Electronic device housing, manufacturing method thereof, and anti-reflection film

Abstract

The present invention provides a technology that is effective in improving the design and scratch resistance of anti-reflection coatings formed on electronic device housings. The component A is a binder resin, the component A1 is a polyvinyl acetal resin, the component B is a black material, and the component B1 is a composite of black pigment and resin. The electronic device housing has an anti-reflection coating on the housing body. The anti-reflection coating is formed from a resin composition and contains at least the components A and B. The component A contains the component A1. The component B contains the component B1, whose average particle size is 2 μm or more and 6 μm or less. The mass ratio of the component B to the component A is 7 or more and 14 or less.

Description

[Technical Field]

[0001] The present invention relates to an electronic device housing, a manufacturing method thereof, and an anti-reflection film. [Background technology]

[0002] Electronic devices such as smartphones, tablets, and personal computers are sometimes coated with a black anti-reflective coating on part or all of their housings for the purposes of improving design, concealing internal wiring, blocking light, and preventing reflections.

[0003] For example, Patent Document 1 discloses a technology for forming a black film on the housing of a portable electronic device such as a smartphone by directly screen-printing an insulating material onto the housing, 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 coating such products with films that have a more striking black color and a more stylish design.In addition, there is also a demand for ensuring scratch resistance during film production (film formation) and handling.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a technique that is effective in improving the design and scratch resistance of an anti-reflection film formed on the housing of an electronic device. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that an anti-reflection film formed on an electronic device housing is effective in improving design and scratch resistance when it satisfies the following requirements. - It is formed from a resin composition in which a binder resin (element a) containing a specific resin (polyvinyl acetal resin) and a black material (element b) containing a specific compound (composite of black pigment and resin) with a particle size within a specific range are mixed at a specified mass ratio (7 to 14 times the mass of element a).

[0008] Although the mechanism of action that manifests this phenomenon is unclear, the inclusion of a specific resin in the a component can impart flexibility and toughness to the resulting film. In addition, because the specific resin is crosslinkable, even a small amount of the a component can result in a high film strength. This reflective effect allows for an increased relative amount of the b component in the resulting film. By incorporating a specific composite into the b component and incorporating a large amount of the b component into the film, the resulting film exhibits lower gloss compared to films formed from conventional resin compositions (hereinafter referred to as "conventional films"). In addition, the resulting film exhibits even lower ultra-low reflectivity, ultra-low L values, and high light-blocking properties compared to conventional films. We believe that this results in a film with excellent designability and scratch resistance.

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

[0010] One aspect of the present invention is An electronic device housing having an anti-reflection film on a housing body; is located.

[0011] The anti-reflection film of the housing is It is formed from a resin composition and contains at least component A and component B, The component A contains the component A1, the component B contains the component B1 having an average particle size of 2 μm or more and 6 μm or less, and the mass ratio of the component B to the component A is 7 or more and 14 or less.

[0012] Another aspect of the present invention is An anti-reflection film formed on an electronic device housing, the anti-reflection film being formed from a resin composition and containing at least component A and component B, an anti-reflection coating, wherein the component A contains the component A1, the component B contains the component B1 having an average particle size of 2 μm or more and 6 μm or less, and the mass ratio of the component B to the component A is 7 or more and 14 or less; is located.

[0013] Another aspect of the present invention is The method for manufacturing the electronic device housing includes: a method for manufacturing an electronic device housing, the method comprising: disposing a resin composition containing at least component A, component B, and component C on a housing body; and removing component C by drying to form an anti-reflection film containing at least component A and component B; is located.

[0014] The resin composition used in the method for producing the electronic device housing is In addition to containing at least components A, B, and C, The A component contains an A1 component, the B component contains a B1 component having an average particle size of 2 μm or more and 6 μm or less, and the mass ratio of the B component to the A component is 7 or more and 14 or less, and The viscosity at 25°C measured with a Brookfield viscometer is adjusted to between 1 mPa·s and 2000 mPa·s.

[0015] The electronic device housing may include the following features. The glossiness of the outermost surface on which the film is formed with respect to incident light at an incident angle of 60° (hereinafter simply referred to as "60° glossiness") may be less than 1%. The glossiness of the outermost surface on which the film is formed with respect to incident light at an angle of incidence of 85° (hereinafter simply referred to as "85° glossiness") may be less than 10%. The reflectance (hereinafter simply referred to as "reflectance") of the outermost surface on which the film is formed to light with a wavelength of 550 nm may be less than 1.5%. The outermost surface on which the film is formed may have an L value of less than 15 in the CIELAB color system according to the SCE method. The optical density of the outermost surface on which the film is formed may be 2 or more.

[0016] The above-described method for manufacturing an electronic device housing may include the following aspects. The resin composition may be applied to the housing body by spray coating. In this case, it is preferable to adjust the viscosity of the resin composition to 1 mPa·s or more and 50 mPa·s or less. The resin composition may be applied to the housing body by dip coating. In this case, it is preferable to adjust the viscosity of the resin composition to 20 mPa·s or more and 500 mPa·s or less. The resin composition may be applied to the housing body by a dispenser method. In this case, it is preferable to adjust the viscosity of the resin composition to 10 mPa·s or more and 300 mPa·s or less. The resin composition may be applied to the housing body by a brush or paint brush (brush application method). In this case, it is preferable to adjust the viscosity of the resin composition to 100 mPa·s or more and 2000 mPa·s or less.

[0017] The above-described electronic device housing, anti-reflection film, and method for manufacturing an electronic device housing may include the following aspects. The content of component A1 in the total amount of component A can be 90 mass % or more. The content of component B1 in the total amount of component B can be 90 mass % or more. Component B1 may contain acrylic resin particles containing carbon black. The anti-reflection coating may have a thickness in the range of 2 μm to 40 μm. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a technique that is effective in improving the design and scratch resistance of an anti-reflection film formed on the housing of an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] 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, when multiple substances corresponding to each component are present in the composition, the total content or amount of the multiple substances present in the composition, unless otherwise specified. In this specification, gloss and reflectance are used to evaluate anti-reflection properties, and optical density is used to evaluate light-blocking properties. Design is evaluated comprehensively based on the above evaluations. In this specification, improving design means suppressing light reflection and incidence and achieving high blackness.

[0021] (Terminology explanation) In this specification, the exterior parts of electronic devices are referred to as "housings." This "housing" may be a single unit or may consist of multiple parts, such as a case and a cover, and its shape is not limited. This term also includes parts attached to the housing body, such as a cover for a memory card. Examples of electronic devices include electronic devices with a display surface or input surface, electronic devices equipped with an optical system, etc. Examples of electronic devices with a display surface or input surface include, but are not limited to, television sets, personal computers, mobile devices (e.g., smartphones, tablets, slate PCs, etc.), digital cameras, digital video cameras, and photo frames. Examples of electronic devices equipped with an optical system include, but are not limited to, digital cameras, digital video cameras, etc.

[0022] 1.<Anti-reflective film> The housing of an electronic device according to one embodiment of the present invention has an anti-reflection film on part or all of the outer surface (hereinafter simply referred to as the "outer surface") of the housing body. The "outer surface" includes a case in which the anti-reflection film is formed directly on the outer surface of the housing body of the electronic device housing, as well as a case in which the anti-reflection film is formed after an optional layer (e.g., a primer layer) is interposed between the outer surface of the housing body and the anti-reflection film. The "part or all" includes a case in which the anti-reflection film is formed on part of the outer surface of the housing body. In this case, the outer surface of the housing body itself is exposed on the outer surface side of the housing body. The anti-reflection film is formed from a resin composition having a predetermined composition.

[0023] 2.<Resin composition> The resin composition according to one embodiment of the present invention (hereinafter also referred to as "the composition") comprises: The present invention is directed to forming a film on the outer surface of the housing body (hereinafter also referred to as "subject to be coated") of an electronic device housing according to one embodiment of the present invention. This composition consists of a film-forming component (solid content) and a volatile component. The film-forming component refers to the components remaining after excluding the volatile components from all components constituting this composition, and is the component that will ultimately form the anti-reflective film. In this specification, the components remaining when the resin composition is dried at 120°C for 3 minutes are considered to be the film-forming component.

[0024] The film-forming components include a binder resin (component A) and a black material (component B), and the volatile components include a diluent solvent (component C). Component A includes a polyvinyl acetal resin (component A1). Component B includes a composite of a black pigment and a resin (component B1) having a specific particle size range. Films formed from this composition containing the above-mentioned components A, B, and C exhibit lower gloss (60° gloss less than 1% and 85° gloss less than 10%) than conventional films. In addition, they exhibit ultra-low reflectivity (less than 1.5%) and ultra-low L value (less than 15), both of which are lower than conventional films, while also exhibiting high film strength. Although the reason for this is unclear, by including component A1, which is tough, flexible, and self-crosslinkable, in component A, the formed film exhibits high film strength even with a small amount of component A. This (a small amount is sufficient) provides a reflective effect, allowing the relative amount of component B, including component B1, to be increased in the formed film. By including component B1 in component B and incorporating a large amount of component B in the film, the formed film exhibits lower gloss than conventional films. In addition, they exhibit ultra-low reflectivity, ultra-low L value, and high light-blocking properties, both of which are lower than conventional films. As a result, the film formed is believed to have high designability and excellent scratch resistance.

[0025] 2-1. <Binder resin (component A)> Component A contained in this composition is a fixing agent for the coating surface and also a binder for component B. Component A 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 a polyvinyl acetal resin (component A1) from the viewpoints of achieving 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.

[0026] By including Component A1 in the thermoplastic resin contained in Component A, flexibility and toughness can be imparted to the film that is formed. In addition, because it is crosslinkable itself, high film strength (scratch resistance) can be achieved even with a small amount of Component A1 in the composition (and therefore in the film).

[0027] 2-1-1.<Polyvinyl acetal resin (A1 component)> Component 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 component A1 include polyvinyl formal, polyvinyl acetoacetal, polyvinyl propylal, and polyvinyl butyral. More specifically, a polymer represented by the following formula (1) is preferred.

[0028] [ka]

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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. When the glass transition temperature (Tg) is within the range of 40°C or higher and 130°C or lower, merits such as improved coating film strength when formed into a coating film can be realized. The higher the glass transition temperature (Tg), the more improved the coating film strength can be expected when formed into a coating film. The glass transition temperature (Tg) can be determined by measuring the change in heat quantity by differential scanning calorimetry (DSC method).

[0033] The x of component A1, 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 surface when formed into a coating, 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 (component B) 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."

[0034] The y of the A1 component, i.e., the content of structural units having a hydroxy group (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 the A1 component contains a structural unit having an acetyl group, the content thereof (hereinafter also referred to as "acetyl group amount") may be preferably 0.0001 mol % or more, more preferably 0.001 mol % or more, from the viewpoint of increasing the content of the black material (B component), and may be preferably 15 mol % or less, more preferably 10 mol % or less, and even more preferably 8 mol % or less.

[0035] The number average molecular weight of component 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 even 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 higher the number average molecular weight of component A1, the better the coating film strength can be expected to be when formed into a coating film. The number average molecular weight of component A1 can be determined as a calculated molecular weight based on the degree of polymerization of the polyvinyl acetal resin used in the reaction. The number average molecular weight refers to a calculated molecular weight.

[0036] Component A1 typically contains an unmodified polyvinyl acetal resin, but from the viewpoint of increasing the cohesive strength of the coating film when formed into a coating film, it may contain a modified polyvinyl acetal resin containing a structural unit having a modifying group other than an acetal group, a hydroxy group, or an acetyl group. Examples of the structural unit having a modifying group include one or more structural units selected from the group consisting of a structural unit having an imine structure, a structural unit having an acid-modifying group, and a structural unit having an amino group or an amide structure. When the modified polyvinyl acetal resin contains a structural unit having an imine structure (a structure having a C=N bond), 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 the acid-modified group include a carboxy group, a sulfonic acid group, a maleic acid group, a phosphate group, and salts thereof. When the modified polyvinyl acetal resin contains a structural unit having an acid-modified group, 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 contents 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.

[0037] The molecular weight, structure, amount of hydroxyl groups, etc. of the polyvinyl acetal resin (modified or unmodified) can be adjusted appropriately by the degree of polymerization of the PVA used and the acetalization reaction conditions. In the component A1, the sum of x, y, and z in the formula (1) is preferably 100 mol %.

[0038] 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 component A1 may be used alone or in combination of two or more.

[0039] 2-1-2. <Other Component A> Component A may contain other thermoplastic resins excluding Component A1 and thermosetting resins together with Component A1. By including a thermosetting resin in Component A, an improvement in the adhesion performance between the coating film and the object to be coated when forming the coating film is expected. Examples of the thermosetting resin include acrylic resins, urethane resins, phenolic resins, melamine resins, urea resins, diallyl phthalate resins, unsaturated polyester resins, epoxy resins, alkyd resins, and the like. The thermosetting resin may be used alone or in combination of two or more. When Component A contains a thermosetting resin, the mass ratio of the thermosetting resin in Component A is preferably 0.1% by mass or more, preferably 0.5% by mass or more, and may be preferably 1.5% by mass or less, more preferably 1% by mass or less, based on the total amount (100% by mass) of the resin solids of Component A1, from the viewpoint of the adhesion between the coating film and the object to be coated when forming the coating film.

[0040] 2-1-3. <Total Amount of Component A1> The content (total amount) of Component A1 in Component A may be an amount that can exhibit the effects of the present invention. From the viewpoint of expecting the expression of the strength of the formed film, it may be, for example, 90% by mass or more, or 95% by mass or more, based on the total amount (100% by mass) of Component A. The upper limit is not particularly limited and is 100% by mass.

[0041] 2-1-4. <Total Amount of Component A> The content (total amount) of Component A in the total solids of the present composition may be an amount that can exhibit the effects of the present invention. From the viewpoint of maintaining the strength of the formed film, it may be, for example, 1% by mass or more, or 5% by mass or more, based on the total amount (100% by mass) of the total solids. The upper limit may be, for example, 25% by mass or less, or 20% by mass or less, from the viewpoint of expecting an improvement in the designability of the formed film.

[0042] 2-2. <Black Material (Component B)> The component B included in this composition is dispersed in a matrix containing the component A to impart predetermined optical properties to the film that is formed. The component B includes a composite of black pigment and resin (component B1). By including component A1 in component A, even with a small amount of component A blended, the resulting film exhibits high film strength due to the reflective effect, allowing for an increase in the relative amount of component B blended. By including component B1 in component B and blending a large amount of component B, the resulting film exhibits low gloss, and can exhibit ultra-low reflectivity, an ultra-low L value, and high light-blocking properties.

[0043] 2-2-1.<Composite of black pigment and resin (B1 component)> Examples of resins constituting the composite of component B1 with the black pigment include epoxy resins, acrylic resins, urethane resins, styrene resins, ethylene resins, phenol resins, urea resins, amide resins, melamine resins, benzoguanamine resins, etc. Among these, from the viewpoint of dispersibility in the composition, acrylic resins or 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.

[0044] The black pigment that constitutes the composite with the resin of component B1 is not particularly limited, but it is preferable to use carbon black (hereinafter simply referred to as "CB"), which has a significant 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.

[0045] Examples of the composite form of the black pigment and resin in component B1 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), or (2) a form in which the resin is bonded to the surface or interior of the black pigment, or a composite form of these.

[0046] Examples of methods for coating the surface of a black pigment with a resin include 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 black pigment is used as a core, the surface of which 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 black pigment core. Furthermore, it is desirable that the colloidal resin particles cover the black pigment core with almost no gaps. However, this does not exclude cases in which the black pigment core is directly exposed to the outside.

[0047] Component B1 may be a black pigment bonded to a resin of approximately the same size as the particles of the black pigment. Alternatively, the 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 and the resin.

[0048] In one embodiment, the composite form is preferably form (1), and more preferably form of resin particles encapsulating a black pigment, from the viewpoint of improving dispersibility in the composition. In the resin particles encapsulating a black pigment, the black pigment is encapsulated in larger-diameter resin particles, so aggregates are less likely to form in the composition compared to when a small-diameter black pigment is directly blended into the composition, contributing to improved dispersibility.

[0049] The content of black pigment (particularly CB) in component B1 (the total amount of black pigment contained in component B1 when the total amount of component B1 is taken as 100% by mass) may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more. The upper limit may be, for example, 50% by mass or less, 40% by mass or less, or 30% by mass or less.

[0050] Component B1 may contain agglomerated secondary particles formed by agglomeration of primary particles (single particles) of component B1. Agglomerated secondary particles are formed by aggregating a plurality of (two or more) primary particles due to intermolecular forces or the like. Component B1 does not have to be entirely in the form of agglomerated secondary particles, and some may be primary particles.

[0051] The average particle size (D50) of component B1 is 2 μm or more, preferably 3 μm or more. The D50 of component B1 is 6 μm or less, preferably 5 μm or less. For primary particles of the same size, the larger the aggregated secondary particle size, the greater the degree of aggregation. In this regard, component B1 has an average particle size of 6 μm or less, and can be said to have a relatively small degree of aggregation. The smaller the degree of aggregation of component B1, the lower the L value of the formed film tends to be (ultra-low L value), so the D50 value of component B1 is an important indicator. If the D50 of component B1 is too small (e.g., smaller than 2 μm), the proportion of aggregated secondary particles in the composition increases, making dispersion difficult. If the D50 of component B1 is too large (e.g., larger than 6 μm), the tinting strength tends to decrease. "Average particle diameter (D50)" is the volume-based cumulative 50% diameter of particles or fillers determined by laser diffraction / scattering. In other words, particle size distribution is measured by laser diffraction / scattering, and a cumulative curve is calculated with the total volume of the particle group as 100%. The particle diameter is the point on the cumulative curve where the cumulative volume is 50% (= cumulative 50% diameter (D1) in the volume cumulative distribution). The D50 of the B1 component is determined by dispersing the B1 component in water and analyzing it by the laser diffraction / scattering method using a laser diffraction / scattering particle size distribution measuring device (LA-920 measuring device, manufactured by Horiba, Ltd.).

[0052] The B1 component preferably has a cumulative 50% diameter (D2) of 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less, in the cumulative number distribution of primary particles measured with an electron microscope. The cumulative 50% diameter (D2) is the median diameter of the primary particles of the B1 component observed with an electron microscope. If the cumulative 50% diameter (D2) is within the above range, the D50 (= cumulative 50% diameter (D1)) of the B1 component described above is likely to fall within the desired value (6 μm or less), which is preferable. The cumulative 50% diameter (D2) of the B1 component is determined by observing the B1 component using a scanning electron microscope (Hitachi High-Technologies Corporation, S-4800), measuring the diameters (longest diameters) of 100 randomly selected primary particles, and expressing these as the cumulative 50% diameter when the number of primary particles is cumulatively distributed.

[0053] The ratio (D1 / D2) of D1 to the cumulative 50% diameter (D2) of the primary particles of the B1 component is preferably 1 or more and 9 or less, more preferably 1 or more and 5 or less, even more preferably 1 or more and 4 or less, and most preferably 1 or more and 2 or less. The ratio (D1 / D2) of D1 to D2 indicates the degree of aggregation of the B1 component when the size of the primary particles is also taken into consideration, and the smaller the value, the lower the degree of aggregation (in other words, the closer it is to primary particles and the closer it is to a monodispersed state). As mentioned above, there is a correlation between the degree of aggregation of the primary particles of the B1 component and the L value of the formed film, and by reducing the value of D1 / D2 (specifically, preferably 9 or less), the L value of the formed film can be further reduced (realizing an ultra-low L value).

[0054] The shape of component B1 is not particularly limited, but from the viewpoint of matte finish, a spherical shape is preferred. Furthermore, in order to achieve a low gloss, low reflectance, and low L value on the surface of the film to be formed, it is preferred to use particles (sharp products) with a narrow particle size distribution as component B1. Examples of particles with a narrow particle size distribution include particles with a CV (Coefficient of Variation) value of, for example, 15 or less, preferably 13 or less, and more preferably 11 or less. The CV value quantifies the degree of spread (variation in particle size) of the particle size distribution relative to the average value of the particle size (arithmetic mean particle size), and represents the uniformity of the particle size. It can be said that the smaller the CV value, the more uniform the particle size. If the CV value is 15 or less, it can be said that the particles have a uniform particle size (also referred to as single-sized particles). To make the CV value 15 or less, a method of appropriately selecting the manufacturing method of the B1 component can be mentioned. For example, by using a method of slurrying the material and manufacturing it by spray drying, it becomes easier to make the CV value 15 or less. Examples of the method for obtaining the CV value include the Coulter method. By using such particles with a narrow particle size distribution, they are uniformly contained in the film and fine irregularities are formed on the film surface, making it easier to achieve a lower gloss, lower reflectance, and lower L value on the film surface. Also, in order to further reduce the glossiness of the formed film surface, amorphous particles may be used as the B1 component. By using amorphous particles as the B1 component, when it becomes a film, light is repeatedly refracted on the surface and inside of the B1 component, and thus the glossiness of the film surface can be further reduced.

[0055] Commercially available products can be used as the B1 component. Examples of those containing urethane beads include Art Pearl C800 Black (average particle size 6.5 μm, CB content 7.5%, Negami Kogyo Co., Ltd.), etc. Examples of those containing acrylic (acrylic copolymer) beads include Art Pearl GR-004BK (average particle size 3 - 5 μm, CB content 35 - 39%, Negami Kogyo Co., Ltd.), Love Color 224 (SMD) Black (average particle size 2 - 3 μm, CB content 18%, Dainichi Seika Kogyo Co., Ltd.), etc. The B1 component may be used alone or in combination of two or more.

[0056] 2-2-2. <Other B components> The B component may contain, together with the B1 component, other black materials excluding the B1 component (for example, black sulfur compounds, porous carbon, carbon black, etc.).

[0057] 2-2-3. <Total amount of B1 component> The content (total amount) of the B1 component in the B component may be any amount as long as the effects of the present invention can be exhibited. From the perspective of expecting an improvement in the design property of the formed film, it may be, for example, 90% by mass or more, or even 95% by mass or more, based on the total amount (100% by mass) of the B component. The upper limit is not particularly limited and is 100% by mass.

[0058] 2-2-4. <Total amount of B component> The content (total amount) of the B component in the total solid content of the present composition may be any amount as long as the effects of the present invention can be exhibited. From the perspective of avoiding inconveniences (such as increased gloss and insufficient optical density) of the formed film, it may be, for example, 60% by mass or more, or even 65% by mass or more, or 75% by mass or more, based on the total amount (100% by mass) of the total solid content. The upper limit may be, for example, 90% by mass or less, or even 85% by mass or less, or 80% by mass or less, from the perspective of avoiding inconveniences to the coated object (such as film peeling due to poor adhesion and insufficient strength) that occur due to a small amount of the A component in the formed film.

[0059] 2-2-5. <Mass ratio of B component to A component> The mass ratio of the B component to the A component (B component / A component) is 7 or more, preferably 8 or more, more preferably 9 or more. From the perspective of improving the design property of the formed film, the higher the better. The upper limit is 14 or less, preferably 12 or less, from the perspective of maintaining the strength of the formed film. By blending the B component within such a mass ratio range, it is possible to achieve an improvement in the design property (low gloss, low reflection, low L value, high light shielding) while maintaining the strength of the formed film. The "mass ratio of the B component to the A component" refers to the total amount of the B component when the total amount of the A component is set to 1.

[0060] 2-3. <Dilution solvent (C component)> [[ID=

[0061] The component C is not particularly limited as long as it is a solvent capable of adjusting the viscosity of the composition. 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. One type of component C may be used alone, or two or more types may be used in combination. The amount of component C may be appropriately determined to adjust the solids concentration of the composition.

[0062] 2-4.<Optional component (D component)> In addition to the above-described components (component A, component B, and component C), the present composition may contain an optional component (component D) to the extent that the effects of the present invention are not impaired. Examples of component D include leveling agents, thickeners, pH adjusters, lubricants, dispersants, antifoaming agents, curing agents, and reaction catalysts. When component D is included, the blending amount may be 100 parts by mass or less, or may be 30 parts by mass or less, per 100 parts by mass of component A.

[0063] 2-4-1.<Hardening agent> By incorporating a curing agent as component D, the hydroxyl groups contained in component A1 can be utilized to promote crosslinking of component A. Examples of curing agents that react with hydroxyl groups include epoxy compounds, methylol compounds, isocyanate compounds, and titanium chelate compounds. Of these, isocyanate compounds are particularly preferred.

[0064] 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.

[0065] 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.

[0066] From the viewpoint of further improving the adhesion of the formed film to the substrate, it is preferable to use an isocyanate compound having a structure in which the nitrogen atom of the isocyanate group is bonded to an aliphatic carbon atom, and at least one selected from aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, and derivatives thereof is preferably used. Among these, from the viewpoint of improving the adhesion and strength of the formed film to the substrate, isocyanurates of aliphatic polyisocyanates, xylylene diisocyanate, and modified polyisocyanates thereof are preferably used as the isocyanate compound. The curing agent may be used alone or in combination of two or more.

[0067] 2-4-2.<Hardening agent blend ratio> When a curing agent is included in the composition, the blending ratio may be 10 to 70 mass% relative to 100 mass% of Component A. By including a curing agent in this range, it is possible to impart greater strength to the film formed, resulting in a film with greater scratch resistance, and the excellent properties of the film surface (improved design) can be maintained for a long period of time.

[0068] 2-4-3.<Reaction catalyst> When a curing agent is included in the composition, a reaction catalyst can be used in combination to promote the reaction between Component A and the curing agent. Examples of reaction catalysts include ammonia and ammonium chloride. When a reaction catalyst is included in the composition, the amount of the reaction catalyst may be 0.1 to 10 parts by mass per 100 parts by mass of the curing agent.

[0069] 2-5.<Preparation> This composition can be prepared (manufactured) by adding component A, component B, and optionally component D to component C, and mixing and stirring them. The order in which the components are mixed is not particularly limited, as long as these components are mixed uniformly.

[0070] 3.<Anti-reflective coating manufacturing method> This composition is placed on the surface of a desired portion (in this example, the outer surface; same below) of an object to be coated (in this example, the housing body of an electronic device housing; same below), and the dilution solvent (component C) is removed by drying, thereby allowing a film (anti-reflective film) formed from this composition to be placed on the desired portion of the object to be coated. The method for applying the present composition to the substrate (application method) is not particularly limited, and examples thereof include application methods (brush application, etc.), droplet ejection methods (dispenser method, spray coating, etc.), and immersion methods (dip coating, etc.).

[0071] 3-1.<Viscosity of resin composition> The viscosity of this composition cannot be generalized because the appropriate range varies depending on the application method, but it should be approximately 1 mPa·s or more and 2000 mPa·s or less. When the viscosity is within this range, the composition has excellent coatability and is easy to form a film (anti-reflective coating) of any desired thickness on the desired part of the substrate. Furthermore, when the composition has a viscosity within this range, the film formed from it is likely to exhibit the desired characteristics (gloss, reflectance, L value, optical density) and film properties (adhesion, scratch resistance). For example, when the application method is a method using a paintbrush or brush (brush application method), the viscosity is preferably about 100 mPa·s or more and 2000 mPa·s or less. When the application method is a dispenser method, the viscosity is preferably about 10 mPa·s or more and 300 mPa·s or less. When the application method is a spray coating method, the viscosity is preferably about 1 mPa·s or more and 50 mPa·s or less. When the application method is a dip coating method, the viscosity is preferably about 20 mPa·s or more and 500 mPa·s or less. The viscosity of the composition is determined by measuring the composition using a Brookfield viscometer at 25°C and a rotation speed of 60 rpm. The measurement is repeated three times, and the average of the three measured values ​​is used.

[0072] In the case of a brush application method, if the viscosity of the composition is too low, the inconvenience of dripping may occur. If the viscosity of the composition is too high, the inconvenience of smearing may occur. In the case of a dispenser method, if the viscosity of the composition is too low, the liquid may splash or drip, and the liquid may be applied to areas that you do not want to apply it to. If the viscosity of the composition is too high, the liquid 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 appearance. In the case of spray coating, if the viscosity of the composition is too low, it may be impossible to form a film thick enough to achieve the desired performance. If the viscosity of the composition is too high, problems such as the liquid (the composition) not coming out of the nozzle or not being able to atomize even if it does come out can occur. In the case of dip coating, if the viscosity of the composition is too low, excessive dripping can occur, resulting in unevenness and making it impossible to form a clean film. If the viscosity of the composition is too high, the liquid (the composition) may not drain well when the substrate is removed from the liquid (the composition), resulting in burrs, or the surface shape of the film formed from the composition may tend to be flat, resulting in a glossy appearance.

[0073] The viscosity of the composition varies depending on the type and molecular weight of the solids (components A and B) contained in the composition. When component D is blended in addition to components A and B, the viscosity of the composition also varies depending on the type and molecular weight of component D. The viscosity of the composition can be easily adjusted by appropriately determining the amount of component C in the composition.

[0074] The composition may be a one-component type or a two-component type. When a curing agent is blended, the composition may be, for example, a two-component type consisting of a first component containing components other than the curing agent and a second component containing the curing agent.

[0075] When the composition is applied by spray coating, even if there are protrusions or steps in the desired area of ​​the object to be coated, a film with a uniform thickness and specific performance can be formed over the entire surface.

[0076] 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.

[0077] When this composition is applied by brush coating, the thickness of the film formed on the desired part of the substrate 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 forms unevenness.

[0078] 3-2.<Process example> After applying the composition to the desired portion of the substrate, the composition is dried by heating to remove component C and form a film. The drying by heating to remove component C may be carried out, for example, at a temperature of 80°C to 120°C for 5 minutes to 30 minutes. If necessary, the formed film may be irradiated with UV light or EB light. When the composition contains a curing agent, the film formed by heat drying may be further heated to cure the film. In this case, it is not necessary to completely remove component C during heating to remove it. The heating conditions for curing the film may be appropriately adjusted depending on the thickness of the film before heating, the heat resistance of the substrate, the type of component C used, and the like. For example, the heating conditions may be 70°C to 150°C for 1 minute to 30 minutes, or 100°C to 130°C for 2 minutes to 10 minutes.

[0079] 4.<Anti-reflection coating thickness> The thickness of the anti-reflective coating is not particularly limited as long as it provides good adhesion strength to the substrate and does not impede the improvement of design. An example of a suitable thickness is preferably 2 μm or more, more preferably 5 μm or more. The upper limit is preferably 40 μm or less, more preferably 25 μm or less. The thickness of the anti-reflective coating refers to the height from the desired surface of the substrate to the portion protruding due to component B of the coating. The thickness can be measured using a method in accordance with JIS K7130.

[0080] 5.<Characteristics of anti-reflective coating> The properties of the film formed from this composition are as follows:

[0081] 5-1.<Optical properties (gloss, reflectance, L value, optical density)> The film formed from this composition preferably has a 60° gloss of less than 1%, an 85° gloss of less than 10%, a reflectance of less than 1.5%, an L value of less than 15, and an optical density of 2 or greater.

[0082] Here, when a film formed from the present composition is exposed on the outermost surface of an electronic device housing, it is preferable that the 60° gloss, 85° gloss, reflectance, L value, and optical density of the film surface are literally within the above-mentioned ranges. When another film is coated on the film formed from the present composition, it is preferable that the 60° gloss, 85° gloss, reflectance, L value, and optical density of the surface of the other film (i.e., the outermost surface of the housing body of the electronic device housing) are within the above-mentioned ranges. Hereinafter, these surfaces are collectively referred to as the "outermost surface of the film."

[0083] The film formed from this composition preferably has an outermost surface with a 60° gloss of less than 1%, an 85° gloss of less than 10%, a reflectance of less than 1.5%, an L value of less than 15, and an optical density of at least 2. When the optical properties of the outermost surface of the film are within the above ranges, the outermost surface of the film can achieve low gloss, low reflectance (excellent anti-reflection properties; the same applies hereinafter), high blackness, and high light-blocking properties, which in turn tends to significantly improve the design.

[0084] The upper limit of the 60° gloss is preferably less than 1%, more preferably less than 0.7%, and even more preferably less than 0.5%. By making the upper limit of the 60° gloss less than 1%, it is easy to effectively prevent the phenomenon in which the film appears whitish due to diffuse reflection of light, and it is easy to significantly improve the design. The lower limit of the 60° gloss is not particularly limited, and the lower the better. The upper limit of the 85° gloss is preferably less than 10%, more preferably less than 5%. By making the upper limit of the 85° gloss of the outermost film surface less than 10%, together with the 60° gloss, it is easy to effectively prevent the phenomenon in which the film appears whitish due to diffuse reflection of light, and angle dependency is eliminated, making it easy to obtain the benefit of improved design. The lower limit of the 85° gloss is not particularly limited, and the lower the better.

[0085] The upper limit of the reflectance is preferably less than 1.5%, more preferably less than 1.25%, and even more preferably less than 1.0%. By making the upper limit of the reflectance less than 1.5%, it is easy to effectively prevent the phenomenon in which the film appears whitish due to diffuse reflection of light, and it is easy to significantly improve the design. The lower limit of the reflectance is not particularly limited, and the lower the better.

[0086] The upper limit of the L value (blackness) is preferably less than 15, 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. The film may be provided in a position visible to the user, and as a result, a higher appearance quality may be required from the film. Specifically, there may be a demand for a black-painted film with a more sophisticated design (for example, a textured film). By ensuring that the L value is less than 15, the above demands are easily met. 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. The CIELAB color system is a uniform color space recommended in 1976 and specified in JIS Z8781 (2013) to measure color differences due to differences in perception and devices. The three coordinates of CIELAB are represented by the L* value, a* value, and b* value. The L* value indicates lightness and is expressed as 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.

[0087] The lower limit of the optical density is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3.2 or more. By setting the lower limit of the optical density to 2 or more, the light-blocking properties can be further improved, which is effective in improving the design. The upper limit of the optical density is not particularly limited, and the higher the value, the better.

[0088] The glossiness, reflectance, L value, and optical density can be measured by the methods described below.

[0089] 5-2.<Membrane properties (adhesion, scratch resistance)> In addition to exhibiting the above optical properties, it is preferable that the film formed from the present composition further exhibits good adhesion to the substrate and high film strength (scratch resistance). As shown in the adhesion evaluation in the Examples below, the adhesion of the film formed from the present composition to the substrate is preferably 90% or more, more preferably 95% or more, or even 100%. If the adhesion to the substrate is good in this way, the film can be prevented from falling off from the substrate. As shown in the evaluation of scratch resistance 1 in the examples below, the film strength of the film formed from the present composition is preferably such that the number of scratches according to JIS K5600-5-10 ISO 7784-3 is 10 or less, or 2 or less, or even 0. Such high film strength makes it easier to ensure scratch resistance during film production (film formation) and handling.

[0090] (Other embodiments) The anti-reflection film in one embodiment described above can be formed on the outer surface of the housing body of the electronic device housing directly without pre-treatment or via a pre-treatment layer, but is not limited to this embodiment. For example, a sheet for anti-reflection film is prepared by forming an anti-reflection film on an ultra-thin plastic film (such as a PET film) by spray coating, and the sheet is cut to fit the shape of the outer surface of the housing body of the electronic device housing to obtain a sheet piece, which is then attached to the housing body of the electronic device housing via an adhesive layer, and finally, an anti-reflection film may be formed on the outer surface of the housing body of the electronic device housing. [Example]

[0091] 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".

[0092] [Constituents of resin composition] As the binder resin (component A), the following polyvinyl acetal resins (component A1) (A1a to A1e) and a non-polyvinyl acetal resin (A2) were prepared. 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)

[0093] As the black material (B component), the following were prepared: a composite of black pigment and resin (B1 component) with an average particle size in the range of 2 μm to 6 μm (Ba); a composite of B1 component but with an average particle size outside the range of 2 μm to 6 μm (Bb); and materials that do not belong to the B1 component at all (Bc to Bf). Ba: Black acrylic beads (average particle size 3-5 μm) (Art Pearl GR-004BK, Negami Chemical Industries, CB content 35-39%) Bb: Black acrylic beads (average particle size 14-16 μm) (Art Pearl GR-400BK, Negami Chemical Industries, CB content 6-10%) ·Bc: CB (average particle size 150nm) (MHI Black #273, Mikuni Pigment Co., Ltd., CB content 9.5%) Bd: Composite silica (average particle size 3 μm) (Vexia ID, Fuji Silysia Chemical Ltd.) Be: Transparent acrylic beads (average particle size 3 μm) (Unipowder MNB0320C, ENEOS Corporation) Bf: Transparent acrylic beads (average particle size 2 μm) (Unipowder MNB0220C, ENEOS Corporation)

[0094] The "Art Pearl GR-004BK" used for Ba and the "Art Pearl GR-400BK" used for Bb are both spherical acrylic resin particles containing CB, and are a type of composite of CB and acrylic resin. The "MHI Black #273" used for Bc (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 acrylic resin. The "Vexia ID" used for Bd (composite silica) is a composite particle of CB and silica with a CB / silica ratio of approximately 25 / 75 (mass ratio).

[0095] The following was prepared as a dilution solvent (component C). C1: Methyl ethyl ketone C2: Butyl acetate

[0096] As an optional component (component D), an isocyanate compound (Takenate D110N, Mitsui Chemicals, Inc., solid content 75%) was prepared.

[0097] [Object to be coated] A smartphone housing (plastic outer box) was prepared as the object to be coated.

[0098] [Experimental Examples 1 to 20, 24, 5a to 16a, 24a] 1. Preparation of resin composition (paint) Each component for each experimental example was added to the specified amount of component C (mixed solvent of C1 and C2) 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.

[0099] 2. Preparation of evaluation samples Using the paint obtained in each experimental example, evaluation samples (films 1 and 2) were prepared as follows. 2-1. Formation of Membrane 1 Using the same spray coating method as in (3-3-1) Coating Property 1 below, the paint was sprayed onto the outer surface of the substrate to form a coating film, and then the coating film was dried by heating at 120°C for 3 minutes, thereby forming a spray coating film 1 on the coated surface of the substrate with an average film thickness of 10 μm.

[0100] 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.

[0101] 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.

[0102] [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, 1 minute, and No. 1 rotor. This measurement was repeated three times, and the average of the three measurements was calculated. The evaluation criteria are as follows:

[0103] 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, 1 minute, and No. 2 rotor. This measurement was repeated three times, and the average of the three measurements was calculated. The evaluation criteria are as follows:

[0104] Good: Viscosity is 100 mPa·s or more and 2000 mPa·s or less (good viscosity) ×: Viscosity exceeds 2000 mPa·s (too high viscosity)

[0105] (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:

[0106] 〇: There was no clogging at all and the paint went into the nozzle smoothly. △: There was no clogging, but the paint was entering the nozzle a little slowly. ×: There was a blockage and paint did not enter the nozzle.

[0107] (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 from a distance of 10 cm from the tip of the airbrush for 10 seconds, 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.

[0108] 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

[0109] (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:

[0110] ◯: 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.

[0111] [Film evaluation] (3-5) Characteristics -Glossiness- The gloss of the surface of the film formed on each substrate was measured at nine points using a gloss meter (VG 7000: Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z8741 to measure the gloss of the measuring light at an incident angle of 60° (60° specular gloss) and the gloss of the measuring light at an incident angle of 85° (85° specular gloss), and the average value was used as the gloss. The evaluation criteria were as follows:

[0112] (60° specular gloss) ◎: Less than 0.5% (excellent low gloss) 〇: 0.5% or more and less than 0.7% (excellent low gloss) △: 0.7% or more and less than 1% (good low gloss) ×: 1% or more (insufficient low gloss)

[0113] (85° specular gloss) ◎: Less than 5% (excellent low gloss) 〇: 5% or more and less than 10% (excellent low gloss) ×: 10% or more (insufficient low gloss)

[0114] (Overall gloss rating) ◎: All ratings for 60° specular gloss and 85° specular gloss are ◎ (excellent low gloss) ◯: At least one of the 60° specular gloss and 85° specular gloss ratings was ◯, and none was × (excellent low gloss) ×: At least one of the evaluations of 60° specular gloss and 85° specular gloss was × (insufficient low gloss)

[0115] -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:

[0116] ◎: 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)

[0117] -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 in the CIELAB color system. CIE Standard Illuminant D65 is specified in JIS Z8720 (2000) "Illuminates (standard light) and standard light sources for colorimetry," 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) "Methods for visual comparison of surface colors," and the same specification is found in ISO / DIS 3668.

[0118] ◎: 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)

[0119] -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 (ortho filter: Nippon Heihan Kizai Co., Ltd.) by irradiating the film side of the substrate with a perpendicular transmitted light beam and calculating the ratio to the state without the film, expressed in log (logarithm). An optical density of 6.0 or higher is the upper detection limit for the measurement. The evaluation criteria are as follows:

[0120] ◎: 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)

[0121] -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:

[0122] ◎: 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)

[0123] -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: Suga Test Instruments Co., Ltd.) 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 on which a film has been formed; 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 was sized to fit the rotating wheel, causing abrasion. The abrasion resistance 1 was evaluated by checking whether scratches were formed on the film surface of the test piece 1. The rotating wheel rotated 0.9° for each reciprocation of the test piece 1, so that the newly abraded surface of the test piece 2 was always abrading the test piece 1. The evaluation criteria were as follows.

[0124] ◎: 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)

[0125] -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:

[0126] ◎: 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)

[0127] -comprehensive evaluation- The glossiness, reflectance, blackness, light-shielding property, adhesion, and scratch resistance 1 and 2 were comprehensively evaluated according to the following criteria.

[0128] ◎: Glossiness, reflectivity, blackness, light blocking, adhesion, and scratch resistance 1 and 2 are all ◎ ◯: At least one of the evaluations of glossiness, reflectance, blackness, light blocking property, adhesion, and scratch resistance 1 and 2 was ◯, and none of them was × ×: At least one of the evaluations of gloss, reflectance, blackness, light-shielding property, adhesion, and scratch resistance 1 and 2 was ×

[0129] [Table 1]

[0130] [Table 2]

[0131] [Table 3]

[0132] 4. Discussion As shown in Table 1, when the paint contains component A1 as component A, and the paint's component B contains component B1 (Ba) that belongs to component B1 and has an average particle size within a specified range, and the mass ratio of component B to component A in the paint is 7 or more and 14 or less (Experimental Examples 5, 12 to 15), all of the paint properties and film properties (optical properties (gloss, reflectance, L value, light blocking properties), film properties (adhesion, scratch resistance 1, 2)) can be satisfied. In contrast, when the coating material did not contain component A1 as component A (Experimental Examples 1 to 4), one or more of the film characteristics, optical characteristics, and film physical properties could not be satisfied. Even when the paint contained the A1 component as the A component (Experimental Examples 5 to 10, 24), when the B component of the paint contained a B1 component (Ba) that belonged to the B1 component but had an average particle size outside the specified range (Bb) (Experimental Example 6), it was not possible to satisfy one or more of the film characteristics, optical characteristics, and film physical properties. Even when the paint contained the A1 component as the A component (Experimental Examples 5-10, 24), when the paint contained a B component that did not belong to the B1 component (Bc-Bf) instead of a B1 component (Ba) that belonged to the B1 component and had an average particle size within a specified range (Experimental Examples 7-10, 24), one or more of the film characteristics, optical characteristics, and film physical properties could not be satisfied. Even if the B component of the paint contains a B1 component (Ba) with an average particle size within a specified range (Experimental Examples 5, 11 to 16), when the mass ratio of B component to A component in the paint is less than 7 (Experimental Example 11) or exceeds 14 (Experimental Example 16), one or more of the film characteristics, optical characteristics, and film physical properties cannot be satisfied.

[0133] As shown in Table 2, when the paint contains component A1 as component A, and the paint's component B contains component B1 (Ba) that belongs to component B1 and has an average particle size within a specified range, and the mass ratio of component B to component A in the paint is 7 or more and 14 or less (Experimental Examples 5a, 12a to 15a), all of the paint's properties and film properties can be satisfied. In contrast, even when the paint contained the A1 component as the A component (Experimental Examples 5a to 10a, 24a), when the paint contained a B component that belonged to the B1 component but did not have an average particle size within the specified range (Bb) instead of a B1 component (Ba) that belonged to the B1 component but had an average particle size outside the specified range (Experimental Example 6a), it was not possible to satisfy one or more of the film characteristics, optical characteristics, and film physical properties. Even when the paint contained the A1 component as the A component (Experimental Examples 5a to 10a, 24a), when the paint's B component contained a non-B1 component (Bc to Bf) instead of a B1 component (Ba) that belonged to the B1 component and had an average particle size within a specified range (Experimental Examples 7a to 10a, 24a), one or more of the film characteristics, optical characteristics, and film physical properties could not be satisfied. Even if the B component of the paint contains a B1 component (Ba) with an average particle size within a specified range (Experimental Examples 5a, 11a to 16a), when the mass ratio of B component to A component in the paint is less than 7 (Experimental Example 11a) or exceeds 14 (Experimental Example 16a), one or more of the film characteristics, optical characteristics, and film physical properties cannot be satisfied.

[0134] As shown in Table 3, when the amount of component A was fixed and the type of component A1 included in component A was changed (Experimental Examples 5, 17 to 20), it was also confirmed that the film strength (scratch resistance 1, 2) improved as the molecular weight and glass transition temperature increased.

[0135] [Experimental Example 21] A paint was prepared with the same composition as in Experimental Example 5, except that Ba (i.e., a compound belonging to the B1 component and having an average particle size within a specified range) was used as the black pigment and resin composite (B1 component) included as the black material (B component), and black acrylic beads (average particle size 5 to 6 μm), which are spherical acrylic resin particles containing CB like Ba but have a slightly larger average particle size, were used.A film was then formed in the same manner as above and evaluated in the same way, and it was confirmed that the same evaluation as in Experimental Example 5 was obtained.

[0136] [Experimental Example 22] A coating material was prepared with the same composition as in Experimental Example 5, except that the content of polyvinyl acetal resin (component A1) relative to the total amount (100% by mass) of binder resin (component A) was 90% by mass, and the remaining 10% by mass was an acrylic resin (molecular weight 10,000 or more, Tg 30°C or more) that belongs to component A but does not belong to component A1. 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.

[0137] [Experimental Example 23] A paint was prepared with the same composition as in Experimental Example 5, except that the content of Ba (i.e., Ba belonging to component B1 and having an average particle size within a specified range) relative to the total amount (100% by mass) of the black material (component B) was 90% by mass, and the remaining 10% by mass was black acrylic beads (average particle size 0.5 to 1.5 μm) belonging to component B1 but having an average particle size outside the specified range. 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. The electronic device housing has an anti-reflection film on the housing body, The anti-reflection film is formed from a resin composition and contains at least component A and component B, An electronic device casing, wherein component A contains component A1, and the content of component A1 in the total amount of component A is 90 mass% or more; component B contains component B1 having an average particle diameter of 2 μm or more and 6 μm or less, and the content of component B1 in the total amount of component B is 90 mass% or more; component B1 is made of resin particles encapsulating a black pigment; and the mass ratio of component B to component A is 7 or more and 14 or less. (Component A) Binder resin (Component A1) Polyvinyl acetal resin (Component B) Black material (Component B1) Composite of black pigment and resin

2. The electronic device housing according to claim 1 , wherein the anti-reflection film has a thickness in the range of 2 μm to 40 μm.

3. 3. The electronic device casing according to claim 1 or 2, wherein the outermost surface on which the film is formed has a glossiness of less than 1% for incident light at an incident angle of 60°, a glossiness of less than 10% for incident light at an incident angle of 85°, a reflectance of less than 1.5% for light with a wavelength of 550 nm, an L value of less than 15 in the CIELAB color system according to the SCE method, and an optical density of 2 or more.

4. An anti-reflection film formed on an electronic device housing, The resin composition includes at least an A component and a B component. an anti-reflection film, wherein the A component contains an A1 component, the content of the A1 component in the total amount of the A component being 90 mass% or more; the B component contains a B1 component having an average particle diameter of 2 μm or more and 6 μm or less, the content of the B1 component in the total amount of the B component being 90 mass% or more; the B1 component is made of resin particles encapsulating a black pigment; and the mass ratio of the B component to the A component is 7 or more and 14 or less. (Component A) Binder resin (Component A1) Polyvinyl acetal resin (Component B) Black material (Component B1) Composite of black pigment and resin

5. A method for manufacturing the electronic device enclosure of claim 1, comprising: Contains at least component A, component B, and component C, the A component contains an A1 component, and the content of the A1 component in the total amount of the A component is 90 mass% or more; the B component contains a B1 component having an average particle diameter of 2 μm or more and 6 μm or less, and the content of the B1 component in the total amount of the B component is 90 mass% or more; the B1 component is made of resin particles encapsulating a black pigment; and the mass ratio of the B component to the A component is 7 or more and 14 or less; A method for manufacturing an electronic device housing, comprising: placing a resin composition, the viscosity of which is adjusted to 1 mPa·s or more and 2000 mPa·s or less at 25°C as measured with a Brookfield viscometer, on a housing body; and removing component C by drying to form an anti-reflection film containing at least component A and component B. (Component C) Dilution solvent

6. 6. The method for manufacturing an electronic device housing according to claim 5, comprising applying a resin composition, the viscosity of which is adjusted to 1 mPa·s or more and 50 mPa·s or less at 25°C as measured by a Brookfield viscometer, by a spray coating method to form an anti-reflection film on the housing body.

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