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 surfactant, wherein the critical micelle concentration of the surfactant relative to water is 0.10% by weight 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 Japanese Patent Laid-Open No. 2022-107267 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 of ink for inkjet recording be replaced from a petroleum-derived raw material to a naturally-derived raw material obtained from plants.

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

[0006] Accordingly, the present disclosure aims to provide an aqueous ink for inkjet recording, an inkjet recording apparatus, and an inkjet recording method that use phycocyanin as a coloring material 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 surfactant, wherein the critical micelle concentration of the surfactant relative to water is 0.10% by weight 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 "Slope value" values ​​presented in this disclosure are shown to two decimal places and rounded to the third decimal place. The "1-dot line width" values ​​presented in this disclosure are shown to one decimal place and rounded to the second 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 now be described. The water-based inks of this disclosure are, for example, colored inks. The colored water-based inks are, for example, water-based inks containing a coloring agent as described later.

[0017] The aqueous ink of this disclosure comprises water, phycocyanin, and a surfactant. 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, for example, be the remainder of the other components.

[0019] The aqueous ink of this disclosure is a cyan ink containing at least phycocyanin as the coloring agent. The aqueous ink of this disclosure may also be a cyan ink containing only phycocyanin as the coloring agent. Here, phycocyanin is a naturally occurring pigment protein. The phycocyanin contains phycocyanobilin as the 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 coloring agent.

[0020] The lower limit of the phycocyanin content in the total weight of the aqueous ink may be, for example, 5.00% by weight or more, or 10.00% by weight or more. The upper limit of the phycocyanin content in the total weight of the aqueous ink may be, for example, 15.00% by weight or less, or 10.00% by weight or less. The phycocyanin content in the total weight of the aqueous ink may be, for example, 5.00% by weight to 15.00% by weight, 5.00% by weight to 10.00% by weight, or 10.00% by weight to 15.00% by weight.

[0021] Further, the aqueous ink of the present disclosure may be, for example, a cyan ink that further contains, as the colorant, in addition to phycocyanin, at least one blue dye selected from the group consisting of gardenia blue pigment, indigo, and clerodendrum trichotomum pigment. Further, in the aqueous ink of the present disclosure, 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, black currant 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, red currant pigment, loganberry pigment, beet red pigment, and monascus pigment may be contained. Further, the aqueous ink of the present disclosure is an ink of a color such as green or purple, which contains, 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 pigment.

[0022] Further, the aqueous ink of the present disclosure may be, for example, an ink that further contains a petroleum-derived pigment as the colorant in addition to phycocyanin. By containing phycocyanin and the petroleum-derived pigment as the colorant, for example, the content of the petroleum-derived pigment contained in the aqueous ink is reduced as compared with the case where only the petroleum-derived pigment is contained.

[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, conventionally known polymer dispersants (also referred to as resin dispersants and the like) and 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; "Disperbyk 190" and "Disperbyk 191" 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 petroleum-derived dye contained in the aqueous ink can be reduced compared to, for example, a 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 surfactant contained in the aqueous ink of this disclosure has a critical micelle concentration of 0.10% by weight or less in water. The upper limit of the critical micelle concentration may be, for example, 0.05% by weight or less, or 0.02% by weight or less. The critical micelle concentration refers to the minimum concentration at which the surfactant begins to form micelles in the solution. Therefore, when the surfactant is contained in water, the critical micelle concentration is always greater than 0% by weight.

[0030] Here, surfactants with a low critical micelle concentration in water readily form micelles in water even at low concentrations. As mentioned above, the phycocyanin binds to form a large protein complex. The presence of this protein complex in aqueous ink can cause nozzle clogging, leading to a decrease in ejection stability. On the other hand, when micelles are present in aqueous ink, they interact with the protein complex, causing the association between the protein complexes to dissociate. Therefore, it is believed that using a surfactant with a low critical micelle concentration in water allows for the dissociation of the phycocyanin even with a relatively small amount of surfactant, improving the ejection stability of the aqueous ink from the inkjet head nozzles.

[0031] On the other hand, according to the above principle, it might seem that increasing the amount of surfactant would improve the ejection stability. However, when a head unit is shipped from the factory, the inkjet head and the ink channels for ink supply are filled with a filler liquid different from ink. Before the first print after shipment from the factory, an initial purge is performed in which the filler liquid in the head unit is discharged from the nozzles while ink is introduced from the ink cartridge, thereby replacing the filler liquid with ink. At this time, the ink introduction efficiency is evaluated as an indicator of the replaceability of the filler liquid with ink. Here, as mentioned above, if the amount of surfactant is increased in the expectation of improving the ejection stability, a side effect may be that the ink introduction efficiency deteriorates. Therefore, from the viewpoint of ink introduction efficiency, it is preferable that the amount of surfactant be small.

[0032] Examples of the aforementioned surfactants include rhamnolipid, sophoroselipid, mannosylerythritollipid, trehaloselipid, cellobioselipid, riamosine, spicrispolic acid, and colinomicolic acid.

[0033] The surfactant may be a commercially available product, for example. Examples of commercially available surfactants include "Genagen C 50 SG Vita," "Genagen C 70 SG Vita," and "Genagen C 100 SG Vita" manufactured by CLARIANT.

[0034] The surfactant may be one type of surfactant or two or more types of surfactants.

[0035] The aqueous ink of this disclosure may have a lower limit of the surfactant content in the total weight of the aqueous ink, for example, 0.01% by weight or more, 0.10% by weight or more, or 0.30% by weight or more. The upper limit of the surfactant content in the total weight of the aqueous ink may have an upper limit, for example, 10.00% by weight or less, 5.00% by weight or less, 4.50% by weight or less, 3.00% by weight or less, 1.00% by weight or less, or 0.50% by weight or less. The surfactant content in the total weight of the aqueous ink may be, for example, 0.01% by weight to 10.00% by weight, 0.01% by weight to 5.00% by weight, or 0.30% by weight to 4.50% by weight.

[0036] The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) may have a lower limit of, for example, 1.00 or more, 2.00 or more, or 2.22 or more. The upper limit of the content ratio (a / b) may have a lower limit of, for example, 1000.00 or less, 100.00 or less, 33.33 or less, or 20.00 or less. The content ratio (a / b) may have a range of, for example, 1.00 to 1000.00, 2.00 to 1000.00, or 2.22 to 33.33. When the content ratio (a / b) is 1.00 or more, it is preferable because, for example, the ink ingressability falls within a practical range. Furthermore, when the content ratio (a / b) is 1000.00 or less, it is preferable because, for example, the line width when printing a single dot ejected from the inkjet head (hereinafter sometimes referred to as "1-dot line width") becomes larger.

[0037] The aqueous inks of this disclosure may further contain, as necessary, raw materials such as water-soluble organic solvents, pH adjusters, viscosity adjusters, preservatives, and fungicides. Alternatively, the aqueous inks of this disclosure may contain, for example, only plant-derived raw materials. That is, in the aqueous inks of this disclosure, for example, all components except water may be plant-derived.

[0038] <Inkjet recording device, inkjet recording method> Next, the inkjet recording apparatus and inkjet recording method of this disclosure will be described.

[0039] 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. The aqueous ink of this disclosure is a cyan ink containing only phycocyanin as the coloring agent.

[0040] 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 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.

[0041] 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.

[0042] 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.

[0043] The purging device 107 sucks up defective ink, including air bubbles, that accumulates inside the inkjet head 102. Furthermore, before the first print run, the purging device 107 replaces the storage liquid filled inside the inkjet head 102 with the aqueous ink. For example, a conventionally known device may be used as the purging device 107 (see, for example, Japanese Patent Application Publication No. 2008-246821).

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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]

[0050] 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.

[0051] (Examples 1-10, Comparative Examples 1-3) The raw materials, excluding the colorant (phycocyanin), in the aqueous ink composition 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 obtained 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 10 and Comparative Examples 1 to 3 shown in Table 1. Comparative Examples 1 to 3 used "Orphine® E1004," "Orphine® E1010," and lecithin, manufactured by Nisshin Chemical Industry Co., Ltd., as surfactants. Table 1 shows the content ratio (a / b) of the colorant, surfactant, other (water, other water-soluble organic solvents), and phycocyanin content (a) to the surfactant content (b). 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.

[0052] For each of the aqueous inks in Examples 1-10 and Comparative Examples 1-3, (a) dispersion stability, (b) ink transferability, and (c) 1-dot line width were evaluated by the following methods.

[0053] (a) Dispersion stability For each of the aqueous inks in Examples 1-10 and Comparative Examples 1-3, 0.4 mL of the mixture before filtration was sealed in a 2 × 50 mm measuring cell. Next, the measuring cell was set in a dispersion stability analyzer (LUM, product name: LUMISIZER®) and centrifuged at 3000 rpm for 3 hours. The behavior was measured using an 865 nm CCD line sensor. The slope value (% / hour) was calculated based on the absorption rate per unit time. The dispersion stability was evaluated according to the evaluation criteria below.

[0054] Furthermore, if the dispersion of colorants in the ink becomes unstable, aggregation of the colorants may occur, increasing the likelihood that ink will not be ejected from the inkjet head nozzles. Therefore, if dispersion stability is low, the ejection stability from the inkjet head nozzles also tends to decrease. Consequently, dispersion stability is one indicator of ejection stability.

[0055] Dispersion stability evaluation criteria A: Slope value is less than 1.00 C:Slope value is 1.00 or higher

[0056] (b) Ink introduction The aqueous inks of Examples 1-10 and Comparative Examples 1-3 were filled into ink cartridges for Brother Industries, Ltd.'s MFC-J904N inkjet printer. After installing the ink cartridges filled with aqueous ink into the inkjet printer, a purging device was used to suction the filler liquid in the ink flow path system and replace it with aqueous ink. Subsequently, the percentage of nozzles with good ejection (hereinafter referred to as the percentage of nozzles with good ejection) relative to all nozzles in the initial ejection immediately after the completion of suction was checked. The ink introduction performance was evaluated according to the evaluation criteria below. Note that the higher the ink introduction performance, the less likely pin drop-offs will occur in the printed image.

[0057] Ink Inletability Evaluation Criteria A: Over 95% of nozzles have good discharge performance. B: Percentage of nozzles with good discharge is less than 95%

[0058] (c) 1 dot line width The water-based inks of Examples 1-10 and Comparative Examples 1-3 were filled into ink cartridges for Brother Industries, Ltd.'s MFC-J904N inkjet printer, and a 1-dot line was recorded on copy paper (ASKUL Corporation, product name: Multi Paper Super White+) at a resolution of 600 dpi x 300 dpi. The line width of the recorded line was measured using the handheld image evaluation system "PIAS®-II" manufactured by Quality Engineering Associates (QEA). The 1-dot line width was evaluated according to the evaluation criteria below.

[0059] 1-dot line width evaluation criteria A: Line width of 1 dot is 70.0 μm or more B: Line width of 1 dot is less than 70.0 μm

[0060] Table 1 shows the aqueous ink compositions and evaluation results of the aqueous inks used in Examples 1-10 and Comparative Examples 1-3.

[0061] [Table 1]

[0062] As shown in Table 1, all evaluation results for Examples 1 to 10 were "B" or higher. In particular, since all of Examples 1 to 10 had a dispersion stability of "A", it was found that they had higher discharge stability compared to Comparative Examples 1 to 3, which will be discussed later.

[0063] Furthermore, in Examples 1 to 10, where the content ratio (a / b) of phycocyanin content (a) to surfactant content (b) was 1.0 to 1000.0, all evaluation results were "B" or higher. In addition, in Examples 1 to 4 and 6 to 10, where the content ratio (a / b) was 2.0 to 1000.0, the ink inletability evaluation result was 90% or higher. Furthermore, in Examples 1, 4 and 7 to 10, where the content ratio (a / b) was 2.2 to 33.3, all evaluation results were "A".

[0064] Furthermore, in Examples 1-4 and 6-10, where the surfactant content relative to the total weight of the water-based ink was 0.01% to 5.00% by weight, the ink inletability evaluation result was 90% or higher. In addition, in Examples 1, 4 and 7-10, where the surfactant content relative to the total weight of the water-based ink was 0.30% to 4.50% by weight, all evaluation results were "A".

[0065] On the other hand, in Comparative Examples 1-3, where the critical micelle concentration of the surfactant relative to water exceeded 0.10% by weight, the dispersion stability evaluation result was "C," and the ink inletability and dot line width evaluation results were "unprintable."

[0066] 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 surfactant. The critical micelle concentration of the surfactant in water is 0.10% by weight or less. Water-based ink for inkjet recording. (Note 2) The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 1.00 to 1000.00. Water-based inkjet recording ink as described in Appendix 1. (Note 3) The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.00 to 1000.00. Water-based inkjet recording ink as described in Appendix 2. (Note 4) The water-based inkjet recording ink described in Appendix 3, wherein the content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.22 to 33.33. (Note 5) In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.01% by weight to 5.00% by weight. Water-based inkjet recording ink as described in any of the notes 1 to 4. (Note 6) In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.30% by weight to 4.50% by weight. Water-based inkjet recording ink as described in Appendix 5. (Note 7) The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.00 to 1000.00. In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.30% by weight to 4.50% by weight. Water-based inkjet recording ink as described in Appendix 1. (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]

[0067] 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]

[0068] 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 surfactant. The critical micelle concentration of the surfactant in water is 0.10% by weight or less. Water-based ink for inkjet recording.

2. The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 1.00 to 1000.

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

3. The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.00 to 1000.

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

4. The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.22 to 33.

33. The aqueous ink for inkjet recording according to claim 3.

5. In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.01% by weight to 5.00% by weight. The aqueous ink for inkjet recording according to claim 1.

6. In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.30% by weight to 4.50% by weight. The aqueous ink for inkjet recording according to claim 5.

7. The content ratio (a / b) of the phycocyanin content (a) to the surfactant content (b) is 2.00 to 1000.

00. In the total weight of the aforementioned aqueous ink, The content of the surfactant is 0.30% by weight to 4.50% by weight. The aqueous ink for inkjet recording according to claim 1.

8. Including the inkjet head, The inkjet head ejects the aqueous inkjet recording ink described in any one of claims 1 to 7 onto a recording medium. Inkjet recording device.

9. The recording step includes ejecting an aqueous inkjet recording ink according to any one of claims 1 to 7 from an inkjet head onto a recording medium and recording the ink on the recording medium. Inkjet recording method.

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