Water-based ink for ink-jet recording, ink-jet recording apparatus, ink-jet recording method, and ink storage container

Abstract

To provide aqueous ink for inkjet recording which is excellent in fixability, image quality and maintainability, and can be fixed onto coat paper by drying at low temperature for a short time.SOLUTION: Aqueous ink for inkjet recording contains a pigment, acrylic resin particles, a surface active agent, trimethylglycine and water, wherein a glass transition temperature of the acrylic resin particles is 25°C or higher and lower than 50°C, and static surface tension of the aqueous ink for inkjet recording is 27 mN / m or less. A solid content blended amount (R) of the acrylic resin particles and a blended amount (B) of the trimethylglycine may satisfy, for example, R / B=0.6 to 1.5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based ink for ink-jet recording, an ink-jet recording apparatus, an ink-jet recording method, and an ink storage container. [Background technology]

[0002] As a water-based ink for ink-jet recording that has excellent fixability to coated paper, a water-based ink containing a vinyl chloride-acrylic copolymer has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-19811 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to fix an aqueous ink containing a vinyl chloride-acrylic copolymer to coated paper, high-temperature, long-term heat drying is required. Therefore, there is a demand for improvement in fixability at low temperatures and in short drying times. Furthermore, there is a demand for further improvements in image quality and maintenance for inkjet recording using aqueous inks for inkjet recording.

[0005] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a water-based ink for ink-jet recording that has excellent fixability, image quality, and maintenance properties, and can be fixed on coated paper by drying at low temperature for a short time. [Means for solving the problem]

[0006] In order to achieve the above object, the water-based ink for ink-jet recording of the present invention comprises: The ink contains a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water, The acrylic resin particles have a glass transition temperature of 25°C or higher and lower than 50°C, The water-based ink for ink-jet recording has a static surface tension of 27 mN / m or less. [Effects of the Invention]

[0007] The water-based ink for ink-jet recording of the present invention contains a surfactant and trimethylglycine in addition to acrylic resin particles having a glass transition temperature within a predetermined range, and by adjusting the static surface tension within a predetermined range, the ink has excellent fixing properties, image quality, and maintenance properties, and can be fixed to coated paper with low temperature drying in a short time. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of an example of an inkjet recording apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, "coated paper" refers to plain paper, such as high-grade printing paper or medium-grade printing paper, on which a coating agent has been applied for the purpose of improving smoothness, whiteness, gloss, etc., and specific examples include high-grade coated paper, medium-grade coated paper, etc. The water-based ink for inkjet recording (hereinafter sometimes referred to as "water-based ink" or "ink") and inkjet recording method of the present invention are suitable for inkjet recording on coated paper, but are not limited thereto, and can also be used for inkjet recording on recording media other than coated paper, such as plain paper, glossy paper, and matte paper.

[0010] The aqueous ink of the present invention will now be described. The aqueous ink of the present invention contains a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water.

[0011] The pigment can be dispersed in water using, for example, a pigment dispersing resin (resin dispersant). Examples of the pigment include, but are not limited to, carbon black, inorganic pigments, and organic pigments. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of inorganic pigments include titanium oxide, iron oxide-based inorganic pigments, and carbon black-based inorganic pigments. Examples of organic pigments include azo pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye lake pigments such as basic dye lake pigments and acid dye lake pigments; nitro pigments; nitroso pigments; and aniline black daylight fluorescent pigments. Other pigments can also be used as long as they are dispersible in an aqueous phase. Specific examples of these pigments include CI Pigment Black 1, 6, and 7; CI Pigment Yellow 1, 2, 3, 12, 13, 14, 15, 16, 17, 55, 74, 78, 150, 151, 154, 180, 185, and 194; CI Pigment Orange 31 and 43; CI Pigment Red 2, 3, 5, 6, 7, 12, 15, 16, 48, 48:1, 53:1, 57, 57:1, 112, 122, 123, 124, 125, 126, 127, 128, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 185, and 186; 39, 144, 146, 149, 150, 166, 168, 175, 176, 177, 178, 184, 185, 190, 202, 209, 221, 222, 224, and 238; CI Pigment Violet 19 and 196; CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 16, 22, and 60; CI Pigment Green 7 and 36; and solid solutions of these pigments.

[0012] The method for dispersing the pigment using the pigment dispersing resin may be, for example, to disperse the pigment using a dispersing device. The dispersing device used for dispersing the pigment is not particularly limited as long as it is a general dispersing machine, and examples thereof include a ball mill, a roll mill, and a sand mill (e.g., a high-speed type).

[0013] The pigment may be a self-dispersing pigment. The self-dispersing pigment is, for example, one in which at least one hydrophilic functional group, such as a carbonyl group, a hydroxyl group, a carboxylic acid group, a sulfonic acid group, or a phosphate group, or a salt thereof, is chemically bonded to the pigment particle, either directly or via another group, thereby enabling dispersion in water without the use of a dispersant. The self-dispersing pigment may be one treated by methods described, for example, in JP-A-8-3498, JP-T-2000-513396, JP-T-2008-524400, JP-T-2009-515007, or JP-T-2011-515535. Both inorganic and organic pigments can be used as raw materials for the self-dispersing pigment. Examples of pigments suitable for the treatment include carbon blacks such as "MA8" and "MA100" manufactured by Mitsubishi Chemical Corporation. The self-dispersing pigment may also be a commercially available product. Examples of commercially available products include "CAB-O-JET (registered trademark) 200," "CAB-O-JET (registered trademark) 250C," "CAB-O-JET (registered trademark) 260M," "CAB-O-JET (registered trademark) 270Y," "CAB-O-JET (registered trademark) 300," "CAB-O-JET (registered trademark) 400," "CAB-O-JET (registered trademark) 450C," "CAB-O-JET (registered trademark) 465M," and "CAB-O-JET (registered trademark) 470Y" manufactured by Cabot Specialty Chemicals; "BONJET (registered trademark) BLACK CW-2" and "BONJET (registered trademark) BLACK CW-3" manufactured by Orient Chemical Industry Co., Ltd.; and "LIOJET (registered trademark) WD BLACK 002C" manufactured by Toyo Ink Mfg. Co., Ltd.

[0014] The amount of pigment solids (pigment solid content) relative to the total amount of the aqueous ink is not particularly limited and can be determined appropriately depending on, for example, the desired optical density. The pigment solid content is, for example, 1% by weight to 10% by weight, 2% by weight to 8% by weight, or 3% by weight to 7% by weight. The pigment solid content is the weight of the pigment only, and does not include the weight of the resin dispersant, etc. (i.e., converted into the amount of active ingredients).

[0015] The pigments may be used alone or in combination of two or more.

[0016] The water is preferably ion-exchanged water or pure water. The amount of water to be blended relative to the total amount of the aqueous ink (water ratio) is determined appropriately depending on the desired ink properties, etc. The water ratio may be, for example, the remainder of the other components. The amount of water to be blended is, for example, 60% to 90% by weight, 65% to 85% by weight, or 70% to 80% by weight.

[0017] As described above, the water-based ink of the present invention further contains acrylic resin particles having a glass transition temperature (Tg) of 25° C. or higher and lower than 50° C., a surfactant, and trimethylglycine.

[0018] The glass transition temperature (Tg) of the acrylic resin particles is, for example, 25°C or higher and lower than 50°C, or 30°C or higher and lower than 50°C. The acrylic resin particles may be contained in, for example, a resin emulsion. The resin emulsion is, for example, composed of acrylic resin particles and a dispersion medium (e.g., water), and the acrylic resin particles are not dissolved in the dispersion medium but are dispersed with a specific particle size. The acrylic resin particles may be, for example, commercially available products. The acrylic resin particles are, for example, resin particles whose main component is polyacrylic acid or a polyacrylic acid ester, and examples of monomers that can be used include (meth)acrylic acid and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, cyclopropyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, tolyl (meth)acrylate, thisyl (meth)acrylate, and phenethyl (meth)acrylate.

[0019] Examples of commercially available acrylic resin particles include "Movinyl (registered trademark) 6899D" (Tg: 49°C, active ingredient concentration: 46% by weight) and "Movinyl (registered trademark) DM774" (Tg: 30°C, active ingredient concentration: 46% by weight) manufactured by Japan Coating Resins Co., Ltd.; and "Saivinol (registered trademark) EK-1920" (Tg: 40°C, active ingredient concentration: 35% by weight) manufactured by Saiden Chemical Co., Ltd.

[0020] The solid content of the acrylic resin particles (equivalent to the amount of active ingredients) relative to the total amount of the aqueous ink is not particularly limited and can be determined appropriately. The solid content of the acrylic resin particles is, for example, 1% by weight to 10% by weight, 2% by weight to 8% by weight, or 3% by weight to 7% by weight. Note that, when a resin emulsion containing the acrylic resin particles is used, the "equivalent to the amount of active ingredients" refers to the amount of the acrylic resin particles themselves excluding the dispersion solvent such as water.

[0021] If the Tg of the acrylic resin particles is less than 25°C, the elastic modulus of the acrylic resin particles will decrease when the dried aqueous ink is exposed to a room temperature environment (e.g., 20°C), resulting in an insufficient strength of the coating film and insufficient fixability.

[0022] The average particle diameter of the acrylic resin particles is, for example, 5 nm to 500 nm, 20 nm to 300 nm, or 30 nm to 200 nm. The average particle diameter of the acrylic resin particles can be measured as an arithmetic mean diameter using, for example, a dynamic light scattering particle size distribution measuring device "LB-550."

[0023] The acrylic resin particles may be used alone or in combination of two or more kinds.

[0024] The surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, a commercially available product may be used. Specific examples of the surfactant include silicone surfactants and fluorine surfactants. Examples of the silicone surfactant include polyether-modified silicone surfactants. The HLB (Hydrophilic-Lipophilic Balance) value of the surfactant is, for example, 5 to 15, 7 to 14, or 12 to 13. The HLB value can be determined, for example, by phase inversion titration. Examples of commercially available surfactants include "Silface (registered trademark) SAG002" (HLB value: 12), "Silface (registered trademark) SAG005" (HLB value: 7, silicone surfactant), "Silface (registered trademark) SAG503A" (HLB value: 11, silicone surfactant), and "Silface (registered trademark) SAG008" (HLB value: 7, silicone surfactant), all manufactured by Nissin Chemical Industry Co., Ltd.; and "Surflon (registered trademark) S-241" (fluorochemical surfactant), "Surflon (registered trademark) S-242" (fluorochemical surfactant), and "Surflon (registered trademark) S-243" (fluorochemical surfactant), all manufactured by AGC Seimi Chemical Co., Ltd.

[0025] The amount of the surfactant to be blended relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose, and is, for example, 0.1% by weight to 5% by weight, 1.5% by weight to 3.5% by weight, or 2% by weight to 3% by weight.

[0026] The surfactants may be used alone or in combination of two or more.

[0027] Trimethylglycine is a zwitterionic organic compound in which the amino group of glycine is trimethylated to form an intramolecular salt. Trimethylglycine is also known as N,N,N-trimethylglycine or betaine.

[0028] The amount of trimethylglycine to be blended relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose, and is, for example, 1% by weight to 10% by weight, 2% by weight to 9% by weight, or 3% by weight to 8% by weight.

[0029] The solid content of the acrylic resin particles (R) and the trimethylglycine content (B) in the total amount of the aqueous ink satisfy, for example, 0.6≦R / B≦1.5 (hereinafter also referred to as condition X). The solid content of the acrylic resin particles (R) and the trimethylglycine content (B) may be appropriately adjusted so as to satisfy condition X, and the solid content of the acrylic resin particles (R) and the trimethylglycine content (B) are, for example, the same as those described above.

[0030] Furthermore, the solid content of the pigment (P), the solid content of the acrylic resin particles (R), and the trimethylglycine (B) in the total amount of the aqueous ink satisfy, for example, 1.2≦(P+R) / B≦3.2 (hereinafter also referred to as condition Y). The solid content of the pigment (P), the solid content of the acrylic resin particles (R), and the trimethylglycine (B) may be appropriately adjusted so as to satisfy condition Y, and the solid content of the pigment (P), the solid content of the acrylic resin particles (R), and the trimethylglycine (B) may be, for example, the same as described above.

[0031] Furthermore, the blending amount (S) of a substance that is solid at room temperature and contains the pigment and the acrylic resin particles, the blending amount (L) of a substance that is liquid at room temperature (25°C) excluding the water, and the blending amount (W) of the water satisfy, for example, L < S < W (hereinafter, also referred to as condition Z). Examples of the solid substance may include trimethylglycine, a dispersion resin, and other substances that are solid in their single form at room temperature. Examples of the liquid substance include the surfactant, penetrant, wetting agent, and other organic solvents. The blending amount (S) of the solid substance, the blending amount (L) of the liquid substance, and the blending amount (W) of the water may be appropriately adjusted to satisfy the above condition Z and are not particularly limited. The blending amount (S) of the solid substance is, for example, 5% by weight to 2�% by weight, 7% by weight to 22% by weight, 10% by weight to 20% by weight, and the blending amount (L) of the liquid substance is, for example, 4% by weight to 15% by weight, 4% by weight to 12% by weight, 5% by weight to 11% by weight, and the blending amount (W) of the water is, for example, the same as described above.

[0032] And the aqueous ink of the present invention has a static surface tension of 27 mN / m or less. Specifically, the static surface tension is, for example, 18 mN / m or more to 27 mN / m or less, 20 mN / m or more to 26.5 mN / m or less, 22 mN / m or more to 26 mN / m or less. The lower limit value of the static surface tension is not particularly limited and may be, for example, 18 mN / m or less. The static surface tension can be measured, for example, using "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. The measurement temperature of the static surface tension is, for example, 25°C. The static surface tension of the aqueous ink can be adjusted, for example, by changing the blending amounts of the respective components of the aqueous ink. Specifically, the static surface tension of the aqueous ink can be adjusted, for example, by changing the type and blending amount of the surfactant contained in the aqueous ink.

[0033] The aqueous ink contains acrylic resin particles having a Tg of 25°C or higher but lower than 50°C, a surfactant, and trimethylglycine, resulting in excellent fixability, image quality, and maintainability. Furthermore, the ink can be fixed on coated paper at a lower temperature and in a shorter drying time. The mechanism by which fixability, image quality, and maintainability are improved is presumed to be as follows: When a polymer with a low Tg is added to an aqueous ink to improve fixability at a lower temperature and in a shorter drying time, a highly volatile solvent must be used to improve the volatility of the solvent. Furthermore, it is common to add a surfactant to reduce the contact angle of droplets during inkjet recording in order to suppress white streak-like unevenness (banding) on ​​coated paper. However, the use of a highly volatile solvent can cause the aqueous ink to easily form a film on the nozzle surface of the inkjet head, potentially affecting maintainability. Furthermore, reducing the contact angle of droplets also reduces the contact angle of aqueous ink droplets on the nozzle surface of the inkjet head, making the aqueous ink difficult to remove during wiping, potentially affecting maintainability. On the other hand, to improve maintenance, it is necessary to reduce the volatility of the solvent while increasing the contact angle of droplets during inkjet recording. Thus, there is a trade-off between fixability, image quality, and maintenance. In contrast, adding trimethylglycine to the aqueous ink improves maintenance because the trimethylglycine remains in the ink residue solidified on the nozzle surface of the inkjet head and redissolves in the solvent in the ink during wiping. Meanwhile, trimethylglycine is dissolved in the aqueous ink when ejected from the inkjet head and penetrates into the coated paper upon impact with the coated paper. This does not adversely affect the coating performance of the acrylic resin particles or the wetting (spreading) of the surfactant on the coated paper. Furthermore, having the static surface tension within a specified range reduces the contact angle of droplets during inkjet recording, improving wetting (spreading) on ​​the coated paper.In other words, the aqueous ink of the present invention can improve fixation by the acrylic resin particles, improve image quality by the surfactant and the static surface tension being within a predetermined range, and improve maintenance by trimethylglycine. However, this mechanism is merely speculation, and the present invention is not limited to this. The drying temperature will be explained later in the inkjet recording method of the present invention.

[0034] Furthermore, by satisfying the condition (Z), the aqueous ink exhibits superior fixability, image quality, and maintainability. The mechanism by which fixability, image quality, and maintainability are improved is presumed to be, for example, as follows. Generally, when a large amount of residual solvent in an aqueous ink is present on coated paper, film formation is difficult and fixability is reduced. In contrast, by increasing the amount of water in the aqueous ink, the residual solvent is significantly reduced when the water on the coated paper evaporates, facilitating film formation and improving fixability. On the other hand, generally, when a large amount of residual solvent is present on the nozzle surface of an inkjet head, the viscosity of the solid on the nozzle surface increases during the evaporation process, making it difficult to wipe off with a wipe. In contrast, by increasing the amount of water in the aqueous ink, the residual solvent is significantly reduced during the evaporation process, resulting in a lower viscosity of the coating film. The low viscosity of the coating film allows the coating film to dry into a trimethylglycine-containing solid in a short time and redissolve upon wiping, thereby improving maintainability. However, this mechanism is merely presumed, and the present invention is not limited thereto.

[0035] The water-based ink of the present invention can be fixed on coated paper with a shorter drying time at a lower temperature, and therefore, for example, users can safely perform printing using the water-based ink of the present invention.

[0036] The aqueous ink may further contain a water-soluble organic solvent other than trimethylglycine, such as a humectant that prevents the aqueous ink from drying on the nozzle surface of the inkjet head and a penetrant that adjusts the drying speed on the recording medium.

[0037] The wetting agent is not particularly limited, and examples thereof include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones such as acetone; ketoalcohols such as diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethers such as polyalkylene glycols; polyhydric alcohols such as alkylene glycol, glycerin, trimethylolpropane, and trimethylolethane; 2-pyrrolidone; N-methyl-2-pyrrolidone; and 1,3-dimethyl-2-imidazolidinone. Examples of the polyalkylene glycol include polyethylene glycol and polypropylene glycol. Examples of the alkylene glycol include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, thiodiglycol, and hexylene glycol. These wetting agents may be used alone or in combination. Among these, polyhydric alcohols such as alkylene glycols and glycerin are preferred.

[0038] The blending amount of the humectant in the total amount of the aqueous ink is, for example, 0% by weight to 95% by weight, 5% by weight to 80% by weight, or 5% by weight to 50% by weight.

[0039] The penetrating agent preferably includes at least one of an alkylene diol and a glycol ether compound. Examples of the alkylene diol include 1,2-hexanediol, 1,2-heptanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, and 3-methyl-1,5-pentanediol. Examples of the glycol ether compounds include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol-n-propyl ether, diethylene glycol-n-butyl ether, diethylene glycol-n-hexyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol-n-propyl ether, tripropylene glycol-n-butyl ether, etc. One type of penetrating agent may be used alone, or two or more types may be used in combination.

[0040] The amount of the penetrant relative to the total amount of the aqueous ink is, for example, 0% by weight to 20% by weight, 0% by weight to 15% by weight, or 1% by weight to 6% by weight.

[0041] The aqueous ink may further contain conventionally known additives as needed. Examples of the additives include surfactants other than the silicone surfactants, pH adjusters, viscosity adjusters, surface tension adjusters, and antifungal agents. Examples of the viscosity adjusters include polyvinyl alcohol, cellulose, and water-soluble resins.

[0042] The ink container of the present invention is an ink container containing an aqueous ink for ink-jet recording, characterized in that the aqueous ink is the aqueous ink for ink-jet recording of the present invention. Examples of the ink container include an ink cartridge, a tank, a pouch, etc. The main body of the ink container can be, for example, a conventionally known one.

[0043] Next, the ink jet recording apparatus and ink jet recording method of the present invention will be described.

[0044] The inkjet recording apparatus of the present invention comprises an ink storage section and ink ejection means, and ejects the ink stored in the ink storage section by the ink ejection means. The inkjet recording apparatus further comprises drying means for heating and drying a portion of a recording made by the ink ejected by the ink ejection means, and is characterized in that the water-based ink for inkjet recording of the present invention is stored in the ink storage section.

[0045] The inkjet recording method of the present invention includes a recording step of ejecting an aqueous ink onto a recording medium by an inkjet system to record, and a fixing step of fixing the aqueous ink adhered to the recording medium in the recording step to the recording medium using a drying means that heats and dries the recorded portion of the recording medium, and is characterized in that the aqueous ink for inkjet recording of the present invention is used as the aqueous ink in the recording step.

[0046] In the inkjet recording method of the present invention, the recording medium may be, for example, coated paper. In the present invention, "coated paper" refers to plain paper containing pulp, such as high-quality printing paper or medium-quality printing paper, to which a coating agent has been applied for the purpose of improving smoothness, whiteness, gloss, etc., and specific examples include high-quality coated paper and medium-quality coated paper. The aqueous ink and inkjet recording method of the present invention are suitable for inkjet recording on coated paper, but are not limited thereto. They can also be used for inkjet recording on recording media other than coated paper, such as plain paper, glossy paper, matte paper, synthetic paper, thermal transfer paper, thermal paper, paperboard, cardboard, and film.

[0047] The inkjet recording method of the present invention can be carried out, for example, by using the inkjet recording apparatus of the present invention. The recording includes printing, photographic printing, printing, and the like.

[0048] The schematic diagram of Figure 1 shows the configuration of one example of an inkjet recording apparatus of the present invention. As shown in Figure 1, this inkjet recording apparatus 100 includes a paper feed tray 101, a transport mechanism such as a roller (not shown), a recording mechanism, a platen 103, drying means 104, a paper discharge tray 105, and an ink storage unit such as an ink cartridge or ink tank (not shown). The inkjet recording apparatus of the present invention may also include, for example, a maintenance unit (not shown). The paper feed tray 101 is capable of supporting a plurality of stacked recording media (e.g., coated paper) P.

[0049] A conveying path (not shown) is formed by a guide member inside the inkjet recording apparatus 100. The recording paper P is conveyed from the paper feed tray 101 to the paper discharge tray 105 by the conveying mechanism and the conveying path, as indicated by the dashed arrow in FIG.

[0050] The recording mechanism includes a carriage 102A and an inkjet head (ink ejection means) 102B. The carriage 102A is supported by two guide rails (not shown) extending perpendicular to the transport direction of the recording paper P. The two guide rails are supported by a housing (not shown) of the inkjet recording device 100. The carriage 102A is connected to a known belt mechanism (not shown) provided on the two guide rails. This belt mechanism is driven by a carriage motor (not shown). The carriage 102A connected to the belt mechanism reciprocates in a direction perpendicular to the transport direction of the recording paper P by being driven by the carriage motor.

[0051] Also extending from the carriage 102A are four ink tubes (not shown) that connect the ink storage unit and the inkjet head 102B, and a flexible flat cable (not shown) that electrically connects the control board (not shown) and the inkjet head 102B. The four ink tubes supply the four colors of water-based ink (yellow, magenta, cyan, and black) stored in the ink storage unit to the inkjet head 102B. At least one of the four colors of water-based ink is the water-based ink for inkjet recording of the present invention. The flexible flat cable transmits control signals output from the control board to the inkjet head 102B.

[0052] As shown in FIG. 1, the inkjet head 102B is mounted on a carriage 102A. A plurality of nozzles 102C are formed on the underside of the inkjet head 102B. The tips of the nozzles 102C are exposed from the undersides of the carriage 102A and the inkjet head 102B. The inkjet head 102B has an actuator (not shown) for applying a force to eject the aqueous ink supplied from the ink storage unit to the inkjet head 102B via the ink tubes. The actuator may be of any type, such as a piezoelectric element type, a thermal ink type, or an electrostatic suction type. As the carriage 102A reciprocates in a direction perpendicular to the conveyance direction of the recording paper P, the inkjet head 102B ejects the aqueous ink as tiny ink droplets from the plurality of nozzles 102C. This records an image on the recording paper P. A platen 103 is disposed opposite the recording mechanism and supports the recording paper P conveyed from the paper feed tray 101. 1 employs a serial inkjet head, the present invention is not limited to this, and the inkjet recording device may employ a line inkjet head or a roll-to-roll head.

[0053] The drying means 104 heats and dries the recorded portion of the recording paper P. The temperature on the recording paper P during this drying process may be, for example, 0.1 to 10 times, 0.2 to 8 times, or 0.5 to 5 times the Tg of the acrylic resin particles. The temperature can be appropriately adjusted by changing the settings of the drying means 104, specifically, for example, 0°C to 400°C, 5°C to 350°C, or 10°C to 250°C. The drying time can also be appropriately adjusted by changing the settings of the drying means 104, for example, more than 0 seconds to 300 seconds or less, 0.05 to 60 seconds, or 0.07 to 30 seconds. The aqueous ink of the present invention can be fixed to coated paper at a lower temperature and in a shorter time than conventional aqueous inks, which require high-temperature, long-term heating and drying. The drying means 104 may be any device capable of heating and drying the recorded portion. Furthermore, the heating method used by the drying means 104 is not particularly limited and may be any method, such as heat transfer, convection, radiation, etc. Examples of the drying means 104 include commercially available dryers (hot air), ovens, belt conveyor ovens, irons, hot presses, plate heaters, and IR heaters, with non-contact drying means that heat and dry the recorded portion of the recording paper P without coming into contact with the recorded portion, such as dryers, ovens, and belt conveyor ovens, being preferred.

[0054] 1 shows an example in which the recording portion of the recording paper P is heated and dried by drying means 104 arranged on the inkjet head 102B side so as to face the recording portion of the recording paper P, but this is not limiting. The drying means 104 only needs to be able to heat and dry the recording portion of the recording paper P, and may be arranged, for example, on the opposite side of the recording portion of the recording paper P, i.e., on the side facing the nozzles 102C of the inkjet head 102B.

[0055] After the recording and drying, the recording paper P is conveyed to a paper discharge tray 105. The fixation of ink onto the recording medium P can be improved without requiring a complicated configuration.

[0056] Next, the maintenance unit will be described. The maintenance unit has a waste liquid foam (not shown), a cap (not shown), a tube (not shown), and a pump (not shown) arranged on one side of the platen 103 in the scanning direction. In addition, a wiper member (not shown) is arranged adjacent to the maintenance unit on the platen 103 side of the maintenance unit. The wiper member is formed in a spatula shape and wipes the tip portions (also called nozzle surfaces or ink ejection surfaces) of the nozzles 102C of the inkjet head 102B as the carriage 102A moves. [Example]

[0057] Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited or restricted by the following examples and comparative examples.

[0058] (Preparation of pigment dispersion A) Pure water was added to 20% by mass of pigment (carbon black) and 7% by mass of styrene-acrylic acid copolymer neutralized with sodium hydroxide (acid value 175 mg KOH / g, molecular weight 10,000) to make a total of 100% by mass, and the mixture was stirred and mixed to obtain a mixture. This mixture was placed in a wet sand mill filled with 0.3 mm diameter zirconia beads and dispersed for 6 hours. The zirconia beads were then removed using a separator, and the mixture was filtered through a 3.0 μm pore size cellulose acetate filter to obtain pigment dispersion A. Styrene-acrylic acid copolymer is a water-soluble polymer commonly used as a pigment dispersant.

[0059] (Examples 1 to 14 and Comparative Examples 1 to 7) The components of the aqueous ink composition (Table 1) except for pigment dispersion A were mixed uniformly to obtain an ink solvent. Next, the ink solvent was added to pigment dispersion A and mixed uniformly. The resulting mixture was then filtered through a cellulose acetate type membrane filter (pore size 3.00 μm) manufactured by Toyo Roshi Kaisha, Ltd., to obtain the aqueous inks for inkjet recording of Examples 1 to 14 and Comparative Examples 1 to 7 shown in Table 1.

[0060] (Static and dynamic surface tension measurements) The static surface tension of the aqueous inks of Examples 1 to 14 and Comparative Examples 1 to 7 was measured using a "CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd. at a measurement temperature of 25° C. The measurement results obtained are shown in Table 1.

[0061] The aqueous inks of Examples 1 to 14 and Comparative Examples 1 to 7 were evaluated for (a) fixation to coated paper, (b) image quality: white streak-like unevenness (banding), and (c) maintenance (ink removability) using the following methods.

[0062] (a) Evaluation of fixation to coated paper Using an inkjet printer MFC-J6995CDW manufactured by Brother Industries, Ltd., single-color patch images were recorded on coated paper ("OK Topcoat+" manufactured by Oji Paper Co., Ltd.) using the aqueous inks of the examples and comparative examples to prepare evaluation samples. The evaluation samples were then dried at 100°C for 60 seconds. The surface of the evaluation sample was then rubbed once with a cotton swab from the area where the aqueous ink was recorded to the non-recorded area (blank area) (hereinafter referred to as the rub resistance test). The degree of peeling of the recorded area was then visually confirmed and evaluated according to the following evaluation criteria.

[0063] Evaluation of fixation to coated paper Evaluation criteria A: There was no change in the recorded area before and after the abrasion resistance test (no peeling). B: Peeling was observed in part of the recorded area before and after the abrasion resistance test. C: Peeling was observed in about half of the recorded area before and after the abrasion resistance test. D: Peeling was observed in the entire recorded area before and after the abrasion resistance test.

[0064] (b) Image quality: White streak-like unevenness (banding) evaluation An image including a black monochrome patch was printed at a resolution of 600 dpi x 300 dpi on plain paper (Xerox "4200") using the aqueous inks of the Examples and Comparative Examples using an inkjet printer MFC-J6995CDW manufactured by Brother Industries, Ltd. Evaluation samples were prepared by visually observing the evaluation samples and evaluating the presence of white streaks (banding) according to the following evaluation criteria.

[0065] White streak-like unevenness (banding) evaluation Evaluation criteria A: No white streak-like unevenness (banding) was observed. B: White spots were observed in some areas. C: White streak-like unevenness (banding) was observed in some parts. D: White streaks (banding) were observed throughout the entire surface.

[0066] (c) Maintenance (ink removal) evaluation 3 μL of each of the aqueous inks from the Examples and Comparative Examples was dropped onto a 52 mm × 40 mm nozzle tip (nozzle surface) of an inkjet head, and the head was stored for 24 hours in an environment of 40°C and 30% humidity. Hereinafter, the position where the aqueous ink was dropped will also be referred to as the "drop position." After storage, the inkjet head was installed in an inkjet printer MFC-J6995CDW manufactured by Brother Industries, Ltd., and maintenance was performed using a wipe at room temperature (20°C). After the maintenance, the nozzle tip was visually inspected and evaluated according to the following evaluation criteria.

[0067] Maintenance (ink removal) evaluation criteria A: There was no water-based ink residue at the tip of the nozzle (water-based ink had been removed). B: The water-based ink moved from the drop position, but there was water-based ink residue at the tip of the nozzle. C: Traces of water-based ink stretched from the drop position were observed. D: The water-based ink has not moved from the drop position.

[0068] Table 1 shows the compositions and evaluation results of the aqueous inks of Examples 1 to 14 and Comparative Examples 1 to 7.

[0069] [Table 1]

[0070] As shown in Table 1, in Examples 1 to 14, the evaluation results for fixation, image quality (white streak-like unevenness (banding)), and maintenance (ink removability) were all "D" or higher, indicating good results. Focusing on Examples 6 and 9, which had the same composition except for the Tg of the acrylic resin particles, Example 6, which used acrylic resin particles with a Tg of 31°C or higher, had better fixation to coated paper than Example 9, which used acrylic resin particles with a Tg of 30°C. Furthermore, among Examples 1 to 8 and 10 to 14, which used acrylic resin particles with a Tg of 31°C or higher, Examples 1, 6, and 10 to 14, which had the same composition except for the amount of trimethylglycine, were focused on. Examples 6 and 11 to 14, in which the amount of trimethylglycine was in the range of 2 to 9 wt%, all received evaluation results for fixation and maintenance (ink removability) of "B" or higher, indicating better results than Examples 1 and 10, in which the amount of trimethylglycine was outside the range of 2 to 9 wt%. Furthermore, looking at Examples 1, 6, and 10 to 14, Examples 6, 12, and 13, in which the amount of trimethylglycine was in the range of 3 to 8% by weight, all had evaluation results of "A" or higher for fixation and maintenance (ink removability), and were better than Examples 1, 10, 11, and 14, in which the amount of trimethylglycine was outside the range of 3 to 8% by weight.

[0071] Furthermore, as shown in Table 1, when attention is focused on Examples 1 to 3, 6, and 10 to 14, which have the same composition except for the HLB value of the silicone surfactant, Examples 1, 6, and 9 to 14, which used silicone surfactants with HLB values ​​of 12 or more, all received evaluation results of "A" or higher in image quality (white streak-like unevenness (banding)), which were better than Examples 2 and 3, which used silicone surfactants with HLB values ​​of less than 12. When attention is focused on Examples 4 to 8, which have the same composition except for the amount of silicone surfactant blended, Examples 5 to 7, in which the amount of silicone surfactant blended was within the range of 2 to 3 wt%, all received evaluation results of "A" or higher in image quality (white streak-like unevenness (banding)) and maintainability (ink removability), which were better than Examples 4 and 8, in which the amount of silicone surfactant blended was outside the range of 2 to 3 wt%.

[0072] Furthermore, as shown in Table 1, when focusing on Examples 1, 5 to 7, and 10 to 14, in which the Tg of the acrylic resin particles was 31°C or higher, the HLB value of the silicone surfactant was 12 or higher, and the amount of the silicone surfactant was within the range of 2 to 3% by weight, Examples 5 to 7, 12, and 13, in which R / B was within the range of 0.6 to 1.5, all received evaluation results of "A" or higher for fixation, image quality (white streak-like unevenness (banding)), and maintenance (ink removability), which were better than Examples 1, 10, 11, and 14, in which R / B was outside the range of 0.6 to 1.5. Similarly, looking at Examples 1, 5 to 7, and 10 to 14, in Examples 5 to 7, 12, and 13, where (P+R) / B=1.2 to 3.2, the evaluation results for fixation, image quality (white streak-like unevenness (banding)), and maintenance (ink removability) were all "A" or higher, and were better than Examples 1, 10, 11, and 14, where (P+R) / B=outside the range of 1.2 to 3.2.

[0073] On the other hand, as shown in Table 1, in Comparative Examples 1 to 7, at least one of the evaluation results of fixation, image quality (white streak-like unevenness (banding)), and maintenance (ink removability) was "D." In Comparative Example 1, in which ester-based resin particles were used instead of the acrylic resin particles, the evaluation results of both fixation and maintenance (ink removability) were poor. In Comparative Example 2, in which acrylic resin particles having a Tg of less than 25°C were used, the evaluation results of both fixation and maintenance (ink removability) were poor. In Comparative Example 3, in which acrylic resin particles having a Tg of 50°C or higher were used, the evaluation result of fixation was poor. In Comparative Example 4, in which 3-aminopropanoic acid was used instead of trimethylglycine, the evaluation result of maintenance (ink removability) was poor. In Comparative Example 5, in which glycerin was used instead of trimethylglycine, the evaluation result of fixation was poor. In Comparative Example 6, in which propylene glycol was used instead of trimethylglycine, the evaluation result of maintenance (ink removability) was poor. Furthermore, in Comparative Example 7, in which the static surface tension was 28 mN / m, the evaluation result of image quality (white streak-like unevenness (banding)) was poor. [Industrial Applicability]

[0074] As described above, the aqueous ink of the present invention has excellent fixability, image quality, and maintainability, and can be fixed on coated paper at a lower temperature and in a shorter drying time. The use of the aqueous ink of the present invention is not limited to inkjet recording on coated paper, but can also be widely applied to inkjet recording on various recording media such as plain paper, glossy paper, and matte paper. [Explanation of symbols]

[0075] 100 Inkjet recording device 101 Paper tray 102A Carriage 102B Inkjet head (ink ejection means) 102C Nozzle 103 Platen 104 Drying means 105 Paper output tray

Claims

1. The ink contains a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water, the acrylic resin particles have a glass transition temperature of 25°C or higher and lower than 50°C; The blending amount of the trimethylglycine is 2% by weight or more and 9% by weight or less, A water-based ink for ink-jet recording, characterized in that the static surface tension is 27 mN / m or less.

2. A composition comprising a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water, the acrylic resin particles have a glass transition temperature of 25°C or higher and lower than 50°C; The blending amount of the acrylic resin particles and the blending amount of the trimethylglycine satisfy the following condition (X): A water-based ink for ink-jet recording, characterized in that the static surface tension is 27 mN / m or less. Condition (X): 0.6≦R / B≦1.5 R: solid content of the acrylic resin particles (wt%) B: Amount of trimethylglycine (wt%)

3. A composition comprising a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water, the acrylic resin particles have a glass transition temperature of 25°C or higher and lower than 50°C; the blending amounts of the pigment, the blending amounts of the acrylic resin particles, and the blending amounts of the trimethylglycine satisfy the following condition (Y), A water-based ink for ink-jet recording, characterized in that the static surface tension is 27 mN / m or less. Condition (Y): 1.2≦(P+R) / B≦3.2 P: solid content of the pigment (wt%) R: solid content of the acrylic resin particles (wt%) B: Amount of trimethylglycine (wt%)

4. A coating composition comprising a pigment, acrylic resin particles, a surfactant, trimethylglycine, and water, the acrylic resin particles have a glass transition temperature of 25°C or higher and lower than 50°C; The blending amount of the water is 70% by weight or more, A water-based ink for ink-jet recording, characterized in that the static surface tension is 27 mN / m or less.

5. An aqueous ink for inkjet recording as described in claim 4, wherein the amounts of substances that are solid at room temperature, including the pigment and the acrylic resin particles, the amounts of substances that are liquid at room temperature excluding water, and the amount of water satisfy the following condition (Z). Condition (Z): L<S<W S: Amount of the solid substance (wt%) L: Amount of the liquid substance (wt%) W: Amount of water blended (wt%)

6. The water-based ink for ink-jet recording according to any one of claims 1 to 5, wherein the acrylic resin particles have a glass transition temperature of 30°C or higher.

7. 7. The water-based ink for ink-jet recording according to claim 1, wherein the blending amount of the trimethylglycine is 3% by weight or more and 8% by weight or less.

8. The water-based ink for ink-jet recording according to any one of claims 1 to 7, wherein the surfactant is a silicone-based surfactant.

9. The water-based ink for ink-jet recording according to any one of claims 1 to 8, wherein the surfactant has an HLB value of 12 or more.

10. The water-based ink for ink-jet recording according to any one of claims 1 to 9, wherein the blending amount of the surfactant is 2% by weight or more and 3% by weight or less.

11. an ink container and an ink ejection means; an inkjet recording apparatus in which the ink contained in the ink containing section is discharged by the ink discharge means, Further, the recording medium includes a drying unit that heats and dries the ink recorded by the ink discharged by the ink discharge unit, An inkjet recording apparatus, wherein the ink reservoir contains the water-based ink for inkjet recording according to any one of claims 1 to 10.

12. a recording step of ejecting a water-based ink onto a recording medium by an inkjet method; a fixing step of fixing the water-based ink adhered to the recording medium in the recording step to the recording medium using a drying means that heats the recording portion of the recording medium, An inkjet recording method, wherein the inkjet recording water-based ink according to any one of claims 1 to 10 is used as the water-based ink in the recording step.

13. An ink container containing a water-based ink for ink-jet recording, wherein the water-based ink is the water-based ink for ink-jet recording according to any one of claims 1 to 10.

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