Resin composition for coating and coating

Abstract

Provided is a resin composition for a coating material, which is capable of forming a film having high designability and excellent scratch resistance. (A) is a resin component, (A1) is a polyvinyl acetal resin, (B) is a black material, and (B1) is a composite of a black pigment and a resin. In this case, the resin composition for a coating material according to the present invention contains at least (A) and (B). (A) contains 90 mass% or more of (A1). (B) contains 90 mass% or more of (B1) having a particle diameter of 2 [mu] m to 6 [mu] m (inclusive), and the mass ratio of (B) to 1 of the resin solid content of (A) is 7 to 14 (inclusive).

Description

Technical Field

[0001] The present invention relates to a resin composition for coating and a coating containing the same. Background Art

[0002] Electronic devices such as smartphones, tablets, and computers often have a black coating applied to part or all of their housings (either the exterior or interior) for purposes such as improving design, concealing internal wiring, and shielding light. Alternatively, a black coating may be applied to a portion of the non-visible surface (e.g., the frame) of a glass cover that is positioned and secured to the visible side of a touch panel. In recent years, there has also been a demand for such coating to be applied to part (e.g., the outer edge) or all of electronic device components such as lenses mounted on various camera units, as well as to assembled models such as plastic models, or to components of assembled models in such model kits.

[0003] For example, Patent Document 1 discloses a technique for forming a film by directly applying screen printing made of an insulating material to a housing of a portable electronic device such as a smartphone, or by in-mold molding a film formed after screen printing. Prior art literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-285093 Summary of the Invention Problems to be solved by the invention

[0005] However, with the recent demand for improved design of industrial products, there is a need for black films (such as concave-convex films) that can impart higher design to such products. Furthermore, it is also required to ensure scratch resistance during film production (film formation) and handling.

[0006] The present invention has been made in view of the above circumstances and has as its object to provide a water-based resin composition for coating, which can form a film having excellent design and scratch resistance, and a coating material thereof. Solutions to the problem

[0007] After intensive research, the inventors discovered that by satisfying the following condition a (including a specific composite material within a specified particle size range in the black material), they were able to successfully increase the amount of black material incorporated into the film. As a result, they discovered that, in addition to achieving low gloss (less than 1%), they could effectively form a film with high design appeal, exhibiting even lower reflectance (less than 1.5%) and an even lower L value (less than 15) than conventional films. Furthermore, they discovered that satisfying the following condition b (including a specific resin in the resin component) facilitated the formation of a film with high strength and excellent scratch resistance, even with a small amount of black material added to the film.

[0008] (a) A black material containing a specific composite (a composite of a black pigment and a resin) having a predetermined particle size range is used. (b) Using a resin component containing a specific resin (polyvinyl acetal resin). Although the mechanism of action that causes the above phenomenon is uncertain, it is believed that by including a specific resin in the resin component, a reflective effect that can produce a high film strength even with a small amount of the specific resin can be achieved. This can increase the relative proportion of the black material containing the specific composite in the film, thereby improving the design of the film.

[0009] Based on these new insights, the present inventors have completed the following invention, which solves the above-mentioned problems. Hereinafter, (A) is a resin component, (A1) is a polyvinyl acetal resin, (B) is a black material, (B1) is a composite of a black pigment and resin, and (C) is a diluent.

[0010] According to the present invention, there is provided a composition which is a resin composition for coating. Contains at least (A) and (B), (A) contains 90% by mass or more of (A1), (B) contains 90% by mass or more of (B1) having a particle size of 2 μm to 6 μm, and the mass ratio of (B) to (A):1 is 7 to 14.

[0011] The above-mentioned composition may include the following forms. (B1) preferably contains acrylic resin particles encapsulating carbon black.

[0012] According to the present invention, a coating can be provided. It comprises the above composition and (C), The viscosity at 25° C. measured using a Brookfield viscometer is 1 mPa·s or more and 2000 mPa·s or less.

[0013] The above-mentioned coating material may include the following forms. Can be used for coating model parts. Can be used for coating camera parts. Can be used for coating by spraying. Can be used for coating using the dip coating method. Can be used for coating using the dispenser method. Can be used for application using a brush.

[0014] According to the present invention, there is provided a film, It is a film formed from the above-mentioned coating material, and, The outermost surface of the surface on which the film is formed has a glossiness of less than 1% with respect to incident light at an incident angle of 60° (hereinafter also referred to as "glossiness"), a reflectivity with respect to light of a wavelength of 550 nm (hereinafter also referred to as "reflectivity") of less than 1.5%, and an L value in the CIELAB color system measured by the SCE method of less than 15.

[0015] The above-mentioned film may have the following forms. When the film is required to have a light-shielding property when it is transparent, the optical density of the outermost surface on which the film is formed may be 2 or more. Effects of the Invention

[0016] According to the present invention, there are provided a coating resin composition and a coating material thereof that can form a film having excellent design and scratch resistance. DETAILED DESCRIPTION

[0017] The following describes the best embodiment of the present invention. However, the present invention is not limited to the following embodiment. Without departing from the scope of the present invention, those skilled in the art can make appropriate changes and improvements to the following embodiment based on common knowledge, and these also fall within the scope of the present invention.

[0018] In the numerical ranges described in this specification, the upper limit or lower limit of some numerical ranges may be replaced by the numerical values ​​disclosed in the Examples. In this specification, the content rate or content of each component in the composition means the total content rate or content of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition.

[0019] <Resin composition for coating> A coating resin composition according to a first embodiment of the present invention (hereinafter referred to simply as "composition") comprises (A) a resin component and (B) a black material. (A) comprises a composite material comprising (A1) a polyvinyl acetal resin and (B) a black pigment (B1) having a particle size within a predetermined range and a resin. Compared to films formed from conventional coating resin compositions, films formed from compositions containing (A) and (B) not only exhibit low gloss (less than 1%), but also exhibit ultra-low reflectivity (less than 1.5%) and ultra-low L values ​​(less than 15) that are even lower than conventional coating resin compositions, and exhibit higher film strength. While the reason for this is unclear, the inclusion of (A1), which is tough, flexible, and inherently crosslinkable, in (A), allows the resulting film to exhibit high film strength despite a small amount of incorporation. It is believed that the reflectivity effect (a small amount is sufficient) allows the relative proportion of (B) to be increased in the film, resulting in the effective expression of low gloss, ultra-low reflectivity, and an ultra-low L value.

[0020] -(A)- (A) used to form the composition is a solidifying material for coating the surface and is also an adhesive for (B). Specifically, it comprises a thermoplastic resin. As thermoplastic resins, for example, polyacrylate resins, polyvinyl chloride resins, polyvinyl acetal resins, styrene-butadiene copolymer resins, etc. can be cited. Among them, from the viewpoint of achieving low gloss, ultra-low reflection, ultra-low L value or film strength of the formed film surface, it is preferably contained (A1) polyvinyl acetal resin. Thermoplastic resins can be used alone or in combination of two or more.

[0021] The thermoplastic resin (A) containing (A1) can impart flexibility and toughness to the formed film. Furthermore, since it is cross-linkable, even a small amount of (A1) in the composition (or even in the film) can provide high film strength (scratch resistance).

[0022] (A1) is a polymer having a structural unit having an acetal group in the molecule, preferably a polymer having a structural unit having an acetal group and a structural unit having a hydroxyl group. Examples of (A1) include polyvinyl formal, polyvinyl acetal, polyvinyl propyral, and polyvinyl butyral. More specifically, a polymer represented by the following formula (1) is preferred.

[0023] [Formula 1]

[0024] In formula (1), R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. x represents the content (mol %) of structural units having a vinyl acetal group, and represents the total content (mol %) of structural units derived from acetalized vinyl alcohol. y represents the content (mol %) of structural units derived from vinyl alcohol, and z represents the content (mol %) of structural units derived from vinyl acetate. x and y may be greater than 0, and z may be 0.

[0025] As R 1 , preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and most preferably a propyl group. That is, as (A1), the most preferred group is one having R 1 A polyvinyl butyral resin having a propyl structural unit.

[0026] Polyvinyl butyral resin can be obtained by reacting polyvinyl alcohol (PVA) and butyraldehyde under acidic conditions to form an acetal. When PVA is acetalized, it is difficult to completely acetalize the PVA, so hydroxyl groups remain locally and irreversibly. In addition, PVA is generally produced by saponifying polyvinyl acetate. However, since a small amount of acetyl groups often remain during the saponification process in the PVA production process, acetyl groups or hydroxyl groups generally remain locally and irreversibly in the polyvinyl butyral resin.

[0027] From the perspective of heat resistance, the glass transition temperature (Tg) of the polyvinyl butyral resin can be from 40°C to 130°C, preferably from 60°C to 120°C. A glass transition temperature (Tg) within these ranges can provide advantages such as improved coating film strength during film formation. The glass transition temperature (Tg) can be determined by measuring the heat change using differential scanning calorimetry (DSC).

[0028] In (A1), x, i.e., the content of structural units having acetal groups (hereinafter also referred to as "acetal group content" or "acetalization degree"), is preferably 60 mol% or more, more preferably 65 mol% or more, and further preferably 70 mol% or more, from the viewpoint of the slip properties of the coating surface during coating. Furthermore, from the viewpoint of the dispersibility of the black material in the composition, it is preferably 95 mol% or less, more preferably 90 mol% or less, and further preferably 85 mol% or less. The acetal group content (x) is the molar fraction calculated by dividing the amount of vinyl groups bonded to acetal groups by the total vinyl group content in the main chain. This corresponds to the content (molar %) of structural units containing acetal groups. The amount of vinyl groups bonded to acetal groups (particularly butyral groups) can be measured using JIS K6728 "Testing methods for polyvinyl butyral."

[0029] In (A1), y, i.e., the content of structural units having hydroxyl groups (hereinafter also referred to as "hydroxyl group amount"), is preferably 10 mol% or more, more preferably 15 mol% or more, further preferably 20 mol% or more, and is preferably 50 mol% or less, more preferably 45 mol% or less, further preferably 40 mol% or less, from the viewpoint of adhesion between the coating film and the coated object during film formation. When (A1) contains a structural unit having an acetyl group, its content (hereinafter also referred to as "acetyl group content") is preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and is preferably 15 mol% or less, more preferably 10 mol% or less, and further preferably 8 mol% or less, from the viewpoint of increasing the content of the black material.

[0030] The molecular weight of (A1) is not particularly limited. However, from the perspective of film strength during film formation, it is preferably 8,000 or greater, more preferably 10,000 or greater, even more preferably 15,000 or greater, and even more preferably 20,000 or greater. It is also preferably 300,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less. The molecular weight of (A1) can be determined by calculation.

[0031] (A1) may contain one or more modified polyvinyl acetal resins selected from the group consisting of structural units having an imine structure, structural units having an acid-modified group, and structural units having an amino group or an amide structure, from the viewpoint of improving the cohesive strength of the coating film during coating. When containing a structural unit having an imine structure (structure of a C=N bond), its content is preferably 0.1 mol% or more, more preferably 1 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less. As acid-modified groups, carboxyl groups, sulfonic acid groups, maleic acid groups, phosphoric acid groups, and their salts can be cited. When containing a structural unit having an acid-modified group, its content is preferably 0.01 mol% or more, more preferably 0.05 mol% or more, and preferably 5 mol% or less, more preferably 3 mol% or less. The content of structural units having an imine structure and structural units having an acid-modified group can be measured, for example, by NMR. In the modified polyvinyl acetal resin, the imine structure, acid-modified group, amino group or amide structure can be directly bonded to the carbon atoms of the main chain or side chain constituting the modified polyvinyl acetal resin, or can be bonded through a connecting group such as an alkylene group.

[0032] The molecular weight, structure, hydroxyl group content, etc. of the modified polyvinyl acetal resin (A1) can be appropriately adjusted according to the polymerization degree of the PVA used or the acetalization reaction conditions. (A1) In the above formula (1), the total of x, y, and z is preferably 100 mol%.

[0033] Examples of commercially available products of polyvinyl acetal (butyraldehyde) resins include Sekisui Chemical Co., Ltd.'s trade name: S-LEC's BL (low molecular weight type) series: BL-1, BL-1H, BL-S, BL-2H; BM (medium molecular weight type) series: BM-1, BM-2(Z), BM-5, BM-S(Z); BH (high molecular weight type) series: BH-S, BH-A; BX (heat-resistant type) series: BX-1, BX-5(Z); KS (high heat-resistant type) series: KS-6Z, KS-5Z; and the like. Examples include Kuraray's Mowital series products. The above-mentioned (A1) may be used alone or in combination of two or more.

[0034] (A) can contain thermosetting resin together with (A1).By (A) containing thermosetting resin, it is expected to improve the performance of the adhesion of the coating film and the coated object during film coating.As thermosetting resin, for example, acrylic resin, urethane resin, phenolic resin, melamine resin, urea resin, diallyl phthalate resin, unsaturated polyester resin, epoxy resin, alkyd resin etc. can be enumerated.Thermosetting resin can be used alone or in combination of two or more.When (A) contains thermosetting resin, the mass ratio of thermosetting resin in (A) is, from the viewpoint of the adhesion of the coating film and the coated object during film coating, relative to the resin solid content of (A1): 1, preferably more than 0.1, more preferably more than 0.5, in addition preferably less than 1.5, more preferably less than 1.

[0035] The content (total amount) of (A1) in (A) is preferably 90% by mass or more, more preferably 95% by mass or more. The upper limit is not particularly limited and is 100% by mass. That is, in the first embodiment, (A1) preferably contains 90% by mass or more in 100% by mass of (A).

[0036] The content (total amount) of (A) is not particularly limited, but considering the ratio with other components, it is preferably 1% by mass or more, more preferably 5% by mass or more, relative to the total solid content (100% by mass) of the composition. In addition, from the viewpoint of the coating strength during film coating, it is preferably 25% by mass or less, more preferably 20% by mass or less.

[0037] -(B)- (B) used to form the composition includes (B1) a composite of a black pigment and a resin. The resin constituting the complex with the black pigment is a water-insoluble resin. Examples of such resins include epoxy resins, acrylic resins, urethane resins, styrene resins, vinyl resins, phenolic resins, urea resins, amide resins, melamine resins, and benzoguanamine resins. Among these, acrylic resins or urethane resins are preferred from the perspective of dispersibility in the composition, and acrylic resins are more preferred. These may be used alone or in combination of two or more. In addition, by adding the resin name before the name of beads, the name of some resin particles can be omitted. For example, resin particles made of acrylic resin can also be called acrylic beads.

[0038] The black pigment that forms the composite with the resin is not particularly limited, but carbon black (hereinafter referred to as "CB") is preferably used because it has a strong blackening effect on the composite and is also cost-effective. By using CB, the formed film will be colored, thereby further enhancing the anti-reflection effect and achieving a good antistatic effect.

[0039] Examples of the composite form of the black pigment and the resin include (1) a form in which the black pigment is coated with the resin (including a form in which the black pigment is encapsulated in resin particles), (2) a form in which the resin is bonded to the surface or inside of the black pigment, and (3) a form in which the resin is attached to the surface or inside of the black pigment, or composite forms thereof.

[0040] As a method of covering the surface of the black pigment with a resin, for example, a microcapsule method can be cited, and more specifically, an interfacial polymerization method, an in-situ polymerization method, a liquid solidification coating method (aperture method), a phase separation method from an aqueous solution, a liquid drying method, etc. can be cited. In addition to the microcapsule method, there is also a method of bonding or attaching a resin to a dispersed black pigment. As an example, there is also a method of using a pigment as a core and covering the surface with a plurality of colloidal resin particles. In the case of using a colorant that covers the core of the black pigment with colloidal resin particles, it is preferred that the size of the surrounding resin particles is sufficiently small relative to the core of the pigment. Furthermore, the colloidal resin particles are preferably intended to cover the core of the pigment almost without any gaps. However, it is not excluded that the core of the pigment is directly exposed to the outside.

[0041] (B1) A resin of the same size as the pigment particles may be bonded to the pigment. Alternatively, a black pigment or black dye may be mixed with other thermoplastic resins or thermosetting resins and pulverized to form a composite of the black pigment and the resin.

[0042] In the first embodiment, from the perspective of improving dispersibility in the composition, the composite form is preferably the form (1), i.e., the form of resin particles encapsulating a black pigment. Since the resin particles encapsulating the black pigment encapsulate the pigment within the larger diameter resin particles, compared to the case of directly incorporating a small diameter pigment into the composition, aggregates are less likely to form in the composition, thereby contributing to improved dispersibility.

[0043] The content of the pigment (especially CB) in (B1) is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less.

[0044] The particle size of (B1) is preferably 2 μm or larger, more preferably 3 μm or larger, further preferably 8 μm or smaller, further preferably 6 μm or smaller, and even more preferably 4 μm or smaller. If the particle size is too small, the number of aggregates in the composition increases, making dispersion difficult. If the particle size is too large, the tinting power tends to decrease. The particle size of (B1) is the particle size (D50) at which the integral value, expressed as an integrated (cumulative) percentage in the particle size distribution, reaches 50%.

[0045] The shape of (B1) is not particularly limited, but is preferably spherical from the viewpoint of extinction. In addition, in order to achieve further low gloss, low reflection, and low L value of the film surface formed, it is preferred to use particles (sharp products) with a narrow particle size distribution (CV (Coefficient of Variation) value of, for example, less than 15). The CV value is a value obtained by digitizing the dispersion (deviation of particle size) degree of the mean value (arithmetic mean particle size) of the particle size distribution relative to the particle size. By using these particles, they are uniformly contained in the film, and fine concave-convex patterns are formed on the film surface, making it easy to achieve further low gloss, low reflection, and low L value of the film surface. In order to further reduce the glossiness of the formed film surface, irregular particles may be used as (B1). By using irregular particles as (B1), after the film is formed, the light is repeatedly refracted on the surface and inside of (B1), which can further reduce the glossiness of the film surface.

[0046] (B1) Commercially available products can be used. Examples of products containing urethane beads include Artpearl C800 Black (particle size 6.5 μm, CB content 7.5%, Negami Industries). Examples of products containing acrylic (acrylic copolymer) beads include Artpearl GR-004BK (particle size 3-5 μm, CB content 35-39%, Negami Industries); and RUBCOULEUR 224 (SMD) Black (average particle size 2-3 μm, CB content 18%, Dainichi Seika Industries).

[0047] The content of (B1) in (B) is preferably 90% by mass or more, more preferably 95% by mass or more. The upper limit is not particularly limited and is 100% by mass. That is, in the first embodiment, (B1) preferably contains 90% by mass or more in 100% by mass of (B).

[0048] In the first embodiment, the mass ratio of (B) to the resin solids content of (A) is 7 or more, preferably 8 or more, more preferably 9 or more, and preferably 14 or less, and even more preferably 12 or less. By incorporating (B) within this mass ratio range, low gloss, low reflection, and a low L value can be achieved while maintaining coating film strength.

[0049] The content (total amount) of (B) relative to the total solid content (100% by mass) of the composition is, for example, 60% by mass or more, preferably 65% ​​by mass or more, more preferably 75% by mass or more, and for example, 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less. If the total amount of (B) is less than 60% by mass, problems such as increased gloss and insufficient optical density may occur. If it exceeds 90% by mass, the amount of (A) in the formed film is relatively reduced, resulting in the film sometimes falling off the coated object.

[0050] - (D) Optional ingredients - In addition to the above components ((A) and (B)), the composition may also contain (D) to the extent that the effects of the present invention are not impaired. Examples of (D) include leveling agents, tackifiers, pH adjusters, lubricants, dispersants, defoamers, curing agents, and reaction catalysts. The amount of (D) in the composition is preferably 0 to 100 parts by mass, more preferably 0 to 30 parts by mass, per 100 parts by mass of (A).

[0051] In particular, by adding a curing agent, the hydroxyl groups contained in (A1) can be utilized to promote the crosslinking of (A). Examples of curing agents that react with hydroxyl groups include epoxy compounds, methylol compounds, isocyanate compounds, and titanium chelate compounds. Among them, isocyanate compounds are particularly preferred.

[0052] As the curing agent, the isocyanate compound preferably used is any compound having two or more isocyanate groups in the molecule. For example, at least one of aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, and derivatives thereof can be mentioned. Here, aromatic aliphatic polyisocyanates are polyisocyanates having a structure in which an isocyanate group is bonded to an aromatic ring via an aliphatic carbon atom.

[0053] Examples of aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, triazine diisocyanate, p-phenylene diisocyanate, triphenylmethane triisocyanate, and tris(isocyanatephenyl)phosphorothioate. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, and bis(isocyanatemethyl)norbornane. Examples of aromatic aliphatic polyisocyanates include xylene diisocyanate, tetramethylxylene diisocyanate, and ω,ω'-diisocyanate-1,4-diethylbenzene. Derivatives of polyisocyanate compounds include multimers such as trimers, dimers, and pentamers of the isocyanurate compounds, and modified polyisocyanates such as adducts, allophanates, and biuret compounds obtained by reacting the isocyanate compounds with polyol compounds such as trimethylolpropane.

[0054] From the perspective of adhesion between the coating film and the coated object during film formation, a structure in which the nitrogen atom of the isocyanate group is bonded to an aliphatic carbon atom is preferred, and at least one of aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, and derivatives thereof is preferably used. Among these, from the perspective of adhesion between the coating film and the coated object during film formation and coating film strength, isocyanurates of aliphatic polyisocyanates, xylene diisocyanate, and modified polyisocyanates thereof are preferably used. The curing agent that can be incorporated into the coating material may be used alone or in combination of two or more.

[0055] When a curing agent is added to the composition, the ratio thereof is preferably 10 to 70% by mass relative to 100% by mass of (A). By adding the curing agent within the above range, a film having higher film strength and better scratch resistance can be obtained, and the optical properties of the film surface can be maintained for a long time.

[0056] When a curing agent is added to the composition, a reaction catalyst may be used in combination to promote the reaction between (A) and the curing agent. Examples of the reaction catalyst include ammonia and ammonium chloride. The proportion of the reaction catalyst added to the composition is preferably 0.1 to 10 parts by mass relative to 100 parts by mass of the curing agent.

[0057] The composition according to the first embodiment of the present invention can be prepared (manufactured) by adding (A), (B), and optionally (D), and mixing and stirring. The order of mixing the components is not particularly limited as long as the components are uniformly mixed.

[0058] <Paint> The coating material according to the first embodiment of the present invention is used to form a film composed of the above-mentioned composition on a coating surface, and includes the above-mentioned composition and (C) a diluting solvent.

[0059] -(C)- (C), used to form the coating, is added to dissolve (A) and adjust the viscosity of the entire composition. The use of (C) improves the uniformity of the coating. Furthermore, the ability to appropriately adjust the viscosity of the coating improves the ease of handling and uniformity of the coating thickness when forming a film on a coating surface, thereby significantly contributing to improved design properties of the resulting article.

[0060] As for (C), there is no particular limitation as long as it is a solvent that can dissolve (A) and adjust the viscosity of the coating. Water, an organic solvent, or a mixture of water and an organic solvent can be mentioned. As an organic solvent, for example, methyl ethyl ketone, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, butanol, etc. can be used. (C) can be used alone or in combination of two or more. As for the blending amount, it can be appropriately set to adjust the solid content concentration of the coating.

[0061] The viscosity of the coating has an appropriate range that varies depending on the coating method, so it cannot be generalized. However, the viscosity at 25°C measured using a B-type viscometer is generally in the range of 1 mPa·s to 2000 mPa·s. For example, when the coating method is a spray coating method, it is preferably in the range of 1 mPa·s to 50 mPa·s. When the coating method is a dip coating method, it is preferably in the range of 20 mPa·s to 500 mPa·s. When the coating method is a dispenser coating method, it is preferably in the range of 10 mPa·s to 300 mPa·s. When the coating method is a method using a pen or brush (pen coating method), it is preferably in the range of 100 mPa·s to 2000 mPa·s.

[0062] In spray coating, if the viscosity of the paint is too low, it may not be possible to form a film thick enough to achieve the desired performance. If the viscosity of the paint is too high, problems such as the liquid not flowing out of the nozzle or even failing to atomize may occur. In dip coating, if the viscosity of the paint is too low, it may cause excessive dripping, resulting in unevenness and failure to form a beautiful film. If the viscosity of the paint is too high, it may be difficult to drain when the coated object is lifted from the paint, resulting in burrs, or the surface of the coating may become smooth and glossy. In the case of the dispenser coating method, if the viscosity of the paint is too low, it may cause splattering or dripping, resulting in coating of undesired areas. If the viscosity of the paint is too high, the liquid may not come out of the nozzle, and even if it does, the surface shape tends to be smooth and glossy. In the case of the brush coating method, if the viscosity of the paint is too low, it may cause dripping. If the viscosity of the paint is too high, it may cause white spots.

[0063] The viscosity of the coating varies depending on the components contained in the composition of the coating, that is, the types and molecular weights of (A) and (B) used to form the composition. In addition, when arbitrary components are blended in addition to the above-mentioned (A) and (B), the viscosity varies depending on the types and molecular weights of the arbitrary components. It can be easily adjusted by appropriately determining the amount of (C) in the coating.

[0064] The coating material according to the first embodiment may be a one-component type or a two-component type. When a curing agent is added, the coating material according to the first embodiment may be a two-component type, i.e., a first liquid containing components other than the curing agent and a second liquid containing the curing agent.

[0065] The coating material according to the first embodiment can be used for coating parts of assembly models, coating camera parts, coating by spray coating, coating by dip coating, coating by dispenser coating, or coating by brush coating.

[0066] <Coating method, coated object> The film according to the first embodiment of the present invention is formed by applying the above-mentioned coating material on an object to be coated to form a coating film, and then drying the coating film to form a film.

[0067] As a coating method for the above-mentioned coating, a spraying method (for example, air spraying, airless spraying, electrostatic spraying, etc.) can be adopted. By using the spraying method, even if there are convex parts or staggered layers on the surface of the coated object, a film with uniform thickness and specific properties can be formed on the entire surface.

[0068] The coating conditions for spray coating are preferably: a spray gun aperture of approximately 0.2 to 1.2 mm, a spray volume of approximately 0.2 to 10 g / min, a minimum distance between the spray gun and the coating surface of the object being coated of approximately 30 to 500 mm, a coating speed of approximately 30 to 300 mm / sec, an overlap distance of approximately 1.5 to 10 mm, and an atomizing air pressure of approximately 0.03 to 0.2 MPa. In addition to using a single spray gun, multiple spray guns may be deployed depending on the size of the object to be coated for increased coating efficiency.

[0069] After the above-mentioned coating is applied to the surface of the coated object, the solvent is removed by drying to form a film. If necessary, the coating film may be irradiated with UV light or EB light. In the case where the above-mentioned coating contains a curing agent, the coating film may also be cured by heating the coating film. The heating conditions can be appropriately adjusted according to the thickness of the coating film before heating, the heat resistance of the coated object, the type of (C) used, etc. As an example of the heating conditions, the heating time is from 70°C to 150°C for 1 minute to 30 minutes, and preferably from 100°C to 130°C for 2 minutes to 10 minutes.

[0070] The coating material may be applied by, for example, a dipping method, a dispenser coating method, or a brush coating method, in addition to the spray coating method.

[0071] When the paint is applied using a brush, the thickness of the film formed on the coated surface tends to vary depending on the location of application. However, the resulting film has the same performance as other coating methods. The reason for this is unclear, but it is believed that the unevenness is achieved by the inclusion of an appropriate amount of pigment.

[0072] The coating object (substance to be coated) is not particularly limited, and any object having a hard surface made of glass, resin, metal, ceramic, wood, etc. The shape of the substrate is also not particularly limited, and examples thereof include plate, (hollow) cylindrical, and film-shaped substrates. Examples of the coating object include the following. ·Electrical and electronic equipment such as mobile phones, smartphones, tablet computers, personal computers, personal computer peripherals (keyboards, printers, external keyboards, etc.), watches, audio equipment, and various OA equipment. ·Household appliances such as refrigerators, vacuum cleaners, microwave ovens, televisions, and video equipment. Stairs, floors, tables, chairs, wardrobes, other furniture, and woodworking products. Various building materials, floors, inner and outer walls of buildings, etc. Vehicles such as automobiles and motorcycles, or their parts: specifically, vehicle bodies, interior components (instrument panel, instrument panel, steering wheel, sensor camera bracket (mounted on the upper inside of the windshield), head-up display (HUD), etc.), bumpers, spoilers, door handles, headlights, taillights, aluminum wheels, motorcycle fuel tanks, etc. Optical applications: for example, lenses mounted on various camera units, the inner wall of lens barrels, inner and outer covers of lens units, spacers between lenses, and other camera parts. Glasses, goggles, and similar products. Products of interest made of resin molded products, and parts for assembling the same (e.g., assembly models (plastic models, etc.), parts for assembling the models in the model kits, etc.).

[0073] The thickness of the film formed by the coating involved in the first embodiment can be appropriately adjusted according to the purpose of the coated object, and is not particularly limited. As an example of a preferred film thickness, it is preferably 2 μm or more, more preferably 5 μm or more, preferably 40 μm or less, and more preferably 25 μm or less. In addition, the thickness of the film formed by the coating involved in the first embodiment refers to the height of the portion protruding from the surface of the coated object including (B) through the film. The thickness of the film can be measured using a method based on JIS K 7130.

[0074] <Film Characteristics> The properties of the film formed from the above-mentioned coating material are as follows.

[0075] (Glossiness, reflectivity, L value, optical density, adhesion, coating strength (scratch resistance) The film formed from the above-mentioned coating material preferably has a surface gloss of less than 1%, a reflectance of less than 1.5%, and an L value of less than 15. When the film formed from the above-mentioned coating material is required to have light-shielding properties when transmitted, in addition to the above-mentioned properties (surface gloss of less than 1%, reflectance of less than 1.5%, and L value of less than 15), it is also preferred that the film surface have an optical density of 2 or greater.

[0076] In the case of a structure where the film formed by the above-mentioned coating material is exposed on the outermost surface, the glossiness, reflectivity, L value, and, if necessary, optical density of the film surface are preferably within the above-mentioned ranges, as described above. In the case where another film is coated on top of the film formed by the above-mentioned coating material, the glossiness, reflectivity, L value, and, if necessary, optical density of the surface of the other film, i.e., the outermost surface of the film formed on the coated object, are preferably within the above-mentioned ranges. These surfaces are collectively referred to as the "outermost surface of the film."

[0077] The film formed from the above-mentioned coating material preferably has a glossiness of less than 1%, a reflectance of less than 1.5%, and an L value of less than 15 on the outermost surface of the film. When light-shielding properties are required for the film formed from the above-mentioned coating material when it is transmitted, in addition to the above-mentioned properties (glossiness of less than 1%, reflectance of less than 1.5%, and L value of less than 15 on the outermost surface of the film), it is also preferred that the optical density of the outermost surface of the film be 2 or greater. When the glossiness, reflectance, L value, and, if necessary, optical density of the outermost surface of the film are within the above-mentioned ranges, low glossiness, low reflectance, high blackness, and, if necessary, high light-shielding properties can be achieved on the outermost surface of the film.

[0078] The upper limit of glossiness is more preferably less than 0.7%, and even more preferably less than 0.5%. By adjusting the glossiness within this range, flare and ghosting caused by diffuse reflection of light can be effectively prevented. The lower limit of glossiness is not particularly limited; the lower the better.

[0079] The upper limit of the reflectivity is more preferably less than 1.25%, and even more preferably less than 1.0%. The lower limit of the reflectivity is not particularly limited; the lower the better. By adjusting the reflectivity within the above range, flare and ghosting caused by diffuse reflection of light can be more effectively prevented.

[0080] The upper limit of the L value, i.e., the blackness, is more preferably less than 12, and even more preferably less than 10. The lower limit of the L value is not particularly limited, but from the perspective of achieving a darker appearance, the lower the better. By adjusting the L value within the above range, the blackness is high, the black color stands out, and the design is excellent, making it suitable for use in camera units of mobile phones such as smartphones. The above L value refers to the SCE method in CIE 1976L * a * b * The lightness L* value of the film's outermost surface in the CIELAB colorimetric system. The so-called SCE method eliminates specular reflection, meaning it measures color by removing specular reflection. The SCE method is defined in JIS Z8722(2009). Because the SCE method eliminates specular reflection, the color is closer to what the human eye actually sees. CIE is the abbreviation of Commission internationale de l'Eclairage, which refers to the International Commission on Illumination. CIELAB represents color and is an equal color space recommended in 1976 to measure color differences caused by differences in perception and equipment, and is specified in JIS Z 8781 (2013). The three coordinates of CIELAB are represented by L* value, a* value, and b* value. The L* value represents lightness and is expressed on a scale of 0 to 100. An L* value of 0 means black, and an L* value of 100 means diffuse white. The a* value represents a color between red and green. If the a* value is negative, it means the color is closer to green, and if it is positive, it means the color is closer to red. The b* value represents a color between yellow and blue. If the b* value is negative, it means the color is closer to blue, and if it is positive, it means the color is closer to yellow.

[0081] When the film formed from the above-mentioned coating needs to have light-shielding properties when penetrated, the lower limit of the optical density is more preferably 2.5 or greater, and even more preferably 3.2 or greater. By adjusting the optical density within this range, light-shielding properties can be further improved. There is no particular upper limit on the optical density; the higher the better.

[0082] The above-mentioned glossiness, reflectance, L value and optical density can be measured by the following methods.

[0083] In addition to the aforementioned properties (gloss, reflectivity, L value, and, if desired, optical density), the film formed from the above-mentioned coating preferably has good adhesion to the coating surface. The adhesion of the film formed from the above-mentioned coating to the coating surface, as shown in the adhesion evaluation in the examples described below, preferably shows a residual coating of 90% or more. Furthermore, the film formed from the above-mentioned coating preferably has high film strength. The film strength of the film formed from the above-mentioned coating, as shown in the scratch resistance evaluation in the examples described below, is preferably 10 or less, more preferably 2 or less, and most preferably 0, according to JIS K 5600-5-10 ISO 7784-3.

[0084] Hereinafter, the present invention will be specifically described based on experimental examples (including Examples and Comparative Examples), but the present invention is not limited to these experimental examples. In the following description, "parts" means "parts by mass" and "%" means "mass %".

[0085] [Components of the composition] As A (resin component), the following components were prepared. A1: Polyvinyl acetal resin (S-LEC, Sekisui Chemical Co., Ltd.) A1a:BL-S (Acetalization degree: approximately 72 mol%, hydroxyl group content: approximately 23 mol%, acetyl group content: 4-6 mol%, calculated molecular weight: approximately 23,000, Tg: 66°C) A1b:BM-S(Z) (Acetalization degree: approximately 72 mol%, hydroxyl group content: approximately 23 mol%, acetyl group content: 4-6 mol%, calculated molecular weight: approximately 55,000, Tg: 67°C) A1c:BH-S (Acetalization degree: approximately 72 mol%, hydroxyl group content: approximately 23 mol%, acetyl group content: 4-6 mol%, calculated molecular weight: approximately 66,000, Tg: 67°C) A1d:BX-5(Z) (Acetalization degree: approximately 72 mol%, hydroxyl group content: approximately 27 mol%, acetyl group content: 3 mol% or less, calculated molecular weight: approximately 130,000, Tg: 92°C) A1e:KS-5Z (Acetalization degree: approximately 74 mol%, hydroxyl group content: approximately 25 mol%, acetyl group content: 3 mol% or less, calculated molecular weight: approximately 130,000, Tg: 113°C) A2: Thermosetting acrylic resin (ACRYDIC A801, DIC Corporation) (Resin Tg 67°C, resin solids content 34%, molecular weight 15,000, acid value 1 mgKOH / g, hydroxyl value 5 mgKOH / g)

[0086] As B (black material), the following materials were prepared. B1a: Black acrylic beads (particle size 3-5 μm) (Art Pearl GR-004BK, Negami Industries, CB content 35-39%) B2a: Black acrylic beads (particle size 14-16 μm) (art pearl GR-400BK, Negami Industries, CB content 6-10%) B2b:CB (particle size 150nm) (MHI Black #273, Mikoku Color Co., Ltd., CB content 9.5%) B2c: Composite silica (particle size 3 μm) (becsiaID, Fuji Silicea Chemical Co., Ltd.) B2d: Transparent acrylic beads (particle size 3μm) (UNI powder MNB0320C, ENEOS) B2e: Transparent acrylic beads (particle size 2μm) (UNI powder MNB0220C, ENEOS)

[0087] Art pearl GR-004BK, used in B1a, and art pearl GR-400BK, used in B2a, are both spherical acrylic resin particles encapsulating CB. They are a composite of CB and acrylic resin. MHI Black #273, used in B2b (CB), is a CB dispersion. Of the 18% solids content, 9.5% is CB, and the remaining 8.5% is other compounds. Of the remaining 8.5%, 3% is a copper compound, and 5.5% is acrylic resin. Becsia ID, used in B2c (composite silica), is a composite particle of CB and silica, with a CB / silica ratio of approximately 25 / 75 (by mass).

[0088] As D (optional component), the following components were prepared. D1: Isocyanate compound (Takenate D110N, Mitsui Chemicals, solid content 75%)

[0089] [Object to be painted] As an object to be coated, a smartphone frame (plastic casing) was prepared.

[0090] [Experimental Examples 1 to 20 and 5a to 16a] 1. Preparation of coating The ratio of the total solid content (mass %) to the solid content of each component was the value shown in Tables 1 to 3. The components of each experimental example were added to a mixed solvent of methyl ethyl ketone and butyl acetate in the specified amounts shown in Tables 1 to 3, and the mixture was stirred and mixed to prepare a coating.

[0091] 2-1. Formation of membrane 1 The coating obtained in each experimental example was sprayed onto the object to be coated by the same spraying method as described in the following (3-3-1) Coating Property 1 to form a coating film. The coating film was then heated and dried at 120°C for 3 minutes to form a film 1 formed by the spraying method with an average thickness of 10 μm on the coated surface of the object to be coated.

[0092] 2-2. Formation of Film 2 A coating film was formed on the object using the same brush coating method as described in (3-3-2) Coating Property 2 below, and then the coating film was heated and dried at 120°C for 3 minutes to form a film 2 formed by the brush coating method with an average thickness of 10 μm on the coated surface of the object.

[0093] 3. Evaluation The various properties (viscosity, pourability, coating properties 1 and 2, and dripping) of the coatings obtained in each experimental example were evaluated using the methods shown below (Coating Evaluation). Furthermore, the various properties of the films formed from the coatings obtained in each experimental example were evaluated using the methods shown below. The results are shown in Tables 1 to 3.

[0094] [Coating Evaluation] (3-1-1) Viscosity 1 The viscosity 1 of the coating material was measured using a B-type viscometer (VISCOMETER BM2, manufactured by Toki Sangyo Co., Ltd.) at 25° C., 60 rpm, 1 minute, and rotor No. 1. The evaluation criteria were as follows.

[0095] ○: Viscosity is 1 mPa·s or more and 50 mPa·s or less (good viscosity) ×: Viscosity exceeds 50 mPa·s (viscosity is too high) (3-1-2) Viscosity 2 The viscosity 2 of the coating material was measured using a B-type viscometer (VISCOMETER BM2, manufactured by Toki Sangyo Co., Ltd.) at 25° C., 60 rpm, 1 minute, and rotor No. 2. The evaluation criteria were as follows.

[0096] ○: Viscosity is 100 mPa·s or more and 2000 mPa·s or less (good viscosity) ×: Viscosity exceeds 2000 mPa·s (viscosity is too high)

[0097] (3-2) Injectability The injectability of the paint was evaluated by observing the paint as it was injected into an air sprayer. Using an air sprayer equipped with an air can (Spraywork Air Can 420D, manufactured by TAMIYA Co., Ltd.) and an air brush (Spraywork HG Single Air Brush, manufactured by TAMIYA Co., Ltd.), the injectability of each paint was evaluated by visually observing the movement of the paint from the air brush cup into the nozzle. The evaluation criteria were as follows.

[0098] ○: No clogging at all, and the liquid enters the nozzle smoothly. △: There is no clogging, but the liquid enters the nozzle slightly slowly. ×: The liquid agent is clogged and does not enter the nozzle.

[0099] (3-3-1) Coating properties 1 The coating properties of the coatings were evaluated by observing the coating unevenness after spraying. 1 Each coating was injected into the air atomizer used in (3-2) above and sprayed onto the outer surface of the object from a distance of 10 cm from the tip of the airbrush for 10 seconds. The coating unevenness of the resulting coating film (before drying) was then visually evaluated. (3-3-2) Coating properties 2 The coating properties of the coatings were evaluated by observing coating unevenness after coating with a brush. 2 Each coating was dipped on the tip of a brush, a 10 cm line was drawn on a SUS plate, and the coating unevenness of the resulting coating film (before drying) was visually evaluated.

[0100] The evaluation criteria for coating properties 1 and coating properties 2 are as follows. ⊚: No coating unevenness (uneven thickness) was observed. ○: Slightly uneven coating was observed. ×: Uneven coating was observed over a wide area.

[0101] (3-4) Dripping The dripping property of the coating was evaluated by observing the dripping from the coated object after spraying. As in (3-3-1) above, each coating was injected into the air atomizer used in (3-2) above. The coating was sprayed onto the outer surface of the object from a distance of 10 cm from the tip of the airbrush for 10 seconds. The dripping properties of the adhering droplets from the object were then evaluated. The evaluation criteria were as follows.

[0102] ○: After application, no dripping occurred even when the coated object was placed vertically. △: When the coated object is placed vertically after coating, the liquid gradually drips. ×: When the coated object is placed vertically after coating, the liquid drips immediately.

[0103] [Membrane Evaluation] (3-5) Characteristics -Glossiness- The glossiness of the film surface formed on each coated object relative to measurement light at an incident angle of 60° (60° specular gloss) was measured using a gloss meter (VG 7000, manufactured by Nippon Denshoku Industries) according to JIS Z 8741 at nine points, and the average value was used as the glossiness. The evaluation criteria were as follows.

[0104] ◎: Glossiness is less than 0.5% (extremely excellent low gloss) ○: Glossiness is 0.5% or more and less than 0.7% (excellent low glossiness) △: Glossiness is 0.7% or more and less than 1% (low glossiness is good) ×: Glossiness is 1% or more (low glossiness is insufficient)

[0105] -Reflectivity- The reflectance of the film surface formed on each coated object with respect to light of a wavelength of 550 nm (550 nm reflectance) was measured at nine points using a spectrophotometer (CM-5, manufactured by Konica Minolta) according to the method described in JIS Z 8722, and the average value was used as the reflectance. The evaluation criteria were as follows.

[0106] ◎: Reflectivity less than 1% (extremely excellent low reflectivity) ○: Reflectivity is 1% or more and less than 1.25% (excellent low reflectivity) △: Reflectance is 1.25% or more and less than 1.5% (good low reflectivity) ×: Reflectance is 1.5% or more (insufficient low reflectivity)

[0107] -Blackness- The blackness of the film surface formed on each coated object was evaluated by measuring the lightness L* value of the film surface in the CIE 1976 L*a*b* (CIELAB) color system using the SCE method. The lightness L* value was measured using a spectrophotometer (CM-5, manufactured by Konica Minolta Co., Ltd.) in accordance with JIS Z 8781-4:2013. The evaluation criteria are as follows. The measurement used CIE standard illuminant D65 as the light source, with a viewing angle of 10°, and the L* value in the CIELAB colorimetric system was determined using the SCE method. CIE standard illuminant D65 is specified in JIS Z 8720 (2000), "Illuminates (Standard Lights) and Standard Illuminants for Color Measurement," and is also specified in ISO 10526 (2007). CIE standard illuminant D65 is used to represent the color of objects illuminated by daylight. The viewing angle of 10° is specified in JIS Z 8723 (2009), "Methods for Visual Comparison of Surface Colors," and is also specified in ISO / DIS 3668.

[0108] ◎: L value is less than 10 (extremely good blackness) ○: L value is 10 or more and less than 12 (excellent blackness) △: L value is 12 or more and less than 15 (good blackness) ×: L value is 15 or more (insufficient blackness)

[0109] -Light blocking properties- The light-shielding property of the film formed on each coated object is evaluated by calculating the optical density of the film. The optical density of the film formed on each coated object is calculated by using an optical densitometer (X-rite 361T (Ortho filter), manufactured by Japan Lithography Materials Co., Ltd.) to irradiate a vertical penetrating light beam to the film side of the coated object, and express the ratio to the state without a film in log (logarithm). An optical density of 6.0 or above is the upper limit of detection for the measurement. The evaluation criteria are as follows. In addition, this evaluation assumes that the coated object itself has permeability, and the film formed thereon is required to have light-shielding properties. If the film is not required to have light-shielding properties, the evaluation here will not affect the comprehensive evaluation.

[0110] ◎: Optical density 3.2 or higher (extremely excellent light-shielding properties) ○: Optical density is 2.5 or more and less than 3.2 (excellent light-shielding properties) △: Optical density is 2 or more and less than 2.5 (good light-shielding properties) ×: Optical density is less than 2 (light-shielding property is insufficient)

[0111] - Adhesion - The adhesion of the film formed on each coated object to the surface of the coated object was evaluated by cutting the film in a checkerboard pattern with a commercially available utility knife, affixing transparent tape (Cellotape, manufactured by Nichiban Co., Ltd.) over the film, and then removing the tape. The remaining film was then visually inspected for adhesion. The evaluation criteria were as follows.

[0112] ◎: Residual film 100% (extremely good adhesion) ○: Residual film 95% or more and less than 100% (excellent adhesion) △: Residual film 90% or more and less than 95% (good adhesion) ×: Residual film is less than 90% (insufficient adhesion)

[0113] - Scratch resistance 1- The scratch resistance 1 of the film formed on each coated object is evaluated by measuring the scratches on the film surface using a wear tester (suga wear tester NUS-IS3) in accordance with JIS K5600-5-10ISO 7784-3. The measurement conditions are a load of 100g (mass corresponding to 100g to 3kg), and a test piece (embodiment 1 of the coated object forming the film. The same applies hereinafter) 1 cut to match the size of the fixture is rubbed back and forth 10 times against a test piece 2 that matches the size of the rotating wheel and is wound on a rotating wheel located below the test piece 1 to cause it to wear. The film surface of the test piece 1 is confirmed for scratches and evaluated. The rotating wheel rotates 0.9° each time the test piece 1 goes back and forth, and the test piece 1 is worn by the new wear surface of the test piece 2. The evaluation criteria are as follows.

[0114] ◎: 0 scratches (extremely excellent scratch resistance) ○: 1 to 2 scratches (excellent scratch resistance) △: 3 to 10 scratches (good scratch resistance) ×: There are 11 or more scratches (insufficient scratch resistance)

[0115] - Scratch resistance 2- The scratch resistance 2 of the film formed on each coated object was evaluated by observing the presence of scratches using a melamine sponge (Gekiochikun, melamine foam, REC Co., Ltd.). The surface of the film formed on each coated object was set to an area of ​​7 cm 2 The test piece was rubbed 30 times with a load of 200 g, and then visually checked for the presence or absence of scratches for evaluation. The evaluation criteria were as follows.

[0116] ◎: No change (extremely excellent scratch resistance) ○: 1 to 2 minor scratches (excellent scratch resistance) △: 3 to 10 minor scratches (good scratch resistance) ×: There are 11 or more minor scratches (insufficient scratch resistance) ××: The entire friction surface has sharp scratches (poor scratch resistance)

[0117] - Comprehensive Assessment - The above-mentioned glossiness, reflectivity, blackness, adhesion, and scratch resistance 1 and 2 were comprehensively evaluated. The evaluation criteria were as follows. As for light shielding properties, as mentioned above, they are sometimes necessary and sometimes not, so they were excluded from the comprehensive evaluation.

[0118] ◎: Glossiness, reflectivity, blackness, adhesion, and scratch resistance 1 and 2 were all ◎ ◯: At least one of the evaluations of glossiness, reflectivity, blackness, adhesion, and scratch resistance 1 and 2 was ◯, and none of them was ×. ×: At least one of the evaluations of glossiness, reflectivity, blackness, adhesion, and scratch resistance 1 and 2 was ×.

[0119] [Table 1]

[0120] [Table 2]

[0121] [Table 3]

[0122] 4. Investigation As shown in Table 1, when the coating composition did not contain (A1) as (A) (Experimental Examples 1 to 4), at least one of the film characteristics 1 and 2, namely, glossiness, reflectivity, L value, adhesion, and scratch resistance, was not satisfied. Even when the composition contained (A1) as (A) (Experimental Examples 5 to 10), and did not contain (B1) having a particle size within the specified range as (B) (Experimental Examples 6 to 10), at least one of the film characteristics 1 and 2, namely, glossiness, reflectivity, L value, adhesion, and scratch resistance, was not satisfied. Even when (B) contained (B1) having a particle size within the specified range (Experimental Examples 5 and 11 to 16), when the mass ratio of (B) to the resin solids content of (A) was less than 7 (Experimental Example 11) or greater than 14 (Experimental Example 16), at least one of the film characteristics 1 and 2, namely, glossiness, reflectivity, L value, adhesion, and scratch resistance, was not satisfied. On the other hand, if the mass ratio of (B) to the resin solid content of (A) is also appropriate (7 to 14) (Experimental Examples 5, 12 to 15), both the coating properties and the film properties can be satisfied.

[0123] As shown in Table 2, even when the coating composition contained (A1) as (A) (Experimental Examples 5a to 10a), when (B) did not contain (B1) having a particle size within the specified range (Experimental Examples 6a to 10a), one or more of the film characteristics 1 and 2, namely, glossiness, reflectivity, L value, adhesion, and scratch resistance, could not be satisfied. Even when (B) contained (B1) having a particle size within the specified range (Experimental Examples 5a, 11a to 16a), when the mass ratio of (B) to the resin solid content of (A) was less than 7 (Experimental Example 11a) or exceeded 14 (Experimental Example 16a), one or more of the film characteristics 1 and 2, namely, glossiness, reflectivity, L value, adhesion, and scratch resistance, could not be satisfied. On the other hand, if the mass ratio of (B) to the resin solid content of (A) is also appropriate (7 to 14) (Experimental Examples 5a, 12a to 15a), both the coating properties and the film properties can be satisfied.

[0124] As shown in Table 3, when the amount of (A) was fixed and the type of (A1) in (A) was changed (Experimental Examples 5, 17 to 20), it was confirmed that the film strength (pencil hardness, scratch resistance) also improved with the increase in molecular weight and glass transition temperature.

[0125] [Experimental Example 21] A coating material was prepared using the same composition as in Experimental Example 5, except that the black material, similar to B1a, was replaced with spherical acrylic resin particles containing CB, but with slightly larger black acrylic beads (5-6 μm). Film formation and evaluation were performed in the same manner as above, and the results were confirmed to be the same as in Experimental Example 5.

Claims

1. A composition, which is a resin composition for coating, comprising at least (A) and (B), (A) contains 90% by mass or more of (A1), (B) contains 90% by mass or more of (B1) having a particle size of 2 μm or more and 6 μm or less, and the mass ratio of (B) to (A):1 is 7 or more and 14 or less, wherein: (A) is a resin component, (A1) is a polyvinyl acetal resin, (B) is black material, (B1) is a composite of a black pigment and a resin.

2. The composition according to claim 1, wherein (B1) Contains acrylic resin particles containing carbon black.

3. A coating, Comprising the composition according to claim 1 or 2 and (C), The viscosity at 25°C measured using a B-type viscometer is 1 mPa·s to 2000 mPa·s. (C) is the dilution solvent.

4. The coating material according to claim 3, which is used for coating model parts. The coating material according to claim 3 , which is used for coating camera parts. The coating material according to claim 3, which is used for coating by a spray coating method and has a viscosity at 25°C measured with a Brookfield viscometer of 1 mPa·s to 50 mPa·s. The coating material according to claim 3 , which is used for coating by a dip coating method and has a viscosity at 25° C. measured using a Brookfield viscometer of 20 mPa·s to 500 mPa·s. The coating material according to claim 3, which is used for coating by a dispenser method and has a viscosity at 25°C measured with a Brookfield viscometer of 10 mPa·s to 300 mPa·s. 9 . The coating material according to claim 3 , which is used for application by a brush coating method and has a viscosity at 25° C. measured using a Brookfield viscometer of 100 mPa·s to 2000 mPa·s.

10. A film formed from the coating material according to claim 3, The outermost surface of the film-formed surface has a glossiness of less than 1% with respect to incident light at an incident angle of 60°, a reflectivity of less than 1.5% with respect to light of a wavelength of 550 nm, and an L value of less than 15 in the CIE LAB color system measured by the SCE method.

11. The film according to claim 10, wherein When the film is required to have light-shielding properties when it is transparent, the optical density of the outermost surface on which the film is formed is 2 or more.

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