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 can improve scratch resistance in coat paper recording.SOLUTION: Aqueous ink for inkjet recording contains a pigment, resin particles, a solvent and water, where the resin particles are an acrylic polymer, and a storage elastic modulus E' at 25°C of a dried and solidified ink film is 9.7×108 Pa or more. The solvent may contain, for example, both diol and glycol ether. The glycol ether may be two or more kinds.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] It is known that aqueous inks have a problem with abrasion resistance in that a portion of the pigment ejected onto a recording medium remains on the surface of the recording medium and peels off when the recording medium is rubbed with a finger, etc. One known solution to this problem is a method of improving the abrasion resistance of the recording medium by adding a polymer to the aqueous ink, as disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-273892 Summary of the Invention [Problem to be solved by the invention]

[0004] Inkjet recording using aqueous inks for jet recording is required to achieve higher image quality and higher speeds, and accordingly, aqueous inks for inkjet recording are required to have further improved abrasion resistance when recording on coated paper.

[0005] Therefore, an object of the present invention is to provide a water-based ink for ink-jet recording that improves abrasion resistance when recording on coated paper. [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: pigment, resin particles, solvent, and water; the resin particles are acrylic polymers, The storage modulus E' of the dried ink film at 25°C is 9.7 × 10 8 Pa or more. [Effects of the Invention]

[0007] The water-based ink for ink-jet recording of the present invention has a storage modulus E' within a predetermined range, and contains the solvent in addition to the resin particles, thereby improving the abrasion resistance during recording on coated paper. [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 of the present invention (hereinafter sometimes referred to as "water-based ink" or "ink") is suitably usable for inkjet recording on coated paper, but is 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, resin particles, a solvent, and water.

[0011] The pigment is not particularly limited and may be, for example, carbon black, inorganic pigments, or 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 may 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 Corporation; "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 and the like (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 resin particles that are acrylic polymers, and a solvent.

[0018] In the aqueous ink, for example, the lower limit of the storage modulus E' of the dried ink film at 25°C is 9.7 × 10 8 Pa or more, 2.1×10 9 Pa or more, and the upper limit is 6.5 × 10 9 Pa or less, 7.3×10 9 However, the upper limit is merely an example and is not limited thereto. For example, it is 7.3×10 9 Pa or more, 1.0×10 10 The storage modulus E' may be equal to or greater than Pa. Here, the "storage modulus E'" is a parameter that expresses the hardness of a sample (dried ink film) in a tensile test. The storage modulus E' can be measured as dynamic viscoelasticity in accordance with, for example, Japanese Industrial Standard JIS-K7244 Part 4: Tensile vibration-non-resonance method.

[0019] The method for producing the ink film is not particularly limited, and the ink film can be produced, for example, by the method described in the examples below.

[0020] The method for measuring the storage modulus E' is not particularly limited, and it can be measured, for example, by the method described in the Examples below.

[0021] In the aqueous ink, the glass transition temperature (Tg) of the resin particles may be, for example, 24° C. or higher and lower than 80° C., or 49° C. or higher and lower than 80° C. From the viewpoint of the environmental temperature when the aqueous ink of the present invention is used, the glass transition temperature (Tg) of the resin particles may be, for example, room temperature or higher, specifically, 24° C. or higher and lower than 80° C., 30° C. or higher and lower than 80° C., or 49° C. or higher and lower than 80° C.

[0022] The resin particles may be contained in, for example, a resin emulsion. The resin emulsion is composed of, for example, the resin particles and a dispersion medium (e.g., water), and the resin particles are not dissolved in the dispersion medium but are dispersed with a specific particle diameter. The resin particles may be, for example, a commercially available product. The 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. The resin particles may be used alone or in combination of two or more kinds.

[0023] Commercially available resin particles include, for example, "Mowinyl (registered trademark) 6899D" (Tg: 49°C, active ingredient concentration: 46% by weight), "Mowinyl (registered trademark) 6800D" (Tg: 80°C, active ingredient concentration: 43% by weight), "Mowinyl (registered trademark) 5450" (Tg: 53°C, active ingredient concentration: 20% by weight), and "Mowinyl (registered trademark) DM774" (Tg: 30°C, active ingredient concentration: 46% by weight), all manufactured by Japan Coating Resins Co., Ltd.; and "Saivinol (registered trademark) EK-61" (Tg: 24°C, active ingredient concentration: 39% by weight), and "Saivinol (registered trademark) EK-1920" (Tg: 40°C, active ingredient concentration: 35% by weight), all manufactured by Saiden Chemical Co., Ltd.

[0024] In the aqueous ink, the solid content of the 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 resin particles is, for example, 1% by weight to 10% by weight, 3% by weight to 7% by weight, or 4.3% by weight to 5.0% by weight. Note that, for example, when a resin emulsion containing the resin particles is used, the "equivalent to the amount of active ingredients" refers to the amount of the resin particles themselves excluding the dispersion solvent such as water.

[0025] The average particle diameter of the 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."

[0026] In the aqueous ink, the solvent includes both a diol and a glycol ether. Examples of the diol include 1,2-hexanediol, 1,6-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, 2-methyl-2,4-pentanediol, and 3-methyl-1,5-pentanediol. As the solvent, one type of diol may be used alone, or two or more types of diols may be used in combination.

[0027] Examples of the glycol ether include dipropylene glycol monopropyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, 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, 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, and tripropylene glycol-n-butyl ether. As the solvent, one type of glycol ether may be used alone, or two or more types of glycol ethers may be used in combination. The combination of two or more glycol ethers is not particularly limited and can be determined appropriately. Specific examples include a combination of dipropylene glycol monopropyl ether with at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether.

[0028] The solvent may be, for example, a commercially available product, such as "DOWANOL (registered trademark) PM," "DOWANOL (registered trademark) DPM," "DOWANOL (registered trademark) TPM," "DOWANOL (registered trademark) PnP," "DOWANOL (registered trademark) DPnP," "DOWANOL (registered trademark) PnB," "DOWANOL (registered trademark) DPnB," or "DOWANOL (registered trademark) TPnB," manufactured by The Dow Chemical Company.

[0029] The amount of the solvent relative to the total amount of the water-based ink is not particularly limited and can be determined appropriately, for example, 3% by weight to 15% by weight, 5% by weight to 12% by weight, or 6% by weight to 10% by weight.

[0030] The amount (A) of dipropylene glycol monopropyl ether and the amount (B) of at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether in the total amount of the aqueous ink may satisfy, for example, B / A≦1 (hereinafter also referred to as condition X). The amounts (A) and (B) may be appropriately adjusted to satisfy condition X, and the amount (A) may be, for example, 1% to 15% by weight, 1% to 10% by weight, or 1% to 5% by weight, and the amount (B) may be, for example, 1% to 20% by weight, 1% to 10% by weight, or 1% to 5% by weight. The lower limit of condition X may be, for example, 0.8, 0.4, or 0.2, but is not limited thereto, and may be, for example, 0.2 or less or 0.1 or less.

[0031] The water-based ink has a storage modulus E' of 9.7 x 10 8By including resin particles that are acrylic polymers and a solvent, the abrasion resistance of the ink film formed on coated paper can be improved by drying at a lower temperature and in a shorter time. The mechanism by which the abrasion resistance of the ink film formed on a recording medium is improved by drying at a lower temperature and in a shorter time is presumed to be as follows: Adding resin particles to aqueous inks is commonly used to improve the abrasion resistance of coated paper. Resin particles that form hard, strong coatings have a glass transition temperature (Tg) higher than room temperature, which correlates with a minimum film-forming temperature (the minimum temperature at which resin particles fuse together to form a film) higher than room temperature. Therefore, unless the ink is heated and dried at a temperature above the minimum film-forming temperature, the aqueous ink coating formed on the coated paper will be soft and brittle, i.e., will have poor abrasion resistance. Thus, there is a trade-off between resin particles that form hard, strong coatings and the temperature and drying time. In contrast, by adding the solvent to the aqueous ink, the minimum film-forming temperature of the resin particles is lowered, so that the temperature can reach or exceed the minimum film-forming temperature even with low-temperature and short-time heating, making it possible to form a hard and strong coating film, i.e., improve abrasion resistance. However, this mechanism is merely speculation, and the present invention is not limited thereto. The drying temperature will be explained later in the inkjet recording method of the present invention.

[0032] On the other hand, depending on the combination of certain resin particles and solvent, there is a problem that the viscosity of the aqueous ink changes over time, i.e., the storage stability decreases. As a result, the coating film may soften, i.e., the abrasion resistance may decrease. In response to this, by adding resin particles that are acrylic polymers to the aqueous ink, both the storage stability and the abrasion resistance are excellent. Furthermore, for example, the storage modulus E' of the dried ink film at 25°C is 9.7 × 10 8 By combining resin particles having a viscosity of 100 Pa or more with a solvent, both storage stability and abrasion resistance are improved. Furthermore, for example, by combining resin particles that are acrylic polymers with a solvent containing both a diol and a glycol ether, both storage stability and abrasion resistance are improved. However, this mechanism is merely speculation, and the present invention is not limited thereto.

[0033] Furthermore, the aqueous ink of the present invention does not require a high-output heating mechanism or a heating mechanism that requires long-term heating, and therefore can be applied to small printers. For the same reason, the inkjet recording apparatus of the present invention can be made smaller. For the same reason, the inkjet recording method of the present invention can be implemented at low cost.

[0034] The aqueous ink of the present invention dries at a lower temperature in a shorter time, and the abrasion resistance of the ink film formed on coated paper is also improved, so that, for example, users can safely print using the aqueous ink of the present invention.

[0035] The aqueous ink may further contain a water-soluble organic solvent other than the solvent described above. Examples of the water-soluble organic solvent include 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The aqueous ink may further contain conventionally known additives as needed. Examples of the additives include surfactants, pH adjusters, viscosity adjusters, surface tension adjusters, and antifungal agents. Examples of the viscosity adjusters include polyvinyl alcohol, cellulose, and water-soluble resins.

[0041] 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.

[0042] Next, the ink jet recording apparatus and ink jet recording method of the present invention will be described.

[0043] 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.

[0044] The drying means may be configured to apply a drying force of, for example, 44 J / cm to the ink-recorded portion. 3 Above, 131J / cm 3 In other words, the drying means may provide a heat amount of 1 cm 3 This means that the heat generated is enough to raise the temperature of the ink by 10 to 30°C. This allows stable, high-quality image formation.

[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, for example, in the fixing step, the ink is applied with 44 J / cm 3 Above, 131J / cm 3 In other words, in the ink jet recording method of the present invention, the amount of heat to be applied is 1 cm 3 This means that the heat generated is enough to raise the temperature of the ink by 10 to 30°C. This allows stable, high-quality image formation.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The drying means 104 heats and dries the recording 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 adjusted appropriately 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 adjusted appropriately by changing the settings of the drying means 104, for example, from more than 0 seconds to 300 seconds or less, 0.05 to 60 seconds, or 0.07 to 30 seconds. Compared to conventional aqueous inks that require high-temperature, long-term heat drying, the aqueous ink of the present invention can be dried at a lower temperature and in a shorter time, thereby improving the abrasion resistance of the ink film formed on coated paper. The drying means 104 may be any device capable of heat-drying the recording 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.

[0055] 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.

[0056] After the recording and drying, the recording paper P is conveyed to a paper discharge tray 105. It is possible to improve the abrasion resistance of the ink film recorded on the recording medium P without requiring a complicated configuration.

[0057] 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 tips (ink ejection surfaces) of the nozzles 102C of the inkjet head 102B as the carriage 102A moves. [Example]

[0058] 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.

[0059] (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.

[0060] (Examples 1 to 11 and Comparative Examples 1 to 11) The components in 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 aqueous inks for inkjet recording of Examples 1 to 11 and Comparative Examples 1 to 11.

[0061] (Method of producing ink film) The ink was dropped onto a Teflon (registered trademark) petri dish and dried in a thermostatic chamber at 100°C for 6 hours to obtain an ink film with an average thickness of 0.4 mm. This ink film was then cut into a rectangular shape with a width of 10 mm to prepare a test piece for measuring the storage modulus E'.

[0062] (Method for measuring storage modulus E') First, the test piece was set in a dynamic viscoelasticity measuring device (TA Instruments "RSA-G2") at 20°C and then cooled to -60°C. After reaching -60°C, dynamic viscoelasticity was measured under the following measurement conditions. The obtained measurement data was taken as "storage modulus E' at 25°C." Measurement temperature range: -60℃~100℃ Heating rate: 2.5℃ / min Frequency: 10Hz ·Initial strain: 0.1% Clamp distance: 10mm

[0063] For the water-based inks of Examples 1 to 11 and Comparative Examples 1 to 11, (a) the rub resistance of the ink film recorded on coated paper was evaluated, and (b) the storage stability was evaluated by the following methods.

[0064] (a) Evaluation of the abrasion resistance of ink films printed on coated paper A contact-type plate heater was used to heat coated paper ("OK Topcoat+" manufactured by Oji Paper Co., Ltd.) until its surface temperature reached 50°C. The surface temperature was measured using a non-contact thermometer. Next, a solid image was recorded on the coated paper using the aqueous inks of the examples and comparative examples using an inkjet printer MFC-J6995CDW manufactured by Brother Industries, Ltd. Next, one second after the paper was ejected, the surface of the solid image was rubbed with a cotton swab under a load of 1 kg. Thereafter, the optical density (OD value) at three points in the solid image was measured using a spectrophotometer SpectroEye manufactured by X-Rite (light source: D50, viewing angle: 2°, ANSI-T), and the average value was calculated. The optical density (OD value) of the coated paper was evaluated according to the following evaluation criteria.

[0065] Evaluation of the abrasion resistance of ink film printed on coated paper Evaluation criteria A: The decrease in optical density (OD value) from when the surface of the solid image was not rubbed was 5% or less. B: The rate of decrease in optical density (OD value) from when the surface of the solid image was not rubbed was more than 5% but 10% or less. C: The rate of decrease in optical density (OD value) compared to when the surface of the solid image was not rubbed exceeded 10%.

[0066] (b) Storage stability evaluation The aqueous inks of the Examples and Comparative Examples immediately after preparation and viscosity measurement were placed in a sealed container and stored in an environment of 60°C for two weeks. The viscosity of the evaluation samples thus prepared was measured, and the storage stability was evaluated according to the following evaluation criteria. The viscosity was measured at 25°C using a cone-plate viscometer (TVE-25 manufactured by Toki Sangyo Co., Ltd.).

[0067] Storage stability evaluation Evaluation criteria A: In the evaluation sample, the rate of change in viscosity from immediately after preparation was 5% or less. B: In the evaluation sample, the rate of change in viscosity from immediately after preparation was more than 5% and 10% or less. C: In the evaluation sample, the rate of change in viscosity from immediately after preparation exceeded 10%.

[0068] Table 1 shows the compositions and evaluation results of the aqueous inks of Examples 1 to 11 and Comparative Examples 1 to 11.

[0069] [Table 1]

[0070] As shown in Table 1, in Examples 1 to 11, the evaluation results for abrasion resistance and storage stability were all "B" or higher, which were good. Focusing on Examples 1 and 9 to 11, which have the same components except for the storage modulus E' of the dried ink film at 25°C, the storage modulus E' was 2.1 × 10 9In Examples 1 and 11, the evaluation results for abrasion resistance and storage stability were all "A" or higher, and the storage modulus E' was 2.1 x 10 9 The storage modulus E' was 9.7 × 10 Pa or less, which was better than that of Examples 9 and 10. 8 Focusing on Examples 1 to 5, which have the same composition except for the Tg of the resin particles, Examples 1 to 3, which used resin particles with a Tg of 49°C or higher, all had storage stability evaluation results of "A" or higher, and were superior to Examples 4 to 5, which used resin particles with a Tg of less than 49°C.

[0071] On the other hand, as shown in Table 1, in Comparative Examples 1 to 11, at least one of the evaluation results of abrasion resistance and storage stability was "C." In Comparative Example 1, in which a styrene-butadiene polymer was used instead of the acrylic polymer, and Comparative Example 2, in which a urethane polymer was used, the evaluation results of both abrasion resistance and storage stability were poor. The storage modulus E' was 9.7 x 10 8 In Comparative Examples 3 and 4, where the viscosity was 0.1 Pa or less, the evaluation results for abrasion resistance were poor. In Comparative Examples 5 and 8, in which butyl triglycol was used as the glycol ether, the evaluation results for abrasion resistance were poor. Furthermore, in Comparative Example 8, the evaluation results for storage stability were also poor. The mechanism behind the poor evaluation results for storage stability in Comparative Example 8 is presumed to be, for example, that the amount of resin particles added was increased compared to Comparative Example 5, thereby amplifying the interaction with the solvent butyl triglycol and reducing the storage stability, but this presumption is not limiting. In Comparative Example 6, in which 1,2-pentanediol was used as the diol, the evaluation results for abrasion resistance were poor. In Comparative Example 7, in which propylene glycol was used as the diol, the evaluation results for abrasion resistance were poor. In Comparative Example 9, in which tripropylene glycol monomethyl ether was used instead of dipropylene glycol monopropyl ether, the evaluation results for both abrasion resistance and storage stability were poor. In Comparative Example 10, in which dipropylene glycol monobutyl ether was used as the glycol ether, and Comparative Example 11, in which tripropylene glycol monobutyl ether was used, the evaluation results of both the abrasion resistance and the storage stability were poor.

[0072] Some or all of the above embodiments and examples may be described as, but are not limited to, the following supplementary notes. (Appendix 1) pigment, resin particles, solvent, and water; the resin particles are acrylic polymers, The storage modulus E' of the dried ink film at 25°C is 9.7 × 10 8 A water-based ink for ink-jet recording characterized by a viscosity of 100 Pa or more. (Appendix 2) The storage modulus E' of the dried ink film at 25°C is 2.1 × 10 9 Attachment 1: The water-based ink for ink-jet recording according to Appendix 1, wherein the viscosity of the ink is 100 Pa or more. (Appendix 3) 3. The water-based ink for ink-jet recording according to claim 1, wherein the solvent contains both a diol and a glycol ether. (Appendix 4) 4. The water-based ink for ink-jet recording according to claim 3, wherein the diol is at least one of 1,2-hexanediol and 1,6-hexanediol. (Appendix 5) 5. The water-based ink for ink-jet recording according to claim 3 or 4, comprising two or more types of glycol ether. (Appendix 6) 6. The water-based ink for ink-jet recording according to claim 5, wherein one of the two or more glycol ethers is dipropylene glycol monopropyl ether, and the other is at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether. (Appendix 7) 7. The water-based ink for ink-jet recording according to claim 6, wherein the blending amount of the solvent is 6% by weight or more and 10% by weight or less, and the following condition (X) is satisfied: Condition (X): B / A≦1 A: Amount of dipropylene glycol monopropyl ether blended (wt%) B: Amount (wt%) of at least one of the propylene glycol monopropyl ether and the propylene glycol monobutyl ether (Appendix 8) pigment, resin particles, solvent, and water; the resin particles are acrylic polymers, The water-based ink for ink-jet recording, wherein the solvent contains both a diol and a glycol ether. (Appendix 9) 9. The water-based ink for ink-jet recording according to claim 8, wherein the diol is at least one of 1,2-hexanediol and 1,6-hexanediol. (Appendix 10) 10. The water-based ink for ink-jet recording according to claim 8 or 9, comprising two or more types of glycol ether. (Appendix 11) 11. The water-based ink for ink-jet recording according to claim 10, wherein one of the two or more glycol ethers is dipropylene glycol monopropyl ether, and the other is at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether. (Appendix 12) 12. The water-based ink for ink-jet recording according to claim 11, wherein the blending amount of the solvent is 6% by weight or more and 10% by weight or less, and the following condition (X) is satisfied: Condition (X): B / A≦1 A: Amount of dipropylene glycol monopropyl ether blended (wt%) B: Amount (wt%) of at least one of the propylene glycol monopropyl ether and the propylene glycol monobutyl ether (Appendix 13) The storage modulus E' of the dried ink film at 25°C is 9.7 × 10 8 13. The water-based ink for ink-jet recording according to any one of Appendices 8 to 12, wherein the viscosity of the ink is 100 Pa or more. (Appendix 14) The storage modulus E' of the dried ink film at 25°C is 2.1×10 9Attachment 14. The water-based ink for ink-jet recording according to claim 13, wherein the viscosity of the ink is 100 Pa or more. (Appendix 15) 15. The water-based ink for ink-jet recording according to any one of claims 1 to 14, wherein the pigment is carbon black. (Appendix 16) 16. The water-based ink for ink-jet recording according to any one of claims 1 to 15, wherein the resin particles have a glass transition temperature of 24°C or higher and 80°C or lower. (Appendix 17) 17. The water-based ink for ink-jet recording according to claim 16, wherein the resin particles have a glass transition temperature of 49° C. or higher. (Appendix 18) 18. The water-based ink for ink-jet recording according to any one of claims 1 to 17, wherein the blending amount of the resin particles is 4.3% by weight or more and 5.0% by weight or less. (Appendix 19) 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 device, wherein the ink reservoir contains the water-based ink for inkjet recording according to any one of appendices 1 to 18. (Appendix 20) The drying means applies 44 J / cm to the ink-recorded portion. 3 Above, 131J / cm 3 20. The inkjet recording apparatus according to claim 19, which applies the following amount of heat: (Appendix 21) 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 a recording portion of the recording medium, An inkjet recording method, wherein the water-based ink for inkjet recording described in any one of Appendices 1 to 18 is used as the water-based ink in the recording step. (Appendix 22) The fixing step uses a drying means for heating the recorded portion of the recording medium, and applies 44 J / cm 3 Above, 131J / cm 3 22. The inkjet recording method according to claim 21, wherein the water-based ink is fixed to the recording medium by applying the following amount of heat: (Appendix 23) 23. The inkjet recording method according to claim 21, wherein the recording medium is coated paper. (Appendix 24) 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 described in any one of Appendices 1 to 18. [Industrial Applicability]

[0073] As described above, the aqueous ink of the present invention can be fixed on coated paper with shorter drying times at lower temperatures, and the use of the aqueous ink of the present invention is not limited to inkjet recording on coated paper, but can be widely applied to inkjet recording on various recording media such as plain paper, glossy paper, and matte paper. [Explanation of symbols]

[0074] 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. It contains all of the pigment, resin particles, solvent, and water. the resin particles are an acrylic polymer having a glass transition temperature of 24° C. or higher and 80° C. or lower; The solvent includes both a diol and a glycol ether; the diol is at least one of 1,2-hexanediol and 1,6-hexanediol; The blending amount of the solvent is 6% by weight or more and 10% by weight or less, and satisfies the following condition (X): The storage modulus E' of the dried ink film at 25°C is 9.7 x 10 ８ 2. A water-based ink for ink-jet recording, characterized in that the viscosity of the ink is 100 Pa or more. Condition (X): B / A≦1 A: Amount of dipropylene glycol monopropyl ether (wt%) B: Amount (wt%) of at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether

2. The storage modulus E' of the dried ink film at 25°C is 2.1 x 10 ９ The water-based ink for ink-jet recording according to claim 1, wherein the viscosity of the ink is 100 Pa or more.

3. The water-based ink for ink-jet recording according to claim 1 or 2, comprising two or more types of glycol ether.

4. 4. The water-based ink for ink-jet recording according to claim 3, wherein one of the two or more glycol ethers is dipropylene glycol monopropyl ether and the other is at least one of propylene glycol monopropyl ether and propylene glycol monobutyl ether.

5. The water-based ink for ink-jet recording according to any one of claims 1 to 4, wherein the pigment is carbon black.

6. The water-based ink for ink-jet recording according to any one of claims 1 to 5, wherein the resin particles have a glass transition temperature of 49°C or higher.

7. 7. The water-based ink for ink-jet recording according to claim 1, wherein the blending amount of the resin particles is 4.3% by weight or more and 5.0% by weight or less.

8. 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 7.

9. The drying means applies 44 J / cm to the ink-recorded portion. ３ Above, 131J / cm ３ 9. The ink jet recording apparatus according to claim 8, wherein the following heat quantity is applied:

10. 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 water-based ink for inkjet recording according to any one of claims 1 to 7 is used as the water-based ink in the recording step.

11. The fixing step uses a drying means for heating the recorded portion of the recording medium, and applies a heat of 44 J / cm ３ Above, 131J / cm ３ The ink-jet recording method according to claim 10, wherein the water-based ink is fixed to the recording medium by applying the following amount of heat:

12. 12. The inkjet recording method according to claim 10, wherein the recording medium is coated paper.

13. An ink container containing a water-based ink for ink-jet recording, wherein the water-based ink for ink-jet recording is the water-based ink for ink-jet recording according to any one of claims 1 to 7.

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