Inkjet ink composition and recording method

Abstract

To provide an ink jet ink composition capable of reducing banding unevenness, delivering outstanding image quality (wet spreadability), providing exceptional storage stability, and significantly reducing deviations in landing positions of the ink.SOLUTION: An ink jet ink composition according to an aspect of the present disclosure includes a pigment, a sparingly water-soluble low-molecular-weight organic compound, and a nonionic water-soluble resin. The pigment is a self-dispersion pigment or a resin dispersion pigment dispersed by a dispersant resin. The nonionic water-soluble resin has a weight-average molecular weight of 2000 or greater, and the content of the nonionic water-soluble resin is 1 mass or less with respect to the total mass of the ink composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an inkjet ink composition and a recording method. [Background technology]

[0002] Inkjet recording is a known method that records images onto a recording medium by ejecting tiny ink droplets from the nozzles of the recording head of an inkjet recording device. For example, its use in sign printing, label printing, and packaging printing is being considered. Among these methods, research is being conducted on recording images onto recording media using water-based inks, in which water is one of the main solvents.

[0003] For example, Patent Document 1 describes an aqueous inkjet ink composition containing a first wax having a melting point of 100°C or higher, a second wax having a melting point of 70°C or lower, and water, which are used together with a reaction solution containing a flocculant that aggregates the components of the ink composition. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-154014 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, in recording using water-based inks, the ink may not spread easily (do not fill well) on the recording medium. Therefore, slight variations in the amount of ink droplets ejected from the nozzle or slight variations in the landing position, which can occur due to individual differences in inkjet head nozzles, tend to cause banding, which is a streaky unevenness in the recorded image.

[0006] On the other hand, in studies to obtain an ink composition with excellent wet-spreading properties on a recording medium, there have also been problems caused by the ink composition, such as deterioration of ink storage stability and occurrence of displacement of the landing position of ink droplets.

[0007] Accordingly, there is a need for an inkjet ink composition that is excellent in image quality (wet-spreading), excellent in storage stability, and excellent in reducing landing position displacement. [Means for Solving the Problem]

[0008] One aspect of the inkjet ink composition according to the present invention is contains a pigment, a poorly water-soluble low-molecular-weight organic compound, and a nonionic water-soluble resin, the pigment is a self-dispersing pigment or a resin-dispersed pigment dispersed with a dispersant resin, the nonionic water-soluble resin has a weight average molecular weight of 2000 or more, a content of 1% by mass or less based on the total mass of the ink composition, and is aqueous.

[0009] One aspect of the recording method according to the present invention is comprises an ink attaching step of ejecting the inkjet ink composition of the above aspect by an inkjet method and attaching it to a recording medium. [Brief Description of the Drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an example of an inkjet recording apparatus. [Figure 2] FIG. 2 is a schematic diagram around a carriage of an example of an inkjet recording apparatus. [Mode for Carrying Out the Invention]

[0011] Embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited in any way to the following embodiments, and also includes various modifications implemented within the scope that does not alter the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

[0012] 1. Inkjet ink composition An inkjet ink composition according to an embodiment of the present invention contains a pigment, a poorly water-soluble low-molecular organic compound, and a nonionic water-soluble resin, wherein the pigment is a self-dispersing pigment or a resin-dispersed pigment dispersed by a dispersant resin, and the nonionic water-soluble resin has a weight average molecular weight of 2000 or more, a content of 1% by mass or less based on the total mass of the ink composition, and is aqueous.

[0013] In recording using aqueous inks, the ink tends to be difficult to wet and spread on a recording medium (poor filling). For this reason, banding unevenness, in which streak unevenness is visible in a recorded image, is likely to occur due to slight deviations in the ejection amount of ink droplets ejected from nozzles and slight deviations in landing positions, which are caused by individual differences among nozzles of an inkjet head or the like.

[0014] It has now been found that when a poorly water-soluble low-molecular organic compound is contained in an ink, banding unevenness can be reduced. This is presumably because the poorly water-soluble low-molecular organic compound has high hydrophobicity, and the wetting and spreading of the ink containing the same on a recording medium can be improved. However, the poorly water-soluble low-molecular organic compound tends to form foreign matter when the ink dries, which tends to deteriorate storage stability and clogging recovery.

[0015] Therefore, after diligent research by the inventors, it was discovered that by further incorporating a specific nonionic water-soluble resin into the ink, superior storage stability and clogging recovery were achieved. This is presumed to be because the compatibility between poorly water-soluble low-molecular-weight organic compounds and solvent components such as water can be improved by the specific nonionic water-soluble resin. However, when the molecular weight of the nonionic water-soluble resin was below a predetermined level, the effect of suppressing the deterioration of storage stability and clogging recovery caused by poorly water-soluble low-molecular-weight organic compounds was not obtained.

[0016] On the other hand, including certain nonionic water-soluble resins sometimes increased the viscosity of the ink or worsened other ink ejection characteristics, leading to misalignment of ink droplets. Therefore, it was found that by limiting the content of certain nonionic water-soluble resins to a predetermined amount or less, misalignment of ink droplets could be significantly reduced. Thus, the inkjet ink composition according to this embodiment reduces banding unevenness, provides excellent image quality (wetting spread), has excellent storage stability, and significantly reduces misalignment of ink droplets. Furthermore, by limiting the content of certain nonionic water-soluble resins to a predetermined amount or less, the abrasion resistance of printed materials is also excellent.

[0017] The following describes each component contained in the inkjet ink composition according to this embodiment.

[0018] 1.1 Pigments The inkjet ink composition according to this embodiment contains a pigment. The pigment has properties that make it resistant to fading when exposed to light, gas, etc. Images formed on a recording medium using the pigment not only have excellent image quality but also excellent water resistance, gas resistance, light resistance, etc., resulting in good storage properties. This property is particularly noticeable when images are formed on recording mediums that are low absorption recording mediums or non-absorption recording mediums.

[0019] The pigments used are not particularly limited, but include inorganic and organic pigments. Inorganic pigments include titanium dioxide and iron oxide, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method. Organic pigments include, for example, azo pigments, polycyclic pigments, nitro pigments, nitroso pigments, and aniline black. Examples of azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments. Examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, and quinoflavone pigments.

[0020] Examples of pigments used in black ink include carbon black. While not limited to carbon black, examples include furnace black, lamp black, acetylene black, or channel black (CI Pigment Black 7). Commercially available examples include No. 2300, 900, MCF88, No. 20B, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA77, MA100, No. 2200B (all brand names, manufactured by Mitsubishi Chemical Corporation), and color blacks FW1, FW2, FW2V, FW18, FW200, S150, S160, S17. Examples include 0, Pritex 35, U, V, 140U, Special Black 6, 5, 4A, 4, 250, etc. (all product names, manufactured by Degussa), Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc. (all product names, manufactured by Columbia Carbon), Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc. (all product names, manufactured by Cabot Japan Co., Ltd.).

[0021] The pigments used in white ink are not particularly limited, but examples include white inorganic pigments such as CI Pigment White 6, 18, 21, titanium dioxide, zinc oxide, zinc sulfide, antimony oxide, magnesium oxide, and zirconium oxide. In addition to these white inorganic pigments, white organic pigments such as white hollow resin fine particles and polymer particles can also be used.

[0022] The pigments used in yellow ink are not particularly limited, but examples include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0023] The pigments used in magenta ink are not particularly limited, but examples include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet. Examples include 19, 23, 32, 33, 36, 38, 43, 50, and solid solutions of the above multiple pigments.

[0024] Pigments used in cyan ink are not particularly limited, but examples include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Bat Blue 4, 60.

[0025] Furthermore, while not particularly limited, pigments used in color inks other than magenta, cyan, and yellow include, for example, CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, and 63.

[0026] Pearl pigments are not particularly limited, but examples include titanium dioxide-coated mica, fish scale foil, and bismuth acid chloride, which are pigments that have a pearly or interference luster.

[0027] The metallic pigments are not particularly limited, but examples include particles made from elements or alloys of aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, etc.

[0028] The above pigments may be used individually or in combination of two or more.

[0029] The pigment contained in the inkjet ink composition according to this embodiment is a self-dispersing pigment or a resin-dispersed pigment dispersed by a dispersant resin.

[0030] 1.1.1 Self-dispersing pigments A "self-dispersing pigment" is a pigment that can be dispersed or dissolved in an aqueous medium without the need for a dispersant. "Dispersing or dissolving in an aqueous medium without a dispersant" means that the pigment remains stable in the aqueous medium due to its hydrophilic groups, even without the use of a dispersant. Self-dispersing pigments do not cause a decrease in defoaming properties due to dispersants, making it easier to prepare inks with suppressed foaming and excellent discharge stability. Furthermore, because the significant increase in viscosity caused by dispersants is suppressed, it is possible to include a larger amount of pigment, allowing for sufficiently high print density, and thus making them easier to handle.

[0031] The hydrophilic group described above is preferably one or more hydrophilic groups selected from the group consisting of -OM, -COOM, -CO-, -SO3M, -SO2M, -SO2NH2, -RSO2M, -PO3HM, -PO3M2, -SO2NHCOR, -NH3, and -NR3.

[0032] In these chemical formulas, M represents a hydrogen atom, an alkali metal, an ammonium group, an optionally substituted phenyl group, or an organic ammonium group, and R represents an alkyl group having 1 to 12 carbon atoms or an optionally substituted naphthyl group. Furthermore, M and R can be selected independently of each other.

[0033] Self-dispersing pigments are manufactured, for example, by physically or chemically treating the pigment to bond (graft) the hydrophilic groups onto the pigment surface. Examples of such physical treatments include vacuum plasma treatment. Examples of such chemical treatments include wet oxidation using an oxidizing agent in water, and methods of bonding carboxyl groups via phenyl groups by bonding p-aminobenzoic acid to the pigment surface.

[0034] 1.1.2 Resin-dispersed pigments A "resin-dispersed pigment" is a pigment that can be dispersed by a dispersant resin. The dispersant resin is a resin used to disperse the pigment, and it is a resin that adheres to, adsorbs, or coats the pigment. The dispersant resin is not particularly limited and includes, for example, polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, etc., and salts thereof. Among these, copolymers of monomers having hydrophobic functional groups and monomers having hydrophilic functional groups, and polymers consisting of monomers having both hydrophobic and hydrophilic functional groups are particularly preferred. The copolymer can be used in any form, such as a random copolymer, a block copolymer, an alternating copolymer, or a graft copolymer.

[0035] Examples of the salts mentioned above include salts with basic compounds such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, diethanolamine, triethanolamine, tri-iso-propanolamine, aminomethylpropanol, and morpholine. The amount of these basic compounds added is not particularly limited as long as it is equal to or greater than the neutralizing equivalent of the dispersant resin.

[0036] A preferred dispersant resin is one in which at least one of (meth)acrylate and (meth)acrylic acid is present in a concentration of preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more of the resin's constituent components.

[0037] A more preferred dispersant resin is a resin in which at least one of C1-C24 alkyl (meth)acrylates and C3-C24 cyclic alkyl (meth)acrylates is polymerized as a monomer component, preferably at a concentration of 70% by mass or more, more preferably at a concentration of 75% by mass or more.

[0038] Specific examples of the monomer component include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, lauryl (meth)acrylate, isobolonyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, tetramethylpiperidyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, and behenyl (meth)acrylate. In addition, other monomer components for polymerization can be hydroxyl group-containing hydroxy(meth)acrylates such as styrene, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and diethylene glycol (meth)acrylate, as well as urethane (meth)acrylate and epoxy (meth)acrylate.

[0039] In this specification, the term (meth)acrylic means at least one of acrylic and methacrylic. The term (meth)acrylate means at least one of acrylate and methacrylate.

[0040] The glass transition temperature (Tg) of the dispersant resin is preferably 80°C or lower, and more preferably 75°C or lower. A Tg of 80°C or lower may result in good ink fixation.

[0041] Furthermore, the weight-average molecular weight of the dispersant resin, as determined by gel permeation chromatography (GPC), is preferably between 10,000 and 200,000. This may further improve the storage stability of the ink. The weight-average molecular weight of the dispersant resin can be measured using gel permeation chromatography (GPC) in the same manner as for the nonionic water-soluble resin described later.

[0042] Resin-dispersed pigments are pigments dispersed by a dispersant resin, in which the dispersant resin adheres to, adsorbs, or coats the pigment. Furthermore, because they tend to have particularly excellent ink fixation, gloss, and color reproduction, resin-dispersed pigments are preferably pigments coated with a dispersant resin, i.e., microencapsulated pigments, and are suitably used.

[0043] Resin-dispersed pigments can be obtained, for example, by kneading and dispersing a pigment and a dispersant resin in water, or, if necessary, in a mixture of water and an organic solvent. Furthermore, among resin-dispersed pigments, pigments coated with a dispersant resin can be obtained, for example, by a phase inversion emulsification method. In a phase inversion emulsification method, for example, the above-mentioned dispersant resin is dissolved in an organic solvent such as methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, and dibutyl ether. The pigment is added to the obtained solution, and then a neutralizing agent and water are added and kneaded and dispersed to prepare an oil-in-water dispersion. Then, by removing the organic solvent from the obtained dispersion, a pigment coated with a dispersant resin can be obtained as an aqueous dispersion. For mixing and dispersion processes, for example, ball mills, roll mills, bead mills, high-pressure homogenizers, and high-speed agitator-type dispersers can be used.

[0044] Preferred neutralizing agents include tertiary amines such as ethylamine and trimethylamine, lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia. The pH of the resulting aqueous dispersion is preferably 6 to 10.

[0045] As a dispersant resin for coating the pigment, one with a weight-average molecular weight of approximately 10,000 to 150,000 determined by GPC is preferable in terms of stably dispersing the pigment.

[0046] The pigment (solids) content is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, relative to the total mass of the ink composition. Furthermore, the pigment (solids) content is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, relative to the total mass of the ink composition. When the pigment content is within the above range, storage stability may be superior.

[0047] 1.2 Poorly water-soluble low-molecular organic compounds The inkjet ink composition according to this embodiment contains a poorly water-soluble low-molecular-weight organic compound. This poorly water-soluble low-molecular-weight organic compound has high hydrophobicity. Therefore, inks containing this compound tend to have a high affinity for low-absorption or non-absorption recording media, and the ink spreads easily. As a result, it is presumed that excellent suppression of banding unevenness was obtained, but the reason is not limited to this.

[0048] In this invention, "poorly water-soluble" means that the solubility in 100g of water at 20°C is 10g or less, and also includes a solubility of 0g.

[0049] The upper limit of solubility of poorly water-soluble low-molecular-weight organic compounds in 100g of water at 20°C is 10g or less, preferably 8g or less, more preferably 6g or less, even more preferably 4g or less, particularly preferably 2g or less, and most particularly preferably 1g or less. The lower limit of solubility of poorly water-soluble low-molecular-weight organic compounds in 100g of water at 20°C is not particularly limited and may be 0g or more, 0.01g or more, 0.5g or more, or 0.1g or more.

[0050] The solubility in this invention is determined by the following method. First, a predetermined amount of the compound is mixed with 100g of water at 20°C and stirred for 30 minutes. After stirring, for compounds that are liquid at room temperature, dissolution is determined if there is no phase separation or sea-island structure. For compounds that are solid at room temperature, dissolution is determined if there are no undissolved particles. In this way, when a predetermined amount of compound is mixed with 100g of water, the largest predetermined amount among those determined to be dissolved is defined as the solubility.

[0051] In this invention, "low molecular weight" means a molecular weight of 300 or less.

[0052] The upper limit of molecular weight for poorly water-soluble low-molecular-weight organic compounds is 300 or less, preferably 250 or less, and more preferably 200 or less.

[0053] The standard boiling point of poorly water-soluble low-molecular-weight organic compounds is not particularly limited, but is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 270°C or lower. The lower limit of the standard boiling point is not particularly limited, but is preferably 100°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, and particularly preferably 250°C or higher.

[0054] The melting point of poorly water-soluble low-molecular-weight organic compounds is preferably 130°C or lower. Furthermore, a melting point of -120°C or higher is preferable. Even more preferably, it is -50 to 60°C, and more preferably -30 to 50°C.

[0055] Examples of poorly water-soluble low-molecular-weight organic compounds include organic solvents (liquid at room temperature) and compounds that are solid at room temperature. Preferably, the poorly water-soluble low-molecular-weight organic compound contains one or more of the following: alkanediols, monoalcohols, and glycol monoethers, and more preferably alkanediols. When the poorly water-soluble low-molecular-weight organic compound contains the above, the ink tends to spread more easily on the recording medium, reducing banding unevenness and resulting in superior image quality (wetting spread). Furthermore, because the ink is less likely to produce foreign matter when it dries, it tends to have superior storage stability and clogging recovery properties.

[0056] 1.2.1 Alkanediols Examples of alkanediols, which are poorly water-soluble, low-molecular-weight organic compounds, include aliphatic diols and alicyclic diols. Examples of aliphatic diols include 1,3-alkanediols and aliphatic diols other than 1,3-alkanediols.

[0057] Examples of aliphatic diols include those with 6 or more carbon atoms, and further, those with 8 to 20 carbon atoms.

[0058] Examples of 1,3-alkanediols include 2,2-diethyl-1,3-propanediol (DEPOD, standard boiling point 240°C, solid at 25°C, solubility 10.0 [g / 100g water]), 2-methyl-2-propyl-1,3-propanediol (MPPD, standard boiling point 230°C, melting point 57°C, solubility 7.5 [g / 100g water]), 2-butyl-2-ethyl-1,3-propanediol (BEPG, standard boiling point 264°C, melting point 43°C, solubility 0.9 [g / 100g water]), and 2,2-diisobutyl-1,3- Examples include propanediol (DIBPD, standard boiling point 253°C, melting point 77°C, solubility 0.5 [g / 100g water]), 2,2-dibutyl-1,3-propanediol (DBPD, standard boiling point 269°C, solubility 0.2 [g / 100g water]), 2,2,4-trimethyl-1,3-pentanediol (TMPD, standard boiling point 232°C, melting point 54°C, solubility 1.9 [g / 100g water]), and 2-ethyl-1,3-hexanediol (EHD, standard boiling point 244°C, melting point -40°C, solubility 4.2 [g / 100g water]).

[0059] Examples of aliphatic diols other than 1,3-alkanediols include 1,2-octanediol (1,2OD, standard boiling point 267°C, melting point 26°C, solubility 0.8 [g / 100g water]), 1,9-nonanediol (1,9ND, standard boiling point 289°C, melting point 46°C, solubility 0.6 [g / 100g water]), 1,2-decanediol (standard boiling point 279°C, melting point 49°C, solubility 0.1 [g / 100g water]), and 2,4-diethyl-1,5-pentanediol (DEPD, standard boiling point 257°C, liquid (25°C), solubility 1.0 [g / 100g water]).

[0060] Examples of alicyclic diols include 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD, standard boiling point 220°C, melting point 126°C, solubility 6.1 [g / 100g water]) and 1,4-cyclohexanedimethanol (CHDM, standard boiling point 286°C, melting point 35°C, solubility 0.8 [g / 100g water]). Examples of alicyclic diols include those with an alicyclic ring having 4 to 10 carbon atoms. The number of carbon atoms in the molecules of alicyclic diols is similar to that of aliphatic diols mentioned above.

[0061] Among these, from the viewpoint of being superior in terms of image quality (wetting spread), storage stability, and clogging recovery, it is preferable that the alkanediols be one or more selected from 2-butyl-2-ethyl-1,3-propanediol (BEPG) and 1,2-octanediol (1,2OD).

[0062] Furthermore, among the above 1,3-alkanediols, those represented by the following general formula (1) are preferred from the viewpoint of being superior in terms of image quality (wetting spread), storage stability, and clogging recovery. [ka] (In formula (1), R1, R2, and R3 are independently hydrogen or alkyl groups. The total number of carbon atoms in R1, R2, and R3 is between 3 and 9.)

[0063] Furthermore, it is preferable that R1 and R2 in the above formula are not both hydrogen atoms. When R1, R2, and R3 are alkyl groups, each alkyl group preferably has 1 to 5 carbon atoms, and more preferably 2 to 4 carbon atoms. The total number of carbon atoms in R1, R2, and R3 is preferably 4 to 5, and more preferably 4 to 6 carbon atoms. It is preferable that R3 is an alkyl group.

[0064] Examples of 1,3-alkanediols represented by the above general formula (1) include 2-methyl-2-propyl-1,3-propanediol (MPPD), 2-butyl-2-ethyl-1,3-propanediol (BEPG), 2,2,4-trimethyl-1,3-pentanediol (TMPD), and 2-ethyl-1,3-hexanediol (EHD), with 2-butyl-2-ethyl-1,3-propanediol (BEPG) being preferred.

[0065] 1.2.2 Monoalcohols Examples of monoalcohols, which are poorly water-soluble, low-molecular-weight organic compounds, include monoalcohols with 4 to 10 carbon atoms. For example, cyclohexanol (standard boiling point 161°C, liquid (25°C), solubility 3.8 [g / 100g water]), 2-methyl-1-propanol (standard boiling point 108°C, liquid (25°C), solubility 7.0 [g / 100g water]), 1-butanol (standard boiling point 118°C, liquid (25°C), solubility 6.6 [g / 100g water]), 2-methyl-1-butanol (standard boiling point 128°C, liquid (25°C), solubility 3.0 [g / 100g water]), 3-methyl Examples include -1-butanol (standard boiling point 132°C, liquid (25°C), solubility 2.6 [g / 100g water]), 1-pentanol (standard boiling point 137°C, liquid (25°C), solubility 2.1 [g / 100g water]), 4-methyl-2-pentanol (standard boiling point 132°C, liquid (25°C), solubility 2.2 [g / 100g water]), and 1-hexanol (1-Hex, standard boiling point 157°C, liquid (25°C), solubility 0.1 [g / 100g water]).

[0066] Among these, monoalcohols are preferably 1-hexanol (1-Hex) because they tend to be superior in terms of image quality (wetting spread), storage stability, and clogging recovery.

[0067] 1.2.3 Glycol monoethers Examples of glycol monoethers, which are poorly water-soluble low-molecular-weight organic compounds, include ethylene glycol monohexyl ether (EGHE, standard boiling point 208°C, melting point -45°C, solubility 1.0 [g / 100g water]), ethylene glycol mono-2-ethylhexyl ether (EHG, standard boiling point 229°C, melting point -105°C, solubility 0.1 [g / 100g water]), and diethylene glycol monohexyl ether (HDG, standard boiling point 259°C, liquid (25°C), soluble). Examples include diethylene glycol mono-2-ethylhexyl ether (EHDG, standard boiling point 277°C, melting point -82°C, solubility 0.5 [g / 100g water]), dipropylene glycol monobutyl ether (BPDG, standard boiling point 230°C, liquid (25°C), solubility 4.0 [g / 100g water]), and tripropylene glycol monobutyl ether (BPTG, standard boiling point 276°C, solubility 4.0 [g / 100g water]).

[0068] Among the glycol monoethers mentioned above, glycol monoethers with 4 or more carbon atoms in the ether portion are preferred, as they tend to have superior image quality (wetting spread), storage stability, and clogging recovery properties. Furthermore, the number of carbon atoms in the ether portion is preferably 6 to 10. The number of carbon atoms in the molecule of glycol monoethers is preferably 6 to 20, and more preferably 8 to 15. Examples of glycol monoethers include ethylene glycol monohexyl ether (EGHE), ethylene glycol mono-2-ethylhexyl ether (EHG), diethylene glycol monohexyl ether (HDG), diethylene glycol mono-2-ethylhexyl ether (EHDG), dipropylene glycol monobutyl ether (BPDG), and tripropylene glycol monobutyl ether (BPTG).

[0069] The content of poorly water-soluble low-molecular-weight organic compounds is preferably 0.1% by mass or more and 2% by mass or less relative to the total mass of the ink composition. Within this content range, it tends to be possible to achieve a good balance between image quality (wetting spread) and clogging recovery. The lower limit of the content is more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 0.7% by mass or more. The upper limit of the content is more preferably 1.7% by mass or less, even more preferably 1.5% by mass or less, and particularly preferably 1.2% by mass or less.

[0070] 1.3 Nonionic water-soluble resins The inkjet ink composition according to this embodiment contains a nonionic water-soluble resin having a weight-average molecular weight of 2000 or more in an amount of 1% by mass or less relative to the total mass of the ink composition. This allows for excellent storage stability and clogging recovery, as well as excellent impact position deviation and abrasion resistance, even when containing the aforementioned poorly water-soluble low-molecular-weight organic compounds. Note that the nonionic water-soluble resin is different from the dispersant resin described above.

[0071] In this invention, "water-soluble" means that the solubility in 100g of water at 20°C is greater than 10g. Nonionic properties are those that are neither anionic nor cationic. For example, a molecule does not contain anionic or cationic groups.

[0072] The solubility of a nonionic water-soluble resin in 100g of water at 20°C is greater than 10g, preferably 11g or more, and more preferably 50g or more. There is no upper limit, and it may be infinite. The solubility of a nonionic water-soluble resin can be determined in the same manner as described above.

[0073] The weight-average molecular weight of the nonionic water-soluble resin is 2000 or more, preferably 3000 or more, more preferably 4000 or more, and even more preferably 5000 or more. The upper limit of the weight-average molecular weight is not particularly limited, but is preferably 50000 or less, more preferably 45000 or less, even more preferably 40000 or less, even more preferably 35000 or less, especially preferably 30000 or less, even more especially preferably 25000 or less, and particularly preferably 20000 or less.

[0074] Furthermore, the weight-average molecular weight of nonionic water-soluble resins can be measured as the weight-average molecular weight in terms of polystyrene equivalent using gel permeation chromatography (GPC) with the Hitachi, Ltd. L7100 system.

[0075] The nonionic water-soluble resin content is 1% by mass or less relative to the total mass of the ink composition. This improves ink ejection characteristics such as misalignment of the point of impact and abrasion resistance. The upper limit of the nonionic water-soluble resin content is preferably 0.9% by mass or less, more preferably 0.8% by mass or less, even more preferably 0.7% by mass or less, particularly preferably 0.6% by mass or less, and most particularly preferably 0.5% by mass or less. This tends to improve ink ejection characteristics such as misalignment of the impact point and abrasion resistance. The lower limit of the nonionic water-soluble resin content is not particularly limited, but it is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more. This tends to further improve storage stability and clogging recovery.

[0076] The nonionic water-soluble resin preferably contains one or more of the following: polyvinylpyrrolidone, poly-N-vinylacetamide, polyvinyl alcohol, and polyalkylene oxide (polyalkylene glycol), with polyvinylpyrrolidone being more preferable. In this case, it is presumed that the compatibility between the poorly water-soluble low-molecular-weight organic compound and solvent components such as water can be further improved. As a result, banding unevenness can be reduced, image quality (wetting spread) can be improved, storage stability can be improved, and impact position deviation can be reduced more effectively.

[0077] Polyvinylpyrrolidone is not limited to homopolymers as long as it is nonionic and water-soluble; copolymers of vinylpyrrolidone with other monomers may also be used. Commercially available polyvinylpyrrolidone may also be used, for example, commercially available reagents, polyvinylpyrrolidone K-30, K-30W (trade names, Nippon Shokubai Co., Ltd.), Pittscol® K-17L, K-30L, K-30AL, K-60L, K-17 (weight-average molecular weight 9000), K-30 (weight-average molecular weight 45000), K-50, Creages® K-30, iFact® K-30PH (trade names, Daiichi Kogyo Seiyaku Co., Ltd.), PVP K-30, PVP K-25, PVP K-17 (trade names, Ashland Pharmaceuticals), Sokalan K 17 P (weight-average molecular weight 9000) (trade name, BASF), etc.

[0078] Poly-N-vinylacetamide is not limited to homopolymers as long as it is nonionic and water-soluble; copolymers of N-vinylacetamide with other monomers may also be used. Commercially available poly-N-vinylacetamides may also be used, such as GE191-107 (weight-average molecular weight 50,000) and GE191-108 (weight-average molecular weight 10,000) (both trade names, Showa Denko Corporation).

[0079] The polyvinyl alcohol is not limited to homopolymers as long as it is nonionic and water-soluble; copolymers of vinyl alcohol and other monomers may also be used. Commercially available polyvinyl alcohols may also be used, such as PVA-203 (weight-average molecular weight 16000) (trade name, Kuraray Co., Ltd.).

[0080] The polyalkylene oxide is not limited to homopolymers as long as it is nonionic and water-soluble; copolymers of alkylene oxides with other monomers may also be used. Furthermore, polyalkylene oxides containing multiple types of alkylene oxides, such as a copolymer of ethylene oxide and propylene oxide, may also be used. Commercially available polyalkylene oxides may also be used, such as PeO(registered trademark)-1, 2, 3, 4, 8, 15, 18, 27, 29 (all trade names, Sumitomo Seika Co., Ltd.), Alcox(registered trademark) L-6 (weight-average molecular weight 60000), L-8, L-11, E-30, E-45, E-60, E-75, E-100, E-160, E-240, E-300, R-150, R-400, R-1000 (all trade names, Meisei Chemical Industry Co., Ltd.), and PEG-6000 (weight-average molecular weight 8300) (all trade names, ADEKA Corporation).

[0081] 1.4 Water The inkjet ink composition according to this embodiment is an aqueous composition. An aqueous composition is a composition that contains at least water as a solvent component.

[0082] The water content is preferably 30 to 100% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 80% by mass, in the liquid medium component. The liquid medium is a solvent component such as water or a water-soluble low-molecular-weight organic compound.

[0083] Furthermore, the water content is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more, based on the total mass of the ink composition. There is no particular upper limit to the water content, but for example, it is preferably 99% by mass or less, more preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, based on the total mass of the ink composition.

[0084] Examples of suitable water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water, which has reduced ionic impurities. Furthermore, using water sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can suppress the growth of bacteria and fungi when storing inkjet ink compositions for extended periods.

[0085] 1.5 Water-soluble low molecular weight organic compounds The inkjet ink composition according to this embodiment may contain a water-soluble low-molecular-weight organic compound. Examples of water-soluble low-molecular-weight organic compounds include those that are liquid at room temperature or solid at room temperature. When the ink contains a water-soluble low-molecular-weight organic compound, it tends to have superior ink clogging recovery properties, storage stability, and image quality.

[0086] The definitions of "water-soluble" and "low molecular weight" in relation to water-soluble low molecular weight organic compounds are as described above. Specifically, for water-soluble low molecular weight organic compounds, the solubility in 100g of water at 20°C is greater than 10g, and the molecular weight is 300 or less. The solubility of water-soluble low molecular weight organic compounds can be determined using the same method as described above.

[0087] The solubility of water-soluble low-molecular-weight organic compounds is preferably 11 g or more, and more preferably 50 g or more. There is no upper limit, and it may be infinite.

[0088] Water-soluble low-molecular-weight organic compounds are preferably compounds that are completely miscible with water, or compounds that are miscible with water. Here, "completely miscible with water" refers to the case where water and the organic compound dissolve in each other, that is, the case where the solubility of the organic compound in 100g of water at 20°C is infinite. Also, "miscible with water" refers to the case where water and the organic compound have a finite solubility, and at least the solubility of the organic compound in 100g of water at 20°C is greater than 10g.

[0089] The molecular weight of the water-soluble low-molecular-weight organic compound is more preferably 250 or less, and even more preferably 200 or less. There is no particular lower limit, but it is preferably 50 or more.

[0090] The water-soluble low molecular weight organic compounds preferably include those with a standard boiling point of 150 to 350°C, and more preferably those with a standard boiling point of 150 to 320°C. Furthermore, the water-soluble low molecular weight organic compounds preferably include compounds with a melting point of 90°C or lower, and more preferably those with a melting point of 80°C or lower. The lower limit of the melting point is not particularly limited, but is preferably -70°C or higher.

[0091] Examples of water-soluble low-molecular-weight organic compounds include resin dissolving agents, polyols, glycol ethers, and alkanolamines. Other water-soluble low-molecular-weight organic compounds may be included as needed.

[0092] Among these, water-soluble low molecular weight organic compounds are preferably resin dissolving substances, polyols, and alkanolamines. More preferably, the water-soluble low molecular weight organic compounds are resin dissolving substances and alkanolamines which are amides, sulfur-containing solvents, or cyclic ethers with a standard boiling point greater than 250°C, and polyols which have a standard boiling point of 250°C or less.

[0093] The inkjet ink composition according to this embodiment preferably contains a water-soluble low-molecular-weight organic compound in an amount of 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total mass of the ink composition. Furthermore, as a lower limit, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on the total mass of the ink composition. When water-soluble low molecular weight organic compounds are included within the above range, the compatibility between the water-soluble low molecular weight organic compounds and the poorly water-soluble low molecular weight organic compounds tends to be better, resulting in superior storage stability.

[0094] The inkjet ink composition according to this embodiment contains a water-soluble low molecular weight organic compound having a standard boiling point of 250°C or lower, and the content of the water-soluble low molecular weight organic compound having a standard boiling point of 250°C or lower is preferably 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 28% by mass or less, even more preferably 15% by mass or more and 26% by mass or less, and particularly preferably 20% by mass or more and 23% by mass or less, based on the total mass of the ink composition. Furthermore, among water-soluble low-molecular-weight organic compounds with a standard boiling point of 250°C or lower, polyols with a standard boiling point of 250°C or lower are preferred, and alkanediols with a standard boiling point of 250°C or lower are more preferred, and their content may be within the above range. In such cases, there is a tendency to achieve a good balance between abrasion resistance, clogging recovery, and impact point deviation.

[0095] 1.5.1 Resin dissolved substances Examples of resin dissolving substances include amides, sulfur-containing solvents, and cyclic ethers. In particular, from the viewpoint of further improving the storage stability of the ink, it is preferable to include any of the amides, sulfur-containing solvents, or cyclic ethers having a standard boiling point above 250°C, and it is more preferable to include amides having a standard boiling point above 250°C. Note that a resin dissolving substance is an organic compound that has the function of dissolving the resin and improving its abrasion resistance, but is not limited to this function.

[0096] (Amids) Examples of amides include cyclic amides (lactams) such as 2-pyrrolidone (2P), 2-piperidone, ε-caprolactam (CPL, standard boiling point 267°C, solid (25°C)), N-methyl-ε-caprolactam, N-cyclohexyl-2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-butylpyrrolidone, 5-methyl-2-pyrrolidone, β-propiolactam, ω-heptalactam, N,N-dimethylacetacetamide, N,N-diethylamide Cetoacetamide, N-methylacetamide, N,N-dimethylisobutyrate, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, 3-methoxy-N,N-dimethylpropanamide (DMPA), 3-n-butoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylpropionamide Ethyl ethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-diethylpropionamide, 3-n-butoxy-N,N-methylethylpropionamide, 3-n-propoxy-N,N-dimethylpropionamide, 3-n-propoxy-N,N-diethylpropionamide, 3-n-propoxy-N, Examples of chain-like amides include N-methylethylpropionamide, 3-iso-propoxy-N,N-dimethylpropionamide, 3-iso-propoxy-N,N-diethylpropionamide, 3-iso-propoxy-N,N-methylethylpropionamide, 3-tert-butoxy-N,N-dimethylpropionamide, 3-tert-butoxy-N,N-diethylpropionamide, and 3-tert-butoxy-N,N-methylethylpropionamide. Among these, from the viewpoint of further improving the storage stability of the ink, any of 2-pyrrolidone (2P), ε-caprolactam (CPL), or 3-methoxy-N,N-dimethylpropanamide (DMPA) is preferred, with ε-caprolactam (CPL) being more preferred.

[0097] (Sulfur-containing solvent) Examples of sulfur-containing solvents include 3-methylsulfolane, sulfolane, ethyl isopropyl sulfone, ethyl methyl sulfone, dimethyl sulfone, dimethyl sulfoxide (DMSO), diethyl sulfoxide, tetramethylene sulfoxide, and methylphenyl sulfoxide. Among these, dimethyl sulfoxide (DMSO) is more preferred from the viewpoint of further improving the storage stability of the ink.

[0098] (Cyclic ethers) Examples of cyclic ethers include isosorbide dimethyl ether, 3-methyl-3-oxetane methanol, 3-ethyl-3-oxetane methanol (DMHD), 2-hydroxymethyl oxetane, tetrahydrofurfuryl alcohol, solketal, glycerol formal, 1,4-dioxane-2,3-diol, and dihydrolevoglucocenone. Among these, 3-ethyl-3-oxetanemethanol (DMHD) is more preferred from the viewpoint of further improving the storage stability of the ink.

[0099] The inkjet ink composition according to this embodiment preferably contains a resin dissolving substance as a water-soluble low molecular weight organic compound in an amount of 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, based on the total mass of the ink composition. Furthermore, there is no particular lower limit, but it is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more. Among the resin dissolving substances, amides are preferred, and amides with a standard boiling point exceeding 250°C are more preferred, and their content may be within the above range. When the content of these resin dissolving substances is within the above range, the compatibility between water-soluble low-molecular-weight organic compounds and poorly water-soluble low-molecular-weight organic compounds in the ink composition is improved, and the storage stability and abrasion resistance tend to be superior.

[0100] 1.5.2 Polyols Polyols are molecules that contain two or more hydroxyl groups. Examples of polyols include diols and polyhydric alcohols.

[0101] Polyols preferably have 15 or fewer carbon atoms in their molecule, and more preferably 10 or fewer. The lower limit of the carbon number is not particularly limited, but preferably 2 or more, and more preferably 3 or more.

[0102] The standard boiling point of polyols is preferably 250°C or lower, and more preferably between 150°C and 250°C.

[0103] (Diols) Diols are molecules that contain two hydroxyl groups. Examples of diols include alkanediols and condensates formed when two or more alkanediol molecules undergo intermolecular condensation at their hydroxyl groups.

[0104] In alkanediols, glycols, or in condensates formed by the intermolecular condensation of two or more molecules of alkanediols via hydroxyl groups, the glycol units preferably have 2 to 10 carbon atoms, and more preferably 3 to 8.

[0105] Examples of alkanediols include ethylene glycol (standard boiling point 198°C, miscible with water), 1,2-propanediol (propylene glycol: PG) (standard boiling point 188°C, completely miscible with water), 1,2-butanediol (standard boiling point 193°C, miscible with water), 1,2-pentanediol (standard boiling point 210°C, miscible with water), 1,2-hexanediol (standard boiling point 224°C, completely miscible with water), 1,3-propanediol (standard boiling point 214°C, completely miscible with water), 1,4-butanediol (standard boiling point 228°C, completely miscible with water), 2,3-butanediol (standard boiling point 177°C, miscible with water), 1,3-butylene glycol (standard boiling point 207°C, completely miscible with water), and 3-methyl-1,3-butanediol (standard boiling point 2 2-methyl-1,3-propanediol (standard boiling point 214°C, completely miscible with water), 2,2-dimethyl-1,3-propanediol (standard boiling point 208°C, solubility 83 [g / 100g water]), 2-methylpentane-2,4-diol (standard boiling point 197°C, completely miscible with water), 2,5-dimethyl-2,5-hexanediol (standard boiling point 208°C, completely miscible with water) Examples include 1,5-pentanediol (standard boiling point 242°C, miscible with water), 3-methyl-1,5-pentanediol (standard boiling point 250°C, completely miscible with water), 1,2-hexanediol (1,2HD, standard boiling point 224°C, miscible with water), and 1,6-hexanediol (standard boiling point 250°C, miscible with water).

[0106] Examples of condensates formed by the intermolecular condensation of two or more alkanediol molecules at their hydroxyl groups include dialkylene glycols such as diethylene glycol (standard boiling point 244°C, completely miscible with water) and dipropylene glycol (standard boiling point 227°C, completely miscible with water), and trialkylene glycols such as triethylene glycol (standard boiling point 276°C, completely miscible with water) and tripropylene glycol (standard boiling point 273°C, completely miscible with water).

[0107] (Polyhydric alcohols) Polyhydric alcohols are compounds that have three or more hydroxyl groups in their molecule. Examples of polyhydric alcohols include compounds with three or more hydroxyl groups that have an alkane or polyether structure as their backbone. Examples of such compounds include glycerin (standard boiling point 290°C, miscible with water), trimethylolethane (standard boiling point 283°C, solubility approximately 60 [g / 100g water]), trimethylolpropane (standard boiling point 295°C, completely miscible with water), and 1,2,6-hexanetriol (completely miscible with water).

[0108] Among the polyols mentioned above, alkanediols with a standard boiling point of 150-250°C and 10 or fewer carbon atoms are more preferable, and alkanediols with a standard boiling point of 150-250°C and 6 or fewer carbon atoms are even more preferable.

[0109] The inkjet ink composition according to this embodiment preferably contains polyols as a water-soluble low molecular weight organic compound in an amount of 30% by mass or less, and more preferably 25% by mass or less, relative to the total mass of the ink composition. Furthermore, as a lower limit, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to the total mass of the ink composition. Among the polyols, polyols with a standard boiling point of 150 to 250°C are preferred, alkanediols with a standard boiling point of 150 to 250°C are more preferred, and alkanediols with a standard boiling point of 150 to 250°C and 10 or fewer carbon atoms are even more preferred, and the content of these may be within the above range. When these water-soluble low-molecular-weight organic compounds are included within the above range, there is a tendency to achieve a good balance of abrasion resistance, clogging recovery, and impact point deviation.

[0110] In this embodiment, the inkjet ink composition preferably contains no more than 3% by mass of polyols having a standard boiling point above 280°C as a water-soluble low-molecular-weight organic compound, relative to the total mass of the ink composition. More preferably, it contains no more than 1% by mass, and even more preferably, no more than 0.5% by mass. In this case, the ink may or may not contain polyols with a standard boiling point exceeding 280°C, and if it does contain them, the amount must be below the above-mentioned limit. When the amount of polyols with a standard boiling point exceeding 280°C is within the above-mentioned range, it is possible to prevent a significant decrease in the drying properties of the ink, and as a result, it tends to prevent a decrease in image fixation even when recording on low-absorption or non-absorption recording media. Furthermore, it tends to be possible to achieve sufficient drying even at a relatively low temperature of the recording media when performing heat drying. An example of such polyols with a standard boiling point exceeding 280°C is glycerin (standard boiling point 290°C).

[0111] 1.5.3 Glycol ethers Glycol ethers are compounds in which one or more hydroxyl groups of glycol have been etherified. Preferred glycol ethers are monoethers or diethers of alkylene glycols. Alkyl ethers are preferred as the etherified ethers. The alkylene in alkylene glycols and the alkyl in alkyl ethers that constitute glycol ethers preferably have 1 to 5 carbon atoms, and more preferably 2 to 4 carbon atoms. Glycol ethers with a standard boiling point of 150 to 250°C are preferred.

[0112] Glycol ethers include alkylene glycol monoalkyl ethers, such as ethylene glycol monomethyl ether (completely miscible with water), ethylene glycol monoethyl ether (miscible with water), ethylene glycol monoisopropyl ether (solubility 100 [g / 100g water]), ethylene glycol monopropyl ether (miscible with water), ethylene glycol monoisobutyl ether (solubility 75.5 [g / 100g water]), ethylene glycol mono-tert-butyl ether (miscible with water), ethylene glycol monobutyl ether (solubility 100 [g / 100g water]), diethylene glycol monomethyl ether (completely miscible with water), diethylene glycol monoethyl ether (completely miscible with water), diethylene glycol monoisopropyl ether (miscible with water), diethylene glycol monoisobutyl ether (completely miscible with water), and diethylene glycol monobutyl ether (miscible with water). Examples include triethylene glycol monomethyl ether (completely miscible with water), triethylene glycol monoethyl ether (completely miscible with water), triethylene glycol monobutyl ether (miscible with water), tetraethylene glycol monomethyl ether (miscible with water), propylene glycol monomethyl ether (miscible with water), propylene glycol monoethyl ether (completely miscible with water), propylene glycol monopropyl ether (miscible with water), dipropylene glycol monomethyl ether (completely miscible with water), dipropylene glycol monopropyl ether (solubility 19 [g / 100g water]), tripropylene glycol monomethyl ether (completely miscible with water), 1,3-propanediol monomethyl ether (3-methoxy-1-propanol) (completely miscible with water), and 1,3-butylene glycol-3-monomethyl ether (3-methoxy-1-butanol) (miscible with water).

[0113] Glycol ethers include alkylene glycol dialkyl ethers (glyme), such as ethylene glycol dimethyl ether (completely miscible with water), diethylene glycol dimethyl ether (completely miscible with water), diethylene glycol methyl ethyl ether (completely miscible with water), diethylene glycol diethyl ether (completely miscible with water), triethylene glycol dimethyl ether (completely miscible with water), tetraethylene glycol dimethyl ether (completely miscible with water), dipropylene glycol dimethyl ether (solubility 52.6 [g / 100g water]), and tripropylene glycol dimethyl ether (solubility 23.6 [g / 100g water]).

[0114] Furthermore, of the glycol ethers mentioned above, diethers tend to dissolve or swell the resin in the ink more easily than monoethers, and are therefore more preferable in terms of improving the scratch resistance of the formed image. On the other hand, monoethers are preferred in terms of superior ink wetting and spreading properties.

[0115] 1.5.4 Alkanolamines Alkanolamines are compounds having an alkane skeleton with a hydroxyl group and an amino group. Alkanolamines have one or more hydroxyl groups in their molecules, preferably 1 to 5, and more preferably 2 to 3. Alkanolamines have 1 to 20 carbon atoms in their molecules, preferably 2 to 10, and even more preferably 6 to 9. The alkane skeleton has 1 to 6 carbon atoms per alkane, more preferably 2 to 4. Alkanolamines have one or more amino groups in their molecules, preferably 1 to 5, and more preferably 1 to 2.

[0116] Alkanolamines are not particularly limited, but examples include ethanolamine (miscible with water), N-methylethanolamine (solubility 100 [g / 100g water]), N,N-dimethylethanolamine (completely miscible with water), N-ethylethanolamine (miscible with water), N-butylethanolamine (miscible with water), N,N-diethylethanolamine (miscible with water), diethanolamine (solubility 100 [g / 100g water]), N-methyldiethanolamine (solubility 100 [g / 100g water]), N-ethyldiethanolamine (miscible with water), N-butyldiethanolamine (miscible with water), N-tert-butyldiethanolamine (completely miscible with water), triethanolamine (completely miscible with water), isopropanolamine (miscible with water), and N,N-dimethylisopropanolamine (completely miscible with water). N,N-Diethylisopropanolamine (miscible with water), Diisopropanolamine (solubility 87 [g / 100g water]), Triisopropanolamine (TIPA, standard boiling point 301℃, solubility 83 [g / 100g water]), N,N-Dimethylpropanolamine (miscible with water), 2-Amino-1-propanol (completely miscible with water), 2-Amino-2-Methyl-1-propanol (completely miscible with water) Examples include 5-amino-1-pentanol (miscible with water), 2-amino-2-methyl-1,3-propanediol (miscible with water), 2-amino-2-hydroxymethyl-1,3-propanediol (miscible with water), 3-amino-1,2-propanediol (miscible with water), 3-methylamino-1,2-propanediol (completely miscible with water), trippropanolamine, and tripbutanolamine.

[0117] Among these, triethanolamine and triisopropanolamine (TIPA) are preferred, with triisopropanolamine (TIPA) being more preferred.

[0118] The content of alkanolamines in the ink composition relative to the total mass is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. The lower limit is not particularly limited, but is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more.

[0119] 1.6 Water-dispersible resin The inkjet ink composition according to this embodiment may contain a water-dispersible resin. The water-dispersible resin can be a water-soluble resin or an emulsion of resin particles. Such a water-dispersible resin may function as a so-called fixing resin, improving the adhesion and abrasion resistance of the pigment ink components attached to the recording medium. The water-dispersible resin is preferably an emulsion of resin particles.

[0120] Examples of water-dispersible resins include polyurethane resins, acrylic resins, fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, ethylene vinyl acetate resins, vinyl acetate resins, butadiene resins, styrene resins, crosslinked acrylic resins, crosslinked styrene resins, benzoguanamine resins, phenolic resins, silicone resins, epoxy resins, paraffinic resins, fluororesins, and the like. These resins are often handled in emulsion form, but may also be in powder form. Furthermore, the resins can be used individually or in combination of two or more types.

[0121] Among these resins, from the viewpoint of further improving abrasion resistance, the water-dispersible resin preferably contains one or more of the following: acrylic resin, polyurethane resin, polyester resin, and polyolefin resin, and more preferably contains one or more of the following: acrylic resin and polyolefin resin.

[0122] Polyurethane resins are a general term for resins that have urethane bonds. In addition to urethane bonds, polyurethane resins may also use polyether-type urethane resins containing ether bonds in the main chain, polyester-type urethane resins containing ester bonds in the main chain, and polycarbonate-type urethane resins containing carbonate bonds in the main chain. Commercially available polyurethane resins may be used, for example, selected from Superflex 210, 460, 460s, 840, E-4000 (product names, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0123] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer, such as (meth)acrylic acid or (meth)acrylic acid ester. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, are examples. Furthermore, copolymers with vinyl monomers such as styrene are also examples. Acrylicamide and acrylonitrile can also be used as acrylic monomers.

[0124] For the resin emulsion made from acrylic resin, commercially available products may be used, such as FK-854 (trade name, manufactured by Chuo Rika Kogyo Co., Ltd.), Movinyl 952B, 718A (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Nipol LX852, LX874 (trade name, manufactured by Nippon Zeon Co., Ltd.), Polysol AT860 (manufactured by Showa Denko K.K.), Boncoat AN-1190S, YG-651, AC-501, AN-1170, 4001 (trade name, manufactured by DIC Corporation, acrylic resin emulsion), etc.

[0125] In this specification, the acrylic resin may be a styrene-acrylic resin as described above. Also, in this specification, the term (meth)acrylic means at least one of acrylic and methacrylic.

[0126] Styrene-acrylic resins are copolymers obtained from styrene monomers and acrylic monomers, and examples include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, and styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers. For styrene-acrylic resins, commercially available products may be used, such as Joncryl 62J, 7100, 390, 711, 511, 7001, 631, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610 (product names, manufactured by BASF), Movinyl 966A, 975N (product names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.).

[0127] The vinyl chloride resin may also be a vinyl chloride-vinyl acetate copolymer.

[0128] Examples of polyolefin resins include resins and copolymers produced from olefins or their derivatives, such as ethylene, propylene, and butylene, specifically polyethylene resins, polypropylene resins, and polybutylene resins. Commercially available polyolefin resins can be used, specifically Nopcoat PEM17 (trade name, manufactured by Sunopco Corporation), Chemipearl W4005 (trade name, manufactured by Mitsui Chemicals, Inc.), AQUACER515, AQUACER593 (both trade names, manufactured by Big Chemie Japan Co., Ltd.), and Hi-Tec E-6500 (manufactured by Toho Chemical Industry Co., Ltd., polyethylene resin).

[0129] The content of the water-dispersible resin is preferably 0.1% by mass or more and 25.0% by mass or less as solid content, more preferably 1.0% by mass or more and 15.0% by mass or less, even more preferably 2.0% by mass or more and 12.0% by mass or less, and particularly preferably 3.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink composition.

[0130] Among the water-dispersible resins, the content of acrylic resin is preferably 0.05% by mass or more and 20.0% by mass or less, more preferably 1.0% by mass or more and 15.0% by mass or less, even more preferably 2.0% by mass or more and 10.0% by mass or less, and particularly preferably 3.0% by mass or more and 8.0% by mass or less.

[0131] Among the water-dispersible resins, the content of polyolefin resins is preferably 0.1% to 5% by mass, more preferably 0.2% to 4% by mass, and even more preferably 0.3% to 3% by mass, based on the total mass of the ink composition.

[0132] 1.7 Surfactants The inkjet ink composition according to this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0133] Acetylene glycol-based surfactants are not particularly limited, but examples include Surfinol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (all of the above are brand names, manufactured by Air Products Japan Co., Ltd.), O Examples include Rufin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP.4001, EXP.4036, EXP.4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all brand names, manufactured by Nisshin Chemical Industry Co., Ltd.), and Acetyleneol E00, E00P, E40, E100 (all brand names, manufactured by Kawaken Fine Chemical Co., Ltd.).

[0134] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and a specific example is BYK-340 (trade name, manufactured by BYK-Chemie Japan Co., Ltd.).

[0135] While not particularly limited, polysiloxane compounds are preferred as silicone-based surfactants. While not particularly limited, examples of such polysiloxane compounds include polyether-modified organosiloxanes. Examples of commercially available polyether-modified organosiloxanes include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348, BYK-349 (all trade names, manufactured by BICK CHEMIE Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, and KF-355A. Examples include KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all product names, manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG503A, Silface SAG014 (all product names, manufactured by Nisshin Chemical Industry Co., Ltd.).

[0136] The above surfactants may be used individually or in combination of two or more.

[0137] The surfactant content is preferably 0.1% by mass or more and 2.0% by mass or less based on the total mass of the ink composition. The upper limit of the surfactant content is more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, particularly preferably 0.8% by mass or less, and most particularly preferably 0.5% by mass or less. The lower limit of the surfactant content is not particularly limited, but may be 0.2% by mass or more, or 0.3% by mass or more. Furthermore, it is also preferable that the content of silicone-based surfactants or fluorine-based surfactants among the above surfactants be within the above range.

[0138] Generally, including silicone-based surfactants in ink compositions tends to improve image quality, but often results in inferior scratch resistance and defoaming properties. However, in the inkjet ink composition according to this embodiment, even with a small amount of additive within the above range, it tends to produce excellent image quality as well as good scratch resistance and defoaming properties.

[0139] 1.8 Other ingredients The inkjet ink composition according to this embodiment may optionally contain various additives other than the above-mentioned components, such as defoaming agents, chelating agents, rust inhibitors, mold inhibitors, antioxidants, reduction inhibitors, and evaporation accelerators.

[0140] 1.9 Preparation method and physical properties The inkjet ink composition according to this embodiment is obtained by mixing the aforementioned components in any order and removing impurities by filtration or other means as necessary. A preferred method for mixing the components is to sequentially add the materials to a container equipped with a stirring device such as a mechanical stirrer or magnetic stirrer and then stir-mix them. As for the filtration method, centrifugal filtration, filter filtration, or the like can be performed as needed.

[0141] The inkjet ink composition according to this embodiment preferably has a surface tension (static surface tension) of 18 mN / m or more and 40 mN / m or less at 20°C, more preferably 20 mN / m or more and 35 mN / m or less, and even more preferably 22 mN / m or more and 33 mN / m or less, from the viewpoint of balancing image quality and reliability as an ink for inkjet recording. The surface tension can be measured, for example, by checking the surface tension when a platinum plate is wetted with ink in an environment of 20°C using an automatic surface tension meter CBVP-Z (product name, manufactured by Kyowa Interface Science Co., Ltd.).

[0142] From a similar viewpoint, the viscosity of the ink at 20°C is preferably 3 mPa·s to 10 mPa·s, and more preferably 3 mPa·s to 8 mPa·s. Viscosity can be measured, for example, using a viscoelasticity tester MCR-300 (product name, manufactured by Pysica) to measure the viscosity under 20°C conditions.

[0143] 1.10 Purpose Preferred applications of the inkjet ink composition according to this embodiment are described below.

[0144] 1.10.1 Recording media The inkjet ink composition according to this embodiment is preferably used for recording on low-absorption recording media or non-absorption recording media. When recording on low-absorption recording media or non-absorption recording media, the ink does not easily wet and spread (does not fill well) on the recording media, so even slight deviations in the amount of ink droplets ejected from the nozzle or slight deviations in the landing position can easily cause banding, which is a streaky unevenness in the recorded image. However, according to the inkjet ink composition according to this embodiment, even when used for recording on such recording media, banding can be reduced, image quality (wetting and spreading) is excellent, storage stability is excellent, and the deviation in landing position is excellent.

[0145] A "low absorption recording medium or non-absorbent recording medium" refers to a recording medium that does not absorb liquid at all or absorbs very little liquid. Quantitatively, a "low absorption recording medium or non-absorbent recording medium" is defined as "a recording medium that, in the Bristow method, absorbs liquid from the start of contact for 30 msec." 1 / 2 Up to 10 mL / m² of water absorption capacity 2 This refers to the recording medium described below. The Bristow method is the most widely used method for measuring liquid absorption in a short time and is also adopted by the Japan Paper & Pulp Technology Association (JAPAN TAPPI). Details of the test method are described in standard No. 51 "Paper and cardboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper & Pulp Test Methods 2000 Edition".

[0146] (Low absorption recording medium) Low absorption recording media are not particularly limited, but examples include coated paper having a coating layer on its surface for receiving ink. Coated paper is not particularly limited, but examples include printing paper such as art paper, coated paper, and matte paper. The coating layer is one that does not easily absorb ink, and examples include those coated with inorganic compound particles together with a binder.

[0147] (Non-absorbing recording medium) Non-absorbent recording media are not particularly limited, but examples include recording media made of plastic, glass, metal, ceramics, etc.

[0148] When the recording medium is made of plastic, examples include plastic films. Examples of such plastic films include polyester films, polyurethane films, polycarbonate films, polyphenylene sulfide films, polyimide films, and polyamide-imide films. Other examples include polyethylene, polyolefins such as polypropylene, and polyvinyl chloride. Biomass-derived plastic films are also an option, with examples including PLA, PBS, PHA, bio-PE, bio-PP, and bio-PET.

[0149] Furthermore, the material may be a film made of plastic, a material in which plastic is coated onto a base material such as paper, or a material in which a plastic film is bonded to a base material such as paper.

[0150] If the recording medium is metal, it may be a substrate made of metal such as iron, silver, copper, or aluminum, or one on which these various metals are deposited onto the recording surface of a non-metallic substrate such as plastic. In other words, it is sufficient if the recording surface is made of metal.

[0151] The recording medium may be a light-transmitting recording medium such as colorless, translucent, or colored transparent. Alternatively, it may be a non-light-transmitting recording medium such as a chromatic opaque or achromatic opaque. Furthermore, the recording medium may be a three-dimensional object such as a sheet, sphere, or rectangular prism, or a paper container.

[0152] Among these low-absorption recording media or non-absorption recording media, non-absorption recording media are preferred from the viewpoint of enjoying the effects of the present invention, and it is more preferable that the recording media be made of plastic. That is, such recording media are particularly prone to banding unevenness because the ink is less likely to spread, but with the inkjet ink composition according to this embodiment, even with such recording media, banding unevenness can be reduced, image quality (wetting spread) is excellent, storage stability is excellent, and the impact position deviation is excellently reduced.

[0153] 1.10.2 Treatment solution The inkjet ink composition according to this embodiment is preferably used for recording together with a processing solution containing a coagulant. By using a processing solution that coagulates the components of the ink, it is possible to improve image quality. However, in such an embodiment, the ink droplets become less likely to spread evenly on the recording medium, making banding unevenness more likely to occur. In contrast, the inkjet ink composition according to this embodiment, even when used for recording together with a processing solution containing a coagulant, tends to reduce banding unevenness, have excellent image quality (wetting spread), have excellent storage stability, and significantly reduce impact point misalignment.

[0154] Note that the "treatment liquid" is not an ink composition used for coloring a recording medium, but an auxiliary liquid used together with an ink composition. Further, the treatment liquid is preferably capable of aggregating or thickening components of the ink composition, and more preferably contains an aggregating agent that aggregates or thickens components of the ink composition. The treatment liquid may contain a coloring material such as a pigment, but the content thereof is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, based on the total mass of the treatment liquid, and the lower limit is 0% by mass. It is preferable that the treatment liquid contains no coloring material.

[0155] Hereinafter, each component contained in the treatment liquid will be described.

[0156] [Aggregating Agent] The treatment liquid contains an aggregating agent. Such an aggregating agent can rapidly react with components such as pigments and resins contained in the ink composition. As a result, the dispersed state of the components in the ink composition is destroyed to cause aggregation, and the aggregate inhibits the penetration of the pigment into the recording medium, which is considered to be excellent in terms of improving the image quality of a recorded image.

[0157] Examples of the aggregating agent include cationic compounds such as polyvalent metal salts, cationic resins, and cationic surfactants, and organic acids. These aggregating agents may be used alone or in combination of two or more. Among these aggregating agents, it is preferable to use at least one aggregating agent selected from the group consisting of polyvalent metal salts, organic acids, and cationic resins from the viewpoint of excellent reactivity with components contained in the ink composition.

[0158] A polyvalent metal salt is a water-soluble compound composed of a divalent or higher polyvalent metal ion and an anion that binds to the polyvalent metal ion. Specific examples of polyvalent metal ions include Ca 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Zn 2+ , Ba 2+ divalent metal ions such as; Al 3+ , Fe 3+, Cr 3+ Examples of trivalent metal ions include Cl. - , I - , Br - SO4 2- , 3- NO 3- , and HCOO - CH3COO - These are some examples. Among these polyvalent metal salts, calcium salts and magnesium salts are preferred from the viewpoint of the stability of the treatment solution and the reactivity as a flocculant.

[0159] Suitable organic acids include, for example, poly(meth)acrylic acid, formic acid, acetic acid, propionic acid, glycolic acid, oxalic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, citric acid, tartaric acid, lactic acid, pyruvate, pyrrolidone carboxylic acid, pyrrone carboxylic acid, pyrrole carboxylic acid, furanic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, or salts thereof. Organic acids may be used individually or in combination of two or more. Salts of organic acids that are also polyvalent metal salts shall be included in the category of polyvalent metal salts.

[0160] Examples of cationic resins include cationic urethane resins, cationic olefin resins, and cationic amine resins. Cationic amine resins can be any resin having amino groups, such as allylamine resins, polyamine resins, quaternary ammonium salt polymers, and polyamide resins. Polyamine resins include those having amino groups in the main skeleton of the resin. Allylamine resins include those having a structure derived from allyl groups in the main skeleton of the resin. Quaternary ammonium salt polymers include resins having quaternary ammonium salts in their structure. Polyamide resins include those having amide groups in the main skeleton of the resin and amino groups in the side chains of the resin. Among cationic resins, cationic amine resins are preferred not only because of their excellent reactivity but also because they are readily available.

[0161] The concentration of the flocculant in the treatment solution is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, based on the total mass of the treatment solution. Furthermore, the concentration of the flocculant in the treatment solution is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less, based on the total mass of the treatment solution.

[0162] 〔water〕 The processing solution may contain water. The type of water that can be used, the amount of water it contains, etc., can be the same as in the inkjet ink composition described above.

[0163] [Water-soluble low molecular weight organic compound] The processing solution may contain water-soluble low-molecular-weight organic compounds. The types of water-soluble low-molecular-weight organic compounds that can be used, the amount of water-soluble low-molecular-weight organic compounds, etc., can be the same as those for the inkjet ink composition described above.

[0164] [Surfactants] The processing solution may contain a surfactant. The type of surfactant that can be used, the amount of surfactant, etc., can be the same as in the inkjet ink composition described above.

[0165] [Other ingredients] The processing solution may also contain components other than those mentioned above, such as poorly water-soluble low-molecular-weight organic compounds, nonionic water-soluble resins, and water-dispersible resins, which are components found in the inkjet ink composition described above, and the content and other aspects may be the same. Furthermore, the processing solution may contain various additives as needed, such as defoamers, chelating agents, rust inhibitors, mold inhibitors, antioxidants, reduction inhibitors, and evaporation accelerators.

[0166] [Preparation method and physical properties] The method for preparing the processing solution and its physical properties can be the same as those for the inkjet ink composition described above.

[0167] 2. Recording Method A recording method according to one embodiment of the present invention includes an ink deposition step of ejecting the above-mentioned inkjet ink composition by an inkjet method and adhering it to a recording medium.

[0168] According to the recording method of this embodiment, since the above-described inkjet ink composition is used, banding unevenness can be reduced, image quality (wetting spread) is excellent, storage stability is excellent, and impact position deviation can be significantly reduced.

[0169] The following describes each step in the recording method according to this embodiment.

[0170] 2.1 Ink application process The recording method according to this embodiment includes an ink attachment step of ejecting the above-described inkjet ink composition by an inkjet method and adhering it to a recording medium.

[0171] The recording medium is not particularly limited and includes, for example, absorbent recording media such as paper, ink-absorbing film, and cloth; low-absorption recording media such as printing paper; and non-absorbent recording media such as metal, glass, and polymers. Among these, low-absorption recording media or non-absorbent recording media are preferred from the viewpoint of enjoying the effects of the present invention to the fullest extent. As low-absorption recording media and non-absorbent recording media are as described above, their explanation will be omitted.

[0172] In the ink application process, the amount of ink composition applied per unit area of ​​the recording medium to the area where the ink is applied is preferably 3 mg / inch. 2 The above is more preferable: 5 mg / inch 2 The above is preferable, and more preferably 10 mg / inch 2 That's all. The amount of ink composition applied per unit area of ​​the recording medium is preferably 20 mg / inch 2 The following is more preferably 18 mg / inch 2 The following, and more preferably 16 mg / inch 2 The following applies: When the amount of ink composition adheres within the above range, banding unevenness tends to be further reduced. Furthermore, it is also preferable to set the amount of ink composition adhered per unit area of ​​the recording medium in the region where the amount of ink adheres to the ink-adhering area of ​​the recording medium is maximum, i.e., the maximum amount of ink adhered, within the above range.

[0173] In the ink application process, it is preferable that the surface temperature of the recording medium is 55°C or lower when the above-mentioned inkjet ink composition is applied to the recording medium. In this case, the ink application process may be carried out without heating the recording medium, or it may be carried out with heating. That is, even when heating is performed, it is preferable to heat the recording medium so that its surface temperature is 55°C or lower.

[0174] The upper limit of the surface temperature of the recording medium when ink is applied is preferably 55°C or lower, more preferably 50°C or lower, even more preferably 45°C or lower, particularly preferably 40°C or lower, even more preferably 35°C or lower, and especially preferably 28°C or lower. On the other hand, the lower limit is preferably 20°C or higher, more preferably 23°C or higher, particularly preferably 25°C or higher. Furthermore, 28°C or higher is preferred, 35°C or higher is more preferred, and 40°C or higher is even more preferred.

[0175] 2.2 Processing liquid application process The recording method according to this embodiment may include a processing liquid attachment step in which a processing liquid containing a coagulant is attached to a recording medium. The processing liquid can be the same as the processing liquid described above.

[0176] The processing liquid application step can be performed simultaneously with, before, or after the ink application step described above.

[0177] Methods for applying the processing solution include, for example, immersion coating, in which the recording medium is immersed in the processing solution; roller coating, in which the processing solution is applied using a brush, roller, spatula, roll coater, etc.; spray coating, in which the processing solution is sprayed using a spray device, etc.; and inkjet coating, in which the processing solution is applied using an inkjet method. Among these, inkjet coating is preferred.

[0178] In the processing liquid adhesion process, the amount of processing liquid adhered to the area of ​​the recording medium where the ink and processing liquid are layered and adhered is preferably 5% by mass or more, more preferably 7% by mass or more, and particularly preferably 9% by mass or more, relative to the amount of ink composition adhered in the ink adhesion process described above. On the other hand, the amount of processing liquid adhered is preferably 25% by mass or less, more preferably 21% by mass or less, even more preferably 17% by mass or less, and particularly preferably 13% by mass or less, relative to the amount of ink composition adhered in the ink adhesion process described above. When the amount of processing liquid adhered is within the above range, it tends to be possible to achieve a good balance between image quality, such as banding unevenness and aggregation unevenness, and scratch resistance. Furthermore, the amount of processing solution adhering to the area where the ink and processing solution are layered and attached to the recording medium is 0.1 to 5 mg / inch. 2 It is preferable. Furthermore, it is also preferable to set the amount of processing solution applied in the region where the amount of ink applied to the recording medium is maximum, within the above range.

[0179] In the processing solution application step, the surface temperature of the recording medium when the above-mentioned inkjet ink composition is applied to the recording medium can be the same as in the ink application step described above.

[0180] 2.3 Primary drying process The recording method according to this embodiment may include a primary drying step for drying the inkjet ink composition attached to the recording medium.

[0181] In recording methods, the inclusion of a primary drying step is preferable because it allows for rapid drying of the ink composition and processing solution on the recording medium, resulting in improved image quality. On the other hand, because the ink dries rapidly in the primary drying step, the ink does not spread easily on the recording medium. In other words, recording methods that include a primary drying step have the problem of being more prone to banding unevenness. However, according to the recording method of this embodiment, even in such cases, banding unevenness can be reduced, resulting in excellent image quality (wetting spread), excellent storage stability, and a tendency to significantly reduce impact position deviation.

[0182] The primary drying step is a step to dry the ink adhering to the recording medium at an early stage. The primary drying step is a step to dry at least a portion of the solvent component of the ink adhering to the recording medium to the extent that the flow of the ink is reduced. Preferably, the primary drying step is performed so that the drying of ink droplets that have landed on the recording medium begins no later than 0.5 seconds after the droplets land. The primary drying step may also be applied to the adhering processing liquid in the same way as the ink.

[0183] Examples of methods for the primary drying process include a fan-assisted method, which involves blowing air at room temperature (room temperature air) or blowing air with heating (hot air) onto the recording medium; a heat transfer method, which involves heating the recording medium with an IR heater, microwave radiation, or platen heater; and methods combining these. It should be noted that the primary drying process in this embodiment is not particularly limited as long as it can improve the drying properties of the ink, and does not necessarily require heating. Therefore, in the primary drying process in this embodiment, a method based on blowing air at room temperature may be used alone. However, it is more preferable that the primary drying process involves heating.

[0184] In the primary drying process, when drying is performed by blowing air, the air velocity is preferably 0.5 to 15 m / s, more preferably 0.5 to 10 m / s, even more preferably 1 to 5 m / s, and particularly preferably 2 to 3 m / s. This air velocity is the air velocity near the surface of the recording medium. The air temperature of the fan is preferably 55°C or lower, and more preferably 10°C or higher. Furthermore, 15 to 50°C is preferred, and 20 to 49°C is more preferred. Even more preferably 23 to 40°C, more preferably 25 to 35°C, and still more preferably 25 to 28°C. The air temperature of the fan may also be room temperature.

[0185] Furthermore, the surface temperature of the recording medium in the primary drying step may be within the temperature range described above as the surface temperature of the recording medium in the ink application step, and is preferred. That is, the surface temperature of the recording medium in the primary drying step is particularly preferably 55°C or lower, and more preferably within the aforementioned surface temperature range. When the drying temperature during the primary drying process is within the above range, banding unevenness can be further reduced, image quality (wetting spread) can be improved, and good clogging recovery can be obtained.

[0186] Furthermore, if heating is involved in the primary drying process, the primary drying process may be carried out so that ink adheres to the heated recording medium, or heating may be carried out as soon as possible after adhesion. In the primary drying process, it is preferable that heating of the ink droplets that have landed on the recording medium begins no later than 0.5 seconds after the ink droplets land. If heating is involved in the primary drying process, the heating can be performed before the ink application process, simultaneously with the application process, or shortly after the application process, and it is preferable that it be performed simultaneously. The ink application process can be carried out with this heating sequence.

[0187] Furthermore, the surface temperature of the recording medium during the primary drying process is the surface temperature of the recording medium at the time of ink application if ink is applied to the recording medium after the primary drying process, and the surface temperature of the recording medium at the time of the primary drying process if the primary drying process is performed soon after ink application. It is also the maximum temperature achieved during the primary drying process. Preferably, the surface temperature of the recording medium during the primary drying process in these cases is within the range of the surface temperature of the recording medium at the time of ink application as described above. Furthermore, the surface temperature of the recording medium when heating is not involved in the primary drying process is the surface temperature of the recording medium at the time of ink application.

[0188] 2.4 Post-heating process The recording method according to this embodiment may include a post-heating step of heating the recording medium after the ink application step described above.

[0189] Since the inkjet ink composition used in the recording method according to this embodiment contains poorly water-soluble low-molecular-weight organic compounds, the drying performance after the ink application step is better compared to cases where poorly water-soluble low-molecular-weight organic compounds are not included. Furthermore, since the recording method according to this embodiment includes a post-heating step, drying performance can be further improved, which tends to result in recordings with superior abrasion resistance, making it preferable.

[0190] The post-heating step is a heating step that completes the recording and heats the recorded material sufficiently so that it can be used. The post-heating step is a heating step that ensures sufficient drying of the solvent components of the ink and processing liquid, and heating of the resins contained in the ink to flatten the ink coating. Preferably, the post-heating step is started more than 0.5 seconds after the ink and processing liquid have adhered to the recording medium. For example, it is preferable to start heating a recording area of ​​the recording medium more than 0.5 seconds after the adhesion of the ink and processing liquid to that area is completely finished. Furthermore, it is preferable that the preferred temperature in the primary drying step is different from the preferred temperature in the post-heating step.

[0191] The heating of the recording medium in the post-heating step can be carried out using, for example, an appropriate heating means when using an inkjet recording device. Furthermore, it is not limited to the heating means provided in the inkjet recording device, but can be carried out using any appropriate heating means. In this case, the surface temperature of the recording medium is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, and particularly preferably 85°C or higher. Furthermore, the surface temperature of the recording medium heated in the post-heating step is preferably 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, and particularly preferably 95°C or lower. According to the recording method of this embodiment, even with a surface temperature of the recording medium within the above range, the ink tends to dry sufficiently, and a recording with excellent abrasion resistance can be obtained.

[0192] 2.5 Recording Method In the recording method according to this embodiment, recording is performed by multiple main scans, and it is preferable to perform multiple main scans on the same scanning area. In such a recording method, the amount of ink droplets deposited by a single main scan is reduced. Therefore, since the ink droplets adhere discretely to the recording medium, the opportunities for contact with adjacent ink droplets are reduced. In other words, in such a recording method, the ink does not fill the recording medium well, and banding, which is a streaky unevenness visible in the recorded image, is more likely to occur. In contrast, according to the recording method according to this embodiment, since the above-described inkjet ink composition is used, even in such a recording method, banding is reduced, image quality (wetting spread) is excellent, storage stability is excellent, and the impact point misalignment is excellently reduced.

[0193] The number of main scans is preferably 2 to 20, more preferably 3 to 15, and even more preferably 4 to 10. "Performing multiple main scans in the same scanning area" means performing a main scan again in an area that has already been scanned once. For example, if the distance of one sub-scan is shorter than the length of the nozzle row that ejects ink in the sub-scanning direction, the scanning area of ​​the main scan will be scanned again. More specifically, if the distance of one sub-scan is one-quarter of the length of the nozzle row that ejects ink in the sub-scanning direction, then four main scans will be performed in the same scanning area. In this case, the number of main scans is said to be four.

[0194] The recording method according to this embodiment may also be a line-type recording method that performs recording in a single scan using a line head. In this case as well, streaky unevenness may occur along the scanning direction, but according to this embodiment, banding unevenness can be reduced and image quality (wetting spread) tends to be superior.

[0195] 2.6 Inkjet Recording Devices An example of an inkjet recording apparatus that can be preferably applied to the recording method according to this embodiment will be described with reference to the drawings.

[0196] Figure 1 is a schematic cross-sectional view illustrating an inkjet recording device. Figure 2 is a perspective view showing an example of the configuration around the carriage of the inkjet recording device 1 in Figure 1. As shown in Figures 1 and 2, the inkjet recording device 1 comprises a recording head 2, an IR heater 3, a platen heater 4, a heating heater 5, a cooling fan 6, a preheater 7, a ventilation fan 8, a carriage 9, a platen 11, a carriage movement mechanism 13, a transport means 14, and a control unit CONT. The operation of the entire inkjet recording device 1 is controlled by the control unit CONT shown in Figure 2.

[0197] The recording head 2 is configured to record onto the recording medium M by ejecting an inkjet ink composition from the nozzles of the recording head 2 and applying it to the recording medium M. The same configuration can be used for the processing liquid. The recording head 2 shown in Figures 1 and 2 is a serial recording head that applies ink and processing liquid to the recording medium M by scanning it multiple times relative to the recording medium M in the main scanning direction. The recording head 2 is mounted on the carriage 9 shown in Figure 2. The recording head 2 is scanned multiple times relative to the recording medium M in the main scanning direction by the operation of the carriage movement mechanism 13, which moves the carriage 9 in the media width direction of the recording medium M. The media width direction is the main scanning direction of the recording head 2. Scanning in the main scanning direction is also called main scanning.

[0198] Here, the main scanning direction is the direction in which the carriage 9, on which the recording head 2 is mounted, moves. In Figure 1, this direction intersects with the sub-scanning direction, which is the transport direction of the recording medium M indicated by arrow SS. In Figure 2, the width direction of the recording medium M, i.e., the direction represented by S1-S2, is the main scanning direction MS, and the direction represented by T1→T2 is the sub-scanning direction SS. Note that in one scan, scanning is performed in the main scanning direction, i.e., in either the direction of arrow S1 or arrow S2. Then, by repeating the main scan of the recording head 2 and the sub-scan, which is the transport of the recording medium M, multiple times, data is recorded on the recording medium M.

[0199] The cartridge 12 that supplies ink and processing fluid to the recording head 2 includes multiple independent cartridges. The cartridge 12 is detachably mounted on the carriage 9 on which the recording head 2 is mounted. Each of the multiple cartridges can be filled with different types of inkjet ink compositions or processing fluids, and the inkjet ink compositions or processing fluids are supplied from the cartridge 12 to each nozzle. Although Figures 1 and 2 show an example where the cartridge 12 is mounted on the carriage 9, it is not limited to this configuration, and may be provided in a location other than the carriage 9, with the ink and fluids supplied to each nozzle by supply pipes (not shown).

[0200] Conventional methods can be used for ejecting the recording head 2. Here, a method is used that ejects droplets using the vibration of a piezoelectric element, that is, an ejection method that forms ink droplets, etc., by the mechanical deformation of an electrostrictive element.

[0201] The inkjet recording device 1 may be equipped with a primary drying mechanism for drying the recording medium M when ejecting ink or processing liquid from the recording head 2 and adhering it to the recording medium. The primary drying mechanism can be of the conduction type, air-blowing type, or radiation type. The conduction type conducts heat to the recording medium from a component in contact with the recording medium. For example, a platen heater can be used. The air-blowing type sends room temperature air or warm air to the recording medium to dry the ink, etc. For example, a fan can be used. The radiation type heats the recording medium by radiating heat-generating radiation to it. For example, IR radiation can be used. In addition, although not shown, a heater similar to the platen heater may be provided immediately downstream of the platen heater 4 in the SS direction. These primary drying mechanisms may be used individually or in combination. For example, the primary drying mechanism may be equipped with an IR heater 3 and a platen heater 4.

[0202] Furthermore, by using the IR heater 3, the recording medium M can be heated radiantly by infrared radiation from the recording head 2 side. This makes it easier for the recording head 2 to be heated at the same time, but the temperature can be raised without being affected by the thickness of the recording medium M, compared to when the recording medium M is heated from the back surface by a platen heater 4 or the like. In addition, various fans (e.g., ventilation fan 8) may be provided to dry the ink, etc. on the recording medium M by blowing warm air or air at the same temperature as the environment onto the recording medium M.

[0203] The platen heater 4 can heat the recording medium M via the platen 11 at a position facing the recording head 2. The platen heater 4 is capable of heating the recording medium M by conduction and is used as needed in the inkjet recording method.

[0204] Furthermore, the inkjet recording device 1 may be equipped with a preheater 7 that preheats the recording medium M before ink or processing liquid is applied to the recording medium M.

[0205] The system may also include a post-heating mechanism that heats the recording medium after the ink application process and the processing liquid application process to dry and fix the ink.

[0206] The heating element 5 used in the post-heating mechanism dries and solidifies the ink and other substances adhering to the recording medium M. When the heating element 5 heats the recording medium M on which the image is recorded, the water and other substances contained in the ink and processing liquid evaporate more quickly and scatter, and an ink film is formed by the resin contained in the ink. In this way, the ink film firmly fixes or adheres to the recording medium M, resulting in excellent film-forming properties, and a high-quality image with excellent resolution can be obtained in a short time.

[0207] The inkjet recording device 1 may have a cooling fan 6. After the ink recorded on the recording medium M dries, the ink on the recording medium M is cooled by the cooling fan 6, thereby forming an ink coating film with good adhesion on the recording medium M.

[0208] Below the carriage 9 are a platen 11 that supports the recording medium M, a carriage movement mechanism 13 that moves the carriage 9 relative to the recording medium M, and a transport means 14 which is a roller that transports the recording medium M in the sub-scanning direction. The operation of the carriage movement mechanism 13 and the transport means 14 is controlled by the control unit CONT.

[0209] 3. Examples The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" below refers to mass.

[0210] 3.1 Preparation of inkjet ink composition Each component was placed in a container to obtain the compositions shown in Tables 1 and 2 below. The mixture was then mixed and stirred with a magnetic stirrer for 2 hours, and then filtered through a 5 μm pore size membrane filter to obtain the inkjet ink compositions for each example and comparative example. The numerical values ​​in the tables for pigments, water-dispersible resins, nonionic water-soluble resins, and other resin components represent their solid content. Pure water was added so that the total mass of the composition was 100% by mass. The pigment used was a pigment dispersion prepared in advance by the following procedure.

[0211] [Preparation of Pigment Dispersion] First, 50 g of methyl ethyl ketone (MEK) was added to a flask equipped with a dropping funnel, nitrogen inlet tube, reflux condenser, thermometer, and stirrer, and heated to 75°C while bubbling with nitrogen. A mixture of monomers consisting of 80 g of butyl methacrylate, 50 g of methyl methacrylate, 15 g of styrene, and 20 g of methacrylic acid, along with 50 g of MEK and 500 mg of polymerization initiator (azobisisobutyronitrile / AIBN), was added dropwise through the dropping funnel over 3 hours. After the dropwise addition, the mixture was heated under reflux for a further 6 hours, and after cooling, the volatile MEK was added to obtain a resin solution (50% by mass of resin solids, acid value 79 mg / KOH, Tg 65°C). To 20 g of the solution, a predetermined amount of 20% by mass sodium hydroxide aqueous solution was added as a neutralizing agent to completely neutralize the salt-forming groups. Then, while stirring, 50 g of pigment (CI pigment blue 15:3) was gradually added, and the mixture was kneaded in a bead mill for 2 hours. 200 g of deionized water was added to the resulting mixture and stirred, then heated under reduced pressure to remove MEK by distillation. The concentration was further adjusted with deionized water to obtain a pigment dispersion (20% by mass pigment solids, 5% by weight resin solids).

[0212] 3.2 Preparation of the treatment solution Each component was placed in a container to obtain the composition shown in Table 3 below. The mixture was then mixed and stirred with a magnetic stirrer for 2 hours, and then filtered through a 5 μm pore size membrane filter to obtain treated solutions A to C. The numerical values ​​in the table for cationic resins represent the solid content. Pure water was added so that the total mass of the composition reached 100% by mass.

[0213] [Table 1]

[0214] [Table 2]

[0215] [Table 3]

[0216] Further explanations are provided for each component shown in Tables 1 to 3 above.

[0217] <Water-soluble low molecular weight organic compounds> • PG: [Propylene glycol, standard boiling point 188°C, liquid (25°C), completely miscible with water] • 1,2HD: [1,2-Hexanediol, standard boiling point 224°C, liquid (25°C), miscible with water] • CPL: [ε-caprolactam, standard boiling point 267°C, solid (25°C)] TIPA: [Triisopropanolamine, standard boiling point 301°C, solubility 83 g / 100 g water, solid (25°C)]

[0218] <Poorly water-soluble low molecular weight organic compounds> BEPG: [2-Butyl-2-ethyl-1,3-propanediol, standard boiling point 264°C, melting point 43°C, solid (25°C), solubility 0.9 [g / 100g water]] • 1,2OD: [1,2-Octanediol, standard boiling point 267°C, melting point 26°C, solid (25°C), solubility 0.8 [g / 100g water]] EHDG: [Diethylene glycol mono-2-ethylhexyl ether, standard boiling point 277°C, melting point -82°C, liquid (25°C), solubility 0.5 [g / 100g water]] • 1-Hex: [1-Hexanol, standard boiling point 157°C, liquid (25°C), solubility 0.1 [g / 100g water]]

[0219] <Surfactants> • BYK-349: [Silicone-based surfactant, product name manufactured by Bic Chemie Japan Co., Ltd.] • Surfinol DF110D: [Acetylene-based surfactant, product name manufactured by Nisshin Chemical Industry Co., Ltd.]

[0220] <Water dispersible resin> • Joncryl 631: [Styrene-acrylic resin emulsion, product name manufactured by BASF Japan] • Hi-Tec E-6500: [Polyethylene-based wax emulsion, product name manufactured by Toho Chemical Industry Co., Ltd.]

[0221] <Specific nonionic water-soluble resins> • PVP (Polyvinylpyrrolidone) Pitzcol K-17: [Polyvinylpyrrolidone, weight-average molecular weight 9000, product name manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] Pitzcol K-30: [Weight-average molecular weight 45,000, product name manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] • PNVA (Poly-N-vinylacetamide) ··GE191-108: [Poly-N-vinylacetamide, weight-average molecular weight 10,000, product name manufactured by Showa Denko Corporation] • PVA (Polyvinyl Alcohol) PVA-203: [Polyvinyl alcohol, weight-average molecular weight 16000, product name manufactured by Kuraray Co., Ltd.] PEG / PEO (Polyethylene Glycol / Polyethylene Oxide) PEG-6000: [Polyethylene glycol, weight-average molecular weight 8300, ADEKA brand name]

[0222] <Other nonionic water-soluble resins> PEG / PEO (Polyethylene Glycol / Polyethylene Oxide) PEG-1000: [Polyethylene glycol, weight-average molecular weight 1000, ADEKA brand name] <Anionic water-soluble resin> • Aron A-30SL: [Ammonium polyacrylate, weight-average molecular weight 6000, product name manufactured by Toagosei Co., Ltd.]

[0223] <Agglutinant> • Catiomaster PD-7: [Amine-epichlorohydrin-based cationic resin, product name manufactured by Yokkaichi Gosei Co., Ltd.]

[0224] 3.3 Printing Conditions The following printing conditions were used in the evaluation test described later. (Printing conditions) • Printer: SC-R5050, modified machine manufactured by Seiko Epson Corporation. Resolution: 1200 x 1200 dpi • Number of scans: 9 • Platen heating temperature: 45℃ ·Secondary drying temperature: 80℃ • Recording medium: "Orajet 3165G-010", manufactured by Orafor Japan, PVC film • Platen gap: 1.7mm

[0225] "Platen heating temperature" refers to the surface temperature of the recording medium in the platen area that faces the print head during recording. "Secondary drying temperature" refers to the surface temperature of the recording medium heated by a secondary heater located downstream of the inkjet print head. The heating and drying process at the secondary drying temperature was performed for approximately 3 minutes.

[0226] 3.4 Evaluation Test 3.4.1 Scratch resistance The inkjet ink composition obtained above was filled into the "SC-R5050," and a solid pattern was printed on the recording medium according to the printing conditions described above. Furthermore, the processing solution obtained above was also filled into the "SC-R5050" as needed, according to the conditions described in Tables 4 to 6 below. At this time, the color ink adhesion amount was 12 mg / inch. 2 The amount of treatment solution adhering to the surface is 1 mg / inch 2 The following criteria were used to determine the degree of ink removal after leaving the sample at room temperature for 30 minutes. The ink-stained area was then cut into a 30 x 150 mm rectangle, and rubbed 100 times using a plain woven cloth with a JSPS-type abrasion resistance tester (load 500 g). The degree of ink removal was visually observed and judged according to the following evaluation criteria. (Evaluation Criteria) AA: No peeling A: Less than 20% of the assessed area is peeling. B: Less than 50% of the assessed area is peeling. C: More than 50% of the evaluated area is peeling.

[0227] 3.4.2 Image Quality (Wet Spread) The inkjet ink composition obtained above was filled into the "SC-R5050," and a solid pattern was printed on the recording medium according to the printing conditions described above. Furthermore, the processing solution obtained above was also filled into the "SC-R5050" as needed, according to the conditions described in Tables 4 to 6 below. At this time, the color ink deposition amount was 20 mg / inch. 2 Using a duty cycle of 100%, patch patterns were printed in 10% increments, and the amount of processing solution applied was set to 10% by mass of the amount of color ink applied. The printed materials were visually inspected and evaluated according to the following criteria. (Evaluation Criteria) AA: No streaky density variations (banding) extending in the main scanning direction are visible. A: There is some banding unevenness, but the difference in density is small and not noticeable. B: There is banding unevenness and a large difference in density, but it is acceptable. C: There is banding unevenness, large differences in density, and it is noticeable.

[0228] 3.4.3 Clogging recovery After filling the "SC-R5050" with the inkjet ink composition obtained above, the nozzle surface was intentionally tapped with a water-moistened Benkot to induce nozzle deactivation. In this state, the printer was run idle for 3 hours under the temperature conditions based on the printing conditions described above. After recording, cleaning was performed three times, the number of unrecovered nozzles was counted, and the results were judged according to the following evaluation criteria. However, the processing liquid was excluded from the evaluation. Each cleaning cycle discharged 1g of ink from the nozzle group. The nozzle group consists of 800 nozzles. (Evaluation Criteria) AA: No nozzle failure to dispense A: Nozzle non-discharge rate is less than 1% B: Nozzle non-discharge rate: 1% or more but less than 3% C: Nozzle non-ejection rate of 3% or more

[0229] 3.4.4 Storage Stability 30 g of each inkjet ink composition obtained above was sealed in an aluminum pack without incorporating air bubbles, and then left to stand in a 60°C constant temperature bath for 6 days. After taking out and allowing to cool naturally, the shear rate was measured at 200 s using a rheometer (MCR702 / Anton Paar GmbH) -1 viscosity was measured, and the thickening rate was calculated by comparison with the initial viscosity (immediately after ink preparation). Storage stability was determined from the obtained thickening rate according to the following evaluation criteria. (Evaluation Criteria) A: Thickening rate less than 3% B: Thickening rate of 3% or more and less than 5% C: Thickening rate of 5% or more

[0230] 3.4.5 Landing Misalignment After filling the "SC-R5050" with the inkjet ink composition obtained above, setting a recording medium, and performing flushing, a nozzle check pattern was recorded immediately after flushing, and normal ejection was confirmed. Thereafter, idle running was performed for 1 minute without ejecting ink under a temperature condition of 45°C for the platen, and the same nozzle check pattern was recorded. The landing misalignment of ink after the idle running operation was compared and evaluated according to the following evaluation criteria. The distance of landing position misalignment in the evaluation criteria was an average value for all nozzles. However, non-ejecting nozzles were excluded, and the treatment liquid was not subject to evaluation. (Evaluation Criteria) A: No difference in landing position B: Misalignment exists within the inter-nozzle distance C: Misalignment exceeds the inter-nozzle distance

[0231]

Table 4

[0232]

Table 5

[0233]

Table 6

[0234] 3.5 Evaluation Results The evaluation results are shown in Tables 4 to 6 above.

[0235] Based on the evaluation results above, the product contains a pigment, a poorly water-soluble low-molecular-weight organic compound, and a nonionic water-soluble resin, wherein the pigment is a self-dispersing pigment or a resin-dispersed pigment dispersed by a dispersant resin. In each example of the water-based inkjet ink composition, the nonionic water-soluble resin had a weight-average molecular weight of 2000 or more, and its content was 1% by mass or less relative to the total mass of the ink composition. This resulted in reduced banding unevenness, excellent image quality (wetting spread), excellent storage stability, and a significant reduction in impact position deviation.

[0236] A comparison between Example 1 and Comparative Example 1 showed that the absence of a nonionic water-soluble resin resulted in inferior storage stability and clogging recovery.

[0237] A comparison of Example 1 with Comparative Examples 2 and 3 showed that when poorly water-soluble low-molecular-weight organic compounds were not included, banding unevenness could not be reduced, resulting in inferior image quality (wetting spread).

[0238] A comparison between Example 1 and Comparative Example 4 revealed that when the content of nonionic water-soluble resin was not below a predetermined amount, the discharge characteristics were inferior and misalignment of the projectile occurred.

[0239] A comparison between Example 1 and Comparative Examples 5 and 6 revealed that when a specific nonionic water-soluble resin was not included, storage stability and clogging recovery were inferior.

[0240] The results from Examples 1 and 2 suggest that when a specific nonionic water-soluble resin is present within a predetermined content range, it tends to improve ink ejection characteristics such as misalignment of the impact point and abrasion resistance while maintaining excellent storage stability.

[0241] From the results of Examples 1 and 3 to 6, various specific nonionic water-soluble resins were excellent in storage stability and clogging recoverability.

[0242] From the results of Examples 1, 7 and 8, when the content of the poorly water-soluble low-molecular-weight organic compound is within a predetermined range, it tended to be able to achieve a good balance between image quality (wetting and spreading) and clogging recoverability.

[0243] From the results of Examples 1 and 9 to 11, various poorly water-soluble low-molecular-weight organic compounds were excellent in image quality (wetting and spreading).

[0244] From the results of Examples 1, 12 and 13, when the content of the water-soluble low-molecular-weight organic compound having a standard boiling point of 250°C or lower is within a predetermined range, it tended to be able to achieve a good balance among abrasion resistance, clogging recoverability and landing position deviation.

[0245] From the results of Examples 1 and 14, when the ink contains a water-dispersible resin, it was more excellent in abrasion resistance.

[0246] From the results of Examples 1 and 15 to 17, even when the ink is used for recording together with a treatment liquid containing a flocculant, it was able to reduce banding unevenness and was excellent in image quality (wetting and spreading).

[0247] Although not described in Tables 4 to 6 above, the reference example using Ink D was also evaluated under the same printing conditions as described above except that the recording medium was a plain paper roll (plain paper manufactured by Seiko Epson Corporation). In this case, the problem of banding unevenness did not occur.

[0248] The following contents are derived from the above-described embodiment.

[0249] One aspect of the inkjet ink composition is comprises a pigment, a poorly water-soluble low-molecular-weight organic compound, and a nonionic water-soluble resin, the pigment is a self-dispersing pigment or a resin-dispersed pigment dispersed by a dispersant resin, The nonionic water-soluble resin has a weight-average molecular weight of 2000 or more, is contained in an amount of 1% by mass or less relative to the total mass of the ink composition, and is water-based.

[0250] In one embodiment of the above inkjet ink composition, The aforementioned poorly water-soluble low molecular weight organic compound may contain one or more of the following: alkanediols, monoalcohols, and glycol monoethers.

[0251] In any embodiment of the above inkjet ink composition, The nonionic water-soluble resin may contain one or more of the following: polyvinylpyrrolidone, poly-N-vinylacetamide, polyvinyl alcohol, and polyalkylene oxide.

[0252] In any embodiment of the above inkjet ink composition, The content of the poorly water-soluble low-molecular-weight organic compound may be 0.1% by mass or more and 2% by mass or less based on the total mass of the ink composition.

[0253] In any embodiment of the above inkjet ink composition, The ink composition may contain a water-soluble low-molecular-weight organic compound having a standard boiling point of 250°C or lower, and the content of the water-soluble low-molecular-weight organic compound having a standard boiling point of 250°C or lower may be 5% by mass or more and 30% by mass or less based on the total mass of the ink composition.

[0254] In any embodiment of the above inkjet ink composition, The material contains a water-dispersible resin, which may contain one or more of the following: acrylic resin, polyurethane resin, polyester resin, or polyolefin resin.

[0255] In any embodiment of the above inkjet ink composition, It may be used for recording on low absorption recording media or non-absorption recording media.

[0256] In any embodiment of the above inkjet ink composition, It may be used for recording purposes in conjunction with a treatment solution containing a coagulant.

[0257] One method of recording is: The system includes an ink application step in which the above-mentioned inkjet ink composition is ejected by an inkjet method and deposited onto a recording medium.

[0258] In one embodiment of the above recording method, Recording may be performed by multiple main scans, and multiple main scans may be performed on the same scanning area.

[0259] In any embodiment of the above recording method, The system may also include a primary drying step for drying the inkjet ink composition adhering to the recording medium.

[0260] In any embodiment of the above recording method, The process may include a post-heating step in which the recording medium is heated after the ink application step.

[0261] The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes configurations that are substantially identical to the configurations described in the embodiments, for example, configurations that have the same function, method and result, or configurations that have the same purpose and effect. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as the configurations described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments. [Explanation of Symbols]

[0262] 1... Inkjet recording device, 2... Recording head, 3... IR heater, 4... Platen heater, 5... Heating heater, 6... Cooling fan, 7... Preheater, 8... Ventilation fan, 9... Carriage, 11... Platen, 12... Cartridge, 13... Carriage movement mechanism, 14... Transport means, CONT... Control unit, MS... Main scanning direction, SS... Sub-scanning direction, M... Recording medium

Claims

1. It contains a pigment, a poorly water-soluble low-molecular-weight organic compound, and a nonionic water-soluble resin. The aforementioned pigment is a self-dispersing pigment or a resin-dispersed pigment dispersed by a dispersant resin. The nonionic water-soluble resin has a weight-average molecular weight of 2000 or more, and its content is 1% by mass or less relative to the total mass of the ink composition. The aforementioned poorly water-soluble low molecular weight organic compound is a 1,3-alkanediol represented by the following general formula (1), in an aqueous inkjet ink composition. 【Chemistry 1】 (In formula (1), R1, R2, and R3 are independently hydrogen or alkyl groups. The total number of carbon atoms in R1, R2, and R3 is between 3 and 9.)

2. The inkjet ink composition according to claim 1, wherein the poorly water-soluble low molecular weight organic compound comprises one or more of 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2-ethyl-1,3-hexanediol.

3. The inkjet ink composition according to claim 1, wherein the nonionic water-soluble resin comprises one or more of polyvinylpyrrolidone, poly-N-vinylacetamide, polyvinyl alcohol, and polyalkylene oxide.

4. The inkjet ink composition according to claim 1, wherein the content of the poorly water-soluble low-molecular-weight organic compound is 0.1% by mass or more and 2% by mass or less based on the total mass of the ink composition.

5. The inkjet ink composition according to claim 1, comprising a water-soluble low molecular weight organic compound having a standard boiling point of 250°C or lower, wherein the content of the water-soluble low molecular weight organic compound having a standard boiling point of 250°C or lower is 5% by mass or more and 30% by mass or less based on the total mass of the ink composition.

6. The inkjet ink composition according to claim 1, comprising a water-dispersible resin, wherein the water-dispersible resin comprises one or more of the following: an acrylic resin, a polyurethane resin, a polyester resin, and a polyolefin resin.

7. The inkjet ink composition according to claim 1, which is used for recording on a low-absorption recording medium or a non-absorption recording medium.

8. The inkjet ink composition according to claim 1, which is used for recording together with a processing liquid containing a coagulant.

9. A recording method comprising an ink application step of ejecting the inkjet ink composition described in claim 1 by an inkjet method and adhering it to a recording medium.

10. The recording method according to claim 9, wherein recording is performed by multiple main scans, and multiple main scans are performed on the same scanning area.

11. The recording method according to claim 9, further comprising a primary drying step of drying the inkjet ink composition adhering to the recording medium.

12. The recording method according to claim 9, further comprising a post-heating step of heating the recording medium after the ink application step.

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