Aqueous inkjet ink composition and recording method

Abstract

Provided are an aqueous inkjet ink composition having excellent storage stability and a recording method. The aqueous inkjet ink composition contains a colorant and fulvic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to an aqueous inkjet ink composition and a recording method. BACKGROUND

[0002] An inkjet recording method is capable of recording a high-fineness image with a relatively simple device, and has rapidly developed in various aspects. In recent years, in consideration of environmental problems, development of an ink composition using a material derived from a natural product has also been conducted. For example, in Patent Literature 1, an inkjet ink composition is disclosed, which is characterized by containing a predetermined chelating agent and water, and has a pH (hydrogen ion index) of more than 7 and 10 or less, with an object of providing an inkjet ink composition containing a chelating agent excellent in biodegradability, and excellent in jetting stability for a long period of time.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2014-185239

[0006] Further improvement in storage stability and jetting stability of such an inkjet ink composition is required. SUMMARY

[0007] The aqueous inkjet ink composition of the present application contains a color material and a fulvic acid.

[0008] The recording method of the present application has an attaching step of jetting the above inkjet ink composition from an inkjet head and attaching it to a recording medium.

[0009] The recorded matter of the present application is a recorded matter in which the above ink composition is attached to a recording medium. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 Table 1 is a table showing evaluation results of Examples.

[0011] Figure 2 Table 2 is a table showing evaluation results of Comparative Examples and Reference Examples.

[0012] Figure 3 Table 3 is a table showing evaluation results of Example 9, Comparative Examples 2 and 3, and Reference Example 1.

[0013] Figure 4 FIG. 1 is a view showing an example of a recording device used in the recording method of the present embodiment.

[0014] EXPLANATION OF REFERENCE NUMERALS

[0015] 10, recording device; 11, conveyance path; 12, feeding section; 14, conveyance section; 16, tape conveyance section; 18, recording section; 20, Fd discharge section; 22, Fd placement section; 24, reversal path section; 26, Fu discharge section; 28, Fu placement section; 30, feeding tray; 32, feeding roller; 34, conveyance drive roller; 36, conveyance driven roller; 38, first roller; 40, second roller; 42, endless belt; 42a, upper side section of endless belt; 44, support body; 46, head holder; 48, inkjet head; 50, first branch section; 52, reversal path; 54, second branch section; 56, discharge roller pair; 64, discharge drive roller; 68, drive shaft; 76, placement surface; 78, convex section; 80, first urging member; 82, second urging member; 84, 86, support shaft; P, recording medium. DETAILED DESCRIPTION

[0016] Hereinafter, an embodiment of the present application (hereinafter referred to as "the present embodiment") will be described in detail as needed with reference to the accompanying drawings, but the present application is not limited to this, and various modifications can be made within the scope of the gist thereof. In addition, in the drawings, the same reference numerals are attached to the same elements, and the repeated description is omitted. Furthermore, the positional relationship of up, down, left, right, and the like is based on the positional relationship shown in the drawings unless specifically described. Furthermore, the dimensional ratio of the drawings is not limited to the ratio shown in the drawings. Figure 1

[0017] 1. Inkjet ink composition

[0018] The inkjet ink composition (hereinafter, also simply referred to as "ink composition") according to the present embodiment contains a color material and a fulvic acid.

[0019] In the ink composition, metal ions that are mixed from the constituent materials thereof, or metal ions that are mixed into the ink composition from the contact parts of the ink composition such as the ink composition container, the ink composition flow path of the printer, or the print head. Such metal ions become a main cause of insoluble salts, foreign matters generated in the ink composition, and thus decrease the storage stability, the ejection stability of the ink composition. Therefore, in the ink composition, sometimes a chelating agent is used in order to capture metal ions.

[0020] However, the chelating agent such as EDTA is pointed out as harmful in GHS classification, or is not decomposed by microorganisms and the like, and thus there is a problem from the viewpoint of environmental protection. In addition, the chelating agent synthesized from a material from petroleum has a problem in terms of environmental adaptability such as reduction of carbon dioxide. In addition to this, as a chelating agent that is decomposed by microorganisms, IDS is known, but it is difficult to form a complex in a state where the pH is low, and the function of the chelating agent decreases. Therefore, there is also a problem that the storage stability, the ejection stability in an acidic state deteriorate. ​

[0021] Therefore, in the present embodiment, fulvic acid is used as the chelating agent. Fulvic acid is derived from plants and is not toxic, and thus has high environmental adaptability. Furthermore, fulvic acid has good water solubility in an acidic or basic environment, and furthermore, the pH dependence of the chelating function is low, and thus it is possible to capture metal ions in a wide range of pH environments, and it is possible to improve the storage stability and the ejection stability.

[0022] Hereinafter, the components that can be contained in the ink composition according to the present embodiment and the manufacturing method will be described in detail.

[0023] 1.1. Colorant

[0024] The colorant is not particularly limited, and pigments and dyes can be given as examples. Among them, pigments are preferred. The colorant can be used alone or in combination with two or more.

[0025] The pigment is not particularly limited, and carbon black (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, channel black, inorganic pigments such as iron oxide, titanium oxide; quinacridone-based pigments, quinacridonequinone-based pigments, dioxazine-based pigments, phthalocyanine-based pigments, anthraquinopyrimidine-based pigments, anthrachrysoidine-based pigments, indanthrone-based pigments, flavanthrone-based pigments, perylene-based pigments, diketopyrrolopyrrole-based pigments, pyromethene-based pigments, quinophthalone-based pigments, anthraquinone-based pigments, thioindigo-based pigments, benzimidazolone-based pigments, isoindolinone-based pigments, azomethine-based pigments, and azo-based pigments, and the like can be given as examples.

[0026] Furthermore, the pigment can also be, for example, prepared charcoal, bamboo charcoal, activated charcoal, white charcoal, black charcoal, molded charcoal, sawdust charcoal, plum charcoal, activated charcoal, oak charcoal, douglas-fir charcoal, seaweed charcoal, mangrove charcoal, coconut shell charcoal, and the like, which are plant carbons obtained by carbonizing plants; plant oil carbons (plant oil carbon black) obtained by carbonizing plant oils, and the like, which are pigments derived from biomass.

[0027] In particular, as the carbon black, carbon black derived from petroleum, carbon black derived from biomass, and carbon black derived from recycling can also be contained. Among them, from the viewpoint of reducing components derived from petroleum, reducing carbon dioxide emissions from components derived from petroleum, and improving environmental adaptability, carbon black derived from biomass is preferred.

[0028] Among them, pigments from biomass or from recycling are preferable, and pigments from biomass are more preferable. Pigments from biomass or from recycling have a tendency to easily contain metal ions of impurities due to the raw material. Therefore, it is easy to make metal ions receive the chelating effect by fulvic acid. Furthermore, in the case of using carbon black as a colorant, due to the influence of impurities, the tendency of the carbon black of pigments from biomass or from recycling to be acidified with the decrease in the pH of the ink composition under long-term storage is particularly remarkable. Therefore, it is preferable to use fulvic acid with low pH dependence of chelating function. Furthermore, pigments from biomass or from recycling have a tendency to have a large average particle diameter and a large particle size distribution in addition to a large amount of impurities, and therefore, it is easy to damage the storage stability due to metal ions. From this point of view, it is also preferable to use fulvic acid to improve the storage stability and the ejection stability.

[0029] In addition, in the present specification, "from biomass" means a substance that is not manufactured from a raw material from fossil fuels such as petroleum, coal, and the like, but is manufactured from a raw material from living organisms such as plants, animals, microorganisms, and the like. Furthermore, from recycling means a substance manufactured from a recycled raw material, and for example, carbon black obtained by thermal decomposition of waste tires and the like can be given.

[0030] In addition, the pigment can be a self-dispersing pigment that can be dispersed in an aqueous medium without a dispersant, or can be a resin-dispersed pigment dispersed by a resin. Among them, the resin-dispersed pigment is preferable.

[0031] The self-dispersing pigment means a pigment that can be dispersed in an aqueous medium without a dispersant. As such a self-dispersing pigment, for example, a pigment that is directly introduced with a hydrophilic functional group or the like on the surface of the pigment by performing physical or chemical surface treatment and dispersed in a solvent can be given.

[0032] The resin-dispersed pigment means a pigment dispersed by a resin. As the resin-dispersed pigment, a pigment that has undergone a process of dispersing treatment of the colorant by a resin dispersant, or a pigment that has undergone a process of surface-coating and encapsulation of the colorant by a resin and dispersed can be given.

[0033] The content of the colorant is preferably 0.1 to 20 mass%, 1 to 15 mass%, 3 to 10 mass%, 5 to 8 mass% with respect to the total amount of the ink composition. By the content of the colorant being within the above range, there is a tendency that the storage stability and the ejection stability are further improved.

[0034] 1.2. Dispersant

[0035] As the dispersant, there is no particular limitation, and for example, lignin sulfonate; as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylate copolymer, vinyl acetate-(meth)acrylate copolymer, vinyl acetate-(meth)acrylic acid copolymer, vinyl naphthalene-(meth)acrylic acid copolymer and the like (meth)acrylic acid-based resin, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, styrene-a-methylstyrene-(meth)acrylic acid copolymer, styrene-a-methylstyrene-(meth)acrylic acid-(meth)acrylate copolymer and salts thereof; as styrene-maleic acid copolymer, styrene-maleic anhydride copolymer and the like and salts thereof; a high molecular compound containing urethane bonds formed by the reaction of isocyanate groups with hydroxyl groups, a polyurethane-based resin which can be linear and / or branched, with or without crosslinked structure, and salts thereof; polyvinyl alcohol; vinyl naphthalene-maleic acid copolymer and salts thereof; vinyl acetate-maleate copolymer and salts thereof; and vinyl acetate-tiglic acid copolymer and salts thereof and the like water-soluble resins. Among them, a copolymer of a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group, and a polymer composed of a monomer having both a hydrophobic functional group and a hydrophilic functional group are preferred. As the form of the copolymer, any one of random copolymer, block copolymer, alternating copolymer, graft copolymer can be used.

[0036] Among them, a lignin sulfonate or an acrylic resin dispersant is preferred. The acrylic resin is a resin using at least an acrylic acid monomer as described above. It can also be an acrylic resin using an acrylic acid monomer and a monomer other than the acrylic acid monomer. Among the acrylic resins, an acrylic-vinyl resin is preferred.

[0037] By using such a dispersant, there is a tendency that the storage stability and the discharge stability are improved.

[0038] As the commercially available lignin sulfonate, for example, Pearllex NP (manufactured by Nippon Paper Industries Co., Ltd.), Pearllex DP (manufactured by Nippon Paper Industries Co., Ltd.), Vanillex N (manufactured by Nippon Paper Industries Co., Ltd.), 471038-100G (manufactured by Sigma-Aldrich), New Calgen WG-4 (manufactured by Takemoto Oil & Fat Co., Ltd.), San X P252 (manufactured by Nippon Paper Industries Co., Ltd.) and the like can be mentioned.

[0039] As commercially available products of the acrylic resin dispersant, for example, X-200, X-1, X-205, X-220, X-228 (manufactured by Star PMC Co., Ltd.), Nopcosperse (registered trademark) 6100, 6110 (manufactured by San Nopco Ltd.), Joncryl 67, 586, 611, 678, 680, 682, 819 (manufactured by BASF Corporation), DISPERBYK-190 (manufactured by BYK Japan KK), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, E-EN10 (manufactured by the First Industrial Co., Ltd.), and the like can be given.

[0040] The content of the dispersant is preferably 1.0 to 15 mass%, 2.0 to 12 mass%, 3.0 to 9.0 mass% with respect to the total amount of the ink composition. By the content of the dispersant being within the above range, there is a tendency that the storage stability and the jetting stability are further improved.

[0041] 1.3. Fulvic acid

[0042] The ink composition contains fulvic acid. In addition, the fulvic acid can also be in the state of a fulvic acid salt. The fulvic acid functions as a chelating agent, and by capturing metal ions, there is a tendency that the storage stability and the jetting stability are further improved.

[0043] Fulvic acid is a general term of a group of substances that are not precipitated by acid among substances contained in humus. It can be obtained by separation and purification from soil using acid and alkali, and can also be obtained as a commercially available product. Furthermore, it is generated in the process of oxidation treatment such as self-dispersion of carbon black. The fulvic acid thus obtained has high water solubility and low pH dependency, and thus can maintain water solubility in a wide pH range, and is not easily foreignized even in the case of a change in pH. That is, even when a change in the state in the ink composition occurs, it can be usefully functional as a chelating agent. Therefore, the storage stability and the like are also excellent.

[0044] In the present embodiment, the fulvic acid can be prepared by mixing another prepared substance, or can be used by concentrating or diluting the fulvic acid separated from the treatment liquid generated incidentally when the carbon black from biomass is subjected to oxidation treatment.

[0045] The fulvic acid preferably has a peak at a fluorescence wavelength (EM) of 380 to 600 nm and an excitation wavelength (EX) of 180 to 320 nm in the excitation fluorescence matrix analysis method, and more preferably has a peak at a fluorescence wavelength (EM) of 400 to 600 nm and an excitation wavelength (EX) of 200 to 300 nm in the excitation fluorescence matrix analysis method. That is, it is preferable to have a peak in the range of the excitation wavelength (EX) corresponding to the range of the above-described fluorescence wavelength (EM).

[0046] The fulvic acid generated when the carbon black is subjected to the oxidation treatment can also have a peak of the fluorescence wavelength and the excitation wavelength in the above-described range. Such fulvic acid has a carbon skeleton similar to that of the carbon black, has high affinity with the carbon black, and easily exerts the dispersion stabilizing effect, and thus has a tendency that the storage stability is further improved.

[0047] The peak position of the fluorescence wavelength in the excitation fluorescence matrix analysis method of the fulvic acid of the present embodiment is preferably 400 to 550 nm, 400 to 500 nm, 420 to 480 nm, or 430 to 460 nm. By having the fluorescence wavelength of the fulvic acid in the above-described range, the fulvic acid has a tendency that the storage stability is further improved.

[0048] The peak position of the excitation wavelength in the excitation fluorescence matrix analysis method of the fulvic acid of the present embodiment is preferably 200 to 320 nm, 200 to 300 nm, 220 to 280 nm, or 240 to 270 nm. By having the excitation wavelength of the fulvic acid in the above-described range, the fulvic acid has a tendency that the storage stability is further improved.

[0049] The number of peaks of the fluorescence wavelength and the excitation wavelength of the fulvic acid in the excitation fluorescence matrix analysis method can be one or more, and for example, can be 1 to 5. Further, it can be 2 to 3. In addition, in the case where the fulvic acid has a plurality of peaks, it is preferable that at least one peak satisfies the above-described wavelength region. It is more preferable that all the peaks satisfy the above-described wavelength region. That is, it is more preferable that there is no peak that does not satisfy the above-described wavelength region.

[0050] The content B of the fulvic acid with respect to the total amount of the ink composition is preferably 0.005 to 5.0 mass%, 0.001 to 4.0 mass%, 0.03 to 3.0 mass%, 0.05 to 2.0 mass%, or 0.10 to 1.0 mass%. By having the content B of the fulvic acid in the above-described range, the fulvic acid has a tendency that the storage stability is further improved.

[0051] The mass ratio (B / A) of the content B of the fulvic acid to the content A of the colorant is preferably 0.0001 to 0.5, 0.001 to 0.4, 0.005 to 0.3, or 0.01 to 0.2. By having the mass ratio of the content B of the fulvic acid to the content A of the colorant in the above-described range, the fulvic acid has a tendency that the storage stability is further improved.

[0052] 1.4. Metal ions

[0053] The less the content of the metal ions contained in the ink composition, the more the decrease in the storage stability and the decrease in the discharge stability from the metal ions are suppressed. From such a viewpoint, the total content of the metal ions of one or more elements selected from the group consisting of Ca, Mg, Al, Fe, Si, Zn, Cu, and Sn with respect to the total amount of the ink composition is preferably 140 ppm or less, 120 ppm or less, 100 ppm or less, 80 ppm or less. In particular, the total content of the metal ions of two or more valences with respect to the total amount of the ink composition is preferably 140 ppm or less, 120 ppm or less, 100 ppm or less, 80 ppm or less. Further, the total content of the metal ions of one or more elements selected from the group consisting of Ca, Mg, Al, Fe, Si, Zn, Cu, and Sn with respect to the total amount of the ink composition is 0 ppm or more, and is preferably 1 ppm or more, 5 ppm or more, 10 ppm or more, 15 ppm or more. Further, it can be 30 ppm or more, or 50 ppm or more.

[0054] By the content of the above metal ions being 140 ppm or less, there is a tendency that the storage stability and the discharge stability are more improved by the action of fulvic acid. Further, by the content of the above metal ions being 1 ppm or more, it is not necessary to excessively refine the ink composition or the raw material, and in addition to the fact that the production of the ink composition becomes easier, even if some metal ions are contained, there is a tendency that the improvement of the storage stability and the discharge stability by fulvic acid is exerted.

[0055] 1.5. Organic solvent

[0056] The ink composition can also contain an organic solvent. As the organic solvent, for example, polyhydric alcohols, glycol ethers, and the like can be given. As the polyhydric alcohols, for example, diethylene glycol, 1,2-hexanediol, propylene glycol, glycerol, and the like can be given. The glycol ethers are single ethers or diethers of alkylene glycols, and for example, ethylene glycol monomethyl ether, triethylene glycol monobutyl ether, and the like can be given. The organic solvent can be used singly or in combination of two or more.

[0057] The content of the organic solvent with respect to the total amount of the ink composition is preferably 1% by mass or more. Further, it is further preferably 5 to 35% by mass, 10 to 30% by mass, 15 to 25% by mass. By the content of the organic solvent being in the above range, there is a tendency that the storage stability and the discharge stability are more improved.

[0058] 1.6. Surfactant

[0059] The ink composition can also contain a surfactant. As the surfactant, for example, a silicone-based surfactant, an acetylenic diol-based surfactant, a fluorine-based surfactant, and the like can be given. The surfactant can be used singly or in combination of two or more.

[0060] As the acetylenic diol-based surfactant, there is no particular limitation, and for example, one or more selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and an alkylene oxide adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and an alkylene oxide adduct of 2,4-dimethyl-5-decyne-4-ol are preferred. As a commercially available product of the acetylenic diol-based surfactant, there is no particular limitation, and for example, the E series (trade name, manufactured by Air Products Corporation) such as olfine 104 series, olfine E1010, Surfynol 61, 104, 465 (trade name, manufactured by Shinto Chemical Industry Co., Ltd.), and the like can be given. Among them, from the viewpoint of more effectively and reliably exerting the effects of the present application, it is preferred to contain olfine E1010 as the surface tension adjusting agent.

[0061] The content of the surfactant is preferably 0.01 to 1.5% by mass, 0.05 to 1% by mass, 0.07 to 0.8% by mass, relative to the total amount of the ink composition. By the content of the surfactant being within the above range, there is a tendency that the storage stability and the ejection stability are further improved.

[0062] 1.7. pH Adjusting Agent

[0063] The ink composition can also contain a pH adjusting agent as needed. As the pH adjusting agent, for example, inorganic acids (for example, sulfuric acid, hydrochloric acid, nitric acid, and the like), inorganic bases (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, and the like), organic acids (for example, adipic acid, citric acid, succinic acid, and the like), organic bases (triethanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, trishydroxymethyl aminomethane) can be given. In addition, the pH adjusting agent can be used singly or in combination of two or more.

[0064] The content of the pH adjusting agent is preferably 0.1 to 2.0% by mass, 0.3 to 1.5% by mass, 0.5 to 1.2% by mass, relative to the total amount of the ink composition. By the content of the pH adjusting agent being within the above range, there is a tendency that the chelating effect of the fulvic acid, the storage stability, and the ejection stability are further improved.

[0065] 1.8. Water

[0066] The content of water is preferably 50 to 95 mass%, 55 to 90 mass%, or 60 to 85 mass% relative to the total amount of the ink composition. By having the content of water within the above range, there is a tendency for the ink composition to have excellent storage stability and ejection stability.

[0067] 1.9. Other Components

[0068] The ink composition can also include components other than the above components. As the other components, a dissolution aid, a viscosity modifier, an antioxidant, a preservative, a mold inhibitor, a corrosion inhibitor, and various additives can be appropriately added.

[0069] 1.10. pH

[0070] The pH of the ink composition of the present embodiment after storage at 40°C for 2 months is preferably 8 or less, 7 or less, less than 7, 6.7 or less, or 6.5 or less. Furthermore, the lower limit of the pH is preferably 4 or more, 5 or more, or 6 or more. The storage condition of storage at 40°C for 2 months is sufficiently assumed to be a storage condition of a general ink composition, but even in the above acidic condition, in the ink composition of the present embodiment, fulvic acid effectively functions as a chelating agent, and thus the storage stability and the ejection stability are excellent.

[0071] In addition, the pH of the ink composition of the present embodiment after storage at 60°C for 1 day is preferably 7 to 10.0, 7.5 to 9.0, or 8.0 to 8.5.

[0072] 2. Recording Method

[0073] The recording method according to the present embodiment has an attaching step of ejecting the above ink composition from an inkjet head and attaching it to a recording medium. Furthermore, the recording method according to the present embodiment can also have a conveying step of conveying the recording medium, and the step of attaching and the step of conveying can be performed simultaneously.

[0074] 3. Recording Device

[0075] The recording device according to the present embodiment is a recording device that performs recording using the above ink composition. The recording device can also be an inkjet recording device that performs recording by an inkjet method, which is preferable.

[0076] The inkjet recording device of the present embodiment is provided with the above ink composition and an inkjet head having a nozzle that ejects the above ink composition toward a recording medium, and is preferably further provided with a supply flow path that circulates the above ink composition and is connected to the inkjet head, and a filter unit provided in the above supply flow path of the above inkjet head.

[0077] In Figure 4 , an example of an inkjet recording device is shown as an example of a recording device that can be used in the present embodiment. The example will be described with reference toFigure 4 The inkjet recording apparatus according to the present embodiment will be described in further detail. Figure 4 The X direction of the X-Y-Z coordinate system shown indicates the length direction of the recording medium, the Y direction indicates the width direction of the recording medium in the conveyance path in the recording apparatus, and the Z direction indicates the apparatus height direction.

[0078] The recording apparatus 10 is a line-type inkjet printer capable of high-speed and high-density printing, for example. The recording apparatus 10 is provided with a feeding section 12 that houses a recording medium P such as a sheet, a conveyance section 14, a belt conveyance section 16, a recording section 18, an Fd (face down) discharge section 20 that is a "discharge section", an Fd (face down) placement section 22 that is a "placement section", a flip path section 24 that is a "flip conveyance mechanism", an Fu (face up) discharge section 26, and an Fu (face up) placement section 28.

[0079] The feeding section 12 is disposed in the lower portion of the recording apparatus 10. The feeding section 12 is provided with a feeding tray 30 that houses the recording medium P and a feeding roller 32 that feeds the recording medium P housed in the feeding tray 30 to the conveyance path 11.

[0080] The recording medium P housed in the feeding tray 30 is fed to the conveyance section 14 along the conveyance path 11 by the feeding roller 32. The conveyance section 14 is provided with a conveyance drive roller 34 and a conveyance driven roller 36. The conveyance drive roller 34 is rotationally driven by a drive source not shown. In the conveyance section 14, the recording medium P is pinched (clamped) between the conveyance drive roller 34 and the conveyance driven roller 36, and is conveyed to the belt conveyance section 16 on the downstream side of the conveyance path 11.

[0081] The belt conveyance section 16 is provided with a first roller 38 on the upstream side on the conveyance path 11, a second roller 40 on the downstream side, an endless belt 42 rotatably installed to the first roller 38 and the second roller 40, and a support body 44 that supports an upper side interval 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0082] The endless belt 42 is driven by the first roller 38 or the second roller 40 driven by a drive source not shown in such a manner that it moves in the upper side interval 42a from the +X direction toward the -X direction. Thus, the recording medium P conveyed from the conveyance section 14 is further conveyed to the downstream side of the conveyance path 11 in the belt conveyance section 16.

[0083] The recording section 18 is provided with a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. In addition, the recording section 18 can also be a serial-type recording section in which an inkjet head is provided on a carriage that reciprocates in the Y-axis direction. The inkjet head 48 is disposed in opposition to the upper interval 42a of the endless belt 42 that is supported by the support body 44. When the recording medium P is conveyed in the upper interval 42a of the endless belt 42, the inkjet head 48 ejects an ink composition toward the recording medium P, and recording is performed. The recording medium P is conveyed by the belt conveying section 16 to the downstream side of the conveying path 11 while recording is performed.

[0084] A first branch section 50 is provided on the downstream side of the conveying path 11 of the belt conveying section 16. The first branch section 50 is configured to be switchable to either the conveying path 11 that conveys the recording medium P to the Fd discharge section 20 or the Fu discharge section 26, or a reversing path 52 of a reversing path section 24 that reverses the recording surface of the recording medium P and conveys the recording medium P again to the recording section 18. In addition, the recording medium P that is conveyed by the first branch section 50 to be switched to the reversing path 52 is reversed in the recording surface during conveyance in the reversing path 52, and is conveyed again to the recording section 18 in a manner in which the face on the opposite side to the original recording surface opposes the inkjet head 48.

[0085] A second branch section 54 is also provided on the downstream side of the first branch section 50 along the conveying path 11. The second branch section 54 is configured to switch the direction of conveyance of the recording medium P to either convey the recording medium P to the Fd discharge section 20, or convey the recording medium P to the Fu discharge section 26.

[0086] In the second branch section 54, the recording medium P that is conveyed to the Fd discharge section 20 is discharged from the Fd discharge section 20 and placed on the Fd placement section 22. At this time, the recording surface of the recording medium P is placed in opposition to the Fd placement section 22. In addition, in the second branch section 54, the recording medium P that is conveyed to the Fu discharge section 26 is discharged from the Fu discharge section 26 and placed on the Fu placement section 28. At this time, the recording surface of the recording medium P is placed facing the side opposite to the Fu placement section 28.

[0087] 4. Recording medium

[0088] As the recording medium used in the present embodiment, there is no particular limitation, and for example, an absorbent recording medium, a low-absorbent recording medium, or a non-absorbent recording medium can be cited, and an absorbent recording medium is preferable.

[0089] Examples of absorbent recording media include ordinary paper such as electrophotographic paper with high ink composition permeability, inkjet paper (inkjet-specific paper with an ink composition absorbent layer composed of silica particles or alumina particles or an ink composition absorbent layer composed of hydrophilic polymers such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), or corrugated cardboard, cotton, silk, blended fabrics, etc.

[0090] Examples of low-absorbency recording media include coated paper, cast-coated paper, and other materials commonly used in offset printing, where the ink composition has relatively low permeability.

[0091] Examples of non-absorbent recording media include films or sheets made of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; metal plates such as iron, silver, copper, and aluminum; metal plates or plastic films made by vapor deposition of these various metals; alloy plates such as stainless steel or brass; and recording media made by bonding (coating) films made of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane onto a paper substrate.

[0092] 5. Records

[0093] The recording medium of this embodiment is obtained by attaching the above-described ink composition to a recording medium. The recording medium of this embodiment using the above-described ink composition can be recorded using an ink composition with excellent preservation and ejection stability. Furthermore, by using an ink composition containing carbon black from biomass or carbon black from recycled raw materials, recording can be performed while considering the environment, using an ink composition with excellent preservation and ejection stability.

[0094] Example

[0095] The present invention will now be described in more detail using examples and comparative examples. The present invention is not limited to the following examples.

[0096] exist Figure 1 Table 1 shows the composition and evaluation results of each ink composition of the examples and comparative examples.

[0097] 1. Preparation of ink composition

[0098] The pigment and dispersant were mixed in the mass ratio described in Table 1 and Table 2, and stirring was performed in water to prepare a pigment dispersion liquid. Then, the obtained pigment dispersion liquid and the remaining ingredients were mixed to obtain an ink composition. In addition, the numerical values of each ingredient shown in each example in the table indicate mass % unless otherwise specified. Furthermore, in the table, each numerical value indicates the mass % of the solid content of the ingredient.

[0099] Further, in order to objectively judge the state of the presence of metal in the ink composition, the ink composition in a state in which metal atoms were added was evaluated. Specifically, the following metal atoms were added to each ink in a manner so as to become the composition described in Table 1 and Table 2. At this time, the CB from plants contains metal from the pigment, so the amount of metal ions in a state in which metal from the pigment is also contained was adjusted to the values shown in Table 1 and Table 2. Furthermore, as necessary, purification of the pigment was also performed so that the amount of metal ions became the values shown in Table 1 and Table 2.

[0100] The details of the product ingredients used in Table 1 and Table 2 are described below.

[0101] Colorant

[0102] CB from petroleum (Aqua-Black 162, manufactured by Tokai Carbon Co., Ltd.)

[0103] Kiriya carbon (manufactured by Kiriya Chemical Industry Co., Ltd.)

[0104] CB from plants (Vegetable oil-based, manufactured by Orion Engineered Carbons)

[0105] Dispersant

[0106] Joncryl 678 (styrene acrylic resin, manufactured by BASF)

[0107] Pearllex NP (Na lignosulfonate, manufactured by Nippon Paper Industries Co., Ltd.)

[0108] Chelating agent

[0109] Fulvic acid (see Adjustment Example 1 described below)

[0110] IDS (iminodisuccinic acid 4Na)

[0111] EDTA (ethylenediamine 4acetate 2Na 2hydrate)

[0112] Organic solvent

[0113] 12HD (1,2-hexanediol)

[0114] PG (propylene glycol)

[0115] Surfactant

[0116] E1010 (manufactured by Nippon Shokubai Co., Ltd., olfine E1010)

[0117] pH adjuster

[0118] TEA (triethanolamine)

[0119] Metal atom

[0120] Ca atom: calcium carbonate solution

[0121] Zn atom: zinc stearate solution

[0122] Mg atom: magnesium stearate solution

[0123] Fe atom: iron carbonate solution

[0124] Al atom: aluminum hydroxide

[0125] Cu atom: copper hydroxide solution

[0126] Sn atom: tin hydroxide solution

[0127] Si atom: 0.1% silica solution (NaOH solution)

[0128] 1.1. Preparation Example 1 (Preparation Example of Fulvic Acid)

[0129] 25 g of carbon black (PRINTEX Nature, manufactured by Orion Engineered Carbons Co., Ltd., vegetable oil carbon black) was stirred and washed with toluene to wash off unburnt components and the like adhering to the surface of the carbon black. For the carbon black after the washing process, 5 g of sodium hypochlorite was added to water, and oxidation treatment was performed. After the treatment, the carbon black was removed by centrifugal separation, the waste liquid was recovered, and the insoluble substance (humic substance) generated by adding an aqueous alkali solution to the waste liquid was separated from the liquid. The liquid remaining after the insoluble substance was removed was further added with an aqueous acid solution, the generated insoluble substance was separated, and the remaining liquid was concentrated and refined to obtain fulvic acid.

[0130] 1.2. Excitation-emission matrix analysis method (EEM)

[0131] The carbon black dispersion liquid prepared as described above was placed in a centrifugal separator (high-speed cooling centrifuge Suprema 21, manufactured by Tomy Seiko Co., Ltd.), and the carbon black was allowed to settle under separation conditions of 20°C, 12000 rpm, and 120 min. In the case where a small particle remained in the supernatant, 0.1% to 0.5% of magnesium sulfate was added to the carbon black as a raw material and allowed to coagulate, and the supernatant was again allowed to settle using a centrifugal separator. Subsequently, the carbon black was removed, and the supernatant was used as a measurement sample.

[0132] The obtained measurement sample was diluted 1000-fold in pure water, and excitation wavelength (Ex) was three-dimensionally measured by side reflection method under the following conditions. In addition, in the case of the measurement sample prepared, surface reflection method can also be selected.

[0133] ・Holder: liquid holder (side light measurement system) or solid holder (surface light measurement system)

[0134] ・Cuvette: face-polished quartz cuvette (10 x 10 mm square quartz cuvette, side light measurement) or two-face-polished quartz cuvette (20 x 10 mm quartz cuvette, surface light measurement)

[0135] ・Measurement wavelength excitation (Ex): 200 to 700 nm

[0136] ・Measurement wavelength fluorescence (Em): 200 to 700 nm

[0137] ・Data interval excitation (Ex): 5.0 nm

[0138] ・Data interval fluorescence (Em): 5.0 nm

[0139] ・Scanning speed: 60,000 nm / min

[0140] ・Slit width excitation (Ex): 5.0 nm

[0141] ・Slit width fluorescence (Em): 5.0 nm

[0142] ・Sensitivity: photomultiplier tube voltage 700 V

[0143] ・Response: 2 ms

[0144] ・Automatic feedback control: on (automatic high-order light cutoff)

[0145] As a result of the measurement by excitation fluorescence matrix analysis method, the fulvic acid obtained in the above Preparation Example 1 had two peaks of excitation wavelength 260 nm and fluorescence wavelength 445 nm, and excitation wavelength 265 nm and fluorescence wavelength 430 nm.

[0146] 1.3. Mass analysis of metal components

[0147] The mass analysis of each metal component in the ink composition was measured by ICP-OES (G8015AA, manufactured by Agilent Technologies, Inc.).

[0148] 1.4. pH

[0149] The pH of the prepared ink composition was measured with a glass electrode pH meter (manufactured by YOKOGAWA Co., Ltd., product name MODEL PH82) after the ink composition was stored at 60°C for 1 day. In addition, there was no large change in the pH from that measured immediately after preparation, no change, or a change of less than 1.

[0150] 2. Evaluation method

[0151] 2.1. Storage stability (60°C, 1 day)

[0152] The ink composition was placed in a polyethylene package and left to stand at 60°C for 1 day, and then left to cool at 25°C for 1 day. The ink composition after cooling was taken out and passed through a filter having a diameter of 10 μm, the filtration collection of the filter was confirmed, and the storage stability was evaluated according to the following evaluation criteria. The observation was performed visually using a microscope at 300 times.

[0153] Evaluation criteria

[0154] A: The number of foreign matters was less than 10

[0155] B: The number of foreign matters was 10 or more but less than 50

[0156] C: The number of foreign matters was 50 or more

[0157] 2.2. Discharge stability (60°C, 1 day)

[0158] The ink composition stored at 60°C for 1 day was filled into a predetermined ink composition containing container, the containing container was mounted on a recording device (PX-H6000 modified machine, manufactured by Seiko Epson Co., Ltd.), the inkjet ink composition was discharged, a full- page pattern was printed on a recording medium (Xerox P paper) at a recording resolution of 1440 x 720 dpi, the discharge condition after printing was confirmed, and the discharge stability was evaluated according to the following evaluation criteria. In addition, the operation environment of the recording device (printer) was set to 40°C, 20 RH%.

[0159] Evaluation criteria

[0160] A: The number of non-discharge nozzles was 3% or less

[0161] B: The number of non-discharge nozzles was more than 3% but 7% or less

[0162] C: The number of non-discharge nozzles was more than 7%

[0163] 2.3. Storage stability (after left to stand at 40°C for 2 months)

[0164] The storage stability was evaluated for Example 9, Comparative Examples 2 and 3, and Reference Example 1 in the same manner as described above, except that the storage condition was set to 40°C for 2 months. Further, the pH of the ink composition at this time (after being left at 40°C for 2 months) was measured with a glass electrode pH meter.

[0165] Evaluation Criteria

[0166] A: Number of foreign matters is less than 10

[0167] B: Number of foreign matters is 10 or more and less than 50

[0168] C: Number of foreign matters is 50 or more

[0169] 2.4. Discharge stability (after being left at 40°C for 2 months)

[0170] The discharge stability was evaluated for Example 9, Comparative Examples 2 and 3, and Reference Example 1 in the same manner as described above for the evaluation of the discharge stability, except that the above ink which had been stored at 40°C for 2 months was used.

[0171] Evaluation Criteria

[0172] A: Number of nozzles not discharging is 3% or less

[0173] B: Number of nozzles not discharging is more than 3% and 7% or less

[0174] C: Number of nozzles not discharging is more than 7%

[0175] 2.5. GHS classification

[0176] Whether the components contained in the ink correspond to the classification of chemicals and the distinction 3 in the Globally Harmonized System (GHS) relating to the display of aquatic environment harmfulness was evaluated for Example 9, Comparative Examples 2 and 3, and Reference Example 1.

[0177] Evaluation Criteria

[0178] Y: Does not correspond

[0179] N: Corresponds

[0180] 3. Evaluation results

[0181] The evaluation results of the ink compositions used in each example are shown in Table 1 and Table 2. As is apparent from Table 1, the water-based inkjet ink composition containing the colorant and the fulvic acid is excellent in storage stability and discharge stability. Further, as shown in Table 3, it is apparent that the water-based inkjet ink composition of the present application is also high in environmental suitability, and is excellent in storage stability and discharge stability even in the case of long-term storage.

Claims

1. An aqueous-based inkjet ink composition characterized in that, contains: a color material; and fulvic acid.

2. The aqueous inkjet ink composition according to claim 1, wherein the content of the fulvic acid is 0.001 to 1.0 mass% relative to the total amount of the inkjet ink composition.

3. The aqueous inkjet ink composition according to claim 1, wherein the fulvic acid has a peak at a fluorescence wavelength of 400 to 600 nm and an excitation wavelength EX of 200 to 300 nm in an excitation fluorescence matrix analysis.

4. The aqueous inkjet ink composition according to claim 1, wherein the total content of metal ions of one or more elements selected from the group consisting of Ca, Mg, Al, Fe, Si, Zn, Cu, and Sn is 140 ppm or less relative to the total amount of the inkjet ink composition.

5. The aqueous inkjet ink composition according to claim 1, wherein the pH after storage at 40°C for 2 months is less than 7.

6. The aqueous inkjet ink composition according to claim 1, wherein the color material includes a pigment.

7. The aqueous inkjet ink composition according to claim 1, wherein the color material includes carbon black from petroleum or carbon black from biomass.

8. The aqueous inkjet ink composition according to claim 1, wherein the color material includes a pigment dispersed by a resin.

9. A recording method, comprising an adhering step of adhering the aqueous inkjet ink composition according to any one of claims 1 to 8 to a recording medium from an inkjet head.

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