Resin composition for paint and paint

Abstract

To provide a resin composition for paint that can form a film having high designability and excellent scratch resistance.SOLUTION: (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 composition according to the present invention contains at least (A) and (B). (A) contains at least 90 mass% of (A1). (B) contains at least 90 mass% of (B1) with a particle diameter of 2-6 μm and the mass ratio of the resin solid content of (A) to (B) is 1:7-14.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] For electronic devices such as smartphones, tablets, and personal computers, a black coating is sometimes applied to part or all of the housing (whether external or internal) or to part of the non-visible surface (e.g., the frame) of a cover glass that is placed and fixed on the visible surface side of a touch panel, for the purposes of improving design, concealing internal wiring, blocking light, etc. In recent years, this requirement has also been applied to part or all of electronic device components (e.g., the outer edge of the lens) such as lenses attached to various camera units, assembly models such as plastic models, or parts of assembly models in such model kits.

[0003] For example, Patent Document 1 discloses a technology for forming a film by directly screen-printing an insulating material onto the housing of a portable electronic device such as a smartphone, or by in-mold molding a screen-printed film-forming film. [Prior art documents] [Patent documents]

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

[0005] However, in recent years, with the demand for improved design of industrial products, there has been a growing demand for such products to be coated with black coatings (e.g., textured coatings) with even more appealing designs. There is also a need 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 an object of the present invention is to provide a resin composition for coating that can form a film with excellent designability and scratch resistance, and a coating material using the same. [Means for solving the problem]

[0007] After extensive research, the inventors have succeeded in increasing the amount of black material in the film formed by satisfying the following requirement a (i.e., by including a specific compound having a predetermined particle size range in the black material). As a result, they have found that this is effective in forming a highly designed film that not only has low gloss (less than 1%) but also exhibits even lower than conventional levels of ultra-low reflectance (less than 1.5%) and ultra-low L value (less than 15). They have also found that satisfying the following requirement b (i.e., by including a specific resin in the resin component) is effective in forming a film that exhibits high film strength and is highly scratch-resistant, even if the amount of black material in the film formed is small relative to the black material.

[0008] (a) A black material containing a specific compound (a compound of black pigment and resin) having a predetermined particle size range is used. (b) A resin component containing a specific resin (polyvinyl acetal resin) is used. Although the mechanism of action that causes the above phenomenon is not clear, it is thought that by including a specific resin in the resin components, high film strength is achieved even with a small amount of that specific resin added, and as a reflective effect, the relative amount of black material containing a specific compound in the film can be increased, and as a result, the designability of the film can be improved.

[0009] Based on these new findings, the present inventors have completed the invention provided below and solved the above-mentioned problems. Hereinafter, (A) resin component, (A1) polyvinyl acetal resin, (B) black material, (B1) composite of black pigment and resin, and (C) dilution solvent are referred to as the components.

[0010] According to the present invention, A resin composition for paint, At least (A) and (B), (A) contains 90 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. is provided.

[0011] The above composition may include the following aspects. (B1) preferably contains acrylic resin particles containing carbon black.

[0012] According to the present invention, The composition includes the above composition and (C), Paint with a viscosity of 1 mPa·s or more and 2000 mPa·s or less at 25°C measured with a B-type viscometer is provided.

[0013] The above paint may include the following aspects. May be used to coat model parts. May be used to coat camera parts. May be for application by spray coating method. May be for application by dip coating method. May be for application by dispenser method. May be for application by brush application.

[0014] According to the present invention, A film formed from the above paint, A film having a glossiness (hereinafter simply referred to as "glossiness") of less than 1% for incident light at an angle of 60° on the outermost surface on which the film is formed, a reflectance (hereinafter simply referred to as "reflectance") of less than 1.5% for light with a wavelength of 550 nm, and an L value of less than 15 in the CIELAB color system according to the SCE method. is provided.

[0015] The membrane may include the following features: When the film is required to have light-blocking properties in transmission, 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 resin composition for coating, which is capable of forming a film having excellent designability and scratch resistance, and a coating material for the resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0017] The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiments. Appropriate modifications and improvements to the following embodiments based on the ordinary knowledge of those skilled in the art are also within the scope of the present invention, as long as they do not deviate from the spirit of the present invention.

[0018] In the numerical ranges described in this specification, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In this specification, the content or amount of each component in a composition means, unless otherwise specified, the total content or amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition.

[0019] <Resin composition for paint> A resin composition for paint (hereinafter simply referred to as "composition") according to one embodiment of the present invention comprises (A) a resin component and (B) a black material. (A) comprises (A1) a polyvinyl acetal resin, and (B) comprises (B1) a composite of a black pigment and a resin having a predetermined particle size range. 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 reflectance (less than 1.5%) and ultra-low L value (less than 15), and they also exhibit high film strength. While the reason for this is unclear, the inclusion of (A1), which is tough, flexible, and self-crosslinkable, in (A), allows high film strength to be achieved even with a small amount in the film formed. The reflective effect of this (a small amount is sufficient) allows the relative amount of (B) containing (B1) to be increased in the film, which is thought to effectively result in low gloss, ultra-low reflectance, and ultra-low L value.

[0020] -(A)- (A) used in forming the composition is a fixing agent for the coating surface and also a binder for (B). Specifically, it contains a thermoplastic resin. Examples of thermoplastic resins include polyacrylic ester resin, polyvinyl chloride resin, polyvinyl acetal resin, and styrene-butadiene copolymer resin. Among these, it is preferable to contain (A1) polyvinyl acetal resin from the viewpoint of realizing low gloss, ultra-low reflectance, and ultra-low L value on the formed film surface, as well as film strength. One type of thermoplastic resin may be used alone, or two or more types may be used in combination.

[0021] By including (A1) in the thermoplastic resin (A), flexibility and toughness can be imparted to the film formed. In addition, because it is crosslinkable itself, high film strength (scratch resistance) can be achieved even with a small amount of (A1) in the composition (and therefore in the film).

[0022] (A1) is a polymer having a structural unit having an acetal group in the molecule, and is 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 acetoacetal, polyvinyl propylal, and polyvinyl butyral. More specifically, a polymer represented by the following formula (1) is preferred.

[0023] [ka]

[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 is represented by 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 are greater than 0, and z may be 0.

[0025] R 1 is 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. 1 A polyvinyl butyral resin having a structural unit in which is a propyl group is most preferred.

[0026] Polyvinyl butyral resin can be obtained by acetalizing polyvinyl alcohol (PVA) with butyraldehyde under acidic conditions. When acetalizing PVA, it is difficult to completely acetalize the PVA, so some hydroxyl groups remain irreversibly. Furthermore, PVA is typically produced by saponifying polyvinyl acetate. Since small amounts of acetyl groups often remain during the saponification process, polyvinyl butyral resin generally contains some acetyl and hydroxyl groups that remain irreversibly.

[0027] From the viewpoint of heat resistance, the glass transition temperature (Tg) of the polyvinyl butyral resin may be 40°C or higher and 130°C or lower, and preferably 60°C or higher and 120°C or lower. Having the glass transition temperature (Tg) within this range can provide benefits such as improved coating strength when formed into a coating film. The glass transition temperature (Tg) can be determined by measuring the change in heat quantity using differential scanning calorimetry (DSC method).

[0028] In (A1), x, i.e., the content of structural units having an acetal group (hereinafter also referred to as the "acetal group amount" or "degree of acetalization"), may be preferably 60 mol % or more, more preferably 65 mol % or more, and even more preferably 70 mol % or more, from the viewpoint of the slipperiness of the coating film surface when formed into a coating film, and may be preferably 95 mol % or less, more preferably 90 mol % or less, and even more preferably 85 mol % or less, from the viewpoint of the dispersibility of the black material in the composition. The amount of acetal groups (x) is a mole fraction obtained by dividing the amount of ethylene groups to which acetal groups are bonded by the total amount of ethylene groups in the main chain, and corresponds to the content (mol %) of structural units having acetal groups. The amount of ethylene groups to which acetal groups (especially butyral groups) are bonded can be measured using JIS K6728 "Test Methods for Polyvinyl Butyral."

[0029] In (A1), y, i.e., the content of structural units having hydroxy groups (hereinafter also referred to as "hydroxy group amount"), may be preferably 10 mol % or more, more preferably 15 mol % or more, and even more preferably 20 mol % or more, from the viewpoint of adhesion between the coating film and the substrate when formed into a coating film, and may be preferably 50 mol % or less, more preferably 45 mol % or less, and even more preferably 40 mol % or less. When (A1) contains a structural unit having an acetyl group, the content thereof (hereinafter also referred to as "acetyl group amount") may be, from the viewpoint of increasing the content of the black material, preferably 0.0001 mol % or more, more preferably 0.001 mol % or more, and may be preferably 15 mol % or less, more preferably 10 mol % or less, and even more preferably 8 mol % or less.

[0030] The molecular weight of (A1) is not particularly limited, but from the viewpoint of the strength of the coating film formed, it is preferably 8,000 or more, more preferably 10,000 or more, even more preferably 15,000 or more, and still more preferably 20,000 or more, and is 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] From the viewpoint of increasing the cohesive strength of the coating film when formed into a coating film, (A1) may contain a modified polyvinyl acetal resin containing at least one member selected from the group consisting of a structural unit having an imine structure, a structural unit having an acid-modified group, and a structural unit having an amino group or an amide structure. When a structural unit having an imine structure (a structure having a C═N bond) is contained, the content thereof 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. Examples of acid-modified groups include a carboxy group, a sulfonic acid group, a maleic acid group, a phosphate group, and salts thereof. When a structural unit having an acid-modified group is contained, the content thereof 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 the structural unit having an imine structure and the structural unit 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 may be directly bonded to a carbon atom constituting the main chain or side chain of the modified polyvinyl acetal resin, or may be bonded via a linking group such as an alkylene group.

[0032] The molecular weight, structure, amount of hydroxyl groups, etc. of (A1) modified polyvinyl acetal resin can be appropriately adjusted by the degree of polymerization of the PVA used and the acetalization reaction conditions. In (A1), it is preferable that the sum of x, y, and z in the formula (1) is 100 mol %.

[0033] Commercially available examples of polyvinyl acetal (butyral) resins include Sekisui Chemical Co., Ltd.'s S-LEC product lines: 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 Mobital series products of Kuraray Co., Ltd. The above (A1) may be used alone or in combination of two or more.

[0034] (A) may contain a thermosetting resin together with (A1). By including a thermosetting resin in (A), improved adhesion between the formed coating film and the substrate is expected. Examples of thermosetting resins include acrylic resins, urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, unsaturated polyester resins, epoxy resins, and alkyd resins. One type of thermosetting resin may be used alone, or two or more types may be used in combination. When (A) contains a thermosetting resin, the mass ratio of the thermosetting resin in (A) to the resin solids content of (A1):1 may be preferably 0.1 or more, more preferably 0.5 or more, and may be preferably 1.5 or less, more preferably 1 or less, from the viewpoint of adhesion between the formed coating film and the substrate.

[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 one embodiment, (A1) may be contained in 100% by mass of (A) at preferably 90% by mass or more.

[0036] The content (total amount) of (A) is not particularly limited, but taking into consideration the blending balance with other components, it may be preferably 1% by mass or more, more preferably 5% by mass or more, relative to the total amount of all solids in the composition (100% by mass); and from the viewpoint of the coating film strength when formed into a coating film, it may be 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 composite with the black pigment is one that is insoluble in water. Examples of such resins include epoxy resins, acrylic resins, urethane resins, styrene resins, ethylene resins, phenol resins, urea resins, amide resins, melamine resins, and benzoguanamine resins. Among these, from the viewpoint of dispersibility in the composition, acrylic resins and urethane resins are preferred, and acrylic resins are more preferred. These may be used alone or in combination of two or more. The term "beads" can be omitted by adding the name of the resin. For example, resin particles made of acrylic resin are sometimes called acrylic beads.

[0038] The black pigment that constitutes the composite with the resin is not particularly limited, but it is preferable to use carbon black (hereinafter simply referred to as "CB"), which has a great effect of blackening the composite and is also advantageous in terms of price. By using CB, the formed film is colored, which further improves the antireflection effect and provides good antistatic effect.

[0039] Examples of composite forms of black pigment and 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 a composite form of these.

[0040] Methods for coating the surface of a black pigment with a resin include, for example, the microencapsulation method, and more specifically, the interfacial polymerization method, in-situ polymerization method, liquid curing coating method (orifice method), phase separation from an aqueous solution, and liquid drying method. In addition to the microencapsulation method, there are also methods for bonding or adhering a resin to a dispersed black pigment. For example, a pigment is used as a core, and its surface is covered with numerous colloidal resin particles. When using a colorant in which the black pigment core is covered with colloidal resin particles, it is desirable that the size of the surrounding resin particles is sufficiently small compared to the pigment core. Furthermore, it is desirable that the colloidal resin particles cover the pigment core with almost no gaps. However, this does not exclude pigment cores directly exposed to the outside.

[0041] (B1) may be a pigment bound to a resin of approximately the same size as the pigment particles. Alternatively, a black pigment or black dye may be kneaded into a thermoplastic or thermosetting resin and then pulverized to form a composite of the black pigment or black dye and the resin.

[0042] In one embodiment, the composite form is preferably form (1), i.e., resin particles encapsulating a black pigment, from the viewpoint of improving dispersibility in the composition. In resin particles encapsulating a black pigment, the pigment is encapsulated in larger-diameter resin particles, so aggregates are less likely to form in the composition compared to when a smaller-diameter pigment is directly blended into the composition, contributing to improved dispersibility.

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

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

[0045] The shape of (B1) is not particularly limited, but from the viewpoint of matte finish, a spherical shape is preferred. Furthermore, to achieve a uniform, low gloss, low reflectance, and low L value on the formed film surface, it is preferable to use particles (sharp products) with a narrow particle size distribution (CV (Coefficient of Variation) value, for example, 15 or less). The CV value is a numerical representation of the degree of particle size distribution (particle size variation) relative to the average particle size (arithmetic mean particle size). By using such particles, they are uniformly contained in the film, forming fine irregularities on the film surface, making it easier to achieve a uniform, low gloss, low reflectance, and low L value on the film surface. In order to further reduce the glossiness of the formed film surface, amorphous particles may be used as (B1). By using amorphous particles as (B1), when a film is formed, light is repeatedly refracted on the surface and inside of (B1), which can further reduce the glossiness of the film surface.

[0046] Commercially available products can be used as (B1). Examples of products containing urethane beads include Art Pearl C800 Black (particle diameter 6.5 μm, CB content 7.5%, Negami Chemical Industrial Co., Ltd.). Examples of products containing acrylic (acrylic copolymer) beads include Art Pearl GR-004BK (particle diameter 3-5 μm, CB content 35-39%, Negami Chemical Industrial Co., Ltd.) and Lovecolor 224 (SMD) Black (average particle diameter 2-3 μm, CB content 18%, Dainichiseika Color & Chemicals Co., Ltd.).

[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 one embodiment, (B1) may be contained in 100% by mass of (B) at a content of preferably 90% by mass or more.

[0048] In one embodiment, the mass ratio of (B) relative to the resin solid content of (A) is 7 or more, preferably 8 or more, more preferably 9 or more, and preferably 14 or less, more preferably 12 or less, relative to 1:1 of the resin solid content of (A). By blending (B) within this mass ratio range, it is possible to achieve low gloss, low reflectance, and a low L value while maintaining the coating film strength.

[0049] The content (total amount) of (B) 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, based on the total amount (100% by mass) of all solids in the composition. If the total amount of (B) is less than 60% by mass, problems such as increased gloss and insufficient optical density occur, while if it exceeds 90% by mass, the amount of (A) in the formed film becomes relatively small, which may result in problems such as the film peeling off from the coated object.

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

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

[0052] The isocyanate compound preferably used as a curing agent can be any compound having two or more isocyanate groups in the molecule. Examples include at least one of aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, and derivatives thereof. Here, araliphatic polyisocyanate refers to a polyisocyanate 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, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, triphenylmethane triisocyanate, and tris(isocyanatophenyl)thiophosphate. 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(isocyanatomethyl)cyclohexane, and bis(isocyanatomethyl)norbornane. Examples of aromatic aliphatic polyisocyanates include xylylene diisocyanate, tetramethylxylylene diisocyanate, ω,ω'-diisocyanato-1,4-diethylbenzene, etc. Derivatives of polyisocyanate compounds include multimers such as trimers, dimers, pentamers, etc., such as the isocyanurates of the isocyanate compounds, adducts obtained by reacting the isocyanate compounds with polyol compounds such as trimethylolpropane, and modified polyisocyanates such as allophanate compounds and biuret compounds.

[0054] From the viewpoint of adhesion between the coating film and the substrate when formed into a coating film, it is preferable that the nitrogen atom of the isocyanate group has a structure bonded to an aliphatic carbon atom, and at least one of aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, and derivatives thereof is preferably used. Among these, from the viewpoint of adhesion between the coating film and the substrate when formed into a coating film and coating strength, isocyanurates of aliphatic polyisocyanates, xylylene diisocyanate, and modified polyisocyanates thereof are preferably used. The curing agents that can be blended into the coating material may be used alone or in combination of two or more.

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

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

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

[0058] <Paint> A coating material according to one embodiment of the present invention is used to form a film made of the composition on a coating surface, and includes the composition and (C) a dilution solvent.

[0059] -(C)- (C) is used to form the coating material and is blended to dissolve (A) and adjust the viscosity of the entire composition. The use of (C) improves the uniformity of the coating material. Furthermore, the viscosity of the coating material can be adjusted appropriately, improving the operability of the coating material and the uniformity of the coating thickness when forming a film on the coating surface, which can greatly contribute to improving the design of the final product.

[0060] (C) is not particularly limited as long as it is a solvent that can dissolve (A) and adjust the coating viscosity. Examples include water, an organic solvent, or a mixture of water and an organic solvent. Examples of organic solvents that can be used include methyl ethyl ketone, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, and butanol. (C) may be used alone or in combination of two or more. The amount of (C) may be appropriately determined to adjust the solids concentration of the coating.

[0061] The appropriate range for paint viscosity varies depending on the application method, so it is difficult to generalize, but the viscosity at 25°C measured with a Brookfield viscometer is roughly between 1 mPa·s and 2000 mPa·s. For example, if the application method is spray coating, a viscosity of between 1 mPa·s and 50 mPa·s is preferable. If the application method is dip coating, a viscosity of between 20 mPa·s and 500 mPa·s is preferable. If the application method is dispenser coating, a viscosity of between 10 mPa·s and 300 mPa·s is preferable. If the application method is using a paint brush or paintbrush (brush coating), a viscosity of between 100 mPa·s and 2000 mPa·s is preferable.

[0062] In the case of 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 coming out of the nozzle or not being able to atomize even if it comes out are likely to occur. In the case of dip coating, if the viscosity of the paint is too low, the liquid may drip excessively, causing unevenness and making it impossible to form a clean film. If the viscosity of the paint is too high, the liquid may not drain well when the coated object is lifted from the paint, resulting in burrs, or the surface shape of the coating may become flat, resulting in a glossy appearance. In the case of the dispenser method, if the viscosity of the paint is too low, splashes and drips may occur, and the paint may end up being applied to areas where you do not want it to be. If the viscosity of the paint is too high, the paint may not come out of the nozzle, or even if it does come out, the surface shape may tend to be flat, resulting in a glossy finish. In the case of the brush application method, if the viscosity of the paint is too low, drips may occur. If the viscosity of the paint is too high, smearing may occur.

[0063] The viscosity of the paint varies depending on the components contained in the composition in the paint, i.e., the types and molecular weights of (A) and (B) used to form the composition, and also on the types and molecular weights of optional components, if any, blended in addition to (A) and (B). However, the viscosity can be easily adjusted by appropriately determining the amount of (C) in the paint.

[0064] The coating material according to one embodiment may be a one-component type or a two-component type. When a curing agent is blended, the coating material according to one embodiment may be a two-component type, for example, consisting of a first component containing components other than the curing agent and a second component containing the curing agent.

[0065] The paint according to one embodiment may be for coating parts of an assembly model, for coating parts of a camera, for coating by a spray coating method, for coating by a dip coating method, for coating by a dispenser method, or for coating by a brush coating method.

[0066] <Application method, object to be coated> The film according to one embodiment of the present invention is formed by applying the coating material to a substrate to form a coating film, and then drying the coating film.

[0067] The coating material may be applied by a spray coating method (e.g., air spray, airless spray, electrostatic spray, etc.). By using the spray coating method, even if the surface of the object to be coated has protrusions, steps, etc., it is possible to form a film of uniform thickness and having specific performance over the entire surface.

[0068] The coating conditions using the spray coating method are preferably a spray gun diameter of about 0.2 to 1.2 mm, a discharge rate of about 0.2 to 10 (g / min), a minimum distance between the spray gun and the surface of the object to be coated of about 30 to 500 mm, a coating speed of about 30 to 300 (mm / sec), an overlap pitch of about 1.5 to 10 mm, and an atomizing air pressure of about 0.03 to 0.2 MPa. Regarding the number of spray guns, in addition to using a single gun, multiple guns may be arranged according to the size of the object to be coated from the viewpoint of coating efficiency.

[0069] After the coating material is applied to the surface of the substrate, the solvent is removed by drying to form a film. If necessary, the coating film may be irradiated with UV light or EB light. When the coating material contains a curing agent, the coating film may be cured by heating. The heating conditions may be adjusted appropriately depending on the thickness of the coating film before heating, the heat resistance of the substrate, the type of (C) used, etc. One example of the heating conditions is a temperature of 70°C to 150°C for 1 minute to 30 minutes, preferably a temperature of 100°C to 130°C for 2 minutes to 10 minutes.

[0070] The coating material may be applied by spray coating, dip coating, dispenser coating, or brush coating, for example.

[0071] When the paint is applied by brush coating, the thickness of the film formed on the surface tends to vary depending on the location, but the performance of the resulting film is equivalent to that of other coating methods. The reason for this is not clear, but it is thought to be because the appropriate amount of pigment content creates unevenness.

[0072] The object to be coated with the paint (substrate) is not particularly limited, and may be, for example, an object with a hard surface made of glass, resin, metal, ceramics, wood, etc. The shape of the substrate is also not particularly limited, and examples include plate-shaped, (hollow) cylindrical, and film-shaped objects. Examples of the substrate to be coated include the following: Electrical and electronic devices such as mobile phones, smartphones, tablets, PCs, PC peripherals (keyboards, printers, external disks, etc.), watches, audio equipment, and various office automation equipment. · Home appliances such as refrigerators, vacuum cleaners, microwave ovens, televisions, and recording devices. Stairs, floors, desks, chairs, dressers, other furniture and woodwork. Various building materials, flooring, interior and exterior walls of buildings, etc. Vehicles such as automobiles and motorcycles or their parts: Specifically, vehicle bodies, interior parts (meter panels, dashboards, handlebars, sensing camera brackets (attached to the upper inside of the windshield, etc.), head-up displays (HUD), etc.), bumpers, spoilers, door handles, headlights, taillights, aluminum wheels, motorcycle gas tanks, etc. Optical applications, such as lenses attached to various camera units, inner walls of lens barrels, inner and outer covers of lens units, lens spacers and other camera parts. Glasses, goggles and similar products. Hobby products made of resin molded products, and parts for assembling them (for example, assembly models (plastic models, etc.), parts for assembly models in model kits, etc.).

[0073] The thickness of the film formed from the coating material according to one embodiment can be adjusted appropriately depending on the application of the substrate, and is not particularly limited. An example of a suitable film thickness is preferably 2 μm or more, more preferably 5 μm or more, and preferably 40 μm or less, more preferably 25 μm or less. The thickness of the film formed from the coating material according to one embodiment refers to the height including the portion of the film protruding from the surface of the substrate due to (B). The film thickness can be measured by a method in accordance with JIS K7130.

[0074] <Film characteristics> The properties of the film formed from the above paint are as follows:

[0075] (Glossiness, reflectance, L value, optical density, adhesion, coating strength (scratch resistance)) The film formed from the above coating 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 a film formed from the above coating is required to have light-blocking properties in transmission, in addition to the above properties (surface gloss of less than 1%, a reflectance of less than 1.5%, and an L value of less than 15), the film surface preferably has an optical density of 2 or more.

[0076] Here, if the film formed from the above coating material is exposed on the outermost surface, it is preferable that the gloss, reflectance, L value, and, if necessary, optical density of the film surface are literally within the above ranges. If another film is coated on the film formed from the above coating material, it is preferable that the gloss, reflectance, 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 substrate, are within the above ranges. Hereinafter, these surfaces are collectively referred to as the "outermost surface of the film."

[0077] The film formed from the above coating preferably has a gloss 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-blocking properties in transmission are required for the film formed from the above coating, in addition to the above properties (gloss 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 preferable that the outermost surface of the film has an optical density of 2 or more. By having the gloss, reflectance, L value, and, if necessary, optical density of the outermost surface of the film within the above ranges, it is possible to achieve low gloss, low reflectance, high blackness, and, if necessary, high light-blocking properties on the outermost surface of the film.

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

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

[0080] The upper limit of the L value (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 viewpoint of obtaining a blacker appearance, the lower the value, the better. By adjusting the L value within the above range, the blackness becomes high and the black stands out, resulting in excellent design, and the film can be suitably used as a camera unit for mobile phones such as smartphones. The above L value is the lightness L* value of the outermost surface of the film in the CIE 1976 L*a*b* (CIELAB) color system according to the SCE method. The SCE method is a specular reflection removal method, which means a method of measuring color by removing specular reflection. The definition of the SCE method is specified in JIS Z8722 (2009). With the SCE method, specular reflection is removed when making measurements, so the color is closer to what the human eye actually sees. CIE is the abbreviation for Commission Internationale de l'Eclairage, which stands for International Commission on Illumination. CIELAB display colors are a uniform color space recommended in 1976 and specified in JIS Z8781 (2013) to measure color differences due to differences in perception and devices. CIELAB's three coordinates are expressed as L*, a*, and b*. L* indicates lightness and is expressed from 0 to 100. An L* value of 0 indicates black, and an L* value of 100 indicates diffuse white. The a* value indicates a color between red and green. A negative a* value indicates a color leaning toward green, and a positive a* value indicates a color leaning toward red. The b* value indicates a color between yellow and blue. A negative b* value indicates a color leaning toward blue, and a positive b* value indicates a color leaning toward yellow.

[0081] When a film formed from the coating material is required to have light-blocking properties in transmission, the lower limit of the optical density is more preferably 2.5 or more, and even more preferably 3.2 or more. By adjusting the optical density within the above range, the light-blocking properties can be further improved. The upper limit of the optical density is not particularly limited, and the higher the better.

[0082] The glossiness, reflectance, L value, and optical density can be measured by the methods described below.

[0083] In addition to the above properties (glossiness, reflectance, L value, and optical density as needed), it is preferable that the film formed from the paint further has good adhesion to the coating surface. The adhesion of the film formed from the paint to the coating surface is preferably such that 90% or more of the film remains, as shown in the adhesion evaluation in the Examples described later. It is also preferable that the film formed from the paint further has high coating strength. As shown in the scratch resistance evaluation in the Examples described later, the coating strength of the film formed from the paint is preferably such that the number of scratches according to JIS K5600-5-10 ISO 7784-3 is 10 or less, more preferably 2 or less, and even more preferably 0. [Example]

[0084] The present invention will be specifically described below 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 "% by mass".

[0085] [Components of the composition] The following was prepared as A (resin component): A1: Polyvinyl acetal resin (S-LEC, Sekisui Chemical Co., Ltd.) A1a: BL-S (Degree of acetalization: about 72 mol%, amount of hydroxyl groups: about 23 mol%, amount of acetyl groups: 4 to 6 mol%, calculated molecular weight: about 23,000, Tg: 66°C) A1b: BM-S(Z) (Degree of acetalization: about 72 mol%, amount of hydroxyl groups: about 23 mol%, amount of acetyl groups: 4 to 6 mol%, calculated molecular weight: about 55,000, Tg: 67°C) A1c: BH-S (Degree of acetalization: about 72 mol%, amount of hydroxyl groups: about 23 mol%, amount of acetyl groups: 4 to 6 mol%, calculated molecular weight: about 66,000, Tg: 67°C) A1d: BX-5(Z) (Degree of acetalization: about 72 mol%, amount of hydroxyl groups: about 27 mol%, amount of acetyl groups: 3 mol% or less, calculated molecular weight: about 130,000, Tg: 92°C) A1e: KS-5Z (Degree of acetalization: about 74 mol%, amount of hydroxyl groups: about 25 mol%, amount of acetyl groups: 3 mol% or less, calculated molecular weight: about 130,000, Tg: 113°C) A2: Thermosetting acrylic resin (Acrydic A801, DIC) (Resin Tg 67°C, resin solids 34%, molecular weight 15,000, acid value 1 mg KOH / g, hydroxyl value 5 mg KOH / g)

[0086] The following was prepared as B (black material): B1a: Black acrylic beads (particle diameter 3-5 μm) (Art Pearl GR-004BK, Negami Chemical Industries, CB content 35-39%) B2a: Black acrylic beads (particle diameter 14-16 μm) (Art Pearl GR-400BK, Negami Chemical Industries, CB content 6-10%) ·B2b: CB (particle size 150nm) (MHI Black #273, Mikuni Pigment Co., Ltd., CB content 9.5%) B2c: Composite silica (particle size 3 μm) (Vexia ID, Fuji Silysia Chemical Ltd.) B2d: Transparent acrylic beads (particle diameter 3 μm) (Unipowder MNB0320C, ENEOS Corporation) B2e: Transparent acrylic beads (particle diameter 2 μm) (Unipowder MNB0220C, ENEOS Corporation)

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

[0088] The following were prepared as optional components D: D1: Isocyanate compounds (Takenate D110N, Mitsui Chemicals, solids content 75%)

[0089] [Object to be coated] A smartphone housing (plastic outer box) was prepared as the object to be coated.

[0090] [Experimental Examples 1 to 20 and 5a to 16a] 1. Preparation of Paint Each component for each experimental example was added to a mixed solvent of methyl ethyl ketone and butyl acetate in the specified amounts shown in Tables 1 to 3 so that the total solid content (mass%) and the solid content ratio of each component were the values ​​shown in Tables 1 to 3, and the paint was prepared by stirring and mixing.

[0091] 2-1. Formation of Membrane 1 The paint obtained in each experimental example was sprayed onto the substrate using a spray coating method similar to the method described in (3-3-1) Coating Property 1 below to form a coating film, which was then heated and dried at 120°C for 3 minutes to form a spray coating film 1 on the coated surface of the substrate with an average film thickness of 10 μm.

[0092] 2-2. Formation of Membrane 2 A coating film was formed on the substrate by brush coating using the same technique as 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 brush-coated film 2 with an average film thickness of 10 μm on the coating surface of the substrate.

[0093] 3. Evaluation The paints obtained in each experimental example were evaluated for various properties (viscosity, pourability, applicability, dripping) using the methods described below (paint evaluation). Furthermore, the films formed from the paints obtained in each experimental example were evaluated for various properties (characteristics) using the methods described below (film evaluation). The results are shown in Tables 1 to 3.

[0094] [Paint evaluation] (3-1-1) Viscosity 1 The viscosity 1 of the paint was measured using a B-type viscometer (VISCOMETER BM2: Toki Sangyo Co., Ltd.) under the conditions of 25°C, 60 rpm, after 1 minute, and No. 1 rotor. The evaluation criteria are as follows:

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

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

[0097] (3-2) Injectability The pourability of the paint was evaluated by observing the state of pouring into the air spray. Using an air sprayer consisting of an air can (Spraywork Air Can 420D, Tamiya) and an airbrush (Spraywork HG Single Airbrush, Tamiya), the paint was visually observed as it entered the nozzle from the cup of the airbrush to evaluate its pourability. The evaluation criteria were as follows:

[0098] 〇: There was no clogging at all and the liquid entered the nozzle smoothly. △: No clogging, but the speed at which the liquid entered the nozzle was a little slow. ×: The liquid was clogged and did not enter the nozzle.

[0099] (3-3-1) Spreadability 1 The coating properties 1 of the paints were evaluated by observing the unevenness of the coating after application by the spray coating method. Each paint was poured into the air spray used in (3-2) above, and sprayed onto the outer surface of the object to be coated for 10 seconds from a distance of 10 cm from the tip of the airbrush, and the formed coating film (before drying) was visually evaluated for unevenness of the coating. (3-3-2) Spreadability 2 The coating properties 2 of the coating were evaluated by observing the unevenness of the coating after application by the brush coating method. Each paint was applied to the tip of a brush and a 10 cm line was drawn on a SUS plate, and the resulting coating film (before drying) was visually evaluated for unevenness in the coating.

[0100] The evaluation criteria for both Coatability 1 and Coatability 2 are as follows: ◎: No uneven coating (uneven thickness) was observed 〇: A small amount of uneven paint was observed ×: Uneven coating was observed in many areas

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

[0102] ◯: No dripping occurred even when the coated object was placed vertically after application. △: When the coated object was placed vertically after application, the liquid gradually began to drip. ×: When the coated object was placed upright after application, the liquid immediately began to drip.

[0103] [Film evaluation] (3-5) Characteristics -Glossiness- The gloss of the surface of the film formed on each substrate with respect to the measuring light at an incident angle of 60° (60° specular gloss) was measured at nine points using a gloss meter (VG 7000: Nippon Denshoku Industries Co., Ltd.) according to the method in accordance with JIS Z8741, and the average value was taken as the gloss. The evaluation criteria are as follows:

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

[0105] -Reflectance- The reflectance of the surface of the film formed on each substrate to light with a wavelength of 550 nm (550 nm reflectance) was measured at nine points using a spectrophotometer (CM-5: Konica Minolta) according to the method of JIS Z8722, and the average value was taken as the reflectance. The evaluation criteria are as follows:

[0106] ◎: Reflectance is less than 1 (extremely low reflectivity) 〇: Reflectance 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 surface of the film formed on each substrate was evaluated by measuring the lightness L* value of the film surface in the CIE 1976 L*a*b* (CIELAB) color system according to the SCE method. The lightness L* value was measured using a spectrophotometer (CM-5: Konica Minolta) in accordance with JIS Z8781-4:2013. The evaluation criteria were as follows: The measurements were performed using CIE Standard Illuminant D65 as the light source, with a viewing angle of 10°, and the L* value was calculated using the SCE method for CIELAB display colors. CIE Standard Illuminant D65 is specified in JIS Z8720 (2000) "Illuminates (standard light) and standard light sources for color measurement," and the same specification is found in ISO 10526 (2007). CIE Standard Illuminant D65 is used when displaying the color of objects illuminated by daylight. The 10° viewing angle is specified in JIS Z8723 (2009) "Method for visual comparison of surface colors," and the same specification is found in ISO / DIS 3668.

[0108] ◎: L value is less than 10 (extremely excellent blackness) 〇: 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 property- The light-blocking properties of the film formed on each substrate were evaluated by calculating the optical density of the film. The optical density of the film formed on each substrate was calculated using an optical densitometer (X-rite 361T (orthofilter): Nippon Heihan Kizai Co., Ltd.) by irradiating the film side of the substrate with a perpendicular transmitted light beam and expressing the ratio to the value without the film in log (logarithm). An optical density of 6.0 or higher is the upper detection limit for measurement. The evaluation criteria are as follows. Note that this evaluation is based on the assumption that the substrate itself is transparent and that the film formed on it is required to have light-blocking properties. If the film is not required to have light-blocking properties, the evaluation here does not affect the overall evaluation.

[0110] ◎: Optical density is 3.2 or higher (excellent light blocking properties) 〇: Optical density is 2.5 or more and less than 3.2 (excellent light blocking properties) △: Optical density is 2 or more and less than 2.5 (good light blocking properties) ×: Optical density is less than 2 (insufficient light blocking properties)

[0111] -Adhesion- The adhesion of the film formed on each substrate to the surface of the substrate was evaluated by making grid-shaped cuts in the film with a commercially available cutter, sticking cellophane tape (Nichiban Co., Ltd.) to the cuts, then peeling it off and visually checking the remaining state of the film. The evaluation criteria are as follows:

[0112] ◎: 100% film remains (excellent adhesion) 〇: Film remaining is 95% or more but less than 100% (excellent adhesion) △: Film remaining is 90% or more but less than 95% (good adhesion) ×: Less than 90% of the film remains (insufficient adhesion)

[0113] -Scratch resistance 1- The scratch resistance 1 of the film formed on each substrate was evaluated by measuring the scratching of the film surface using an abrasion tester (Suga Abrasion Tester NUS-ISO3) in accordance with JIS K5600-5-10 and ISO 7784-3. The measurement conditions were a load of 100 g (corresponding to weights of 100 g to 3 kg). A test piece (a form of a coated substrate with a film formed thereon; the same applies below) 1, cut to a size that fit the jig, was rotated back and forth 10 times against a test piece 2, which was wrapped around a rotating wheel positioned below the test piece 1 and sized to fit the rotating wheel, causing abrasion. The evaluation was based on whether scratches were generated on the film surface of the test piece 1. The rotating wheel rotated 0.9° for each reciprocation of the test piece 1, ensuring that the newly worn surface of the test piece 2 always abraded the test piece 1. The evaluation criteria were as follows:

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

[0115] -Scratch resistance 2- The scratch resistance 2 of the film formed on each substrate was evaluated by observing the presence or absence of scratches using a melamine sponge (Gekiochikun, Melamine Foam, Reck Co.). The surface of the film formed on each substrate was examined by a 7cm2 installation area. 2 The surface was rubbed 30 times with a load of 200 g, and then visually inspected for scratches and evaluated. The evaluation criteria were as follows:

[0116] ◎: No change (excellent scratch resistance) Good: 1-2 thin scratches (excellent scratch resistance) △: 3 to 10 thin scratches (good scratch resistance) ×: 11 or more thin scratches (insufficient scratch resistance) ××: Sharp scratches on the entire surface of the abrasion surface (poor abrasion resistance)

[0117] -comprehensive evaluation- The glossiness, reflectance, blackness, adhesion, and scratch resistance 1 and 2 were evaluated comprehensively. The evaluation criteria are as follows. As mentioned above, light blocking ability is sometimes necessary and sometimes not, so it was excluded from the comprehensive evaluation.

[0118] ◎: Glossiness, reflectivity, blackness, adhesion, and scratch resistance 1 and 2 are all ◎ ◯: At least one of the evaluations of gloss, reflectance, blackness, adhesion, and scratch resistance 1 and 2 was ◯, and none was × ×: At least one of the evaluations of gloss, reflectance, blackness, adhesion, and scratch resistance 1 and 2 was ×

[0119] [Table 1]

[0120] [Table 2]

[0121] [Table 3]

[0122] 4. Discussion As shown in Table 1, when (A1) was not included in the composition contained in the paint as (A) (Experimental Examples 1 to 4), it was not possible to satisfy one or more of the film properties: gloss, reflectance, L value, adhesion, and scratch resistance 1 and 2. Even when (A1) was included in the composition as (A) (Experimental Examples 5 to 10), when (B1) having a particle size within a predetermined range was not included in (B) (Experimental Examples 6 to 10), it was not possible to satisfy one or more of the film properties: gloss, reflectance, L value, adhesion, and scratch resistance 1 and 2. Even when (B) contains (B1) having a particle size within a predetermined range (Experimental Examples 5, 11 to 16), if the mass ratio of (B) to the resin solid content of (A): 1 was less than 7 (Experimental Example 11) or more than 14 (Experimental Example 16), one or more of the film properties of gloss, reflectance, L value, adhesion, and scratch resistance 1 and 2 could not be satisfied. In contrast, when the mass ratio of (B) to the resin solid content of (A): 1 was appropriate (7 or more and 14 or less) (Experimental Examples 5, 12 to 15), all of the coating properties and film properties could be satisfied.

[0123] As shown in Table 2, even when (A1) was included in the composition of the coating material as (A) (Experimental Examples 5a to 10a), or when (B1) having a particle size within the specified range was not included in (B) (Experimental Examples 6a to 10a), one or more of the film properties of gloss, reflectance, L value, adhesion, and scratch resistance 1 and 2 could not be satisfied. Even when (B1) having a particle size within the specified range was included in (B) (Experimental Examples 5a, 11a to 16a), if the mass ratio of (B) to the resin solid content of (A): 1 was less than 7 (Experimental Example 11a) or more than 14 (Experimental Example 16a), one or more of the film properties of gloss, reflectance, L value, adhesion, and scratch resistance 1 and 2 could not be satisfied. In contrast, when the mass ratio of (B) to the resin solid content of (A): 1 was appropriate (7 or more and 14 or less) (Experimental Examples 5a, 12a to 15a), all of the paint properties and film properties could 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 and scratch resistance) improved as the molecular weight and glass transition temperature increased.

[0125] [Experimental Example 21] A paint was prepared with the same composition as in Experimental Example 5, except that instead of B1a, black acrylic beads (particle diameter 5 to 6 μm), which are spherical acrylic resin particles encapsulating CB like B1a but have a slightly larger particle diameter, were used. A film was then formed in the same manner as above, and the same evaluation was carried out, confirming that the same evaluation as in Experimental Example 5 was obtained.

Claims

1. A resin composition for paint, 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 diameter of 2 μm or more and 6 μm or less, the mass ratio of (B) to (A):1 is 7 or more and 14 or less, and (B1) contains acrylic resin particles encapsulating carbon black. (A) Resin component (A1) Polyvinyl acetal resin (B) Black material (B1) Composite of black pigment and resin

2. The composition of claim 1 and (C), A coating material having a viscosity of 1 mPa·s or more and 2000 mPa·s or less at 25°C as measured by a Brookfield viscometer. (C) Dilution solvent

3. The paint of claim 2 for coating model parts.

4. The paint according to claim 2, which is used to coat camera parts.

5. 3. The coating material according to claim 2, which is intended for application by spray coating and has a viscosity of 1 mPa·s or more and 50 mPa·s or less at 25° C. as measured with a Brookfield viscometer.

6. 3. The coating material according to claim 2, which is for application by dip coating and has a viscosity of 20 mPa·s or more and 500 mPa·s or less at 25° C. as measured by a Brookfield viscometer.

7. 3. The coating material according to claim 2, which is intended for application by a dispenser method and has a viscosity at 25°C measured with a Brookfield viscometer of 10 mPa·s or more and 300 mPa·s or less.

8. 3. The paint according to claim 2, which is for application by brush coating and has a viscosity of 100 mPa·s or more and 2000 mPa·s or less at 25°C as measured by a Brookfield viscometer.

9. A film formed from the paint according to claim 2, A film having a glossiness of less than 1% for incident light at an incident angle of 60°, a reflectance of less than 1.5% for light with a wavelength of 550 nm, and an L value of less than 15 in the CIELAB color system according to the SCE method on the outermost surface on which the film is formed.

10. 10. The film according to claim 9, wherein the outermost surface on which the film is formed has an optical density of 2 or more when the film is required to have light-shielding properties in transmission.

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