Method for producing inkjet color dispersion

Abstract

Provided are a colored dispersion for inkjet and a method for producing the same, the colored dispersion comprising a colorant, a dispersant, a tellurium compound, and water, wherein: the dispersant is an A-B block polymer; monomers constituting an A block are (meth)acrylic acid and butyl (meth)acrylate; the content of the (meth)acrylic acid in the A block is 26-42 mass%; a monomer constituting a B block includes cyclohexyl (meth)acrylate; the acid value of the dispersant is 100-159 mg KOH / g; and the mass-average molecular weight of the dispersant is 10,000-50,000. Moreover, provided are: an inkjet recording ink containing said dispersion; an inkjet recording method using said ink; recording media to which said ink adheres; and an inkjet printer equipped with a container containing said ink.

Description

[Technical Field]

[0001] The present invention relates to inkjet color dispersions. Liquid manufacturing method Regarding. [Background technology]

[0002] Among various color recording methods, the recording method using an inkjet printer (inkjet recording method), which is one of the most representative methods, generates small droplets of ink and deposits them on various recording media (paper, plastic film, fabric, etc.) This recording method has been rapidly gaining popularity in recent years because it is easy to make it smaller and faster, and is expected to continue to grow significantly in the future.

[0003] Inkjet recording methods may use recording media with high ink absorption capacity, such as inkjet paper with an ink-receiving layer, glossy paper, or general-purpose plain paper, as well as recording media with low ink absorption capacity, such as coated paper or plastic film, or recording media that does not absorb ink at all. When printing on such recording media with low ink absorption capacity or no ink absorption capacity using aqueous inkjet ink, the ink does not easily penetrate into the recording media, and therefore takes a long time to dry. For this reason, when performing high-speed automatic double-sided printing in which the recording media printed on the front side is immediately flipped in the inkjet printer and printed on the back side, problems such as contamination of reversing rollers by undried ink can occur.

[0004] To solve the above problems, inks with high drying properties have been proposed. However, such inks with high drying properties have the problem of easily clogging the nozzles of inkjet heads. When solid matter in the ink, such as colorants and resin particles, clogs the nozzles, ink ejection becomes unstable, resulting in a significant deterioration in the quality of printed images.

[0005] These problems can be solved by improving the redispersibility of the ink after drying. Even if the ink dries near the nozzles, if the dried ink can be redispersed by the ink itself supplied from the head to the nozzles, making clogging less likely, the above problems can be solved and ejection stability can be improved. Increasing the hydrophilicity of the dispersant that disperses the colorant in the ink is effective for improving the redispersibility of aqueous inkjet inks. However, increasing the hydrophilicity of the dispersant reduces the water resistance of the recorded image, raising concerns that the image may easily peel off when water adheres to the printed material and is rubbed. As such, redispersibility and water resistance are contradictory properties, and there is a strong demand for inks that achieve a good balance between these properties.

[0006] Patent Document 1 discloses an ink composition that is said to be capable of forming an image with excellent tackiness, fixability, and water resistance on a recording medium that is poorly ink-absorbent or non-ink-absorbent.

[0007] Patent Document 2 discloses an ink that is said to exhibit good drying properties even when printed on a non-porous substrate, and that the printed area has high gloss, abrasion resistance, and ethanol resistance. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2017-66215 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-240451 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a color dispersion for inkjet printing that is excellent in redispersibility after drying and also in water resistance of recorded images. Liquid manufacturing method The objective is to provide the following. [Means for solving the problem]

[0010] Specific means for solving the above problems include the following embodiments. 1) Contains a colorant, a dispersant, a tellurium compound, and water, the dispersant is an AB block polymer, the monomers constituting the A block of the AB block polymer are (meth)acrylic acid and butyl (meth)acrylate, the content of (meth)acrylic acid in the total mass of the monomers constituting the A block is 26 to 42 mass%, and the monomer constituting the B block of the AB block polymer contains cyclohexyl (meth)acrylate; The acid value of the dispersant is 100 to 159 mg KOH / g, The dispersant has a mass average molecular weight of 10,000 to 50,000.

[0011] 2) 1) The color dispersion for inkjet according to 1), wherein the total content of the tellurium compounds in terms of metallic tellurium is 160 ppm or less by mass. 3) The color dispersion for inkjet according to 1) or 2), wherein the dispersant has an acid value of 112 to 135 mgKOH / g. 4) The color dispersion liquid for inkjet recording according to any one of items 1) to 3), wherein the dispersant has a mass average molecular weight of 10,000 to 30,000. 5) The color dispersion for inkjet according to any one of 1) to 4), wherein the colorant is a colorant selected from the group consisting of pigments and disperse dyes. 6) The color dispersion for inkjet according to any one of items 1) to 5), wherein a monomer constituting the B block of the AB block polymer contains (meth)acrylic acid.

[0012] 7) An inkjet recording ink containing the inkjet color dispersion liquid according to any one of 1) to 6). 8) 7) An inkjet recording method in which droplets of the ink for inkjet recording according to 7) are ejected from an inkjet printer to record on a recording medium. 9) 8) The inkjet recording method according to 8), wherein the recording medium is a recording medium that is poorly ink-absorbent or non-ink-absorbent. 10) 9) The inkjet recording method according to 9), wherein the recording medium is a recording medium that has been subjected to at least one surface modification treatment selected from the group consisting of corona discharge treatment, plasma treatment, and flame treatment. 11) 7) A recording medium colored with the inkjet recording ink according to 7). 12) 7) An ink-jet printer equipped with a container containing the ink for ink-jet recording according to 7). 13) The method for producing a colored dispersion liquid for inkjet according to any one of 1) to 6), comprising a step of coating the surface of the colorant with the dispersant. 14) 13) The method according to 13), wherein the surface of the colorant is coated with the dispersant by a phase inversion emulsification method. [Effects of the Invention]

[0013] According to the present invention, there is provided a color dispersion for inkjet printing which has excellent redispersibility after drying and excellent water resistance of the recorded image. Liquid manufacturing method can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0014] Specific embodiments to which the present invention is applied will be described in detail below. In this specification, each of the components contained in the inkjet color dispersion liquid and the inkjet recording ink may be used alone or in combination of two or more kinds. In addition, the term "(meth)acrylic acid" is used herein to mean both "acrylic acid" and "methacrylic acid." The same applies to "(meth)acrylate" and the like. Furthermore, in this specification, when a unit is written for only one of the upper and lower limits of a range, such as "X to Y mass %, " it means that the units for the upper and lower limits of the range are the same, i.e., "X mass % to Y mass %".

[0015] <Color dispersion for inkjet> The inkjet color dispersion (hereinafter simply referred to as "dispersion") according to this embodiment contains a colorant, a dispersant, a tellurium compound, and water, wherein the dispersant is an AB block polymer, the monomers constituting the A block of the AB block polymer are (meth)acrylic acid and butyl (meth)acrylate, and the content of (meth)acrylic acid in the total mass of the monomers constituting the A block is 26 to 42 mass%, the monomer constituting the B block of the AB block polymer contains cyclohexyl (meth)acrylate, the acid value of the dispersant is 100 to 159 mg KOH / g, and the mass average molecular weight of the dispersant is 10,000 to 50,000. The components contained in the dispersion according to this embodiment are described in detail below.

[0016] [Coloring agent] The colorant contained in the dispersion liquid according to this embodiment is not particularly limited as long as it is a water-insoluble colorant, and known pigments, disperse dyes, etc. can be used. In this specification, a water-insoluble colorant refers to a colorant whose solubility in water at 25°C is usually 5 g / L or less, preferably 3 g / L or less, more preferably 1 g / L or less, and even more preferably 0.5 g / L or less. The lower limit of the solubility includes 0 g / L. Hereinafter, unless otherwise specified, "colorant" refers to a "water-insoluble colorant."

[0017] Examples of pigments include inorganic pigments, organic pigments, and extender pigments, and any of these pigments can be used. It is also possible to combine these pigments, and for example, a dispersion can be prepared by adding an extender pigment to an organic pigment.

[0018] Examples of inorganic pigments include carbon black, titanium oxide, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides.

[0019] When preparing a black dispersion, preferred inorganic pigments are carbon blacks such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Commercially available carbon blacks include the Raven series manufactured by Columbia Carbon Corporation, the Monarch series, Regal series, and Mogul series manufactured by Cabot Corporation, the HiBlack series, ColorBlack series, Printex series, SpecialBlack series, and Nerox series manufactured by Orion Engineered Carbons, and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 manufactured by Mitsubishi Chemical Corporation.

[0020] Examples of inorganic pigments other than carbon black include CI Pigment White 6 and 27; aluminum hydroxide; and the like.

[0021] Examples of organic pigments include azo, diazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone. These organic pigments can also be used in combination with the inorganic pigments listed above. For example, to improve the fluidity of solids, organic pigments can be used in combination with extender pigments.

[0022] Specific examples of organic pigments include yellow pigments such as CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 180, 185, 193, 199, 202, and 213; and CI Pigment Red Red pigments such as 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, and 272; blue pigments such as CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, and 80; violet pigments such as CI Pigment Violet 19, 23, 29, 37, 38, and 50; orange pigments such as CI Pigment Orange 13, 16, 43, 68, 69, 71, and 73; and CI Pigment Green green pigments such as CI Pigment Black 1; and the like.

[0023] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, white carbon, etc. Extender pigments are often used in combination with other colorants.

[0024] The disperse dye may be any known disperse dye, and among them, dyes selected from CI Disperses are preferred. Specific examples thereof include yellow dyes such as CI Dispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, and 237; red dyes such as CI Dispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, and 283; and CI Dispers Orange. Orange dyes such as 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, and 97; violet dyes such as CI Dispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, and 79:1; blue dyes such as CI Dispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, and 368; and the like.

[0025] The average particle size of the colorant is usually 50 to 300 nm, preferably 60 to 250 nm. In this specification, the term "average particle size" refers to the average particle size of particles measured using a laser light scattering method.

[0026] The colorant is preferably one whose surface is coated with a dispersant. In this specification, "coated" includes both a state in which only a portion of the surface of the colorant is coated with a dispersant and a state in which the entire surface of the colorant is coated with a dispersant.

[0027] The content of the colorant in the dispersion liquid according to this embodiment is usually 0.1 to 30% by mass, preferably 0.5 to 20% by mass, and more preferably 1 to 15% by mass. The content of the colorant in the ink according to this embodiment, which will be described later, is usually 1 to 30% by mass, preferably 1 to 10% by mass, and more preferably 2 to 7% by mass.

[0028] [Dispersant] The dispersant contained in the dispersion according to this embodiment is an AB block polymer, which means a polymer in which an A polymer (hereinafter referred to as the "A block") and a B polymer (hereinafter referred to as the "B block") are chemically bonded together, and A and B each mean a polymer composed of one or more types of addition-polymerizable monomers.

[0029] The role that the AB block polymer (hereinafter also referred to as "block copolymer") plays in dispersing the colorant will be described in detail below.

[0030] A common method for stabilizing the dispersion of a colorant in water is to use a polymer dispersant such as a resin to inhibit aggregation of colorants through entropic, ionic, or steric repulsion, thereby stabilizing the dispersion. Here, a polymer dispersant is a polymer having a hydrophilic portion and a hydrophobic portion, in which the hydrophobic portion functions to adsorb to the colorant surface and the hydrophilic portion functions to disperse the colorant in water. Random polymers (hereinafter also referred to as "random copolymers") in which the hydrophilic and hydrophobic portions are irregularly arranged, and the above-mentioned block copolymers are mainly used as the polymer dispersant.

[0031] In random copolymers, the hydrophilic and hydrophobic portions are irregularly arranged, and as a result, the copolymer adsorbs sparsely to the colorant surface, failing to adequately coat the colorant surface, and the copolymer may also have insufficient affinity for liquid media such as water, water-soluble organic solvents, etc. In this state, when attacked by the solvent in the ink, the dispersant can easily peel off, potentially causing the colorant to aggregate.

[0032] On the other hand, block copolymers have a structure in which a polymer with consecutively arranged hydrophilic moieties is bonded to a polymer with consecutively arranged hydrophobic moieties. Compared to random copolymers, block copolymers can adsorb to the colorant surface over a larger coverage area. Furthermore, the hydrophilic blocks have good affinity with the liquid medium, making them less susceptible to dispersant detachment even when attacked by solvents, etc., and thus maintaining a stable dispersion state. Furthermore, block copolymers are more hydrophilic than random copolymers, making them easier to redisperse with newly supplied ink even if the ink dries near the nozzle, reducing nozzle clogging. Meanwhile, block copolymers also have high dispersion stability, so even if the water in the ink evaporates first during drying on the recording medium, increasing the relative solvent concentration in the ink, they can form a coating film without causing colorant aggregation. As a result, a coating film with high smoothness and a resin-coated surface can be formed, providing high water resistance.

[0033] As a method for obtaining the above-mentioned block copolymer, the TERP (Organotellurium-Mediated Living Radical Polymerization) method using an organotellurium compound is known. The TERP method will be described in detail below.

[0034] The TERP method is a polymerization method in which a radically polymerizable compound (vinyl monomer) is polymerized using an organic tellurium compound as a chain transfer agent, and is described in, for example, WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, WO 2004 / 096870, etc. Specific polymerization methods of the TERP method include the following (a) to (d). (a) A vinyl monomer is polymerized using an organotellurium compound represented by the following formula (1): (b) A vinyl monomer is polymerized using a mixture of an organotellurium compound represented by the following formula (1) and an azo-based polymerization initiator. (c) A vinyl monomer is polymerized using a mixture of an organic tellurium compound represented by the following formula (1) and an organic ditelluride compound represented by the following formula (2). (d) A vinyl monomer is polymerized using a mixture of an organic tellurium compound represented by the following formula (1), an azo-based polymerization initiator, and an organic ditelluride compound represented by the following formula (2).

[0035] [ka] [In formula (1), R 1 represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. 2 and R 3 R each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. 4 represents an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group, or a propargyl group. 1 represents an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

[0036] Specific examples of the organic tellurium compound represented by the above formula (1) include ethyl-2-methyl-2-n-butyltellanyl-propionate, ethyl-2-n-butyltellanyl-propionate, (2-hydroxyethyl)-2-methyl-methyltellanyl-propionate, and the compounds described in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, and WO 2004 / 096870. Specific examples of the organic ditelluride compound represented by the above formula (2) include dimethyl ditelluride, dibutyl ditelluride, and the like. The azo polymerization initiator is not particularly limited as long as it is an azo polymerization initiator used in ordinary radical polymerization, and examples thereof include 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70).

[0037] In the polymerization step, a vinyl monomer, an organotellurium compound represented by the above formula (1), and, depending on the type of vinyl monomer, an azo-based polymerization initiator and / or an organic ditelluride compound represented by the above formula (2) are mixed in a vessel purged with an inert gas for the purposes of accelerating the reaction and controlling the molecular weight and molecular weight distribution. Examples of inert gases include nitrogen, argon, and helium, with argon and nitrogen being preferred. The amount of vinyl monomer used in the above steps (a) to (d) may be adjusted appropriately depending on the physical properties of the desired copolymer.

[0038] The polymerization reaction can be carried out without a solvent, but it can also be carried out by stirring the mixture using an aprotic or protic solvent commonly used in radical polymerization. Examples of aprotic solvents include anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, and tetrahydrofuran (THF). Examples of protic solvents include water, methanol, and 1-methoxy-2-propanol. One solvent may be used alone, or two or more may be used in combination. The amount of solvent used is not particularly limited, and is preferably 0.01 to 50 mL per 1 g of vinyl monomer. The reaction temperature and reaction time can be adjusted appropriately depending on the molecular weight and molecular weight distribution of the resulting copolymer. Typically, the mixture is stirred at 0 to 150°C for 1 minute to 100 hours. After completion of the polymerization reaction, the solvent and residual vinyl monomer can be removed from the resulting reaction mixture by conventional separation and purification techniques, and the target copolymer can be isolated.

[0039] The monomers constituting the A block of the AB block polymer are (meth)acrylic acid and butyl (meth)acrylate, with a combination of methacrylic acid and butyl methacrylate being preferred. The monomers constituting the B block of the AB block polymer include cyclohexyl (meth)acrylate, preferably cyclohexyl methacrylate. The A block, which has a hydrophilic portion, dissolves in the liquid medium, while the B block, which has a hydrophobic portion, adsorbs to the colorant surface, resulting in a stable dispersion. The A block contains a carboxyl group, which can be neutralized with a neutralizing agent to dissolve it in the liquid medium. Meanwhile, the B block is practically insoluble in the liquid medium, but adsorbs to the highly hydrophobic colorant surface in the liquid medium, maintaining a coated state. The cyclohexyl (meth)acrylate constituting the B block contains a six-membered monocyclic saturated hydrocarbon group, resulting in a highly hydrophobic and flexible molecular structure. This allows them to flexibly change their structure to accommodate various chemical surface modifications and structures of colorants, allowing them to adsorb with stronger interactions, compared to cyclic aromatic hydrocarbons, which have a planar structure, or polycyclic saturated hydrocarbons, which are structurally restricted in the conformations they can adopt. As a result, they achieve dispersion stability that is resistant to attack by solvents in the ink.

[0040] The content of (meth)acrylic acid in the total mass of the monomers constituting the A block is usually 26 to 42 mass%, preferably 31 to 40 mass%, more preferably 31 to 37 mass%, and even more preferably 33 to 35 mass%. By setting the lower limit of the content to the above-mentioned percentages, sufficient hydrophilicity as a dispersant is obtained, and dispersion stability and redispersibility tend to be good. Furthermore, by setting the upper limit of the content to the above-mentioned percentages, appropriate hydrophilicity as a dispersant is maintained, detachment of the dispersant from the colorant is less likely to occur, and dispersion stability tends to be good.

[0041] The content of cyclohexyl (meth)acrylate in the total mass of the monomers constituting the B block is usually 80 to 100% by mass, preferably 90 to 99.8% by mass, and more preferably 95 to 99% by mass. The monomers constituting the B block may further contain an additional monomer. The content of the additional monomer is usually 0 to 20% by mass, preferably 0.2 to 10% by mass, and more preferably 1 to 5% by mass, relative to the total mass of the monomers constituting the B block. The additional monomer is preferably (meth)acrylic acid. The content of (meth)acrylic acid in the total mass of the monomers constituting the B block is usually 0.1 to 10% by mass, and preferably 0.5 to 5% by mass. Incorporation of a small amount of hydrophilic (meth)acrylic acid into the hydrophobic B block increases the structural flexibility of the dispersant in the liquid medium, making it easier to adsorb to the colorant and tending to improve dispersion stability.

[0042] The proportion of the A block in the AB block polymer is usually 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass.

[0043] The acid value of the dispersant is 100 to 159 mgKOH / g, preferably 112 to 135 mgKOH / g. By setting the lower limit of the acid value to the above-mentioned values, sufficient solubility in the liquid medium tends to be obtained and re-dispersibility tends to be improved. Furthermore, by setting the upper limit of the acid value to the above-mentioned values, the water resistance and color development of the recorded image tends to be improved. The acid value of the dispersant is measured by the method described in the examples below.

[0044] The mass average molecular weight of the dispersant is 10,000 to 50,000, preferably 10,000 to 30,000. By setting the mass average molecular weight within each of the above ranges, the stability of the dispersion tends to be improved. The mass average molecular weight of the dispersant is measured by the method described in the examples below.

[0045] The acid groups of the dispersant can be neutralized using a neutralizing agent, such as alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, aliphatic amine compounds, and alcohol amine compounds.

[0046] Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of alkaline earth metal hydroxides include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, etc. Among these, alkali metal hydroxides are preferred, and lithium hydroxide and sodium hydroxide are more preferred.

[0047] The ammonia is not particularly limited and may be in the form of a gas or a liquid dissolved in water or an organic solvent, with aqueous ammonia being preferred.

[0048] Examples of the aliphatic amine compound include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamine.

[0049] Examples of the alcoholamine compound include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, methylethanolamine, dimethylethanolamine, and N-methyldiethanolamine.

[0050] The "degree of neutralization" is "100%" when the total amount of acid groups in the dispersant is neutralized with a theoretically equivalent amount of neutralizing agent. The upper limit of the degree of neutralization can exceed 100%. The degree of neutralization of the dispersant is usually 30 to 200%, and preferably 50 to 150%.

[0051] The ratio of the total mass of dispersants to the total mass of colorants is generally expressed as a numerical value called the limiting ratio, which can be calculated using the following formula: Fractional ratio = total mass of dispersant / total mass of colorant

[0052] The limiting ratio of the dispersion liquid according to this embodiment and the ink-receiving liquid according to this embodiment, which will be described later, is usually 0.1 to 1.0, preferably 0.1 to 0.6, and more preferably 0.1 to 0.5. By setting the limiting ratio within the above ranges, dispersion stability becomes good, and deterioration of the recorded image tends to be suppressed.

[0053] [Tellurium compounds derived from chain transfer agents] The growing end of the block copolymer obtained by the TERP method is -TeR 1 (In the formula, R 1 are synonymous with the above formulas (1) and (2). ) and the tellurium atoms are removed from the growing ends by separation and purification means after the polymerization reaction is complete. After the removal of the tellurium atoms, tellurium compounds derived from the chain transfer agent may remain in the block copolymer.

[0054] In this embodiment, the content of tellurium compounds derived from the chain transfer agent can be controlled by separating and purifying the block copolymer after the polymerization reaction. Therefore, the content of tellurium compounds derived from the chain transfer agent in the total mass of the dispersion is not particularly limited. The total content of the tellurium compounds, calculated as metallic tellurium, is 0.01 ppm or more, preferably 0.1 ppm or more, more preferably 1 ppm or more, and preferably 160 ppm or less, based on mass.

[0055] [water] The dispersion according to this embodiment is an aqueous dispersion containing water. Although there is no limitation on the water that can be used, it is preferable to use water that contains few impurities such as inorganic ions. Examples of such water include ion-exchanged water and distilled water.

[0056] The water content of the dispersion liquid according to this embodiment is usually 50 to 90 mass %, preferably 60 to 90 mass %, and more preferably 70 to 90 mass % relative to the total mass of the ink according to this embodiment, which will be described later, is usually 20 to 90 mass %, preferably 35 to 90 mass %, and more preferably 50 to 90 mass % relative to the total mass of the ink.

[0057] [Method of manufacturing dispersion liquid] The method for producing a dispersion according to this embodiment includes a step of dispersing a colorant. A known method can be used to disperse the colorant. Examples of such methods include a sand mill (bead mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, or the like. After preparing the dispersion, it is preferable to remove components with large particle sizes by filtration, centrifugation, or the like.

[0058] A trace amount of an antifoaming agent can be added to suppress foaming during the preparation of the dispersion. However, some antifoaming agents inhibit dispersion and microparticulation, and it is preferable to use one that does not affect dispersion or stability after dispersion. Examples of the antifoaming agent include silicone-based and acetylene glycol-based antifoaming agents. Examples of the silicone-based antifoaming agent include Surfynol DF-58 manufactured by Nissin Chemical Co., Ltd. and BYK1770 manufactured by BYK-Chemie. Examples of the acetylene glycol-based antifoaming agent include Olfine SK-14 manufactured by Nissin Chemical Co., Ltd.

[0059] The method for producing a dispersion according to this embodiment preferably further includes a step of coating the surface of the colorant with a dispersant. This makes it possible to obtain a dispersion containing a colorant whose surface is coated with a dispersant. The step of coating the surface of the colorant with a dispersant may be performed after the step of dispersing the colorant, or may be performed simultaneously with the step of dispersing the colorant.

[0060] Methods for coating the surface of a colorant with a dispersant can be broadly divided into physical / mechanical methods and chemical methods. Specific methods include, for example, surface precipitation and interfacial polymerization (surface polymerization), both of which are well-known methods. Here, the surface precipitation method is a method of coating the colorant by precipitating a dispersant on the surface of the colorant by adjusting the pH of a liquid medium containing the colorant or by utilizing the difference in solubility of the colorant in the liquid medium. This method includes acid precipitation and phase inversion emulsification. The interfacial polymerization method involves adsorbing or bonding a compound having a polymerizable functional group, such as a monomer, oligomer, or pigment derivative, to the surface of the colorant, followed by a polymerization reaction with another monomer that forms a dispersant, thereby forming a dispersant that coats the surface of the colorant. Among these, the surface precipitation method is preferred, and the phase inversion emulsification method is more preferred.

[0061] The phase inversion emulsification method involves mixing and dispersing a colorant and a dispersant in an organic solvent, and then adding water to uniformly adsorb the dispersant onto the pigment surface. There are six known specific manufacturing processes: 1. A process of mixing a solution of a colorant dispersed in a hydrophilic organic solvent and a dispersant that disperses or dissolves in water with a liquid whose main component is water, and then removing the solvent. Note that components other than water in the "liquid whose main component is water" include, for example, surfactants, preservatives, etc. 2. A process of mixing a solution of a colorant dispersed in a hydrophilic organic solvent and a dispersant that disperses or dissolves in water upon neutralization with a mixed liquid containing water and a neutralizing agent, and then removing the solvent. 3. A process in which a solution of a mixed solvent of a hydrophilic organic solvent and a hydrophobic organic solvent, in which a dispersant disperses or dissolves in water and in which a colorant is dispersed, is mixed with a liquid whose main component is water, and then the solvent is removed. 4. A process of mixing a solution of a mixed solvent of a hydrophilic organic solvent and a hydrophobic organic solvent, in which the colorant is dispersed and the dispersant disperses or dissolves in water upon neutralization, with a mixed liquid containing water and a neutralizing agent, and then removing the solvent. 5. A process in which a colorant is mixed with a solution of a hydrophilic organic solvent of a dispersant that disperses or dissolves in water and a mixed solvent whose main component is water, to disperse the pigment in the solution, and then the solvent is removed. 6. A process in which a solution of a hydrophobic organic solvent in which a dispersant has been dissolved is mixed with a liquid whose main component is water and which contains a neutralizing agent to form an emulsified liquid (emulsion or microemulsion), to which a colorant is added and mixed and dispersed, and then more water is added to remove the solvent.

[0062] Examples of the organic solvent include alcohol solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, and halogenated aliphatic hydrocarbon solvents. Examples of the alcohol solvent include methanol, ethanol, propanol, isopropanol, and butanol. Examples of the ketone solvent include acetone and 2-butanone.

[0063] As the surfactant, for example, the above-mentioned antifoaming agents can be used, and they can be added in an amount that does not inhibit dispersion even in the phase inversion emulsification method.

[0064] Examples of the preservatives include organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloaryl sulfone compounds, iodopropargyl compounds, haloalkylthio compounds, nitrile compounds, pyridine compounds, 8-oxyquinolines, benzothiazole compounds, isothiazolinone compounds, dithiols, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, triazine compounds, thiazine compounds, anilides, adamantane compounds, dithiocarbamates, brominated indanone compounds, benzyl bromoacetate compounds, and inorganic salt compounds. Specific examples of commercially available preservatives include Proxel GXL(S) and Proxel XL-2(S) manufactured by Arch Chemical Co., and Rosima 640 manufactured by Dow Chemical Co.

[0065] By using the above method, it is possible to easily obtain a colorant having a dispersant on its surface and an average particle size of 250 nm or less. The average particle size of the colorant can be controlled by selecting the type of colorant, the type of dispersant, the acid value, the mass-average molecular weight, etc. The average particle size of the colorant is usually 50 to 180 nm, and preferably 60 to 150 nm.

[0066] <Inkjet recording ink> The inkjet recording ink according to this embodiment (hereinafter simply referred to as "ink") contains the dispersion liquid according to this embodiment described above, and may further contain other ink preparation agents as necessary. Such ink preparation agents include solvents, surfactants, preservatives, antifungal agents, pH adjusters, chelating agents, rust inhibitors, water-soluble UV absorbers, antioxidants, resin emulsions, wax agents, slip agents, etc.

[0067] The solvent is preferably an organic solvent. Examples of the organic solvent include C1-C6 alkanols having 1 to 3 hydroxy groups, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, 1,2-hexanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, and hexane-1,2,6-triol; amides, such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams, such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one; cyclic ureas, such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimid-2-one; ketones, such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate. cyclic ethers such as tetrahydrofuran and dioxane; mono-, oligo-, or polyalkylene glycols or thioglycols having a C2-C6 alkylene unit, such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol or polypropylene glycol having a molecular weight of 400 or more, thiodiglycol, dithiodiglycol, etc.; polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane;Examples of the glycol ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, propylene glycol n-butyl ether, propylene glycol monopropyl ether, triethylene glycol monobutyl ether, tripropylene glycol methyl ether, dimethyl glycol, dimethyl diglycol, dimethyl triglycol, methyl ethyl diglycol, diethyl diglycol, dibutyl diglycol, dimethyl propylene diglycol, dipropylene glycol methyl ether, dipropylene glycol n-butyl ether, dipropylene glycol n-propyl ether, and 3-methoxy-3-methyl-1-butanol (preferably, an alkyl or alkenyl ether of an alkylene glycol having 1 to 5 (more preferably 1 to 4, and even more preferably 1 to 3) C2-C4 alkanediol repeating units); γ-butyrolactone, and dimethyl sulfoxide. ;

[0068] Among these solvents, it is preferable to use a solvent selected from glycol ethers and a solvent selected from alkanols.

[0069] The content of the solvent is usually 3 to 50% by mass, and preferably 5 to 40% by mass, relative to the total mass of the ink.

[0070] As the solvent, not only water-soluble organic solvents but also water-insoluble organic solvents can be used. Examples of water-insoluble organic solvents include C8-C16 (preferably C8-12) alkyls having hydroxyl groups and acyloxy groups. Specific examples include Texanol. When using a water-insoluble organic solvent, it is preferable to adjust the content ratio with the water-soluble organic solvent, for example, to prevent separation from the ink.

[0071] The printing speed of industrial inkjet printers is usually variable. Therefore, it is preferable to appropriately adjust the surface tension of the ink depending on the printing speed. The surface tension of the ink can be adjusted by using a surfactant.

[0072] Examples of the surfactant include anionic, cationic, nonionic, amphoteric, silicone-based, and fluorine-based surfactants.

[0073] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acylamino acids or salts thereof, N-acylmethyl taurines, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosin acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol phosphates, alkyl phosphates, alkylaryl sulfonates, diethyl sulfosuccinates, diethylhexyl cyrsulfosuccinates, and dioctyl sulfosuccinates.

[0074] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly(4-vinylpyridine) derivatives.

[0075] Examples of amphoteric surfactants include lauryl dimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, polyoctyl polyaminoethyl glycine, and imidazoline derivatives.

[0076] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene tridecyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, and polyoxyethylene alkyl ethers; polyoxyalkylene acylates such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; polyoxyethylene aryl ethers such as polyoxyalkylene styrenated phenyl ether; acetylene glycol (alcohol) surfactants such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol; and polyglycol ether surfactants. Various types of nonionic surfactants can be easily purchased, for example, the Surfynol series, such as Surfynol 465, manufactured by Nissin Chemical Co., Ltd., the Olfine series; the Emulgen series, manufactured by Kao Corporation; the Newcol series, manufactured by Nippon Nyukazai Co., Ltd.; and the Noigen series, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

[0077] Examples of silicone surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes, etc. Examples thereof include Dynol 960 and Dynol 980 manufactured by Air Products Co., Ltd.; Silface SAG001, Silface SAG002, Silface SAG003, Silface SAG005, Silface SAG503A, Silface SAG008, Silface SAG009, and Silface SAG010 manufactured by Nissin Chemical Industry Co., Ltd.; and BYK-345, BYK-347, BYK-348, BYK-349, BYK-3450, BYK-3451, BYK-3455, BYK-LPX23288, BYK-LP X23347, and BYK-LP G20726 manufactured by BYK-Chemie.

[0078] Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains, such as Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, and CApstone, manufactured by DuPont. Examples of the surfactants include FS-30 and FS-31; PF-151N and PF-154N manufactured by Omnova; F-114, F-410, F-444, EXP. TF-2066, EXP. TF-2148, EXP. TF-2149, F-430, F-477, F-552, F-553, F-554, F-555, F-556, F-557, F-558, F-559, F-561, F-562, R-40, R-41, RS-72-K, RS-75, RS-76-E, RS-76-NS, RS-77, EXP. TF-1540, and EXP. TF-1760 manufactured by DIC Corporation; and BYK-3440 and BYK-3441 manufactured by BYK-Chemie.

[0079] Among these, surfactants selected from nonionic and silicone surfactants are preferred.

[0080] As the preservative, the preservatives described above can be used in the same manner.

[0081] Examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof.

[0082] Any substance can be used as the pH adjuster as long as it does not adversely affect the prepared ink and can control the pH to 5 to 11. Specific examples include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (aqueous ammonia); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0083] Examples of chelating agents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0084] Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0085] Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0086] As the antioxidant, various organic and metal complex anti-fading agents can be used, such as hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles.

[0087] The ink according to this embodiment is preferably subjected to microfiltration to remove impurities. When performing microfiltration, a membrane filter, glass filter paper, or the like can be used. The pore size of the filter used for microfiltration is usually 0.5 to 20 μm, and preferably 0.5 to 10 μm.

[0088] The pH of the ink according to this embodiment is typically 5 to 11, and preferably 6 to 10, from the viewpoint of improving storage stability. The surface tension of the ink according to this embodiment at 25°C is typically 10 to 50 mN / m, and preferably 20 to 40 mN / m. The viscosity of the ink according to this embodiment at 25°C is typically 30 mPa·s or less, and preferably 20 mPa·s or less. There is no particular lower limit to the viscosity, but it is typically around 2 mPa·s.

[0089] <Inkjet recording method, recording media, inkjet printer> The inkjet recording method according to this embodiment involves ejecting droplets of the ink according to this embodiment from an inkjet printer to record on a recording medium.

[0090] There are no particular limitations on the ink nozzles, heads, etc. of inkjet printers, and they can be selected appropriately depending on the purpose. In recent years, circulation heads have been actively developed, which have a mechanism for preventing ink from drying near the nozzles by circulating the ink up to the vicinity of the nozzles. The inkjet recording method according to this embodiment can also be suitably applied to such heads.

[0091] Known inkjet recording methods can be used, including, for example, a charge control method that uses electrostatic attraction to eject ink, a drop-on-demand method (also called a pressure pulse method) that uses the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink, and then uses the radiation pressure to eject the ink, and a thermal inkjet method that heats the ink to form bubbles and uses the resulting pressure.

[0092] Inkjet recording methods include a method in which a large number of inks, called photo inks, each with a low content of colorant, are ejected in a small volume; a method in which multiple inks having substantially the same hue but different content of colorant are used to improve image quality; and a method in which a colorless, transparent ink and an ink containing a colorant are used in combination to improve the fixability of the colorant to the recording medium.

[0093] Although there are no particular limitations on the recording medium, poorly ink-absorbent or non-ink-absorbent recording media are preferred. Examples of poorly ink-absorbent recording media include plain paper without an ink-receiving layer; recording media used in gravure printing, offset printing, etc.; art paper, coated paper, matte paper, cast paper, etc. Furthermore, examples of non-ink-absorbent recording media include PET (polyethylene terephthalate) sheets, PP (polypropylene) sheets, vinyl chloride sheets, glass, rubber, etc. Note that poorly ink-absorbent or non-ink-absorbent recording media refers to recording media having a surface with low water permeability, absorbency, and / or adsorption, and also includes materials that have many cavities inside but are not open to the outside. More quantitatively, in the Bristow method, 1 / 2 Water absorption up to 10mL / m 2 This refers to the following recording media:

[0094] When using the above recording media, better images can be obtained by subjecting the media to surface modification treatment.

[0095] The surface modification treatment is preferably a treatment selected from the group consisting of corona discharge treatment, plasma treatment, and flame treatment. It is generally known that the effect of surface-modified recording media decreases over time. For this reason, it is preferable to perform the surface modification treatment of the recording media and inkjet recording on that recording media consecutively. In particular, it is preferable to perform the surface modification treatment of the recording media immediately before inkjet recording. The strength of the effect of the surface modification treatment of the recording media can also be changed by adjusting the number of treatments, treatment time, treatment conditions, etc.

[0096] When recording on a recording medium using the inkjet recording method according to this embodiment, for example, a container containing the ink according to this embodiment can be loaded into a predetermined position of an inkjet printer, and recording can be performed on the recording medium using the above-described recording method.

[0097] In the inkjet recording method according to this embodiment, four ink colors, yellow, magenta, cyan, and black, can be used in combination with other ink colors, such as green, blue (or violet), and red (or orange), as needed. Each ink color is poured into a respective container, and each container can be loaded into a predetermined position in an inkjet printer for use in inkjet recording. To achieve high printing speeds, industrial inkjet printers are preferably configured as line-head inkjet printers, and single-pass printing is also preferred. The ink according to this embodiment can achieve excellent ejection properties even under such printing conditions.

[0098] For all of the above-mentioned items, a combination of preferred items is more preferred, and a combination of more preferred items is even more preferred. The same applies to a combination of a preferred item with a more preferred item, a combination of a more preferred item with an even more preferred item, etc. [Example]

[0099] 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 examples, Preparation Examples 1 to 10, 18, and 19 should be read as Examples 1 to 10, 18, and 19, and Preparation Examples 11 to 17 and 20 should be read as Comparative Examples 11 to 17 and 20. Furthermore, Examples 1 to 12 should be read as Reference Examples 1 to 12, and Comparative Examples 1 to 8 should be read as Reference Comparative Examples 1 to 8.

[0100] In the examples, unless otherwise specified, "parts," "%," and "ppm" are all based on mass. In the examples, all synthetic reactions, crystallization, and other operations were carried out under stirring unless otherwise specified. Furthermore, when it was necessary to measure the pigment solid content of the dispersion, it was determined by the dry weight method using an MS-70 (manufactured by A&D Co., Ltd.). The pigment solid content in the examples is a converted value of only the pigment solid content measured by the dry weight method.

[0101] In the examples, the mass average molecular weight (Mw), molecular weight distribution (PDI), acid value, and polymerization rate of the block copolymer were evaluated according to the following methods.

[0102] [Weight average molecular weight (Mw) and molecular weight distribution (PDI)] The molecular weight was determined by gel permeation chromatography (GPC) using a high-performance liquid chromatograph (Tosoh Corporation, Model: HLC-8320). The carboxyl groups of the polymerized product were methylated using a trimethylsilyldiazomethane-hexane solution (concentration: 0.6 mol / L) prior to measurement. Two TSKgel SuperMultipore HZ-H (Φ4.6 mm × 150 mm) columns (Tosoh Corporation) were used, with tetrahydrofuran as the mobile phase and a refractive index detector. The measurement conditions were a column temperature of 40°C, a sample concentration of 10 mg / mL, a sample injection volume of 10 μL, and a flow rate of 0.35 mL / min. A calibration curve was prepared using polystyrene (Tosoh Corporation, TSK Standard) as the standard, and the mass-average molecular weight (Mw) and number-average molecular weight (Mn) were measured. The molecular weight distribution (PDI = Mw / Mn) was calculated from these measurements.

[0103] [Acid value] The acid value represents the mass of potassium hydroxide required to neutralize the acidic components per 1 g of solid content. The measurement sample was dissolved in tetrahydrofuran, a few drops of phenolphthalein ethanol solution was added as an indicator, and neutralization titration was performed with 0.1 mol / L potassium hydroxide / 2-propanol solution, and the acid value (A) was calculated using the following formula. A=56.11×Vs×0.1×f / w A: Acid value (mgKOH / g) Vs: Amount (mL) of 0.1 mol / L potassium hydroxide / 2-propanol solution required for titration f: Potency of 0.1 mol / L potassium hydroxide / propanol solution w: Mass of the measurement sample (g) (solid content equivalent)

[0104] [Polymerization rate] Using a nuclear magnetic resonance (NMR) measurement device (manufactured by Bruker, model: AVANCE500 (frequency 500 MHz)), 1 H-NMR was measured (solvent: deuterated chloroform, internal standard: tetramethylsilane). From the obtained NMR spectrum, the integral ratio of the peaks of the vinyl group derived from the monomer and the ester side chain derived from the polymer was calculated, and the polymerization rate of the monomer was calculated.

[0105] <Synthesis of dispersant (block copolymer)> [Synthesis Example 1: Synthesis of Dispersant a] In a nitrogen-purged glove box, the B block monomer, ethyl 2-methyl-2-n-butyltellanyl propionate (BTEE), dibutyl ditelluride (DBDT), 2,2'-azobis(isobutyronitrile) (AIBN), and methyl ethyl ketone (MEK) in the proportions shown in Table 1, which had been previously purged with nitrogen, were charged and reacted. The A block monomer in the proportions shown in Table 1, which had also been previously purged with nitrogen, was added to this reaction solution and reacted. After the reaction was completed, the reaction solution was diluted with THF and poured into stirred heptane. The precipitated polymer was filtered by suction and dried to obtain the target dispersant a. The resulting dispersant a was incinerated and measured by inductively coupled plasma mass spectrometry (ICP / MS), and the total tellurium compound content was calculated in terms of metallic tellurium. The Mw was 18613, the PDI was 1.22, the acid value was 105 mgKOH / g, and the total content of tellurium compounds converted to metallic tellurium (hereinafter also referred to as "metallic tellurium content") was 7519 ppm.

[0106] [Synthesis Examples 2 to 19: Synthesis of Dispersants b to s] Dispersants b to s were obtained by the same procedure as in Synthesis Example 1, except that the B block monomer and A block monomer were used in the proportions shown in Tables 1 to 3. The Mw, PDI, acid value, and metallic tellurium content of the obtained dispersants b to s were as shown in Tables 1 to 3.

[0107] <Synthesis of dispersant (random copolymer)> [Synthesis Example 20: Synthesis of dispersant t] The monomers, BTEE, DBDT, AIBN, and MEK in the proportions shown in Table 4, which had been previously purged with nitrogen, were charged into a nitrogen-purged glove box and reacted. After the reaction was completed, the reaction solution was diluted with THF and poured into stirred heptane. The precipitated polymer was filtered by suction and dried to obtain the target dispersant t. The resulting dispersant t was incinerated and measured by inductively coupled plasma mass spectrometry (ICP / MS), and the total tellurium compound content was calculated in terms of metallic tellurium. The Mw was 19603, the PDI was 1.33, the acid value was 121 mg KOH / g, and the metallic tellurium content was 297 ppm.

[0108] [Table 1]

[0109] [Table 2]

[0110] [Table 3]

[0111] [Table 4]

[0112] The meanings of the abbreviations in Tables 1 to 4 are as follows. BMA: Butyl methacrylate MAA: methacrylic acid CHMA: Cyclohexyl methacrylate BzMA: benzyl methacrylate IBXMA: Isobornyl methacrylate DCPMA: dicyclopentanyl methacrylate

[0113] <Preparation of Dispersion> [Preparation Example 1: Preparation of Dispersion a] Dispersant a (5.4 parts) obtained in Synthesis Example 1 was dissolved in 2-butanone (12.5 parts) to prepare a homogeneous solution. To this was added a solution of 28% aqueous ammonia (0.6 parts) dissolved in ion-exchanged water (62.7 parts), followed by Surfynol DF-58 (Nissin Chemical Industry Co., Ltd.) (0.3 parts) and Rosima 640 (Dow Chemical Company) (0.5 parts). The mixture was stirred for 1 hour to prepare an emulsified solution containing the dispersant. No crystal precipitation occurred during this process. CI Pigment Red 122 (Clariant, Ink Jet Magenta E 02) (18.0 parts) was added to the mixture to a fractionation ratio of 0.3, and the mixture was dispersed using a sand grinder (Imex Co., Ltd., Model 6TSG-1 / 8). Dispersion was carried out at 1500 rpm for 10 hours. Subsequently, ion-exchanged water (100 parts) was added dropwise, and the dispersion beads were removed by filtration. 2-Butanone and a portion of the water were then distilled off under reduced pressure using an evaporator, yielding dispersion a with a pigment solids content of 12%. Since the dispersant concentration in dispersion a was 0.3 as described above, the calculated dispersant concentration in dispersion a was 3.6%, and since the metallic tellurium content in dispersant a was 7519 ppm as described above, the calculated metallic tellurium content in the total mass of dispersion a was 271 ppm.

[0114] [Preparation Examples 2 to 20: Preparation of Dispersions b to t] In the same manner as in Preparation Example 1, dispersions b to t were prepared by mixing the components shown in Tables 5 to 7 below.

[0115] [Table 5]

[0116] [Table 6]

[0117] [Table 7]

[0118] <Ink Preparation> [Examples 1 to 12 and Comparative Examples 1 to 8] Dispersions a to t obtained in Dispersion Examples 1 to 20 were mixed with the components shown in Tables 8 to 10, and then filtered through a syringe filter with a pore size of 5 μm (Minisart, manufactured by Sartorius) to obtain the inks of Examples 1 to 12 and Comparative Examples 1 to 8. The pigment solid content of each ink was adjusted to 5%, with the remainder being ion-exchanged water.

[0119] [Table 8]

[0120] [Table 9]

[0121] [Table 10]

[0122] The meanings of the abbreviations in Tables 8 to 10 are as follows: BYK3450: Silicone surfactant (manufactured by BYK Chemie)

[0123] <Preparation of clear ink> Dipropylene glycol-n-propyl ether (30.0 parts), ethylene glycol monoisopropyl ether (30.0 parts), 3-methoxy-3-methyl-1-butanol (15.0 parts), BYK3450 (manufactured by BYK-Chemie) (2.1 parts), and ion-exchanged water (207.9 parts) were mixed, and then filtered through a membrane filter with a pore size of 0.45 μm (manufactured by Toyo Roshi Kaisha, Ltd., Advantech Dismic-25CS) to obtain a colorless, transparent clear ink.

[0124] This clear ink is a liquid composition that assumes a composition in which the pigment solid content has been removed from the inks of the above Examples and Comparative Examples. Even if the ink dries near the nozzles of an inkjet head, the dried ink can be redispersed by the ink itself supplied from inside the head, making it less likely to clog and ensuring ejection stability. Therefore, the more easily the ink redisperses when the above clear ink is added to dried ink, the less likely it is to clog the nozzles after drying, and can be said to be superior.

[0125] <Evaluation> [Redispersibility evaluation] 20 μL of each of the inks from Examples 1 to 12 and Comparative Examples 1 to 8 was dropped onto a 67 mm diameter glass petri dish and allowed to dry for 10 minutes in a thermo-hygrostat at 45°C to obtain a dried ink. Then, 10 mL of the above clear ink was dropped onto the dried ink, and the glass petri dish was slowly shaken and allowed to stand for 1 hour. The glass petri dish was then slowly shaken again, and redispersion was visually observed and evaluated according to the following criteria. The results are shown in Tables 11 and 12. Redispersed solutions can be judged visually because the colored solution spreads without leaving any residue, like bleeding. The greater the residue, the poorer the redispersibility. A rating of 3 or higher below is practically desirable. -Evaluation criteria- 5: No residue left and the dried ink was completely redispersed. 4: A very small amount of residue was observed, but most of the dried ink was redispersed. 3: There was a small amount of residue, but the dried ink was redispersed to some extent. 2: A large amount of residue was observed, and the dried ink was not redispersed well. 1: There was no change in the dried ink and it was hardly redispersed.

[0126] [Water resistance evaluation] Each of the inks from Examples 1 to 12 and Comparative Examples 1 to 8 was dropped in an amount of 20 μL onto a PET film (E5102, manufactured by Toyobo Co., Ltd.) and coated using an automatic coater (PI-1210, manufactured by Tester Sangyo Co., Ltd.) and a bar coater No. 3 (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). The coated PET film was then dried in a thermo-hygrostat at 70°C for 3 minutes. The ink coating film was then rubbed back and forth over a 1 cm width using a cotton swab moistened with ion-exchanged water, and the number of strokes required until the ink coating film at the rubbed area was completely peeled off was measured. Measurements were performed at a total of five locations on the same coating film, and water resistance was evaluated using the average number of strokes. The results are shown in Tables 11 and 12. The greater the number of strokes required until the ink coating film peeled off, the better the water resistance; six or more strokes is practically desirable. The values ​​in the "Water Resistance" column in Tables 11 and 12 are the number of strokes required.

[0127] [Table 11]

[0128] [Table 12]

[0129] As is clear from Table 11, Example 1 is an example that achieves both good redispersibility and water resistance. Furthermore, Examples 2 to 4 are examples in which the metallic tellurium content in the dispersion is lower than that of Example 1, and it can be seen that the water resistance is further improved while maintaining the same redispersibility. This is thought to be because the low metallic tellurium content derived from the dispersant increases the adsorption force of the dispersant to the colorant, improving dispersion stability. Therefore, even after drying after ink application, the colorant does not aggregate, and a smooth coating film can be formed while remaining in a better dispersed state.

[0130] Examples 5 to 8 are examples in which the physical properties of the block copolymer structure, such as Mw, acid value, and MAA content ratio in the A block, are higher than those of Example 4, but it can be seen that, like Example 4, they achieve both good redispersibility and water resistance.

[0131] Examples 9 to 12 are particularly preferred examples that achieve both excellent redispersibility and water resistance.

[0132] On the other hand, Comparative Example 8 is an example of a random copolymer having roughly the same monomer ratio and physical properties as the block copolymer of Example 9, but both redispersibility and water resistance were significantly worse than those of the examples. This is thought to be due to the fact that the hydrophilic and hydrophobic portions are arranged in a disordered manner, resulting in low hydrophilicity to the liquid medium and poor dispersion stability, which causes the dispersant to easily detach during drying and the colorant to aggregate. This example demonstrates that the structure of the block copolymer has excellent effects on redispersibility and water resistance.

[0133] Comparative Example 1 is an example in which the Mw, acid value, and MAA content in the A block were all lower than those of the Examples, and the redispersibility was very poor and the water resistance was also poor.

[0134] Comparative Example 2 was also an example in which the acid value and the MAA content in the A block were low, and the redispersibility and water resistance both showed poor results.

[0135] Comparative Example 3 was an example with a low acid value, resulting in poor water resistance. From Comparative Examples 1 to 3 above, it was found that by using a dispersant that balances Mw, acid value, and the MAA content in the A block with the polymer structure and physical properties, it is possible to achieve both good ink redispersibility and water resistance.

[0136] Comparative Examples 4 and 5 are examples in which the B block is composed of benzyl methacrylate, which is a cyclic aromatic hydrocarbon having a planar structure, and the redispersibility was poor compared to the Examples.

[0137] Comparative Example 6 is an example in which the B block is composed of isobornyl methacrylate, a polycyclic saturated hydrocarbon with structural limitations on the conformation that it can assume, and the redispersibility and water resistance were both very poor compared to the Examples. Similarly, Comparative Example 7 is an example in which the B block is composed of dicyclopentanyl methacrylate, and the redispersibility was also poor.

[0138] From the above Comparative Examples 4 to 7, it was found that even if the structure and physical properties of the block copolymer satisfy the conditions, changing the type of monomer constituting the hydrophobic portion makes it difficult to achieve both redispersibility and water resistance. Therefore, cyclohexyl methacrylate, the B block monomer of this example, is a preferred embodiment.

[0139] The results in Tables 11 and 12 above show that the inks of the Examples are excellent inks having both high redispersibility and high water resistance compared to the inks of the Comparative Examples.

Claims

1. A method for producing a color dispersion for inkjet printing, comprising: the inkjet color dispersion contains a colorant, a dispersant, a tellurium compound, and water; the dispersant is an A-B block polymer, the monomers constituting the A block of the A-B block polymer are (meth)acrylic acid and butyl (meth)acrylate, the content of (meth)acrylic acid in the total mass of the monomers constituting the A block is 26 to 42 mass%, and the monomer constituting the B block of the A-B block polymer contains cyclohexyl (meth)acrylate; The acid value of the dispersant is 100 to 159 mg KOH / g, The dispersant has a mass average molecular weight of 10,000 to 50,000; A method for producing a colored dispersion for inkjet printing, comprising a step of coating the surface of the colorant with the dispersant by a phase inversion emulsification method.

2. A method for producing a color dispersion liquid for inkjet as described in claim 1, wherein the total content of the tellurium compounds in the color dispersion liquid for inkjet in terms of metallic tellurium is 160 ppm or less by mass.

3. 3. The method for producing a colored dispersion liquid for inkjet according to claim 1, wherein the dispersant has an acid value of 112 to 135 mgKOH / g.

4. The method for producing a colored dispersion liquid for inkjet according to any one of claims 1 to 3, wherein the dispersant has a mass average molecular weight of 10,000 to 30,000.

5. The method for producing a colored dispersion liquid for inkjet according to any one of claims 1 to 4, wherein the colorant is a colorant selected from the group consisting of pigments and disperse dyes.

6. The method for producing a colored dispersion liquid for inkjet according to any one of claims 1 to 5, wherein a monomer constituting the B block of the AB block polymer contains (meth)acrylic acid.

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