The urethane resin is a general term for resins having a urethane bond, and is not particularly limited, but examples thereof include polyether-type urethane resins having an ether bond in the main chain, polyester-type urethane resins having an ester bond in the main chain, and polycarbonate-type urethane resins having a carbonate bond in the main chain. The urethane resin may be a preparation prepared by a known method, or a commercially available product.

[0034] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component. The acrylic resin is not particularly limited, but examples thereof include polymerized (meth)acrylic monomers such as (meth)acrylic acid or a (meth)acrylic acid ester, and copolymerized (meth)acrylic monomers with other monomers, such as styrene-acrylic resin. The acrylic resin may be a prepared product prepared by a known method, or a commercially available product may be used.

[0035] The resin content is preferably 1 to 5% by mass relative to the total amount of the ink composition. When the resin content is within this range, clogging recovery tends to be further improved.

[0036] 1.3.Organic Solvents The ink composition of this embodiment contains an organic solvent represented by the following formula (1).

[0037] [ka]

[0038] Here, n is an integer of 4 to 8, and R is an alkyl group having 5 to 7 carbon atoms which may have a substituent. Examples of the substituent include a halogen atom, an amino group, a thiol group, a hydroxy group, a nitrile group, an amide group, a nitro group, and a nitroso group. R may not have a substituent.

[0039] In the organic solvent represented by the above formula (1), the number n of relatively hydrophilic ethylene glycol chains is 4 to 8, and the number of carbon atoms R of the relatively hydrophobic alkyl group is 5 to 7. Thus, the organic solvent represented by the above formula (1) has a good balance between hydrophilicity and hydrophobicity. Therefore, the use of the organic solvent represented by the above formula (1) tends to improve the solubility of an acetylene glycol surfactant having an HLB value of 6 or less, as described below, in a solvent such as water. Therefore, the inkjet ink composition of this embodiment can achieve both good ejection stability and good clogging recovery properties due to the inclusion of an acetylene glycol surfactant having an HLB value of 6 or less.

[0040] Furthermore, the organic solvent represented by the above formula (1) has a degree of polymerization n of 4 to 8, and therefore has a large molecular weight and is less likely to volatilize, so that good ejection stability and good clogging recovery can be maintained even if the nozzles continue to dry out over a long period of time.

[0041] The organic solvent represented by the above formula (1) is not particularly limited, and examples thereof include tetraethylene glycol monopentyl ether, tetraethylene glycol mono-2-ethylpropyl ether, tetraethylene glycol mono-3-methylbutyl ether, tetraethylene glycol monohexyl ether, tetraethylene glycol mono-2-methylpentyl ether, tetraethylene glycol mono-3-ethylbutyl ether, tetraethylene glycol monoheptyl ether, tetraethylene glycol mono-4-methylhexyl ether, tetraethylene glycol mono-2-ethylpentyl ether, pentaethylene glycol monopentyl ether, pentaethylene glycol mono-2-ethylpropyl ether, pentaethylene glycol mono-3-methylbutyl ether, pentaethylene glycol monohexyl ether, pentaethylene glycol mono-2-methylpentyl ether, pentaethylene glycol mono-3-ethylbutyl ether, pentaethylene glycol monoheptyl ether, pentaethylene glycol mono-4-methylhexyl ether, pentaethylene glycol mono-2-ethylpentyl ether, ether, hexaethylene glycol monopentyl ether, hexaethylene glycol mono 2-ethylpropyl ether, hexaethylene glycol mono 3-methylbutyl ether, hexaethylene glycol monohexyl ether, hexaethylene glycol mono 2-methylpentyl ether, hexaethylene glycol mono 3-ethylbutyl ether, hexaethylene glycol monoheptyl ether, hexaethylene glycol mono 4-methylhexyl ether, hexaethylene glycol mono 2-ethylpentyl ether, heptaethylene glycol monopentyl ether, heptaethylene glycol mono 2-ethylpropyl ether, heptaethylene glycol mono 3-methylbutyl ether, heptaethylene glycol monohexyl ether, heptaethylene glycol mono 2-methylpentyl ether, heptaethylene glycol mono 3-ethylbutyl ether, heptaethylene glycol monoheptyl ether, heptaethylene glycol mono 4-methylhexyl ether, heptaethylene glycol mono 2-ethylpentyl ether, octaethylene glycol monopentyl ether,Examples of the organic solvent mixture include octaethylene glycol mono-2-ethylpropyl ether, octaethylene glycol mono-3-methylbutyl ether, octaethylene glycol monohexyl ether, octaethylene glycol mono-2-methylpentyl ether, octaethylene glycol mono-3-ethylbutyl ether, octaethylene glycol monoheptyl ether, octaethylene glycol mono-4-methylhexyl ether, octaethylene glycol mono-2-ethylpentyl ether, and mixtures thereof. The mixture of the above organic solvents is not particularly limited, but examples thereof include a mixture of tetraethylene glycol monohexyl ether, pentaethylene glycol monohexyl ether, hexaethylene glycol monohexyl ether, heptaethylene glycol monohexyl ether, and octaethylene glycol monohexyl ether.

[0042] The ink composition of this embodiment may contain an organic solvent other than the organic solvent represented by the above formula (1). Examples of the other organic solvent include, but are not limited to, monohydric alcohols, polyols, and glycol ethers. The other organic solvents may be used alone or in combination.

[0043] The monohydric alcohols are not particularly limited, but examples thereof include methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol.

[0044] The polyols are not particularly limited, but examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and glycerin.

[0045] Alkanediols having 5 or more carbon atoms, such as 1,2-hexanediol, are preferred because they have the effect of increasing the water solubility of acetylene glycol surfactants having an HLB value of 6 or less and suppressing phase separation. As the alkanediol having 5 or more carbon atoms, an alkanediol having 5 to 10 carbon atoms is more preferred.

[0046] The glycol ethers are not particularly limited, but examples thereof include triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, tetraethylene glycol monooctyl ether, triethylene glycol monohexyl ether, and nonylethylene glycol monohexyl ether.

[0047] Among the polyols, polyols having a normal boiling point of 280° C. or higher are not particularly limited, but examples thereof include triethylene glycol, tetraethylene glycol, and glycerin.

[0048] Furthermore, the polyols having a normal boiling point of less than 280°C are not particularly limited, but examples thereof include ethylene glycol, diethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol.

[0049] The content of the organic solvent represented by formula (1) is preferably 0.5 to 15.0 mass%, 1.0 to 10.0 mass%, 1.1 to 7.5 mass%, 1.2 to 5.0 mass%, or 1.3 to 4.0 mass%, relative to the total amount of the ink composition. When the content of the organic solvent represented by formula (1) is within the above range, clogging recovery properties and ejection stability tend to be further improved.

[0050] The content of the other organic solvent is preferably 5.0 to 30.0 mass %, 7.5 to 25.0 mass %, or 10.0 to 20.0 mass % relative to the total amount of the ink composition. When the content of the other organic solvent is within the above range, clogging recovery property and ejection stability tend to be further improved.

[0051] The content of the organic solvent represented by the formula (1) is preferably 5.0 to 50.0 mass%, 6.0 to 40.0 mass%, 7.0 to 30.0 mass%, 8.0 to 25.0 mass%, 9.0 to 22.5 mass%, or 10.0 to 20.0 mass%, relative to the total amount of organic solvents. When the content of the organic solvent represented by the formula (1) is within the above range, clogging recovery properties and ejection stability tend to be further improved.

[0052] The content of polyols having a normal boiling point of 280°C or higher is preferably 1.0 to 20.0 mass%, 2.5 to 17.5 mass%, or 5.0 to 15.0 mass%, relative to the total amount of the ink composition. When the content of polyols having a normal boiling point of 280°C or higher is within the above range, the ink composition tends to be less prone to drying, and ejection stability tends to be further improved.

[0053] 1.4.Surfactants 1.4.1. Acetylene glycol surfactants with an HLB value of 6 or less The ink composition of this embodiment contains an acetylene glycol surfactant with an HLB value of 6 or less. This tends to improve the ejection stability of the ink composition. Furthermore, it tends to improve the permeability of the ink composition into a recording medium. Higher permeability is preferable because it reduces the likelihood that a recording medium to which the ink composition has been applied will contaminate other recording media or components within a recording device when the recording medium comes into contact with these media. Permeability can be evaluated by measuring the contact angle of the inkjet ink composition on a recording medium. The smaller the contact angle, the higher the permeability.

[0054] The HLB value of the acetylene glycol surfactant is 6 or less, preferably 5 or less, or 4 or less. When the HLB value is 6 or less, the penetration of the ink composition tends to be further improved. The lower limit of the HLB value is preferably 0 or more, 1 or more, or 2 or more. When the HLB value is within the above range, phase separation is less likely to occur, and ejection stability and clogging recovery tend to be further improved.

[0055] Here, the HLB value is a value that represents the balance between hydrophobicity and hydrophilicity of a surfactant, and the smaller the HLB value, the more hydrophobic the surfactant is, and the larger the HLB value, the more hydrophilic the surfactant is. In the present invention, the HLB value is calculated by the Griffin method.

[0056] The acetylene glycol surfactant having an HLB value of 6 or less is not particularly limited, and examples thereof include acetylene glycol as represented by the following formula (2) and an alkylene oxide adduct of acetylene glycol as represented by the following formula (3). The use of such an acetylene glycol surfactant tends to further improve ejection stability, clogging recovery, and penetration. The acetylene glycol surfactant having an HLB value of 6 or less may be used alone or in combination of two or more.

[0057] [ka]

[0058] R 1 ~R 4 are each independently an alkyl group having 1 to 4 carbon atoms which may have a substituent.

[0059] [ka]

[0060] R 1 ~R 4 each independently represents an alkyl group having 1 to 4 carbon atoms which may have a substituent, and m and n each independently represent 0 or an integer of 1 or more, and m+n=1 to 30 is satisfied.

[0061] m is preferably 1 to 15, 1 to 10, or 1 to 5. n is preferably 1 to 15, 1 to 10, or 1 to 5.

[0062] R 1 ~R 4 is not particularly limited, and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl. Examples of the substituent include an alkyl group, an alkynyl group, an alkenyl group, a halogen atom, an imino group, an amino group, a thiol group, a hydroxy group, an acyl group, a nitrile group, a formyl group, an amide group, an acryl halide group (-CH2CH2-C(=O)-X; X is a halogen atom), an ester group, a carboxy group, an alkoxy group, a thioalkoxy group, a nitro group, and a nitroso group.

[0063] Specific structures of acetylene glycol surfactants having an HLB value of 6 or less include compounds represented by formula (2) and compounds represented by formula (3), and in the compound represented by formula (3), n and m are preferably within the above-mentioned ranges or less, 15 or less, 9 or less, and 8 or less, respectively. Although not particularly limited, examples include 2,4,7,9-tetramethyl-5-decyne-4,7-diol or its alkylene oxide adduct, in which the number of moles added (n, m) of the adduct are within the above-mentioned ranges or less, 15 or less, 9 or less, and 8 or less, respectively.

[0064] Examples of product names of acetylene glycol surfactants having an HLB value of 6 or less include Olfine D-10PG (manufactured by Air Products Co., Ltd.) and Surfynol 420 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0065] The content of the acetylene glycol surfactant having an HLB value of 6 or less is preferably 0.1 to 2.0 mass%, 0.2 to 1.5 mass%, or 0.3 to 1.0 mass%, relative to the total amount of the ink composition. When the content of the acetylene glycol surfactant having an HLB value of 6 or less is within the above range, ejection stability tends to be further improved.

[0066] The content of the acetylene glycol surfactant having an HLB value of 6 or less is preferably 10 to 85 mass%, 15 to 80 mass%, 20 to 75 mass%, or 30 to 70 mass%, relative to the total amount of surfactants. When the content of the acetylene glycol surfactant having an HLB value of 6 or less is within the above range, ejection stability tends to be further improved.

[0067] Where A is the content of the acetylene glycol surfactant having an HLB value of 6 or less relative to the total amount of the ink composition, and B is the content of the organic solvent represented by formula (1) relative to the total amount of the ink composition, the total content A+B is 15% by mass or less, and preferably 1.0 to 15.0% by mass, 1.2 to 12.5% ​​by mass, 1.4 to 10.0% by mass, or 1.5 to 7.5% by mass. Having the total content A+B within the above ranges tends to improve clogging recovery and ejection stability.

[0068] Furthermore, the content ratio A / B is 1.00 or less, preferably 0.02 to 1.00, 0.04 to 0.75, or 0.06 to 0.50. When the content ratio A / B is within the above range, clogging recovery and ejection stability tend to be improved.

[0069] 1.4.2. Acetylene glycol surfactants with an HLB value greater than 6 The ink composition of this embodiment may contain an acetylene glycol-based surfactant having an HLB value of greater than 6. By including an acetylene glycol-based surfactant having an HLB value of greater than 6 together with an acetylene glycol-based surfactant having an HLB value of 6 or less, the penetration of the ink composition into the recording medium is further improved, making it less likely that unpenetrated ink composition will remain. This prevents the unpenetrated ink composition from contaminating the transport path, causing contamination of the transport path to be transferred to another recording medium, or reducing transportability. Furthermore, using an acetylene glycol-based surfactant having an HLB value of greater than 6 in combination with an acetylene glycol-based surfactant having an HLB value of 6 or less tends to improve ejection stability. Furthermore, the presence of an acetylene glycol-based surfactant with a high HLB value is preferable because it improves the compatibility of the acetylene glycol-based surfactant with a low HLB value with water.

[0070] The HLB value of the acetylene glycol surfactant is greater than 6, preferably 7 or greater, or 8 or greater. The upper limit of the HLB value is preferably 14 or less, 13 or less, or 12 or less. When the HLB value is within the above range, phase separation tends to be less likely to occur, and ejection stability tends to be further improved. The upper and lower limits can be arbitrarily combined to form a suitable numerical range. For example, the preferred range of the HLB value of the acetylene glycol surfactant may be 7 to 14, 8 to 13, or 7 to 13.

[0071] The specific structure of the acetylene glycol surfactant having an HLB value of greater than 6 is not particularly limited, but examples include 5,8-dimethyl-6-dodecyne-5,8-diol or its alkylene oxide adduct, 4,7-dimethyl-5-decyne-4,7-diol or its alkylene oxide adduct, and alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, in which any one or each of the mole numbers of addition of the adducts is 9 or more, 10 or more, or 16 or more. Also included are compounds represented by the above formula (3) in which any one or each of the mole numbers of addition of the adducts (n, m) is 9 or more, 10 or more, or 16 or more. Acetylene glycol surfactants having an HLB value of greater than 6 may be used alone, or two or more may be used in combination.

[0072] An example of a product name of an acetylene glycol surfactant having an HLB value of more than 6 is Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0073] The content of the acetylene glycol surfactant having an HLB value of greater than 6 is preferably 0.1 to 5.0 mass%, 0.2 to 2.5 mass%, or 0.3 to 1.0 mass%, relative to the total amount of the ink composition. When the content of the acetylene glycol surfactant having an HLB value of greater than 6 is within the above range, ejection stability tends to be further improved.

[0074] The content of the acetylene glycol surfactant having an HLB value of greater than 6 is preferably 15 to 85 mass%, 20 to 80 mass%, 25 to 75 mass%, or 30 to 70 mass%, relative to the total amount of surfactants. When the content of the acetylene glycol surfactant having an HLB value of greater than 6 is within the above range, ejection stability tends to be further improved.

[0075] 1.4.3. Other surfactants The ink composition of this embodiment may or may not contain other surfactants in addition to the above-mentioned acetylene glycol-based surfactant. Examples of other surfactants include, but are not limited to, silicone-based surfactants and fluorine-based surfactants. The other surfactants may be used alone or in combination of two or more.

[0076] Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Commercially available silicone surfactants include, but are not limited to, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, and BYK-UV3500 (all trade names, manufactured by BYK Japan K.K.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0077] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkyl amine oxide compound. Commercially available fluorine-based surfactants are not particularly limited, but examples thereof include S-144, S-145 (manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, Fluorad-FC4430 (manufactured by Sumitomo 3M Limited); FSO, FSO-100, FSN, FSN-100, FS-300 (manufactured by DuPont); and FT-250, 251 (manufactured by Neos Corporation).

[0078] The content of the other surfactants relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 1.0% by mass.

[0079] 1.5.Other Ingredients In addition to the components described above, the ink composition of this embodiment may contain other known components that can be used in conventional ink compositions. Examples of such other components include, but are not limited to, solubilizers, viscosity adjusters, pH adjusters such as triethanolamine, antioxidants, preservatives, corrosion inhibitors, chelating agents for capturing specific metal ions that affect dispersion, and other additives, as well as organic solvents other than those described above. The content of such other components may be one type alone, or two or more types may be used in combination. The content of such other components relative to the total amount of the ink composition is not particularly limited, but is, for example, 0.1 to 1.0% by mass.

[0080] 1.6.Water The ink composition of this embodiment may contain water. The water is not particularly limited, but examples thereof include ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water.

[0081] The ink composition of this embodiment may be a water-based ink composition. A water-based ink composition is an ink composition in which the solvent component contained in the ink is at least primarily water.

[0082] The content of water is preferably 50 to 90% by mass, and more preferably 55 to 85% by mass, based on the total amount of the ink composition.

[0083] 2. Method for producing inkjet ink composition The ink composition of this embodiment is not particularly limited, and may be, for example, a mixture of the above components. Alternatively, a colorant dispersion liquid may be prepared by dispersing a colorant and a dispersant in a solvent, and the obtained colorant dispersion liquid may be mixed with the other above components. The solvent in which the colorant and dispersant are dispersed is not limited to water.

[0084] 3. Recording Media The recording medium used for recording with the ink composition of this embodiment is not particularly limited, but examples thereof include absorbent recording media, low absorbent recording media, and non-absorbent recording media. The ink composition of this embodiment is preferably used for recording on absorbent recording media.

[0085] Absorbent recording media are not particularly limited, but examples include plain paper such as electrophotographic paper with high ink permeability, inkjet paper (paper specifically for inkjet printers with an ink absorbing layer made of silica particles or alumina particles, or an ink absorbing layer made of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), and fabric.

[0086] The low-absorbency recording medium is not particularly limited, but examples thereof include art paper, coated paper, cast paper, and the like, which are used in general offset printing and have relatively low ink permeability.

[0087] Non-absorbent recording media are not particularly limited, but examples include films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc.; plates of metals such as iron, silver, copper, aluminum, etc.; metal plates and plastic films manufactured by vapor deposition of these various metals, and alloy plates such as stainless steel and brass; and recording media in which a plastic film such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc. is adhered (coated) to a paper substrate.

[0088] "Low-absorbency recording medium" or "non-absorbency recording medium" is defined as a medium that absorbs water in an amount of 10 mL / m2 or less within 30 msec from the start of contact in the Bristow method. 2 "Absorbent recording media" refers to recording media with a water absorption capacity of 10 mL / m 2 This refers to a recording medium that exceeds the specified limit. The Bristow method is the most widely used method for measuring liquid absorption in a short period of time, and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51 "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of the "JAPAN TAPPI Paper and Pulp Test Method 2000 Edition."

[0089] 4. Recording device The recording apparatus of this embodiment is an inkjet recording apparatus used in printing using the ink composition of this embodiment. As an example of an inkjet recording apparatus, FIG. 1 shows a perspective view of a serial printer. As shown in FIG. 1, the serial printer 20 includes a conveying unit 220 and a recording unit 230. The conveying unit 220 conveys the recording medium F fed to the serial printer to the recording unit 230 and ejects the recording medium after recording outside the serial printer. Specifically, the conveying unit 220 has feed rollers and conveys the fed recording medium F in the sub-scanning direction T2.

[0090] The recording unit 230 also includes an inkjet head 231 that ejects ink, etc. onto the recording medium F sent from the conveying unit 220, a carriage 234 that carries these, and a carriage movement mechanism 235 that moves the carriage 234 in the main scanning directions S1 and S2 of the recording medium F.

[0091] In the case of a serial printer, an inkjet head 231 having a length smaller than the width of the recording medium is provided, and the head moves to perform recording in multiple passes. In a serial printer, the head 231 is mounted on a carriage 234 that moves in a predetermined direction, and the head moves in conjunction with the movement of the carriage, thereby ejecting the ink composition onto the recording medium F. In this way, recording is performed in two or more passes. A pass is also called a main scan. A sub-scan is performed to transport the recording medium between passes. In other words, main scans and sub-scans are performed alternately.

[0092] Although not shown, the serial printer may be provided with a drying mechanism. By providing a drying mechanism, the solvent and the like can be quickly evaporated and dispersed from the ink composition applied to the recording medium, thereby enabling the rapid formation of a recorded image and the like. The drying mechanism is not particularly limited as long as it has a configuration that promotes the evaporation and dispersion of the solvent and the like contained in the ink composition. Examples of the drying mechanism include a heating mechanism that applies heat to the recording medium, a blowing mechanism that blows air onto the ink composition, and a mechanism that combines these. Examples of the drying mechanism include a forced air heater, a radiant heater, an electric conduction heater, a high-frequency dryer, and a microwave dryer.

[0093] The inkjet device of this embodiment is not limited to the serial printer, but may be a line printer, which uses a line head, an inkjet head whose length is equal to or greater than the recording width of the recording medium, to perform recording on the recording medium in a single scan.

[0094] As an example of an inkjet recording apparatus, a perspective view of a line printer is shown in Figure 2. The inkjet recording apparatus 1 performs recording on a recording medium M using an inkjet head 2. The recording medium M is transported in a sub-scanning direction SS along a recording medium transport path that supports the recording medium M from below, while an ink composition is ejected from the inkjet head 2.

[0095] The inkjet head 2 is a line head that extends in the recording medium width direction, which is the back-to-front direction in Fig. 5. In the example of Fig. 5, the inkjet recording device is equipped with an IR heater 3, a platen heater 4, a heating heater 5, a cooling fan 6, a preheater 7, and a blower fan 8. In the case of a line-type printer, for example, the inkjet head 131 is equipped with a line head that is longer than the width of the recording medium, and the head is fixed (almost) without moving, and recording is performed in one pass (single pass). A pass is also called a scan.

[0096] In a line printer, the head is fixed and does not move, and printing is performed in one pass (single pass), so line printers have an advantage over serial printers in that they have a faster printing speed.

[0097] 5. Inkjet recording method The inkjet recording method of this embodiment includes an ink deposition step of ejecting the ink composition of this embodiment from an inkjet head and depositing it on a recording medium. If necessary, the method may also include other steps, such as a transport step of transporting the recording medium.

[0098] 5.1.Ink deposition process In the ink deposition step, the ink composition of this embodiment is ejected from an inkjet head and deposited on a recording medium. More specifically, a pressure generating means provided in the inkjet head is driven to eject the ink composition filled in the pressure generating chamber of the inkjet head from the nozzle.

[0099] Inkjet heads used in the ink deposition step include line heads that perform recording by a line method and serial heads that perform recording by a serial method.

[0100] In the line method using a line head, for example, an inkjet head having a width equal to or greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved in the sub-scanning direction (the direction in which the recording medium is transported), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0101] In the serial method using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved in the main scanning direction (the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0102] 5.2.Transportation process The inkjet recording method using the ink composition of this embodiment may include a transport step. In the transport step, the recording medium is transported in a predetermined direction within the recording device. More specifically, the recording medium is transported from a paper feed section to a paper discharge section of the recording device using a transport roller or a transport belt provided within the recording device. During this transport process, the ink composition ejected from the inkjet head adheres to the recording medium, forming a recorded product. The ink adhesion step and the transport step may be performed simultaneously or alternately. [Example]

[0103] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples. Unless otherwise specified, the experiments in the examples and comparative examples were carried out at room temperature (25°C) and 1 atmosphere.

[0104] 1. Preparation of Inkjet Ink Composition The inkjet ink compositions used in each example were obtained by placing each component in a stainless steel mixing tank, mixing and stirring at room temperature, and removing impurities and foreign matter as needed by filtration, etc., so as to obtain the compositions shown in Figures 3 to 5. The numerical values ​​for each component shown in each example in the figures represent % by mass unless otherwise specified. The % by mass of colorant and resin represent the solids concentration. The components in the figures represent the following:

[0105] Self-dispersing pigment dispersion: CAB-O-JET 300 (Cabot Corporation, carboxylate-treated self-dispersing pigment) Dye: WATER BLACK 191-L (Direct Black 19, manufactured by Orient Chemical Industry Co., Ltd.) Resin particles: X-436 (Seiko PMC, styrene acrylic resin particles) Olfine E1010: manufactured by Nissin Chemical Industry Co., Ltd. Olfine D-10PG: Manufactured by Air Products Surfynol 420: Manufactured by Air Products, alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol

[0106] In the figure, polyethylene glycol monohexyl ether (degree of polymerization 4 to 8) indicates a mixture of polyethylene glycol monohexyl ethers having an ethylene glycol polymerization degree of 4 to 8, i.e., a mixture of tetraethylene glycol monohexyl ether, pentaethylene glycol monohexyl ether, hexaethylene glycol monohexyl ether, heptaethylene glycol monohexyl ether, and octaethylene glycol monohexyl ether.

[0107] The resin-dispersed pigment dispersion liquid shown in the figure was prepared by the following method. 20 parts by mass of an organic solvent (methyl ethyl ketone), 0.03 parts by mass of a polymerization chain transfer agent (2-mercaptoethanol), 15 parts by mass of polypropylene glycol monomethacrylate (propylene oxide group = 9), 15 parts by mass of poly(ethylene glycol·propylene glycol) monomethacrylate (propylene oxide group = 7, ethylene oxide group = 5), 12 parts by mass of methacrylic acid, 50 parts by mass of styrene monomer, 10 parts by mass of styrene macromer, and 10 parts by mass of benzyl methacrylate were placed in a reaction vessel that had been thoroughly purged with nitrogen gas. 0.9 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) dissolved in 40 parts by mass of methyl ethyl ketone was added to 100 parts by mass of the monomer components and the mixture was polymerized with stirring at 75°C, and the mixture was aged at 80°C for 1 hour to obtain a polymer solution.

[0108] 7.5 parts by mass of the water-insoluble polymer obtained above was dissolved in 45 parts by mass of methyl ethyl ketone, a predetermined amount of 20% aqueous sodium hydroxide solution (neutralizing agent) was added to the solution to neutralize the salt-forming groups, and 20 parts by mass of Black Pearls 880 (manufactured by Cabot Corporation) was added as a pigment and kneaded for 2 hours in a bead mill. 120 parts by mass of ion-exchanged water was added to the kneaded mixture obtained in this way and stirred, and then the methyl ethyl ketone was removed under reduced pressure at 6°C, and some of the water was further removed to obtain a resin-dispersed pigment dispersion with a solids concentration of 20% by mass.

[0109] The water-soluble acrylic resin in the figure was produced by the following method. A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 93.4 parts of butanol and purged with nitrogen gas. After heating to 110°C, a mixture of 101.5 parts of styrene, 38.5 parts of acrylic acid, 60.0 parts of maleic acid, and 6 parts of a polymerization initiator (trade name "V-601" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise over 2 hours to carry out the polymerization reaction. After reacting at 110°C for 3 hours, 0.6 parts of polymerization initiator was added, and the reaction was continued at 110°C for 1 hour to obtain a resin solution. After cooling to room temperature, 37.1 parts of dimethylaminoethanol was added to neutralize the mixture, and 100 parts of water was added. The butanol was distilled off by heating above 100°C to form an azeotrope with water, and the concentration was adjusted. This resulted in a liquid containing 20.0% acrylic resin by mass. The acid value of the acrylic resin was 440 mgKOH / g and the weight-average molecular weight was 12,000.

[0110] 2. Evaluation Method 2.1.Clogging recovery The ink compositions of each example and comparative example were filled into the inkjet head of a modified Seiko Epson inkjet printer "LX-10000F." Then, with the head cap removed from the inkjet head filled with the ink composition, the inkjet printer was left in an environment of a temperature of 40°C and a relative humidity of 20% for 7 days. After that, the inkjet head was cleaned, and the results were evaluated according to the following evaluation criteria. [Evaluation criteria] A: Head clogging can be cleared by cleaning the head six times or less. B: The head clog will be cleared after seven head cleanings. C: The head is not clogged even after cleaning the head seven times.

[0111] 2.2.Discharge stability The ink compositions of each example and comparative example were filled into the inkjet head of a modified Seiko Epson inkjet printer "LX-10000F." A test pattern was then recorded on a recording medium, Super Fine paper (manufactured by Seiko Epson) at a temperature of 32°C and a relative humidity of 20% (first recording). The inkjet head, filled with the ink composition, was then subjected to air feeding for 20 seconds at a temperature of 32°C and a relative humidity of 20%. A test pattern was then recorded on a recording medium, Nautilus Classic (manufactured by Mondi), at a temperature of 32°C and a relative humidity of 20% (second recording). The test patterns obtained by the first recording and the second recording were compared to measure the deviation in the impact position of the ink composition on the recording medium before and after air feeding, and evaluated according to the following evaluation criteria. [Evaluation criteria] A: The amount of deviation in landing position is 0 μm or more and less than 50 μm. B: The amount of deviation in landing position is 50 μm or more and less than 100 μm. C: The amount of deviation in landing position is 100 μm or more and less than 200 μm. D: The amount of deviation in landing position is 200 μm or more.

[0112] 2.3. Media compatibility (contact angle evaluation) Using a portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.), a 0.5 μL droplet of the ink composition of each example and comparative example was dropped onto a recording medium, Nautilus Classic (manufactured by Mondi), in an environment of 10°C temperature and 80% relative humidity, and the contact angle was measured 2.6 seconds after impact. [Evaluation criteria] A: The contact angle is less than 15°. B: The contact angle is 15° or more and less than 20°. C: The contact angle is 20° or more and less than 25°. D: The contact angle is 25° or more. [Explanation of symbols]

[0113] 1...line printer, 2...inkjet head, 3...IR heater, 4...platen heater, 5...heating heater, 6...cooling fan, 7...preheater, 8...blower fan, M...recording medium, SS...sub-scanning direction, 20...serial printer, 220...conveyor unit, 230...recording unit, 231...inkjet head, 234...carriage, 235...carriage movement mechanism, F...recording medium, S1, S2...main scanning direction, T2...sub-scanning direction

Claims

1. The ink contains a colorant, an acetylene glycol surfactant having an HLB value of 6 or less, and an organic solvent represented by the following formula (1): wherein the content A of the acetylene glycol surfactant having an HLB value of 6 or less relative to the total amount of the inkjet ink composition and the content B of the organic solvent represented by formula (1) relative to the total amount of the inkjet ink composition are such that the content ratio A / B is 1.00 or less, and the total content A+B is 15% by mass or less; Inkjet ink composition. 【Chemical 1】 (wherein n is an integer of 4 to 8, and R is an alkyl group having 5 to 7 carbon atoms which may have a substituent.)

2. The content ratio A / B is 0.02 to 1.

00. The ink-jet ink composition of claim 1 .

3. The total content A+B is 1 to 15% by mass. The ink-jet ink composition of claim 1 .

4. Used for recording on absorbent recording media, The ink-jet ink composition of claim 1 .

5. The colorant is a pigment or a dye. The ink-jet ink composition of claim 1 .

6. Contains polyols having a normal boiling point of 280°C or higher, The ink-jet ink composition of claim 1 .

7. an ink deposition step of ejecting the inkjet ink composition according to any one of claims 1 to 6 from an inkjet head and depositing it on a recording medium; Inkjet recording method.

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