JP2005152841A - Metal tone coating film and wheel for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal tone coating film having high weatherability and easy to be produced. <P>SOLUTION: In the metal tone coating film 1 in which a primer layer 2 composed of powdery paint, a metallic base layer 3, and a clear layer 4 are formed in this order on the surface of a metal substrate 1, the metallic base layer 3 contains a rich coloring pigment 32 and a metallic pigment 31 containing leaved aluminum flake 32, and has a thickness ranging from 3 to 50μm. At least a part of the metallic pigments 31 are oriented along the surface of the clear layer 4, and many rich coloring pigments 32 are distributed at the side near the primer layer 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metallic paint formed on the surface of a substrate such as an aluminum alloy, and a vehicle wheel formed entirely of an aluminum alloy and coated with a metallic paint film.

  For car bodies and parts of automobiles (for example, passenger cars), a metallic silver coating (plating coating) that is reminiscent of a polished surface of the metal is applied to the surface of the base in order to have a high-quality appearance. Has been done. In recent years, in order to further enhance the texture, it has a higher brightness than this metallic silver paint, giving it a high-density feeling that does not make the grainy grain feel like a normal silver metallic paint, and a great shading depending on the visual direction. Metallic paint is required. Various proposals have been made to realize such a metallic coating film.

  In Patent Document 1, a base coating layer (film thickness 100 μm) is formed on an object to be coated, and after the base coating layer is cured, the vapor deposited metal film is crushed thereon to form a metal piece. By forming a coating layer (film thickness 1 μm) of a metallic paint containing a pigment having a pigment concentration of 15% or more, the glitter pigment is oriented along the surface of the base coating layer, and then on the clear It describes that a coating layer (thickness 30 μm) is formed. According to this method of forming a multilayer coating film, a very thin metal piece is used as the glitter pigment, and the base coating layer is cured, so that the glitter pigment is oriented along the surface of the base coating layer. There is an advantage that an appropriate metallic gloss surface can be obtained.

  Patent Document 2 discloses a clear or colored paint (film thickness 12 μm), a paint containing aluminum in the form of flakes having a thickness of 0.01 to 0.2 μm and an aspect ratio of 100 to 300 (film thickness 1 to 3 μm). And a clear coating (film thickness 40 μm) is sequentially applied. According to this metallic finishing method, flaky aluminum (having a specific aspect ratio) is used, and the film thickness of the paint on the clear or colored paint is reduced. There is an advantage that a metallic coating film that can be easily oriented in parallel to the surface, white, excellent in metallic luster, and strong in flip-flop properties can be formed. Patent Document 2 describes that the flip-flop property is enhanced when a dark-colored coating film such as black, brown, or blue is used as the color tone of the coating film made of a colored paint.

In Patent Document 3, a powder primer, a solvent or an aqueous color base coat, a plating-like coat containing an aluminum flake pigment of a smooth thin film (thickness of 1 μm or less) and a solvent or a powder top coat are formed on the surface of the aluminum wheel. And forming a color coat (a color based on black or gray when the appearance design needs are chrome plating). According to this coating film structure, since the film thickness of the plating coat is thin, the aluminum flake pigments are arranged in parallel, the mirror reflection is obtained, and the plating coat exists on the color coat. There is an advantage that a color coat is added to the reflection of aluminum flakes, and a deep color tone is obtained.
Japanese Patent No. 2957560 (page 2-3, FIG. 1) JP-A-11-106686 (page 2-5) JP 2000-140756 A (Page 2-5, FIG. 2)

According to the coating film structure described in each of the above patent documents, a metallic coating film exhibiting metallic luster is obtained, but there are some points to be improved in order to provide practical use. That is, in the coating film structure described in Patent Document 1, since the coating layer of the metallic paint is thin in order to orient the glitter pigment, it is easy to transmit ultraviolet rays, and the base layer existing under the layer is, for example, When formed with a paint containing an epoxy resin, the epoxy group is decomposed to cause a decrease in weather resistance. Even in the coating film structure described in Patent Document 2, since the layer containing scaly aluminum is thin, it cannot be said that the weather resistance is sufficient as in Patent Document 1.
Also, as described in Patent Document 2, when the paint under the oriented aluminum flakes (for example, a powder coating primer layer) is made dark, it is used in a shape with unevenness such as a vehicle wheel. , Flip-flop properties can be improved. However, if the primer layer is made dark as in Patent Document 2, it becomes an obstacle to industrial production. In other words, since a plurality of types of coating are usually performed in a single coating line (a primer layer having a plurality of hues is formed), the same is applied after powder coating of a dark primer layer as in Patent Document 2. Manufacture another product using a powder coating machine. At this time, when a general light primer layer is powder-coated, the remaining dark powder coating material is mixed, and the primer layer is liable to have an unclear (turbid) hue. In particular, in the case of vehicle casting wheels, etc., in which the primer layer is powder-coated to hide the unevenness of the casting surface, a dedicated coating line is required for each color of the primer layer, which is still an obstacle to industrial production. .
When the four-layer coating structure described in Patent Document 3 can prevent the primer layer from becoming cloudy due to powder coating, it is performed in a coating line that performs coating (three layers) other than metallic coatings. Requires that the object to be coated be painted four times on the painting line, which reduces productivity.

  Accordingly, a first object of the present invention is to provide a metal-tone coating film that has high weather resistance, has a higher brightness than conventional silver coating, and can be efficiently produced with a three-layer coating film. .

  The second object of the present invention is to provide a vehicle wheel having a higher quality than ever before.

  In order to achieve the first object, a metal-tone coating film according to the first invention comprises a primer layer made of a powder paint formed on the surface of a metal substrate, and a metallic base formed on the primer layer. And a clear layer formed on the metallic base layer, the metallic base layer comprising a metallic pigment containing leafed metal flakes and a dark pigment, and in a range of 3 to 50 μm. The metallic pigment has a certain thickness, and at least a part of the metallic pigment is oriented along the surface of the clear layer, and the dark pigment is dispersed on the side close to the primer layer. is there.

  In the metal-tone coating film of the first invention, the metal flakes are preferably vapor-deposited aluminum flakes having an average particle size of less than 10 μm. In order to eliminate the rough appearance, it is preferable that the average particle diameter is less than 1 μm.

  In the metal-tone coating film of the first invention, the metallic base layer may contain a microgel in the vicinity of the interface with the clear layer.

  In order to achieve the first object, the metallic coating film of the second invention comprises a primer layer made of a powder coating formed on the surface of a substrate, a metallic base layer formed on the primer layer, A clear layer formed on the metallic base layer, and the metallic base layer includes a metallic pigment made of vapor-deposited aluminum flakes and a deep color pigment dispersed on the side close to the primer layer. It has a thickness in the range of ˜50 μm and contains a microgel in the vicinity of the interface between the metallic base layer and the clear layer.

  In the metallic paint film of the first and second inventions, the metallic pigment may further contain crushed aluminum flakes having a thickness of 0.3 to 0.5 μm and a particle size of 5 to 10 μm.

  In order to achieve the second object, the vehicle wheel of the third invention is an aluminum alloy wheel in which the base body has a rim portion and a disk portion, and any one of the metallic paint films is formed on the surface thereof. It is characterized by being formed.

  In the vehicle wheel of the third invention, the primer layer is preferably formed of an epoxy powder coating.

According to the first and second inventions, the metallic base layer formed on the primer layer has a specific thickness, and the leafed metal flakes and / or the deposited aluminum flakes are formed on the surface of the metallic base layer. Further, since the dark pigment is unevenly distributed on the lower layer side of the metallic base layer, it is possible to provide a dense appearance with improved flip-flop properties in the visual direction. Further, since the metallic base layer has a specific thickness, it is difficult for ultraviolet rays to reach the primer layer, and the weather resistance is good. Furthermore, since the metallic base layer contains a colored pigment, the primer layer may be a colorless or light powder primer layer, which can improve flip-flop properties and can be applied to general coatings other than metallic coatings. However, it can be handled with only a single powder coating machine. In addition, since the metallic base layer contains a deep color pigment, the metallic tone more than the conventional four-layer structure can be expressed with a three-layer structure, and the cost can be reduced at a low cost.

  According to the present invention, since the surface of the wheel is coated with a coating film having a higher brightness than the conventional metallic silver coating, a vehicle wheel with an increased high texture that can be reminiscent of a polished surface of metal is obtained. be able to.

Details of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a diagram schematically showing a cross section of the metallic coating film of the present invention. In FIG. 1, reference numeral 1 denotes a substrate formed of a metal such as Al, Mg, Fe or an alloy thereof, and three layers of a powder primer layer 2, a metallic base layer 3 and a clear layer 4 are coated on the surface thereof. A film is formed. Usually, before the coating film is formed, a pretreatment is applied to the surface of the substrate 1 in order to enhance the corrosion resistance. When the substrate 1 is an aluminum alloy, it is preferable to perform a chemical conversion treatment represented by alkali degreasing and chromate treatment. When the chromate treatment is performed, the chemical conversion film is formed to have an adhesion amount of 3 mg / m ² or more (preferably 5 to 20 mg / m ² ). The substrate 1 after the chromate treatment is washed with water and dried.

  The powder primer layer 2 is formed to a thickness of, for example, 80 to 100 μm by applying and baking a powder coating containing a solid resin finely pulverized to several μm to several tens of μm by a known method (spray etc.). . When the substrate 1 is an aluminum alloy, for example, an epoxy powder paint or an acrylic powder paint is used as the powder paint. Among these powder coatings, epoxy powder coatings (glycidyl ether type (for example, bisphenol A type), glycidyl ester type, glycidyl amine type, cyclic oxirane type epoxy resin having good adhesion to metal due to the orientation of hydroxyl groups. Is mainly used). Among the epoxy-based powder coatings, from the viewpoint of cost and adhesion to the substrate, it is particularly composed of a glycidyl group / carboxyl group cross-linked epoxy resin having an acid-terminated polyester resin as a curing agent, and has a high solid content concentration (40 ~ 60 mass%) Epoxy / polyester powder coating is preferred. By baking the epoxy polyester / hybrid powder coating material at a temperature of 150 to 180 ° C. for 10 to 30 minutes, a smooth and strong polymer cross-linked coating film is formed.

  The metallic base layer 3 is formed such that a metallic pigment 31 containing leafed metal flakes and a deep color pigment 32 are dispersed in a binder resin and have a thickness in the range of 3 to 50 μm. The metallic pigment 31 is formed of a metal such as aluminum, titanium, nickel, gold, or silver, and will be described below with an example of aluminum flakes. Many of the flat (scale-like) flakes that become the metallic pigment 31 are unevenly distributed in the vicinity of the interface with the clear layer 4 so as to be aligned (aligned) along the clear layer 4 in parallel. Leafed aluminum flakes are used to facilitate flake orientation. Leafed aluminum flakes can be obtained by coating with saturated fatty acids (eg stearic acid). This aluminum flake is oriented parallel to the clear layer and has a thickness of 0.1 to 1 μm and a particle size of 1 μm or more and 20 μm or less in order to obtain a coating film having a high brightness feeling by reflected light or interference light. It is preferable that the flakes are thin films in the range of.

  Leafed vapor deposited aluminum flakes can also be used. These vapor-deposited aluminum flakes are produced by vapor-depositing aluminum on the surface of a plastic film and then crushing and dissolving and removing the base material. The thickness is 0.01 to 0.1 μm, and the particle size is 0.1 μm or more and 1 μm. Since the flakes are in the following ranges, they can be oriented in parallel along the clear layer 4. Further, in the present invention, it is possible to obtain a higher brightness feeling by adding vapor deposition aluminum flakes together with leafed aluminum flakes. Furthermore, in the present invention, it is possible to create another design feeling by adding ground aluminum flakes in addition to the leafed aluminum flakes and / or vapor-deposited aluminum flakes.

In the present invention, for example, about 1 to 20% by mass of the microgel 33 used as a viscosity modifier for the paint may be added to the metallic base layer 3. The microgel is a gel fine particle in which a polymer is bound in a three-dimensional network and is internally cross-linked, and has a multi-layered particle structure such as a core-shell type or a core hair type, and a primary particle size of 0.02 to 0.00. When it is 1 μm and is used in a powder state as in the present invention, it becomes secondary associated particles having a particle size of several μm to several tens of μm. When a microgel is added to the metallic base layer 3, the orientation of the metallic pigment 31 such as aluminum flakes can be improved. In addition, the microgel floats above the metallic base layer 3 and covers the interface with the clear layer 4. Even if the clear layer is applied without baking the metallic base layer, the paint contained in the clear layer is still metallic. Intrusion into the base layer 3 can be prevented. In order to float the microgel 33 on the upper surface of the metallic base layer, the solubility parameter (SP value, unit: (MJ / m ³ ) ^1/2 ) of the outer side of the microgel is changed to the solubility parameter of the binder resin of the metallic base layer. Is preferably lower.

  The microgel is produced by, for example, emulsion polymerization of a polyfunctional monomer and an acrylic or vinyl monomer copolymerizable therewith, and a white polymer having a specific gravity in the range of 1.1 to 1.5. Particles. When emulsion polymerization is performed, a polymerization initiator such as an inorganic persulfate, a water-soluble organic peroxide, or an azo compound, and an emulsifier such as an anionic type, a cation type, or a zwitterionic type are used. Multifunctional (crosslinkable) monomers include glycol diacrylate, pentaerythritol tetraacrylate, ethylene glycol dimethacrylate ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, trimethylol poppan triacrylate, neopenty route , Diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, divinylbenzene and the like. Examples of acrylic or vinyl monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, and styrene. Typical copolymer compositions include styrene / divinylbenzene copolymer, alkyl acrylate / divinylbenzene copolymer, alkyl acrylate / ethylene glycol / dimethacrylate copolymer.

  As the deep color pigment 32 contained in the metallic base layer 3, for example, an inorganic pigment or an organic color pigment exhibiting a black to brown or blue hue can be used in order to improve flip-flop properties. These pigments include carbon black, lamp black, bone black, graphite, magnetite, hematite (brown), copper / chromium black, cobalt black, copper / manganese / iron black and other inorganic black pigments, ultramarine blue, bitumen, cobalt Examples thereof include inorganic blue pigments such as blue, and organic blue pigments such as phthalocyanine blue.

  The metallic base layer 3 is dissolved in an organic solvent by adding a metallic pigment 31, a dark pigment 32, and, if necessary, a microgel or a binder resin, and is dissolved in an organic solvent by a known method such as spraying. For example, it is formed by baking at a temperature of 150 to 200 ° C. for 10 to 30 minutes after coating on the surface. Here, if the thickness of the metallic base layer 3 is less than 3 μm, the ultraviolet rays easily reach the clear layer, the weather resistance is lowered, and if the thickness exceeds 50 μm, the layer formation time becomes longer. It is set to a range of ˜50 μm. A preferable thickness of the metallic base layer 3 is in the range of 10 to 30 μm.

  The clear layer 4 formed on the metallic base layer 3 can be formed using a solvent-based clear paint or a powder-type clear paint in which a polymer or oligomer is dissolved in an organic solvent. As the clear paint, it is preferable to use an acrylic paint excellent in transparency, gloss, weather resistance and the like, for example, an acrylic solvent paint having a solid content concentration of about 40 to 50% by mass. For the acrylic paint, a thermosetting acrylic resin obtained by solution polymerization of an acrylic monomer and a functional monomer such as an epoxy group, a carboxyl group, or a hydroxyl group is used. In particular, a curable acrylic resin using melamine as a crosslinking agent is used, and it is preferable to use an acrylic solvent paint having a resin solid content concentration of about 40 to 50% by mass. The clear layer 4 is formed to a thickness of, for example, 20 to 30 μm by baking at a temperature of 130 to 180 ° C. after being applied to the surface of the metallic base layer. In this case, the clear layer 4 can be formed by a two-coat one-bake method in which a metallic base layer is applied on the primer layer, and is applied to the surface and then baked.

(Example 1)
A base body (integrated aluminum wheel by low pressure casting) made of an Al—Si—Mg alloy (equivalent to JIS AC4CH material) was subjected to alkali degreasing and chromate treatment, then washed with pure water, dried and pretreated. An epoxy polyester hybrid powder paint (HB2000, manufactured by Nippon Paint Co., Ltd.) was applied to the surface of this substrate and baked at 160 ° C. for 40 minutes to form a primer layer having a thickness of 80 μm. Leafed evaporated aluminum flakes (average thickness 0.05 μm, average particle size 0.5 μm) 15 parts by mass, carbon black 10 parts by mass, microgel (styrene acrylic, particle size 0.3 μm) 20 parts by mass Then, 100 parts by mass of a binder resin (polyester resin) and 100 parts by mass of xylene were kneaded, applied to the surface of the primer layer, and baked at 140 ° C. for 20 minutes to form a metallic base layer having a thickness of 20 μm. An acrylic solvent paint (AW10 clear, manufactured by Nippon Paint Co., Ltd.) having a resin solid content of 50% by mass is applied to the surface of this metallic base layer and baked at 140 ° C. for 20 minutes to form a clear layer having a thickness of 30 μm. As a result, a metallic paint film having the layer structure shown in FIG. 1 was prepared. The following evaluation tests were performed on the coating film.

(1) Lightness (L value): A value measured with a commercially available color difference meter (CR300, manufactured by Minolta Co., Ltd.), which is an index representing luminance (whiteness).
(2) Flip-flop property (FF value): An index representing a brightness difference that varies depending on the visual direction with a value measured by a commercially available metallic feeling evaluation device (ALCOP LMR100, manufactured by Fuji Kogyo Co., Ltd.).

(Example 2)
A base body (integrated aluminum wheel by low pressure casting) made of an Al—Si—Mg alloy (equivalent to JIS AC4CH material) was subjected to alkali degreasing and chromate treatment, then washed with pure water, dried and pretreated. An epoxy polyester hybrid powder paint (HB2000, manufactured by Nippon Paint Co., Ltd.) was applied to the surface of this substrate and baked at 160 ° C. for 40 minutes to form a primer layer having a thickness of 80 μm. Next, the same paint as the metallic base coat layer used in Example 1 was used except for removing 20 parts by weight of microgel (leafed aluminum flakes (average thickness 0.05 μm, average particle size 0 0.5 μm) 15 parts by mass, 10 parts by mass of carbon black, 100 parts by mass of binder resin (polyester resin), and 100 parts by mass of xylene), and similarly, a metallic base layer was formed on the surface of the primer layer. An acrylic solvent paint (AW10 clear, manufactured by Nippon Paint Co., Ltd.) having a resin solid content of 50% by mass is applied to the surface of this metallic base layer and baked at 140 ° C. for 20 minutes to form a clear layer having a thickness of 30 μm. By doing so, another metal-tone coating film of the present invention was prepared. Table 1 shows the results of the evaluation test conducted in the same manner as in Example 1.

(Example 3)
A base body (integrated aluminum wheel by low pressure casting) made of an Al—Si—Mg alloy (equivalent to JIS AC4CH material) was subjected to alkali degreasing and chromate treatment, then washed with pure water, dried and pretreated. An epoxy polyester hybrid powder paint (HB2000, manufactured by Nippon Paint Co., Ltd.) was applied to the surface of this substrate and baked at 160 ° C. for 40 minutes to form a primer layer having a thickness of 80 μm. Next, the same paint as the metallic base coat layer used in Example 1 was used except that ordinary non-leafed aluminum flakes were used (deposited aluminum flakes (average thickness 0.05 μm, average particle size 0 0.5 μm) 15 parts by mass, carbon black 10 parts by mass, microgel (styrene acrylic, particle size 0.3 μm) 20 parts by weight, binder resin (polyester resin) 100 parts by mass, xylene 100 parts by mass) Similarly, a metallic base layer was formed on the surface of the primer layer. An acrylic solvent paint (AW10 clear, manufactured by Nippon Paint Co., Ltd.) having a resin solid content of 50% by mass is applied to the surface of this metallic base layer and baked at 140 ° C. for 20 minutes to form a clear layer having a thickness of 30 μm. By doing so, another metal-tone coating film of the present invention was prepared. Table 1 shows the results of the evaluation test conducted in the same manner as in Example 1.

(Comparative Example 1)
A comparison was made with a conventional metallic paint having a four-layer structure. A color base layer 5 is formed on the surface of the primer layer 2, and a metallic layer 6 having a thickness of 0.5 μm made of vapor-deposited aluminum flakes (average thickness is 0.05 μm and average particle size is 0.5 μm) is formed on the surface. A metallic silver coating film shown in FIG. 2 was prepared in the same procedure as in Example 1 except that. The color base layer 5 is a layer in which an acrylic solvent paint (SP5000, manufactured by Nippon Paint Co., Ltd.) having a resin solid content of 50% by mass is applied and baked at 140 ° C. for 20 minutes to a thickness of 20 μm. The evaluation results of this metallic silver coating film are shown in Table 1.

(Comparative Example 2)
A comparison was made with a metallic coating in which ground aluminum flakes having a conventional three-layer structure were added to the color base layer 5. The metallic silver coating shown in FIG. 3 is performed in the same manner as in Example 1 except that the color base layer 5 containing ground aluminum flakes (average thickness 0.5 μm, average diameter 5 μm) 51 is formed on the surface of the primer layer 2. A membrane was created. Note that the pulverized aluminum flakes in FIG. 3 have the same size as the vapor-deposited aluminum flakes in FIG. The color base layer 5 is a layer in which an acrylic solvent metallic paint having a resin solid content of 50% by mass (SP5000, manufactured by Nippon Paint Co., Ltd.) is applied and baked at 140 ° C. for 20 minutes to a thickness of 20 μm. The evaluation results of this silver coating film are shown in Table 1.

  The metal-tone coating film according to Example 1 from Table 1 has a higher L value and FF value than the coating films of Comparative Example 1 and Comparative Example 2, and a high texture superior to conventional metal-tone silver coating is obtained. I understand that.

It is a figure which shows typically an example of the metal-tone coating film of this invention. It is a figure which shows typically an example of the metal-tone coating film concerning a reference example. It is a figure which shows typically an example of the metal-tone coating film concerning another reference example.

Explanation of symbols

1: substrate, 2: powder primer layer, 3: metallic base layer, 31: metallic pigment, 32: dark pigment, 33: microgel, 4: clear layer, 5: color base layer, 51: ground aluminum flakes, 6: Metallic layer

Claims (7)

A primer layer made of a powder coating formed on the surface of a metal substrate, a metallic base layer formed on the primer layer, and a clear layer formed on the metallic base layer, The metallic base layer includes a metallic pigment including leafed metal flakes and a deep color pigment, and has a thickness in the range of 3 to 50 μm, and at least a part of the metallic pigment is formed on the surface of the clear layer. A metallic paint film characterized by being oriented along and the dark pigment being dispersed on the side close to the primer layer. 2. The metal-tone coating film according to claim 1, wherein the metal flakes are vapor-deposited aluminum flakes having a particle size of less than 10 [mu] m. The metallic coating film according to claim 2, wherein the metallic base layer contains a microgel mainly distributed in the vicinity of the interface with the clear layer. A primer layer made of a powder coating formed on the surface of the substrate, a metallic base layer formed on the primer layer, and a clear layer formed on the metallic base layer, the metallic base The layer includes a metallic pigment composed of vapor-deposited aluminum flakes and a deep color pigment dispersed on the side close to the primer layer, and has a thickness in the range of 3 to 50 μm, and the metallic base layer includes the clear layer and A metal-tone coating film characterized by containing a microgel mainly distributed in the vicinity of the interface. The metallic paint film according to any one of claims 1 to 4, wherein the metallic pigment contains ground aluminum flakes having a thickness of 0.3 to 0.5 µm and a particle size of 5 to 10 µm. 6. The vehicle wheel according to claim 1, wherein the base body is an aluminum alloy cast wheel having a rim portion and a disk portion, and the surface thereof has the metallic coating film formed thereon. . The vehicle wheel according to claim 6, wherein the primer layer is made of an epoxy powder coating material.

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