Inkjet painting method using metallic paints

Abstract

This invention provides an inkjet painting method using metallic paint that can achieve the metallic luster required for the exterior of automobiles and other vehicles. [Solution] In an inkjet coating method in which a metallic paint containing a luminous pigment is applied by an inkjet method, a first metallic paint and a second metallic paint are prepared, each having a 50% average particle size that is different from the other, and a first coating film T1 made of the first metallic paint and a second coating film T2 made of the second metallic paint are applied separately depending on the target coating area.

Description

[Technical Field]

[0001] The present invention relates to an inkjet coating method using a metallic paint containing a luminous pigment. [Background technology]

[0002] An ink composition containing a metallic pigment for use in an inkjet head with a nozzle diameter of 30 μm or less is known, wherein the ratio of the 50% average particle diameter of the metallic pigment to the nozzle diameter (average particle diameter / nozzle diameter) is 0.15 or less, the metallic pigment has foil pieces of aluminum or an aluminum compound, the 50% average particle diameter is 1.0 μm or more and 4.0 μm or less, the maximum particle diameter is 12 μm or less, and the average thickness of the foil pieces is 30 nm or more and less than 100 nm (Patent Document 1). According to this ink composition, it is possible to create printed materials with metallic luster using a printer having an inkjet nozzle with a nozzle diameter of 30 μm or less. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5214103 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, since the above-mentioned conventional ink compositions are mainly applied to printed materials such as paper media, there is a problem in that the metallic luster required for the appearance of automobiles cannot be obtained when these conventional ink compositions are applied to automotive coatings.

[0005] The problem that this invention aims to solve is to provide an inkjet coating method using metallic paint that can obtain the metallic luster required for the exterior of automobiles and the like. [Means for solving the problem]

[0006] The present invention solves the above problem by preparing a first metallic paint and a second metallic paint, each having a 50% average particle size of different luminous pigments, and applying the first metallic paint and the second metallic paint separately using an inkjet method according to the desired application area. [Effects of the Invention]

[0007] According to the present invention, it is possible to obtain the metallic luster required for the exterior of automobiles, etc. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an example of an inkjet coating apparatus for carrying out an inkjet coating method according to one embodiment of the present invention. [Figure 2] Figure 1 is a side view showing the inkjet coating apparatus, and is a view taken along arrow II in Figure 1. [Figure 3] Figure 1 is a diagram showing an example of an inkjet coating unit. [Figure 4] This is a plan view (viewed from arrow IV in Figure 1) showing an inkjet coating method according to one embodiment of the present invention. [Figure 5] This graph shows the relationship between the particle size of the luminous pigment contained in metallic paint and the force acting on the luminous pigment. [Figure 6] This is a cross-sectional view of a wet coating film showing the relationship between the particle size of the luminous pigment contained in metallic paint and the liquid crosslinking adhesion force acting on the luminous pigment. [Figure 7] This is a cross-sectional view of a wet coating showing the relationship between the viscosity and surface tension of a metallic paint. [Figure 8] This is a schematic diagram illustrating the behavior of luminous pigments with different particle sizes. [Figure 9] This graph shows the relationship between liquid crosslinking adhesion and viscosity for examples and comparative examples of metallic coatings according to the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, an exemplary embodiment for implementing the present invention will be described with reference to the drawings. The present invention is an inkjet coating method for applying a metallic paint containing a glitter pigment by an inkjet method. In particular, a first metallic paint and a second metallic paint having different average particle diameters of 50% of the glitter pigment are prepared, and these first metallic paint and second metallic paint are applied separately according to the target application site. The coating method of the present invention is not particularly limited, but can be applied to the coating process of automotive parts such as the outer panel, inner panel, or bumper of an automobile body. In the following, first, an example of an inkjet coating unit for implementing the coating method of the present invention and an inkjet coating apparatus including the same will be described. Next, an example of a metallic paint used in the coating method of the present invention will be described. Finally, an embodiment of the coating method of the present invention will be described.

[0010] 《Embodiment of Inkjet Coating Apparatus 1》 FIG. 1 is a perspective view showing an example of an inkjet coating apparatus 1 for implementing an inkjet coating method according to an embodiment of the present invention. FIG. 2 is a side view showing the inkjet coating apparatus 1 of FIG. 1, a view taken in the direction of arrow II in FIG. 1. FIG. 3 is a configuration diagram showing an example of the inkjet coating unit 2 of FIG. 1. The metallic paint according to the present invention can be obtained by adjusting the particle diameter of the glitter pigment and the paint viscosity based on conventionally known paints such as photocurable paints including ultraviolet curable paints, thermosetting paints, and two-component curable paints. In the following embodiments, the present invention will be described by taking as an example a metallic paint based on an ultraviolet curable paint. However, the present invention may be a metallic paint based on a thermosetting paint or a two-component curable paint.

[0011] As shown in FIGS. 1 and 2, the inkjet coating apparatus 1 of this example includes a coating unit 2 and an ultraviolet irradiation unit 3. The coating unit 2 applies an ultraviolet curable metallic paint 5 to the coating surface 4 and is attached to the robot hand of the coating robot 6 and moves relative to the coating surface 4 along a predetermined movement locus 7.

[0012] The ultraviolet irradiation unit 3 is positioned behind the coating unit 2 in the direction of movement along the movement trajectory 7, and irradiates ultraviolet light toward the coating surface 4. In other words, the ultraviolet irradiation unit 3 has the function of curing the wet coating film 55 applied to the coating surface 4 by irradiating it with infrared light after the coating unit 2 has applied the paint.

[0013] Figure 3 is a configuration diagram showing an example of the inkjet coating unit 2 of this embodiment. Since the inkjet coating unit 2 of this example is widely known by the name "inkjet coating apparatus," the term "ink" will be used in this specification. However, since the object to be painted according to the present invention is an automobile body such as the outer / inner panels and bumpers, this ink actually means "automotive paint" (the above-mentioned ultraviolet-curing metallic paint). The inkjet coating unit 2 has the advantage of significantly reducing the amount of paint dust scattered compared to air atomizing spray guns and rotary atomizing spray guns, thus significantly improving the efficiency of paint use and providing a remarkably high improvement in the working environment.

[0014] The coating unit 2 of this embodiment includes a nozzle 21 having a paint introduction section 211, a paint chamber 212, and a paint discharge section 213; a needle 22 with at least its tip 221 positioned in the paint chamber 212 and the tip 221 being capable of reciprocating in the axial direction Y toward the discharge section 213; an actuator 23 that moves the needle 22 forward and backward in the axial direction Y such that the tip 221 approaches the discharge section 213 when the needle 22 moves forward and moves away from the discharge section 213 when the needle 22 moves backward; a pressure sensor 24 that detects the pressure of the paint 5 in the paint chamber 212; and a control unit 25 that controls the actuator 23.

[0015] The nozzle 21 has a hollow housing 214 made of a metal, resin, or ceramic material, with an introduction section 211 formed on one side, a discharge section 213 formed at the tip, and a paint chamber 212 formed inside. The paint 5 is introduced from the introduction section 211 into the paint chamber 212 and is pushed by the needle 22 to be discharged (dripped) to the outside from the discharge section 213. The inside of the housing 214 is liquid-tightly partitioned into the paint chamber 212 and the actuator chamber 115 by a sealing member 223.

[0016] The needle 22 is a needle-shaped rod made of metal, resin, or ceramic material, with its tip 221 positioned in the paint chamber 212 and its base end 222 positioned in the actuator chamber 115, with a sealing member 223 provided between them. An actuator 23 is fixed to the base end 222 of the needle 22. The needle 22 is provided within the housing 214 so as to be movable in the axial direction Y.

[0017] The actuator 23 is, for example, made up of multiple stacked piezoelectric elements and has the characteristic of extending and contracting in the axial direction Y in response to the voltage applied to the electrodes. The voltage to the actuator 23 is applied by the control unit 25, and by applying voltage to the actuator 23 according to a command signal from the control unit 25, the needle 22 can be moved forward and backward in the axial direction Y. Alternatively, the stroke start position of the needle 22 may be controlled based on the pressure of the paint 5 in the paint chamber 212 detected by the pressure sensor 24.

[0018] The paint 5 in this embodiment is the ultraviolet-curing paint described above, and although details will be described later, it is stored in the paint tank 51 in a state adjusted to an appropriate viscosity and supplied by the paint pump 53 via the paint piping 52. Alternatively, paint piping may be provided to return the paint 5 introduced into the paint chamber 212 of the nozzle 21 to the paint tank 51, and the paint 5 may be supplied while circulating.

[0019] Returning to Figure 1, in this embodiment, the painting apparatus 1 has an ultraviolet irradiation unit positioned behind the inkjet coating unit 2, which was described with reference to Figure 3, in the direction of movement along the movement trajectory 7. The ultraviolet irradiation unit 3 is fixed directly or indirectly to the coating unit 2 and moves along the movement trajectory 7 together with the coating unit 2, which is fixed to the robot arm of the painting robot 6.

[0020] The ultraviolet irradiation unit 3 is equipped with an ultraviolet lamp that irradiates ultraviolet light toward the coated surface 4. Here, ultraviolet light is an invisible electromagnetic wave with a wavelength of 10 nm to 400 nm, and its wavelength is shorter than that of visible light. Ultraviolet light is sometimes classified into UV-A (380 to 315 nm), UV-B (315 to 280 nm), and UV-C (280 to 100 nm) depending on its wavelength.

[0021] The ultraviolet lamp used in the ultraviolet irradiation unit 3 of the coating apparatus 1 of this embodiment can be any lamp that emits ultraviolet light at a wavelength that properly cures the ultraviolet-curable paint 5. Therefore, ultraviolet lamps with wavelengths of 10 to 400 nm, including UV-A, UV-B, and UV-C as described above, can be used. However, if ultraviolet light with a wavelength of less than 200 nm is used, oxygen in the air is activated and ozone is generated. From the viewpoint of suppressing ozone generation, it is more preferable to use an ultraviolet lamp with a wavelength of 200 nm or more.

[0022] Furthermore, if painting is to be performed from left to right, in the opposite direction to the movement trajectory 7, as shown in Figure 2, the robot arm should be rotated 180 degrees so that the ultraviolet irradiation unit 3 is positioned to the left of the coating unit 2, and then the coating unit 2 and the ultraviolet irradiation unit 3 should be moved to the right.

[0023] The present invention is an inkjet coating method that involves preparing a first metallic coating and a second metallic coating, each having a 50% average particle size different from the other, and applying these first and second metallic coatings according to the target coating area. Therefore, the coating apparatus 1 for implementing this method is a system that includes at least two coating units 2, each containing a coating tank 51 as shown in Figure 3.

[0024] Embodiments of the UV-curing paint of the present invention As the UV-curable paint used in the coating method of this embodiment, a paint can be used which is obtained by compounding a known UV-curable resin composition with a late-stage pigment and, if necessary, a colorant as well as known paint additives (for example, defoaming agents such as silicone oil, fluorine-based surfactants, silicone-based surfactants, leveling agents such as acrylic copolymers, thickeners, and viscosity reducers). UV-curable resin compositions are broadly classified into UV radical-curable resin compositions and cationic-curable resin compositions, but either type of UV-curable resin composition can be used in the coating apparatus 1 of this embodiment.

[0025] UV radical-curable resin compositions comprise a UV-curable monomer or prepolymer and a photoradical polymerization initiator. The UV-curable monomer or prepolymer may be a monomer or prepolymer having multiple ethylene-based unsaturated groups in its molecule, or a mixture thereof. Typical examples include epoxy acrylate resins, urethane acrylate resins, thermosetting acrylic resins, and thermosetting polyester resins.

[0026] Typical photoradical polymerization initiators used in combination with UV-curable monomers or prepolymers include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and other benzoin and its alkyl ethers; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, and 2-hydroxycyclohexylphenyl ketone. These include acetophenones such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one; anthraquinones such as 2-methylanthraquinone and 2-amylanthraquinone; thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone or xanthones; and so on.

[0027] These photoradical polymerization initiators are generally used in a ratio of 0.1 to 30 parts by weight, particularly 1 to 25 parts by weight, per 100 parts by weight of the UV-curable resin component described above. In addition, at least one known and conventional photopolymerization accelerator, such as a benzoic acid-based or tertiary amine-based agent, may be used in combination with the photoradical polymerization initiator.

[0028] In contrast, the cationic curable resin composition contains an ultraviolet curable epoxy resin as a resin component and a cationic ultraviolet polymerization initiator as a photopolymerization initiator.

[0029] UV-curable epoxy resins contain epoxy resin components having an alicyclic group in the molecule and adjacent carbon atoms of the alicyclic group forming an oxirane ring. For example, epoxy compounds having at least one epoxycycloalkane group in the molecule, such as an epoxycyclohexane ring or an epoxycyclopentane ring, are used alone or in combination. Suitable examples of UV-curable epoxy resins include vinylcyclohexene diepoxide, vinylcyclohexene monoepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carbonate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-m-dioxane, bis(3,4-epoxycyclohexyl) adipate, and limonene dioxide.

[0030] Furthermore, cationic ultraviolet polymerization initiators used in combination with the epoxy resins described above decompose upon exposure to ultraviolet light, releasing Lewis acids, which polymerize epoxy groups. Suitable examples include aromatic iodonium salts, aromatic sulfonium salts, aromatic selenium salts, and aromatic diazonium salts.

[0031] The ultraviolet-curable paint used in the coating method of this embodiment includes at least two types of metallic paints, namely a first metallic paint and a second metallic paint. The luminous pigment is not particularly limited, but mainly consists of at least one of aluminum, indium, titanium, manganese, vanadium, aluminum compounds, indium compounds, titanium compounds, manganese compounds, or vanadium compounds. The first metallic paint and the second metallic paint are metallic paints in which the 50% mean particle diameter of the luminous pigment differs from each other. The 50% mean particle diameter is defined as the particle diameter in which the proportion of particles less than or equal to the 50% value of the cumulative distribution function of the particle diameter distribution is 50%, and is also called the median diameter.

[0032] The UV-curable paint used in the painting method of this embodiment is not particularly limited, but the 50% average particle diameter of the glitter pigment in the first metallic paint is less than 1 μm, while the 50% average particle diameter of the glitter pigment in the second metallic paint is 1 μm or more. That is, the 50% average particle diameter of the glitter pigment in the first metallic paint is at the nano level (for example, 200 to 800 nm), while the 50% average particle diameter of the glitter pigment in the second metallic paint is at the micron level (for example, 1 to 5 μm).

[0033] And the UV-curable paint used in the painting method of this embodiment is not particularly limited, but the liquid cross-linking adhesion force of the first metallic paint is 0.72 N / m or more, while the liquid cross-linking adhesion force of the second metallic paint is less than 0.72 N / m. The liquid cross-linking adhesion force refers to the adhesion force between two particles or between a plane (a particle with an infinite diameter) and a particle caused by the cross-linking of a liquid. It is the most dominant among the adhesion forces between fine particles in the gas phase and can be about one order of magnitude larger than the van der Waals force. Also, the UV-curable paint used in the painting method of this embodiment is not particularly limited, but the viscosity of the first metallic paint is 100 cP or more.

[0034] Figure 5 is a graph showing the relationship between the particle diameter of the glitter pigment contained in the metallic paint and the force acting on the glitter pigment. In the glitter pigment contained in the metallic paint, as shown in the figure, the liquid cross-linking adhesion force F l , the van der Waals force F w , the electrostatic force F e , and the gravitational force F g act. When the particle diameter of the glitter pigment is in the range of 10 -2 to 10 1 μm, as shown in the figure, the liquid cross-linking adhesion force F l , the van der Waals force F w , and the electrostatic force F e act, but since the van der Waals force F w is less than or equal to one-tenth of the liquid cross-linking adhesion force F l , it can be said that the liquid cross-linking adhesion force F l is dominant. And according to the empirical rule, the liquid cross-linking adhesion force F l(F) is proportional to the 7 / 3 power of the particle size r of the luminous pigment. l ∝r 7 / 3 ).

[0035] Figure 6 is a cross-sectional view of a wet coating film showing the relationship between the particle size of the luminous pigment contained in the metallic paint and the liquid crosslinking adhesion force acting on the luminous pigment in the wet coating film. As described above, the liquid crosslinking adhesion force F l (F) is proportional to the 7 / 3 power of the particle size r of the luminous pigment. l ∝r 7 / 3 Therefore, as shown in the left diagram of Figure 6, if the particle size of the luminous pigment is large, the liquid crosslinking adhesion force F l When the particle size of the luminous pigment is small, as shown in the right diagram of Figure 6, the liquid crosslinking adhesion force F l It becomes larger. And the liquid crosslinking adhesion force F l A large value means that the adhesion between particles of the luminous pigment is strong, making the particles of the luminous pigment more prone to aggregation. In contrast, the liquid crosslinking adhesion force F l A small size means that the adhesion between particles of the luminous pigment is small, making it difficult for the particles of the luminous pigment to aggregate.

[0036] Figure 7 is a cross-sectional view of a wet coating showing the relationship between the viscosity and surface tension of a metallic paint. As shown in the left panel of Figure 7, when the viscosity of the metallic paint is low, the surface tension of the wet coating is low, and as shown in the right panel of Figure 7, when the viscosity of the metallic paint is high, the surface tension of the wet coating is high. Furthermore, when the surface tension is high, the particles of the luminous pigment tend to aggregate easily, while when the surface tension is low, the particles of the luminous pigment tend not to aggregate easily.

[0037] Figure 8 is a schematic diagram showing the behavior of luminous pigments with different particle sizes. The luminous pigment contained in the first metallic paint of this embodiment has a 50% average particle size of less than 1 μm and a viscosity of 100 cP or more, so the liquid crosslinking adhesion force F lBoth the surface tension and the particle size are high. Therefore, when these nano-level luminous pigments are in close proximity, they aggregate and self-assemble. The inventors have confirmed that this self-assembly of luminous pigments is active in the region where the 50% average particle size is less than 1 μm. In addition, increasing the viscosity of the metallic paint also increases the surface tension, further promoting self-assembly. The luminous pigments that aggregate through self-assembly then become reflectors, which form a mirror-like coating.

[0038] The photograph shown in the lower right of Figure 8 is an SEM image of a cross-section of the coating film of the first metallic paint, and it can be seen that the flaky luminous pigments (black objects) contained in the coating film are aggregated, aligned, and layered.

[0039] In contrast, the luminous pigment contained in the second metallic paint of this embodiment has a 50% average particle size of 1 μm or more and a viscosity of about 100 cP, so the liquid crosslinking adhesion force F l Both the surface tension and the particles themselves are relatively low. Therefore, even when these micron-level luminous pigments are close together, they do not aggregate or self-organize. Consequently, the coating film of the second metallic paint exhibits only the metallic color (such as gray) of the luminous pigments.

[0040] Figure 9 is a graph showing the relationship between liquid crosslinking adhesion and viscosity for examples and comparative examples of metallic coatings according to the present invention. Example 1 of the present invention is a second metallic coating containing a luminous pigment with a 50% average particle size of 1.8 μm and adjusted to a viscosity of 100 cP. Example 2 is a first metallic coating containing a luminous pigment with a 50% average particle size of 0.7 μm and adjusted to a viscosity of 200 cP. Example 3 is a first metallic coating containing a luminous pigment with a 50% average particle size of 0.4 μm and adjusted to a viscosity of 500 cP. The comparative example is the metallic coating of Patent Document 1, which contains a luminous pigment with a 50% average particle size of 1 to 4 μm and adjusted to four viscosity levels from 1 to 5 cP. The conditions for these examples and comparative examples are shown in Table 1 below. The liquid crosslinking adhesion in the table was calculated using the following formula obtained from empirical rules.

number

[0041] As shown in Figure 9, in the first metallic paint, where the liquid crosslinking adhesion strength is 0.72 N / m or more and the viscosity is 100 cP or more, the luminous pigment self-organizes and aggregates, making it possible to obtain a glossy coating film including a mirror finish. On the other hand, in the second metallic paint, where the liquid crosslinking adhesion strength is less than 0.72 N / m, the luminous pigment does not self-organize and aggregate, making it possible to obtain a non-glossy coating film exhibiting the metallic color of the luminous pigment.

[0042] Embodiments of the coating method of the present invention Next, embodiments of the coating method of the present invention will be described. Figures 4(A) to 4(C) are plan views (viewpoint of arrow IV in Figure 1) showing an inkjet coating method according to one embodiment of the present invention. The solid and dashed lines in Figure 4 are spaced apart to make it easier to understand the composition of the coating films T1 and T2, but in reality, the coating films T1 and T2 are applied in contact with each other. The present invention is an inkjet coating method that applies a metallic paint containing a lustrous pigment using an inkjet method, and in particular, a first metallic paint and a second metallic paint having different 50% average particle sizes of the lustrous pigment are prepared, and these first metallic paint and second metallic paint are applied according to the target coating area.

[0043] As described above, when using a first metallic paint containing a luminous pigment with a 50% average particle size of less than 1 μm and a second metallic paint containing a luminous pigment with a 50% average particle size of 1 μm or more, as shown in Figure 4(A), the first coating film T1 made of the first metallic paint (shown by a solid line) and the second coating film T2 made of the second metallic paint (shown by a dashed line) can be painted in multiple rows. Painting in this manner makes it possible to obtain a coating with a design in which glossy coating films T1 and non-glossy coating films T2 are arranged alternately.

[0044] Alternatively, as shown in Figure 4(B), a first coating T1 made of the first metallic paint, indicated by a solid line, and a second coating T2 made of the second metallic paint, indicated by a dashed line, may be painted alternately along a single line.

[0045] Alternatively, as shown in Figure 4(C), a first coating T1 made of the first metallic paint indicated by a black circle and a second coating T2 made of the second metallic paint indicated by a black triangle may be applied randomly.

[0046] As described above, the inkjet coating method of this embodiment is an inkjet coating method in which a metallic paint containing a lustrous pigment is applied by an inkjet method, and a first metallic paint and a second metallic paint are prepared, each having a 50% average particle size of the lustrous pigment that is different from each other, and the first metallic paint and the second metallic paint are applied separately according to the target coating area, thereby making it possible to obtain the metallic luster required for the appearance of automobiles, etc.

[0047] Furthermore, in the inkjet coating method of this embodiment, the 50% average particle size of the first metallic paint is less than 1 μm, and the 50% average particle size of the second metallic paint is 1 μm or more. Therefore, depending on whether or not self-assembly occurs, the coating film made with the first metallic paint will have a high-gloss appearance, and the coating film made with the second metallic paint will have a low-gloss appearance.

[0048] Furthermore, in the inkjet coating method of this embodiment, the liquid crosslinking adhesion strength of the first metallic paint is 0.72 N / m or more, and the liquid crosslinking adhesion strength of the second metallic paint is less than 0.72 N / m. Therefore, depending on whether or not self-assembly occurs, the coating film made with the first metallic paint will have a high-gloss appearance, and the coating film made with the second metallic paint will have a low-gloss appearance.

[0049] Furthermore, in the inkjet coating method of this embodiment, since the viscosity of the first metallic paint is 100 cP or higher, self-organization is further promoted, and the coating film made of the first metallic paint has an even higher gloss appearance.

[0050] Furthermore, in the inkjet coating method of this embodiment, since the glossy pigment mainly consists of at least one of aluminum, indium, titanium, manganese, vanadium, aluminum compounds, indium compounds, titanium compounds, manganese compounds, or vanadium compounds, depending on whether or not self-assembly occurs, the coating film made with the first metallic paint will have a high-gloss appearance, and the coating film made with the second metallic paint will have a low-gloss appearance.

[0051] Furthermore, since the inkjet coating method of this embodiment applies the first metallic paint and the second metallic paint in multiple rows, it is possible to obtain a design in which a high-gloss coating film and a low-gloss coating film are placed side by side.

[0052] Furthermore, since the inkjet coating method of this embodiment applies the first metallic paint and the second metallic paint alternately in a line, it is possible to obtain a design in which a high-gloss coating film and a low-gloss coating film are arranged in a line.

[0053] Furthermore, since the inkjet coating method of this embodiment applies the first metallic paint and the second metallic paint randomly, it is possible to obtain a design in which high-gloss and low-gloss coating films are randomly arranged. [Explanation of Symbols]

[0054] 1…Painting equipment 2…Coating unit 21…Nozzle 211...Introduction 212…Paint room 213...Discharge part 214… Housing 22... Needle 221...Tip 222...Proximal end 223...Sealing material 23…Actuator 24…Pressure sensor 25... Control Unit 26...Shielding plate 3… UV irradiation unit 31… Ultraviolet rays 4…Coated surface 5… UV-curing metallic paint 51…Paint tank 52…Paint piping 53... Paint pump 54...droplet 55...Wet coating 56…Cured coating film 6…Painting robot 7…Movement trajectory T1...First coating T2…Second coating

Claims

1. In an inkjet coating method for applying metallic paint containing a luminous pigment using an inkjet method, An inkjet coating method is provided in which a first metallic paint and a second metallic paint are prepared, each having a 50% average particle size that differs from the other, and the first metallic paint and the second metallic paint are applied separately depending on the target application area.

2. The 50% average particle size of the first metallic paint is less than 1 μm. The inkjet coating method according to claim 1, wherein the 50% average particle size of the second metallic paint is 1 μm or more.

3. The liquid crosslinking adhesion force of the first metallic coating is 0.72 N / m or more. The inkjet coating method according to claim 2, wherein the liquid crosslinking adhesion strength of the second metallic paint is less than 0.72 N / m.

4. The inkjet coating method according to claim 3, wherein the viscosity of the first metallic paint is 100 cP or more.

5. The inkjet coating method according to any one of claims 1 to 4, wherein the luminous pigment mainly consists of at least one of aluminum, indium, titanium, manganese, vanadium, an aluminum compound, an indium compound, a titanium compound, a manganese compound, or a vanadium compound.

6. The inkjet coating method according to any one of claims 1 to 4, wherein the first metallic paint and the second metallic paint are each applied in multiple rows.

7. The inkjet coating method according to any one of claims 1 to 4, wherein the first metallic paint and the second metallic paint are applied alternately along a line.

8. The inkjet coating method according to any one of claims 1 to 4, wherein the first metallic paint and the second metallic paint are applied randomly.

Images