Coating film containing bismuth sulfide particles, coating composition, and methods for producing the same

Abstract

To provide a coating film that enables simultaneous realization of high antireflection performance, high hardness in the coating film, high blackness, and high scratch resistance.SOLUTION: A coating film comprising bismuth sulfide particles. Under observation with a scanning electron microscope, the bismuth sulfide particles in the coating film exhibits a morphology with one end of 10 or more needle-like components being aggregated and / or a morphology of a substantially spherical body having on its surface multiple projections in the form of plate-like fragments and / or needle-like fragments. In the IR spectrum by FT-IR for the coating film, an infrared absorption peak derived from Amide-II is observed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coating film containing bismuth sulfide particles, a coating composition, and methods for producing the same. [Background technology]

[0002] In optical devices such as cameras and video cameras, stray light caused by diffuse reflection or scattering in the optical path of the lens barrel, etc., can cause ghosts and flares in the formed image, which can be one of the causes of image quality degradation. To prevent this degradation of optical performance due to stray light, a black anti-reflective coating is applied to the optical path of the lens barrel, aperture, etc., to form an anti-reflective coating film. From the standpoint of design, coatings with a high degree of blackness are required for automobile interiors, head-up displays, mobile phones, the exterior panels of home electrical appliances such as audio equipment, and the interiors of houses.

[0003] For example, Patent Document 1 discloses a black coating film that includes a resin light-shielding layer having an uneven shape and a blackened layer formed on the resin light-shielding layer, and that the resin light-shielding layer is composed of carbon black as a coloring and conductive material, an acrylic resin as a resin, polyisocyanate as a curing agent, and an acrylic filler as a matting agent.

[0004] Furthermore, Patent Document 2 discloses a light-shielding member having a light-shielding layer formed thereon, and discloses that the light-shielding layer is composed of carbon black as a coloring and conductive material, urethane resin as a resin, polyisocyanate as a curing agent, and acrylic filler as a matting agent.

[0005] Furthermore, Patent Document 3 discloses a black coating film using bismuth sulfide, a specific binder (resin component), and a clear coating.

[0006] Finally, Patent Document 4 discloses a black ink layer containing a binder resin, carbon black, and resin fine particles. It also discloses that a laminate having the ink layer exhibits low reflectivity in the visible light region and excellent scratch resistance (the degree to which the black ink rubs off). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-107896 [Patent Document 2] Japanese Patent Application Publication No. 2018-004844 [Patent Document 3] International Publication No. WO2022 / 210032 [Patent Document 4] Patent No. 7298107 Summary of the Invention [Problem to be solved by the invention]

[0008] When forming an anti-reflection coating with high blackness on a sliding member of an optical device, a coating with particularly high hardness is required. Also, when forming a coating on a part that is to be held by hand, a coating with abrasion resistance and whose blackness does not decrease even when held by hand is required. However, none of the above patent documents discloses a coating film that can simultaneously achieve high anti-reflection performance, high hardness of the coating film, high abrasion resistance, and high blackness. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to obtain a coating film that can simultaneously achieve high anti-reflection performance, high coating film hardness, high abrasion resistance, and high blackness. As a result, they have found that a coating film that contains bismuth sulfide particles of a specific shape and in which an infrared absorption peak derived from Amide-II is observed in the IR spectrum by FT-IR has the above properties, and have completed the present invention.

[0010] That is, the present invention is as follows. [1] A coating film containing bismuth sulfide particles, wherein the shape of the bismuth sulfide particles contained in the coating film, when observed with a scanning electron microscope, is a shape in which one end of 10 or more needle-like constituent elements is gathered and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR. [2] The coating film according to [1], wherein the bismuth sulfide particles are contained in an amount of 30% or more and 70% or less in terms of pigment volume concentration (PVC). [3] A coating composition comprising a resin component, bismuth sulfide particles, and a solvent, wherein the hydroxyl value of the solid content of the resin component is 60 mgKOH / g or less, and the shape of the bismuth sulfide particles observed with a scanning electron microscope is a shape in which one end of 10 or more needle-like constituent elements is gathered and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and the pigment volume concentration (PVC) of the bismuth sulfide particles in the coating composition is 30% or more and 70% or less. [4] The coating composition according to [3], wherein the resin component is an acrylic resin. [5] The coating composition according to [3] or [4], wherein the glass transition temperature of the resin component is 55°C or higher. [6] A paint set comprising the paint composition according to any one of [3] to [5] and a composition containing a curing agent. [7] A method for producing a coating film, comprising the following steps (1) to (3), wherein an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR: Step (1): A step of mixing a resin component, bismuth sulfide particles, and a solvent to obtain a coating composition, wherein the hydroxyl value of the solid content of the resin component is 60 mgKOH / g or less, the shape of the bismuth sulfide particles observed with a scanning electron microscope is a shape in which one ends of 10 or more needle-like constituent elements are gathered together and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and the pigment volume concentration (PVC) of the bismuth sulfide particles in the coating composition is 30% or more and 70% or less; Step (2): A step of applying the coating composition obtained in step (1) onto an object to be coated to obtain a coated object; Step (3): A step of heating the coated object obtained in the step (2); [8] The method for producing a coating film according to [7], which comprises, in the step (2), a step of mixing a composition containing a curing agent with the coating composition. [9] The crosslink density of the coating film formed by mixing the composition containing the resin component and the curing agent is 1.0 × 10 -6 mol / cc or more 7.0×10 -4 mol / cc or less,

[10] The method for producing a coating film according to any one of [7] to [9], wherein the resin component is an acrylic resin.

[11] The method for producing a coating film according to any one of [7] to

[10] , wherein the glass transition temperature of the resin component is 55°C or higher.

[12] A coated article coated with a coating film comprising the coating film according to [1] or [2], or the coating composition according to any one of [3] to [5], or the coating set according to [6]. And so on. [Effects of the Invention]

[0011] The coating film of the present invention has high anti-reflection performance, and also has high hardness, abrasion resistance and blackness, and is therefore applicable to a variety of applications including optical equipment applications such as cameras. [Brief explanation of the drawings]

[0012] [Figure 1] This is an SEM image of coating film 1. [Figure 2] 1 is an SEM image (enlarged view) of coating film 1. [Figure 3] 1 is an SEM image of coating film 12. [Figure 4] 1 is an SEM image (enlarged view) of coating film 12. [Figure 5] 1 is an IR spectrum obtained by FT-IR measurement of coating film 1. [Figure 6] 1 is an IR spectrum obtained by FT-IR measurement of coating film 8. [Figure 7] 1 shows the reflectance spectrum of coating film 1 on white chart paper, measured with a UV-visible-near-infrared spectrophotometer V-670 (manufactured by JASCO Corporation) using a Spectralon standard reflector (manufactured by Labsphere). [Figure 8] 1 shows the reflectance spectrum of coating film 1 on black chart paper, measured with a UV-visible-near-infrared spectrophotometer V-670 (manufactured by JASCO Corporation) using a Spectralon standard reflector (manufactured by Labsphere). [Figure 9] This is an SEM image of coating film 2. [Figure 10] 1 is an SEM image of coating film 3. [Figure 11] 1 is an SEM image of coating film 4. [Figure 12] 1 is an SEM image of coating film 5. [Figure 13] 1 is an SEM image of coating film 6. [Figure 14] 1 is an SEM image of coating film 7. [Figure 15] 1 is an SEM image of coating film 8. [Figure 16] 1 is an SEM image of coating film 9. [Figure 17] 1 is an SEM image of coating film 10. [Figure 18] 1 is an SEM image of coating film 11. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention relates to a coating film containing bismuth sulfide particles, wherein the shape of the bismuth sulfide particles contained in the coating film when observed with a scanning electron microscope is such that the shape of the particles is a collection of 10 or more needle-like components at one end and / or a shape of a roughly spherical body with multiple plate-like and / or needle-like protrusions on the surface, and an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR.

[0014] The coating film of the present invention has a visible light reflectance of 0.5% or more and 3.5% or less, measured as follows. The visible light reflectance is preferably 0.5% or more and 3.0% or less, and more preferably 0.5% or more and 2.0% or less. The visible light reflectance can be used as an index of the performance of suppressing the ratio of reflected light to incident light. The visible light reflectance is a value measured by a measurement method that includes specular reflected light (the SCI (Specular Component Include) method), and when the visible light reflectance of the coating film is within the above range, it can be said that the anti-reflection performance of the coating film is sufficiently high.

[0015] The visible light reflectance of the coating film is measured as follows. Using a spectrophotometer SD-7000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the reflectance of the coating film is measured at wavelengths of 380 nm to 780 nm, and the reflectance at a wavelength of 550 nm is defined as the visible light reflectance of the coating film. Other measurement conditions are as follows. Light source / field of view: D65 / 10° Illumination / light receiving conditions: Reflection: di: 8° (diffuse illumination: 8° receiving light) including specular reflection (SCI) Measurement wavelength: 380-780nm (5nm interval output) Measurement diameter: LAV (φ19mm)

[0016] In this application, the hardness of a coating film means the hardness evaluated by pencil hardness. The coating film of the present invention has a pencil hardness of 5B or more, preferably B or more, and more preferably HB or more. The pencil hardness is the pencil hardness in accordance with JIS K5600-5-4:1999 (General testing methods for paints - Part 5: Mechanical properties of coating films - Section 4: Scratch hardness (pencil method)). When the coating film of the present invention has a pencil hardness of 5B or more, the hardness of the coating film can be said to be sufficiently high.

[0017] The coating film of the present invention is L * a * b * L in color space * The value of L is 22.0 or less, preferably 20.0 or less, more preferably 15.0 or less, and even more preferably 12.0 or less. * The values ​​are CIE 1976 Lab(L * a * b * It is an index that represents the brightness of a color space. The smaller the value, the lower the brightness. * The smaller the value, the higher the blackness of the coating (an index showing blackness). * a * b * The "CIELAB color space" is a color space recommended by the CIE (International Commission on Illumination) in 1976, and is sometimes abbreviated as CIELAB. * If the value is 22.0 or less, the blackness is said to be sufficiently high.

[0018] L of the coating film * The values ​​are measured using a spectrophotometer SD-7000 (manufactured by Nippon Denshoku Industries Co., Ltd.) under the following measurement conditions. Light source / field of view: D65 / 10° Illumination / light receiving conditions: Reflection: di: 8° (diffuse illumination: 8° receiving light) including specular reflection (SCI)

[0019] In this application, abrasion resistance refers to the property of a coating film in which the change in blackness is small even when the coating film surface is rubbed. The coating film of the present invention shows little visual change in blackness when touched with a finger or the like. When the coating film surface is lightly pressed with the middle finger of a nitrile glove and rubbed back and forth 3 to 5 times, if there is little visual change in blackness before and after the finger touch test, it can be said that the abrasion resistance is high.

[0020] The coating film of the present invention has a visible light reflectance of 0.5% or more and 3.5% or less, a pencil hardness of 5B or more, a small change in the blackness of the coating film before and after the finger touch test, and an L of the coating film before touching. * Therefore, the coating film of the present invention can be said to have high anti-reflection performance, high coating hardness, high abrasion resistance, and high blackness.

[0021] The coating film of the present invention has a visible light reflectance of 0.5% or more and 3.5% or less, and * The visible light reflectance is 0.5% or more and 3.0% or less, and the L * It is more preferable that the visible light reflectance is 0.5% or more and 2.0% or less, and the L * It is more preferable that the value is 15.0 or less. * When the value is within the above range, it can be said that the coating film has high anti-reflection performance and sufficiently excellent black color.

[0022] The coating film of the present invention has a visible light reflectance of 0.5% or more and 3.5% or less, and a pencil hardness of 5B or more. Within these ranges, the coating film can be said to have high anti-reflection performance and high hardness. Furthermore, the coating film of the present invention preferably has a visible light reflectance of 0.5% or more and 3.0% or less, and a pencil hardness of B or more, and more preferably has a visible light reflectance of 0.5% or more and 2.0% or less, and a pencil hardness of HB or more.

[0023] In addition, the coating film of the present invention is L * a * b* a of the paint film in the color system * The value can be set to -2.0 or more and 0.5 or less, and the b * The value can be between -4.0 and 0.0. * value, b * The value is L * a * b * It is an index that represents the hue saturation of the color system, and a * The larger the value, the more reddish it is, and the larger the value, the more greenish it is. * The larger the value on the positive side, the stronger the yellowness, and the larger the value on the negative side, the stronger the blueness. * value, b * For values, see L * Measure in the same way as the value.

[0024] The coating film of the present invention can achieve a specular gloss of 0.1 or less at a 20° geometrical condition and a specular gloss of 5.0 or less at a 60° geometrical condition, as measured in accordance with JIS K 5600-4-7 (1999), thereby providing what is known as matte performance. It can also achieve a specular gloss of 30.0 or less at an 85° geometrical condition, thereby sufficiently suppressing what is known as bottom gloss.

[0025] The coating film of the present invention may have a surface roughness within a certain range of arithmetic mean roughness Ra, ten-point mean height Rz, and arithmetic mean height Sa. For example, Ra may be 0.3 μm to 2.0 μm, Rz may be 2.0 μm to 12.0 μm, and Sa may be 0.1 μm to 4.0 μm. These measurements were performed in accordance with ISO 25178 Surface Texture (area roughness measurement) and JIS B 0601:2001 / ISO 4287:1997 (line roughness measurement) using a digital microscope (measuring unit VK-X1050, control unit VK-X1000) (manufactured by Keyence Corporation) at 480x magnification, and measured using the analysis software Multifile Analysis Application. The arithmetic mean roughness Ra is calculated by dividing the average surface irregularities into a reference line and expressing the average distance from that reference line. The lower this value, the flatter and smoother the surface. The ten-point average height Rz represents the difference between the average elevation of the top five peaks and the average elevation of the bottom five valleys measured in the longitudinal direction from a line that is parallel to but does not cross the average line on the measured roughness curve. The arithmetic mean height Sa represents the average absolute value of the difference in elevation from the average surface. [Measurement conditions] Measurement magnification: 480x Reference plane correction: all areas Scan mode: Laser confocal Laser wavelength: 661nm [Arithmetic mean roughness Ra, ten-point mean height Rz] Measurement mode: Multi-line roughness Measurement area: horizontal line Number of perimeters: 5 Interval: Every 4 bars [Arithmetic mean height Sa] Measurement mode: Surface roughness Measurement area: all areas

[0026] The coating film of the present invention may have a solar reflectance of 25.0% or more, 35.0% or more, or 40.0% or more in the wavelength range of 780 nm to 2500 nm. If the solar reflectance is 25.0% or more, it can be said that the heat-shielding performance of the coating film is sufficiently high.

[0027] The solar reflectance of a coating film in the wavelength range of 780 nm to 2500 nm is measured as follows. Using a spectrophotometer, the reflectance of the coating film in the wavelength range of 780 to 2500 nm is measured. From the obtained reflectance, the solar reflectance of the coating film is calculated in accordance with JIS K 5602 (2008). The spectrophotometer used is a UV-Visible-Near-Infrared Spectrophotometer V-670 (product name) (manufactured by JASCO Corporation).

[0028] In the FT-IR spectrum of the coating film of the present invention, an infrared absorption peak derived from Amide-II is observed, and the coating film in which the infrared absorption peak can be observed has high antireflection performance, high blackness, high coating film hardness, and high abrasion resistance. In the present application, the phrase "infrared absorption peaks derived from Amide-II are observed" refers to the Amide-II band (approximately 1520 to 1560 cm) derived mainly from C (carbon atom)-N (nitrogen atom) stretching vibration and NH (hydrogen atom) bending vibration. -1 ) is observed. The infrared absorption peak attributed to the Amide-II band is observed when a -C(=O)-N(-H) structure is present in the coating film. For example, a resin may have this structure, or a reaction product of a resin and a curing agent may have this structure. Specific examples include reaction products of a resin component such as a urethane resin, an acrylic resin, a phenolic resin, or an amino resin with a polyisocyanate compound.

[0029] The presence of the infrared absorption peak derived from Amide-II can be confirmed by referring to the values ​​described in the literature ( Journal of the Society of Rubber Science and Technology of Japan, Vol. 55, No. 3, pp. 182-188 (1982)). Furthermore, a Fourier transform infrared spectrometer FT / IR-6600FV (manufactured by JASCO Corporation) is used to obtain the IR spectrum. The infrared absorption peak observed in the above absorption band can be determined to be an absorption peak derived from Amide-II.

[0030] The coating film of the present invention contains bismuth sulfide particles. The presence of bismuth sulfide in the coating film of the present invention is revealed by identifying bismuth sulfide (BiS, etc.) through EDX analysis of the surface of the coating film of the present invention using a scanning electron microscope.

[0031] The bismuth sulfide particles contained in the coating film of the present invention may be contained in the coating film in the form of aggregated secondary particles formed by aggregation of primary particles of the bismuth sulfide particles. The aggregated secondary particles are formed by the aggregation of a plurality (two or more) of primary particles due to intermolecular forces or the like. The bismuth sulfide particles contained in the coating film of the present invention do not all need to be in the form of aggregated secondary particles, and some may be primary particles.

[0032] The bismuth sulfide particles contained in the coating film of the present invention, when observed with a scanning electron microscope, are present in a shape where one end of 10 or more needle-like components is gathered and / or in a state where a plurality of (specifically 10 or more) plate-like and / or needle-like projections are present on the surface of a roughly spherical body. The term "roughly spherical" encompasses not only a spherical shape but also a spherical-like shape, such as an ellipsoid. It can also be said that the bismuth sulfide particles contained in the coating film of the present invention, when observed with a scanning electron microscope, are present in a state where they have a sea-urchin-like shape similar to that of a purple sea urchin (hereinafter, this specification may refer to this as "spiky").

[0033] The fact that the bismuth sulfide particles contained in the coating film of the present invention are thorny becomes clear when the surface (or cross section) of the coating film is observed using a scanning electron microscope. Specifically, the bismuth sulfide particles contained in the coating film can be said to be thorny if they have a shape in which one end of 10 or more needle-like components are gathered together and / or if they have a state in which the surface of a substantially spherical body has multiple (specifically 10 or more) plate-like and / or needle-like protrusions.

[0034] In bismuth sulfide particles with a sea-urchin-like shape, the needle-like components form numerous tiny spaces from the tip of the needle-like portion of the bismuth sulfide toward the spherical portion of the bismuth sulfide. Light incident on the surface of the bismuth sulfide particles is repeatedly absorbed and reflected within the tiny spaces inside the particles, reducing the light (especially visible light) emitted from the particle surface, i.e., the reflectance, and the bismuth sulfide particles appear black. Even if the bismuth sulfide particles themselves are thorn-like, if the resin component in the coating film penetrates into the tiny spaces and the thorns disappear, the above effect cannot be achieved and the reflectance of the coating film increases. Here, the bismuth sulfide particles contained in the coating film of the present invention maintain their sea-urchin-like shape at least within the coating film (preferably near the surface of the coating film). Therefore, the coating film of the present invention has a high reflectance and L * It is understood that the effect of reducing the reflection value can be fully exerted, resulting in the realization of higher anti-reflection performance and higher blackness.

[0035] The bismuth sulfide particles contained in the coating film of the present invention preferably have a cumulative 50% diameter (referred to as "D1") of 0.2 μm or more and 10.0 μm or less in a volume cumulative distribution measured with a laser diffraction / scattering particle size distribution analyzer. D1 is more preferably 1.0 μm or more and 6.0 μm or less, and even more preferably 1.0 μm or more and 5.0 μm or less. Assuming that all bismuth sulfide particles have approximately the same primary particle diameter, the larger the aggregated secondary particle diameter, the greater the degree of aggregation. In this regard, the bismuth sulfide particles preferably have a D1 of 10.0 μm or less, which means that the degree of aggregation is relatively small. The smaller the degree of aggregation of the bismuth sulfide particles contained in the coating film of the present invention, the better the antireflection performance of the coating film of the present invention and the higher the blackness, so the cumulative 50% diameter (D1) is an important indicator.

[0036] The cumulative 50% diameter (D1) of the bismuth sulfide particles contained in the coating film of the present invention refers to the cumulative 50% diameter in the volume cumulative distribution when a dispersion of bismuth sulfide particles dispersed in a dispersing medium such as water is used as a sample and the particle size distribution is measured using a laser diffraction / scattering particle size distribution analyzer LA-950 (manufactured by Horiba, Ltd.). Detailed measurement conditions are as follows. The dispersion is prepared using an ultrasonic cleaner UT-305 (manufactured by SHARP) as a disperser. [Measurement conditions] Sample refractive index: 2.13 Solvent refractive index: 1.33 Circulation speed: 10 Ultrasonic intensity: 1 Ultrasonic time: 2 minutes Stirring intensity: 10 Transmittance (R) for laser light (650 nm): 95-70% Transmittance (B) for LED light (405 nm): 90-80%

[0037] The bismuth sulfide particles contained in the coating film of the present invention preferably have a cumulative 50% diameter (referred to as "D2") in the cumulative number distribution of primary particles measured with a scanning electron microscope of 0.2 μm to 3.0 μm, more preferably 0.5 μm to 2.0 μm. D2 is the median diameter of the primary particles of bismuth sulfide observed with a scanning electron microscope. If D2 is within the above range, it is easy to set the above-mentioned D1 to a preferred value (specifically, 10.0 μm or less), which is preferable.

[0038] The above D2 means the cumulative 50% diameter when the diameters (longest diameters) of 100 randomly selected primary particles are measured and expressed as a cumulative number distribution of primary particles by observing the bismuth sulfide particles contained in the coating film of the present invention using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation). The bismuth sulfide particles contained in the coating film of the present invention preferably have a ratio (D1 / D2) of D1 to the cumulative 50% diameter (D2) of the primary particles of greater than 1 and less than 6, more preferably greater than 1 and less than 5, and even more preferably greater than 1 and less than 4.

[0039] The D1 / D2 ratio represents the degree of aggregation of bismuth sulfide particles when the size of the primary particles is taken into consideration, and the smaller the value, the smaller the degree of aggregation (the closer the primary particles are to existing independently without aggregation). As mentioned above, there is a correlation between the degree of aggregation of the primary particles of the bismuth sulfide particles contained in the coating film of the present invention and the anti-reflection performance or blackness of the coating film of the present invention, and by reducing the value of D1 / D2 (specifically, to 6 or less), the anti-reflection performance and blackness can be further improved.

[0040] The bismuth sulfide particles contained in the coating film of the present invention preferably have a difference between the cumulative 90% diameter (D90) and the cumulative 10% diameter (D10), calculated from the number-cumulative particle distribution measured with a Coulter Counter particle size distribution analyzer, divided by the cumulative 50% diameter (D50) (when this ratio is expressed as "D3", D3 = (D90 - D10) / D50) of 3.0 or less, more preferably 2.0 or less, and even more preferably 1.2 or less. The D90, D50, and D10 are measured as follows. 7920 g of ISOTON II diluted solution (Beckman Coulter) was mixed with 80 g of Nopcosperse 5600 (San Nopco) and stirred for at least 1 hour. After stirring, the mixture was filtered through a 0.45 μm membrane filter (JHWP09025 2-3051-16, Merck) to prepare an electrolyte solution. A sample equivalent to 0.1 g of solids is weighed out and mixed with the electrolyte to prepare 20.0 g of sample mixture. The sample mixture is dispersed for 5 minutes using an ultrasonic disperser (360 W, AU-180C EYELA (registered trademark), manufactured by Tokyo Rikakikai Co., Ltd.) to prepare a dispersion. 2.0 g of the dispersion is weighed out and mixed with 18.0 g of the electrolyte to prepare a diluted solution. 3 cc of the diluted solution is weighed out and mixed with 200 g of the electrolyte weighed into a 200 mL round-bottom beaker to prepare the measurement sample. A MultisiZer 4 (manufactured by Beckman Coulter) is used as the measurement device, and the measurement sample is measured while being stirred. Detailed measurement conditions are as follows. Aperture diameter: 30 μm Measurement particle size range: 0.6 to 18 μm Measurement conditions: Quantitative (80μL) Stirrer rotation speed: 15

[0041] The D3 is an index of the breadth of the particle size distribution of the bismuth sulfide particles, and a smaller value means a narrower distribution, and a larger value means a wider distribution.

[0042] In the bismuth sulfide particles contained in the coating film of the present invention, where the D1 / D2 ratio is greater than 1 and not greater than 6, a small D3 (narrow particle size distribution) means that the proportion of coarse particles and fine particles present is low. Since the coarse particles are understood to be agglomerated secondary particles with a high degree of agglomeration, a smaller D3 is understood to mean a smaller degree of agglomeration of the coarse particles. This can further improve the anti-reflection performance and blackness of the coating film of the present invention. As mentioned above, it is understood that bismuth sulfide particles repeatedly absorb and reflect incident light in the minute spaces formed by the needle-like components, thereby reducing the light reflectance and exhibiting a black color. Here, reducing the proportion of particles with very small primary particle diameters or agglomerated secondary particles of these particles (collectively referred to as fine particles) is preferable from the viewpoint of avoiding a situation in which, when the proportion is high, the above-mentioned minute spaces are not sufficiently formed and the light reflectance cannot be sufficiently reduced. In other words, by reducing the proportion of fine particles, the anti-reflection performance and blackness of the coating film of the present invention can be further improved.

[0043] The bismuth sulfide particles contained in the coating film of the present invention may contain at least one element X selected from the group consisting of Al, Ce, La, Fe, and Y, and the element X may be Al or Ce.

[0044] The element X is preferably contained so that the ratio of the number of moles of X atoms to the number of moles of Bi atoms in the bismuth sulfide particles (i.e., the X / Bi molar ratio) is greater than 0 and not greater than 0.15, and more preferably greater than 0 and not greater than 0.05. The X / Bi ratio can be calculated, for example, from the results of measuring the bismuth sulfide particles contained in the coating film of the present invention by X-ray fluorescence analysis. An example of an apparatus for performing the X-ray fluorescence analysis is ZSX (registered trademark) Primus IV (manufactured by Rigaku Co., Ltd.).

[0045] It is understood that when element X is contained in bismuth sulfide particles, some of the bismuth atoms are substituted with element X, or element X enters between lattices formed by bismuth atoms, thereby forming impurity levels within the band gap, thereby enabling further improvements in anti-reflection performance and blackness.

[0046] The bismuth sulfide particles contained in the coating film of the present invention may contain 0.1% by mass or more and 5% by mass or less of carbon, which can be measured using an elemental analyzer, such as a Vario EL cube (manufactured by Elementar).

[0047] The surfaces of the bismuth sulfide particles contained in the coating film of the present invention may be coated with various inorganic or organic compounds. Examples of inorganic compounds include metal oxides and / or metal hydrous oxides of silicon, aluminum, titanium, zirconium, tin, antimony, etc. Examples of organic compounds include organosilicon compounds, organometallic compounds, polyol-based, amine-based, and carboxylic acid-based organic compounds (specifically, trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, dimethylethanolamine, triethanolamine, stearic acid, oleic acid, and salts thereof). The surfaces of the bismuth sulfide particles may be coated with the inorganic compounds described above and then further coated with the organic compounds described above. The coating amount of the inorganic or organic compound can be appropriately set.

[0048] The bismuth sulfide particles contained in the coating film of the present invention can be synthesized, for example, as follows.

[0049] The bismuth sulfide particles contained in the coating film can be produced, for example, by heating a bismuth compound and a sulfur compound in a dispersion medium in the presence of a protective agent at 30°C to 100°C. The above temperature range is preferred from the viewpoint of avoiding a situation where the reaction does not proceed if the heating temperature is lower than 30°C, and a hydrothermal device is required if the heating temperature is higher than 100°C. The heating temperature is more preferably 30°C to 90°C, and even more preferably 30°C to 85°C.

[0050] Examples of bismuth compounds that can be used include bismuth sulfate, bismuth nitrate, bismuth nitrate pentahydrate, bismuth subnitrate, bismuth hydroxide, bismuth oxide, bismuth chloride, bismuth bromide, bismuth iodide, bismuth oxychloride, bismuth subcarbonate, bismuth basic carbonate, etc. The bismuth compound is not limited to those in the form of powder, and a solution or suspension in which the powder is previously dissolved in various solvents (water, formic acid, methanol, ethanol, 1-propanol, 2-propanol, etc.) can also be used.

[0051] The bismuth compound may be wet-pulverized when the powder is suspended in various solvents. Known wet-pulverizing devices can be used, such as Star Mill LME20 (manufactured by Ashizawa Finetech Co., Ltd.). The grinding media used in the wet-pulverization, the particle size of the grinding media, the packing ratio of the media, or the solids concentration in the slurry may be adjusted as appropriate.

[0052] Furthermore, the bismuth compound may be produced by a known method. For example, bismuth hydroxide can be produced as follows: Bismuth nitrate pentahydrate and nitric acid are mixed and heated. Sodium hydroxide is added to the mixture, and the mixture is aged to obtain a suspension containing bismuth hydroxide. The obtained suspension is subjected to solid-liquid separation, and the solid content (specifically, bismuth hydroxide) is washed.

[0053] The sulfur compound may be sulfur itself, or may be, for example, a thiocyanate such as potassium thiocyanate or sodium thiocyanate, a thiosulfate such as sodium thiosulfate, potassium thiosulfate, or ammonium thiosulfate, or an organic sulfur compound such as thiourea or thioacetamide. The sulfur compound may be an anhydride or a hydrate, and either may be used. Furthermore, the sulfur compound is not limited to being in powder form; a solution or suspension in which the powder is pre-dissolved in various solvents (water, formic acid, methanol, ethanol, 1-propanol, 2-propanol, etc.) may also be used. Furthermore, a known acid or base may be added to dissolve the powder suspended in the solvent.

[0054] The protective agent acts as a dispersion stabilizer for the synthesized bismuth sulfide particles, and known protective agents can be used in the present invention. Examples include protein-based materials such as gelatin, gum arabic, casein, sodium caseinate, and ammonium caseinate; natural polymers such as starch, dextrin, agar, and sodium alginate; cellulose-based materials such as hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose; vinyl-based materials such as polyvinyl alcohol (also referred to as "PVA" in the present application) and polyvinylpyrrolidone; acrylic acid-based materials such as sodium polyacrylate and ammonium polyacrylate; and synthetic polymers such as polyethylene glycol. One or more of these may be used. Among these, water-soluble polymers are preferred. Examples of water-soluble polymers include gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol. Polyvinyl alcohol (PVA), polyethylene glycol, and polyvinylpyrrolidone are particularly preferred. The protecting agent can also be used as a solution dissolved in various solvents (water, formic acid, methanol, ethanol, 1-propanol, 2-propanol, etc.).

[0055] The protective agent is understood to be adsorbed onto the surface of the bismuth sulfide particles synthesized in the dispersion medium, and the steric hindrance of the adsorbed protective agent is understood to suppress aggregation of the bismuth sulfide particles.

[0056] The dispersion medium is one whose main component is water, i.e., one whose water content is 50% by mass or more. The water content in the aqueous dispersion medium is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass. Components other than water include various organic solvents that dissolve in water (methanol, ethanol, 2-propanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc.).

[0057] The above raw materials may be mixed in any order. That is, the bismuth compound, sulfur compound, and dispersion medium may be mixed in advance and the protective agent may be added thereto; the sulfur compound, protective agent, and dispersion medium may be mixed in advance and the bismuth compound may be added thereto; or the bismuth compound, protective agent, and dispersion medium may be mixed in advance and the sulfur compound may be added thereto. Alternatively, all raw materials may be added to the dispersion medium at once and mixed, or the bismuth compound, sulfur compound, and protective agent may be mixed into the dispersion medium one by one. Among these, it is preferable to mix the protective agent and dispersion medium in advance and add the bismuth compound thereto, and then add the sulfur compound. This allows each raw material to be more uniformly dissolved in the solvent. The temperature of the raw material mixing can be set appropriately and is usually the temperature of the aqueous dispersion medium without heating, for example, in the range of 5 to 30°C. Alternatively, the aqueous dispersion medium may be heated, for example, in the range of 10 to 50°C.

[0058] In the raw material mixing step, the sulfur compound and the bismuth compound are preferably mixed so that the S / Bi molar ratio is 3.5 or more and 20 or less, more preferably 4 or more and 12.5 or less, and even more preferably 4.5 or more and 10 or less. By adjusting the ratio within such a range, bismuth sulfide particles with a higher degree of blackness can be produced. The S / Bi molar ratio is a ratio calculated by dividing the number of moles of sulfur atoms in the sulfur compound by the number of moles of bismuth atoms in the bismuth compound.

[0059] In the raw material mixing step, the amount of the protective agent mixed can be adjusted appropriately depending on the type of protective agent. For example, when polyvinyl alcohol is used as the protective agent, it is preferably mixed in an amount of 250% by mass to 3000% by mass, more preferably 400% by mass to 2000% by mass, based on the raw material bismuth compound. When polyethylene glycol is used as the protective agent, it is preferably mixed in an amount of 1500% by mass to 5000% by mass, more preferably 2000% by mass to 4000% by mass, based on the raw material bismuth compound.

[0060] In the raw material mixing step, additives such as dispersants, emulsifiers, thickeners, antifoaming agents, and anti-settling agents may be added as needed.

[0061] The pH of the mixture obtained by the mixing step is preferably adjusted appropriately depending on the raw materials used. For example, when bismuth hydroxide, sodium thiosulfate, polyvinyl alcohol, and water are used as raw materials, or when bismuth oxide, sodium thiosulfate, polyvinyl alcohol, and water are used as raw materials, it is preferable to add a pH adjuster to the mixture obtained after the mixing step to adjust the pH to 5 or less. More preferably, the pH is adjusted to 4 or less, and even more preferably, the pH is adjusted to 3 or less. By keeping the pH within the above range, the synthesis reaction of bismuth sulfide particles can be promoted at 100°C or less, which is preferable. The pH adjuster is not particularly limited, and known acids or bases such as sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide, and potassium hydroxide can be used. Note that sulfuric acid used here is not included in the sulfur compounds.

[0062] The above raw materials can be mixed using a known mixer such as a stirrer, a mixer, a homogenizer, or an agitator.

[0063] The heating time at the above temperature can be set arbitrarily, but is preferably 0.5 hours or more and 10 hours or less.

[0064] Furthermore, the method may include a step of maintaining the temperature of the mixed solution obtained in the mixing step before the heating step, and the maintaining temperature is set to the heating temperature or lower, and the maintaining temperature is preferably 10°C or higher and 40°C or lower, and more preferably 12°C or higher and 35°C or lower. The maintaining time is preferably 1 hour or higher and 24 hours or lower, more preferably 2 hours or higher and 20 hours or lower, and even more preferably 3 hours or higher and 18 hours or lower. In this way, the antireflection performance and blackness of the bismuth sulfide particles can be further improved, and ultimately the antireflection performance and blackness of the coating film containing the bismuth sulfide can also be further improved.

[0065] The holding step may be carried out at any stage before the heating step. That is, the holding step may be carried out after the raw material mixing or after the pH adjustment step, but is preferably carried out after the pH adjustment step. Furthermore, if heating is performed during the mixing step, the temperature may be maintained. Furthermore, during the holding step, the mixed solution may be mixed using the known mixer.

[0066] The mechanism by which the holding step improves the anti-reflection performance and blackness of the bismuth sulfide particles can be understood as follows. By performing heating after the holding step, the nucleation process of the bismuth sulfide particles can be separated from the growth process of the resulting nuclei. The particle size distribution of the bismuth sulfide particles obtained in this manner is narrower (i.e., the aforementioned D3 is smaller) than that obtained without the holding step.

[0067] The method for producing bismuth sulfide particles may further include a step of mixing a bismuth compound with a compound of at least one element X selected from the group consisting of Al, Ce, La, Fe, and Y. That is, this method involves heating a bismuth compound, a sulfur compound, and a compound of at least one element X selected from the group consisting of Al, Ce, La, Fe, and Y in a dispersion medium in the presence of a protective agent at a predetermined temperature, thereby allowing the element X to be contained in the bismuth sulfide particles. The element X is more preferably Al or Ce, and even more preferably Al.

[0068] Examples of compounds containing Al as element X include aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum nitrate, aluminum sulfate, and sodium aluminate. Examples of compounds containing Ce as element X include cerium(III) oxide (Ce2O3), cerium(IV) oxide (CeO2), cerium(III) sulfate octahydrate (Ce2(SO4)3·8H2O), cerium(III) sulfate tetrahydrate (Ce(SO4)2·4H2O), cerium(III) chloride heptahydrate (CeCl3·7H2O), and cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O). Examples of compounds containing La as element X include lanthanum nitrate hexahydrate (La(NO3)3·6H2O), lanthanum oxide (La2O3), and lanthanum chloride (La2Cl3). Examples of compounds in which Fe is the element X include iron nitrate nonahydrate (Fe(NO3)3·9H2O), metallic iron, iron(II) oxide (FeO), iron(III) oxide (Fe2O3), triiron tetroxide (Fe3O4), iron(II) sulfate (FeSO4) or its hydrate, iron(III) sulfate (Fe2(SO4)3) or its hydrate, iron(II) chloride (FeCl2) or its hydrate, and iron(III) chloride (FeCl3) or its hydrate. Examples of compounds in which Y is the element X include yttrium nitrate hexahydrate (Y(NO3)3·6H2O), yttrium oxide (YO3), yttrium(III) fluoride (YF3), yttrium(III) chloride (YCl3), and yttrium(III) bromide (YBr3). The compound of element X is not limited to being in the form of a powder, and a solution in which the powder is dissolved in various solvents (water, formic acid, methanol, ethanol, 1-propanol, 2-propanol, etc.) or a suspension in which the powder is suspended can also be used.

[0069] The compound of element X may be mixed at any time. That is, it is preferable to mix the compound during any of the steps of mixing the bismuth compound, sulfur compound, dispersion medium, and protective agent, the holding step, and the heating step. When bismuth hydroxide is produced as the bismuth compound, the compound may be mixed at that time.

[0070] Furthermore, when mixing a compound of element X when producing bismuth hydroxide, the order of mixing is not particularly limited. That is, bismuth nitrate pentahydrate and the compound of element X may be mixed and then dissolved in nitric acid, or nitric acid and the compound of element X may be mixed and then bismuth nitrate pentahydrate may be dissolved in the mixture, or bismuth nitrate pentahydrate, nitric acid, and the compound of element X may be mixed all at once, or an aqueous solution of sodium hydroxide and the compound of element X may be mixed.

[0071] The compound of element X is mixed so that the ratio of the number of moles of X atoms to the number of moles of bismuth atoms (X / Bi molar ratio) is preferably greater than 0 and less than 10, more preferably greater than 0 and less than 8, and even more preferably greater than 0 and less than 5.

[0072] After the heating step, if necessary, the mixed liquid may be evaporated to dryness or subjected to solid-liquid separation. A known filtration method can be used for solid-liquid separation, and examples of such methods include pressure filtration devices typically used in industry, such as rotary presses and filter presses, and vacuum filtration devices, such as Buchner (Nutsche) and Moore filters. Centrifugal separation can also be used. If necessary, washing with pure water or the like may be performed, and washing with hot water (specifically, pure water at 70°C or higher) is particularly preferred. It is sufficient to wash the mixed liquid until the resistivity of the filtrate reaches 10,000 Ω·cm or higher.

[0073] The method may also include a step of drying the solid fraction obtained by the solid-liquid separation. When a drying step is included, the drying temperature and drying time can be set as desired. For example, the drying temperature is preferably 30°C or higher and 120°C or lower, and the drying time is preferably 0.5 hours or higher and 10 hours or lower. For the drying step, for example, a dryer, oven, electric furnace, spray dryer, freeze dryer, vacuum dryer, etc. can be used.

[0074] The particle size of the bismuth sulfide particles produced by the above method may be appropriately adjusted using a known grinder, classifier, or the like.

[0075] The method may include a step of coating the surfaces of the bismuth sulfide particles with an inorganic compound or an organic compound. Conventional surface treatment methods can be used to coat the surfaces of the bismuth sulfide particles with an inorganic compound or an organic compound, similar to the methods used to coat general pigments such as titanium dioxide pigments. Specifically, the coating is preferably performed by adding an inorganic compound to a slurry of the bismuth sulfide particles, and more preferably by neutralizing the inorganic compound in the slurry and precipitating it on the surfaces of the bismuth sulfide particles. Alternatively, the coating may be performed by dry-mixing a powder of bismuth sulfide particles with the inorganic compound or the organic compound.

[0076] The coating film of the present invention preferably contains bismuth sulfide particles in a pigment volume concentration (PVC) of 30% to 70%, more preferably 30% to 60%, and even more preferably 40% to 55%. By adjusting the content within this range, it is possible to improve the antireflection performance, blackness, hardness, and abrasion resistance of the coating film. The reason for this is understood as follows. The coating film of the present invention contains at least a cured product of a resin component (or a composition containing a resin component and a curing agent) and pigment particles (mainly bismuth sulfide particles). Regarding the PVC, a small PVC means that the coating contains fewer pigment particles and more cured resin, while a large PVC means that the coating contains more pigment particles and less cured resin. As mentioned above, it is understood that the visible light reflectance of the coating film is reduced by the needle-like components present on the surface of the bismuth sulfide particles contained in the coating film. Here, as mentioned above, in the coating film of the present invention, the bismuth sulfide particles contained in the coating film maintain the sea urchin-like shape at least in the coating film (preferably near the coating film surface), but when the concentration of bismuth sulfide particles in the coating film is relatively high (specifically, PVC is 30% or more), more bismuth sulfide particles maintaining the sea urchin-like shape are present in the coating film (preferably near the coating film surface), so the visible light reflectance is further reduced, and L * It is understood that the value will be reduced. On the other hand, when the amount of cured resin component (or composition containing resin component and curing agent) contained in the coating film is relatively high (specifically, PVC is 70% or less), it is understood that the bismuth sulfide particles in the coating film are sufficiently fixed by the cured component, and the hardness of the coating film is improved. Furthermore, it is understood that the bismuth sulfide particles on the coating film surface can better maintain their thorn-like state in the coating film after the finger tactile test, so the visual change in the blackness of the coating film before and after the finger tactile test is smaller (i.e., abrasion resistance can be improved).

[0077] The pigment volume concentration (PVC) of the bismuth sulfide particles in the coating film of the present invention is a value calculated from the volume of bismuth sulfide (P) and the total volume of all resins (R) using formula 1: P / (P+R) × 100. Specifically, the mass of the coating film is measured, and the coating film is heated. The mass of the material remaining after heating is measured, and the mass reduced by heating is calculated. The mass of the material remaining after heating is the mass of bismuth sulfide, and the mass reduced by heating is the mass of the resin component. The mass of the bismuth sulfide and the mass of the resin component are divided by their respective specific gravities to calculate the volume of the bismuth sulfide and the volume of the resin component. The specific gravity of bismuth sulfide is calculated as 6.78. The specific gravity of the resin component is calculated as 1. The volumes of the bismuth sulfide particles and the resin component calculated as above are substituted into formula 1 above to calculate the PVC of the bismuth sulfide particles in the coating film of the present invention.

[0078] The coating film may have a constant thickness. Specifically, it may be 10 μm or more and 70 μm or less, but a thickness of 10 μm or more is preferable because the coating film can sufficiently hide the surface of the object to be coated (substrate). The thickness of the coating film can be measured by observing the cross section of the coating film with a scanning electron microscope or by using an electromagnetic / eddy-current film thickness meter SWT-9000 (manufactured by Sanko Electronics Laboratory).

[0079] The coating film of the present invention may have a clear coating film. The thickness of the clear coating film can be measured by observing the cross section of the coating film with a scanning electron microscope.

[0080] Next, the invention of a coating composition will be described. The coating composition of the present invention comprises a resin component, bismuth sulfide particles, and a solvent. The hydroxyl value of the solid content of the resin component is 60 mgKOH / g or less, the bismuth sulfide particles are contained in a pigment volume concentration (PVC) of 30% to 70%, and the shape of the bismuth sulfide particles observed under a scanning electron microscope is a collection of 10 or more needle-like components at one end and / or a shape of a roughly spherical body with multiple plate-like and / or needle-like projections on the surface. By using the coating composition of the present invention, a coating film of the present invention can be formed that has high anti-reflection performance, as well as high coating film hardness, abrasion resistance, and blackness. The coating composition of the present invention contains bismuth sulfide particles that, when observed under a scanning electron microscope, have a shape in which one end of 10 or more needle-like elements is gathered together and / or a shape in which a substantially spherical body has a plurality of plate-like and / or needle-like projections on its surface. By using bismuth sulfide particles of such a shape, when a coating film is formed, the bismuth sulfide particles can exist in the coating film in a state in which one end of 10 or more needle-like elements is gathered together and / or a substantially spherical body has a plurality of plate-like and / or needle-like projections on its surface, and the coating film of the present invention can be formed with high anti-reflection performance and high coating film hardness, abrasion resistance, and blackness.

[0081] The coating composition of the present invention contains a resin component having a hydroxyl value in the solid content of 60 mgKOH / g or less. The hydroxyl value in the solid content is preferably 50 mgKOH / g or less. By adjusting the hydroxyl value in this range, the anti-reflection performance, blackness, hardness, and abrasion resistance of the coating film can be improved. The hydroxyl value can be measured in accordance with JIS K 0070-1992. The hydroxyl value in the solid content is calculated by dividing the hydroxyl value in the solution of the resin by the ratio of the solid content in the resin, and the detailed procedure is as described in the examples below.

[0082] When a commercially available resin component is used, the hydroxyl value of the resin component in solution is determined by referring to the catalog value. When the hydroxyl value in solution is listed as a range in the catalog, the median value may be used, and the median value is calculated by dividing the sum of the lower and upper limits of the range listed in the catalog by 2.

[0083] When the hydroxyl value in the solid content of the resin component is 60 mgKOH / g or less, the anti-reflection performance, blackness, hardness and abrasion resistance of the coating film are improved. The mechanism by which this is achieved is understood as follows. As mentioned above, the visible light reflectance of the coating is reduced by the acicular components present in the bismuth sulfide particles in the coating. Here, it is believed that if the hydroxyl value in the solid content of the resin component is small (specifically, 60 mgKOH / g or less), the wettability between the resin component and the bismuth sulfide particles will decrease. If the wettability decreases, when the resin component and the bismuth sulfide particles are mixed, the resin component can be prevented from penetrating into the needle-like portions on the surface of the bismuth sulfide particles. Therefore, the bismuth sulfide particles at least in the coating film (preferably on the surface of the coating film) maintain the sea urchin-like shape, thereby reducing the visible light reflectance and improving the L * It is understood that the effect of reducing the value can be fully exerted. Furthermore, when the resin component penetrates into the bismuth sulfide particles, the amount of resin component required to bond the bismuth sulfide particles decreases, resulting in the generation of bismuth sulfide particles that are not bonded by the resin component, thereby reducing the hardness of the coating film. However, as described above, the resin component with low wettability does not penetrate into the needle-shaped parts of the bismuth sulfide particles, ensuring the amount of resin component required to bond the bismuth sulfide particles, which is understood to improve the hardness of the coating film. It is also understood that even when the coating film comes into contact with a human finger or the like, the needle-like shape of the surface of the bismuth sulfide particles can be maintained, thereby improving abrasion resistance.

[0084] As the resin component, as long as the hydroxyl value in the solid content is 60 mgKOH / g or less, a resin component can be used that exhibits an infrared absorption peak derived from Amide-II in the FT-IR spectrum of the coating film after formation. The resin component may also have a urethane bond, or may form a urethane bond by reacting with a composition containing a curing agent during application. Other resin components may also be used in combination. Examples of the resin component include acrylic resins, phenolic resins, amino resins, urethane resins, epoxy resins, alkyd resins, and polyester resins. These resins can be used alone or in combination of two or more. Among these, acrylic resins are preferred. The acrylic resin may be a commercially available product or may be synthesized. Examples of commercially available products include Acrydic A814, Acrydic AU7007, and Acrydic 57-773 (all manufactured by DIC Corporation).

[0085] The coating composition of the present invention contains bismuth sulfide particles. As the bismuth sulfide particles contained in the coating composition, the above-mentioned bismuth sulfide particles can be used.

[0086] The coating composition of the present invention contains a solvent. Known solvents can be used as the solvent, and examples thereof include aqueous solvents, non-aqueous solvents such as alcohols (e.g., methanol, butanol, ethylene glycol), esters (e.g., ethyl acetate), ethers (e.g., propylene glycol monomethyl ether (sometimes referred to as "PGME" in the present application), ketones (e.g., acetone, methyl ethyl ketone), aromatic hydrocarbons (e.g., toluene, xylene, mineral spirits), and aliphatic hydrocarbons (these non-aqueous solvents are sometimes referred to as "solvents" in the present application), and mixtures thereof.

[0087] The coating composition of the present invention contains the bismuth sulfide particles in an amount of 30% to 70%, preferably 30% to 60%, and more preferably 40% to 55%, calculated as PVC. By adjusting the content within this range, the anti-reflection performance, hardness, and abrasion resistance of the coating film produced using the coating composition of the present invention can be improved.

[0088] The PVC of the coating composition of the present invention may be calculated in the same manner as the PVC of the coating film.

[0089] The resin component preferably has a glass transition temperature (Tg) of 55° C. or higher and 120° C. or lower, and more preferably 70° C. or higher and 100° C. By setting the Tg within this range, the anti-reflection performance and hardness of the coating film can be improved.

[0090] The glass transition temperature can be measured by a known method, for example, by referring to International Publication No. WO2021 / 125251.

[0091] Furthermore, if the resin used is a commercially available product, the glass transition temperature of the resin component is determined by referring to the catalog value.

[0092] When the glass transition temperature is high (specifically, 55°C or higher), molecular vibration is less likely to occur, which is thought to improve the hardness of the coating film. Furthermore, although there is no particular upper limit for the glass transition temperature, it is preferably 120°C or lower from the viewpoint of improving the handleability of the coating film.

[0093] The resin component used in the coating composition of the present invention preferably has a hydroxyl value of 60 mgKOH / g or less and a glass transition temperature of 55° C. or more, and more preferably a hydroxyl value of 50 mgKOH / g or less and a glass transition temperature of 70° C. or more. Within these ranges, the anti-reflection performance, blackness, hardness, and abrasion resistance of the coating film can be improved.

[0094] The paint set of the present invention comprises the paint composition and a composition containing a curing agent. Forming the paint set is preferable because the hardness of the paint film produced using the paint set is improved.

[0095] The composition containing the curing agent contains, in addition to the curing agent, the above-mentioned solvent, etc. Examples of the curing agent include a polycarbodiimide compound, an amino resin, a polyisocyanate compound, and a blocked polyisocyanate compound.

[0096] The curing agent can react with hydroxyl groups (sometimes referred to as "crosslinkable functional groups" in this application) in the resin component to cure the coating composition.

[0097] The compositions containing the curing agent can be used alone or in combination of two or more kinds.

[0098] The composition containing the curing agent used in the paint set can be selected appropriately depending on the resin component used. For example, when an acrylic resin, a urethane resin, a phenolic resin, or an amino resin is used as the resin component, the composition containing the curing agent preferably contains a polyisocyanate compound.

[0099] The polyisocyanate compound refers to a compound having two or more isocyanate groups per molecule. Examples of the polyisocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, araliphatic polyisocyanates, aromatic polyisocyanates, and derivatives of the polyisocyanates. Polyisocyanates include low molecular weight compounds, oligomers, and polymers. The crosslinkable functional groups of the polyisocyanates and the resin components can undergo a crosslinking reaction via a urethane bond.

[0100] The composition containing the curing agent may be synthesized or may be a commercially available product. Examples of commercially available products include Takenate D110N (manufactured by Mitsui Chemicals, Inc.). For example, when Acrydic A814, Acrydic AU7007, and Acrydic 57-773 are used as resin components, it is preferable to use Takenate D110N as the composition containing the curing agent from the viewpoint of improving the hardness of the coating film.

[0101] The coating composition or coating set of the present invention may contain various additives as needed, such as commonly used dispersants, emulsifiers, antifreeze agents, pH adjusters, thickeners, antifoaming agents, film-forming aid resin beads, and matting agents.

[0102] The present invention is a method for producing a coating film, comprising the following steps (1) to (3), in which an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR. Step (1): A step of mixing a resin component, bismuth sulfide particles, and a solvent to obtain a coating composition, wherein the resin component has a hydroxyl value of 60 mgKOH / g or less, the shape of the bismuth sulfide particles in the coating composition as observed with a scanning electron microscope is a shape in which one end of 10 or more needle-like constituent elements is gathered and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and the pigment volume concentration (PVC) of the bismuth sulfide particles in the coating composition is 30% or more and 70% or less; Step (2): A step of applying the coating composition obtained in step (1) onto an object to be coated to obtain a coated object. Step (3): A step of heating the coated object obtained in step (2)

[0103] The step (1) is explained below. Step (1) is a step of obtaining a coating composition by mixing a resin component having a hydroxyl value of 60 mgKOH / g or less in the solid content, bismuth sulfide particles of a specific shape, and a solvent so that the bismuth sulfide particles account for 30% to 70% of the PVC. The coating composition described above can be used as such a coating composition.

[0104] The resin component, the bismuth sulfide particles, and the solvent may be those described above. The bismuth sulfide particles used in step (1) may be used as powder or may be dispersed (or suspended) in a solvent. The solvent for dispersing the bismuth sulfide particles may be any of the solvents described above. Dispersion (suspension) may be performed using a known mixer such as a stirrer, mixer, homogenizer, or agitator. Conditions related to the stirring intensity, such as the stirring time, during dispersion (suspension) may be appropriately set.

[0105] When bismuth sulfide particles are dispersed in a solvent, the aqueous solvent of the aqueous dispersion containing the bismuth sulfide particles may be replaced with a solvent other than an aqueous solvent. For example, the aqueous solvent of the aqueous dispersion of bismuth sulfide particles can be replaced with a solvent as follows.

[0106] The aqueous dispersion of bismuth sulfide particles is filtered to obtain a cake of bismuth sulfide particles. The cake is then mixed with a solvent and subjected to solid-liquid separation. The solid content obtained by the solid-liquid separation is mixed with a solvent to obtain a solvent dispersion. The process of mixing the bismuth sulfide particles with a solvent and subjecting them to solid-liquid separation may be performed once or multiple times.

[0107] The solid content concentration of the dispersion during solid-liquid separation is not particularly limited, but is preferably 10% by mass or more and 70% by mass or less. A solid content of 10% by mass or more ensures a sufficient amount of solvent dispersion (of bismuth sulfide particles), while a solid content of 70% by mass or less can prevent thickening of the solvent dispersion. The solid content concentration can be calculated by dividing the remaining amount after drying the bismuth sulfide cake (or the solid content after solid-liquid separation) by the weight before drying. Drying conditions of 150°C or higher for 15 minutes or longer are sufficient.

[0108] The mixing may be performed using known devices such as a stirrer, a (rotating / revolving) mixer, a homogenizer, an agitator, an ultrasonic disperser, or a paint shaker. For example, a THINKY THINKY Mixer (manufactured by THINKY Corporation) may be used. The mixing conditions may be set appropriately. Furthermore, known filtration methods may be used for the solid-liquid separation. For example, pressure filtration devices such as a rotary press or a filter press, vacuum filtration devices such as a Buchner (Nutsche) or a Moore filter, centrifugation, or a membrane filter may be used.

[0109] The mixing procedure is not particularly limited. For example, the bismuth sulfide particles and the resin component may be added to the solvent, the solvent and the bismuth sulfide particles may be mixed together and the resin component may be added thereto, or the solvent, the bismuth sulfide particles, and the resin component may be mixed together at the same time.

[0110] Next, step (2) will be described. Step (2) is a step in which the coating composition obtained in step (1) is applied to an article to be coated to obtain a coated article.

[0111] Examples of the object to be coated (substrate) include ceramic products, glass products, metal products, plastic products, and paper products.

[0112] The coating composition of the present invention can be applied by any common method without limitation, such as spin coating, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, or by dropping droplets. The tool used to apply the solvent composition or coating composition can be appropriately selected from known tools such as a spin coater, spray gun, roller, brush, bar coater, doctor blade (film applicator), etc.

[0113] Furthermore, in order to improve the hardness of the coating film, step (2) may include a step of mixing a composition containing a curing agent with the coating composition. As mentioned above, when the composition containing a curing agent is added, the coating composition begins to harden, so when the composition containing a curing agent is mixed, it is desirable to apply the coating composition to the substrate without waiting too long.

[0114] When the composition containing the curing agent contains an isocyanate compound, the curing agent is mixed so that the isocyanate groups contained in the isocyanate compound are preferably 1.0 to 2.0 equivalents, more preferably 1.1 to 1.5 equivalents, relative to the amount (mol) of hydroxyl groups (sometimes referred to as "crosslinkable functional groups" in this application) in the resin component. It is understood that there is a concern that the isocyanate groups may react not only with the crosslinkable functional groups in the resin component but also with moisture in the air or solvent. It is preferable that the isocyanate groups are 1 equivalent or more relative to the amount (mol) of hydroxyl groups in the resin component, because even if the isocyanate groups in the curing agent composition react with moisture in the air or solvent, the remaining isocyanate groups can sufficiently react with the crosslinkable functional groups in the resin component. Furthermore, a concentration of 2.0 equivalents or less is preferable because it effectively avoids inefficient synthesis reactions due to an excess amount of the curing agent composition.

[0115] The method for mixing the coating composition and the composition containing the curing agent is not limited. A known agitator such as a stirrer, mixer, homogenizer, or disperser may be used, or the mixture may be manually stirred for 1 minute using a φ7 mm × 200 mm PCTFE agitator (manufactured by AS ONE Corporation). The mixing conditions may be set as appropriate.

[0116] The resin component is such that the crosslink density of a coating film formed by mixing a composition containing the resin component and a curing agent is 1.0×10 -6 mol / cc or more 7.0×10 -4 mol / cc or less is preferable, and 1.0 × 10 -6 mol / cc or more 5.0×10 -4It is more preferable that the crosslink density is mol / cc or less. If the crosslink density is within the above range, the hardness of the coating film can be improved. The crosslink density means the reaction points between the hydroxyl groups in the resin component and the curing agent. When the crosslink density is within the above range, the mechanism by which the hardness of the coating film is improved is as follows. Because the crosslink density is the reaction site between the hydroxyl groups and the curing agent, if the crosslink density is within the above range, the number of hydroxyl groups in the resin component decreases due to crosslinking between the resin component and the curing agent, and the wettability between the resin component and the bismuth sulfide particles decreases. As described above, resin components with low wettability do not penetrate into the needle-shaped parts of the bismuth sulfide particles, so it is possible to ensure an amount of resin component that can fix the bismuth sulfide particles, which is thought to result in high anti-reflection performance, high blackness, and improved hardness of the coating film.

[0117] The crosslink density is measured as follows: A composition containing a resin component and a curing agent described below is mixed, and the mixture is applied to a polypropylene (hereinafter sometimes referred to as "PP" in this specification) plate using an 8-mil applicator. After coating, the coating film is dried under suitable drying conditions. The coating film having a thickness of 0.04 mm obtained after the drying step is cut into a piece having a width of 5 mm and a length of 10 mm, which is used as a measurement sample. The measurement sample is set in a dynamic viscoelasticity measuring device, and the dynamic viscoelastic modulus of the measurement sample is measured under the following conditions while changing the absolute temperature T. The crosslink density n (mol / cc) can be calculated from the relational expression E'=3nRT (R is the gas constant) between the equilibrium modulus E' (minimum value of dynamic viscoelasticity) and the absolute temperature T at that time. The dynamic viscoelasticity measuring device used is a LEOGEL E-4000 (manufactured by UBM). [Measurement conditions] Measurement method: Dynamic viscoelasticity measurement (sine wave) Measurement mode: Temperature dependence ·Frequency (Hz): 11 ·Starting temperature (℃): 20 ·End temperature (℃): 200 Step temperature (℃): 2 Heating rate (℃ / min): 10

[0118] After the coating composition is applied to the substrate, it is allowed to set at room temperature for 10 minutes or more, and a drying step may be performed as needed. The drying conditions are not particularly limited, but may be, for example, in the air, at a temperature of 20°C or higher and 100°C or lower, for a drying time of 1 to 60 minutes.

[0119] Next, the step (3) will be described. The step (3) is a step of heating the coated article obtained in the step (2).

[0120] The heating conditions can be set as appropriate, but for example, the heating time can be about 1 to 120 minutes in an air atmosphere at a temperature range of 40°C to 200°C. By setting these conditions, sufficient heating can be achieved in the drying furnace of the coil coating line.

[0121] The drying step or heating step may be carried out using known equipment, such as a dry oven (manufactured by ESPEC).

[0122] The coating film production method of the present invention may include a method of forming a clear coating film after the above coating film formation. The clear paint for forming the clear coating film may use the above resin component.

[0123] The method for applying the clear coating may be the same as the method for applying the coating composition.

[0124] The heating conditions for the clear coating film may be the same as those described above. [Example]

[0125] The present invention will be described in more detail with reference to the following Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In these Examples, "parts" and "%" are by mass unless otherwise specified.

[0126] 20 mL of pure water was added to 1.0 g of the bismuth sulfide cake described below, and the mixture was dispersed for 1 minute in an ultrasonic cleaner UT-305 (manufactured by SHARP) to produce a dispersion. The particle size distribution of the dispersion was measured using a laser diffraction / scattering particle size distribution analyzer LA-950 (manufactured by HORIBA, Ltd.) under the following conditions. Sample refractive index: 2.13 (bismuth sulfide) Solvent refractive index: 1.33 (pure water) Circulation speed: 10 Ultrasonic intensity: 1 Ultrasonic time: 2 minutes Stirring intensity: 10 Transmittance (R) for laser light (650 nm): 95-70% Transmittance (B) for LED light (405 nm): 90-80%

[0127] Based on the particle size distribution obtained above, the cumulative 50% diameter (D1) in the volume cumulative distribution of the bismuth sulfide particles was calculated.

[0128] 10 g of the resin component shown in Table 1 was weighed out and placed in an aluminum cup, and dried in a dryer at 80°C for 30 minutes, then heated to 125°C and dried at 125°C for another 30 minutes. After drying, the aluminum cup was removed and the amount of solids remaining in the aluminum cup was measured. The solids amount was divided by the amount of resin component (10 g) added to calculate the solids ratio in the resin component. Next, with reference to the DIC catalog (https: / / www.dic-global.com / images / product_file / file / coatingcatalog.pdf), the median hydroxyl value in the solution was calculated for the resin in English listed in Table 1. The median hydroxyl value in the solution was divided by the ratio of solids in the resin component to calculate the hydroxyl value in the solids. Table 1 shows the resin components used, the ratio of solids in the resin components, the hydroxyl value in the solution (upper limit, lower limit, median), and the hydroxyl value in the solids.

[0129] [Table 1]

[0130] The resin components (listed in Table 2) and the composition containing the curing agent were weighed out as shown in Table 3. First, 10 g of propylene glycol monomethyl ether (PGME, manufactured by Sankyo Chemical Co., Ltd.) was added to the resin components and mixed. Finally, the composition containing the curing agent was added and manually stirred for 1 minute using a φ7 mm x 200 mm PCTFE stirring rod (manufactured by AS ONE Corporation). After stirring, the mixture was applied to a PP plate (TP Giken DG02) using an 8 mil applicator and dried in a dryer (Yamato Scientific DF611S) at 100°C for 30 minutes. After drying, the resulting 0.04 mm thick coating was cut into a 5 mm wide x 10 mm long sample to serve as a measurement sample. The measurement sample was set in a dynamic viscoelasticity measuring device (Leogel E-4000, manufactured by UBM), and the dynamic viscoelastic modulus was measured under the following conditions: The crosslink density n (mol / cc) was calculated from the relational expression E' = 3nRT (R is the gas constant: 8.314 J / mol K) between the equilibrium modulus E' (minimum value of the dynamic viscoelastic modulus) and the absolute temperature T (K) at that time. [Measurement conditions] Measurement method: Dynamic viscoelasticity measurement (sine wave) Measurement mode: Temperature dependence ·Frequency (Hz): 11 ·Starting temperature (℃): 20 ·End temperature (℃): 200 Step temperature (℃): 2 Heating rate (℃ / min): 10

[0131] [Table 2] In the table, "-" indicates that the measurement was not carried out and the catalog value is unknown.

[0132] [Table 3]

[0133] (Production Example 1) 43.6 kg of bismuth oxide (Bismuth Oxide S, manufactured by Nippon Chemical Industry Co., Ltd.) was added to 176.3 kg of pure water and stirred. The mixture was then wet-pulverized using a horizontal bead mill (Star Mill LME20, manufactured by Ashizawa Finetech Co., Ltd.) to obtain a bismuth oxide slurry. The wet-pulverization conditions are as follows:

[0134] [Wet grinding conditions] Vessel capacity: 16.3L Beads: Zirconia beads (Toray Industries: Treceram) Bead diameter: 1mmφ Bead filling rate: 80% Bead weight: 49.3kg Circumferential speed: 10m / s Flow rate: 3.5L / min Dwell time: 2 minutes 18 seconds Number of passes: 1

[0135] 3259.2 g of pure water, 2.5 g of an antifoaming agent (SN Deformer 485, manufactured by San Nopco Co., Ltd.), and 367.6 g of PVA with a purity of 94.0% (Kuraray Poval 22-88, manufactured by Kuraray Co., Ltd.) were stirred for 1 hour to obtain an aqueous PVA solution.

[0136] 612.6 g of purified water and sodium thiosulfate (crystalline sodium thiosulfate, manufactured by Japan Air Water Performance Chemicals Inc.) were stirred to obtain an aqueous sodium thiosulfate solution.

[0137] The PVA aqueous solution was stirred at 340 rpm with a stirring blade (diameter 118 mm) while adjusting the liquid temperature to 30°C, and 303.8 g of the bismuth oxide slurry and 104.2 g of pure water were added thereto. The solid content of the bismuth oxide slurry added to the PVA aqueous solution was 21.0 mass%. Then, 931.2 g of a sodium thiosulfate aqueous solution was added, and 35 mass% hydrochloric acid was added thereto to adjust the pH to 1.80±0.2, thereby obtaining a reaction solution. In this production example, 105 g of hydrochloric acid was added. The reaction solution was stirred for 4 hours while maintaining the temperature at 30° C. After stirring, the temperature was raised to 70° C., and after reaching 70° C., it was maintained for 2 hours. After maintaining the temperature, 139.2 g of a 20% by mass aqueous sodium hydroxide solution (manufactured by Takasugi Pharmaceutical Co., Ltd.) was added to obtain a bismuth sulfide slurry. The bismuth sulfide slurry was diluted 3 times by weight with pure water to obtain a diluted solution. 500 g of the diluted solution was weighed into a centrifuge tube and centrifuged at 2000 G for 5 minutes using a centrifugal separator (Himac CR-21, manufactured by Eppendorf). After centrifugation, the supernatant was removed, and an equal amount of pure water was added and stirred to obtain a repulp slurry. The repulp slurry was filtered and washed using hot water (specifically, pure water at 70°C or higher) using a Buchner funnel (diameter 185 mm) lined with filter paper until the filtrate resistivity reached 10,000 Ω cm or higher, yielding a bismuth sulfide cake. The D1 of the bismuth sulfide particles contained in the bismuth sulfide cake was 2.71 μm.

[0138] 3 g of the bismuth sulfide cake was weighed out and dried at 150°C for 15 minutes. The solid content of the cake was calculated by dividing the remaining amount after drying by the amount of the bismuth sulfide cake before drying. Based on the solid content, the bismuth sulfide cake was weighed into a 150 cc disposable cup so that the solid content was 30 g. Propylene glycol monomethyl ether (PGME, manufactured by Kanto Chemical Co., Ltd.) was added to the cake so that the solid content was 55% by mass. After the addition of PGME, the mixture was stirred at 2000 rpm for 10 minutes using a planetary centrifugal mixer (Awatori Rentaro ARE-310, manufactured by THINKY Co., Ltd.). After stirring, 100 mL of PGME was added, and the mixture was filtered through a 0.45 μm membrane filter (manufactured by Merck) to obtain solid content (A). The solid content (A) and 50 mL of PGME were mixed in a beaker and dispersed for 5 minutes using an ultrasonic disperser (UT-305S, manufactured by SHARP). After dispersion, the solid content (B) was obtained using a 0.45 μm membrane filter (manufactured by Merck). The solid content (B) was heated at 150°C for 15 minutes, and the solid content concentration of the solid content (B) was calculated from the remaining amount. Based on the solid content concentration, PGME was added so that the concentration of the solid content (B) in the dispersion became 55 mass%, and the mixture was stirred at 2000 rpm for 10 minutes using a planetary centrifugal mixer (Awatori Rentaro ARE-310, manufactured by THINKY Corporation), to obtain a bismuth sulfide solvent dispersion of Production Example 1.

[0139] (Production Example 2) 20 g of bismuth sulfide particles (bismuth(III) sulfide, Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed out and pulverized for 10 minutes using an agate mortar. 30 g of 0.8 mm diameter zirconia beads (Toray Industries, Inc.) were weighed into a 50 mL polypropylene (PP) container, and 11 g of the pulverized bismuth sulfide particles and 9 g of PGME (Sankyo Chemical Co., Ltd.) were added to the PP container. After the addition, the PP container was placed in a paint conditioner (Red Devil Co., Ltd.), and the contents were dispersed for 30 minutes to obtain a solvent dispersion of bismuth sulfide particles of Production Example 2. Note that the D1 of the bismuth sulfide particles after pulverization using the agate mortar was 2.59 μm.

[0140] (Presence or absence of thorns in bismuth sulfide solvent dispersion) The bismuth sulfide powder obtained by heating the solid component (B) described in Production Example 1 at 150 ° C for 15 minutes was fixed to a sample stage with carbon tape and coated with a thin layer of platinum under vacuum conditions using an E-1045 (Hitachi High-Tech Corporation) (discharge current: 15 mA, irradiation time: 90 seconds, irradiation distance: 30 mm). Then, using a scanning electron microscope S-4800 (Hitachi High-Tech Corporation) under the following conditions, the shape of the bismuth sulfide particles in the bismuth sulfide solvent dispersion of Production Example 1 was confirmed to have a shape in which one end of 10 or more needle-like components was gathered and / or a shape with multiple protrusions of plate-like and / or needle-like pieces on the surface of a roughly spherical body (i.e., the presence or absence of thorns was confirmed). The bismuth sulfide solvent dispersion prepared in Production Example 2 was also confirmed to have the presence or absence of thorns in the bismuth sulfide particles using a similar method. [Measurement conditions] Accelerating voltage: 5 kV Focal length WD: 8mm Measurement magnification: 20,000x, 50,000x

[0141] Example 1 20.0 g of the bismuth sulfide solvent dispersion prepared in Production Example 1 and 2.3 g of a resin component (Acrydic A814, manufactured by DIC Corporation) were weighed into a 150 mL container. They were then mixed at 2000 rpm for 10 minutes using a planetary centrifugal mixer (Awatori Rentaro ARE-310, manufactured by THINKY Corporation). 0.5 g of a composition containing a curing agent (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) was added to the mixture, and the mixture was manually stirred for 1 minute using a φ7 mm × 200 mm PCTFE stirring rod (manufactured by AS ONE Corporation), yielding coating composition 1 of Example 1. The crosslink density of the coating film obtained by mixing Acrydic A814 and Takenate D110N was 1.81 × 10 -4 It was mol / cc. 1 mL of the coating composition was placed on black-and-white chart paper (Form 5C Opacity Chart, manufactured by Leneta Company, Inc.) and on a dull steel plate (coated with an undercoat and sanded with water), and the coating composition was applied to each plate by drawing a 15 cm distance over 2 seconds using an 8 mil applicator (manufactured by Taiyu Kizai Co., Ltd.). After application, the coating was left to set at room temperature for 10 minutes or more and then heated at 100°C for 20 minutes to obtain Coating Film 1 of Example 1.

[0142] Example 2 A coating composition and coating film were prepared in the same manner as in Example 1, except that the resin component was changed to 3.7 g of Acrydic AU7007 (manufactured by DIC Corporation) and the curing agent was changed to 0.4 g, thereby obtaining coating composition 2 and coating film 2 of Example 2. The crosslink density of the coating film obtained by mixing Acrydic AU-7007 and Takenate D110N was 9.08 × 10 -5 It was mol / cc.

[0143] Example 3 A coating composition and coating film were prepared in the same manner as in Example 1, except that the resin component in Example 1 was changed to 2.7 g of Acrydic 57-773 (manufactured by DIC Corporation), thereby obtaining Coating Composition 3 and Coating Film 3 of Example 3. The crosslink density of the coating film obtained by mixing Acrydic 57-773 and Takenate D110N was 2.09 × 10 -4 It was mol / cc.

[0144] Example 4 A coating composition and a coating film were prepared in the same manner as in Example 1, except that the resin component was changed to 5.2 g and the composition containing a curing agent was changed to 1.2 g, thereby obtaining a coating composition 4 and a coating film 4 of Example 4.

[0145] Example 5 In Example 1, except that the resin component was changed to 1.5 g and the composition containing the curing agent was changed to 0.3 g, a coating composition and a coating film were prepared in the same manner as in Example 1, and coating composition 5 and coating film 5 of Example 5 were obtained.

[0146] Example 6 A coating composition and a coating film were prepared in the same manner as in Example 1, except that the resin component in Example 1 was changed to 1.0 g and the composition containing a curing agent was changed to 0.2 g, thereby obtaining a coating composition 6 and a coating film 6 of Example 6.

[0147] (Comparative Example 1) 20.0 g of the bismuth sulfide solvent dispersion prepared in Preparation Example 1 and 2.3 g of nax Aegis TS Clear (manufactured by Nippon Paint Co., Ltd.) as the resin component were weighed into a 150 mL container. They were then mixed at 2000 rpm for 10 minutes using a planetary centrifugal mixer (Awatori Rentaro ARE-310, manufactured by THINKY Co., Ltd.). 0.8 g of nax Aegis (3:1) TS Clear Hardener (manufactured by Nippon Paint Co., Ltd.), a composition containing a curing agent, was added to the mixture, and the mixture was manually stirred for 1 minute using a φ7 mm x 200 mm PCTFE stirring rod (manufactured by AS ONE Corporation), yielding Coating Composition 7 of Comparative Example 1. Coating composition 8 was applied to black and white chart paper (Form 5C Opacity Chart manufactured by Leneta Company, Inc.) and a dull steel plate (coated with an undercoat paint and sanded with water) using an 8 mil applicator. After application, the coating was allowed to set at room temperature for 10 minutes or more, and then heated at 60°C for 30 minutes to obtain coating film 7 of Comparative Example 1.

[0148] (Comparative Example 2) In Comparative Example 1, 1.3 g of Admira α901 binder (manufactured by Nippon Paint Co., Ltd.) and 4.4 g of Admira α280 correction clear (manufactured by Nippon Paint Co., Ltd.) were used as the resin components, and a coating composition and coating film were prepared in the same manner as in Comparative Example 1, except that no curing agent was used, thereby obtaining Coating Composition 8 and Coating Film 8 of Comparative Example 2.

[0149] (Comparative Example 3) In Comparative Example 2, except that the resin components were changed to 3.0 g of Admira α901 binder (manufactured by Nippon Paint Co., Ltd.) and 10.1 g of Admira α280 correction clear (manufactured by Nippon Paint Co., Ltd.), respectively, a paint composition and a paint film were prepared in the same manner as in Comparative Example 2, and paint composition 9 and paint film 9 of Comparative Example 3 were obtained.

[0150] Comparative Example 4 In Example 1, except that the resin component was changed to 12.7 g and the composition containing the curing agent was changed to 2.9 g, a coating composition and a coating film were prepared in the same manner as in Example 1, and a coating composition 10 and a coating film 10 of Comparative Example 4 were obtained.

[0151] (Comparative Example 5) A coating composition and coating film were prepared in the same manner as in Example 1, except that the resin component was changed to 1.6 g of Acrydic A801-P (manufactured by DIC Corporation) and the composition containing a curing agent was changed to 1.0 g, thereby obtaining coating composition 11 and coating film 11 of Comparative Example 5. The crosslink density of the coating film obtained by mixing Acrydic A-801-P and Takenate D110N was 8.14 × 10 -4 It was mol / cc.

[0152] (Comparative Example 6) A coating composition and coating film were prepared in the same manner as in Example 1, except that the resin component was changed to 1.2 g of Acrydic WLU-738 (manufactured by DIC Corporation) and the composition containing a curing agent was changed to 1.1 g, thereby obtaining a coating composition 12 and a coating film 12 of Comparative Example 6. The crosslink density of the coating film obtained by mixing Acrydic WLU-738 and Takenate D110N was 8.45 × 10 -4 It was mol / cc.

[0153] (Comparative Example 7) 20.0 g of the bismuth sulfide solvent dispersion prepared in Preparation Example 2 and 2.3 g of a resin component (Acrydic A814, manufactured by DIC Corporation) were weighed into a 50 mL PP container. The mixture was then mixed for 10 minutes using a paint conditioner (manufactured by Red Devil Co., Ltd.). After mixing, 0.5 g of a composition containing a curing agent (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) was added, and the mixture was manually stirred for 1 minute using a φ7 mm × 200 mm PCTFE stirring rod (manufactured by AS ONE Corporation), yielding a coating composition 13 of Comparative Example 7. The coating composition 13 was applied to black and white chart paper (Form 5C Opacity Chart manufactured by Leneta Company, Inc.) and a dull steel plate (coated with an undercoat paint and sanded with water) using an 8 mil applicator. After application, the coating was dried at 100°C for 20 minutes to obtain a coating film 13 of Comparative Example 7.

[0154] (Comparative Example 8) 2.6 g of carbon black MA-100 (Mitsubishi Chemical), 30 g of toluene (Kanto Chemical) as a solvent, 32 g of Acrydic A814 (DIC) as a resin component, and 50 g of φ0.8 mm zirconia beads were weighed into a 100 mL polypropylene (PP) container and mixed for 30 minutes using a paint conditioner (Red Devil). After mixing, 7.38 g of Takenate D110N (Mitsui Chemicals) as a curing agent composition was added, and the mixture was stirred manually for 1 minute using a φ7 mm x 200 mm PCTFE stirring rod (AS ONE Corporation) to obtain coating composition 14 of Comparative Example 8. The coating composition was applied to black and white chart paper (Form 5C Opacity Chart manufactured by Leneta Company, Inc.) and a dull steel plate (coated with an intermediate coating and sanded with water) using a #10 bar coater. After application, the coating was heated at 100°C for 20 minutes to obtain a coating film 14 of Comparative Example 8.

[0155] The presence or absence of thorns confirmed by the above-mentioned method for the fillers used in the above examples and comparative examples, and the PVC (%) in the paint composition are shown in Table 4. In the table, "-" means that the measurement was not performed.

[0156] [Table 4]

[0157] (Presence or absence of thorns on the coating surface) Each of the coatings 1-13 on black-and-white chart paper was cut into 1 cm squares, fixed to a sample stage with carbon tape, and coated with a thin layer of platinum under vacuum conditions using an E-1045 (Hitachi High-Tech Corporation) microscope (discharge current: 15 mA, exposure time: 90 seconds, exposure distance: 30 mm). Then, using a scanning electron microscope S-4800 (Hitachi High-Tech Corporation) under the following conditions, the shape of the bismuth sulfide particles present in the coating was confirmed to be a collection of ten or more needle-like components and / or a roughly spherical body with multiple plate-like and / or needle-like protrusions on its surface (i.e., the presence or absence of thorns). A "thorny" condition was determined when the resin component did not penetrate into the microscopic spaces of the bismuth sulfide particles and the acicular shape of the bismuth sulfide particle surface was confirmed in the coating. [Measurement conditions] Accelerating voltage: 5 kV Focal length WD: 8mm Measurement magnification: 20,000x, 50,000x

[0158] (visible light reflectance of coating film) The coating films 1 to 14 were set in a spectrophotometer SD-7000 (manufactured by Nippon Denshoku Industries Co., Ltd.) and the reflectance was measured at wavelengths from 380 nm to 780 nm under the following conditions to obtain a reflectance spectrum. In the obtained reflectance spectrum, the reflectance at a wavelength of 550 nm was taken as the visible light reflectance. [Measurement conditions] Light source / field of view: D65 / 10° Illumination / light receiving conditions: Reflection: di: 8° (diffuse illumination: 8° receiving light) including specular reflection (SCI) Measurement wavelength: 380-780nm (5nm interval output) Measurement diameter: LAV (φ19mm)

[0159] (Abrasion resistance of coating film) A finger tactile test was performed to check the abrasion resistance of Coatings 1 to 6 by lightly pressing the coating surface with the middle finger of a nitrile glove (manufactured by AS ONE Corporation) and rubbing it back and forth three times. Abrasion resistance is an index showing the change in the blackness of the coating film before and after the finger tactile test. The change in the blackness of the coating film before and after the finger tactile test was evaluated visually.

[0160] (paint film brightness) Coating films 1 to 14 were set in a spectrophotometer SD-7000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the L of the coating film was measured under the following conditions. * value, a * value, b * The values ​​were measured respectively. Measurement conditions Light source / field of view: D65 / 10° Illumination / light receiving conditions: Reflection: di: 8° (diffuse illumination: 8° receiving light) including specular reflection (SCI)

[0161] (Coating film hardness) The pencil hardness of each coating film was measured for coating films 1 to 14 in accordance with JIS K5600-5-4:1999 (General testing methods for paints - Part 5: Mechanical properties of coating films - Section 4: Scratch hardness (pencil method)). The test equipment used was a pencil hardness tester 750g (manufactured by Allgood Co., Ltd.), and the pencil used was a Mitsubishi Uni pencil for pencil hardness testing.

[0162] (Solar reflectance of coating film) The reflectance of Coating Film 1 was measured in the wavelength range of 780 nm to 2500 nm using a UV-Vis-Near-Infrared Spectrophotometer V-670 (manufactured by JASCO Corporation) with a Spectralon standard reflector (manufactured by Labsphere). From the reflectances obtained in the wavelength range from 780 nm to 2500 nm, the solar reflectance in the wavelength range from 780 nm to 2500 nm was calculated in accordance with JIS K 5602 (2008).

[0163] (Specular gloss of coating film) For the coating films 1 to 14, the specular gloss was measured at angles of 20°, 60°, and 85° using a haze gloss meter Cat. No. 4601 (manufactured by Big-Gardner) in accordance with JIS K 5600-4-7 (1999).

[0164] (Presence or absence of absorption peak of Amide-II band in coating film) The IR spectra of the coating films 1 to 14 were measured under the following conditions using a Fourier transform infrared spectrophotometer FT / IR-6600FV (manufactured by JASCO Corporation). [Measurement conditions] Incident angle: 45° Number of measurements: 1 Prism: Ge

[0165] (Observation of the coating surface) For coating films 1 to 13, a portion of the coating film was cut out and fixed to a sample stage, and observed using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation).

[0166] (Surface roughness of coating film) For coating films 1 to 12 and 14, the coating surfaces were observed using a digital microscope (measurement unit VK-X1050, control unit VK-X1000) (manufactured by Keyence Corporation), and the arithmetic mean roughness Ra, ten-point mean height Rz, and arithmetic mean height Sa were measured. [Measurement conditions] Measurement magnification: 480x Reference plane correction: all areas Scan mode: Laser confocal Laser wavelength: 661nm [Arithmetic mean roughness Ra, ten-point mean height Rz] Measurement mode: Multiple line roughness Measurement area: horizontal line Number of perimeters: 5 Interval: Every 4 bars [Arithmetic mean height Sa] Measurement mode: Surface roughness Measurement area: all areas

[0167] The coating film measured by the above method was examined for the presence or absence of thorns on the coating surface, the Amide-II band in the IR spectrum of 1520-1560 cm -1 Absorption peak, specifically 1530cm -1 Absorption peak, visible light reflectance, pencil hardness, L * value, a * value, b * The values ​​are shown in Table 5. In the table, "-" means that the measurement was not performed. In the table, "6H↑" means that the pencil hardness is greater than 6H, and "6B↓" means that the pencil hardness is less than 6B.

[0168] [Table 5]

[0169] The specular gloss of the coating film measured by the above-mentioned method is shown in Table 6.

[0170] [Table 6]

[0171] The solar reflectance of the coating film (Example 1) measured by the above-mentioned method is shown in Table 7.

[0172] [Table 7]

[0173] The surface roughness of the coating film measured by the above-mentioned method is shown in Table 8. In the table, "-" means that the measurement was not performed.

[0174] [Table 8]

[0175] From Table 4, for coating films 1 to 6, the IR spectrum of 1530 cm -1 The coating film has an absorption peak due to Amide-II and contains thorn-shaped bismuth sulfide particles. This coating film has a visible light reflectance of 0.5% to 3.5% and a pencil hardness of 5B or higher, which indicates that the coating film has excellent anti-reflection performance and excellent hardness.

[0176] Furthermore, for coating films 1 to 6, a finger touch test showed no significant change in the visual blackness, confirming that the coating films also have excellent abrasion resistance.

[0177] Furthermore, it can be seen that the 60° gloss values ​​of coating films 1 to 6 are all 5.0 or less, and that they have excellent matte properties.

[0178] On the other hand, the IR spectrum obtained by FT-IR shows a peak at 1530 cm -1 For coating films 7 to 14, which do not have an absorption peak due to Amide-II and / or do not contain thorn-shaped bismuth sulfide particles, either the visible light reflectance or the pencil hardness exceeds 3.5% or is less than 5B, and it cannot be said that both anti-reflection performance and coating hardness are achieved. [Industrial Applicability]

[0179] The coating film of the present invention has high anti-reflection performance, high blackness, and high hardness and abrasion resistance. Such a coating film can be used for optical components such as light-shielding members and low-reflectivity materials. For example, it can be used in automobile interiors, outer panels of household electrical appliances such as head-up displays, mobile phones, and audio equipment, interiors of houses, and optical elements such as lenses used in various optical instruments such as cameras, binoculars, microscopes, and semiconductor exposure devices.

Claims

1. A coating film containing bismuth sulfide particles, wherein the shape of the bismuth sulfide particles contained in the coating film, when observed with a scanning electron microscope, is a shape in which one end of 10 or more needle-like constituent elements is gathered and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR.

2. 2. The coating film according to claim 1, wherein the bismuth sulfide particles are contained in an amount of 30% to 70% in terms of pigment volume concentration (PVC).

3. A coating composition comprising a resin component, bismuth sulfide particles, and a solvent, wherein the hydroxyl value of the solid content of the resin component is 60 mgKOH / g or less, the shape of the bismuth sulfide particles observed with a scanning electron microscope is a shape in which one end of 10 or more needle-like constituent elements is gathered and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and the pigment volume concentration (PVC) of the bismuth sulfide particles in the coating composition is 30% or more and 70% or less.

4. 4. The coating composition according to claim 3, wherein the resin component is an acrylic resin.

5. 5. The coating composition according to claim 3, wherein the resin component has a glass transition temperature of 55°C or higher.

6. A paint set comprising the paint composition according to claim 3 or 4 and a composition containing a curing agent.

7. A method for producing a coating film, comprising the following steps (1) to (3), wherein an infrared absorption peak derived from Amide-II is observed in the IR spectrum of the coating film by FT-IR: Step (1): A step of mixing a resin component, bismuth sulfide particles, and a solvent to obtain a coating composition, wherein the hydroxyl value of the solid content of the resin component is 60 mgKOH / g or less, the shape of the bismuth sulfide particles observed with a scanning electron microscope is a shape in which one ends of 10 or more needle-like constituent elements are gathered together and / or a shape in which a plurality of plate-like and / or needle-like projections are formed on the surface of a substantially spherical body, and the pigment volume concentration (PVC) of the bismuth particles in the coating composition is 30% or more and 70% or less; Step (2): A step of applying the coating composition obtained in step (1) onto an object to be coated to obtain a coated object; Step (3): A step of heating the coated object obtained in step (2)

8. The method for producing a coating film according to claim 7, further comprising the step of mixing a composition containing a curing agent with the coating composition in the step (2).

9. The crosslink density of the coating film formed by mixing the composition containing the resin component and the curing agent is 1.0 × 10 －６ mol / cc or more 7.0×10 －４ 9. The method for producing a coating film according to claim 8, wherein the viscosity is 100 s, ...

10. The method for producing a coating film according to claim 7 or 8, wherein the resin component is an acrylic resin.

11. The method for producing a coating film according to claim 7 or 8, wherein the resin component has a glass transition temperature of 55°C or higher.

12. A coated article coated with the coating film according to claim 1 or a coating film comprising the coating composition according to claim 3.

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