Painting method for creating a gradient effect

Abstract

This invention provides a gradient painting method that uses a paint spraying device to create a gradient section with excellent appearance, a method for manufacturing a painted product having a gradient section, and a gradient painted product obtained by the manufacturing method. [Solution] A painting method in which, using a spray painting device, a first color paint is sprayed onto a first region E1 of a workpiece 6 placed on a rotating stationary device 30, and a second color paint is sprayed onto a second region E2 of the workpiece, thereby creating a gradient portion in the overlapping area between the first and second regions, wherein the painting pattern of the spray painting device is substantially elliptical, and the major axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the workpiece.

Description

Technical Field

[0001] The present disclosure relates to a painting method and the like that provides a gradation portion.

Background Art

[0002] Tubular bodies such as toothbrushes, golf shafts, and bottle containers used for cosmetics are variously painted, for example, to give them an aesthetic and decorative appearance . As painting methods for tubular bodies, spray painting, rubbing painting, and the like have been performed. Spray painting is a method in which a paint is sprayed in a mist using a spraying device and sprayed onto a product to be painted. On the other hand, rubbing painting is an old painting method of "thinly and many times" in which the object to be painted is immersed in a tank containing paint many times, and is suitable for uniformly painting rod-shaped tubular bodies such as pencils, fishing rods, and golf shafts. Since it is a method of squeezing out excess paint with a rubber plate or the like, if the shape is constant, the whole can be uniformly painted at once, and a good finished appearance can be obtained. However, it is difficult to produce a painted surface with a gradation by rubbing painting. Therefore, in order to enhance the aesthetic and decorative appearance, a painted body with a gradation is obtained by a spray painting method.

[0003] For example, in Patent Document 1, a painting method is described in which a tubular body is installed in the longitudinal direction, and two spraying devices whose positions and moving speeds in the longitudinal direction are independently controlled are used to obtain a tubular body having a gradation with two painted colors.

[0004] In Patent Document 2, a painting method is described in which a tubular body is arranged so as to be vertical in the axial direction, and while the tubular body is rotated around the axis, the outlet of a paint spraying device is moved up and down and sprayed, and a partition wall is provided in the region between the up and down movement range of the paint spraying portion and the tubular body, and a tubular body having a gradation is obtained depending on the presence or absence of the spraying. However, this conventional painting method had the problem of making it difficult to adjust the length of the gradient.

[0005] Therefore, Patent Document 3 describes a method for coating a tubular body using a device having a structure in which a spray coating device or a tubular body fixing device moves along a linear guide, comprising: (Step 1) changing the spraying angle of the paint spray device to an arbitrary angle; and (Step 2) spraying paint onto a tubular body that is rotating in the circumferential direction while moving the paint spray device or tubular body fixing device along a linear guide, thereby forming a gradient in the axial direction. In Patent Document 3, a tubular body with an arbitrary gradient width is obtained by adjusting the angle of the paint spray nozzle. However, the spray coating apparatus described in Patent Document 3 only changes the spray angle relative to the object to be coated. In other words, Patent Document 3 does not describe or suggest a coating method in which the coating pattern of the spray coating apparatus is a substantially elliptical pattern, and the major axis of the coating pattern is inclined with respect to the rotation axis of the object to be coated. Therefore, there is a need for a gradient painting method that further enhances the design and aesthetic appeal of the painted appearance. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2007-111176 [Patent Document 2] Japanese Patent Publication No. 2007-222550 [Patent Document 3] Japanese Patent Publication No. 2016-010772 [Overview of the project] [Problems that the invention aims to solve]

[0007] This disclosure aims to provide a gradient painting method that uses a paint spraying device to create a gradient section with excellent appearance (particle texture, uniform coating properties, and gradient effect). Furthermore, this disclosure aims to provide a method for manufacturing a painted product having a gradient portion with excellent appearance (particle texture, uniform coating properties, and gradient effect), and a painted product having a gradient portion obtained by the manufacturing method. [Means for solving the problem]

[0008] The inventors diligently studied to develop a workpiece having a gradient painted surface that enhances the design and aesthetic appeal of the painted appearance. As a result, they found that the above objective can be achieved by using a spray painting device to spray a first color paint onto a first region of a workpiece placed on a rotating stationary device, spraying a second color paint onto a second region of the workpiece, and creating a gradient section in the overlapping portion between the first and second regions where the colors gradually change from the first to the second color, wherein the painting pattern of the spray painting device is substantially elliptical, and the long axis of the painting pattern is inclined with respect to the rotation axis of the workpiece. This disclosure is completed based on this finding.

[0009] In other words, this disclosure is as follows: Section 1. A painting method comprising spraying a first color paint onto a first region of an object to be painted, which is placed on a rotating stationary device, using a spray painting device, and spraying a second color paint onto a second region of the object to be painted, thereby creating a gradient portion in the overlapping area between the first and second regions, where the color gradually changes from the first to the second color. The painting pattern of the spray painting apparatus is a substantially elliptical pattern. A painting method wherein the long axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the object to be painted. Section 2. The painting method according to item 1, wherein the long axis of the painting pattern is inclined at an angle of 10 to 80 degrees with respect to the rotation axis of the object to be painted. Section 3. The painting method according to item 1, wherein the long axis of the painting pattern is inclined at an angle of 30 to 60 degrees with respect to the rotation axis of the object to be painted. Section 4. The spray coating apparatus described above moves linearly in the direction of the rotation axis of the object to be coated, according to the coating method described in item 1. Section 5. A method for manufacturing a painted product having a gradient portion, wherein the first region is painted with a first color, the second region is painted with a second color, and the overlapping portion between the first and second regions is painted to provide a gradient portion that gradually changes from the first color to the second color, The process includes a step of spraying the first and second color paints onto the object to be painted, which is placed on a rotating stationary device, using a spray painting device. The painting pattern of the aforementioned spray painting apparatus is a substantially elliptical pattern. A method for manufacturing a painted product having a gradient portion, wherein the long axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the object to be painted. Section 6. The manufacturing method according to item 5, wherein the long axis of the coating pattern is inclined at an angle of 10 to 80 degrees with respect to the rotation axis of the object to be coated. Section 7. The manufacturing method according to item 5, wherein the long axis of the coating pattern is inclined at an angle of 30 to 60 degrees with respect to the rotation axis of the object to be coated. Section 8. The spray coating apparatus moves linearly in the direction of the rotation axis of the object to be coated, as described in item 5. Section 9. A painted product having a gradient portion obtained by the painting method described in any one of items 1 to 4, or the manufacturing method described in any one of items 5 to 8.

[0010] In the present disclosure, for inventions of products defined in the manufacturing process, at present, it is impossible or extremely difficult in practice to specify all aspects, such as what components are included in the above-mentioned gradation part and to what extent, or what the structure is, etc. Therefore, it is described by product - by - process claims.

Advantages of the Invention

[0011] According to the present disclosure, a gradation coating method capable of providing a gradation part excellent in appearance (particle feeling, uniform coating property, and gradation feeling) by using a paint spraying device can be provided. Moreover, according to the present disclosure, a manufacturing method of a coated product provided with a gradation part excellent in appearance (particle feeling, uniform coating property, and gradation feeling), and a gradation coated product obtained by the manufacturing method can be provided.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a coating device used in the coating method of the present disclosure. [Figure 2] FIG. 2(1) is a view (front view) of the gas cap 7 seen from the paint spraying side, FIG. 2(2) is a view (side view) of the gas cap 7 seen from the side, and FIG. 2(3) is a view showing a coating pattern applied at the position of the gas cap. [Figure 3] FIG. 3 is a diagram explaining the relationship between the angle of the coating pattern of the spray - coated paint (FIGS. 3(1) to (4)) and the angle of the gas cap 7 for forming the coating pattern (FIGS. 3(5) to (8)). [Figure 4]Figure 4 illustrates the relationship between the object to be painted 6 and the angle of the paint pattern (Figures 4(0) to 4(4)). Figure 4(0) shows the object to be painted 6. Figure 4(1) shows the case where the angle of the paint pattern is 0 degrees relative to the object to be painted 6. Figure 4(2) shows the case where the angle of the paint pattern is 45 degrees relative to the object to be painted 6. Figure 4(3) shows the case where the angle of the paint pattern is 90 degrees relative to the object to be painted 6. Figure 4(4) shows the case where the angle of the paint pattern is -45 degrees relative to the object to be painted 6. [Figure 5] Figure 5 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the angle of the painting pattern is 0 degrees. [Figure 6] Figure 6 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the painting pattern angle is 45 degrees. [Figure 7] Figure 7 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the angle of the painting pattern is 90 degrees. [Figure 8] Figure 8 is a diagram that adds photographs of the appearance of painted objects A and B to Table 1. [Figure 9] Figure 9 shows photographs of the painted cosmetic containers of Example 3 and Comparative Example 2. [Figure 10] Figure 10 shows photographs of the painted toothbrushes of Example 3 and Comparative Example 2. [Figure 11] Figure 11 is a photograph of the painted toothbrush of Example 6. [Modes for carrying out the invention]

[0013] Painting method for creating a gradient effect The painting method for creating a gradient portion according to this disclosure will be described below with reference to Figure 1. Figure 1 is an explanatory diagram showing an example of a painting apparatus used in the painting method according to this disclosure. In this embodiment, the painting apparatus 20 is equipped with two spray painting apparatuses 10. Specifically, the spray painting apparatus 10 consists of a first spray painting apparatus 10a that applies the first color paint and a second spray painting apparatus 10b that applies the second color paint. Note that if three or more colors of paint are to be applied, the spray painting apparatus 10 only needs to be equipped with as many apparatuses as there are colors to be applied.

[0014] In this disclosure, the painting method for providing a gradient section G (hereinafter sometimes referred to as the "gradient painting method") is performed using the painting apparatus 20 shown in Figure 1. By using spray painting apparatuses 10a and 10b to spray a first color paint onto a first region E1 of the object to be painted 6, which is placed on a rotating stationary device 30, and spraying a second color paint onto a second region E2 of the object to be painted 6, a gradient section G that gradually changes from the first color to the second color can be provided 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 and 10b, a paint of a first color is sprayed onto a first region E1 of a workpiece 6 placed on a rotating stationary device 30, and a paint of a second color is sprayed onto a second region E2 of the workpiece, thereby providing a gradient section G in the overlapping portion of the first region E2 and the second region E2 that gradually changes from the first color to the second color, 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 greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the workpiece.

[0015] Painting apparatus 20 An example of a painting apparatus 20 used in the painting method for providing the gradient section G of this disclosure will be described. As shown in Figure 1, the painting apparatus 20 comprises a fixing device 30 for holding the object to be painted 6, spray painting devices 10a and 10b for spraying paint onto the object to be painted 6, and a shaft 4 for sliding the spray painting devices 10a and 10b.

[0016] Fixation device 30 The fixing device 30 comprises a base portion 31 and a fixing portion 32 for holding the object to be painted 6. The fixing portion 32 is rotatably mounted relative to the base portion 31. The fixing device 30 is not particularly limited as long as it can hold the object to be painted 6 and rotate the object to be painted 6. The fixing device 30 may be moved by a conveying device on a plane perpendicular to the rotation axis while holding the object to be painted 6. By moving the object to be painted 6, the objects to be painted 6 can be painted sequentially without having to replace each object to be painted 6 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 will be referred to as the "radial direction," and the direction along the arc centered on the axis P will be referred to as the "circumferential direction." Furthermore, within the circumferential direction, the clockwise direction when viewing the component from a predetermined direction will be referred to as "one side of the circumferential direction," and the counterclockwise direction will be referred to as "the other side of the circumferential direction." However, this definition of direction is not intended to limit the orientation in which the object to be painted 6 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 component that slides the spray painting devices 10a and 10b. The shaft 4 is provided extending parallel to the axis P of the fixing portion 32 of the fixing device 30.

[0018] Spray coating apparatus 10a, 10b In this disclosure, examples of spray coating apparatuses 10a and 10b used for applying paint are shown in Figures 1 and 2. As shown in Figure 1, the spray painting apparatus 10a and 10b comprises spray painting apparatus bodies 1a and 1b, fixing parts 3a and 3b for fixing the spray painting apparatus bodies 1a and 1b to the shaft 4, and on the paint spraying side (tip) opposite to the fixing parts 3a and 3b, spray nozzles 2a and 2b, gas caps 7a and 7b for injecting compressed gas, and side air nozzles 8a and 8b. Note that the spray painting apparatus can be referred to as a spray gun.

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

[0020] The gas caps 7a and 7b are attached to the paint spraying end of the spray coating apparatus bodies 1a and 1b. The gas caps 7a and 7b have a spray nozzle opening 11 (see Figure 2) through which the paint discharge port 9 at the tip of the spray nozzles 2a and 2b passes, and are configured so that when attached to the spray coating apparatus bodies 1a and 1b, the tips of the spray nozzles 2a and 2b protrude from the spray nozzle opening 11. In addition, the gas caps 7a and 7b have a pair of side air nozzles 8a and 8b located radially outside the spray nozzle opening 11, extending parallel to the spray nozzles 2a and 2b in the spraying direction of the spray nozzles 2a and 2b, and opening toward the center of the spraying direction of the spray nozzles 2a and 2b at symmetrical positions on either side of the center of the spray nozzles 2a and 2b. Furthermore, the gas caps 7a and 7b have atomizing nozzle holes 5 located radially outside the spray nozzle opening 11 and radially inside the side air nozzles 8a and 8b, which inject air to atomize the paint discharged from the paint discharge port 9.

[0021] Compressed air is injected from side air holes (pattern adjustment gas outlets) 12, which are opened in a pair of side air nozzles 8a and 8b of the gas cap 7. These side air holes 12 are opened to form an elliptical spray pattern. The side air holes 12 are opened symmetrically, with one or more openings on each side. The amount of air injected from the side air holes 12 is adjusted by a pattern opening adjustment device (not shown), thereby adjusting the fan-shaped opening of the spray pattern. Furthermore, air is supplied from an air passage inside the spray coating apparatus to the center of the gas cap 7 provided on the spray nozzle 1. The center of the gas cap 7 has a paint discharge port 9, a spray nozzle opening 11, and atomizing nozzle holes (auxiliary air holes) 5. The atomizing nozzle holes (auxiliary air holes) 5 are provided to balance the spray force from the side air holes 12 in order to form the spray pattern, and there are one or more of them.

[0022] The spray coating devices 10a and 10b are attached to the shaft 4 of the coating device 20 by fixing parts 3a and 3b so as to be movable along the shaft 4. The fixing parts 3a and 3b and the shaft 4 have any known configuration in which the fixing parts 3a and 3b are slidable relative to the shaft 4 and can be stopped at predetermined positions relative to the shaft 4. In Figure 1, the shaft 4 is made up of one shaft, but the shaft 4 may be provided in the same number as the spray coating devices 10a and 10b, with each shaft 4 equipped with a spray coating device 10a or 10b. It is preferable that the spray coating devices 10a and 10b move linearly in the direction of the rotation axis of the object to be coated 6. For example, as shown in Figures 5 to 7, the spray coating devices 10a and 10b move along the shaft 4 in the upward direction Ra, Rb or the downward direction Sa, Sb while coating the object to be coated 6 which is rotating in the circumferential direction.

[0023] The spray coating apparatuses 10a and 10b used in this disclosure are not particularly limited as long as they are capable of spray coating, and known spray coating apparatuses can be used. For example, spray coating apparatuses 10a and 10b include air spray pressure regulating devices, spray gun types such as spray guns that atomize liquid with compressed gas, etc.

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

[0025] Object to be painted 6 The object to be painted 6 is not particularly limited, and examples include tubular bodies (e.g., rod-shaped articles, containers, etc.), spherical bodies, plate-shaped bodies, etc. The cross-section of the tubular body, that is, the cross-section cut by a plane perpendicular to the axial direction, may be any shape, not just a perfect circle, but also a roughly circular or roughly square shape. Examples of objects to be painted 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 body panels of automobiles such as passenger cars, trucks, motorcycles, and buses; and automobile parts such as bumpers. Of these, toothbrushes, stationery, containers, exterior panels of automobile bodies, and automobile parts are preferred, with toothbrushes and containers being particularly preferred.

[0026] The material of the object to be painted is not particularly limited and includes, for example, metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, and 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, mixtures of these resins, and various fiber-reinforced plastics (FRP); inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Of these, metal materials and resin materials are preferred. Furthermore, the object to be painted may be a combination of the above-mentioned metal material and resin material.

[0027] Paint pattern Generally, there are two types of coating patterns for spray coating devices 10a and 10b: a round spray pattern and a flat spray pattern. In this disclosure, the coating pattern used is a pattern of a coating surface (also called a coating surface, etc.) that is not a perfect circle (round spray pattern). That is, as shown on the right side of Figure 2, the coating pattern Z produced by spray coating devices 10a and 10b is an approximately elliptical pattern having a major axis and a minor axis of the coating pattern. C represents 1 / 2 the length of the major axis (radius of the major axis), and D represents 1 / 2 the length of the minor axis (radius of the minor axis). Here, "approximately elliptical" includes not only ellipses but also other approximately elliptical shapes such as convex lens shapes and track shapes.

[0028] A roughly elliptical paint pattern can be obtained using a commercially available spray painting device (spray gun). For example, spray painting devices described in Japanese Utility Model Publication No. 07-039954, Japanese Patent Publication No. 2008-142586, Japanese Patent Publication No. 2008-161788, etc., can be used. Furthermore, more specifically, examples of roughly elliptical paint patterns include straight patterns, semi-tulip patterns, and tulip patterns. In other words, in this disclosure, the term "approximately elliptical" also includes shapes that are close to a rhombus or a tulip. An ellipse has a major axis (major axis) and a minor axis (minor axis). Here, in a two-dimensional Cartesian coordinate system, an ellipse where the origin O is the intersection of the major and minor axes is (x 2 / C 2 )+(y 2 / D 2 This can be written as )=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). There are no particular limitations on the size of the paint pattern, but for example, it is an elliptical flat spray pattern with a major axis length of 1 to 30 cm and a minor axis length of 0.1 to 10 cm, and the major axis length > minor axis length, preferably an elliptical flat spray pattern with a major axis length of 2 to 15 cm and a minor axis length of 1 to 10 cm, and the major axis length > minor axis length, and more preferably an elliptical flat spray pattern with a major axis length of 3 to 12 cm and a minor axis length of 2 to 10 cm, and the major axis length > minor axis length. The area (S) of the painted pattern can be calculated using the formula: pi (π) × radius of the major axis (C) × radius of the minor axis (D). There are no specific limitations on the area of ​​the painted pattern, but for example, it can range from 0.3 to 1000 cm². 2 Preferably 1 to 500 cm 2 And more preferably 10-100 cm 2 That is the case.

[0029] Angle of the paint pattern (Θ) In this specification, the angle of the coating pattern refers to the angle of the major axis of a substantially elliptical coating pattern with respect to the rotation axis P of the uncoated object 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, that is, the angle of the line M connecting the pair of side air nozzles 8 with respect to the rotation axis P of the uncoated object 6.

[0030] The tip of the spray coating apparatus 10a, 10b is typically composed mainly of spray nozzles 2a, 2b having paint discharge ports 9 and gas caps 7a, 7b having atomizing nozzle holes 5 and side air nozzles 8. The combination of these determines the state in which the liquid is atomized and sprayed onto the object to be coated 6, i.e., the shape of the coating pattern and the distribution of spray particles. Furthermore, the airflow from the side air nozzles 8a and 8b is designed to intersect with the paint flow from the paint nozzle. As a result, the paint ejected from the spray nozzles 2a and 2b is formed, for example, as an elliptical paint pattern by compressed air ejected from the side air holes 12 located in the side air nozzles 8a and 8b of the gas caps 7a and 7b.

[0031] In other words, in this disclosure, the angle of the paint pattern can be adjusted by changing the angle of the gas cap 7. Specifically, the gas cap 7 can be loosened counterclockwise relative to the spray painting apparatus body 1. By loosening the gas cap 7, the angle Θ of the paint pattern can be changed by adjusting the orientation of the pair of side air nozzles 8 on the gas cap 7 to the positions shown in Figures 3(5) to (8), for example.

[0032] Figure 3 illustrates the relationship between the angle of the paint pattern of the sprayed paint (Figures 3(1) to (4)) and the angle of the gas cap 7 for forming the paint pattern (Figures 3(5) to (8)). Figure 4 also illustrates the relationship between the object to be painted 6 and the angle of the paint pattern shown in Figures 3(1) to (4). As shown in Figure 3, the line M connecting the pair of side air nozzles 8 on the gas cap 7 intersects at a right angle (orthogonal) with the major axis of the roughly elliptical paint pattern of the sprayed paint.

[0033] The angle of the paint pattern is 0 degrees Figures 3(1), 4(1), and 5 show the painting pattern when the angle of the painting pattern, that is, the major axis of the approximately elliptical painting pattern, is 0 degrees with respect to the rotation axis P direction of the object to be painted 6 (Figure 4(0)). Here, Figure 5 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the angle of the painting pattern is 0 degrees. As shown in Figure 3(5), when paint is sprayed with the line M connecting a pair of side air nozzles 8 perpendicular to the rotation axis P of the object to be painted (90 degrees, horizontal direction), the angle of the substantially elliptical paint pattern sprayed onto the object to be painted 6 is 0 degrees, that is, a paint pattern is obtained in which the major axis of the substantially ellipse is aligned with the rotation axis P of the object to be painted 6 (0 degrees, coincides) (Figures 3(1), 4(1), and 5).

[0034] The angle of the paint pattern is 45 degrees. Figures 3(2), 4(2), and 6 show the painting patterns when the angle of the painting pattern, that is, the major axis of the approximately elliptical painting pattern, is 45 degrees with respect to the rotation axis P direction of the object to be painted 6. Here, Figure 6 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the angle of the painting pattern is 45 degrees. As shown in Figure 3(6), when paint is sprayed with the line M connecting a pair of side air nozzles 8 inclined at -45 degrees with respect to the rotation axis P of the object to be painted 6, the angle of the substantially elliptical paint pattern sprayed onto the object to be painted 6 is 45 degrees, that is, a paint pattern is obtained in which the major axis of the substantially ellipse is inclined at 45 degrees with respect to the rotation axis P of the object to be painted 6 (Figures 3(2), 4(2), and 6).

[0035] The angle of the paint pattern is 90 degrees. Figures 3(3), 4(3), and 7 show the painting patterns when the angle of the painting pattern, that is, the major axis of the approximately elliptical painting pattern, is 90 degrees with respect to the rotation axis P direction of the object to be painted 6. Here, Figure 7 shows the object to be painted 6, the painted surface, and the spray painting apparatus 10 when the angle of the painting pattern 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 with the rotation axis P of the object to be painted (0 degrees, vertical direction), the angle of the substantially elliptical paint pattern sprayed onto the object to be painted 6 is 90 degrees, that is, a paint pattern is obtained in which the major axis C of the substantially ellipse is perpendicular to the rotation axis P of the object to be painted 6 (90 degrees) (Figures 3(3), 4(3), and 7).

[0036] The angle of the paint pattern is -45 degrees. Figures 3(4) and 4(4) show the painting pattern when the angle of the painting pattern, that is, the major axis of the approximately elliptical painting pattern, is -45 degrees with respect to the rotation axis P direction of the object to be painted 6. As shown in Figure 3(8), when paint is sprayed with the line M connecting a pair of side air nozzles 8 inclined at 45 degrees with respect to the rotation axis P of the object to be painted 6, the angle of the major axis C of the substantially elliptical paint pattern sprayed onto the object to be painted 6 is -45 degrees, that is, a paint pattern is obtained in which the major axis C of the substantially elliptical pattern is inclined at -45 degrees with respect to the rotation axis P of the object to be painted 6 (Figures 3(4) and 4(4)).

[0037] The angle of the paint pattern should be in the range of greater than 0 degrees and less than 90 degrees. That is, 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 rotation axis P of the object to be painted 6 (horizontal direction) and a state where it is aligned with the rotation axis P of the object to be painted 6 (vertical direction) (excluding the horizontal and vertical directions), then a paint pattern can be obtained in which the major axis of a roughly ellipse is inclined at a rate of greater than 0 degrees and less than 90 degrees with respect to the rotation axis P of the object to be painted 6. 0 degrees can be rephrased as 180 degrees or -90 degrees. Furthermore, the range between 0 degrees and less than 90 degrees can be rephrased as between 180 degrees and less than 90 degrees. In the painting method for providing a gradient portion according to the present disclosure, the long axis of the painting pattern is preferably inclined at 10 to 80 degrees with respect to the rotation axis of the object to be painted, and more preferably at 30 to 60 degrees.

[0038] As described in Patent Document 3 above, the gradient width around the axis can also be adjusted by changing the spraying angle of the spray coating devices 10a and 10b. Specifically, the gradient width is adjusted by fixing the paint spraying angle of the spray coating devices 10a and 10b to an arbitrary angle in the axial direction (hereinafter referred to as the "vertical direction" in accordance with Figure 1), from a direction along a plane perpendicular to the axial direction (hereinafter referred to as the "horizontal direction" in accordance with Figure 1). Fixing in the horizontal direction refers to the state in which the spray painting devices 10a and 10b are held horizontally with respect to the object to be painted 6, while fixing in the vertical direction at an arbitrary angle refers to the direction in which the spray painting devices 10a and 10b are angled relative to the same axis as the object to be painted 6. Here, if we define the angle at which the nozzle is fixed horizontally as 0 degrees, the spray angle is generally fixed at 0 degrees horizontally in order to reduce the amount of paint exhausted. To paint the bottom, top, etc. (and in the case of a container, the shoulder, etc.) of the object to be painted 6, this can be achieved by fixing the spray nozzle 2 of the spray painting apparatus 10a and 10b at an arbitrary angle perpendicular to the same axis. Within this angle range, the spray painting apparatus 10a and spray painting apparatus 10b shown in Figure 1 can be tilted from more than 0 degrees to less than 90 degrees (-90 degrees). This makes it possible to obtain a painted object 6 that is painted on the bottom, top, etc. (and in the case of a container, the shoulder, etc.).

[0039] The painted workpiece 6 obtained by the painting method of this disclosure has a first solid color section F1, a gradient section G, and a second solid color section F2. Here, the gradient section G refers to a section where the color gradually changes from the first color to the second color. The solid color sections F1 and F2 refer to sections painted with a single color. When three or more spray painting devices 10 are used, the painted workpiece 6 can have two or more gradient sections and three or more solid color sections.

[0040] Rotation in the circumferential direction When the paint is sprayed, the object to be painted 6 rotates in the circumferential direction while being painted. The faster the rotation speed, the more uniform the color of the painted object 6 will be. A motor can be used for rotation. The rotation speed of this motor can be set to, for example, 60Hz. There are no particular limitations on the type of motor.

[0041] paint The coatings used in this disclosure can impart an excellent appearance to the object to be coated. Appearance refers to particle texture, uniform coating properties, and a gradation effect. This appearance allows the coated object to possess design, aesthetic appeal, gloss, and other qualities. There are no particular limitations on the type of paint used; examples include resin-based paints and metallic paints.

[0042] There are no particular limitations on the resin-based paints used; for example, acrylic resin paints, polyurethane resin paints, fluororesin paints, silicone resin paints, and melamine resin paints can be used, and commercially available products can be used. From the viewpoint of paint durability and workability, acrylic resin paints and polyurethane resin paints are preferred.

[0043] There are no particular limitations on the metallic paints, and examples 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, metallic titanium flake pigments, stainless steel flake pigments, plate-like iron oxide pigments, metal-plated glass flake pigments, metal oxide coated glass flake pigments, hologram pigments, vapor-deposited aluminum flake pigments, flake pigments with a multilayer thin film structure of a metallic reflective layer, and flake pigments made of cholesteric liquid crystal polymers.

[0044] It is acceptable to use not only one type of paint, but also two or more types of paint simultaneously. The movement speed, rotation speed, paint spray volume, etc., of the spray coating devices 10a, 10b or the fixing device 30 for the object to be coated 6 may be controlled independently of each other. The movement speed of the spray coating apparatus 10a, 10b or the fixing device 30 for the object to be coated 6 is controlled independently of the paint spray volume of the spray coating apparatus 10a, 10b. Control can be performed using known control methods and is carried out by a control unit. The control unit has an input section for inputting control conditions and is typically controlled by a device equipped with a CPU and memory. The temperature and humidity during the painting process can be set as appropriate. For example, the painting process can be carried out at room temperature and humidity. The painting time can also be set as appropriate.

[0045] Therefore, the present disclosure relates to a method for manufacturing a painted product having a gradient portion, wherein the first region is painted with a first color, the second region is painted with a second color, and the overlapping portion between the first and second regions is painted to provide a gradient portion that gradually changes from the first color to the second color. The process includes a step of spraying the first and second color paints onto the object to be painted, which is placed on a rotating stationary device, using a spray painting device. The painting pattern of the aforementioned spray painting apparatus is a substantially elliptical pattern. The method for manufacturing a painted product includes a gradient portion in which the long axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the object to be painted. In the method for manufacturing a painted product having the gradient portion, the long axis of the painting pattern is preferably inclined at 10 to 80 degrees with respect to the rotation axis of the object to be painted, and more preferably at 30 to 60 degrees. Furthermore, in the method for manufacturing a painted product having the gradient portion, it is preferable that the spray painting apparatus moves linearly in the direction of the rotation axis of the object to be painted. Furthermore, this disclosure also includes painted products having a gradient portion obtained by a painting method for providing the gradient portion, or a manufacturing method for a painted product having the gradient portion. [Examples]

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

[0047] Example 1 <Material> • Object to be painted A (Cosmetic container (bottle): Made of white polypropylene resin (PP)) The size (shape) of cosmetic containers is as follows: Opening: Diameter 30.0mm Body: Diameter 80.3mm Length (from mouth): 170mm) Length (at the widest point): 150mm

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

[0049] • Object to be painted C (Toothbrush: Made of transparent polyethylene terephthalate (PET) resin)

[0050] • Paint: Acrylic resin paint (First color: purple, Second color: yellow)

[0051] Painting method for creating a gradient section and manufacturing method for a painted product having a gradient section. The object to be painted A or B was fixed to a fixing device and rotated only in the circumferential direction (clockwise when viewed from above) without moving it in place. Painting was performed by spraying two types of paint (purple from the upper first spray painting device 10a and yellow from the lower second spray painting device 10b) onto the object to be painted 6 using two spray guns (manufactured by Anest Iwata Corporation, product name: WIDER1A) as spray painting devices 10a and 10b (see Figure 1, etc.). In this process, the gas cap pattern (the line M connecting the pair of side air nozzles 8) of the spray coating devices 10a and 10b was inclined at -75 degrees with respect to the rotation axis P of the object to be coated. By moving the device up and down on the shaft 4, paint was sprayed over the entire rotation axis P direction (the angle of the coating pattern was 15 degrees), resulting in a gradient-coated product 1A (bottle) and a coated product 1B (toothbrush) with a length (width) of 25 mm. The pattern pressure of the gas cap was 0.11 MPa. The movement speed of the spray coating devices 10a and 10b was 20 mm per second, and the vertical (lifting and lowering) movement distance was approximately 80 mm. The distance between the painted surface and the paint discharge port 9 of the spray nozzle 2 was approximately 150 mm. The above-mentioned painted product 1A (bottle) had a gradient section approximately 45 mm wide (length). Similarly, the above-mentioned painted product 1B (toothbrush) also had a gradient section approximately 45 mm wide (length).

[0052] Example 2 Painted products 2A and 2B having the gradient portion of Example 2 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 tilted at -60 degrees with respect to the rotation axis P direction of the object to be painted, and the angle of the painting pattern was changed to 30 degrees. The painted product 2A described above had a gradient section approximately 40 mm wide (length). Similarly, the painted product 2B described above also had a gradient section approximately 40 mm wide (length).

[0053] Example 3 Painted products 3A and 3B having the gradient portion of Example 3 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 inclined at -45 degrees with respect to the rotation axis P direction of the object to be painted, thereby changing the angle of the painting pattern to 45 degrees. In this disclosure, as shown in Figures 6-8, the first spray coating apparatus 10a and the second spray coating apparatus 10b were simultaneously moved in the direction of Ra (upward direction) and the direction of Rb (upward direction), respectively, together with the shaft 4 and the fixed parts 3a and 3b. Subsequently, the first spray coating apparatus 10a and the second spray coating apparatus 10b were simultaneously moved in the direction of Sa (downward direction) and the direction of Sb (downward direction), respectively. In Examples 1, 2, 4, and 5, and Comparative Examples 1 and 2, the spray coating apparatuses 10a and 10b were moved in a similar manner. The painted product 3A described above had a gradient section approximately 30 mm wide (length). Similarly, the painted product 3B described above also had a gradient section approximately 30 mm wide (length).

[0054] Example 4 Painted products 4A and 4B having the gradient portion of Example 4 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 tilted at -30 degrees with respect to the rotation axis P direction of the object to be painted, and the angle of the painting pattern was changed to 60 degrees. The painted product 4A described above had a gradient section approximately 35 mm wide (length). Similarly, the painted product 4B described above also had a gradient section approximately 35 mm wide (length).

[0055] Example 5 Painted products 5A and 5B having the gradient portion of Example 5 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 inclined at -15 degrees with respect to the rotation axis P direction of the object to be painted, and the angle of the painting pattern was changed to 75 degrees. Painted product 5A had a gradient section approximately 35 mm wide (length). Painted product 5B also had a gradient section approximately 35 mm wide (length).

[0056] Comparative Example 1 Comparative coated product 1A and comparative coated product 1B having the gradient 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 to 90 degrees (perpendicular) to the rotation axis P direction of the object to be coated, and the angle of the coating pattern was changed to 0 degrees. The comparative painted product 1A had a gradient section approximately 30 mm wide (length). Similarly, comparative painted product 1B also had a gradient section approximately 30 mm wide (length).

[0057] Comparative Example 2 Comparative coated product 2A and comparative coated product 2B having the gradient portion of Comparative Example 2 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 to 0 degrees (parallel) with respect to the rotation axis P direction of the object to be coated, and the angle of the coating pattern was changed to 90 degrees. The above comparative painted product 2A had a gradient section approximately 25 mm wide (length). Similarly, the above comparative painted product 2B also had a gradient section approximately 25 mm wide (length).

[0058] Sensory evaluation test For painted products with gradient areas, sensory evaluations were conducted on the following aspects of appearance: particle texture (gradient area), gradient effect (gradient area), and paint uniformity (solid color area).

[0059] Appearance (graininess) The particle state of the gradient areas after paint application was observed using the following 5-point scale. A score of 5 to 3 is considered passing. 5: The particles are particularly fine 4: Fine particles 3. The particles are slightly coarser than those in item 4 above, but this does not pose a practical problem. 2: The particles are slightly coarse. 1: Coarse particles

[0060] Appearance (gradient effect) The gradient effect of the painted areas was observed using the following 5-point scale. A score of 3 to 5 is considered passing. 5: Especially good Somewhere between 4:5 and 3 3: Good 2: Slightly poor 1: Defective

[0061] Appearance (uniformity of paint finish, presence or absence of unevenness) The appearance of the painted surface after application was observed using the following 5-point scale. A score of 5 to 2 is considered passing. 5: The entire coating has a uniform color and there are no noticeable color inconsistencies. 4: Slight color unevenness is visible in some parts of the paint film, but this does not affect practical use. 3: There are slight color variations throughout the paint film, but this does not pose a practical problem. 2: Significant color unevenness is visible in some parts of the paint film, but this does not pose a practical problem. 1: Significant color unevenness is visible throughout the paint film.

[0062] comprehensive evaluation Based on the above test results, the scores for particle texture (gradient area), gradient effect (gradient area), and paint uniformity (solid color area) were added together to determine the overall evaluation. The results are shown in Table 1 below. An overall score of 13 points or higher is considered a passing score.

[0063] The results of the sensory evaluation test described above are shown in Table 1 below, and in Figure 8, which further includes photographs of the appearance of painted objects A and B in addition to Table 1.

[0064] [Table 1]

[0065] Furthermore, Figure 9 shows photographs of the appearance of the painted cosmetic containers of Example 3 and Comparative Example 2, and Figure 10 shows photographs of the appearance of the painted toothbrushes of Example 3 and Comparative Example 2.

[0066] result Examples 1-5 (where the painting pattern angle was greater than 0 degrees but less than 90 degrees) were found to have superior appearance (particle texture, gradation, and uniform coating) compared to Comparative Examples 1 and 2. Among the examples, Example 3 yielded the best overall evaluation.

[0067] Example 6 A painted product 6C (toothbrush) with the gradient of Example 6 was manufactured in the same manner as in Example 3, except that the paint was replaced with a metallic paint (flaky aluminum pigment, manufactured by Toyo Kogyo Paint Co., Ltd.) and the object to be painted C. A photograph of the appearance of the painted toothbrush of Example 6 is shown in Figure 11. The resulting painted product 6C (toothbrush) had a gradient section approximately 30 mm wide (length).

[0068] result The painted product 6C (toothbrush) of Example 6 (painting pattern angle of 45 degrees) had excellent appearance (graininess, gradation, and uniformity of coating were all rated 5), similar to the painted product 3B (toothbrush) of Example 3. [Explanation of Symbols]

[0069] 1. Spray painting apparatus main unit 1a Main body of the first spray coating apparatus 1b Second spray coating apparatus main body 2 spray nozzles 2a First spray nozzle 2b Second spray nozzle 3 Fixed part 3a 1st fixed part 3b Second fixed part 4 shafts 5 Atomizing nozzle holes 6 Object to be painted 7. Gas cap 7a First gas cap 7b Second gas cap 8. Side air nozzles 8a First side air nozzle 8b Second side air nozzle 9 Paint outlet 9a 1st paint outlet 9b 2nd paint outlet 10. Spray coating apparatus 10a First spray coating apparatus (first color) 10b Second spray coating apparatus (second color) 11. Opening for spray nozzle 12. Side air vents (gas outlets for pattern adjustment) 20 Painting equipment 30 Fixation device 31 Base 32 Fixed part C: Radius of the major axis D: Radius of the minor axis E1 1st area E2 2nd area F1 First solid color area F2 Second solid color area G gradient section M: A line connecting a pair of side air nozzles 8. P Rotation axis Q Circumferential direction Ra First spray coating device (first color) movement direction (upward direction) Rb Direction of movement (upward direction) of the second spray coating device (second color) Sa First spray coating device (first color) movement direction (downward direction) Sb Second spray coating device (second color) movement direction (downward direction)

Claims

1. A painting method comprising spraying a first color paint onto a first region of an object to be painted, which is placed on a rotating stationary device, using a spray painting device, and spraying a second color paint onto a second region of the object to be painted, thereby creating a gradient portion in the overlapping area between the first and second regions, where the color gradually changes from the first to the second color. The painting pattern of the aforementioned spray painting apparatus is a substantially elliptical pattern. A painting method wherein the long axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the object to be painted.

2. The painting method according to claim 1, wherein the long axis of the painting pattern is inclined at an angle of 10 to 80 degrees with respect to the rotation axis of the object to be painted.

3. The painting method according to claim 1, wherein the long axis of the painting pattern is inclined at an angle of 30 to 60 degrees with respect to the rotation axis of the object to be painted.

4. The painting method according to claim 1, wherein the spray painting apparatus moves linearly in the direction of the rotation axis of the object to be painted.

5. A method for manufacturing a painted product having a gradient portion, wherein the product is manufactured by applying a coating to a first region, a second region, and a gradient portion in the overlapping area between the first and second regions, where the color gradually changes from the first to the second color. The process includes a step of spraying the first and second color paints onto the object to be painted, which is placed on a rotating stationary device, using a spray painting device. The painting pattern of the aforementioned spray painting apparatus is a substantially elliptical pattern. A method for manufacturing a painted product having a gradient portion, wherein the long axis of the painting pattern is inclined at an angle greater than 0 degrees and less than 90 degrees with respect to the rotation axis of the object to be painted.

6. The manufacturing method according to claim 5, wherein the long axis of the coating pattern is inclined at an angle of 10 to 80 degrees with respect to the rotation axis of the object to be coated.

7. The manufacturing method according to claim 5, wherein the long axis of the coating pattern is inclined at an angle of 30 to 60 degrees with respect to the rotation axis of the object to be coated.

8. The spray coating apparatus moves linearly in the direction of the rotation axis of the object to be coated, as described in claim 5.

9. A painted product having a gradient portion obtained by the painting method described in any one of claims 1 to 4, or the manufacturing method described in any one of claims 5 to 8.

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