Painting Method

Abstract

To provide a coating technique effective to form a projecting and recessed decorative pattern on an object to be coated.SOLUTION: A coating method according to the embodiment includes: a first step S101 of forming a base coating film on a surface of a to-be-coated object; a second step S102 of drying the base coating film formed in the first step S101 and fixing it to the to-be-coated object; and a third step S103 of jetting paint only from a selection nozzle selected from a plurality of nozzles of an ink jet head to form a projecting and recessed decorative pattern on a surface of the base coating film fixed in the second step S102.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a coating method. [Background technology]

[0002] The following Patent Document 1 discloses a rotary atomizing head type coating device used to coat objects such as automobile bodies. When using this coating device, paint is supplied to the rotary atomizing head while rotating at high speed with a high voltage applied. As a result, the paint is centrifugal atomized by the rotary atomizing head into electrically charged paint particles of a certain particle size range, which are sprayed onto the object by shaping air that is sprayed toward the object. At this time, the paint particles flow to form a flat and smooth coating film, a property known as "leveling," and the paint is layered on the object with a roughly constant film thickness. As a result, it is possible to ensure the rust prevention, weather resistance, and high appearance of the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-262696 Summary of the Invention [Problem to be solved by the invention]

[0004] By the way, a decoration technique is known in which a decorative film that has been patterned or processed in advance to decorate a coated object is attached. This decoration technique has the disadvantage that the cost is high because an expensive decorative film is used. Therefore, as a new technique to replace this decoration technique, a painting technique that decorates a coated object at low cost using a paint that is cheaper than the decorative film is required.

[0005] In response to such a request, when the coating device disclosed in Patent Document 1 is used, the paint is sprayed irregularly over a wide area of ​​the workpiece with a large variation in average particle size, making it difficult to partially control the paint layer height to form an uneven decorative pattern. In addition, paints used in painting automobile bodies are generally known to have high smoothness on the body to be coated. For this reason, even if the paint can be sprayed on the surface of the body so that the layer height varies partially, the film thickness changes to a roughly constant value due to the effect of subsequent paint leveling, which can result in a problem in which the desired uneven pattern cannot be formed.

[0006] The present invention has been made in view of the above problems, and aims to provide a coating technique that is effective for forming an uneven decorative pattern on an object to be coated. [Means for solving the problem]

[0007] One aspect of the present invention is A base coating step of forming a base coating film on a surface of a coating object constituting an automobile; a fixing step in which the base coating film formed in the base coating step is fixed to the surface of the substrate by drying; a decorative coating step in which an inkjet head having a plurality of nozzles regularly arranged is disposed relative to the object to be coated, and paint is sprayed only from selected nozzles selected from the plurality of nozzles of the inkjet head to form an uneven decorative pattern on the surface of the base coating film fixed in the fixing step; having the inkjet head is configured to continuously flow the paint between an internal reservoir and an external reservoir; The surface of the above-mentioned object The surface tension is in the range of 20 to 50 N / m, and The surface of the above-mentioned object Surface roughness range is 0.01~0.5 μm and Above coating Fee Viscosity is in the range of 25 to 110 cps. The above paint Surface tension is in the range of 10 to 35 N / m. R,Painting method, is located. Effect of the Invention

[0008] In the coating method of the above aspect, a base coating film is formed on the surface of the object to be coated in the base coating step. After that, the base coating film formed in the base coating step is dried in the fixing step. This allows the base coating film to be fixed to the surface of the object to be coated. In the decorative coating step, after the fixing step, paint is sprayed toward the base coating film only from a selected nozzle selected from among the multiple nozzles of the inkjet head. According to this decorative coating step, the thickness of the decorative coating film laminated on the surface of the base coating film can be made different between a portion corresponding to the selected nozzle and a portion corresponding to a portion other than the selected nozzle. As a result, a portion where the coating film is laminated and a portion where the coating film is not laminated or where the laminated height is relatively low are formed on the surface of the base coating film, and a concave-convex decorative pattern can be formed by utilizing the thickness difference between these portions.

[0009] Here, the base coating film on the surface of the object to be coated is formed by the paint becoming a film, and exerts the function of suppressing the flow and smoothing of the paint particles newly sprayed on the surface. Therefore, in a state where the film thickness of only the portion of the base coating film where the paint is sprayed from the selected nozzle is increased, the progress of leveling of the paint particles thereafter can be suppressed. This makes it possible to maintain the state in which the desired uneven shape is formed on the surface of the base coating film. As a result, it is possible to form the desired uneven decorative pattern on the object to be coated using paint that is less expensive than the decorative film.

[0010] As described above, according to the above-mentioned embodiment, it is possible to provide a coating technique that is effective for forming an uneven decorative pattern on an object to be coated. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing a state in which an automobile body is decoratively painted using the painting method of the first embodiment. [Diagram 2]2 is a flowchart showing the coating method of the first embodiment. [Diagram 3] 3 is a flowchart of the decoration process in FIG. 2 . [Figure 4] FIG. 2 is a plan view showing a schematic diagram of a nozzle in use when forming a base coating film on the surface of an object to be coated in the coating method of embodiment 1. [Diagram 5] 1 is a cross-sectional view showing a schematic diagram of a base coating film being formed on the surface of an object to be coated in the coating method of embodiment 1. FIG. [Figure 6] FIG. 2 is a cross-sectional view showing a schematic diagram of a decorative coating film being formed on the surface of a base coating film in the coating method of the first embodiment. [Figure 7] FIG. 2 is a plan view showing a schematic state of a nozzle in use when forming a decorative coating film on the surface of a base coating film in the coating method of the first embodiment. [Figure 8] FIG. 2 is a plan view showing a schematic diagram of a decorative coating film being formed on the surface of a base coating film in the coating method of the first embodiment. [Figure 9] 4 is a flowchart of a coating method according to a second embodiment, which corresponds to the decorating process of FIG. 3 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A description will now be given of preferred embodiments of the above aspects.

[0013] In the coating method of the above aspect, in the decorative coating step, it is preferable that the spraying process of spraying paint from the selected nozzle onto the surface of the base coating film is repeated multiple times based on the planned film thickness of the decorative pattern.

[0014] According to this coating method, the paint is sprayed repeatedly from the selected nozzle multiple times to gradually increase the thickness of the coating film laminated on the surface of the base coating film, thereby making it possible to form the decorative pattern into the desired uneven shape.

[0015] In the coating method of the above aspect, in the decorative coating step, it is preferable that the spraying treatment is repeated a number of times using the same selected nozzle.

[0016] According to this coating method, the process of forming a decorative pattern can be simplified by repeatedly spraying paint from the same selected nozzle multiple times.

[0017] In the coating method of the above aspect, in the base coating step, paint is preferably sprayed from the plurality of nozzles of the inkjet head to form the base coating film.

[0018] According to this coating method, the same inkjet head is used for both the base coating step and the decorative coating step, making it possible to reduce the cost required to form a decorative pattern on the object to be coated.

[0019] In the coating method of the above aspect, it is preferable that at least one of the droplet diameter of the paint sprayed from the plurality of nozzles and the number of droplets per spray is set individually.

[0020] According to this painting method, the diameter of the paint droplets from the multiple nozzles and the number of droplets per spray are individually set, so it is possible to finely adjust the thickness of the decorative coating film laminated on the surface of the base coating film in the decorative painting step for each part corresponding to each selected nozzle. This allows for an increased variety of decorative patterns.

[0021] (Embodiment 1) The coating method of the first embodiment will be described below with reference to the drawings.

[0022] In the drawings referred to in the description of this specification, unless otherwise specified, a first direction along the surface of the substrate is indicated by arrow X, a second direction along the surface of the substrate and perpendicular to the first direction is indicated by arrow Y, and a third direction perpendicular to both the first and second directions is indicated by arrow Z.

[0023] 1, the coating method of the first embodiment is for applying decorative coating to a surface Wa of a workpiece W, which is a coating object, using an inkjet head 10. In the first embodiment, an example is shown in which decorative coating is performed on a steel plate constituting an automobile body, which is the coating object W.

[0024] The inkjet head 10 has a plurality of nozzles 11 each opening toward the workpiece W, and is configured to be able to spray paint P temporarily stored in an internal storage section 12 from each nozzle 11 toward the surface Wa of the workpiece W by an injection mechanism (not shown). The inkjet head 10 is preferably configured to continuously flow paint P between the internal storage section 12 and an external storage section (not shown). With this configuration, when the paint P has a higher viscosity than paints generally used for painting wood materials and the like, it is possible to prevent the paint P from accumulating in the storage section 12 and interfering with the spraying from each nozzle 11. The inkjet head 10 is attached to a robot arm 21 of a painting robot 20.

[0025] Regarding the structure of the inkjet head 10, a first head structure in which the nozzle diameters of the multiple nozzles 11 are the same, or a second head structure in which the nozzle diameters of the multiple nozzles 11 are individually determined can be appropriately adopted.

[0026] By adopting the first head structure, the paint P can be sprayed from the multiple nozzles 11 with a generally constant droplet diameter by controlling the number of sprays and amplitude in the spray mechanism. The droplet diameter of the paint P can be controlled to be generally constant within a range of, for example, about 30 to 80 μm with an error of about several μm, with the variation suppressed. On the other hand, by adopting the second head structure, the droplet diameter of the paint P sprayed from the multiple nozzles 11 can be set individually and used. In contrast, when a rotary atomizing head type coating device is used, the droplet diameter generally varies and is distributed randomly over a wide range, for example, about several μm to 150 μm, which is disadvantageous in forming the desired decorative pattern 2.

[0027] As a further specific structure of the inkjet head 10, for example, the structure of an inkjet head disclosed in JP 2016-30332 A, JP 2016-30388 A, etc. can be adopted. In this case, as the inkjet head 10, an on-demand type structure (for example, an electro-mechanical conversion type that uses deformation of a piezoelectric diaphragm to eject droplets of paint P, an electro-thermal conversion type that uses the generation of bubbles due to heat to eject droplets of paint P, an electrostatic suction type that ejects droplets of paint P by electrostatic suction, etc.) can be appropriately used.

[0028] In the coated object W constituting an automobile, the surface Wa to be coated with decorative paint includes an electrodeposition coated surface, an undercoat coated surface, and a clear coated surface. In other words, three types of coated surfaces are assumed as the decorative coated surface. In this case, the electrodeposition coated surface as the decorative coated surface has a surface tension in the range of 30 to 50 N / m and a surface roughness (surface roughness Ra specified in JIS B 0601) of 0.2 to 0.5. μm The surface tension of the undercoat coating surface as the decorative coating surface is preferably in the range of 25 to 35 N / m and the surface roughness is preferably in the range of 0.1 to 0.3. μm The clear coating surface as the decorative coating surface has a surface tension in the range of 20 to 30 N / m and a surface roughness of 0.01 to 0.15. μm In summary, the surface tension of such a decorative coating surface is preferably in the range of 20 to 50 N / m and the surface roughness is preferably in the range of 0.01 to 0.5. μm Therefore, compared to wooden materials such as decorative building boards, the droplets of paint P tend to flow easily, making it difficult to form a decorative pattern in a desired shape. Therefore, in this embodiment, a painting method described below is adopted.

[0029] It is preferable to use water-based or solvent-based paint P having a viscosity in the range of 25 to 110 cps and a surface tension in the range of 10 to 35 N / m. If necessary, a metallic pigment may be added to this paint P.

[0030] Specifically, the base coat paint is preferably classified into paints having amino-acrylic resins, amino-alkyd resins, amino-polyester resins, polyisocyanate-acrylic resins, etc. as vehicle components. The form of these paints is not particularly limited, and any form such as organic solvent type, non-aqueous dispersion type, aqueous solution type, powder type, etc. can be used. When the base coat paint contains a metallic pigment made of aluminum flakes, mica flakes, etc., organic color pigments or inorganic color pigments may be added as necessary.

[0031] The control panel 30 incorporates a first control unit 31 electrically connected to the inkjet head 10 and a second control unit 32 electrically connected to the painting robot 20 .

[0032] The first control unit 31 has a function of controlling the inkjet head 10. Specifically, the first control unit 31 individually controls each of the multiple nozzles 11 of the inkjet head 10, selects a selection nozzle 11A to be used from the multiple nozzles 11, and reads out the spraying conditions of the paint P to be sprayed from the selection nozzle 11A.

[0033] The ejection conditions typically include control parameters for directly or indirectly controlling the number of ejections per unit time of each selected nozzle 11A, the number of droplets per unit ejection of each selected nozzle 11A, and the like.

[0034] The second control unit 32 has a function of controlling the painting robot 20. Specifically, the trajectory and posture of the tip of the robot arm 21 are controlled by the second control unit 32.

[0035] When using the inkjet head 10, if the surface Wa of the workpiece W includes a curved surface, it is preferable to set the inkjet head 10 close to the workpiece W so that the distance d between the surface Wa and the inkjet head 10 is about 3 to 30 mm. When the surface Wa of the workpiece W is composed of only flat surfaces, the distance d can also be set to about 5 to 15 mm. This distance d is significantly shorter than the distance (e.g., 200 to 300 mm) from the rotary atomizing head to the surface Wa of the workpiece W when a known rotary atomizing head type coating device is used. In this case, coating can be performed with the distance d kept small by controlling the coating robot 20 by the second control unit 32.

[0036] Therefore, compared to the case where a known rotary atomizing head type coating device is used, the amount of scattering of paint P (i.e., dust) during coating can be reduced. As a result, a simple coating booth with low initial equipment costs and low energy costs can be used, and the need for masking and other protective measures for coating can be omitted.

[0037] The data reading device 40 has a function of reading and storing image data relating to a desired decorative pattern. The data reading device 40 is electrically connected to the first control unit 31 in order to control the inkjet head 10 based on the image data.

[0038] Next, the coating method of the first embodiment will be specifically described with reference to FIGS.

[0039] 2, the coating method of the first embodiment is achieved by sequentially executing at least the process indicated in the first step S101 to the process indicated in the third step S103. Note that, if necessary, another step may be added to these steps, or at least one of these steps may be divided into a plurality of steps.

[0040] 2 is a base coating step for forming a base coating film 1 on the surface Wa of the workpiece W. In this first step S101, the coating robot 20 is controlled to position the inkjet head 10 so that the multiple nozzles 11 face the surface Wa of the workpiece W and stop it in that position. Thereafter, paint P is sprayed from all of the multiple nozzles 11 provided on the inkjet head 10 based on predetermined conditions.

[0041] 4, a plurality of nozzles 11 are formed on one surface of the inkjet head 10 and are regularly arranged in a two-dimensional rectangular lattice. The nozzle centers of the nozzles 11 are arranged on the intersections of a plurality of imaginary straight lines La all of which extend in the first direction X and a plurality of imaginary straight lines Lb all of which extend in the second direction Y. At this time, the two imaginary straight lines La and Lb are perpendicular to each other. In this first step S101, all of the nozzles 11 are set to an on state, which is a usage state.

[0042] In addition, regarding the arrangement of the multiple nozzles 11, the distance Da between two adjacent virtual straight lines La and the distance Db between two adjacent virtual straight lines Lb may be the same dimension, or the distance Da and the distance Db may be different dimensions. Also, a lattice arrangement or a staggered arrangement in which the virtual straight lines Lb diagonally intersect with the virtual straight lines La may be adopted.

[0043] As shown in Fig. 5(a), in a first step S101, coating particles Pa of approximately uniform droplet diameter sprayed from each nozzle 11 adhere to the surface Wa of the workpiece W. Thereafter, as shown in Fig. 5(b), each coating particle Pa flows along the surface Wa of the workpiece W due to a leveling effect, forming a base coating film 1 on the surface Wa of the workpiece W.

[0044] The second step S102 in FIG. 2 is a fixing step in which the base coating film 1 formed in the first step S101 is fixed to the surface Wa of the object W. At this time, the body of the automobile is carried into a drying booth, and the base coating film 1 is dried under predetermined drying conditions (drying temperature and drying time). According to this second step S102, the moisture contained in the paint P of the base coating film 1 is removed by drying, and the base coating film 1 is fixed as a solid layer on the surface Wa of the object W. In order to shorten the drying time, it is preferable to select a temperature in the low temperature range above the room temperature range and below the high temperature range of 100° C. or higher as the drying temperature. It is also possible to perform the drying process in the room temperature range depending on the influence of the external environment or by extending the drying time.

[0045] It is preferable to carry out this second step S102 before the base coating film 1 is leveled to a completely flat state. For this reason, it is preferable to determine the drying conditions in the second step S102 so that the paint P can be fixed to the surface 1a of the base coating film 1 in a state where leveling is suppressed (i.e., a state where the surface tension of the paint particles Pa is controlled) in step S106 described below. This makes it possible to leave on the surface 1a of the base coating film 1 a relatively large uneven shape that is effective for fixing the paint P to the surface 1a of the base coating film 1 in a state where leveling is suppressed.

[0046] 2 is a decorative coating step in which paint P is sprayed only from a selected nozzle 11A selected from the multiple nozzles 11 of the inkjet head 10 after the second step S102 to form an uneven decorative pattern 2 on the surface 1a of the base coating film 1. This third step S103 is achieved by sequentially executing the processes from step S104 to step S108 as shown in FIG.

[0047] Step S104 in Fig. 3 is a step of setting a selected nozzle 11A from among the multiple nozzles 11. According to this step S104, as shown in Fig. 6, each of the multiple nozzles 11 is classified as either a selected nozzle 11A (see the solid line in Fig. 6) or a non-selected nozzle 11B (see the two-dot chain line in Fig. 6). Then, the selected nozzle 11A is set to an ON state in which it sprays paint P, and the non-selected nozzle 11B is set to an OFF state in which it does not spray paint P.

[0048] 3 is a step of reading the above-mentioned jetting conditions for each selected nozzle 11A. The jetting conditions at this time are preferably determined by the first control unit 31 based on image data (e.g., three-dimensional data of a decorative pattern) transmitted from the data reading device 40. Then, the jetting conditions are temporarily stored in the first control unit 31.

[0049] 3 is a step of controlling the selected nozzle 11A under the spraying conditions read in step S105, and spraying the paint P from this selected nozzle 11A onto the surface 1a of the base coating film 1. According to this step S106, it is possible to form a partial uneven shape on the surface 1a of the base coating film 1 by the paint P.

[0050] Step S107 in Fig. 3 is a step for determining whether or not to continue decorative painting after step S106 based on the spraying conditions read in step S105. That is, it is determined that decorative painting is to be continued when it is predicted that the thickness of the decorative coating film will not reach the planned thickness of the decorative pattern 2. On the other hand, it is determined that decorative painting is not to be continued when it is predicted that the thickness of the decorative coating film will reach the planned thickness of the decorative pattern 2. According to this step S107, if decorative painting is to be continued (if "Yes" in step S107), proceed to step S108, and if not (if "No" in step S107), end the decorative painting process.

[0051] 3 is a step for determining whether or not to change the selected nozzle 11A after step S107. According to this step S108, if the selected nozzle 11A is to be changed (if "Yes" in step S108), the process returns to step S104, and the selected nozzle 11A is reset from among the multiple nozzles 11. In contrast, if the selected nozzle 11A is not to be changed (if "No" in step S108), the process returns to step S106, and the paint P is sprayed onto the surface 1a of the base coating film 1 from the same selected nozzle 11A.

[0052] 7 and 8 show an example of a spraying process in which paint P is sprayed from the selected nozzle 11A onto the surface 1a of the base coating film 1. For ease of explanation, this spraying process simulates a case in which each selected nozzle 11A sprays one droplet at a time.

[0053] 7(a) and 8(a), the coating particles Pa adhered to the surface 1a of the base coating film 1 during the first spray from the selection nozzle 11A are layered in the thickness direction, which is the third direction Z, on top of the coating particles Pa during the second spray. This allows the paint P to be applied twice over a portion of the surface 1a of the base coating film 1. By increasing the number of times that the spray process using the selection nozzle 11A is repeated, the layered height of the coating particles Pa in the third direction Z can be increased.

[0054] The number of times the ejection process by the selected nozzle 11A is repeated is not particularly limited, and can be appropriately selected based on the ejection conditions read in step S105. Alternatively, the ejection process by the selected nozzle 11A may be performed a preset fixed number of times.

[0055] As shown in Figures 7(b) and 8(b), some of the coating particles Pa attached to the surface 1a of the base coating film 1 are then fluidized to form an uneven decorative pattern 2. In this decorative pattern 2, the areas corresponding to the selected nozzle 11A become convex portions 2a, and the areas other than the selected nozzle 11A become concave portions 2b. At this time, since the base coating film 1 is formed in advance on the surface Wa of the workpiece W in the first step S101 in Figure 2, the wettability (also called "affinity") and compatibility of the coating particles Pa with the base coating film 1 can be suppressed. As a result, the desired uneven shape of the decorative pattern 2 can be maintained.

[0056] After the third step S103 in Fig. 2 is completed, a clear topcoat paint can be applied to the surface Wa of the workpiece W including the decorative pattern 2, if necessary. The application is performed using a known rotary atomizing head type application device (not shown), and a baking process is performed after the application. This baking process is performed under processing conditions at a higher temperature and for a longer time than the drying process in step S102.

[0057] When a clear topcoat paint is used, specifically, an organic solvent diluted paint such as amino-acrylic resin, amino-alkyd resin, acrylic resin, amino oil-free alkyd resin, silicon polyester resin, fluororesin, urethane resin, etc. can be used.

[0058] The effects of the above-mentioned first embodiment will be described below.

[0059] In the coating method of the first embodiment, a base coating film 1 is formed on the surface Wa of the object W in the first step S101. After that, the base coating film 1 formed in the first step S101 is dried in the second step S102. This allows the base coating film 1 to be fixed to the surface Wa of the object W. In the third step S103, after the second step S102, paint P is sprayed toward the base coating film 1 only from the selected nozzle 11A selected from the multiple nozzles 11 of the inkjet head 10. According to this third step S103, the thickness of the decorative coating film laminated on the surface 1a of the base coating film 1 can be made different between the portion corresponding to the selected nozzle 11A and the portion corresponding to the nozzle other than the selected nozzle 11A. As a result, the surface 1a of the base coating film 1 has a portion where the decorative coating film is laminated and a portion where the decorative coating film is not laminated or where the laminated height is relatively low, and the uneven decorative pattern 2 can be formed by utilizing the thickness difference between these portions.

[0060] Here, the base coating film 1 on the surface Wa of the workpiece W is formed by the paint P becoming a film, and exerts a function of suppressing the flow and smoothing of the paint particles Pa newly sprayed on the surface 1a. Therefore, in a state where the film thickness of only the portion of the base coating film 1 where the paint P is sprayed from the selection nozzle 11A is increased, the leveling of the paint particles Pa thereafter can be suppressed. This makes it possible to maintain the state where the desired uneven shape is formed on the surface 1a of the base coating film 1. As a result, the desired uneven decorative pattern 2 can be formed on the workpiece W using the paint P, which is less expensive than the decorative film.

[0061] Also, by using the same inkjet head 10 in both the first step S101 and the third step S103, it is possible to reduce the cost required to form the decorative pattern 2 on the workpiece W. Moreover, by using the same paint P in both the first step S101 and the third painting step S103, the boundary between the base coating film 1 and the decorative pattern 2 becomes less noticeable, preventing the appearance of the decorative coating from becoming poor.

[0062] As described above, according to the above-mentioned first embodiment, a coating technique capable of forming an uneven decorative pattern 2 on the workpiece W can be provided.

[0063] In the coating method of the first embodiment, when the droplet diameter of the paint P by the multiple nozzles 11 and the number of droplets per spray are set individually, it becomes possible to finely adjust the thickness of the decorative coating film laminated on the surface 1a of the base coating film 1 in the third step S103 for each part corresponding to each selected nozzle 11A. This allows the variety of decorative patterns 2 to be increased.

[0064] Furthermore, in the coating method of the first embodiment, when the paint P is repeatedly sprayed from the selection nozzle 11A multiple times based on the planned film thickness of the decorative pattern 2, the film thickness of the decorative coating film laminated on the surface 1a of the base coating film 1 is gradually increased, so that the decorative pattern 2 having the desired uneven shape can be easily formed. In particular, the process of forming the decorative pattern 2 can be simplified by repeatedly spraying the paint P multiple times from the same selection nozzle 11A.

[0065] Hereinafter, other embodiments related to embodiment 1 will be described with reference to the drawings. In the other embodiments, the same elements as those in embodiment 1 are denoted by the same reference numerals, and the description of the same elements will be omitted.

[0066] (Embodiment 2) As shown in FIG. 9, in the second embodiment, instead of the decorative painting process of the first embodiment (see FIGS. 2 and 3), the process is achieved by sequentially executing the processes from step S104A to step S107A.

[0067] Step S104A is a step for performing the same process as step S104 in embodiment 1. Step S105A is a step for performing the same process as step S105 in embodiment 1. Step S106A is a step for performing the same process as step S106 in embodiment 1. Step S107A is a step for determining whether or not to end decorative painting after step S106A. According to this step S107A, if decorative painting is to be continued (if "Yes" in step S107A), the decorative painting process is ended, and if not (if "No" in step S107A), the process returns to step S106A.

[0068] The rest is the same as in the first embodiment.

[0069] According to the second embodiment, the number of processing steps can be reduced compared to the first embodiment, and the processing involved in the coating method can be simplified.

[0070] In addition, the same effects as those of the first embodiment are achieved.

[0071] The present invention is not limited to the exemplary embodiment described above, and various applications and modifications are possible without departing from the scope of the present invention. For example, the following embodiments can be implemented by applying the above-described embodiment.

[0072] In the above embodiment, the same inkjet head 10 is used in both the first step S101 and the third step S103, but instead, different inkjet heads 10 may be used in the first step S101 and the third step S103. Also, the first step S101 may be performed by a coating method other than the inkjet method.

[0073] In the above embodiment, an example was given of decorative painting using a steel plate constituting an automobile body as the object to be coated W, but decorative painting can also be performed on exterior parts other than the automobile body (e.g., a bumper, etc.) if necessary. [Explanation of symbols]

[0074] 1 Base coating 1a surface 2. Decorative patterns 10 Inkjet head 11 Nozzle 11A Select Nozzle P paint W Object to be coated Wa Surface S101 1st step (base painting step) S102 2nd step (fixing step) S103 3rd step (decorative painting step)

Claims

1. A base coating step of forming a base coating film on a surface of a coating object constituting an automobile; a fixing step in which the base coating film formed in the base coating step is fixed to the surface of the substrate by drying; a decorative coating step in which an inkjet head having a plurality of nozzles regularly arranged is placed against the object to be coated, and paint is sprayed only from selected nozzles selected from the plurality of nozzles of the inkjet head to form an uneven decorative pattern on the surface of the base coating film fixed in the fixing step; having the inkjet head is configured to continuously flow the paint between an internal reservoir and an external reservoir; The surface tension of the surface of the substrate is in the range of 20 to 50 N / m, and the surface roughness of the surface of the substrate is in the range of 0.01 to 0.5 μm; The coating method, wherein the viscosity of the coating is in the range of 25 to 110 cps, and the surface tension of the coating is in the range of 10 to 35 N / m.

2. 2. The coating method according to claim 1, wherein in the decorative coating step, a spraying process of spraying paint from the selected nozzle onto the surface of the base coating film is repeated a number of times based on a planned film thickness of the decorative pattern.

3. The coating method according to claim 2 , wherein in the decorative coating step, the spraying process is repeated a number of times using the same selected nozzle.

4. 4. The coating method according to claim 1, wherein in the base coating step, paint is sprayed from the plurality of nozzles of the inkjet head to form the base coating film.

5. 5. The coating method according to claim 1, wherein at least one of the diameter of droplets of paint sprayed from said plurality of nozzles and the number of droplets per spray is set individually.

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