Coating method for inorganic board and inorganic board with coating film

Abstract

To provide a coating method for an inorganic board and an inorganic board with a coating film enabling, simply by single-colored coating, imparting a finish feeling with unevenness of inorganic board surface outstandingly appealing three-dimensionally.SOLUTION: A coating method for an inorganic board with a surface provided with an uneven designed portion comprises: applying a sealer to a surface of an inorganic board 2 to form a sealer layer 3; performing monochrome coating with a color used as a base color on the sealer layer 3 to form a base coat layer 4 thereon; and applying a color clear coat containing a color pigment to the designed portion in a manner like causing the coat flowing down from a salient top side of the designed portion to form a topcoat layer 5. Therein: a content of the color pigment in the topcoat layer 5 after drying is 0.15 to 5.0 wt.%; and the topcoat layer 5 varies in thickness along with the unevenness thereof.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coating method for improving the design of the surface of an inorganic board having a variety of designs such as embossed patterns or ribs, and a coated inorganic board formed by the method, which can provide a gradation effect in which the color tone changes within the same panel rather than a uniform paint finish, and to the coated inorganic board. [Background technology]

[0002] Traditionally, the factory painting of inorganic boards has often involved painting with a single color (monochrome painting). In particular, in the case of design panels made of extruded cement boards with uneven surfaces, the shadows caused by the uneven surfaces are larger than those of other inorganic boards, even with a monochromatic paint, and the apparent shadows and color differences have provided high designability. However, there has been an increasing demand for more realistic textures, finishes that do not look like paint at first glance, and finishes that are not consistent but have an uneven feel.

[0003] When painting inorganic boards, a uniform coat of paint is first applied to slate boards or fiber cement boards (boards about 3 to 6 mm thick) with a textured surface (e.g. an embossed pattern), and then a color clear coat is applied by allowing the paint to flow down, thereby changing the color tone at the convex and concave parts of the texture.

[0004] The method in Patent Document 1 involves applying a colored paint to the entire pattern surface of a substrate having a concave-convex pattern, drying the colored paint until it is dry to the touch of a finger, applying a colored clear paint having a viscosity of 30 seconds or less according to Ford Cup No. 4 and a different color from the colored paint to the entire painted surface, which is held upward and approximately horizontal, allowing most of the colored clear paint on the flat convex parts of the concave-convex pattern to flow down into the concave parts, and then drying the paint.

[0005] The method in Patent Document 2 involves computer-controlled use of multiple spray guns to paint anywhere on an uneven building material surface that has been coated with a base coat. A paint with low viscosity and low coloring pigment components that allows the paint to flow easily along the coated surface immediately after application is sprayed onto the building material surface having an uneven pattern, and before the paint dries, the paint is allowed to flow down into the recesses, making the color of the recesses darker than the tops of the protrusions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 54-152576 [Patent Document 2] Patent Publication No. 2003-251267 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, painting is performed on the surface of a slate or the like that has a concave-convex pattern, but there is no description of the shape of the concave-convex pattern. In the case of a thin inorganic board such as slate, the depth of the concave-convex pattern is at most about 3 mm, and painting is performed on this. In Patent Document 2, painting is performed on a fiber-reinforced cement board that has a concave-convex pattern with a difference in size of 3 mm on the surface.

[0008] In both patents, the clear paint flows downward, making the color of the concave parts darker than the convex parts, creating a three-dimensional pattern. However, the maximum size of the concave and convex patterns is about 3 mm, and the three-dimensional effect and gradation achieved are not particularly significant.

[0009] In view of the problems of the prior art, the present invention aims to provide a coating method for inorganic boards, which can achieve a finished look in which the unevenness of the inorganic board surface stands out more three-dimensionally, even when painted in a single color, and an inorganic board with a coating film. [Means for solving the problem]

[0010] The coating method for inorganic boards of the present invention is a coating method for inorganic boards having a design portion made of recesses and projections on the surface thereof, which comprises applying a sealer to the surface of the inorganic board to form a sealer layer, applying a single-color paint of a base color on top of this sealer layer to form a base coat layer, and then coating a color clear coat containing a color pigment so as to flow down from the top of the projections of the design portion to form a top coat layer, characterized in that the content of the color pigment in the top coat layer after drying is 0.15 to 5.0 weight % and the thickness of the top coat layer varies between the recesses and projections.

[0011] According to the present invention, a color clear coat containing a color pigment is applied so as to flow down from the top of the design portion to form a top coat layer, and the content of the color pigment in the top coat layer after drying is 0.15 to 5.0% by weight, and the thickness of the top coat layer varies between the projections and recesses, so that the top coat layer has a non-uniform coating thickness, and even though it is a single-color coating, non-uniform shading occurs between the projections and recesses. This creates a three-dimensional effect of the projections and recesses, as well as a non-uniform shading pattern (gradation pattern) due to the coating film, resulting in a finish in which the projections and recesses stand out more three-dimensionally.

[0012] When the color clear coat is a deep color, the content of the color pigment in the top coat layer after drying is preferably 0.15 to 0.6% by weight. Here, "deep color" means that the brightness in the Munsell color system is 4 or less. This allows the coating film to have a non-uniform shading pattern (gradation pattern) when a deep color pigment is used, resulting in a finished look in which the unevenness stands out more three-dimensionally.

[0013] It is preferable that the range of the hiding ratio of the top coat layer at a coating thickness of 10 μm is 3 to 9%, the range of the hiding ratio at a coating thickness of 60 μm is 18 to 100%, and the difference in the hiding ratio between the coating thicknesses of 10 μm and 60 μm is 15 to 91%. Due to such a difference in hiding ratio depending on the coating thickness, it is possible to achieve a finish in which the unevenness stands out more three-dimensionally.

[0014] When the color clear coat is a pale color, the content of the color pigment in the top coat layer after drying is preferably 1.55 to 5.0% by weight. Here, "pale color" means that the brightness in the Munsell color system is 7 or more. This allows the coating film to produce a non-uniform shading pattern (gradation pattern) when a pale color clear coat is used, resulting in a finished look in which the unevenness stands out more three-dimensionally.

[0015] It is preferable that the range of the hiding ratio of the top coat layer at a coating thickness of 10 μm is 6 to 20%, the range of the hiding ratio at a coating thickness of 60 μm is 50 to 81%, and the difference in the hiding ratio at coating thicknesses of 10 μm and 60 μm is 44 to 61%. Due to such a difference in hiding ratio depending on the coating thickness, it is possible to achieve a finish in which the unevenness stands out more three-dimensionally.

[0016] When forming the topcoat layer, it is preferable to set the viscosity of the color clear coat to 8 to 20 seconds by Iwata Cup NK-2. In this case, even if the height difference of the unevenness is large, excessive flow-down of the color clear coat can be suppressed. In addition, the film thickness of the topcoat layer changes greatly depending on the shape, height and inclination angle of various unevenness, and various gradation patterns can be obtained in addition to the shape of the unevenness.

[0017] When forming the top coat layer, it is preferable to set the temperature of the inorganic board to 20 to 60° C. In this case, the flow of the color clear coat is appropriately adjusted, and a non-uniform gradation pattern can be efficiently formed.

[0018] If an overcoat layer is further formed on the topcoat layer, the durability of the inorganic board can be improved.

[0019] By making the design part with the projections and recesses into, for example, an embossed pattern, a grid pattern with well-shaped grooves, or continuous ribs arranged in parallel in one direction, a gradation pattern can be added to these patterns to create a complex pattern, thereby significantly improving the design.

[0020] By using an extruded cement board as the inorganic board, the unevenness of the surface of the extruded cement board can be made to stand out more three-dimensionally, and the variety of finishes can be increased.

[0021] The height of the protruding parts of the design part is preferably 1 to 30 mm. Within this range of the protruding part height, if the height is about 1 to 6 mm, the shadows can be clearly seen even in a pattern that is difficult to make shadows appear in the shade, and if the height is about 6 to 30 mm, a pattern with a larger amount of change can be obtained.

[0022] The present invention is a coated inorganic board coated by the above-mentioned inorganic board coating method, characterized in that the top coat layer increases in thickness downward from the top of the convex portion of the design part.

[0023] According to the present invention, a color clear coat containing a color pigment is applied so as to flow down from the top of the design portion to form a top coat layer, and the content of the color pigment in the top coat layer after drying is 0.15 to 5.0% by weight, and the thickness of the top coat layer varies between the projections and recesses, so that the top coat layer has a non-uniform coating thickness, and even though it is a single-color coating, non-uniform shading occurs between the projections and recesses. This creates a three-dimensional effect of the projections and recesses, as well as a non-uniform shading pattern (gradation pattern) due to the coating film, resulting in a finish in which the projections and recesses stand out more three-dimensionally. Effect of the Invention

[0024] According to the present invention, the content of the color pigment in the top coat layer after drying is 0.15 to 5.0% by weight, and the thickness of the top coat layer varies between the projections and recesses, so that the top coat layer has a non-uniform coating thickness, and even though it is a single-color coating, non-uniform shading occurs between the projections and recesses. This creates a three-dimensional effect of the projections and recesses, as well as a non-uniform shading pattern (gradation pattern) due to the coating, resulting in a finish in which the projections and recesses stand out more three-dimensionally. [Brief description of the drawings]

[0025] [Figure 1] 1 is a partial cross-sectional view of a coating-coated inorganic board according to one embodiment of the present invention, which is formed by the coating method for inorganic boards. [Diagram 2] 1 is a graph showing the relationship between film thickness and hiding ratio when a deep color pigment is used. [Diagram 3] 1 is a graph showing the relationship between film thickness and hiding ratio when a pale color pigment is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention aims to improve the added value of a coated inorganic board by applying a clear coat under specified conditions to an inorganic board that serves as a base material and has a design part formed on the surface by unevenness. Specifically, the paint is intentionally and effectively caused to flow downwards and the degree of paint flow is changed depending on various conditions including the color density, fluidity, and uneven surface shape of the color clear coat used in the top coat layer that is the outermost layer of the coated inorganic board. This intentionally changes the paint thickness between the unevenness, makes the hiding rate different corresponding to the paint thickness, and generates a color difference shade according to the uneven shape.

[0027] 1 is a partial cross-sectional view of a coated inorganic board according to one embodiment formed by the coating method for inorganic boards of the present invention. The coated inorganic board 1 of this embodiment comprises an inorganic board 2 serving as a substrate, a sealer layer 3 formed on the inorganic board 2, a base coat layer 4 formed on the sealer layer 3, and a top coat layer 5 formed on the base coat layer 4. In the drawings, the film thicknesses of the sealer layer 3, the base coat layer 4, and the top coat layer 5 are drawn thicker than that of the inorganic board 2 for the purpose of explaining this embodiment.

[0028] The coated inorganic board 1 of this embodiment can be manufactured by the following coating method. That is, this is a coating method for an inorganic board having a design part formed by recesses and projections on its surface, in which a sealer is applied to the surface of the inorganic board 2 to form a sealer layer 3, a monochromatic coating of a base color is applied on this sealer layer 3 to form a base coat layer 4, and then a color clear coat containing a color pigment is applied so as to flow down from the convex apex side of the design part to form a top coat layer 5, and the content of the color pigment in the top coat layer 5 after drying is 0.15 to 5.0 wt %, and the thickness varies between the recesses and projections in the top coat layer 5. This makes it possible to form a top coat layer 5 whose thickness increases from the convex apex of the design part downward.

[0029] An example of application to an extruded cement board with a hollow portion will be described as the inorganic board 2. An extruded cement board is manufactured by kneading cement, aggregate, fiber, admixture, etc., extruding it into a predetermined shape, and curing and hardening it. When extruding, various designs can be applied to the surface of the extruded cement board using uneven surfaces.

[0030] These design features include embossed patterns that mimic wood grain, stone texture, and the scraped surface of concrete, grid patterns with well-shaped grooves, ribs that run parallel to one direction, etc. Note that the design features formed on the surface are not limited to these, and include various shapes created by unevenness.

[0031] The height of the convex portion in the design portion (height difference between the convex and concave portions: from the bottom of the concave portion to the top of the convex portion) is preferably 1 to 30 mm, more preferably 3 to 20 mm, and the rising angle of the convex portion is not limited, but is, for example, about 5 to 90 degrees. This rising angle refers to the inclination angle of the wall surface of the convex portion.

[0032] By making the height of the convex portions 1 mm or more, a gradation pattern is easily produced after application of the color clear coat that forms the top coat layer 5, and by making the height 30 mm or less, the color clear coat can be made to flow down effectively from the tops of the convex portions. Furthermore, when the height of the convex portions is about 1 to 6 mm, clear shadows can be produced even in patterns that are difficult to produce in the shade, and when the height is about 6 to 30 mm, a pattern with greater variation can be obtained.

[0033] For example, a rib having a square cross section with a height of 2 to 30 mm, a width of 2 to 50 mm, and a rise angle of 30 to 86 degrees is preferred. This rise angle allows the color clear coat to flow down at an appropriate speed, producing a beautiful gradation pattern.

[0034] (Sealer layer) The sealer layer 3 is applied to condition the surface of the extrusion molded cement board (base), and is required to have adhesion to the surface, adhesion to the base coat layer 4 above it, chemical resistance from the front and back sides, barrier properties against penetrating substances, paintability (pot life, paintability, etc.), and drying properties. By making the film thickness of the sealer layer 3 12 to 300 μm, adhesion, chemical resistance, and barrier properties can be obtained.

[0035] The paint used for the sealer layer 3 is selected mainly depending on the paint used for the upper base coat layer 4. Preferable examples of the paint used for the sealer layer 3 include chlorinated rubber paint, vinyl resin paint, epoxy resin paint, alkyd resin paint, polyester resin paint, acrylic resin paint, polyurethane resin paint, acrylic silicone paint, fluororesin paint, organic-inorganic hybrid paint, and inorganic paint. More preferable examples include epoxy resin paint, acrylic silicone resin paint, organic-inorganic hybrid paint, and inorganic paint.

[0036] (Base coat layer) The base coat layer 4 formed on the sealer layer 3 is formed by a single-color painting that serves as a base color as a base coat. The base coat layer 4 is required to have adhesion to the sealer layer 3, adhesion to the top coat layer 5, color variation, hiding power, weather resistance, chemical resistance, barrier properties, paint workability (pot life, paintability, finish, etc.), and drying properties.

[0037] The base coat layer 4 is a coating film that becomes the base color of the surface of the extrusion molded cement board, and examples of the paint used for the base coat layer 4 include, preferably, alkyd resin paint, polyester resin paint, acrylic resin paint, polyurethane resin paint, acrylic silicone paint, fluororesin paint, organic-inorganic hybrid paint, inorganic paint, etc. More preferably, fluororesin paint, organic-inorganic hybrid paint, and inorganic paint are used. By setting the film thickness of the base coat layer 4 to 15 to 300 μm, a sufficient hiding effect can be obtained.

[0038] (Topcoat layer) The color clear coat for forming the top coat layer 5 is a colored transparent paint that is required to have adhesion to the base coat layer 4, color variation, appropriate hiding power, weather resistance, chemical resistance, paint workability (pot life, paintability, finish, etc.), and drying properties. In this embodiment, the color clear coat is made by blending an enamel paint containing a predetermined amount of color pigment with an uncolored clear resin. The enamel paint used here is intended to make the color pigment uniformly dispersed in the clear resin.

[0039] The content of the color pigment is adjusted to be 0.15 to 5.0% by weight with respect to the top coat layer 5 after drying. Therefore, in the coating process of the top coat layer 5, the amount of enamel paint containing the color pigment to be mixed with the clear resin is adjusted so that the content of the color pigment after drying is within the above range. The content of the color pigment in the top coat layer 5 is selected so that the range of the transparency of the coating film is adjusted according to the color pigment of the deep color and the color pigment of the light color.

[0040] The color pigment is not limited, but examples thereof include titanium oxide, carbon black, iron oxide, organic color pigments, and fine silica. Of these, color pigments used for deep color clear coats are carbon black, iron oxide, titanium oxide, and organic color pigments, while color pigments used for light color clear coats are mainly titanium oxide, carbon black, iron oxide, and organic color pigments. Other known color pigments can be used as deep color pigments and light color pigments.

[0041] In addition, in paints containing colored pigments used in color clear coats, "dark colors" are colors with a Munsell color system brightness of 4 or less, and "light colors" are colors with a Munsell color system brightness of 7 or more. Colors with a Munsell color system brightness of more than 4 and less than 7 are medium colors. Brightness is a value determined by visual comparison with standard paint colors issued by the Japan Paint Manufacturers Association.

[0042] By setting the color pigment at 0.15% by weight or more, a moderate coloring effect is obtained and the coloring of the base coat layer 4 does not become too strong, and by setting the coloring pigment at 5.0% by weight or less, the coloring of the top coat layer 5 does not become too strong. By allowing the color clear coat to flow down from the peak side to the valley side, the top coat layer 5 becomes thicker from the peak to the bottom (see Figure 1), and the degree of transparency changes gradually from the thin film part near the peak to the thick film part near the valley.

[0043] In other words, the hiding power increases gradually from the thin film portions near the peaks of the convex portions to the thick film portions near the valleys of the convex portions, with the same pigment content, and the color of the base coat layer 4 increases in the thin film portions and decreases in the thick film portions. By varying the degree of coloring in each portion of the top coat layer 5 in this way, a gradation pattern is effectively created.

[0044] When using a deep color clear coat, by setting the content to 0.15 to 0.6% by weight, uneven shading patterns (gradation patterns) in the deep colors will appear effectively, resulting in a finished look in which the unevenness stands out more three-dimensionally.

[0045] Furthermore, when using a deep color clear coat, the range of hiding power at the thin film portion of the top coat layer 5, which is a coating thickness of 10 μm, is 3 to 9%, and the range of hiding power at the thick film portion, which is a coating thickness of 60 μm, is 18 to 100%, and the range of the difference in hiding power between the thin film portion and the thick film portion is 15 to 91%, thereby achieving a finish in which the unevenness stands out more three-dimensionally.

[0046] When using a pale-colored clear coat, the content should be 1.55 to 5.0% by weight, which will effectively create a non-uniform light and dark pattern (gradation pattern) using the pale color, resulting in a finished look in which the unevenness stands out more three-dimensionally.

[0047] Furthermore, when using a pale color clear coat, the hiding rate of the thin film portion of the top coat layer, which has a coating thickness of 10 μm, is in the range of 6 to 20%, and the hiding rate of the thick film portion, which has a coating thickness of 60 μm, is in the range of 50 to 81%, and the difference in hiding rate between the thin film portion and the thick film portion is in the range of 44 to 61%, thereby achieving a finish in which the unevenness stands out more three-dimensionally.

[0048] The hiding rate indicates the degree to which the coating film conceals the color difference of the base, and is measured using a hiding rate test paper in accordance with JIS K5600-4-1:1999, Method B. The hiding rate was not measured for only the topcoat layer formed by actually applying a color clear coat on the sealer layer 3 and basecoat layer 4, but was measured for a coating film that would become the topcoat layer separately.

[0049] As the clear resin used in the color clear coat, preferably, alkyd resin paint, polyester resin paint, acrylic resin paint, polyurethane resin paint, acrylic silicone paint, fluororesin paint, organic-inorganic hybrid paint, and inorganic paint are mentioned. More preferably, fluororesin paint, organic-inorganic hybrid paint, and inorganic paint are mentioned. As the enamel paint, there is no particular limitation as long as it has the functionality of uniformly dispersing the color pigment in the clear resin, but known resins such as acrylic resins and urethane resins, paints, and colorants can be used.

[0050] The thickness of the top coat layer 5 is not uniform, but is in the range of 1 to 1000 μm. The preferred thickness range is 5 to 300 μm, and the most preferred range is 10 to 100 μm. By forming the top coat layer 5 with a thickness in this range, a good gradation pattern can be effectively expressed, and durability, weather resistance, and barrier properties can be maintained.

[0051] In the topcoat layer 5, the paint is made to flow down from the convex apex side of the design part at an appropriate flow rate, so that the thickness varies between the convex and concave portions. This makes the thickness of the topcoat layer 5 increase downward from the convex apex side, and makes it possible to create a non-uniform light and dark pattern on the surface of the extrusion molded cement board.

[0052] For this purpose, it is important to adjust the viscosity of the color clear coat that forms the top coat layer 5. The viscosity of the color clear coat is preferably set to 8 to 20 seconds using Iwata Cup NK-2. By setting the viscosity of the color clear coat in this range, the amount of the color clear coat flowing down from the convex apex side is appropriately adjusted, and even if there is a large difference in height between the convex and concave portions, the flowing down of the color clear coat can be suppressed. In addition, the film thickness of the top coat layer 5 changes depending on the shape of the convex and concave portions, and a variety of gradation patterns can be obtained. This allows a high gradation effect to appear.

[0053] Multiple topcoat layers may be formed. Specifically, on top of the above-mentioned topcoat layer (first topcoat layer), a color clear coat containing a color pigment is further applied as a second topcoat layer so that it flows down from the top of the convex design portion, so that the content of the color pigment after drying is a predetermined amount and the thickness varies between the convex and concave portions. By forming multiple topcoat layers in this way, a coated inorganic board having a more complicated pattern can be obtained.

[0054] Regarding the combination of paints constituting the above-mentioned respective layers, for example, when the base coat layer 4 is a two-component solvent type fluororesin paint, the sealer layer 3 can be made of a two-component solvent type epoxy resin paint.

[0055] In the present invention, in addition to the above layers, other layers may be formed, for example, an overcoat layer may be further formed on the topcoat layer 5 to improve the durability of the inorganic board. For example, a clear paint containing no pigment may be used as the overcoat layer. By setting the thickness of the overcoat layer to 10 to 300 μm, weather resistance and barrier properties can be obtained.

[0056] The method for coating each of the above layers is not limited, and for example, roll coater coating, air spray coating, airless spray coating, flow coater coating, and other known methods can be used. Since inorganic boards such as extrusion-molded cement boards are generally large, a coating robot equipped with an air spray gun in a horizontal position is preferably used.

[0057] In order to adjust the amount of color clear coat flowing down to form the top coat layer 5, it is preferable to set the temperature of the inorganic board 2 to 20 to 60°C when forming the top coat layer 5 after forming the base coat layer 4. This temperature is the temperature inside the furnace in which the object to be coated is placed. By setting the temperature of the inorganic board 2 higher than 20°C, excessive flowing down of the paint can be prevented, and by not exceeding 60°C, a state in which the paint does not flow down can be prevented. If the temperature is lower than 20°C, the minimum film thickness may not be obtained, and if it exceeds 60°C, there is no difference in the film thickness, so a gradation pattern may not be obtained.

[0058] In this way, the flow rate of the color clear coat is appropriately adjusted, and a non-uniform gradation pattern can be efficiently formed, and a high gradation effect can be obtained. After the top coat layer 5 is formed, a heat treatment may be performed at a furnace temperature of 80 to 180°C. By performing the heat treatment, the drying speed can be accelerated, and the manufacturing cost can be reduced.

[0059] As described above, by adjusting the flow rate of the color clear coat according to the design portion of the surface of the extruded cement board, the paint viscosity, the substrate temperature, etc., it is possible to make the film thickness of the top coat layer 5 thin in the high unevenness areas and thick in the low unevenness areas. In the thin film areas of the top coat layer 5, the coloring due to the color pigment of the color clear coat is less, and the coloring of the base coat layer 4 is stronger. Conversely, in the thick film areas of the top coat layer 5, the coloring due to the color pigment of the color clear coat is stronger, and the coloring of the base coat layer 4 is weaker. In this way, a gradation effect can be obtained by coloring according to the design portion of the inorganic board.

[0060] According to this embodiment, after a sealer layer 3 and a base coat layer 4 are formed on the surface of the inorganic board 2, a color clear coat containing a color pigment is applied so as to flow down from the convex top side of the design portion to form a top coat layer 5. After drying, the content of the color pigment in the top coat layer 5 is 0.15 to 5.0 weight %, and the thickness varies between the convex and concave portions in the top coat layer 5. As a result, the top coat layer 5 has a non-uniform coating thickness, and although it is a single-color coating, non-uniform shading occurs between the convex and concave portions.

[0061] This not only creates a three-dimensional effect from the unevenness, but also creates a non-uniform shading pattern (gradation pattern) from the paint film, making the unevenness stand out more three-dimensionally. It also provides a new textured paint finish with a color difference gradation that differs from a single color paint, and increases the color variations by combining the base coat color and the color clear coat color.

[0062] By forming the design part with projections and recesses in, for example, an embossed pattern, a grid pattern with well-shaped grooves, or a rib pattern with continuous parallel ribs in one direction, a gradation pattern can be added to these patterns to create a complex pattern, which can significantly improve the design. EXAMPLES

[0063] The following describes the present invention with examples and comparative examples. A sealer layer and a base coat layer were formed by air spraying on the patterned surface of an extrusion-molded cement board with a width of 600 mm, a length of 1400 mm, and a thickness of 60 mm, which had a wood grain pattern with a height of 1 to 6 mm on the surface, and a top coat layer was formed on the upper surface to produce a coated inorganic board. The sealer layer, base coat layer, and top coat layer were each applied to an average thickness of 30 μm. When forming the top coat layer, the extrusion-molded cement board was heated to a specified temperature for application. The extrusion-molded cement board coated with the top coat layer was heated in a hot air circulation drying oven to harden the coating.

[0064] A two-component solvent-based epoxy resin paint (New Garmet #8000N Sealer) was used for the sealer layer, a two-component solvent-based fluororesin paint (New Garmet #2000SF) was used for the base coat layer, and for the color clear coat to form the top coat layer, a two-component solvent-based fluororesin paint (New Garmet DC #230 3-minute gloss clear) was used as the clear paint and a two-component solvent-based fluororesin paint (New Garmet DC #200) was used as the enamel paint.

[0065] Here, for the deep color clear coat, a black carbon black pigment was used as the main color pigment, and the brightness was set to 4 or less. For the light color clear coat, a white titanium oxide pigment was used as the main color pigment, and the brightness was set to 7 or more. The brightness was measured by applying the enamel paint before mixing with the clear paint to a hiding rate test paper specified in JIS K5600-4-1 so that the dry film thickness was 25 μm or more, and using a colorimeter (Spectrophotometer SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[0066] The mixing ratio (wt%) of the color pigment, the viscosity of the color clear coat for forming the topcoat layer, and the temperature of the substrate (extrusion molded cement board) when forming the topcoat layer were changed, and painting was performed under the conditions shown in Examples 1 to 13 in Table 1, in which a deep color clear coat was used, Examples 14 to 26 in Table 2, in which a light color clear coat was used, and Comparative Examples 1 to 6 in Table 3, and the surface finish state of the obtained inorganic board with a coating was evaluated. The amount of enamel paint added in the table is the ratio to the combined weight of the liquid clear resin and the liquid enamel paint. The hiding rate of the topcoat layer is listed for each film thickness (μm) of the topcoat layer. The hiding rate was measured according to Method B of JIS K5600-4-1:1999, except that an air spray gun was used instead of an applicator. That is, the color clear coat was applied to a hiding ratio test paper in a predetermined thickness using an air spray gun, and the hiding ratio was calculated from the Y value measured using a colorimeter (Spectrophotometer SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0067] The patterned surface of each Example and Comparative Example was visually inspected and evaluated according to the following criteria. The evaluation results of each Example and Comparative Example are shown in Tables 1 to 3. ◎: The topcoat layer flows well and the gradation of light and dark is noticeable. ○: Differences in gradation shade are observed due to the flow of the topcoat layer. △: There is little flow of the topcoat layer, but differences in gradation are visible ×: No difference in gradation is visible

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] In Examples 1 to 13 in Table 1, where a deep color clear coat was used, the difference in gradation shade was observed, and in Examples 14 to 26 in Table 2, where a light color clear coat was used, the difference in gradation shade was observed. In Comparative Example 1 in Table 3, the top coat layer was transparent and the difference in gradation shade was not observed, and in Comparative Example 2, the concealment of the top coat layer was strong due to the high proportion of color pigment, and the difference in gradation shade was not observed. In Comparative Example 3, the top coat layer was transparent and the difference in gradation shade was not observed, and in Comparative Example 4, the difference in the concealment rate was low and the difference in gradation shade was not observed, and in Comparative Example 5, although the difference in the concealment rate was within the standard, the difference in the gradation shade was not observed due to the high proportion of color pigment, and in Comparative Example 6, the concealment of the top coat layer was strong due to the high proportion of color pigment, and the difference in gradation shade was not observed.

[0072] FIG. 2 is a graph showing the relationship between film thickness and hiding ratio when a deep color clear coat is used, and FIG. 3 is a graph showing the relationship between film thickness and hiding ratio when a light color clear coat is used. As shown in the examples (Table 1) using a deep color clear coat, from Example 1, which has the least amount of color pigment, to Example 13, which has the most, the hiding ratio at a coating thickness of 10 μm of the top coat layer ranges from 3 to 9%, and the hiding ratio at a coating thickness of 60 μm ranges from 18 to 100%. In addition, the difference in hiding ratio between coating thicknesses of 10 μm and 60 μm ranges from 15 to 91%. As shown in the graph in FIG. 2, it is recognized that the hiding ratio increases as the amount of enamel paint added increases and the color pigment ratio increases.

[0073] As shown in the examples (Table 2) in which a pale color clear coat was used, from Example 14, which contains the least amount of color pigment, to Example 26, which contains the most, the hiding ratio at a coating thickness of 10 μm of the topcoat layer ranges from 6 to 20%, and at a coating thickness of 60 μm, the hiding ratio ranges from 50 to 81%. In addition, the difference in hiding ratio at coating thicknesses of 10 μm and 60 μm ranges from 44 to 61%. As shown in the graph in Figure 3, it can be seen that the hiding ratio increases as the amount of enamel paint added increases and the proportion of color pigment increases.

[0074] The scope of the present invention is not limited to the above embodiment, and various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. For example, other layers may be provided within the scope of the present invention without impairing the function of the present invention, and inorganic boards made of other materials may be used. In order to manufacture the inorganic board with coating according to the present invention, other processes not described in the above embodiment may be introduced. For example, when forming a sealer layer or a base coat layer, the temperature of the inorganic board may be set to a predetermined temperature to improve work efficiency, etc. These naturally fall within the technical scope of the present disclosure. The present invention is applicable to various industrial fields, and a representative industrial field is the construction industry. [Explanation of symbols]

[0075] 1. Inorganic board with coating 2 Inorganic board 3 Sealer layer 4 Basecoat Layer 5 Topcoat layer

Claims

1. A coating method for an inorganic board having a design portion formed on its surface by projections and recesses, comprising the steps of: This coating method for inorganic boards is characterized in that a sealer is applied to the surface of the inorganic board to form a sealer layer, a single-color paint of a base color is applied on this sealer layer to form a base coat layer, and then a color clear coat containing a color pigment is applied so as to flow down from the convex top side of the design part to form a top coat layer, and the content of the color pigment in the top coat layer after drying is 0.15 to 5.0 weight % and the thickness of the top coat layer varies between the convexities and concaves.

2. 2. The method for coating an inorganic board according to claim 1, wherein when the color clear coat is a deep color, the content of the color pigment in the top coat layer after drying is 0.15 to 0.6% by weight.

3. The method for manufacturing an inorganic board according to claim 2, characterized in that the range of the hiding rate of the top coat layer at a coating thickness of 10 μm is 3 to 9%, the range of the hiding rate at a coating thickness of 60 μm is 18 to 100%, and the range of the difference in the hiding rate at a coating thickness of 10 μm and 60 μm is 15 to 91%.

4. 2. The method for coating an inorganic board according to claim 1, wherein when the color clear coat is a pale color, the content of the color pigment in the top coat layer after drying is 1.55 to 5.0% by weight.

5. The method for manufacturing an inorganic board according to claim 4, characterized in that the range of the hiding rate of the top coat layer at a coating thickness of 10 μm is 6 to 20%, the range of the hiding rate at a coating thickness of 60 μm is 50 to 81%, and the range of the difference in the hiding rate at a coating thickness of 10 μm and 60 μm is 44 to 61%.

6. 6. The method for coating an inorganic board according to claim 1, wherein when forming the top coat layer, the viscosity of the color clear coat is set to 8 to 20 seconds as measured by Iwata Cup NK-2.

7. 2. The method for coating an inorganic board according to claim 1, wherein the temperature of the inorganic board is set to 20 to 60° C. when the top coat layer is formed.

8. 2. The method for coating an inorganic board according to claim 1, further comprising forming an overcoat layer on the topcoat layer.

9. 2. The coating method for an inorganic board according to claim 1, wherein the height of the convex portion of the design portion is 1 to 30 mm.

10. 2. The method for coating an inorganic board according to claim 1, wherein the design portion formed by the projections and recesses is an embossed pattern, a grid pattern in which well-shaped grooves are formed, or ribs which are parallel and continuous in one direction.

11. 2. The coating method for an inorganic board according to claim 1, wherein the inorganic board is an extruded cement board.

12. An inorganic board having a coating film coated by the coating method for inorganic boards according to claim 1, A coated inorganic board, characterized in that the thickness of the top coat layer increases downward from the top of the convex portion of the design portion.

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