Inkjet ink composition and recording method

Abstract

To provide an inkjet ink composition that can suppress the curling of a recorded material obtained therefrom and also has an excellent clogging recovery property.SOLUTION: An inkjet composition, being a water-based ink, comprises a colorant, inorganic oxide particles, water-soluble silicate, and water, the content of the water-soluble silicate being 0.5 mass% or less relative to the total amount of the ink.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink-jet ink composition and a recording method. [Background technology]

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment and have been rapidly developing in various fields. Various studies have been conducted on color development, ejection stability, and the like. For example, Patent Document 1 discloses an ink composition containing pigment particles, a predetermined amount of inorganic oxide particles, and a lactam solvent, with the volume average particle diameters of the pigment particles and inorganic oxide particles specified within a predetermined range, with the aim of providing an ink composition that exhibits excellent color development and excellent wet friction properties of printed matter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-176235 Summary of the Invention [Problem to be solved by the invention]

[0004] The nozzle plate of an inkjet head has good water repellency, which prevents the ink composition ejected from the nozzle from adhering to the periphery of the nozzle. However, it has been found that ink compositions containing inorganic oxide particles, as in Patent Document 1, are not easily water-repellent by the nozzle plate, and the ink is prone to adhering to the periphery of the nozzle. [Means for solving the problem]

[0005] The inkjet ink composition of the present invention comprises a colorant, inorganic oxide particles, a water-soluble silicate, and water, and the content of the water-soluble silicate is 0.5 mass% or less relative to the total amount of the ink, making it a water-based ink.

[0006] The recording method of the present invention comprises a step of ejecting any one of the ink-jet ink compositions described above from an ink-jet head and depositing it onto a recording medium. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram illustrating an example of a recording apparatus used in the recording method of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0009] 1. Inkjet ink composition The inkjet ink composition according to this embodiment (hereinafter also simply referred to as the "ink composition") is a water-based ink that contains a colorant, inorganic oxide particles, a water-soluble silicate, and water, and the content of the water-soluble silicate is 0.5 mass % or less relative to the total amount of the ink.

[0010] Conventionally, when recording on plain paper or the like using an aqueous ink composition, there is a problem of curling of the recorded material. Therefore, a method of suppressing curling of the resulting recorded material by using an ink composition containing inorganic oxide particles has been known. However, it has been found that ink compositions simply containing inorganic oxide particles have low water repellency of nozzle plates, making the ink more likely to adhere to the periphery of the nozzles. Such ink adhesion can cause deflection of the ink flight, impairing intermittent printing stability and requiring cleaning of the nozzle plate. Furthermore, when the ink dries near the nozzles, the inorganic oxide particles precipitate as aggregates, causing nozzle clogging and impairing clogging recovery.

[0011] In contrast, the ink composition of this embodiment can improve the water repellency of the nozzle plate by using a predetermined amount of water-soluble silicate together with inorganic oxide particles. This not only suppresses curling due to the inorganic oxide particles, but also improves intermittent printing stability. Furthermore, adjusting the amount of water-soluble silicate used can also improve clogging recovery.

[0012] The components that may be contained in the inkjet ink composition according to this embodiment, its physical properties, and a method for producing the composition will be described below.

[0013] 1.1.Colorants The coloring material is not particularly limited, but examples thereof include pigments and dyes. One type of coloring material may be used alone, or two or more types may be used in combination.

[0014] The content of the colorant relative to the total amount of the ink composition is preferably 0.5 to 15% by mass, more preferably 1.0 to 12.5% ​​by mass, and even more preferably 3.0 to 10% by mass. When the content of the colorant is within the above range, color development tends to be further improved.

[0015] 1.1.1.Pigments The ink composition of this embodiment may contain a pigment as a colorant. The pigment is not particularly limited, but examples thereof include organic pigments such as azo pigments (including, for example, azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), polycyclic pigments (such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments), nitro pigments, nitroso pigments, and aniline black; inorganic pigments such as carbon black (such as furnace black, thermal lamp black, acetylene black, and channel black), metal oxides, metal sulfides, and metal chlorides; and extender pigments such as calcium carbonate and talc.

[0016] The pigment may be added to the ink as a pigment dispersion obtained by dispersing the pigment in water with a dispersant, or as a pigment dispersion obtained by dispersing a self-dispersing surface-treated pigment in which hydrophilic groups have been introduced to the pigment particle surface using a chemical reaction (hereinafter also referred to as a "self-dispersing pigment") in water, or as a pigment dispersion obtained by dispersing a polymer-coated pigment (hereinafter also referred to as a "resin-dispersed pigment") in water. Among these, it is preferable to use a self-dispersing pigment. The use of a self-dispersing pigment tends to further improve the water repellency of the nozzle plate and the intermittent printing stability.

[0017] The pigment and dispersant constituting the pigment dispersion may each be used alone or in combination of two or more.

[0018] 1.1.2.Dye The dye is not particularly limited, but examples thereof include acid dyes such as CI Acid Yellow, CI Acid Red, CI Acid Blue, CI Acid Orange, CI Acid Violet, and CI Acid Black; basic dyes such as CI Basic Yellow, CI Basic Red, CI Basic Blue, CI Basic Orange, CI Basic Violet, and CI Basic Black; direct dyes such as CI Direct Yellow, CI Direct Red, CI Direct Blue, CI Direct Orange, CI Direct Violet, and CI Direct Black; reactive dyes such as CI Reactive Yellow, CI Reactive Red, CI Reactive Blue, CI Reactive Orange, CI Reactive Violet, and CI Reactive Black; and disperse dyes such as CI Disperse Yellow, CI Disperse Red, CI Disperse Blue, CI Disperse Orange, CI Disperse Violet, and CI Disperse Black. The above dyes may be used alone or in combination of two or more.

[0019] 1.2. Inorganic oxide particles The inorganic oxide particles are not particularly limited, but examples thereof include silica particles, alumina particles, titania particles, zirconia particles, antimony oxide particles, tin oxide particles, tantalum oxide particles, zinc oxide particles, cerium oxide particles, lead oxide particles, and indium oxide particles. Among these, silica particles are preferred. By using such inorganic oxide particles, curling of the resulting recorded material can be further suppressed. The inorganic oxide particles may be used alone or in combination of two or more.

[0020] The inorganic oxide particles may be surface-treated. For example, silica may be surface-treated with alumina. This tends to broaden the pH range in which silica can be stably dispersed, further improving dispersion stability.

[0021] As the silica, commercially available products can be used, such as SI-45P, SI-80, SI-30P, and S-40 from the Cataloid series manufactured by JGC Catalysts and Chemicals Co., Ltd., and Snowtex 20, Snowtex 30P, Snowtex 40, Snowtex O, Snowtex N, and Snowtex C manufactured by Nissan Chemical Industries, Ltd. Of the above silicas, it is preferable to use SI-45P and / or SI-80, from the viewpoint of more effectively and reliably achieving the effects of the present invention.

[0022] The inorganic oxide particles preferably have an average particle size of 10 to 200 nm, more preferably 20 to 150 nm, and even more preferably 30 to 100 nm. When the inorganic oxide particles have an average particle size of 200 nm or less, color development, intermittent printing stability, and clogging recovery tend to be further improved. Furthermore, when the inorganic oxide particles have an average particle size of 10 nm or more, curling tends to be further suppressed.

[0023] The average particle size of inorganic oxide particles can be measured using a particle size distribution analyzer that uses dynamic light scattering as its measurement principle. An example of such a particle size distribution analyzer is the "Zeta Potential, Particle Size, and Molecular Weight Measurement System ELSZ2000ZS" (product name) manufactured by Otsuka Electronics Co., Ltd., which uses a homodyne optical system as a frequency analysis method. In this specification, "average particle size" refers to the average particle size based on the number of particles, unless otherwise specified.

[0024] The content of inorganic oxide particles, as solid content, is preferably 1.0 to 10% by mass, more preferably 2.0 to 9.0% by mass, and even more preferably 3.0 to 8.0% by mass, relative to the total amount of ink. When the content of inorganic oxide particles is 1.0% by mass or more, curling of the resulting recorded material is further suppressed, thereby further improving the conveyance speed of the recording medium. Furthermore, when the content of inorganic oxide particles is 10% by mass or less, color development, water repellency of the nozzle plate, intermittent printing stability, and clogging recovery tend to be further improved.

[0025] The content of inorganic oxide particles, on a mass basis, is preferably equal to or greater than the content of water-soluble silicate, which will be described later. The ratio of the content of inorganic oxide particles to the content of water-soluble silicate (inorganic oxide particles / water-soluble silicate) is preferably from 3 to 50,000, more preferably from 5 to 25,000, and even more preferably from 5 to 10,000. When the ratio (inorganic oxide particles / water-soluble silicate) is within the above range, curling is further suppressed, and color development, water repellency of the nozzle plate, intermittent printing stability, and clogging recovery tend to be further improved.

[0026] In this embodiment, the solid content of the ink composition is preferably 5.0% by mass or more, more preferably 6.0 to 20% by mass, even more preferably 7.0 to 15% by mass, and even more preferably 8.0 to 12.5% ​​by mass. By keeping the solid content within the above range, it tends to be easier to suppress deterioration in the color development of the resulting recorded matter. The solid content includes inorganic oxide particles and coloring materials.

[0027] 1.3. Water-soluble silicates The ink composition of this embodiment contains a water-soluble silicate. By using the inorganic oxide particles and the water-soluble silicate in combination, the water repellency of the nozzle plate is improved, and intermittent printing stability is further improved.

[0028] The water-soluble silicate is not particularly limited, and examples thereof include alkali metal salts of silicic acid and ammonium salts of silicic acid. The alkali metal salts of silicic acid are composed of silicon dioxide and a metal oxide, and are not particularly limited as long as they are water-soluble compounds, and examples thereof include alkali metal salts of metasilicic acid and alkali metal salts of orthosilicate. Furthermore, examples of ammonium salts of silicic acid include ammonium salts of metasilicic acid and ammonium salts of orthosilicate. Furthermore, in this embodiment, "water-soluble" means that it dissolves in water at 20°C at a concentration of 1% by mass or more. The water-soluble silicates may be used alone or in combination of two or more types.

[0029] Specifically, the alkali metal silicate or ammonium salt of silicic acid is preferably at least one compound represented by the following general formula (1). x(A2O)·y(SiO2) general formula (1)

[0030] In the general formula (1), A represents sodium, potassium, or tetraalkylammonium (NR4), x represents 1 or 2, and y represents an integer of 1 to 4. R represents an alkyl group having 1 to 4 carbon atoms (methyl, ethyl, propyl, or butyl).

[0031] In the case of an alkali metal salt of silicic acid (A = alkali metal) represented by the general formula (1), when x = 1 and y = 1 it is called an alkali metal metasilicate, and when x = 2 and y = 1 it is called an alkali metal orthosilicate, both of which are water-soluble alkali metal silicates.

[0032] Furthermore, the ammonium salt of silicic acid represented by the general formula (1) (A = tetraalkylammonium) is a tetraalkylammonium salt of metasilicic acid when x = 1 and y = 1, and a tetraalkylammonium salt of orthosilicate when x = 2 and y = 1, both of which are water-soluble ammonium silicates.

[0033] The content of the water-soluble silicate is 0.5% by mass or less, preferably 0.00001 to 0.5% by mass, more preferably 0.0005 to 0.5% by mass, even more preferably 0.001 to 0.5% by mass, still more preferably 0.005 to 0.5% by mass, and even more preferably 0.01 to 0.4% by mass, relative to the total amount of the ink composition. When the content of the water-soluble silicate is 0.5% by mass or less, clogging recovery tends to be further improved. Furthermore, when the content of the water-soluble silicate is 0.00001% by mass or more, the water repellency of the nozzle plate is improved, and intermittent printing stability tends to be further improved.

[0034] 1.4.Water The ink composition of this embodiment is a water-based ink composition containing water. A water-based ink is an ink that contains at least water as a main solvent component of the ink. The water content is preferably 30% by mass or more relative to the total amount of ink. It is also preferably 98% by mass or less, more preferably 80% by mass or less, even more preferably 40% by mass or more and 75% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less. By having the water content be in the above range or more, an increase in the viscosity of the ink is suppressed even when part of the water evaporates, and clogging recovery tends to be further improved. Furthermore, by having the water content be 90% by mass or less, curling tends to be further suppressed.

[0035] 1.5. Water-soluble organic solvents The ink composition of this embodiment preferably contains a water-soluble organic solvent. When the ink composition contains a water-soluble organic solvent, the storage stability tends to be further improved.

[0036] The water-soluble organic solvent is not particularly limited, but examples thereof include glycerin, N-methylpyrrolidone, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propanediol, butanediol, pentanediol, hexylene glycol, etc. Among these, glycerin is preferred in terms of its moisturizing effect. The content of the water-soluble organic solvent is preferably 0.5 to 40% by mass, more preferably 1 to 20% by mass, even more preferably 3 to 15% by mass, and particularly preferably 5 to 12% by mass, relative to the total amount of the ink.

[0037] SP value is 27.5 (J / cm 3 ) 1 / 2The content of the water-soluble organic solvent S1 is preferably 35% by mass or less, based on the total amount of the water-soluble organic solvents. The content of the water-soluble organic solvent S1 is more preferably 5.0 to 32% by mass, even more preferably 10 to 30% by mass, and even more preferably 15 to 28% by mass, based on the total amount of the water-soluble organic solvents. When the content of the water-soluble organic solvent S1 is within the above range, storage stability tends to be further improved.

[0038] The SP value means the solubility parameter, and in this specification, the SP value is a value introduced by Hildebrand and defined by regularity theory. The SP value of an organic solvent is a value calculated from the evaporation energy and molar volume of atoms and atomic groups according to Fedors, described in "Coating Basics and Engineering" (page 53, by Harasaki Yuji, Processing Technology Research Association). The unit of the SP value in this embodiment is (J / cm 3 ) 1 / 2 However, 2.046×10 3 (J / m 3 ) 1 / 2 =1(cal / cm 3 ) 1 / 2 by (cal / m 3 ) 1 / 2 It can also be converted into units of

[0039] SP value is 27.5 (J / cm 3 ) 1 / 2The water-soluble organic solvent S1 is not particularly limited, and examples thereof include triethylene glycol monobutyl ether (BTG, also known as butyl triglycol, SP value 21.1), triethylene glycol monomethyl ether (MTG, also known as methyl triglycol, SP value 22.1), 2-methylpentane-1,3-diol (SP value 21.1), 2-methylpentane-1,4-diol, ethylene glycol monoethyl ether (SP value 21.5), ethylene glycol monobutyl ether (SP value 19.4), diethylene glycol monoethyl ether (SP value 20.9), diethylene glycol monobutyl ether (SP value 20.9), and ethylene glycol diacetate (SP value 20.5). Among these, triethylene glycol monobutyl ether and triethylene glycol monomethyl ether are preferred.

[0040] The water-soluble organic solvent other than those described above is not particularly limited and examples thereof include glycerin, propylene glycol, triethylene glycol, glycol monoethers, etc. Among these, from the viewpoint of more effectively and reliably achieving the effects of the present invention, it is preferable that the ink composition contains glycerin and / or triethylene glycol.

[0041] The content of the water-soluble organic solvent is preferably 0.5 to 25% by mass, more preferably 3.0 to 20% by mass, and even more preferably 5.0 to 15% by mass, relative to the total amount of the ink. When the content of the water-soluble organic solvent is within the above range, storage stability tends to be further improved.

[0042] Amino Acids The ink composition of this embodiment preferably contains an amino acid. In this specification, an amino acid refers to a compound having an amino group and a carboxyl group in the same molecule. The use of an amino acid tends to further improve storage stability and clogging recovery properties.

[0043] The amino acids contained in the ink composition are not particularly limited, and examples thereof include tertiary amino acids such as dimethylglycine, dimethylalanine, dimethylglutamic acid, and diethylglycine; and quaternary amino acids such as trimethylglycine, trimethylalanine, trimethylglutamic acid, and triethylglycine. Among these, quaternary amino acids having a quaternary ammonium group are preferred, and trimethylglycine is more preferred. The use of such amino acids tends to further improve storage stability and clogging recovery. The amino acids may be used alone or in combination of two or more.

[0044] The content of the amino acid is preferably 1.0% by mass or more and 20% by mass or less, more preferably 2.0% by mass or more and 10% by mass or less, and even more preferably 3.0% by mass or more and 7.0% by mass or less, relative to the total amount of the ink composition. When the content of the amino acid is within the above range, the storage stability and clogging recovery properties of the resulting recorded matter tend to be further improved.

[0045] 1.7.Surfactants The ink composition of this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants. Among these, acetylene glycol surfactants are preferred from the viewpoint of clogging recovery.

[0046] The acetylene glycol surfactant is not particularly limited, but is preferably at least one selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol. Commercially available acetylene glycol surfactants are not particularly limited, but examples include the E series (trade names: Olfin 104 series, Olfin E1010, etc., manufactured by Air Products Co., Ltd.), and Surfynol 61, 104, and 465 (trade names, manufactured by Nissin Chemical Industry Co., Ltd.). Among these, Olfin E1010 and / or Surfynol 104 are preferred, from the viewpoint of more effectively and reliably achieving the effects of the present invention. The acetylene glycol surfactants may be used alone or in combination of two or more.

[0047] The fluorosurfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds. Commercially available fluorosurfactants are not particularly limited, but examples thereof include S-144 and S-145 (manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, and Fluorad-FC4430 (manufactured by Sumitomo 3M Limited); FSO, FSO-100, FSN, FSN-100, and FS-300 (manufactured by DuPont); and FT-250 and 251 (manufactured by Neos Corporation). The fluorosurfactants may be used alone or in combination of two or more.

[0048] Examples of silicone surfactants include polysiloxane compounds, polyether-modified organosiloxanes, etc. Commercially available silicone surfactants are not particularly limited, but specific examples include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345 (all trade names, manufactured by BYK Japan KK), KF-351A, KF-352A, KF-353, KF-354L, KF-355A (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

[0049] The content of the surfactant is preferably 0.1 to 5.0% by mass, and more preferably 0.2 to 3.0% by mass, relative to the total mass of the ink. When the content of the surfactant is within this range, clogging recovery tends to be further improved.

[0050] 1.7. Method for producing inkjet ink composition The method for producing the inkjet ink composition of this embodiment is not particularly limited, and examples thereof include a method of mixing a colorant, inorganic oxide particles, a water-soluble silicate, and water so that the content of the water-soluble silicate is 0.5 mass% or less relative to the total amount of ink. The inorganic oxide particles may be mixed in the form of a colloidal solution, or, if a pigment is used, may be mixed in the form of a pigment dispersion.

[0051] 2. Inkjet method The inkjet method according to this embodiment includes a discharge step of discharging the inkjet ink composition onto a recording medium using a predetermined inkjet head, and a transport step of transporting the recording medium. The discharge step and the transport step may be performed simultaneously or alternately.

[0052] 2.1.Discharge process In the ejection process, ink is ejected from the inkjet head and deposited on the recording medium. More specifically, a pressure generating means provided in the inkjet head is driven to eject ink filled in the pressure generating chamber of the inkjet head from the nozzle. This ejection method is also called the inkjet method.

[0053] Inkjet heads used in the ejection step include a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0054] In the line method using a line head, for example, an inkjet head having a width equal to or greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved in the sub-scanning direction (the direction in which the recording medium is transported), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement to record an image on the recording medium.

[0055] In the serial method using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then 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 this movement to record an image on the recording medium.

[0056] 2.2.Transportation process In the conveying process, the recording medium is conveyed in a predetermined direction within the recording device. More specifically, the recording medium is conveyed from the paper feed section to the paper discharge section of the recording device using a conveying roller or conveying belt provided within the recording device. During this conveying process, ink ejected from the inkjet head adheres to the recording medium, forming a recorded product. Conveyance may be performed continuously or intermittently.

[0057] 2.3. Recording Media The recording medium used in this embodiment is not particularly limited, but examples thereof include absorbent and non-absorbent recording media. Among these, absorbent recording media are prone to problems such as curling, so the present invention, which uses inorganic oxide particles but has excellent clogging recovery properties, is effective. In other words, the ink composition of this embodiment is preferably used for recording on absorbent recording media.

[0058] Absorbent recording media include, but are not limited to, plain paper such as electrophotographic paper, which has high ink permeability, inkjet paper (paper specifically for inkjet printing, which has an ink absorbing layer made of silica particles or alumina particles, or an ink absorbing layer made of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), art paper, coated paper, cast paper, and the like, which are used in general offset printing and have relatively low ink permeability.

[0059] Non-absorbent recording media are not particularly limited, but examples include films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc.; plates of metals such as iron, silver, copper, aluminum, etc.; metal plates and plastic films manufactured by vapor deposition of these various metals, and alloy plates such as stainless steel and brass; and recording media in which a plastic film such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, polyurethane, etc. is adhered (coated) to a paper substrate.

[0060] 3. Recording device The recording apparatus of this embodiment includes an inkjet head having nozzles for ejecting an inkjet ink composition onto a recording medium, and a transport means for transporting the recording medium. The inkjet head includes pressure chambers to which ink is supplied and nozzles for ejecting the ink. The transport means includes transport rollers and a transport belt provided within the recording apparatus.

[0061] The recording device according to this embodiment will be described below with reference to Fig. 1. In the XYZ coordinate system shown in Fig. 1, the X direction indicates the length direction of the recording medium, the Y direction indicates the width direction of the recording medium on the transport path within the recording device, and the Z direction indicates the height direction of the device.

[0062] As an example, the recording device 10 is a line-type inkjet printer capable of high-speed, high-density printing. The recording device 10 includes a feed unit 12 that stores recording media P such as paper, a conveyance unit 14, a belt conveyance unit 16, a recording unit 18, an Fd (face-down) discharge unit 20 as an "discharge unit," an Fd (face-down) loading unit 22 as a "loading unit," a reversing path unit 24 as a "reversing conveyance mechanism," an Fu (face-up) discharge unit 26, and an Fu (face-up) loading unit 28.

[0063] The feeding unit 12 is disposed at the bottom of the recording device 10. The feeding unit 12 includes a feeding tray 30 that stores recording media P, and a feeding roller 32 that sends the recording media P stored in the feeding tray 30 to the transport path 11.

[0064] The recording medium P stored in the feed tray 30 is fed by a feed roller 32 along the conveying path 11 to the conveying unit 14. The conveying unit 14 includes a conveying drive roller 34 and a conveying driven roller 36. The conveying drive roller 34 is driven to rotate by a drive source (not shown). In the conveying unit 14, the recording medium P is nipped between the conveying drive roller 34 and the conveying driven roller 36 and conveyed to the belt conveying unit 16 located downstream of the conveying path 11.

[0065] The belt conveying section 16 includes a first roller 38 located upstream on the conveying path 11, a second roller 40 located downstream, an endless belt 42 rotatably attached to the first roller 38 and the second roller 40, and a support 44 that supports the upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40.

[0066] The endless belt 42 is driven by the first roller 38 or the second roller 40, which is driven by a drive 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 unit 14 is further conveyed downstream of the conveying path 11 in the belt conveying unit 16.

[0067] The recording unit 18 includes a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. The recording unit 18 may also be a serial type in which the inkjet head is mounted on a carriage that moves back and forth in the Y-axis direction. The inkjet head 48 is disposed to face the upper section 42a of the endless belt 42 supported by the support body 44. The inkjet head 48 ejects ink toward the recording medium P as the recording medium P is transported in the upper section 42a of the endless belt 42, thereby performing recording. The recording medium P is transported downstream of the transport path 11 by the belt transport unit 16 while recording is being performed.

[0068] It should be noted that a "line-type inkjet head" is a head used in a recording device in which the nozzle area formed in a direction intersecting the transport direction of the recording medium P is arranged so as to be able to cover the entire intersecting direction of the recording medium P, and in which an image is formed by fixing one of the head or the recording medium P and moving the other. It should be noted that the nozzle area in the intersecting direction of the line head does not have to be able to cover the entire intersecting direction of all recording media P that the recording device supports.

[0069] Furthermore, a first branch section 50 is provided downstream of the conveying path 11 of the belt conveying unit 16. The first branch section 50 is configured to be switchable between the conveying path 11 that conveys the recording medium P to the Fd discharge unit 20 or the Fu discharge unit 26 and a reversing path 52 of the reversing path section 24 that reverses the recorded side of the recording medium P and conveys the recording medium P again to the recording unit 18. Note that the recording medium P that is switched to the reversing path 52 by the first branch section 50 and conveyed has its recorded side reversed during the conveying process on the reversing path 52, and is conveyed again to the recording unit 18 so that the side opposite to the initially recorded side faces the inkjet head 48.

[0070] A second branch section 54 is further provided downstream of the first branch section 50 along the conveying path 11. The second branch section 54 is configured to be able to switch the conveying direction of the recording medium P so that the recording medium P is conveyed toward the Fd discharge section 20 or the recording medium P is conveyed toward the Fu discharge section 26.

[0071] The recording medium P transported from the second branching section 54 toward 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 medium P is placed so that the recorded surface faces the Fd placement section 22. Also, the recording medium P transported from the second branching section 54 toward 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 medium P is placed so that the recorded surface faces away from the Fu placement section 28.

[0072] Although the above description is of an example in which a line-type inkjet head is used, the recording device according to this embodiment may also be a printer that uses a serial-type inkjet head (serial printer). In a serial printer, printing is performed by transporting the recording medium in the transport direction while moving the inkjet head in a direction intersecting the transport direction. [Example]

[0073] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0074] 1. Preparation of Ink Composition Each component was placed in a mixing tank, mixed and stirred, and filtered through a 5 μm membrane filter to obtain the inkjet ink composition shown in Tables 1 to 3. The numerical values ​​for each component shown in the tables represent % by mass unless otherwise specified. The numerical values ​​for inorganic oxide particles and pigment dispersions in the tables represent % by mass of the solid content.

[0075] Details of the abbreviations and product ingredients used in Tables 1 to 3 are as follows, and the numbers to the right of the solvent abbreviations indicate the SP values ​​of the solvents. [Pigment dispersion] Resin-dispersed carbon black (MICROPIGMO WMBK-71, manufactured by Orient Chemical Industries Co., Ltd.) Self-dispersing carbon black (CAB-O-JET300, manufactured by Cabot Corporation) [Water-soluble silicates] Potassium silicate (manufactured by Nippon Chemical Industry Co., Ltd.) Sodium silicate (manufactured by Nippon Chemical Industry Co., Ltd.) [Inorganic oxide particles] Cataroid SI-45P (product name of the Cataroid series, manufactured by JGC Catalysts and Chemicals Co., Ltd., average particle size 45 nm) Cataroid SI-80 (product name of the Cataroid series, manufactured by JGC Catalysts and Chemicals Co., Ltd., average particle size 80 nm) [Solvent (water-soluble organic solvent)] BTG (triethylene glycol monobutyl ether, SP value: 21.1) MTG (triethylene glycol monomethyl ether, SP value: 22.1) TEG (triethylene glycol, SP value: 27.54) Glycerin (SP value: 34.2) [Surfactants] Olfine E1010 (trade name, acetylene glycol surfactant, manufactured by Air Products) Surfynol 104 (trade name, acetylene glycol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) [amino acid] Trimethylglycine (DuPont)

[0076] 2. Evaluation Method 2.1.Color development Each of the prepared ink compositions was filled into an ink cartridge for an inkjet printer "PX-S7050" (product name, manufactured by Seiko Epson Corporation). As a recording medium, A4 size (210 mm x 297 mm) copy paper "Xerox P Paper" (product name, manufactured by Fuji Xerox Co., Ltd., basis weight 64 g / m 2 A sheet of paper (88 μm thick) was prepared. A solid pattern was printed on the recording medium at a print duty of 100%. After printing, the optical density (hereinafter also referred to as "OD value") was measured using a colorimeter "Xrite i1" (product name, manufactured by Xrite Corporation), and the color development was evaluated according to the following evaluation criteria. (Evaluation criteria) A: The maximum OD value is 1.2 or more. B: The maximum OD value is 1.1 or more and less than 1.2. C: The maximum OD value is less than 1.1.

[0077] 2.2.Storability The ink composition was placed in an ink pack, which was then sealed and stored at 70°C for 6 days. The viscosity of the ink composition at 20°C before and after storage was measured using a reverse flow Cannon-Fenske viscometer, and the increase in viscosity before and after storage was calculated. Based on the results, the ink storage stability was evaluated according to the following evaluation criteria. (Evaluation criteria) A: Viscosity increase of 0.1 mm 2 / s B: Viscosity increase of 0.1 mm 2 / s or more 0.3mm 2 / s C: Viscosity increase of 0.3 mm 2 / s or more

[0078] 2.3. Intermittent printing stability Using each ink composition prepared, a ruled line was printed using an inkjet printer PX-S7050 in an environment of 30°C temperature and 20% humidity, and the head was allowed to idle for 40 seconds, after which another ruled line was printed. The ruled lines before and after the idle run were compared to evaluate the amount of ink landing deviation. The results were evaluated for intermittent printing stability based on the following criteria. (Evaluation criteria) A: The landing deviation is less than 30 μm B: The landing deviation is 30 μm or more and less than 50 μm C: The landing deviation is 50 μm or more and less than 70 μm D: The landing deviation is 70 μm or more

[0079] 2.4. Evaluation of clogging recovery The ink cartridge of the inkjet printer PX-S7050 was filled with ink, and it was confirmed that ink could be ejected from all nozzles. After that, the inkjet head was shifted from the position of the cap provided on the printer, and the head was left uncapped in an environment of 40°C and 20% humidity for 7 days.

[0080] After leaving it as it was, the inkjet head was cleaned by suctioning ink from the nozzles once, counting the number of nozzles that could not eject ink, and repeating the cleaning operation until all nozzles were restored.The clogging recovery was then evaluated according to the following criteria based on the number of cleanings performed when all nozzles were restored. (Evaluation criteria) A: Less than 6 cleanings B: The number of cleanings is between 6 and 9 C: Cleaning count is 9 or more, or no recovery

[0081] 2.5.Evaluation of Primary Curl The ink cartridge of the inkjet printer PX-S7050 was filled with ink, and the recording medium (postcard-sized Xerox P paper, Fuji Xerox copy paper, 64 g / m²) was used. 2 A solid pattern was printed on a sheet of paper (88μm thick) at a temperature of 25°C and humidity of 50% with a print duty of 100%. After printing, the sheet was left face down, and the angle between the point where the sheet touched the floor and the edge of the sheet was measured as an index of primary curl. Primary curl was evaluated based on the following evaluation criteria. (Evaluation criteria) A: The maximum curl angle is less than 90° B: The maximum curl angle is 90° or more and less than 110° C: The maximum curl angle is 110° or more

[0082] 2.6.Nozzle plate water repellency Using a silicon nozzle plate with a water-repellent film formed from single-crystal silicon, the ink composition of each example was dropped in a volume of 5 μL over a period of 100 ms at a temperature of 25°C, and the contact angle with the nozzle plate was measured. A portable contact angle meter PCA-1 (manufactured by Kyowa Interface Science Co., Ltd.) was used as the contact angle meter. The water repellency of the nozzle plate was evaluated based on the following evaluation criteria. (Evaluation criteria) A: The contact angle is 60° or more. B: Contact angle is 40° or more and less than 60° C: Contact angle is less than 40°

[0083] [Table 1]

[0084] [Table 2]

[0085] [Table 3]

[0086] 3. Evaluation Results The composition and evaluation results of the ink used in each example are shown in Tables 1 to 3. Tables 1 to 3 show that by containing a colorant, inorganic oxide particles, a predetermined amount of water-soluble silicate, and water, curling of the resulting recorded matter is suppressed, and even ink containing inorganic oxide particles has excellent clogging recovery properties.

[0087] In particular, Comparative Example 1 shows that curling is likely to occur when inorganic oxide particles are not used, and Comparative Examples 4 and 5 show that the water repellency of the nozzle plate and intermittent printing stability are further reduced when only inorganic oxide particles are included.Furthermore, Comparative Examples 2 and 3 show that clogging recovery is reduced when the amount of water-soluble silicate is too high. [Explanation of symbols]

[0088] 10 recording device, 11 transport path, 12 feeding section, 14 transport section, 16 belt transport section, 18 recording section, 20 Fd discharge section, 22 Fd placement section, 24 reversing path section, 26 Fu discharge section, 28 Fu placement section, 30 feeding tray, 32 feeding roller, 34 transport drive roller, 36 transport driven roller, 38 first roller, 40 second roller, 42 endless belt, 42a upper section of endless belt, 44 support, 46 head holder, 48 inkjet head, 50 first branch section, 52 reversing path, 54 second branch section, 56 discharge roller pair, 64 discharge drive roller, 68 drive shaft, 76 placement surface, 78 convex portion, 80 first urging member, 82 second urging member, 84, 86 support shaft, P recording medium

Claims

1. The ink contains a colorant, inorganic oxide particles, a water-soluble silicate, water, and a water-soluble organic solvent, the content of the water-soluble silicate is 0.5% by mass or less relative to the total amount of the ink composition; the content of the inorganic oxide particles is 1.0% by mass or more and 10% by mass or less with respect to the total amount of the ink composition, SP value is 27.5 (J / cm 3 ) 1 / 2 The water-soluble organic solvent S 1 the content of the water-soluble organic solvent is 35% by mass or less based on the total amount of the water-soluble organic solvent, The ink-jet ink composition is a water-based ink.

2. the content of the inorganic oxide particles is 2.0% by mass or more and 8.0% by mass or less with respect to the total amount of the ink composition; The ink-jet ink composition of claim 1 .

3. The solid content of the ink composition is 5.0% by mass or more relative to the total amount of the ink composition. The ink-jet ink composition according to claim 1 or 2.

4. the content of the coloring material is 0.5% by mass or more and 10% by mass or less with respect to the total amount of the ink composition; The ink-jet ink composition according to any one of claims 1 to 3.

5. the content of the water-soluble silicate is 0.00001% by mass or more and 0.5% by mass or less with respect to the total amount of the ink composition; The ink-jet ink composition according to any one of claims 1 to 4.

6. The colorant contains a self-dispersing pigment. The ink-jet ink composition according to any one of claims 1 to 5.

7. the ratio of the content of the inorganic oxide particles to the content of the water-soluble silicate (inorganic oxide particles / water-soluble silicate) is 3 or more and 50,000 or less; The ink-jet ink composition according to any one of claims 1 to 6.

8. SP value is 27.5 (J / cm 3 ) 1 / 2 The water-soluble organic solvent S 1 The content of the water-soluble organic solvent is 5.0% by mass or more and 30% by mass or less based on the total amount of the water-soluble organic solvent. The ink-jet ink composition according to any one of claims 1 to 7.

9. the content of the water is 80% by mass or less relative to the total amount of the ink composition; The ink-jet ink composition according to any one of claims 1 to 8.

10. Contains amino acids, The ink-jet ink composition according to any one of claims 1 to 9.

11. It is used for recording on an absorbent recording medium, The ink-jet ink composition according to any one of claims 1 to 10.

12. A method for producing an ink jet recording medium, comprising a step of ejecting the ink jet ink composition according to any one of claims 1 to 11 from an ink jet head and depositing the ink jet ink composition on a recording medium. Recording method.

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