Inkjet ink composition and inkjet recording method

Abstract

Provided are an inkjet ink composition and an inkjet recording method having excellent gloss, ejection stability, and storage stability. The inkjet ink composition comprises a metallic pigment and a liquid medium, wherein the liquid medium comprises at least one selected from the group consisting of an organic solvent and water, wherein the metallic pigment is surface-modified with a predetermined surface treatment agent, wherein the metallic pigment is a scaly particle, and wherein the volume average particle size D of the metallic pigment is 50 (μm) is 1.0 μm or less, and the volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness Z (μm) of the metallic pigment (D 50 / Z) is 17 or more, the metallic pigment is ejected from an inkjet head for recording, and the volume average particle size D 50 The ratio (D 50 / L) is 0.050 or less.

Description

Technical Field

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

[0002] Metallic pigment compositions using metallic pigments can provide recorded materials and adherends with excellent metallic gloss, and therefore, development of applications suitable for these fields is progressing in the inkjet printing field, the coating field, and the like.

[0003] For example, Patent Document 1 discloses a non-aqueous inkjet composition comprising surface-treated metal powder and having a predetermined dissolved oxygen reduction rate, with the goal of providing an ink composition that exhibits excellent ejection stability and storage stability even when using an ink composition containing metal powder. Patent Document 1 discloses that surface treatment imparts to the metal powder a surface activity sufficient to react with oxygen contained in the composition but sufficient to prevent reaction with water and other substances contained in the composition, thereby improving ejection stability and storage stability.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-43722.

[0007] However, glossiness and ejection stability are still insufficient. Summary of the Invention

[0008] The inkjet ink composition of the present invention comprises a metallic pigment and a liquid medium, wherein the liquid medium comprises at least one selected from the group consisting of an organic solvent and water, and the metallic pigment is surface-modified by a surface treatment agent, wherein the surface treatment agent comprises at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2).

[0009] The above-mentioned metallic pigments are flaky particles.

[0010] The volume average particle size D of the above metallic pigment is 50 (μm) is less than 1.0μm,

[0011] The volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness Z (μm) of the metallic pigment (D 50 / Z) is 17 or more, the metallic pigment is ejected from an inkjet head for recording, and the volume average particle size D 50 The ratio (D 50 / L) is 0.050 or less.

[0012] (R 1 -)P(O)(OH)2(1)

[0013] (In the above formula (1), R 1 It is a hydrocarbon group having 14 or more carbon atoms and which may be substituted by a substituent.

[0014] (R 2 -O-) a P(O)(OH) 3-a (2)

[0015] (In the above formula (2), R 2 Each of them is independently a hydrocarbon group having a carbon skeleton with 14 or more carbon atoms which may be substituted by a substituent, and a is 1 or 2.

[0016] The inkjet recording method of the present invention comprises a step of depositing the inkjet ink composition by ejecting it from an inkjet head having a nozzle diameter L (μm) and depositing it on a recording medium.

[0017] The volume average particle size D 50 (μm) to the above nozzle diameter L (μm) (D 50 / L) is 0.050 or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a diagram showing an example of a recording device used in the attachment method of this embodiment.

[0019] Figure 2 This is a diagram showing a cross section of a main portion of an example of an inkjet head used in this embodiment.

[0020] Explanation of symbols

[0021] 1. Recording device; 2. 100. Inkjet head; 3. IR heater; 4. Press plate; 5. Heater; 6. Cooling fan; 7. Preheater; 8. Ventilation fan; M. Recording medium; 10. Nozzle plate; 12. Nozzle hole; 13. Nozzle face; 20. Pressure chamber; 30. Vibration plate; 32. Piezoelectric element; 40. Ink supply chamber; 110. Connecting plate; 120. Pressure chamber substrate; 126. Supply port; 127. Connecting hole; 128. Ejection port; 140. Compliance sheet; 150. Cover. DETAILED DESCRIPTION

[0022] Below, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the accompanying drawings as needed. However, the present invention is not limited thereto and various modifications can be made without departing from the scope of the present invention. It should be noted that in the accompanying drawings, the same symbols are marked for the same elements, and repeated descriptions are omitted. In addition, the positional relationships such as up and down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Moreover, the dimensional ratios in the drawings are not limited to the ratios shown in the drawings.

[0023] 1. Inkjet ink composition

[0024] The inkjet ink composition of this embodiment comprises a metallic pigment and a liquid medium, wherein the liquid medium comprises at least one selected from the group consisting of an organic solvent and water, the metallic pigment is surface-modified by a surface treatment agent, the surface treatment agent comprises at least one selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2), the metallic pigment is a scaly particle, and the volume average particle size D of the metallic pigment is 50 (μm) is 1.0 μm or less, and the volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness Z (μm) of the metallic pigment (D 50 / Z) is 17 or more, the metallic pigment is ejected from an inkjet head for recording, and the volume average particle size D 50 The ratio (D 50 / L) is less than 0.05.

[0025] (R 1 -)P(O)(OH)2(1)

[0026] (In the above formula (1), R 1 It is a hydrocarbon group having 14 or more carbon atoms and which may be substituted by a substituent.

[0027] (R 2 -O-) a P(O)(OH) 3-a (2)

[0028] (In the above formula (2), R 2 Each of them is independently a hydrocarbon group having a carbon skeleton with 14 or more carbon atoms which may be substituted by a substituent, and a is 1 or 2.

[0029] In the past, inkjet ink compositions containing metallic pigments surface-treated with fluorine-based surface treatment agents, etc., have been studied for the purpose of improving ejection stability and storage stability. However, there is room for further research to improve ejection stability during high-temperature ejection and storage stability during long-term storage at high temperatures. Furthermore, there is a desire for even better gloss. Furthermore, it is desirable to develop ink components that achieve excellent metallic gloss while also taking environmental considerations into account.

[0030] Furthermore, to further enhance gloss, thin, flaky (flat) metallic pigments have been developed. This increases the surface area of ​​each metallic pigment particle and the thinner its thickness. This increases the surface area per mass of metallic pigment, making it easier for the flaky metal particles to align parallel to the plane of the recording medium. This allows the flaky metal particles to form a glossy layer, resulting in excellent glossiness in the resulting recorded material. This orientation is also known as "floating."

[0031] However, although such flaky metallic pigments improve the gloss of the resulting recorded material, they tend to aggregate easily, which can reduce ejection stability. Furthermore, due to aggregation, the desired glossiness may not be achieved.

[0032] Furthermore, when ink flows through a narrow flow path, the surface orientation of the flaky particles aligns with the ink flow direction. This allows the flaky particles to move within the ink flow path without going against the flow of the ink. On the other hand, if flaky particles are stacked on the main surface to form coarse particles, the surface orientation of the flaky particles will not align with the ink flow direction, making it difficult for them to move within the ink flow path, potentially reducing ejection stability.

[0033] In contrast, the inkjet ink composition of this embodiment can improve gloss, discharge stability, and storage stability by including a metallic pigment surface-treated with a predetermined surface treatment agent and having a predetermined external shape and a liquid medium.

[0034] Next, the inkjet ink composition and the inkjet recording method according to the present embodiment will be described in detail.

[0035] 1.1. Metallic pigments

[0036] The metallic pigment of this embodiment is a pigment that has been surface-treated with a predetermined surface treatment agent described later and is a scaly particle. The volume average particle size D of the metallic pigment is 50 (μm) is 1.0 μm or less, and the volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness Z (μm) of the metallic pigment (D 50 / Z) is 17 or more, the metallic pigment is ejected from an inkjet head and used for recording, and the volume average particle size D 50 The ratio (D 50 / L) is less than 0.05.

[0037] The relationship between the metallic pigment and the surface treatment agent of this embodiment is not particularly limited. For example, the surface can be modified using a specific surface treatment agent described later, so that the -OH groups on the surface of the metallic pigment react with the phosphate groups or phosphonic acid groups of the surface treatment agent, thereby chemically bonding the metal particles to the above-mentioned surface treatment agent.

[0038] The metallic pigment is not particularly limited. For example, the metallic pigment may be entirely composed of a metallic material, or may have a base composed of a non-metallic material and a coating composed of a metallic material covering the surface of the base. It should be noted that the non-metallic base may be, for example, a scaly resin, the entire surface of which may be covered with a metallic material.

[0039] The content of the metallic pigment relative to the total amount of the inkjet ink composition may preferably be 0.1% by mass or greater, 0.3% by mass or greater, 0.5% by mass or greater, 1.0% by mass or greater, or 1.5% by mass or greater. Furthermore, the content of the metallic pigment relative to the total amount of the inkjet ink composition may preferably be 20% by mass or less, 15% by mass or less, 10% by mass or less, 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less.

[0040] 1.1.1. Constituent materials

[0041] The type of metal constituting the metallic pigment is not particularly limited, and for example, a single metal or various alloys thereof can be used. Such metal types are not particularly limited, and for example, aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, iron, copper, etc. can be cited. Among them, it is preferred that the metallic pigment contains one or more selected from the group consisting of aluminum and aluminum alloys. Thus, among various metal materials, there is a tendency to have an excellent glossiness. In addition, compared with other types of metal materials, the specific gravity is lower, and therefore, there is a tendency to have excellent ejection stability and storage stability. Moreover, it is also excellent in suppressing the increase in the production cost of the colored body manufactured using the inkjet ink composition. It should be noted that the metallic pigment can be used alone or in combination of two or more.

[0042] 1.1.2. Shape

[0043] As the shape of the metallic pigment, as long as (D 50 / Z) and ratio (D50 The particle size (L) is not particularly limited within the above range and can be any shape, such as flaky (flat), spherical, spindle-shaped, or needle-shaped. Of these, flaky is preferred, and more preferably, the metallic pigment is flaky and thin. When the metallic pigment is flaky, the wider surface of the particles on the recording medium is arranged along the surface of the recording medium, which tends to further enhance the gloss of the resulting colored article.

[0044] In particular, when metallic pigments are thin and scaly, the number of metallic pigment particles increases due to the thinness of the metallic pigment, and the total surface area of ​​the metallic pigment in the metallic pigment increases compared to other methods containing the same mass of metallic pigment. Therefore, when metallic pigments are thin and scaly, they tend to float when colored, resulting in a tendency for the gloss to be excellent.

[0045] In this embodiment, the so-called scale-like shape refers to a shape such as a flat plate or a curved plate, in which the area when viewed from a predetermined angle, for example, when viewed from above, is larger than the area when viewed from an angle perpendicular to the viewing direction. As an indicator of such a scale-like shape, the area S1 [μm] when viewed from the direction with the largest projected area, i.e., when viewed from above, can be used. 2 ] and the area S0 [μm] when observed from the direction with the largest area among the directions perpendicular to the observation direction 2 The ratio S1 / S0 is preferably 2 or more. Further, it is preferably 2 or more and 1000 or less, more preferably 5 or more and 500 or less, further preferably 8 or more and 100 or less, and even more preferably 10 or more and 80 or less.

[0046] The calculation of S1 / S0 is not particularly limited. For example, 50 particles of any metallic pigment may be observed and the average value of the values ​​calculated for these particles may be used. Such observation is not particularly limited and may be performed using, for example, electron microscopy or atomic force microscopy (hereinafter also referred to as AFM). Alternatively, the volume average particle size D of the metallic pigment may be calculated. 50 The ratio (D 50 / Z), and the ratio is set in the above range as an indicator of scaly shape.

[0047] When the metallic pigment is flaky in shape, it tends to be difficult to improve the ejection stability even after surface treatment. However, according to this embodiment, even when the metallic pigment is flaky, it is possible to improve the ejection stability while ensuring the excellent gloss brought by the flaky shape.

[0048] Unless otherwise specified, the physical properties of the pigment particles observed below are based on the AFM method. The atomic force microscope is not particularly limited, and for example, Nano Navi E-Sweep (manufactured by SII Nanotechnologies Co., Ltd.) can be used.

[0049] 1.1.3. Thickness

[0050] The average thickness Z of the metallic pigment is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, even more preferably 25 nm or less, and even more preferably 20 nm or less. Furthermore, the average thickness Z of the metallic pigment is preferably 1 nm or greater, more preferably 3 nm or greater, and even more preferably 5 nm or greater. When the average thickness of the metallic pigment is 100 nm or less, the gloss tends to be excellent.

[0051] 1.1.4. Volume average particle size

[0052] Volume average particle size D of metallic pigment 50 It is preferably 1.5 μm or less, more preferably 1.0 μm or less, further preferably 0.8 μm or less, and further preferably 0.6 μm or less. Furthermore, it is preferably 0.5 μm or less, and more preferably 0.4 μm or less. 50 It is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more. 50 When the volume average particle size D is 1.5 μm or less, there is a tendency for the ejection stability to be further improved. 50 When the particle size is 0.1 μm or more, the glossiness tends to be further improved.

[0053] It should be noted that the so-called volume average particle size D 50 This refers to the median particle size of the volume distribution obtained by measuring a particle dispersion using the laser diffraction-scattering method. When multiple measurements are expressed as the cumulative abundance ratio of each size, the size of the particle that represents exactly 50% of the median value is expressed. In the case of scaly metal particles, the volume average particle size is calculated based on the shape and size of the metal particles if converted to spherical form.

[0054] Volume average particle size D of metallic pigment 50 The ratio of the thickness (μm) to the average thickness Z (μm) (D 50 / Z) is 17 or more, preferably 17 or more and 60 or less, more preferably 20 or more and 48 or less, and further preferably 25 or more and 40 or less. 50 When / Z is 17 or more, the gloss tends to be excellent.

[0055] In addition, the volume average particle size D of the metallic pigment is 50 The ratio (D) of the inkjet head diameter (μm) to the nozzle diameter L (μm) of the inkjet head included in the recording device for recording by ejecting ink from the inkjet head 50 / L) is 0.050 or less, preferably 0.010 or more and 0.050 or less, more preferably 0.015 or more and 0.040 or less, and further preferably 0.020 or more and 0.030 or less. 50 When / L is 0.050 or less, there is a tendency for excellent discharge stability.

[0056] Here, the nozzle diameter L (μm) of the inkjet head used together with the inkjet ink composition of this embodiment is preferably 40 μm or less, more preferably 5 μm or more and 30 μm or less, further preferably 10 μm or more and 30 μm or less, and even more preferably 15 μm or more and 30 μm or less.

[0057] 1.2. Surface treatment agent

[0058] The surface treatment agent of this embodiment is used for the surface treatment of the metallic pigment of this embodiment, and comprises one or more selected from the group consisting of the compound represented by formula (1) and the compound represented by formula (2). Among these, the compound represented by formula (1) is preferred from the viewpoint of excellent gloss, ejection stability, and storage stability. It should be noted that one surface treatment agent may be used alone, or two or more surface treatment agents may be used simultaneously.

[0059] (R 1 -)P(O)(OH)2 (1)

[0060] (In the above formula (1), R 1 It is a hydrocarbon group having 14 or more carbon atoms and which may be substituted by a substituent.

[0061] (R 2 -O-) a P(O)(OH) 3-a (2)

[0062] (In the above formula (2), R 2 are each independently a hydrocarbon group having 14 or more carbon atoms which may be substituted by a substituent, and a is 1 or 2.

[0063] As described above, the surface treatment agent has a phosphate or phosphonic acid group as a hydrophilic group and a hydrocarbon group as a hydrophobic group. The reasons for achieving excellent gloss, ejection stability, and storage stability by treating the metallic pigment with the surface treatment agent of this embodiment are not limited to the following. For example, it is believed that this is due to the phosphate or phosphonic acid group chemically bonding by reacting with the OH groups on the metallic pigment surface. Furthermore, it is believed that the hydrophobic groups that are not involved in bonding with the metallic pigment surface moderately cover the metallic pigment surface, thereby improving gloss, ejection stability, and storage stability.

[0064] In the above formulas (1) and (2), R 1 and R 2 are hydrocarbon groups having 14 or more carbon atoms which may be substituted by a substituent. A hydrocarbon group having 14 or more carbon atoms means a hydrocarbon group having a skeleton in which 14 or more carbon atoms are continuously bonded. 1 and R 2 The number of carbon atoms does not include the number of carbon atoms of substituents.

[0065] The type of substituent is not particularly limited, and examples thereof include carboxyl, hydroxyl, amino, and oxyalkylene groups. 1 and R 2 In the example, a portion of the hydrogen atoms in the hydrocarbon group may be substituted with such a substituent, R 1 and R 2 The number of substituents possessed is preferably 1 or less (including hydrocarbon groups having no substituent), and more preferably no substituent.

[0066] In addition, as R 1 and R 2 , can be a saturated hydrocarbon group without double or triple bonds between carbon atoms, or an unsaturated hydrocarbon group with double or triple bonds between carbon atoms. In addition, the hydrocarbon group can be an aromatic hydrocarbon group with an aromatic ring structure in the carbon skeleton, or a chain or cyclic aliphatic hydrocarbon group.

[0067] Among them, R 1 and R 2 A chain aliphatic hydrocarbon group is preferred. The chain aliphatic hydrocarbon group includes branched and straight chain types, but a straight chain type is preferred.

[0068] As such R 1 and R 2 Specific examples of are not particularly limited, and include n-tetradecyl, n-pentadecyl, n-hexadecyl (n-cetyl), n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, and n-tetracosyl.

[0069] In formula (1), R as a hydrocarbon group1 Any carbon atom in is directly bonded to the phosphorus atom of formula (1), but R 1 The carbon atom directly bonded to the phosphorus atom is preferably R 1 The carbon atom at the end of the molecular chain.

[0070] Likewise, in formula (2), R as a hydrocarbon group 2 Any carbon atom in formula (2) (R 2 -O-) is directly bonded to the oxygen atom, which is directly bonded to the phosphorus atom, but R 2 The atom directly bonded to the oxygen atom is preferably R 2 The carbon atom at the end of the molecular chain.

[0071] R 1 and R 2 The number of carbon atoms is 14 or more, preferably 15 or more and 30 or less from the viewpoint of excellent gloss, ejection stability, and storage stability, more preferably 16 or more and 27 or less, further preferably 17 or more and 25 or less, and still further preferably 18 or more and 24 or less. This tends to result in excellent gloss, ejection stability, and storage stability.

[0072] The content of the surface treatment agent relative to the total amount of the metallic pigment of this embodiment is preferably 1.0% by mass to 50% by mass, more preferably 3.0% by mass to 40% by mass, even more preferably 5.0% by mass to 30% by mass, and even more preferably 10% by mass to 20% by mass. When the content of the surface treatment agent is within this range, excellent ejection stability and storage stability tend to be achieved.

[0073] Liquid medium

[0074] The inkjet ink composition of this embodiment includes a liquid medium. The term "liquid medium" refers to a liquid component capable of dispersing solutes such as metal particles. It is also referred to as a solvent component. The components of the liquid medium are not particularly limited, and examples thereof include water and various organic solvents.

[0075] The inkjet ink composition of this embodiment may be an aqueous composition containing water as the main liquid medium component, or a solvent-based composition containing an organic solvent as the main liquid medium component. It should be noted that an aqueous composition is a composition containing water as the main liquid medium component. The water content is preferably 40% by mass or greater relative to the total amount of the composition.

[0076] Furthermore, a solvent-based composition is a composition containing an organic solvent as the main liquid medium component. The organic solvent content is preferably 60% by mass or greater relative to the total amount of the composition. The water content of the solvent-based composition is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with the lower limit being 0% by mass.

[0077] When the inkjet ink composition is a water-based composition or a solvent-based composition, the viscosity of the ink can be made relatively low, which is preferable in that the ejection stability is excellent and the ink easily floats and has excellent gloss.

[0078] The inkjet ink composition of this embodiment is preferably not an ultraviolet curable composition.

[0079] The content of the liquid medium relative to the total amount of the inkjet ink composition may preferably be 60% by mass or greater, 70% by mass or greater, or 80% by mass or greater. Furthermore, the content of the liquid medium relative to the total amount of the inkjet ink composition may preferably be 98% by mass or less, 90% by mass or less, or 80% by mass or less.

[0080] When the inkjet ink composition is an aqueous composition, the water content relative to the total amount of the liquid medium may be 30% by mass or greater, preferably 40% by mass or greater, 50% by mass or greater, 60% by mass or greater, 70% by mass or greater, or 80% by mass or greater. Furthermore, the water content relative to the total amount of the liquid medium may preferably be 98% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less.

[0081] When the inkjet ink composition is an aqueous composition, the water content relative to the total amount of the inkjet ink composition is preferably greater than 40% by mass, and may be 50% by mass or greater, 60% by mass or greater, 70% by mass or greater, or 80% by mass or greater. Furthermore, the water content relative to the total amount of the liquid medium may preferably be 98% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0082] The aqueous composition may further contain an organic solvent as a liquid medium component. The content of the organic solvent may be 40% by mass or less, preferably 30% by mass or less, 20% by mass or less, or 15% by mass or less, relative to the total amount of the aqueous composition. Furthermore, the content of the organic solvent may be 0% by mass or greater, preferably 0.5% by mass or greater, 1% by mass or greater, or 5% by mass or greater, relative to the total amount of the aqueous composition.

[0083] When the inkjet ink composition of this embodiment is a solvent-based composition, the content of the organic solvent relative to the total amount of the liquid medium may be 70% by mass or greater, preferably 80% by mass or greater, 90% by mass or greater, or 98% by mass or greater. Furthermore, the content of the organic solvent relative to the total amount of the liquid medium may preferably be 98% by mass or less, 90% by mass or less, or 80% by mass or less.

[0084] When the inkjet ink composition is a solvent-based composition, the content of the organic solvent is preferably 60% by mass or greater, 70% by mass or greater, 80% by mass or greater, or 90% by mass or greater, relative to the total amount of the inkjet ink composition. Furthermore, the content of the organic solvent is preferably 98% by mass or less, 90% by mass or less, or 80% by mass or less, relative to the total amount of the inkjet ink composition.

[0085] 1.3.1. Organic solvents

[0086] The inkjet ink composition of this embodiment may contain a water-soluble organic solvent. Examples of such organic solvents include, but are not limited to, alcohols, hydrocarbon compounds, ether compounds, glycol ethers, ketones, esters, propylene carbonate, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, cyclohexanone, and acetonitrile.

[0087] When the inkjet ink composition of this embodiment is an aqueous composition, a diol compound is preferably used as the organic solvent. The use of a diol compound tends to further improve the gloss, ejection stability, and storage stability of the resulting recorded material due to a synergistic effect with the surface treatment agent. It should be noted that the organic solvents may be used singly or in combination of two or more.

[0088] The organic solvent is not particularly limited, and examples thereof include: monohydric alcohol compounds such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, tert-butanol, isobutanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol; diol compounds such as 1,2-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; aromatic alcohol compounds such as 2-phenoxyethanol, phenoxydiglycol, (methoxyphenoxy)ethanol, methylphenoxyethanol, hydroquinone-bis(β-hydroxyethyl) ether, nonylphenol, phenol, cresol, resorcinol, catechol, hydroquinone, naphthol, and furfuryl alcohol; and polyol compounds such as glycerol.

[0089] The organic solvent in the inkjet ink composition preferably contains at least one diol compound, preferably two or more. The use of such an alcohol compound as the organic solvent tends to further improve the gloss, ejection stability, and storage stability of the resulting recorded material due to a synergistic effect with the surface treatment agent. Furthermore, from the same perspective, the use of at least one of 1,2-hexanediol and propylene glycol is preferred, and the use of both 1,2-hexanediol and propylene glycol is more preferred.

[0090] On the other hand, when the inkjet ink composition of this embodiment is a solvent-based composition, it is preferred to use one or more organic solvents selected from the group consisting of glycol ethers and esters as the organic solvent. The use of glycol ethers and / or esters tends to further improve the gloss, ejection stability, and storage stability of the resulting recorded material due to a synergistic effect with the surface treatment agent. It should be noted that the organic solvents may be used singly or in combination of two or more.

[0091] The glycol ethers are not particularly limited, and examples thereof include triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, dipropylene glycol monopropyl ether, and tetraethylene glycol monobutyl ether.

[0092] Esters are not particularly limited, and examples thereof include ethyl acetate, propyl acetate, and butyl acetate. Esters also include cyclic esters. Cyclic esters are not particularly limited, and examples thereof include lactones such as γ-butyrolactone.

[0093] By using such glycol ethers and / or esters as the organic solvent, the gloss, ejection stability, and storage stability of the obtained recorded material tend to be further improved due to a synergistic effect with the surface treatment agent.

[0094] Furthermore, from the same viewpoint, it is preferred to use one or more selected from the group consisting of diethylene glycol diethyl ether, tetraethylene glycol monobutyl ether, and γ-butyrolactone, more preferably to use two or more thereof, and even more preferably to use three or more thereof.

[0095] 1.4. Resin

[0096] The inkjet ink composition of this embodiment may further include a resin. Such resins are not particularly limited, and examples thereof include resin particles composed of urethane resins, acrylic resins (including styrene 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. Among them, urethane resins, acrylic resins, polyolefin resins, and polyester resins are preferred. These resin particles are mostly processed in the form of emulsions, but can also be supplied in the form of powders. In addition, the resin particles can be used alone or in combination of two or more.

[0097] Urethane resins are a general term for resins containing urethane bonds. Urethane resins are not particularly limited; examples thereof include polyether urethane resins containing ether bonds in the main chain in addition to urethane bonds, polyester urethane resins containing ester bonds in the main chain in addition to urethane bonds, and polycarbonate urethane resins containing carbonate bonds in the main chain in addition to urethane bonds.

[0098] Acrylic resins are a general term for polymers obtained by polymerizing at least one acrylic monomer, such as (meth)acrylic acid or (meth)acrylate esters. While not particularly limited, examples thereof include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. Examples include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers. Examples of vinyl monomers include styrene.

[0099] The content of the resin is preferably 0.02% by mass to 0.20% by mass, more preferably 0.08% by mass to 0.12% by mass, and even more preferably 0.06% by mass to 0.16% by mass, relative to the total amount of the inkjet ink composition.

[0100] 1.5.Methods for producing metallic pigments

[0101] The preparation method of the metallic pigment is not particularly limited, and known methods can be used. As such a method, for example, a flaky metallic pigment can be obtained by forming a metal film on one surface of a sheet-like substrate using a vapor deposition method, and then peeling and crushing the metal film from the sheet-like substrate. According to this vapor deposition method, a flaky metallic pigment with little deviation in film thickness and high surface flatness can be obtained, which can more effectively show the metallic luster of the metallic pigment. It should be noted that the thickness of the film is the thickness of the flaky metallic pigment. In addition, the metallic pigment obtained in this way can be classified as needed to arbitrarily adjust its particle size distribution. Moreover, ion plating or sputtering can also be used instead of the above-mentioned vapor deposition method.

[0102] Furthermore, when preparing metallic pigments made of aluminum or aluminum alloys, it is preferred to use a film formed by vapor phase film formation and then pulverize it to more effectively develop its gloss. This method can also be used to prepare relatively thin metallic pigments.

[0103] The sheet-like substrate used in the above-mentioned vapor deposition method is not particularly limited; for example, plastic films such as polyethylene terephthalate (PET) can be used. Furthermore, to improve releasability, a release agent such as silicone oil may be pre-coated on the film-forming surface of the sheet-like substrate, or a release resin layer may be pre-formed. The resin used in the release resin layer is not particularly limited; examples thereof include polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polymethacrylic acid, polyacrylates, polymethacrylates, polyacrylamide, cellulose derivatives such as cellulose acetate butyrate, and modified nylon resins.

[0104] The peeling and pulverization of the metal film are not particularly limited, and can be performed, for example, by irradiating the film with ultrasonic waves in an organic solvent or stirring it with a homogenizer to apply an external force. The organic solvent used at this time is not particularly limited, and for example, alcohols such as methanol, ethanol, propanol, and butanol; hydrocarbon compounds such as n-heptane, n-octane, decane, dodecane, tetradecane, toluene, xylene, isopropyl toluene, durene, indene, dipentene, tetralin, decalin, and cyclohexylbenzene; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, etc. can be appropriately used. Ether compounds such as ether, diethylene glycol monobutyl ether acetate, diethylene glycol n-butyl ether, tripropylene glycol dimethyl ether, triethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, and 1,4-dioxane; and polar organic solvents such as propylene carbonate, γ-butyrolactone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, cyclohexanone, and acetonitrile. The use of such organic solvents can prevent unintended oxidation of the metallic pigment and reduce variations in the size, shape, and properties of the particles.

[0105] 1.6. Surface treatment methods

[0106] When using metallic pigments after surface treatment, known surface treatment methods can be used. While not particularly limited, such methods can include adding a surface treatment agent to a dispersion of the metallic pigment in an organic solvent, followed by ultrasonic irradiation, thereby bonding the surface treatment agent to the metallic pigment surface. In this case, the amount of surface treatment agent used can be adjusted to the amount described above. Furthermore, heating can be performed during ultrasonic irradiation. The heating temperature is preferably 40°C or higher, more preferably 50°C or higher. This is believed to be because heating at such temperatures forms covalent bonds between the metallic pigment surface and the surface treatment agent, increasing the bonding strength.

[0107] The surface treatment agent can be applied directly to the surface of the metallic pigment, but it can also be applied to a metallic pigment that has been pre-treated with an acid or alkali. This allows for more reliable chemical modification of the metallic pigment surface with the surface treatment agent, enabling more effective expression of the aforementioned effects of the present invention. Furthermore, the acid or alkali treatment can remove the oxide film on the metallic pigment, thereby improving gloss.

[0108] The acid used in the pretreatment is not particularly limited, and examples thereof include protonic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid, acetic acid, carbonic acid, formic acid, benzoic acid, chlorous acid, hypochlorous acid, sulfurous acid, dithionous acid, nitrous acid, dithionous nitrous acid, phosphorous acid, and hypophosphorous acid. On the other hand, the base used in the pretreatment is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0109] 1.7. Other ingredients

[0110] The inkjet ink composition may contain components other than the above components. Such components are not particularly limited, and examples thereof include leveling agents, binders, surfactants, penetration enhancers, moisturizers, chelating agents, etc., which may be appropriately added as needed.

[0111] 2. Inkjet recording method

[0112] The inkjet recording method of this embodiment is an inkjet recording method comprising a deposition step in which the inkjet ink composition is ejected from an inkjet head having a nozzle diameter L (μm) and deposited on a recording medium, wherein the volume average particle size D of the inkjet composition is 50 The ratio of (μm) to the above nozzle diameter L (μm) (D 50 / L) is 0.05 or less, and the inkjet recording method of this embodiment includes the following adhesion step. In addition, other steps may be included as needed.

[0113] 2.1. Attachment process

[0114] In the adhesion process, an inkjet ink composition (hereinafter referred to as ink) is ejected from an inkjet head and adheres to the recording medium. More specifically, the pressure generating mechanism within the inkjet head is driven to eject the ink from the nozzles within the pressure generating chamber of the inkjet head. This ejection method is also known as the inkjet method.

[0115] Examples of the inkjet head used in the attachment step include a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0116] In a line method using a line head, for example, an inkjet head having a width greater than the recording width of the recording medium is fixed to the recording device. The recording medium is then moved in the sub-scanning direction (the direction in which the recording medium is transported), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement, thereby recording an image on the recording medium.

[0117] In a serial method using a serial head, for example, an inkjet head is mounted on a carriage that is movable in the width direction of a recording medium. The carriage is then moved in the main scanning direction (the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with this movement, thereby recording an image on the recording medium.

[0118] 2.2. Primary heating process

[0119] The inkjet recording method according to this embodiment preferably includes a heating step for rapidly heating the ink attached to the recording medium. During the heating step, at least a portion of the liquid medium of the ink in the inkjet ink composition attached to the recording medium is dried to a degree that at least reduces the flow of the ink. The heating step can cause the ink to adhere to the heated recording medium, or it can be rapidly heated after attachment. Furthermore, the heating step is preferably performed for each attached inkjet ink composition. Heating of the ink droplets is preferably initiated within 0.5 seconds after the ink droplets adhere to the recording medium. This heating step is a heating step in the ink attachment step and is also referred to as a primary heating step.

[0120] In the case of a primary heating process, the ink composition can be dried quickly on the recording medium, thereby suppressing ink bleeding, which is preferred. For example, in the case of not having a primary heating process, the ink droplets attached to the recording medium will not be dried for a period of time, so the ink droplets will gather together and ooze out, and the image quality will deteriorate. This tendency is particularly present when the ink is a water-based composition or a solvent-based composition. In addition, in the inkjet recording method, black ink, cyan ink, yellow ink, magenta ink, etc. are sometimes used together with the inkjet ink composition of this embodiment for recording. In the case of not having a primary heating process, the image quality of these inks is particularly prone to deterioration. Therefore, the recording method preferably has a primary heating process.

[0121] In the heating step, it is preferable to use an IR heater, microwave radiation, a platen heater, or blowing warm air to the recording medium using a fan.

[0122] The heating in the heating step may be performed at least at one of the following times: before the ink adhesion step, simultaneously with adhesion, and early after adhesion, and preferably simultaneously. The ink adhesion step may be performed in this heating order.

[0123] The heating temperature of the recording medium and recorded material in the heating step is preferably 30°C to 50°C, more preferably 40°C to 50°C. The above heating temperature refers to the surface temperature of the recording medium at the time of ink deposition when heating is performed before deposition, or the surface temperature of the recording medium during heating when heating is performed after deposition.

[0124] From the perspective of handleability of recorded materials and the aforementioned image quality, it is conceivable to accelerate drying of the ink composition adhered to the recording medium by heating. However, if drying is accelerated, the inkjet ink composition of this embodiment may dry before sufficient floating occurs, resulting in reduced glossiness. Alternatively, heating of the platen, for example, may accelerate aggregation of the metallic pigment within the nozzle, thereby reducing ejection stability. However, the use of the ink composition of this embodiment allows for the production of recorded materials with excellent glossiness without compromising ejection stability, even with such heating, making it preferable.

[0125] 2.3. Post-heating process

[0126] The recording method of this embodiment may include a post-heating step (secondary heating step) to heat the recording medium after the ink adhesion step. The post-heating step is a heating step that heats the recording medium sufficiently after recording is complete to a point where the recorded material can be used. The post-heating step is a heating step used to thoroughly dry the liquid medium of the ink. The post-heating step is preferably started more than 0.5 seconds after the ink has adhered to the recording medium. For example, heating of a specific recording area of ​​the recording medium is preferably started more than 0.5 seconds after the ink has completely adhered to the recording medium.

[0127] The recording medium can be heated in the post-heating step using, for example, an appropriate heating means. The surface temperature of the recording medium in this case is preferably 45°C or higher, more preferably 50°C or higher. The upper limit is not limited, but is preferably 120°C or lower. Furthermore, it is more preferably 75°C or lower, 70°C or lower, or 60°C or lower. Furthermore, the heating temperature is preferably below the softening point of the recording medium substrate.

[0128] 2.4. Recording Media

[0129] The recording medium used in this embodiment is not particularly limited, and examples thereof include absorptive recording media, and low-absorptive or non-absorptive recording media.

[0130] There are no particular limitations on the absorptive recording medium, and examples thereof include ordinary paper such as electrophotographic paper having high ink permeability, inkjet paper (inkjet paper having an ink-absorbing layer composed of silica particles and / or alumina particles or an ink-absorbing layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) and / or polyvinyl pyrrolidone (PVP), etc., and coated paper, coated paper, cast-coated paper, etc. used in general offset printing having relatively low ink permeability.

[0131] The non-absorbent recording medium is not particularly limited, and examples thereof include: films and / or plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; plates of metals such as iron, silver, copper, and aluminum; or metal plates and / or plastic films produced by vapor deposition of these various metals, plates of alloys such as stainless steel and / or brass; recording media obtained by bonding (coating) a film of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane to a paper substrate, etc.

[0132] Low-absorbency recording media are recording media with a recording surface that has a low absorbency, second only to non-absorbency recording media. Examples of low-absorbency recording media include those having a coating layer (receiving layer) on the surface for receiving liquids. For example, when the substrate is paper, a printing substrate such as paper can be used. Examples of coating layers that are less likely to absorb ink include layers formed by applying particles such as inorganic compounds together with a binder.

[0133] The low-absorption or non-absorption recording medium is a recording medium that does not absorb liquid at all or hardly absorbs liquid. For example, the non-absorption or low-absorption recording medium preferably has a "Bristow method from the start of contact to 30 msec" 1 / 2 The water absorption is 10mL / m 2 The following recording medium".

[0134] The Bristol method is the most popular method for measuring liquid absorption over a short period of time and is also adopted by the Japan Pulp and Paper Industry Association (JAPAN TAPPI). Details of the test method are described in "JAPAN TAPPI Pulp and Paper Testing Methods 2000 Edition," Standard No. 51, "Paper and Board - Liquid Absorption Test Method - Bristol Method."

[0135] In contrast, an absorptive recording medium refers to a recording medium that does not fall under the categories of non-absorptive and low-absorptive recording media.

[0136] The shape of the recording medium is not particularly limited, and may be any shape such as a sheet, a plate, or an object.

[0137] 3. Inkjet recording device

[0138] As an example of a recording apparatus that executes the recording method of the present embodiment, there can be exemplified a recording apparatus that includes an inkjet head that discharges an ink composition and performs recording by the above-described recording method.

[0139] 3.1. Overview of the device structure

[0140] Figure 1 FIG is a schematic cross-sectional view schematically showing a recording device. Figure 1 As shown, the recording device 1 includes an inkjet head 2, an IR heater 3, a platen 4, a heater 5, a cooling fan 6, a preheater 7, and a ventilation fan 8. The inkjet head 2 is mounted on a carriage (not shown) and performs a main scan in the back-to-front direction in the figure, depositing ink onto the recording medium M. A platen heater (not shown) is also provided on the platen 4. The recording device 1 includes a control unit (not shown) that controls the various components to perform recording. The inkjet head 2 receives ink from an ink container (not shown).

[0141] 3.2. Inkjet head structure

[0142] The inkjet head 2 as an inkjet head has a structure that performs recording on the recording medium M by ejecting an ink composition from the nozzles of the inkjet head 2 and causing the ink composition to adhere. Figure 1 The inkjet head 2 shown is a serial-type inkjet head that scans the recording medium M multiple times in the main scanning direction, depositing ink onto the recording medium M. The inkjet head 2 is mounted on a carriage (not shown). The inkjet head 2 scans the recording medium M multiple times in the main scanning direction by operating a carriage movement mechanism that moves the carriage in the width direction of the recording medium M (the back-to-front direction in the figure). The width direction of the medium refers to the main scanning direction of the inkjet head 2. Scanning in the main scanning direction is also called main scanning.

[0143] In addition, here, the main scanning direction is the direction in which the carriage carrying the inkjet head 2 moves. Figure 1 The main scanning direction is a direction intersecting the sub-scanning direction indicated by arrow SS, which is the conveyance direction of the recording medium M. Recording is performed on the recording medium M by repeating main scanning of the inkjet head 2 and sub-scanning as the conveyance direction of the recording medium M multiple times.

[0144] A conventionally known method can be used for ejection by the inkjet head 2. For example, a method of ejecting droplets using the vibration of a piezoelectric element, that is, an ejection method of forming ink droplets by mechanical deformation of an electrostrictive element, can be used.

[0145] 3.3. Primary heating mechanism

[0146] The recording device 1 may be provided with a primary heating mechanism as follows: the primary heating mechanism performs a primary heating process, and the primary heating process is a process of heating the recording medium M when the ink is ejected from the inkjet head 2 and adhered to the recording medium. The primary heating mechanism may be a conductive type, an air supply type, a radial type, or the like. The conductive type conducts heat from a component in contact with the recording medium to the recording medium. For example, a platen heater may be mentioned. It should be noted that, although not shown in the figure, the platen heater is integrated with the platen 4. The air supply type sends normal temperature air or warm air to the recording medium and dries the ink. For example, an air supply fan may be mentioned. The radial type radiates heat-generating radiation to the recording medium to heat the recording medium. For example, IR radiation may be mentioned. In addition, although not shown in the figure, a heater similar to the platen heater may be provided immediately downstream of the platen 4 in the SS direction. These primary heating mechanisms may be used alone or in combination.

[0147] For example, the primary heating mechanism includes an IR heater 3 and a platen heater.

[0148] It should be noted that when the IR heater 3 is used, the recording medium M can be heated radially by infrared radiation from the inkjet head 2 side. This makes it easier for the inkjet head 2 to be heated simultaneously, but compared to a platen heater or the like that heats the back side of the recording medium M, the temperature can be increased without being affected by the thickness of the recording medium M. It should be noted that the primary heating mechanism may also include various fans (e.g., ventilation fans 8) that blow warm air or air at the same temperature as the ambient temperature onto the recording medium M to dry the ink on the recording medium M.

[0149] The platen heater can heat the recording medium M via the platen 4 at a position facing the inkjet head 2. The platen heater can heat the recording medium M in a conductive manner and is used as needed in the inkjet recording method.

[0150] Furthermore, the recording apparatus 1 may include a preheater 7 for preheating the recording medium M before the ink adheres to the recording medium M.

[0151] 3.4. Post-heating mechanism

[0152] A post-heating mechanism may be provided for performing a post-heating step of heating the recording medium after the attachment step to dry and fix the ink.

[0153] The heater 5 used in the post-heating mechanism dries and solidifies the ink adhered to the recording medium M. The heater 5 heats the recording medium M, on which the image is recorded, causing water and other substances contained in the ink to evaporate and disperse more rapidly, thereby forming an ink film from the resin contained in the ink. This securely fixes or adheres the ink film to the recording medium M, resulting in excellent film-forming properties and enabling the production of high-quality images in a short period of time. The recording device 1 may also include a cooling fan 6. After the ink recorded on the recording medium M is dried, the cooling fan 6 cools the ink on the recording medium M, thereby forming a well-adhered ink film on the recording medium M.

[0154] 3.5. Others

[0155] Figure 1 The recording device shown is a serial printer that performs recording in a so-called serial method. The recording device may also be a line printer that includes a line head and performs recording in a line method.

[0156] The line head includes a nozzle array with multiple nozzles arranged in the width direction of the recording medium. It has a length greater than the width of the conveyed recording medium M and can record an image across the width of the conveyed recording medium M all at once. Furthermore, recording can be performed with a single scan. Alternatively, after performing a scan while conveying the recording medium once, the recording medium can be returned in the opposite direction of the conveyance direction and conveyed again for another scan, thereby performing recording by performing two or more scans.

[0157] Note that scanning may be performed by a head fixed in position relative to the conveyed recording medium, or by moving the head relative to the recording medium fixed to the platen area.

[0158] It should be noted that the recording device capable of line recording can be the same as the one described above except that the inkjet head 2 is changed to a line head. Figure 1 Specifically, Figure 1 The ventilation fan 8, IR heater 3, platen heater, preheater 7 and other heating mechanisms shown above the inkjet head 2 can be similarly arranged above or below the line head. Figure 1 The heater 5 and / or cooling fan 6 etc. are shown as the post-heating mechanism.

[0159] 3.6. Details of the inkjet head

[0160] Figure 2 1 is a schematic diagram of a cross section of a main part of an inkjet head 100 as an example of an inkjet head included in a recording device. Figure 2In FIG. 1 , the flow of ink from the ink supply chamber 40 to the nozzle hole 12 during the ink ejection operation is schematically shown by dotted arrows.

[0161] It should be noted that in Figure 2 In FIG. 1 , the piezoelectric element 32 is shown in a simplified manner.

[0162] like Figure 2 As shown, the inkjet head 100 includes: a nozzle plate 10 having a plurality of nozzle holes 12; a plurality of pressure chambers 20 respectively connected to the plurality of nozzle holes 12 formed on the nozzle plate 10; a vibration plate 30 for changing the volume of each of the plurality of pressure chambers 20; and an ink supply chamber 40 for supplying ink to the plurality of pressure chambers 20. It should be noted that the plurality of structures are arranged along the depth direction of the drawing. Figure 2 A cross section of one set of their structures is shown.

[0163] The nozzle plate 10 has a plurality of nozzle holes 12 for ejecting ink. These nozzle holes 12 are arranged in a row, and a nozzle surface 13 is formed on the surface of the nozzle plate 10. The number of nozzle holes 12 provided in the nozzle plate 10 is not particularly limited. The diameter of the nozzle hole 12 is the nozzle diameter L.

[0164] The inkjet head 100 includes a pressure chamber substrate 120 for forming the pressure chamber 20. Figure 2 As shown, a communication plate 110, serving as a flow path-forming substrate, is provided between the pressure chamber substrate 120 and the nozzle plate 10. The communication plate 110 partitions the space between the nozzle plate 10 and the pressure chamber substrate 120, thereby forming an ink supply chamber 40 (liquid storage portion), a supply port 126 communicating with the ink supply chamber 40, and a pressure chamber 20 communicating with the supply port 126. In other words, the ink supply chamber 40, the supply port 126, and the pressure chamber 20 are partitioned by the nozzle plate 10, the communication plate 110, the pressure chamber substrate 120, and the vibration plate 30.

[0165] The communication plate 110 has a communication hole 127 that connects the pressure chamber 20 to the nozzle hole 12. An ink ejection port 128 is formed at the end of the communication hole 127 formed on the surface of the communication plate 110 that contacts the nozzle plate 10. The ejection port 128 communicates with the nozzle hole 12 formed in the nozzle plate 10.

[0166] The vibration plate 30 is provided in contact with the pressure chamber substrate 120, and a piezoelectric element 32 is formed in contact with the vibration plate 30. The piezoelectric element 32 is electrically connected to a piezoelectric element drive circuit (not shown) and can operate (vibrate, deform) based on signals from the piezoelectric element drive circuit. The vibration plate 30 is deformed by the operation of the piezoelectric element 32, and the internal pressure of the pressure chamber 20 can be changed by changing the volume of the pressure chamber 20. The piezoelectric element 32 is not particularly limited, and for example, an element that deforms when a voltage is applied (electromechanical conversion element) can be used.

[0167] The inkjet head 100 also includes a compliant sheet 140, which forms part of the ink flow path, and a cover 150 that houses the piezoelectric element 32. A supply port 126 communicating with the ink supply chamber 40 is formed between the compliant sheet 140 and the communication plate 110. The compliant sheet 140 is a flexible elastic film that functions as a damper for ink ejection and circulation, and also functions to suppress damage to the inkjet head 100 by deforming when the ink expands in volume.

[0168] In this embodiment, although the ink supply chamber 40, supply port 126, pressure chamber 20 and communication hole 127 are described separately, they are all liquid flow paths and can be designed arbitrarily as long as the pressure chamber 20 is formed.

[0169] The pressure chamber 20 formed by the above structure refers to the space defined by the connecting plate 110, the pressure chamber substrate 120, and the vibrating plate 30, excluding the supply port 126, the connecting hole 127, the ejection port 128, and the nozzle hole 12. Specifically, the pressure chamber 20 comprises the space opposite the vibrating plate 30, the pressure chamber substrate 120, the connecting plate 110, and other areas that apply pressure to the ink, as well as the space adjacent to this space and having a cross-sectional area equal to that of this space in the direction of ink movement. The volume of the pressure chamber 20 is defined as the above-mentioned volume. Thus, the pressure chamber 20 is defined as a space whose volume changes according to the displacement of the vibrating plate 30, excluding narrow flow paths communicating with this space. The volume of the pressure chamber is preferably 1000 to 4000 pl, more preferably 1500 to 3700 pl, and even more preferably 2000 to 3300 pl. The volume of the pressure chamber refers to the volume of each pressure chamber.

[0170] The distance from the pressure chamber of the inkjet head to the nozzle is the distance from the position at the end of the pressure chamber where the ink flows from the pressure chamber toward the nozzle hole to the tip of the nozzle hole. Figure 2 In the example of the inkjet head, the distance from the pressure chamber to the nozzle is the distance from the pressure chamber 20 to the nozzle hole 12. Figure 2In the example of , it is equal to the sum of the length d1 of the communication plate 110 in the thickness direction and the length of the nozzle plate 10 in the thickness direction.

[0171] The distance from the pressure chamber of the inkjet head to the nozzle is not limited, but is preferably 5 mm or less. Furthermore, it is preferably 0.2 to 4 mm, more preferably 0.5 to 3 mm, more preferably 0.7 to 2 mm, and even more preferably 0.8 to 1.5 mm. A distance from the pressure chamber of the inkjet head to the nozzle within this range is preferred because it provides greater freedom in the design of the pressure chamber and nozzle positions within the inkjet head.

[0172] There is a gap between the pressure chamber of the inkjet head and the nozzle. Figure 2 In the case of such a narrow ink flow path, the following problems are likely to occur.

[0173] When flaky metallic pigments flow through a narrow flow path like a capillary tube, the surface of the scales orients parallel to the direction of ink movement, allowing the metallic pigment to move in this manner. This facilitates ink movement within the flow path, positively impacting ink ejection stability. However, if the metallic pigment is unstable in dispersion, the flaky metallic pigment's surface tends to aggregate and form coarse particles due to the large amounts of overlap. When the flaky metallic pigments are stacked on the surface, forming coarse particles, their surface orientation becomes difficult to align with the direction of ink movement, making them difficult to move. Furthermore, they no longer appear to be flaky. In such cases, the ink composition has difficulty flowing through the nozzle. The flow path from the pressure chamber of the inkjet head to the nozzle is capillary-like, presumably the primary reason for the difficulty in circulating such ink compositions.

[0174] However, since the ink composition used in the recording method of this embodiment contains a metallic pigment treated with a specific phosphorus-based treatment agent, such a decrease in fluidity hardly occurs, and stable discharge can be achieved even at a high discharge frequency.

[0175] Example

[0176] 1. Preparation of inkjet ink composition

[0177] The components listed in Tables 1 to 3 were added to a mixing tank, mixed and stirred, and then filtered to obtain the respective inkjet ink compositions. The numerical values ​​for the components listed in Tables 1 to 3 are expressed in mass % unless otherwise specified. The values ​​for metallic pigments in the tables are expressed in solids mass %.

[0178] Table 1

[0179]

[0180] Table 2

[0181]

[0182] Table 3

[0183]

[0184] The abbreviations used in Tables 1 to 3 and the details of the product ingredients are as follows:

[0185] metallic pigments

[0186] Metallic pigment: This is a pigment produced as follows.

[0187] A release layer was formed by applying an acetone solution of a release resin onto a polyethylene terephthalate (PET) substrate using a roll coater. Next, an aluminum layer was deposited on the release layer in a vacuum deposition apparatus to a thickness corresponding to each example. The film thickness was adjusted by adjusting the deposition amount.

[0188] The PET substrate with the aluminum layer formed thereon was immersed in a tetrahydrofuran (THF) bath and irradiated with ultrasound to peel the aluminum layer from the PET substrate and pulverize it, yielding a dispersion of aluminum particles dispersed in THF. Subsequently, after the THF was removed using a centrifugal separator, an appropriate amount of diethylene glycol diethyl ether was added to the aluminum particles to yield an aluminum pigment suspension with an aluminum concentration of 5%.

[0189] The obtained aluminum pigment suspension (5%, diethylene glycol diethyl ether) was further pulverized using a circulating high-power ultrasonic pulverizer (20 kHz) until the target average particle size was reached, thereby obtaining particles having the sizes (D 50 ) of aluminum pigments.

[0190] Jeffamine M2070 as a poly(oxyethylene / oxypropylene)amine dispersant was then added to the aluminum pigment suspension to give an aluminum concentration of 5%. The suspension was then heat treated at 55°C for 1 hour under ultrasonication to dissolve aggregates and disperse the aluminum pigment into primary particles.

[0191] The following surface treatment agents were added to the aluminum pigment suspension dispersed into primary particles at the mass ratios listed in the table relative to the aluminum pigment concentration. The suspension was then heat-treated at 55°C for 3 hours under ultrasonic irradiation to allow the surface treatment agent to react with the pigment surface. The aluminum dispersion was then heat-treated under various conditions to produce an aluminum dispersion. This yielded an aluminum dispersion with an organic solvent as the liquid medium. It should be noted that in each case, the dispersion was separately removed for verification and centrifuged to remove diethylene glycol diethyl ether. The presence of the diethylene glycol diethyl ether was not confirmed in each case. This suggests that the surface treatment agent had adhered to the metallic pigment. For the aqueous composition examples, the aluminum dispersion was centrifuged to remove the organic solvent and replace it with water, yielding an aluminum dispersion with water as the liquid medium. The aluminum dispersion was then mixed with the other ingredients listed in the table to produce the ink compositions listed in the table.

[0192] resin

[0193] Paraloid B60: Acrylic resin, "Paraloid B60" manufactured by Dow Chemical Company

[0194] Resamine D1030: A water-based urethane resin, manufactured by Dainichi Seika Industries, Ltd.

[0195] organic solvents

[0196] BTGH: Tetraethylene glycol monobutyl ether

[0197] γBL: γ-butyrolactone

[0198] DEDG: Diethylene glycol diethyl ether

[0199] PG: Propylene glycol

[0200] 1,2-Hexanediol

[0201] surface treatment agent

[0202] Cetyl alcohol phosphate: a surface treatment agent represented by the above formula (2), wherein R 2 A mixture of a compound wherein a is 1 and a compound wherein a is 2, which is n-hexadecyl (n-cetyl).

[0203] Octadecyl phosphate: a surface treatment agent represented by the above formula (2), wherein R 2 A mixture of a compound wherein a is 1 and a compound wherein a is 2, which is n-octadecyl.

[0204] Octadecylphosphonate: a surface treatment agent represented by the above formula (1), wherein R 1It is a compound containing n-octadecyl.

[0205] ·Tetracosyl phosphate: It is a surface treatment agent represented by the above formula (2), and R in formula (2) 2 A mixture of a compound wherein a is 1 and a compound wherein a is 2, which are n-tetracosyl.

[0206] Tridecyl phosphate: a surface treatment agent represented by the above formula (2), wherein R 2 A mixture of a compound wherein a is 1 and a compound wherein a is 2, which is n-tridecyl.

[0207] Dodecyl phosphate: It is a surface treatment agent represented by the above formula (2). 2 A mixture of a compound in which a is 1 and a compound in which a is 2, which is n-dodecyl.

[0208] ·FHP: (CHEMINOX FHP-2-OH (trade name), 2-(perfluorohexyl)ethylphosphonic acid, manufactured by Unimatec Co., Ltd.)

[0209] Octadecyltrimethoxysilane

[0210] 2. Measurement and evaluation methods

[0211] 2.1. Shape, etc.

[0212] The volume average particle size of the metallic pigment (D 50 ) was measured using a Microtrac MT-3300 (manufactured by Microtrac-Bel, a laser diffraction-scattering particle size distribution analyzer). The average thickness Z of the metallic pigment was measured using an atomic force microscope using a NanoNavi E-Sweep (manufactured by SII Nanotechnologies). It should be noted that all metallic pigments were flaky.

[0213] 2.2. Gloss evaluation

[0214] As a recording device, a modified SC-S80650 manufactured by Seiko Epson was prepared. The nozzle density of the inkjet head was set to 360 npi, with 360 nozzles. The inkjet head was filled with ink, and the drive waveform of the inkjet head was optimized so that the filled ink could be ejected optimally. Figure 2With this configuration, the distance from the pressure chamber to the nozzle was set to 1 mm, and the pressure chamber volume was set to 2900 pl. During recording, the platen heater was controlled so that the surface temperature of the recording medium on the platen during recording was set to the heating temperatures (°C) listed in Tables 1 to 3. Simultaneously, the secondary heater was activated for a post-heating process, and the surface temperature of the adhered medium during the post-heating process was set to 50°C. A polyvinyl chloride film (Mactac 5829R, manufactured by Mactac) was used as the adhered medium for recording.

[0215] The ink adhesion amount in the recording pattern during recording was set to 3 mg / inch 2 , the recording resolution was set to 1440×1440 dpi. A recording test was conducted in this manner. The recorded material thus obtained was placed in a thermostatic chamber (temperature 40°C, humidity 100%) for 5 days. The recorded material was then removed from the thermostatic chamber, and the glossiness of the recorded portion of the recorded material at a turning angle of 60° was measured using a MINOLTA MULTI GLOSS 268 gloss meter. The gloss of the solvent-based composition and the water-based composition were evaluated based on the following evaluation criteria. The larger the value, the more excellent the metallic gloss. The evaluation results are shown in Tables 1 to 3.

[0216] Evaluation criteria for solvent-based compositions

[0217] A: Glossiness is 350 or higher.

[0218] B: Glossiness is 300 or more and less than 350.

[0219] C: Glossiness is 270 or more and less than 300.

[0220] D: Glossiness is less than 270.

[0221] Evaluation criteria for aqueous compositions

[0222] A: Glossiness is 250 or more.

[0223] B: The glossiness is 200 or more and less than 250.

[0224] C: Glossiness is 150 or more and less than 200.

[0225] D: Glossiness is less than 150.

[0226] 2.3. Evaluation of ejection stability

[0227] After the recording device was placed in a constant temperature room, the above-mentioned recording test was continuously carried out for 5 hours under the conditions of a temperature of 40°C and a humidity of 80%. After recording, a nozzle inspection was performed to confirm the occurrence of poor nozzle ejection, that is, no ejection or landing position deviation. For landing position deviation, a case where the nozzle is deviated from the normal position by more than 30% of the distance between the nozzles is considered defective. Then, based on the following evaluation criteria, the solvent-based composition and the water-based composition were evaluated respectively. This recording test is a test for confirming the ejection stability during recording. The evaluation results are shown in Tables 1 to 3.

[0228] Evaluation criteria for solvent-based compositions

[0229] A: The number of nozzles with ejection failure is less than 1% of the total number of nozzles.

[0230] B: The number of nozzles with ejection failure is 1% or more and less than 3% of the total number of nozzles.

[0231] C: The number of nozzles with ejection failure is 3% or more relative to the total number of nozzles.

[0232] Evaluation criteria for aqueous compositions

[0233] A: The number of nozzles with ejection failure is less than 2% of the total number of nozzles.

[0234] B: The number of nozzles with ejection failure is 2% or more and less than 5% of the total number of nozzles.

[0235] C: The number of nozzles with ejection failure is 5% or more relative to the total number of nozzles.

[0236] 2.4. Storage stability evaluation

[0237] The inkjet ink composition prepared above was placed in a spiral tube and placed in a thermostat at 45°C with the cap on for 10 days. The volume average particle size D at 20°C before placement was measured using a particle size distribution analyzer. 50 and the volume average particle size D at 20°C after standing for 5 days 50 The viscosity change rate was calculated and the storage stability was evaluated according to the following evaluation criteria. The evaluation results are shown in 1 to 3.

[0238] Evaluation Benchmarks

[0239] A: Volume average particle size D 50 The increase rate is less than 1%.

[0240] B: Volume average particle size D 50 The increase rate is more than 1% and less than 3%.

[0241] D: volume average particle size D 50 The increase rate exceeded 3%.

[0242] 3. Evaluation results

[0243] A comparison of Examples 1 to 20 with Comparative Examples 1 to 18 shows that the inkjet ink composition according to this embodiment is superior in gloss, discharge stability, and storage stability compared to the inkjet ink compositions according to Comparative Examples 1 to 18 that do not meet the constituent requirements of the inkjet ink composition.

[0244] The ink contains a metallic pigment treated with a compound represented by formula (1) or formula (2), and the volume average particle size D of the metallic pigment is 50 (μm) is 1.0 μm or less, and the volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness of the metallic pigment (Z (μm)) 50 / Z) is 17 or more, the volume average particle size D 50 The ratio of (μm) to the nozzle diameter L (μm) (D 50 All Examples in which the gloss and ejection stability were excellent ( / L) were 0.050 or less.

[0245] In Comparative Examples 1, 2, and 12, the volume average particle size D of the metallic pigment is 50 (μm) is not less than 1.0 μm, the volume average particle size D of the metallic pigment 50 The ratio of (μm) to the nozzle diameter L (μm) (D 50 / L) is not less than 0.050, and the discharge stability is poor.

[0246] In Comparative Examples 3, 4, 5, and 13, the volume average particle size D 50 The ratio of the thickness of the metallic pigment (μm) to the average thickness of the metallic pigment (Z (μm)) 50 / Z) is not above 17, and the gloss is poor.

[0247] In Comparative Examples 6 to 10 and 14 to 17, the inks did not contain the metallic pigment treated with the compound represented by formula (1) or (2), and had poor gloss and ejection stability.

[0248] In Comparative Examples 11 and 18, the volume average particle size D of the metallic pigment is 50 The ratio of (μm) to the nozzle diameter L (μm) (D 50 / L) is not less than 0.050, and the discharge stability is poor.

Claims

1. An inkjet recording method, characterized in that The method comprises a step of depositing an inkjet ink composition by ejecting the inkjet ink composition from an inkjet head having a nozzle diameter L and depositing the inkjet ink composition on a recording medium, wherein the depositing step comprises a primary heating step of heating the recording medium on a platen and depositing the inkjet ink composition on the heated recording medium. The inkjet ink composition comprises a metallic pigment and a liquid medium, The liquid medium comprises one or more selected from the group consisting of organic solvents and water, The metallic pigment is surface-modified by a surface treatment agent. The surface treatment agent comprises one or more selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2), The metallic pigment is a scaly particle. The volume average particle size D of the metallic pigment 50 0.4μm or less, The average thickness Z of the metallic pigment is less than 30 nm, The volume average particle size D 50 The ratio D to the average thickness Z 50 / Z is 17 or more, The metallic pigment is ejected from an inkjet head for recording, The volume average particle size D 50 The ratio D to the nozzle diameter L of the inkjet head 50 / L is less than 0.050, The inkjet head includes a nozzle having the nozzle diameter L and a pressure chamber for applying pressure to the inkjet ink composition to eject the inkjet ink composition from the nozzle, wherein a distance of a flow path through which the inkjet ink composition flows from the pressure chamber to the nozzle is 0.5 mm to 5 mm. (R 1 -)P(O)(OH)2(1) In the above formula (1), R 1 is a hydrocarbon group having 17 or more carbon atoms that may be substituted by a substituent, (R 2 -O-) a P(O)(OH) 3-a (2) In the above formula (2), R 2 Each independently represents a hydrocarbon group having a carbon skeleton having 17 or more carbon atoms which may be substituted by a substituent, and a represents 1 or 2.

2. The inkjet recording method according to claim 1, wherein It is a water-based composition or an organic solvent-based composition.

3. The inkjet recording method according to claim 1 or 2, wherein The ink composition may contain water at a content of 40% by mass or more of the water relative to the total amount of the ink composition, or may contain an organic solvent at a content of 60% by mass or more of the organic solvent relative to the total amount of the ink composition.

4. The inkjet recording method according to claim 1, wherein The volume average particle size D of the metallic pigment 50 It is 0.1 μm or more and 0.4 μm or less.

5. The inkjet recording method according to claim 1, wherein The average thickness Z is 25 nm or less.

6. The inkjet recording method according to claim 1, wherein The nozzle diameter L is 30 μm or less.

7. The inkjet recording method according to claim 1, wherein The content of the surface treatment agent is 1.0% by mass to 50% by mass relative to the total amount of the metallic pigment.

8. The inkjet recording method according to claim 1, wherein The R 1 and R 2 At least any one of them contains an unsubstituted hydrocarbon group.

9. The inkjet recording method according to claim 1, wherein The R 1 and R 2 At least any one of them contains a hydrocarbon group having 17 to 30 carbon atoms.

10. The inkjet recording method according to claim 1, wherein The metallic pigment includes one or more selected from the group consisting of aluminum and aluminum alloys.

11. The inkjet recording method according to claim 1, wherein The content of the liquid medium is 60% by mass or more relative to the total amount of the inkjet ink composition.

12. The inkjet recording method according to claim 1, wherein A secondary heating step is provided after the above-mentioned attachment step.

13. The inkjet recording method according to claim 1, wherein The surface temperature of the recording medium when the ink composition adheres in the primary heating step is 30°C to 50°C.

14. The inkjet recording method according to claim 13, wherein The heating temperature of the primary heating step is 40°C to 50°C.

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