Water-based inkjet ink composition and inkjet recording method

Abstract

Provided is a water-based inkjet ink composition and an inkjet recording method that have excellent jetting reliability. The water-based inkjet ink composition contains a colorant, a water-soluble polyurethane resin, and an acetylenic diol-based surfactant having an HLB value of 6 or less, the content A of the acetylenic diol-based surfactant being 0.1% by mass or more relative to the total mass of the inkjet ink composition, and the ratio (A / U) of the content A of the acetylenic diol-based surfactant relative to the content U of the water-soluble polyurethane resin being 0.3 to 2.3.

Description

TECHNICAL FIELD

[0001] The present application relates to an aqueous inkjet ink composition and an inkjet recording method. BACKGROUND

[0002] An inkjet recording method is capable of recording a high-fineness image by a simple device, and has been rapidly developed in various aspects. For example, in Patent Literature 1, an inkjet recording ink composition containing at least a pigment, an acetylenic diol surfactant, triethylene glycol monobutyl ether, 2-pyrrolidone, water, and a water-soluble organic solvent is disclosed for the purpose of improving the jetting stability and clogging reliability of ink droplets.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-146255

[0006] However, it is known that if an inkjet ink composition containing an acetylenic diol surfactant is dried in a nozzle, a decrease in jetting reliability such as flight bending easily occurs. SUMMARY

[0007] The inkjet ink composition of the present application is an aqueous inkjet ink composition containing a colorant, a water-soluble polyurethane resin, and an acetylenic diol surfactant having an HLB value of 6 or less, the content A of the acetylenic diol surfactant being 0.1% by mass or more relative to the total mass of the inkjet ink composition, and the ratio (A / U) of the content A of the acetylenic diol surfactant to the content U of the water-soluble polyurethane resin being 0.3 to 2.3.

[0008] The inkjet recording method of the present application includes an ink adhering step of jetting the above-described inkjet ink composition from an inkjet head and adhering it to a recording medium. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a view showing an example of a recording apparatus used in the present embodiment.

[0010] EXPLANATION OF REFERENCE NUMERALS

[0011] 20: serial printer, 220: conveyance section, 230: recording section, 231: inkjet head, 234: carriage, 235: carriage moving mechanism, F: recording medium, S1, S2: main scanning direction, T1: sub scanning direction DETAILED DESCRIPTION

[0012] Hereinafter, an embodiment of the present application (hereinafter referred to as "the present embodiment") will be described in detail, but the present application is not limited thereto, and various modifications can be made within the scope of the gist thereof.

[0013] 1. An inkjet ink composition

[0014] The water-based inkjet ink composition (hereinafter referred to as "ink composition") according to the present embodiment contains a colorant, a water-soluble polyurethane resin, and an acetylenic diol-based surfactant having an HLB value of 6 or less, the content A of the acetylenic diol-based surfactant is 0.1% by mass or more with respect to the total mass of the ink composition, and the ratio (A / U) of the content A of the acetylenic diol-based surfactant to the content U of the water-soluble polyurethane resin is 0.3 to 2.3.

[0015] According to the permeability of the ink composition to a recording medium, even in the case of an absorbent recording medium such as ordinary paper, the ink composition sometimes remains on the recording medium temporarily. If such ink composition before permeation adheres to a conveyance path such as a conveyance belt or a conveyance roller, other recording media can be contaminated. In addition, the conveyability of the recording medium can be reduced due to the adhesion of the ink composition. For example, the state of the surface of the conveyance path changes due to the adhesion of the ink composition, the friction between the recording medium and the conveyance path, or the like changes, and the conveyability can be reduced. In addition, if a part of the conveyance path is an electrostatic adsorption belt, the resistance value of the electrostatic adsorption belt of the conveyance path decreases due to the adhesion of the ink composition, the adsorbability of the recording medium decreases, and the conveyability can be reduced.

[0016] Therefore, in order to improve the permeability of the ink composition to a recording medium, it can be considered to use an acetylenic diol-based surfactant having a low HLB value. Thereby, the permeability of the ink composition to a recording medium is further improved, and thus the unpermeated ink composition can be suppressed from being transferred to other parts. However, it is known that by using an acetylenic diol-based surfactant having a low HLB value, flight bending, scattering, or the like occurs, and the ejection reliability decreases. In particular, when the ink in the nozzle is dried due to the fact that the inkjet head is left as it is or left for a long time without being capped, the ejection reliability easily decreases.

[0017] The cause of such decrease in ejection reliability can be considered to be the phase separation of the acetylenic diol-based surfactant from water due to the occurrence of drying of the ink. In particular, the acetylenic diol-based surfactant having a low HLB value, although excellent in permeability, has high hydrophobicity and low solubility in water, and thus the above phase separation easily occurs. However, the cause of the decrease in ejection reliability is not limited thereto.

[0018] Thus, in the present embodiment, by using a low HLB value acetylenic diol surfactant and a water-soluble polyurethane resin in a prescribed ratio, the penetration is improved while the decrease in jetting reliability is suppressed. The factor that suppresses the decrease in jetting reliability caused by the water-soluble polyurethane resin can be considered to be that the water-soluble polyurethane resin absorbs or includes the acetylenic diol surfactant at the time of drying of the ink composition or the like, and thus the occurrence of phase separation is suppressed. However, the factor that suppresses the decrease in jetting reliability is not limited to this.

[0019] Further, depending on the kind of the resin component, sometimes foreign matter occurs at the gas-liquid interface where the ink composition comes into contact with a gas, and causes jetting failure. However, the water-soluble polyurethane resin is less likely to cause such foreign matter on the gas-liquid interface.

[0020] Hereinafter, each component of the ink composition of the present embodiment will be described in detail.

[0021] 1.1. Colorant

[0022] The colorant is not particularly limited, and for example, dyes, pigments, and the like can be given, and among them, from the viewpoint of the width of the recording medium that can be used, the property of not being easily faded by light, a gas, or the like, and the like, it is preferable to use a pigment.

[0023] The pigment is not particularly limited, and for example, organic pigments such as azo pigments (for example, including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, and the like), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, and the like), nitro pigments, nitroso pigments, aniline black, and the like; inorganic pigments such as carbon black (for example, furnace black, thermal lamp black, acetylene black, channel black, and the like), metal oxides, metal sulfides, metal chlorides, and the like; and extender pigments such as silica, calcium carbonate, talc, and the like can be given. One kind of pigment can be used alone, or two or more kinds of pigments can be used in combination.

[0024] The pigment is not particularly limited, and for example, resin-dispersed pigments in which a dispersant resin is covered, or self-dispersed pigments in which a dispersant resin is not used, and the like can be given.

[0025] The resin-dispersed pigment is a pigment dispersed with a resin. The resin used for the dispersion of the pigment is also referred to as a dispersant resin. The dispersant resin refers to a resin used for covering the surface of the pigment in order to improve the water dispersibility of the pigment. The resin-dispersed pigment is a pigment in which the dispersant resin is adsorbed, attached, or covered to the pigment or the like. As the dispersant resin, a water-soluble resin, a water-insoluble resin, or the like can be used. The resin-dispersed pigment can be produced, for example, by a method in which the dispersant resin and the pigment are stirred and dispersed in water, a method in which the dispersant resin and the pigment are stirred and dispersed in an organic solvent, and then transferred and emulsified in a water layer, or the like.

[0026] The self-dispersible pigment is a pigment in which a functional group for improving water dispersibility of the pigment is directly or indirectly introduced to the surface of the pigment by chemical bonding. The functional group is a hydrophilic group, preferably an acidic group. As the hydrophilic group, for example, a carboxyl group, a sulfonic group, a phosphoric acid group, and the like can be given.

[0027] The pigment more preferably contains any one or more of a self-dispersible pigment and a resin-dispersible pigment. Here, in the case where a dispersant resin or other dispersant is used, one can be used alone, or two or more can be used in combination.

[0028] In addition, in the present embodiment, the "dispersant resin" refers to a resin that disperses a pigment, and is also called a resin dispersant. Thus, it is different from a dispersant resin, a resin particle, a resin emulsion, and a resin for fixing purposes that are not used as a dispersant for a pigment in this point.

[0029] The content of the colorant is preferably 1.0 to 14 mass%, 2.0 to 12 mass%, 4.0 to 10 mass%, or 6.0 to 8.0 mass% with respect to the total amount of the ink composition.

[0030] 1.2. Acetylenic diol-based surfactant

[0031] 1.2.1. Acetylenic diol-based surfactant having an HLB value of 6 or less

[0032] By containing the acetylenic diol-based surfactant having an HLB value of 6 or less, the permeability of the ink composition to the recording medium is further improved, and the unpermeated ink composition becomes less likely to remain. Thus, it is possible to suppress contamination of the transport path by the unpermeated ink composition, transfer of dirt of the transport path to other recording media, or reduction in transportability.

[0033] The HLB value of the above-described acetylenic diol-based surfactant is 6 or less, preferably 5 or less, 4 or less. By having an HLB value of 6 or less, there is a tendency that the permeability of the ink composition is further improved. In addition, the lower limit of the HLB value is preferably 0 or more, 1 or more, 2 or more. By having the lower limit of the HLB value in the above-described range, phase separation is less likely to occur, and there is a tendency that the ejection reliability is further improved. Here, the HLB value is a value indicating the balance between the hydrophobicity and the hydrophilicity of the surfactant, and the smaller the HLB value, the more hydrophobic it is, and the larger the HLB value, the more hydrophilic it is. In the present invention, the HLB value is calculated by the Griffin method as in the method of the examples described later.

[0034] As the acetylenic diol surfactant having an HLB value of 6 or less, there is no particular limitation, and for example, an acetylenic diol represented by the following formula (1) and an alkylene oxide adduct of an acetylenic diol represented by the following formula (2) can be given. Among them, the acetylenic diol represented by formula (1) is preferred. By using such an acetylenic diol surfactant, there is a tendency that the permeability is further improved.

[0035] [Chemical Formula 1]

[0036]

[0037] (R 1 ~R 4 each independently represents an alkyl group having 1 to 4 carbon atoms

[0038] [Chemical Formula 2]

[0039]

[0040] (R 1 ~R 4 each independently represents an alkyl group having 1 to 4 carbon atoms, m, n each independently represents an integer of 1 or more, and satisfies m + n = 1 to 30

[0041] m is preferably 1 to 15, 1 to 10, 1 to 5. n is preferably 1 to 15, 1 to 10, 1 to 5.

[0042] R 1 ~R 4 There is no particular limitation, and for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl can be given.

[0043] As the specific structure of the acetylenic diol surfactant having an HLB value of 6 or less, a compound represented by formula (1), a compound represented by formula (2) can be given, and as the compound represented by formula (2), n, m are each preferably 15 or less, 9 or less, 8 or less, in the above range. There is no particular limitation, and for example, 2,4,7,9-tetramethyl-5-decyn-4,7-diol or an alkylene oxide adduct thereof can be given, and the addition mole number (n, m) of the adduct is each 15 or less, 9 or less, 8 or less, in the above range.

[0044] The content A of the acetylenic diol-based surfactant having an HLB value of 6 or less is preferably 0.1% by mass or more, 0.2% by mass or more, 0.25% by mass or more, relative to the total amount of the ink composition. By the content A of the acetylenic diol-based surfactant having an HLB value of 6 or less being 0.1% by mass or more, there is a tendency for the permeability to improve and for the transfer evaluation to become good. Furthermore, the content A of the acetylenic diol-based surfactant having an HLB value of 6 or less is preferably 1.0% by mass or less, 0.8% by mass or less, 0.6% by mass or less, 0.4% by mass or less, relative to the total amount of the ink composition. By the content A of the acetylenic diol-based surfactant having an HLB value of 6 or less being within the above range, there is a tendency for the ejection reliability to further improve.

[0045] The ratio (A / U) of the content A of the acetylenic diol-based surfactant to the content U of the water-soluble polyurethane resin described later is 0.3 to 2.3, preferably 0.5 to 2.1, 0.7 to 1.9, 0.9 to 1.7, 1.0 to 1.5. By the ratio (A / U) being 0.3 or more, there is a tendency for the permeability to further improve and for the transfer to be further suppressed. By the ratio (A / U) being 2.3 or less, there is a tendency for the ejection stability to further improve.

[0046] 1.2.2. Acetylenic diol-based surfactant having an HLB value greater than 6

[0047] The ink composition of the present embodiment can also include an acetylenic diol-based surfactant having an HLB value greater than 6. By including an acetylenic diol-based surfactant having an HLB value greater than 6 together with an acetylenic diol-based surfactant having an HLB value of 6 or less, the permeability of the ink composition into the recording medium further improves and the ink composition that does not permeate becomes less likely to remain. As a result, it is possible to prevent the ink composition that does not permeate from contaminating the conveyance path, the dirt of the conveyance path from being transferred to other recording media, or the conveyability from decreasing. Furthermore, by using an acetylenic diol-based surfactant having an HLB value greater than 6 in combination with an acetylenic diol-based surfactant having an HLB value of 6 or less, it is possible to simultaneously improve the permeability and the ejection reliability. Furthermore, by the presence of an acetylenic diol-based surfactant having a large HLB value, the compatibility of the acetylenic diol-based surfactant having a small HLB value with water improves, and thus it is preferable.

[0048] The HLB value of the above-described acetylenic diol-based surfactant is greater than 6, and is preferably 7 or more, 8 or more. By the lower limit of the HLB value being within the above range, there is a tendency for phase separation to be less likely to occur and for the ejection reliability to further improve. Furthermore, the upper limit of the HLB value is preferably 14 or less, 13 or less, 12 or less. By the upper limit of the HLB value being within the above range, there is a tendency for the permeability of the ink composition to further improve.

[0049] The specific structure of the acetylenic diol-based surfactant having an HLB value of more than 6 is not particularly limited, and examples thereof include 5,8-dimethyl-6-dodecyne-5,8-diol or an alkylene oxide adduct thereof, 4,7-dimethyl-5-decyne-4,7-diol or an alkylene oxide adduct thereof, and an alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, each of which has an addition mole number of 9 or more, 10 or more, or 16 or more, or each of which has an addition mole number of 9 or more, 10 or more, and 16 or more. In the compound represented by the above formula (2), each of the addition mole numbers (n, m) of the adducts can be 9 or more, 10 or more, or 16 or more, or each of the addition mole numbers of the adducts can be 9 or more, 10 or more, and 16 or more.

[0050] The content of the acetylenic diol-based surfactant having an HLB value of more than 6 is preferably 1% by mass or less, 0.8% by mass or less, or 0.5% by mass or less, relative to the total amount of the ink composition. By setting the content of the acetylenic diol-based surfactant having an HLB value of more than 6 within the above range, the tendency to improve the permeability and to make the transfer evaluation good is exhibited. In addition, the content of the acetylenic diol-based surfactant having an HLB value of more than 6 is preferably 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more, relative to the total amount of the ink composition. By setting the content of the acetylenic diol-based surfactant having an HLB value of more than 6 within the above range, the tendency to further improve the ejection reliability is exhibited.

[0051] In addition, the total content of the acetylenic diol-based surfactant having an HLB value of 6 or less and the acetylenic diol-based surfactant having an HLB value of more than 6 is 0.1% by mass or more, preferably 0.1 to 2.0% by mass, 0.4 to 1.0% by mass, or 0.5 to 0.8% by mass, relative to the total amount of the ink composition.

[0052] 1.3. Water-soluble polyurethane resin

[0053] The water-soluble polyurethane resin refers to a polyurethane resin having a polar group in the structure and being water-soluble. The polar group can also be in the state of a salt. In addition, the polar group is preferably an acidic group (acidic group). The acidic group can be exemplified by a carboxyl group, a sulfonic acid group, and a phosphorus-containing group such as a phosphoric acid group. In addition, the "water-soluble resin" in the present application refers to a resin that is dissolved in water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent, and in particular, is dissolved in water, and can exist in water or the aqueous medium without having a particle diameter when measured by a dynamic light scattering method.

[0054] As described above, the acetylenic diol-based surfactant having an HLB value of 6 or less improves the permeability, but has low solubility in water and the like. Therefore, when drying of the ink composition occurs, there is a tendency to separate from water and to reduce the ejection reliability. However, by using such an acetylenic diol-based surfactant and a water-soluble polyurethane resin in combination, there is a tendency to suppress the above phase separation and to have excellent ejection reliability.

[0055] The water-soluble polyurethane resin has repeating units from a polyisocyanate and a polyol, but among them, a resin having repeating units from a polyol having an acidic group is preferable, and a resin having repeating units from each of a polyisocyanate, a polyol not having an acidic group, and a polyol having an acidic group is preferable. The water-soluble polyurethane resin can also have repeating units from a polyamine.

[0056] The polyisocyanate refers to a compound having two or more isocyanate groups in its molecular structure, and is not particularly limited, and examples thereof include aliphatic polyisocyanates, aromatic polyisocyanates, and the like.

[0057] As the aliphatic polyisocyanate, there is no particular limitation, and examples thereof include polyisocyanates having a chain structure such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, and the like; polyisocyanates having a cyclic structure such as isophorone diisocyanate, hydrogenated xylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and the like.

[0058] As the aromatic polyisocyanate, there is no particular limitation, and examples thereof include toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyl diphenylmethane diisocyanate, tetraalkyl diphenylmethane diisocyanate, α,α,α',α'-tetramethyl xylene diisocyanate, and the like.

[0059] The polyol refers to a compound having two or more hydroxyl groups in its molecular structure. As the polyol of the present embodiment, there is no particular limitation, and examples thereof include a polyol not having an acidic group and a polyol having an acidic group.

[0060] As the polyol having an acidic group, there is no particular limitation, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, and the like.

[0061] As the polyether polyol, there is no particular limitation, and examples thereof include addition polymers of alkylene oxides and polyols, diols, and the like.

[0062] As the alkylene oxide, there is no particular limitation, and examples thereof include ethylene oxide, propylene oxide, butylene oxide, α-olefin oxide, and the like. As the polyol to be added to the alkylene oxide, there are no particular limitations, and examples thereof include diols such as 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4-dihydroxyphenylpropane, 4,4-dihydroxyphenylmethane, hydrogenated bisphenol A, dimethylol urea, and derivatives thereof; triols such as glycerol, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, trimethylol melamine, and derivatives thereof; and polyoxypropylene triol; and the like.

[0063] As the diol, there are no particular limitations, and examples thereof include (poly)alkylene glycols such as tetramethylene glycol, hexamethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, (poly)tetramethylene glycol, and the like; ethylene glycol-propylene glycol copolymer; and the like.

[0064] As the polyester polyol, there are no particular limitations, and examples thereof include acid esters and the like. As the acid component of the acid ester, there are no particular limitations, and examples thereof include aromatic dicarboxylic acids such as phthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, tetrahydrophthalic acid, and the like; alicyclic dicarboxylic acids such as hydrogenated products of these aromatic dicarboxylic acids; aliphatic dicarboxylic acids such as malonic acid, succinic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkyl succinic acid, linolenic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, and the like; and the like. These acid anhydrides, salts, derivatives (alkyl esters, acid halides), and the like can also be used as the acid component. Furthermore, as the component to form an ester with the acid component, there are no particular limitations, and examples thereof include polyols such as diols and triols; diols such as (poly)alkylene glycols; and the like. As the polyols and diols, there are no particular limitations, and examples thereof include the substances exemplified as the components of the above-described polyether polyols and the like.

[0065] As the polycarbonate polyol, there are no particular limitations, and examples thereof include polycarbonate polyols manufactured by publicly known methods, and specifically, examples thereof include alkane diol-based polycarbonate diols such as polyhexamethylene carbonate diol and the like. Furthermore, examples thereof include polycarbonate diols obtained by reacting a carbonate component such as an alkylene carbonate, a diaryl carbonate, a dialkyl carbonate, or phosgene with an aliphatic diol component, and the like.

[0066] As the polyol having an acidic group, there are no particular limitations, and examples thereof include polyols having an acidic group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and the like. Among these, one or more of a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group, and the like, that is, a phosphorus-containing group is preferable, and a carboxylic acid group is more preferable.

[0067] As the polyol having a carboxylic acid group, there is no particular limitation, and examples that can be given include dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutyric acid, and the like.

[0068] The acidic group of the polyol having an acidic group can also be in a salt state. As the cation forming such a salt, there is no particular limitation, and examples that can be given include alkali metal ions, cations of organic amines, and the like. As the alkali metal ion, there is no particular limitation, and examples that can be given include lithium, sodium, potassium, and the like. As the cation of the organic amine, there is no particular limitation, and examples that can be given include ammonium ions, dimethylamine, and the like.

[0069] As the polyamine, there is no particular limitation, and examples that can be given include monoamines having multiple hydroxyl groups such as dimethylol ethylamine, diethanol methylamine, dipropanol ethylamine, dibutanol methylamine, and the like; difunctional polyamines such as ethylenediamine, propylenediamine, hexylenediamine, isophorone diamine, xylylenediamine, diphenylmethane diamine, hydrogenated diphenylmethane diamine, hydrazine, and the like; and polyamines having three or more functions such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyamide polyamine, polyethylene polyimine, and the like.

[0070] The acid value of the water-soluble polyurethane resin is preferably 40 to 90 mgKOH / g, 45 to 80 mgKOH / g, 50 to 70 mgKOH / g. The acid value of the water-soluble polyurethane resin is not particularly limited, and for example, can be adjusted by the amount of use of the polyol having an acidic group. Furthermore, as the method of measuring the acid value, the method of the Examples described later can be used.

[0071] The weight average molecular weight Mw of the water-soluble polyurethane resin is preferably 5000 to 150000, 10000 to 100000, 15000 to 50000, 20000 to 30000, 20000 to 23000. The weight average molecular weight Mw of the water-soluble polyurethane resin is not particularly limited, and for example, can be adjusted by the reaction temperature, reaction time, and the like of the polyisocyanate and the polyol. Furthermore, as the method of measuring the weight average molecular weight Mw, the method of the Examples described later can be used.

[0072] The number average molecular weight Mn of the water-soluble polyurethane resin is preferably 2000 to 7000, 3500 to 5000. The number average molecular weight Mn of the water-soluble polyurethane resin is not particularly limited, and for example, can be adjusted by the reaction temperature, reaction time, and the like of the polyisocyanate and the polyol. Furthermore, as the method of measuring the number average molecular weight Mn, the method of the Examples described later can be used.

[0073] The content U of the water-soluble polyurethane resin with respect to the total amount of the ink composition is preferably 0.05 to 0.9 mass%, 0.1 to 0.8 mass%, 0.2 to 0.7 mass%. By the content U of the water-soluble polyurethane resin being within the above range, there is a tendency for the jetting reliability to be further improved.

[0074] 1.4. Dispersion resin

[0075] The ink composition of the present embodiment can contain a dispersion resin, and can not contain a dispersion resin. The dispersion resin refers to a resin for improving the fixing property of the ink composition to a recording medium, and is distinguished from a resin dispersant. The dispersion resin can be in a dispersion form, a particle form, or an emulsion form.

[0076] As the dispersion resin, there is no particular limitation, and for example, resin particles composed of a polyurethane-based resin, an acrylic-based resin, a fluorene-based resin, a polyolefin-based resin, a rosin-modified resin, a terpene-based resin, a polyester-based resin, a polyamide-based resin, an epoxy-based resin, a vinyl chloride-based resin, or an ethylene-vinyl acetate-based resin, or the like can be given. The dispersion resin can be used alone or in combination of two or more.

[0077] The polyurethane-based resin is a general term for resins having urethane bonds, and is not particularly limited, and for example, a polyether polyurethane resin having an ether bond in the main chain, a polyester polyurethane resin having an ester bond in the main chain, and a polycarbonate polyurethane resin having a carbonate bond in the main chain can be given. As the polyurethane-based resin, a product prepared by a known method can be used, and a commercially available product can also be used.

[0078] The acrylic-based resin is a general term for polymers obtained by polymerization of at least one component of an acrylic monomer such as (meth)acrylic acid or (meth)acrylate. As the acrylic-based resin, there is no particular limitation, and for example, a resin obtained by polymerization of a (meth)acrylic monomer such as (meth)acrylic acid or (meth)acrylate, or a resin obtained by copolymerization of a (meth)acrylic monomer with another monomer such as a styrene-acrylic acid resin can be given. As the acrylic-based resin, a product prepared by a known method can be used, and a commercially available product can also be used.

[0079] In the case where the dispersion resin is contained or in the case where the dispersion resin is not contained, the content of the dispersion resin with respect to the total amount of the ink composition is preferably 0.4% by mass or less, 0.2% by mass or less, less than 0.2% by mass, 0.15% by mass or less, or 0.1% by mass or less. Furthermore, the dispersion resin can not be contained in the ink composition. By the content of the dispersion resin being 0.4% by mass or less, the tendency to further suppress foreign matter at the gas-liquid interface is exhibited.

[0080] In addition, in the recording device, as a site where the gas-liquid interface is generated, there is no particular limitation, and for example, a component such as an ink container or a sub tank of a non-pack type or the like that forms an air layer and an ink layer can be given. Furthermore, in addition to the ink container or the like, a filter, a valve, or the like disposed in an ink flow path from the ink flow path to the inkjet head can also be a site where the gas-liquid interface is generated.

[0081] 1.5. Inorganic oxide particles

[0082] The ink composition of the present embodiment preferably contains inorganic oxide particles. The inorganic oxide particles refer to microparticles of inorganic oxides, and are in a state of being dispersed in a dispersion medium.

[0083] By the ink composition containing inorganic oxide particles, there is a tendency to have excellent curl resistance and color development.

[0084] As the inorganic oxide particles, there is no particular limitation, and for example, metal oxides such as silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, antimony oxide, tin oxide, tantalum oxide, zinc oxide, cerium oxide, lead oxide, and indium oxide; metal nitrides such as silicon nitride, titanium nitride, and aluminum nitride; metal carbides such as silicon carbide and titanium carbide; metal sulfides such as zinc sulfide; carbonates of metals such as calcium carbonate and magnesium carbonate; sulfates of metals such as calcium sulfate and magnesium sulfate; silicates of metals such as calcium silicate and magnesium silicate; phosphates of metals such as calcium phosphate; borates of metals such as aluminum borate and magnesium borate; and complexes thereof can be given. The inorganic oxide particles can also be particles of a salt. Furthermore, one kind of inorganic oxide particles can be used alone, or two or more kinds thereof can be used in combination.

[0085] Among them, from the viewpoint of improving curl resistance and color development, it is preferable to contain one or more of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium oxide, and it is more preferable to contain silicon dioxide.

[0086] The average particle diameter of the inorganic oxide particles is preferably 100 nm or less, 20 to 100 nm, 30 to 80 nm, or 40 to 60 nm. By the average particle diameter of the inorganic oxide particles being in the above range, there is a tendency to have excellent curl resistance, color development, and ejection reliability.

[0087] In addition, the average particle diameter of the inorganic oxide particles can be measured by a particle size distribution measuring device using a dynamic light scattering method as the measurement principle. As such a particle size distribution measuring device, there is no particular limitation, and for example, "Zeta Potential / Particle Size / Molecular Weight Measuring System ELSZ2000ZS" (trade name) manufactured by Otsuka Electronics Co., Ltd. using a homodyne optical system as a frequency analysis method can be given. In addition, the above average particle diameter refers to the average particle diameter on a number basis.

[0088] The content of the inorganic oxide particles is preferably 0.1 to 8.0% by mass, 0.5 to 6.0% by mass, 1.0 to 5.0% by mass, or 2.0 to 4.0% by mass of the total amount of the ink composition based on the mass of the solid content. By the content of the inorganic oxide particles being in the above range, there is a tendency to have excellent curl resistance and color development.

[0089] 1.6. Organic solvent

[0090] The ink composition of the present embodiment can also contain an organic solvent. As the organic solvent, there is no particular limitation, and for example, monohydric alcohols, polyhydric alcohols, and glycol ethers, and the like can be given. Among them, polyhydric alcohols are more preferable, and further preferably, polyhydric alcohols having a standard boiling point exceeding 280°C are contained. Thereby, there is a tendency that the jetting reliability is further improved. The organic solvent can be used singly, or two or more kinds can be used in combination.

[0091] As the monohydric alcohol, there is no particular limitation, and for example, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutyl alcohol, and 2-methyl-2-propanol, and the like can be given.

[0092] As the polyhydric alcohol, there is no particular limitation, and for example, 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, glycerol, and the like can be given.

[0093] As the glycol ether, there is no particular limitation, and for example, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monopropyl ether, and the like can be given.

[0094] As the polyhydric alcohol having a standard boiling point exceeding 280°C among the polyhydric alcohols, there is no particular limitation, and for example, triethylene glycol, tetraethylene glycol, and glycerol, and the like can be given.

[0095] Further, as the polyhydric alcohol having a standard boiling point of 280°C or less, there is no particular limitation, and for example, 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, 1,6-hexanediol, and the like can be given.

[0096] The content of the organic solvent with respect to the total amount of the ink composition is preferably 5 to 35% by mass, 8 to 30% by mass, 10 to 26% by mass, 12 to 22% by mass, 14 to 18% by mass.

[0097] The content of the polyhydric alcohol having a standard boiling point exceeding 280°C with respect to the total amount of the ink composition is preferably 7 to 19% by mass, 9 to 17% by mass, 11 to 15% by mass. By the content of the polyhydric alcohol having a standard boiling point exceeding 280°C being within the above range, there is a tendency that the jetting reliability is further improved.

[0098] 1.7. Water

[0099] The water contained in the ink composition of the present embodiment is not particularly limited, and examples thereof include ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water.

[0100] The content of the water is preferably 65 to 85% by mass, 67.5 to 82.5% by mass, 70 to 80% by mass, or 72.5 to 77.5% by mass, relative to the total amount of the ink composition.

[0101] 1.8. Other Components

[0102] The ink composition of the present embodiment can contain other components known to be used in conventional ink compositions, in addition to the above-described components. The other components are not particularly limited, and examples thereof include dissolution aids, viscosity regulators, pH regulators, antioxidants, preservatives, corrosion inhibitors, and chelating agents for capturing specified metal ions that affect dispersion, other additives, and organic solvents other than the above-described ones. The other components can be used singly or in combination of two or more.

[0103] 2. Recording Medium

[0104] The recording medium used for recording the ink composition of the present embodiment is not particularly limited, and examples thereof include absorbent recording media, low-absorbent recording media, and non-absorbent recording media. Among them, the ink composition of the present embodiment is preferably used for recording to an absorbent recording medium.

[0105] The absorbent recording medium is not particularly limited, and examples thereof include ordinary paper such as electrophotographic paper having high permeability to ink, inkjet paper (inkjet-specific paper provided with an ink-absorbing layer composed of silica particles or alumina particles, or an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), and cloth.

[0106] The low-absorbent recording medium is not particularly limited, and examples thereof include art paper, copper plate paper, and cast-coated paper, which are used in general offset printing and have relatively low permeability to ink.

[0107] As the non-absorbing recording medium, there is no particular limitation, and for example, a film or a plate of plastic such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, or the like; a plate of metal such as iron, silver, copper, aluminum, or the like; or a film of metal or plastic, a plate of alloy such as stainless steel or brass, which is manufactured by vapor deposition of these various metals; a recording medium in which a film of plastic such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, or the like is adhered (coated) to a paper substrate, or the like can be exemplified.

[0108] 3. Inkjet recording method

[0109] The inkjet recording method of the present embodiment has an ink adhering step of ejecting the inkjet ink composition from the inkjet head and adhering it to the recording medium. Prior to the ink adhering step, a supplying step of supplying the inkjet ink composition from the ink container to the inkjet head via the ink flow path can also be provided.

[0110] 3.1. Supplying step

[0111] In the supplying step, the ink composition of the present embodiment is supplied from the ink container to the inkjet head via the ink flow path. In the supplying step, an air-liquid interface can be generated in the ink composition, but the ink composition of the present embodiment has a tendency that problems such as filter clogging caused by foreign matter generated at the air-liquid interface are less likely to occur by containing the water-soluble polyurethane resin.

[0112] The above-described air-liquid interface can be generated at a place where the ink composition exists in the printer. For example, the air-liquid interface is generated in the ink container, the sub tank, or the like. In addition, a small air-liquid interface is also generated in the filter, the valve, or the like.

[0113] 3.2. Ink adhering step

[0114] In the ink adhering step, the ink composition of the present embodiment is ejected from the inkjet head and adhered to the recording medium. More specifically, a pressure generating unit provided in the inkjet head is driven, and the ink composition filled in a pressure generating chamber of the inkjet head is ejected from a nozzle.

[0115] As the inkjet head used in the ink adhering step, a line head that performs recording by a line method and a serial head that performs recording by a serial method can be exemplified.

[0116] In the line method using the line head, for example, an inkjet head having a width of the recording width of the recording medium or more is fixed to a recording device. Then, the recording medium is moved in a sub-scanning direction (a conveying direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with the movement, whereby an image is recorded on the recording medium.

[0117] In a serial system using a serial head, for example, an inkjet head is mounted on a carriage that is able to move in the width direction of a recording medium. Then, the carriage is caused to move 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, whereby an image is recorded on the recording medium.

[0118] 4. Recording apparatus

[0119] As an example of an inkjet apparatus, Figure 1 A perspective view of a serial printer is shown. As Figure 1 indicated, the serial printer 20 is provided with a conveyance section 220 and a recording section 230. The conveyance section 220 conveys a recording medium F supplied to the serial printer to the recording section 230, and discharges the recorded recording medium to the outside of the serial printer. Specifically, the conveyance section 220 has conveyance rollers that convey the recording medium F conveyed to the sub scanning direction T2.

[0120] Further, the recording section 230 is provided with a carriage 234 that mounts an inkjet head 231 having nozzles that eject an ink composition onto the recording medium F conveyed from the conveyance section 220, and a carriage movement mechanism 235 that moves the carriage 234 in the main scanning direction S1, S2 of the recording medium F.

[0121] In the case of a serial printer, the inkjet head 231 is provided with a head portion having a length that is smaller than the width of the recording medium, and the head portion is moved to record in multiple passes. Further, in the serial printer, the carriage 234 that moves in a prescribed direction mounts the inkjet head 231, and the head portion moves in conjunction with the movement of the carriage, whereby the ink composition is ejected onto the recording medium F. Thus, recording is performed in two or more passes. The pass is also referred to as the main scan. The sub scan in which the recording medium is conveyed is performed between passes. That is, the main scan and the sub scan are alternately performed.

[0122] Further, the inkjet apparatus of the present embodiment is not limited to the serial system printer described above, and can also be a line system printer described above. The line system printer uses a line head that is an inkjet head having a length that is equal to or greater than the recording width of the recording medium, and is a printer that records on the recording medium in one scan.

[0123] The inkjet apparatus of the present embodiment is particularly useful in terms of reducing the tendency of the recording medium to become dirty, particularly in the case where the recording speed is fast (the number of sheets of the recording medium recorded per unit time is large), the number of sheets of the recording medium stacked after recording increases, and there is no time for the ink to penetrate into the recording medium. As an example of an inkjet apparatus in which the recording speed is fast, a line system printer or the like can be given.

[0124] Example

[0125] The present application will be described more specifically below using examples and comparative examples. The present application is not limited by the examples below.

[0126] 1. Preparation of inkjet ink composition

[0127] Each component was added to a mixture tank, mixed and stirred, and further filtered with a membrane filter, to thereby obtain the inkjet ink composition of the examples and comparative examples, in the composition as described in Tables 1-2. In addition, the values of each component shown in the tables represent mass % unless otherwise specified. Furthermore, the content (mass %) of the colorant, the dispersing resin, the water-soluble resin, and the inorganic oxide particles in Tables 1-2 represents the solid content concentration.

[0128] [Table 1]

[0129] Table 1

[0130]

[0131] [Table 2]

[0132] Table 3

[0133]

[0134] The materials shown in Tables 1-2 are described below.

[0135] <colorant>

[0136] • CAB-O-JET 300 (manufactured by Cabot Corporation, self-dispersible pigment, solid content 15%)

[0137] <dispersing resin>

[0138] • Dispersing resin 1: "Vinyblan 2586" (manufactured by Shin-Etsu Chemical Co., Ltd., acrylic resin emulsion)

[0139] • Dispersing resin 2: "Superflex 420" (manufactured by DKS Co., Ltd., polyurethane resin emulsion)

[0140] <water-soluble resin>

[0141] • Water-soluble polyurethane resin 1:

[0142] The water-soluble polyurethane resin 1 was prepared by the following method.

[0143] First, a four-necked flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube was prepared. To the four-necked flask, 41.7 parts by weight of isophorone diisocyanate, 40.1 parts by weight of polypropylene glycol (number average molecular weight: 2,000), 13.2 parts by weight of dimethylolpropionic acid, and 200.0 parts by weight of methyl ethyl ketone were added, and the mixture was reacted at 80°C for 6 hours under a nitrogen gas atmosphere (primary reaction). Next, 0.6 parts by weight of ethylenediamine, 2.0 parts by weight of methanol, 2.4 parts by weight of dimethylolpropionic acid, and 100.0 parts by weight of methyl ethyl ketone were added. The residual rate of isocyanate groups was confirmed by FT-IR, and the mixture was reacted at 80°C until the desired residual rate was obtained (secondary reaction) to obtain a reaction liquid. After the obtained reaction liquid was cooled to 40°C, ion-exchanged water was added, and an aqueous potassium hydroxide solution was added while stirring at high speed with a homogenizer. Methyl ethyl ketone was removed from the obtained liquid by heating and distillation under reduced pressure to obtain a liquid containing a water-soluble polyurethane resin 1.

[0144] The acid value of the obtained water-soluble polyurethane resin 1 was measured by potentiometric titration using a potassium hydroxide-methanol titrant, and the result was 65 mgKOH / g.

[0145] In addition, the number average molecular weight was a value measured by gel permeation chromatography (GPC).

[0146] Further, the weight average molecular weight of the polyurethane resin, which was measured by gel permeation chromatography (GPC), was 21000 in terms of polystyrene for the obtained water-soluble polyurethane resin 1.

[0147] • Water-soluble polyurethane resin 2:

[0148] In the preparation of the above water-soluble polyurethane resin 1, a water-soluble polyurethane resin 2 was prepared by the same preparation method as that of the water-soluble polyurethane resin 1, except that the amount of addition of polypropylene glycol was reduced and the amount of addition of dimethylolpropionic acid in the above primary reaction and secondary reaction was increased. Further, the acid value and the weight average molecular weight were measured by the same measurement method as that of the water-soluble polyurethane resin 1, and the result was that the acid value of the water-soluble polyurethane resin 2 was 75 mgKOH / g and the weight average molecular weight was 21000.

[0149] • Water-soluble acrylic resin

[0150] The water-soluble acrylic resin was prepared by the following method.

[0151] A four-necked flask equipped with a stirrer, a thermometer, a reflux cooler, and a nitrogen inlet tube was prepared. Into the flask, 200.0 parts by weight of ethylene glycol monobutyl ether was charged, and the mixture was stirred under a nitrogen atmosphere and warmed to 130°C. While the mixture was being stirred, 62.0 parts by weight of styrene monomer, 22.0 parts by weight of butyl acrylate, 16.0 parts by weight of acrylic acid, and 4.0 parts of a polymerization initiator (t-butyl hydroperoxide) were added dropwise over 3 hours. After the mixture was aged for 2 hours, the ethylene glycol monobutyl ether was distilled off under reduced pressure to obtain a water-soluble acrylic resin.

[0152] <Inorganic oxide particles>

[0153] • "Cataloid SI-45P" (manufactured by Nippon Shokubai Co., Ltd., silica particle dispersion sol, average particle diameter 45 nm)

[0154] <Alkynediol surfactant>

[0155] • "Olfine E1010": manufactured by DKS Co., Ltd.

[0156] • "Surfynol 104PG50": manufactured by Air Products Japan, Inc., 2,4,7,9-tetramethyl-5-decyne-4,7-diol

[0157] • "Surfynol 420": manufactured by Air Products Japan, Inc., alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol

[0158] <Organic solvent>

[0159] • Glycerin

[0160] • Triethylene glycol (expressed as TEG in the table)

[0161] • Triethylene glycol monobutyl ether (expressed as TEGmBE in the table)

[0162] • Triethylene glycol monomethyl ether (expressed as TEGmME in the table)

[0163] <Water>

[0164] • Ion exchange water

[0165] The HLB value of the alkynediol surfactant was calculated by the Griffin method.

[0166] Griffin method: HLB value = 20 x sum of formula weights of hydrophilic portions / molecular weight

[0167] In addition, "low HLB surfactant" in the expression "ratio (A) of low HLB surfactant to water-soluble resin" in Tables 1 and 2 means an acetylenic diol surfactant having an HLB value of 6 or less.

[0168] Further, the "hydrophilic portion" is not particularly limited as long as it is a group having a high affinity with water, and is, for example, an acidic group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group, and a basic group such as an amino group.

[0169] 2. Evaluation

[0170] 2.1. Evaluation of foreign matter at gas-liquid interface

[0171] In each 50 mL screw vial, 30 g of each of the ink compositions of Examples and Comparative Examples was placed, and left to stand in a constant temperature bath at 60°C for 5 days. Each of the ink compositions after standing was returned to room temperature, 10 mL was dropped on a filter having a diameter of 8 μm, and the foreign matter collected on the surface of the filter was observed.

[0172] [Criteria for Evaluation]

[0173] A: No foreign matter was present on the surface of the filter.

[0174] B: One or more but less than 9 foreign matters were present on the surface of the filter.

[0175] C: 10 or more foreign matters were present on the surface of the filter.

[0176] 2.2. Evaluation of transfer (evaluation of charge resistance)

[0177] An inkjet recording device LX-10000F (manufactured by Seiko Epson Corporation) was modified to fill each of the ink compositions of Examples and Comparative Examples, and 500 sheets of recording medium Nautilus Classic (manufactured by Mondi) were subjected to double-sided printing under a condition of 10°C, 80% relative humidity, 600 x 1200 dpi, 6.7 ng / dot, and 100% dot density. After printing, the belt unit was removed from the modified LX-10000F, and the resistance value on the belt after printing was measured using a resistivity meter (Hiresta UX MCP-HT800) in accordance with JIS K6911.

[0178] [Criteria for Evaluation]

[0179] A: The resistance value of the belt did not decrease due to printing, and the resistance value of the belt after printing was 1.0 x 10 15 [Ω] or more.

[0180] B: The resistance value of the belt decreased due to printing, and the resistance value of the belt after printing was 1.0 x 10 14[Ω] or more and less than 1.0 x 10 15 [Ω].

[0181] C: The resistance value of the conveyance belt was decreased by printing, and the resistance value of the conveyance belt after printing was 1.0 x 10 13 [Ω] or more and less than 1.0 x 10 14 [Ω].

[0182] D: The resistance value of the conveyance belt was decreased by printing, and the resistance value of the conveyance belt after printing was less than 1.0 x 10 13 [Ω].

[0183] 2.3. Transfer Evaluation (Contact Angle Evaluation)

[0184] The contact angle after 2.6 seconds after landing was measured using a portable contact angle meter PCA-1 (Kosugi Interface Science Co., Ltd.) for each of the ink compositions of the filling examples and the comparative examples, with respect to a recording medium Nautilus Classic (Mondi Co., Ltd.), by dripping 0.5 μL of ink droplets at 600 x 1200 dpi, 6.7 ng / dot, and a dot density of 100% under an environment of 10°C and a relative humidity of 80%.

[0185] [evaluation criteria]

[0186] A: The contact angle was less than 15°.

[0187] B: The contact angle was 15° or more and less than 20°.

[0188] C: The contact angle was 20° or more and less than 25°.

[0189] D: The contact angle was 25° or more.

[0190] 2.4. Ejection Reliability Evaluation (Flying Evaluation)

[0191] The ink compositions of the filling examples and the comparative examples were recorded on a recording medium Superfine Paper (Seiko Epson Co., Ltd.) by an inkjet recording device LX-10000F (Seiko Epson Co., Ltd.) modified machine under an environment of 32°C and a relative humidity of 20%. Thereafter, under the same conditions as above, the ink compositions were recorded on a recording medium Nautilus Classic (Mondi Co., Ltd.) after 20 seconds of air feeding under an environment of 32°C and a relative humidity of 20% in a state where the ink compositions were filled in the inkjet head. The two test patterns obtained above were compared, the shift of the landing position of the ink composition with respect to the recording medium before and after air feeding was measured, and the evaluation was performed according to the following evaluation criteria.

[0192] [Evaluation Criteria]

[0193] A: Landing position offset amount is 0 μm or more and less than 50 μm.

[0194] B: Landing position offset amount is 50 μm or more and less than 100 μm.

[0195] C: Landing position offset amount is 100 μm or more and less than 200 μm.

[0196] D: Landing position offset amount is 200 μm or more.

[0197] 2.5. Evaluation of curl resistance

[0198] Each of the ink compositions of the Examples and Comparative Examples was filled into an inkjet recording device PX-S840 manufactured by Seiko Epson Corporation, and a solid pattern was printed on a postcard-sized recording medium Xerox P (manufactured by Fuji Xerox Co., Ltd., basis weight 64 g / m2, paper thickness 88 μm) at 600 x 1200 dpi, 13 ng / dot, and a dot density of 100% under an environment of 25°C and a relative humidity of 50%. After printing, the angle of the paper end of the paper placed face down with respect to the place where the paper was set on the floor was measured over time, and the maximum curling angle was calculated. 2

[0199] [Evaluation Criteria]

[0200] A: Maximum curling angle is less than 90°.

[0201] B: Maximum curling angle is 90° or more.

[0202] 2.6. Evaluation of color development

[0203] Each of the ink compositions of the Examples and Comparative Examples was filled into an inkjet recording device PX-S840 manufactured by Seiko Epson Corporation, and a solid pattern was printed on a postcard-sized recording medium Xerox P (manufactured by Fuji Xerox Co., Ltd., basis weight 64 g / m2, paper thickness 88 μm) at 600 x 1200 dpi, 6.7 ng / dot, and a dot density of 100% under an environment of 25°C and a relative humidity of 50%. The OD value (optical density) was measured using an i1Pro2 (manufactured by X-Rite Corporation). 2

[0204] [Evaluation Criteria]

[0205] A: OD value is 1.3 or more.

[0206] B: OD value is 1.2 or more and less than 1.3.

[0207] C: OD value is 1.1 or more and less than 1.2.

[0208] D: OD value is less than 1.1.​​

[0209] 3. Evaluation results

[0210] From the evaluation results of Tables 1 to 2, it was found that Examples 1 to 12 were superior in gas-liquid interface foreign matter evaluation, transfer evaluation, and jetting reliability, as compared with Comparative Example 1 in which the content of acetylenic diol-based surfactant A was below the prescribed ratio, Comparative Examples 2 to 4 in which the content of acetylenic diol-based surfactant was outside the prescribed range relative to the content of water-soluble polyurethane resin, Comparative Examples 5 to 7 in which resins other than water-soluble polyurethane resin were used, Comparative Example 8 in which no resin was used, and Comparative Example 9 in which neither resin nor surfactant was used.

Claims

1. An aqueous-based inkjet ink composition characterized in that, contains: a color material; a water-soluble polyurethane resin; and an acetylenic diol-based surfactant having an HLB value of 6 or less, a content A of the acetylenic diol-based surfactant is 0.1% by mass or more relative to a total mass of the water-based inkjet ink composition, a ratio A / U of the content A of the acetylenic diol-based surfactant relative to a content U of the water-soluble polyurethane resin is 0.3 to 2.

3.

2. The water-based inkjet ink composition according to claim 1, wherein the content U of the water-soluble polyurethane resin is 0.1 to 0.8% by mass relative to a total mass of the water-based inkjet ink composition.

3. The water-based inkjet ink composition according to claim 1, wherein the content A of the acetylenic diol-based surfactant is 0.1 to 0.8% by mass relative to a total mass of the water-based inkjet ink composition.

4. The water-based inkjet ink composition according to claim 1, wherein the water-soluble polyurethane resin includes a water-soluble polyurethane resin having an acidic group.

5. The water-based inkjet ink composition according to claim 1, wherein the water-soluble polyurethane resin includes a water-soluble polyurethane resin having an acid value of 40 to 90 mgKOH / g.

6. The water-based inkjet ink composition according to claim 1, wherein the color material includes any one or more of a self-dispersible pigment and a resin-dispersible pigment.

7. The water-based inkjet ink composition according to claim 1, wherein the water-based inkjet ink composition further includes a dispersing resin at a content of less than 0.2% by mass relative to a total mass of the water-based inkjet ink composition, or does not include a dispersing resin.

8. The water-based inkjet ink composition according to claim 1, wherein the acetylenic diol-based surfactant includes a compound represented by formula (1), In the formula, R 1 ~R 4 each independently represents an alkyl group having 1 to 4 carbon atoms.

9. The water-based inkjet ink composition according to claim 1, wherein the water-based inkjet ink composition further contains inorganic oxide particles.

10. The water-based inkjet ink composition according to claim 1, wherein the water-based inkjet ink composition further contains an organic solvent, the organic solvent includes a polyol having a standard boiling point of more than 280°C.

11. The water-based inkjet ink composition according to claim 1, wherein the water-based inkjet ink composition is used for recording to an absorbent recording medium.

12. An ink-jet recording method characterized by, including: an ink adhering step of ejecting the water-based inkjet ink composition according to any one of claims 1 to 11 from an inkjet head and adhering it to a recording medium.

13. The inkjet recording method according to claim 12, wherein the inkjet recording method has a supply step of supplying the water-based inkjet ink composition from an ink container to the inkjet head via an ink flow path, a gas-liquid interface is generated in the water-based inkjet ink composition in the supply step.

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