Painting method for creating gradation areas

Abstract

The present disclosure aims to provide a gradation coating method that uses a paint spray device to create a gradation part with excellent appearance (grainy feel, uniform coating ability, and gradation feel). The present disclosure also aims to provide a manufacturing method for a painted product having a gradation portion with excellent appearance (graininess, uniform coating ability, and gradation appearance), and a gradation painted product obtained by the manufacturing method. [Solution] A coating method in which a coating device is used to spray a first color of paint onto a first area of ​​a coating object placed on a rotating fixing device, spray a second color of paint onto a second area of ​​the coating object, and provide a gradation area in which the first color gradually changes to the second color at an overlapping portion between the first and second areas, comprising: The coating pattern of the spray coating device is a substantially elliptical pattern, A coating method in which the major axis of the coating pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece.

Description

[Technical field]

[0001] The present disclosure relates to a coating method for providing a gradation portion. [Background technology]

[0002] 2. Description of the Related Art Tubular bodies such as toothbrushes, golf shafts, bottle containers used for cosmetics, and the like are painted with various coatings in order to impart design and aesthetic appeal to their appearance, for example. As a method for painting the tubular body, spray painting, ironing painting, etc. have been used. Spray painting is a method in which paint is sprayed in a mist form using a spray device and sprayed onto the product to be painted. On the other hand, roll painting is an old painting method in which the object to be painted is repeatedly immersed in a tank containing paint and "applied thinly and repeatedly," and is suitable for uniformly painting rod-shaped tubular objects such as pencils, fishing rods, golf shafts, etc. Since the excess paint is rubbed off with a rubber sheet or the like, if the shape is consistent, the entire object can be painted evenly in one go, resulting in a good finished appearance. However, it is difficult to produce a gradational painted surface by ironing. Therefore, in order to improve the design and aesthetics of the exterior, a spray painting method is used to obtain a painted body with gradation.

[0003] For example, Patent Document 1 describes a coating method in which a tubular body is arranged in the longitudinal direction and two spray devices whose longitudinal positions and moving speeds are controlled independently of each other are used to obtain a tubular body having a gradation of two coating colors.

[0004] Patent Document 2 describes a coating method in which a tubular body is arranged vertically in the axial direction, the tubular body is rotated around the axis, and the nozzle of a paint spraying device is moved up and down while spraying, and a partition is provided in the area between the up and down movement range of the paint nozzle and the tubular body, resulting in a tubular body with a gradation formed depending on whether or not the paint is sprayed. However, with such conventional painting techniques, it was difficult to adjust the length of the gradation.

[0005] Therefore, Patent Document 3 describes a coating method for a tubular body using a spray coating device or a device having a structure in which a fixing device for the tubular body moves along a linear guide, which includes (step 1) a step of changing the spray angle of the paint spray device to an arbitrary angle, and (step 2) a step of spraying paint onto the tubular body rotating in the circumferential direction while moving the paint spray device or the fixing device for the tubular body along the linear guide, thereby forming a gradation in the axial direction. Patent Document 3 describes a method of obtaining a tubular body with an arbitrary gradation width by adjusting the angle of the paint spray nozzle. However, the spray applicator described in Patent Document 3 only changes the spray angle relative to the workpiece. In other words, Patent Document 3 does not describe or suggest at all a coating method in which the coating pattern of the spray applicator is a substantially elliptical pattern with the major axis of the coating pattern inclined relative to the direction of the rotation axis of the workpiece. Therefore, there is a demand for a gradation coating method that improves the design and aesthetic appeal of the painted exterior. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-111176 A [Patent Document 2] JP 2007-222550 A [Patent Document 3] JP 2016-010772 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure aims to provide a gradation coating method that uses a paint spray device to create a gradation part with excellent appearance (grainy feel, uniform coating ability, and gradation feel). The present disclosure also aims to provide a method for manufacturing a painted product having a gradation portion with excellent appearance (grainy feel, uniform paintability, and gradation feel), and a painted product having a gradation portion obtained by the manufacturing method. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to develop a workpiece having a gradation-coated surface with improved design and aesthetics in the paint appearance, and have found that the above object can be achieved by using a spray coating device to spray a first color of paint onto a first region of the workpiece placed on a rotating fixing device, spray a second color of paint onto a second region of the workpiece, and provide a gradation portion in which the first color gradually changes to the second color at an overlapping portion between the first and second regions, in which the coating pattern of the spray coating device is a substantially elliptical pattern and the major axis of the coating pattern is inclined with respect to the direction of the rotation axis of the workpiece. The present disclosure has been completed based on such findings.

[0009] That is, the present disclosure is as follows. Section 1. A coating method comprising the steps of: spraying a first color of paint onto a first region of a coating object placed on a rotating fixing device; spraying a second color of paint onto a second region of the coating object using a spray coating device; and providing a gradation portion in which the first color gradually changes to the second color at an overlapping portion between the first and second regions, the method comprising the steps of: The coating pattern of the spray coating device is a substantially elliptical pattern, A coating method in which the major axis of the coating pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece. Section 2. Item 2. The coating method according to item 1, wherein the major axis of the coating pattern is inclined at an angle of 10 degrees to 80 degrees with respect to the direction of the rotation axis of the object to be coated. Section 3. Item 2. The coating method according to item 1, wherein the major axis of the coating pattern is inclined at an angle of 30 degrees to 60 degrees with respect to the direction of the rotation axis of the object to be coated. Section 4. 2. The coating method according to item 1, wherein the spray coating device moves linearly in the direction of the rotation axis of the object to be coated. Section 5. A method for manufacturing a painted product with a gradation portion, the product being manufactured by applying a first color to a first region, applying a second color to a second region, and applying a coating to an overlapping portion between the first region and the second region to provide a gradation portion that gradually changes from the first color to the second color, The method includes a step of spraying the first color and the second color paint onto the object to be coated placed on a rotating fixing device using a spray coating device, The coating pattern of the spray coating device is a substantially elliptical pattern, A method for manufacturing a painted product having a gradation portion, in which the major axis of the paint pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece. Section 6. Item 6. The manufacturing method according to item 5, wherein the major axis of the coating pattern is inclined at an angle of 10 degrees to 80 degrees with respect to the direction of the rotation axis of the object to be coated. Section 7. Item 6. The manufacturing method according to item 5, wherein the major axis of the coating pattern is inclined at an angle of 30 degrees to 60 degrees with respect to the direction of the rotation axis of the object to be coated. Section 8. 6. The manufacturing method according to item 5, wherein the spray coating device moves linearly in the direction of the rotation axis of the object to be coated. Section 9. A coated product having a gradation portion obtained by the coating method according to any one of items 1 to 4 or the manufacturing method according to any one of items 5 to 8.

[0010] In addition, the invention of the product defined by the manufacturing process in this disclosure is described using a product-by-process claim because it is currently impossible or impractically difficult to specify, for example, what components are contained in the gradation portion and to what extent, or what its structure is. Effect of the Invention

[0011] According to the present disclosure, a gradation coating method can be provided that uses a paint spray device to create a gradation portion with excellent appearance (grainy feel, uniform coating ability, and gradation feel). Furthermore, the present disclosure can provide a manufacturing method for a painted product having a gradation portion with excellent appearance (graininess, uniform coating ability, and gradation), and a gradation painted product obtained by the manufacturing method. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a coating apparatus used in the coating method of the present disclosure. [Diagram 2] Figure 2(1) is a view (front view) of the gas cap 7 from the paint spraying side, Figure 2(2) is a view (side view) of the gas cap 7 from the side, and Figure 2(3) is a diagram showing the paint pattern applied at the gas cap position. [Diagram 3] FIG. 3 is a diagram explaining the relationship between the angle of the coating pattern of the sprayed paint (FIGS. 3(1)-(4)) and the angle of the gas cap 7 for forming the coating pattern (FIGS. 3(5)-(8)). [Figure 4]FIG. 4 is a diagram explaining the relationship between the object 6 to be coated and the angle of the paint pattern (FIG. 4(0) to FIG. 4(4)). FIG. 4(0) is a diagram showing the object 6 to be coated. FIG. 4(1) is a diagram showing a case where the angle of the paint pattern relative to the object 6 to be coated is 0 degrees. FIG. 4(2) is a diagram showing a case where the angle of the paint pattern relative to the object 6 to be coated is 45 degrees. FIG. 4(3) is a diagram showing a case where the angle of the paint pattern relative to the object 6 to be coated is 90 degrees. FIG. 4(4) is a diagram showing a case where the angle of the paint pattern relative to the object 6 to be coated is -45 degrees. [Diagram 5] FIG. 5 is a diagram showing the workpiece 6, the surface to be coated, and the spray coating device 10 when the coating pattern angle is 0 degrees. [Figure 6] FIG. 6 is a diagram showing an object 6 to be coated, a surface to be coated, and a spray coating device 10 when the coating pattern angle is 45 degrees. [Figure 7] FIG. 7 is a diagram showing an object 6 to be coated, a surface to be coated, and a spray coating device 10 when the coating pattern angle is 90 degrees. [Figure 8] FIG. 8 is a diagram in which photographs of the appearance of coated objects A and B are further provided in addition to Table 1. [Figure 9] FIG. 9 shows photographs of the exterior appearance of the painted cosmetic containers of Example 3 and Comparative Example 2. [Figure 10] FIG. 10 shows photographs of the exterior appearance of the painted toothbrushes of Example 3 and Comparative Example 2. [Figure 11] FIG. 11 is a photograph showing the appearance of the painted toothbrush of Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Painting method for creating gradation areas Hereinafter, the coating method for providing a gradation portion according to the present disclosure will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram showing an example of a coating device used in the coating method according to the present disclosure. In this embodiment, the coating apparatus 20 includes two spray coating devices 10. That is, the spray coating device 10 includes a first spray coating device 10a that applies a first color of paint and a second spray coating device 10b that applies a second color of paint. When applying three or more colors of paint, the number of spray coating devices 10 may be the same as the number of paints to be applied.

[0014] In the present disclosure, a coating method for providing a gradation portion G (hereinafter also referred to as a "gradation coating method") is performed using a coating device 20 shown in Fig. 1. A coating object 6 is placed on a rotating fixing device 30, and spraying a first color of paint onto a first region E1 of the coating object 6 and spraying a second color of paint onto a second region E2 of the coating object 6 using spray coating devices 10a, 10b, thereby providing a gradation portion G in which the color gradually changes from the first color to the second color in the overlapping portion between the first region E1 and the second region E2. In other words, the present disclosure is a painting method in which, using spray painting devices 10a, 10b, a first color of paint is sprayed onto a first region E1 of an object 6 placed on a rotating fixing device 30, and a second color of paint is sprayed onto a second region E2 of the object 6, and a gradation section G in which the color gradually changes from the first color to the second color is provided at the overlapping portion between the first region E2 and the second region E2, wherein the painting pattern of the spray painting device is a substantially elliptical pattern, and the major axis of the painting pattern is inclined at an angle of more than 0 degrees and less than 90 degrees relative to the direction of the rotational axis of the object 6.

[0015] Painting equipment 20 An example of a coating device 20 used in the coating method for providing a gradation portion G of the present disclosure will be described. As shown in Fig. 1, the coating device 20 includes a fixing device 30 for holding an object 6 to be coated, spray coating devices 10a and 10b for spraying paint onto the object 6 to be coated, and a shaft 4 for sliding the spray coating devices 10a and 10b.

[0016] Fixation device 30 The fixing device 30 includes a base 31 and a fixing part 32 that holds the object 6 to be coated. The fixing part 32 is rotatably provided with respect to the base 31. The fixing device 30 is not particularly limited as long as it is a device that can hold the object 6 to be coated and rotate the object 6 to be coated. The fixing device 30 may be moved on a plane perpendicular to the rotation axis direction by a conveying device while holding the object 6 to be coated. By moving the object 6 to be coated, the objects 6 to be coated can be painted sequentially without replacing them one by one. Hereinafter, the direction parallel to the axis P of the fixing part 32 will be referred to as the "axial direction", the direction perpendicular to the axis P as the "radial direction", and the direction along the arc centered on the axis P as the "circumferential direction". In addition, among the circumferential directions, the clockwise direction when the component is viewed from a specified direction will be referred to as the "one circumferential side", and the counterclockwise direction will be referred to as the "other circumferential side". However, this definition of the direction is not intended to limit the orientation of the workpiece 6 when it is painted in this disclosure. The fixing device 30 can also be moved along the axial direction.

[0017] Shaft 4 The shaft 4 is a member that slides the spray coating devices 10a and 10b. The shaft 4 is provided to extend parallel to the axis P of the fixing portion 32 of the fixing device 30.

[0018] Spray coating device 10a, 10b In the present disclosure, an example of a spray coating device 10a, 10b used for coating paint is shown in FIG. 1 and FIG. As shown in Fig. 1, spray coating devices 10a, 10b are provided with spray coating device main bodies 1a, 1b, fixing parts 3a, 3b for fixing the spray coating device main bodies 1a, 1b to a shaft 4, and spray nozzles 2a, 2b, gas caps 7a, 7b for spraying compressed gas, and side air nozzles 8a, 8b on the paint spraying side (tip) opposite the fixing parts 3a, 3b. The spray coating device can also be referred to as a spray gun.

[0019] Figure 2(1) is a view (front view) of the gas cap 7 from the paint spraying side, Figure 2(2) is a view (side view) of the gas cap 7 from the side, and Figure 2(3) is a diagram showing the paint pattern applied at the gas cap position.

[0020] The gas caps 7a, 7b are attached to the paint spraying side end of the spray coating device main bodies 1a, 1b. The gas caps 7a, 7b have a spray nozzle opening 11 (see FIG. 2) through which the paint outlet 9 at the tip of the spray nozzle 2a, 2b penetrates, and are configured so that the tips of the spray nozzles 2a, 2b protrude from the spray nozzle opening 11 when attached to the spray coating device main bodies 1a, 1b. The gas caps 7a, 7b also have a pair of side air nozzles 8a, 8b that extend in the spray direction of the spray nozzles 2a, 2b parallel to the spray nozzles 2a, 2b on the radial outside of the spray nozzle opening 11, and open toward the center of the spray direction of the spray nozzles 2a, 2b at symmetrical positions across the center of the spray nozzles 2a, 2b. Furthermore, the gas caps 7a, 7b have atomization nozzle holes 5 radially outside the spray nozzle opening 11 and radially inside the side air nozzles 8a, 8b, which inject air to atomize the paint discharged from the paint discharge port 9.

[0021] Compressed air is sprayed from side air holes (gas outlets for adjusting the pattern) 12 opened in a pair of side air nozzles 8a, 8b of the gas cap 7. The side air holes 12 are opened to form an elliptical spray pattern. The side air holes 12 are opened symmetrically, with one or more on each side. The amount of air sprayed from the side air holes 12 is adjusted by a pattern opening adjustment device (not shown) to adjust the fan-shaped opening of the spray pattern. Air is also sent from an air passage inside the spray coating device to the center of a gas cap 7 provided on the spray nozzle 1. A paint discharge port 9, a spray nozzle opening 11, and an atomization nozzle hole (auxiliary air hole) 5 are opened in the center of the gas cap 7. The atomization nozzle hole (auxiliary air hole) 5 is opened to balance the spray force from the side air hole 12 in forming a spray pattern, and one or more holes are opened.

[0022] The spray coating devices 10a, 10b are attached to the shaft 4 of the coating device 20 by the fixing parts 3a, 3b so as to be movable along the shaft 4. The fixing parts 3a, 3b and the shaft 4 have any known configuration in which the fixing parts 3a, 3b are slidable relative to the shaft 4 and the fixing parts 3a, 3b are capable of stopping at predetermined positions relative to the shaft 4. In FIG. 1, the shaft 4 is configured as a single shaft, but a configuration may also be adopted in which the same number of shafts 4 as the spray coating devices 10a, 10b are provided and each shaft 4 is provided with a spray coating device 10a, 10b. The spray coating devices 10a, 10b preferably move linearly in the direction of the rotation axis of the workpiece 6. As shown in Figures 5 to 7, for example, the spray coating devices 10a, 10b paint the workpiece 6 rotating in the circumferential direction while moving in upward directions Ra, Rb or downward directions Sa, Sb along the shaft 4.

[0023] The spray coating devices 10a and 10b used in the present disclosure are not particularly limited as long as they are capable of spray coating, and any known coating spray device can be used. For example, the spray coating devices 10a and 10b include an air spray pressure regulator, a spray gun type spray gun that atomizes liquid with compressed gas, and the like.

[0024] The spray coating devices 10a, 10b used in the present disclosure produce an approximately elliptical coating pattern whose area changes depending on the distance between the paint outlet 9 of the spray nozzles 2a, 2b and the object 6 to be coated, the air pressure, the type of paint (components, viscosity, etc.), etc. The distance between the paint discharge port 9 of the spray nozzles 2a, 2b and the object 6 to be coated is not particularly limited, and is, for example, 100 to 150 mm. The air pressure of the spray coating devices 10a, 10b is not particularly limited and is, for example, 0.1 to 1 MPa.

[0025] Object to be painted 6 The object 6 to be coated is not particularly limited, and examples thereof include a tubular body (e.g., a rod-shaped article, a container, etc.), a spherical body, a plate-shaped body, etc. The cross section of the tubular body, i.e., a cross section cut along a plane perpendicular to the axial direction, may be any shape, such as not only a perfect circle but also a substantially circular shape, a substantially rectangular shape, etc. Examples of the objects 6 to be coated include daily necessities such as toothbrushes; stationery such as mechanical pencils, ballpoint pens, and fountain pens; containers such as cosmetic containers (bottles), shampoo containers, and conditioner containers; household electrical appliances such as mobile phones, mobile phone cases, hair dryers, and facial massagers; exterior panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; and automobile parts such as bumpers. Among these, toothbrushes, stationery, containers, outer panels of automobile bodies, and automobile parts are preferred, with toothbrushes and containers being particularly preferred.

[0026] The material of the above-mentioned object to be coated is not particularly limited, and examples thereof include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel, resins (plastics) such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, and mixtures of these resins, resin materials such as various fiber-reinforced plastics (FRP), inorganic materials such as glass, cement, concrete, wood, fibrous materials such as paper, cloth, etc. Among these, metal materials and resin materials are preferred. The object to be coated may also be a combination of the above-mentioned metal material and resin material.

[0027] Paint Pattern Generally, the types of coating patterns of the spray coating devices 10a, 10b include a round spray pattern and a flat spray pattern. In the present disclosure, a coating pattern is used in which the surface to be coated (also referred to as a coated surface, etc.) is not a perfect circle (round spray pattern). That is, as shown on the right side of FIG. 2, the coating pattern Z by the spray coating devices 10a, 10b is a substantially elliptical pattern having a major axis and a minor axis of the coating pattern. C indicates 1 / 2 the length of the major axis (the radius of the major axis), and D indicates 1 / 2 the length of the minor axis (the radius of the minor axis). Here, the term "approximately elliptical" includes not only an elliptical shape, but also a convex lens shape, a track shape, and other approximately elliptical shapes.

[0028] The approximately elliptical coating pattern can be obtained by using a commercially available spray coating device (spray gun), such as those described in Japanese Utility Model Application Publication No. 07-039954, Japanese Patent Application Publication No. 2008-142586, and Japanese Patent Application Publication No. 2008-161788. More specifically, examples of the approximately elliptical coating pattern include a straight pattern, a semi-tulip pattern, and a tulip pattern. In other words, in the present disclosure, a substantially elliptical shape also includes shapes that are close to a diamond shape or a tulip shape. An ellipse has a major axis length (major diameter) and a minor axis length (minor diameter). In a two-dimensional orthogonal coordinate system, the ellipse whose major and minor axes intersect at the origin O has the following dimensions: (x 2 / C 2 )+(y 2 / D 2 ) = 1. This is called the standard form. When C>D>0, 2C is the length of the major axis (major axis), and 2D is the length of the minor axis (minor axis). The size of the coating pattern is not particularly limited, but is, for example, an elliptical flat-spray pattern in which the major axis length is 1 to 30 cm, the minor axis length is 0.1 to 10 cm, and the major axis length is greater than the minor axis length, preferably an elliptical flat-spray pattern in which the major axis length is 2 to 15 cm, the minor axis length is 1 to 10 cm, and the major axis length is greater than the minor axis length, and more preferably an elliptical flat-spray pattern in which the major axis length is 3 to 12 cm, the minor axis length is 2 to 10 cm, and the major axis length is greater than the minor axis length. The area (S) of the coating pattern can be calculated by the ratio of the circumference of the circle to the major axis (C) and the minor axis (D). The area of ​​the coating pattern is not particularly limited, but may be, for example, 0.3 to 1000 cm. 2 and preferably 1 to 500 cm 2 and more preferably 10 to 100 cm 2 It is.

[0029] Paint pattern angle (Θ) In this specification, the angle of the coating pattern refers to the angle of the major axis of the approximately elliptical coating pattern relative to the direction of the rotation axis P of the object to be coated 6, as shown in Figures 3(1) to (4). The angle of the coating pattern shown in Figure 3 can be adjusted by changing the angle of the gas cap 7 at the tip of the spray coating device 10, i.e., the angle of the line M connecting a pair of side air nozzles 8 relative to the direction of the rotation axis P of the object to be coated 6.

[0030] The tip of the spray coating device 10a, 10b is usually mainly composed of a spray nozzle 2a, 2b having a paint outlet 9, and a gas cap 7a, 7b having an atomizing nozzle hole 5 and a side air nozzle 8. The combination of these components determines how the liquid is atomized and sprayed onto the workpiece 6, i.e., the shape of the coating pattern and the distribution of the spray particles. In addition, the air flow from the side air nozzles 8a, 8b can be sprayed so as to intersect with the paint flow from the paint outlet, so that the paint sprayed from the spray nozzles 2a, 2b can be formed into, for example, an elliptical coating pattern by the compressed air sprayed from the side air holes 12 opened in the side air nozzles 8a, 8b of the gas caps 7a, 7b.

[0031] That is, in the present disclosure, the angle of the coating pattern can be adjusted by changing the angle of this gas cap 7. Specifically, the gas cap 7 can be loosened counterclockwise relative to the spray coating device body 1. By loosening this gas cap 7, the orientation of a pair of side air nozzles 8 on the gas cap 7 can be adjusted to, for example, the positions shown in Figures 3(5) to (8), thereby changing the angle Θ of the coating pattern.

[0032] Fig. 3 is a diagram for explaining the relationship between the angle of the coating pattern of the sprayed paint (Fig. 3(1)-(4)) and the angle of the gas cap 7 for forming the coating pattern (Fig. 3(5)-(8)). Fig. 4 is a diagram for explaining the relationship between the object 6 to be coated and the angle of the coating pattern shown in Fig. 3(1)-(4). As shown in FIG. 3, a line M connecting a pair of side air nozzles 8 on the gas cap 7 intersects at a right angle (is perpendicular) with the major axis of the approximately elliptical coating pattern of the sprayed paint.

[0033] Paint pattern angle is 0 degrees The angle of the paint pattern, i.e., the major axis of the approximately elliptical paint pattern, is 0 degrees relative to the direction of the rotation axis P of the workpiece 6 (Figure 4(0)), as shown in Figures 3(1), 4(1), and 5. FIG. 5 is a diagram showing the workpiece 6, the surface to be coated, and the spray coating device 10 when the coating pattern angle is 0 degrees. As shown in Figure 3 (5), when paint is sprayed in a state in which the line M connecting a pair of side air nozzles 8 is perpendicular to the direction of the rotation axis P of the workpiece 6 (90 degrees, horizontal), the angle of the approximately elliptical paint pattern sprayed onto the workpiece 6 is 0 degrees, that is, the major axis of the approximately ellipse is along the direction of the rotation axis P of the workpiece 6 (0 degrees, coincident) (Figures 3 (1), 4 (1), and 5).

[0034] The paint pattern angle is 45 degrees 3(2), 4(2), and 6 show coating patterns in which the angle of the coating pattern, i.e., the major axis of the approximately elliptical coating pattern, is at an angle of 45 degrees with respect to the direction of the rotation axis P of the workpiece 6. FIG. 6 is a diagram showing an object 6 to be coated, a surface to be coated, and a spray coating device 10 when the coating pattern angle is 45 degrees. As shown in Figure 3 (6), when paint is sprayed in a state where the line M connecting a pair of side air nozzles 8 is inclined at -45 degrees relative to the direction of the rotation axis P of the workpiece 6, the angle of the approximately elliptical paint pattern sprayed onto the workpiece 6 is 45 degrees, that is, the long axis of the approximately ellipse is inclined at 45 degrees relative to the direction of the rotation axis P of the workpiece 6 (Figures 3 (2), 4 (2), and 6).

[0035] The paint pattern angle is 90 degrees 3(3), 4(3), and 7 show coating patterns in which the angle of the coating pattern, i.e., the major axis of the approximately elliptical coating pattern, is at an angle of 90 degrees with respect to the direction of the rotation axis P of the workpiece 6. FIG. 7 is a diagram showing an object 6 to be coated, a surface to be coated, and a spray coating device 10 when the coating pattern angle is 90 degrees. As shown in Figure 3 (7), when paint is sprayed with the line M connecting a pair of side air nozzles 8 aligned along the direction of the rotation axis P of the workpiece 6 (0 degrees, vertical), the angle of the approximately elliptical paint pattern sprayed onto the workpiece 6 is 90 degrees, that is, the major axis C of the approximately ellipse is perpendicular (90 degrees) to the direction of the rotation axis P of the workpiece 6 (Figures 3 (3), 4 (3), and 7).

[0036] Paint pattern angle is -45 degrees 3(4) and 4(4) show a coating pattern in which the angle of the coating pattern, i.e., the major axis of the approximately elliptical coating pattern, is at an angle of -45 degrees with respect to the direction of the rotation axis P of the workpiece 6. As shown in Figure 3 (8), when paint is sprayed in a state in which the line M connecting a pair of side air nozzles 8 is inclined at 45 degrees relative to the direction of the rotation axis P of the workpiece 6, the angle of the major axis C of the approximately elliptical paint pattern sprayed onto the workpiece 6 is -45 degrees, that is, a paint pattern is obtained in which the major axis C of the approximately elliptical shape is inclined at -45 degrees relative to the direction of the rotation axis P of the workpiece 6 (Figure 3 (4) and Figure 4 (4)).

[0037] The angle of the coating pattern should be in the range of more than 0 degrees and less than 90 degrees. In other words, if the paint is sprayed so that the line M connecting the pair of side air nozzles 8 on the gas cap 7 is between a state where it is perpendicular to the direction of the rotation axis P of the workpiece 6 (horizontal direction) and a state where it is along the direction of the rotation axis P of the workpiece 6 (vertical direction) (excluding the horizontal and vertical directions), a coating pattern can be obtained in which the major axis of a substantially ellipse is inclined at an angle of more than 0 degrees and less than 90 degrees with respect to the direction of the rotation axis P of the workpiece 6. 0 degrees can be rephrased as 180 degrees or -(-)90 degrees. Note that the range of more than 0 degrees and less than 90 degrees can also be rephrased as more than 180 degrees and less than 90 degrees. In the coating method for providing a gradation portion according to the present disclosure, the major axis of the coating pattern is preferably inclined at an angle of 10 degrees to 80 degrees, and more preferably at an angle of 30 degrees to 60 degrees, relative to the direction of the rotation axis of the workpiece.

[0038] As described in the above Patent Document 3, the gradation width in the direction around the axis can also be adjusted by changing the spray angle of the spray coating devices 10a, 10b. Specifically, the gradation width can be adjusted by fixing the paint spray angle of the spray coating devices 10a, 10b at an arbitrary angle in the axial direction (hereinafter referred to as the "vertical direction" in FIG. 1) from the direction along a plane perpendicular to the axial direction (hereinafter referred to as the "horizontal direction" in FIG. 1). Fixing in the horizontal direction refers to a state in which the spray coating devices 10a, 10b are held horizontally relative to the workpiece 6, and fixing at any angle in the vertical direction refers to a direction in which the spray coating devices 10a, 10b are angled relative to the same axis as the workpiece 6. Here, if the angle at which the nozzle is fixed horizontally is taken as 0 degrees, then generally the spray angle is often fixed at 0 degrees, which is horizontal, to reduce the amount of paint exhausted. In order to paint the bottom, top, etc. of the workpiece 6 (and shoulders, etc. in the case of a container), the spray angle of the spray nozzle 2 in the spray coating devices 10a, 10b can be fixed at any angle perpendicular to the same axis. As the range of this angle, the spray coating device 10a and the spray coating device 10b shown in Fig. 1 can each be tilted from more than 0 degrees to less than 90 degrees (-90 degrees). This makes it possible to obtain the workpiece 6 in which the bottom, top, etc. of the workpiece (and shoulders, etc. in the case of a container) are also coated.

[0039] The workpiece 6 that has been painted by the painting method of the present disclosure has a first solid area F1, a gradation area G, and a second solid area F2. Here, the gradation area G refers to an area where the color gradually changes from the first color to the second color. The solid areas F1 and F2 refer to areas that have been painted with one color. When three or more spray painting devices 10 are used, the workpiece 6 that has been painted can have two or more gradation areas and three or more solid areas.

[0040] Rotates in the circumferential direction When the paint is sprayed, the workpiece 6 is rotated in the circumferential direction while being coated. The faster the rotation speed, the more uniform the color of the workpiece 6 that can be obtained. A motor can be used for the rotation. The rotation speed of this motor can be, for example, 60 Hz. There is no particular limitation on the type of motor.

[0041] paint The paint used in the present disclosure can impart an excellent appearance to the object to be coated. The appearance refers to a grainy texture, uniform coating property, and gradation. This appearance can provide the coated object with design, aesthetics, gloss, etc. The paint is not particularly limited, and examples thereof include resin-based paints and metal-based paints.

[0042] The resin-based paint is not particularly limited, and examples thereof include acrylic resin-based paint, polyurethane resin-based paint, fluororesin-based paint, silicon resin-based paint, and melamine resin-based paint. Commercially available paints can be used. From the viewpoints of paint durability and workability, acrylic resin-based paint and polyurethane resin-based paint are preferred.

[0043] The metallic paint is not particularly limited, and examples thereof include aluminum flake pigments, metal oxide-coated alumina flake pigments, metal oxide-coated silica flake pigments, graphite pigments, bronze powder, tin foil, gold foil, plastic-coated metal pigments, phthalocyanine flake pigments, interference mica pigments, colored mica pigments, titanium metal flake pigments, stainless steel flake pigments, plate-like iron oxide pigments, metal-plated glass flake pigments, metal oxide-coated plated glass flake pigments, hologram pigments, vapor-deposited aluminum flake pigments, flake pigments having a multilayer thin film structure of a metal reflective layer, and flake pigments made of cholesteric liquid crystal polymers.

[0044] The paint may be used not only in one type but also in two or more types at the same time. The moving speed, rotation speed, paint spray amount, etc. of the spray coating devices 10a, 10b or the fixing device 30 for the workpiece 6 may be controlled independently of each other. The moving speed of the spray coating devices 10a, 10b or the fixing device 30 for the workpiece 6 is controlled independently of the amount of paint sprayed by the spray coating devices 10a, 10b. The control may be performed by a known control method, and is performed by each control unit. The control unit has an input unit for inputting control conditions, and is typically controlled by a device equipped with a CPU and memory. The temperature and humidity in the coating process can be appropriately set. For example, the coating process can be performed at room temperature and room humidity. The coating time can also be appropriately set.

[0045] Therefore, the present disclosure provides a method for producing a painted product with a gradation portion, the painted product being produced by applying a first color to a first region, applying a second color to a second region, and applying a coating to an overlapping portion between the first region and the second region to provide a gradation portion that gradually changes from the first color to the second color, The method includes a step of spraying the first color and the second color paint onto the object to be coated placed on a rotating fixing device using a spray coating device, The coating pattern of the spray coating device is a substantially elliptical pattern, The method includes a method for producing a coated product having a gradation portion in which the major axis of the coating pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece. In the manufacturing method for a painted product having a gradation portion, the major axis of the paint pattern is preferably inclined at an angle of 10 degrees to 80 degrees, and more preferably at an angle of 30 degrees to 60 degrees, relative to the direction of the rotation axis of the object to be painted. In the method for producing a coated product having a gradation portion, it is preferable that the spray coating device moves linearly in the direction of the rotation axis of the object to be coated. Furthermore, the present disclosure also includes a coating method for providing the gradation portion, or a coated product having a gradation portion obtained by the ... manufacturing method for the coated product having the gradation portion. EXAMPLES

[0046] The present disclosure will be described more specifically below with reference to examples, but the technical scope of the present disclosure is not limited to these examples.

[0047] Example 1 <Material> · Coating object A (cosmetic container (bottle): made of white polypropylene resin (PP)) The sizes (shapes) of cosmetic containers are as follows: Opening: Diameter 30.0mm Body: Diameter 80.3mm Length (from mouth) 170mm) Length (thickest part) 150mm

[0048] · Coating object B (toothbrush: made of white polypropylene resin (PP)) The sizes (shapes) of the toothbrushes are as follows: Head: 8.6mm in front and 4.6mm on the sides Chest: 11.8mm in front and 10.7mm on the sides (from chest to painted surface) Waist: 7.2mm in front and 6.1mm on the sides Buttocks: 14.0mm in front and 10.9mm on the sides Length: 187mm

[0049] - Coating object C (toothbrush: made of transparent polyethylene terephthalate (PET) resin)

[0050] Paint: Acrylic resin paint (1st color: purple, 2nd color: yellow)

[0051] Coating method for providing gradation portion and manufacturing method for coated product with gradation portion The above-mentioned object A or object B to be coated was fixed to a fixing device and rotated only in the circumferential direction (clockwise when viewed from above), without being moved in place, and coating was performed by spraying two types of paint (purple for the first spray coating device 10a on the upper side and yellow for the second spray coating device 10b on the lower side) onto the object 6 using two spray guns (manufactured by Anest Iwata Corporation, product name: WIDER1A) as spray coating devices 10a, 10b (see Figure 1, etc.). At that time, the gas cap pattern (line M connecting a pair of side air nozzles 8) of the spray coating device 10a, 10b was inclined at -75 degrees with respect to the direction of the rotation axis P of the coating object, and by moving up and down with the shaft 4, the paint was sprayed and coated over the entire direction of the rotation axis P (the angle of the coating pattern was 15 degrees), and a gradation coated product 1A (bottle) and a coated product 1B (toothbrush) with a length (width) of 25 mm were obtained. The pattern pressure of the gas cap was 0.11 MPa. The moving speed of the spray coating device 10a, 10b was 20 mm per second, and the vertical (lifting and lowering) movement distance was about 80 mm. The distance between the coating surface and the paint outlet 9 of the spray nozzle 2 was about 150 mm. The coated product 1A (bottle) had a gradation part with a width (length) of about 45 mm, and the coated product 1B (toothbrush) had a gradation part with a width (length) of about 45 mm.

[0052] Example 2 Painted products 2A and 2B with gradation portions of Example 2 were manufactured in the same manner as Example 1, except that the gas cap pattern (the line M connecting a pair of side air nozzles 8) was inclined at -60 degrees relative to the direction of the rotation axis P of the workpiece and the angle of the painting pattern was changed to 30 degrees. The coated product 2A had a gradation portion with a width (length) of about 40 mm. The coated product 2B had a gradation portion with a width (length) of about 40 mm.

[0053] Example 3 The coated products 3A and 3B having the gradation portion of Example 3 were manufactured in the same manner as Example 1, except that the gas cap pattern (the line M connecting a pair of side air nozzles 8) was inclined at -45 degrees with respect to the direction of the rotation axis P of the workpiece, and the angle of the coating pattern was changed to 45 degrees. In the present disclosure, as shown in Figs. 6 to 8, the first spray coating device 10a and the second spray coating device 10b are simultaneously moved together with the shaft 4 and the fixed parts 3a and 3b in the directions Ra (upward) and Rb (upward), respectively. After that, the first spray coating device 10a and the second spray coating device 10b are simultaneously moved together with the shaft 4 and the fixed parts 3a and 3b in the directions Sa (downward) and Sb (downward), respectively. In Examples 1, 2, 4, and 5 and Comparative Examples 1 and 2, the spray coating devices 10a and 10b move in the same manner. The coated product 3A had a gradation portion with a width (length) of about 30 mm. The coated product 3B had a gradation portion with a width (length) of about 30 mm.

[0054] Example 4 Painted products 4A and 4B with gradation portions of Example 4 were manufactured in the same manner as Example 1, except that the gas cap pattern (the line M connecting a pair of side air nozzles 8) was inclined at -30 degrees relative to the direction of the rotation axis P of the workpiece and the angle of the painting pattern was changed to 60 degrees. The coated product 4A had a gradation portion with a width (length) of about 35 mm. The coated product 4B had a gradation portion with a width (length) of about 35 mm.

[0055] Example 5 The coated products 5A and 5B having the gradation portion of Example 5 were manufactured in the same manner as Example 1, except that the gas cap pattern (the line M connecting a pair of side air nozzles 8) was inclined at -15 degrees relative to the direction of the rotation axis P of the workpiece and the angle of the coating pattern was changed to 75 degrees. The coated product 5A had a gradation portion with a width (length) of about 35 mm. The coated product 5B had a gradation portion with a width (length) of about 35 mm.

[0056] Comparative Example 1 Comparative painted product 1A and comparative painted product 1B having the gradation portion of Comparative Example 1 were manufactured in the same manner as in Example 1, except that the gas cap pattern (the line M connecting a pair of side air nozzles 8) was set at 90 degrees (perpendicular) to the direction of the rotation axis P of the workpiece and the angle of the painting pattern was changed to 0 degrees. The comparative painted product 1A had a gradation portion with a width (length) of about 30 mm.The comparative painted product 1B had a gradation portion with a width (length) of about 30 mm.

[0057] Comparative Example 2 Comparative painted product 2A and comparative painted product 2B having the gradation portion of Comparative Example 2 were manufactured in the same manner as in Example 1, except that the gas cap pattern (line M connecting a pair of side air nozzles 8) was set at 0 degrees (parallel) to the direction of the rotation axis P of the workpiece and the angle of the painting pattern was changed to 90 degrees. The comparative painted product 2A had a gradation portion with a width (length) of about 25 mm. The comparative painted product 2B had a gradation portion with a width (length) of about 25 mm.

[0058] Sensory evaluation test For the painted products with gradation areas, a sensory evaluation was conducted on the appearance of each product, including the graininess (gradation area), the gradation feel (gradation area), and the paint uniformity (solid paint area), as described below.

[0059] Appearance (grainy texture) After the paint was applied, the state of the particles in the gradation area was observed using the following 5-point scale. A score of 5 to 3 is a passing grade. 5: Particularly fine particles 4: Fine grain 3: The particles are slightly coarser than 4 above, but are not a problem for practical use. 2: The grain is somewhat coarse 1: Grainy

[0060] Appearance (Gradient) The gradation of the painted area was evaluated using the following 5-point scale, with a score of 5 to 3 being a passing grade. 5: Particularly good Between 4:5 and 3 3: Good 2: Somewhat poor 1: Defective

[0061] Appearance (uniform paintability, presence or absence of unevenness) After painting, the appearance of the painted surface (uniformity of paint, presence or absence of unevenness) was observed using the following 5-point rating system. A rating of 5 to 2 is a passing grade. 5: The entire coating has a uniform color, with no noticeable color unevenness. 4: There is slight color unevenness in some parts of the coating, but this does not affect the practical use. 3: There is slight color unevenness across the entire coating, but this does not pose any practical problems. 2: Significant color unevenness is observed in some areas of the coating, but this does not pose a problem for practical use. 1: Significant color unevenness is observed throughout the entire coating

[0062] comprehensive evaluation Based on the above test results, the score for the graininess (gradation area), the score for the gradation appearance (gradation area), and the score for the coating uniformity (solid coating area) were added together to give an overall evaluation. The results are shown in Table 1 below. A score of 13 or more is considered a passing grade for the overall evaluation.

[0063] The results of the sensory evaluation test are shown in Table 1 below, and in FIG. 8, which further includes photographs of the appearances of coated objects A and B.

[0064] [Table 1]

[0065] Further, FIG. 9 shows external photographs of the painted cosmetic containers of Example 3 and Comparative Example 2, and FIG. 10 shows external photographs of the painted toothbrushes of Example 3 and Comparative Example 2.

[0066] result It was found that Examples 1 to 5 (coating pattern angle exceeding 0 degrees and less than 90 degrees) were superior to Comparative Examples 1 and 2 in appearance (graininess, gradation, and uniform coating ability). Among the Examples, Example 3 achieved the best overall evaluation result.

[0067] Example 6 A coated product 6C (toothbrush) having gradation of Example 6 was produced in the same manner as in Example 3, except that the paint was changed to a metallic paint (flake-shaped aluminum pigment, manufactured by Toyo Kogyo Toryo Co., Ltd.) and the object to be coated was changed to C. A photograph of the appearance of the coated toothbrush of Example 6 is shown in FIG. The resulting coated product 6C (toothbrush) had a gradation portion with a width (length) of about 30 mm.

[0068] result Coated product 6C (toothbrush) of Example 6 (painting pattern angle of 45 degrees) had excellent appearance (graininess, gradation, and uniform coating all rated 5) like coated product 3B (toothbrush) of Example 3. [Explanation of symbols]

[0069] 1 Spray coating device body 1a First spray coating device body 1b Second spray coating device body 2 Spray nozzle 2a 1st spray nozzle 2b Second spray nozzle 3 Fixed part 3a 1st fixed part 3b Second fixed part 4 Shaft 5 Atomizing nozzle hole 6 Object to be painted 7 Gas Cap 7a First gas cap 7b Second gas cap 8 Side Air Nozzle 8a First side air nozzle 8b 2nd side air nozzle 9 Paint outlet 9a 1st paint outlet 9b 2nd paint outlet 10 Spray painting equipment 10a 1st spray painting device (1st color) 10b 2nd spray painting device (2nd color) 11 Spray nozzle opening 12 Side air vent (gas outlet for adjusting pattern) 20 Painting equipment 30 Fixation device 31 Base 32 Fixed part C Major axis radius D minor axis radius E1 1st area E2 2nd area F1 First solid painting section F2 2nd solid painting section G Gradation section M A line connecting a pair of side air nozzles 8 P Rotational axis Q Circumferential direction Ra Direction of movement of the first spray coating device (first color) (upward) Rb Direction of movement of the second spray coating device (second color) (upward) Sa Direction of movement of the first spray coating device (first color) (downward) Sb Direction of movement of the second spray coating device (second color) (downward)

Claims

1. A coating method comprising the steps of: spraying a first color of paint onto a first region of a coating object placed on a rotating fixing device; spraying a second color of paint onto a second region of the coating object using a spray coating device; and providing a gradation portion in which the color gradually changes from the first color to the second color at an overlapping portion between the first and second regions, the method comprising the steps of: The coating pattern of the spray coating device is a substantially elliptical pattern, A coating method in which the major axis of the coating pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece.

2. 2. The coating method according to claim 1, wherein the major axis of the coating pattern is inclined at an angle of 10 degrees to 80 degrees with respect to the direction of the rotation axis of the workpiece.

3. 2. The coating method according to claim 1, wherein the major axis of the coating pattern is inclined at an angle of 30 degrees to 60 degrees with respect to the direction of the rotation axis of the workpiece.

4. 2. The coating method according to claim 1, wherein the spray coating device moves linearly in the direction of the axis of rotation of the object to be coated.

5. A method for manufacturing a painted product with a gradation portion, the painted product being manufactured by applying a first color to a first region, applying a second color to a second region, and applying a paint to an overlapping portion between the first region and the second region to provide a gradation portion in which the color gradually changes from the first color to the second color, A step of spraying the first color and the second color paint onto the object to be coated placed on a rotating fixing device using a spray coating device, The coating pattern of the spray coating device is a substantially elliptical pattern, A method for manufacturing a painted product having a gradation portion, in which the major axis of the paint pattern is inclined at an angle greater than 0 degrees and less than 90 degrees relative to the direction of the rotation axis of the workpiece.

6. The manufacturing method according to claim 5, wherein the major axis of the coating pattern is inclined at an angle of 10 degrees to 80 degrees with respect to the direction of the rotation axis of the workpiece.

7. The manufacturing method according to claim 5, wherein the major axis of the coating pattern is inclined at an angle of 30 degrees to 60 degrees with respect to the direction of the rotation axis of the workpiece.

8. The method according to claim 5, wherein the spray coating device moves linearly in the direction of the axis of rotation of the object to be coated.

9. A coated product having a gradation portion obtained by the coating method according to any one of claims 1 to 4 or the manufacturing method according to any one of claims 5 to 8.

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