Ink jet ink composition and recording device

Abstract

To provide an ink jet ink composition that has favorable color developability of an image and that suppresses sedimentation of a pigment effectively.SOLUTION: An aqueous ink jet ink composition comprising a pigment, the pigment comprising a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group, and a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than the phosphorus-containing group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink-jet ink composition and a recording apparatus. [Background technology]

[0002] Inkjet printing is used in a wide range of fields. It is widely used for both home and business purposes. Furthermore, with the rise in remote work and SOHO, printing at home is also on the rise. Inkjet printers with large ink tanks are being considered because they reduce the hassle of replacing ink cartridges and allow for continuous printing.

[0003] For example, Patent Document 1 discloses an ink composition that contains a pigment, a resin, and an organic solvent and is poured into an ink container that has an ink chamber that can be refilled with the ink composition and an ink inlet that can be opened and closed, and the ink chamber can be communicated with the outside air. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-061896 Summary of the Invention [Problem to be solved by the invention]

[0005] Inkjet prints are inferior in color development on plain paper compared to printing methods such as electrophotography, partly because the inkjet ink composition is a liquid, and the coloring material penetrates into the recording medium along with the ink and does not remain on the surface.

[0006] Furthermore, when the printer is left unused for a long period of time, there is a concern that the pigment may settle in the ink inside the tank, cartridge, or flow path, resulting in uneven printing. In inks containing pigments that are prone to settling, the pigment may turn into a cake-like substance, potentially causing blockages in the flow path.

[0007] For this reason, the color developing ability and the suppression of sedimentation are both insufficient. [Means for solving the problem]

[0008] One embodiment of the inkjet ink composition according to the present invention comprises: a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group; a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group; The pigment contains:

[0009] One aspect of the recording method according to the present invention is to The method includes a step of ejecting the ink-jet ink composition from an ink-jet head and depositing it onto a recording medium. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a schematic configuration of a first embodiment of a recording apparatus in a see-through state. [Figure 2] FIG. 2 is a perspective view showing an ink supply unit provided in the housing of the recording apparatus. [Figure 3] FIG. [Figure 4] FIG. 4 is a partially broken cross-sectional view taken along line 4-4 in FIG. 3. [Figure 5] FIG. 4 is a perspective view of the ink container with the cap removed. [Figure 6] FIG. 10 is a partially cutaway front view showing a state in which ink is being refilled into the ink storage container. [Figure 7] Table 1 shows the formulation of the compositions of the examples. [Figure 8] Table 2 shows the formulation of the compositions of the examples. [Figure 9] Table 3 shows the formulations of the compositions of the examples and comparative examples. [Figure 10] Table 4 shows the formulations of the compositions of comparative examples and reference examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes embodiments of the present invention. The embodiments described below are examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0012] 1. Inkjet ink composition The inkjet ink composition according to this embodiment contains a pigment including a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group, and a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group.

[0013] The aforementioned pigment settling can be suppressed by using pigments with an average particle size of a specified size or less. However, pigments with a small average particle size have a low ability to remain near the surface of the recording medium, which can reduce print density. Among recording media, plain paper can sometimes result in insufficient color development (print density) depending on the type. Therefore, the ink of this embodiment achieves excellent suppression of settling and color development.

[0014] 1.1. Self-dispersing pigment A The inkjet ink composition of this embodiment contains a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group.

[0015] A self-dispersing pigment is a pigment that can be dispersed and / or dissolved in an aqueous medium without the use of a dispersant such as a resin or a surfactant. Here, "dispersion and / or dissolution in an aqueous medium without a dispersant" refers to a state in which the pigment is stably present in the aqueous medium due to hydrophilic groups on its surface, even without the use of a dispersant to disperse the pigment.

[0016] An inkjet ink composition containing a self-dispersing pigment does not require the inclusion of a dispersant to disperse the pigment, and is prone to excellent ejection stability because it is virtually free of the generation of bubbles or reduced defoaming properties caused by the dispersant. Furthermore, the ejection reliability is also excellent because the generation of foreign matter due to drying at the gas-liquid interface caused by the dispersant is suppressed. Furthermore, because a significant increase in viscosity caused by the dispersant is suppressed, it is possible to incorporate a larger amount of pigment, thereby achieving higher print density.

[0017] Self-dispersing pigments tend to have slightly inferior image fixation properties compared to pigments in which an anionic resin is physically adsorbed onto the surface of pigment particles, or resin-dispersed pigments in which the pigment is encapsulated and dispersed in an anionic resin. However, the inkjet ink composition of this embodiment can achieve excellent image optical density by using a combination of self-dispersing pigment A and self-dispersing pigment B, which will be described later.

[0018] When the recording medium contains calcium, the self-dispersing pigment A reacts with the calcium to easily form an image with excellent color development. Self-dispersing pigment A having a phosphorus-containing group such as a phosphate group or a phosphonate group bonded to its surface makes it easier to obtain color development. The phosphorus-containing group is preferably a phosphorus-containing acid group such as a phosphate group or a phosphonate group.

[0019] Examples of self-dispersing pigment A include pigments in which hydrophilic groups are bonded to the pigment surface directly or via other atomic groups, such as pigments in which functional groups containing phosphorus-containing groups are bonded to the surface of pigment particles, and pigments in which anionic resins containing phosphorus-containing groups are chemically bonded to the surface of pigment particles.

[0020] Examples of phosphorus-containing groups present on the surface of self-dispersing pigment A include -PO3HM and -PO3M2, and the pigment may also have other hydrophilic groups. Examples of other hydrophilic groups include -OM, -COOM, -CO-, -SO3M, -SO2M, -SON2NH2, -RSO2M, -SON2NHCOR, -NH3, -NR3, and groups in which some of the hydrogen atoms in a propyleneoxy chain have been substituted with M. In these formulas, M represents a hydrogen atom, an alkali metal, ammonium, or an organic amine, and R represents an alkyl group having from 1 to 12 carbon atoms or a naphthyl group which may have a substituent.

[0021] Further, examples of other atomic groups include linear or branched alkylene groups having from 1 to 12 carbon atoms, phenylene groups, naphthylene groups, amide groups, sulfonyl groups, amino groups, carbonyl groups, ester groups, ether groups, and groups combining these groups.

[0022] Examples of the self-dispersing pigment A include those in which a phosphorus-containing group is bonded to the surface of pigment particles by a known method, and those in which a functional group containing a phosphorus-containing group is bonded to the surface of pigment particles by diazo coupling or the like, and either of these can be suitably used. A self-dispersing pigment in which an anionic resin is bonded to the surface of pigment particles is formed by bonding a resin having, as a hydrophilic unit, at least a unit having a phosphorus-containing group to the surface of pigment particles directly or via another atomic group.

[0023] The phosphorus-containing group is preferably a phosphonic acid group. Examples of the phosphonic acid group include a bisphosphonic acid group and a monophosphonic acid group, and a bisphosphonic acid group is more preferred.

[0024] The pigment that can be made self-dispersible is not particularly limited, and examples of pigment types that can be used include inorganic pigments such as carbon black, calcium carbonate, and titanium oxide, and organic pigments such as azo pigments, isoindolinone pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, quinacridone pigments, and anthraquinone pigments.

[0025] Examples of black pigments include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Columbia Carbon Co.), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (all manufactured by Cabot Corporation), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (all manufactured by Degussa), etc.

[0026] White pigments include CI Pigment White 1 (basic lead carbonate), 4 (zinc oxide), 5 (mixture of zinc sulfide and barium sulfate), 6 (titanium oxide), 6:1 (titanium oxide containing other metal oxides), 7 (zinc sulfide), 18 (calcium carbonate), 19 (clay 1), 20 (titanium mica), 21 (barium sulfate), 22 (natural barium sulfate), 23 (gloss white), 24 (alumina white), 25 (gypsum), 26 (magnesium oxide / silicon oxide), 27 (silica), 28 (anhydrous calcium silicate), etc.

[0027] Examples of yellow pigments 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, 167, 172, and 180.

[0028] Magenta pigments 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, and CI Pigment Violet 19, 23, 32, 33, 36, 38, 43, 50, and the like.

[0029] Cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Vat Blue 4 and 60.

[0030] Examples of pigments other than black, white, yellow, magenta, and cyan include 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, 63, and the like.

[0031] Examples of color pigments include pigments such as Pigment Yellow, Pigment Red, Pigment Violet, and Pigment Blue listed in the Color Index, as well as phthalocyanine, azo, anthraquinone, azomethine, and fused ring pigments. Other examples include organic pigments such as Yellow No. 4, No. 5, No. 205, and No. 401; Orange No. 228 and No. 405; and Blue No. 1 and No. 404; and inorganic pigments such as titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine, Prussian blue, and chromium oxide.

[0032] The pigments exemplified above may be pigments in which a phosphorus-containing group is bonded to the particle surface directly or via another atomic group.

[0033] For example, when carbon black is used as the self-dispersing pigment A, it is produced by subjecting the carbon black to a physical or chemical treatment to bond (graft) phosphorus-containing groups to the surface of the carbon black. Examples of such physical treatments include vacuum plasma treatment. Examples of chemical treatments include oxidation treatment with hypohalous acid and / or a hypohalite, oxidation treatment with ozone, or oxidation treatment with persulfuric acid and / or a persulfate.

[0034] On the other hand, examples of self-dispersing pigments other than carbon black include those in which a phosphorus-containing group is bonded to the pigment surface via a phenyl group. As a surface treatment method for bonding, various known surface treatment methods can be applied, and examples include a method in which a phosphorus-containing group is bonded to the pigment surface via a phenyl group by bonding sulfanilic acid, p-aminobenzoic acid, 4-aminosalicylic acid, etc. The functional group may be in the form of a salt.

[0035] The content of self-dispersion pigment A (solid content) is preferably 1.0% by mass or more and 6.0% by mass or less, more preferably 1.5% by mass or more and 5.0% by mass or less, and even more preferably 1.8% by mass or more and 4.5% by mass or less, relative to the total mass of the inkjet ink composition. When the content of self-dispersion pigment A is within the above range, the color development and clogging recovery properties may be improved.

[0036] The volume average particle diameter D50 of the self-dispersing pigment A is 150 nm or less. The volume average particle diameter D50 of the self-dispersing pigment A is preferably 50 nm or more and 150 nm or less, more preferably 70 nm or more and 150 nm or less, and even more preferably 80 nm or more and 120 nm or less. If the volume average particle diameter D50 is within this range, it is easy to prevent the pigment from settling and agglomerating in an ink tank, etc. Furthermore, if the volume average particle diameter D50 of the self-dispersing pigment A is 70 nm or more, images with even better color development can be formed.

[0037] The volume average particle diameter D50 of the self-dispersion pigment can be measured using, for example, Microtrac MT-3300 (a laser diffraction / scattering particle size distribution measuring device manufactured by Microtrac Bell).

[0038] 1.2. Self-dispersing pigment B The inkjet ink composition of this embodiment contains a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group.

[0039] When the recording medium contains calcium, self-dispersing pigment B reacts with it to easily form an image with excellent color development. If self-dispersing pigment B has a carboxyl group, sulfo group, or the like bonded to its surface, rather than a phosphorus-containing group such as a phosphate group or a phosphonate group, the interaction with self-dispersing pigment A results in even better color development.

[0040] Examples of self-dispersing pigment B include pigments in which hydrophilic groups other than phosphorus-containing groups are bound to the pigment surface directly or via other atomic groups. Examples include pigments in which functional groups containing anionic groups other than phosphorus-containing groups are bound to the surface of pigment particles, and pigments in which anionic resins having hydrophilic groups other than phosphorus-containing groups are chemically bound to the surface of pigment particles.

[0041] Examples of hydrophilic groups present on the surface of self-dispersing pigment B include -OM, -COOM, -CO-, -SO3M, -SO2M, -SON2NH2, -RSO2M, -SON2NHCOR, -NH3, -NR3, and groups in which some of the hydrogen atoms in a propyleneoxy chain have been substituted with M. In the formula, M represents a hydrogen atom, an alkali metal, ammonium, or an organic amine, and R represents an alkyl group having from 1 to 12 carbon atoms or a naphthyl group which may have a substituent.

[0042] Further, examples of other atomic groups include linear or branched alkylene groups having from 1 to 12 carbon atoms, phenylene groups, naphthylene groups, amide groups, sulfonyl groups, amino groups, carbonyl groups, ester groups, ether groups, and groups combining these groups.

[0043] Examples of the self-dispersing pigment B include those in which anionic groups other than phosphorus-containing groups are bonded to the surface of pigment particles by oxidation treatment using a known method, and those in which functional groups containing anionic groups other than phosphorus-containing groups are bonded to the surface of pigment particles by diazo coupling or the like, and either of these can be suitably used. A self-dispersing pigment in which an anionic resin is bonded to the surface of pigment particles is formed by bonding, as a hydrophilic unit, a resin having at least a unit having an anionic group other than phosphorus-containing groups to the surface of pigment particles directly or via another atomic group.

[0044] The pigment that can be made self-dispersible is not particularly limited, and is the same as that described above in the section on self-dispersible pigment A.

[0045] The above-exemplified pigments can be made into self-dispersing pigments B in which an anionic group other than the phosphorus-containing group is bound to the particle surface directly or via another atomic group.

[0046] For example, when carbon black is used as the self-dispersing pigment B, it is produced by subjecting the carbon black to a physical or chemical treatment to bond (graft) hydrophilic groups other than phosphorus-containing groups to the surface of the carbon black. Examples of such physical treatments include vacuum plasma treatment. Examples of chemical treatments include oxidation treatment with hypohalous acid and / or a hypohalous acid salt, oxidation treatment with ozone, or oxidation treatment with persulfuric acid and / or a persulfate salt.

[0047] Furthermore, as the carbon black for the self-dispersing pigment B, commercially available products can also be used, such as CAB-O-JET (registered trademark) 300 (manufactured by Cabot Specialty Chemicals, Inc.).

[0048] On the other hand, examples of self-dispersing pigments B other than carbon black include those in which a hydrophilic group is bonded to the pigment surface via a phenyl group. As a surface treatment method for bonding the functional group or its salt, which is a hydrophilic group other than a phosphorus-containing group, to the pigment surface via a phenyl group, various known surface treatment methods can be applied, and examples thereof include a method in which a hydrophilic group is bonded to the pigment surface via a phenyl group by bonding sulfanilic acid, p-aminobenzoic acid, 4-aminosalicylic acid, or the like.

[0049] As the self-dispersing pigment B of such a color pigment, commercially available products can be used, such as CAB-O-JET (registered trademark) 250C, CAB-O-JET (registered trademark) 260M, and CAB-O-JET (registered trademark) 470Y (all manufactured by Cabot Specialty Chemicals, Inc.).

[0050] The content of self-dispersing pigment B (solid content) is preferably 1.0% by mass or more and 6.0% by mass or less, more preferably 1.5% by mass or more and 5.0% by mass or less, and even more preferably 1.8% by mass or more and 4.5% by mass or less, relative to the total mass of the inkjet ink composition. When the content of self-dispersing pigment B is within the above range, the color development and clogging recovery properties may be improved. The functional group introduced onto the surface of the pigment may be in the form of a salt.

[0051] The volume average particle diameter D50 of the self-dispersion pigment B is 90 nm or more and 150 nm or less. The volume average particle diameter D50 of the self-dispersion pigment B is preferably 90 nm or more and 120 nm or less, more preferably 90 nm or more and 110 nm or less, and even more preferably 95 nm or more and 105 nm or less. If the volume average particle diameter D50 is within this range, it is easy to prevent the pigment from settling and agglomerating in an ink tank, etc.

[0052] 1.3. Relationship between self-dispersing pigment A and self-dispersing pigment B The mass ratio (A / B) of the contents of self-dispersion pigment A and self-dispersion pigment B is preferably 0.1 or more and 3.0 or less, more preferably 0.3 or more and 2.5 or less, even more preferably 0.4 or more and 2.3 or less, and even more preferably 0.6 or more and 2.0 or less. In this way, images with even better color development can be formed.

[0053] The total content of self-dispersing pigment A and self-dispersing pigment B is The content of the pigment is preferably 2% by mass or more and 10% by mass or less, more preferably 4% by mass or more and 8% by mass or less, and even more preferably 5% by mass or more and 7% by mass or less, based on the total mass of the composition. This makes it possible to further prevent the pigment from settling and agglomerating in the ink tank, etc., and to obtain images with even better color development.

[0054] Furthermore, it is more preferable that the volume average particle diameter D50 of self-dispersion pigment A is larger than the volume average particle diameter D50 of self-dispersion pigment B. This further suppresses pigment sedimentation. Self-dispersion pigment B is relatively more hydrophobic than self-dispersion pigment A. For this reason, it is presumed that particles of self-dispersion pigment B tend to gather together in water, sediment, and are difficult to redisperse. For this reason, to prevent sedimentation, it is preferable that self-dispersion pigment B has a smaller volume average particle diameter D50 than self-dispersion pigment A. The volume average particle diameter D50 of self-dispersion pigment A is more preferably 5 nm or more larger than the volume average particle diameter D50 of self-dispersion pigment B, and more preferably 10 nm or more but 60 nm or less.

[0055] 1.4.Other Ingredients The inkjet ink composition of this embodiment may include the following components.

[0056] 1.4.1.Water The inkjet ink composition of this embodiment is an aqueous composition containing water. An "aqueous" composition refers to a composition in which water is one of the main solvents. Examples of water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as water with reduced ionic impurities such as ultrapure water. Furthermore, using water sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can suppress the growth of bacteria and fungi when the inkjet ink composition is stored for a long period of time.

[0057] The water content is 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, based on the total amount (100% by mass) of the ink-jet ink composition. The upper limit of the water content is preferably 97% by mass or less, even 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 amount (100% by mass) of the ink-jet ink composition.

[0058] 1.4.2. Betaine The inkjet ink composition of this embodiment may contain betaines. Betaine refers to a compound that has a positive charge and a negative charge at non-adjacent positions within the same molecule, and the positively charged atom is not bound to a dissociable hydrogen atom, so that it can form an intramolecular salt, and the molecule as a whole does not have a charge. In this embodiment, the betaine is preferably one in which the positively charged site is a quaternary ammonium cation.

[0059] When the inkjet ink composition contains betaine, it is possible to suppress deflection of the inkjet ink composition or ejection failure caused by the inkjet ink composition drying in the nozzles of an inkjet head, and it is possible to improve clogging resistance.

[0060] The above-described self-dispersing pigment A is a hydrophilic substance, and its dispersibility may decrease in a liquid in a hydrophobic environment after water has evaporated, as in a clogging recovery test. In particular, in the inkjet ink composition of this embodiment, the above-described self-dispersing pigment A and the above-described self-dispersing pigment B coexist, and it is thought that the self-dispersing pigment A is likely to become a nucleus for foreign matter, and the self-dispersing pigment B is likely to become a foreign matter by becoming entangled in the nucleus. However, if the inkjet ink composition of this embodiment contains a betaine, this phenomenon is more unlikely to occur, which is preferable.

[0061] The betaines are not particularly limited, and examples thereof include trialkylglycines such as trimethylglycine and triethylglycine, γ-butyrobetaine, homarine, trigonelline, carnitine, homoserine betaine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, stachydrine, and glutamic acid betaine. Among these, the glycine contained in the inkjet ink composition is preferably selected from trialkylglycines, and more preferably contains trimethylglycine. Trialkylglycines are compounds in which three alkyl groups are substituted on the nitrogen atom of glycine. This tends to further improve clogging resistance. The betaines may be used alone or in combination of two or more.

[0062] The number of carbon atoms constituting the betaine is preferably from 4 to 12, more preferably from 4 to 7, and even more preferably from 4 to 6. When the number of carbon atoms in the betaine is within the above range, pigment sedimentation tends to be more significantly suppressed.

[0063] When a betaine is contained in the inkjet ink composition, the content thereof is preferably from 2.0 to 10.0% by mass, more preferably from 3.0 to 9.0% by mass, and even more preferably from 4.0 to 8.0% by mass, relative to the total mass of the inkjet ink composition. By containing the betaine within the above range, it is possible to further suppress the settling of the pigment and the formation of foreign matter, and to further improve the clogging recovery properties.

[0064] Organic Solvents The inkjet ink composition of this embodiment may contain the following organic solvents: Examples of organic solvents include alkyl polyols, glycol ethers, and nitrogen-containing compounds.

[0065] (Alkyl polyol) The inkjet ink composition of this embodiment may contain an alkyl polyol. An alkyl polyol is a compound having a skeleton and two or more hydroxyl groups (substituted with two or more hydroxyl groups). Examples of the skeleton include an alkyl chain and a polyalkyleneoxy chain. The number of hydroxyl groups in the molecule is two or more, preferably 2 to 4, and more preferably 2 or 3. The number of carbon atoms in the molecule is preferably 2 to 10.

[0066] The alkyl polyol conceptually includes polyhydric alcohols, and when an alkyl polyol is contained, the ink-jet ink composition has improved moisture retention, and excellent ejection stability when used in an ink-jet method, while effectively suppressing water evaporation from the recording head when left unused for a long period of time. This also makes it possible to maintain good recovery from storage and continuous ejection stability even when a colorant that is prone to nozzle clogging is used.

[0067] Specific examples of alkyl polyols include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, triethylene glycol, and tetraethylene glycol. These alkyl polyols may be used alone or in combination of two or more.

[0068] The inkjet ink composition more preferably contains an alkyl polyol containing an alkanediol having from 3 to 6 carbon atoms. Examples of alkanediols having from 3 to 6 carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, and 2-methylpentane-2,4-diol.

[0069] When the inkjet ink composition contains an alkanediol having 3 to 6 carbon atoms, the viscosity can be further suppressed and the ejection stability (reliability of continuous ejection) can be improved in some cases. In addition, the solubility and dispersibility of the colorant can be easily improved, and good clogging recovery can be achieved.

[0070] When the inkjet ink composition contains an alkyl polyol, it more preferably contains a polyol having a normal boiling point of greater than 280°C. Examples of polyols having a normal boiling point of greater than 280°C include glycerin and triethylene glycol. By including such a polyol, the drying speed of the inkjet ink composition can be suppressed, and clogging resistance and ejection stability can be improved in some cases. The amount of alkyl polyol relative to the total amount of the inkjet ink composition is preferably 2 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 8 to 15% by mass.

[0071] (glycol ether) The inkjet ink composition of this embodiment may contain a glycol ether. Examples of glycol ethers include monoalkyl ethers or dialkyl ethers of glycols selected from ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene glycol. More specific examples include methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), and dipropylene glycol monopropyl ether, with diethylene glycol monobutyl ether being a typical example.

[0072] The inkjet ink composition more preferably contains one or more glycol ethers selected from glycol ethers represented by the following formula (1). R 1 -O-(CH2-CH2-O) n -R 2 ···(1) (In formula (1), R 1 represents H or an alkyl group having 1 to 4 carbon atoms, and R 2 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 to 3.

[0073] Examples of glycol ethers represented by formula (1) include methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), triethylene glycol dimethyl ether, triethylene glycol dibutyl ether, and diethylene glycol dibutyl ether.

[0074] A mixture of two or more glycol ethers may be used. When a glycol ether is used, the amount of glycol ether to be used is determined based on the viscosity adjustment and moisturizing effect of the ink-jet ink composition. From the viewpoint of preventing clogging, the total amount of the ink-jet ink composition is from 0.5% to 30% by mass, preferably from 1.0% to 20% by mass, and more preferably from 3.0% to 10.0% by mass.

[0075] (Nitrogen-containing substances) The inkjet ink composition of this embodiment may contain a nitrogen-containing compound. The nitrogen-containing compound is preferably, for example, an amide. Examples of the amide include cyclic amides and non-cyclic amides. The nitrogen-containing compound is expected to have the effect of suppressing solidification and drying of the inkjet ink composition.

[0076] Examples of cyclic amides include compounds having a ring structure containing an amide group. Examples of such compounds include γ-lactams such as 2-pyrrolidone, 1-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), 1-ethyl-2-pyrrolidone (N-ethyl-2-pyrrolidone), 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, and N-vinyl-2-pyrrolidone (NVP), β-lactams, δ-lactams, and ε-lactams such as ε-caprolactam. These cyclic amides may be used alone or in combination of two or more.

[0077] (Other organic solvents) The inkjet ink composition of this embodiment may contain other organic solvents, such as lactones such as γ-butyrolactone, and betaine compounds.

[0078] The content of the organic solvent is preferably from 2 to 30% by mass, more preferably from 5 to 20% by mass, and even more preferably from 8 to 15% by mass, based on the total amount of the inkjet ink composition.

[0079] 1.4.4.Resin particles The inkjet ink composition may contain resin particles. In this specification, resin particles are also referred to as dispersion resin. Resin particles tend to reduce clogging resistance, so whether or not they are contained, their content is preferably 1% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably less than 0.1% by mass, relative to the total mass of the inkjet ink composition. For the same reason, it is more preferable that the inkjet ink composition does not contain resin particles.

[0080] When ink contains resin particles, the surfactant (dispersant) used to disperse the resin makes the ink prone to foaming and air bubbles, especially when the ink is injected into the ink container through the ink inlet.

[0081] Furthermore, the resin particles themselves tend to become foreign matter at the gas-liquid interface inside the ink container. When bubbles are generated, the gas-liquid interface increases, and foreign matter is more likely to be generated at the gas-liquid interface.

[0082] Furthermore, since the resin particles are insoluble in water, there are concerns about environmental problems caused by microplastics when the ink is released into the natural environment. Examples of resin dispersions include dispersion resins dispersed with a surfactant and soapless dispersion resins dispersed without the use of a surfactant.

[0083] Surfactants The inkjet ink composition according to this embodiment may contain a surfactant. The surfactant can be used to reduce the surface tension of the inkjet ink composition and adjust and improve the wettability with a recording medium, for example, the permeability into fabrics and the like. As the surfactant, any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used, and these may also be used in combination. In addition, among the surfactants, However, acetylene glycol surfactants, silicone surfactants, and fluorine surfactants are more preferably used.

[0084] The acetylene glycol surfactant is not particularly limited, but examples thereof include Surfynol 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, and DF110D (trade names, Air Products and Chemicals). Examples of suitable acrylic acid esters include Olfine B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, PD-005, EXP.4001, EXP.4036, EXP.4051, EXP.4123, EXP.4200, EXP.4300, D-10PG, AF-103, AF-104, AK-02, SK-14, and AE-3 (trade names, manufactured by Nissin Chemical Industry Co., Ltd.), and Acetylenol E00, E00P, E40, and E100 (trade names, manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0085] The silicone surfactant is not particularly limited, but a polysiloxane compound is preferred. The polysiloxane compound is not particularly limited, but for example, a polyether-modified organosiloxane is exemplified. Commercially available polyether-modified organosiloxanes include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, and BYK-348 (trade names, manufactured by BYK), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0086] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and an example thereof is BYK-340 (trade name, manufactured by BYK Japan KK).

[0087] When a surfactant is added to the inkjet ink composition, the total amount of the surfactant is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, even more preferably 0.1% by mass or more and 1.5% by mass or less, and particularly preferably 0.2% by mass or more and 1% by mass or less, based on the total amount of the inkjet ink composition.

[0088] When a surfactant is blended into the inkjet ink composition, it is more preferable to select a surfactant having antifoaming properties. By including an antifoaming surfactant in the inkjet ink composition, it is possible to make it more difficult for bubbles to form, and for example, stability when the ink is ejected from a head tends to be improved.

[0089] 1.4.6. Chelating Agents The ink-jet ink composition of this embodiment may use a chelating agent, which can remove certain ions in the ink-jet ink composition.

[0090] Examples of chelating agents include ethylenediaminetetraacetic acid and its salts such as EDTA, EDTA-2Na (ethylenediaminetetraacetic acid dihydrogen disodium salt), EDTA-3Na (ethylenediaminetetraacetic acid monohydrogen trisodium salt), EDTA-4Na (ethylenediaminetetraacetic acid tetrasodium salt), and EDTA-3K (ethylenediaminetetraacetic acid monohydrogen tripotassium salt); diethylenetriaminepentaacetic acid and its salts such as DTPA, DTPA-2Na (diethylenetriaminepentaacetic acid disodium salt), and DTPA-5Na (diethylenetriaminepentaacetic acid pentasodium salt); nitrilotriacetic acid such as NTA, NTA-2Na (nitrilotriacetic acid disodium salt), and NTA-3Na (nitrilotriacetic acid trisodium salt). Examples of suitable iminodiacetic acid include methyl-N,N'-iminodiacetic acid and its salts, ethylenediamine-N,N'-disuccinic acid and its salts, 3-hydroxy-2,2'-iminodisuccinic acid and its salts, L-aspartic acid-N,N'-diacetic acid and its salts, L-glutamic acid diacetic acid and its salts, N-(1-carboxylatomethyl)iminodiacetic acid and its salts, and N-(2-hydroxyethyl)iminodiacetic acid and its salts.

[0091] Examples of chelating agents other than acetic acid analogs include ethylenediaminetetramethylenephosphonic acid and its salts, ethylenediaminetetrametaphosphoric acid and its salts, ethylenediaminepyrophosphoric acid and its salts, and ethylenediaminemetaphosphoric acid and its salts.

[0092] When a chelating agent is contained in the inkjet ink composition of this embodiment, one or more types selected from the above examples can be used.

[0093] pH adjusters A pH adjuster may be added to the inkjet ink composition of this embodiment. The pH adjuster is not particularly limited, but may be a suitable combination of an acid, a base, a weak acid, or a weak base. Examples of acids and bases used in such combinations include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; inorganic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium dihydrogen phosphate, disodium hydrogen phosphate, potassium carbonate, sodium carbonate, sodium bicarbonate, and ammonia; organic bases such as triethanolamine, tripropanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, and trishydroxymethylaminomethane (THAM); and organic acids such as adipic acid, citric acid, succinic acid, lactic acid, and N,N-bis(2-hydroxyethyl)-2-amine. Other buffers that may be used include Good's buffers such as benzyl acetamide (BES), 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), morpholinoethanesulfonic acid (MES), morpholinopropanesulfonic acid (MOPS), carbamoylmethyliminobisacetic acid (ADA), piperazine-1,4-bis(2-ethanesulfonic acid) (PIPES), N-(2-acetamido)-2-aminoethanesulfonic acid (ACES), cholamine hydrochloride, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (TES), acetamidoglycine, tricine, glycinamide, and bicine, as well as phosphate buffer, citrate buffer, and Tris buffer. Furthermore, among these, it is preferable that the pH adjuster contains, as part or all of a tertiary amine such as triethanolamine or triisopropanolamine, or a carboxyl group-containing organic acid such as adipic acid, citric acid, succinic acid or lactic acid, since this makes it possible to obtain a more stable pH buffering effect.

[0094] 1.4.8.Ureas Ureas may be used as a moisturizing agent for the inkjet ink composition or as a dyeing aid that improves the dyeing property of the dye. Specific examples of ureas include urea, ethylene urea, tetramethyl urea, thiourea, and 1,3-dimethyl-2-imidazolidinone. When ureas are contained, the content thereof can be 1% by mass or more and 10% by mass or less relative to the total mass of the inkjet ink composition.

[0095] 1.4.9. Antiseptics, mildew inhibitors, and rust inhibitors The inkjet ink composition may contain a preservative or an antifungal agent. Examples of the preservative or antifungal agent include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, and 1,2-dibenzisothiazolin-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN, and Proxel TN, both of which are available from Zeneca). LV), 4-chloro-3-methylphenol (Preventol CMK manufactured by Bayer, etc.), etc. Examples of the rust inhibitor include benzotriazole.

[0096] Sugars The inkjet ink composition may contain sugars. Specific examples of sugars include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose.

[0097] Other In addition to the above components, the ink composition may contain additives that can be commonly used in ink-jet ink compositions, such as antioxidants, ultraviolet absorbers, oxygen absorbers, and solubilizing agents.

[0098] 1.5.Uses etc. The inkjet ink composition of this embodiment may be used in an inkjet recording apparatus having an ink reservoir with an ink inlet. An inkjet recording apparatus having an ink reservoir with an ink inlet will now be described.

[0099] The inkjet recording apparatus is an inkjet recording apparatus comprising the inkjet ink composition described above, an ink storage container for storing the inkjet ink composition, and a recording head for ejecting the inkjet ink composition, wherein the ink storage container has an ink inlet that can be opened and closed for filling the inkjet ink composition.

[0100] The inkjet recording apparatus comprises the inkjet ink composition described above, an ink storage container in which the inkjet ink composition is stored, and a recording head that ejects the inkjet ink composition, and the ink storage container has an ink inlet that can be opened and closed for filling with the inkjet ink composition.

[0101] An example of an inkjet recording apparatus according to an embodiment will be described with reference to the drawings. The ink storage container serves as an ink tank for an inkjet printer (inkjet recording apparatus) that records (prints) an image or the like on a medium by ejecting ink onto the medium. In the following description, the inkjet recording apparatus may be simply referred to as the recording apparatus, and the inkjet ink composition may be simply referred to as the ink.

[0102] As shown in FIG. 1, the recording device 21 includes a rectangular parallelepiped housing 22 with its longitudinal direction extending in the left-right direction. FIG. 1 also shows a simplified perspective view of the interior of the housing 22 of the recording device 21. A support base 23, with its longitudinal direction extending in the left-right direction, is provided in a lower portion near the rear of the housing 22, with its upper surface aligned substantially horizontally. Paper P, an example of a medium, is supported on the upper surface of the support base 23 and transported forward in the transport direction. A guide shaft 24 extending in the left-right direction is installed above the support base 23 within the housing 22. A carriage 26, which includes a recording head 25 (inkjet head) that ejects ink, is supported on the guide shaft 24. The carriage 26 is supported so as to be reciprocable in the left-right direction relative to the guide shaft 24, with the guide shaft 24 inserted through a support hole 27 that penetrates the housing 22 in the left-right direction.

[0103] A drive pulley 28 and a driven pulley 29 are rotatably supported in the housing 22 at positions near both ends of the guide shaft 24. An output shaft of the carriage motor 30 is connected, and an endless timing belt 31, a portion of which is connected to the carriage 26, is wound between the drive pulley 28 and the driven pulley 29. When the carriage 26 is driven by the carriage motor 30 and guided by the guide shaft 24 via the timing belt 31 to move back and forth along the left-right direction, which is the scanning direction for the paper P, ink is ejected from the recording head 25 on the underside of the carriage 26 onto the paper P, which is transported forward on the support base 23.

[0104] The recording device may be a serial type recording device in which a carriage equipped with a recording head moves and ejects ink from the recording head to perform recording, as shown in Fig. 1. Alternatively, the recording device may be a line type recording device in which ink is ejected from a line head having a length equal to or greater than the recording width of the recording medium to perform recording.

[0105] 1, a rectangular discharge opening 32 is opened at a position on the front side of the housing 22 in front of the support base 23, through which paper P, on which recording has been performed by ejecting ink from the recording head 25 as the paper is transported on the support base 23 within the housing 22, is discharged forward. A rectangular plate-shaped discharge tray 33 capable of supporting paper P discharged from the housing 22 is provided at the discharge opening 32 so as to be movable forward in the discharge direction. A paper feed cassette 34 capable of accommodating a plurality of sheets of paper P to be used for recording in a stacked state is attached below the discharge tray 33 within the discharge opening 32 so as to be removable in the front-to-rear direction.

[0106] 1, on the front side of the housing 22, at a position closer to the left-right end than the outlet 32 ​​(the right end in FIG. 1), there is provided an opening / closing door 35 whose front and top are rectangular and whose right side is shaped like a right triangle, so that it can be opened and closed in the front-rear direction around a rotation shaft 36 provided at the bottom of the opening / closing door 35 and extending in the left-right direction. A window 37 made of a rectangular transparent member is formed on the front side of the opening / closing door 35, so that the user can see inside the housing 22 (particularly, the back side of the front side of the opening / closing door 35) when the opening / closing door 35 is closed.

[0107] An ink supply unit 40 that supplies ink to the recording head 25 is housed inside the housing 22 of the recording device 21 at a position behind the opening / closing door 35, that is, at a position closer to the front and closer to the end (closer to the right end in this case). The ink supply unit 40 is a structure that includes a plurality of (five in this embodiment) ink containing containers 41-45 and can be handled as a unit, and as will be described later, each of the ink containing containers 41-45 can be replenished with ink.

[0108] 2 and 3, the ink supply unit 40 includes five ink containers 41 to 45 each having a rectangular box shape that is elongated in the front-to-rear direction, five ink supply tubes 46 extending from the rear side of each ink container 41 to 45, and a rectangular parallelepiped ink supply adapter 47 to which the ink containers 41 to 45 are attached together. The ink supply adapter 47 is attached to stepped portions 48 cut out and formed in the upper front half portions of all the ink containers 41 to 45 when all the ink containers 41 to 45 are arranged side by side with their thicknesses aligned left to right, thereby integrating the ink containers 41 to 45. As shown in FIG. 1, the ink supply tubes 46 extending from the ink containers 41 to 45 are connected to ink flow paths (not shown) formed in the carriage 26 and are connected to the recording head 25 via the ink flow paths. The ink supply adapter 47 may be a part of the housing 22 that covers the ink containers 41-45, or may be formed integrally with the ink containers 41-45.

[0109] As shown in Fig. 4, the ink containing containers 41 to 45 each have an ink storage chamber 49 therein capable of storing an ink composition IK. In the present embodiment, the ink storage chamber 49 of the ink containing container 41 located at the right end in the lateral arrangement direction stores black ink. The ink storage chambers 49 of the other ink storage containers 42 to 45 arranged to the left of the right-end ink storage container 41 in the horizontal arrangement direction store ink of colors other than black (cyan, magenta, yellow, etc.). Furthermore, the front wall of each of the ink storage containers 41 to 45, which is visible through the window 37 on the front surface of the housing 22, is provided with a visibility portion 50 made of a transparent resin that allows the liquid level of the ink composition IK in the ink storage chamber 49 to be visible. The visibility portion 50 is marked with an upper limit mark 51 that indicates the upper limit of the liquid level of the ink composition IK stored in the ink storage chamber 49 (an example of an indication of the amount of ink that can be poured without the ink overflowing from the ink inlet 53), and a lower limit mark 52 that indicates the lower limit (for example, an indication to encourage ink replenishment).

[0110] As shown in FIG. 4, an ink inlet 53 (ink inlet) that can be opened and closed is provided above the horizontal portion of the stepped portion 48 in each of the ink storage containers 41-45, allowing ink to flow from the outside into the ink storage chamber 49. The ink inlet 53 includes a needle 56 that extends vertically upward and has flow paths 54, 55 that connect the inside of the ink storage chamber 49 to the outside. The flow paths 54, 55 of the needle 56 are composed of two flow paths 54, 55 whose tip openings are arranged side by side in a radial direction from the needle 56. One of the two flow paths 54, 55 (the flow path 54 on the right side in FIG. 4) has a lower tip opening and a larger cross-sectional area than the other flow path 55 (the flow path 54 on the left side in FIG. 4). A remaining amount sensor 57 is provided at a lower rear portion of the ink storage chamber 49 to detect the remaining amount of ink composition IK in the ink storage chamber 49. The remaining amount sensor 57 is not required.

[0111] 2 to 4, ink supply adapter 47 has an upper surface 58 that is a horizontal surface extending in a direction perpendicular to (intersecting with) the direction in which needle 56 extends, and a through-hole 60 that serves as an ink inlet formation portion is formed in upper surface 58 and extends vertically to lower surface 59. This through-hole 60 is made up of a circular ink inlet 53 with needle 56 located in the center, and a pair of rectangular holes connected to the front and rear of ink inlet 53, and the lower opening is closed by the horizontal portion of step 48 that protrudes needle 56 upward in ink containing containers 41 to 45.

[0112] Therefore, in the through-hole 60, a pair of front and rear rectangular hole portions with their lower openings blocked form a pair of front and rear recesses 61 that open upward, in the direction in which the needle 56 extends, recessed in the depth direction vertically downward and symmetrically about the ink inlet 53. That is, in the ink refill adapter 47 integrated with the ink containers 41 to 45, a plurality of recesses 61 (two pairs of front and rear recesses in this case) are formed that are point-symmetrical about the ink inlet 53 in the area outside the ink inlet 53, including the needle 56. In this case, the tip of the needle 56, which is located at the center of the circular ink inlet 53, is located closer to the ink storage chamber 49 than the top surface 58 of the ink refill adapter 47, which forms the opening edge of the through-hole 60 that includes the ink inlet 53 and the recesses 61. That is, an upper surface 58 of the ink supply adapter 47 extends in a direction intersecting the extension direction of the needle 56 at a position outside the tip of the needle 56 in the extension direction of the needle 56. On the other hand, a lower surface 59 of the ink supply adapter 47 functions as a tank engaging portion that collectively engages from above with a plurality of ink containing containers 41 to 45 that are arranged side by side in the left-right direction.

[0113] Furthermore, the upper surface 58 of the ink supply adapter 47, the peripheral portion of the opening edge on the upper side of each through-hole 60, is colored a specific color. That is, it is colored the same color as the color of the ink stored in the ink storage chamber 49 of the ink containing container 41-45 into which ink flows through the ink inlet 53 of the through-hole 60. In this respect, the peripheral portion of the opening edge on the upper side of each through-hole 60 in the ink supply adapter 47 functions as a first portion that externally indicates information related to the ink stored inside the ink containing container 41-45 whose ink inlet 53 of the through-hole 60 communicates with the ink storage chamber 49. There are no particular restrictions on the ink to be used, but if the ink storage container supplied from the ink storage container containing the ink composition of this embodiment is the ink storage container 41, black or gray ink will be stored therein, and therefore the surrounding area of ​​the upper opening of the through hole 60, where the ink inlet 53 communicating with the ink storage chamber 49 of the ink storage container 41 is located, is colored black or gray.

[0114] Furthermore, on the inner surface of the recess 61 (specifically, the inner surface along the vertical direction), a first uneven portion (first key structure portion) 62 having a characteristic uneven shape in the horizontal direction is provided at a position closer to the bottom surface than the upper opening edge of the recess 61 (i.e., closer to the horizontal portion of the stepped portion 48), so as to extend along the depth direction of the recess 61 (in other words, the direction of the central axis of the ink inlet 53). As shown in FIGS. 2 and 3 , the first uneven portion 62 is provided for each of the ink inlets 53 of the multiple (five in this embodiment) ink containers 41 to 45. Therefore, in the ink refill adapter 47, the rectangular recess 61 in each through hole 60 formed at a position corresponding to each of the ink containers 41 to 45 in the vertical direction has a first uneven portion 62 formed therein that is different from the first uneven portions 62 provided on the inner surface of the recess 61 of each of the other through holes 60. That is, these first uneven portions 62 function as identification portions that enable identification of ink bottles 63 having ink outlets 65 that are connected to ink inlets 53 in the through-holes 60 in which the first uneven portions 62 are formed. Note that "a position that is closer to the bottom than the upper opening edge of the recess 61" means that it is sufficient that the position is set back slightly from the opening edge toward the bottom.

[0115] Next, we will explain the ink bottle 63, which constitutes an ink supply system together with the ink containing containers 41 to 45 and serves as an ink supply container for replenishing ink to the ink containing containers 41 to 45 when the remaining ink level is low. The ink bottle 63 contains the inkjet ink composition described above.

[0116] 5, the ink bottle 63 comprises a cylindrical container body 64 that forms the main body of the ink bottle 63; an ink outlet forming portion 66 that is provided at the tip of the container body 64 and has an ink outlet 65 formed at its tip to allow ink to flow out of the ink bottle 63; and a container attachment portion 67 that is attached to the ink outlet forming portion 66 so as to surround the ink outlet 65. The ink outlet 65 of the ink outlet forming portion 66, together with the surrounding container attachment portion 67, is covered by a cylindrical cap 68 with a bottom, so that it is concealed from the outside when the ink bottle 63 is stored. That is, a male thread portion 69 is formed on the outer peripheral surface of the cylindrical lower end of the container attachment portion 67, while a female thread portion (not shown) is formed on the inner peripheral surface of the cap 68. By screwing the female thread portion of the cap 68 onto the male thread portion 69 of the container attachment portion 67, the cap 68 is attached to the tip of the ink bottle 63 so as to cover the ink outlet 65.

[0117] The entire outer surface of the container additional portion 67 is colored a specific color. That is, it is colored the same color as the ink contained in the container main body 64 to which the container additional portion 67 is attached. Incidentally, the outer surface of the container additional portion 67 of an ink bottle 63 containing black or gray ink is colored black or gray. Furthermore, multiple (four in this embodiment) protrusions 70 are formed at equal angular intervals (for example, 90-degree intervals) on the outer periphery of each base end of the container main body 64 and the cap 68. Incidentally, these protrusions 70 are formed to prevent the cylindrical ink bottle 63 from rolling. Furthermore, for example, the container main body 64 of an ink bottle 63 containing black ink may be formed thicker than the container main body 64 of an ink bottle 63 containing other colors of ink. In this case, the ink outlet forming portion 66 for black ink and the other colors of ink may have the same thickness and shape.

[0118] The material of the container body 64 is not limited, and plastic, metal, glass, etc. can be used. Among these, plastic is preferable in terms of light weight, etc. Among these, soft plastic is preferable. Soft plastic is plastic that can be dented by pinching both sides of the container body 64 with hands. A container body 64 made of soft plastic is preferable because it is easy to push the ink out of the ink outlet 65 by turning the container body 64 upside down and pinching both sides of the container body 64 with your fingers to dent it.

[0119] As shown in FIG. 6 , the user holds an ink bottle 63 containing the ink composition to be used for ink refilling upside down so that the ink outlet 65 is positioned above the rightmost through-hole 60 of the ink refill adapter 47. That is, the central axis of the ink outlet 65 of the ink bottle 63 is aligned with the central axis of the ink inlet 53 of the ink containing container 41 to be refilled. At this time, the user compares the color (second portion) of the container attachment portion 67 of the ink bottle 63 being held with the color (first portion) of the periphery of the upper opening edge of the through-hole 60 where the ink inlet 53 of the ink containing container 41 to be refilled. If the colors are the same (in this case, both are black), the user confirms that the ink bottle 63 being held is suitable for this ink refill and proceeds with the ink refill. That is, the user refills the ink containing container from the ink bottle.

[0120] 6, it is preferable to turn the ink bottle 63 upside down and position the ink bottle 63 above the ink inlet 53 of the ink containing container 41 to easily replenish the ink. Note that the position of the ink bottle 63 when replenishing the ink is not limited to above the ink inlet 53, but may be diagonally above the ink inlet 53.

[0121] 6, when refilling ink with the ink outlet 65 of the ink bottle 63 in contact with the vicinity of the ink inlet 53 of the ink containing container 41, it is preferable as it is less likely to cause ink to spill. Furthermore, because the ink bottle 63 is fixed in position near the ink inlet 53 of the ink containing container 41, it is easy to dent the container body 64 of the ink bottle 63, making it easy to push out the ink and refill it.

[0122] On the other hand, in these cases, the ink is easily pushed out from the ink outlet 65 of the ink bottle 63, which makes the ink prone to foaming and air bubbles to form, and foreign matter is also likely to form at the air-liquid interface. However, according to this embodiment, the generation of air bubbles and foreign matter can be reduced, which is preferable.

[0123] 2 etc., the ink inlet 53 may be covered with a lid or cap (not shown) except when ink is being replenished. In other words, the ink inlet 53 may be openable and closable with a lid or cap.

[0124] When the inkjet ink composition described above is applied to the inkjet recording apparatus described above, it is possible to suppress the settling of the pigment in the ink storage container (ink tank). It is clear that the inkjet ink composition of this embodiment can also suppress the settling of the pigment in, for example, the ink flow path or the ink cartridge, when applied to a recording apparatus that does not have an ink tank.

[0125] 1.6. Manufacturing and Properties The inkjet ink composition of this embodiment can be obtained by mixing the above-mentioned components in any order, and removing impurities by filtration or the like as necessary. A suitable mixing method is to sequentially add the materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and then stir and mix them. Filtration methods such as centrifugal filtration and filter filtration can be used as necessary.

[0126] The inkjet ink composition of this embodiment has high reliability as an inkjet ink. From this viewpoint, the surface tension at 20°C is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 22 mN / m or more and 35 mN / m or less. From the same viewpoint, the viscosity of the ink at 20°C is preferably 1.5 mPa·s or more and 10 mPa·s or less, and more preferably 2 mPa·s or more and 8 mPa·s or less. One method for adjusting the surface tension and viscosity within the above ranges is to adjust the types of the water-soluble resin, organic solvent, and surfactant, as well as the amounts of these and water added.

[0127] 1.7. Effects, etc. The inkjet ink composition of this embodiment uses a pigment with a volume average particle diameter D50 of 150 nm or less, which can prevent the pigment from settling and agglomerating in an ink tank, etc. Furthermore, this inkjet ink composition uses two types of pigments that have been subjected to two different surface treatments, which makes it easier for the pigments to remain on the surface of a recording medium, allowing images with excellent color development to be obtained.

[0128] On recording media rich in cations (highly reactive recording media), such as so-called color lock paper, a pigment with relatively high cation reactivity (self-dispersing pigment A) reacts with the ink and remains near the surface of the recording medium, improving print density. However, self-dispersing pigment A contains a phosphorus-containing group (such as phosphonic acid) and is highly hydrophilic. As a result, the ink that lands on the recording medium is difficult to separate from the ink's solvent component, which is primarily water, and the sealing effect is weak.

[0129] In recording media with low cation content (low reactivity recording media), such as so-called non-color lock paper, the print density (color development) can be improved by combining the above self-dispersing pigment A with self-dispersing pigment B (a pigment with relatively low cation reactivity).

[0130] Self-dispersing pigment B has functional groups other than phosphorus-containing groups (such as carboxyl groups and sulfo groups), making it more hydrophobic than pigment A. When the ink lands on the recording medium, it quickly separates into solid and liquid components from the ink's solvent component, which is primarily water, and the self-dispersing pigment B fills the voids in the recording medium (filling effect). This allows self-dispersing pigment A to remain on the recording medium in a filled state, resulting in excellent color development. This can improve print density.

[0131] It is thought that self-dispersing pigment B roughly fills the gaps in the recording medium, and self-dispersing pigment A is densely spread on top of that, enhancing color development.

[0132] It is thought that by using two pigments with different surface treatments, the surface of the recording medium is first filled with self-dispersing pigment B, and self-dispersing pigment A tends to remain on top of that. It is thought that this effect occurs due to some kind of interaction, such as mutual repulsion or affinity, between the two pigments with different surface treatments.

[0133] In the case of recording media with low reactivity, it is believed that a volume average particle diameter D50 of 90 nm or more of self-dispersion pigment B will provide a sealing effect. On the other hand, although there is no lower limit for the volume average particle diameter D50 of self-dispersion pigment A, it is believed that a larger particle diameter will result in better color development, as this will allow the pigment to be spread over the self-dispersion pigment B and enhance color development.

[0134] Sedimentation properties are thought to be mainly affected by the volume average particle diameter D50 of self-dispersing pigment A and self-dispersing pigment B. In addition, because both self-dispersing pigment A and self-dispersing pigment B are present, it is thought that these pigments mix together and settle more easily.

[0135] 2. Recording method The recording method of this embodiment includes a step of ejecting the inkjet ink composition from an inkjet head and depositing it on a recording medium. The ink jet recording method may be carried out using an ink jet recording apparatus having an ink container with an ink inlet as described above, and further includes a step of ejecting the ink jet ink composition from an ink jet head of the ink jet recording apparatus and depositing it onto a recording medium.

[0136] According to this inkjet recording method, the inkjet ink composition contains a self-dispersing pigment, a water-soluble resin, and betaine, the content of the self-dispersing pigment is from 3.5% to 8.5% by mass, both inclusive, relative to the total mass of the ink composition, the mass ratio of the self-dispersing pigment to the water-soluble resin (self-dispersing pigment / water-soluble resin) is from 2.8 to less than 30 by mass, and the content of the betaine is from 2.5% to 9.5% by mass, both inclusive, relative to the total mass of the ink composition. As a result, foaming of the inkjet ink composition and generation of foreign matter are suppressed, and images with good color development and abrasion resistance can be formed.

[0137] The recording medium is not particularly limited, and may be one having a recording surface that absorbs liquid, or one that does not have a recording surface that absorbs liquid. Therefore, the recording medium is not particularly limited, and for example, paper, film, cloth, metal, glass, polymer, etc. can be used. Transfer paper for performing sublimation transfer onto the recording medium can also be a recording medium.

[0138] The recording medium on which recording is performed by the recording method of this embodiment is preferably a liquid-absorbent recording medium. 1 / 2 Water absorption up to 10mL / m 2 The Bristow method is the most widely used method for measuring liquid absorption in a short period of time, and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51 "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of the "JAPAN TAPPI Paper and Pulp Test Method 2000 Edition."

[0139] The liquid-absorbent recording medium may be a recording medium that has a liquid-absorbing receiving layer provided on the surface of the recording medium. For example, inkjet paper (paper specifically for inkjet printing) may be used. The liquid-absorbent receiving layer may be a layer made of a liquid-absorbent resin or liquid-absorbent inorganic fine particles.

[0140] Liquid-absorbent recording media include recording media whose substrate itself is liquid-absorbent. Examples include fabrics made of fibers and paper made of pulp. Examples of paper include plain paper, cardboard, and liner paper. Examples of liner paper include paper made of kraft pulp and recycled paper.

[0141] Ordinary paper is particularly preferred. Examples of ordinary paper include fine paper and recycled paper. Among ordinary papers, there are ordinary papers with a relatively high cation content and ordinary papers with a relatively low cation content. Ordinary paper with a relatively high cation content tends to react more easily with pigments than ordinary paper with a relatively low cation content, and tends to have higher color development due to reaction with pigments.

[0142] The ink of this embodiment provides excellent color development even on plain paper with a relatively low cation content, and is also preferable for both types of plain paper. Examples of cations include calcium salts. Calcium salts can generate calcium ions, which are cations, when the ink is applied.

[0143] The recording method of this embodiment may be used to record on an absorbent recording medium, and even if the recording medium is an absorbent recording medium, the pigment can be easily retained on the surface of the recording medium, and good color development of the image can be obtained.

[0144] The step of depositing the inkjet ink composition on a recording medium can be carried out using the inkjet recording apparatus described above. That is, the inkjet ink composition is filled into an inkjet head so that it can be ejected from a predetermined nozzle, and then ejected in this state onto a recording medium at a predetermined timing, thereby depositing the inkjet ink composition on a recording medium.

[0145] The recording method of this embodiment may also include a step of heating the recording medium as appropriate. For example, when an inkjet recording apparatus is used, the step of heating the recording medium can be performed using the drying means described above. Furthermore, the step can be performed by any suitable drying means, not limited to an inkjet recording apparatus. This dries the resulting image, thereby preventing image bleeding and allowing the image to be fixed more efficiently. The method may also include a step of refilling the ink into the ink container.

[0146] The recording method of this embodiment can further include other steps as appropriate, and may include, for example, a step of applying another composition, a cleaning step, etc. The recording method of this embodiment uses the inkjet ink composition described above, and therefore can suppress foaming of the inkjet ink composition and generation of foreign matter, and can form images with good quality and robustness.

[0147] According to the recording method of this embodiment, an inkjet ink composition containing a pigment having a volume average particle diameter D50 of 150 nm or less is used, which makes it possible to prevent the pigment from settling and agglomerating in an ink tank, etc. Furthermore, according to this recording method, the inkjet ink composition uses two types of pigments that have been subjected to two different types of surface treatment, which makes it easier for the pigments to remain on the surface of the recording medium, and makes it possible to obtain images with excellent color development.

[0148] 3. Examples and Comparative 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. Hereinafter, "parts" and "%" are based on mass unless otherwise specified. The mass % of the pigment in the tables refers to the mass % of the pigment solid content. The evaluations were carried out in an environment of a temperature of 25.0°C and a relative humidity of 40.0%, unless otherwise specified.

[0149] 3.1. Preparation of Inkjet Ink Composition The components were placed in a container so as to obtain the compositions shown in Tables 1 to 4, and mixed and stirred for 2 hours using a magnetic stirrer, followed by filtering through a membrane filter with a pore size of 5 μm to obtain inkjet ink compositions according to Examples, Comparative Examples, and Reference Examples. The pigment used was the pigment dispersion liquid prepared as described below.

[0150] The substances other than those listed by compound name in Tables 1 to 4 are as follows:

[0151] Self-dispersing pigment A1: Produced as follows: 20.0 g of the pigment, 11.0 mmol of ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid monosodium salt, 20.0 mmol of nitric acid, and 200 mL of pure water were mixed. Carbon black (product name "Black Pearls 880" manufactured by Cabot) was used as the pigment. The mixture was mixed at 6,000 rpm using a Silverson mixer at room temperature. After 30 minutes, 20.0 mmol of sodium nitrite dissolved in a small amount of water was slowly added to the mixture. The temperature of the mixture reached 60°C by adding sodium nitrite. The mixture was allowed to react for 1 hour. After that, the mixture was washed with water and the pH was adjusted to 10 using an aqueous sodium hydroxide solution. The resulting pigment has -C6H4-CONH-CH-(PO(OH)( It was a self-dispersing pigment with ONa))(PO(OH)2) groups attached.

[0152] Self-dispersing pigment A2: Produced as follows: The same procedure was carried out except that the phosphonic acid source of Self-Dispersion Pigment A1 was changed to 4-aminobenzylphosphonic acid, thereby obtaining a self-dispersion pigment having a benzenephosphonic acid group bonded thereto.

[0153] Self-dispersing pigment B1: Produced as follows: A classification operation was carried out on CAB-O-JET (a carboxylate-treated self-dispersing pigment manufactured by Cabot Corporation) to obtain a pigment dispersion having the required particle size.

[0154] Self-dispersing pigment B2: Produced as follows: A solution of 5 g of concentrated hydrochloric acid dissolved in 5.5 g of water was cooled to 5°C and 1.96 g of p-aminobenzenesulfonic acid was added. Next, the container containing this solution was placed in an ice bath and stirred to keep the solution at 10°C or below. A solution of 2.2 g of potassium nitrite dissolved in 9 g of 5°C water was added to this solution. After stirring this solution for an additional 15 minutes, 6 g (solid content) of carbon black (specific surface area 220 m) was added. 2 A 100g (100g / g, DBP oil absorption 105mL / 100g) was added under stirring. The mixture was then stirred for another 15 minutes. The resulting slurry was filtered through filter paper (trade name "Standard Filter Paper No. 2" manufactured by Advantec), and the particles were thoroughly cooled with water and dried in an oven at 110°C. The potassium ions were then replaced with ammonium ions using an ion exchange method to obtain a pigment dispersion with a pigment content of 10.0%. Classification was then performed to obtain a pigment dispersion with the required particle size. In this way, self-dispersing pigment B2 (pigment dispersion B2) was obtained, in which a self-dispersing pigment having benzenesulfonic acid groups with ammonium counterions bonded to the surface of the pigment particles was dispersed in water.

[0155] Resin-dispersed pigment: Produced as follows: 20 parts by mass of an organic solvent (methyl ethyl ketone), 0.03 parts by mass of a polymerization chain transfer agent (2-mercaptoethanol), 15 parts by mass of polypropylene glycol monomethacrylate (propylene oxide group = 9), 15 parts by mass of poly(ethylene glycol·propylene glycol) monomethacrylate (propylene oxide group = 7, ethylene oxide group = 5), 12 parts by mass of methacrylic acid, 50 parts by mass of styrene monomer, 10 parts by mass of styrene macromer, and 10 parts by mass of benzyl methacrylate were placed in a reaction vessel that had been thoroughly purged with nitrogen gas. 0.9 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) dissolved in 40 parts by mass of methyl ethyl ketone was added to 100 parts by mass of the monomer components and the mixture was polymerized with stirring at 75°C, and the mixture was aged at 80°C for 1 hour to obtain a polymer solution. 7.5 parts by mass of the water-insoluble polymer obtained above was dissolved in 45 parts by mass of methyl ethyl ketone, and a predetermined amount of 20% aqueous sodium hydroxide solution (neutralizing agent) was added to the solution to neutralize the salt-forming groups. 20 parts by mass of carbon black (product name "Black Pearls 880", manufactured by Cabot) was then added as a pigment and kneaded for 2 hours in a bead mill. 120 parts by mass of ion-exchanged water was added to the kneaded mixture obtained in this way and stirred, after which the methyl ethyl ketone was removed under reduced pressure at 6°C, and some of the water was further removed to obtain a resin-coated pigment dispersion with a solids concentration of 20% by mass.

[0156] After preparing each pigment dispersion, it was classified using a centrifuge to obtain a pigment dispersion having a volume average particle diameter of D50 for each example.

[0157] Olfine E1010: Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant Olfine D-10PG: Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant

[0158] 3.2.Evaluation Method 3.2.1. Recording test We modified a Seiko Epson PX-M886FL printer and installed an ink container with an ink inlet. The ink container was as shown in the figure. The recording medium used for the recording test was Xerox P (manufactured by Fuji Xerox Co., Ltd.). The amount of ink adhered to the recording medium was 4 mg / inch. 2 A monochrome 100% duty pattern was recorded.

[0159] 3.2.2.Clogging The head of a recording device was filled with each ink of each example, and after a recording test, the head was left uncapped in an environment of 40°C and 20% RH for 7 days, and then head cleaning was performed. The recovery from clogging was evaluated based on the number of cleanings using the following criteria, and the results are shown in Tables 1 to 4. A rating of B or higher is desirable. A: Recover within 6 times B: Recover in 7 times C: Not recovered in 7 times

[0160] 3.2.3.Optical density Ink deposition amount 4mg / inch 2 A single-color 100% duty pattern was printed in an environment of 20°C and 50% RH and measured with a colorimeter. The obtained OD values ​​were evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 4. In addition to XP paper (XeroxP paper), CopyPlus paper (CP paper, manufactured by HAMMERMILL) was also used as a recording medium. CP paper is a plain paper with a relatively high cation content, while XP paper is a plain paper with a relatively low cation content. Note that CP paper is a recording medium that requires high color development, so the evaluation criteria are different from those for XP paper. It is desirable that both are C or higher, and it is more preferable that they are B or higher.

[0161] XP paper optical density (OD value) When printed on Xerox P paper (XP paper) (low-reactivity recording medium), A:OD value 1.2 or more B: OD value 1.15 or more and less than 1.2 C: OD value 1.1 or more and less than 1.15 D:OD value less than 1.1

[0162] CP paper optical density (OD value) When printed on CopyPlus paper (CP paper) (highly reactive recording medium), A:OD value 1.3 or more B: OD value 1.2 or more and less than 1.3 C: OD value 1.15 or more and less than 1.2 D:OD value less than 1.15

[0163] 3.2.4.Air-liquid interface foreign matter Approximately 30 g of ink was placed in a 50 mL screw tube, and left in a 60°C environment with the lid closed for 5 days. The tube was judged based on whether or not foreign matter was generated, and the results are shown in Tables 1 to 4. A was desirable. A: No foreign matter is generated B: Foreign matter occurs

[0164] 3.2.5. Sedimentation The ink reservoir of the recording tester was filled with 50 mL of ink, and the ink was allowed to settle naturally (left to stand) for two weeks before printing. The same patterns as those used in the optical density test were printed across the entire surface of a single recording medium (XP paper). The color difference (ΔE value) between the lightest and darkest patterns was measured. The color difference is the ΔE value in the CIE Lab color system. Color measurements were performed using a spectrophotometer (GretagMacbeth, model: Spectrolino) under a D65 light source. The results are shown in Tables 1 to 4. C or higher is desirable, and B or higher is more preferable. A: ΔE<1.0 B: 1.0≦ΔE<2.0 C:2.0≦ΔE<2.5 D:2.5≦ΔE

[0165] 3.3.Evaluation Results Tables 1 to 4 show that the inkjet ink compositions of the examples, each containing a pigment comprising self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group, and self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group, produced good image color development and effectively suppressed pigment sedimentation.

[0166] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations that add publicly known technology to the configurations described in the embodiments.

[0167] The following can be derived from the above-described embodiment and modifications.

[0168] The inkjet ink composition comprises a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group; a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group; The pigment contains:

[0169] This inkjet ink composition uses a pigment with a volume average particle diameter D50 of 150 nm or less, which can prevent the pigment from settling and agglomerating in the ink tank, etc. Furthermore, this inkjet ink composition uses two types of pigments that have been subjected to two different surface treatments, which makes it easier for them to remain on the surface of the recording medium, allowing for the production of images with excellent color development.

[0170] In the inkjet ink composition, The ink jet recording device may be used in an ink jet recording apparatus having an ink tank with an ink inlet.

[0171] This ink-jet ink composition can prevent pigment sedimentation in an ink tank even if the recording apparatus has an ink tank with an ink inlet.

[0172] In the inkjet ink composition, The volume average particle diameter D50 of the self-dispersion pigment A is 70 nm or more and 150 nm or less. good.

[0173] According to this inkjet ink composition, the volume average particle diameter D50 of the self-dispersion pigment A is 70 nm or more, so that images with even better color development can be formed.

[0174] In the inkjet ink composition, The mass ratio (A / B) of the self-dispersion pigment A to the self-dispersion pigment B may be 0.4 or more and 2.5 or less.

[0175] This inkjet ink composition makes it possible to form images with even better color development.

[0176] In the inkjet ink composition, The total content of the self-dispersion pigment A and the self-dispersion pigment B may be 4% by mass or more and 8% by mass or less with respect to the total mass of the inkjet ink composition.

[0177] This inkjet ink composition can further inhibit the pigment from settling and agglomerating in an ink tank or the like, and can also provide images with even better color development.

[0178] In the inkjet ink composition, Betaines may also be contained.

[0179] This inkjet ink composition can further improve clogging recovery properties.

[0180] In the inkjet ink composition, The content of the betaines may be 3% by mass or more and 10% by mass or less relative to the total mass of the inkjet ink composition.

[0181] This inkjet ink composition can further improve clogging recovery properties.

[0182] In the inkjet ink composition, The volume average particle diameter D50 of the self-dispersion pigment A may be larger than the volume average particle diameter D50 of the self-dispersion pigment B.

[0183] This inkjet ink composition can further suppress pigment sedimentation.

[0184] In the inkjet ink composition, It may also be used for recording on absorbent recording media.

[0185] This inkjet ink composition makes it easy to retain the pigment on the surface of the recording medium, even if it is an absorbent recording medium, and can provide images with good color development.

[0186] The recording method is The method includes a step of ejecting any one of the ink-jet ink compositions described above from an ink-jet head and depositing it onto a recording medium.

[0187] This recording method uses an inkjet ink composition containing a pigment with a volume average particle diameter D50 of 150 nm or less, which makes it possible to prevent the pigment from settling and agglomerating in an ink tank, etc. Furthermore, this recording method uses two types of pigments that have been subjected to two different surface treatments, which makes it easier for the pigments to remain on the surface of the recording medium, making it possible to obtain images with excellent color development. [Explanation of symbols]

[0188] 21...recording device, 22...casing, 23...support stand, 24...guide shaft, 25...recording head, 26...carriage, 27...support hole, 28...drive pulley, 29...driven pulley, 30...carriage motor, 30g...methacrylic acid, 31...timing belt, 32...discharge outlet, 33...discharge tray, 34...paper feed cassette, 35...opening / closing door, 36...rotating shaft, 37...window portion, 40...ink supply unit, 41...ink storage container, 42...ink storage container, 43...ink storage container, 44...ink storage container, 45...ink storage container, 46...ink supply tube, 47...ink refill adapter, 48...step portion, 49...ink storage chamber, 50...visibility portion, 51...upper limit mark, 52...lower limit mark, 53...ink inlet, 54...flow path, 55...flow path, 56...needle, 57...remaining amount sensor, 58...upper surface, 59...lower surface, 60...through hole, 61...recess, 62...first uneven portion, 63...ink bottle, 64...container main body portion, 65...ink outlet, 66...ink outlet forming portion, 67...container additional portion, 68...cap, 69...male thread portion, 70...protrusion, IK...ink composition, P...paper

Claims

1. a self-dispersing pigment A having a volume average particle diameter D50 of 150 nm or less and having a phosphorus-containing group; a self-dispersing pigment B having a volume average particle diameter D50 of 90 nm or more and 150 nm or less and having a functional group other than a phosphorus-containing group; 1. A water-based ink-jet ink composition containing a pigment comprising:

2. In claim 1, An ink-jet ink composition for use in an ink-jet recording apparatus having an ink tank with an ink inlet.

3. In claim 1, The ink-jet ink composition, wherein the self-dispersion pigment A has a volume average particle diameter D50 of 70 nm or more and 150 nm or less.

4. In claim 1, the mass ratio (A / B) of the self-dispersion pigment A to the self-dispersion pigment B is 0.4 or more and 2.5 or less.

5. In claim 1, the total content of the self-dispersion pigment A and the self-dispersion pigment B is 4% by mass or more and 8% by mass or less, based on the total mass of the inkjet ink composition.

6. In claim 1, An ink-jet ink composition containing betaines.

7. In claim 6, The inkjet ink composition has a betaine content of 3% by mass or more and 10% by mass or less relative to the total mass of the inkjet ink composition.

8. In claim 1, the self-dispersion pigment A has a volume average particle diameter D50 greater than the volume average particle diameter D50 of the self-dispersion pigment B.

9. In claim 1, An inkjet ink composition for use in recording on an absorbent recording medium.

10. A recording method, comprising a step of ejecting the ink-jet ink composition according to claim 1 from an ink-jet head and depositing it onto a recording medium.

Images