JPH11147069A - Method for forming coating film of three-coating one-baking type high saturation metallic color - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a coating film of a metallic color which is of high saturation and excellent in hiding power and decoration by a method in which a coat of high hiding power, a high saturation coat containing a brightening agent, and a clear coat are formed on metal substrate by a wet on-wet method, and these coats are heated to cure simultaneously. SOLUTION: When a coating film of a high saturation metallic color is formed on a metal substrate, first, the first coat of high hiding power having a hiding film 50 μm or less in thickness is formed on the substrate on which only an electrodeposition coating film or the electrodeposition coating film and an intermediate coating film are formed in turn. Next, the second coat of high saturation containing a brightening agent having a hiding film 50-300 μm in thickness is formed on the first coat by a wet-on-wet method. Next, a clear coat having a hiding film exceeding 300 μm in thickness is formed on the second coat by a wet-on-wet method. After that, the first, second, and third coats are heated to be cured. In this process, coatings for the first and the second coats are selected so that the Munsell value saturation of the final coating film is at the lowest 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

DESCRIPTION OF THE TERMS In the present invention, "the first coat and the second coat are substantially similar in color" means that the hue which is exhibited by the coloring pigment contained in the first coat and the second coat Means that the hues presented together with the coloring pigments contained in the color arrangement of the Munsell color system hue circle (10 hues) are in a close relationship combination. When a high-saturation coating color design is performed using the method of the present invention, if a large difference occurs between the hue of the first coat and the hue of the second coat, the color tone may be different due to thickness unevenness, or the saturation may change or May be reduced, and the overall appearance may be reduced. Therefore, it is preferable that the difference between the two hues does not substantially occur.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a highly saturated metallic coating film on a metal coating object such as an automobile body, and more particularly to a method for forming a metal coating film including an electrodeposition coating film and an intermediate coating film. The present invention relates to a method for sequentially forming a high-concealment first coat, a highly-colored metallic coating film containing a glitter, and a clear coating film on an object.

[0003]

2. Description of the Related Art Automobile bodies, in which aesthetic appearance is important,
The outer layers of motorcycles, electric appliances, and the like, and the outer layers of these components are generally finished with a thermosetting paint having excellent smoothness, sharpness, weather resistance, and the like.
The method of forming this finish coating is to first form a cationic electrodeposition coating film on the substrate, and then to prevent weathering deterioration of the electrodeposition surface due to light transmission of the top coating and to hide the color of the base,
Form a dark gray, gray or white intermediate coat. Next, a thermosetting coloring paint containing a coloring pigment is applied on the intermediate coating film, and a clear coating is applied by so-called wet-on-wet without curing the thermosetting coloring paint. Both the film and the clear coating are heat cured at one time. This method of heating and curing both the colored coating film and the clear coating film at a time is particularly called a “two-coat one-bake method”.

[0004] In general, a vehicle body has a design viewpoint,
That is, in order to tighten the impression of the entire vehicle, a sash black coating film is formed on the window frame (sash) portion of the vehicle or on the edge or lower portion of the vehicle body. The black sash coating is formed after forming the intermediate coating and before forming the colored overcoat. The sash black coating is a black coating as the name implies, and depending on the hue of the colored overcoat formed thereon, the color of the sash black coating may be seen through. . This is even more pronounced with the colorful (high chroma) metallic coatings that consumers have been looking for recently.
As a result, the commercial value is lost.

In general, in the above-mentioned two-coat one-bake method, when a metallic paint is applied and then a clear paint is applied wet-on-wet, the metallic paint and the clear paint are mixed (compatible) with each other. Due to the disorder of the arrangement of the metallic pigments contained in the metallic coating film or the poor adaptability of the above two paints, the irregularities based on the metallic pigment projecting on the surface of the metallic coating film are directly subjected to clear coating. May appear on the film surface. The disorder of the arrangement of the metallic pigments described above causes a reduction in gloss (gloss), or the influence of the unevenness of the metallic pigments reduces the aesthetics of the coating film.

As a method of improving the above problem, for example, Japanese Patent Application Laid-Open No. 1-245881 discloses a method in which metallic paints having different metallic pigment concentrations are applied in two steps without changing the conventional two-coat one-bake method. Thereafter, a method of forming a metallic coating film, in which a clear paint is applied by wet-on-wet, is described. Specifically, first, a base (cationic electrodeposition coating and intermediate coating) is formed on the object to be coated,
After applying a paint having a high metallic pigment concentration as a first step and applying a paint having a low metallic pigment concentration or containing no metallic pigment as a second step, a clear paint is applied on a wet-on-wet basis, Perform baking treatment. In the method described in Japanese Patent Application Laid-Open No. 1-245881, by controlling only the concentration of the metallic pigment in the two kinds of paints, the unevenness caused by the metallic pigment contained in the first-stage coating film is removed. Absorbed by coating with the second coating film, and can be flattened by forming a clear coating film on it, but when a black sash coating film is included as a base, the color of the base is completely There are cases where it cannot be hidden. That is, Japanese Patent Laid-Open No.
Even if the technique described in Japanese Patent No. 245881 is to be practiced, the color of the undercoating film cannot be easily hidden by controlling only the concentrations of the metallic pigments of the two kinds of paints, It is also difficult to achieve high chroma and deep color of the coating film.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to completely hide a base coat including a black sash coat,
It is another object of the present invention to provide a coating method capable of easily forming a metallic color coating film having high saturation and color depth.

[0008]

According to the present invention, (i) the above-mentioned electrodeposition coating film or a metal coating material on which an electrodeposition coating film and an intermediate coating film are formed in this order, Forming a high concealing first coat having a concealing film thickness of 50 μm or less on the intermediate coating film; (ii) forming a concealing film thickness of 50 on the first coat;
forming a bright-agent-containing high-chroma second coat having a thickness of more than 300 μm and exceeding 300 μm by wet-on-wet; (iii)
On the second coat, as a third coat, a concealed film thickness of 3
Forming a clear coat exceeding 00 μm by wet-on-wet, and then (iv) curing all of the first to third coats by heating, so that the saturation of the Munsell value of the final coating film is The present invention provides a method for forming a metallic color coating film, wherein the first coating material and the second coating material are selected so as to be 9 or more.

In the method of the present invention, as the first coat, a coat having a high concealing property (that is, a pigment content is high and there are many pigments having a high concealing property) is used. A high-saturation second coat of the same color, which has a low concealing property containing a brightener (that is, a low pigment content and uses a large amount of highly transparent pigments) is applied in layers, and By controlling both the concealing film thickness and the saturation (chromer) of the Munsell value of the entire formed coating film, a colored film having excellent concealing properties can be formed. In the method of the present invention, by making the first coat and the second coat substantially the same color, it is possible to easily adjust the hue and the color tone of the laminated coating film to be formed, and particularly to increase the chroma in the sash black paint coating portion ( (Munsell value of 9 or more) is possible. In addition, since the high concealment is enabled, light deterioration of the surface of the electrodeposition coating film can be prevented even in a coating step in which the intermediate coating film is omitted, so that the invention can be applied.

In the second aspect of the present invention, crosslinkable resin particles can be incorporated into the coat. The crosslinkable resin particles that can be used in the present invention are, for example, polyfunctional organic resin particles described in Japanese Patent Application No. 58-129066, and the viscosity of the coating film is finely adjusted by the action of the crosslinkable bond. it can. Thereby, even when the interval between each coat formation is short, the next coat is wet-on-wet on the first and second coats, which are the lower coats (i.e., the previously formed uncured coats). Does not mix the upper coating film and the lower coating film.

Further, in the method of the present invention, since the curing of all of the first to third coats can be performed simultaneously by heating, resource saving and energy saving can be achieved.

As another aspect of the present invention, there is also provided an article having a colored coating film formed on the surface layer by the above method.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method of the present invention will be described in more detail.

The metal coated object used in the present invention is not particularly limited as long as it is a metal product which can be subjected to cationic electrodeposition coating. Examples of such a metal coated object include iron,
Examples include steel, aluminum, tin, zinc, and the like, and alloys containing these metals, and plated or vapor-deposited products of these metals. Specifically, the body of an automobile (passenger car, truck, motorcycle, bus, etc.) manufactured using these metal members is exemplified. These metal objects may be in a degreased state, but are preferably subjected to a chemical conversion treatment with a phosphate, a chromate or the like in advance.

Prior to the step (i) of the present invention, an electrodeposition coating film or an electrodeposition coating film and an intermediate coating film are sequentially formed on the above-mentioned metal coating object. As the electrodeposition coating and the intermediate coating used in the present invention, any of conventionally known coatings can be used, and they are applied and cured by a conventional method, respectively.
Form a coating. When only the electrodeposition coating film is formed on the metal coating material, it may vary depending on the type of the metal coating material to be used, but the dry film thickness of the electrodeposition coating film is 10 to 50 μm. Preferably, it is in the range. Similarly, when an intermediate coating film is formed on the electrodeposition coating film, the dry film thickness of each coating film is 10 to 50 μm for the electrodeposition coating film and 15 to 50 μm for the intermediate coating film.
It is preferable that the thickness be in the range of μm. When the thickness of the electrodeposition coating and the intermediate coating exceeds 50 μm,
Defects such as sagging and cracking may occur, and when the coating is thinner than the above lower limits (electrodeposited coating: 10 μm, intermediate coating: 15 μm), the appearance is reduced.

The first coat used in the step (i) may be a metal coating material or a color of the above-mentioned electrodeposition coating film and / or intermediate coating film having a sash black coating film formed on at least a part thereof. Hereinafter, these are collectively referred to as a “base” color.) A high concealment that can conceal the color of the second coat formed thereon and exhibit a visually highly saturated color. It is a functional coating film.

The first coat includes a base resin, a curing agent,
It can be formed from a colored paint comprising a pigment, water and / or an organic solvent.

The base resin suitable for the first coating material is
A thermosetting resin that can be dissolved or dispersed in water or an organic solvent, for example, a thermosetting acrylic resin, polyester resin, epoxy resin, urethane resin, or the like. Particularly, a thermosetting acrylic resin or a thermosetting polyester resin is preferable.

The thermosetting resin used in the method of the present invention preferably has an acid value of 3 to 200, a hydroxyl value of 30 to 200, and a number average molecular weight of 500 to 50,000, more preferably an acid value of 3 to 200. A hydroxyl value of 30 to 200, a thermosetting acrylic resin having a number average molecular weight of 2000 to 50,000, an acid value of 3 to 200, and a hydroxyl value of 30 to 20;
And a thermosetting polyester resin having a number average molecular weight of 500 to 20,000. Examples of the thermosetting acrylic resin include thermosetting acrylic resin A having a hydroxyl group (manufactured by Nippon Paint Co., Ltd., hydroxyl value 45, acid value 15, number average molecular weight 18,000, solid content 50%) or Dianal HR2048 (manufactured by Mitsubishi Rayon) , Thermosetting acrylic resin)
Is mentioned. When the number average molecular weight is less than 2000,
If the coating film performance such as durability is reduced, and if it exceeds 50,000, the smoothness of the film may be reduced, and neither is preferable. Similarly, when the number-average molecular weight of the thermosetting polyester resin suitable for the present invention exceeds 20,000, the appearance of the coating film is reduced, or the number-average molecular weight is 50%.
When the value is less than 0, the coating film performance is deteriorated, and thus both are not preferable.

The coating for the first coat used in the method of the present invention may be either a water-based coating or an organic solvent-based coating. When the first coating material is water-based, a hydrophilic base resin (for example, a resin having a hydroxyl group, a carboxyl group, an amino group, a methylol group, a sulfonic acid group, a polyoxyethylene bond, etc.) among the above-mentioned base resins. ) Can be neutralized with sodium hydroxide or amines, used as a salt, and dissolved or dispersed in water.

When the first coat is prepared as an aqueous solution or aqueous dispersion, the acid value is preferably in the range of 10 to 200 and the hydroxyl value of 30 to 200.

On the other hand, when the coating material for the first coat is made of an organic solvent, an organic solvent usually used in the art (for example, hydrocarbons such as toluene and xylene; ethyl acetate, butyl acetate, ethylene glycol) Ester systems such as monomethyl ether acetate and diethylene glycol monoethyl ether acetate; ether systems such as ethylene glycol monomethyl ether and ethylene glycol diethyl ether; alcohol systems such as n-butanol, isobutanol, propanol and cyclohexanol; methyl ethyl ketone, methyl isobutyl ketone; And a ketone such as cyclohexanone).

The curing agent contained in the coating material for the first coat is generally intended to cross-link and cure the base resin by heating, and examples thereof include amino resins, particularly melamine resins and block isocyanates. Isocyanate compounds or blocked polyisocyanate compounds are also preferred. Particularly preferably, an alkoxymethylmelamine resin or an alkylated melamine resin (particularly, a butylated melamine resin) can be used.

A combination of a base resin and a curing agent suitable for use in the present invention is, for example, a combination of a thermosetting acrylic resin and a melamine resin.

In the method of the present invention, the weight ratio between the base resin and the curing agent in the coating material for the first coat is 90:10 to 40: 6.
0, preferably in the range of 80:20 to 60:40. When the compounding ratio of the curing agent is less than 90:10, the crosslink density of the coating film becomes low, so that the coating film strength is weak.
When the ratio exceeds 40:60, the internal stress of the formed coating film is increased, which may cause cracks and the like, and thus both are not preferred.

The pigment contained in the coating material for the first coat used in the method of the present invention is for imparting a high concealing property to the formed coating film and for exhibiting a metallic color. Metallic pigments such as aluminum powder, bronze powder, copper powder, tin powder, lead powder, zinc powder, iron phosphide, pearl-like metal-coated mica powder, and iron oxide iron; titanium dioxide, carbon black, phthalocyanine blue, and phthalocyanine green , Carbazole violet, anthrapyridine, azo orange, yellow, flavanthrone yellow, isoindoline yellow, azo yellow, induthrone blue, dibromanzathrone red, perylene red, azo red, anthraquinone red, quinacridone red, violet, etc. Pigments;
Barita powder, precipitated barium sulfate, barium carbonate, gypsum,
Clay, silica, white carbon, diatomaceous earth, talc,
Extenders such as magnesium carbonate, alumina white, gloss white, satin white, and mica powder;
Each of these pigments can be used alone,
Also, two or more kinds may be used in combination. In the paint for the first coat,
Among the above pigments, a coloring pigment is an essential pigment component.

The coating material for the first coat used in the method of the present invention may optionally contain a dye in addition to the above-mentioned pigment, to improve light resistance and solubility in water and / or an organic solvent. Excellent dyes are preferred. Specific examples of such dyes include 1: 2 chrome anchor black, 1: 2 chromium complex yellow, and 1: 2 cobalt complex yellow, and one or more selected from these may be blended. it can.

In the method of the present invention, the above-mentioned pigment (and dye) is usually added to the first coat paint in an amount of 10 to 10% based on the resin solid content (ie, the total amount of the base resin and the curing agent) in the paint. It may be contained at 60% by weight.

In another aspect of the present invention, the coating material for the first coat may contain a crosslinkable resin particle to adjust the viscosity at the time of coating. The crosslinkable resin particles are one kind of viscosity control agents (those having a thixotropic property generally known as a "sagging inhibitor"), and are added in order to prevent the interlayer from becoming familiar or reversing after the coating film is formed. obtain. As such crosslinkable resin particles, those which are insoluble in the organic solvent used in the first coating composition and have an average particle diameter of 0.02 to 0.5 μm are preferable. Particles having an average particle diameter of more than 0.5 μm are not preferred because the storage stability of the paint is reduced.

The crosslinkable resin particles may be polymerized with a resin having an emulsifying ability, such as an alkyd resin or a polyester resin synthesized using a monomer having a zwitterionic group in the molecule as a polyhydric alcohol component. It is preferred that the ethylenically unsaturated monomer is emulsified in an aqueous medium in the presence of an initiator. As the monomer having a zwitterionic group in the molecule, a hydroxyl group-containing aminosulfonic acid-type zwitterionic compound is preferable. Specific examples include bishydroxyethyl taurine.

The resin having an emulsifying zwitterionic group in the molecule, which is synthesized using the above monomers, has an acid value of 30 to 150 mgKOH / g, preferably 40 to 15 mgKOH / g.
0 mgKOH / g, and number average molecular weight of 500 to 500
It is preferred to use 0, preferably 700-3000 polyester resins. Both the acid value and the number average molecular weight are the above upper limits (that is, the acid value is 150 mg
And a number average molecular weight of 5000), the handleability of the resin is reduced, and the lower limit (that is, the acid value of 3)
If it is less than 0 mgKOH / g and a number average molecular weight of 500), the resin having an emulsifying ability may be desorbed or may have a reduced solvent resistance when formed into a coating film, which is not preferable.

The ethylenically unsaturated monomer used in the synthesis of the crosslinkable resin particles and emulsion-polymerized includes a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule. 0.1 to 0.1
It is preferable to contain it in the range of 10% by weight. This amount is selected so as to obtain sufficient cross-linking not to dissolve the fine particle polymer in the solvent.

The crosslinkable resin particles used in the present invention are:
In general, a monomer containing a low molecular emulsifier or protective colloid which is contained in an emulsion resin and reduces the performance when formed into a film, and which has two or more radically polymerizable ethylenically unsaturated groups in the molecule. Since it is crosslinked by copolymerization, the coating film is excellent in water resistance, solvent resistance, gloss and the like.

The viscosity of the crosslinkable resin particles can be adjusted by blending them in an amount of 1 to 20% by weight based on the resin solid content in the first coat.

The viscosity of the first coating composition when used in the step (i) may be adjusted to a suitable diluent such as water or an organic solvent commonly used in the art (for example, hydrocarbons such as toluene and xylene; Ester system such as ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate; ether system such as ethylene glycol monomethyl ether and ethylene glycol diethyl ether; alcohol system such as n-butanol, isobutanol, propanol and cyclohexanol : Ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone), and the like, and a mixture thereof, and the temperature is preferably adjusted to 10 to 30 seconds (Ford cup # 4/20 ° C). If the viscosity is lower than the above range, there is a risk of mixing with the paint to be applied next, and, if the viscosity exceeds the above range, it is difficult to handle, and the coating film is dried early,
It is not preferable because the surface of the coating film cannot be covered or repaired by the next coating film to such an extent that it cannot be repaired.

Further, the first coating material may contain, if necessary, a conventionally known curing catalyst in the art, additives such as an ultraviolet absorber and an antioxidant, and various surface conditioners. Good.

Alternatively, the first coating composition used in the method of the present invention may be a conventional intermediate coloring composition.

In the method of the present invention, the first coat has a desired color and a concealing film thickness (a film thickness essential for concealing the underlying color) of 50 μm or less, preferably 4 μm or less.
It is formed by a conventional method such as spray coating so that the thickness is 5 μm or less, particularly 40 μm or less.

In step (ii) of the method of the present invention, the first
On the coat, a high-chroma second coat containing a luminous agent and having a concealing film thickness of more than 50 μm and 300 μm or less is formed.
The second coat is a brilliant colored coating film having a lower hiding power (that is, a lighter hue and a higher saturation) than the first coat.
The second coat is formed on the first coat by wet-on-wet.

The composition of the second coating composition can be mainly composed of a base resin, a curing agent, a pigment, water and / or an organic solvent. The coating can be aqueous or organic solvent-based, including aqueous dispersions and organic solvent dispersions. Second
The method for preparing the coating composition for coating may be a generally known method, similarly to the method for preparing the coating composition for first coating.

A base resin contained in the second coating material,
As the curing agent and the organic solvent, any of those described for the first coat can be used. As the combination of the base resin and the curing agent, for example, acrylic resin /
Melamine resin curing agent system is mentioned, particularly, as acrylic resin, acid value 10-200, hydroxyl value 30-200,
Those having a number average molecular weight of 2,000 to 50,000 are preferred. The compounding ratio of the base resin and the curing agent is preferably in the range of 10 to 60% by weight based on the resin solid content (base resin + curing agent).

The pigment contained in the coating material for the second coat used in the method of the present invention contains a brilliant, for example,
Metallic pigments such as aluminum powder, bronze powder, copper powder, tin powder, lead powder, zinc powder, iron phosphide, pearl-like metal coating mica coating, mica-like iron oxide; titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, Coloring pigments such as carbazole violet, anthrapyridine, azo orange, yellow, flavanthrone yellow, isoindoline yellow, azo yellow, indathrone blue, dibromoanzathrone red, perylene red, azo red, anthraquinone red, quinacridone red, and violet; Barita powder, precipitated barium sulfate, barium carbonate, gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, gloss white, satin white, mica powder, etc. It may be a body pigment, and the like. These pigments can be used alone or in combination of two or more. In the paint for the second coat, a brilliant pigment or a pearlescent pigment is an essential pigment component among the above pigments.

The second coat, like the first coat, may contain a conventionally known dye. The total amount of the pigment and the dye contained in the second coat paint is usually combined with the first coat so as to form a high-saturation coating film having a Munsell value of 9 or more. On the other hand, it is in the range of 1 to 20% by weight.

Here, the Munsell value is a measure representing hue, lightness, and saturation. Among them, the saturation of the Munsell value, which is an important factor in the present invention, can be easily measured using a spectrophotometer.

In the method of the present invention, the color of the first coat and the color of the second coat
The color of the second coat is essentially the same as the color of the first coat, since the purpose is to form a highly saturated coating film in combination with the colors of the coats.

The method of the present invention is characterized in that the hue of the first coat can be finely adjusted by the second coat. Second
By adjusting the total amount of pigment and dye contained in the coating paint to adjust the hiding film thickness and saturation, the undercoat layer (intermediate coating or black coating film for automobile sash)
Hue or color tone combined with the color of the first coat without being affected by the first coat.

As described for the first coat, the viscosity of the second coat can be adjusted by blending the crosslinkable resin particles with the second coat. As the crosslinkable resin particles, the same as those described above can be used. Further, the compounding amount in the paint is 1 to 20% by weight based on the resin solid content in the paint.

The coating material for the second coat used in the step (ii) of the present invention has a viscosity suitable for a diluent (for example,
Water, ethyl acetate, butyl acetate, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, aromatic solvents such as Solvesso 100 and 150 (manufactured by Esso), and a mixture thereof, for 10 to 30 seconds (Ford). (Cup # 4/20 ° C.). If the above viscosity is lower than the above range, there is a risk of mixing with the paint to be applied next, and if it exceeds the above range, it is difficult to handle, and the coating film solidifies early, and the next coating film Is not preferable because surface irregularities may occur to the extent that they cannot be covered or repaired.

Further, the coating material for the second coat may include, if necessary, a curing catalyst, an ultraviolet absorber, and the like conventionally known in the art.
It may contain additives such as antioxidants and various surface conditioners.

In the method of the present invention, the second coat, together with the hue of the first coat, forms a solid color high-color coating film having a Munsell value of 9 or more, and has a concealing film thickness of more than 50 μm and 300 μm or less. The paint is applied by a conventional method such as spray coating so that the thickness is preferably 52 μm or more and 280 μm or less, particularly 55 μm or more and 260 μm or less. Second
Even if the concealing film thickness of the coat is 50 μm or less or 300 μm or more, the composite effect of the color with the first coat is not obtained, and the saturation is not improved to a desired value.

In step (iii) of the method of the present invention, a conventionally known clear coat is formed on the second coat as a third coat by wet-on-wet. After forming the second coat, the clear coat can be formed as a coating film having a concealing film thickness of 300 μm or more after an interval (for example, 3 to 20 minutes) sufficient for the second coat to dry. The clear coat is intended to prevent discoloration of the first and second coats. The clear coating includes a cloudy clear coat (ie, a clear coat solution obtained by adding a highly transparent pigment and / or dye to a clear coat solution), and may be a functional clear coat.

The third coat is usually applied on a wet-on-wet basis, but if it is an aqueous coat, a preheating step may be incorporated before the step (iv).
Such a preheating step comprises, after the formation of the first to third coats, a treatment at 60 to 100 ° C. for 2 to 10 minutes using a conventional heating means such as a warm air heater or a far infrared heater.

In the method of the present invention, in step (iv),
The first to third coats are all baked / cured simultaneously by heating to complete the process. In this step (iv), the coating is carried out at a temperature of 80 to 200 ° C. for 10 to 60 hours.
By heating for minutes, all the uncured coatings,
It means to cure.

[0054]

The present invention will be described below with reference to examples.
The present invention is not limited to the following examples. Department,
All percentages and ratios represent parts by weight, percentages by weight, and percentages by weight, unless otherwise specified.

Preparation of paint 1) Preparation of paint (A) for first coat A paint (A) for first coat was prepared by mixing the following components. Composition Parts by weight Pigment: Shinkasha Magenta RT-343D (Ciba-Geigy, purple pigment) 5.0 Rionogen Red YF (Toyo Ink, red pigment) 1.5 Irgazine Red DPP-BO (Ciba-Geigy, red pigment) 3.7 Bayferox 120FS (manufactured by Bayer Japan, brown pigment) 8.5 Taipaek R-820 (manufactured by Ishihara Sangyo, white pigment) 1.2 Degussa carbon FW-200P (made by Degussa, black pigment) 0.1 base Resin: Thermosetting acrylic resin 67.8 (manufactured by Nippon Paint Co., Ltd., hydroxyl value 45, acid value 15, number average molecular weight 21,000, solid content 55%) Diamond HR2048 31.2 (manufactured by Mitsubishi Rayon, thermosetting acrylic resin, Uban 20N60 40.0 (Mitsui Cytec, butylated melamine resin, solid content 60%) Crosslinkable resin particles (Nippon Paint, solid content 20%) 16.0 Surface conditioner: DIS PARON KS273N (Kusumoto Kasei) 0.2 Solvent: n-butanol 4.0 Xylol 7.0 Toluene 13.8 Total 20.0

2) Preparation of First Coating Paint (B) A first coating material (B) was prepared by mixing the following components. Composition Parts by weight Pigment: Taipaque R-820 (Ishihara Sangyo, white pigment) 1.7 Irgazine Red DPP-BO (Ciba-Geigy, red pigment) 5.8 Shinka Sha Magenta RT-343D (Ciba-Geigy, purple pigment) 2.9 Shinkasha Red Y RT-759D (Ciba-Geigy, red pigment) 3.6 Bayferox 120FS (Bayer Japan, brown pigment) 6.0 Base resin: thermosetting acrylic resin 67.8 (Nippon Paint) Manufacture, hydroxyl value 45, acid value 15, number average molecular weight 21000, solid content 55%) Dianal HR2048 31.2 (manufactured by Mitsubishi Rayon, thermosetting acrylic resin, solid content 60%) Uban 20N60 40.0 (Mitsui Scitech) Butylamine melamine resin, solid content 60%) Crosslinkable resin particles (Nippon Paint, solid content 20%) 16.0 Surface conditioner: Dispalon KS273N (Kusumoto Kasei) 0.2 Solvent: n- Ethanol 4.0 xylol 7.0 toluene 13.8 Total 200.0

3) Preparation of second coating composition (a) The following composition was blended to prepare a second coating composition (a). Composition Parts by weight Pigment: Shinkasha Magenta RT-343D (Ciba-Geigy, purple pigment) 1.3 Irgagin Red DPP-BO (Ciba-Geigy, red pigment) 3.7 Chromophthal Red A2B (Ciba-Geigy, red pigment) 1 0.0 Degussa Carbon FW-200P (made by Degussa, black pigment) 0.1 Exterior Marlin Super Lasset 9.5 (made by Marl, mica powder) Exterior Marlin Highlight Red 4.2 (made by Marl, mica powder) Base resin: heat Curable acrylic resin 72.3 (manufactured by Nippon Paint Co., Ltd., hydroxyl value 45, acid value 15, number average molecular weight 21,000, solid content 55%) Diamond HR2048 33.1 (manufactured by Mitsubishi Rayon, thermosetting acrylic resin, solid content 60) %) Uban 20N60 42.5 (Mitsui Cytec, butylated melamine resin, solid content 60%) Crosslinkable resin particles (Nippon Paint, solid content) 0%) 17.0 surface conditioner: Disparlon KS273N (Kusumoto Chemicals Ltd.) 0.2 Solvent: n-butanol 4.0 xylol 6.1 Toluene 9.8 Total 204.8

4) Preparation of second coating composition (b) The following composition was mixed to prepare first coating composition (b). Composition Parts by weight Pigment: Shinkasha Magenta RT-343D (Ciba-Geigy, purple pigment) 1.0 Irgazine Red DPP-BO (Ciba-Geigy, red pigment) 3.0 Chromophthal Red A2B (Ciba-Geigy, red pigment) 0 .7 Exterior Marlin Super Russet 7.1 (Mal, mica powder) Exterior Marlin Highlight Red 3.2 (Mal, mica powder) Base resin: Thermosetting acrylic resin 72.3 (Nippon Paint, hydroxyl value 45) , Acid value 15, number average molecular weight 21,000, solid content 55%) Dianal HR2048 33.1 (manufactured by Mitsubishi Rayon, thermosetting acrylic resin, solid content 60%) Uban 20N60 42.5 (manufactured by Mitsui Cytec, butylated melamine) Resin, solid content 60%) Crosslinkable resin particles (Nippon Paint, solid content 20%) 17.0 Surface conditioner: DISPARON KS273N Kusumoto Kasei) 0.2 Solvent: n-butanol 4.0 xylol 6.1 Toluene 9.8 Total 200.0

5) Preparation of second coating composition (c) The following composition was blended to prepare second coating composition (c). Composition Parts by weight Pigment: Irgazine Red DPP-BO (Ciba-Geigy, red pigment) 1.9 Chromophthal Red A2B (Ciba-Geigy, red pigment) 1.5 Shinkasha Magenta RT-343D (Ciba-Geigy, purple pigment) 1 .2 Exterior Marlin Super Russet 8.9 (Mal, mica powder) Alpaste 7640 0.1 (Toyo Aluminum, solid content 65%) Base resin: Thermosetting acrylic resin 72.3 (Nippon Paint, hydroxyl value) 45, acid value 15, number average molecular weight 21,000, solid content 55%) Dianal HR2048 33.1 (manufactured by Mitsubishi Rayon, thermosetting acrylic resin, solid content 60%) Uban 20N60 42.5 (manufactured by Mitsui Cytec, butylated melamine) Resin, solid content 60%) Crosslinkable resin particles (Nippon Paint, solid content 20%) 17.0 Surface conditioner: Dispalon KS273N (Kusumoto Kasei ) 0.2 Solvent: n-butanol 4.0 xylol 6.1 Toluene 9.8 Total 200.0

6) Third Coat (Clear Coat) As the third coat, "Olga TO-563 Clear" (acrylic / melamine-curable clear paint) manufactured by Nippon Paint was used.

7) Third coat (turbid clear coat) Pigment: Irgagin Red DPP-B0 and Chromophthal Red A2B were added to clear coat paint "Olga TO-563 Clear".
(All of them were made by Ciba-Geigy) were added and dispersed by 0.5% by weight based on the solid content, respectively, to obtain a turbid clear coat.

Example 1 Dull steel sheet (dimensions: 0.8 mm ×
First, a cationic electrodeposition paint ("Power Top U-50", manufactured by Nippon Paint Co., Ltd.) is applied to the electrode to a dry film thickness of about 20 μm, and baked at 160 ° C. for 30 minutes. A cationic electrodeposition coating was formed. Next, a gray intermediate coating (Nippon Paint Co., Ltd., “Orga P-2 Gray”) was spray-coated on the cationic electrodeposition coating film so as to have a dry film thickness of about 40 μm.
It was baked for 0 minutes (formation of a coating film for base).

Before using the first coat (A) prepared above, diluent: ethyl acetate / toluene / solvesso 100 /
Solvesso 150 = 20/50/20/10
The viscosity was adjusted to 13 seconds (Ford Cup # 4/20 ° C.). The diluted first coat (A) on the undercoating film
To an electrostatic coating machine (manufactured by Randsburg Gema, "Auto
REA ”) at an atomization pressure of 5 kg / cm ² .
Spray coating was performed by stage coating so as to have a dry film thickness of about 10 μm. After the coating, the setting was left for 5 minutes.

Next, the second coat (a) prepared above
Was diluted in the same manner as in the first coat (viscosity: 13 seconds (Ford cup # 4/20 ° C.)). This is referred to as the first
On a wet-on-wet coat, using an electrostatic coating machine, at an atomizing pressure of 5 kg / cm ² , a dry film thickness of about 10 μm
m was spray-coated. After the coating, the setting was left for 5 minutes.

Then, the third coat (clear coat) was diluted with S100 / xylene = 60/40 diluent to a viscosity of 2
Dilute to 0 seconds (Ford Cup # 4/20 ° C.). It was spray-coated on the second coat by wet-on-wet so as to have a dry film thickness of about 40 μm, and the setting was left for 7 minutes. Finally, it was baked and cured at 140 ° C. for 30 minutes to prepare a metallic color coated plate for evaluation.

Example 1 'In the base coat forming step, a black paint for sash (window frame) of an automobile body ("Olga P-2 Sash Black" manufactured by Nippon Paint Co., Ltd.) was applied by intermediate coating and wet-on-wet. A metallic coated plate for evaluation was produced in the same manner as in Example 1 except that spray coating was performed so as to have a dry film thickness of 15 μm and baking was performed at 140 ° C. for 30 minutes.

Example 1 "In the step of forming the undercoating film, on the cationic electrodeposition coating film,
Without intermediate coating, a black paint for sash (window frame) of an automobile body ("Olga P-2 Sash Black" manufactured by Nippon Paint Co., Ltd.) is spray-coated so as to have a dry film thickness of 15 [mu] m. A metallic color evaluation plate for evaluation was produced in the same manner as in Example 1, except that baking for another minute was added.

Example 2 A metallic coated plate for evaluation was produced in the same manner as in Example 1 except that the second coat (a) was changed to the second coat (b).

Example 2 'In the step of forming the undercoating film,
Medium paint and wet-on-wet, black paint for car body sash (window frame) (Nippon Paint, Olga
P-2 sash black ”), spray-coated to a dry film thickness of 15 μm, baked at 140 ° C. for 30 minutes, and changed the second coat (a) to the second coat (b). Except for the above, a metallic coated plate for evaluation was produced in the same manner as in Example 1.

Example 2 "In the undercoating film forming step,
Without intermediate coating, a black paint for sash (window frame) of an automobile body ("Olga P-2 Sash Black" manufactured by Nippon Paint Co., Ltd.) is spray-coated so as to have a dry film thickness of 15 [mu] m. A metallic coated plate for evaluation was produced in the same manner as in Example 1, except that baking for an additional minute was added and the second coat (a) was changed to the second coat (b).

Example 3 The same procedure as in Example 1 was carried out except that the second coat (a) was changed to the second coat (b), and the third clear coat was changed to a turbid clear coat. Was prepared.

Example 3 'In the undercoating film forming step, a black paint for a sash (window frame) of an automobile body (Nippon Paint Co., Ltd., "Olga P-2 Sash Black") was applied by intermediate coating and wet-on-wet. Spray painting to a dry film thickness of 15 μm, baking at 140 ° C. for 30 minutes was added, and the second coat (a) was changed to the second coat (b), and the third clear coat was changed to a cloudy clear coat. Except for the change, a metallic color coated plate for evaluation was produced in the same manner as in Example 1.

Example 3 "In the undercoating film forming step,
Without intermediate coating, a black paint for sash (window frame) of an automobile body ("Olga P-2 Sash Black" manufactured by Nippon Paint Co., Ltd.) is spray-coated so as to have a dry film thickness of 15 [mu] m. Minutes, and then add the second coat (a) to the second coat (b)
Example 1 except that the clear was changed to a cloudy clear
In the same manner as in the above, a metallic color coated plate for evaluation was produced.

Comparative Example 1 Example 1 was repeated except that the dry film thickness of the first coat (A) was 20 μm and the second coat (a) was not applied.
In the same manner as in the above, a colored coating plate for evaluation was produced.

Comparative Example 1 ' The first coat (A) had a dry film thickness of 20 μm, the second coat was not applied, and in the base coat forming step, the intermediate coat and the wet coat were applied on the cationic electrodeposition coat. On-wet, black paint (Nippon Paint, "Olga P-2 Sash Black") for sash (window frame) of car body,
Spray paint to a dry film thickness of 15 μm.
A colored coated plate for evaluation was prepared in the same manner as in Example 1 except that baking was performed at 30 ° C. for 30 minutes.

COMPARATIVE EXAMPLE 1 The first coat (A) had a dry film thickness of 20 μm, the second coat was not applied, and in the base coat forming step, an intermediate coat was applied on the cationic electrodeposition coat. Instead, spray paint a black paint for car body sash (window frame) (Nippon Paint Co., Ltd., Olga P-2 Sash Black) to a dry film thickness of 15 μm and bake at 140 ° C for 30 minutes. Except that, the same as in Example 1,
A colored coating plate for evaluation was prepared.

Comparative Example 2 A colored coating plate for evaluation was prepared in the same manner as in Example 1 except that the first coat was not applied and the dry thickness of the second coat (a) was 20 μm.

Comparative Example 2 ′ The first coat was not applied, the second coat (a) was applied with a dry film thickness of 20 μm, and in the base coat forming step, a medium Spray-coating and wet-on-wet spray coating with black paint for car body sash (window frame) (Nippon Paint Co., Ltd., Olga P-2 Sash Black) to a dry film thickness of 15 μm. A colored coated plate for evaluation was produced in the same manner as in Example 1, except that baking for an additional minute was added.

Comparative Example 2 " The first coat was not applied, and the second coat (a) was applied with a dry film thickness of 20 μm. Without painting, apply a black paint (Nippon Paint Co., Ltd., Olga P-2 Sash Black) for sash (window frame) of the car body.
A colored coating plate for evaluation was produced in the same manner as in Example 1 except that spray coating was performed so as to have a thickness of 5 μm and baking was performed at 140 ° C. for 30 minutes.

Example 4 The first coat (A) was changed to the first coat (B), and
A metallic coated plate for evaluation was produced in the same manner as in Example 1 except that the coat (a) was changed to the second coat (c) and the dry film thickness was changed to 8 μm.

Example 4 'In the step of forming a base coat,
Medium paint and wet-on-wet, black paint for car body sash (window frame) (Nippon Paint, Olga
P-2 Sash Black ”), spray-coated to a dry film thickness of 15 μm, baked at 140 ° C. for 30 minutes, and added the first coat (A) to the first coat (B).
And the second coat (a) was changed to the second coat (c), and the dry film thickness was changed to 8 μm, to produce a solid color coated board for evaluation in the same manner as in Example 1.

Example 4 "In the step of forming the undercoating film,
Without intermediate coating, a black paint for sash (window frame) of an automobile body ("Olga P-2 Sash Black" manufactured by Nippon Paint Co., Ltd.) is spray-coated so as to have a dry film thickness of 15 [mu] m. The first coat (A) was changed to the first coat (B), the second coat (a) was changed to the second coat (c), and the dry film thickness was set to 8 μm. Except for the above, a solid color coated board for evaluation was produced in the same manner as in Example 1.

Method for Determining Concealed Film Thickness Each coating material was separately coated on a black and white test paper for concealed film thickness evaluation to form a coating film. The film thickness at the position where the black and white grid pattern described on the test sample became invisible was measured and defined as the concealed film thickness. The following table summarizes the hiding film thickness of each paint.

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[Table 1] Coating hiding film thickness (μm) First coat (A) 25 First coat (B) 38 Second coat (a) 76 Second coat (b) 100 Second coat (c) 100 Third coat (Clear coat) ≧ 300 Third coat (turbid clear coat) ≧ 300

Preparation of Control Sample In each of the corresponding Examples and Comparative Examples, the color difference was determined in the same manner as in Example 1 except that the dry film thickness of the first coat and the second coat was set to the concealing film thickness shown in Table 1. (ΔE) Measurement control samples (# 1-6, # 1′-6 ′ and # 1 ″ -6 ″) were prepared. The types of the first and second coats used for each control sample and the corresponding Example / Comparative Example numbers are summarized in Table 2 below.

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Table 2 Control sample First coat Second coat Corresponding Example / Comparative Example # 1 (A) (a) Example 1 # 2 (A) (b) Example 2 # 3 ⁺ (A) (b) Example 3 # 4 (B) (c) Example 4 # 5 (A)-Comparative example 1 # 6- (a) Comparative example 2

# 1 ′ (A) (a) Example 1 ′ # 2 ′ (A) (b) Example 2 ′ # 3 ′ ⁺ (A) (b) Example 3 ′ # 4 ′ (B) ( c) Example 4 '# 5' (A)-Comparative Example 1 '# 6'-(a) Comparative Example 2 '

# 1 "(A) (a) Example 1"# 2 "(A) (b) Example 2"# 3 " ⁺ (A) (b) Example 3"# 4 "(B) ( c) Example 4 "# 5" (A)-Comparative Example 1 "# 6"-(a) Comparative Example 2 "In the table, control samples # 3, # 3 'and # 3" were used as the third coat. A cloudy clear coat was used.

Evaluation method Metallic color coated plates for evaluation prepared in Examples 1 to 4, 1 'to 4' and 1 "to 4" and Comparative Examples 1, 2, 1 ', 2', 1 "and 2" The colored coated plate was evaluated for the following items. 1) Measurement of Color Difference (ΔE) The lightness of the evaluation metallic color coated plate and the colored coated plate prepared in the above Examples and Comparative Examples was measured using a color difference meter “SM Color Computer SM-4” manufactured by Suga Test Co., Ltd. Next, the brightness of each control sample was measured in the same manner, and the difference in brightness between each sample and the control sample was defined as a color difference (ΔE). However, the color difference was the absolute value of the difference in lightness.

2) Visual Evaluation (Hiding Sensation and High Saturation of Design) The metallic colored plates for evaluation produced in each of Examples and Comparative Examples were visually evaluated based on the following evaluation criteria.

Evaluation criteria of concealment ○: concealed. Δ: Partly visible. ×: The base is seen through. Evaluation criterion 5 for high chroma of design : Excellent. 4: Excellent. 3: Standard. 2: Slightly inferior. 1: considerably poor.

3) Munsell value The Munsell value was measured using a spectrophotometer (CM-1000 manufactured by Minolta).

Table 3 shows the evaluation results for the above evaluation items.
Summarize in ~ 5. The sign +) in Tables 3 to 5 means that a turbid clear coat was used as the third clear coat.

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[Table 3]

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[Table 4]

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[Table 5]

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According to the present invention, a metallic color coating film that completely conceals the underlying coating film on a metal substrate and has a high chroma of Munsell value of 9 or more and has excellent durability and cosmetic properties can be obtained with high production efficiency. It can be produced effectively. Further, since a coating film whose viscosity can be easily adjusted is used, even when the coating is performed wet-on-wet in a short interval, the upper coating film and the lower coating film are not mixed.

Claims (5)

[Claims] 1. A method comprising: (i) concealing the electrodeposition coating film or the intermediate coating film on a metal substrate on which the electrodeposition coating film and the intermediate coating film are sequentially formed; Forming a high-concealment first coat having a thickness of 50 μm or less; (ii) forming the first coat
Forming a bright-agent-containing high-chroma second coat having a concealing film thickness of more than 50 μm and not more than 300 μm on the coat by wet-on-wet; (iii) forming a third coat on the second coat;
Forming a clear coat having a concealing film thickness of more than 300 μm as a coat by wet-on-wet, and then (iv) heating to cure all of the first to third coats. A method of forming a metallic coating film, wherein the first coating material and the second coating material are selected such that the saturation of the Munsell value becomes 9 or more. 2. The method according to claim 1, wherein a black sash coating is formed at least partially on the electrodeposition coating or on the electrodeposition coating and the intermediate coating. 3. The method of claim 1, wherein the first coat and the second coat are substantially similar in color. 4. The method according to claim 1, wherein the first coat and the second coat include crosslinkable resin particles. 5. An article in which a high chroma metallic color coating film formed by the method according to claim 1 is formed on a surface layer.