Inkjet ink composition, recording method and recorded matter

Abstract

The present invention relates to an inkjet ink composition, a recording method, and a recorded object, and provides an aqueous inkjet ink composition that suppresses viscosity increase over time and has excellent storage stability. The inkjet ink composition is an aqueous inkjet ink composition, comprising a colorant derived from plant charcoal, lignin sulfonate, and one or more elements A selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr, and Ba, wherein the content of the element A is 50 mass ppm or more and 1700 mass ppm or less relative to the total amount of the ink composition.

Description

Technical Field

[0001] The present invention relates to an inkjet ink composition, a recording method and a recorded object. Background Art

[0002] The inkjet recording method can record high-definition images with a relatively simple device, and has been rapidly developed in various aspects. Among them, environmental issues have been paid attention to in recent years, and inks that use materials derived from natural products to solve environmental problems are being developed. As such, as inks using materials derived from natural products, for example, in Patent Document 1, in order to provide a safe and highly edible inkjet ink, an inkjet ink containing water, sodium iron chlorophyllin and / or sodium copper chlorophyllin, and plant charcoal pigments has been developed.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-008275

[0004] Conventionally, the nozzle plate of an inkjet head has good water repellency, so that the ink composition ejected from the nozzle is not easy to adhere to the nozzle area. However, as shown in Patent Document 1, the ink composition using plant charcoal has increased sedimentation due to its large particle size, and there is a concern that the ejection stability may be deteriorated. Summary of the invention

[0005] The inkjet ink composition of the present invention is aqueous and contains a colorant derived from plant charcoal, lignin sulfonate, and one or more elements A selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr and Ba, wherein the content of the above-mentioned element A is 50 mass ppm or more and 1700 mass ppm or less relative to the total amount of the ink composition.

[0006] The recording method of the present invention comprises the step of discharging the above-mentioned inkjet ink composition from an inkjet head and causing it to adhere to a recording medium.

[0007] The recorded matter of the present invention is obtained by allowing the above-mentioned inkjet ink composition to adhere to a recording medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 1 is a diagram showing an example of a recording device used in the recording method of this embodiment.

[0009] Description of Reference Numerals

[0010] 10: recording device; 11: conveying path; 12: feeding section; 14: conveying section; 16: belt conveying section; 18: recording section; 20: Fd discharge section; 22: Fd loading section; 24: reversing path section; 26: Fu discharge section; 28: Fu loading section; 30: feeding tray; 32: feeding roller; 34: conveying drive roller; 36: conveying driven roller; 38: first roller; 40: second roller; 42: endless belt; 42a: upper section of the endless belt; 44: supporting body; 46: head bracket; 48: inkjet head; 50: first branch section; 52: reversing path; 54: second branch section; 56: discharge roller pair; 64: discharge drive roller; 68: driving shaft; 76: loading surface; 78: convex portion; 80: first force member; 82: second force member; 84, 86: supporting shaft; P: recording medium. DETAILED DESCRIPTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the accompanying drawings as needed, but the present invention is not limited thereto and various modifications can be made without departing from the main purpose thereof. It should be noted that in the accompanying drawings, the same elements have the same symbols and are not described in detail. In addition, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the accompanying drawings unless otherwise specified. Furthermore, the dimensional ratios of the accompanying drawings are not limited to the ratios shown in the drawings.

[0012] 1. Inkjet ink composition

[0013] The inkjet ink composition involved in this embodiment (hereinafter, also simply referred to as "ink composition") is an aqueous ink composition, which contains a colorant derived from plant charcoal, lignin sulfonate, and one or more elements A selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr and Ba, and the content of the above element A is greater than 50 mass ppm and less than 1700 mass ppm relative to the total amount of the ink composition.

[0014] In recent years, due to concerns about environmental issues, black inks using plant charcoal such as bamboo charcoal and charcoal as pigments are being studied as natural colorants for inks. Carbon black is one of the existing pigments derived from petroleum, in which the content of metals contained as impurities is small, while the characteristic of plant-derived colorants is that they contain a large amount of metals. The metal will dissolve in the ink, so the molecules are easy to form a multi-faceted network structure with the dissolved metal as the starting point. It can be seen from this that the ink containing the colorant derived from plant charcoal has the problem of increasing viscosity over time and reducing the ejection stability.

[0015] Therefore, the present inventors have conducted intensive research and found that lignin sulfonate can further improve the dispersion stability of the colorant derived from vegetable charcoal, and as a result, further improve the storage stability and printing stability. Although not particularly limited, the reason is that the metal derived from vegetable charcoal and the lignin sulfonate form a chelate and stably exist on the surface of the colorant derived from vegetable charcoal.

[0016] Next, components that may be included in the ink composition according to the present embodiment, physical properties, and a production method are described.

[0017] 1.1. Pigment

[0018] The ink composition contains a colorant derived from plant charcoal as a colorant, and may further contain other colorants. The colorants may be used alone or in combination of two or more.

[0019] 1.1.1. Colorants from plant charcoal

[0020] The ink composition of the present embodiment includes a colorant derived from plant charcoal. The colorant derived from plant charcoal is not particularly limited, and examples thereof include binchotan charcoal, bamboo charcoal, activated carbon, white charcoal, black charcoal, molded charcoal, sawdust charcoal, plum charcoal, activated carbon, kasu charcoal, Douglas fir charcoal, seaweed charcoal, mangrove charcoal, and coconut shell charcoal. From the viewpoint of further improving the storage stability of the ink composition, the plant charcoal is preferably at least one of binchotan charcoal and bamboo charcoal.

[0021] In this specification, "colorant derived from plant charcoal" may be a colorant obtained by treating and carbonizing plants under high temperature conditions. Here, "high temperature conditions" are not particularly limited as long as they are conditions that can carbonize plants, and can be, for example, high temperature conditions of 250°C or higher known as "charcoal burning" that can burn bamboo or woody plants into ash, high temperature conditions of 350°C or higher that eliminate uncarbonized components, or high temperature conditions of 700°C or higher using a charcoal kiln or the like.

[0022] The content of the colorant derived from plant charcoal is not particularly limited, and is, for example, 1.0% by mass or more and 30% by mass or less relative to the total amount of the ink composition. From the viewpoint of further improving the storage stability of the ink composition, the content of the colorant derived from plant charcoal is preferably 2.0% by mass or more and 20% by mass or less relative to the total amount of the ink composition, more preferably 3.0% by mass or more and 15% by mass or less, and even more preferably 4.0% by mass or more and 10% by mass or less.

[0023] The volume average particle size D50 of the colorant derived from plant charcoal corresponding to the cumulative degree of 50% is not particularly limited, and is, for example, 30 nm or more and 500 nm or less. From the viewpoint of suppressing the reduction of the sedimentation property of the ink composition and improving the storage stability, the volume average particle size D50 of the colorant derived from plant charcoal is preferably 50 nm or more and 450 nm or less, more preferably 80 nm or more and 400 nm or less, further preferably 100 nm or more and 300 nm or less, and further preferably 120 nm or more and 200 nm or less.

[0024] The particle size D90 (hereinafter referred to as "particle size D90") when the cumulative value from the smallest particle size in the cumulative distribution of the volume-based particle size of the colorant derived from vegetable charcoal reaches 90% as a whole is not particularly limited, and is, for example, 50 nm or more and 1200 nm or less. From the viewpoint of improving the storage stability of the ink composition, it is preferably 80 nm or more and 1000 nm or less, more preferably 90 nm or more and 800 nm or less, further preferably 100 nm or more and 600 nm or less, and further preferably 120 nm or more and 500 nm or less.

[0025] The ratio of the particle diameter D90 to the volume average particle diameter D50 (D90 / D50) is not particularly limited, and is, for example, 1.1 to 5.0. From the viewpoint of improving the storage stability of the ink composition, it is preferably 1.2 to 4.5, more preferably 1.2 to 4.0, further preferably 1.3 to 3.5, and even more preferably 1.3 to 3.0.

[0026] The volume average particle size of the present embodiment can be measured by a particle size distribution measuring instrument using a dynamic light scattering method as the measuring principle. Alternatively, it can be measured by a particle size distribution measuring instrument using a dynamic light scattering method and an electrophoretic light scattering method as the measuring principle. As such a particle size distribution measuring instrument, for example, the "ELSZ-2000ZS" (trade name) manufactured by Otsuka Electronics Co., Ltd., which uses a homodyne optical system as a frequency analysis method, can be cited. It should be noted that, in the present embodiment, the average particle size of the colorant derived from plant charcoal can also be measured by measuring the average particle size of the ink composition.

[0027] 1.1.1.1. Metal elements

[0028] Since the ink composition contains a colorant derived from plant charcoal, it contains one or more elements A selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr and Ba. In addition, the type of elements contained in the ink composition is not particularly limited, and in addition to the above-mentioned element A, it may further contain, for example, K, P, S, etc. It should be noted that the element A contained in the ink composition may be derived from plant charcoal, or may be added in the preparation process of the ink composition.

[0029] The metal element may be present in the form of a metal compound, a metal ion, or a metal element alone, but preferably in the form of a water-soluble metal salt or a metal ion.

[0030] The content of the element A is 50 mass ppm or more and 1700 mass ppm or less relative to the total amount of the ink composition. By setting the content of the element A within the above range, the ink composition has excellent storage stability and / or ejection stability during recording. From the same viewpoint, the content of the element A is preferably 80 mass ppm or more and 1620 mass ppm or less relative to the total amount of the ink composition, more preferably 100 mass ppm or more and 1500 mass ppm or less, further preferably 140 mass ppm or more and 1400 mass ppm or less, and further preferably 200 mass ppm or more and 1300 mass ppm or less.

[0031] In the element A of the ink composition, the total content of Ca, Mg, Sr and Ba is preferably 50 mass ppm or more and 1500 mass ppm or less relative to the total amount of the ink composition. By setting the total content of Ca, Mg, Sr and Ba within the above range, there is a tendency that the storage stability of the ink composition is further improved. From the same viewpoint, the total content of Ca, Mg, Sr and Ba is preferably 100 mass ppm or more and 1420 mass ppm or less relative to the total amount of the ink composition, more preferably 200 mass ppm or more and 1350 mass ppm or less, and even more preferably 300 mass ppm or more and 1200 mass ppm or less.

[0032] In the element A of the ink composition, the total content of Fe, Cr and Ni is preferably 10 mass ppm or more and 500 mass ppm or less relative to the total amount of the ink composition. By setting the total content of Fe, Cr and Ni within the above range, there is a tendency that the storage stability of the ink composition is further improved. From the same viewpoint, the total content of Fe, Cr and Ni is more preferably 30 mass ppm or more and 400 mass ppm or less, further preferably 50 mass ppm or more and 320 mass ppm or less, and further preferably 70 mass ppm or more and 300 mass ppm or less relative to the total amount of the ink composition.

[0033] In the element A of the ink composition, the total content of Al and Si is preferably 0 mass ppm or more and 250 mass ppm or less relative to the total amount of the ink composition. By making the total content of Al and Si within the above range, there is a tendency that the storage stability of the ink composition is further improved. From the same viewpoint, the total content of Al and Si is more preferably 150 mass ppm or less, further preferably 100 mass ppm or less, and further preferably 50 mass ppm or less relative to the total amount of the ink composition. The lower limit of the total content of Al and Si is not particularly limited, and can be, for example, 0 mass ppm, 10 mass ppm, etc.

[0034] The method for examining the mass of the metal element in the ink composition is not particularly limited, and examples thereof include inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), etc. In the ink composition of the present embodiment, inductively coupled plasma optical emission spectroscopy (ICP-OES) is preferred.

[0035] 1.1.1.2. Refining of colorants derived from vegetable charcoal

[0036] Since plants contain metal (mineral) components required for plant growth and development, the colorant derived from plant charcoal also contains various metal components. Therefore, the colorant derived from plant charcoal contained in the ink composition can be a colorant that has been refined through a refining process. The refining process can adjust the element A contained in the ink composition to a specified range.

[0037] The method for purifying the plant charcoal-derived colorant is not particularly limited as long as it is a method that can adjust the amount of metal components in the plant charcoal-derived colorant. For example, one method is described below.

[0038] For 100g of plant charcoal, add about 0.6g of sodium hydroxide, about 3.0g of chelating agent (for example, disodium ethylenediaminetetraacetate, etc.), and add pure water as the balance to make the total amount reach about 700g. Stir the obtained solution and heat it at about 90°C for about 4 hours. Return to room temperature, centrifuge and recover the plant charcoal. Add to pure water and stir, centrifuge again, and repeat the above operation. Dry the final recovery with a dryer to obtain refined plant charcoal.

[0039] It should be noted that the amount of metal components in the purified plant charcoal-derived colorant can be appropriately adjusted by adjusting the types, mass ratios, heating temperature, heating time, and the like of the above-mentioned reagents.

[0040] 1.1.2. Other pigments

[0041] The ink composition may also contain colorants other than the colorants derived from plant charcoal. That is, it may contain colorants derived from plants other than plant charcoal, colorants derived from animals, synthetic colorants, and the like. As colorants derived from plant charcoal other than plant charcoal, for example, anthocyanin pigments, carotenoid pigments, quinone pigments, flavonoid pigments, betaine pigments, and the like may be cited. In addition, as colorants derived from animals, for example, sepia ink (sepia dye), cochineal red, and capsicum purple may be cited. And, as synthetic colorants, for example, isoindolinone, diketopyrrolopyrrole, quinacridone, dioxazine, phthalocyanine, and the like may be cited. From the viewpoint of environmental concerns, the ink composition preferably contains a colorant selected from a colorant derived from a plant or a colorant derived from an animal as a colorant other than the colorant derived from plant charcoal, and more preferably contains a colorant derived from a plant.

[0042] In addition, in the ink composition, the content of colorants other than colorants derived from plant charcoal is not particularly limited, and is, for example, greater than 0 mass % and less than 10 mass % relative to the total amount of the ink composition, preferably greater than 0 mass % and less than 8.0 mass %, more preferably greater than 0.1 mass % and less than 7.0 mass %, and further preferably greater than 0.3 mass % and less than 5.0 mass %.

[0043] 1.2. Lignin sulfonate

[0044] The ink composition of this embodiment includes lignin sulfonate. By making the ink composition include lignin sulfonate, the colorant derived from plant charcoal is stably dispersed in the ink composition, which helps to improve the storage stability and printing stability of the ink composition. The main reason is not clear, but it is speculated that it is because lignin sulfonate and its derivatives easily capture polyvalent metal ions and form complexes, so after multiple lignins are bonded with the metal components in the ink, they are stably covered on the surface of the plant charcoal, thereby further improving the dispersion stability and then improving the storage stability. It is therefore believed that the lignin sulfonate in the ink composition forms a complex with the above-mentioned element A.

[0045] It should be noted that the lignin sulfonic acid is not particularly limited as long as it is lignin or a lignin degradation product, and the lignin or the lignin degradation product has at least one sulfone group. The lignin sulfonate is not particularly limited, and examples thereof include lignin sulfonate alkali metal salts such as lignin sulfonate sodium salt, lignin sulfonate lithium salt, lignin sulfonate potassium salt, and lignin sulfonate ammonium salt. In addition, the lignin sulfonate may be used alone or in combination of two or more.

[0046] The weight average molecular weight of the lignin sulfonate is, for example, 1000 to 80000. From the viewpoint of further improving the storage stability and / or ejection stability of the ink composition, the weight average molecular weight of the lignin sulfonate is preferably 3000 to 70000, more preferably 5000 to 60000, further preferably 10000 to 50000, further preferably 15000 to 40000, and particularly preferably 20000 to 35000.

[0047] The lignin sulfonate or its derivative is not particularly limited, and examples thereof include, as product names, PEARLLEX NP (manufactured by Nippon Paper Industries, Ltd.), PEARLLEX DP (manufactured by Nippon Paper Industries, Ltd.), VANILLEX N (manufactured by Nippon Paper Industries, Ltd.), 471038-100G (manufactured by Sigma-Alorich Co., Ltd.), NEW KARGEN WG-4 (manufactured by Takemoto Oil & Fats Co., Ltd.), and SANEX P252 (manufactured by Nippon Paper Industries, Ltd.). From the viewpoint of further improving the effect of the ink composition of the present invention, the lignin sulfonate is preferably PEARLLEX NP, VANILLEX N, PEARLLEX DP, 471038-100G, NEW KARGEN WG-4, and SANEX P252, and more preferably PEARLLEX NP, VANILLEX N, PEARLLEX DP, 471038-100G, and NEW KARGEN WG-4.

[0048] As the lignin sulfonate or its derivative, it is preferable to use a purified high-purity product. By using a purified high-purity lignin sulfonate, the chelation of the plant charcoal can be promoted, and the sedimentation property and / or storage stability can be reduced.

[0049] The ratio (C / B) of the content (C) of the lignin sulfonate to the content (B) derived from the plant charcoal is not particularly limited, and is, for example, 0.2 or more and 4.2 or less. From the viewpoint of improving the storage stability and / or ejection stability of the ink composition, the above-mentioned content ratio (C / B) is preferably 0.3 or more and 3.5 or less, more preferably 0.5 or more and 3.0 or less, further preferably 0.7 or more and 2.5 or less, and further preferably 1.0 or more and 2.0 or less.

[0050] The content of the lignin sulfonate is not particularly limited, and is, for example, 0.1% by mass or more and 40% by mass or less relative to the total amount of the ink composition. From the viewpoint of more effectively and reliably achieving the effects of the present invention, the content of the lignin sulfonate is preferably 0.3% by mass or more and 35% by mass or less relative to the total amount of the ink composition, more preferably 0.5% by mass or more and 30% by mass or less, further preferably 1.0% by mass or more and 25% by mass or less, and still more preferably 3.0% by mass or more and 18% by mass or less.

[0051] 1.3. Water

[0052] The ink composition of the present embodiment is an aqueous ink composition containing water. The aqueous ink composition is an ink composition containing at least water as a main solvent component of the ink.

[0053] The water content is preferably 30% by mass or more relative to the total amount of the ink. In addition, the water content is preferably 98% by mass or less, more preferably 90% by mass or less, further preferably 40% by mass or more and 85% by mass or less, and further preferably 50% by mass or more and 80% by mass or less. By making the water content above the above range, there is a tendency to suppress the viscosity increase of the ink even when part of the water evaporates, and to suppress the sedimentation property. In addition, by making the water content below 90% by mass, there is a tendency to further suppress curling.

[0054] 1.4. Water-soluble organic solvents

[0055] The ink composition of this embodiment preferably contains a water-soluble organic solvent. When the ink composition contains a water-soluble organic solvent, there is a tendency that the storage stability is further improved. It should be noted that the water-soluble organic solvent can be used alone or in combination of two or more.

[0056] The water-soluble organic solvent is not particularly limited, and examples thereof include glycerol, N-methylpyrrolidone, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, etc. Among them, glycerol is preferred from the viewpoint of moisturizing effect. It should be noted that the water-soluble organic solvent may be used alone or in combination of two or more.

[0057] The content of the water-soluble organic solvent is not particularly limited, and is, for example, 1.0% by mass or more and 50% by mass or less relative to the total amount of the ink composition. From the viewpoint of making the effect brought about by the present invention more effective and reliable, the content of the water-soluble organic solvent is preferably 3.0% by mass or more and 40% by mass or less, more preferably 5.0% by mass or more and 30% by mass or less, and further preferably 8.0% by mass or more and 20% by mass or less relative to the total amount of the ink composition.

[0058] 1.5. Sugar

[0059] The ink composition of this embodiment preferably contains sugars. The substances classified as sugars are not particularly limited, and examples thereof include monosaccharides such as pentoses, hexoses, heptoses, and octose, or polysaccharides such as disaccharides, trisaccharides, and tetrasaccharides, or sugar alcohols as derivatives thereof, reduced derivatives such as deoxy acids, oxidized derivatives such as aldonic acids and uronic acids, dehydrated derivatives such as glycosides, amino acids, sulfoses, etc. Polysaccharides refer to sugars in a broad sense, including substances widely present in nature such as alginic acid, dextrin, cyclodextrin, and cellulose. From the viewpoint of making the effects brought about by the present invention more effective and reliable, dextrin is preferably used as the sugar contained in the ink composition. It should be noted that the sugars can be used alone or in combination of two or more.

[0060] The content of sugars is not particularly limited, and is, for example, 0.1% by mass or more and 10% by mass or less relative to the total amount of the ink composition. The content of sugars is preferably 1.0% by mass or more and 8.0% by mass or less, and more preferably 2.0% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition.

[0061] 1.6. Surface tension modifier

[0062] The ink composition of this embodiment preferably contains a surface tension adjuster (hereinafter, it is shown as having the same meaning as "surfactant"). The surface tension adjuster is not particularly limited, and examples thereof include acetylene glycol surfactants, fluorine surfactants, and silicone surfactants. Among them, acetylene glycol surfactants are preferred from the viewpoint of improving the storage stability of the ink composition. It should be noted that the surface tension adjuster may be used alone or in combination of two or more.

[0063] The acetylene glycol surfactant is not particularly limited, and is preferably selected from, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol alkylene oxide adducts, and 2,4-dimethyl-5-decyne-4-ol and 2,4-dimethyl-5-decyne-4-ol alkylene oxide adducts. Commercially available products of the acetylene glycol surfactant are not particularly limited, and examples thereof include OLFINE 104 series and OLFINE E1010 and other E series (trade names manufactured by Airproducts), SURFYNOL 61, 104, 465 (trade names manufactured by Nissin Chemical Industry Co., Ltd.), etc. Among them, from the viewpoint of making the effect of the present invention more effective and reliable, it is preferred to include OLFINE E1010 as the surface tension modifier.

[0064] The content of the surface tension modifier is not particularly limited, and is, for example, 0.1% by mass or more and 5.0% by mass or less relative to the total amount of the ink composition. The content of the surface tension modifier is preferably 0.2% by mass or more and 3.0% by mass or less, and more preferably 0.3% by mass or more and 1.0% by mass or less relative to the total amount of the ink composition.

[0065] 1.7. Chelating agents

[0066] The ink composition of this embodiment preferably contains a chelating agent. By making the ink composition contain a chelating agent, there is a tendency to have excellent storage stability. The chelating agent is not particularly limited, and examples thereof include: ethylenediaminetetraacetate, edetic acid disalt, pyrophosphate, hexametaphosphate, citric acid, tartaric acid, gluconic acid, etc. From the viewpoint of more effectively and reliably achieving the effect brought about by the present invention, ethylenediaminetetraacetate is preferred as the chelating agent. It should be noted that the chelating agent can be used alone or in combination of two or more.

[0067] The content of the chelating agent is not particularly limited, and is, for example, 0.01% by mass or more and 10.0% by mass or less relative to the total amount of the ink composition. From the viewpoint of further improving the storage stability and / or ejection stability of the ink composition, the content of the chelating agent is preferably 0.01% by mass or more and 7.0% by mass or less, more preferably 0.05% by mass or more and 5.0% by mass or less, and even more preferably 0.1% by mass or more and 2.0% by mass or less, relative to the total amount of the ink composition.

[0068] 1.8. Method for producing inkjet ink composition

[0069] The method for producing the inkjet ink composition of the present embodiment is not particularly limited, and the following method can be mentioned: a colorant derived from plant charcoal, lignin sulfonate, and one or more elements A selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr, and Ba are mixed, and the content of the element A is adjusted to be 50 mass ppm or more and 1700 mass ppm or less relative to the total amount of the ink composition. It should be noted that the colorant derived from plant charcoal and the lignin sulfonate may be purified or unpurified.

[0070] 2. Inkjet recording method

[0071] The inkjet method of this embodiment comprises: a discharge step of discharging the inkjet ink composition using a predetermined inkjet head and attaching it to a recording medium; and a conveying step of conveying the recording medium. It should be noted that the discharge step and the conveying step may be performed simultaneously or alternately.

[0072] 2.1. Spraying process

[0073] In the ejection process, ink is ejected from the inkjet head and attached to the recording medium. More specifically, the pressure generating device provided in the inkjet head is driven to eject the ink filled in the pressure generating chamber of the inkjet head from the nozzle. Such an ejection method is also called an inkjet method.

[0074] Examples of the inkjet head used in the discharge step include a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0075] In the line method using a line head, for example, an inkjet head having a width greater than or equal to the recording width of a recording medium is fixed to a recording device. Then, the recording medium is moved in a sub-scanning direction (the conveying direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with the movement, thereby recording an image on the recording medium.

[0076] In the serial method using a serial head, for example, an inkjet head is mounted on a carriage that can move in the width direction of a recording medium. Then, the carriage is moved in the main scanning direction (the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with the movement, thereby recording an image on the recording medium.

[0077] 2.2. Conveying process

[0078] In the conveying process, the recording medium is conveyed in a predetermined direction in the recording device. More specifically, the recording medium is conveyed from the paper feeding section to the paper discharge section of the recording device using a conveying roller or a conveying belt provided in the recording device. During the conveying process, the ink ejected from the inkjet head adheres to the recording medium to form a recorded object. The conveying can be performed continuously or intermittently.

[0079] 2.3. Recording medium

[0080] The recording medium used in the present embodiment is not particularly limited, and examples thereof include absorptive or non-absorptive recording media.

[0081] The absorptive recording medium is not particularly limited, and examples thereof include ordinary paper such as electronic photographic paper having high ink permeability, inkjet paper (inkjet-specific paper having an ink-absorbing layer composed of silica particles or alumina particles or an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP), and coated paper, coated paper, cast-coated paper, etc. used for ordinary offset printing having low ink permeability.

[0082] The non-absorbent recording medium is not particularly limited, and examples thereof include: plastic films and plates such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; metal plates such as iron, silver, copper, and aluminum; or metal plates and plastic films manufactured by vapor deposition of the above various metals, alloy plates such as stainless steel and brass; recording media in which plastic films such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane are bonded (coated) to a paper substrate, etc.

[0083] 3. Recording device

[0084] The recording device of this embodiment includes an inkjet head having a nozzle for ejecting an inkjet ink composition onto a recording medium, and a conveying unit for conveying the recording medium. The inkjet head includes a pressure chamber for supplying ink thereto and a nozzle for ejecting ink. In addition, the conveying unit is composed of a conveying roller or a conveying belt provided in the recording device.

[0085] Below, reference Figure 1 The recording device involved in this embodiment is described. It should be noted that Figure 1 In the XYZ coordinate system shown, the X direction indicates the length direction of the recording medium, the Y direction indicates the width direction of the recording medium on the conveyance path in the recording device, and the Z direction indicates the height direction of the device.

[0086] An example of the recording device 10 is a line-type inkjet printer capable of high-speed and high-density printing. The recording device 10 includes a feed unit 12 for storing a recording medium P such as paper, a conveying unit 14, a belt conveying unit 16, a recording unit 18, an Fd (face down) discharge unit 20 as a "discharge unit", an Fd (face down) placement unit 22 as a "placement unit", a reversing path unit 24 as a "reversing conveying mechanism", a Fu (face up) discharge unit 26, and a Fu (face up) placement unit 28.

[0087] The feed unit 12 is disposed at the lower portion of the recording device 10 . The feed unit 12 includes a feed tray 30 for storing recording media P, and a feed roller 32 for feeding the recording media P stored in the feed tray 30 along the transport path 11 .

[0088] The recording medium P stored in the feed tray 30 is fed to the conveying section 14 along the conveying path 11 by the feed roller 32. The conveying section 14 includes a conveying drive roller 34 and a conveying driven roller 36. The conveying drive roller 34 is driven to rotate by a driving source not shown in the figure. In the conveying section 14, the recording medium P is nipped (nip) between the conveying drive roller 34 and the conveying driven roller 36 and conveyed to the belt conveying section 16 located on the downstream side of the conveying path 11.

[0089] The belt conveying section 16 includes: a first roller 38 located on the upstream side of the conveying path 11, a second roller 40 located on the downstream side, an endless belt 42 rotatably mounted on the first roller 38 and the second roller 40, and a support body 44 supporting an upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0090] The endless belt 42 is driven by the first roller 38 or the second roller 40 driven by a driving source (not shown) so as to move from the +X direction to the -X direction in the upper section 42a. Therefore, the recording medium P conveyed from the conveying section 14 is further conveyed to the downstream side of the conveying path 11 by the belt conveying section 16.

[0091] The recording unit 18 includes a line-type inkjet head 48 and a head holder 46 for holding the inkjet head 48. It should be noted that the recording unit 18 may also be a serial type in which an inkjet head is provided on a carriage that reciprocates along the Y-axis direction. The inkjet head 48 is arranged to face the upper section 42a of the endless belt 42 supported by the support body 44. When the recording medium P is transported in the upper section 42a of the endless belt 42, the inkjet head 48 ejects ink toward the recording medium P to perform recording. The recording medium P is transported to the downstream side of the transport path 11 by the belt transport unit 16 while recording.

[0092] It should be noted that the "line-type inkjet head" refers to a head used in the following recording devices: the area of ​​the nozzles formed in the direction intersecting with the conveying direction of the recording medium P can cover the entire intersecting direction of the recording medium P, so that one of the head or the recording medium P is fixed and the other is moved, thereby forming an image. It should be noted that the area of ​​the nozzles of the line head in the intersecting direction may not cover the entire intersecting direction of all the recording media P corresponding to the recording device.

[0093] In addition, a first branching portion 50 is provided on the downstream side of the conveying path 11 of the belt conveying portion 16. The first branching portion 50 is configured to be switchable between the conveying path 11 for conveying the recording medium P to the Fd discharge portion 20 or the Fu discharge portion 26 and the reversing path 52 of the reversing path portion 24 for reversing the recording surface of the recording medium P and conveying the recording medium P to the recording portion 18 again. It should be noted that the recording medium P conveyed by switching to the reversing path 52 by the first branching portion 50 reverses the recording surface during the conveyance on the reversing path 52, and is re-conveyed to the recording portion 18 in a manner such that the surface opposite to the initial recording surface faces the inkjet head 48.

[0094] A second branch portion 54 is provided downstream of the first branch portion 50 along the conveying path 11. The second branch portion 54 is configured to switch the conveying direction of the recording medium P so as to convey the recording medium P to the Fd discharge portion 20 or to the Fu discharge portion 26.

[0095] The recording medium P conveyed to the Fd discharge section 20 in the second branch section 54 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 so as to face the Fd placement section 22. In addition, the recording medium P conveyed to the Fu discharge section 26 in the second branch section 54 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 so as to face the side opposite to the Fu placement section 28.

[0096] It should be noted that the above description is based on an example of using a line-type inkjet head, but the recording device of this embodiment may also be a printer using a serial-type inkjet head (serial printer). In a serial printer, printing is performed by conveying the recording medium along a conveying direction and moving the inkjet head in a direction intersecting the conveying direction.

[0097] 4. Records

[0098] The recorded matter of this embodiment is obtained by attaching the ink composition to a recording medium. The ink composition has good sedimentation resistance and storage stability, and as a result, excellent ejection stability, so that even when repeated recording is performed, a recorded matter can be obtained stably.

[0099] Example

[0100] The present invention will be described in more detail below using Examples and Comparative Examples. The present invention is not limited to the following Examples at all.

[0101] 1. Preparation of ink composition

[0102] Each component is added to a mixture tank and mixed and stirred to achieve the composition described in Tables 1 to 5, and then filtered with a membrane filter to obtain the inkjet ink composition of each example. Among them, the plant charcoal used is the plant charcoal purified by the above method. It should be noted that, unless otherwise specified, the numerical values ​​of each component shown in each example in the table represent mass %. In addition, in the table, the numerical value of the plant charcoal represents the mass % of the solid content.

[0103] The abbreviations used in Tables 1 to 5 and the details of the product components are as follows. It should be noted that the term "high-purity purified" refers to a purified compound.

[0104] Colorant (vegetable charcoal)

[0105] ·Binchotan (manufactured by KIRIYA Chemical Co., Ltd.)

[0106] ·Bamboo charcoal (manufactured by KIRIYA Chemical Co., Ltd.)

[0107] High purity refined sodium lignin sulfonate

[0108] ·L1(M w : 30000, PEARLLEX NP, manufactured by Nippon Paper Co., Ltd.)

[0109] ·L2(M w : 9800, VANILLEX N, manufactured by Nippon Paper Co., Ltd.)

[0110] ·L3(M w : 15000, PEARLLEX DP, manufactured by Nippon Paper Co., Ltd.)

[0111] ·L4(M w :50000, 471038-100G, manufactured by Sigma-Alorich Co.)

[0112] ·L5(M w : 70000, NEW KARGEN WG-4, Takemoto Oil Co., Ltd.)

[0113] Unrefined sodium lignin sulfonate

[0114] ·L6(M w:30000, SANEX P252, manufactured by Nippon Paper Industries, Ltd.)

[0115] Other dispersants

[0116] Glycerol fatty acid ester (DECAGLYN 1-L, manufactured by Nikko Chemicals Co., Ltd.)

[0117] Solvent (water-soluble organic solvent)

[0118] Glycerin (commercially available)

[0119] carbohydrate

[0120] ·Dextrin (α-cyclodextrin) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0121] Surface tension modifier

[0122] ·OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.)

[0123] Chelating agents

[0124] EDTA (ethylenediaminetetraacetic acid)

[0125] 2. Determination method

[0126] 2.1. Determination of particle size in ink

[0127] The average particle size in the ink was measured by a particle size distribution measuring instrument (ELSZ-1000, manufactured by Otsuka Electronics Co., Ltd.). The D50 diameter is shown in Tables 1 to 5 as "D50 particle size" according to the scattering intensity distribution standard. It should be noted that the average particle size in the ink is interpreted as the particle size of the colorant particles derived from plant charcoal, and is shown to have the same meaning as the average particle size of the colorant derived from plant charcoal.

[0128] 2.2. Quality analysis of metal components

[0129] The mass analysis of each metal component in the ink was measured by ICP-OES (G8015AA, manufactured by Agilent Technologies, Inc.).

[0130] 3. Evaluation Method

[0131] 3.1. Storage stability

[0132] The ink was placed in a sealed glass container and left at 50°C for 3 days. The ink was taken out and the shear rate of 200 [S] was measured using a rheometer (MCR-306, manufactured by Anton Paar). -1 ] when the viscosity.

[0133] Evaluation Criteria

[0134] AA: Change rate is less than 10%;

[0135] A: The change rate is more than 10% and less than 20%;

[0136] B: The change rate is more than 20% and less than 30%;

[0137] C: The change rate is 30% or more.

[0138] 2.2. Ejection stability

[0139] The ink cartridge of a modified recording device (PX-S840, manufactured by Seiko Epson Corporation) was filled with each ink composition listed in Tables 1 to 5, and a solid pattern was printed at a resolution of 1440 dpi in the horizontal direction and 720 dpi in the vertical direction, with the recording area set to A4 size and a duty of 100%. The number of nozzles that failed to eject after 50 consecutive prints was counted.

[0140] It should be noted that in this specification, "Duty" is a value calculated according to the following formula.

[0141] Duty (%) = actual printing dots / (vertical resolution × horizontal resolution) × 100

[0142] (In the formula, "actual number of printed dots" is the actual number of printed dots per unit area, "vertical resolution" and "horizontal resolution" are the resolutions per unit area, respectively. In addition, "Duty 100%" indicates the maximum ink weight of a single color per unit pixel.)

[0143] Evaluation Criteria

[0144] AA: Less than 5 nozzles are missing;

[0145] A: There are more than 5 and less than 10 leaking nozzles;

[0146] B: There are more than 10 and slightly more than 20 nozzles missing;

[0147] C: There are more than 20 leaking nozzles.

[0148] 2.3. Sedimentation rate

[0149] The ink composition was placed in a centrifuge tube and the lid was closed so that the total mass of the centrifuge tube, the lid and the water-based inkjet ink composition was 55 g. The centrifuge tube with the lid was placed in a centrifuge (manufactured by Hitachi Koki Co., Ltd., model "CR-20B2", ROTOR NO.36), and after being processed at a speed of 10,000 rpm for 15 minutes, the supernatant (the area 5 g away from the gas-liquid interface) was collected. The absorbance of the supernatant obtained as above and the water-based inkjet ink composition before centrifugation at a wavelength of 500 nm was measured. The ratio of the absorbance (C0) of the water-based inkjet ink composition to the absorbance (C1) of the supernatant was calculated by the following formula, and the sedimentation rate (P1) was evaluated according to the following evaluation criteria.

[0150] P1(%)=(C1 / C0)100

[0151] Evaluation Criteria

[0152] AA: above 90%;

[0153] A: 80% or more and less than 90%;

[0154] B: more than 70% and less than 80%;

[0155] C: Less than 70%.

[0156]

Table 1

[0157]

[0158]

Table 2

[0159]

[0160]

Table 3

[0161]

[0162]

Table 4

[0163]

[0164]

Table 5

[0165]

[0166] 3. Evaluation results

[0167] The composition and evaluation results of the ink used in each example are shown in Tables 1 to 5. As shown in Tables 1 to 4, the ink composition of the example contains a colorant derived from plant charcoal, lignin sulfonate, and a predetermined amount of a predetermined metal element, so that the sedimentation rate of the ink composition is reduced, and the storage stability is excellent, and the printing stability is excellent.

[0168] In contrast, it is found that the storage stability, printing stability, and sedimentation properties are poor in Comparative Example 1 having a relatively high metal element content and Comparative Example 2 having a low metal element content. In addition, the storage stability and printing stability are reduced in Comparative Example 3 not using a colorant derived from plant charcoal, and the storage stability, printing stability, and sedimentation properties are further reduced in Comparative Example 4 not using lignin sulfonic acid.

[0169] On the other hand, Reference Example 1 simulates the existing pigment ink, and is adjusted to not contain the colorant derived from plant charcoal and to have a small amount of metal elements. The ink composition of Reference Example 1 thus obtained has excellent storage stability, printing stability and sedimentation properties. However, Reference Example 1 does not use natural colorants and cannot solve the problems related to environmental issues.

Claims

1. An inkjet ink composition, It is characterized in that It is a water-based inkjet ink composition. The inkjet ink composition comprises: Colorants derived from vegetable charcoal; lignin sulfonates; as well as Element A is one or more selected from the group consisting of Ca, Mg, Mn, Fe, Al, Si, Cr, Ni, Sr and Ba, The content of the element A is 50 ppm by mass or more and 1700 ppm by mass or less relative to the total amount of the ink composition. The colorant derived from plant charcoal is a colorant processed and carbonized under high temperature conditions, and the inkjet ink composition is a black ink.

2. The inkjet ink composition according to claim 1, It is characterized in that The lignin sulfonate forms a complex with the element A.

3. The inkjet ink composition according to claim 1, It is characterized in that The colorant derived from plant charcoal is dispersed in the ink composition through the lignin sulfonate.

4. The inkjet ink composition according to claim 1, It is characterized in that Among the elements A, the total content of Ca, Mg, Sr, and Ba is 50 mass ppm or more and 1500 mass ppm or less relative to the total amount of the ink composition.

5. The inkjet ink composition according to claim 1, It is characterized in that Among the elements A, the total content of Fe, Cr, and Ni is 10 ppm by mass or more and 500 ppm by mass or less relative to the total amount of the ink composition.

6. The inkjet ink composition according to claim 1, It is characterized in that In the element A, the total content of Al and Si is 0 mass ppm or more and 250 mass ppm or less relative to the total amount of the ink composition.

7. The inkjet ink composition according to claim 1, It is characterized in that The colorant has a volume average particle diameter D50 corresponding to a cumulative degree of 50% of 80 nm or more and 400 nm or less.

8. The inkjet ink composition according to claim 1, It is characterized in that The weight average molecular weight of the lignin sulfonate is 15,000 or more and 50,000 or less.

9. The inkjet ink composition according to any one of claims 1 to 8, It is characterized in that The ratio of the content of the lignin sulfonate to the content of the plant charcoal-derived colorant is 0.5 or more and 3.0 or less.

10. A recording method, It is characterized in that The recording method comprises the step of ejecting the inkjet ink composition according to any one of claims 1 to 9 from an inkjet head and causing the inkjet ink composition to adhere to a recording medium.

11. A record, It is characterized in that The recorded matter is obtained by allowing the inkjet ink composition according to any one of claims 1 to 9 to adhere to a recording medium.

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