Electronic device housing, its manufacturing method, and anti-reflective coating

Abstract

This invention provides a technique for effectively improving the design and scratch resistance of an anti-reflective film formed on an electronic device housing. An adhesive resin is designated as component A, a polyvinyl acetal resin as component A1, a black material as component B, and a composite of black pigment and resin as component B1. The electronic device housing has an anti-reflective film on its body. The anti-reflective film is formed from a resin composition and includes at least component A and component B. Component A includes component A1, and component B includes component B1 with an average particle size of 2 μm or more and 6 μm or less. The mass ratio of component B to component A is 7 or more and 14 or less.

Description

Technical Field

[0001] This invention relates to an electronic device housing, its manufacturing method, and an anti-reflective film. Prior Technology

[0002] Anti-reflective coatings are applied to a portion or all of the casing of electronic devices such as smartphones, tablets, and personal computers to enhance design, conceal internal wiring, provide light shielding, and prevent reflections.

[0003] For example, Patent Document 1 discloses a technique for directly applying screen printing made of insulating material to the casing of portable electronic devices such as smartphones, or forming a black film by in-mold molding of a screen-printed film. [Previous Technical Documents] [Patent Documents]

[0004] Patent Document 1: Japanese Patent Application Publication No. 2007-285093 Summary of the Invention

[0005] [Problem to be Solved by the Invention] However, with the increasing demand for improved design in industrial products in recent years, there is a need to apply films with a higher degree of blackness that better highlights the design of these products. In addition, it is sometimes necessary to ensure the abrasion resistance of the film during manufacturing (film formation) and handling.

[0006] The present invention was made in view of the above circumstances, and its object is to provide a technique for effectively improving the design and scratch resistance of anti-reflective films formed on electronic device housings. [Methods used to solve problems]

[0007] Through in-depth research, the inventors have discovered that anti-reflective films formed on the casing of electronic devices can effectively improve design and scratch resistance by meeting the following requirements. • A resin composition is formed by comprising an adhesive resin (a element) containing a specific resin (polyvinyl acetal resin) and a black material (b element) having a specific composite material (a composite material of black pigment and resin) having a particle size within a specified range, in a specified mass ratio (7 or more and 14 or less relative to 1 element a).

[0008] The mechanism underlying the aforementioned phenomena is not yet clear, but by incorporating a specific resin into element a, the resulting film can be endowed with softness and toughness. Furthermore, because the specific resin itself is cross-linkable, even a small amount of element a results in a film exhibiting high strength. As a reflective effect, the relative amount of element b in the resulting film can be increased. By incorporating a specific complex into element b and including a large amount of element b in the film, the resulting film exhibits lower gloss compared to films formed from conventional resin compositions (hereinafter referred to as "conventional films"), and expresses even lower ultra-low reflectance and ultra-low L-value, as well as higher light-blocking properties. This suggests that a highly designable and scratch-resistant antireflective film can be obtained.

[0009] Based on these new insights, the inventors have completed the invention described below, solving the aforementioned problems. Hereinafter, the adhesive resin is designated as component A, the polyvinyl acetal resin (a specific resin) as component A1, the black material as component B, the complex of black pigment and resin (a specific complex) as component B1, and the diluent as component C.

[0010] One aspect of the present invention is an electronic device housing, the housing body of which has an anti-reflective film.

[0011] The anti-reflective coating of the aforementioned shell, Formed from a resin composition, comprising at least component A and component B. Component A contains component A1, and component B contains component B1 with an average particle size of 2 μm or more but less than 6 μm. The mass ratio of component B to component A is 7 or more and 14 or less.

[0012] Another embodiment of the invention is an anti-reflective film formed on the casing of an electronic device. Formed from a resin composition, comprising at least component A and component B. Component A contains component A1, and component B contains component B1 with an average particle size of 2 μm or more but less than 6 μm. The mass ratio of component B to component A is 7 or more and 14 or less.

[0013] Another aspect of the present invention is a method for manufacturing an electronic device housing, which is the aforementioned method for manufacturing an electronic device housing. It involves disposing a resin composition containing at least components A, B, and C on a housing body, removing component C by drying, and forming an antireflective film containing at least components A and B.

[0014] The resin composition used in the manufacturing method of the above-mentioned electronic machine housing, In addition to containing at least components A, B, and C, Component A contains component A1, and component B contains component B1 with an average particle size of 2 μm or more and 6 μm or less, and the mass ratio of component B to component A is 7 or more and 14 or less. The viscosity measured at 25°C using a type B viscometer was adjusted to be above 1 mPa·s and below 2000 mPa·s.

[0015] The aforementioned electronic device housing may include the following forms: • The gloss of the outermost surface of the film-forming surface with respect to incident light at an angle of 60° (hereinafter referred to as "60° gloss") may be less than 1%. • The gloss of the outermost surface of the film-forming surface with respect to incident light at an angle of 85° (hereinafter referred to as "85° gloss") may not reach 10%. • The reflectivity (hereinafter referred to as "reflectivity") of the outermost surface of the film-coated surface to light with a wavelength of 550nm may not reach 1.5%. • The L value in the CCIELAB color system based on the SCE method for forming the film on the outermost surface may not reach 15. • The optical density of the outermost surface of the film can be 2 or higher.

[0016] The above-mentioned method for manufacturing electronic device housings may include the following forms: • The resin composition can be applied to the housing body by spraying. In this case, the viscosity of the resin composition is preferably adjusted to be 1 mPa·s or more and 50 mPa·s or less. The resin composition can be applied to the shell body using an impregnation coating method. In this case, the viscosity of the resin composition is preferably adjusted to be 20 mPa·s or more and 500 mPa·s or less. The resin composition can be applied to the shell body using a dispensing method. In this case, the viscosity of the resin composition is preferably adjusted to be 10 mPa·s or more and 300 mPa·s or less. • The resin composition can also be applied to the housing body using a pen or brush (brush method). In this case, the viscosity of the resin composition is preferably adjusted to be 100 mPa·s or more and 2000 mPa·s or less.

[0017] The aforementioned electronic device housing, anti-reflective film, and manufacturing method of the electronic device housing may include the following forms: • Of the total amount of component A, the content of component A1 can be 90% or more by mass. • Of the total amount of component B, the content of component B1 can be above 90% by mass. Component B1 may contain acrylic resin particles encapsulated with carbon black. • The thickness of the anti-reflective coating can be in the range of more than 2 μm and less than 40 μm. [Invention Effects]

[0018] This invention provides a technique to effectively improve the design and scratch resistance of anti-reflective coatings formed on electronic device housings. Implementation

[0019] The preferred embodiments of the present invention will be described below. However, the present invention is not limited to the following embodiments. Without departing from the spirit of the present invention, those skilled in the art can make appropriate changes and improvements to the following embodiments based on common knowledge, and these also fall within the scope of the present invention.

[0020] The numerical ranges described in this specification may also be replaced by the numerical values ​​disclosed in the embodiments, which may replace the upper or lower limits of certain numerical ranges. In this specification, the content or percentage of each component in the composition is, unless otherwise stated, the total content or percentage of the multiple substances present in the composition when there are multiple substances equivalent to each component in the composition. In this specification, gloss and reflectivity are used to evaluate anti-reflective performance, and optical density is used to evaluate light-blocking performance. A comprehensive design evaluation is conducted based on these evaluations. In this specification, "design enhancement" refers to achieving high blackness while suppressing light reflection and incident light.

[0021] (Terminology Explanation) In this specification, the external components of an electronic device are referred to as the "casing". The "casing" may consist of a single unit or multiple components such as a housing and a cover, and its shape is not limited. It also includes components belonging to the housing body, such as a memory card cover. As electronic machines, examples include electronic machines with a display or input surface, electronic machines with an optical system, etc. Examples of electronic machines with a display or input surface include televisions, personal computers, mobile devices (such as smartphones, tablets, Slate PCs, etc.), digital cameras, digital camcorders, and picture frames, but these are not exhaustive. Examples of electronic machines with an optical system include digital cameras, digital camcorders, etc., but these are not exhaustive.

[0022] 1. Anti-reflective coating According to one aspect of the present invention, an electronic device housing has an anti-reflective film on a portion or all of the outer surface of the housing body (hereinafter referred to as the "outer surface"). Because it is "on the outer surface," the anti-reflective film includes not only those formed directly on the outer surface of the housing body, but also those formed by intervening any layer (e.g., a primer layer) between the outer surface of the housing body and the anti-reflective film. Because it is "partial or complete," the anti-reflective film includes the case where it is formed on a portion of the outer surface of the housing body. In this case, the housing body itself will be exposed on the outer surface side of the housing body. The aforementioned antireflective film is formed from a resin composition with a specified composition.

[0023] 2. <Resin Composition> The resin composition of one aspect of the present invention (hereinafter also referred to as "the composition") is used to form a film on the outer surface of the housing body (hereinafter also referred to as "the coating") of an electronic device housing of one aspect of the present invention. This composition consists of a film-forming component (solid content) and volatile components. The film-forming component refers to the component remaining after removing the volatile components from all the components constituting this composition, ultimately forming the antireflective film. In this specification, the component remaining after drying the resin composition at 120°C for 3 minutes is used as the film-forming component.

[0024] The film-forming components include an adhesive resin (component A) and a black material (component B), while the volatile components include a diluent (component C). Component A includes polyvinyl acetal resin (component A1). Component B includes a composite of a black pigment and resin having a specified particle size range (component B1). The film formed from this composition, comprising components A, B, and C, exhibits lower gloss (less than 1% gloss at 60° and less than 10% gloss at 85°) compared to conventional films. Furthermore, it displays lower ultra-low reflectance (less than 1.5%) and ultra-low L-value (less than 15) compared to conventional films, while also exhibiting high strength. The reason for this is not yet certain, but because component A contains component A1, which is tough, flexible, and self-crosslinking, even a small amount of component A results in a film with high strength. Therefore, as a result of its (sufficient amount) reflective effect, the relative proportion of component B, which contains component B1, is increased in the formed film. Because component B contains component B1 and this component B is incorporated into the film in large quantities, the resulting film exhibits lower gloss compared to conventional films. In addition, it displays lower ultra-low reflectance and ultra-low L-value, and higher light-blocking properties compared to conventional films. As a result, the formed membrane exhibits high designability and excellent scratch resistance.

[0025] 2-1. <Adhesive Resin (Component A)> Component A in this composition is used as a fixing material for the coated surface and also as an adhesive for component B. Component A contains a thermoplastic resin. Examples of thermoplastic resins include polyacrylate resin, polyvinyl chloride resin, polyvinyl acetal resin, and styrene-butadiene copolymer resin. Among these, from the viewpoint of achieving low gloss, ultra-low reflectivity, ultra-low L-value, and film strength of the formed film surface, polyvinyl acetal resin (component A1) is preferred. One thermoplastic resin may be used alone, or two or more may be used in combination.

[0026] The thermoplastic resin contained in component A, which includes component A1, imparts softness and toughness to the formed film. Furthermore, due to its own cross-linking properties, even a small amount in this composition (or even in the film) can result in high film strength (abrasion resistance).

[0027] 2-1-1. <Components of Polyvinyl Acetal Resin A1> Component A1 is a polymer having structural units with acetal groups within the molecule, preferably a polymer having structural units with acetal groups and structural units with hydroxyl groups. Examples of components A1 include polyvinyl formal, polyvinyl acet acetal, polyvinyl propyral, and polyvinyl butyral, and more specifically, polymers shown in formula (1) below are preferred.

[0028] [Chemistry 1]

[0029] In formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. x represents the content (moles%) of structural units having a vinyl acetal group, expressed as the total content (moles%) of structural units derived from acetalized vinyl alcohol. y represents the content (moles%) of structural units derived from vinyl alcohol, and z represents the content (moles%) of structural units derived from vinyl acetate. x and y can be greater than 0, and z can be 0.

[0030] R1 is preferably an alkyl group having 1 to 10 hydrogen atoms or carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and most preferably propyl. That is, as component A1, polyvinyl butyral resin having a propyl group as the structural unit is most preferably polyvinyl butyral resin.

[0031] Polyvinyl butyral resin can be obtained by reacting polyvinyl alcohol (PVA) and butyraldehyde under acidic conditions and then acetalizing them. During the acetalization of PVA, it is difficult to completely acetalize the PVA, thus irreversibly leaving some hydroxyl groups. Furthermore, PVA is usually manufactured by saponifying polyvinyl acetate, but since small amounts of acetyl groups are often left behind during the saponification process in PVA manufacturing, polyvinyl butyral resin generally contains some irreversibly remaining acetyl or hydroxyl groups.

[0032] From a heat resistance perspective, the glass transition temperature (Tg) of polyvinyl butyral resin can be between 40°C and 130°C, preferably between 60°C and 120°C. A glass transition temperature (Tg) within the range of 40°C to 130°C offers advantages such as improved coating strength during coating formation. A higher glass transition temperature (Tg) generally indicates greater improvement in coating strength during coating formation. The glass transition temperature (Tg) can be determined by measuring the change in heat using differential scanning calorimetry (DSC).

[0033] From the viewpoint of the slipperiness of the coating surface during coating formation, the content of x, i.e., the content of structural units with acetal groups in component A1 (hereinafter also referred to as "acetal group content" or "acetalization degree"), is preferably 60 mol% or more, more preferably 65 mol% or more, and even more preferably 70 mol% or more. In addition, from the viewpoint of the dispersibility of the black material (component B) in this composition, it is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less. The acetal content (x) is a mole fraction obtained by dividing the amount of vinyl groups bonded to the acetal group by the total amount of vinyl groups in the main chain, and is equivalent to the content (moles %) of structural units with acetal groups. The amount of vinyl groups bonded to acetal groups (especially butyral groups) can be determined using JIS K6728 "Test Method for Polyvinyl Butyral".

[0034] From the viewpoint of the adhesion between the coating film and the substrate during coating formation, the content of y, i.e., the structural unit with hydroxyl groups in component A1 (hereinafter also referred to as "hydroxyl content"), is preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less. When component A1 contains structural units with acetyl groups, its content (hereinafter also referred to as "acetyl content") is preferably 0.0001 mol% or more, more preferably 0.001 mol% or more, and even more preferably 15 mol% or less, more preferably 10 mol% or less, and even more preferably 8 mol% or less, from the viewpoint of increasing the content of black material (component B).

[0035] There is no particular limitation on the number average molecular weight of component A1, but from the viewpoint of coating strength during coating formation, it is preferably 8000 or more, more preferably 10000 or more, further preferably 15000 or more, even more preferably 20000 or more, and preferably 300000 or less, more preferably 200000 or less, and even more preferably 150000 or less. The higher the number average molecular weight of component A1, the greater the expected improvement in coating strength during coating formation. The number average molecular weight of component A1 can be calculated based on the degree of polymerization of the polyvinyl acetal resin used in the reaction. The number average molecular weight is the calculated molecular weight.

[0036] The A1 component typically contains unmodified polyethylene acetal resin. However, from the viewpoint of improving the cohesiveness of the coating film during coating, it can contain modified polyethylene acetal resin with structural units having modified groups other than acetal, hydroxyl, and acetyl groups. Examples of structural units with modified groups include, for example, structural units selected from the group consisting of structural units having imine structures, structural units having acid-modified groups, and structural units containing amine or acetylamine structures. When the modified polyethylene acetal resin contains structural units having an imine structure (a structure having C=N bonds), its content is preferably 0.1 mol% or more, more preferably 1 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less. Examples of acid-modifying groups include carboxyl groups, sulfonic acid groups, maleic acid groups, phosphate groups, and their salts. When the modified polyethylene acetal resin contains structural units having acid-modifying groups, its content is preferably 0.01 mol% or more, more preferably 0.05 mol% or more, and preferably 5 mol% or less, more preferably 3 mol% or less. The content of structural units having an imine structure and structural units having acid-modifying groups can be determined, for example, by NMR. In modified polyethylene acetal resin, imine structure, acid-modifying group, amine group or amide structure can be directly bonded to the carbon atoms of the main chain or side chain constituting the modified polyethylene acetal resin, or they can be bonded by linking groups such as alkylene groups.

[0037] The molecular weight, structure, and hydroxyl content of polyvinyl acetal resin (modified and unmodified) can be appropriately adjusted according to the degree of polymerization of the PVA or the acetalization reaction conditions used. The A1 component is, in the aforementioned formula (1), preferably the sum of x, y, and z is 100 moles.

[0038] Examples of commercially available polyvinyl acetal (butyraldehyde) resins include Sekisui Chemicals Co., Ltd.'s S-LEC series: BL (low molecular weight): BL-1, BL-1H, BL-S, BL-2H; BM (medium molecular weight): BM-1, BM-2(Z), BM-5, BM-S(Z); BH (high molecular weight): BH-S, BH-A; BX (heat resistant): BX-1, BX-5(Z); KS (high heat resistant): KS-6Z, KS-5Z; etc. Additionally, Kuraray's Mowital series products can also be cited. Component A1 can be used alone or in combination with two or more components.

[0039] 2-1-2. <Other Component A> Component A can include other thermoplastic resins or thermosetting resins in addition to Component A1. By containing a thermosetting resin in Component A, an improvement in the adhesion between the coating film and the object to be coated during film formation can be 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, etc. The thermosetting resin can be used alone or in combination of two or more. When Component A contains a thermosetting resin, from the viewpoint of the adhesion between the coating film and the object to be coated during film formation, the mass ratio of the thermosetting resin in Component A is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 1.5% by mass or less, more preferably 1% by mass or less, relative to the total amount (100% by mass) of the resin solids of Component A1.

[0040] 2-1-3. <Total amount of Component A1> The content (total amount) of Component A1 in Component A only needs to be an amount capable of expressing the effects of the present invention. From the viewpoint of expecting to express the strength of the formed film, for example, it is preferably 90% by mass or more, more preferably 95% by mass or more, relative to 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> In the total solid content of this composition, the content (total amount) of Component A only needs to be an amount capable of expressing the effects of the present invention. From the viewpoint of maintaining the strength of the formed film, for example, it is preferably 1% by mass or more, more preferably 5% by mass or more, relative to the total amount (100% by mass) of the total solid content. The upper limit is, from the viewpoint of expecting to improve the designability of the formed film, for example, 25% by mass or less, and can also be 20% by mass or less.

[0042] 2-2. <Black material (Component B)> Component B contained in this composition is dispersed in the matrix containing Component A to impart prescribed optical properties to the formed film. Component B includes a complex (Component B1) of a black pigment and a resin. By including Component A1 in Component A, as the ratio of Component A is relatively small and the formed film exhibits a high-strength reflection effect, the relative compounding amount of Component B can be increased. By including Component B1 in Component B and increasing the ratio of Component B, the formed film can achieve low gloss and exhibit ultra-low reflection, ultra-low L value, and high light-shielding properties.

[0043] 2-2-1. <A complex of black pigment and resin (component B1)> As a component B1, the resin constituting the complex with the black pigment can be, for example, epoxy resin, acrylic resin, carbamate resin, styrene resin, vinyl resin, phenolic resin, urea resin, amide resin, melamine resin, benzoguanamine resin, etc. Among these, from the viewpoint of dispersibility in the composition, acrylic resin or carbamate resin is preferred, and acrylic resin is more preferred. One of these can be used alone, or two or more can be used in combination. Additionally, by adding the resin name before the bead name, the name of some resin particles can be omitted. For example, resin particles made of acrylic resin can also be called acrylic (acrylic) beads.

[0044] The black pigment that forms the complex with the resin in component B1 is not particularly limited, but carbon black (hereinafter referred to as "CB"), which has a great blackening effect and is also cost-effective, is preferred. By using CB, the film formed will be colored, thus further improving the anti-reflective effect and achieving a good antistatic effect.

[0045] As a component of B1, the composite form of black pigment and resin can be, for example, any one of (1) the form in which black pigment is coated with resin (including the form in which black pigment is encapsulated in resin particles), (2) the form in which resin is bonded to the surface or interior of black pigment, or a composite form of these.

[0046] Methods for coating the surface of black pigment with resin include, for example, microencapsulation, and more specifically, interfacial polymerization, in-situ polymerization, liquid-curing coating (sharp-pore method), aqueous phase separation, and liquid-drying. In addition to microencapsulation, there are methods for bonding or adhering resin to dispersed black pigment. For example, a method involves using a black pigment core and covering the surface with multiple colloidal resin particles. When using a colorant that coats the black pigment core with colloidal resin particles, the size of the surrounding resin particles is preferably sufficiently small relative to the black pigment core. Furthermore, the colloidal resin particles are preferably coated with the black pigment core almost without gaps. However, it is not excluded that the black pigment core is directly exposed to the outside.

[0047] Component B1 can also bond resin particles of the same size as the black pigment to the black pigment. Alternatively, black pigments or dyes can be compounded with resins by mixing them into other thermoplastic or thermosetting resins and then pulverizing them.

[0048] From the viewpoint of improving the dispersibility of the composition, the composite form is preferably the form of (1), and the form of resin particles containing black pigment is more preferably. Since the resin particles containing black pigment contain black pigment, it is less likely to form aggregates in the composition compared to the case where black pigment with a small diameter is directly incorporated into the composition, which helps to improve dispersibility.

[0049] The content of black pigment (especially CB) in component B1 (the total amount of black pigment contained therein when the total amount of component B1 is 100% by mass) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. Its upper limit is, for example, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0050] Component B1 can include condensed secondary particles formed by the condensation of primary particles (single particles) of component B1. Condensed secondary particles are formed by the condensation of multiple (two or more) primary particles through intermolecular forces, etc. Component B1 does not necessarily exist entirely in the form of condensed secondary particles; some of it may also 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. If the primary particles are of the same size, the larger the secondary particle size, the greater the degree of aggregation. In this respect, the average particle size of component B1 is less than 6 μm, indicating a relatively low degree of aggregation. The lower the aggregation degree of component B1, the lower the L value of the formed film tends to be (ultra-low L value). Therefore, the D50 value is an important indicator for component B1. If the D50 of component B1 is too small (e.g., less than 2 μm), the proportion of aggregated secondary particles in this composition will increase, thus making it difficult to disperse. If the D50 of component B1 is too large (e.g., greater than 6 μm), the tinting strength tends to decrease. "Average particle size (D50)" is the cumulative 50% diameter of the particle or filler volume, obtained by laser diffraction and scattering. That is, the particle size distribution is determined by laser diffraction and scattering, and a cumulative curve is obtained with the total volume of the particle group as 100%. The particle size at the point on the cumulative curve that represents 50% of the cumulative volume is (= the cumulative 50% diameter (D1) in the volume cumulative distribution). The D50 of component B1 was obtained by dispersing component B1 in water and analyzing it using a laser diffraction and scattering method with a laser diffraction and scattering particle size distribution measuring device (Horiba Manufacturing Co., Ltd., LA-920 measuring instrument).

[0052] The cumulative 50% diameter (D2) of the primary particle number distribution of component B1, as measured by electron microscopy, is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less. The cumulative 50% diameter (D2) is the median diameter of the primary particles of component B1 as observed by electron microscopy. If the cumulative 50% diameter (D2) is within the above range, the D50 (= cumulative 50% diameter (D1)) of the above-mentioned component B1 is easily achieved to the desired value (6 μm or less), and therefore is more suitable. The cumulative 50% diameter (D2) of component B1 is determined by observing component B1 using a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, S-4800), randomly extracting the diameter (longest diameter) of 100 primary particles, and expressing it as the cumulative 50% diameter when the number of primary particles is cumulatively distributed.

[0053] The ratio (D1 / D2) of the primary particle cumulative 50% diameter (D2) of component B1 is preferably 1 or more and 9 or less, more preferably 1 or more and 5 or less, further preferably 1 or more and 4 or less, and most preferably 1 or more and 2 or less. The ratio (D1 / D2) signifies the degree of aggregation of component B1 considering the size of the primary particles; a smaller ratio indicates a lower degree of aggregation (in other words, closer to primary particles, closer to a monodisperse state). As mentioned above, there is a correlation between the degree of aggregation of primary particles in component B1 and the L value of the formed film. By reducing the D1 / D2 ratio (specifically, preferably 9 or less), the L value of the formed film can be further reduced (achieving an ultra-low L value).

[0054] The shape of the B1 component is not particularly limited, but from the viewpoint of extinction, a spherical shape is preferred. Furthermore, in order to achieve further low gloss, low reflectance, and low L value on the formed film surface, particles with a narrow particle size distribution (sharp particles) are preferably used as the B1 component. Examples of particles with a narrow particle size distribution include those 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 is a numerical representation of the dispersion (deviation) of particle size distribution relative to the average particle size (arithmetic mean particle size). It indicates the uniformity of particle size. The smaller the CV value, the more uniform the particle size. If the CV value is below 15, the particles are considered to be of uniform size (also known as particles of a single diameter, etc.). To reduce the CV value to below 15, appropriate manufacturing methods for the B1 component can be employed. For example, by slurrying the material and using spray drying, the CV value can easily be reduced to below 15. Methods for calculating the CV value include, for example, the Coulter counter method. By using these particles with narrow particle size distribution, they can be uniformly contained in the membrane and form fine irregularities on the membrane surface, making it easy to achieve further low gloss, low reflectivity, and low L value on the membrane surface. In addition, to further reduce the gloss of the formed film surface, amorphous particles can also be used as the B1 component. By using amorphous particles as the B1 component, when the film is formed, the gloss of the film surface can be further reduced by the repeated refraction of light on the surface and inside the B1 component.

[0055] Component B1 can be commercially available products. Examples of products containing urethane beads include: Art Pearl C800 Black (average particle size 6.5 μm, CB content 7.5%, Negami Kogyosha). Examples of products containing acrylic (acrylic copolymer) beads include: Art Pearl GR-004BK (average particle size 3-5 μm, CB content 35-39%, Negami Kogyosha); RUBCOULEUR 224 (SMD) Black (average particle size 2-3 μm, CB content 18%, Dainippon Seika Kogyosha). Component B1 can be used alone or in combination with two or more.

[0056] 2-2-2. <Other Component B> Component B may contain other black materials besides component B1 (such as black sulfur compounds, porous carbon, carbon black, etc.).

[0057] 2-2-3. Total amount of Component B1 The content (total amount) of Component B1 in Component B is an amount sufficient to exhibit the effects of the present invention. From the viewpoint of expecting to improve the designability of the formed film, it is preferably 90% by mass or more, more preferably 95% by mass or more, relative to the total amount (100%) of Component B. The upper limit is not particularly limited and is 100% by mass.

[0058] 2-2-4. Total amount of Component B The content (total amount) of Component B in the total solid content of the present composition is an amount sufficient to exhibit the effects of the present invention. From the viewpoint of avoiding defects (increase in gloss, insufficient optical density) in the formed film, it is, for example, 60% by mass or more, preferably 65% by mass or more, more preferably 75% by mass or more, relative to the total amount (100% by mass) of the total solid content. The upper limit is, from the viewpoint of avoiding adverse effects on the coated object (film peeling due to poor adhesion or insufficient strength) caused by a small amount of Component A in the formed film, for example, 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less.

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

[0060] 2-3. Dilution solvent (Component C) Component C contained in the present composition is blended for the purpose of adjusting the viscosity of the present composition. By including Component C, the uniformity of the present composition is improved. In addition, the viscosity of the present composition can be appropriately adjusted, so it can be very useful in improving the operability of the present composition when disposing the present composition on the coating surface and the uniformity of the disposed thickness.

[0061] As component C, any solvent capable of adjusting the viscosity of this composition is acceptable and is not particularly limited. Examples include water, organic solvents, or mixtures of water and organic solvents. Examples of organic solvents include methyl ethyl ketone, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, etc. Component C can be used alone or in combination of two or more. The amount of component C can be appropriately set to adjust the solid content concentration of this composition.

[0062] 2-4. <Any Component (Component D)> In addition to the aforementioned components (components A, B, and C), this composition may also include any component (component D) to the extent that it does not impair the effects of the present invention. Examples of component D include leveling agents, tackifiers, pH adjusters, lubricants, dispersants, defoamers, curing agents, and reaction catalysts. The proportion of component D included is 100 parts by weight or less, or 30 parts by weight or less, relative to 100 parts by weight of component A.

[0063] 2-4-1. <Curing Agent> In particular, by incorporating a curing agent as component D, the cross-linking of component A can be promoted by utilizing the hydroxyl groups contained in component A1. Examples of curing agents that react with hydroxyl groups include epoxy compounds, hydroxymethyl compounds, isocyanate compounds, and titanium chelates. Among these, isocyanate compounds are particularly preferred.

[0064] The preferred isocyanate compound used as a curing agent is any compound having two or more isocyanate groups in its molecule. Examples include at least one of aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, and their derivatives. Here, aromatic aliphatic polyisocyanates refer to polyisocyanates in which the isocyanate groups are bonded to an aromatic ring via an aliphatic carbon atom.

[0065] Examples of aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or mixtures of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, triazine diisocyanate, terephthalic diisocyanate, triphenylmethane triisocyanate, and tri(phenylisocyanate)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(methylisocyanate)cyclohexane, and bis(methylisocyanate)norbornene. Examples of aromatic aliphatic polyisocyanates include xylene diisocyanate, tetramethylxylene diisocyanate, and ω,ω'-diisocyanate-1,4-diethylbenzene. Derivatives of polyisocyanate compounds include trimers, dimers, pentamers, and other polymers such as isocyanurates of the aforementioned isocyanate compounds, or modified polyisocyanates such as adducts, urea esters, and biuret esters formed by reacting the aforementioned isocyanate compounds with polyols such as trimethylolpropane.

[0066] From the viewpoint of further improving the adhesion of the formed film to the coated object, the isocyanate compound is preferably a structure in which the nitrogen atom having an isocyanate group is bonded to an aliphatic carbon atom. At least one of aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic aliphatic polyisocyanates, and their derivatives is preferred. From the viewpoint of further improving the adhesion and strength of the formed film to the coated object, the isocyanate compound preferably includes isocyanurate fractions of aliphatic polyisocyanates, xylene diisocyanate, and modified polyisocyanates thereof. One type of curing agent can be used alone, or two or more types can be used in combination.

[0067] 2-4-2. <Formulation of Curing Agent> When a curing agent is incorporated into this composition, the ratio can be 10-70% by mass relative to 100% by mass of component A. By adding a curing agent within the above range, the formed film can be endowed with higher strength, resulting in a film with better scratch resistance, and the excellent surface properties of the film can be maintained for a long time (enhancing designability).

[0068] 2-4-3. <Reaction Catalyst> When a curing agent is incorporated into this composition, a reaction catalyst may also be used to promote the reaction between component A and the curing agent. Examples of reaction catalysts include ammonia or ammonium chloride. The ratio of the reaction catalyst incorporated into this composition is 0.1 to 10 parts by mass relative to 100 parts by mass of the curing agent.

[0069] 2-5. <Preparation> This composition can be prepared (manufactured) by adding component A and component B to component C, and adding component D as needed, and then mixing and stirring. There are no particular restrictions on the order of mixing the components, as long as they are mixed evenly.

[0070] 3. <Preparation Method of Anti-reflective Film> Apply this composition to the desired portion (the outer surface side in this example) of the object to be coated (the housing body of an electronic device, hereinafter the same), and dry to remove the diluent (component C). This allows the film (anti-reflective film) formed by this composition to be applied to the desired portion of the object to be coated. There are no particular limitations on the method of applying this composition to the object to be coated (coating method), for example, coating method (brush method, etc.), droplet spraying method (dispensing coating method, spraying method, etc.), and immersion method (immersion coating method, etc.).

[0071] 3-1. <Viscosity of Resin Composition> The suitable viscosity range of this composition varies depending on the coating method, and therefore cannot be generalized. However, a viscosity range of 1 mPa·s or higher and 2000 mPa·s or lower is generally acceptable. When the viscosity is within this range, this composition exhibits excellent coatability and easily forms a film (anti-reflective film) of any thickness on the desired area of ​​the coated object. Furthermore, when the viscosity of this composition is within this range, the film formed by it readily expresses the specified properties (gloss, reflectivity, L-value, optical density) and film properties (adhesion, scratch resistance). For example, when the coating method uses a pen or brush (brush method), a viscosity of 100 mPa·s or more and 2000 mPa·s or less is preferred. When the coating method is a dotting method, a viscosity of 10 mPa·s or more and 300 mPa·s or less is preferred. When the coating method is a spray method, a viscosity of 1 mPa·s or more and 50 mPa·s or less is preferred. When the coating method is a dip coating method, a viscosity of 20 mPa·s or more and 500 mPa·s or less is preferred. The viscosity of this composition was measured using a Type B viscometer at 25°C and 60 rpm. The measurement was repeated three times, and the average of the three measurements was taken.

[0072] In the brush application method, if the viscosity of this composition is too low, dripping may occur. If the viscosity is too high, it may cause smearing and blurring. In the dispensing method, if the viscosity is too low, it may cause splattering or dripping, resulting in coating onto areas that do not need coating. If the viscosity is too high, the liquid may not flow from the nozzle, or even if it does flow, the surface shape may become smooth and glossy. In the case of spray coating, if the viscosity of this composition is too low, it may sometimes be impossible to form a film of the thickness that expresses the specified properties. If the viscosity of this composition is too high, it is easy for problems such as the liquid (this composition) not flowing out of the nozzle, or even if it flows out, it cannot be atomized. In the case of dip coating, if the viscosity of this composition is too low, it may sometimes drip severely, resulting in unevenness and failure to form a good film. If the viscosity of this composition is too high, it may be difficult to drain when the coated object is lifted from the liquid (this composition), resulting in burrs, or the surface of the film formed by this composition may become smooth and glossy.

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

[0074] This composition can be either a single-component or a two-component composition. When a curing agent is incorporated, this composition can be, for example, a two-component composition, comprising a first liquid containing components other than the curing agent, and a second liquid containing the curing agent.

[0075] When the coating method of this composition is spraying, even if there are protrusions or misalignments in the desired part of the object to be coated, a film with uniform thickness and specific properties can be formed on the entire surface of these objects.

[0076] Preferred coating conditions for spraying include: a spray gun nozzle diameter of approximately 0.2–1.2 mm, a spray volume of approximately 0.2–10 g / min, a minimum distance between the spray gun and the substrate surface of approximately 30–500 mm, a coating speed of approximately 30–300 mm / s, an overlap spacing of approximately 1.5–10 mm, and an atomizing air pressure of approximately 0.03–0.2 MPa. Regarding the number of spray guns, in addition to using a single spray gun, multiple spray guns can be configured according to the size of the substrate from the perspective of coating efficiency.

[0077] When this composition is coated using a brush method, the film thickness formed on the desired area of ​​the substrate can easily vary depending on the location of the coating. However, the properties of the resulting film are the same as those obtained using other coating methods. The reason for this is unclear, but it is believed to be due to the presence of a suitable amount of pigment, which creates unevenness.

[0078] 3-2. <Example Steps> After applying this composition to the desired area of ​​the substrate, component C is removed by heating and drying to form a film (film formation). The heating and drying process for removing component C can be, for example, at a temperature between 80°C and 120°C for 5 minutes to 30 minutes. If necessary, the formed film can also be irradiated with UV or EB light. When this composition contains a curing agent, the film formed by heat drying can be cured by further heating. In this case, if heating is performed to remove component C, it is not necessary to completely remove component C. The heating conditions for curing the film can be appropriately adjusted according to the thickness of the film before heating, the heat resistance of the coated object, and the type of component C used. As an example of heating conditions, the curing time can be from 70°C to 150°C for 1 minute to 30 minutes, or from 100°C to 130°C for 2 minutes to 10 minutes.

[0079] 4. <Film thickness of anti-reflective coating> There are no particular limitations on the thickness of the antireflective film, as long as it has good adhesion to the substrate and does not hinder design improvements. As a preferred example, a film thickness of 2 μm or more is preferable, more preferably 5 μm or more, and its upper limit is preferably 40 μm or less, more preferably 25 μm or less. Furthermore, the thickness of the antireflective film refers to the height from the surface of the desired area of ​​the substrate to the portion protruding due to component B of the film. The film thickness can be measured according to the method in JIS K 7130.

[0080] 5. <Characteristics of Anti-reflective Coatings> The properties of the membrane formed from this composition are as follows.

[0081] 5-1. <Optical Properties (Gloss, Reflectivity, L-value, Optical Density)> The film formed from this composition is preferably characterized by a surface gloss of less than 1% at 60°, less than 10% at 85°, a reflectivity of less than 1.5%, an L value of less than 15, and an optical density of 2 or higher.

[0082] Here, if the structure is such that the film formed by this composition is exposed on the outermost surface of the electronic device housing, then as described above, the 60° gloss, 85° gloss, reflectance, L-value, and optical density of the film surface are preferably within the above-mentioned ranges. When other films are coated on top of the film formed by this composition, the 60° gloss, 85° gloss, reflectance, L-value, and optical density of the surface of those other films (i.e., the outermost surface of the housing body of the electronic device housing) are preferably within the above-mentioned ranges. Hereinafter, these surfaces will be collectively referred to as the "outermost surface of the film."

[0083] The film formed from this composition preferably has a gloss level of less than 1% at 60°, a gloss level of less than 10% at 85°, a reflectivity of less than 1.5%, an L-value of less than 15, and an optical density of 2 or higher on its outermost surface. By utilizing the optical properties of the outermost surface within the above-mentioned range, low gloss, low reflectivity (excellent anti-reflective properties, the same below), high blackness, and high light-blocking properties can be achieved on the outermost surface of the film, thereby easily and significantly improving design flexibility.

[0084] The upper limit of 60° gloss is preferably less than 1%, more preferably less than 0.7%, and even more preferably less than 0.5%. By setting the upper limit of 60° gloss to less than 1%, the phenomenon of retinal whitening due to diffuse reflection of light can be effectively prevented, which can significantly improve design. There is no particular limitation on the lower limit of 60° gloss, the lower the better. The upper limit of 85° gloss is preferably less than 10%, more preferably less than 5%. Together with 60° gloss, by setting the upper limit of 85° gloss on the outermost surface of the film to less than 10%, the phenomenon of the film appearing white due to diffuse reflection of light can be effectively prevented, angle dependence can be easily suppressed, and the benefits of improved design can be easily obtained. There is no particular limitation on the lower limit of 85° gloss; the lower the better.

[0085] The upper limit of reflectivity is preferably less than 1.5%, more preferably less than 1.25%, and even more preferably less than 1.0%. By setting the upper limit of reflectivity to less than 1.5%, the phenomenon of retinal whitening due to diffuse reflection of light can be effectively prevented, and the design feasibility can be significantly improved. There is no particular limitation on the lower limit of reflectivity; 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. There is no particular limitation on the lower limit of the L-value, but from the viewpoint of requiring a darker appearance, the lower the better. Since the film may also be placed in a position visible to the user, the appearance quality of the film is required to be high. Specifically, sometimes a black coating with a high degree of design appeal (e.g., an embossed film) is required. By having an L-value less than 15, the above requirements can be easily met. The L value mentioned above refers to the lightness L* value of the outermost surface of the film in the CIE 1976 L*a*b* (CIELAB) colorimetric system using the SCE method. The SCE method is a method of measuring color by removing orthogonal reflected light. The definition of the SCE method is specified in JIS Z 8722 (2009). Because the SCE method measures color by removing orthogonal reflected light, the color is close to the color actually seen by the human eye. CIE stands for Commission internationale de l'Eclairage, referring to the International Commission on Illumination. The CIELAB color system was recommended in 1976 and defined in JIS Z 8781 (2013) as an equal color space to measure color differences caused by variations in perception and device. CIELAB uses three coordinates: L*, a*, and b*. L* represents lightness, ranging from 0 to 100. An L* value of 0 signifies black, and an L* value of 100 signifies the diffuse color of white. a* represents a color between red and green. A negative a* value indicates a color closer to green, while a positive value indicates a color closer to red. b* represents a color between yellow and blue. A negative b* value indicates a color closer to blue, while a positive value indicates a color closer to yellow.

[0087] The lower limit of optical density is preferably 2 or higher, more preferably 2.5 or higher, and even more preferably 3.2 or higher. By setting the lower limit of optical density to 2 or higher, the light-blocking performance can be further improved, and the design can be improved more effectively. There is no particular limitation on the upper limit of optical density; the higher the better.

[0088] The gloss, reflectance, L value and optical density mentioned above can be determined by the methods described later.

[0089] 5-2. <Film Properties (Seam Adhesion, Abrasion Resistance)> In addition to exhibiting the aforementioned optical properties, the film formed from this composition is preferably characterized by good adhesion to the coated object and high film strength (abrasion resistance). As shown in the adhesion evaluation results in the embodiments described later, the adhesion of the film formed by this composition to the coated object is such that the film retention rate is preferably 90% or more, more preferably 95% or more, and even more preferably 100%. Such good adhesion to the coated object can prevent the film from falling off the coated object. As shown in the scratch resistance evaluation 1 in the following examples, the film strength of the film formed from this composition, according to the number of scratches in JIS K5600-5-10 ISO 7784-3, is preferably 10 or less, more preferably 2 or less, and even more preferably 0. Such high film strength makes it easy to ensure scratch resistance during film manufacturing (film formation) and operation.

[0090] (Other implementation forms) The anti-reflective film of the above-mentioned form can be formed directly on the outer surface of the electronic device housing without pretreatment, or formed by a pretreatment layer, but it is not limited to this form. For example, the following form can be adopted: an anti-reflective film sheet is prepared to form an anti-reflective film on an extremely thin plastic film (such as PET film) by spraying, and then the sheet is cut into segments that conform to the shape of the outer surface of the electronic device housing, and then the segments are attached to the housing body of the electronic device housing through an adhesive layer, and finally an anti-reflective film is formed on the outer surface of the housing body of the electronic device housing. [Example]

[0091] The present invention will now be described in detail based on experimental examples (including embodiments 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] [Composition of the resin composition] As adhesive resins (component A), the following (A1A~A1e) belonging to polyvinyl acetal resin (component A1) and others (A2) are prepared. • A1: Polyvinyl acetal resin (S-LEC, Sekisui Chemicals Co., Ltd.) ·A1a: BL-S (Degree of acetalization: approximately 72 mol%, Hydroxyl content: approximately 23 mol%, Acetyl content: 4-6 mol%, Calculated molecular weight: approximately 23,000, Tg: 66℃) •A1b: BM-S(Z) (Degree of acetalization: approximately 72 mol%, hydroxyl content: approximately 23 mol%, acetylation content: 4-6 mol%, calculated molecular weight: approximately 55,000, Tg: 67℃) ·A1c: BH-S (Degree of acetalization: approximately 72 mol%, hydroxyl content: approximately 23 mol%, acetylation content: 4-6 mol%, calculated molecular weight: approximately 66,000, Tg: 67℃) ·A1d: BX-5(Z) (Degree of acetalization: approximately 72 mol%, hydroxyl content: approximately 27 mol%, acetylation content: less than 3 mol%, calculated molecular weight: approximately 130,000, Tg: 92℃) A1e: KS-5Z (Degree of acetalization: approximately 74 mol%, hydroxyl content: approximately 25 mol%, acetylation content: less than 3 mol%, calculated molecular weight: approximately 130,000, Tg: 113℃) • A2: Thermosetting acrylic resin (ACRYDIC A801, DIC Corporation) (Resin Tg 67℃, resin solids content 34%, molecular weight 15000, acid value 1mgKOH / g, hydroxyl value 5mgKOH / g)

[0093] As black materials (component B), the following substances were prepared: (Ba) is a complex of black pigment and resin (component B1) with an average particle size of 2 μm or more and 6 μm or less; (Bb) is a component B1, but the average particle size is not in the range of 2 μm or more and 6 μm or less; (Bc to Bf) are not components B1 at all. Ba: Black acrylic beads (average particle size 3~5μm) (Art Pearl GR-004BK, Genjo Kogyo Co., Ltd., CB content 35~39%) • Bb: Black acrylic beads (average particle size 14~16μm) (Art Pearl GR-400BK, Genjo Kogyo Co., Ltd., CB content 6-10%) • Bc: CB (average particle size 150nm) (MHI Black #273, Yuguo Pigment Company, CB content 9.5%) • Bd: Composite silicon dioxide (average particle size 3 μm) (Becsia ID, Fujisilicea Chemical Co., Ltd.) • Be: Transparent acrylic beads (average particle size 3μm) (UNI powder MNB0320C, ENEOS company) • Bf: Transparent acrylic beads (average particle size 2μm) (UNI powder MNB0220C, ENEOS company)

[0094] "Art Pearl GR-004BK" for Ba and "Art Pearl GR-400BK" for Bb are both spherical acrylic resin particles encapsulated with copper phosphate (CB), representing a composite of CB and acrylic resin. "MHI Black_#273" for Bc (CB) is a CB dispersion; of its total solids content of 18%, 9.5% is CB, and the remaining 8.5% is other compounds. Of the remaining 8.5% compounds, 3% are copper compounds and 5.5% are acrylic resin. "Becsia ID" 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 were prepared as a diluent (component C). C1: Methyl ethyl ketone C2: Butyl acetate

[0096] An isocyanate compound (Takenate D110N, Mitsui Chemicals, 75% solids) was prepared as an optional component (component D).

[0097] [Object to be painted] As the object to be coated, a smartphone case (plastic outer box) was prepared.

[0098] [Experimental Examples 1-20, 24 and 5a-16a, 24a] 1. Preparation of resin components (coatings) Each component of each experimental example was added to the specified amount of component C (a mixed solvent of C1 and C2) shown in Tables 1-3. The ratio of the total solids content (mass%) to the solids content of each component was the value recorded in Tables 1-3. The coating was prepared by stirring and mixing.

[0099] 2. Preparation of the evaluation samples Evaluation samples (films 1 and 2) were prepared using the coatings obtained in each experimental example, following the method described below. 2-1. Formation of Membrane 1 By means of the same spraying method as described in (3-3-1) Coating property 1 below, the paint is sprayed onto the outer surface of the object to form a coating film, and then the coating film is heated and dried at 120°C for 3 minutes, thereby forming a film 1 with an average thickness of 10 μm by spraying on the coating surface of the object.

[0100] 2-2. Formation of Membrane 2 Using the same brush method as described in (3-3-2) Coating property 2 below, a coating film is formed on the object to be coated, and then the coating film is heated and dried at 120°C for 3 minutes, thereby forming a film 2 with an average thickness of 10 μm by brush method on the coated surface of the object.

[0101] 3. Evaluation The various properties (viscosity, injection properties, coatability, dripping properties) of the coatings obtained in each experimental example were evaluated using the methods shown below (coating evaluation). Additionally, the various properties of the films formed from the coatings obtained in each experimental example were evaluated using the methods shown below (film evaluation). The results are shown in Tables 1 to 3.

[0102] [Paint Review] (3-1-1) Viscosity 1 The viscosity of the coating was measured using a Type B viscometer (VISCOMETER BM2, manufactured by Toki Sangyo Co., Ltd.) at 25°C, 60 rpm, for 1 minute, with rotor No. 1. This measurement was repeated three times, and the average of the three measurements was calculated. The evaluation criteria are as follows.

[0103] 〇: Viscosity above 1 mPa·s and below 50 mPa·s (good viscosity) ×: Viscosity exceeds 50 mPa·s (viscosity is too high) (3-1-2) Viscosity 2 The viscosity of the coating was measured using a Type B viscometer (VISCOMETER BM2, manufactured by Toki Sangyo Co., Ltd.) at 25°C, 60 rpm, for 1 minute, with rotor No. 2. This measurement was repeated three times, and the average of the three measurements was calculated. The evaluation criteria are as follows.

[0104] 〇: Viscosity above 100 mPa·s and below 2000 mPa·s (good viscosity) ×: Viscosity exceeds 2000 mPa·s (viscosity is too high)

[0105] (3-2) Injectable The injectability of paint is evaluated by observing how the paint is injected into an air sprayer. An air sprayer with an air brush (spray work HG Single Air Brush, TAMIYA) mounted on an air canister (spray work Air Can 420D, TAMIYA) was used to evaluate the injectability of each paint component by visually observing the flow of paint from the brush cup into the nozzle. The evaluation criteria are as follows.

[0106] 〇: There was no blockage at all, and the paint entered the nozzle smoothly. △: No blockage, but the paint enters the nozzle at a slightly slower speed. ×: There is a blockage; the paint is not entering the nozzle.

[0107] (3-3-1) Coating properties 1 The coatability of the coating was evaluated by observing the coating unevenness after spraying. Each coating was injected into the air sprayer used in (3-2) above, and sprayed onto the outer surface of the object to be coated for 10 seconds from 10 cm away from the tip of the air brush. The coating unevenness of the resulting coating film (before drying) was then evaluated by visual inspection. (3-3-2) Coating properties 2 The coatability of the paint was evaluated by observing the coating unevenness after brush application. 2. Each paint was dipped onto the tip of a brush and a 10cm line was drawn on an SUS board. The coating unevenness of the resulting film (before drying) was evaluated by visual inspection.

[0108] The evaluation criteria for coating properties 1 and coating properties 2 are as follows. ◎: No uneven coating (uneven thickness) was observed. ○: A very small number of areas showed uneven coating. ×: Uneven coating was observed over a large area.

[0109] (3-4) Dripping properties The drip properties of paint are evaluated by observing how it drips from the object after being sprayed. Similar to (3-3-1) above, each coating is injected into the air sprayer 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 air brush. Then, the dripping properties of the adhering droplets from the object to be coated are evaluated. The evaluation criteria are as follows.

[0110] ○: After coating, no liquid drips even when the coated object is placed vertically. △: After coating, when the object to be coated is placed vertically, the liquid gradually drips down. ×: After coating, the liquid drips immediately when the object to be coated is placed vertically.

[0111] [Membrane Evaluation] (3-5) Characteristics -Glossiness- The gloss of the film surface formed on each coated object with respect to the incident light at an angle of 60° (60° specular gloss) and the gloss of the film surface with respect to the incident light at an angle of 85° (85° specular gloss) were measured using a gloss meter (VG 7000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) at 9 points according to the method shown in JIS Z8741, and the average value was taken as the gloss. The evaluation criteria are as follows.

[0112] (60° mirror finish) ◎: Less than 0.5% (extremely excellent low gloss) 〇: 0.5% or higher but less than 0.7% (excellent low gloss) △: 0.7% or higher but less than 1% (good low gloss) ×: 1% or more (insufficient low gloss)

[0113] (85° mirror finish) ◎: Less than 5% (extremely excellent low gloss) 0: 5% or more but less than 10% (excellent low gloss) ×: 10% or more (insufficient low gloss)

[0114] (Overall evaluation of gloss) ◎: Both the 60° and 85° specular gloss ratings are rated ◎ (extremely excellent low gloss performance). 〇: At least one of the evaluations for 60° specular gloss and 85° specular gloss is 〇, and none of them are × (excellent low gloss). ×: At least one of the evaluations for 60° specular gloss and 85° specular gloss is × (insufficient low gloss).

[0115] -Reflectivity- The reflectance of the film surface formed on each coated object to light with a wavelength of 550 nm (550 nm reflectance) was measured using a spectrophotometer (CM-5, manufactured by KONICA MINOLTA) at 9 points according to the method of JIS Z8722, and the average value was taken as the reflectance. The evaluation criteria are as follows.

[0116] ◎: Reflectivity less than 1% (extremely excellent low reflectivity) 〇: Reflectivity is above 1% but below 1.25% (excellent low reflectivity) △: Reflectance is above 1.25% but below 1.5% (good low reflectivity) ×: Reflectance is above 1.5% (insufficient low reflectivity)

[0117] -Blackness- The blackness of the film surface formed on each coated object was evaluated by measuring the lightness L* value of the film surface in the CIE 1976 L*a*b* (CIELAB) color system using the SCE method. The lightness L* value was measured using a spectrophotometer (CM-5, manufactured by KONICA MINOLTA) according to the method of JIS Z8781-4:2013. The evaluation criteria are as follows. In the measurement, the CIE standard illuminant D65 was used as the light source, with a viewing angle of 10°. The L* value in the CIELAB colorimetric system was determined using the SCE method. The CIE standard illuminant D65 is specified in JIS Z 8720 (2000) "Illuminate (standard light) and standard illuminant for colorimetry" and is also specified in ISO 10526 (2007). The CIE standard illuminant D65 is used to represent the color of objects illuminated by sunlight. The 10° viewing angle is specified in JIS Z 8723 (2009) "Visual comparison method for surface colors" and is also specified in ISO / DIS 3668.

[0118] ◎: L value less than 10 (extremely excellent blackness) 〇: L value is 10 or higher but less than 12 (excellent blackness) △: L value is 12 or higher but less than 15 (good blackness) ×: L value is 15 or higher (insufficient blackness)

[0119] -Light blocking- The light-blocking properties of the film formed on each coated object are evaluated by calculating the optical density of the film. The optical density of the film formed on each coated object is calculated using an optical densitometer (X-rite 361T (Ortho filter), manufactured by Nippon Lithography Equipment Co., Ltd.). A perpendicularly penetrating light beam is shone onto the film side of the coated object, and the density is expressed as logarithmically as a ratio to the uncoated state. An optical density of 6.0 or higher is the upper limit for measurement. The evaluation criteria are as follows.

[0120] ◎: Optical density of 3.2 or higher (extremely excellent light-blocking properties) 〇: Optical density is 2.5 or higher but less than 3.2 (excellent light-blocking performance) △: Optical density is 2 or higher but less than 2.5 (good light-blocking properties) ×: Optical density not reaching 2 (insufficient light blocking)

[0121] -Seamless Fit- The adhesion of the film formed on each coated object to the object surface was assessed by cutting a checkerboard pattern into the film using a commercially available utility knife, applying transparent tape (Cellotape, manufactured by NICHIBAN) to it, and then peeling it off. The residual state of the film was then visually inspected for evaluation. The evaluation criteria are as follows.

[0122] ◎: 100% residual film (extremely excellent adhesion) 〇: Residual film of 95% or more but less than 100% (excellent adhesion) △: Residual film of 90% or more but less than 95% (good adhesion) ×: Residual film not reaching 90% (insufficient adhesion)

[0123] -Abrasion resistance 1- The scratch resistance 1 of the film formed on each coated object was evaluated by measuring the scratches on the film surface using an abrasion testing machine (Suga Abrasion Testing Machine NUS-ISO3; Suga Testing Machine Co., Ltd.) according to JIS K 5600-5-10 ISO7784-3. The test conditions were as follows: a load of 100g (corresponding to a weight range of 100g to 3kg), and a test piece (a form of the coated object forming the film, hereinafter the same) 1, cut to the size matching the fixture, was rubbed back and forth 10 times against a test piece 2, which was wound around a rotating wheel located below the test piece 1 and matched to the size of the rotating wheel, to wear it down. The evaluation was conducted by checking whether there were scratches on the film surface of the test piece 1. The rotating wheel rotated 0.9° each time the test piece 1 was rubbed back and forth, and the test piece 1 was always worn down by the newly worn surface of the test piece 2. The evaluation criteria were as follows.

[0124] ◎: 0 scratches (extremely excellent scratch resistance) 〇: 1-2 scratches (excellent scratch resistance) △: 3-10 scratches (good scratch resistance) ×: More than 11 scratches (insufficient scratch resistance)

[0125] -Abrasion resistance 2- The scratch resistance of the film formed on each coated object was evaluated by observing for scratches using a melamine sponge (Gekiochikun, melamine foam, REC). The film surface formed on each coated object was rubbed 30 times with a load of 7 cm² × 200 g, and then the presence of scratches was visually checked for evaluation. The evaluation criteria are as follows.

[0126] ◎: No change (extremely excellent scratch resistance) 〇: Minor scratches, 1-2 lines (excellent scratch resistance) △: Minor scratches: 3-10 (good scratch resistance) ×: More than 11 minor scratches (insufficient scratch resistance) ××: The entire surface of the friction surface has sharp scratches (poor scratch resistance).

[0127] -Overall Evaluation- The evaluation criteria for gloss, reflectivity, blackness, light-blocking properties, adhesion, and scratch resistance 1 and 2 are as follows.

[0128] ◎: All evaluations for gloss, reflectivity, blackness, opacity, adhesion, and scratch resistance 1 and 2 are ◎. 〇: At least one of the evaluations of gloss, reflectivity, blackness, opacity, adhesion, and scratch resistance 1 and 2 is 〇, and none of them are ×. ×: At least one of the following evaluations is ×: gloss, reflectivity, blackness, opacity, adhesion, and scratch resistance 1 and 2.

[0129] [Table 1]

[0130] [Table 2]

[0131] [Table 3]

[0132] 4. Inspection As shown in Table 1, when the coating contains component A1 as component A, and component B of the coating contains component B1 with an average particle size within the specified range (Ba), and the mass ratio of component B to component A in the coating is 7 or more and 14 or less (Experimental Examples 5, 12~15), it can meet all the characteristics of the coating and film characteristics (optical characteristics (gloss, reflectivity, L value, light blocking), film properties (adhesion, scratch resistance 1, 2)). In contrast, when the coating does not contain component A1 as component A (Experimental Examples 1-4), it cannot satisfy more than one of the optical properties and physical properties of the film. Even if the coating contains component A1 as component A (Experimental Examples 5-10, 24), if the coating component B replaces component (Ba) which belongs to component B1 and has an average particle size within the specified range, and includes component (Bb) which belongs to component B1 but has an average particle size outside the specified range (Experimental Example 6), the optical properties of the film properties and more than one of the film properties cannot be satisfied. Even if the coating contains component A1 as component A (Experimental Examples 5-10, 24), if the coating component B replaces component (Ba) which belongs to component B1 and has an average particle size within the specified range, and includes components (Bc-Bf) which do not belong to component B1 (Experimental Examples 7-10, 24), it is still not possible to satisfy more than one of the optical properties or physical properties of the film. Even if the coating component B contains (Ba) which belongs to component B1 and has an average particle size within the specified range (Experimental Examples 5, 11-16), if the mass ratio of component B in the coating relative to component A is less than 7 (Experimental Example 11) or more than 14 (Experimental Example 16), it cannot meet the optical properties of the film properties, or more than one of the physical properties of the film.

[0133] As shown in Table 2, the coating contains component A1 as component A, and component B of the coating contains component B1 with an average particle size within the specified range (Ba). When the mass ratio of component B to component A in the coating is 7 or more and 14 or less (Experimental Examples 5a, 12a~15a), all coating characteristics and film characteristics can be satisfied. In contrast, even if the coating contains component A1 as component A (Experimental Examples 5a~10a, 24a), if component B of the coating contains component B1 (Bb) but whose average particle size is not within the specified range, instead of component B1 (Ba) which has an average particle size within the specified range (Experimental Example 6a), it is still impossible to satisfy more than one of the optical and physical properties of the film. Even if the coating contains component A1 as component A (Experimental Examples 5a~10a, 24a), if component B (Bc~Bf) which does not belong to component B1 is used to replace component B1 (Ba) which belongs to component B1 and has an average particle size within the specified range (Experimental Examples 7a~10a, 24a), it is still not possible to satisfy more than one of the optical properties and physical properties of the film. Even if component B of the coating contains (Ba) which belongs to component B1 and has an average particle size within the specified range (Experimental Examples 5a, 11a~16a), if the mass ratio of component B to component A in the coating is less than 7 (Experimental Example 11a) or more than 14 (Experimental Example 16a), it will not be able to satisfy more than one of the optical properties and physical properties of the film.

[0134] As shown in Table 3, with the amount of component A fixed and the types of component A1 contained in component A changed (Experimental Examples 5, 17-20), it was also confirmed that the film strength (scratch resistance 1, 2) also increased with the increase of molecular weight and glass transition temperature.

[0135] [Experiment Example 21] In the composite material (B1 component) containing black pigment and resin, which is the black material (B component), instead of Ba (i.e., belonging to B1 component and with an average particle size within the specified range), black acrylic beads (average particle size 5-6 μm), which are spherical acrylic resin particles containing CB encapsulated, were used, although they are the same as Ba. Otherwise, the coating was prepared with the same composition as in Experimental Example 5. Furthermore, a film was formed using the same method as described above, and the same evaluation was performed, confirming the same evaluation results as in Experimental Example 5.

[0136] [Experiment Example 22] The coating was prepared with the same composition as in Experimental Example 5, relative to the total amount (100% by mass) of the adhesive resin (component A). The content of polyvinyl acetal resin (component A1) was 90% by mass, with the remainder being 10% by mass. An acrylic resin (molecular weight ≥ 10000, Tg ≥ 30°C) belonging to component A but not component A1 was used. Furthermore, the coating was formed using the same method as described above, and the same evaluation was performed, confirming the same results as in Experimental Example 5.

[0137] [Experiment Example 23] The content of Ba (i.e., belonging to component B1 and with an average particle size within the specified range) relative to the total amount (100% by mass) of the black material (component B) was 90% by mass, with the remainder being 10% by mass. Black acrylic beads (average particle size 0.5~1.5 μm) belonging to component B1 but with an average particle size outside the specified range were used. Otherwise, the coating was prepared with the same composition as in Experimental Example 5. Furthermore, a film was formed using the same method as described above, and the same evaluation was performed, confirming the same evaluation results as in Experimental Example 5.

Claims

1. An electronic device housing having an anti-reflective film on its body, the anti-reflective film being formed of a resin composition containing at least component A and component B, component A comprising component A1, wherein the content of component A1 in the total amount of component A is 90% by mass or more, component B comprising component B1 having an average particle size of 2 μm or more and 6 μm or less, wherein the content of component B1 in the total amount of component B is 90% by mass or more, component B1 being composed of resin particles encapsulating black pigment, and the mass ratio of component B to component A is 7 or more and 14 or less, wherein (component A) is an adhesive resin, (component A1) is a polyvinyl acetal resin, (component B) is a black material, and (component B1) is a complex of black pigment and resin.

2. The electronic machine housing as claimed in claim 1, wherein, The thickness of the anti-reflective coating ranges from 2μm to 40μm.

3. The electronic device housing as requested in item 1 or 2, wherein, The surface of the film has a gloss level of less than 1% for incident light at an angle of 60°, a gloss level of less than 10% for incident light at an angle of 85°, a reflectance of less than 1.5% for light with a wavelength of 550nm, an L value of less than 15 in the CIELAB color system according to the SCE method, and an optical density of 2 or higher.

4. An antireflective film formed on an electronic device housing, formed of a resin composition comprising at least component A and component B, wherein component A comprises component A1, the content of component A1 in the total amount of component A is 90% by mass or more, component B comprises component B1 with an average particle size of 2 μm or more and 6 μm or less, the content of component B1 in the total amount of component B is 90% by mass or more, component B1 is composed of resin particles encapsulating black pigment, and the mass ratio of component B to component A is 7 or more and 14 or less, wherein (component A) is an adhesive resin, (component A1) is a polyvinyl acetal resin, (component B) is a black material, and (component B1) is a complex of black pigment and resin.

5. A method for manufacturing an electronic device housing, which is the method for manufacturing an electronic device housing according to claim 1, comprising the following steps: disposing a resin composition comprising at least component A, component B, and component C on a housing body; removing component C by drying to form an anti-reflective film comprising at least component A and component B; component A comprising component A1, wherein the content of component A1 in the total amount of component A is 90% by mass or more; component B comprising component B1 with an average particle size of 2 μm or more and 6 μm or less, wherein the content of component B1 in the total amount of component B is 90% by mass or more; component B1 is composed of resin particles containing black pigment, and the mass ratio of component B to component A is 7 or more and 14 or less; the viscosity of the resin composition at 25°C, measured by a type B viscometer, is adjusted to 1 mPa·s or more and 2000 mPa·s or less; and component C is a diluent.

6. The method for manufacturing an electronic device housing as claimed in claim 5, comprising the following steps: preparing a resin composition, the viscosity of which is determined by a type B viscometer at 25°C and adjusted to be 1 mPa·s or more and 50 mPa·s or less, by spraying, and forming an anti-reflective film on the housing body.

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