Method of manufacturing coating film, and method of measuring film thickness of coating film

Abstract

To provide a method of manufacturing a coating film which can objectively guarantee a coating film on an exterior wall.SOLUTION: A method of manufacturing a coating film includes the step of forming an inorganic coating film layer by applying an inorganic coating composition on an approximately flat base including an electrically conductive metallic portion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a coating film and a method for measuring the thickness of a coating film. [Background technology]

[0002] Architectural paints hold the largest share of the domestic paint market. Within this architectural paint market, home renovation applications account for the largest proportion. As the home renovation market is a growing market, many renovation companies have entered the market. When renovating exterior walls, clients want to improve the durability of the paint film and extend the span of expensive home renovations as much as possible. In response to this demand, renovation companies are differentiating themselves by using durable paints containing tetrafluoroethylene resins and offering paint film guarantees.

[0003] However, the coating guarantees that have been made so far have been conceptual, such as "whether or not there is a significant change in the visual appearance," and lack objectivity, so the reality is that they have not been fully trusted by clients. There is a need for coating thickness guarantees based on quantitative and clear criteria. As such, there is a need for coating (painting) technology and coating thickness measurement technology that will enable coating guarantees for exterior walls.

[0004] Patent Document 1 discloses a method for measuring the thickness of a coating film including a conductive primer layer using an eddy current film thickness meter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-206412 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for manufacturing a coating film that can provide objective coating film guarantees for exterior walls. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by applying an inorganic coating composition onto a substrate including a substantially smooth conductive metal portion, and have completed the present invention.

[0008] That is, the present invention relates to a method for producing a coating film, which comprises a step of applying an inorganic coating composition onto a substrate including a substantially smooth conductive metal portion to form an inorganic coating film layer.

[0009] It is preferable that the step between the conductive metal portion and the underlying layer other than the conductive metal portion is 2000 μm or less.

[0010] The conductive metal portion is preferably formed by a conductive metal member embedded in a substrate.

[0011] The conductive metal portion is preferably made of stainless steel.

[0012] The wet thickness of the inorganic coating layer is preferably 100 μm or more.

[0013] The dry thickness of the resulting coating film is preferably 50 μm or more.

[0014] Furthermore, it is preferable to include a step of forming a primer layer on the surface of the base before the step of forming the inorganic coating film layer.

[0015] The present invention also relates to a film thickness measurement method including the steps of forming a coating film by the above-described production method and measuring the film thickness of the formed coating film with an eddy current film thickness meter or an electromagnetic film thickness meter. [Effects of the Invention]

[0016] According to the coating film manufacturing method of the present invention, a coating film that can achieve objective coating film guarantee can be obtained for exterior walls. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a cross-sectional view showing a coating film during film thickness measurement. [Figure 2] 1 is a schematic top view of a siding board and a base consisting of a conductive metal portion. DETAILED DESCRIPTION OF THE INVENTION

[0018] <<Method for producing a coating film>> The method for producing a coating film of the present invention (hereinafter also referred to as the production method of the present invention) is characterized by comprising a step of applying an inorganic coating composition onto a base including a substantially smooth conductive metal portion to form an inorganic coating film layer.

[0019] <Base> The base material is not particularly limited as long as it is one used in building materials, but is preferably a material with low or no conductivity, and is preferably non-metallic. Non-metallic materials include inorganic materials such as concrete, calcium silicate board, ALC board, gypsum board, and slate board, fibrous materials such as glass wool, rock wool, and cellulose fiber, resin materials such as polyethylene foam, polystyrene foam, polyurethane foam, and polyvinyl chloride, wood materials, and any combination thereof.

[0020] The form of the substrate is not particularly limited and may be a siding board, a heat insulating material, or the like, but a siding board is preferred, and a siding board containing cement, a fiber material, a wood material, vinyl chloride, or the like is more preferred.

[0021] <Conductive Metal Portion> The substrate includes a substantially smooth conductive metal portion. By including the conductive metal portion in the substrate, the thickness of the coating film can be precisely measured with an electromagnetic film thickness gauge or an eddy current film thickness gauge, even on exterior walls that are not conductive or magnetic, such as concrete or siding boards. The material of the conductive metal portion is not particularly limited, but examples include stainless steel, copper, aluminum, zinc, magnesium, silver, chromium, and tin. The material of the conductive metal portion is preferably stainless steel. The surface area of ​​the conductive metal portion is not particularly limited as long as the thickness of the inorganic coating layer can be measured with an electromagnetic film thickness gauge or an eddy current film thickness gauge, but is preferably 0.8 cm 2 More than 1.5cm is preferable. 2 The upper limit is not particularly limited, but is generally 3.1 cm. 2 The following is the result.

[0022] By making the conductive metal portion substantially smooth, the thickness of the coating film can be measured accurately. In this specification, "substantially smooth" specifically means that the arithmetic mean roughness Ra of the conductive metal portion is 0.3 μm or less. The arithmetic mean roughness Ra of the conductive metal portion is preferably 0.2 μm or less.

[0023] It is preferable that the step between the conductive metal portion and the underlying layer other than the conductive metal portion is small. By reducing this step, the film thickness of the inorganic coating layer can be measured using an electromagnetic film thickness meter or an eddy current film thickness meter. The step is preferably 2000 μm or less, more preferably 1000 μm or less.

[0024] The color of the conductive metal part is not particularly limited and may be the color of the material itself, but it is preferable to make it the same color as the base, which can avoid the conductive metal part being conspicuous and damaging the design even when a transparent coating film is formed.

[0025] The method for forming the conductive metal portion is not particularly limited, and examples include embedding a conductive metal member in a substrate or forming a coating film containing a conductive metal on a substrate. However, the method of embedding a conductive metal member in a substrate is preferred because it allows for precise film thickness measurement. That is, it is preferable that the conductive metal portion be formed by a conductive metal member embedded in a substrate. The form of the conductive metal member is not particularly limited, and examples include bolts, screws, screws, nails, etc. These conductive metal members are embedded in the substrate so that a portion of them is exposed on the surface of the substrate, as shown in Figure 1. As shown in Figure 2, the portion of the conductive metal member exposed from the substrate becomes the conductive metal portion. For example, when a screw is used as the conductive metal member, the screw is screwed into the substrate, and the head of the screw exposed on the surface of the substrate becomes the conductive metal portion.

[0026] <Inorganic Coating Composition> The inorganic coating composition used in the manufacturing method of the present invention is not particularly limited as long as it can form an inorganic coating film layer by applying it to a substrate. In the present invention, the inorganic coating composition refers to a coating composition containing an inorganic binder. The amount of the inorganic binder in the inorganic coating composition is preferably 5 to 50 wt %, more preferably 10 to 30 wt %.

[0027] Specific examples of inorganic binders include binders whose main skeleton is a polyorganosiloxane compound. In binders whose main skeleton is a polyorganosiloxane compound, the main skeleton contains an -Si-O- bond and may have any of a linear structure, a branched structure, and a cyclic structure. The content of the polyorganosiloxane compound in the inorganic coating composition is preferably 5 to 50 wt%, more preferably 10 to 30 wt%. The inorganic binder preferably has a terminal reactive functional group such as a hydroxyl group, an amino group, a carboxylic acid, an acid anhydride group, a vinyl group, an allyl group, an acrylate group, a methacrylate group, an isoprenyl group, an acrylamide group, a methacrylamide group, an epoxy group, or an oxetane group.

[0028] The inorganic coating composition may contain a curing agent in addition to the inorganic binder. As the curing agent, a compound having a reactive functional group at its terminal, such as an isocyanate group, a hydroxyl group, an amino group, a carboxylic acid, an acid anhydride group, a vinyl group, an allyl group, an acrylate group, or a methacrylate group, can be used, and an isocyanate compound is preferred because it can undergo a curing reaction at room temperature.

[0029] Specific examples of inorganic coating compositions include (1) a two-component composition consisting of a polyorganosiloxane compound having hydroxyl groups at its terminals and an isocyanate compound, (2) a one-component composition in which a polyorganosiloxane compound having hydroxyl groups at its terminals and an isocyanate compound are mixed without reacting, and (3) a composition containing a resin with a polysiloxane structure and hydrophilic functional groups, obtained by previously subjecting a polyorganosiloxane compound having silanol groups to a dehydration condensation reaction with a hydroxyl group-containing compound.

[0030] (1) When using a two-component composition, a polyorganosiloxane compound and an isocyanate compound are mixed immediately before application and applied to a substrate, resulting in the formation of a polymer structure containing a polyorganosiloxane structure through a chemical reaction. Two-component compositions are preferred because they allow for a wide range of combinations of polyorganosiloxane compounds and isocyanate compounds and make it easy to control the quality of the coating film.

[0031] (2) The one-component composition is made into a one-component composition by encapsulation or the like to prevent contact between the polyorganosiloxane compound and the isocyanate compound. One-component compositions are preferred because they are easy to handle and easy to control the quality.

[0032] (3) The composition containing the polysiloxane structure and the resin with hydrophilic functional groups is easy to handle and can be used as a one-component paint because the reaction has already been completed. Furthermore, by making this composition into an emulsion-type water-based paint incorporating polyorganosiloxane, it can reduce the environmental impact while maintaining the quality of inorganic paints.

[0033] The inorganic coating composition used in the production method of the present invention may be a solvent-based coating or a water-based coating, and the inorganic coating film layer is formed by applying the inorganic coating composition to a substrate by a common method such as spraying, brushing, or roller.

[0034] The thickness of the inorganic coating layer formed in one coating step is preferably 50 μm or more, more preferably 70 μm or more, and even more preferably 100 μm or more, in wet film thickness. The wet film thickness is measured by applying a wet gauge to the smooth part of the substrate to which the inorganic coating composition has been applied. If the substrate does not have a smooth part, the coating weight per unit area can be used as an index instead of the film thickness. The coating weight is measured as a wet film thickness of 50 g / m 2 More than 70g / m 2 More preferably, 100 g / m 2 When a plurality of inorganic coating layers are formed, it is preferable that the wet film thickness of each inorganic coating layer is within the above-mentioned range.

[0035] The coating film formed by the production method of the present invention has excellent durability because it is formed from an inorganic coating composition, and preferably has an expected service life of 20 years or more.

[0036] <Primer Layer> It is preferable to include a step of forming a primer layer on the surface of the substrate before the step of forming an inorganic coating layer on the substrate. The primer layer can be formed by applying a silicone primer, an epoxy primer, the aforementioned inorganic coating composition, or the like to the substrate. The thickness of the primer layer is preferably 50 μm or more, more preferably 80 μm or more, and even more preferably 120 μm or more, in wet film thickness. In the production method of the present invention, when the coating film has a primer layer, the inorganic coating layer can be laminated on the primer layer. Furthermore, multiple inorganic coating layers may be laminated; for example, the coating film may have a base, a primer layer, an inorganic coating layer as an intermediate coat, and an inorganic coating layer as a top coat.

[0037] <Film Thickness> The dry film thickness of the coating film obtained by the production method of the present invention is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. The dry film thickness can be measured using an electromagnetic film thickness meter or an eddy current film thickness meter. The coating film thickness here refers to the total film thickness present on the substrate, and if there is a primer layer or multiple inorganic coating layers, it is the total film thickness of those layers.

[0038] <<Film Thickness Measurement Method>> The film thickness measurement method of the present invention comprises the steps of forming a coating film containing an inorganic coating layer by the production method of the present invention, and measuring the film thickness of the formed coating film with an eddy current film thickness meter or an electromagnetic film thickness meter. With regard to the production method of the coating film in the step of forming a coating film containing an inorganic coating layer, the coating film containing an inorganic coating layer may be formed using the above-mentioned base, inorganic coating composition, etc.

[0039] In the film thickness measurement process, the dry film thickness of the dried coating film, including the inorganic coating layer, is measured using a film thickness gauge. When measuring the film thickness, the detection head of the film thickness gauge is pressed against the conductive metal part of the substrate, as shown in Figure 1. The film thickness gauge used is either an eddy current film thickness gauge or an electromagnetic film thickness gauge. When using an eddy current film thickness gauge, the coating film is measured based on the electrical resistance between the detection head and the conductive metal part. When using an electromagnetic film thickness gauge, the coating film is measured based on the magnetism between the detection head and the conductive metal part. The choice of whether to use an eddy current film thickness gauge or an electromagnetic film thickness gauge can be made depending on the conductivity and magnetism of the conductive metal part. For example, when the conductive metal part is made of stainless steel, either an eddy current film thickness gauge or an electromagnetic film thickness gauge may be used. When the conductive metal part is made of aluminum or copper, it is preferable to use an eddy current film thickness gauge.

[0040] The substrate and film thickness measurement method of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional schematic diagram showing the process of measuring the film thickness of a coating. A conductive metal member 20 is embedded in a substrate 10. An inorganic coating layer 30 is laminated on the substrate 10 and the conductive metal member 20. The detection head 41 of a film thickness meter 40 is pressed against the location of the conductive metal member 20 in the substrate to measure the film thickness of the inorganic coating layer.

[0041] 2 is a schematic top view of a substrate made up of a siding board and a conductive metal portion. The conductive metal portion 50 is present on the siding board 60. [Example]

[0042] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Furthermore, unless otherwise specified, "parts" means parts by weight.

[0043] (1) Example 1 (1-1) Metal screw installation A metal screw (product name: Resilience Film Thickness Measurement Pin, stainless steel screw manufactured by PL Japan Co., Ltd.) was screwed into the surface of the siding board. The arithmetic mean roughness Ra of the screw head (conductive metal part) exposed on the surface of the siding board was 0.1 μm.

[0044] (1-2) Undercoat A primer (product name: Super Hybrid Binder Si II, a silicone-based primer manufactured by PL Japan Co., Ltd.) was applied to the siding board surface, and the wet film thickness was confirmed to be 120 μm or more.

[0045] (1-3) Undercoat Twelve hours after application of the primer, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard, a two-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as an intermediate coating, and the wet film thickness was measured and confirmed to be 150 μm or more.

[0046] (1-4) Top coat Eight hours after application of the intermediate coat, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard, a two-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as a top coat, and the wet film thickness was measured and confirmed to be 150 μm or more. The intermediate coat and top coat were the same paint, and were applied a total of two times.

[0047] (1-5) Film Thickness Measurement One day after the topcoat application, the thickness of the dried coating was measured using an electromagnetic coating thickness meter (product name: SWT-9300, manufactured by Sanko Electronics Laboratory Co., Ltd.) and found to be 200 μm. Furthermore, the surface condition of the coating was visually evaluated and no significant change in design was observed.

[0048] (1-6) Evaluation of coating film This siding board was placed in a Super UV accelerated weather resistance tester (product name: iSuper UV Tester, Super UV tester manufactured by Iwasaki Electric Co., Ltd.), and the condition of the coating film on the siding board surface was observed after 1000 hours, and no significant decrease in gloss was observed.

[0049] In Examples 1 to 3 and Comparative Examples 1 to 3, the measurement conditions for the Super UV accelerated weather resistance tester (I-Super UV Tester manufactured by Iwasaki Electric Co., Ltd.) are as follows. Wavelength: 295~450nm UV irradiance: 150mW / cm 2 Black panel (BP) temperature: 63℃ 50%RH 4 hour irradiation → 4 hour condensation cycle

[0050] (2) Example 2 (2-1) Metal screw installation A metal screw (product name: Resilience Film Thickness Measurement Pin, stainless steel screw manufactured by PL Japan Co., Ltd.) was screwed into the surface of the siding board. The arithmetic mean roughness Ra of the screw head (conductive metal part) exposed on the surface of the siding board was 0.1 μm.

[0051] (2-2) Undercoat A primer (product name: Micro Cation Base, a cationic primer manufactured by PL Japan Co., Ltd.) was applied to cover the siding board surface, and the wet film thickness was confirmed to be 120 μm or more.

[0052] (2-3) Undercoat Four hours after application of the primer, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard Aqua, a two-component water-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as an intermediate coating, and the wet film thickness was measured and confirmed to be 150 μm or more.

[0053] (2-4) Top coat Eight hours after application of the intermediate coat, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard Aqua, a two-component water-based inorganic coating made by PL Japan Co., Ltd.) was applied once as a top coat, and the wet film thickness was measured and confirmed to be 150 μm or more. The intermediate coat and top coat were the same paint, and were applied a total of two times.

[0054] (2-5) Film Thickness Measurement One day after the topcoat application, the thickness of the dried coating was measured using an electromagnetic coating thickness meter (product name: SWT-9300, manufactured by Sanko Electronics Laboratory Co., Ltd.) and found to be 200 μm. Furthermore, visual evaluation of the surface condition of the coating showed no significant change in design.

[0055] (2-6) Evaluation of coating film This siding board was placed in a Super UV accelerated weather resistance tester (product name: iSuper UV Tester, Super UV tester manufactured by Iwasaki Electric Co., Ltd.), and the condition of the coating film on the siding board surface was observed after 1000 hours, and no significant decrease in gloss was observed.

[0056] (3) Example 3 (3-1) Metal screw installation A metal screw (product name: Resilience Film Thickness Measurement Pin, stainless steel screw manufactured by PL Japan Co., Ltd.) was screwed into the surface of the siding board. The arithmetic mean roughness Ra of the screw head (conductive metal part) exposed on the surface of the siding board was 0.1 μm.

[0057] (3-2) Undercoat A primer (product name: Super Hybrid Binder Si II, a silicone-based primer manufactured by PL Japan Co., Ltd.) was applied to cover the siding board surface, and the wet film thickness was confirmed to be 120 μm or more.

[0058] (3-3) Undercoat Twelve hours after application of the primer, an inorganic coating composition (product name: Zenith, a one-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as an intermediate coating, and the wet film thickness was measured and confirmed to be 150 μm or more.

[0059] (3-4) Top coat Eight hours after application of the intermediate coat, an inorganic coating composition (product name: Zenith, a one-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as a top coat, and the wet film thickness was measured and confirmed to be 150 μm or more. The intermediate coat and top coat were the same paint, and were applied a total of two times.

[0060] (3-5) Film Thickness Measurement One day after the topcoat application, the thickness of the dried coating was measured using an electromagnetic coating thickness meter (product name: SWT-9300, manufactured by Sanko Electronics Laboratory Co., Ltd.) and found to be 180 μm. Furthermore, visual evaluation of the surface condition of the coating showed no significant change in design.

[0061] (3-6) Evaluation of coating film This siding board was placed in a Super UV accelerated weather resistance tester (product name: iSuper UV Tester, Super UV tester manufactured by Iwasaki Electric Co., Ltd.), and the condition of the coating film on the siding board surface was observed after 1000 hours, and no significant decrease in gloss was observed.

[0062] (4) Comparative Example 1 (4-1) Preparation and application of the base The undercoat, intermediate coat and top coat were applied in the same manner as in Example 1, except that the metal screws were not screwed in.

[0063] (4-2) Film Thickness Measurement One day after the topcoat application, the thickness of the dried coating film was measured using an eddy current film thickness meter (product name: SWT-9300, manufactured by Sanko Electronics Laboratory), but the dry film thickness could not be measured.

[0064] (4-3) Evaluation of coating film This siding board was placed in a Super UV accelerated weather resistance tester (product name: iSuper UV Tester, Super UV tester manufactured by Iwasaki Electric Co., Ltd.), and after 1000 hours, the surface of the siding board was observed, and no significant decrease in gloss was observed.

[0065] (5) Comparative Example 2 (5-1) Metal screw installation As in Example 1, metal screws were inserted.

[0066] (5-2) Undercoat A primer (product name: 1-component Fine Sealer, an epoxy-based sealer manufactured by Nippon Paint Co., Ltd.) was applied to cover the siding board surface, and the wet film thickness was measured, confirming that it was approximately 50 μm.

[0067] (5-3) Undercoat Three hours after application of the primer, a urethane paint (product name: one-component fine urethane, urethane paint manufactured by Nippon Paint Co., Ltd.) was applied, and the wet film thickness was measured, confirming that it was 150 μm or more.

[0068] (5-4) Top coat 15 hours after application of the undercoat, a urethane paint (product name: one-component fine urethane, urethane paint manufactured by Nippon Paint Co., Ltd.) was applied, and the wet film thickness was measured and confirmed to be 150 μm or more.

[0069] (5-5) Film Thickness Measurement One day after the topcoat application, the thickness of the dried coating film was measured using an eddy current film thickness meter (product name: SWT-9300, film thickness meter manufactured by Sanko Electronics Laboratory Co., Ltd.), and it was confirmed that the dry film thickness was 180 μm.

[0070] (5-6) Evaluation of coating film This siding board was placed in a Super UV accelerated weathering tester (product name: iSuper UV Tester, manufactured by Iwasaki Electric Co., Ltd.), and after 1000 hours, the surface of the siding board was observed. The gloss had significantly decreased, becoming almost completely dull. The coating was also severely cracked, with some parts peeling off.

[0071] (6) Comparative Example 3 (6-1) Metal tape installation A 10 cm square piece of copper foil tape (copper foil tape manufactured by Nitto Denko Corporation, film thickness 0.03 mm) was attached to the surface of the siding board. The arithmetic mean roughness Ra of the copper foil tape (conductive metal part) varied so much that it was impossible to measure.

[0072] (6-2) Undercoat A primer (product name: Super Hybrid Binder Si II, a silicone-based primer manufactured by PL Japan Co., Ltd.) was applied to cover the siding board surface, and the wet film thickness was confirmed to be 120 μm or more.

[0073] (6-3) Undercoat Twelve hours after application of the primer, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard, a two-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as an intermediate coating, and the wet film thickness was measured and confirmed to be 150 μm or more.

[0074] (6-4) Top coat Eight hours after application of the intermediate coat, an inorganic coating composition (product name: Inorganic Hybrid Titanium Guard, a two-component, weak solvent-based inorganic coating manufactured by PL Japan Co., Ltd.) was applied once as a top coat, and the wet film thickness was measured and confirmed to be 150 μm or more. The intermediate coat and top coat were the same paint, and were applied a total of two times.

[0075] (6-5) Film Thickness Measurement One day after applying the top coat, the thickness of the dried coating was measured using an eddy current coating thickness meter (product name: SWT-9300, manufactured by Sanko Electronics Laboratory Co., Ltd.). The thickness varied greatly depending on the measurement location, with variations of over 50 μm. This is thought to be due to the lack of smoothness of the copper foil, which resulted in large variations in thickness due to uneven areas.

[0076] (6-6) Evaluation of coating film This siding board was placed in a Super UV accelerated weather resistance tester (product name: iSuper UV Tester, Super UV tester manufactured by Iwasaki Electric Co., Ltd.), and the condition of the coating film on the siding board surface was observed after 1000 hours, and no significant decrease in gloss was observed.

[0077] (7) Results The results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1. The criteria for each evaluation item are as follows:

[0078] (7-1) Appearance of the coating The coating film was visually inspected for any changes in appearance (damage to the smoothness of the coating film or peeling) and evaluated according to the following criteria. ◎: No change in the appearance of the coating film 〇: Almost no change in the appearance of the coating △: Changes in the appearance of the coating film are observed ×: Abnormalities are observed in the appearance of the coating film

[0079] (7-2) Weather resistance of coating film In a weather resistance test using a super UV accelerated weather resistance tester, the degree of gloss loss of the coating film was evaluated according to the following criteria. ◎: No loss of gloss observed (gloss retention rate of 70% or more) 〇: Almost no loss of gloss is observed (gloss retention rate is 50% or more but less than 70%) △: Gloss reduction observed (gloss retention rate 30% to less than 50%) ×: Gloss reduction observed (gloss retention rate less than 30%)

[0080] (7-3) Objective Film Thickness Measurement The dry film thickness was measured using a film thickness meter. Measurements were repeated five times at different locations on the same coating film, and the difference between the maximum and minimum values ​​was used to evaluate the film thickness according to the following criteria. ◎: The difference between the maximum and minimum values ​​is less than 2 μm ○: The difference between the maximum and minimum values ​​is 2 μm or more and less than 5 μm △: The difference between the maximum and minimum values ​​is 5 μm or more and less than 50 μm ×: The difference between the maximum and minimum values ​​is 50 μm or more, or the film thickness cannot be measured.

[0081] [Table 1]

[0082] In Comparative Example 1, no conductive metal member was used, so objective film thickness measurement was not possible. In Comparative Example 2, a paint containing a urethane resin was used, so the weather resistance of the coating film was insufficient. In Comparative Example 3, copper foil tape was used as the conductive metal member, so the smoothness of the conductive metal part was insufficient, making objective film thickness measurement impossible and weather resistance was slightly reduced. In Examples 1 to 3, the appearance and weather resistance of the coating film were excellent, and objective film thickness measurement was also possible.

[0083] The present disclosure (1) is a method for producing a coating film, which includes a step of applying an inorganic coating composition onto a substrate including a substantially smooth conductive metal portion to form an inorganic coating film layer.

[0084] The present disclosure (2) is a method for producing a coating film according to the present disclosure (1), in which the step between the conductive metal portion and the underlying layer other than the conductive metal portion is 2000 μm or less.

[0085] The present disclosure (3) is a method for producing a coating film according to the present disclosure (1) or (2), in which the conductive metal portion is formed by a conductive metal member embedded in a substrate.

[0086] The present disclosure (4) is the method for producing a coating film according to any one of the present disclosures (1) to (3), in which the material of the conductive metal portion is stainless steel.

[0087] The present disclosure (5) is a method for producing a coating film according to any one of the present disclosures (1) to (4), wherein the wet thickness of the inorganic coating film layer is 100 μm or more.

[0088] The present disclosure (6) is a method for producing a coating film according to any one of the present disclosures (1) to (5), in which the dry thickness of the resulting coating film is 50 μm or more.

[0089] The present disclosure (7) is a method for producing a coating film according to any one of the present disclosures (1) to (6), further comprising the step of forming a primer layer on the surface of the base prior to the step of forming the inorganic coating film layer.

[0090] The present disclosure (8) is a film thickness measurement method including a step of forming a coating film by the manufacturing method described in any one of the present disclosures (1) to (7), and a step of measuring the film thickness of the formed coating film with an eddy current film thickness meter or an electromagnetic film thickness meter. [Explanation of symbols]

[0091] 10 Base 20 Conductive metal parts 30 Inorganic coating layer 40 Film Thickness Gauge 41 Detector head 50 Conductive metal parts 60 siding board

Claims

1. A method for producing a coating film, comprising the step of applying an inorganic coating composition onto a substrate including a substantially smooth conductive metal portion to form an inorganic coating film layer.

2. The method for producing a coating film according to claim 1, wherein the step between the conductive metal portion and the underlying layer other than the conductive metal portion is 2000 μm or less.

3. The method for producing a coating film according to claim 1 or 2, wherein the conductive metal portion is formed by a conductive metal member embedded in a substrate.

4. The method for producing a coating film according to claim 1 or 2, wherein the conductive metal portion is made of stainless steel.

5. The method for producing a coating film according to claim 1 or 2, wherein the inorganic coating layer has a wet thickness of 100 μm or more.

6. The method for producing a coating film according to claim 1 or 2, wherein the dry thickness of the resulting coating film is 50 μm or more.

7. The method for producing a coating film according to claim 1 or 2, further comprising the step of forming a primer layer on the surface of the base prior to the step of forming the inorganic coating film layer.

8. A step of forming a coating film by the manufacturing method according to claim 1 or 2; and measuring the thickness of the formed coating film with an eddy current film thickness meter or an electromagnetic film thickness meter; Film thickness measurement method.

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