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

Abstract

To provide a water-based ink for inkjet recording that has improved color saturation and enables a reduction of VOC generation.SOLUTION: A water-based ink for inkjet recording includes water, a colorant, and a water-soluble organic solvent. The water-soluble organic solvent includes a penetrating agent and a wetting agent. The penetrating agent includes a compound of formula (1), and the wetting agent includes a specific compound such as tripropylene glycol or dipropylene glycol. In formula (1), x is 4 or more, and y is 2 or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] A known method for improving the saturation of a recorded matter using a water-based ink for inkjet recording is to increase the concentration of a colorant in the water-based ink for inkjet recording (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2009-533526 Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the colorant concentration increases the cost and decreases the stability of the aqueous ink.

[0005] Furthermore, from the perspective of protecting the global environment, there is a need to reduce the generation of VOCs (volatile organic compounds).

[0006] Therefore, an object of the present invention is to provide an aqueous dye ink for inkjet recording that can improve saturation without increasing the colorant concentration and can reduce VOC emissions. [Means for solving the problem]

[0007] In order to achieve the above object, the water-based ink for ink-jet recording of the present invention comprises: Contains water, a colorant, and a water-soluble organic solvent, the water-soluble organic solvent includes a penetrating agent and a wetting agent; The penetrating agent contains a compound represented by the following formula (1): The wetting agent is characterized by containing a compound represented by the following formula (2): [ka] In formula (1), x is 4 or greater, y is 2 or greater. [ka] In equation (2), x is 2 or greater. [Effects of the Invention]

[0008] The water-based ink for ink-jet recording of the present invention contains water, a colorant, and a specific water-soluble organic solvent, and therefore can increase saturation and reduce VOC emissions. [Brief explanation of the drawings]

[0009] [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

[0010] In the present invention, "mass" may be read as "weight" unless otherwise specified. For example, "mass ratio" may be read as "weight ratio" unless otherwise specified, and "mass%" may be read as "weight%" unless otherwise specified.

[0011] In the present invention, chroma (C * ) is, for example, the L standardized by the International Commission on Illumination (CIE) in 1976. * a * b * Color system (CIE1976(L) * a * b * ) color system) based on a* and b * It is calculated from the following formula (see JIS Z 8729): C * ={(a *2 )+(b *2 )} 1 / 2

[0012] The water-based ink for ink-jet recording (hereinafter, sometimes referred to as "water-based ink" or "ink") of the present invention will be described. The water-based ink of the present invention contains water, a colorant, and a water-soluble organic solvent.

[0013] The water may be ion-exchanged water, pure water, or the like. The amount of water 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 may be, for example, 50.0% to 95.0% by mass, 55.0% to 90.0% by mass, or 60.0% to 80.0% by mass.

[0014] The colorant may be either a pigment or a dye, and a mixture of a pigment and a dye may also be used as the colorant.

[0015] 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; Examples of pigments suitable for the aqueous ink of the present invention include 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. The aqueous ink of the present invention may be prepared by dispersing the pigment in water with a dispersant. Examples of the dispersant include, for example, a common polymer dispersant (pigment dispersion resin, resin dispersant), which may be prepared in-house. Furthermore, in the aqueous ink of the present invention, the pigment may be encapsulated in a polymer.

[0016] 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).

[0017] 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 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.

[0018] The pigment may be used alone or in combination of two or more types. The solid content of the pigment (pigment solid content amount) in the total amount of the aqueous ink is not particularly limited and can be determined appropriately. The pigment solid content amount is, for example, 0.1% by mass to 20.0% by mass, 1.0% by mass to 10.0% by mass, or 2.0% by mass to 8.0% by mass. The pigment solid content amount is the mass of the pigment only, and does not include the mass of the resin dispersant and the like (i.e., converted into the amount of active ingredients).

[0019] The dye is not particularly limited, and examples thereof include direct dyes, acid dyes, basic dyes, reactive dyes, and food dyes. Specific examples of the dyes include CI Direct Black, CI Direct Blue, CI Direct Red, CI Direct Yellow, CI Direct Orange, CI Direct Violet, CI Direct Brown, CI Direct Green, CI Acid Black, CI Acid Blue, CI Acid Red, CI Acid Yellow, CI Acid Orange, CI Acid Violet, CI Basic Black, CI Basic Blue, CI Basic Red, CI Basic Violet, CI Reactive Blue, CI Reactive Red, CI Reactive Yellow, CI Food Black, CI Food Red, and CI Food Yellow. Examples of the CI Direct Black include CI Direct Black 17, 19, 22, 31, 32, 51, 62, 71, 74, 108, 112, 113, 146, 154, 168, and 195. Examples of the CI Direct Blue include CI Direct Blue 1, 6, 15, 22, 25, 41, 71, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, and 226. Examples of the CI Direct Red include CI Direct Red 1, 2, 4, 9, 11, 17, 20, 23, 24, 28, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, and 230. Examples of the CI Direct Yellow include CI Direct Yellow 8, 11, 12, 24, 26, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, 142, and 173. Examples of the CI Direct Orange include CI Direct Orange 34, 39, 44, 46, and 60. Examples of the CI Direct Violet include CI Direct Violet 47 and 48.Examples of the CI Direct Brown include CI Direct Brown 109. Examples of the CI Direct Green include CI Direct Green 59. Examples of the CI Acid Black include CI Acid Black 2, 7, 24, 26, 31, 48, 51, 52, 63, 110, 112, 115, 118, and 156. Examples of the CI Acid Blue include CI Acid Blue 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 93, 100, 102, 104, 117, 120, 127, 138, 158, 161, 167, 220, and 234. Examples of the CI Acid Red include CI Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 80, 83, 85, 87, 89, 92, 94, 106, 114, 115, 133, 134, 145, 158, 180, 198, 249, 256, 265, 289, 315, and 317. Examples of the CI Acid Yellow include CI Acid Yellow 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 61, 71, 76, 98, and 99. Examples of the CI Acid Orange include CI Acid Orange 7 and 19. Examples of the CI Acid Violet include CI Acid Violet 49. Examples of the CI Basic Black include CI Basic Black 2. Examples of the CI Basic Blue include CI Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, and 29. Examples of the CI Basic Red include CI Basic Red 1, 2, 9, 12, 13, 14, and 37. Examples of the CI Basic Violet include CI Basic Violet 7, 14, and 27.Examples of the CI Reactive Blue include CI Reactive Blue 4, 5, 7, 13, 14, 15, 18, 19, 21, 26, 27, 29, 32, 38, 40, 44, and 100. Examples of the CI Reactive Red include CI Reactive Red 7, 12, 13, 15, 17, 20, 23, 24, 31, 42, 45, 46, and 59. Examples of the CI Reactive Yellow include CI Reactive Yellow 2, 3, 17, 25, 37, and 42. Examples of the CI Food Black include CI Food Black 1 and 2. Examples of the CI Food Red include CI Food Red 87, 92, and 94. Examples of the CI Food Yellow include CI Food Yellow 3.

[0020] The dye may be used alone or in combination of two or more. The content of the dye in the total amount of the aqueous ink is, for example, 0.1% by mass to 10.0% by mass, 0.2% by mass to 8.0% by mass, or 0.3% by mass to 6.0% by mass.

[0021] As described above, the water-based ink of the present invention further contains a water-soluble organic solvent, which contains at least a penetrating agent and a wetting agent.

[0022] Examples of the penetrating agent include alkylene diols and glycol ether compounds. Examples of the alkylene diols 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-based 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, 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, and tripropylene glycol-n-butyl ether. One type of penetrating agent may be used alone, or two or more types may be used in combination. For example, commercially available penetrating agents may be used.

[0023] The aqueous ink contains, as the penetrant, at least a compound represented by the following formula (1): [ka]

[0024] In the formula (1), x is not particularly limited as long as it is 4 or more. For example, x is preferably 4. Furthermore, in the formula (1), y is not particularly limited as long as it is 2 or more. For example, y is preferably 2 or 3. x and y may be linear or branched, but linear chains are preferred.

[0025] Examples of the compound represented by formula (1) include dipropylene glycol-n-butyl ether (BFDG; x=4, y=2) and tripropylene glycol-n-butyl ether (TPnB; x=4, y=3). The compound represented by formula (1) may be, for example, a commercially available product. The penetrating agent may be used alone or in combination of two or more.

[0026] The amount of the compound represented by formula (1) relative to the total amount of the aqueous ink may be, for example, more than 0% by mass and not more than 20% by mass, more than 0% by mass and not more than 13% by mass, 0.1% by mass or more and not more than 3.0% by mass, 0.1% by mass or more and not more than 2.0% by mass, or 0.3% by mass or more and not more than 2.0% by mass.

[0027] The aqueous ink may further contain another penetrant (a penetrant other than the compound represented by formula (1)) within a range that does not impair the effects of the present invention. The other penetrant is not particularly limited and may be, for example, a penetrant having a normal boiling point of 250°C or higher, or, as will be described later, a penetrant having a normal boiling point of 250°C or lower.

[0028] When the penetrant is a combination of two or more penetrants containing the compound represented by formula (1), the amount of the penetrant relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose. The amount of the penetrant relative to the total amount of the aqueous ink can be, for example, more than 0% by mass to 20.0% by mass or less, more than 0% by mass to 13.0% by mass or less, or 0.1% by mass to 3.0% by mass or less.

[0029] Examples of the wetting agent 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; polyhydric alcohols such as polyalkylene glycols and alkylene glycols; 2-pyrrolidone; N-methyl-2-pyrrolidone; and 1,3-dimethyl-2-imidazolidinone. The polyalkylene glycol is not limited, and examples thereof include polyethylene glycol and polypropylene glycol. The alkylene glycol is not limited, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, thiodiglycol, and hexylene glycol. Among these, polyhydric alcohols such as alkylene glycols are preferred. The wetting agents may be used alone or in combination. The wetting agent may be, for example, a commercially available product.

[0030] The aqueous ink contains, as the wetting agent, at least a compound represented by the following formula (2): In the following formula (2), x is 2 or more. [ka]

[0031] Examples of the compound represented by formula (2) include tripropylene glycol (TPG; x=3) and dipropylene glycol (DPG; x=2). The compound represented by formula (2) may be, for example, a commercially available product. The wetting agent may be used alone or in combination of two or more.

[0032] The amount of the compound represented by formula (2) relative to the total amount of the aqueous ink may be, for example, 0.1% by mass to 20.0% by mass, 0.2% by mass to 15.0% by mass, 0.3% by mass to 12.0% by mass, 1.0% by mass to 10.0% by mass, or 3.0% by mass or more and 10.0% by mass or less.

[0033] The aqueous ink may further contain another humectant (a humectant other than the compound represented by formula (2)) within a range that does not impair the effects of the present invention. An example of the other humectant is glycerin. The amount of glycerin to be added relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose.

[0034] When the humectant is a combination of two or more humectants containing the compound represented by formula (2), the amount of the humectant relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose. The amount of the humectant relative to the total amount of the aqueous ink can be, for example, more than 0% by mass to 95.0% by mass or less, 1.0% by mass to 80.0% by mass or less, or 3.0% by mass to 50.0% by mass or less.

[0035] The aqueous ink contains a compound represented by formula (1) as a penetrant and a compound represented by formula (2) as a wetting agent, thereby increasing saturation and reducing VOC emissions. The mechanism by which high saturation and reduced VOC emissions can be achieved simultaneously is presumed to be as follows: First, the use of a highly hydrophobic material reduces the contact angle of the ink droplets after impact. Furthermore, the use of a highly hydrophobic material reduces the dispersion stability of the hydrophilic pigment, making the ink droplets more likely to aggregate at a low water evaporation rate. These factors make it easier for the colorant to remain on the surface of the printing medium, thereby improving saturation. Second, the use of a solvent with a high molecular weight reduces the vapor pressure, thereby reducing VOC emissions. However, this mechanism is merely presumed, and the present invention is not limited thereto.

[0036] The aqueous ink may contain, for example, a penetrant and a wetting agent (hereinafter referred to as a low-boiling organic solvent) with a normal boiling point of 250°C or less, but preferably does not. If the low-boiling organic solvent is contained, the amount is preferably equal to or less than the VOC regulatory standard. Here, the VOC regulatory standard conforms to the standard for obtaining the "Blue Angel Mark" established in Germany. Specifically, for example, in the case of color printing, the VOC emission rate per unit time (VOC emission rate) is preferably 18 mg / h or less, and in the case of monochrome printing, the VOC emission rate per unit time is preferably 10 mg / h or less. The VOC emission rate per unit time can be determined, for example, by performing continuous printing for approximately 5 minutes or more in a thermostatic chamber (conditions: temperature 23°C, relative humidity 50%) and determining the total amount of volatile organic compounds emitted during the printing.

[0037] Furthermore, when the low-boiling point organic solvent is included, it is preferable to perform printing with a reduced amount of ink used (ejection amount) (reduced ink amount printing). This reduces the amount of water-based ink used, thereby reducing VOC emissions. On the other hand, when the low-boiling point organic solvent is not included, VOC emissions are reduced even when printing without reducing the amount of ink used (normal printing).

[0038] The water-soluble organic solvent may contain other solvents in addition to the penetrating agent and the wetting agent, such as a surfactant.

[0039] 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-based surfactants and acetylene-based surfactants.

[0040] Examples of commercially available silicone surfactants include "Silface (registered trademark) SAG002," "Silface (registered trademark) SAG005," and "Silface (registered trademark) SAG503A," all manufactured by Nissin Chemical Industry Co., Ltd.

[0041] Examples of commercially available acetylene surfactants include "Olfine (registered trademark) E1004," "Olfine (registered trademark) E1008," and "Olfine (registered trademark) E1010" manufactured by Nissin Chemical Industry Co., Ltd.; "Surfynol (registered trademark) 440," "Surfynol (registered trademark) 465," and "Surfynol (registered trademark) 485" manufactured by Air Products and Chemicals, Inc.; and "Acetylenol (registered trademark) E40" and "Acetylenol (registered trademark) E100" manufactured by Kawaken Fine Chemicals Co., Ltd.

[0042] The water-based ink may contain other surfactants in addition to or in place of the silicone-based surfactant and the acetylene-based surfactant. Examples of the other surfactants include nonionic surfactants manufactured by Kao Corporation such as the "EMULGEN (registered trademark)" series, "RHEODOL (registered trademark)" series, "EMASOL (registered trademark)" series, "EXCEL (registered trademark)" series, "EMANON (registered trademark)" series, "AMIET (registered trademark)" series, and "AMINON (registered trademark)" series; nonionic surfactants manufactured by Toho Chemical Industry Co., Ltd. such as the "SORBON (registered trademark)" series; nonionic surfactants manufactured by Lion Corporation such as the "DOBANOX (registered trademark)" series, "LEOCOL (registered trademark)" series, "LEOX (registered trademark)" series, "LAOL,LEOCOL (registered trademark)" series, "LIONOL (registered trademark)" series, "CADENAX (registered trademark)" series, "LIONON (registered trademark)" series, and "LEOFAT (registered trademark)" series; and anionic surfactants manufactured by Kao Corporation such as the "EMAL (registered trademark)" series, "LATEMUL (registered trademark)" series, "VENOL (registered trademark)" series, and "NEOPELEX (registered trademark)" series, NS SOAP, KS SOAP, OS SOAP and the "PELEX (registered trademark)" series, etc.; anionic surfactants manufactured by Lion Corporation such as the "LIPOLAN (registered trademark)" series, "LIPON (registered trademark)" series, "SUNNOL (registered trademark)" series, "LIPOTAC (registered trademark) TE, ENAGICOL" series, "LIPAL (registered trademark)" series and "LOTAT (registered trademark)" series; and cationic surfactants manufactured by Daiichi Kogyo Seiyaku Co., Ltd. such as "Catiogen (registered trademark) ES-OW" and "Catiogen (registered trademark) ES-L".

[0043] The surfactants may be used alone or in combination of two or more.

[0044] The amount of the surfactant relative to the total amount of the aqueous ink can be appropriately selected depending on the purpose. The amount of the surfactant is, for example, 0.1% by mass to 5.0% by mass, 0.5% by mass to 3.5% by mass, or 1.0% by mass to 3.0% by mass. The amount of the surfactant referred to here is the total amount of two or more surfactants.

[0045] The aqueous ink may further contain conventionally known additives as needed. Examples of the additives include a pH adjuster, a viscosity adjuster, a surface tension adjuster, and an antifungal agent. Examples of the viscosity adjuster include polyvinyl alcohol, cellulose, and a water-soluble resin.

[0046] 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.

[0047] Next, the ink jet recording apparatus and ink jet recording method of the present invention will be described.

[0048] The inkjet recording device of the present invention includes an ink storage container and an ink ejection unit, and ejects ink stored in the ink storage container by the ink ejection unit, and is characterized in that the ink storage container contains the water-based ink for inkjet recording of the present invention.

[0049] Figure 1 shows the configuration of one example of an inkjet recording apparatus of the present invention. As shown in the figure, this inkjet recording apparatus 1 includes, as its main components, four ink containers (ink cartridges 2), an ink ejection section (inkjet head) 3, a head unit 4, a carriage 5, a drive unit 6, a platen roller 7, and a purging device 8. The inkjet recording apparatus of the present invention may also include, as an optional component, a control section 9 (CPU, GPU, etc.).

[0050] The four ink cartridges 2 contain one each of four colors of water-based ink: yellow, magenta, cyan, and black. For example, at least one of the four colors of water-based ink is the water-based ink of the present invention. In this example, a set of four ink cartridges 2 is shown, but instead, an integrated ink cartridge whose interior is partitioned to form a water-based yellow ink container, a water-based magenta ink container, a water-based cyan ink container, and a water-based black ink container may be used. The ink cartridge body may be, for example, a conventionally known one.

[0051] The inkjet head 3 installed in the head unit 4 performs recording on a recording medium (e.g., recording paper) P. Four ink cartridges 2 and the head unit 4 are mounted on the carriage 5. A drive unit 6 moves the carriage 5 back and forth in a linear direction. As the drive unit 6, for example, a conventionally known drive unit can be used (see, for example, Japanese Patent Application Laid-Open No. 2008-246821). A platen roller 7 extends in the direction in which the carriage 5 reciprocates, and is disposed opposite the inkjet head 3.

[0052] The control unit 9 is responsible for overall control of the inkjet recording apparatus of the present invention. In the inkjet recording apparatus of the present invention, the control unit 9, for example, executes various programs and reads and writes various information. The control unit 9 functions as, for example, a determination unit 91 and an image processing unit 92.

[0053] The determination unit 91 determines whether the state of the inkjet recording device satisfies a specific condition. The specific condition is not particularly limited, but the control unit 9 determines that the specific condition is satisfied when, for example, at least one of the following conditions is indicated: there may be a delay in the supply of ink from the ink storage container to the inkjet head 3; a user has instructed to reduce the amount of ink; the remaining ink level is low; or a large amount of ink will be used when printing based on received image data. The determination unit 91, for example, determines the ejection mode to be either a first ejection mode or a second ejection mode (third ejection mode or fourth ejection mode) described below, in accordance with the determination, and drives the inkjet head 3 to eject the water-based ink and perform the inkjet recording operation.

[0054] The image processing unit 92 performs image processing on the received image data. The image processing unit 92 changes the parameters of the image processing in the first ejection mode, thereby reducing the ejection amount of the water-based ink in the second ejection mode compared to the ejection amount of the water-based ink in the first ejection mode.

[0055] Here, the image processing performed on the received image data by the image processing unit 92 will be described. Upon receiving image data, the inkjet recording apparatus 1 executes image processing including color conversion, color adjustment, ink volume control, halftone processing, and interlace processing. The color conversion process converts the image data, which is RGB pixel data constituting bitmap data, into CMYK pixel data that expresses pixel colors using gradation values ​​(e.g., 256 gradations) of four elements: cyan (C), magenta (M), yellow (Y), and black (K), which are the ink colors used in the recording. The conversion is performed using, for example, a lookup table that associates RGB pixel data with CMYK pixel data. The color adjustment process is, for example, a step of executing a calibration process. The calibration process corrects the values ​​of each element of the CMYK pixel data so that the density of the color actually recorded on the recording medium changes linearly with changes in the value of each element of the CMYK pixel data before the color correction process. The caption reduces differences in color density due to the characteristics. The ink amount adjustment step is, for example, a step of adjusting the values ​​of each element of the corrected CMYK pixel data so that the amount of water-based ink ejected (also referred to as ink amount) required for recording is equal to or less than a reference amount. The halftone processing is performed using a known method such as a dither method or an error diffusion method. The interlace processing step is, for example, a step of setting an interlace method to be performed by an inkjet recording device.

[0056] The inkjet head 3 may perform the recording by selecting, for example, either a "first ejection mode" or a "second ejection mode" for ejecting the aqueous ink. Furthermore, if the second ejection mode is selected, the inkjet head 3 may perform the recording by selecting, for example, either a "third ejection mode" or a "fourth ejection mode." Specifically, if the determination unit 91 determines that the specific condition is not satisfied, the inkjet head 3 receives a command from the control unit 9 and performs the recording in a first ejection mode in which the inkjet recording aqueous ink is ejected from the inkjet head 3 based on the received image data. The first ejection mode is also referred to as a normal printing mode, for example. On the other hand, if the determination unit 91 determines that the specific condition is satisfied, the inkjet head 3 receives a command from the control unit 9 and performs the recording in a second ejection mode. The second ejection mode is a mode in which the inkjet recording aqueous ink is ejected at a lower ejection rate than in the first ejection mode. That is, when the same image data is received, the amount of ink used in the second ejection mode is less than the amount of ink used in the first ejection mode.

[0057] The second ejection mode may include at least one of a third ejection mode and a fourth ejection mode. The inkjet head 3 performs the recording in at least one of the third ejection mode and the fourth ejection mode, for example, in response to a user selection.

[0058] The third ejection mode is a mode in which the water-based ink is ejected by changing the recording duty in the first ejection mode, and is also referred to as a duty change mode, for example. The change in recording duty is performed by changing at least some of the dot sizes of the water-based ink for inkjet recording that land on the recording medium in the first ejection mode. The change in recording duty in the second ejection mode will be described in more detail. Droplets ejected by the inkjet head 3 land on the recording medium. The inkjet head 3 may, for example, continuously eject multiple droplets onto the same point on the recording medium. The dot sizes of the droplets that land on the recording medium can be classified into, for example, small, medium, and large sizes. The classification criteria for each size are not particularly limited and can be set arbitrarily. The dot size can be measured, for example, using a known method. The recording duty can be adjusted by the ratio of the dot sizes, i.e., the ratio of small, medium, and large droplets. The dot size and its ratio can be changed, for example, by changing the parameters of the halftone process as parameters of the image processing. As described above, if the size of at least some of the dots changes, the ratio changes, and the printing duty also changes. In this way, in the third ejection mode, changing the dot size and adjusting the printing duty makes it possible to print with a reduced amount of ink.

[0059] The fourth ejection mode is a mode in which the ejection amount of the inkjet recording aqueous ink in the first ejection mode is changed by changing characteristics specific to the inkjet recording device 1, thereby ejecting the inkjet recording aqueous ink. The fourth ejection mode is also referred to as, for example, an ink-saving printing mode or a high-speed mode. In the fourth ejection mode, the ejection amount of the inkjet recording aqueous ink can be reduced, for example, by changing the color adjustment processing parameters (for example, the calibration processing parameters, which are characteristic values ​​specific to the inkjet recording device) as parameters of the image processing. The characteristic values ​​are values ​​specific to each inkjet recording device, and changing these characteristic values ​​can change the printed color, for example. The characteristic values ​​are, for example, stored in advance in the inkjet recording device. Other characteristic values ​​include, for example, head characteristic values. The head characteristic values ​​are values ​​based on mechanical positional misalignment and ejection variations (for example, variations in ejection speed and ejection direction) of the multiple ink ejection orifices provided in the inkjet head 3. Mechanical positional misalignment and ejection variations of the multiple ink ejection orifices may affect the print results. In this way, in the fourth ejection mode, by changing the ejection amount of the water-based ink during the calibration process, printing with a reduced amount of ink becomes possible.

[0060] The aqueous inks in the first, second, third, and fourth ejection modes are all aqueous inks for inkjet recording according to the present invention. The inkjet head 3 capable of executing the first, second, third, and fourth ejection modes can be, for example, a conventionally known inkjet head (see, for example, JP 2002-36599 A, JP 2020-044679 A, ​​and JP 2020-131576 A). This also enables printing with reduced ink volume (recording in the second ejection mode (the third and fourth ejection modes)).

[0061] The purging device 8 sucks out defective ink containing air bubbles and the like that accumulates inside the inkjet head 3. As the purging device 8, for example, a conventionally known device can be used (for example, see Japanese Patent Application Laid-Open No. 2008-246821).

[0062] A wiper member 20 is disposed adjacent to the purging device 8 on the platen roller 7 side of the purging device 8. The wiper member 20 is formed in a spatula shape and wipes the nozzle formation surface of the inkjet head 3 as the carriage 5 moves. In Figure 1, a cap 18 covers the multiple nozzles of the inkjet head 3, which are returned to the reset position when recording is completed, to prevent the water-based ink from drying.

[0063] In the inkjet recording apparatus 1 of this example, the four ink cartridges 2 are mounted on a single carriage 5 together with the head unit 4. However, the present invention is not limited to this. In the inkjet recording apparatus 1, each of the four ink cartridges 2 may be mounted on a carriage separate from the head unit 4. Alternatively, each of the four ink cartridges 2 may be disposed and fixed within the inkjet recording apparatus 1 without being mounted on the carriage 5. In these embodiments, for example, each of the four ink cartridges 2 and the head unit 4 mounted on the carriage 5 are connected by a tube or the like, and the water-based ink is supplied from each of the four ink cartridges 2 to the head unit 4. In these embodiments, four bottle-shaped ink bottles may be used instead of the four ink cartridges 2. In this case, it is preferable that the ink bottles have an inlet for injecting ink from the outside into the ink bottles.

[0064] Inkjet recording using this inkjet recording apparatus 1 is performed, for example, as follows. First, recording paper P is fed from a paper feed cassette (not shown) provided to the side or below the inkjet recording apparatus 1. The recording paper P is introduced between the inkjet head 3 and the platen roller 7. A predetermined recording is made on the introduced recording paper P using aqueous ink ejected from the inkjet head 3. This ejection may be performed in the "first ejection mode" or "second ejection mode (at least one of the third ejection mode and the fourth ejection mode)" depending on the determination of the determination unit 91, as described above. After recording, the recording paper P is ejected from the inkjet recording apparatus 1. In FIG. 1, the paper feed mechanism and paper ejection mechanism for the recording paper P are not shown.

[0065] 1 employs a serial inkjet head, but the present invention is not limited to this. The inkjet recording device may employ a line inkjet head or a roll-to-roll system.

[0066] The inkjet recording method of the present invention includes a recording step of ejecting an aqueous ink onto a recording medium by an inkjet method, 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. The inkjet recording method of the present invention can be carried out, for example, using the inkjet recording apparatus of the present invention. The recording includes printing, photographic printing, printing, etc.

[0067] The inkjet recording method of the present invention may optionally include, for example, a determination step and an image processing step. The determination step is a step of determining whether the state of the inkjet recording device satisfies specific conditions. The image processing step is a step of performing image processing on received image data. The determination step can be performed, for example, by a determination unit 91, and the image processing step can be performed, for example, by an image processing unit 92.

[0068] When the determination is made, the recording process may select, for example, either the "first ejection mode" or the "second ejection mode" to perform the recording. Furthermore, when the second ejection mode is selected, the recording process may select, for example, either the "third ejection mode" or the "fourth ejection mode" to perform the recording. The first ejection mode, the second ejection mode, the third ejection mode, and the fourth ejection mode are the same as those described above. Specifically, when it is determined in the determination process that the specific condition is not satisfied, the inkjet head 3 receives a command from the control unit 9 and performs the recording in the first ejection mode based on the received image data. On the other hand, when it is determined in the determination process that the specific condition is satisfied, the inkjet head 3 receives a command from the control unit 9 and performs the recording in the second ejection mode. At least one of the third mode and the fourth ejection mode is selected by the user from the second ejection modes. Then, the inkjet head 3 performs the recording in the selected mode, for example. The aqueous inks in the first ejection mode, the second ejection mode, the third ejection mode, and the fourth ejection mode are all the aqueous inks for inkjet recording of the present invention. [Example]

[0069] 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.

[0070] (Examples 1 to 10 and Comparative Examples 1 to 5) The components of the aqueous ink composition (Table 1) except for the pigment were mixed uniformly to obtain an ink solvent. Next, the ink solvent was added to the pigment and mixed uniformly. The resulting mixture was then filtered through a cellulose acetate 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 9 and Comparative Examples 1 to 5 shown in Table 1.

[0071] The aqueous inks of Examples 1 to 10 and Comparative Examples 1 to 5 were evaluated for (a) saturation and (b) VOC emissions by the following methods.

[0072] (a) Saturation evaluation Using an inkjet recording apparatus MFC-J6580CDW manufactured by Brother Industries, Ltd., images were recorded on a recording medium ("Multi Paper Super White +" manufactured by Askul Corporation) at a recording duty of 100% using the aqueous inks of Examples 1 to 9 and Comparative Examples 1 to 5. The saturation (C * ) was measured using a spectrophotometer XRite-939 manufactured by X-Rite (light source: D65, viewing angle: 10°, ANSI-T), and the average value was calculated. * ) in Comparative Example 1, in which the image was produced using only a water-based magenta ink (CI Pigment Red 122) without using a penetrant containing the compound represented by formula (1). * ) to obtain the saturation (C * Similarly, the difference in chroma (C * ) in Comparative Example 4, in which the image was produced using only a water-based yellow ink (CI Pigment Yellow 74) without using a penetrant containing the compound represented by formula (1). * ) in Example 8 is subtracted, and the saturation (C * ) in Comparative Example 5, in which the image was produced using only an aqueous cyan ink (CI Pigment Blue 15:3) without using a penetrant containing the compound represented by formula (1). * ) to obtain the saturation (C * The magenta saturation, yellow saturation, and cyan saturation were then evaluated according to the following evaluation criteria.

[0073] Saturation evaluation criteria A: Saturation (C * ) was +4 or more. B: Saturation (C * ) was greater than or equal to +2 and less than +4. C: Saturation (C* ) was less than +2.

[0074] (b) VOC emission assessment The degree of VOC emission for each penetrant and each wetting agent in the aqueous inks of the Examples and Comparative Examples was evaluated according to the following evaluation criteria.

[0075] VOC emission evaluation criteria A: The boiling points of all the penetrants and humectants contained in water-based inks exceed 250°C. B: The boiling point of at least one of the penetrants and humectants contained in the aqueous ink was 210°C or higher and 250°C or lower. C: The boiling point of at least one of the penetrants and humectants contained in the aqueous ink was lower than 210°C.

[0076] Table 1 shows the compositions and evaluation results of the aqueous inks of Examples 1 to 10 and Comparative Examples 1 to 5.

[0077] [Table 1]

[0078] As shown in Table 1, in Examples 1 to 10, the saturation (C *) was evaluated as "B" or higher, which was good. In addition, in Examples 1 to 9, the VOC emission evaluation was evaluated as "B" or higher, which was good. Example 1, which used tripropylene glycol-n-butyl ether (x=4, y=3) as the compound represented by formula (1) and tripropylene glycol (x=3) as the compound represented by formula (2), was superior in the VOC emission evaluation compared to Example 2, which used dipropylene glycol-n-butyl ether (x=4, y=2) as the compound represented by formula (1), and Example 6, which used dipropylene glycol (x=2) as the compound represented by formula (2). In addition, Example 5, in which the blending amount of the compound represented by formula (1) was 0.3% by mass or more and 2.0% by mass or less and the blending amount of the compound represented by formula (2) was 3.0% by mass or more and 10.0% by mass or less, was superior in the chroma (C * ) had better evaluation results.

[0079] On the other hand, Comparative Examples 1, 4, and 5, in which triethylene glycol monobutyl ether was used instead of the compound represented by the formula (1), had a lower chroma (C * In addition, in Comparative Example 2, which did not use the compound represented by the formula (2), the chroma (C * Furthermore, Comparative Example 3, in which dipropylene glycol-n-propyl ether was used instead of the compound represented by formula (1), had a poor evaluation of VOC emission.

[0080] Next, for the aqueous inks of Examples 1, 3, 4, and 5 and Comparative Example 1, (c) image quality evaluation during printing with reduced ink amount was carried out by the following method.

[0081] (c) Image quality evaluation when printing with reduced ink volume Using an inkjet recording apparatus MFC-J6580CDW manufactured by Brother Industries, Ltd., images were recorded on plain paper ("Multi Paper Super White+" manufactured by Askul Corporation) by ejecting the aqueous inks of Examples 1, 3, 4, and 5 and Comparative Example 1 in print modes 1 to 6 described below. The saturation (C * ) was measured using a spectrophotometer XRite-939 (light source: D65, viewing angle: 10°, ANSI-T) manufactured by X-Rite Corporation, and the average value was calculated. * ) indicates better image quality.

[0082] There are six print modes: In the following, with print mode 1 as the reference, print mode 1 corresponds to the normal print mode (the first ejection mode), print modes 2 and 3 correspond to the duty change mode (the third ejection mode), print mode 4 corresponds to the ink-saving print mode (the fourth ejection mode), and print modes 5 and 6 correspond to a combination of the duty change mode (the third ejection mode) and the ink-saving mode (the fourth ejection mode). These print modes can be implemented by changing the settings of the inkjet printer. Specifically, print mode 1 is a mode in which no mode built into the inkjet printer is selected (mode not selected) and is set to print at a recording duty of 100%. print modes 2 and 3 are the same as print mode 1 except that the recording duty setting is changed. print mode 4 is a mode in which the "high-speed mode" built into the inkjet printer is selected and is set to print at a recording duty of 100%. print modes 5 and 6 are the same as print mode 4 except that the recording duty setting is changed. Here, "high-speed mode" refers to a mode in which the characteristic values ​​of the inkjet printer are changed without changing the recording duty, and the amount of aqueous ink ejected is reduced compared to the amount of aqueous ink ejected when the mode is not selected. Print mode 1: Recording duty 100%, mode not selected Print mode 2: Recording duty 70%, mode not selected Print mode 3: Recording duty 40%, mode not selected Print mode 4: Recording duty 100%, high-speed mode Print mode 5: Recording duty 70%, high-speed mode Print mode 6: Recording duty 40%, high-speed mode

[0083] The evaluation results of the aqueous inks of Examples 1, 3, 4, and 5 and Comparative Example 1 are shown in Tables 2 and 3. In Tables 2 and 3, the aqueous ink compositions of the aqueous inks of Examples 1, 3, 4, and 5 and Comparative Example 1 are omitted because they are the same as the ink compositions shown in Table 1.

[0084] [Table 2]

[0085] [Table 3]

[0086] As shown in Tables 2 and 3, in Examples 1, 3, 4, and 5, even if the ejection amount is reduced by changing at least one of the recording duty and the characteristic value, the saturation (C * ) was high. In other words, when the aqueous inks of Examples 1, 3, 4, and 5 were used, there was less deterioration in image quality than when the aqueous ink of Comparative Example 1 was used. These results show that the aqueous inks of Examples 1, 3, 4, and 5 can reduce the amount of aqueous ink ejected and the amount of VOC generated without compromising image quality, compared to the aqueous ink of Comparative Example 1. Furthermore, it can be seen that the aqueous inks of Examples 1, 3, 4, and 5 can record higher image quality than the aqueous ink of Comparative Example 1, even when thinning printing is performed. [Industrial Applicability]

[0087] As described above, the water-based ink of the present invention has excellent saturation and can reduce VOC emissions. The water-based ink of the present invention can be widely used for inkjet recording on various recording media. [Explanation of symbols]

[0088] 1. Inkjet recording device 2 ink cartridges 3. Ink ejection section (inkjet head) 4 Head Unit 5 Carriage 6 Drive Unit 7 Platen roller 8 Purging device 9 Control Unit

Claims

1. Contains water, a colorant, and a water-soluble organic solvent, the water-soluble organic solvent includes a penetrating agent and a wetting agent; The penetrating agent contains a compound represented by the following formula (1): The wetting agent contains a compound represented by the following formula (2): The amount of the compound represented by the following formula (1) is 0.3% by mass or more and 2.0% by mass or less, 1. A water-based ink for ink-jet recording, comprising a compound represented by the following formula (2) in an amount of 3.0% by mass or more and 10.0% by mass or less: 【Chemistry 1】 In formula (1), x is 4 or greater; y is 3 or greater. 【Chemistry 2】 In formula (2), x is 3 or greater.

2. a recording step of ejecting a water-based ink for ink-jet recording onto a recording medium by an ink-jet method, 2. An ink-jet recording method, wherein the ink-jet recording water-based ink according to claim 1 is used as the ink-jet recording water-based ink in the recording step.

3. Further, a determination step of determining whether a specific condition is satisfied is included, If the determining step determines that the specific condition is not satisfied, the recording step includes performing the recording in a first ejection mode in which the water-based ink for inkjet recording is ejected based on the received image data; When the determining step determines that the specific condition is satisfied, The inkjet recording method according to claim 2 , wherein the recording step is performed in a second ejection mode in which the inkjet recording water-based ink is ejected in an amount smaller than that in the first ejection mode.

4. further comprising an image processing step of performing image processing on the received image data, 4. The inkjet recording method according to claim 3, wherein the image processing step changes a parameter of the image processing in the first ejection mode, and reduces the ejection amount of the water-based ink for inkjet recording in the second ejection mode to be less than the ejection amount of the water-based ink for inkjet recording in the first ejection mode.

5. 5. The inkjet recording method according to claim 4, wherein the second ejection mode includes at least one of a third ejection mode in which the water-based ink for inkjet recording is ejected by changing the printing duty in the first ejection mode by changing the dot sizes of at least some of the dot sizes in the first ejection mode, and a fourth ejection mode in which the water-based ink for inkjet recording is ejected by changing the ejection amount of the water-based ink for inkjet recording in the first ejection mode by changing characteristics specific to the inkjet recording device.

6. In the third ejection mode, the ejection amount is reduced by changing a parameter of a halftone process as a parameter of the image processing, 6. The ink jet recording method according to claim 5, wherein in the fourth ejection mode, the ejection amount is reduced by changing a parameter of a color adjustment process as a parameter of the image processing.

7. an ink container and an ink ejection unit; an inkjet recording apparatus that ejects ink contained in the ink containing container by the ink ejection unit, 2. An ink-jet recording apparatus, wherein the water-based ink for ink-jet recording according to claim 1 is contained in the ink container.

8. Further, a determination unit for determining whether a specific condition is satisfied, When the determination unit determines that the specific condition is not satisfied, the ink ejection unit executes a first ejection mode in which the water-based ink for inkjet recording is ejected based on the received image data; When the determination unit determines that the specific condition is satisfied, 8. The inkjet recording apparatus according to claim 7, wherein the ink ejection section executes a second ejection mode in which the ink ejection amount of the water-based ink for inkjet recording is reduced compared to the first ejection mode.

9. further comprising an image processing unit that performs image processing on the received image data; 9. The inkjet recording apparatus according to claim 8, wherein the image processing unit changes parameters of the image processing in the first ejection mode, and reduces the ejection amount of the water-based ink for inkjet recording in the second ejection mode to be less than the ejection amount of the water-based ink for inkjet recording in the first ejection mode.

10. 10. The inkjet recording device according to claim 9, wherein the second ejection mode includes at least one of a third ejection mode in which the water-based ink for inkjet recording is ejected by changing the printing duty in the first ejection mode by changing the dot sizes of at least some of the dot sizes in the first ejection mode, and a fourth ejection mode in which the water-based ink for inkjet recording is ejected by changing the ejection amount of the water-based ink for inkjet recording in the first ejection mode by changing characteristics unique to the inkjet recording device.

11. In the third ejection mode, the ejection amount is reduced by changing a parameter of a halftone process as a parameter of the image processing, 11. The inkjet recording apparatus according to claim 10, wherein in the fourth ejection mode, the ejection amount is reduced by changing a parameter of a color adjustment process as a parameter of the image processing.

12. 2. 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 claim 1.

Images