White Inkjet Ink Composition and Inkjet Recording Method

Abstract

To provide a white ink jet ink composition that has excellent sedimentation and color development.SOLUTION: A white ink jet ink composition includes hollow resin particles, resin particles, and water. The hollow resin particles have a glass transition temperature of 120°C or more, the resin particles are composed of an acrylic resin or a urethane resin, and the content of the resin particles is 5 mass% or more relative to the total mass of the ink composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a white inkjet ink composition and an inkjet recording method.

Background Art

[0002] In inkjet recording, in order to obtain good color development of a recorded matter even on a colored recording medium, a white inkjet ink composition (hereinafter also referred to as "white ink" or "white ink composition". Sometimes simply referred to as "ink" or "ink composition".) may be applied as an underlayer under an image formed by color ink.

[0003] As a white coloring material contained in white ink, titanium oxide pigment has been conventionally used. However, since such a pigment has a large specific gravity, it is inferior in sedimentation property (it is likely to sediment over time), and it is necessary to provide a mechanism for circulating white ink in a recording apparatus. However, when such a mechanism is adopted, there is a problem that the recording apparatus becomes large-sized.

[0004] On the other hand, a white inkjet ink composition that does not use such an easily sedimentable titanium oxide pigment and uses hollow resin particles as a white coloring material is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, depending on the hollow resin particles used, the color-developing property may not be sufficient. In addition, the hollow resin particles may penetrate into the interior of the recording medium, resulting in insufficient color development. This was particularly noticeable when the recording medium was a fabric. Therefore, a white inkjet ink composition excellent in sedimentation property and color-developing property is required.

Means for Solving the Problems

[0007] One aspect of the white inkjet ink composition according to the present invention contains hollow resin particles, resin particles, and water, wherein the glass transition temperature of the hollow resin particles is 120°C or higher, the resin particles are made of an acrylic resin or a urethane resin, and the content of the resin particles is 5% by mass or more based on the total mass of the ink composition.

[0008] One aspect of the inkjet recording method according to the present invention includes a white ink adhesion step of discharging the white inkjet ink composition of the above aspect from a recording head and adhering it to a recording medium.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0010] Embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms implemented within the scope of not changing the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

[0011] 1. White Inkjet Ink Composition The white inkjet ink composition according to an embodiment of the present invention contains hollow resin particles, resin particles, and water, wherein the glass transition temperature of the hollow resin particles is 120°C or higher, the resin particles are made of an acrylic resin or a urethane resin, and the content of the resin particles is 5% by mass or more based on the total mass of the ink composition.

[0012] The white inkjet ink composition according to this embodiment uses hollow resin particles as a white coloring material instead of titanium oxide pigment which has a large specific gravity and is likely to sediment over time, so that sedimentation of the white coloring material can be suppressed well. On the other hand, when hollow resin particles are used as a white coloring material in the ink, when the recording medium is heated and dried after printing, the resin may melt and the hollow structure may be broken, resulting in a decrease in color developability. Therefore, by using hollow resin particles having a glass transition temperature of a specific temperature or higher, a decrease in color developability can be suppressed. However, even when such specific hollow resin particles are used, the hollow resin particles may penetrate into the recording medium, and the color developability may not be sufficient.

[0013] In contrast, the white inkjet ink composition according to this embodiment further has a configuration in which a specific resin is used in a predetermined content or more. Thereby, it is possible to obtain a plugging effect on the recording medium, that is, an effect of suppressing the penetration of the hollow resin particles into the recording medium, and the color developability can be made good. As described above, according to the white inkjet ink composition according to this embodiment, which contains hollow resin particles having a glass transition temperature of a specific temperature or higher and a specific amount or more of resin particles, both color developability and sedimentation can be excellent.

[0014] Hereinafter, each component contained in the white inkjet ink composition according to the present embodiment will be described.

[0015] 1.1 Hollow resin particles The white inkjet ink composition according to the present embodiment contains hollow resin particles, and the glass transition temperature of the hollow resin particles is 120°C or higher.

[0016] (Particle structure) In the present invention, the "hollow resin particles" refer to resin particles having a void portion inside the resin particles and filled with a liquid or a gas in the void portion. As a method for determining hollowness, when observing the particle cross-section with a scanning electron microscope, if a structure with a void portion is observed inside the particles, it is determined to be hollow resin particles. Alternatively, as a method for determining hollowness, when observing the particles with a transmission electron microscope, if a structure with a difference in contrast of transmitted electrons is observed, it is determined to be hollow resin particles. In transmission electron microscope observation, when the resin particles have a void portion inside, the internal void portion is easily penetrated by the electron beam and is observed with a bright contrast. Therefore, the presence or absence of the internal void portion can be determined based on the presence or absence of the difference in contrast of transmitted electrons.

[0017] The outer shell of the hollow resin particles is preferably formed of a liquid-permeable resin. With such a configuration, in the ink composition, the internal voids of the hollow resin particles are filled with an aqueous medium. Since the particles filled with the aqueous medium have a specific gravity almost equal to that of the external aqueous medium, they can maintain dispersion stability without sedimenting in the white ink composition. Thereby, the storage stability and ejection reliability of the white ink composition can be improved.

[0018] Further, when the white inkjet ink composition according to the present embodiment is ejected onto paper or other recording media, the aqueous medium inside the particles escapes during drying and becomes a cavity. Since the particles contain air inside, the particles form resin layers and air layers with different refractive indices, and can effectively scatter incident light, so that white can be exhibited.

[0019] Resin Examples of the resin for the hollow resin particles include known resins such as urethane resins, acrylic resins, fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, and ethylene-vinyl acetate resins. These resins can be used alone or in combination of two or more.

[0020] Among these resins, the hollow resin particles used in the present invention preferably contain an acrylic resin. When the hollow resin particles contain an acrylic resin and the resin particles contained in the white ink composition (described later) are acrylic resins, since these resins are of the same resin type, the adhesion at the interface between the hollow resin particles and the resin particles can be improved, and the abrasion resistance can be improved.

[0021] The acrylic resin is a general term for polymers obtained by polymerizing at least one acrylic monomer such as acrylic acid, methacrylic acid, acrylic acid ester, and methacrylic acid ester. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers and other monomers. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, can be mentioned. Further, for example, copolymers with vinyl monomers such as styrene can be mentioned.

[0022] In addition, when distinguishing a resin that is both an acrylic resin and applicable to other types of resins between acrylic resins and other types of resins, if the structure derived from acrylic monomers is 50% by mass or more of the resin, it is regarded as an acrylic resin.

[0023] Acrylamide, acrylonitrile, etc. can also be used as the acrylic monomer. In this specification, the acrylic resin may be a styrene-acrylic resin described later.

[0024] Styrene acrylic resin is a copolymer obtained from a styrene monomer and an acrylic monomer, and examples thereof include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, and the like. As described above, styrene acrylic resin is included in acrylic resin.

[0025] (Physical properties, etc.) The glass transition temperature of the hollow resin particles contained in the white inkjet ink composition according to the present embodiment is 120°C or higher. The glass transition temperature of the hollow resin particles may be 125°C or higher, 130°C or higher, 140°C or higher, or 150°C or higher, but it is more preferably not lower than the surface temperature of the recording medium heated in the heat drying step in the inkjet recording method described later. On the other hand, the upper limit value of the glass transition temperature of the hollow resin particles is not particularly limited, but is preferably 180°C or lower, more preferably 170°C or lower, still more preferably 160°C or lower, and particularly preferably 150°C or lower.

[0026] When the glass transition temperature of the hollow resin particles is within the above range, a decrease in color development property can be suppressed. In order to obtain good rub resistance, it is necessary to perform heat drying after adhering the white ink composition to the recording medium. However, when heated at this time, the hollow resin particles may melt or the like, and the hollow structure may be destroyed. Since the particles with the destroyed hollow structure cannot effectively scatter incident light, the color development property (whiteness) decreases. On the other hand, the hollow resin particles of the present invention can suppress the destruction of the hollow structure of the hollow resin particles even when heated to a heating temperature at which good rub resistance is easily obtained because the glass transition temperature thereof is within the above range, and as a result, a decrease in color development property can be suppressed.

[0027] When the glass transition temperature of the hollow resin particles is obtained by polymerizing the hollow resin particles, it can be changed by changing at least one of the type and composition ratio of the vinyl monomer used, the polymerization conditions, and the modification of the resin. Examples of the polymerization conditions include the temperature during polymerization, the type of the medium containing the vinyl monomer, the vinyl monomer concentration in the medium, the type and amount of the polymerization initiator and catalyst used during polymerization, and the like. The glass transition temperature can be measured by differential scanning calorimetry (DSC method) based on JIS K7121.

[0028] The particle diameter (outer diameter) of the hollow resin particles is preferably 400 to 1000 nm. Further, the particle diameter of the hollow resin particles is preferably 450 nm or more, more preferably 475 nm or more. On the other hand, the particle diameter of the hollow resin particles is preferably 800 nm or less, more preferably 600 nm or less. When the outer diameter exceeds 1000 nm, the particles may sediment and the dispersion stability may be impaired, and the reliability such as clogging of the inkjet recording head may be impaired. On the other hand, when the outer diameter is less than 400 nm, the whiteness tends to be insufficient. That is, when the particle diameter (outer diameter) of the hollow resin particles is within the above range, good sedimentation property (the particles are difficult to sediment) and good color development property can be achieved at the same time. The inner diameter of the hollow resin particles is suitably about 100 to 800 nm.

[0029] Further, when the particle diameter (outer diameter) of the hollow resin particles is within the above range, the amount of the hollow resin particles required for color development can be reduced. Thereby, it becomes possible to increase the amount of the resin particles with respect to the hollow resin particles, more easily suppress the penetration of the hollow resin particles into the inside of the recording medium, and the color development property tends to be further improved.

[0030] In this specification, the "particle size" refers to the volume-based average particle size. The average particle size of the hollow resin particles can be measured, for example, by a particle size distribution measuring device using the laser diffraction scattering method as the measurement principle. As the laser diffraction type particle size distribution measuring device, for example, a particle size distribution meter using the dynamic light scattering method (for example, "Microtrac UPA" manufactured by Nikkiso Co., Ltd.) can be used.

[0031] The content (solid content) of the hollow resin particles is preferably 5 to 20% by mass, more preferably 8 to 15% by mass, and still more preferably 9 to 12% by mass with respect to the total mass of the white ink composition. If the content (solid content) of the hollow resin particles exceeds 20% by mass, the reliability may be impaired, such as clogging of the inkjet recording head. On the other hand, if it is less than 5% by mass, the whiteness tends to be insufficient.

[0032] Also, the content ratio A / B of the content (A) of the hollow resin particles and the content (B) of the resin particles described later is preferably 0.8 to 2.0, more preferably 0.9 to 1.5, and still more preferably 1.0 to 1.3. When the content ratio of the hollow resin particles and the resin particles is within the above range, color development, abrasion resistance, and ejection reliability may be favorably compatible.

[0033] (Manufacturing method) The manufacturing method of the hollow resin particles is not particularly limited, and known methods can be applied. As the manufacturing method of the hollow resin particles, for example, the so-called emulsion polymerization method can be applied, in which a vinyl monomer, a surfactant, a polymerization initiator, a crosslinking agent, and an aqueous dispersion medium are stirred while heating in a nitrogen atmosphere to form a hollow resin particle emulsion.

[0034] Examples of vinyl monomers include nonionic monoethylenically unsaturated monomers, such as styrene, vinyltoluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth)acrylamide, (meth)acrylic acid, (meth)acrylic acid esters, and the like. Examples of (meth)acrylic acid esters include methyl acrylate, methyl methacrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and the like.

[0035] In addition, a bifunctional vinyl monomer can also be used as the vinyl monomer. Examples of bifunctional vinyl monomers include divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and the like. By copolymerizing the above monofunctional vinyl monomer and the above bifunctional vinyl monomer to highly crosslink, it tends to be possible to obtain hollow resin particles having not only light scattering properties but also properties such as heat resistance, solvent resistance, and solvent dispersibility.

[0036] The surfactant may be any one that forms molecular aggregates such as micelles in water. Examples thereof include anionic surfactants such as sodium alkylbenzene sulfonate, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0037] As the polymerization initiator, a known compound soluble in water can be used. Examples thereof include hydrogen peroxide and potassium persulfate.

[0038] Examples of the crosslinking agent include 1,3-diethylbenzene and the like. Examples of the aqueous dispersion medium include water, water containing a hydrophilic organic solvent, and the like.

[0039] Alternatively, commercially available hollow resin particles may be used. Examples of such commercially available products include ROPAQUE HT1432 (trade name of The Dow Chemical Company, styrene-acrylic resin, Tg: 123°C, particle diameter 500 nm).

[0040] 1.2 Resin Particles The white inkjet ink composition according to the present embodiment contains resin particles, the resin particles are made of an acrylic resin or a urethane resin, and the content of the resin particles is 5% by mass or more based on the total mass of the ink composition.

[0041] (Resin) The resin particles have a function as a so-called fixing resin that improves the adhesion of the ink adhered to the recording medium. Examples of the resin particles used in the present invention include resin particles made of an acrylic resin or a urethane resin. These resin particles are often handled in an emulsion form, but may also be in a powder form.

[0042] The acrylic resin is a general term for polymers obtained by polymerizing at least acrylic acid, methacrylic acid, acrylic esters, meth acrylic acid esters and other acrylic monomers as one component. Examples include resins obtained from acrylic monomers, copolymers of acrylic monomers and other monomers, and the like. For example, acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers, can be mentioned. Further, for example, copolymers with vinyl monomers such as styrene can be mentioned.

[0043] When distinguishing a resin that is also an acrylic resin and applies to other types of resins into either an acrylic resin or other types of resins, if the structure derived from acrylic monomers is 50% by mass or more of the resin, it is regarded as an acrylic resin.

[0044] As acrylic monomers, acrylamide, acrylonitrile, etc. can also be used. In this specification, the acrylic resin may be a styrene-acrylic resin described later.

[0045] Commercially available products may be used for the resin emulsion made from acrylic resin. For example, Boncoat (registered trademark) 4001: product name manufactured by DIC Corporation, Polyzol (registered trademark) AM-710, AM-920, AM-2300, AP-4735, AT-860, PSASE-4210E: product name manufactured by Showa Denko K.K., Cybinol (registered trademark) SK-200: product name manufactured by Siden Chemical Co., Ltd., AE-120A: product name manufactured by JSR Corporation, Vinibran (registered trademark) 2682: product name manufactured by Nisshin Chemical Industry Co., Ltd., Mobinyl (registered trademark) 952B, 718A: product name manufactured by Nippon Synthetic Chemical Industry Co., Ltd., K-854: product name manufactured by Chuo Rika Kogyo Co., Ltd., Nipol LX852, LX874: product name manufactured by Zeon Corporation, etc.

[0046] The styrene-acrylic resin is a copolymer obtained from a styrene monomer and an acrylic monomer, and examples include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, etc. Note that the styrene-acrylic resin is considered to be included in the acrylic resin.

[0047] For the resin emulsion using styrene-acrylic resin as the raw material, commercially available products may be used. For example, Microgel (registered trademark) E-1002, E-5002: product names manufactured by Nippon Paint Co., Ltd., Boncoat (registered trademark) 5454: product name manufactured by DIC Corporation, Polyzol (registered trademark) AP-7020, SAE1014: product names manufactured by Showa Denko K.K., Vinibran (registered trademark) 2586: product name manufactured by Nisshin Chemical Industry Co., Ltd., Arrowbase (registered trademark) CB-1200, CD-1200: product names manufactured by Unitika Ltd., Mobinyl (registered trademark) 966A, 7320, 975N: product names manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Joncryl 62J, 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, 7610: product names manufactured by BASF SE, etc. can be mentioned.

[0048] The urethane resin is a general term for resins having a urethane bond. In addition to the urethane bond, for the urethane resin, a polyether type urethane resin containing an ether bond in the main chain, a polyester type urethane resin containing an ester bond in the main chain, a polycarbonate type urethane resin containing a carbonate bond in the main chain, etc. may be used.

[0049] For the resin emulsion using urethane resin as the raw material, commercially available products may be used. For example, Superflex (registered trademark) 870, 800, 150, 420, 460, 470, 610, 700, 460s, 840, E-4000: product names manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Permalin (Registered Trademark) UA-150: Product name of Sanyo Chemical Industries, Ltd., Sun Cure (Registered Trademark) 2710: Product name of Lubrizol Japan Ltd., NeoRez (Registered Trademark) R-9660, R-9637, R-940: Product name of Kusumoto Chemicals, Ltd., Adeka Bon Titer (Registered Trademark) HUX-380, 290K: Product name of ADEKA Corporation, Resamin (Registered Trademark) D-1060, D-2020, D-4080, D-4200, D-6300, D-6455: Product name of Dainichi Kasei Kogyo Co., Ltd., Take Rak (Registered Trademark) W-6020, W-635, W-6061, W-605, W-635, W-6021, W-512-A-6: Product name of Mitsui Chemicals Polyurethane Co., Ltd., etc. can be mentioned.

[0050] Among these resins, the resin particles used in the present invention are preferably acrylic resins. When the resin particles are acrylic resins and the aforementioned hollow resin particles contain acrylic resins, since these resins are of the same resin system, the adhesion at the interface between the hollow resin particles and the resin particles can be improved, and the abrasion resistance can be improved. On the other hand, when the resin particles are urethane resins, the color developability may be improved.

[0051] (Physical properties, etc.) The glass transition temperature (Tg) of the resin particles is preferably -50°C or higher and 200°C or lower, more preferably -50°C or higher and 100°C or lower, still more preferably -50°C or higher and 0°C or lower, and particularly preferably -40°C or higher and -20°C or lower. When the glass transition temperature (Tg) of the resin particles is within the above range, the plugging effect of the recording medium is good and the color developability tends to be further improved. The measurement of the glass transition temperature can be carried out, for example, in accordance with the plastic transition temperature measurement method JIS K7121 using a differential scanning calorimeter "DSC7000" manufactured by Hitachi High-Tech Science Corporation.

[0052] The content (solid content) of the resin particles is 5.0% by mass or more, preferably 5.5% by mass or more, more preferably 6.0% by mass or more, still more preferably 6.5% by mass or more, and particularly preferably 7.0% by mass or more with respect to the total mass of the ink composition. Further, 7.5% by mass or more is more preferable, 8.0% by mass or more is still more preferable, and 8.5% by mass or more is particularly preferable. On the other hand, the upper limit of the content (solid content) of the resin particles is not particularly limited, but is preferably 15% by mass or less, more preferably 13% by mass or less, and still more preferably 11% by mass or less with respect to the total mass of the ink composition. By using resin particles in a specific content or more, a plugging effect can be obtained on the recording medium, penetration of the hollow resin particles into the inside of the recording medium can be suppressed, and thus color developability can be made good.

[0053] 1.3 Water The white inkjet ink composition according to the present embodiment contains water. Water may be contained as a main solvent component of the white inkjet ink composition and is a component that evaporates and scatters by drying.

[0054] As the water, it is preferably pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, distilled water, etc., from which ionic impurities have been removed as much as possible. Further, using water sterilized by ultraviolet irradiation or hydrogen peroxide addition is suitable because it can suppress the generation of mold and bacteria when the ink is stored for a long time.

[0055] The content of water is preferably 45% by mass or more, more preferably 50% by mass or more and 98% by mass or less, and still more preferably 55% by mass or more and 95% by mass or less with respect to the total mass of the ink composition.

[0056] 1.4 Organic solvent The white inkjet ink composition according to the present embodiment preferably contains an organic solvent. That's right. As the organic solvent, a water-soluble organic solvent is preferred. One of the functions of the organic solvent is to improve the wettability of the ink with respect to the recording medium and to enhance the moisture retention of the ink. Examples of the water-soluble organic solvent include polyhydric alcohols, alkylene glycol ethers, esters, cyclic esters, nitrogen-containing solvents, and the like.

[0057] <Polyhydric alcohol> Examples of the polyhydric alcohol include polyhydric alcohols having a standard boiling point of 270 °C or higher, polyhydric alcohols having a standard boiling point of 150 °C or higher and lower than 270 °C, and the like.

[0058] (Standard boiling point is 270 °C or higher) Examples of the polyhydric alcohol having a standard boiling point of 270 °C or higher include triethylene glycol (standard boiling point: 287 °C), glycerin (standard boiling point: 290 °C), trimethylolpropane (standard boiling point: 295 °C), polyethylene glycol monomethyl ether, and the like.

[0059] The white inkjet ink composition according to this embodiment preferably contains, as the water-soluble organic solvent, a polyhydric alcohol having a standard boiling point of 270 °C or higher in an amount of 15% by mass or less based on the total mass of the ink composition. On the other hand, it is preferably contained in an amount of 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more.

[0060] By containing a polyhydric alcohol having a standard boiling point of 270 °C or higher within the above range, it is possible to ensure ejection reliability and suppress a decrease in color developability. When a large amount of a polyhydric alcohol having a standard boiling point of 270 °C or higher is contained in the ink, it is necessary to heat at a high temperature or for a long time during drying of the ink. In such a case, the hollow resin particles contained in the ink may melt and deform, and the color developability may decrease. Therefore, in order to suppress a decrease in color developability, it is preferable that the polyhydric alcohol having a standard boiling point of 270 °C or higher is below a predetermined amount. On the other hand, in order to suppress clogging and the like in nozzles and the like due to resin particles and ensure ejection reliability, it is preferable to contain a polyhydric alcohol having a standard boiling point of 270 °C or higher.

[0061] In addition, when the polyhydric alcohol having a standard boiling point of 270 °C or higher is within the above range, it is difficult for the organic solvent to remain on the recording medium during drying, and the rubbing resistance may be improved in some cases. In the recording method described later, the color developability may be improved by increasing the ink adhesion amount in the white ink adhesion step or lowering the heating temperature in the heat drying step. However, in such a recording method, the drying of the ink tends to be insufficient, and the rubbing resistance tends to be poor. On the other hand, when the white inkjet ink composition according to the present embodiment contains a polyhydric alcohol having a standard boiling point of 270 °C or higher within the above range, since the drying property of the ink is good, even when the above recording method is adopted, it is easy to ensure good rubbing resistance.

[0062] (Standard boiling point is 150 °C or higher and less than 270 °C) Examples of the polyhydric alcohol having a standard boiling point of 150 °C or higher and less than 270 °C include 1,2-alkanediols and polyols.

[0063] Examples of 1,2-alkanediols include ethylene glycol, propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, and the like.

[0064] Examples of the polyols include diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-pro panediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, and the like.

[0065] The white inkjet ink composition according to the present embodiment preferably contains 5% by mass or more of a polyhydric alcohol having a standard boiling point of 150°C or higher and lower than 270°C as a water-soluble organic solvent, and may contain 7% by mass or more, may contain 10% by mass or more, or may contain 14% by mass or more. On the other hand, the upper limit of the polyhydric alcohol having a standard boiling point of 150°C or higher and lower than 270°C is not particularly limited, but is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. When the polyhydric alcohol having a standard boiling point of 150°C or higher and lower than 270°C is contained within the above range, the drying property of the ink tends to be good. If so, the amount of heat required during drying can be reduced, and a decrease in color developability can be suppressed.

[0066] As described above, by the white ink composition containing a polyhydric alcohol having a standard boiling point of 270°C or higher within the above range and a polyhydric alcohol having a standard boiling point of 150°C or higher and lower than 270°C within the above range, good color developability and good ejection reliability can be obtained.

[0067] <Alkylene glycol ethers> The alkylene glycol ethers may be a monoether or a diether of an alkylene glycol, and an alkyl ether is preferred.

[0068] Examples of alkylene glycol monoalkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monobutyl ether.

[0069] Examples of alkylene glycol dialkyl ethers include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol dimethyl ether.

[0070] The content of the alkylene glycol ether is not particularly limited, but may be The content is preferably 0.1 to 4.0 mass %, more preferably 0.3 to 3.0 mass %, further preferably 0.5 to 2.0 mass %, and particularly preferably 0.7 to 1.5 mass %.

[0071] <Esters> Examples of the esters include glycol monoacetates and glycol diesters.

[0072] Examples of glycol monoacetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and methoxybutyl acetate.

[0073] Examples of glycol diesters include ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, diethylene glycol acetate butyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, dipropylene glycol acetate butyrate, and dipropylene glycol acetate propionate.

[0074] <Cyclic esters> Examples of cyclic esters include cyclic esters (lactones) such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, β-butyrolactone, β-valerolactone, γ-valerolactone, β-hexanolactone, γ-hexanolactone, δ-hexanolactone, β-heptanolactone, γ-heptanolactone, δ-heptanolactone, ε-heptanolactone, γ-octanolactone, δ-octanolactone, ε-octanolactone, δ-nonalactone, ε-nonalactone, ε-decanolactone, etc., and compounds in which the hydrogen of the methylene group adjacent to the carbonyl group is substituted with an alkyl group having 1 to 4 carbon atoms.

[0075] <Nitrogen-containing solvent> Examples of nitrogen-containing solvents include cyclic amides, acyclic amides, etc. Examples of acyclic amides include alkoxyalkylamides, etc.

[0076] (Cyclic amides) Examples of cyclic amides include lactams, such as pyrrolidones such as 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, etc. These are preferable in terms of promoting the film formation of resin particles, and 2-pyrrolidone is particularly more preferable.

[0077] (Acyclic amides) Examples of alkoxyalkylamides include, for example, 3-methoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-dimethylpropionamide, 3-n -Butoxy-N,N-diethylpropionamide, 3-n-butoxy-N,N-methylethylpropionamide, 3-n-propoxy-N,N-dimethylpropionamide, 3-n-propoxy-N,N-diethylpropionamide, 3-n-propoxy-N,N-methylethylpropionamide, 3-iso-propoxy-N,N-dimethylpropionamide, 3-iso-propoxy-N,N-diethylpropionamide, 3-iso-propoxy-N,N-methylethylpropionamide, 3-tert-butoxy-N,N-dimethylpropionamide, 3-tert-butoxy-N,N-diethylpropionamide, 3-tert-butoxy-N,N-methylethylpropionamide, etc. can be exemplified.

[0078] Also, as acyclic amides, it is also preferable to use alkoxyalkylamides which are compounds represented by the following general formula (1).

[0079] R 1 -O-CH2CH2-(C=O)-NR 2 R 3 ···(1)

[0080] In the above formula (1), R 1 represents an alkyl group having 1 to 4 carbon atoms, and R 2 and R 3 each independently represent a methyl group or an ethyl group. The "alkyl group having 1 to 4 carbon atoms" can be a linear or branched alkyl group, for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group. The compound represented by the above formula (1) may be used alone or in combination of two or more.

[0081] These organic solvents may be used alone or in combination of two or more.

[0082] 1.5 Lubricant The white inkjet ink composition according to this embodiment preferably contains a lubricant (wax).

[0083] Examples of the lubricant include plant and animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; mineral waxes such as montan wax and ozokerite; paraffin wax which is a so-called petroleum wax; synthetic waxes such as carbon wax, Host wax, polyolefin wax, silicone wax, and stearic acid amide; and waxes such as natural and synthetic wax emulsions and compounded waxes like α-olefin maleic anhydride copolymer.

[0084] These waxes can be used alone or in combination of two or more. Among these, silicone wax, polyolefin wax, paraffin wax, etc. are preferably used.

[0085] Examples of commercially available silicone waxes include SM8706EX, SM7036EX, SM7060EX, SM7025EX, SM490EX, SM8701EX, SM8709SR, SM8716SR, IE-7045, IE-7046T, SH7024, BY22-744EX, BY22-818EX, FZ-4658, FZ-4634EX, FZ-4602 (the above are product names, manufactured by Toray Dow Corning Co., Ltd.), POLON-MF-14, POLON-MF-14EC, POLON-MF-23, POLON-MF-63, POLON-MF-18T, POLON-MF-56, POLON-MF-49, POLON-MF-33A, POLON-MF-55T, POLON-MF-28T, POLON-MF-50, POLON-MK-206, POLON-SR-CONC, KM-9771, KM-9774, KM-2002-T, KM-2002-L-1, KM-9772, KS-7002, KS-701, X-51-1264 (the above are product names, manufactured by Shin-Etsu Chemical Co., Ltd.) etc.

[0086] Examples of polyolefin waxes include waxes produced from olefins such as ethylene, propylene, butylene, etc. or their derivatives, and copolymers thereof, specifically, polyethylene-based waxes, polypropylene-based waxes, polybutylene-based waxes, etc. The polyolefin waxes can be used alone or in combination of two or more.

[0087] Examples of commercially available polyolefin waxes include the AQUACER series such as AQUACER513, AQUACER507, AQUACER515, AQUACER840, AQUACER1547 (above are trade names, manufactured by Big Chemie Japan Co., Ltd., polyethylene-based waxes), and the Hi-Tech series such as Hi-Tech E-7025P, Hi-Tech E-2213, Hi-Tech E-6500, Hi-Tech E-6314, Hi-Tech E-9460, Hi-Tech E-9015 (melting point 137 °C), Hi-Tech E-4A, Hi-Tech E-5403P, Hi-Tech E-8237 (melting point 106 °C) (above are trade names, manufactured by Toho Chemical Co., Ltd., polyethylene-based waxes), and Nopcoat PEM-17 (trade name, manufactured by San Nopco Ltd., polyethylene emulsion, average particle size 40 nm), etc.

[0088] Paraffin wax is a so-called petroleum-based wax. Here, paraffin means an alkane having 20 or more carbon atoms. In this embodiment, paraffin wax refers to a mixture of hydrocarbons having a molecular weight of about 300 to 500, mainly composed of linear paraffinic hydrocarbons having 20 to 30 carbon atoms and containing a small amount of iso-paraffins.

[0089] Examples of commercially available paraffin waxes include AQUACER537, AQUACER539 (above are trade names, manufactured by Big Chemie Japan Co., Ltd.), etc.

[0090] In the present embodiment, it is preferable that the lubricant is contained in the ink in a particulate state, that is, in an emulsion state or a suspension state. This makes it easier to adjust the viscosity of the ink to an appropriate range for ejection using an inkjet head, and also makes it easier to ensure ejection reliability and intermittent ejection characteristics during recording.

[0091] The melting point of the lubricant is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. Also, although not limited, the melting point of the lubricant is preferably 80°C or higher. The hollow resin particles contained in the white inkjet ink composition according to the present embodiment may have their hollow structure destroyed by heat, resulting in a decrease in color developability. Therefore, in the recording method described later, in order to prevent the shape of the hollow resin particles from changing and impairing the color developability, the heating temperature in the heat drying step may be lowered or the heating time may be shortened. However, in such cases, some organic solvent remains in the recording medium, and the rubbing resistance tends to be poor. On the other hand, in the present embodiment, further containing a lubricant having a melting point within the above range contributes to improving the rubbing resistance, and thus can achieve both color developability and rubbing resistance.

[0092] The content of the lubricant is preferably 0.1 to 10% by mass, more preferably 0.5 to 2.0% by mass, based on the total mass of the ink composition. When the content of the lubricant is within the above range, there is a tendency to obtain a recording material with more excellent rubbing resistance.

[0093] 1.6 Crosslinking agent The white inkjet ink composition according to the present embodiment preferably contains a crosslinking agent.

[0094] The crosslinking agent is not particularly limited as long as it can cause a crosslinking reaction between resin particles, between hollow resin particles, or between resin particles and hollow resin particles. Examples thereof include carboxyl group-reactive crosslinking agents, hydroxyl group-reactive crosslinking agents, carbonyl group-reactive crosslinking agents, and the like. Here, the crosslinking reaction refers to a reaction in which polymers having a chain structure are linked by some method to form new chemical bonds and develop a three-dimensional network structure. This includes cases where polymers already having a partially crosslinked structure are further crosslinked, and cases where a resin that was dissolved precipitates due to further polymerization. Also, so-called curing reactions are included in the crosslinking reaction here.

[0095] Examples of the carboxyl group-reactive crosslinking agent include polycarbodiimide-based having a carbodiimide group in the molecule, oxazoline-based having an oxazoline group in the molecule, aziridine-based, and the like. Examples of carbodiimide include Carbodilite E-02 and E-03A manufactured by Nisshinbo Chemical Inc., and examples of oxazoline include Epocros K-2010E, K-2020E (reaction temperature 80 to 100 °C), and K-2030E manufactured by Nippon Shokubai Co., Ltd.

[0096] Examples of the hydroxyl group-reactive crosslinking agent include melamine resin-based such as butylated melamine and fully etherified melamine, and isocyanate-based typified by aqueous blocked isocyanate. In such isocyanate-based crosslinking agents, the active isocyanate groups are protected by a blocking agent and remain stable in the normal state. However, upon heat treatment, the blocking agent dissociates, the active isocyanate groups are regenerated, and a crosslinking reaction occurs. Specific examples of such crosslinking agents include Elastron BN-69 and 11 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., SU-268A, NBP-8730, and NBP-211 (reaction temperature 150 °C or higher) manufactured by Meisei Chemical Industry Co., Ltd.

[0097] Examples of the carbonyl group-reactive crosslinking agent include dihydrazide-based.

[0098] The crosslinking agent may be used alone or in combination of two or more.

[0099] Among these crosslinking agents, a crosslinking agent with a reaction temperature of 130 °C or lower is preferred, 120 °C or lower is more preferred, 110 °C or lower is even more preferred, and 100 °C or lower is particularly preferred. A crosslinking agent with a reaction temperature within the above range can be crosslinked at a relatively low temperature. Since the hollow resin particles contained in the white inkjet ink composition according to the present embodiment may have their hollow structure destroyed by heat and the color developability may decrease, in the recording method described later, the heating temperature in the heat drying step may be lowered or the heating time may be shortened so that the shape of the hollow resin particles does not change and the color developability is not impaired. However, in such a case, some organic solvent remains in the recording medium and is likely to be inferior in rubbing resistance. On the other hand, in the present embodiment, further containing a crosslinking agent that can be crosslinked even at a relatively low temperature contributes to improving the rubbing resistance, and thus can achieve both color developability and rubbing resistance.

[0100] It is preferable to contain the crosslinking agent in an amount of 0.04 parts by mass or more and 1.0 part by mass or less, more preferably 0.05 parts by mass or more and 0.5 part by mass or less, even more preferably 0.08 parts by mass or more and 0.3 part by mass or less, and particularly preferably 0.1 parts by mass or more and 0.2 part by mass or less, based on 1.0 part by mass of the above resin particles. When the content of the crosslinking agent is within the above range, the rubbing resistance and ejection reliability tend to be further improved.

[0101] Also, the content of the crosslinking agent is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 3.0% by mass or less, and even more preferably 0.5% by mass or more and 1.5% by mass or less, based on the total mass of the ink composition. When the content of the crosslinking agent is within the above range, the rubbing resistance and ejection reliability tend to be further improved.

[0102] 1.7 Other components The white inkjet ink composition according to the present embodiment may contain a pH adjuster, a surfactant, and the like.

[0103] <pH adjuster> The white inkjet ink composition according to this embodiment may contain a pH adjuster for the purpose of adjusting the pH. The pH adjuster is not particularly limited, and examples include acids, bases, weak acids, weak bases, and appropriate combinations thereof, such as tertiary alkanolamines such as triethanolamine and triisopropanolamine. When adding a pH adjuster, for example, it is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 0.1% by mass or more and 1.0% by mass or less, and even more preferably 0.2% by mass or more and 0.5% by mass or less, based on the total mass of the ink composition.

[0104] <Surfactant> The white inkjet ink composition according to this embodiment may contain a surfactant. The surfactant can be used as a wetting agent for reducing the surface tension of the ink composition and adjusting the wettability and permeability to the recording medium. Further, by containing a surfactant in the ink composition, the ejection reliability from the inkjet head is ensured.

[0105] As the surfactant, any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used, and these may be used in combination. Among the surfactants, acetylene glycol-based surfactants, silicone-based surfactants, and fluorine-based surfactants can be preferably used.

[0106] Although not particularly limited, examples of the acetylene glycol - based surfactant include Surfynol (registered trademark) 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG - 50, 104S, 420, 440, 465, 485, SE, SE - F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (the above are product names, manufactured by Nissin Chemical Industry Co., Ltd.), Orfin (registered trademark) B, Y, P, A, STG, SPC, E1004, E1010, PD - 001, PD - 002W, PD - 003, PD - 004, PD - 005, EXP.4001, EXP.4300, EXP.4036, EXP.4051, AF - 103, AF - 104, AK - 02, SK - 14, AE - 3 (the above are product names, manufactured by Nissin Chemical Industry Co., Ltd.), and Acetylenol (registered trademark) E00, E00P, E40, E100 (the above are product names, manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0107] Although not particularly limited, silicone - based surfactants preferably include polysiloxane - based compounds. Although not particularly limited, examples of the polysiloxane - based compounds include polyether - modified organosiloxanes. Commercially available products of the polyether - modified organosiloxanes include, for example, BYK (registered trademark) - 306, BYK - 307, BYK - 333, BYK - 341, BYK - 345, BYK - 346, BYK - 348 (the above are product names, manufactured by BYK), KF - 351A, KF - 352A, KF - 353, KF - 354L, KF - 355A, KF - 615A, KF - 945, KF - 640, KF - 642, KF - 643, KF - 6020, X - 22 - 4515, KF - 6011, KF - 6012, KF - 6015, KF - 6017 (the above are product names, manufactured by Shin - Etsu Chemical Co., Ltd.), etc.

[0108] As the fluorine - based surfactant, it is preferable to use a fluorine - modified polymer. Although not particularly limited, for example, BYK (registered trademark) - 340 (product name, manufactured by Big Chemie Japan Co., Ltd.) can be mentioned.

[0109] When the ink composition contains a surfactant, a plurality of types of the surfactants can be used, and the total content thereof is preferably 0.01% by mass or more and 3.0% by mass or less, more preferably 0.05% by mass or more and 2.0% by mass or less, still more preferably 0.1% by mass or more and 1.5% by mass or less, and particularly preferably 0.2% by mass or more and 1.0% by mass or less with respect to the total mass of the ink.

[0110] <Components other than the above> The white inkjet ink composition according to the present embodiment may contain, as components other than the above, additives that can be usually used in inks for inkjet, such as chelating agents, preservatives, fungicides, rust inhibitors such as benzotriazole, antioxidants, ultraviolet absorbers, oxygen absorbers, and dissolution aids.

[0111] 1.8 Preparation Method and Physical Properties

[0112] The white inkjet ink composition according to the present embodiment can be obtained by mixing the above-described components in an arbitrary order and, if necessary, performing filtration or the like to remove impurities. As a method for mixing the components, a method of sequentially adding materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirring and mixing is preferably used. As a filtration method, centrifugal filtration, filter filtration, or the like can be performed as necessary.

[0113] In the present embodiment, from the viewpoint of the balance between print quality and reliability as an ink for inkjet, the surface tension of the ink composition at 20°C is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 30 mN / m or more and 36 mN / m or less. When within the above range, the inkjet recording has excellent ejection reliability, and when the ink adheres to the recording medium, the ink easily spreads uniformly and penetrates on the recording medium. As a result, the ink may easily adhere to the recording medium.

[0114] In addition, the surface tension can be measured, for example, by using an automatic surface tension meter CBVP-Z (trade name, manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the ink in an environment at 20°C. As one method of setting the surface tension within the above range, appropriate adjustment can be made to the types of the above-mentioned organic solvents and surfactants, and the addition amounts of these and water.

[0115] Moreover, the viscosity of the ink at 20°C is preferably 1.5 mPa·s or more and 15.0 mPa·s or less, more preferably 1.5 mPa·s or more and 5.0 mPa·s or less, and even more preferably 1.5 mPa·s or more and 3.6 mPa·s or less. When the viscosity of the ink at 20°C is within the above range, the ink is more likely to be fixed when adhering to the recording medium, and the color development property may be improved.

[0116] The viscosity can be measured, for example, by using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica). As one method of setting the viscosity within the above range, appropriate adjustment can be made to the types of the above-mentioned organic solvents and surfactants, and the addition amounts of these and water.

[0117] 1.9 Use The white inkjet ink composition according to the present embodiment is preferably applied and used in a recording apparatus including a recording head having a circulation path. Further, the white inkjet ink composition according to the present embodiment is preferably used for inkjet printing.

[0118] 1.9.1 Recording Apparatus Including a Recording Head Having a Circulation Path The white inkjet ink composition according to this embodiment is preferably applied and used in a recording apparatus equipped with a recording head having a circulation path. Since the amount of resin particles contained in the white inkjet ink composition according to this embodiment is relatively large, aggregates are likely to be generated in the nozzles of the recording head and clogging is likely to occur. In particular, when the polyhydric alcohol having a standard boiling point of 270 °C or higher is set to a predetermined amount or less as the water-soluble organic solvent, clogging is likely to occur remarkably with the improvement of the drying property. Therefore, by applying the white inkjet ink composition according to this embodiment to a recording apparatus equipped with a recording head having a circulation path, clogging derived from aggregates of resin particles is likely to be suppressed by the circulation of the ink, and the ejection reliability can be improved, which is preferable.

[0119] As an example of a recording apparatus applicable in this embodiment, an inkjet recording apparatus equipped with a recording head (hereinafter, also referred to as an "inkjet head") that ejects ink by an inkjet method will be described.

[0120] Further, as an example of a recording apparatus applicable in this embodiment, an on-carriage type printer in which an ink cartridge is mounted on a carriage will be described. The recording apparatus applicable in this embodiment is not limited to an on-carriage type printer, and may be an off-carriage type printer in which an ink cartridge is fixed outside.

[0121] The printer used in the following description is a serial printer in which a recording inkjet head is mounted on a carriage that moves in a predetermined direction, and droplets are ejected onto a recording medium as the inkjet head moves with the movement of the carriage. The recording apparatus applicable in this embodiment is not limited to a serial printer, and may be a line printer. A line printer is a printer in which an inkjet head is formed wider than the width of a recording medium, and droplets are ejected onto the recording medium without the inkjet head moving.

[0122] Hereinafter, a recording apparatus including a recording head having a circulation path that can be suitably used for the white inkjet ink composition according to the present embodiment will be described with reference to the drawings. In each of the drawings used in the following description, the scale of each member is appropriately changed in order to make each member recognizable.

[0123] FIG. 1 is a schematic perspective view showing an inkjet recording apparatus that can be applied and used in the present embodiment. The inkjet recording apparatus is a device that performs recording by landing droplets on a recording medium by an inkjet head as an ink ejection unit that ejects minute droplets of an ink composition.

[0124] As shown in FIG. 1, the printer 1 includes an inkjet head 3, a carriage 4, a main scanning mechanism 5, a platen roller 6, and a control unit (not shown) that controls the operation of the entire printer 1. The carriage 4 mounts the inkjet head 3 and is detachable ink cartridges 7a, 7b, 7c, 7d, 7e, 7f that store the ink composition supplied to the inkjet head 3.

[0125] The main scanning mechanism 5 includes a timing belt 8 connected to the carriage 4, a motor 9 that drives the timing belt 8, and a guide shaft 10. The guide shaft 10 is installed as a support member of the carriage 4 in the scanning direction of the carriage 4, that is, in the main scanning direction. The carriage 4 is driven by the motor 9 via the timing belt 8 and can reciprocate along the guide shaft 10. Thereby, the main scanning mechanism 5 has a function of reciprocating the carriage 4 in the main scanning direction.

[0126] The platen roller 6 has a function of conveying the recording medium 2 in the sub-scanning direction orthogonal to the main scanning direction, that is, in the length direction of the recording medium 2. Thereby, the recording medium 2 is conveyed in the sub-scanning direction. The carriage 4 on which the inkjet head 3 is mounted can reciprocate in the main scanning direction substantially coinciding with the width direction of the recording medium 2, and the inkjet head 3 is configured to be able to scan relatively with respect to the recording medium 2 in the main scanning direction and the sub-scanning direction.

[0127] The ink cartridges 7a, 7b, 7c, 7d, 7e, 7f are six independent ink cartridges. The ink cartridges 7a, 7b, 7c, 7d, 7e, 7f can store the white inkjet ink composition according to this embodiment. In these ink cartridges, color ink compositions such as black, cyan, magenta, yellow, orange, etc., other than the white inkjet ink composition, may be individually stored and can be used in any combination. In FIG. 1, the number of ink cartridges is six, but it is not limited to this. At the bottom of the ink cartridges 7a, 7b, 7c, 7d, 7e, 7f, supply ports (not shown) for supplying the ink composition stored in each ink cartridge to the inkjet head 3 are provided.

[0128] The inkjet head 3 is a means for ejecting and attaching the ink supplied from the ink cartridges 7a, 7b, 7c, 7d, 7e, 7f to the recording medium 2 from a plurality of nozzles N under the control of a control unit (not shown). The inkjet head 3 includes a plurality of nozzles (see FIG. 2) that eject ink and attach it to the recording medium 2 on the surface facing the recording medium 2 to which the ink is to be attached. These plurality of nozzles are arranged in a column to form a nozzle row, and the nozzle row is individually arranged corresponding to each color ink composition. Each color ink composition is supplied from each ink cartridge to the inkjet head 3 and is ejected as droplets from the nozzles by an actuator (not shown) in the inkjet head 3. The droplets of the ejected ink composition land on the recording medium 2, and images, texts, patterns, colors, etc. made of ink are formed in the recording area of the recording medium 2.

[0129] Here, in the inkjet head 3, a piezoelectric element is used as the actuator which is the driving means, but it is not limited to this method. For example, an electromechanical conversion element that displaces a diaphragm as the actuator by electrostatic adsorption, or an electrothermal conversion element that ejects the ink composition as droplets by bubbles generated by heating may be used.

[0130] In this example, the inkjet head 3 is a head having a pressure chamber C (see FIG. 2) and a circulation path for circulating the ink composition in the pressure chamber C. By having the circulation path in the inkjet head 3, the ink in the pressure chamber C and the nozzle N (see FIG. 2) is refreshed. As a result, clogging of the nozzle N is suppressed, and the ejection reliability and the intermittent ejection characteristics can be improved.

[0131] In the present embodiment, the nozzle diameter is preferably 20 μm or more and 30 μm or less, and more preferably 22 μm or more and 28 μm or less. When the nozzle diameter is 20 μm or more, ejection can be performed without deterioration of ink turbulence in the flow path, and the intermittent ejection characteristics are improved. Further, by using the head having the above-described circulation path, the intermittent ejection characteristics are further improved. Further, when the nozzle diameter is 30 μm or less, the surface area of the ink liquid surface is appropriate, and drying of the ink hardly progresses, so that ejection is stabilized. In the present specification, the nozzle diameter refers to the inner diameter of the nozzle formed on the surface of the nozzle plate (that is, the inner diameter d1).

[0132] FIG. 2 is a cross-sectional view of the inkjet head 3 in a cross-section perpendicular to the Y direction, and FIG. 3 is a partial exploded perspective view of the inkjet head 3. In FIG. 2, for example, a plane parallel to the surface of the recording medium 2 is defined as the X-Y plane, and the direction perpendicular to the X-Y plane is hereinafter referred to as the Z direction. The ejection direction of the ink by the inkjet head 3 corresponds to the Z direction. Further, the main scanning direction corresponds to the X direction, and the direction orthogonal to the main scanning direction (sub-scanning direction) corresponds to the Y direction.

[0133] The plurality of nozzles N of the inkjet head 3 are arranged in the Y direction to form a nozzle row. A plane passing through the central axis parallel to the Y direction in the inkjet head 3 and parallel to the Z direction, that is, the Y-Z plane O is hereinafter referred to as the "central plane" in the following description.

[0134] As shown in FIG. 2, the inkjet head 3 has a structure in which elements related to the nozzles N in the first row L1 and elements related to the nozzles N in the second row L2 are arranged symmetrically with respect to the central plane O. That is, in the inkjet head 3, the structure of the positive side in the X direction (hereinafter also referred to as the "first part") P1 and the negative side in the X direction (hereinafter also referred to as the "second part") P2 sandwiching the central plane O is substantially common. A plurality of nozzles N in the first row L1 are formed in the first part P1, and a plurality of nozzles N in the second row L2 are formed in the second part P2. The central plane O corresponds to the boundary surface between the first part P1 and the second part P2.

[0135] As shown in FIG. 2, the inkjet head 3 includes a flow path forming portion 30. The flow path forming portion 30 is a structure that forms flow paths for supplying ink to the plurality of nozzles N. In this example, the flow path forming portion 30 is composed of a laminate of a first flow path substrate 32 and a second flow path substrate 34. Each of the first flow path substrate 32 and the second flow path substrate 34 is a plate-like member that is long in the Y direction. The second flow path substrate 34 is installed on the negative side surface Fa of the first flow path substrate 32 in the Z direction using, for example, an adhesive.

[0136] As shown in FIG. 2, on the surface Fa of the first flow path substrate 32, in addition to the second flow path substrate 34, a housing portion 48 is installed. On the other hand, on the positive side in the Z direction of the first flow path substrate 32, that is, on the surface Fb opposite to the surface Fa, a nozzle plate 52 and a vibration absorber 54 are installed. Each element of the inkjet head 3 is generally a plate-like member that is long in the Y direction, similar to the first flow path substrate 32 and the second flow path substrate 34, and is joined to each other using, for example, an adhesive. It is also possible to recognize the direction in which the first flow path substrate 32 and the second flow path substrate 34 are laminated, the direction in which the first flow path substrate 32 and the nozzle plate 52 are laminated, or the direction perpendicular to the surface of each plate-like element as the Z direction.

[0137] The nozzle plate 52 is a plate-like member in which a plurality of nozzles N are formed, and is installed on the surface Fb of the first flow path substrate 32 using, for example, an adhesive. Each of the plurality of nozzles N is a circular through-hole through which ink passes. In the nozzle plate 52 of the first embodiment, a plurality of nozzles N constituting the first row L1 and a plurality of nozzles N constituting the second row L2 are formed. Specifically, in the region on the positive side in the X direction as viewed from the center plane O of the nozzle plate 52, a plurality of nozzles N in the first row L1 are formed along the Y direction, and in the region on the negative side in the X direction, a plurality of nozzles N in the second row L2 are formed along the Y direction. The nozzle plate 52 is a single plate-like member that is continuous across the portion where the plurality of nozzles N in the first row L1 are formed and the portion where the plurality of nozzles N in the second row L2 are formed. The nozzle plate 52 is manufactured by processing a single crystal silicon substrate using semiconductor manufacturing techniques, such as processing techniques like dry etching and wet etching. However, known materials and manufacturing methods can be arbitrarily adopted for the manufacture of the nozzle plate 52.

[0138] As shown in FIG. 2, in the first flow path substrate 32, for each of the first portion P1 and the second portion P2, a space Ra, a plurality of supply paths 61, and a plurality of communication paths 63 are formed. The space Ra is an opening formed in a long shape along the Y direction in a plan view, that is, as viewed from the Z direction, and the supply paths 61 and the communication paths 63 are through-holes formed for each nozzle N. The plurality of communication paths 63 are arranged in the Y direction in a plan view and are arranged in the Y direction between the arrangement of the plurality of communication paths 63 and the space Ra. The plurality of supply paths 61 communicate with the space Ra in common. Also, any one of the communication paths 63 overlaps with the nozzle N corresponding to the communication path 63 in a plan view. Specifically, any one of the communication paths 63 in the first portion P1 communicates with one nozzle N in the first row L1 corresponding to the communication path 63. Similarly, any one of the communication paths 63 in the second portion P2 communicates with one nozzle N in the second row L2 corresponding to the communication path 63.

[0139] As shown in Fig. 2, the second flow path substrate 34 is a plate-like member in which a plurality of pressure chambers C are formed for each of the first portion P1 and the second portion P2. The plurality of pressure chambers C are arranged in the Y direction. Each pressure chamber C is formed for each nozzle N and is an elongated space along the X direction in plan view. The first flow path substrate 32 and the second flow path substrate 34 are manufactured by processing a single crystal silicon substrate using, for example, semiconductor manufacturing technology, similar to the aforementioned nozzle plate 52. However, known materials and manufacturing methods can be arbitrarily adopted for the manufacture of the first flow path substrate 32 and the second flow path substrate 34. As shown in the above example, the flow path forming portion 30 and the nozzle plate 52 include substrates formed of silicon. Therefore, by using semiconductor manufacturing technology as in the above example, there is an advantage that fine flow paths can be formed with high precision in the flow path forming portion 30 and the nozzle plate 52.

[0140] As shown in Fig. 2, a vibrating portion 42 is installed on the surface of the second flow path substrate 34 opposite to the first flow path substrate 32. The vibrating portion 42 in this example is an elastically vibratable plate-like member. It is also possible to integrally form the second flow path substrate 34 and the vibrating portion 42 by selectively removing a part in the plate thickness direction in the region corresponding to the pressure chamber C among plate-like members having a predetermined plate thickness.

[0141] As shown in Fig. 2, the surface Fa of the first flow path substrate 32 and the vibrating portion 42 face each other with a gap inside each pressure chamber C. The pressure chamber C is a space located between the surface Fa of the first flow path substrate 32 and the vibrating portion 42, and generates a pressure change in the ink filled in the space. Each pressure chamber C is, for example, a space having the X direction as the longitudinal direction and is formed individually for each nozzle N. For each of the first row L1 and the second row L2, a plurality of pressure chambers C are arranged in the Y direction. As shown in Fig. 2, the end on the center plane O side of any one pressure chamber C overlaps the communication path 63 in plan view, and the end on the side opposite to the center plane O overlaps the supply path 61 in plan view. Therefore, in each of the first portion P1 and the second portion P2, the pressure chamber C communicates with the nozzle N via the communication path 63 and also communicates with the space Ra via the supply path 61. It is also possible to add a predetermined flow path resistance by forming a throttle flow path with a narrowed flow path width in the pressure chamber C.

[0142] As shown in FIG. 2, on the surface of the vibrating portion 42 opposite to the pressure chamber C, for each of the first portion P1 and the second portion P2, a plurality of piezoelectric elements 44 corresponding to different nozzles N are installed. The piezoelectric element 44 is a passive element that deforms when a drive signal is supplied. The plurality of piezoelectric elements 44 are arranged in the Y direction so as to correspond to each pressure chamber C. Any one piezoelectric element 44 is, for example, a laminate in which a piezoelectric layer is interposed between two electrodes facing each other. It is also possible to define, as the piezoelectric element 44, the portion that deforms when a drive signal is supplied, that is, the active portion that vibrates the vibrating portion 42. In this example, when the vibrating portion 42 vibrates in conjunction with the deformation of the piezoelectric element 44, the pressure in the pressure chamber C fluctuates, so that the ink filled in the pressure chamber C passes through the communication path 63 and the nozzle N and the ink is ejected.

[0143] The protective member 46 in FIG. 2 is a plate-like member for protecting the plurality of piezoelectric elements 44, and is installed on the surface of the vibrating portion 42 or the surface of the second flow path substrate 34. The material and manufacturing method of the protective member 46 are arbitrary, but similar to the first flow path substrate 32 and the second flow path substrate 34, for example, a single crystal substrate of silicon can be processed by semiconductor manufacturing technology to form the protective member 46. The plurality of piezoelectric elements 44 are accommodated in recesses formed on the surface of the protective member 46 on the vibrating portion 42 side.

[0144] The end of the wiring substrate 28 is joined to the surface of the vibrating portion 42 opposite to the flow path forming portion 30 or the surface of the flow path forming portion 30. The wiring substrate 28 is a flexible mounting component on which a plurality of wirings (not shown) for electrically connecting a control unit (not shown) and the inkjet head 3 are formed. Among the wiring substrates 28, the end portion extending to the outside through the opening formed in the protective member 46 and the opening formed in the housing portion 48 is connected to the control unit. A flexible wiring substrate 28 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably adopted.

[0145] The housing portion 48 is a case for storing ink supplied to a plurality of pressure chambers C and further a plurality of nozzles N. The positive surface of the housing portion 48 in the Z direction is joined to the surface Fa of the first flow path substrate 32 with, for example, an adhesive. Known techniques and manufacturing methods can be arbitrarily adopted for manufacturing the housing portion 48. For example, it is possible to form the housing portion 48 by injection molding of a resin material.

[0146] As shown in FIG. 2, in the housing portion 48, a space Rb is formed for each of the first portion P1 and the second portion P2. The space Rb in the housing portion 48 and the space Ra in the first flow path substrate 32 communicate with each other. The space composed of the space Ra and the space Rb functions as a liquid storage chamber R for storing ink supplied to the plurality of pressure chambers C. The liquid storage chamber R is a common liquid chamber shared for the plurality of nozzles N. A liquid storage chamber R is formed in each of the first portion P1 and the second portion P2. The liquid storage chamber R of the first portion P1 is located on the positive side in the X direction when viewed from the center plane O, and the liquid storage chamber R of the second portion P2 is located on the negative side in the X direction when viewed from the center plane O. An inlet 482 for introducing ink supplied from a liquid container (not shown) into the liquid storage chamber R is formed on the surface of the housing portion 48 opposite to the first flow path substrate 32.

[0147] On the surface Fb of the first flow path substrate 32, a vibration absorber 54 is provided for each of the first portion P1 and the second portion P2. The vibration absorber 54 is a flexible film that absorbs pressure fluctuations of the ink in the liquid storage chamber R, that is, a compliance substrate. For example, the vibration absorber 54 is installed on the surface Fb of the first flow path substrate 32 so as to block the space Ra in the first flow path substrate 32 and the plurality of supply paths 61 and constitutes the wall surface, specifically the bottom surface, of the liquid storage chamber R.

[0148] On the surface Fb of the first flow path substrate 32 facing the nozzle plate 52, a space (hereinafter referred to as "circulating liquid chamber") 65 is formed. The circulating liquid chamber 65 in this example is a long bottomed hole extending in the Y direction in plan view. The opening of the circulating liquid chamber 65 is closed by the nozzle plate 52 joined to the surface Fb of the first flow path substrate 32. The circulating liquid chamber 65 continues over a plurality of nozzles N along, for example, the first row L1 and the second row L2. Specifically, the circulating liquid chamber 65 is formed between the arrangement of the plurality of nozzles N in the first row L1 and the arrangement of the plurality of nozzles N in the second row L2. Therefore, the circulating liquid chamber 65 is located between the communication path 63 in the first portion P1 and the communication path 63 in the second portion P2. In this way, the flow path forming portion 30 is a structure in which the pressure chamber C and the communication path 63 in the first portion P1, the pressure chamber C and the communication path 63 in the second portion P2, and the circulating liquid chamber 65 located between the communication path 63 in the first portion P1 and the communication path 63 in the second portion P2 are formed. As shown in FIG. 2, the flow path forming portion 30 includes a wall-like portion (hereinafter referred to as "partition portion 69") that partitions between the circulating liquid chamber 65 and each communication path 63.

[0149] As described above, in each of the first portion P1 and the second portion P2, a plurality of pressure chambers C and a plurality of piezoelectric elements 44 are arranged in the Y direction. Therefore, it can also be said that the circulating liquid chamber 65 extends in the Y direction so as to continue over the plurality of pressure chambers C or the plurality of piezoelectric elements 44 in each of the first portion P1 and the second portion P2. Also, as shown in FIG. 2, it is also possible that the circulating liquid chamber 65 and the liquid storage chamber R extend in the Y direction with a space therebetween, and the pressure chamber C, the communication path 63, and the nozzle N are located within the space.

[0150] FIG. 3 is an enlarged cross-sectional view of a portion near the circulation liquid chamber 65 in the inkjet head 3. As shown in FIG. 3, one nozzle N in the present embodiment includes a first section n1 and a second section n2. The first section n1 and the second section n2 are circular spaces formed coaxially and communicating with each other. The second section n2 is located on the side of the flow path forming portion 30 as viewed from the first section n1. In the present embodiment, the central axis Qa of each nozzle N is located on the side opposite to the circulation liquid chamber 65 as viewed from the central axis Qb of the communication passage 63. The inner diameter d2 of the second section n2 is larger than the inner diameter d1 of the first section n1. According to the configuration in which each nozzle N is formed in a stepped shape as described above, there is an advantage that it is easy to set the flow path resistance of each nozzle N to desired characteristics. In this example, the central axis Qa of each nozzle N is located on the side opposite to the circulation liquid chamber 65 as viewed from the central axis Qb of the communication passage 63.

[0151] As shown in FIG. 3, a plurality of discharge paths 72 are formed on the surface of the nozzle plate 52 facing the flow path forming portion 30 for each of the first portion P1 and the second portion P2. The plurality of discharge paths 72 in the first portion P1 correspond one-to-one to the plurality of nozzles N in the first row L1 or the plurality of communication passages 63 corresponding to the first row L1. Also, the plurality of discharge paths 72 in the second portion P2 correspond one-to-one to the plurality of nozzles N in the second row L2 or the plurality of communication passages 63 corresponding to the second row L2.

[0152] Each discharge path 72 is a groove portion extending in the X direction, that is, a long bottomed hole, and functions as a flow path for circulating ink. The discharge path 72 in this example is formed at a position separated from the nozzle N, specifically, on the side of the circulation liquid chamber 65 as viewed from the nozzle N corresponding to the discharge path 72. For example, by a semiconductor manufacturing technique, such as a processing technique such as dry etching or wet etching, the plurality of nozzles N, particularly the second section n2 and the plurality of discharge paths 72, are formed in a batch in a common process.

[0153] Each discharge path 72 is linearly formed with a channel width Wa equal to the inner diameter d2 of the second section n2 of the nozzle N. Further, the channel width Wa of the discharge path 72 in this example is smaller than the channel width Wb of the pressure chamber C. Therefore, it is possible to increase the flow resistance of the discharge path 72 as compared with a configuration in which the channel width Wa of the discharge path 72 is larger than the channel width Wb of the pressure chamber C. On the other hand, the depth Da of the discharge path 72 with respect to the surface of the nozzle plate 52 is constant over the entire length. Specifically, each discharge path 72 is formed to have the same depth as the second section n2 of the nozzle N. According to the above configuration, there is an advantage that it is easier to form the discharge path 72 and the second section n2 as compared with a configuration in which the discharge path 72 and the second section n2 are formed at different depths. Note that the "depth" of the flow path means the depth of the flow path in the Z direction, for example, the height difference between the formation surface of the flow path and the bottom surface of the flow path.

[0154] Any one of the discharge paths 72 in the first portion P1 is located on the circulating liquid chamber 65 side when viewed from the nozzle N corresponding to the discharge path 72 in the first row L1. Also, any one of the discharge paths 72 in the second portion P2 is located on the circulating liquid chamber 65 side when viewed from the nozzle N corresponding to the discharge path 72 in the second row L2. And, the side of each discharge path 72 opposite to the center plane O overlaps with one communication path 63 corresponding to the discharge path 72 in a plan view. That is, the discharge path 72 communicates with the communication path 63. On the other hand, the end portion of each discharge path 72 on the center plane O side overlaps with the circulating liquid chamber 65 in a plan view. That is, the discharge path 72 communicates with the circulating liquid chamber 65. Thus, each of the plurality of communication paths 63 communicates with the circulating liquid chamber 65 via the discharge path 72. Therefore, as shown by the dashed arrows in FIG. 3, the ink in each communication path 63 is supplied to the circulating liquid chamber 65 via the discharge path 72. That is, in this example, the plurality of communication paths 63 corresponding to the first row L1 and the plurality of communication paths 63 corresponding to the second row L2 communicate with one circulating liquid chamber 65 in common.

[0155] FIG. 3 shows the flow path length La of the portion of any one discharge path 72 that overlaps the circulation liquid chamber 65, the flow path length of the portion of the discharge path 72 that overlaps the communication path 63, that is, the dimension Lb in the X direction, and the flow path length of the portion of the discharge path 72 that overlaps the partition wall portion 69 of the flow path forming portion 30, that is, the dimension Lc in the X direction. The flow path length Lc corresponds to the thickness of the partition wall portion 69. The partition wall portion 69 functions as a throttling portion of the discharge path 72. Therefore, the longer the flow path length Lc corresponding to the thickness of the partition wall portion 69, the greater the flow path resistance of the discharge path 72. In this example, the relationship that the flow path length La is longer than the flow path length Lb and the flow path length La is longer than the flow path length Lc holds. Further, in this example, the relationship that the flow path length Lb is longer than the flow path length Lc holds. According to the above configuration, there is an advantage that ink easily flows from the communication path 63 into the circulation liquid chamber 65 via the discharge path 72 as compared with a configuration in which the flow path lengths La and Lb are shorter than the flow path length Lc. The partition wall portion 69 functions as a throttling portion of the discharge path 72. Therefore, the longer the flow path length Lc corresponding to the thickness of the partition wall portion 69, the greater the flow path resistance of the discharge path 72. In this example, the relationship that the flow path length La is longer than the flow path length Lb and the flow path length La is longer than the flow path length Lc holds. Further, in this example, the relationship that the flow path length Lb is longer than the flow path length Lc holds. According to the above configuration, there is an advantage that ink easily flows from the communication path 63 into the circulation liquid chamber 65 via the discharge path 72 as compared with a configuration in which the flow path lengths La and Lb are shorter than the flow path length Lc.

[0156] As described above, in the inkjet head 3, the pressure chamber C communicates with the circulation liquid chamber 65 indirectly via the communication path 63 and the discharge path 72. That is, the pressure chamber C and the circulation liquid chamber 65 do not communicate directly. In the above configuration, when the pressure in the pressure chamber C fluctuates due to the operation of the piezoelectric element 44, a part of the ink flowing in the communication path 63 is ejected from the nozzle N to the outside, and the remaining part flows from the communication path 63 into the circulation liquid chamber 65 via the discharge path 72. Then, the inertances of the communication path 63, the nozzle, and the discharge path 72 are selected such that the ejection of the ink ejected through the nozzle N among the ink flowing through the communication path 63 by one drive of the piezoelectric element 44 exceeds the circulation amount of the ink flowing into the circulation liquid chamber 65 via the discharge path 72 among the ink flowing through the communication path 63. Assuming that all the piezoelectric elements 44 are driven simultaneously, it can also be said that the total circulation amount flowing from the plurality of communication paths 63 into the circulation liquid chamber 65, for example, the flow rate per unit time in the circulation liquid chamber 65, is larger than the total ejection amount by the plurality of nozzles N.

[0157] Specifically, the flow resistances of the communication path 63, the nozzle, and the discharge path 72 are determined such that the ratio of the circulation amount of the ink flowing through the communication path 63 is 70% or more, that is, the ratio of the ejection amount of the ink is 30% or less. According to the above configuration, it is possible to effectively circulate the ink near the nozzle to the circulation liquid chamber 65 while ensuring the ejection amount of the ink. Generally speaking, the greater the flow resistance of the discharge path 72, the smaller the circulation amount while the ejection amount increases, and the smaller the flow resistance of the discharge path 72, the greater the circulation amount while the ejection amount decreases.

[0158] For example, the printer 1 is configured to include a circulation mechanism (not shown). The circulation mechanism is a mechanism for supplying, that is, circulating, the ink in the circulation liquid chamber 65 to the liquid storage chamber R. The circulation mechanism is configured to include, for example, a suction mechanism that sucks ink from the circulation liquid chamber 65, such as a pump, a filter mechanism (not shown) that collects bubbles and foreign matters mixed in the ink, and a heating mechanism that reduces thickening by heating the ink. The ink from which bubbles and foreign matters have been removed and the thickening has been reduced by the circulation mechanism is supplied from the circulation mechanism to the liquid storage chamber R through the inlet 482. Thereby, the ink circulates along the path of liquid storage chamber R → supply path 61 → pressure chamber C → communication path 63 → discharge path 72 → circulation liquid chamber 65 → circulation mechanism → liquid storage chamber R. The supply path 61 and the discharge path 72 together are referred to as a circulation path.

[0159] In this way, when the discharge path 72 that connects the communication path 63 and the circulation liquid chamber 65 is formed in the nozzle plate 52, it is possible to efficiently circulate the ink near the nozzle N to the circulation liquid chamber 65. Further, since the communication path 63 corresponding to the first row L1 and the communication path 63 corresponding to the second row L2 communicate with the circulation liquid chamber 65 therebetween in common, compared with a configuration in which the circulation liquid chamber with which each discharge path 72 corresponding to the first row L1 communicates and the circulation liquid chamber with which each discharge path 72 corresponding to the second row L2 communicates are provided separately, there is also an advantage that the configuration of the inkjet head 3 is simplified, and thus miniaturization is achieved.

[0160] Note that the discharge path 72 and the nozzle N may be configured to be continuous with each other instead of being spaced apart from each other. Further, in addition to the circulation liquid chamber 65, a configuration may be adopted in which circulation liquid chambers corresponding to each of the first portion P1 and the second portion P2 are formed.

[0161] In this example, it is preferable to provide the printer 1 with drying means and heating means (both not shown). The drying means and the heating means are means for efficiently drying the ink adhered to the recording medium 2 in the inkjet recording method described later. The drying means and the heating means are not particularly limited as long as they are provided at a position where the recording medium 2 can be dried and heated, and may be installed independently of the printer 1. In order to efficiently dry the ink adhered to the recording medium 2, for example, in FIG. 1, the drying means and the heating means can be installed at a position facing the inkjet head 3.

[0162] Examples of the drying means and the heating means include a print heater mechanism that heats the recording medium 2 by bringing it into contact with a heat source, a mechanism that irradiates infrared rays or microwaves, which are electromagnetic waves having a peak wavelength of about 2,450 MHz, and a dryer mechanism that blows warm air. The heating of the recording medium 2 is performed before, when, or after the droplets ejected from the nozzles of the inkjet head 3 adhere to the recording medium 2. The control of various heating conditions, for example, the timing of heating, the heating temperature, the heating time, etc., is performed by the control unit.

[0163] Further, the drying means and the heating means may be installed on the downstream side in the conveyance direction of the recording medium 2. In this case, after the ink ejected from the nozzles adheres to the recording medium 2 and an image is formed, the recording medium 2 is heated. Thereby, the drying property of the ink adhered to the recording medium 2 is improved.

[0164] Furthermore, in this example, the printer 1 may be configured to include a pretreatment agent attaching means for treating a recording medium, or may be an inkjet recording system provided with a pretreatment agent attaching means separately from the printer 1. Also, in this example, the pretreatment agent attaching means is not an essential component.

[0165] In this example, when the pretreatment agent attaching means is provided in the printer 1 and the inkjet application is performed by ejecting ink from the nozzles of the ink head for ejecting ink, the pretreatment agent composition can be uniformly attached to the recording medium. When the pretreatment agent attaching means is inkjet application, the treatment liquid can be stored in any one of the ink cartridges 7a, 7b, 7c, 7d, 7e, 7f shown in FIG. 1. Other pretreatment agent attaching means include dipping means for dipping the recording medium in the pretreatment agent composition, a roller for applying the pretreatment agent composition with a roll coater or the like, a spray for spraying the pretreatment agent composition with a spray device or the like.

[0166] 1.9.2 Inkjet Dyeing The white inkjet ink composition according to the present embodiment is preferably used for inkjet dyeing.

[0167] Here, "inkjet dyeing" means recording (printing) an ink composition on a recording medium including a fabric using an inkjet method, and is a kind of inkjet recording. Also, "dyeing" means recording (printing) ink on a recording medium including a fabric, and is also called "printing".

[0168] When using an ink containing hollow resin particles as a white coloring material, when the recording medium is heated and dried after printing, the resin may melt or the like and the hollow structure may be broken, and as a result, the color developability tends to decrease. Therefore, by using hollow resin particles having a glass transition temperature of a specific temperature or higher, it is possible to suppress a decrease in color developability. However, even when such specific hollow resin particles are used, the hollow resin particles may easily penetrate into the recording medium and the color developability may not be sufficient. In particular, in inkjet printing on fabric, the color developability is more likely to be inferior. On the other hand, according to the white inkjet ink composition according to the present embodiment, in addition to the configuration of using hollow resin particles having a glass transition temperature of a specific temperature or higher, a specific By using a resin in a predetermined content or more, a plugging effect on the fabric can be obtained, and even when used for inkjet printing, the color developability and rubbing resistance can be made good.

[0169] 2. Inkjet recording method The inkjet recording method according to an embodiment of the present invention includes a white ink adhesion step of discharging the above-described white inkjet ink composition from a recording head and adhering it to a recording medium.

[0170] The white inkjet ink composition used in the inkjet recording method according to the present embodiment uses hollow resin particles as a white coloring material instead of titanium oxide pigment having a large specific gravity and being likely to sediment over time, so that sedimentation of the white coloring material can be suppressed well and thus it is excellent in sedimentation property. On the other hand, when using hollow resin particles as a white coloring material in the ink, when the recording medium is heated and dried after printing, the resin may melt or the like and the hollow structure may be broken, and as a result, the color developability tends to decrease. Therefore, by using hollow resin particles having a glass transition temperature of a specific temperature or higher, it is possible to suppress a decrease in color developability. However, even when such specific hollow resin particles are used, the hollow resin particles may easily penetrate into the recording medium and the color developability may not be sufficient.

[0171] On the other hand, the white inkjet ink composition used in the inkjet recording method according to the present embodiment further has a configuration in which a specific resin is used in a predetermined content or more. Thereby, it is possible to obtain a plugging effect on the recording medium, that is, an effect of suppressing the penetration of the hollow resin particles into the inside of the recording medium, and the color developability can be made good. As described above, according to the inkjet recording method according to the present embodiment using a white inkjet ink composition containing hollow resin particles having a glass transition temperature of a specific temperature or higher and a specific resin particles of a predetermined amount or more, both the color developability and the sedimentation property can be excellent.

[0172] Hereinafter, each step of the inkjet recording method according to the present embodiment will be described.

[0173] 2.1 White Ink Adhesion Step In the white ink adhesion step, the above-described white inkjet ink composition is discharged from the recording head and adhered to the recording medium.

[0174] In this step, as shown in FIG. 1, using a printer 1, droplets of the above-described white inkjet ink composition are discharged from the recording head and adhered to the recording medium to form an image or the like.

[0175] In the white ink adhesion step, as the recording head for discharging the ink, a recording head having a circulation path as shown in FIGS. 2 and 3 may be used, or a recording head having no circulation path may be used.

[0176] In the white ink adhesion step, the ink adhesion amount to the recording medium is preferably 30 mg / inch 2 or more, more preferably 45 mg / inch 2 or more, still more preferably 60 mg / inch 2 or more, particularly preferably 75 mg / inch 2 or more, and most preferably 90 mg / inch 2It is even more preferable that it is as described above. On the other hand, the upper limit of the ink adhesion amount in the white ink adhesion step is not particularly limited, but it is preferably 150 mg / inch 2 or less, more preferably 135 mg / inch 2 or less, and even more preferably 120 mg / inch 2 or less. When the ink adhesion amount is within the above range, a relatively large amount of the white ink composition will adhere to the recording medium, so the color development property may be improved. However, if the ink adhesion amount is large, the ink is likely to dry insufficiently and is likely to be inferior in rubbing resistance. On the other hand, in such a case, in order to obtain good rubbing resistance, heating at a high temperature or heating for a long time may cause the hollow structure of the hollow resin particles to be destroyed and the color development property to be inferior. In contrast, according to the white inkjet ink composition used in the present embodiment, even when the ink adhesion amount is within the above range, it is easy to ensure excellent color development property and good rubbing resistance.

[0177] The recording medium may have a recording surface that absorbs liquid or may not have a recording surface that absorbs liquid. Therefore, there is no particular limitation on the recording medium, and for example, paper, film, fabric, metal, glass, polymer, etc. can be used.

[0178] The material constituting the fabric is not particularly limited, and examples include natural fibers such as cotton, hemp, wool, and silk, synthetic fibers such as polypropylene, polyester, acetate, triacetate, polyamide, and polyurethane, biodegradable fibers such as polylactic acid, etc., and these blended fibers may also be used.

[0179] Examples of the form of the fabric include fabrics, clothing, and other accessories. Fabrics include woven fabrics, knitted fabrics, non-woven fabrics, etc. Clothing and other accessories include sewn T-shirts, handkerchiefs, scarves, towels, tote bags, cloth bags, curtains, sheets, bed covers, and other furniture such as wallpaper, as well as fabrics before and after cutting as parts before sewing. These forms include long ones rolled in a roll shape, those cut to a predetermined size, those in a product shape, and the like.

[0180] The basis weight of the fabric is not particularly limited and may be 1.0 oz or more and 10.0 oz or less, preferably 2.0 oz or more and 9.0 oz or less, more preferably 3.0 oz or more and 8.0 oz or less, and even more preferably 4.0 oz or more and 7.0 oz or less. If the basis weight of the fabric is within such a range, good recording can be performed. Furthermore, in the inkjet recording method according to the present embodiment, it can be applied to a plurality of types of fabrics with different basis weights, and good printing can be performed.

[0181] As the fabric, a cotton fabric pre-colored with a dye may be used. Examples of the dye for pre-coloring the fabric include water-soluble dyes such as acid dyes and basic dyes, disperse dyes used in combination with a dispersant, reactive dyes, and the like. When using a cotton fabric for the fabric, it is preferable to use a reactive dye suitable for dyeing cotton.

[0182] Among these recording media, the recording medium is preferably a fabric, and more preferably a fabric treated with a cationic compound. When recording on a fabric using an ink containing hollow resin particles, even if the fabric is treated with a component that aggregates the ink, the hollow resin particles may not easily penetrate into the fabric and sufficient color development may not be obtained. However, since the inkjet recording method according to the present embodiment uses the above-described white inkjet ink composition, excellent color development can be obtained.

[0183] <Cationic compound treatment> As a method for treating a fabric with a cationic compound, there is no particular limitation, but the fabric can be treated with a cationic compound by applying a pretreatment agent containing the cationic compound to the fabric and drying it.

[0184] 〔Pretreatment agent〕 When using a pretreatment agent, it is only necessary to contain a cationic compound. It may contain resin particles, an organic solvent, water, etc. that can be contained in the above-described white inkjet ink composition. Examples of the pretreatment agent include those containing a cationic compound, resin particles, and water. That is.

[0185] The cationic compound has a function of aggregating the components in the ink composition. Therefore, when the ink composition is adhered to the fabric to which the pretreatment agent is adhered, the cationic compound promotes the aggregation of the ink particles or increases the viscosity of the ink, suppressing the absorption into the gaps or inside of the fibers constituting the fabric. In this way, since the cationic compound retains the ink on the surface of the fabric, the color developability of the ink in the recording material is improved. Also, bleeding and bleeding are suppressed.

[0186] Examples of the cationic compound include polyvalent metal salts such as calcium salts and magnesium salts, cationic urethane resins, cationic resins such as olefin resins and allylamine resins, cationic surfactants, inorganic acids or organic acids, etc. Among these, it is preferable to use a polyvalent metal salt in terms of improving color developability and being suitable for cotton fabrics. These cationic compounds may be used alone or in combination of two or more.

[0187] The content of the cationic compound contained in the pretreatment agent is not particularly limited, but it is preferably 0.1% by mass or more, more preferably 2.0% by mass or more, and even more preferably 5.0% by mass or more based on the total mass of the pretreatment agent. Also, the content of the cationic compound contained in the pretreatment agent is preferably 40.0% by mass or less, more preferably 25.0% by mass or less, and even more preferably 10.0% by mass or less based on the total mass of the pretreatment agent.

[0188] 〔Coating method〕 The coating method is not particularly limited as long as the pretreatment agent can be adhered to at least a part of the fabric area. Examples of the coating method include dipping coating in which the fabric is immersed in the pretreatment agent, roller coating in which the pretreatment agent is adhered using a brush, roller, spatula, roll coater, etc., spray coating in which the pretreatment agent is sprayed with a spray device, inkjet coating in which the pretreatment agent is adhered by an inkjet method, and the like. Among them, it is preferable to use dipping coating, roller coating, spray coating, etc., in which the configuration of the device is simple and the adhesion of the pretreatment agent can be performed quickly.

[0189] The coating amount of the pretreatment agent is not particularly limited, but when using fabric as the recording medium, it is preferably coated at 5 to 30 g per A4 size area, more preferably 10 to 25 g, and even more preferably 15 to 25 g.

[0190] 〔Drying method〕 The drying method is not particularly limited, and examples include drying by a hot press machine and an oven. The heating temperature is preferably 100°C or higher, more preferably 110 to 200°C, and even more preferably 120 to 180°C. Also, the heating time is preferably within 2 minutes. When the heating temperature is 100°C or higher, the fixing property of the cationic compound tends to be good. When using a hot press machine, the pressing pressure is not particularly limited, but it is preferably carried out at about 3.0 to 5.0 N / cm 2 degree.

[0191] 2.2 Heating and drying process The inkjet recording method according to this embodiment may include a step of heating and drying the ink adhered to the recording medium after the white ink adhesion step.

[0192] The heating and drying method is not particularly limited, and examples thereof include a heat press method, an atmospheric pressure steam method, a high pressure steam method, a thermofix method, and the like. The heat source during heating and drying is not particularly limited, and for example, an infrared lamp or the like can be used.

[0193] The heating and drying temperature is preferably a temperature at which the resin particles of the ink are fused and a medium such as moisture volatilizes. For example, it is preferably about 100°C or higher and about 200°C or lower, more preferably 170°C or lower, and even more preferably 150°C or lower. Here, the heating and drying temperature in the heating and drying step refers to the surface temperature of an image or the like formed on the recording medium. The time for performing heating and drying is not particularly limited, but for example, it is preferably 30 seconds or more and 20 minutes or less, and more preferably 5 minutes or more and 10 minutes or less.

[0194] 2.3 Other steps The inkjet recording method according to this embodiment may include a step of washing the printed recording medium with water and a step of performing heating and drying again after the heating and drying step. In the water washing, if necessary, as a soaping treatment, components such as ink that have not been fixed to the recording medium may be washed away using a hot soapy solution or the like.

[0195] 3. Examples Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples. Hereinafter, “%” is based on mass unless otherwise specified.

[0196] 3.1 Preparation of white inkjet ink composition Each component was mixed at the contents shown in Table 1 to Table 3 below, stirred at room temperature for 2 hours, and then filtered using a membrane filter with a pore size of 5 μm to obtain each white inkjet ink composition. Note that the unit of the content of the ink composition shown in Table 1 to Table 3 below is mass%, and water was added so that the total mass of the ink was 100 mass%. Further, the ink composition is described in terms of solid content concentration, the pigment fine particles are in terms of pigment concentration, and the resin fine particles are in terms of solid content concentration.

[0197] Also, the hollow resin dispersions C and D of pigment fine particles were produced as follows.

[0198] <Production Example of Hollow Resin Dispersion C> (Synthesis of Seed Particle Emulsion) Into a four-neck separable flask equipped with a stirrer, thermometer, cooler, and dropping funnel, 726.0 parts by mass of deionized water, 5.0 parts by mass of methyl methacrylate, and 0.1 part by mass of methacrylic acid were charged and heated with stirring. Next, when the internal temperature in the separable flask reached 70 °C, 1.0 part by mass of a 10% by mass aqueous ammonium persulfate solution was added and heated at 80 °C for 20 minutes.

[0199] On the other hand, 141.0 parts by mass of methyl methacrylate, 94.9 parts by mass of methacrylic acid, 5.0 parts by mass of sodium alkylbenzene sulfonate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Neogen SF-20) as an anionic emulsifier, and 120.0 parts by mass of deionized water were emulsified with a homodisper and made into a pre-emulsion, and then charged into a dropping funnel.

[0200] Next, while maintaining the internal temperature in the separable flask at 80 °C, the pre-emulsion obtained above was uniformly dropped over 3 hours, and at the same time, 10.0 parts by mass of a 10% by mass aqueous ammonium persulfate solution was uniformly dropped over 3 hours. After the dropping was completed, it was aged at 80 °C for 3 hours, cooled, and filtered using a 120-mesh filter cloth to obtain a seed particle emulsion.

[0201] (First-stage Polymerization) Into a four-neck separable flask equipped with a stirrer, thermometer, cooler, and dropping funnel, 188.2 parts by mass of deionized water was charged, 66.0 parts by mass of the seed particle emulsion obtained above was dropped, and it was heated to 80 °C with stirring. On the other hand, 2.4 parts by mass of butyl acrylate, 1.1 parts by mass of butyl methacrylate, 19.5 parts by mass of methyl methacrylate, 0.7 A mass portion, 5.0 parts by mass of sodium alkylbenzene sulfonate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen SF-20), and 55.3 parts by mass of deionized water were emulsified with a homodisper to obtain a pre-emulsion 1, which was then charged into a dropping funnel.

[0202] Next, while maintaining the internal temperature in the separable flask at 80 °C, the pre-emulsion 1 obtained above was uniformly dropped over 30 minutes, and simultaneously, 1.2 parts by mass of a 10% by mass aqueous sodium persulfate solution was uniformly dropped over 30 minutes.

[0203] (Second-stage polymerization) 60.1 parts by mass of styrene, 0.5 parts by mass of 1,3-diethylbenzene, 5.0 parts by mass of sodium alkylbenzene sulfonate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen SF-20), and 51.8 parts by mass of deionized water were emulsified with a homodisper to obtain a pre-emulsion 2, which was then charged into a dropping funnel.

[0204] Next, while maintaining the internal temperature in the separable flask at 80 °C, 1 hour after the dropping of the pre-emulsion 1 was completed, the pre-emulsion 2 obtained above was uniformly dropped over 60 minutes, and simultaneously, 3.5 parts by mass of a 10% by mass aqueous sodium persulfate solution was uniformly dropped over 60 minutes.

[0205] After the dropping of the pre-emulsion 2 was completed, 7.5 parts by mass of 28% by mass aqueous ammonia was dropped to swell and dissolve the seed particles, and the mixture was aged at 80 °C for 1 hour. After cooling, it was filtered using a 120-mesh filter cloth to obtain a hollow resin dispersion C.

[0206] <Production Example of Hollow Resin Dispersion D> In the production example of the above hollow resin dispersion C, it was obtained in the same manner as the production example of the above hollow resin dispersion C, except that the styrene in the second-stage polymerization was 20.5 parts by mass.

[0207] <Inorganic Particle Dispersion> Also, the following commercially available products were used as the inorganic particle dispersion. · Titanium Dioxide Slurry; NanoTek(R) Slurry (trade name, manufactured by C.I. Kasei Co., Ltd., titanium dioxide solid content 20% by mass, average particle diameter 250 nm)

[0208] 3.2 Preparation of Pretreatment Agent Each component was mixed at the contents shown in Table 4 below, stirred at room temperature for 2 hours, and then filtered using a membrane filter with a pore diameter of 5 μm to obtain each pretreatment agent. The unit of the content of the pretreatment agent composition shown in Table 4 below is mass%, and water was added so that the total mass of the pretreatment agent was 100 mass%. The pretreatment agent composition is described in terms of solid content concentration.

[0209]

Table 1

[0210]

Table 2

[0211]

Table 3

[0212]

Table 4

[0213] Supplementary explanations are provided for each component shown in Table 1 to Table 4 above. <White Inkjet Ink Composition> 〔Pigment Fine Particles〕 · ROPAQUE HT1432 (trade name, manufactured by The Dow Chemical Company, styrene-acrylic resin, Tg: 123 °C, particle diameter 500 nm) · SX868B (trade name, manufactured by JSR Corporation, styrene-acrylic resin, Tg: 109 °C, particle diameter 500 nm) · Dispersion C (prepared according to the production example of the above hollow resin dispersion C, styrene-acrylic resin, Tg: 131 °C, particle diameter 700 nm) · Dispersion D (prepared according to the production example of the above hollow resin dispersion D, styrene-acrylic resin, Tg: 124 °C, particle size 280 nm) 〔Resin fine particles〕 · Mobinyl 966A (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content 45% by mass, Tg: -32 °C) · Bon Titer HUX-380 (trade name, manufactured by ADEKA Corporation, Tg: -5 °C to -35 °C) 〔Surfactant〕 · BYK348 (trade name, manufactured by BYK-Chemie Japan Co., Ltd., silicone-based surfactant) 〔Crosslinking agent〕 · NBP-211 (trade name, manufactured by Meisei Chemical Industry Co., Ltd., solid content 40% by mass, blocked isocyanate-based crosslinking agent, reaction temperature 150 °C or higher) · Epocross K2010E (trade name, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd., oxazoline-based crosslinking agent, reaction temperature 80 - 100 °C) 〔Wax〕 · Hi-Tech E-9015 (trade name, manufactured by Toho Chemical Industry Co., Ltd., polyolefin wax, melting point 137 °C) · Hi-Tech E-8237 (trade name, manufactured by Toho Chemical Industry Co., Ltd., polyolefin wax, melting point 106 °C)

[0214] <Pretreatment agent> 〔Fixing agent〕 · Mobinyl 966A (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content 45% by mass, Tg: -32 °C) · Unisense 104L (trade name, manufactured by Senka Corporation, dimethylamine-epichlorohydrin condensate)

[0215] 3.3 Recording method As the fabric of the object to be treated, the pretreatment agent of each example and each comparative example obtained above was spray-coated on a T-shirt (black, 100% cotton) manufactured by Hanes so as to be 15 - 20 g per A4 size, and then dried at 130 °C for 1 minute with a heat press machine (manufactured by Itsumi, AF-54TEN) so that the press pressure was 4.2 N / cm 2 and returned to 25 °C to obtain a pretreated fabric.

[0216] As recording devices, an inkjet device without an ink circulation mechanism in the head and an inkjet device with an ink circulation mechanism in the head (both are modified machines of SC-F2000 manufactured by Seiko Epson Corporation) were prepared. Each white inkjet ink composition of each example and each comparative example obtained above was filled into the recording device, and the images described in each evaluation method were printed on the pretreated fabric respectively.

[0217] 3.4 Evaluation Method The evaluation methods for whiteness, sedimentation property, rubbing resistance, and ejection reliability in each example and each comparative example are as follows.

[0218] 3.4.1 Whiteness The white ink composition that had been sufficiently stirred to recover sedimentation was inkjet-coated on the fabric pretreated by the above method with each ink adhesion amount described in Table 1 to Table 3 above. Then, using a conveyor drying oven (manufactured by M&R: Economax_D conveyor drying oven), a heat drying treatment was performed at 150°C for 5 minutes. After that, the printed fabric was immersed in water at a water temperature of 25°C and 2 L of water, and the container was shaken at a frequency of 1 time / 2 sec for 5 minutes for washing, and the moisture was removed with a towel. Then, the printed fabric was subjected to a heat drying treatment at 150°C for 5 minutes. After that, using a colorimeter (manufactured by Gretag, Spectrolino), L * was measured and judged according to the following judgment criteria. 〔Judgment Criteria〕 S: 85 ≤ L * A: 70 ≤ L * < 85 A-: 60 ≤ L * < 70 B: L * < 60

[0219] 3.4.2 Sedimentation Property The white ink composition of each example that had been sufficiently stirred to restore sedimentation was poured into a glass screw tube bottle (manufactured by AS ONE Corporation, Labolance Screw Tube Bottle No. 8) in an amount of 100 mL. Using a pipette, 5 mL of the ink was collected 10 mm below the ink liquid level to obtain a pre-test sample. Subsequently, the screw tube bottle was left standing in an environment at 20°C. After 168 h, 5 mL of the ink was again collected 10 mm below the ink liquid level using a pipette to obtain a post-test sample. The pre-test and post-test samples were sufficiently stirred to restore sedimentation, and 0.5 mg was collected from each using a pipette. Dilution was performed with pure water using a 1-L volumetric flask to prepare 1 L of a diluted solution, and the absorbance (Abs) was measured using an ultraviolet-visible spectrophotometer (trade name " - "770 series", manufactured by JASCO Corporation). Subsequently, the percentage change in absorbance was calculated according to the following formula and judged according to the following criteria. Percentage change in absorbance: {(Abs after the test) - (Abs before the test)} / (Abs before the test) × 100 〔Judgment criteria〕 A: -5% or more B: Less than -5%

[0220] 3.4.3 Rub resistance Using the above recording device, on one surface of the pre-treated fabric as the object to be treated, the white ink composition of each example was discharged so as to have the coating density of each example to print a 20 cm square solid image. Subsequently, using a conveyor drying furnace (manufactured by M&R: Economax_D conveyor drying furnace), a heat drying treatment was performed at 150°C for 10 minutes, and after returning to 25°C, a printed fabric was obtained.

[0221] Next, using a Kagaku-Shinkou type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., AB-301S), the image on the printed fabric was rubbed 20 times with a load of 200 g using a cotton white cloth. Then, the image of the printed fabric after friction was visually observed, and the ratio of the area of the region where the ink had peeled off from the fabric to the area of the rubbed region was judged according to the following criteria. 〔Judgment criteria〕 S: No peeling A: The peeling area is less than 30% A-: The peeling area is 30% or more and less than 70% B: The peeling area is 70% or more

[0222] 3.4.4 Spit reliability The white ink compositions of each example were filled into the color ink cartridges of the above recording device, and nozzle check images were printed on a transparent PET film using the nozzle check function built into the SC-F2000. After confirming that the nozzle check images were printed normally and the ink was ejected normally from all nozzles, the automatic head cleaning function was set to OFF, and the recording device was left standing in an environment of 25°C room temperature and 40% relative humidity for 15 minutes without attaching an anti-drying cap to the head nozzles. During this period, a circulation operation was performed on the recording device having a circulation flow path. Further, it was left standing for 24 hours with the anti-drying cap attached. Then, the nozzle check images were printed again, the number of nozzles where the nozzle check images were not printed was counted, and the determination was made according to the following criteria.

[0223] In the case of nozzle dropout, a recovery operation was performed once using the head cleaning function built into the SC-F2000, the nozzle check images were printed, the number of nozzle dropouts was counted, and the determination was made according to the following criteria. 〔Determination criteria〕 S: No nozzle dropout A: Nozzle dropout occurs, but there is no nozzle dropout after the recovery operation B: Nozzle dropout occurs, and there is still nozzle dropout after the recovery operation

[0224] 3.5 Evaluation results The evaluation results of each example and each comparative example are shown in Tables 1 to 3 above.

[0225] In each example containing hollow resin particles having a glass transition temperature of a predetermined temperature or higher and a specific resin particles of a predetermined amount or more, all were excellent in color development (whiteness) and sedimentation. Also, in each example, all were excellent in abrasion resistance.

[0226] In contrast, in each of the comparative examples, it was not possible to achieve both excellent color development (whiteness) and sedimentation resistance. More specifically, in Comparative Example 1, it did not contain hollow resin particles having a glass transition temperature of a predetermined temperature or higher and was inferior in color development (whiteness). In Comparative Example 2, it did not contain a predetermined amount or more of specific resin particles and was inferior in color development (whiteness). In Comparative Example 3, it did not contain specific resin particles and was inferior in color development (whiteness). In Comparative Example 4, titanium dioxide was used instead of hollow resin particles, and the sedimentation resistance was inferior.

[0227] The following content is derived from the above-described embodiments.

[0228] One aspect of the white inkjet ink composition is containing hollow resin particles, resin particles, and water, wherein the glass transition temperature of the hollow resin particles is 120°C or higher, the resin particles are made of an acrylic resin or a urethane resin, and the content of the resin particles is 5% by mass or more based on the total mass of the ink composition.

[0229] In one aspect of the above white inkjet ink composition, furthermore, as the water-soluble organic solvent, a polyhydric alcohol having a standard boiling point of 270°C or higher may be contained in an amount of 15% by mass or less.

[0230] In any aspect of the above white inkjet ink composition, furthermore, as the water-soluble organic solvent, a polyhydric alcohol having a standard boiling point of 150°C or higher and less than 270°C may be contained in an amount of 5% by mass or more.

[0231] In any aspect of the above white inkjet ink composition, the hollow resin particles may contain an acrylic resin.

[0232] In any aspect of the above white inkjet ink composition, The resin particles may be acrylic resins.

[0233] In any aspect of the above white inkjet ink composition, The particle diameter of the hollow resin particles may be 400 to 1000 nm.

[0234] In any aspect of the above white inkjet ink composition, Furthermore, it may contain a lubricant with a melting point of 130°C or lower.

[0235] In any aspect of the above white inkjet ink composition, Furthermore, it may contain a crosslinking agent with a reaction temperature of 130°C or lower.

[0236] In any aspect of the above white inkjet ink composition, It may be applied and used in a recording apparatus equipped with a recording head having a circulation path.

[0237] In any aspect of the above white inkjet ink composition, It may be used for inkjet printing.

[0238] One aspect of the inkjet recording method is Including a white ink adhesion step of discharging the white inkjet ink composition of any of the above aspects from a recording head and attaching it to a recording medium.

[0239] In one aspect of the above inkjet recording method, The recording medium may be a fabric, and the fabric may be treated with a cationic compound.

[0240] In any aspect of the above inkjet recording method, The ink application amount in the white ink adhesion step may be 30 mg / inch 2 or more.

[0241] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiments, for example, a configuration having the same functions, methods, and results, or a configuration having the same objectives and effects. Further, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiments is replaced. Further, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiments or a configuration that can achieve the same objective. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiments.

Explanation of Reference Numerals

[0242] 1... printer, 2... recording medium, 3... inkjet head, 4... carriage, 5... main scanning mechanism, 6... platen roller, 7a, 7b, 7c, 7d, 7e, 7f... ink cartridge, 8... timing belt, 9... motor, 10... guide shaft, 28... wiring board, 30 ... flow path forming portion, 32... first flow path board, 34... second flow path board, 42... vibrating portion, 44... piezoelectric element, 46... protective member, 48... housing portion, 482... inlet, 52... nozzle plate, 54... vibration absorber, 61... supply path, 63... communication path, 65... circulation liquid chamber, 69... partition portion, 72... discharge path, C... pressure chamber, R... liquid storage chamber, Ra, Rb... space, Fa, Fb... surface, O... center plane, P1... first portion, P2... second portion, N... nozzle, L1... first row, L2... second row, n1... first section, n2... second section, d1... inner diameter of the first section, d2... inner diameter of the second section, Qa... central axis of the nozzle, Qb... central axis of the communication path, La, Lb, Lc... flow path length, Da... depth of the discharge path

Claims

[

1. ] A white inkjet ink composition containing hollow resin particles having voids inside the resin particles and filled with a liquid or gas in the voids, fixing resin particles having a function as a fixing resin, and water, wherein the glass transition temperature of the hollow resin particles is 120° C. or higher, the fixing resin particles are made of an acrylic resin or a urethane resin, the content of the fixing resin particles is 5% by mass or more based on the total mass of the ink composition, and the content ratio (A / B) of the content A of the hollow resin particles to the content B of the fixing resin particles is 0.8 to 2.

0. [

2. ] The white inkjet ink composition according to claim 1, further containing, as a water-soluble organic solvent, a polyhydric alcohol having a standard boiling point of 270° C. or higher in an amount of 15% by mass or less. [

3. ] The white inkjet ink composition according to claim 1 or 2, further containing, as a water-soluble organic solvent, a polyhydric alcohol having a standard boiling point of 150° C. or higher and less than 270° C. in an amount of 5% by mass or more. [

4. ] The white inkjet ink composition according to any one of claims 1 to 3, wherein the hollow resin particles contain an acrylic resin. [

5. ] The white inkjet ink composition according to any one of claims 1 to 4, wherein the fixing resin particles are an acrylic resin. [

6. ] The white inkjet ink composition according to any one of claims 1 to 5, wherein the particle diameter of the hollow resin particles is 400 to 1000 nm. [

7. ] The white inkjet ink composition according to any one of claims 1 to 6, further containing a lubricant having a melting point of 130° C. or lower. [

8. ] Furthermore, a crosslinking agent capable of crosslinking the fixing resin particles with each other, the hollow resin particles with each other, or the fixing resin particles and the hollow resin particles by a crosslinking reaction, and containing a crosslinking agent having a reaction temperature of the crosslinking reaction of 130° C. or lower. The white inkjet ink composition according to any one of claims 1 to 7. [

9. ] The white inkjet ink composition according to any one of claims 1 to 8, which is applied and used in a recording apparatus equipped with a recording head having a circulation path. [

10. ] The white inkjet ink composition according to any one of claims 1 to 9, which is used for inkjet printing. [

11. ] An inkjet recording method including a white ink adhesion step of discharging the white inkjet ink composition according to any one of claims 1 to 10 from a recording head and attaching it to a recording medium.

12. The inkjet recording method according to claim 11, wherein the recording medium is a fabric and is a fabric treated with a cationic compound.

13. The ink application amount in the white ink adhesion step is 30 mg / inch ２ or more, and the inkjet recording method according to claim 11 or claim 12.

Images