Coating composition

Abstract

Provided is a coating composition containing a coloring material, a resin, an organic solvent, and water which is applied to an object to be coated by an inkjet method, wherein the coating composition has a storage modulus of from 0.1 Pa to 85 Pa, a loss modulus of from 1.0 Pa to 30 Pa, and satisfies formula (1) A×B≤110…(1), where A is the static surface tension and B is the loss tangent.

Description

paint composition

[0001] The present invention relates to a coating composition.

[0002] Inkjet recording is a method of recording characters and images by ejecting small droplets of ink (colored liquid or paint) from tiny nozzles onto a recording medium such as paper. It is widely used as a home printer because it is low noise, the process is simple, and it is easy to make it into a color printer.

[0003] In recent years, inkjet recording has been widely used in commercial printing due to its advantages such as variable printing and compatibility with a wide range of media. Commercial printing involves printing on a wide variety of papers, which can be broadly divided into plain paper and coated paper.

[0004] In addition to paper, direct printing on film and metal is also becoming more common, and the required functions differ from those of paper. In particular, it is extremely difficult to satisfy all the required properties for metal, such as adhesion, ink sagging (image drying), abrasion resistance, light resistance, bleeding, beading, and ejection stability.

[0005] To solve these problems, methods have been proposed, such as applying a material in advance to the recording medium surface to fix the coating composition when an image is formed on the surface with a coating composition such as ink, or heating the surface, etc. However, these proposals require costs, labor hours, and operating facilities, and have not become widely used in terms of labor hours and expenses.

[0006] Furthermore, non-absorbent media such as metals have surface properties different from those of paper, so the coating composition either does not wet and spread and instead coalesces as droplets, or, conversely, wets and spreads too much, resulting in dripping. Therefore, the coating composition needs to be leveled evenly after landing, but doing so results in the generation of mist during dispensing.

[0007] To address this, various coating compositions and coating devices have been proposed. For example, from the viewpoint of improving discharge stability and fixation, there is a technology that uses an aqueous latex liquid composition using a solvent that does not easily evaporate, and a technology that uses a device that discharges a liquid containing the aqueous latex liquid composition (for example, Patent Document 1).

[0008] However, coating compositions used in conventional printers tend to drip on vertical surfaces such as assembled automobile bodies or already assembled, upright substrates (e.g., the sides of cars and trucks), making it difficult to print a satisfactory image. Furthermore, such coating compositions tend to splatter when ejected, making it difficult to create clean dots. Therefore, it is difficult to form a uniformly coated surface on a vertical surface with conventional coating compositions.

[0009] An object of the present invention is to provide a coating composition that can form a highly uniform coated surface even on vertical surfaces.

[0010] In order to solve the above-mentioned problems, one aspect of the present invention is a coating composition which contains a colorant, a resin, an organic solvent, and water and is applied to a substrate by an inkjet system, the coating composition having a storage modulus of 0.1 Pa or more and 85 Pa or less, a loss modulus of 1.0 Pa or more and 30 Pa or less, and which satisfies the following formula (1): A×B≦110 (1) where A is the static surface tension and B is the loss tangent.

[0011] According to one aspect of the present invention, it is possible to provide a coating composition that can form a highly uniform coated surface even on a vertical surface.

[0012] FIG. 1 is a perspective view of a discharge head in a first embodiment of a coating device to which the coating composition of the present invention is applied. FIG. 2 is a cross-sectional view at section S1 in FIG. 1. FIG. 3 is a cross-sectional view of one discharge module of the discharge head. FIG. 4 is an enlarged cross-sectional view of a main part of the discharge module. FIG. 5 is an enlarged view of a holding member of the discharge module. FIG. 6 is a view used to explain printing an aircraft as a printing object (subject to be coated) in a second embodiment of a coating device to which the coating composition of the present invention is applied. FIG. 7 is a perspective view of a second embodiment of a coating device to which the coating composition of the present invention is applied. FIG. 8 is a perspective view of a driving unit in the coating device of FIG.

[0013] <Coating Composition> The coating composition of the present invention contains a colorant, a resin, an organic solvent, and water, and is applied to an object to be coated by an inkjet method.

[0014] <<Coloring Material>> The coloring material is not particularly limited, and pigments and dyes can be used.

[0015] The pigment may be an inorganic pigment or an organic pigment. These may be used alone or in combination of two or more. The pigment may also contain mixed crystals.

[0016] Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, optical interference pigments, and metallic pigments.

[0017] Examples of inorganic pigments that can be used include clay, kaolin, titanium oxide, iron oxide, calcium carbonate, barium sulfate, talc, silica, alumina white, aluminum hydroxide, barium yellow, cadmium red, molybdenum red, chrome yellow, chromium oxide, Prussian blue, cobalt blue, and composite metal oxide pigments, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method.

[0018] Examples of organic pigments that can be used include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, threne pigments, and diketopyrrolopyrrole pigments), dye chelates (e.g., basic dye chelates and acid dye chelates), nitro pigments, nitroso pigments, and aniline black.

[0019] Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

[0020] Specific examples of pigments for black include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (C.I. Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (C.I. Pigment Black 1).

[0021] Furthermore, for color, C.I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 (Red Iron), 1 04, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. Pigment Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38, C.I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63, C.I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

[0022] The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone, or two or more types may be used in combination.

[0023] Examples of dyes include C.I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. Acid Red 52, 80, 82, 249, 254, 289, C.I. Acid Blue 9, 45, 249, C.I. Acid Black 1, 2, 24, 94, C.I. Food Black 1, 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. Reactive Red 14, 32, 55, 79, 249, C.I. Reactive Black 3, 4, 35.

[0024] <<<Content in Coating Composition>>> The content of the colorant in the coating composition is preferably 1% by mass or more and 70% by mass or less, and more preferably 5% by mass or more and 60% by mass or less, based on the total solid content in the coating composition, from the viewpoints of color development, improvement in image density, fixability, discharge stability, and the like.

[0025] <<<Method for Dispersing Colorant>>> Methods for dispersing a colorant in a coating composition include a method of introducing a hydrophilic functional group into the colorant to make it a self-dispersible colorant, a method of dispersing the colorant by coating the surface of the colorant with a resin, and a method of dispersing the colorant using a dispersant.

[0026] As a method for introducing a hydrophilic functional group into a colorant to make it a self-dispersible colorant, for example, a self-dispersible pigment can be used, which is made dispersible in water by adding a functional group such as a sulfonic group or a carboxyl group to a pigment (e.g., carbon).

[0027] As a method for coating the surface of a colorant with a resin and dispersing it, a colorant can be encapsulated in microcapsules and made dispersible in water. This can be referred to as a resin-coated colorant. In this case, it is not necessary for all of the colorant blended into the coating composition to be coated with a resin; uncoated or partially coated colorants may be dispersed in the coating composition as long as the effects of the present invention are not impaired.

[0028] Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a high molecular weight dispersant, such as a surfactant.

[0029] As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the colorant. In addition, nonionic surfactants (T-100, manufactured by Takemoto Yushi Co., Ltd.) and sodium naphthalenesulfonate formalin condensate can also be suitably used as the dispersant. One type of dispersant may be used alone, or two or more types may be used in combination.

[0030] <<<Preparation of Colorant>>> A coating composition can be obtained by mixing a colorant with materials such as water, an organic solvent, etc. Alternatively, a coating composition can be produced by mixing a colorant with other materials such as water or a dispersant to form a colorant dispersion, and then mixing this with materials such as water or an organic solvent.

[0031] The colorant dispersion is obtained by dispersing water, a colorant, a colorant dispersant, and optionally other components, and adjusting the particle size. Dispersion is preferably carried out using a disperser.

[0032] The particle size of the colorant in the colorant dispersion is not particularly limited, but from the viewpoints of the dispersion stability, ejection stability, image density, etc. of the colorant, the volume-based median diameter D50 is preferably 5 nm or more and 800 nm or less, and more preferably 10 nm or more and 300 nm or less. The particle size of the colorant can be measured by a dynamic light scattering method using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac-Bell).

[0033] The content of the colorant in the colorant dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of ejection stability, image density, and the like, the content of the colorant is preferably from 10% by mass to 98% by mass, and more preferably from 20% by mass to 95% by mass, based on the total solid content in the colorant dispersion.

[0034] It is preferable that the colorant dispersion is degassed, if necessary, by filtering out coarse particles using a filter, a centrifugal separator, or the like.

[0035] <<Resin>> The resin contributes to the viscoelasticity of the coating composition. The type of resin contained in the coating composition is not particularly limited and can be appropriately selected depending on the purpose, and examples include polyurethane resin, polyester resin, acrylic resin, polyether resin, polycarbonate resin, acrylic-modified urethane resin, polyester-modified urethane resin, polyolefin resin, epoxy resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, and acrylic silicone resin.

[0036] Resin particles made of these resins may also be used. A coating composition can be obtained by mixing the resin particles in the form of a resin emulsion dispersed in water as a dispersion medium with materials such as a colorant and an organic solvent. The resin particles may be appropriately synthesized or commercially available. These may be used alone or in combination of two or more types of resin particles.

[0037] From the viewpoint of weather resistance and the like, the resin preferably contains a reactive functional group-containing resin.

[0038] The reactive functional group-containing resin is not particularly limited as long as it is a resin containing a reactive functional group, and can be appropriately selected depending on the purpose, and examples thereof include a hydroxyl group, an amino group, an epoxy group, a carboxyl group, an isocyanate group, an alkoxysilyl group, etc. These can be used alone or in combination of two or more.

[0039] The reactive functional group-containing resin preferably contains a hydroxyl group-containing resin from the viewpoint of improving the weather resistance of the coating film formed from the coating composition.

[0040] <<<Hydroxyl Group-Containing Resin>>> The hydroxyl group-containing resin is not particularly limited as long as it is a resin that contains hydroxyl groups, and can be appropriately selected depending on the purpose. Among them, it is preferable to include one of a hydroxyl group-containing acrylic resin and a hydroxyl group-containing polyester resin.

[0041] The hydroxyl group-containing acrylic resin can be produced, for example, by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer by a method known per se, such as a solution polymerization method in an organic solvent or an emulsion polymerization method in water.

[0042] <<<<Hydroxyl Group-Containing Acrylic Resin>>>> The hydroxyl group-containing polymerizable unsaturated monomer is a compound having one or more hydroxyl groups and one or more polymerizable unsaturated bonds per molecule. Examples of the hydroxyl group-containing polymerizable unsaturated monomer include monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms, such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate; ε-caprolactone-modified monoesters of (meth)acrylic acid and dihydric alcohols having 2 to 8 carbon atoms; N-hydroxymethyl(meth)acrylamide; allyl alcohol; and (meth)acrylates having a polyoxyethylene chain terminally terminated with a hydroxyl group. However, in the present invention, monomers corresponding to the polymerizable unsaturated monomer having an ultraviolet-absorbing functional group (xvii) described below should be defined as other polymerizable unsaturated monomers copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer, and are excluded from the hydroxyl group-containing polymerizable unsaturated monomer. These can be used alone or in combination of two or more kinds.

[0043] As other polymerizable unsaturated monomers copolymerizable with the above-mentioned hydroxyl group-containing polymerizable unsaturated monomers, for example, the following monomers (i) to (xx) can be used. These polymerizable unsaturated monomers can be used alone or in combination of two or more.

[0044] (i) Alkyl or cycloalkyl (meth)acrylates: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like.

[0045] (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc.

[0046] (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc.

[0047] (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc.

[0048] (v) Aromatic ring-containing polymerizable unsaturated monomers: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, and the like.

[0049] (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc.

[0050] (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, and the like.

[0051] (viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group.

[0052] (ix) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc.

[0053] (x) Carboxyl group-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc.

[0054] (xi) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylenebis(meth)acrylamide, ethylenebis(meth)acrylamide, adducts of glycidyl (meth)acrylate and amine compounds, and the like.

[0055] (xii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc.

[0056] (xiii) Epoxy group-containing polymerizable unsaturated monomers: glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, allyl glycidyl ether, and the like.

[0057] (xiv) (meth)acrylates having a polyoxyethylene chain with an alkoxy group at the molecular terminal.

[0058] (xv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc.

[0059] (xvi) Polymerizable unsaturated monomers having a phosphoric acid group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene)glycol (meth)acrylate, acid phosphooxypoly(oxypropylene)glycol (meth)acrylate, etc.

[0060] (xvii) Polymerizable unsaturated monomers having an ultraviolet absorbing functional group: 2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2-hydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-methacryloyloxy-2-hydroxypropoxy)benzophenone, 2,2'-dihydroxy-4-(3-acryloyloxy-2-hydroxypropoxy)benzophenone, 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, etc.

[0061] (xviii) Light-stable polymerizable unsaturated monomers: 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and the like.

[0062] (xix) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), and the like.

[0063] (xx) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0064] In this specification, the term "polymerizable unsaturated group" refers to an unsaturated group that can undergo radical polymerization. Examples of such polymerizable unsaturated groups include vinyl groups and (meth)acryloyl groups.

[0065] In addition, in this specification, "(meth)acrylate" means acrylate or methacrylate. "(meth)acrylic acid" means acrylic acid or methacrylic acid. "(meth)acryloyl" means acryloyl or methacryloyl. "(meth)acrylamide" means acrylamide or methacrylamide.

[0066] The proportion of the hydroxyl-containing polymerizable unsaturated monomer used in producing the hydroxyl-containing acrylic resin is preferably within a range of 1 to 50% by mass, more preferably within a range of 2 to 40% by mass, and even more preferably within a range of 3 to 30% by mass, based on the total amount of the monomer components.

[0067] From the viewpoint of weather resistance and the like, the hydroxyl group-containing acrylic resin preferably has a hydroxyl group value in the range of 1 to 150 mgKOH / g, more preferably in the range of 2 to 120 mgKOH / g, and even more preferably in the range of 5 to 100 mgKOH / g.

[0068] From the viewpoints of ejection stability, uniformity of the coated surface, dripping, etc., the acid value of the hydroxyl group-containing acrylic resin is preferably within the range of 1 to 150 mgKOH / g, more preferably within the range of 5 to 100 mgKOH / g, and even more preferably within the range of 5 to 80 mgKOH / g.

[0069] When the hydroxyl group-containing acrylic resin is obtained by emulsion polymerization in water, the emulsion polymerization can be carried out by a conventional method. For example, it can be carried out by emulsion polymerization of a polymerizable unsaturated monomer mixture using a polymerization initiator in the presence of an emulsifier. Anionic emulsifiers and nonionic emulsifiers can be suitably used as the emulsifier.

[0070] Examples of the anionic emulsifier include sodium salts and ammonium salts of alkylsulfonic acid, alkylbenzenesulfonic acid, alkylphosphate, and the like.

[0071] Examples of nonionic emulsifiers include polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, and polyoxyethylene sorbitan monolaurate.

[0072] Also usable are polyoxyalkylene group-containing anionic emulsifiers having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule, and reactive anionic emulsifiers having an anionic group and a radically polymerizable unsaturated group in one molecule. Examples of such reactive anionic emulsifiers include sodium salts of sulfonic acid compounds having a radically polymerizable unsaturated group such as an allyl group, a methallyl group, a (meth)acryloyl group, a propenyl group, or a butenyl group, and ammonium salts of such sulfonic acid compounds.

[0073] The amount of emulsifier used is preferably about 0.1 to 15% by mass, more preferably about 0.5 to 10% by mass, and even more preferably about 1 to 5% by mass, based on the total amount of all monomers used.

[0074] Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butyl peroxylaurate, tert-butylperoxyisopropyl carbonate, tert-butyl peroxyacetate, and diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis(2,4-dimethylamino)benzoate; Examples of the polymerization initiator include azo compounds such as azobis(2-methyl-N-(2-hydroxyethyl)-propionamide), azobis(valeronitrile), azobis(2-methylpropionitrile), azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanobutanoic acid), dimethylazobis(2-methylpropionate), azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], and azobis{2-methyl-N-[2-(1-hydroxybutyl)]-propionamide}; and persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate. These polymerization initiators can be used alone or in combination of two or more.

[0075] Furthermore, if necessary, the above polymerization initiators can be used in combination with reducing agents such as sugars, sodium formaldehyde sulfoxylate, and iron complexes to form redox initiators.

[0076] The amount of the polymerization initiator used is generally preferably within a range of 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total amount of all monomers used. The method of adding the polymerization initiator is not particularly limited and can be appropriately selected depending on the type and amount, etc. For example, the polymerization initiator can be previously added to the monomer mixture or aqueous medium, or can be added all at once or dropwise during polymerization.

[0077] From the viewpoints of ejection stability, uniformity of the coated surface, dripping, etc., the hydroxyl group-containing acrylic resin preferably contains a hydroxyl group-containing acrylic resin having a core / shell structure.

[0078] Here, the "shell portion" refers to the polymer layer present in the outermost layer of the resin particle, the "core portion" refers to the polymer layer present in the inner layer of the resin particle excluding the shell portion, and the "core / shell structure" refers to a structure having the core portion and the shell portion. The core / shell structure is generally a layer structure in which the core portion is completely covered by the shell portion, but depending on the mass ratio of the core portion to the shell portion, the amount of monomer in the shell portion may be insufficient to form a layer structure.

[0079] In such cases, the above-described complete layer structure is not necessary, and the core may be partially coated with the shell, or the core may be partially graft-polymerized with a polymerizable unsaturated monomer, which is a component of the shell. The concept of the multilayer structure in the core / shell structure also applies to the case where a multilayer structure is formed in the core of a hydroxyl group-containing acrylic resin. The core / shell structure can be obtained, for example, by reacting monomer compositions having different compositions in multiple stages.

[0080] When the coating composition of the present invention contains the above-mentioned hydroxyl-containing acrylic resin having a core / shell structure, the content of the hydroxyl-containing acrylic resin having a core / shell structure is preferably in the range of 30 to 100% by mass, more preferably in the range of 40 to 90% by mass, and even more preferably in the range of 50 to 80% by mass, based on the total resin solids content of the hydroxyl-containing acrylic resin, from the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc.

[0081] When the coating composition of the present invention contains the above-mentioned hydroxyl group-containing acrylic resin, the content of the hydroxyl group-containing acrylic resin is preferably in the range of 1 to 70 mass %, more preferably in the range of 2 to 60 mass %, and even more preferably in the range of 3 to 50 mass %, based on the total resin solid content in the coating composition, from the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc.

[0082] In this specification, the term "solid content" refers to non-volatile components such as resins, curing agents, and coloring materials that remain after drying for 1 hour at 110° C. The solid content can be determined, for example, by weighing a sample into a heat-resistant container such as an aluminum foil cup, spreading the sample on the bottom of the container, drying it for 1 hour at 110° C., and weighing the mass of the components remaining after drying.

[0083] In addition, in this specification, the "solid content concentration" means the mass ratio of the solid content in the composition. Therefore, for example, the solid content concentration of the composition can be calculated by weighing out the composition into a heat-resistant container such as an aluminum foil cup, spreading the composition on the bottom of the container, drying it at 110°C for 1 hour, weighing the mass of the components in the composition remaining after drying, and determining the ratio of the mass of the components remaining after drying to the total mass of the composition before drying.

[0084] <<<<<Hydroxyl Group-Containing Polyester Resin>>>> The hydroxyl group-containing polyester resin can be synthesized by a known method, following a standard procedure, by subjecting a polybasic acid and a polyhydric alcohol to an esterification reaction.

[0085] The polybasic acid is a compound having two or more carboxyl groups in one molecule, such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid, and anhydrides thereof. The polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule, such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxypivalic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propanediol, and the like. Examples thereof include diols such as diol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, and hydrogenated bisphenol A; trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, and pentaerythritol; and hydroxycarboxylic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolpentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid.

[0086] Alternatively, monoepoxy compounds such as α-olefin epoxides such as propylene oxide and butylene oxide, and glycidyl esters of synthetic highly branched saturated fatty acids (Cardura E10P, manufactured by HEXION, "Cardura" is a registered trademark) may be reacted with an acid to introduce these compounds into the polyester resin.

[0087] The hydroxyl group-containing polyester resin may be a fatty acid-modified polyester resin modified with a (semi-)drying oil fatty acid such as linseed oil fatty acid, coconut oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, perilla oil fatty acid, hemp oil fatty acid, tall oil fatty acid, or dehydrated castor oil fatty acid. The amount of modification with these fatty acids is generally suitable to be 30% by mass or less in terms of oil length. The hydroxyl group-containing polyester resin may also be partially reacted with a monobasic acid such as benzoic acid.

[0088] The hydroxyl group-containing polyester resin can be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound, an acrylic resin, or the like during or after the preparation of the resin.

[0089] Examples of the fatty acids include coconut oil fatty acids, cottonseed oil fatty acids, hempseed oil fatty acids, rice bran oil fatty acids, fish oil fatty acids, tall oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, tung oil fatty acids, rapeseed oil fatty acids, castor oil fatty acids, dehydrated castor oil fatty acids, and safflower oil fatty acids.

[0090] As the monoepoxy compound, for example, a glycidyl ester of a synthetic highly branched saturated fatty acid (Cardura E10P, manufactured by HEXION) can be suitably used.

[0091] Examples of the polyisocyanate compound include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; and aliphatic diisocyanate compounds such as hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,3-(isocyanatomethyl)cyclohexane. Examples of suitable polyisocyanates include cyclic diisocyanate compounds, aromatic diisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate, organic polyisocyanates themselves such as trivalent or higher polyisocyanates such as lysine triisocyanate, adducts of these organic polyisocyanates with polyhydric alcohols, low-molecular-weight polyester resins, water, and the like, and cyclized polymers (for example, isocyanurates) and biuret-type adducts of these organic polyisocyanates. These polyisocyanate compounds can be used alone or in combination of two or more.

[0092] Furthermore, known methods can be used to modify a hydroxyl group-containing polyester resin with an acrylic resin, and examples of such methods include a method of polymerizing a mixture of a polymerizable unsaturated group-containing polyester resin and a polymerizable unsaturated monomer, and a method of reacting a hydroxyl group- and carboxyl group-containing polyester resin with an acrylic resin.

[0093] From the viewpoint of weather resistance and the like, the hydroxyl value of the hydroxyl group-containing polyester resin is preferably in the range of 1 to 250 mgKOH / g, more preferably in the range of 2 to 200 mgKOH / g, and even more preferably in the range of 5 to 200 mgKOH / g.

[0094] Furthermore, from the viewpoints of ejection stability, uniformity of the coated surface, dripping, etc., the acid value of the hydroxyl group-containing polyester resin is preferably in the range of 1 to 150 mgKOH / g, more preferably in the range of 2 to 100 mgKOH / g, and even more preferably in the range of 2 to 50 mgKOH / g.

[0095] The number average molecular weight of the hydroxyl group-containing polyester resin is preferably within the range of 800 to 100,000, more preferably within the range of 1,000 to 50,000, and even more preferably within the range of 1,200 to 10,000.

[0096] In this specification, the average molecular weight is a value calculated from a chromatogram measured by gel permeation chromatography (GPC) using the molecular weight of standard polystyrene as a reference. For gel permeation chromatography (GPC), "HLC8120GPC" (manufactured by Tosoh Corporation) was used.

[0097] Four columns, "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation), were used, and the conditions were as follows: mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 mL / min, and detector: RI.

[0098] When the coating composition of the present invention contains a hydroxyl group-containing polyester resin, the content of the hydroxyl group-containing polyester resin is preferably in the range of 1 to 70 mass %, more preferably in the range of 2 to 50 mass %, and even more preferably in the range of 3 to 30 mass %, based on the total resin solid content in the coating composition, from the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc.

[0099] <<<Polyurethane Resin>>> Polyurethane resins can be obtained by a conventional method, for example, by reacting a polyol with a polyisocyanate compound. After the reaction, the chain can be extended in the presence of a chain extender, which is a low-molecular-weight compound having at least two active hydrogen atoms per molecule, such as a diol or diamine. The resin can also be modified with an acrylic resin or the like during or after preparation.

[0100] Examples of the polyol include low-molecular-weight dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and hexamethylene glycol, and trihydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol. Examples of high-molecular-weight polyols include polyether polyols, polyester polyols, acrylic polyols, and epoxy polyols. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of polyester polyols include polycondensates of the above-mentioned dihydric alcohols, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol with dibasic acids such as adipic acid, azelaic acid, and sebacic acid, lactone-based ring-opening polymer polyols such as polycaprolactone, and polycarbonate diols. Carboxyl-containing polyols such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid can also be used. The above polyols may be used alone or in combination of two or more kinds.

[0101] Examples of polyisocyanate compounds to be reacted with the above polyols include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; and biuret-type adducts and isocyanurate ring adducts of these polyisocyanates; isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and methylcyclohexane-2,4-(or -2,6-)diisocyanate. Alicyclic diisocyanates such as 1,3-(or 1,4-)di(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, and 1,2-cyclohexane diisocyanate; and biuret-type adducts and isocyanurate ring adducts of these polyisocyanates; xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, aromatic diisocyanate compounds such as 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, (m- or p-)phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, bis(4-isocyanatophenyl)sulfone, isopropylidenebis(4-phenylisocyanate); and polyisocyanates thereof. Examples of suitable isocyanate compounds include biuret-type adducts and isocyanurate ring adducts of isocyanates; polyisocyanates having three or more isocyanate groups in one molecule, such as triphenylmethane-4,4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, and 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate; and biuret-type adducts and isocyanurate ring adducts of these polyisocyanate compounds.

[0102] Examples of diols as chain extenders include ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and cyclohexanediol. Examples of diamines include ethylenediamine, propylenediamine, xylylenediamine, and N-(2-hydroxyethyl)ethylenediamine.

[0103] From the viewpoint of weather resistance and the like, the polyurethane resin preferably has a hydroxyl value in the range of 0 to 250 mgKOH / g, more preferably in the range of 0 to 200 mgKOH / g, and even more preferably in the range of 0 to 150 mgKOH / g.

[0104] Furthermore, from the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc., the acid value of the polyurethane resin is preferably within a range of 1 to 100 mgKOH / g, more preferably within a range of 2 to 50 mgKOH / g, and even more preferably within a range of 2 to 30 mgKOH / g.

[0105] The weight average molecular weight of the polyurethane resin is preferably 3,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more.

[0106] From the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc., the content of the polyurethane resin in the coating composition of the present invention is preferably in the range of 2 to 70 mass %, more preferably in the range of 5 to 50 mass %, and even more preferably in the range of 10 to 40 mass %, based on the total resin solid content in the coating composition.

[0107] <<<Diameter of Resin Particles>>> The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of obtaining good fixability and high image density, it is preferably 50 nm or more and 3,000 nm or less, and more preferably 100 nm or more and 2,500 nm or less. Here, the volume average particle size can be measured, for example, by a dynamic light scattering method using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac-Bell Corporation).

[0108] <<<Resin Content>>> The resin content is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of fixation, etc., it is preferably from 10% to 98% by mass, and more preferably from 20% to 95% by mass, based on the total solid content in the coating composition. Furthermore, in order to adjust the viscoelasticity, the storage modulus and / or loss modulus can be increased by increasing the content, or the storage modulus and / or loss modulus can be decreased by decreasing the content.

[0109] <<Organic Solvent>> The organic solvent used in the coating composition of the present invention is not particularly limited, and examples thereof include alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.

[0110] Specific examples of organic solvents include methanol, ethanol, isopropanol, n-butanol, sec-butanol, isobutanol, 1-hexanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-decanol, benzyl alcohol, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, and triethylene glycol. alcohol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,Alcohols such as 3-pentanediol and petriol; polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol-n-butyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; n-butyl acetate, isobutyl acetate, methyl amyl acetate, ethylene glycol acetate, ester solvents such as diol monobutyl ether and n-butyl propionate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-heptanone, ethyl n-amyl ketone, diisobutyl ketone, isophorone, and cyclohexanone; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate.

[0111] The organic solvent not only functions as a wetting agent but also has good drying properties, so it is preferable to use an organic solvent having a boiling point of 250° C. or less.

[0112] From the viewpoint of uniformity of the coated surface, etc., the organic solvent preferably contains at least one organic solvent selected from n-butanol, 2-ethyl-1-hexanol, ethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol-n-butyl ether.

[0113] <<<Organic Solvent Content>>> The content of the organic solvent in the coating composition is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of drying properties, discharge stability, etc., the content is preferably 3% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less.

[0114] <<Other Components>> Other components may be added to the coating composition as necessary. Examples of other components include a curing agent, an oligomer, a curing catalyst, a surfactant, an antifoaming agent, an antiseptic and antifungal agent, a rust inhibitor, a pH adjuster, a viscosity adjuster, a surface conditioner, an ultraviolet absorber, and a light stabilizer.

[0115] <<<Curing Agent>>> The coating composition of the present invention can contain a curing agent. When the resin contains a reactive functional group-containing resin, the curing agent is a compound that can react with the reactive functional group in the reactive functional group-containing resin and can form a crosslinked structure by the reaction. It is preferable that the reactive functional group in the resin is a hydroxyl group, and the curing agent is a compound that is reactive with the hydroxyl group.

[0116] Specific examples of the curing agent that can be suitably used include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, etc. Among these, from the viewpoint of the hardness and weather resistance of the coating film to be formed, it is preferable that the curing agent contains an amino resin.

[0117] As the amino resin that can be used as a curing agent, a partially methylolated amino resin or a completely methylolated amino resin obtained by the reaction of an amino component with an aldehyde component can be used.

[0118] Examples of the amino component include melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide, etc. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, etc.

[0119] Alternatively, the methylolated amino resins may be partially or completely etherified with an appropriate alcohol, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, or 2-ethylhexanol.

[0120] The amino resin is preferably a melamine resin. As the melamine resin, for example, an alkyl-etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin are partially or completely etherified with the above-mentioned alcohol can be used.

[0121] Suitable examples of the alkyl etherified melamine resin include methyl etherified melamine resins obtained by partially or completely etherifying the methylol groups of partially or completely methylolated melamine resins with methyl alcohol; butyl etherified melamine resins obtained by partially or completely etherifying the methylol groups of partially or completely methylolated melamine resins with butyl alcohol; and methyl-butyl mixed etherified melamine resins obtained by partially or completely etherifying the methylol groups of partially or completely methylolated melamine resins with methyl alcohol and butyl alcohol.

[0122] From the viewpoint of the uniformity of the coated surface to be formed, the weight average molecular weight of the melamine resin is preferably in the range of 400 to 6,000, more preferably 500 to 5,000, and even more preferably 500 to 4,000.

[0123] The melamine resin may be a commercially available product, such as "Cymel 202," "Cymel 203," "Cymel 238," "Cymel 251," "Cymel 303," "Cymel 323," "Cymel 324," "Cymel 325," "Cymel 327," "Cymel 350," "Cymel 385," "Cymel 1156," "Cymel 1158," "Cymel 1116," and "Cymel 1130" (all manufactured by Allnex Japan, "Cymel" is a registered trademark), "U-Ban 120," "U-Ban 20HS," "U-Ban 20SE60," "U-Ban 2021," "U-Ban 2028," and "U-Ban 28-60" (all manufactured by Mitsui Chemicals, Inc., "U-Ban" is a registered trademark).

[0124] The above-mentioned melamine resins can be used either alone or in combination of two or more.

[0125] When the coating composition of the present invention contains the amino resin as a curing agent, the content thereof is preferably within the range of 5 to 60 mass %, more preferably 15 to 50 mass %, and even more preferably 25 to 45 mass %, based on the total resin solid content in the coating composition, from the viewpoint of the uniformity of the formed coated surface, etc.

[0126] The polyisocyanate compound is a compound having at least two isocyanate groups in one molecule, and examples thereof include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, araliphatic polyisocyanate compounds, aromatic polyisocyanate compounds, and derivatives of the polyisocyanate compounds.

[0127] Examples of the aliphatic polyisocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate), isocyanate); and aliphatic triisocyanate compounds such as 2-isocyanatoethyl 2,6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

[0128] Examples of alicyclic polyisocyanate compounds include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name: isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), and 2-methyl-1,3-cyclohexylene diisocyanate. alicyclic diisocyanate compounds such as 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylenebis(4,1-cyclohexanediyl)diisocyanate (common name: hydrogenated MDI), and norbornane diisocyanate; 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)- 2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2-(3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2-isocyanatoethyl)-

[0033] Examples of the alicyclic triisocyanate compounds include alicyclic triisocyanate compounds such as 2-isocyanatoethyl-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, and 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane.

[0129] Examples of the aromatic aliphatic polyisocyanate compound include aromatic aliphatic diisocyanate compounds such as methylenebis(4,1-phenylene)diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; and aromatic aliphatic triisocyanate compounds such as 1,3,5-triisocyanatomethylbenzene.

[0130] Examples of aromatic polyisocyanate compounds include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and 2,4-tolylene diisocyanate (common name: 2,4-TD4,4').

[0131] Furthermore, examples of derivatives of polyisocyanate compounds include dimers, trimers, biurets, allophanates, uretdione, uretoimine, isocyanurates, oxadiazinetrione, polymethylene polyphenyl polyisocyanates (crude MDI, polymeric MDI), crude TDI, and the like of the above-mentioned polyisocyanate compounds.

[0132] The above polyisocyanate compounds and derivatives thereof may be used alone or in combination of two or more kinds.

[0133] As the polyisocyanate compound, from the viewpoint of the uniformity of the formed coating surface, it is preferable to use at least one selected from aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and derivatives thereof, and it is more preferable to use an aliphatic polyisocyanate compound and / or a derivative thereof.

[0134] As the aliphatic polyisocyanate compound and / or its derivative, it is preferable to use an aliphatic diisocyanate compound and / or its isocyanurate, and it is more preferable to use hexamethylene diisocyanate and / or its isocyanurate.

[0135] The blocked polyisocyanate compound that can be used as a curing agent is a compound in which the isocyanate group of the above polyisocyanate compound is blocked with a blocking agent.

[0136] Examples of the blocking agent include phenol-based agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; lactam-based agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; aliphatic alcohol-based agents such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, and lauryl alcohol; ether-based agents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, butyl lactate, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate ... alcohol-based solvents such as hydroxyethyl methacrylate; oxime-based solvents such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexane oxime; active methylene-based solvents such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, and methylthiophenone mercaptans such as acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetic amide, stearic acid amide, benzamide, and other acid amides; imides such as succinimide, phthalic acid imide, and maleic acid imide; amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazoles such as imidazole and 2-ethylimidazole;Examples of the azole compounds include urea-based compounds such as urea, thiourea, ethyleneurea, ethylenethiourea, and diphenylurea; carbamate ester-based compounds such as N-phenylphenylcarbamate; imine-based compounds such as ethyleneimine and propyleneimine; sulfite-based compounds such as sodium bisulfite and potassium bisulfite; and azole-based compounds. Examples of the azole-based compounds include pyrazole or pyrazole derivatives such as pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-phenylimidazole; and imidazoline derivatives such as 2-methylimidazoline and 2-phenylimidazoline.

[0137] Among these, preferred blocking agents include oxime-based blocking agents, active methylene-based blocking agents, pyrazole, and pyrazole derivatives.

[0138] When blocking (reacting with a blocking agent), a solvent can be added as needed. The solvent used in the blocking reaction is preferably one that is not reactive with isocyanate groups, and examples thereof include ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and N-methyl-2-pyrrolidone (NMP).

[0139] When the coating composition of the present invention contains the above-mentioned blocked polyisocyanate compound as a curing agent, the content of the blocked polyisocyanate compound is preferably within the range of 5 to 60 mass%, more preferably 15 to 50 mass%, and even more preferably 25 to 45 mass%, based on the total resin solid content in the coating composition, from the viewpoint of the uniformity of the formed coated surface, etc. The above-mentioned curing agents can be used either alone or in combination of two or more.

[0140] By including such a curing agent in the coating composition of the present invention, the weather resistance of the coating film formed from the coating composition can be improved.

[0141] <<<Oligomer>>> The coating composition of the present invention may contain an oligomer.

[0142] From the viewpoint of the uniformity of the coated surface to be formed, the weight average molecular weight of the oligomer is preferably in the range of 200 to 2,000, more preferably in the range of 300 to 1,600, and even more preferably in the range of 350 to 1,500.

[0143] Specific examples of the oligomer include polyoxyalkylene glycols such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol, and etherified products thereof.

[0144] Commercially available products can be used as the oligomer. Examples of commercially available products include "Sanix GP250," "Sanix GP400," "Sanix GP600," and "Sanix GP100" (all manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glyceryl ether; "Sanix" is a registered trademark), "Sanix PP200," "Sanix PP400," and "Sanix PP1000" (all manufactured by Sanyo Chemical Industries, Ltd., polyoxypropylene glycol), and "PTMG250," "PTMG650," "PTMG1000," and "PTMG2000" (all manufactured by Mitsubishi Chemical Corporation, polyoxytetramethylene glycol).

[0145] When the coating composition of the present invention contains the above-mentioned oligomer, the content of the oligomer is preferably in the range of 0.5 to 30 mass %, more preferably in the range of 1.0 to 20 mass %, and even more preferably in the range of 2.0 to 10 mass %, based on the total resin solid content in the coating composition, from the viewpoint of the uniformity of the coating surface to be formed.

[0146] <<<<Surfactant>>> As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, anionic surfactants and cationic surfactants can be used.

[0147] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among them, those that do not decompose even at high pH are preferred, and examples thereof include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and side-chain both-end modified polydimethylsiloxane, and those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred in that they exhibit good properties as an aqueous surfactant.

[0148] Such surfactants may be synthesized appropriately or commercially available products, such as those available from BYK, Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoei Chemical Co., Ltd.

[0149] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include those represented by the following general formulas (1) and (2), in which a polyalkylene oxide structure is introduced into the Si moiety side chain of dimethylpolysiloxane.

[0150]

[0151] (In general formula (1), m, n, a, and b represent integers. In general formula (2), R and R′ represent an alkyl group or an alkylene group.) As the polyether-modified silicone surfactant, commercially available products can be used, and examples thereof include KF-618, KF-642, KF-643 (all manufactured by Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (all manufactured by Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (all manufactured by Dow Corning Toray Silicones Co., Ltd.), BYK-33, BYK-387 (all manufactured by BYK-Chemie KK, "BYK" is a registered trademark), and TSF4440, TSF4452, TSF4453 (all manufactured by Toshiba Silicones Co., Ltd.).

[0152] As the fluorine-based surfactant, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains are particularly preferred because of their low foaming properties.

[0153] Examples of perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acids, perfluoroalkyl sulfonate salts, etc. Examples of perfluoroalkyl carboxylic acid compounds include perfluoroalkyl carboxylic acids, perfluoroalkyl carboxylate salts, etc.

[0154] Examples of polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group on the side chain include sulfate salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain, and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain.

[0155] Counter ions of the salts in these fluorine-based surfactants include Li, Na, K, NH ４ , N.H. ３ CH ２ CH ２ OH, NH ２ (CH ２ CH ２ OH) ２ , NH(CH ２ CH ２ OH) ３ etc.

[0156] As the fluorine-based surfactant, a compound having 2 to 16 fluorine-substituted carbon atoms is preferred, and a compound having 4 to 16 fluorine-substituted carbon atoms is more preferred.

[0157] Examples of fluorine-based surfactants include perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains.

[0158] Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are preferred because they have little foaming properties, and fluorine-based surfactants represented by the following general formulas (3) and (4) are particularly preferred.

[0159] In the compound represented by the above general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility.

[0160] In the compound represented by the general formula (4), Y is H, or CnF2n+1, where n is an integer from 1 to 6, or CH2CH(OH)CH2-CnF2n+1, where n is an integer from 4 to 6, or CpH2p+1, where p is an integer from 1 to 19, and a is an integer from 4 to 14.

[0161] Commercially available fluorine-based surfactants may be used, such as Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by AGC Seimi Chemical Co., Ltd., "Surflon" is a registered trademark); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC- -431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F-1405, F-474 (all manufactured by DIC Corporation, "Megafac" is a registered trademark); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont); FT-110, FT-250, FT FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Corporation), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (all manufactured by Omnova), and Unidyne DSN-403N (manufactured by Daikin Industries, Ltd., "Unidyne" is a registered trademark). Among these, FS-300 manufactured by DuPont, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Corporation, Polyfox PF-151N manufactured by Omnova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred in terms of achieving good print quality, particularly significant improvements in color development, penetration into paper, wettability, and dye leveling.

[0162] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0163] Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.

[0164] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.

[0165] Examples of cationic surfactants include alkyltrimethylammonium chloride, polyoxyethylene alkylmethylammonium chloride, mono- or di-alkylmethylated ammonium chloride, alkylpentamethylpropylenediamine chloride, alkyldimethylbenzalkonium chloride, and benzethonium chloride.

[0166] These surfactants may be used alone or in combination of two or more.

[0167] The content of the surfactant in the coating composition is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of wettability, discharge stability, uniformity of the coated surface, etc., the content is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less, based on the total solid content in the coating composition.

[0168] <<<Antifoaming Agent>>> The antifoaming agent is not particularly limited, and examples thereof include silicone-based antifoaming agents, polyether-based antifoaming agents, and fatty acid ester-based antifoaming agents. These may be used alone or in combination of two or more. Among these, silicone-based antifoaming agents are preferred because of their excellent foam-breaking effect.

[0169] <<<Antiseptic and Antirust Agent>>> The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

[0170] <<<<Rust Inhibitor>>> The rust inhibitor is not particularly limited, and examples thereof include acid sulfites and sodium thiosulfate.

[0171] <<<pH Adjusting Agent>>> The pH adjusting agent is not particularly limited as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

[0172] <<<Viscosity Adjuster>>> The coating composition of the present invention may contain a viscosity adjuster.

[0173] Specific examples of the viscosity modifier include silica-based fine powders, mineral-based viscosity modifiers, barium sulfate fine powder, polyamide (polyamide)-based viscosity modifiers such as fatty acid amides, polyamides, acrylamides, long-chain polyaminoamides, aminoamides, and salts thereof (e.g., phosphates), aminoplast-based viscosity modifiers such as hydrophobically modified ethoxylate aminoplasts, organic resin fine particle viscosity modifiers, diurea-based viscosity modifiers, urethane association-type viscosity modifiers, polyacrylic acid-based viscosity modifiers (also called alkali-swelling viscosity modifiers), and cellulose-based viscosity modifiers.

[0174] From the viewpoint of drip resistance, the viscosity modifier is preferably a mineral-based viscosity modifier, a polyacrylic acid-based viscosity modifier, a cellulose-based viscosity modifier, or a urethane association-type viscosity modifier, and more preferably contains at least one selected from the group consisting of a cellulose-based viscosity modifier, a polyacrylic acid-based viscosity modifier, and a urethane association-type viscosity modifier, with a urethane association-type viscosity modifier being particularly preferred. These viscosity modifiers can be used either alone or in appropriate combination of two or more.

[0175] The mineral viscosity modifier may be an inorganic layered compound viscosity modifier such as a swelling layered silicate having a 2:1 crystal structure.Specific examples include natural or synthetic smectite clay minerals such as montmorillonite, saponite, hectorite, stevensite, beidellite, nontronite, bentonite, and laponite; swelling mica clay minerals such as Na-type tetrasilicic fluorine mica, Li-type tetrasilicic fluorine mica, Na-salt-type fluorine taeniolite, and Li-type fluorine taeniolite; vermiculite; substitution products or derivatives thereof; and mixtures thereof.

[0176] Examples of the urethane associative viscosity modifier include polyether polyol-based urethane prepolymers and urethane-modified polyether viscosity modifiers.

[0177] Commercially available urethane associative viscosity modifiers include the ADEKA NOL series, such as "ADEKA NOL UH-814N," "UH-752," "UH-756VF," "UH-420," and "UH-462" (all manufactured by ADEKA Corporation; "ADEKA NOL" is a registered trademark), "SN Thickener 621N" and "SN Thickener 623N" (all manufactured by San Nopco Limited), "RHEOLATE 244," and "RHEOLATE 278" (all manufactured by Elementis Japan Co., Ltd.).

[0178] Examples of polyacrylic acid viscosity modifiers include sodium polyacrylate and polyacrylic acid-(meth)acrylic acid ester copolymers.

[0179] Examples of commercially available polyacrylic acid viscosity modifiers include "Primal ASE-60," "Primal TT615," and "Primal RM5" (all manufactured by The Dow Chemical Company; "Primal" is a registered trademark), "SN Thickener 613," "SN Thickener 618," "SN Thickener 630," "SN Thickener 634," and "SN Thickener 636" (all manufactured by San Nopco Limited).

[0180] The acid value of the solid content of the polyacrylic acid-based viscosity modifier is preferably 30 mgKOH / g or more and 300 mgKOH / g or less, and more preferably 80 mgKOH / g or more and 280 mgKOH / g or less.

[0181] Examples of cellulose-based viscosity adjusters include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, cellulose nanofiber, etc., and among these, cellulose nanofiber is preferred from the viewpoint of drip resistance, etc.

[0182] The cellulose nanofibers are also called cellulose nanofibrils, fibrillated cellulose, or nanocellulose crystals.

[0183] From the viewpoint of dripping resistance and the like, the cellulose nanofibers preferably have a number average fiber diameter of 2 nm or more and 500 nm or less, more preferably 2 nm or more and 250 nm or less, and even more preferably 2 nm or more and 150 nm or less, and a number average fiber length of preferably 0.1 μm or more and 20 μm or less, more preferably 0.1 μm or more and 15 μm or less, and even more preferably 0.1 μm or more and 10 μm or less.

[0184] The number average fiber diameter and number average fiber length are measured and calculated from an image obtained by, for example, dispersing a sample of cellulose nanofibers diluted with water, casting it on a carbon film-coated grid that has been hydrophilized, and observing the result with a transmission electron microscope (TEM).

[0185] The cellulose nanofibers can be prepared by defibrating a cellulose raw material and stabilizing it in water. Here, the cellulose raw material refers to various forms of materials primarily composed of cellulose, including, for example, pulp (wood pulp, pulp derived from herbs such as jute, Manila hemp, and kenaf); natural cellulose such as cellulose produced by microorganisms; regenerated cellulose obtained by dissolving cellulose in a solvent such as a cuprammonium solution or a morpholine derivative and then spinning it; and fine cellulose obtained by depolymerizing the cellulose raw material by subjecting the cellulose to mechanical treatments such as hydrolysis, alkaline hydrolysis, enzymatic decomposition, explosive treatment, and vibration ball milling.

[0186] Anion-modified cellulose nanofibers can also be used as the cellulose nanofibers. Examples of anion-modified cellulose nanofibers include carboxylated cellulose nanofibers, carboxylmethylated cellulose nanofibers, sulfonic acid group-containing cellulose nanofibers, and phosphate group-containing cellulose nanofibers. The anion-modified cellulose nanofibers can be obtained, for example, by introducing functional groups such as carboxyl groups and carboxylmethyl groups into a cellulose raw material using a known method, washing the resulting modified cellulose to prepare a dispersion of the modified cellulose, and then defibrating this dispersion. The carboxylated cellulose is also known as oxidized cellulose.

[0187] The oxidized cellulose can be obtained, for example, by oxidizing the cellulose raw material in water with an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds, bromides, and iodides, or a mixture thereof.

[0188] Examples of commercially available cellulose nanofibers include Leocrysta (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. and Aurovisco (registered trademark) manufactured by Oji Holdings Co., Ltd.

[0189] By including such a viscosity modifier in the coating composition of the present invention, the transparency, water resistance and finished appearance of the coating film formed from the coating composition can be improved.

[0190] <<<Surface Conditioner>>> The coating composition of the present invention may contain a surface conditioner.

[0191] Examples of surface conditioners include silicone-based surface conditioners, acrylic-based surface conditioners, vinyl-based surface conditioners, and fluorine-based surface conditioners, and among these, it is preferable to contain a silicone-based surface conditioner, from the viewpoint that when used as an undercoat paint composition, the coating properties on the base and the leveling properties of the paint composition are adjusted to improve the finish and coating film properties, and foam-inhibiting or defoaming effects can be expected. The above surface conditioners can be used alone or in appropriate combination of two or more.

[0192] Examples of silicone surface conditioners include organopolysiloxanes such as dimethylpolysiloxane, and modified silicones obtained by modifying organopolysiloxanes. Specific examples of modified silicones include alkyl-modified polysiloxanes, phenyl-modified polysiloxanes, and polyether-modified polysiloxanes. These may be used alone or in combination of two or more.

[0193] Specific examples include dimethylpolysiloxane, methylphenylpolysiloxane, polyether-modified siloxanes such as polyether-modified polydimethylsiloxane and polyether-modified dimethylpolysiloxane, polyester-modified polyalkylsiloxanes such as polyester-modified dimethylpolysiloxane and polyester-modified polydimethylsiloxane, polymethylalkylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyether-modified acrylic group-containing polydimethylsiloxane, polyester-modified acrylic group-containing polydimethylsiloxane, etc. Among these, polyether-modified siloxanes are preferred.

[0194] The weight-average molecular weight of the polyether-modified siloxane is preferably in the range of 400 to 3,000, and particularly preferably in the range of 500 to 2,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0195] Commercially available products can be used as the polyether-modified siloxane, and specific examples include commercially available products such as BYK-345, BYK-347, BYK-348, BYK-349, BYK-UV3500, BYK-3510, BYK-3530, and BYK-3570 (all manufactured by BYK-Chemie Japan KK), and TEGO Wet 245, TEGO Wet 250, TEGO Wet 260, TEGO Wet 270, and TEGO Wet 280 (all manufactured by Evonik Degussa AG; "TEGO" is a registered trademark).

[0196] Examples of surface conditioners other than those mentioned above include silicone-based, acetylene-based, acrylic-based, fluorine-based, and vinyl-based agents other than the polyether-modified siloxanes mentioned above.

[0197] The content of the silicone-based surface conditioner is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of improving the wettability and finish of the coating composition, the content of the silicone-based surface conditioner is preferably within the range of 0.01 to 10 mass%, more preferably 0.3 to 5.0 mass%, and even more preferably 0.5 to 2.0 mass%, based on the total solid content in the coating composition.

[0198] By including such a surface conditioner in the coating composition of the present invention, the coating properties of the coating composition to the substrate and the leveling properties of the coating composition can be improved, and by including such a surface conditioner in the coating composition of the present invention, foam suppression and defoaming effects can be expected.

[0199] <<<Ultraviolet Absorber>>> Examples of ultraviolet absorbers include benzotriazole-based absorbers, triazine-based absorbers, salicylic acid derivative-based absorbers, and benzophenone-based absorbers.

[0200] <<<Light Stabilizer>>> Examples of the light stabilizer include hindered amine light stabilizers.

[0201] <<Water>> The water may be ion-exchanged water, etc. The content of water in the coating composition is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoints of dripping resistance and the uniformity of the formed coated surface, it is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 60% by mass or less.

[0202] <<Solids content concentration of coating composition>> The solids content concentration of the coating composition of the present invention is preferably 10% by mass or more, more preferably 12% by mass or more, and even more preferably 15% by mass or more, from the viewpoints of discharge stability, uniformity of the coated surface, dripping, etc. Furthermore, from the viewpoints of uniformity of the coated surface, discharge stability, etc., the solids content concentration of the coating composition is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 40% by mass or less.

[0203] When the solid content concentration of the coating composition is 10% by mass or more and 60% by mass or less, the coating composition can be discharged stably, the coating surface can be uniform, and dripping can be suppressed.

[0204] <<Substrate>> The substrate is an object to be coated with the coating composition or a recording medium used for recording. The substrate is not particularly limited, and examples thereof include paper, film, cloth, metal, and plastic materials. In addition, the metal may have a surface that has been subjected to a surface treatment.

[0205] A coating film may be further formed on an object that may or may not have been surface-treated. For example, a substrate to be coated may be surface-treated as needed, and a primer coating film may be formed thereon, or an intermediate coating film may be formed on the primer coating film, or a topcoat coating film may be formed on the intermediate coating film. For example, when the substrate to be coated is an automobile body, the primer coating film, intermediate coating film, and topcoat coating film may be formed using known primer, intermediate coating, and topcoat paints that are commonly used in painting automobile bodies.

[0206] <<Inkjet Method>> The inkjet method is a method of ejecting ink (droplets) onto a recording medium to form an image on the surface of the recording medium. In this embodiment, the coating composition is applied to the substrate by the inkjet method. By applying the coating by the inkjet method in this manner, the ejected droplets of the coating composition can be made small, and the coating composition can be applied uniformly to the substrate.

[0207] <<Physical Properties of Coating Composition>> The coating composition has the following physical properties.

[0208] <<<Storage Modulus>>> The storage modulus of the coating composition is 0.1 Pa or more and 85 Pa or less, preferably 0.3 Pa or more and 60 Pa or less, and more preferably 1.5 Pa or more and 40 Pa or less.

[0209] In this specification, the storage modulus is a storage modulus obtained by measurement using a rheometer.

[0210] <<<<Loss Modulus>>> The loss modulus of the coating composition is 1.0 Pa or more and 30 Pa or less, preferably 2.0 Pa or more and 25 Pa or less, and more preferably 3.0 Pa or more and 20 Pa or less.

[0211] In this specification, the loss modulus is a loss modulus obtained by measurement using a rheometer, similar to the storage modulus.

[0212] <<<Static Surface Tension>>> The static surface tension of the coating composition is a static surface tension obtained by measurement using a contact angle meter.

[0213] <<<Loss Tangent>>> The loss tangent of the coating composition is a loss tangent obtained by measurement using a rheometer, similar to the storage modulus.

[0214] <<<<A×B>>> The coating composition satisfies the following formula (1): A×B≦110 (1), preferably A×B≦95, and more preferably A×B≦80, where A is the static surface tension and B is the loss tangent.

[0215] <<<Shear Viscosity>>> The shear viscosity of the coating composition indicates the viscosity at a shear rate of 10 (1 / s) and the viscosity at a shear rate of 10,000 (1 / s).

[0216] <<<<C / D>>>> When the viscosity of the coating composition at a shear rate of 10 (1 / s) is C and the viscosity at a shear rate of 10,000 (1 / s) is D, the following formula (2) is satisfied: 7≦C / D≦155 (2), preferably 8≦C / D≦145, and more preferably 9≦C / D≦135.

[0217] <<<<Other Physical Properties>>> Other physical properties of the coating composition are not particularly limited and can be selected appropriately depending on the purpose. For example, the pH of the coating composition is preferably 6 to 12, and more preferably 7 to 11, from the viewpoints of preventing corrosion of metal members that come into contact with the coating composition and the stability of the coating composition.

[0218] <<Coating Apparatus>> Hereinafter, an embodiment of a coating apparatus to which the coating composition of the present invention is applied will be described with reference to the accompanying drawings. Fig. 1 is a perspective view of a discharge head in a coating apparatus according to a first embodiment, and Fig. 2 is a cross-sectional view taken along section S1 in Fig. 1. Fig. 3 is a cross-sectional view of one discharge module of the discharge head, and Fig. 4 is an enlarged cross-sectional view of a main portion of the discharge module. Fig. 5 is an enlarged view of a holding member of the discharge module.

[0219] The coating apparatus of this embodiment is a coating apparatus that applies a coating composition to an object to be coated by an inkjet method.

[0220] <<<Configuration of Coating Apparatus>>> The coating apparatus of this embodiment has a discharge head 1. The discharge head 1 is equipped with a nozzle 111, a valve body 113, and a piezoelectric element 114. The nozzle 111 discharges a coating composition described below. The valve body 113 opens and closes the nozzle 111. The piezoelectric element 114 drives the valve body 113.

[0221] Specifically, the discharge head 1 has a plurality of discharge modules 100 arranged in one or more rows inside a housing 10. A pressurized liquid (paint composition) is supplied to each discharge module 100 from the outside via a supply port 11, and any paint composition that is not discharged is recovered to the outside via a recovery port 12. In addition, a connector 2 is provided on the housing 10.

[0222] The discharge module 100 includes a nozzle plate 101 having a nozzle 111 formed thereon for discharging the paint composition, a flow path 112 to which the nozzle 111 is connected and through which the pressurized paint composition is supplied, a needle-shaped valve body 113 for opening and closing the nozzle 111, and a piezoelectric element 114 for driving the valve body 113.

[0223] The nozzle plate 101 and the housing 10 are joined together. The flow path 112 is a flow path common to the plurality of ejection modules 100 formed in the housing 10, and as described above, the pressurized liquid (coating composition) is supplied through the supply port 11 and the coating composition is recovered from the recovery port 12.

[0224] An elastic body 113a is provided at the tip of the valve body 113, which reliably closes the nozzle 111 when pressed against the nozzle plate 101. A bearing 121 is provided between the valve body 113 and the housing 10, and a seal member 122 such as an O-ring is provided between the bearing 121 and the valve body 113.

[0225] The piezoelectric element 114 is accommodated in a piezoelectric element accommodating space 123 of the housing 10. The piezoelectric element 114 is held in a central space 115a of a holding member 115, which also serves as a biasing means. The piezoelectric element 114 and the valve body 113 are coaxially connected via a tip end 115b of the holding member 115.

[0226] The holding member 115 has a central space 115 a that houses the piezoelectric element 114 , a tip end 115 b side that is connected to the valve body 113 , and a rear end 115 c side that is fixed by a piezoelectric element fixing shaft 124 attached to the housing 10 .

[0227] The holding member 115 has a holding leaf spring 116 as a biasing means. The holding leaf spring 116 has elastically deformable spring portions 116a and 116b at both ends in the longitudinal direction, which corresponds to the expansion and contraction direction of the piezoelectric element 114. The spring portion 116a is located on the side of the tip portion 115b where the valve body 113 is attached, and the spring portion 116b is located on the side of the rear end portion 115c opposite the side of the tip portion 115b where the valve body 113 is attached.

[0228] The spring portions 116a and 116b have a spring function provided by providing slits 115d alternately in the lateral direction perpendicular to the longitudinal direction and leaving them in a crank shape. In this embodiment, the spring constants of the spring portions 116a and 116b are approximately the same, or include the same ones.

[0229] Here, the length of the central space 115a of the holding member 115 (the axial length of the valve body 113) is shorter than the length of the piezoelectric element 114. Therefore, when the piezoelectric element 114 is fitted into the central space 115a of the holding member 115, the spring portions 116a and 116b of the holding leaf spring 116 are in an extended state.

[0230] As a result, when the piezoelectric element 114 contracts in the direction of arrow a in FIG. 4, the holding plate spring 116 also contracts in the direction of arrow b, and a biasing force acts on the valve body 113 to pull the valve body 113 in the direction in which the nozzle 111 opens.

[0231] Here, when a voltage is applied by the voltage application means 200, the piezoelectric element 114 operates in the D31 mode and drives the valve body 113 in the direction to open the nozzle 111. In other words, when a voltage is applied to the piezoelectric element 114, the valve body 113 is driven in the direction to open the nozzle 111.

[0232] Therefore, when no voltage is applied to the piezoelectric element 114, the valve body 113 closes the nozzle 111, so that even if pressurized liquid (paint composition) is supplied to the flow path 112, the paint composition will not be ejected from the nozzle 111.

[0233] When a voltage is applied to the piezoelectric element 114, the piezoelectric element 114 contracts and pulls the valve body 113 via the holding member 115, causing the valve body 113 to move away from the nozzle 111 and open the nozzle 111. As a result, the pressurized liquid (paint composition) supplied to the flow path 112 is ejected from the nozzle 111.

[0234] In the coating device of this embodiment, it is preferable that the distance between the nozzle 111 and the object to be coated is 5 mm or more.

[0235] In this embodiment, the piezoelectric element 114 is held by a holding member 115 having a biasing means (holding leaf spring 116) in parallel with the piezoelectric element 114. In other words, a biasing means is provided in parallel with the piezoelectric element 114 to bias the valve body 113 in the direction in which the nozzle 111 opens.

[0236] As a result, when a voltage is applied to the piezoelectric element 114 to cause it to contract and move the valve body 113 in the direction in which the nozzle 111 opens, the movement of the valve body 113 to the open position is assisted by the contraction of the retaining leaf spring 116.

[0237] Therefore, the force that moves the valve element 113 increases, the responsiveness of the valve element 113 in moving the nozzle 111 to open is improved, and the variation in the ejection characteristics is reduced.

[0238] In contrast, if a biasing means such as a spiral spring is arranged in series with the piezoelectric element 114, the movement of the biasing means will be independent of the movement of the piezoelectric element, which causes the disadvantage that vibrations in a direction that inhibits the movement of the piezoelectric element will also occur when the piezoelectric element vibrates freely.

[0239] In this embodiment, the piezoelectric element and the biasing means are parallel, and the spring force (biasing force) is generated depending on the shape of the piezoelectric element, so the movement (displacement) of the piezoelectric element and the biasing force can be perfectly synchronized, thereby providing assistance.

[0240] Next, a second embodiment of a coating apparatus to which the coating composition of the present invention is applied will be described with reference to Figures 6 and 7. Figure 6 is a diagram illustrating the coating apparatus according to this embodiment when printing an aircraft as a printing object (subject to be coated), and Figure 7 is a perspective view of the same coating apparatus.

[0241] The coating device 500 is equipped with a linear rail 504 that moves a carriage, which is a moving body equipped with a discharge unit 501 including the above-mentioned discharge head 1, back and forth in a straight line, and an articulated robot 505 that moves the linear rail 504 to a predetermined position as appropriate and holds it in that position.

[0242] The articulated robot 505 is equipped with a robot arm 505a that has multiple joints that allow it to move freely like a human arm, and the tip of the robot arm 505a can be moved freely and positioned accurately.

[0243] The articulated robot 505 may be, for example, a six-axis controlled industrial robot equipped with six axes, i.e., six joints. With a six-axis articulated robot, by teaching information regarding the operation in advance, it is possible to very accurately and quickly position the linear rail 504 at a predetermined position on the printing object 700 (aircraft). The robot 505 is not limited to six axes, and an articulated robot equipped with an appropriate number of axes, such as five axes or seven axes, may be used. The printing object 700 is an example of an object to be coated.

[0244] A fork-shaped support member 524 that branches into two branches is provided on the robot arm 505a of this robot 505, and a vertical linear rail 523a is attached to the tip of the left branch 524a of this support member 524, and a vertical linear rail 523b is attached to the tip of the right branch 524b so that they are parallel to each other.

[0245] The linear rail 504 movably holding the discharge unit 501 is supported at both ends by being bridged over two vertical linear rails 523 a and 523 b .

[0246] The discharge unit 501 includes, for example, a plurality of discharge heads 1 for discharging paint compositions of each color, which will be described later, or a discharge head 1 having a plurality of nozzle rows. The paint compositions of each color are supplied under pressure from a liquid tank 530 to each discharge head 1 or each nozzle row of the discharge head 1 of the discharge unit 501.

[0247] In this coating device 500, a robot 505 moves a linear rail 504 to a position facing a required printing area of ​​a printing object 700. Then, while moving the discharge unit 501 along the linear rail 504 in accordance with print data, the piezoelectric element 114 (or piezoelectric element 134) of each discharge module 100 of the discharge head 1 is driven to perform printing.

[0248] Then, when printing of one line is completed, the vertical linear rails 523a and 523b are driven to move the ejection head 1 of the ejection unit 501 from one line to the next line.

[0249] By repeating this operation, printing can be performed on the desired printing area of ​​the printing object 700.

[0250] Next, a third embodiment of the present invention will be described with reference to Figures 8 and 9. Figure 8 is a perspective view of a coating device according to the third embodiment, and Figure 9 is a perspective view of a drive unit of the device.

[0251] The coating device 500 includes a movable frame unit 802 that is installed facing a printing object 700 having a curved surface, such as a vehicle hood. A movable unit 813 is attached to left and right frame members 810 and 811 that constitute the frame unit 802 so as to span the frame members 810 and 811 and be capable of moving up and down in the vertical direction (Y direction).

[0252] The movable unit 813 is equipped with a drive unit 803 incorporating a motor that is arranged so as to be able to move back and forth horizontally (in the X direction) on the movable unit 813, and a discharge unit 501 that is attached to the drive unit 803 and discharges the paint composition toward the printing object 700.

[0253] The printer also includes a controller 805 that controls the discharge of the coating composition from the discharge unit 501, the reciprocating movement of the drive unit 803, and the elevation of the movable unit 813, and an information processing device 806 such as a PC (personal computer) that issues instructions to the controller 805. A database section (DB section) 807 that records and saves information about the printing object 700, such as its shape and size, is connected to the information processing device 806.

[0254] The frame unit 802 comprises upper, lower, left and right frame members 808, 809, 810, and 811 formed from metal pillars or the like, and left and right leg members 812a and 812b attached horizontally and at right angles to both sides of the lower frame member 809 to enable the frame unit 802 to stand on its own.

[0255] A movable unit 813 spanning the left and right frame members 810 and 811 is configured to be able to move up and down while supporting the drive unit 803 .

[0256] The printing object 700 is placed perpendicular to the direction of ejection of the coating composition (Z direction), that is, facing the plane formed by the upper, lower, left and right frame members 808 , 809 , 810 , and 811 of the frame unit 802 .

[0257] In this case, the printing object 700 can be positioned at a predetermined position where printing is to be performed by, for example, using a chuck attached to the tip of the arm of an articulated arm robot to suction and hold the back side of the printing area of ​​the printing object 700. Using an articulated arm robot makes it possible to accurately position the printing object 700 at the printing position, and also makes it possible to change the posture of the printing object 700 as needed.

[0258] 9, the drive unit 803 is arranged so as to be able to move back and forth in the horizontal direction (X direction) on the movable unit 813. The movable unit 813 is composed of a rail 830 arranged horizontally so as to span the left and right frame members 810, 811 of the frame unit 802, a rack gear 831 arranged parallel to the rail 830, a linear guide 832 fitted onto a part of the rail 830 and moving while sliding, a pinion gear unit 833 connected to the linear guide 832 and meshing with the rack gear 831, a motor 834 with a reducer 836 that rotates and drives the pinion gear unit 833, and a rotary encoder 835 for detecting the printing point position.

[0259] By driving the motor 834 (forward or reverse), the discharge unit 501 is moved rightward or leftward along the movable unit 813. The drive unit 803 functions as a drive mechanism for the discharge unit 501 in the X direction. Limit switches 37a and 37b are attached to both sides of the housing of the reducer 836.

[0260] The discharge unit 501 includes a plurality of discharge heads 1 for discharging paint compositions of each color, which will be described later, or a discharge head 1 having a plurality of nozzle rows. The paint compositions of each color are supplied under pressure from an ink tank to each discharge head 1 or each nozzle row of the discharge head 1 of the discharge unit 501.

[0261] In this coating device 500 , the movable unit 813 is moved in the Y direction, and the discharge unit 501 is moved in the X direction, to print a desired image on the printing object 700 .

[0262] As described above, the coating apparatus according to this embodiment uses a coating composition having a storage modulus of 0.1 Pa or more and 85 Pa or less, a loss modulus of 1.0 Pa or more and 30 Pa or less, and a static surface tension A and a loss tangent B that satisfy the relationship A × B ≦ 110. This allows the ratio of the surface tension and the loss tangent of the coating composition to be set within a specified range, maintaining the fluidity of the liquid, and thereby enabling the formation of a highly uniform coated surface by droplet coating.

[0263] Furthermore, as described above, even if the viscosity of the coating composition is high, the coating composition has liquid properties, and the liquid on the surface after coating becomes more mobile in accordance with the ratio of surface tension to loss tangent, so that a highly uniform coated surface can be formed even on metals and surfaces that have been surface-treated.

[0264] In the coating apparatus according to this embodiment, as described above, the viscosity C of the coating composition at a shear rate of 10 (1 / s) and the viscosity D at a shear rate of 10,000 (1 / s) satisfy the relationship 7≦C / D≦155. This makes it possible to suppress the generation of scattering mist when the coating composition is discharged, and at the same time, to suppress dripping.

[0265] As described above, the coating device of this embodiment has the discharge head 1. The discharge head 1 also includes a nozzle 111 that discharges the coating composition, a valve body 113 that opens and closes the nozzle 111, and a piezoelectric element 114 that drives the valve body 113. When a voltage is applied to the piezoelectric element 114, the valve body 113 is driven in the direction in which the nozzle 111 opens. This ensures that a uniformly coated surface is formed on a vertical surface.

[0266] Furthermore, in the coating device of this embodiment, the distance between the nozzle 111 and the object to be coated is 5 mm or more, which reliably prevents the generation of scattering mist when the coating composition is ejected, while also reliably preventing dripping.

[0267] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" are by mass unless otherwise specified. In addition, various tests and evaluations were performed according to the following methods.

[0268] <Production of Hydroxyl-Containing Acrylic Resin> [Production Example 1] A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device was charged with 100 parts of deionized water and 0.5 parts of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), and the mixture was stirred and mixed in a nitrogen stream and heated to 80°C. Next, 10.3 parts of a 1% and 3% aqueous ammonium persulfate solution of the total amount of Monomer Emulsion 1 described below was introduced into the reaction vessel and maintained at 80°C for 15 minutes. Thereafter, the remaining Monomer Emulsion 1 was added dropwise to the reaction vessel over 3 hours, and after completion of the dropwise addition, the mixture was aged for 1 hour. Thereafter, Monomer Emulsion 2 below was added dropwise over 2 hours, and after aging for 1 hour, 42 parts of a 5.0% aqueous dimethylethanolamine solution was gradually added to the reaction vessel while cooling to 30°C. The mixture was then discharged while being filtered through a 100-mesh nylon cloth to obtain a hydroxyl-containing acrylic resin I having a core / shell structure and an average particle size of 100 nm, an acid value of 32 mg KOH / g, a hydroxyl value of 43 mg KOH / g, and a solids content of 30% by mass. The average particle size was measured at 20°C using a submicron particle size distribution analyzer (COULTER N4 model, manufactured by Beckman Coulter, Inc., "COULTER" is a registered trademark) after dilution with deionized water.

[0269] (Monomer emulsion 1) Monomer emulsion 1 was obtained by mixing and stirring 70 parts of deionized water, 1 part of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), 3 parts of methylenebisacrylamide, 4 parts of styrene, 13 parts of methyl methacrylate, 30 parts of ethyl acrylate, and 20 parts of n-butyl acrylate.

[0270] (Monomer emulsion 2) Monomer emulsion 2 was obtained by mixing and stirring 10 parts of deionized water, 1 part of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), 0.1 parts of ammonium persulfate, 3 parts of styrene, 6 parts of methyl methacrylate, 2 parts of ethyl acrylate, 4 parts of n-butyl acrylate, 10 parts of hydroxyethyl acrylate, and 5 parts of methacrylic acid.

[0271] [Production Example 2] A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device was charged with 100 parts of deionized water and 0.5 parts of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), and the mixture was stirred and mixed in a nitrogen stream and heated to 80°C. Next, 10.3 parts of a 1% and 3% aqueous ammonium persulfate solution of the total amount of Monomer Emulsion 3 below was introduced into the reaction vessel and maintained at 80°C for 15 minutes. Thereafter, the remaining Monomer Emulsion 3 was added dropwise to the reaction vessel over 3 hours, and after completion of the dropwise addition, the mixture was aged for 1 hour. Thereafter, Monomer Emulsion 4 below was added dropwise over 2 hours, and after aging for 1 hour, 42 parts of a 5.0% aqueous dimethylethanolamine solution was gradually added to the reaction vessel while cooling to 30°C. The mixture was then discharged while being filtered through a 100-mesh nylon cloth to obtain a hydroxyl-containing acrylic resin II having a core / shell structure and an average particle size of 100 nm, an acid value of 19 mg KOH / g, a hydroxyl value of 22 mg KOH / g, and a solids content of 30% by mass. The average particle size was measured at 20°C using a submicron particle size distribution analyzer (COULTER N4, manufactured by Beckman Coulter, Inc.) after dilution with deionized water.

[0272] (Monomer emulsion 3) Monomer emulsion 3 was obtained by mixing and stirring 70 parts of deionized water, 1 part of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), 3 parts of acrylamide, 10 parts of styrene, 20 parts of methyl methacrylate, and 27 parts of n-butyl acrylate.

[0273] (Monomer emulsion 4) Monomer emulsion 4 was obtained by mixing and stirring 10 parts of deionized water, 1 part of polyoxyethylene alkyl ether sulfate ester ammonium salt (Aqualon KH-10, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., active ingredient 97%), 0.1 parts of ammonium persulfate, 10 parts of methyl methacrylate, 10 parts of ethyl acrylate, 12 parts of n-butyl acrylate, 5 parts of hydroxyethyl acrylate, and 3 parts of methacrylic acid.

[0274] [Production Example 3] A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, and dropping device was charged with 35 parts of propylene glycol monomethyl ether and heated to 85°C. A mixture of 30 parts of methyl methacrylate, 20 parts of 2-ethylhexyl acrylate, 29 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl acrylate, 6 parts of acrylic acid, 15 parts of propylene glycol monomethyl ether, and 2.3 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) was added dropwise over 4 hours, and the mixture was aged for 1 hour after completion of the dropwise addition. Thereafter, a mixture of 10 parts of propylene glycol monomethyl ether and 1 part of 2,2'-azobis(2,4-dimethylvaleronitrile) was added dropwise over 1 hour, and the mixture was aged for 1 hour after completion of the dropwise addition. Furthermore, 7.4 parts of diethanolamine and 13 parts of propylene glycol monomethyl ether were added to obtain a hydroxyl group-containing acrylic resin III solution with a solids content of 55%. The resulting hydroxyl group-containing acrylic resin III solution had an acid value of 47 mgKOH / g, a hydroxyl value of 72 mgKOH / g, and a weight average molecular weight of 58,000.

[0275] Production Example 4 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device was charged with 82 parts of deionized water and 1.0 part of ammonium salt of α-sulfo-ω-(1-(alkoxy)methyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl) (ADEKA REASOAP SR-1025, active ingredient 25%, manufactured by ADEKA Corporation), and the mixture was stirred and mixed in a nitrogen stream and heated to 75°C. Next, 3% of the total amount of Monomer Emulsion 5 below and 10 parts of a 0.5% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 75°C for 2 hours. Thereafter, the remaining emulsion of monomers and initiator was added dropwise to the reaction vessel over 5 hours, and after completion of the dropwise addition, the mixture was aged for 6 hours. Thereafter, the mixture was cooled to 30°C, and the solids content was adjusted to 40% and the pH to 6.8 using a 5.0% aqueous dimethylethanolamine solution and deionized water. The mixture was then filtered through a 200-mesh nylon cloth to obtain a hydroxyl-containing acrylic resin IV having an average particle size of 140 nm, an acid value of 11 mg KOH / g, a hydroxyl value of 24 mg KOH / g, a weight-average molecular weight of 2,900,000, and a solids content of 40%. The average particle size was measured at 20°C using a submicron particle size distribution analyzer (COULTER N4, manufactured by Beckman Coulter, Inc.) after dilution with deionized water.

[0276] (Monomer Emulsion 5) Monomer emulsion 5 was obtained by mixing and stirring 55 parts of deionized water, 4 parts of sodium polyoxyethylene alkyl ether sulfate (Latemul E-118B, manufactured by Kao Corporation, active ingredient 26%, "Latemul" is a registered trademark), 10 parts of styrene, 53.5 parts of methyl methacrylate, 30 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl acrylate, 1.5 parts of acrylic acid, and 0.2 parts of 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0277] <Production of Hydroxyl-Containing Polyester Resin> [Production Example 5] A reactor equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator was charged with 236 parts of 1,6-hexanediol, 308 parts of hexahydrophthalic anhydride, and 490 parts of Cardura E10P, and the mixture was allowed to react at 100 to 230°C for 3 hours. 230 parts of trimellitic anhydride was then added, and the mixture was allowed to undergo a condensation reaction at 180°C. The mixture was then diluted with propylene glycol monomethyl ether to obtain a solution of hydroxyl-containing polyester resin I with a solids content of 70%. The resulting hydroxyl-containing polyester resin I had an acid value of 50 mgKOH / g, a hydroxyl value of 69 mgKOH / g, and a number average molecular weight of 1,900.

[0278] [Production Example 6] A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator was charged with 113 parts of trimethylolpropane, 131 parts of neopentyl glycol, 80 parts of 1,2-cyclohexanedicarboxylic anhydride, 93 parts of isophthalic acid, and 91 parts of adipic acid. The temperature was raised from 160°C to 230°C over 3 hours, and then a condensation reaction was carried out at 230°C for 4 hours. Next, 33.5 parts of trimellitic anhydride was added, and the mixture was reacted at 170°C for 30 minutes. After that, the mixture was diluted with propylene glycol monomethyl ether to obtain a hydroxyl-containing polyester resin II solution with a solids content of 70%. The resulting hydroxyl-containing polyester resin II had an acid value of 40 mgKOH / g, a hydroxyl value of 161 mgKOH / g, and a number average molecular weight of 1,300.

[0279] <Production of Hydroxyl-Containing Acrylic Urethane Composite Resin> [Production Example 7] A reaction vessel equipped with a thermometer, thermostat, stirrer, and reflux condenser was charged with 24.3 parts of 1,6-hexanediol-based polycarbonate diol (manufactured by Ube Industries, Ltd., ETERNACOLL UH-100, molecular weight approximately 1,000, "ETERNACOLL" is a registered trademark), 35 parts of 2-ethylhexyl acrylate, 0.008 parts of butylhydroxytoluene, and 0.03 parts of dibutyltin laurate. The mixture was heated to 90°C, and 5.7 parts of hydrogenated MDI was added dropwise over 30 minutes. The temperature was then maintained at 90°C, and the reaction was continued until the NCO value reached 1 mg / g or less. 2 parts of n-butyl acrylate and 3 parts of allyl methacrylate were added to the reaction product to obtain a hydroxyl-containing polyurethane resin diluted with acrylic monomers. The urethane resin component of the resulting polyurethane resin had a hydroxyl value of 10 mgKOH / g and a weight average molecular weight of 30,000.

[0280] Thereafter, the following components were placed in a glass beaker and stirred for 15 minutes at 2000 rpm using a disper to produce a preliminary emulsion, which was then subjected to high-pressure treatment at 100 MPa using a high-pressure emulsifier to obtain a polyurethane-containing acrylic monomer emulsion having an average particle size of 290 nm for dispersed particles.

[0281] <Composition of polyurethane-containing acrylic monomer emulsion> Acrylic monomer diluted hydroxyl group-containing polyurethane resin: 70 parts Anionic emulsifier having a polyoxyethylene chain (Newcol 707SF, manufactured by Nippon Nyukazai Co., Ltd., solids concentration 30% by mass, "NEWCOL" is a registered trademark): 4.7 parts Deionized water: 65.3 parts

[0282] 140 parts of the polyurethane-containing acrylic monomer emulsion 1 was transferred to a flask and diluted with 42.5 parts of deionized water. The temperature was raised to 70°C with stirring, and an initiator solution prepared by dissolving 0.2 parts of an emulsion polymerization initiator (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.) in 10 parts of deionized water was added dropwise to the flask over 30 minutes. The mixture was stirred for 2 hours while maintaining the temperature. Subsequently, a solution prepared by dissolving 0.15 parts of "VA-057" in 7.5 parts of deionized water and the monomer emulsion 6 having the following composition was added dropwise over 1.5 hours. The mixture was stirred for 1 hour while maintaining the temperature, and then an initiator solution prepared by dissolving 0.1 parts of "VA-057" in 5 parts of deionized water was added to the flask. The mixture was stirred for 2 hours while maintaining the temperature, and then cooled to obtain an aqueous dispersion of acrylic urethane composite resin I.

[0283] (Monomer Emulsion 6) 8 parts of 2-ethylhexyl acrylate, 3 parts of n-butyl acrylate, 14 parts of methyl methacrylate, 3.5 parts of 2-hydroxyethyl methacrylate, 0.5 parts of acrylic acid, 1 part of allyl methacrylate, 2.0 parts of an anionic emulsifier having a polyoxyethylene chain (Newcol 707SF, manufactured by Nippon Nyukazai Co., Ltd., solids concentration 30% by mass), and 18 parts of deionized water were mixed and stirred to obtain Monomer Emulsion 6. The resulting aqueous dispersion of acrylic urethane composite resin I had a mass solids concentration of 40%, an average particle size of 210 nm, a hydroxyl value of the acrylic resin component of 21.6 mg KOH / g, and an acid value of 5.6 mg KOH / g. The average particle size was measured using a submicron particle size distribution analyzer (manufactured by Beckman Coulter, Inc., "COULTER N4 Model") at 20 °C after dilution with deionized water.

[0284] <Production of Viscosity Modifier> [Production Example 8] 129 parts of deionized water and 0.8 parts of an anionic emulsifier having a polyoxyethylene chain (Newcol 707SF, manufactured by Nippon Nyukazai Co., Ltd., solids concentration 30% by mass) were added to a four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube. After nitrogen substitution, the mixture was maintained at 82°C with stirring. First, a mixture of 5 parts of the following Monomer Emulsion 7 and 0.3 parts of ammonium persulfate dissolved in 3 parts of deionized water was added thereto. After 20 minutes, a solution of the remaining Monomer Emulsion 7 and 0.3 parts of ammonium persulfate dissolved in 3 parts of deionized water was added dropwise over 4 hours to carry out emulsion polymerization. This resulted in an emulsion of viscosity modifier I with a solids content of 30%. The average particle size of viscosity modifier I was 120 nm.

[0285] (Monomer Emulsion 7) Monomer emulsion 7 was obtained by stirring and emulsifying 100 parts of deionized water, 0.5 parts of an anionic emulsifier having a polyoxyethylene chain (Newcol 707SF, manufactured by Nippon Nyukazai Co., Ltd., solid content concentration 30% by mass), 20 parts of styrene, 35 parts of methyl methacrylate, 39 parts of n-butyl acrylate, 5 parts of 1,6-hexanediol diacrylate, and 1 part of acrylic acid.

[0286] <Preparation of colorant dispersion> [Production Example 9] In a container equipped with a stirrer, 18.2 parts of the hydroxyl group-containing acrylic resin III solution obtained in Production Example 3 (solid content 10 parts), 4 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, Carbon MA-100, solid content concentration 100% by mass), 5 parts of barium sulfate pigment (manufactured by Sakai Chemical Industry Co., Ltd., Varifine BF-20, solid content concentration 100% by mass) and 50 parts of deionized water were added and mixed uniformly to form a mixed solution, and 2-(dimethylamino)ethanol was added to the mixed solution to adjust the pH to 7.5. Next, the mixed solution with the adjusted pH was placed in a wide-mouth glass bottle, and glass beads with a diameter of about 1.3 mm were added as a dispersion medium, and the bottle was sealed. The mixture was dispersed for 4 hours using a paint shaker to obtain a colorant dispersion (P-1).

[0287] [Production Examples 10 to 20] Colorant dispersions P-2 to P-12 were obtained in the same manner as in Production Example 9, except that the blending compositions in Production Example 9 were as shown in Table 1 below.

[0288] The values ​​shown in Table 1 refer to solid contents.

[0289]

[0290] The components listed in Table 1 are as follows: "TITANIX JR-903": manufactured by Teika Corporation, titanium oxide, solid content concentration 100% by mass ("TITANIX" is a registered trademark), "Chlorinated Copper Cyanine Blue G-314": manufactured by Sanyo Dye Co., Ltd., phthalocyanine blue pigment, solid content concentration 100% by mass, "PERRIND MAROON 179 229-6440": manufactured by Sun Chemical Co., Ltd., organic perylene pigment, solid content concentration 100% by mass, "YELLOW 2GLMA": manufactured by Dominion Colour Corporation, bismuth vanadate yellow pigment, solid content concentration 100% by mass, "JR-806": manufactured by Teika Corporation, rutile titanium dioxide, solid content concentration 100% by mass, "Variace B-35": manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder, solid content concentration 100% by mass, "MICRO ACE S-3": talc powder manufactured by Nippon Talc Co., Ltd., solid content concentration 100% by mass, "STAPA IL Hydrolan 2153": aluminum flake pigment manufactured by Ecart, solid content concentration 65% by mass, "XIRALLIC T60-10 SW Crystal Silver": metal oxide-coated alumina flake pigment manufactured by Merck & Co., Ltd., solid content concentration 100% by mass ("XIRALLIC" is a registered trademark), "Paliocrom Orange L2800": iron oxide-coated scaly aluminum pigment manufactured by BASF, solid content concentration 65% by mass.

[0291] <Preparation of Coating Composition> [Example 1] Into a stirring mixing vessel were added 77.2 parts (19 parts solids) of the colorant dispersion (P-1) obtained in Production Example 9, 33.3 parts (10 parts solids) of the hydroxyl-containing acrylic resin I having a core / shell structure obtained in Production Example 1, 66.7 parts (20 parts solids) of the hydroxyl-containing acrylic resin II having a core / shell structure obtained in Production Example 2, 21.4 parts (15 parts solids) of the hydroxyl-containing polyester resin I obtained in Production Example 5, 28.6 parts (10 parts solids) of a urethane emulsion (U-coat UX-8100, manufactured by Sanyo Chemical Industries, Ltd., solids concentration 35%, "U-coat" is a registered trademark), and 28.6 parts (10 parts solids) of a polyether polyol (Sanyo Chemical Industries, Ltd., Sannix). 5 parts (solid content: 5 parts) of GP-1000 (number average molecular weight 1,000, solid content 100%), 42.9 parts (solid content: 30 parts) of methylbutyl-mixed etherified melamine resin (manufactured by Allnex Japan Co., Ltd., Cymel 250, solid content 70%), urethane associative viscosity modifier (manufactured by ADEKA Corporation, Adekanol) UH-756VF, solids concentration 32%) 5.6 parts (solids content 1.8 parts), polyacrylic acid-based thickener (Rohm and Haas, Primal ASE-60, solids concentration 28%) 3.6 parts (solids content 1.0 part), silicone-based surface conditioner (BYK, BYK-Chemie, solids concentration 100%) 1 part (solids content 1.0 part), polyether phosphate ester (Kusumoto Chemicals, Disparlon AQ-330, solids concentration 100%, "Disparlon" is a registered trademark) 4.0 parts (solids content 4.0 parts), polyether-modified siloxane (BYK-Chemie Japan, BYK015, solids concentration 100%) 2.0 parts (solids content 2.0 parts), benzotriazole-based ultraviolet absorber (BASF, TINUVIN 1.1 parts (1 part solids) of BASF TINUVIN 123 (solids concentration 100%) light stabilizer (1.0 part solids), 7.5 parts ethylene glycol monobutyl ether, and 7.5 parts n-butanol were uniformly mixed, and 2-(dimethylamino)ethanol and deionized water were added to obtain Coating Composition No. 1, which had a pH of 8.0 and a coating solids concentration of 23.0%. The formulation of Coating Composition No. 1 is shown in Table 2 below.

[0292] [Examples 2 to 31] and [Comparative Examples 1 to 4] Coating compositions No. 2 to No. 35 were obtained in the same manner as in Example 1, except that the formulations in Example 1 were as shown in Tables 2 to 5 below. The formulations of coating compositions No. 2 to No. 35 are shown in Tables 2 to 5 below.

[0293] The values ​​shown in Tables 2 to 5 refer to solid contents.

[0294]

[0295]

[0296]

[0297]

[0298] The components listed in Tables 2 to 5 are as follows: "Cymel 303LF": manufactured by Allnex Corporation, melamine resin, solids concentration 100% by mass, "Bayhydur VPLS2310": manufactured by Sumika Covestro Urethane Co., Ltd., blocked polyisocyanate compound, solids concentration 38% by mass ("Bayhydur" is a registered trademark), "Leocrysta I-2SX": manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., cellulose nanofiber, viscosity modifier, solids concentration 2.0% by mass, "Disparlon AQ-600": manufactured by Kusumoto Chemicals Co., Ltd., polyamide amine salt, solids concentration 20% by mass, "Megafac F-444": manufactured by DIC Corporation, fluorine-based surface conditioner, solids concentration 100% by mass.

[0299] <Storage Modulus, Loss Modulus> The coating composition was left to stand overnight to adjust the temperature to 23°C, the coating composition was placed on a measurement table, the plate was lowered to a specified gap, and then trimmed, and the storage modulus (Pa) and loss modulus (Pa) were measured using a rheometer under the following conditions. A cone plate with a diameter of 50 mm and an angle of 0.5° was used as the plate for the rheometer, and the results of the storage modulus and loss modulus at a stress of 0.1 Pa from the measurement data are shown in Tables 2 to 5.

[0300] [Measurement conditions] Apparatus: Rheometer (MCR302e, manufactured by Anton Paar) Measurement: Dynamic viscoelasticity, stress dependency control Measurement range: Stress 0.1 to 20 Pa (data acquisition at 24 points) Measurement temperature: 23°C Measurement gap: 0.05 mm Frequency: 0.5 Hz <Loss tangent> The ratio (G'' / G') of the storage modulus (G') to the loss modulus (G'') was defined as the loss tangent.

[0301] <Static Surface Tension> Using a surface tensiometer, the static surface tension (mJ / m2) of the coating composition was measured by the platinum ring method under the following conditions. The results are shown in Tables 2 to 5.

[0302] [Measurement conditions] Apparatus: Surface tensiometer (DCAT25, manufactured by Eiko Seiki Co., Ltd.) Measurement: Denuiring method Measurement temperature: 23°C Measurement speed: 0.20 mm / s The value of A x B was calculated, where A is the static surface tension and B is the loss tangent. The results are shown in Tables 2 to 5.

[0303] <Shear Viscosity> The coating composition was left to stand overnight to adjust the temperature to 23°C, then placed on a measuring table, the plate was lowered to the specified gap, and trimmed. The shear viscosity was measured using a rheometer under the following conditions: viscosity (mPa s) at a shear rate of 10 (1 / s) and viscosity (mPa s) at a shear rate of 10,000 (1 / s). A cone plate with a diameter of 50 mm and an angle of 0.5° was used as the plate for the rheometer. The results are shown in Tables 2 to 5.

[0304] [Measurement conditions] Apparatus: Rheometer (MCR302e, manufactured by Anton Paar) Measurement: Shear rate dependency Measurement range: Shear rate 0.01 to 10,000 (1 / s) Measurement temperature: 23°C Measurement gap: 0.05 mm

[0305] <C / D> The value of C / D was calculated by defining the viscosity at a shear rate of 10 (1 / s) as C and the viscosity at a shear rate of 10,000 (1 / s) as D. The results are shown in Tables 2 to 5.

[0306] <Uniformity of coated surface> Using an auto body printer, one scan was printed on an aluminum composite plate, and after coating, the plate was dried and visually inspected for unevenness. A grade of B or higher was considered acceptable based on the following evaluation criteria. The evaluation results are shown in Tables 6 and 7.

[0307] [Evaluation criteria] A: A highly uniform coating surface was formed (no dot marks were visible) B: Slight dot marks were visible (not visible from a distance of 10 cm) C: Dot marks were visible (not visible from a distance of 30 cm) D: Dot marks were visible (visible from a distance of more than 30 cm)

[0308] <Scattered Mist (Mist Generation Rank)> Using an auto body printer, one scan was printed on an aluminum composite panel at a hydraulic pressure of 0.4 MPa, and mist scattered on areas other than the coated surface was checked. According to the following evaluation criteria, a grade of B or higher was considered acceptable. The evaluation results are shown in Tables 6 and 7.

[0309] [Evaluation criteria] A: No mist generated B: Slight mist generated (cannot be seen from a distance of 10 cm) C: Mist generated (cannot be seen from a distance of 30 cm) D: Mist generated (can be seen from a distance of 30 cm)

[0310] <Dripping> Using an auto body printer, lines were printed on an aluminum composite board, and a 5 cm square solid print was made, and the occurrence of dripping was visually evaluated. According to the following evaluation criteria, a grade of B or higher was considered acceptable. The evaluation results are shown in Tables 6 and 7.

[0311] [Evaluation criteria] AA: None at all A: Unevenness due to dripping can be seen within the solid patch at a distance of 0.5 m B: Unevenness due to dripping can be seen within the solid patch at a distance of 1 m C: Unevenness due to dripping can be seen within the solid patch at a distance of 2 m D: Dripping occurs outside the patch

[0312]

[0313]

[0314] As shown in Tables 6 and 7 for Examples 1 to 31, coating compositions in which the storage modulus was 0.1 Pa or more and 85 Pa or less, the loss modulus was 1.0 Pa or more and 30 Pa or less, and the static surface tension A and loss tangent B satisfied the relationship A×B≦110, were good in the evaluations of the uniformity of the coated surface, scattering mist, and dripping.

[0315] In contrast, as shown in Table 7 for Comparative Examples 1 to 4, coating compositions in which the storage modulus was 0.1 Pa or more and 85 Pa or less, the loss modulus was 1.0 Pa or more and 30 Pa or less, and the static surface tension A and the loss tangent B did not satisfy the relationship A×B≦110, were poor in at least one of the evaluations of the uniformity of the coated surface, scattering mist, and dripping.

[0316] The above-disclosed embodiments include, for example, the following aspects.

[0317] (Appendix 1) A coating composition comprising a colorant, a resin, an organic solvent, and water, which is to be applied to a substrate by an inkjet method, the coating composition having a storage modulus of 0.1 Pa or more and 85 Pa or less, a loss modulus of 1.0 Pa or more and 30 Pa or less, and satisfying the following formula (1): A×B≦110 (1), where A is the static surface tension and B is the loss tangent.

[0318] (Appendix 2) A coating composition according to Appendix 1, which satisfies the following formula (2): 7≦C / D≦155... (2), where C is the viscosity at a shear rate of 10 (1 / s) and D is the viscosity at a shear rate of 10,000 (1 / s).

[0319] (Appendix 3) The coating composition according to appendix 1 or 2, wherein the resin comprises a hydroxyl group-containing resin.

[0320] (Appendix 4) The coating composition according to any one of Appendices 1 to 3, further comprising a curing agent.

[0321] (Appendix 5) The coating composition according to any one of Appendices 1 to 4, further comprising a viscosity modifier.

[0322] (Appendix 6) The coating composition according to any one of Appendices 1 to 5, further comprising a surface conditioner.

[0323] (Appendix 7) The coating composition according to any one of Appendices 1 to 6, wherein the solid content of the coating composition is in the range of 10% by mass to 60% by mass.

[0324] (Appendix 8) A coating composition to be applied to a substrate by an inkjet coating device having a discharge head, the discharge head comprising: a nozzle for discharging the coating composition; a valve body for opening and closing the nozzle; and a piezoelectric element for driving the valve body, the valve body being driven in the direction in which the nozzle opens when a voltage is applied to the piezoelectric element, the coating composition being as described in any one of Appendices 1 to 7.

[0325] (Appendix 9) The coating composition according to appendix 8, wherein the distance between the nozzle and the object to be coated is 5 mm or more.

[0326] Although the embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the invention described in the claims.

[0327] This application claims priority based on Japanese Patent Application No. 2024-012198, filed on January 30, 2024, the entire contents of which are incorporated herein by reference.

[0328] REFERENCE SIGNS LIST 1 Discharge head 10 Housing 100 Discharge module 101 Nozzle plate 111 Nozzle 113 Valve body 114 Piezoelectric element 115 Holding member 116 Holding plate spring (biasing means) 123 Piezoelectric element accommodating space 200 Voltage application means 500 Coating device 501 Discharge unit 700 Printing object (coated object)

[0329] Japanese Patent Application Laid-Open No. 2018-154696

Claims

1. A coating composition containing a colorant, a resin, an organic solvent, and water, which is applied to a substrate by inkjet printing, and which has a storage modulus of 0.1 Pa or more and 85 Pa or less, a loss modulus of 1.0 Pa or more and 30 Pa or less, and satisfies the following formula (1): A x B ≦ 110... (1) where A is the static surface tension and B is the loss tangent.

2. The coating composition according to claim 1, which satisfies the following formula (2): 7≦C / D≦155... (2), where C is the viscosity at a shear rate of 10 (1 / s) and D is the viscosity at a shear rate of 10,000 (1 / s).

3. The coating composition according to claim 1, wherein the resin comprises a hydroxyl group-containing resin.

4. The coating composition according to claim 1, further comprising a curing agent.

5. The coating composition according to claim 1, further comprising a viscosity modifier.

6. The coating composition according to claim 1, further comprising a surface conditioner.

7. The coating composition according to claim 1, wherein the solid content of the coating composition is in the range of 10% by mass to 60% by mass.

8. A paint composition according to any one of claims 1 to 7, which is applied to a substrate by an inkjet type coating device having a discharge head comprising: a nozzle for discharging the paint composition; a valve body for opening and closing the nozzle; and a piezoelectric element for driving the valve body, wherein the valve body is driven in the direction in which the nozzle opens when a voltage is applied to the piezoelectric element.

9. The coating composition according to claim 8, wherein the distance between the nozzle and the object to be coated is 5 mm or more.

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