Inkjet ink composition and recording method

Abstract

To provide an inkjet ink composition that achieves superior color development and superior discharge stability, including recovery from clogging.SOLUTION: A water-based inkjet ink composition according to one embodiment contains dimethyl isosorbide, betaine, and a colorant.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, the applications of inkjet printing have expanded, and inkjet printing is now used not only in office and home printing machines, but also in commercial printing, textile printing, etc. As inkjet inks, water-based inkjet inks containing water as the main liquid component have been developed in consideration of environmental impact, etc. Among these, the use of penetrating solvents has been investigated in order to improve the ink functions.

[0003] For example, Patent Document 1 describes a water-based inkjet recording ink for recording on plain paper, which contains an organic solvent of glycol ethers as a penetrating solvent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-007444 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the color development and ejection stability (ability to recover from clogging) are still insufficient. [Means for solving the problem]

[0006] One embodiment of the ink-jet ink composition according to the present invention comprises: It is a water-based product containing dimethyl isosorbide, betaine, and a coloring material.

[0007] 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 of the above embodiment from an ink-jet head and depositing the ink-jet ink composition on a recording medium. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side cross-sectional view showing a configuration of an inkjet recording apparatus. [Diagram 2] FIG. 1 shows examples of ink-jet ink compositions and evaluation results (Table 1). [Diagram 3] FIG. 2 shows examples of ink-jet ink compositions and evaluation results (Table 2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described. The embodiment described below is an example of the present invention. The present invention is not limited to the following embodiment, and includes various modified forms that are implemented within the scope that does not change the gist of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0010] 1. Inkjet ink composition An ink-jet ink composition according to one embodiment of the present invention is a water-based ink composition containing dimethyl isosorbide, betaine, and a coloring material.

[0011] Conventionally, when using water-based inks, particularly when recording on plain paper, organic solvents of glycol ethers such as triethylene glycol monobutyl ether have been used as penetrating solvents. Penetrating solvents have the function of increasing the permeability, wetting spreadability, and ejection stability of the ink into the recording medium. However, conventional penetrating solvents are still insufficient in terms of color development and ejection stability.

[0012] This time, it was found that by using dimethyl isosorbide as a penetrating solvent, the ink's penetrability (wetting and spreading properties) and ejection stability could be further improved, and the ink also had excellent color development. Dimethyl isosorbide is highly hydrophobic, but also has a high polarizability and is easily soluble in water, so it can be used in water-based inks. It is presumed that dimethyl isosorbide has the effect of improving the penetrability of ink droplets into the recording medium, particularly the wetting and spreading properties in the planar direction of the recording medium.

[0013] However, dimethyl isosorbide is still highly hydrophobic, so as the ink dries, it turns into foreign matter, which tends to cause clogging in the inkjet head. After extensive research, we found that the use of betaine in the ink can reduce clogging. We speculate that this is due to the strong water retention properties of betaine.

[0014] Therefore, the inkjet ink composition according to this embodiment can have excellent color development and ejection stability (clogging recovery properties).

[0015] Each component contained in the inkjet ink composition according to this embodiment will be described below. In the following, the inkjet ink composition may be simply referred to as the "ink composition" or "ink." Furthermore, unless otherwise specified, "ejection stability" refers to ejection stability in both clogging recovery and intermittency.

[0016] 1.1 Dimethylisosorbide The inkjet ink composition according to this embodiment contains dimethyl isosorbide. Dimethyl isosorbide is easily soluble in water, and is assumed to have the effect of improving the permeability of ink droplets into a recording medium. Furthermore, dimethyl isosorbide is assumed to have the effect of solubilizing hydrophobic compounds in water, but since dimethyl isosorbide has a cyclic structure, it is relatively less likely to attack resin components, and therefore it is unlikely to impair the stability of other components in the ink and deteriorate storage stability. In addition, since dimethyl isosorbide has a cyclic structure, it has a lower viscosity than compounds with a straight chain structure, and is advantageous in terms of ejection stability.

[0017] Dimethyl isosorbide is also known as isosorbide dimethyl ether and 1,4:3,6-dianhydro-2-O,5-O-dimethyl-D-glucitol.

[0018] The lower limit of the content of dimethyl isosorbide is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, particularly preferably 2.0% by mass or more, and more particularly preferably 2.5% by mass or more, based on the total amount of the ink composition. When the content of dimethyl isosorbide is in the above range, the ink permeability (wetting and spreading ability) is further improved, and the color development tends to be more excellent.

[0019] The upper limit of the dimethyl isosorbide content is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, particularly preferably 7% by mass or less, and more particularly preferably 5% by mass or less, relative to the total amount of the ink composition. If the dimethyl isosorbide content is within the above range, the ejection stability and storage stability of the ink tend to be more excellent.

[0020] 1.2 Betaine The inkjet ink composition according to this embodiment contains betaine.

[0021] Betaine means a compound having a positive charge and a negative charge at non-adjacent positions in the same molecule, with no dissociable hydrogen bonded to the positively charged atom, forming an intramolecular salt, and the molecule as a whole having no charge. In addition, betaine is preferably a compound having both amino and carboxy functional groups. From the viewpoint of stability, the amino group is preferably a tertiary amino group or a quaternary amino group. Such betaines are not particularly limited, but include, for example, tertiary betaines such as dimethylglycine, dimethylalanine, dimethylglutamic acid, and diethylglycine; and quaternary betaines such as trimethylglycine, trimethylalanine, trimethylglutamic acid, and triethylglycine.

[0022] Among the tertiary betaines, dialkyl glycines such as dimethyl glycine and diethyl glycine are preferred, and among the quaternary betaines, trialkyl glycines such as trimethyl glycine and triethyl glycine are preferred.

[0023] Among these, the betaine is preferably trialkylglycine. As the trialkylglycine, one or more selected from trimethylglycine and triethylglycine are preferred, and trimethylglycine is more preferred. By using such a betaine, the moisture retention and moisture absorption properties of the ink composition tend to be improved, and the ejection stability (clogging recovery property) tends to be further improved. Note that the betaine may be used alone or in combination of two or more kinds.

[0024] The number of carbon atoms constituting the betaine is preferably 3 to 12, more preferably 3 to 7, and even more preferably 4 to 6. When the number of carbon atoms in the betaine is within the above range, stability against disturbances such as the inclusion of charged foreign matter is further improved, and the storage stability of the ink may be further improved.

[0025] The lower limit of the betaine content is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, particularly preferably 3.0% by mass or more, and more particularly preferably 4.0% by mass or more, based on the total amount of the ink composition. When the betaine content is within the above range, the occurrence of clogging can be further reduced, and the ejection stability (clogging recovery property) tends to be more excellent.

[0026] The upper limit of the betaine content is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 12% by mass or less, particularly preferably 10% by mass or less, and more particularly preferably 8% by mass or less, based on the total amount of the ink composition. When the betaine content is within the above range, the color development tends to be more excellent.

[0027] 1.3 Colorants The inkjet ink composition according to this embodiment contains a coloring material. Examples of the coloring material include pigments and dyes.

[0028] 1.3.1 Pigments As the pigment, for example, inorganic pigments including carbon black and titanium white, organic pigments, etc. can be used.

[0029] As the inorganic pigment, carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, titanium oxide, zinc oxide, silica, and the like can be used.

[0030] Examples of carbon black include No. 2300, 900, MCF88, No. 20B, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B manufactured by Mitsubishi Chemical Corporation. Examples of carbon black include Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, and S170, Pretex 35, U, V, and 140U, and Special Black 6, 5, 4A, 4, and 250 manufactured by Degussa. Examples of carbon black include Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, and 700 manufactured by Columbia Carbon Corporation. Examples of such tires include Cabot Corporation's Regal 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, and Elftex 12.

[0031] Examples of organic pigments include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments.

[0032] Specific examples of organic pigments that can be used in the ink-jet ink composition include the following.

[0033] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc.; CI Bat Blue 4, 60, etc., and preferably, one or a mixture of two or more selected from the group consisting of CI Pigment Blue 15:3, 15:4, and 60 can be exemplified.

[0034] Examples of magenta pigments include CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 168, 184, 202, and CI Pigment Violet 19. Preferred examples include one or a mixture of two or more pigments selected from the group consisting of CI Pigment Red 122, 202, and 209, and CI Pigment Violet 19.

[0035] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 119, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, and 185. Of these, preferred examples include one or a mixture of two or more selected from the group consisting of CI Pigment Yellow 74, 109, 110, 128, 138, 155, and 180.

[0036] Examples of orange pigments include CI Pigment Orange 36 or 43, or mixtures thereof. Examples of green pigments include CI Pigment Green 7 or 36, or mixtures thereof.

[0037] Luster pigments may also be used, and are not particularly limited as long as they can exhibit lustre when attached to a medium, but examples thereof include metal particles of one or more alloys (also called metal pigments) selected from the group consisting of aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, and copper, and pearl pigments having pearly luster. Representative examples of pearl pigments include pigments having pearly luster or interference luster, such as titanium dioxide-coated mica, fish scale foil, and bismuth oxychloride. Luster pigments may also be surface-treated to suppress reaction with water.

[0038] White pigments may also be used, and examples of such pigments include metal oxides, barium sulfate, calcium carbonate, and other metal compounds. Examples of metal oxides include titanium dioxide, zinc oxide, silica, alumina, magnesium oxide, and other. As the white pigment, particles having a hollow structure may also be used.

[0039] The pigments may be used alone or in combination of two or more. From the viewpoint of storage stability such as light resistance, weather resistance, and gas resistance, the pigment is preferably an organic pigment.

[0040] The volume average particle diameter (D50) of the pigment, as measured by a dynamic light scattering method, is 20 nm or more and 300 nm or less, more preferably 30 nm or more and 200 nm or less, and even more preferably 40 nm or more and 100 nm or less.

[0041] The volume average particle diameter may be measured, for example, by a Nanotrack Series particle distribution measuring device manufactured by Microtrackbell Co., Ltd. Examples of a method for adjusting the volume average particle diameter include a method for adjusting the degree of pulverization of the pigment before dispersion, a method for adjusting the stirring conditions during dispersion (e.g., stirring speed, stirring temperature, etc.), and a method for adjusting by filtration using a filter after dispersion.

[0042] The pigment may be dispersed using a pigment dispersant, or may be dispersed as a self-dispersing pigment by oxidizing or sulfonating the pigment surface with ozone, hypochlorous acid, fuming sulfuric acid, or the like.

[0043] (Resin-dispersed pigment) The pigment dispersant has the function of dispersing the pigment in the inkjet ink composition. The pigment dispersant may be water-soluble, but is preferably not completely water-soluble, and is considered to disperse the pigment by partially or entirely bonding or adsorbing to the pigment and increasing the hydrophilicity of the pigment surface. The pigment dispersant is preferably a polymer compound, and more preferably a resin. The pigment dispersed by the pigment dispersant which is a resin is also called a resin-dispersed pigment.

[0044] Examples of the resin of the pigment dispersant include acrylic resins and salts thereof, such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid copolymer, vinyl naphthalene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, and styrene-α-methylstyrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer. In this specification, a polymer having a skeleton derived from (meth)acrylic acid and not having a skeleton derived from maleic acid or a compound similar thereto is referred to as an acrylic resin. In this specification, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

[0045] Examples of the resin for the pigment dispersant include maleic acid-based resins and salts thereof, such as styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-maleic acid copolymer, and vinyl acetate-maleic acid ester copolymer; urethane-based resins and salts thereof, which may or may not have a crosslinked structure; polyvinyl alcohols; and vinyl acetate-crotonic acid copolymers and salts thereof.

[0046] In addition to the above-mentioned polymers of acrylic monomers, the acrylic resin may be a copolymer of an acrylic monomer and another monomer. For example, an acrylic vinyl resin, which is a copolymer of a vinyl monomer as another monomer, is also called an acrylic resin. For example, among the above-mentioned styrene resins, a copolymer of a styrene monomer and an acrylic monomer is also included in the acrylic resin. Furthermore, when the acrylic resin is called an acrylic resin, its salts and esters are also included.

[0047] Examples of commercially available pigment dispersants include X-200, X-1, X-205, X-220, and X-228 (manufactured by Seiko PMC Co., Ltd.), Nopcosperse (registered trademark) 6100 and 6110 (manufactured by San Nopco Ltd.), Joncryl 67, 586, 611, 678, 680, 682, and 819 (manufactured by BASF), DISPERBYK-190 (manufactured by BYK Japan KK), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, and E-EN10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0048] Commercially available acrylic pigment dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, and BYK-199 (manufactured by BYK-Chemie Co., Ltd.), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, and CL-2 (manufactured by Toagosei Co., Ltd.).

[0049] Commercially available urethane pigment dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by BYK-Chemie Co., Ltd.), TEGO Disperse710 (manufactured by Evonic Tego Chemi), and Borchi (registered trademark) Gen1350 (manufactured by OMG Borschers).

[0050] The pigment dispersant may be used alone or in combination of two or more. The total content of the pigment dispersant is 0.1% by mass or more and 30% by mass or less, preferably 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, based on 100% by mass of the ink. By making the content of the pigment dispersant 0.1% by mass or more, it is possible to ensure the dispersion stability of the pigment. In addition, if the content of the pigment dispersant is 30% by mass or less, it is possible to keep the viscosity of the inkjet ink composition low.

[0051] The weight average molecular weight of the pigment dispersant is more preferably at least 500. By using such a pigment dispersant, it is possible to reduce odor and further improve the dispersion stability of the pigment.

[0052] When the pigment is dispersed by a pigment dispersant, the ratio of the pigment to the pigment dispersant is preferably from 10:1 to 1:10, and more preferably from 4:1 to 1:3.

[0053] (Self-dispersing pigment) The self-dispersing pigment refers to a pigment whose surface has been modified by directly or indirectly bonding to its surface one or more functional groups selected from the group consisting of carbonyl groups, carboxyl groups, aldehyde groups, hydroxyl groups, sulfone groups, ammonium groups, and salts thereof.

[0054] Self-dispersing pigments are more likely to aggregate on recording media than other color materials, so they can increase the optical density of printed areas. In particular, plain paper (business documents) requires a high black density, and self-dispersing pigments, especially carbon black, are needed to achieve this.

[0055] In addition, since the self-dispersing pigment has high dispersion stability, it is not necessary to disperse it using a dispersant such as a resin, and the viscosity can be made moderate. Therefore, when the self-dispersing pigment is used, even if the content is increased, it is easy to handle and an image with excellent color development can be formed. On the other hand, in the case of a pigment that is not a self-dispersing pigment, a dispersant is required, which has a drawback such as increasing the viscosity of the ink, and there is a problem with ejection stability. Therefore, the content of the coloring material in the ink cannot be increased, which is disadvantageous in terms of obtaining a high ink concentration.

[0056] Thus, self-dispersing pigments are useful in that they do not require the use of a dispersant and can make the ink viscosity relatively low. In particular, self-dispersing pigments are useful in that they can keep the ink viscosity low even when high-density printing is desired and the pigment concentration of the ink is desired to be relatively high. On the other hand, self-dispersing pigments tend to have a tendency to be less stable in dispersion once the pigment aggregates, such as when the ink dries, and to be less likely to be redispersed, compared to pigments dispersed with a dispersant such as a resin. In particular, this tendency is strong in self-dispersing pigments in which the amount of functional groups introduced to the pigment surface is kept below a certain level.

[0057] In the inkjet ink composition according to this embodiment, even when such a self-dispersing pigment is used, there is a tendency for the inkjet ink composition to have excellent ejection stability (ability to recover from clogging).

[0058] Examples of self-dispersing pigments include organic pigments such as carbon black, azo lake, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dioxazine pigments, anthraquinone pigments, nitro pigments, nitroso pigments, and aniline black; and inorganic pigments such as titanium white, zinc white, lead white, carbon black, red iron oxide, vermilion, cadmium red, yellow lead, ultramarine blue, cobalt blue, cobalt purple, and zinc chromate.

[0059] Of these, the self-dispersing pigment is preferably carbon black, from the viewpoints of being able to print black at a high density and being more excellent in ejection reliability.

[0060] The self-dispersing pigment may be a commercially available product or a preparation prepared by a known method, such as "Microjet CW1" and "Microjet CW2" manufactured by Orient Chemical Industry Co., Ltd., and "CAB-O-JET 200" and "CAB-O-JET 300" manufactured by Cabot Corporation.

[0061] 1.3.2 Dyes The ink-jet ink composition may contain a dye as a coloring material. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, basic dyes, and disperse dyes can be used.

[0062] The yellow dye is not particularly limited, but examples thereof include CI Acid Yellow 1, 3, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 59, 61, 70, 72, 75, 76, 78, 79, 98, 99, 110, 111, 127, 131, 135, 142, 162, 164, and 165, and CI Direct Yellow 1, 8, 11, 12, 24, 26, 27, and 33. , 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 110, 132, 142, 144, 162, 165, CI Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42, CI Food Yellow 3, 4, CI Solvent Yellow 15, 19, 21, 30, 109.

[0063] Examples of magenta dyes include, but are not limited to, CI Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, and 130. , 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211, 215, 219, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, CI Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, CI Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, CI Solubilize Red 1, and CI Food Red 7, 9, and 14.

[0064] Examples of cyan dyes include CI Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, and 131. , 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 199, 203, 204, 205, 229, 234, 236, 249, CI Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86 , 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249, CI Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 1 4, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 46, CI Solubilize Bat Blue 1, 5, 41, CI Bat Blue 4, 29, 60, CI Food Blue 1, 2, CI Basic Blue 9, 25, 28, 29, 44.

[0065] Examples of orange dyes include Acid Orange 3, 7, 8, 10, 19, 22, 24, 33, 45, 51, 51S, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168, and Direct Orange. Range 1, 6, 8, 10, 26, 27, 34, 39, 40, 46, 49, 102, 105, 107, 118; Reactive Orange 1, 2, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107.

[0066] The above dyes may be used alone or in combination of two or more kinds.

[0067] Among these, the coloring material is preferably any one of a resin-dispersed pigment, a self-dispersed pigment, and a dye. Such coloring materials can be favorably dispersed in water-based inks, and therefore tend to have improved color development and ejection stability.

[0068] The lower limit of the content of the coloring material is not particularly limited, but is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 3.0% by mass or more, and particularly preferably 4.0% by mass or more, based on the total amount of the ink composition. When the content of the coloring material is within the above range, the color development tends to be more excellent.

[0069] The upper limit of the content of the coloring material is not particularly limited, but is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 12% by mass or less, even more preferably 10% by mass or less, particularly preferably 8% by mass or less, and even more particularly preferably 7% by mass or less, relative to the total amount of the ink composition. When the content of the coloring material is within the above range, the ejection stability tends to be more excellent.

[0070] 1.4 Water The inkjet ink composition according to this embodiment is water-based and contains water. In this specification, "water-based" refers to containing at least water as a solvent component, and may contain water as a main solvent component. 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, by using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, the growth of bacteria and fungi can be suppressed when the inkjet ink composition is stored for a long period of time.

[0071] The content of water in the liquid medium component is preferably 30% by mass or more, and more preferably 30 to 99% by mass. It is further preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 80% by mass. The liquid medium is a solvent component such as water or an organic solvent.

[0072] 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, relative to the total mass of the ink composition. The upper limit of the water content is not particularly limited, but is, for example, preferably 99% 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, relative to the total mass of the ink composition.

[0073] 1.5 Surfactants The inkjet ink composition according to this embodiment may contain a surfactant. Examples of such surfactants include, but are not limited to, acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0074] The acetylene glycol surfactant is not particularly limited, but for example, one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol are preferred. Commercially available acetylene glycol surfactants are not particularly limited, but for example, E series such as Olfin 104 series and Olfin E1010 (trade names manufactured by Air Products Japan, Inc.), Surfynol 465 and Surfynol 61 (trade names manufactured by Nissin Chemical Industry CO.,Ltd.) can be mentioned. The acetylene glycol surfactant may be used alone or in combination of two or more kinds.

[0075] The fluorosurfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkyl amine oxide compound. The commercially available fluorosurfactant is not particularly limited, but examples thereof include S-144, S-145 (manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, and Fluorad-FC4430 (manufactured by Sumitomo 3M Co., Ltd.); FSO, FSO-100, FSN, FSN-100, and FS-300 (manufactured by Dupont Co., Ltd.); and FT-250 and 251 (manufactured by Neos Co., Ltd.). The fluorosurfactant may be used alone or in combination of two or more kinds.

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

[0077] Among these, the inkjet ink composition according to the present embodiment preferably contains an acetylene glycol surfactant. Acetylene glycol surfactants have excellent defoaming properties, so ejection defects caused by bubbles in the ink are unlikely to occur. On the other hand, because they have low solubility in water, phase separation is likely to occur in the water-based ink, and this is particularly noticeable when the ink is dried and the amount of water is reduced. When phase separation occurs in the ink, ejection stability tends to deteriorate. In contrast, according to the inkjet ink composition according to the present embodiment, dimethyl isosorbide contained in the ink has the effect of solubilizing hydrophobic compounds in water, so that even when the ink composition contains an acetylene glycol surfactant, phase separation is unlikely to occur and good ejection stability tends to be obtained.

[0078] The content of the surfactant is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less, based on the total mass of the ink composition. If the content of the surfactant is within the above range, the ejection stability tends to be more excellent. In addition, the lower limit of the content of the surfactant is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on the total mass of the ink composition.

[0079] 1.6 Resin The inkjet ink composition according to this embodiment may contain a resin. When the ink composition contains a resin, it tends to be possible to prevent the ink from being transferred to the transport path or to the stacked recording media when the recording media are transported in the printer or when the recording media are stacked. On the other hand, the resin may become a foreign matter in the ink or inside the inkjet head, which may deteriorate the ejection stability. In contrast, according to the inkjet ink composition according to this embodiment, dimethyl isosorbide contained in the ink has the effect of solubilizing hydrophobic compounds in water, and can prevent the resin from becoming a foreign matter, so that good ejection stability tends to be obtained.

[0080] The resin may be, for example, in the form of resin particles or a water-soluble resin.

[0081] 1.6.1 Resin particles The resin particles are not water-soluble resins, but resins dispersed in particulate form in a solvent in the ink, such as resin emulsions.

[0082] Examples of the resin particles include resin particles made of urethane-based resins, acrylic-based resins (including styrene-acrylic-based resins), fluorene-based resins, polyolefin-based resins, rosin-modified resins, terpene-based resins, polyester-based resins, polyamide-based resins, epoxy-based resins, vinyl chloride-based resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate-based resins, etc. Among these, urethane-based resins, acrylic-based resins, polyolefin-based resins, and polyester-based resins are preferred. These resin particles are often handled in the form of an emulsion, but may also be in the form of a powder. The resin particles may be used alone or in combination of two or more types.

[0083] The urethane resin is a general term for resins having a urethane bond, and is not particularly limited, but examples thereof include polyether-type urethane resins having an ether bond in the main chain, polyester-type urethane resins having an ester bond in the main chain, and polycarbonate-type urethane resins having a carbonate bond in the main chain. The urethane resin may be a preparation prepared by a known method, or a commercially available product.

[0084] The acrylic resin is a general term for a polymer obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component. The acrylic resin is not particularly limited, but examples thereof include those obtained by polymerizing a (meth)acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester, and those obtained by copolymerizing a (meth)acrylic monomer with another monomer, such as a styrene-acrylic resin. The acrylic resin may be a preparation prepared by a known method, or a commercially available product may be used. Examples of commercially available products include X-436 (Seiko PMC Co., Ltd., styrene acrylic resin).

[0085] The content of the resin particles is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and particularly preferably 4% by mass or less, based on the total mass of the ink composition. When the content of the resin particles is within the above range, the ejection stability tends to be more excellent. In addition, the lower limit of the content of the resin particles is not particularly limited, but is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, based on the total mass of the ink composition.

[0086] 1.6.2 Water-soluble resin The water-soluble resin means a resin that can be dissolved in water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent, and can exist in water or an aqueous medium in a state that does not have a particle size when measured by a dynamic light scattering method. As the water-soluble resin, a resin that makes the resin used in the above-mentioned resin particles water-soluble is preferable, and a water-soluble urethane resin is more preferable.

[0087] The water-soluble urethane resin has repeating units derived from polyisocyanate and polyol, among which those having repeating units derived from polyol having an acid group are preferred, and resins having repeating units derived from polyisocyanate, polyol having no acid group, and polyol having an acid group are preferred. The water-soluble urethane resin may further have repeating units derived from polyamine.

[0088] The polyisocyanate refers to a compound having two or more isocyanate groups in its molecular structure, and includes, but is not limited to, aliphatic polyisocyanates such as isophorone diisocyanate, and aromatic polyisocyanates such as tolylene diisocyanate.

[0089] A polyol is a compound having two or more hydroxyl groups in its molecular structure. The polyol in the present embodiment is not particularly limited, but may be a polyol having no acid group, such as a polyether polyol, or a polyol having an acid group, such as a carboxylic acid group.

[0090] The polyether polyol is not particularly limited, but examples thereof include addition polymers of alkylene oxides such as ethylene oxide and polyols such as 1,3-propanediol, and glycols such as polypropylene glycol.

[0091] The polyol having a carboxylic acid group is not particularly limited, but examples thereof include dimethylol acetic acid, dimethylol propionic acid, dimethylol butanoic acid, and dimethylol butyric acid.

[0092] The polyamine is not particularly limited, but examples thereof include monoamines having a plurality of hydroxy groups, such as dimethylolethylamine; bifunctional polyamines, such as ethylenediamine; and trifunctional or higher polyamines, such as diethylenetriamine.

[0093] The acid value of the water-soluble urethane resin is preferably 40 to 100 mgKOH / g, more preferably 40 to 90 mgKOH / g, even more preferably 45 to 80 mgKOH / g, and even more preferably 50 to 70 mgKOH / g. The acid value of the water-soluble urethane resin is not particularly limited, but can be adjusted, for example, by the amount of polyol having an acid group. In addition, the method of measuring the acid value can be the method described in the examples below.

[0094] The weight average molecular weight of the water-soluble urethane resin is preferably 5000 to 150000, more preferably 10000 to 100000, even more preferably 15000 to 50000, even more preferably 20000 to 30000, and even more preferably 20000 to 23000. The weight average molecular weight within the above range tends to improve the ejection reliability. The weight average molecular weight of the water-soluble urethane resin is not particularly limited, but can be adjusted, for example, by the reaction temperature and reaction time of the polyisocyanate and the polyol. In addition, the method of measuring the weight average molecular weight can be the method described in the examples below.

[0095] The content of the water-soluble resin is preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.3% by mass or less, based on the total mass of the ink composition. When the content of the water-soluble resin is within the above range, the ejection stability tends to be more excellent. In addition, the lower limit of the content of the water-soluble resin is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the total mass of the ink composition.

[0096] 1.7 Inorganic fine particles The inkjet ink composition according to this embodiment may contain inorganic fine particles. The inorganic fine particles are fine particles of an inorganic compound such as an inorganic oxide. The inorganic fine particles function as a sealant for the recording medium and can prevent the ink from penetrating too much into the recording medium, thereby further improving color development. On the other hand, the inorganic fine particles may become foreign matter in the ink or inkjet head, which may deteriorate the ejection stability. In contrast, according to the inkjet ink composition according to this embodiment, dimethyl isosorbide contained in the ink has the effect of solubilizing hydrophobic compounds in water, and can prevent the inorganic fine particles from becoming foreign matter, so that good ejection stability tends to be obtained.

[0097] The inorganic fine particles are not particularly limited, but examples thereof include metal oxides such as silica, alumina, titania, zirconia, antimony oxide, tin oxide, tantalum oxide, zinc oxide, cerium oxide, lead oxide, and indium oxide; metal nitrides such as silicon nitride, titanium nitride, and aluminum nitride; metal carbides such as silicon carbide and titanium carbide; metal sulfides such as zinc sulfide; metal carbonates such as calcium carbonate and magnesium carbonate; metal sulfates such as calcium sulfate and magnesium sulfate; metal silicates such as calcium silicate and magnesium silicate; metal phosphates such as calcium phosphate; metal borates such as aluminum borate and magnesium borate, and composites thereof. The inorganic fine particles may form a salt. In addition, the inorganic fine particles may be used alone or in combination of two or more types.

[0098] The average particle size of the inorganic fine particles is preferably 100 nm or less, more preferably 20 to 100 nm, even more preferably 30 to 80 nm, and even more preferably 40 to 60 nm. When the average particle size of the inorganic fine particles is within the above range, there is a tendency for the intermittency to be excellent.

[0099] The average particle size of inorganic fine particles can be measured by a particle size distribution measuring device that uses dynamic light scattering as the measurement principle. Such particle size distribution measuring devices are not particularly limited, but an example thereof is the "Zeta Potential, Particle Size, and Molecular Weight Measuring System ELSZ2000ZS" (product name) manufactured by Otsuka Electronics Co., Ltd., which uses a homodyne optical system as a frequency analysis method. The above-mentioned average particle size means the average particle size based on the number of particles.

[0100] The content of the inorganic fine particles is preferably 0.1 to 8.0% by mass, more preferably 0.5 to 6.0% by mass, further preferably 1.0 to 5.0% by mass, and particularly preferably 2.0 to 4.0% by mass, based on the total amount of the ink composition as a solid content. When the content of the inorganic fine particles is 0.1% by mass or more, color development tends to be improved, and when the content of the inorganic fine particles is 8.0% by mass or less, aggregation of the inorganic fine particles is easily suppressed, and intermittency and clogging recovery tend to be excellent.

[0101] 1.8 Organic Solvents The inkjet ink composition according to this embodiment may contain an organic solvent other than the above-mentioned dimethyl isosorbide and betaine. Such organic solvents are not particularly limited, but include, for example, monohydric alcohols, polyols, and glycol ethers. Among them, it is more preferable to contain polyols, and it is even more preferable to contain polyols having a normal boiling point of more than 280°C. When the inkjet ink composition according to this embodiment contains a polyol having a normal boiling point of more than 280° C., the drying resistance of the ink can be improved, making it less likely for foreign matter to be generated and tending to further improve ejection stability.

[0102] The monohydric alcohols are not particularly limited, but examples thereof include methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol.

[0103] Among the polyols, polyols having a normal boiling point of more than 280°C are not particularly limited, but examples thereof include triethylene glycol (normal boiling point: 287°C), tetraethylene glycol (normal boiling point: 314°C), and glycerin (normal boiling point: 290°C). The content of the polyol having a normal boiling point of more than 280°C is preferably 1 to 20 mass %, more preferably 3 to 18 mass %, even more preferably 5 to 15 mass %, and particularly preferably 7 to 12 mass %, relative to the total amount of the ink composition.

[0104] Examples of polyols having a normal boiling point of 280° C. or less include, but are not limited to, ethylene glycol, diethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol (1,2-HD), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. The content of polyols having a normal boiling point of 280° C. or less is preferably 0.1 to 8 mass %, more preferably 0.2 to 5 mass %, even more preferably 0.3 to 3 mass %, and particularly preferably 0.5 to 2 mass %, relative to the total amount of the ink composition.

[0105] The glycol ethers are not particularly limited, but examples thereof include triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether (BTG), diethylene glycol monobutyl ether, and dipropylene glycol monopropyl ether.

[0106] The organic solvent may be used alone or in combination of two or more kinds.

[0107] The content of the organic solvent other than the above-mentioned dimethyl isosorbide and betaine is preferably 5 to 30 mass %, more preferably 6 to 25 mass %, even more preferably 7 to 20 mass %, and still more preferably 8 to 15 mass %, relative to the total amount of the ink composition.

[0108] Furthermore, the inkjet ink composition according to this embodiment preferably does not contain triethylene glycol monobutyl ether in an amount of 1% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.3% by mass or more, particularly preferably 0.1% by mass or more, and more particularly preferably does not contain any triethylene glycol monobutyl ether (0% by mass), relative to the total mass of the ink composition. In the inkjet ink composition according to this embodiment, when the triethylene glycol monobutyl ether is within the above range, the ejection stability tends to be further improved.

[0109] 1.9 Resin-soluble compounds The inkjet ink composition according to this embodiment may contain a resin-dissolving compound. The resin-dissolving compound is an organic compound that has a function of dissolving resin, but is not limited to this function. Examples of the resin-dissolving compound include amides, sulfur-containing solvents, and cyclic ethers. Dimethyl isosorbide is not included in the resin-dissolving compound.

[0110] Examples of the amides include cyclic amides (lactams) such as 2-pyrrolidone, 2-piperidone, and ε-caprolactam (CPL), and chain amides such as 3-methoxy-N,N-dimethylpropanamide.

[0111] Examples of sulfur-containing solvents include dimethyl sulfone and dimethyl sulfoxide.

[0112] An example of the cyclic ethers is 3-ethyl-3-oxetanemethanol.

[0113] Among these, the inkjet ink composition according to this embodiment preferably contains amides, and more preferably contains cyclic amides. When such compounds are contained, the wettability of the ink to a recording medium may be increased, and color development may be improved.

[0114] The content of the resin-soluble compound, particularly the cyclic amides, relative to the total amount of the ink composition is preferably 0.1 to 10 mass%, more preferably 0.5 to 8 mass%, even more preferably 1 to 5 mass%, and even more preferably 2 to 4 mass%.

[0115] 1.10 Other Ingredients In addition to the above-mentioned components, the inkjet ink composition according to the present embodiment may contain other known components that can be used in conventional ink compositions. The other components are not particularly limited, but may include, for example, a dissolution aid, a viscosity adjuster, a pH adjuster, an antioxidant, a preservative, a corrosion inhibitor, a chelating agent for capturing a specific metal ion that affects dispersion, other additives, and organic solvents other than those mentioned above. The other components may be used alone or in combination of two or more.

[0116] 1.11 Recording media The recording medium used for recording with the inkjet ink composition according to the present embodiment is not particularly limited, and examples thereof include absorbent recording media, low absorbent recording media, and non-absorbent recording media. Among these, it is preferable to use a recording medium for recording on an absorbent recording medium. In this case, the effect of the present invention, which is excellent in the permeability of ink droplets into the recording medium, particularly in the wet spreadability in the planar direction of the recording medium, can be more fully enjoyed, and color development tends to be more excellent.

[0117] Examples of absorbent recording media include plain paper such as electrophotographic paper that has high ink permeability, and inkjet paper (paper specifically for inkjet printers that has an ink absorbing layer made of silica particles or alumina particles, or an ink absorbing layer made of hydrophilic polymers such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)). Fabrics are also examples.

[0118] The low-absorbency recording medium may be, for example, a recording medium having a low-absorbency coating layer on its surface, which is called coated paper.For example, the substrate may be paper, such as art paper, coated paper, matte paper, or other printing paper, and the substrate may be a plastic film, such as polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, or other plastic film coated with a polymer or other particles together with a binder.

[0119] Examples of non-absorbent recording media include those in which a plastic is coated on a substrate such as paper, those in which a plastic film is adhered to a substrate such as paper, plastic films that do not have an absorption layer (receptive layer), etc. Examples of such plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, polypropylene, etc.

[0120] Here, the term "low-absorbency or non-absorbency recording medium" refers to a recording medium that does not absorb liquid at all or absorbs very little liquid. Quantitatively, a low-absorbency or non-absorbency recording medium is one that "has a low-absorbency or non-absorbency within 30 msec from the start of contact in the Bristow method." 1 / 2 Water absorption up to 10mL / m 2 This refers to a recording medium that is either: "absorbent or non-absorbent." The Bristow method is the most widely used method for measuring the amount of liquid absorbed 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." In contrast, absorbent recording media refers to recording media that do not fall under the category of low absorbency or non-absorbent recording media.

[0121] 1.12 Recording Devices The inkjet ink composition according to this embodiment is preferably used in an inkjet recording apparatus equipped with an inkjet head (line head) in which nozzles for ejecting ink formed in a direction intersecting the transport direction of a recording medium are formed so as to cover the intersecting direction in a printing area of ​​the recording medium.

[0122] In an inkjet recording device equipped with a line head, the recorded recording medium is immediately transported through a transport path at high speed, and a large amount of recorded recording media is often stacked, so that transfer resistance is particularly likely to be an issue. In contrast, according to the inkjet ink composition according to this embodiment, even when used in an inkjet recording device equipped with such a line head, there is a tendency that good ejection stability can be obtained while preventing the ink from being transferred to the transport path or the stacked recording media when the recording media are transported in the printer or when the recording media are stacked.

[0123] An example of an inkjet recording apparatus (hereinafter, also simply referred to as a "recording apparatus") equipped with a line head will be described with reference to FIG.

[0124] In the XYZ coordinate system shown in FIG. 1, the X direction indicates the length direction of the recording medium, the Y direction indicates the width direction of the recording medium on the transport path within the recording apparatus, and the Z direction indicates the height direction of the apparatus.

[0125] The recording device 10 is, for example, a line-type inkjet printer. The recording device 10 includes a feed section 12 that stores a recording medium P such as paper, a conveying section (conveying means) 14, a belt conveying section 16, and a recording section 18.

[0126] The feeding unit 12 is disposed at the bottom of the recording device 10. The feeding unit 12 includes a feeding tray 30 that stores recording media P, and a feeding roller 32 that sends out the recording media P stored in the feeding tray 30 to the transport path 11.

[0127] The recording medium P stored in the feed tray 30 is fed by a feed roller 32 along the transport path 11 to the transport section 14. The transport section 14 includes a transport drive roller 34 and a transport driven roller 36. The transport drive roller 34 is driven to rotate by a drive source (not shown). In the transport section 14, the recording medium P is nipped between the transport drive roller 34 and the transport driven roller 36 and transported to the belt transport section 16 located downstream of the transport path 11.

[0128] In the transport section 14, it is preferable to transport the recording medium P at a speed of 0.5 m / sec or more relative to the inkjet head 48. In a line inkjet with such high-speed transport, transfer resistance is a particular issue, but when the inkjet ink composition according to this embodiment is used, there is a tendency that good ejection stability can be obtained while preventing the ink from being transferred to the transport path or stacked recording media.

[0129] The belt conveying section 16 comprises a first roller 38 located upstream on the conveying path 11, a second roller 40 located downstream, an endless belt 42 rotatably attached to the first roller 38 and the second roller 40, and a support 44 supporting an upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0130] The endless belt 42 is driven to move from the +X direction to the -X direction in the upper section 42a by the first roller 38 or the second roller 40 driven by a drive source (not shown). Therefore, the recording medium P conveyed from the conveying unit 14 is further conveyed in the belt conveying unit 16 to the downstream side of the conveying path 11.

[0131] The recording unit 18 includes a line-type inkjet head (line head) 48 having a length equal to or greater than the width of the recording medium P, and a head holder 46 that holds the inkjet head 48. The inkjet head 48 is disposed so as to face the upper section 42a of the endless belt 42 supported by the support 44. When the recording medium P is transported in the upper section 42a of the endless belt 42, the inkjet head 48 ejects the inkjet ink composition toward the recording medium P to perform recording. The recording medium P is transported by the belt transport unit 16 to the downstream side of the transport path 11 while recording is being performed.

[0132] It should be noted that a "line-type inkjet head" is a head used in a recording device in which a nozzle area formed in a direction intersecting the transport direction of a recording medium P is provided so as to cover the entire intersecting direction of the printing area of ​​the recording medium P, and an image is formed by fixing one of the head or the recording medium P and moving the other. It should be noted that the nozzle area in the intersecting direction of a line head does not have to be able to cover the entire intersecting direction of all recording media P that the recording device supports.

[0133] 2. Recording method A recording method according to one embodiment of the present invention comprises a step of ejecting the above-mentioned ink-jet ink composition from an ink-jet head and depositing it onto a recording medium.

[0134] According to the recording method of this embodiment, since the inkjet ink composition described above is used, excellent color development and ejection stability (clogging recovery properties) can be obtained.

[0135] 2.1 Ink application process The recording method according to this embodiment includes a step of ejecting the inkjet ink composition from an inkjet head and depositing it on a recording medium (ink depositing step). More specifically, the ink depositing step is a step of driving a pressure generating means provided in the inkjet head to eject the ink composition filled in the pressure generating chamber of the inkjet head from the nozzle.

[0136] The inkjet head used in the ink application step may be a line head that performs recording by a line method or a serial head that performs recording by a serial method. In the recording method according to the present embodiment, the inkjet head is preferably a line head from the viewpoint of obtaining the effects of the present invention.

[0137] In the line method using a line head, for example, an inkjet head having a width equal to or greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved along the sub-scanning direction (the recording medium transport direction), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium. Note that the line head refers to the above-mentioned "line-type inkjet head."

[0138] In the serial method using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved in the main scanning direction (width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0139] The amount of the ink composition applied is 1 to 20 mg / inch per unit area of ​​the recording medium. 2 is preferably 3 to 15 mg / inch 2 More preferably, the density is 5 to 12 mg / inch. 2 It is also preferable that the maximum adhesion amount of the ink composition on the recording medium is within the above range.

[0140] 2.2 Transportation process The recording method according to the present embodiment may include a transport step. In the transport step, the recording medium is transported in a predetermined direction in the recording device. More specifically, the recording medium is transported from a paper feed section to a paper discharge section of the recording device using a transport roller or a transport belt provided in the recording device. During the transport process, the ink composition discharged from the inkjet head adheres to the recording medium, forming a recorded matter. The ink adhesion step and the transport step may be performed simultaneously or alternately.

[0141] 3. Working Example The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "%" is based on mass unless otherwise specified.

[0142] 3.1 Preparation of Inkjet Ink Composition Inkjet ink compositions of Examples and Comparative Examples were obtained by placing each component in a mixing tank, mixing and stirring, and filtering through a membrane filter so as to obtain the compositions shown in Tables 1 and 2 (Figs. 2 and 3). The numerical values ​​of each component shown in each example in the tables represent mass % unless otherwise specified. The contents (mass %) of color materials (self-dispersed pigments, resin-dispersed pigments, dyes), resin particles, water-soluble resins, and inorganic fine particles (colloidal silica) in Tables 1 and 2 (Figs. 2 and 3) represent solid content concentrations.

[0143] The following supplementary explanations are provided for the descriptions in Tables 1 and 2 (FIGS. 2 and 3). Water-based self-dispersing pigment: "CAB-O-JET300" (Cabot Corporation, solid content 15%) Water-based resin-dispersed pigment: Carbon black (CI Pigment Black 7) was mixed with water and stirred using a dispersant resin, a water-soluble styrene-acrylic resin, in a pigment:dispersant resin mass ratio of 3:1 to prepare a pigment dispersion. Water-based dye: Acid Blue 7

[0144] Resin particles: "X-436" (Seiko PMC, styrene acrylic resin)

[0145] ·Water-soluble resin: The water-soluble resin was prepared in the following manner. First, a four-neck flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube was prepared. 41.7 parts by weight of isophorone diisocyanate, 40.1 parts by weight of polypropylene glycol (number average molecular weight 2,000), 13.2 parts by weight of dimethylolpropionic acid, and 200.0 parts by weight of methyl ethyl ketone were placed in this four-neck flask, and reacted at 80°C for 6 hours under a nitrogen gas atmosphere (primary reaction). Next, 0.6 parts by weight of ethylenediamine, 2.0 parts by weight of methanol, 2.4 parts by weight of dimethylolpropionic acid, and 100.0 parts by weight of methyl ethyl ketone were added. The residual rate of isocyanate groups was confirmed by FT-IR, and the reaction was continued at 80°C until the desired residual rate was reached (secondary reaction) to obtain a reaction liquid. The resulting reaction liquid was cooled to 40°C, and then ion-exchanged water was added, and an aqueous potassium hydroxide solution was added while stirring at high speed with a homomixer. Methyl ethyl ketone was distilled off from the resulting liquid by heating and reducing the pressure, to obtain a liquid containing a water-soluble resin. For the obtained water-soluble resin, hydrochloric acid was added to a liquid containing the water-soluble resin to precipitate the water-soluble resin, and the resin was then vacuum dried overnight at 40°C. The resin was then dissolved in tetrahydrofuran to prepare a sample, and the acid value of the water-soluble resin was measured by potentiometric titration using a potassium hydroxide-methanol titrant, and the acid value was 65 mgKOH / g. The resulting water-soluble resin had a weight average molecular weight of about 21,000 in terms of polystyrene of the urethane resin as measured by gel permeation chromatography (GPC).

[0146] Colloidal silica: "Cataloid SI-45P" (manufactured by JGC Catalysts and Chemicals Co., Ltd., silica particle dispersion sol, average particle size 45 nm)

[0147] BTG: Triethylene glycol monobutyl ether 1,2-HD: 1,2-Hexanediol

[0148] Acetylene glycol surfactant: "Olfine E1010" (manufactured by Nissin Chemical Industry Co., Ltd.) Silicone surfactant: "BYK348" (manufactured by BYK Japan)

[0149] 3.2 Recording test A modified inkjet recording apparatus LX-10050MF (manufactured by Seiko Epson) equipped with a line head, manufactured by Seiko Epson, was filled with each of the inkjet ink compositions of the Examples and Comparative Examples, and a recording medium (A4 size Xerox P paper, copy paper manufactured by Fuji Xerox Co., Ltd., basis weight 64 g / m 2 , paper thickness 88μm) ink deposition amount 7mg / inch 2 A test pattern was recorded and a recording was obtained.

[0150] 3.3 Evaluation 3.3.1 Discharge stability (intermittency) A modified inkjet recording device LX-10050MF (manufactured by Seiko Epson) equipped with a line head was filled with each of the ink compositions of the Examples and Comparative Examples and allowed to idle for 10 minutes. After that, recording was performed under the same conditions as in the recording test described above, and the results were evaluated according to the following evaluation criteria. [Evaluation Criteria] A: Discharged normally. B: There is some deviation in flight. C: The flight curve is noticeable.

[0151] 3.3.2 Discharge stability (clogging recovery) A modified inkjet recording device LX-10050MF (manufactured by Seiko Epson) equipped with a line head was filled with each of the ink compositions of the Examples and Comparative Examples, and it was confirmed that ink could be ejected from all of the nozzles. After that, the inkjet head was left uncapped, shifted from the position of the cap provided on the printer, and the inkjet head was left uncapped for 7 days in an environment of 40°C and a relative humidity of 20°C. After leaving it as it is, the ink in the nozzles was repeatedly sucked out to clean the inkjet head while recording was performed in the same manner as above. The number of cleanings required until all the nozzles had recovered was used as the basis for evaluation according to the following criteria. [Evaluation Criteria] A: Full recovery within 3 cleanings. B: Full recovery after 4 to 5 cleanings. C: Full recovery after 6 to 7 cleanings. D: Not fully recovered after 7 cleanings.

[0152] 3.3.3 Storage stability Each ink composition of the Examples and Comparative Examples was filled into a sealable storage bottle, capped, and stored in an environment of 40° C. for 7 days. The viscosity of each ink composition was measured before and after leaving it, and the presence or absence of aggregates was visually confirmed, and evaluated according to the following criteria. The viscosity was measured using a rheometer (MCR300, manufactured by Anton Paar) under conditions of a temperature of 20° C. and humidity of 50%, at a shear rate of 200. [Evaluation Criteria] A: The viscosity does not change. B: Viscosity changes slightly. C: Viscosity changes by more than ±10%, or foreign matter is generated.

[0153] 3.3.4 Transferability Under the same conditions as the above recording test, recording was performed at a recording speed of 60 ppm (page per minute), and the recorded sheets were stacked on the discharge tray with the recorded side facing up. After recording on 60 sheets, the recorded sheets at the bottom of the discharge tray were visually observed and judged according to the following criteria. [Evaluation Criteria] A: There is no transfer of the printed surface even when printing at 60 ppm. B: Transfer occurs when printing at 60 ppm, but is not noticeable. C: Transfer occurs significantly when printing at 60 ppm.

[0154] 3.3.5 Foaming and defoaming properties Each ink composition of the Examples and Comparative Examples was filled into a modified inkjet recording device LX-10050MF (manufactured by Seiko Epson) equipped with a line head, manufactured by Seiko Epson Corporation, and the ink was ejected from the inkjet head into the head cap until the ink formed a liquid surface on the inner bottom of the cap. The inside of the head cap was visually observed and judged according to the following criteria. [Evaluation Criteria] A: No bubbles are generated inside the head cap. B: Foam is generated inside the head cap, but it disappears quickly. C: Bubbles generated inside the head cap do not disappear.

[0155] 3.3.6 Color development (OD value) The OD value of the recorded surface of the recorded matter obtained in the above recording test was measured using a colorimeter (Xrite i1, manufactured by Xrite Corporation), and the color development was evaluated according to the following evaluation criteria. [Evaluation Criteria] A:OD value is 1.4 or more. B:OD value is less than 1.4 and more than 1.1. C:OD value is less than 1.1.

[0156] 3.4 Evaluation results The evaluation results are shown in Tables 1 and 2 (Figures 2 and 3).

[0157] The evaluation results in Tables 1 and 2 (FIGS. 2 and 3) show that all of the Examples, which are water-based inkjet ink compositions containing dimethyl isosorbide, betaine, and a coloring material, are excellent in color development and ejection stability (clogging recovery).

[0158] In contrast, the comparative examples, which are inkjet ink compositions other than those described above, were found to be inferior in at least one of color development and ejection stability (ability to recover from clogging).

[0159] The following can be derived from the above-described embodiment.

[0160] One embodiment of the inkjet ink composition comprises: It is a water-based product containing dimethyl isosorbide, betaine, and a coloring material.

[0161] In one embodiment of the inkjet ink composition, An acetylene glycol surfactant may be included.

[0162] In any of the embodiments of the ink-jet ink composition described above, The betaine may be a trialkylglycine.

[0163] In any of the embodiments of the ink-jet ink composition described above, It may contain a resin.

[0164] In any of the embodiments of the ink-jet ink composition described above, The color material may be any one of a resin-dispersed pigment, a self-dispersed pigment, and a dye.

[0165] In any of the embodiments of the ink-jet ink composition described above, It may contain inorganic fine particles.

[0166] In any of the embodiments of the ink-jet ink composition described above, It may contain cyclic amides.

[0167] In any of the embodiments of the ink-jet ink composition described above, Polyols having a normal boiling point of more than 280°C may be contained.

[0168] In any of the embodiments of the ink-jet ink composition described above, The ink jet head may be used in an ink jet recording device having an ink jet head in which nozzles for ejecting ink are formed in a direction intersecting the transport direction of the recording medium so as to cover the intersecting direction in the printing area of ​​the recording medium.

[0169] In any of the embodiments of the ink-jet ink composition described above, It may be used for recording on an absorbent recording medium.

[0170] In any of the embodiments of the ink-jet ink composition described above, The ink composition may contain no more than 1% by mass of triethylene glycol monobutyl ether relative to the total mass of the ink composition.

[0171] One aspect of the recording method is The method includes a step of ejecting the ink-jet ink composition according to any one of the above aspects from an ink-jet head and depositing the ink-jet ink composition on a recording medium.

[0172] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiment, for example, a configuration that has the same function, method, and result, or a configuration that has the same purpose and effect. The present invention also includes a configuration in which non-essential parts of the configuration described in the embodiment are replaced. The present invention also includes a configuration that has the same action and effect as the configuration described in the embodiment, or a configuration that can achieve the same purpose. The present invention also includes a configuration in which publicly known technology is added to the configuration described in the embodiment. [Explanation of symbols]

[0173] 10...recording device, 12...feed section, 14...transport section, 16...belt transport section, 18...recording section, 30...feed tray, 32...feed roller, 34...transport drive roller, 36...transport driven roller, 38...first roller, 40...second roller, 42...endless belt, 42a...upper section of endless belt, 44...support, 46...carriage, 48...inkjet head, P...recording medium.

Claims

1. A water-based ink-jet ink composition comprising dimethyl isosorbide, betaine, and a coloring material.

2. The ink-jet ink composition of claim 1 , further comprising an acetylene glycol surfactant.

3. The ink-jet ink composition of claim 1 , wherein the betaine is a trialkylglycine.

4. The ink-jet ink composition of claim 1 , further comprising a resin.

5. The ink-jet ink composition according to claim 1 , wherein the colorant is any one of a resin-dispersed pigment, a self-dispersed pigment, and a dye.

6. The ink-jet ink composition according to claim 1 , further comprising inorganic fine particles.

7. The ink-jet ink composition of claim 1 , comprising cyclic amides.

8. The ink-jet ink composition of claim 1 , comprising polyols having a normal boiling point of greater than 280° C.

9. 2. The ink-jet ink composition according to claim 1, which is used in an ink-jet recording device equipped with an ink-jet head, in which nozzles for ejecting ink, which are formed in a direction intersecting a transport direction of a recording medium, are formed so as to cover a printing area of ​​the recording medium in the intersecting direction.

10. The ink-jet ink composition of claim 1 for use in recording on an absorbent recording medium.

11. The ink-jet ink composition according to claim 1 , wherein the ink composition contains no more than 1% by mass of triethylene glycol monobutyl ether based on the total mass of the ink composition.

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

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