Recording method and recording device

Abstract

To provide a recording method capable of suppressing pigment precipitation in an ink chamber and differences in color development of a recorded matter.SOLUTION: There is provided a recording method which comprises a supply step of supplying an ink composition from an ink chamber to an inkjet head and an adhering step of discharging the ink composition from the inkjet head to adhere the ink composition to a recording medium, wherein the ink chamber receives a supply of the ink composition from an ink storage container and has a capacity of 40 mL or more and the ink composition is a water-based ink composition comprising a pigment and inorganic oxide particles having a specific gravity higher than the specific gravity of the pigment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a recording method and a recording apparatus. [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. In the process, various studies have been conducted on ejection stability, etc. For example, Patent Document 1 discloses a recording method in which an ink composition containing a predetermined water-soluble organic solvent is heated to a predetermined viscosity and then ejected, with the aim of improving intermittent ejection stability when a recording device equipped with a main tank and a sub-tank is used for a long period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-001392 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to prevent printing from being suddenly interrupted when the ink in the ink container runs out, it is conceivable to provide an ink chamber between the ink container and the inkjet head in a recording device. However, in such an ink chamber, the pigments contained in the ink composition may settle, and this settling of the pigments may affect the image quality of the recorded material. [Means for solving the problem]

[0005] The recording method of the present invention comprises a supplying step of supplying an ink composition from an ink chamber to an inkjet head, and an adhering step of ejecting the ink composition from the inkjet head and adhering it to a recording medium, wherein the ink chamber receives the ink composition from an ink storage container and has a capacity of 40 mL or more, and the ink composition is an aqueous ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment.

[0006] The recording device of the present invention also includes an ink chamber and an inkjet head to which an ink composition is supplied from the ink chamber, the ink chamber being supplied with the ink composition from an ink storage container, the ink chamber having a capacity of 40 mL or more, and the ink composition being an aqueous ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic view showing an ink chamber and the like of a recording device used in the recording method of the present embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view of a recording apparatus that can be 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. Recording method The recording method of this embodiment includes a supplying step of supplying an ink composition from an ink chamber to an inkjet head, and an adhering step of ejecting the ink composition from the inkjet head and adhering it to a recording medium, wherein the ink chamber receives the ink composition from an ink storage container and has a capacity of 40 mL or more, and the ink composition is an aqueous ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment.

[0010] In order to prevent printing from being suddenly interrupted when the ink in the ink container runs out, it is conceivable to provide an ink chamber between the ink container and the inkjet head in the recording device. In particular, it is useful to provide such ink chambers in recording devices such as line printers that often perform large-volume printing. Furthermore, when a pigment with excellent color development is used, settling of the pigment occurs, which affects the image quality of the recorded material.

[0011] However, it has been found that in such ink chambers, pigments and other components of the ink composition contained therein settle while the recording device is stopped, resulting in uneven density and color difference in the recorded material before and after the recording device is stopped.

[0012] One approach to eliminating this sedimentation is to shake the ink chamber by hand. However, the ink chamber is often fixed between the ink container and the inkjet head of the recording device, making it difficult to agitate the sediment by shaking only the ink chamber. Another approach is to provide an agitation mechanism or circulation mechanism in the ink chamber to suppress the sedimentation of pigments, etc. However, providing such a mechanism would complicate the device configuration and increase costs.

[0013] In contrast to this, in the present embodiment, in a recording method using a recording apparatus equipped with an ink chamber, by using an ink composition containing inorganic oxide particles having a higher specific gravity than the pigment, it is possible to suppress sedimentation of the pigment and thereby suppress uneven density and color difference. The reason for this is not particularly limited, but it is presumed that the inorganic oxide particles settle out before the pigment, and the electrostatic repulsion of the settled inorganic oxide particles and the like suppresses the sedimentation of the pigment.

[0014] The configuration of the recording method of this embodiment will be described in detail below.

[0015] 1.1. Supply process The supplying step is a step of supplying the ink composition from the ink chamber to the inkjet head. FIG. 1 shows a schematic diagram of a recording apparatus that includes an ink chamber as a sub-tank. As shown in FIG. 1, the recording apparatus 1 that implements the recording method of this embodiment has an ink chamber 10, an inkjet head 20, and a first ink flow path 40. The ink composition stored in the ink chamber 10 is supplied to the inkjet head 20 through the first ink flow path 40.

[0016] 1.1.1.Ink chamber The ink chamber 10 receives a supply of the ink composition from the ink storage container 30. The ink chamber 10 in this embodiment is not particularly limited, but may be, for example, a sub-tank or an ink storage chamber provided in a continuous ink supply system (CISS).

[0017] The capacity of the ink chamber 10 is 40 mL or more, preferably 50 to 500 mL, more preferably 60 to 400 mL, and even more preferably 60 to 300 mL. When the capacity of the ink chamber 10 is 40 mL or more, the pigment tends to settle, making the present invention particularly useful. The material of the ink chamber is not limited, but metal, glass, resin, etc. can be used as long as it can contain the ink composition.

[0018] 1.1.1.1. Subtank The ink chamber 10, which is a sub-tank, receives a supply of ink composition from the ink storage container 40, which is a main tank, and supplies the supplied ink composition to the inkjet head 20 via the first ink flow path 40. Here, the ink storage container 40 is not particularly limited, but examples thereof include containers that store ink composition, such as ink cartridges and ink packs. The ink capacity of the ink storage container 40 is not limited, but is preferably, for example, 100 to 3000 ml.

[0019] The supply of the ink composition to the ink chamber 10 serving as a sub-tank may be performed automatically under the control of the recording apparatus as the ink composition is consumed. Alternatively, the supply of the ink composition to the ink chamber 10 serving as a sub-tank and the supply of ink from the ink chamber 10 serving as a sub-tank to the inkjet head 20 may be performed simultaneously under the control of the recording apparatus. In this case, the recording method of this embodiment may further include a step of supplying the ink composition from the ink storage container 40 to the ink chamber 10.

[0020] The location of the ink chamber 10 serving as a sub-tank is not particularly limited as long as it is between the inkjet head 20 and the ink storage container 40, and it may be provided, for example, inside the inkjet head 20. The ink composition may also be supplied from above in the vertical direction of the ink chamber 10. Supplying the ink composition from above tends to agitate the ink composition in the ink chamber 10 and prevent pigment sedimentation. The ink composition may also be supplied to the inkjet head 20 from below in the vertical direction of the ink chamber 10. This tends to prevent air bubbles from being mixed into the ink composition supplied to the inkjet head 20.

[0021] 1.1.1.2.Continuous ink supply system The term "continuous ink supply system" refers to a system in which an ink composition is replenished into an ink chamber provided in a recording device, and recording is performed using the ink composition replenished into the ink chamber. For example, in a continuous ink supply system, an ink chamber 10 has an ink inlet and receives a supply of ink composition from an ink containing container 40. The supplied ink composition is then supplied to the inkjet head 2 via a first ink flow path 40. Here, the ink containing container 40 is not particularly limited, but examples thereof include an ink bottle that is connected to the ink chamber 10 only when the ink composition is to be supplied to the ink chamber 10. The connection is not limited to a connection made via a connecting member, and may be a connection in which the ink composition is supplied directly from the ink bottle to the ink inlet without using a connecting member.

[0022] In the continuous ink supply system, the ink composition may be supplied to the ink chamber 10 manually through an ink inlet. In addition, the supply of ink from the ink chamber 10 to the inkjet head 20 in the continuous ink supply system may be automatically controlled by the recording apparatus as the ink composition is consumed. Furthermore, since the continuous ink supply system performs recording using the ink composition replenished in the ink chamber, the supply of the ink composition to the ink chamber 10 in the continuous ink supply system and the supply of ink from the ink chamber 10 to the inkjet head 20 in the continuous ink supply system do not have to be performed simultaneously.

[0023] 1.1.2.Inkjet head The inkjet head 20 is not particularly limited, but examples thereof include a line head that performs printing by a line method and a serial head that performs printing by a serial method.

[0024] In the line method using a line head, for example, a liquid jet head having a width equal to or greater than the recording width of the recording medium is fixed to an inkjet device. The recording medium is then moved along the scanning direction (the longitudinal direction of the recording medium, the transport direction), and an image is recorded on the recording medium by scanning in which ink droplets are ejected from the nozzles of the liquid jet head in conjunction with this movement.

[0025] Alternatively, the recording medium is fixed to the recording device. An inkjet head having a width equal to or greater than the recording width of the recording medium is moved along a scanning direction, and an image is recorded on the recording medium by ejecting ink droplets from the nozzles of the inkjet head in conjunction with this movement. The scanning direction is the direction of scanning.

[0026] FIG. 2 shows a schematic cross-sectional view of a recording device that can be used in the recording method of the present invention. The inkjet head 20 is a line head having a length equal to or greater than the recording width of the recording medium, and is a means for ejecting an ink composition and depositing it on the recording medium M. The inkjet head 20 has a nozzle row (not shown) on a nozzle surface 11 facing the recording medium M, which is a row of nozzles aligned in the recording width direction D2 of the recording medium. The recording medium M is supported by a belt B and transported in a transport direction D1. The number of inkjet heads 20 is not limited to two, but may be one or more. The belt B is moved in the transport direction D1 by a belt roller 60. The ink chambers and the like mentioned above are not shown in FIG. 1. The recording device may also be equipped with a paper feed tray, a paper output tray, and the like (not shown).

[0027] In the serial method using a serial head, for example, a liquid ejection 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 lateral or width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement, thereby recording an image on the recording medium.

[0028] Among these, it is preferable to perform recording by a line-type recording method using an inkjet head having a width equal to or greater than the recording width of the recording medium. The line-type recording method is suitable for high-speed printing and large-volume printing, but since ink shortages tend to occur, it is preferable to provide an ink chamber. Therefore, the present invention, which can eliminate pigment sedimentation in the ink chamber and color differences caused by sedimentation, is particularly useful.

[0029] 1.1.3.Ink flow path The ink flow path refers to a flow path for distributing ink in a recording device. Examples of the ink flow path include a first ink supply path 40 for supplying the ink composition from an ink chamber 10 storing the ink composition to an inkjet head 20, a second ink supply path 50 for supplying the ink composition from an ink storage container 30 to the ink chamber 10, and a flow path for distributing the ink composition to a nozzle opening within the inkjet head 20.

[0030] The distance of the first ink supply path 40 from the ink chamber 10 to the inkjet head 20 is preferably 100 mm or more, or 1500 mm or less. It is further preferably 200 to 1500 mm, more preferably 300 to 1000 mm, and even more preferably 400 to 750 mm. By having the distance of the first ink supply path 40 within the above range, the settled content tends to be easily re-agitated as the ink composition passes through the first ink supply path 40. The distance to the inkjet head 20 is from the ink chamber 10 to the nozzle of the inkjet head 20.

[0031] 1.2.Attachment process The deposition step is a step in which the ink composition is ejected from an inkjet head and deposited onto a recording medium.

[0032] Methods for ejecting an ink composition from a nozzle in an inkjet head include a method in which a pressure generating means is driven to eject the composition filled in a pressure generating chamber of the inkjet head from the nozzle, and a method in which thermal energy is applied to eject the composition. Such ejection methods are also called inkjet methods. Methods for applying pressure to the ink composition in the nozzle are not particularly limited, but examples include a piezoelectric method in which a piezoelectric element is used to eject droplets of the ink composition, and a thermal method in which heat is used to eject droplets.

[0033] 1.3. Ink composition The ink composition is a water-based ink composition containing a pigment and inorganic oxide particles having a higher specific gravity than the pigment. In addition to the above, the ink composition may further contain water, a water-soluble organic solvent, a lactam compound, a resin emulsion, a surfactant, a pH adjuster, etc., as necessary.

[0034] 1.3.1.Pigments The pigment is not particularly limited, and 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. The pigments may be used alone or in combination.

[0035] Among these, it is preferable that the pigment contains either carbon black or an organic pigment, as this tends to reduce the specific gravity and further inhibit the sedimentation of the pigment.

[0036] The specific gravity of the pigment is preferably 0.1 to 2.0, further preferably 0.1 to 1.9, even more preferably 0.2 to 1.8, and preferably 0.3 to 1.7. When the specific gravity of the pigment is within the above range, sedimentation of the pigment tends to be further suppressed.

[0037] The pigment can be used as a pigment dispersion obtained by dispersing the pigment in water with a dispersant, for example, a pigment using a dispersant resin as the dispersant (hereinafter also referred to as a "resin-dispersed pigment"). Alternatively, examples include those obtained by dispersing in water a self-dispersing surface-treated pigment (hereinafter also referred to as a "self-dispersing pigment") in which hydrophilic groups have been introduced onto the surface of pigment particles by utilizing a chemical reaction. Alternatively, a pigment coated with a polymer and dispersed in water may be used. Among these, it is preferable to contain a self-dispersing pigment, as the use of a self-dispersing pigment tends to further improve the water repellency of the nozzle plate and the intermittent printing stability.

[0038] The pigment and dispersant constituting the pigment dispersion may each be used alone or in combination of two or more.

[0039] The volume average particle size of the pigment is preferably 20 to 250 nm, more preferably 40 to 230 nm, still more preferably 60 to 210 nm, particularly preferably 80 to 190 nm, and even more preferably 100 to 180 nm. When the volume average particle diameter of the pigment is 20 nm or more, color development tends to be further improved, and when the volume average particle diameter of the pigment is 250 nm or less, sedimentation of the pigment tends to be further suppressed.

[0040] The pigment content, as solid content, is preferably 0.5% by mass or more relative to the total amount of the ink composition. It is also preferably 1.0 to 10% by mass, more preferably 3.0 to 10% by mass, and even more preferably 4.0 to 8.0% by mass. By keeping the colorant content within this range, sedimentation is suppressed, and color development tends to be further improved.

[0041] 1.3.2. Inorganic oxide particles The inorganic oxide particles are not particularly limited as long as they have a higher specific gravity than the pigment. The inorganic oxide particles can suppress the settling of the pigment. They can also suppress the penetration of ink into the recording medium, resulting in excellent color development of the recorded material.

[0042] The specific gravity of the inorganic oxide particles is preferably 2.0 to 6.0, more preferably 2.0 to 5.0, and more preferably 2.0 to 4.0. When the true specific gravity of the inorganic oxide particles is within the above range, sedimentation of the pigment tends to be further suppressed.

[0043] The specific gravity of the inorganic oxide particles is preferably at least 0.1 higher than the specific gravity of the pigment, more preferably 0.2 to 3.0 higher, even more preferably 0.3 to 2.0 higher, and still more preferably 0.3 to 1.0 higher.

[0044] The inorganic oxide particles are not particularly limited, but examples thereof include silica, alumina, zirconia, titania, ceria, antimony oxide, tin oxide, tantalum oxide, zinc oxide, lead oxide, and indium oxide. Among these, it is preferable to include at least one selected from the group consisting of silica, alumina, zirconia, titania, and ceria. By using such inorganic oxide particles, curling of the resulting recording material is further suppressed, and stackability is further improved. The inorganic oxide particles may be used alone or in combination of two or more. The inorganic oxide particles may be particles containing at least an inorganic oxide. Particles made of an inorganic oxide are preferred.

[0045] 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.

[0046] 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.

[0047] The volume-average particle diameter of the inorganic oxide particles is preferably 100 nm or less, or preferably 5 nm or more. It is more preferably 10 to 95 nm, even more preferably 20 to 90 nm, and even more preferably 40 to 80 nm. When the volume-average particle diameter of the inorganic oxide particles is 100 nm or less, the resulting recorded matter is prevented from becoming whitish, and pigment sedimentation tends to be further suppressed. Furthermore, when the volume-average particle diameter of the inorganic oxide particles is greater than or equal to the above range, color development tends to be further improved.

[0048] 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 (D50) based on the number of particles, unless otherwise specified.

[0049] The content of the inorganic oxide particles, as solid content, relative to the total amount of the ink composition is preferably 0.5 to 8.0 mass %, more preferably 1.0 to 6.0 mass %, and even more preferably 1.5 to 4.5 mass %. When the content of the inorganic oxide particles is within the above range, sedimentation is further suppressed and color development tends to be further improved.

[0050] 1.3.3.Water The ink composition of this embodiment is a water-based ink. A water-based ink is an ink that contains water as a main solvent component. The water content in the water-based ink is preferably 40% by mass or more, and more preferably 40 to 98% by mass, based on the total amount of the ink composition. It is also 45% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 75% by mass or less, and even more preferably 55% by mass or more and 70% by mass or less.

[0051] 1.3.4. 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.

[0052] The water-soluble organic solvent is not particularly limited, but examples thereof include triol or higher polyols such as glycerin; nitrogen-containing solvents such as 2-pyrrolidone and N-methylpyrrolidone; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, propanediol, butanediol, pentanediol, and 1,2-hexanediol; and glycol monoalkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, and triethylene glycol monobutyl ether.

[0053] The content of the water-soluble organic solvent is preferably 5.0 to 25% by mass, more preferably 7.5 to 20% by mass, and even more preferably 10 to 15% by mass, relative to the total amount of the ink composition. When the content of the water-soluble organic solvent is within the above range, sedimentation of the pigment is further suppressed, and printing continuity tends to be further improved.

[0054] 1.3.5. Lactam compounds The ink composition of this embodiment may contain a lactam compound. By containing a lactam compound, even if the inorganic oxide particles aggregate, the resolubility thereof is improved, and printing continuity tends to be improved.

[0055] The lactam compound is preferably a water-soluble compound. Among the lactam compounds, water-soluble compounds that are liquid at room temperature are also the water-soluble organic solvents described above. The lactam compound has a 3- or more-membered ring, preferably a 3- to 9-membered ring, and more preferably a 5- to 8-membered ring.

[0056] The lactam compound is not particularly limited, but examples thereof include 2-pyrrolidone, N-methyl-2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, 3-methoxy-2-pyrrolidone, 3-acetoxy-2-pyrrolidone, 4-pentanelactam, and ε-caprolactam.

[0057] The content of the lactam compound is preferably 1.0 to 10% by mass, more preferably 1.5 to 8.0% by mass, and even more preferably 2.0 to 6.0% by mass, relative to the total amount of the ink composition. When the content of the lactam compound is within the above range, printing continuity tends to be further improved.

[0058] 1.3.6.Resin emulsion The ink may further contain a resin emulsion. The resin emulsion is not particularly limited, but examples thereof include (meth)acrylic resin emulsion and urethane resin emulsion. By using such a resin emulsion, bleeding of the obtained image tends to be further suppressed and abrasion resistance tends to be further improved. The resin emulsion may be used alone or in combination of two or more.

[0059] The acrylic resin emulsion is not particularly limited, but examples thereof include those obtained by polymerizing (meth)acrylic monomers such as (meth)acrylic acid and (meth)acrylic acid esters, and those obtained by copolymerizing (meth)acrylic monomers with other monomers, such as styrene-acrylic resins. Among these, anionic acrylic resin fine particles are preferred.

[0060] The urethane resin emulsion is not particularly limited as long as it is a resin emulsion having a urethane bond in the molecule, and examples thereof include polyether-type urethane resins having an ether bond in the main chain, polyester-type urethane resins having an ester bond in the main chain, and polycarbonate-type urethane resins having a carbonate bond in the main chain. Among these, anionic urethane resin fine particles are preferred.

[0061] The content of the resin emulsion, as solid content, relative to the total amount of the ink composition is preferably 0.1 to 5.0 mass%, more preferably 0.1 to 3.0 mass%, and even more preferably 0.1 to 1.0 mass%. When the content of the resin emulsion is within the above range, printing continuity tends to be further improved.

[0062] Surfactants The ink composition of this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples thereof include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0063] The acetylene glycol surfactant is not particularly limited, but is preferably at least one selected from, for example, alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and 2,4-dimethyl-5-decyne-4-ol. The acetylene glycol surfactants may be used alone or in combination of two or more.

[0064] The fluorine-based surfactant 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. The fluorine-based surfactants may be used alone or in combination of two or more.

[0065] Examples of silicone surfactants include polysiloxane compounds, polyether-modified organosiloxanes, etc. The silicone surfactants may be used alone or in combination of two or more.

[0066] The content of the surfactant is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 2.0% by mass, and even more preferably 0.3 to 1.5% by mass, relative to the total amount of the ink composition. When the content of the surfactant is within the above range, printing continuity tends to be further improved.

[0067] pH adjusters The pH adjuster is not particularly limited, but examples thereof include inorganic acids (e.g., sulfuric acid, hydrochloric acid, nitric acid, etc.), inorganic bases (e.g., lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, etc.), organic bases (triethanolamine, diethanolamine, monoethanolamine, tripropanolamine), and organic acids (e.g., adipic acid, citric acid, succinic acid, etc.). Among these, organic bases are preferred. The pH adjuster may be used alone or in combination of two or more.

[0068] The content of the pH adjuster is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.1 to 1.0% by mass, relative to the total amount of the ink composition. When the content of the pH adjuster is within the above range, precipitation is further suppressed, and printing continuity tends to be further improved.

[0069] 1.4. Recording Media The recording medium is not particularly limited, but examples thereof include absorbent recording media, low absorbent recording media, and non-absorbent recording media. Among these, absorbent recording media and low absorbent recording media are preferred, and absorbent recording media are more preferred. The higher the absorbency, the more easily the inorganic oxide fine particles can exert a sealing effect, which in turn improves color development, making the present invention particularly useful.

[0070] Here, a "low-absorbency recording medium" or a "non-absorbency recording medium" is defined as a medium having a water absorption of 10 mL / m2 or less within 30 msec from the start of contact in the Bristow method. 2 This refers to a recording medium that is as follows: The Bristow method is the most widely used method for measuring liquid absorption in a short period of time, and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51 "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method" of the "JAPAN TAPPI Paper and Pulp Test Method 2000 Edition."

[0071] The low-absorbency recording medium has a water absorption capacity of 5 mL / m 2 More than 10mL / m2 On the other hand, an absorbent recording medium is a recording medium having a water absorption rate of 10 mL / m or less. 2 This refers to a recording medium that is superior to

[0072] The absorbent recording medium is not particularly limited, but examples thereof include plain paper such as electrophotographic paper that has high ink composition permeability, inkjet paper (paper specifically for inkjet printers that 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)), etc. Also included are fabrics.

[0073] The low-absorbency recording medium is not particularly limited, but examples thereof include coated paper having a coating layer on the surface for receiving oil-based ink, and examples of coated paper include, but are not particularly limited to, printing paper such as art paper, coated paper, and matte paper.

[0074] 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.

[0075] 2. Recording device The recording device of this embodiment includes an ink chamber and an inkjet head to which an ink composition is supplied from the ink chamber. The ink chamber receives the ink composition from an ink storage container, and the ink chamber has a capacity of 40 mL or more. The ink composition is an aqueous ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment. [Example]

[0076] 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.

[0077] 1. Ink Preparation Each component was placed in a mixing tank and mixed to obtain the composition shown in Tables 1 to 3, followed by filtration through a 5 μm membrane filter to obtain the inkjet ink of each example. The numerical values ​​for each component shown in each example in the tables represent % by mass unless otherwise specified. The numerical values ​​for inorganic oxide particles, pigment dispersions, and resins in the tables represent % by mass of the solid content.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] The abbreviations and product ingredients used in Tables 1 to 3 are as follows:

[0082] [Pigment dispersion] Black pigment A (average particle size 130 nm, carbon black) Black pigment B (average particle size 180 nm, carbon black) Black pigment C (average particle size 80 nm, carbon black) Black pigment D (average particle size 250 nm, carbon black) Black pigment E (average particle size 60 nm, carbon black) Cyan pigment (average particle size 130nm Pigment Blue15:3) Magenta pigment (average particle size 130 nm, Pigment Violet 19) Yellow pigment (average particle size 130 nm) Pigment Yellow 74 White pigment (titanium oxide, carbon black, average particle size 250 nm, Ishihara Sangyo Co., Ltd. R-550) [Inorganic oxide particles] Colloidal silica (average particle size 45 nm, JGC Catalysts and Chemicals SI-45P) Colloidal silica (average particle size 25 nm, JGC Catalysts and Chemicals SI-50) Colloidal silica (average particle size 80 nm, JGC Catalysts and Chemicals SI-80P) Alumina (average particle size 40 nm, BYK NANOBYK-3600) [Water-soluble organic solvent] glycerin triethylene glycol Triethylene Glycol Monobutyl Ether Triethylene glycol monomethyl ether 1,2-Hexanediol [Lactam compounds] 1-(2-hydroxyethyl)-2-pyrrolidone ε-caprolactam [Resin emulsion] Styrene-acrylic resin emulsion (Seiko PMC, X-436, Tg: 33°C, acid value 33 mg KOH / g) [Surfactant] Olfine E1010 (trade name of Air Products, acetylene glycol surfactant) Surfynol 104 (trade name of Nissin Chemical Industry Co., Ltd., acetylene glycol surfactant) Olfine EXP4300 (product name of Air Products, acetylene glycol surfactant) [pH adjuster] Triethanolamine

[0083] 1.1. Preparation examples of pigment dispersions for black pigments A to E Carbon black pigment base particles were mixed with water and stirred and pulverized in a bead mill. The average particle size of the resulting particles was adjusted to the above values ​​by changing the stirring time. The pulverized particles were then surface-treated to introduce hydrophilic groups onto the particle surface. Self-dispersing black pigments A to E were obtained as pigment dispersions. The surface treatment was carried out as follows. 20.0 g of pigment, 11.0 mmol of ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid monosodium salt, 20.0 mmol of nitric acid, and 200 mL of pure water were mixed. Carbon black (trade name "Black Pearls 880" manufactured by Cabot) was used as the pigment. The mixture was mixed at 6,000 rpm using a Silverson mixer at room temperature. After 30 minutes, 20.0 mmol of sodium nitrite dissolved in a small amount of water was slowly added to the mixture. The temperature of the mixture reached 60°C upon addition of sodium nitrite. The mixture was allowed to react under this condition for 1 hour. After washing with water, the pH of the mixture was adjusted to 10 using aqueous sodium hydroxide. The resulting pigment was a self-dispersing pigment in which -CH-CONH-CH-(PO(OH)(ONa))(PO(OH)) groups were bonded to the pigment particle surface.

[0084] 1.2. Preparation example of pigment dispersion for color pigment The cyan pigment base particles were mixed with water and stirred and pulverized in a bead mill to prepare the cyan pigment base particles. The average particle size of the resulting particles was adjusted to the above range by changing the stirring time. 20.0 g of this pigment, 3.5 mmol of ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid monosodium salt, 10.0 mmol of nitric acid, and 200 mL of pure water were mixed. The mixture was then mixed at 6,000 rpm using a Silverson mixer at room temperature. After 30 minutes, 10.0 mmol of sodium nitrite dissolved in a small amount of water was slowly added to the mixture. The temperature of the mixture reached 60°C upon addition of the sodium nitrite. The mixture was allowed to react under this condition for 1 hour. After washing with water, the pH of the mixture was adjusted to 10 using an aqueous sodium hydroxide solution. A self-dispersing pigment was obtained in which -C6H4-CONH-CH-(PO(OH)(ONa))(PO(OH)2) groups were bonded to the pigment particle surface. In this way, a pigment dispersion of a self-dispersing cyan pigment was obtained. The same procedure was carried out except that the pigments were changed to those mentioned above, and pigment dispersions of magenta pigment and yellow pigment were also obtained.

[0085] 1.3. Preparation example of white pigment dispersion The above titanium oxide particles were used as pigment base particles, and a dispersant (DISPERBYK-190 manufactured by BYK Chemie) was mixed with water in a mass ratio of pigment:dispersant=3:1 and stirred to prepare a pigment dispersion.

[0086] The specific gravities were 1.9 for carbon black, 1.4 to 1.6 for color pigments, 4.2 for titanium oxide, 2.2 for silica, and 4.0 for alumina.

[0087] 2. Evaluation An LX10000F (manufactured by Seiko Epson) was modified to create a line printer equipped with sub-tanks of the capacities listed in Tables 1 to 3, and filled with the inks listed in Tables 1 to 3 so that they could be ejected. The ink could be supplied to the sub-tanks from the ink cartridges. The ink could also be supplied from the sub-tanks to the inkjet head. A line head like the one shown in Figure 2 was used as the inkjet head. The nozzle density in the width direction was 600 npi. The distance of the ink supply channel flow path from the sub-tank to the nozzle of the inkjet head is shown as the flow path length in the table. For the example without a sub-tank, the distance was from the ink cartridge to the nozzle of the inkjet head.

[0088] In the example with the stirring mechanism and ink circulation mechanism, a screw was installed in the sub-tank. Furthermore, an ink return path was provided between the inkjet head and the sub-tank, allowing the ink to circulate between the inkjet head and the sub-tank. In this way, while the ink was left to stand for the sedimentation test described below, the ink in the sub-tank was stirred by the screw, and the ink was circulated between the inkjet head and the sub-tank.

[0089] Then, a solid pattern was recorded on plain paper (Xerox P paper) under the conditions of an ink deposition amount of 6 ng / dot and a recording resolution of 600×600 dpi.

[0090] 2.1. Sedimentation test The subtank was left to stand for two weeks with the ink filled to capacity. After leaving it, a solid pattern was printed under the above conditions, and continuous printing was carried out until the ink in the subtank's capacity was used up. The solid pattern recorded before leaving it and the solid pattern recorded on each sheet during continuous printing were measured, and the maximum color difference between each solid pattern was obtained. Based on the obtained color difference, sedimentation was evaluated according to the following evaluation criteria. For the example without a subtank, printing was carried out until the ink in the ink cartridge was used up.

[0091] The colorimetric measurements were performed by measuring the L*a*b* values ​​defined by CIELAB using a colorimeter "Spectrolino" manufactured by GretagMacbeth, and the difference between the values ​​(ΔE) was determined as the color difference.

[0092] (Evaluation criteria) A: The maximum color difference between each solid pattern is less than 1.0 B: The maximum color difference between each solid pattern is 1.0 or more and less than 2.0 C: The maximum color difference between each solid pattern is 2.0 or more and less than 2.5 D: The maximum color difference between each solid pattern is 2.5 or more

[0093] 2.2.Color development The OD value of the printed solid pattern before standing was measured using a reflection densitometer (trade name: Spectrolino, manufactured by Gretag Co.) Based on the obtained OD value, the color development was evaluated according to the following evaluation criteria. (Evaluation criteria) A:OD value is 1.33 or more B: OD value is 1.25 or more and less than 1.33 C:OD value is 1.20 or more and less than 1.25 D:OD value is less than 1.20

[0094] 2.3.Print Continuity The subtank was filled with ink to its capacity, and ink was not supplied from the ink cartridge to the subtank, and an evaluation was made to see how much printing was possible with the ink in the subtank. For the evaluation, a monochrome pattern specified in ISO / IEC 19752 was printed. The number of pages that could be printed before the ink in the subtank ran out was counted, and printing continuity was evaluated according to the following evaluation criteria. The example without a subtank was deemed impossible to print, as it was not possible to print without the ink cartridge. (Evaluation criteria) A: More than 10,000 sheets can be printed. B: Printing capacity of 6,000 or more sheets, but less than 10,000 sheets C: Less than 6,000 sheets can be printed D: Unable to print

[0095] 3. Evaluation Results Comparing the Examples and Comparative Examples, it was found that by using an ink composition containing inorganic oxide particles that have a higher specific gravity than the pigment, the settling of the pigment is suppressed and color development is improved, even in recording devices that have sub-tanks. In Comparative Examples 1, 4, and 5, the ink did not contain inorganic oxide particles or did not contain inorganic oxide particles with a higher specific gravity than the pigment, and the pigment sedimentation suppression was poor. In Comparative Examples 4 and 5, the recording apparatus was not provided with a sub-tank or was not provided with a sub-tank with a capacity of 40 ml or more, and therefore, although the pigment sedimentation was effectively suppressed, the printing continuity was poor. In Comparative Example 6, the ink did not contain inorganic oxide particles, so it was not possible to suppress the penetration of the ink into the recording medium, and the color development was poor because a pigment with relatively low color development was used.Furthermore, when a pigment with relatively low color development was used, the pigment sedimentation was less likely to occur.

[0096] In addition, instead of using a line printer equipped with a sub-tank, we also performed a separate test in which the sub-tank was replaced with a CISS tank of the same capacity. The results were similar to those of the sub-tank, and the results were comparable. [Explanation of symbols]

[0097] 10... ink chamber, 20... inkjet head, 30... ink storage container, 40... first ink flow path, 50... second ink flow path

Claims

1. a supplying step of supplying the ink composition from the ink chamber to the inkjet head; a deposition step of ejecting the ink composition from the inkjet head and depositing it onto a recording medium, the ink chamber is supplied with the ink composition from an ink storage container and has a capacity of 40 mL or more; The ink composition is a water-based ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment. Recording method.

2. The volume average particle diameter of the pigment is 20 to 250 nm. The recording method according to claim 1 .

3. the content of the inorganic oxide particles is 0.5 to 8.0% by mass relative to the total amount of the ink composition; 3. The recording method according to claim 1 or 2.

4. The volume average particle diameter of the inorganic oxide particles is 100 nm or less. The recording method according to any one of claims 1 to 3.

5. the ink composition contains a water-soluble organic solvent, the content of the water-soluble organic solvent is 5.0 to 25% by mass with respect to the total amount of the ink composition; The recording method according to any one of claims 1 to 4.

6. a distance of an ink flow path from the ink chamber to the inkjet head is 50 to 1500 mm; The recording method according to any one of claims 1 to 5.

7. The pigment includes any one of carbon black and an organic pigment. The recording method according to any one of claims 1 to 6.

8. The inorganic oxide particles contain at least one selected from the group consisting of silica, alumina, zirconia, titania, and ceria. The recording method according to any one of claims 1 to 7.

9. The ink composition contains a lactam compound. The recording method according to any one of claims 1 to 8.

10. the content of the pigment is 1.0 to 10% by mass relative to the total amount of the ink composition; The recording method according to any one of claims 1 to 9.

11. In the adhering step, recording is performed by a line recording method using the inkjet head having a width equal to or greater than the width of the recording medium. The recording method according to any one of claims 1 to 10.

12. The recording medium is an absorbent recording medium. The recording method according to any one of claims 1 to 11.

13. An ink chamber, an inkjet head to which the ink composition is supplied from the ink chamber, the ink chamber receives a supply of an ink composition from an ink storage container; The capacity of the ink chamber is 40 mL or more, The ink composition is a water-based ink composition containing a pigment and inorganic oxide particles having a specific gravity higher than that of the pigment. Recording device.

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