Water-based ink for inkjet recording, inkjet recording device, and inkjet recording method

Abstract

This invention provides an aqueous inkjet recording ink that uses phycocyanin as a coloring agent and exhibits excellent nozzle ejection stability. [Solution] The aqueous inkjet recording ink of this disclosure comprises water, phycocyanin, and a water-soluble organic solvent, wherein the water-soluble organic solvent is a water-soluble organic solvent whose logP value, which is the common logarithm of the octanol / water partition coefficient P, is 0.2000 or less.

Description

Technical Field

[0001] The present disclosure relates to an aqueous ink for inkjet recording, an inkjet recording apparatus, and an inkjet recording method.

Background Art

[0002] Patent Document 1 discloses an ink for inkjet recording that contains only a coloring material made from a petroleum-derived raw material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, from the perspective of decarbonization, it is desired that the blue coloring material in ink for inkjet recording be replaced from a petroleum-derived raw material to a naturally derived raw material obtained from plants.

[0005] Here, several naturally derived raw materials exist as blue coloring materials, among which phycocyanin is a water-soluble pigment that exhibits a very vivid blue color and is attracting attention. On the other hand, inks for inkjet recording containing phycocyanin tend to have low ejection stability from the nozzles of the inkjet head.

[0006] Accordingly, an object of the present disclosure is to provide an aqueous ink for inkjet recording, an inkjet recording apparatus, and an inkjet recording method that use phycocyanin as a colorant and have excellent ejection stability from nozzles.

Means for Solving the Problems

[0007] To achieve the above objective, the aqueous inkjet recording ink of this disclosure comprises water, phycocyanin, and a water-soluble organic solvent, wherein the water-soluble organic solvent includes a water-soluble organic solvent whose logP value, which is the common logarithm of the octanol / water partition coefficient P, is 0.2000 or less.

[0008] The inkjet recording apparatus of this disclosure includes an inkjet head, which ejects the aqueous inkjet recording ink of this disclosure onto a recording medium.

[0009] The inkjet recording method of this disclosure includes a recording step of ejecting the aqueous inkjet recording ink of this disclosure from an inkjet head onto a recording medium and recording the ink on the recording medium. [Effects of the Invention]

[0010] This disclosure provides an aqueous ink for inkjet recording, an inkjet recording apparatus, and an inkjet recording method that use phycocyanin as a coloring agent and exhibit excellent nozzle ejection stability. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic perspective view showing the configuration of an example of an inkjet recording apparatus according to this disclosure. [Modes for carrying out the invention]

[0012] In this disclosure, the term "weight" may be interpreted as "mass" unless otherwise specified. For example, "weight ratio" may be interpreted as "mass ratio" unless otherwise specified, and "weight%" may be interpreted as "mass%" unless otherwise specified.

[0013] In this disclosure, when a numerical range is indicated for each raw material and parameter, unless otherwise specified, the numerical range means a numerical range that includes the lower and upper limits that define the numerical range. For example, when a numerical range of "1 to 10" is indicated, the numerical range means a numerical range that includes the lower limit of 1 and the upper limit of 10 that define "1 to 10" (i.e., 1 or more and 10 or less). Furthermore, when multiple upper limits and / or multiple lower limits are given as examples in this disclosure, any example upper and lower limits can be combined as the upper and lower limits of the numerical range.

[0014] The "weight %" values ​​presented in this disclosure are shown to two decimal places and rounded to the third decimal place. The "content ratio (a / b)" values ​​presented in this disclosure are shown to two decimal places and rounded to the third decimal place. The "logP" values ​​presented in this disclosure are shown to four decimal places and rounded to the fifth decimal place. The "viscosity" values ​​presented in this disclosure are shown to one decimal place and rounded to the second decimal place. The "particle diameter based on scattered light intensity" (hereinafter referred to as "particle diameter based on scattered light intensity") presented in this disclosure are shown to zero decimal places and rounded to the first decimal place.

[0015] In the following embodiments and examples, when referring to mechanisms, the described mechanisms are merely presumed and are not limited to those described.

[0016] <Water-based ink for inkjet recording> The water-based inkjet recording inks of this disclosure (hereinafter sometimes referred to as "water-based inks" or "inks") will be described below.

[0017] The aqueous ink of this disclosure comprises water, a colorant, and a water-soluble organic solvent. The water may be deionized water, pure water, or the like.

[0018] The water content in the total weight of the aqueous ink is, for example, 10.00% to 90.00% by weight, or 20.00% to 80.00% by weight. The water content may be, for example, the remainder of the other raw materials.

[0019] The aqueous ink of this disclosure is, for example, a cyan ink containing at least phycocyanin as a colorant. The aqueous ink of this disclosure may also be a cyan ink containing only phycocyanin as the colorant. Here, phycocyanin is a naturally occurring pigment protein. The phycocyanin contains phycocyanobilin as a pigment. The phycocyanin contains a hexameric disk formed by phycocyanobilin molecules. The hexameric disk is formed by combining two trimer disks. The trimer disk contains one molecule of phycocyanobilin bound to an α subunit and two molecules of phycocyanobilin bound to a β subunit. Furthermore, the hexameric disk forms a rod-like structure by binding to a specific protein, becoming a large, water-soluble pigment-protein complex. In this disclosure, phycocyanin is used, for example, as a colorant.

[0020] The aqueous ink of the present disclosure may, for example, further be a cyan ink containing, as the colorant, in addition to phycocyanin, at least one blue dye selected from the group consisting of gardenia blue pigment, indigo, and grey mangrove pigment. Further, the aqueous ink of the present disclosure may contain, as the colorant, in addition to phycocyanin, at least one red dye selected from the group consisting of gardenia red, monascus, safflower red pigment, cochineal pigment, lac pigment, madder pigment, gardenia red pigment, capsicum pigment, annatto pigment, red radish pigment, red cabbage pigment, red rice pigment, elderberry pigment, cowberry pigment, gooseberry pigment, cranberry pigment, salmonberry pigment, perilla pigment, sim blueberry pigment, strawberry pigment, dark sweet cherry pigment, cherry pigment, hibiscus pigment, huckleberry pigment, grape juice pigment, grape skin pigment, blackcurrant pigment, blackberry pigment, blueberry pigment, plum pigment, whortleberry pigment, boysenberry pigment, mulberry pigment, purple sweet potato pigment, purple corn pigment, purple yam pigment, raspberry pigment, redcurrant pigment, loganberry pigment, beet red pigment, and monascus pigment. Furthermore, the aqueous ink of the present disclosure is an ink of a color such as purple or green, containing, as the colorant, in addition to phycocyanin, at least one yellow dye selected from the group consisting of gardenia yellow pigment, safflower yellow pigment, turmeric pigment, and monascus yellow.

[0021] The lower limit of the content of the phycocyanin in the total weight of the aqueous ink may be, for example, 5.00 wt% or more, or 10.00 wt% or more. The upper limit of the content of the phycocyanin in the total weight of the aqueous ink may be, for example, 15.00 wt% or less, or 10.00 wt% or less. The content of the phycocyanin in the total weight of the aqueous ink may be, for example, 5.00 wt% to 15.00 wt%, 5.00 wt% to 10.00 wt%, or 10.00 wt% to 15.00 wt%.

[0022] Furthermore, the aqueous ink of this disclosure may also include, for example, a petroleum-derived pigment in addition to phycocyanin as a coloring agent. By including both phycocyanin and the petroleum-derived pigment as coloring agents, the amount of petroleum-derived pigment is reduced compared to, for example, the case in which only the petroleum-derived pigment is included.

[0023] Examples of the aforementioned pigments include carbon black, inorganic pigments, and organic pigments. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of the aforementioned inorganic pigments include titanium dioxide, iron oxide-based inorganic pigments, and carbon black-based inorganic pigments. Examples of the aforementioned organic pigments include: azo pigments such as azo lakes, 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-type lake pigments and acid dye-type lake pigments; nitro pigments; nitroso pigments; aniline black daylight fluorescent pigments; and so on. In addition, other pigments can be used as long as they are dispersible in the aqueous phase. Specific examples of the aforementioned pigments include, for example, CI Pigment White 1, 4, 5, 6, 7, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, and 28; 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, and 48: Examples include 1, 53:1, 57, 57:1, 112, 122, 123, 139, 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 the aforementioned pigments.

[0024] The pigment may be dispersed in a solvent by a resin dispersant (also referred to as a resin-dispersed pigment). As the resin dispersant, for example, a conventionally known polymer dispersant (also referred to as a resin dispersant or the like) or the like may be used. Further, in the aqueous ink of the present disclosure, the pigment may be encapsulated with a polymer. As the resin dispersant, for example, one containing at least one of methacrylic acid and acrylic acid as a monomer may be used, and for example, a commercially available product may be used. The resin dispersant may be, for example, a hydrophobic monomer such as styrene, a styrene derivative, vinylnaphthalene, a vinylnaphthalene derivative, or an aliphatic alcohol ester of an α,β-ethylenically unsaturated carboxylic acid, or a block copolymer composed of two or more monomers selected from the group consisting of acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives. Further, the resin dispersant may be a graft copolymer composed of two or more monomers selected from the group consisting of acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, or a random copolymer composed of two or more monomers selected from the group consisting of acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives. Furthermore, the dispersant may be a hydrophobic monomer, a salt of a block copolymer, a salt of a graft copolymer, a salt of a random copolymer, or the like. Examples of the commercially available products include "JONCRYL (registered trademark) 611", "JONCRYL (registered trademark) 60", "JONCRYL (registered trademark) 586", "JONCRYL (registered trademark) 687", "JONCRYL (registered trademark) 63" and "JONCRYL (registered trademark) HPD296" manufactured by BASF; "Disperbyk190" and "Disperbyk191" manufactured by BYK-Chemie; "Solsperse 20000" and "Solsperse 27000" manufactured by Lubrizol Corporation; and the like.

[0025] A method for dispersing the pigment using the aforementioned pigment dispersion resin includes, for example, a method of dispersing the pigment using a dispersion apparatus. The dispersion apparatus used for dispersing the pigment is not particularly limited as long as it is a general-purpose dispersion machine, but examples include ball mills, roll mills, sand mills (e.g., high-speed type), etc.

[0026] The pigment may be a self-dispersing pigment. The self-dispersing pigment is such that, for example, at least one of a hydrophilic functional group such as a carbonyl group, hydroxyl group, carboxylic acid group, sulfonic acid group, or a salt thereof is chemically bonded to the pigment particles, either directly or via other groups, so that it can be dispersed in water without the use of a dispersant. The self-dispersing pigment may be one in which the pigment has been treated by the method described in, for example, Japanese Patent Publication No. 8-3498, Japanese Patent Publication No. 2000-513396, Japanese Patent Publication No. 2008-524400, Japanese Patent Publication No. 2009-515007, Japanese Patent Publication No. 2011-515535, etc. The raw material for the self-dispersing pigment may be either an inorganic pigment or an organic pigment. Examples of pigments suitable for the above treatment include carbon black such as "MA8" and "MA100" manufactured by Mitsubishi Chemical Corporation. The self-dispersing pigment may be a commercially available product, for example. Examples of the aforementioned 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" from Cabot Corporation; "BONJET(registered trademark) BLACK CW-2" and "BONJET(registered trademark) BLACK CW-3" from Orient Chemical Industry Co., Ltd.; and "LIOJET(registered trademark) WD BLACK 002C" from artience Co., Ltd.

[0027] Furthermore, the aqueous ink of this disclosure may also contain, for example, a petroleum-derived dye in addition to phycocyanin as the coloring agent. By including both phycocyanin and the petroleum-derived dye as the coloring agent, the amount of the petroleum-derived dye can be reduced compared to, for example, the case in which only the petroleum-derived dye is included.

[0028] The petroleum-derived dyes are not particularly limited and include, for example, direct dyes, acid dyes, basic dyes, and reactive dyes. Specific examples of the dyes include, for example, 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, and CI Food Black. Examples of CI Direct Black include CI Direct Black 17, 19, 32, 51, 71, 108, 146, 154, and 168. Examples of CI Direct Blue include CI Direct Blue 6, 22, 25, 71, 86, 90, 106, and 199. Examples of CI Direct Red include CI Direct Red 1, 4, 17, 28, 83, and 227. Examples of CI Direct Yellow include CI Direct Yellow 12, 24, 26, 86, 98, 132, 142, and 173. Examples of CI Direct Orange include CI Direct Orange 34, 39, 44, 46, and 60. Examples of CI Direct Violet include CI Direct Violet 47 and 48. Examples of CI Direct Brown include CI Direct Brown 109. Examples of CI Direct Green include CI Direct Green 59. Examples of CI Acid Black include CI Acid Black 2, 7, 24, 26, 31, 52, 63, 112, and 118. Examples of the aforementioned CI Acid Blue include CI Acid Blue 9, 22, 40, 59, 90, 93, 102, 104, 117, 120, 167, 229, and 234.Examples of the aforementioned CI Acid Red include CI Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 180, 256, 289, 315, and 317. Examples of the aforementioned CI Acid Yellow include CI Acid Yellow 11, 17, 23, 25, 29, 42, 61, and 71. Examples of the aforementioned CI Acid Orange include CI Acid Orange 7 and 19. Examples of the aforementioned CI Acid Violet include CI Acid Violet 49. Examples of the aforementioned CI Basic Black include CI Basic Black 2. Examples of the aforementioned CI Basic Blue include CI Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, and 29. Examples of the aforementioned CI Basic Red include CI Basic Red 1, 2, 9, 12, 13, 14, and 37. Examples of the aforementioned CI Basic Violet include CI Basic Violet 7, 14, and 27. Examples of the aforementioned CI Hood Black include CI Hood Black 1 and 2.

[0029] The aqueous ink of this disclosure contains a water-soluble organic solvent, wherein the value of logP, which is the common logarithm of the octanol / water partition coefficient P, is 0.2000 or less. The upper limit of the value of logP may be, for example, 0.1000 or less, 0.0000 or less, -0.5000 or less, -1.0000 or less, -1.5000 or less, or less than -1.5000. The lower limit of the value of logP may be, for example, -2.0000 or more, -1.5000 or more, -1.0000 or more, -0.5000 or more, or 0.0000 or more. The value of logP may be, for example, -2.0000 to 2.0000, -1.5000 to 2.0000, or -1.5000 to -0.5000.

[0030] Here, logP is an index indicating the affinity of a chemical substance for water. A positive logP value with a large absolute value indicates high hydrophobicity, while a negative logP value with a large absolute value indicates low hydrophilicity. Here, if the aqueous ink contains a water-soluble organic solvent with a negative logP value with a large absolute value, for example, the phycocyanin, which is a water-soluble protein, is stabilized by selective hydration by the water-soluble organic solvent, and the association between phycocyanins is thought to be relaxed. Also, if the aqueous ink contains a water-soluble organic solvent with a positive logP value with a large absolute value, for example, the water-soluble organic solvent interacts with the hydrophobic side chains of the phycocyanin, causing the phycocyanin to denature, and thus promoting the association between phycocyanins. Therefore, if the aqueous ink contains a water-soluble organic solvent with a negative logP value with a large absolute value, the association is relaxed by the effect of the water-soluble organic solvent, and the ejection stability of the aqueous ink from the nozzle of the inkjet head is thought to be improved. Therefore, the value of logP is preferably a negative value with a large absolute value, and the lower limit is not particularly limited.

[0031] Examples of the water-soluble organic solvents include, but are not limited to, glycerin, 1,3-propanediol, 3-methyl-1,3-butanediol, diethylene glycol, triethylene glycol, 2-ethyl-1,3-hexanediol, and 3-methyl-1,5-pentanediol.

[0032] The logP may be, for example, an experimental value or a calculated value. If the logP is calculated, it may be calculated using the method disclosed in, for example, "Wildman, Scott A., and Gordon M. Crippen (1999). "Prediction of physicochemical parameters by atomic contributions." Journal of chemical information and computer sciences Vol.39, Issue 5, pp. 868-873. DOI: 10.1021 / ci990307l".

[0033] Furthermore, the aqueous organic solvent may include, for example, an aqueous organic solvent with a logP value of 0.2000 or less, as well as an aqueous organic solvent with a logP value exceeding 0.2000 (hereinafter sometimes referred to as "other aqueous organic solvents"). Even if the aqueous ink of this disclosure contains other aqueous organic solvents, including an aqueous organic solvent with a logP value of 0.2000 or less can mitigate the association between phycocyanins.

[0034] The lower limit of the content of the water-soluble organic solvent in the total weight of the water-based ink may be, for example, 1.00% by weight or more, 5.00% by weight or more, 10.00% by weight or more, 15.00% by weight or more, or 25.00% by weight or more. The upper limit of the content of the water-soluble organic solvent in the total weight of the water-based ink may be, for example, 75.00% by weight or less, 50.00% by weight or less, 45.00% by weight or less, 40.00% by weight or less, or 30.00% by weight or less. The content of the water-soluble organic solvent in the total weight of the water-based ink may be, for example, 1.00% by weight to 75.00% by weight, 5.00% by weight to 50.00% by weight, 25.00% by weight to 40.00% by weight, or 25.00% by weight to 30.00% by weight.

[0035] The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) may have a lower limit of, for example, 0.10 or more, 0.20 or more, 0.25 or more, or 0.30 or more. The upper limit of the content ratio (a / b) may have a lower limit of, for example, 5.00 or less, 2.00 or less, 1.00 or less, 0.70 or less, 0.50 or less, or 0.40 or less. The content ratio (a / b) may have a range of, for example, 0.20 to 2.00, or 0.25 to 2.00.

[0036] The viscosity of the aqueous inks of this disclosure at 25°C may have an upper limit, for example, less than 10.0 mPa·s, 9.0 mPa·s or less, 8.0 mPa·s or less, 7.0 mPa·s or less, or 6.0 mPa·s or less. The viscosity of the aqueous inks of this disclosure at 25°C may have a lower limit, for example, not particularly limited, but for example, 1.0 mPa·s or more, or 2.0 mPa·s or more. The viscosity may be measured, for example, by the method described in the examples below.

[0037] The reason why the viscosity of the aqueous ink in this disclosure at 25°C is less than 10.0 mPa·s is as follows, for example. From the viewpoint of reducing environmental impact, it is preferable to use aqueous ink as inkjet recording ink. Also, when ink is ejected from an inkjet head using an inkjet recording device, the lower the viscosity of the ink, the lower the ejection energy (for example, the applied voltage for ejecting the ink) can be. Therefore, from the viewpoint of reducing environmental impact, it is more preferable to use low viscosity aqueous ink. Here, the appropriate viscosity of an inkjet head capable of ejecting aqueous ink is set to less than 10.0 mPa·s in most cases. Although there are inkjet heads with an appropriate ink viscosity of 10.0 mPa·s or higher, when low viscosity ink is ejected using such an inkjet head, it may not be possible to generate droplets that can stably fly through the air after ejection. Therefore, the viscosity of the aqueous ink in this disclosure at 25°C is preferably less than 10.0 mPa·s, not only from the viewpoint of reducing environmental impact but also from the viewpoint of the appropriate viscosity of the inkjet head.

[0038] The particle diameter of the particles contained in the aqueous ink of this disclosure, based on scattered light intensity, may have an upper limit, for example, less than 1000 nm, 500 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, 18 nm or less, 16 nm or less, 15 nm or less, or 14 nm or less. The particle diameter based on scattered light intensity may also be, for example, a D95 particle diameter where 95% of the particles in the cumulative distribution of particle diameters are less than or equal to the particle diameter based on scattering intensity. The particle diameter based on scattered light intensity may be measured, for example, by the method described in the examples below.

[0039] The aqueous inks of this disclosure may further contain, if necessary, additives such as water-soluble organic solvents with a logP value exceeding 0.2000, surfactants, pH adjusters, viscosity modifiers, preservatives, and fungicides. Furthermore, the pH adjusters, surfactants, viscosity modifiers, and fungicides may all be plant-derived additives. The aqueous inks of this disclosure may also contain colorants, penetrants, preservatives, pH adjusters, surfactants, viscosity modifiers, and fungicides that are all plant-derived materials.

[0040] <Inkjet recording device, inkjet recording method> Next, the inkjet recording apparatus and inkjet recording method of this disclosure will be described.

[0041] The inkjet recording apparatus of this disclosure includes an inkjet head, which ejects the aqueous inkjet recording ink of this disclosure onto a recording medium.

[0042] Figure 1 shows the configuration of an example of the inkjet recording device. As shown in the figure, this inkjet recording device 1 mainly includes an ink cartridge 101, an inkjet head 102, a carriage 103, a drive unit 105, a platen roller 106, a purge device 107, a cap component 108, and a wiper member 109. Although not shown, the ink cartridge 101 and the inkjet head 102 may be connected by an ink channel, and the aqueous ink contained in the ink cartridge 101 may be supplied to the ink channel, and the inkjet head 102 may apply the aqueous ink to the recording medium P which is to be recorded. The recording medium P may be, for example, plain paper, glossy paper, etc.

[0043] The ink cartridge 101 contains the aqueous ink. The housing of the ink cartridge that contains the aqueous ink may be, for example, a conventionally known one.

[0044] The inkjet head 102 ejects ink toward the recording medium P to be recorded. The carriage 103 is equipped with an ink cartridge 101 and the inkjet head 102. The drive unit 105 moves the carriage 103 back and forth in the main scanning direction. When recording an image on the recording medium P, the inkjet head 102 ejects ink while the carriage 103 moves back and forth in the main scanning direction, thereby recording on the recording medium P. For example, a conventionally known drive unit 105 may be used (see, for example, Japanese Patent Application Publication No. 2008-246821). The platen roller 106 extends in the main scanning direction.

[0045] The purging device 107 sucks up defective ink containing air bubbles and other impurities that accumulate inside the inkjet head 102. For example, a conventionally known purging device 107 may be used (see, for example, Japanese Patent Application Publication No. 2008-246821).

[0046] As shown in Figure 1, in the main scanning direction, a wiper member 109 is positioned adjacent to the purge device 107 between the purge device 107 and the platen roller 106. The wiper member 109 is a rubber plate-shaped blade that wipes the nozzle forming surface of the inkjet head 102 as the carriage 103 moves.

[0047] In Figure 1, the cap 108 contacts the nozzle-forming surface of the inkjet head 102 and covers multiple nozzles. When recording is complete, the carriage 103 moves to a standby position where the inkjet head 102 faces the cap 108. Then, the cap 108 approaches the inkjet head 102, contacts the nozzle-forming surface, and covers multiple nozzles provided on the nozzle-forming surface.

[0048] In the inkjet recording device 1 of this example, the ink cartridge 101 is mounted on the carriage 103 together with the inkjet head 102, but this is not particularly limited. For example, the ink cartridge 101 may not be mounted on the carriage 103, but may be located inside the inkjet recording device 1. Specifically, the ink cartridge 101 and the inkjet head 102 mounted on the carriage 103 are fluidly connected via the ink flow path such as a tube, and the ink is supplied from the ink cartridge 101 to the inkjet head 102. Alternatively, a bottle-shaped ink bottle may be used instead of the ink cartridge 101. In this case, the inkjet recording device 1 is equipped with an ink tank fixed inside, and the ink tank has an inlet. The user inserts the ink bottle into the inlet of the ink tank and replenishes the ink from the ink bottle into the ink tank.

[0049] The recording process using this inkjet recording device 1 is carried out, for example, as follows. First, a recording medium P is supplied from the rear or below the inkjet recording device 1. The recording medium P is transported by the platen roller 106 to the area facing the inkjet head 102. Once transported, the recording medium P is used to record an image or the like by ejecting aqueous ink from the inkjet head 102. After recording, the recording medium P is discharged from the inkjet recording device 1. In Figure 1, the transport mechanism and discharge mechanism until the recording medium P reaches the platen roller 106 are not shown.

[0050] The apparatus shown in Figure 1 employs a serial inkjet head, but a line-type inkjet head may also be used. Furthermore, the apparatus shown in Figure 1 may employ a roll-to-roll system where the leading edge of the roll paper is wound up by a winding machine. The serial inkjet head prints by reciprocating the inkjet head in the width direction of the recording medium. A line-type inkjet head is longer than the maximum width of the recording medium that the inkjet recording device 1 can record on, and the inkjet head does not reciprocate in the width direction. An inkjet recording device equipped with a line-type inkjet head prints by ejecting ink from the inkjet head toward the paper while transporting the paper.

[0051] Next, the inkjet recording method of this disclosure is an inkjet recording method that includes a recording step of ejecting the aqueous ink from an inkjet head onto a recording medium and recording it on the recording medium. The inkjet recording method of this disclosure can be carried out, for example, using the inkjet recording apparatus of this disclosure. The recording includes printing of characters and images. [Examples]

[0052] Next, embodiments of this disclosure will be described together with comparative examples. However, this disclosure is not limited to or restricted by the embodiments and comparative examples described below.

[0053] (Examples 1-13, Comparative Examples 1-2) The raw materials, excluding the colorant (phycocyanin), in the aqueous ink compositions shown in Table 1 below were uniformly mixed to obtain an ink solvent. Next, the colorant was added to the ink solvent and uniformly mixed. Subsequently, the resulting mixture was filtered through a cellulose acetate type membrane filter (pore size 3.00 μm) manufactured by Toyo Roshi Co., Ltd. to obtain the inkjet recording aqueous inks of Examples 1 to 13 and Comparative Examples 1 to 2 shown in Table 1. In Table 1, the ratio (a / b) of the content of colorant, water-soluble organic solvent, other (water, other water-soluble organic solvents), and phycocyanin to the content of water-soluble organic solvent (b) is shown. Note that "other (water, other water-soluble organic solvents)" is not limited to water and other water-soluble organic solvents, but may also include pH adjusters, viscosity adjusters, preservatives, and antifungal agents.

[0054] For each of the aqueous inks in Examples 1-13 and Comparative Examples 1-2, (a) particle size (D95) based on scattered light intensity, (b) viscosity, and (c) particle size (D95) based on scattered light intensity of the ink after evaporation were evaluated by the following method.

[0055] (a) Particle size (D95) based on scattered light intensity The particle size (D95) based on scattered light intensity was measured for each of the aqueous inks in Examples 1-13 and Comparative Examples 1-2. The particle size (D95) based on scattered light intensity was measured using a dynamic light scattering particle size distribution analyzer (product name: LB-550) manufactured by Horiba, Ltd., on a diluted solution prepared by adding pure water to the aqueous ink to achieve a colorant concentration of 0.1%. The particle size (D95) based on scattered light intensity was evaluated according to the evaluation criteria below.

[0056] Particle size (D95) evaluation criteria based on scattered light intensity A: Less than 1000nm B:1000nm or more

[0057] Furthermore, "Thakur, N., & Murthy, H. (2022). Simulation study of droplet formation in inkjet printing using ANSYS FLUENT. “Journal of Physics: Conference Series” Vol. 2161, No. 1, p. 012026. IOP Publishing." indicates that a method to avoid clogging of inkjet head nozzles is to make the diameter of the particles contained in the inkjet recording ink less than one-tenth of the nozzle diameter. Therefore, for example, when using an inkjet head with a nozzle diameter of 10 μm, the particle diameter (D95) based on the scattered light intensity should be less than 1000 nm, which is one-tenth of the nozzle diameter.

[0058] (b) Viscosity The viscosity of the aqueous inks in Examples 1-13 and Comparative Examples 1-2 was measured. Viscosity measurements were performed using an E-type viscometer (product name: TVE25L viscometer) manufactured by Toki Sangyo Co., Ltd. Viscosity was evaluated according to the following evaluation criteria.

[0059] Viscosity evaluation criteria A: Less than 10.0 mPa·s B:10.0mPa·s or more

[0060] (c) Particle size (D95) based on scattered light intensity of the ink after evaporation 5g each of the aqueous inks from Examples 1-13 and Comparative Examples 1-2 was placed in No. 2 standard bottles (hereinafter referred to as "test samples"). Next, the test samples were stored in a 40°C constant temperature bath for 6 hours with the bottles unsealed. The particle size (D95) based on scattered light intensity was measured using a dynamic light scattering particle size distribution analyzer (product name: LB-550) manufactured by Horiba, Ltd., on a diluted solution prepared by adding pure water to the stored test samples to a colorant concentration of 0.1%. The particle size (D95) based on scattered light intensity of the ink after evaporation was evaluated according to the evaluation criteria below.

[0061] Particle size (D95) evaluation criteria based on scattered light intensity of ink after evaporation A: Less than 1000nm B:1000nm or more

[0062] Even if the evaluation result for particle size (D95) based on scattered light intensity is "A", if the evaluation result for particle size (D95) based on scattered light intensity of the ink after evaporation is "B", it means that the particle size (D95) based on scattered light intensity will increase after evaporation. Therefore, it is necessary to have a maintenance sequence in place to discharge the ink before the particle size (D95) based on scattered light intensity increases. Also, for example, in the case of an inkjet printer, if it is used at least once a week, it is unlikely to reach the same conditions as the ink after evaporation as described in the evaluation method for "(c) Particle size (D95) based on scattered light intensity of the ink after evaporation". Therefore, even if the evaluation result for particle size (D95) based on scattered light intensity of the ink after evaporation is "B", if the evaluation result for particle size (D95) based on scattered light intensity is "A", there is no problem in use. However, if it is used at a low frequency, such as once a month, the particle size (D95) based on scattered light intensity is more likely to increase due to evaporation compared to use at least once a week. Therefore, water-based inks with an evaluation result of "A" for the particle size (D95) based on scattered light intensity after evaporation are of high value to all users, regardless of how often they use their inkjet printers, but are especially of high value to users who use their inkjet printers infrequently.

[0063] Table 1 shows the aqueous ink compositions and evaluation results for Examples 1-13 and Comparative Examples 1-2. LogP was calculated according to the method disclosed in "Wildman, Scott A., and Gordon M. Crippen (1999). Prediction of physicochemical parameters by atomic contributions. “Journal of chemical information and computer sciences” Vol. 39 Issue 5, pp. 868-873. DOI: 10.1021 / ci990307l".

[0064] [Table 1]

[0065] As shown in Table 1, all evaluation results for Examples 1 to 13 were "B" or higher. In particular, since the particle size (D95) based on scattered light intensity for Examples 1 to 13 was all "A", it was found that the ejection stability was higher compared to Comparative Examples 1 to 2, which will be described later. Although the particle size (D95) based on scattered light intensity for the ink after evaporation for Examples 10 to 13 was all "B", this is unlikely to occur if an inkjet printer equipped with the aqueous ink of this disclosure is used at least once a week, so there are no problems in use. On the other hand, since both the particle size (D95) based on scattered light intensity for Examples 1 to 9 and the particle size (D95) based on scattered light intensity for the ink after evaporation were "A", this aqueous ink is of high value to all users regardless of how often they use their inkjet printer, but it is particularly of high value to users who use it infrequently, such as once a month.

[0066] Furthermore, in Examples 1, 2, 4-11, and 13, where the content ratio (a / b) of phycocyanin content (a) to water-soluble organic solvent content (b) was 0.25-2.00, the evaluation results for particle size (D95) and viscosity based on scattered light intensity were all "A".

[0067] Examples 1, 2, 4-11, and 13, in which the content of water-soluble organic solvent in the total weight of the water-based ink was between 5.00% by weight and 40.00% by weight, all received an "A" rating for particle size (D95) and viscosity based on scattered light intensity. Furthermore, Examples 1, 2, 4-11, in which the logP value was -0.5000 or less, all received an "A" rating for particle size (D95) and viscosity based on scattered light intensity.

[0068] Examples 4 to 9, in which the logP was between -1.5000 and -0.5000, and the content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) was between 0.40 and 2.00, all received an evaluation result of "A". Similarly, Examples 1 and 2, in which the logP was less than -1.5000, and the content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) was between 0.25 and 0.40, also received an evaluation result of "A".

[0069] On the other hand, in Comparative Examples 1 and 2, where logP exceeded 0.2000, nozzle clogging could occur due to the large particle size (D95) based on scattered light intensity, resulting in low discharge stability.

[0070] The above embodiments and some or all of the examples may also be described as follows, but are not limited to these. (Note 1) It contains water, phycocyanin, and a water-soluble organic solvent. The aforementioned water-soluble organic solvent includes a water-soluble organic solvent in which the value of logP, which is the common logarithm of (octanol / water partition coefficient P), is 0.2000 or less. Water-based ink for inkjet recording. (Note 2) The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.20 to 2.00. Water-based inkjet recording ink as described in Appendix 1. (Note 3) The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.25 to 2.00. Water-based inkjet recording ink as described in Appendix 2. (Note 4) In the total weight of the aforementioned aqueous ink, The content of the aforementioned water-soluble organic solvent is 5.00% by weight to 40.00% by weight. Water-based inkjet recording ink as described in Appendix 1. (Note 5) The logP value of the water-soluble organic solvent is -0.5000 or less. Water-based inkjet recording ink as described in Appendix 3 or 4. (Note 6) The aforementioned logP is in the range of -1.5000 to -0.5000. The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.40 to 2.00. Water-based inkjet recording ink as described in Appendix 5. (Note 7) The aforementioned logP is less than -1.5000, The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.25 to 0.40. Water-based inkjet recording ink as described in Appendix 5. (Note 8) Including the inkjet head, The aforementioned inkjet head ejects an aqueous inkjet recording ink described in any of appendices 1 to 7 onto a recording medium. Inkjet recording device. (Note 9) The recording process includes ejecting an inkjet water-based inkjet recording ink described in any of Appendix 1 to 7 from an inkjet head onto a recording medium, and recording the ink on the recording medium. Inkjet recording method. [Industrial applicability]

[0071] As described above, this disclosure provides an aqueous inkjet recording ink that uses phycocyanin as a coloring agent and exhibits excellent nozzle ejection stability. The aqueous ink, inkjet recording apparatus, and inkjet recording method of this disclosure are widely applicable to inkjet recording on various recording media. [Explanation of Symbols]

[0072] 1. Inkjet recording device 101 Ink Cartridges 102 Inkjet Heads 103 Carriage 105 Drive Unit 106 Platen Roller 107 Purge device 108 Cap 109 Wiper components

Claims

1. It contains water, phycocyanin, and a water-soluble organic solvent. The aforementioned water-soluble organic solvent includes a water-soluble organic solvent in which the value of logP, which is the common logarithm of (octanol / water partition coefficient P), is 0.2000 or less. Water-based ink for inkjet recording.

2. The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.20 to 2.

00. The aqueous ink for inkjet recording according to claim 1.

3. The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.25 to 2.

00. The aqueous ink for inkjet recording according to claim 2.

4. In the total weight of the aforementioned aqueous ink, The content of the water-soluble organic solvent is 5.00% by weight to 40.00% by weight. The aqueous ink for inkjet recording according to claim 1.

5. The logP value of the water-soluble organic solvent is -0.5000 or less. The aqueous ink for inkjet recording according to claim 3 or 4.

6. The logP is between -1.5000 and -0.5000. The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.40 to 2.

00. The aqueous ink for inkjet recording according to claim 5.

7. The logP is less than -1.5000, The content ratio (a / b) of the phycocyanin content (a) to the water-soluble organic solvent content (b) is 0.25 to 0.

40. The aqueous ink for inkjet recording according to claim 5.

8. Including the inkjet head, The inkjet head ejects the aqueous inkjet recording ink described in claim 1 onto a recording medium. Inkjet recording device.

9. The recording step includes ejecting the aqueous inkjet recording ink described in claim 1 from an inkjet head onto a recording medium and recording the ink on the recording medium. Inkjet recording method.

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