JP2002301426A - Method for forming double-layer coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a double-layer metallic coating film excellent in designability, of which the brightness of a highlight part is exhibited by a lower layer, and the brightness of a shade part is exhibited by an upper layer. SOLUTION: In the method, a substrate is coated with a backing shielding metallic coating (A), a transparent metallic coating (B), and a clear coating (C) in turn to form the double-layer metallic coating film. The transparent metallic coating contains 0.5-10 pts.wt. of a metallic coating per 100 pts.wt. of a solid resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decorative metallized film in which the glitter of a highlight portion is a lower metallic coating film, and the glitter of a shade portion is a transparent metallic coating film thereover. The present invention relates to a method for forming a multi-layer metallic coating film having excellent characteristics.

[0002]

2. Description of the Related Art A metallic paint containing a metallic pigment such as aluminum flake is applied, a clear paint is applied to the uncured coating surface, and then the two paint films are cured together by heating. A method for forming a metallic coating film by the coat 1 bake method (2C1B) is known. This method requires only one heat-curing step of the coating film, so that the productivity is high and it is widely used for the top coating of automobile outer panels.

[0003] The thus-obtained metallic coating film has a brilliant feeling in the highlight portion, and has better design properties than the solid color coating film. However, in recent years, the demand for the finished appearance (especially the design) of a top coat applied to an automobile outer panel or the like has been advanced and diversified, and the conventional method of forming a metallic coating by 2C1B meets the demand. Therefore, development of a method for forming a new design coating film is strongly desired. One example is the development of a method for forming a metallic coating film having excellent glitter on both the highlight portion and the shade portion.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate defects in a conventional metallic coating formed by 2C1B, and to provide a metallic coating having excellent glitter in both a highlight portion and a shade portion. We are developing a method for forming a coating film. As a result of diligent research, it was found that a multilayer metallic coating film formed by sequentially applying a base metal concealing metallic paint, a transparent metallic paint containing a specific amount of a metallic pigment, and a clear paint can solve the above-described defects and achieve the object. And completed the present invention.

Thus, according to the present invention, a multi-layer metallic coating film is formed by sequentially applying a metallic paint (A), a transparent metallic paint (B) and a clear paint (C) on a substrate to be coated. A method for forming a multilayer coating film, wherein the content of the metallic pigment in the transparent metallic paint (B) is 0.5 to 10 parts by weight per 100 parts by weight of the resin solid content. You.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for forming a multilayer coating film of the present invention (hereinafter, referred to as “the present method”) will be specifically described.

A substrate to be coated is a substrate on which a multilayer coating film is formed by the present method, and a metal or plastic passenger car, a light car, a motorcycle, a bus, a truck, and other automobile outer panels are particularly suitable. Further, an outer panel for an automobile, which is previously coated with an undercoat paint such as a cationic electrodeposition paint or an ordinary middle coat paint (can be omitted) and cured, is also included as an object to be coated.

Undercoat metallic coating (A): A paint to be applied to an object to be coated prior to the transparent metallic paint (B), which has a glittering brilliancy and has excellent base concealing properties. It is a metallic paint that can form a film. Specifically, it is a liquid paint containing a resin composition, a metallic pigment, and a solvent as main components, and further appropriately blending a solid color pigment, an extender pigment, and other paint additives as needed.

As the resin composition, a thermosetting resin composition for coatings is preferable. For example, a hydroxyl group, a carboxyl group,
Silicon-containing group, epoxy group, (block) isocyanate
Acrylic resin, vinyl resin, polyester resin having one or more functional groups selected from
One or more base resins selected from alkyd resins, urethane resins, etc., and melamine resins, urea resins, (block) polyisocyanate compounds, carboxyl group-containing compounds, epoxy group-containing compounds which react with these functional groups Examples thereof include a mixture of one or more crosslinking agents selected from compounds and the like. The ratio between the base resin and the crosslinking agent is
Based on the total solid weight of both components, the base resin is 50
~ 90%, especially 65-85%, crosslinker 50-50%,
Particularly, 35 to 15% is suitable.

[0010] The metallic pigment is a pigment for imparting an excellent glitter and a base concealing property to the coating film of the metallic paint (A), and is, for example, flaky or flaky aluminum, vapor-deposited aluminum. , Aluminum oxide, stainless steel, copper, etc., which are made of a metal which does not transmit light at all or hardly. Although the particle size is not particularly limited, the thickness is 0.001 to 1.0 μm, particularly 0.2 to 0.5 μm, the longitudinal dimension is 1 to 30 μm,
Particularly, the range of 3 to 15 μm is suitable.

In particular, in the present method, the metallic paint (A)
It is preferable to use a metallic pigment having a medium-to-small particle size in order to have excellent brilliancy in a highlight portion and to reduce the thickness of the underlayer concealing film. 0.005 to 1.0 μm, especially 0.01
~ 0.5 μm, longitudinal dimension is 1 ~ 15μm, especially 3 ~
It is particularly preferable to use one that falls within the range of 10 μm.

The mixing ratio of the metallic pigment in the metallic paint (A) is 100 parts by weight (solid content) of the resin composition.
The suitable range is 5 to 30 parts by weight, especially 10 to 20 parts by weight.

By using such a metallic pigment, the thickness of the metallic coating (A) can be reduced. The underlayer concealed film thickness is JISK5400
7.2 A black-and-white grid pattern concealing force test paper specified in 7.2 (2) (f) is stuck on a mild steel sheet, and a metallic paint (A) is obliquely coated so that the film thickness changes continuously, and then dried and cured. The minimum film thickness (μm) at which the black and white lattice pattern of the opaque paper is not visible when the painted surface is visually observed under diffuse daylight, and is the value measured with an electromagnetic film thickness meter. Paint (A)
The underlayer concealed film thickness is 15 μm or less, based on the cured coating film,
Preferably it is 3 to 12 μm.

As the solvent, an organic solvent and / or water can be used. Examples of the organic solvent include hydrocarbons such as hexane, heptane, xylene, toluene and cyclohexane; esters such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether and diethylene glycol monomethyl ether; isopropyl ether; Ethers such as ter, ethylene glycol monomethyl ether and diethylene glycol monobutyl ether; alcohols such as ethyl alcohol, butyl alcohol and hexyl alcohol; ketones such as methyl isobutyl ketone, methyl ethyl ketone and isophorone System.

Achromatic and chromatic color pigments can be used as solid color pigments, for example, titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chrome ero, chromium oxide, prussian blue, and cobalt blue. And organic pigments such as azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, sulene pigments and perylene pigments. These can be used alone or in combination of two or more. By using these solid color pigments together with the metallic pigment, the metallic coating film of the metallic paint (A) can be colored to an arbitrary color tone.
The compounding amount of the solid color face is within a range in which the glitter does not disappear. Also, as a solid color pigment, the particle size is 20
By incorporating fine particle titanium oxide of ~ 80 nm, bicolor properties can be imparted, such as Mie scattering and Rayleigh scattering of light, where the highlight part is gold and the shade part is bluish white, and the color changes depending on the viewing angle. It is more preferable since a metallic coating film can be formed.

The metallic coating (A) can be prepared by mixing and dispersing the above-mentioned components in a solvent, and has a solids content of 20 to 60% by weight, preferably 25 to 5% by weight at the time of coating.
0% by weight, viscosity: 10-30 seconds / Ford cup # 4
It is preferable to adjust the temperature to / 20 ° C.

The metallic paint (A) is applied to an object to be coated with an air spray, an airless spray or an electrostatic coating machine.
It is preferable to apply the coating so that the film thickness based on the cured coating film is equal to or more than the above-described underlayer concealing film thickness.

[0018] Metallic paint (A) applied to the object to be coated
100 to 170 ° C., preferably 120 to 160 ° C.
C. for 10 to 40 minutes can be cured by heating, but in this method, after the coating film is cured by heating or in an uncured state without being cured, a transparent metallic paint is applied to the coated surface. (B) can be painted. When an aqueous paint is used as the metallic paint (A), the coating film is preheated at 60 to 100 ° C. for 3 to 10 minutes to evaporate moisture and the like, and then the transparent metallic paint (B) Is preferably applied.

Transparent metallic paint (B): A paint to be applied to the heat-cured or uncured coating surface of the metallic paint (A). Specifically, the paint contains a resin composition, a metallic pigment and a solvent as main components. Further, it is a liquid paint obtained by appropriately blending a solid color pigment, an extender pigment, and other paint additives as needed. The coating film of the transparent metallic paint (B) forms a coating film having a glittering glitter at the shade portion, and the entire surface is not coated with the metallic pigment, and there is a gap between the metallic pigment particles. , Through the gap, the lower metallic paint (A)
Can be visually observed.

As the resin composition, a metallic paint (A)
The mixture of the base resin and the cross-linking agent described in the above can be suitably used, and the ratio of these is 50 to 90%, particularly 65 to 85%, and the cross-linking agent is 50 to 90%, based on the total weight of both components.
10%, especially 35-15%, is suitable.

The metallic pigment is a pigment for imparting a glittering glitter to the coating film of the transparent metallic paint (B). Examples of the metallic pigment include scaly or flaky aluminum, vapor-deposited aluminum, aluminum oxide, Suitable examples include stainless steel, copper, mica, mica whose surface is coated with titanium dioxide and iron oxide, and iron oxide. The particle size is not particularly limited, but the thickness is 0.1 to 1.0 μm.
m, especially 0.2 to 0.5 μm, and the longitudinal dimension is 5 to 30
μm, especially in the range of 3 to 15 μm, the average particle size is 5 to 2
5 μm, especially 15 to 25 μm, is suitable.

The content of the metallic pigment in the transparent metallic paint (B) is as follows:
It is within the range of 0.5 to 10 parts by weight, preferably 2 to 7 parts by weight, more preferably 3 to 6 parts by weight. When the content of the metallic pigment is less than 0.5 part by weight, the glitter in the shade portion is reduced, and when it is more than 10 parts by weight, the glitter in the highlight portion is reduced, and neither is preferable.

By adjusting the content of the metallic pigment in the transparent metallic paint (B) within the above range, gaps are formed between the metallic pigment particles, and the area ratio of the metallic pigment on the coating surface is 3 to 30. %, Preferably within the range of 5 to 20%, and a metallic coating film in a slim state is formed. The coating film of the lower metallic coating (A) can be visually observed through the gap. Quantitative measurement of the transparent state of the metallic pigment of the transparent metallic paint (B) coating film is performed by coating the paint on a transparent plastic film to a thickness of about 10 to 20 μm and curing by heating.
An image was taken with an optical microscope at a magnification of 100 to 200 times, and the area measured by image processing software was recorded as the number of pixels M. Then, only the metallic pigment portion was extracted and the area was recorded as the number of pixels S, and the area ratio was%. = 100 × (S / M).

As the solvent, an organic solvent and / or water can be used. As the organic solvent, the organic solvents described for the metallic paint (A) are preferable.

The transparent metallic coating (B) has a solid content of 20 to 60% by weight, preferably 25 to 5% by weight, at the time of coating.
0% by weight, viscosity: 10-30 seconds / Ford cup # 4
/ 20 ° C., and the thickness based on the cured coating film is not less than the concealing film thickness, for example, 5 μm, on the (un) cured coating surface of the metallic coating material (A) using an air spray, an airless spray or an electrostatic coating machine. As described above, the coating is particularly preferably performed so as to have a thickness of 20 to 70 μm.

The present method comprises the steps of: applying an uncured coated surface of the transparent metallic paint (B) thus coated;
After curing by heating at 0 ° C. for 10 to 60 minutes, the clear paint (C) is applied.

The clear paint (C) is a paint for forming a transparent coating film to be applied to the cured or uncured coating surface of the transparent metallic paint (B). Specifically, the clear paint (C) comprises a resin composition and an organic solvent. A liquid paint as a main component can be suitably used.

As the resin composition, a metallic paint (A)
The ratio of the base resin to the cross-linking agent is 50 to 90%, preferably 65 to 85%, and the cross-linking agent is 50 to 1% based on the total weight of the two components.
0%, especially 35-15%, is suitable. Examples of the organic solvent include the organic solvents described in the above-mentioned paint (A).

Although the clear paint (C) does not contain coloring pigments and metallic pigments in principle, these pigments can be contained as long as the transparency is not impaired. The clear paint (C) can be prepared by mixing and dispersing the resin composition in an organic solvent, and has a viscosity of 10 to 30 seconds / form.
The temperature is adjusted to 4/20 ° C, and the film thickness based on the cured coating film on the (un) cured coating surface of the transparent metallic paint (B) is adjusted to 15 to 20 with an air spray, an airless spray or an electrostatic coating machine. Paint to 70 μm. After applying the clear paint (C), the method is achieved by heating and curing at 120 to 160 ° C. for 10 to 60 minutes.

In this method, an object to be coated is coated with the above-described metallic base coating material (A), transparent metallic coating material (B) and clear coating material (C) in that order to form a three-coat, one-bake (3C1B), This is achieved by forming a multilayer coating film by a three-coat two-bake (3C2B) or three-coat three-bake (3C3B) method. In addition, the method includes the steps of: curing the uncured coating at about 50 to about 100 ° C. in 3C1B and 3C2B
It is also preferable to pre-dry the coating so that the gel fraction of the coating is about 60% by weight or less.

[0031]

[Effects of the present invention] It was possible to form a multi-layer coating film having excellent glitter in the highlight portion and having a glittering feeling even in the shade portion.

2. The multi-layer coating film using the base opaque metallic paint (A) using a small to medium particle size aluminum flake pigment, and the transparent metallic paint (B) using a high brightness, medium to large particle size aluminum flake pigment, Excellent undercoat concealment, good highlights and brilliant, and a glittering coating on the shaded part.

[0033]

EXAMPLES Examples and comparative examples according to the present invention will be described. All parts and percentages are based on weight, and the thickness of the coating film is based on the cured coating film. The mixing ratio of the components of each paint is a solid content weight ratio.

1. Preparation of sample 1) Coating object Steel sheet (JIS 314) that has been degreased and treated with zinc phosphate
1. A cationic electrodeposition paint ("Elecron 9400HB", manufactured by Kansai Paint Co., Ltd., trade name, epoxy resin polyamine-based cationic resin was used as a curing agent for a block size polyisocyanate compound in a size of 400 × 300 × 0.8 mm). Is coated by a conventional method so as to have a film thickness of 20 μm, heated at 170 ° C. for 20 minutes to crosslink and cure the coating, and then coated with an intermediate coating (“Luga Bake Intermediate Gray”, Kansai Paint Co., Ltd.) ), Product name, polyester resin / melamine resin type, organic solvent type) was applied to a thickness of 30 μm and heated at 140 ° C. for 30 minutes to crosslink and cure the coating film.

2) Preparation of Metallic Coating (A) Concealing Base (A-1): Hydroxyl-containing acrylic resin (having a hydroxyl value of 12)
0, acid value 5, number average molecular weight 13000) 75 parts and butyl etherified melamine resin 25 parts (number average molecular weight 100
0), aluminum flakes (“5654N
S ", manufactured by Toyo Aluminum Co., Ltd., trade name, average particle size 11μ
m, thickness 0.2-0.5 μm, surface area 15000 cm ²
/ G, small particle size and high brightness type), mixed and dispersed in an organic solvent (ethyl acetate / xylene = 1/1 weight ratio), solid content 50%, viscosity 13 sec. A base opaque metallic paint (A-1) having a concealment film thickness of 8 μm at 4/20 ° C. was obtained.

3) Preparation of Transparent Metallic Paint (B) (B-1): Hydroxyl-containing acrylic resin (having a hydroxyl value of 10)
0, acid value 6, number average molecular weight 13000) 75 parts and butyl etherified melamine resin (number average molecular weight 1000) 2
For 5 parts, aluminum flakes (“5422N
S ", manufactured by Toyo Aluminum Co., Ltd., trade name, average particle size 20μ
m, thickness 0.2-0.5 μm, surface area 7500 cm ² /
g, large particle size, high brightness type), mixed and dispersed in an organic solvent (ethyl acetate / xylene = 1/1 weight ratio), solid content 50%, viscosity 13 sec./Food cup # 4/20 ° C, a transparent metallic paint (B-1) was obtained.

(B-2): Hydroxyl group-containing acrylic resin (hydroxyl value 100, acid value 6, number average molecular weight 13000) 75
Parts and butyl etherified melamine resin (number average molecular weight 1
000) to 25 parts of aluminum flakes (“5
422 NS ", manufactured by Toyo Aluminum Co., Ltd., trade name, average particle diameter 20 μm, thickness 0.2 to 0.5 μm, surface area 7500
5 parts by mass of a high-brightness particle size of cm ² / g), mixed and dispersed in an organic solvent (ethyl acetate / xylene = 1/1 weight ratio), solid content 50%, viscosity 13 sec / f -Cup # 4/20 ° C. to obtain a transparent metallic paint (B-2).

(B-3): Hydroxyl group-containing acrylic resin (hydroxyl value 100, acid value 6, number average molecular weight 13000) 75
Parts and butyl etherified melamine resin (number average molecular weight 1
000) to 25 parts of aluminum flakes (“5
422 NS ", manufactured by Toyo Aluminum Co., Ltd., trade name, average particle diameter 20 μm, thickness 0.2 to 0.5 μm, surface area 7500
0.3 parts by mass of a high-brightness particle size of cm ² / g) and an organic solvent (ethyl acetate / xylene = 1/1 weight ratio).
, A solid content of 50%, a viscosity of 13 seconds / ford cup # 4/20 ° C, and a transparent metallic paint (B-
3) was obtained.

(B-4): Hydroxyl group-containing acrylic resin (hydroxyl value 100, acid value 6, number average molecular weight 13000) 75
Parts and butyl etherified melamine resin (number average molecular weight 1
000) to 25 parts of aluminum flakes (“5
422 NS ", manufactured by Toyo Aluminum Co., Ltd., trade name, average particle diameter 20 μm, thickness 0.2 to 0.5 μm, surface area 7500
11 parts by mass cm ² / g large particle size high brightness type)
It was mixed and dispersed in an organic solvent (ethyl acetate / xylene = 1/1 weight ratio) to obtain a transparent metallic paint (B-4) having a solid content of 50%, a viscosity of 13 seconds / a hood cup # 4/20 ° C. .

4) Clear paint (C-1) "Lugabake clear" (trade name, manufactured by Kansai Paint Co., Ltd.)
1. Acrylic resin / amino resin organic solvent type clear paint) EXAMPLES AND COMPARATIVE EXAMPLES An undercoating metallic paint (A
-1) or (A-2) using a mini-bell type rotary electrostatic coating machine, using a discharge rate of 180 cc and a rotation speed of 40000 rpm
m, shaping pressure 1Kg / cm ² , gun distance 30c
m, conveyor speed 4.2m / min, booth temperature 20
The coating was performed at a temperature of 75 ° C. and a booth humidity of 75%. The coating thickness is 8
μm. The transparent metallic paint (B
-1) to (B-4) in two stages with REA
Using a gun, discharge amount 180cc, atomization pressure 2.5Kg
/ Cm ² , pattern pressure 3.0Kg / cm ² , gun distance 3
5cm, conveyor speed 4.2m / min, booth temperature 2
Painting was performed at 0 ° C. and a booth humidity of 75%. The coating thickness of each stage is 4 to 5 μm, and the total thickness is 8 to 10 μm. Thereafter, the clear paint (C-1) was applied to the uncured transparent metallic paint coated surface using a mini-bell type rotary electrostatic coating machine at a discharge rate of 320 cc and a rotation speed of 40000 rpm.
m, shaping pressure 1.2Kg / cm ² , gun distance 30
cm, conveyor speed 4.2m / min, booth temperature 20
The coating was performed at 75 ° C. and a booth humidity of 75%. The coating thickness is 8
μm. After painting these, leave them at room temperature for 3 minutes, then heat them at 140 ° C for 30 minutes in a hot-air circulation drying oven,
The three-layer coating was cured simultaneously.

Underlying metallic paint (A-1) or (A-2), transparent metallic paints (B-1) to (B-
Table 1 shows the coating process of 4) and the clear paint (C-1) and the performance test results of the obtained multilayer coating film.

[0042]

[Table 1] Table 1

The concealing property of the base concealing metallic paint (A): A black and white lattice pattern concealing test paper is stuck on the above-mentioned intermediate coating surface of the object to be coated, and the base concealing metallic paint (A) is placed thereon.
-1), (A-2) is applied to a thickness of 8 μm,
This is the result of visually observing the shaded part from the highlight part, ○ indicates no black and white lattice pattern in both parts, Δ indicates a slight black and white lattice pattern in the shaded part, × indicates clear black and white lattice pattern in the shaded part Show what you can see.

Area ratio of aluminum flakes: Transparent metallic paints (B-1) to (B-4) are applied to a transparent plastic film (OHP sheet) to a film thickness of 8 to 10 μm.
The sample was heated at 0 ° C. for 30 minutes to obtain a sample. This sample was photographed with a video microscope at a magnification of 200 times, the image was stored in TIFF format, and the image processing software NIHima
This is a result obtained by calculating the area ratio of aluminum flakes by the following formula (I) using ge (prepared by the US Insurance Agency and distributed as free software).

Aluminum flake area ratio = 100 × (the number of pixels occupied by aluminum flakes / the number of pixels in the entire measurement area) Expression (I) Luminance of highlight portion: measured value of formed multilayer coating film . After measuring the spectral reflectance at a highlight-side angle of 15 degrees (the angle is represented by an opening angle with the regular reflection light being 0 degree) using a portable variable-angle spectrophotometer MA68 manufactured by US X-Rite, JISZ8701 Was used to determine the tristimulus values XYZ, of which the Y value indicating the brightness was defined as IV (luminance). The higher the value, the stronger the brightness.

Glitter in Shaded Area: The formed multilayer coating film was visually evaluated. The amount of light reflected from the aluminum flakes of the transparent metallic coating layer appearing in the shaded area and the glitter were visually determined when the painted plate was rotated from an observation state in which highlights were observed and a shaded portion was seen. ◎ indicates that the optimum glitter was obtained, は indicates that the glitter was obtained, Δ indicates that the glitter was slightly inferior, and X indicates that the glitter was inferior.

Finishing property of clear coating film: Visual observation was carried out under the conditions of 85 ° incidence and 85 ° light reception of the formed multilayer coating film.
The smoothness of the clear coating layer was observed. ○ indicates good smoothness, △ indicates slightly poor smoothness, and × indicates poor smoothness.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B05D 7/24 302 B05D 7/24 302T 302V 303 303B F-term (Reference) 4D075 BB26Z CB13 DA06 DB02 DC12 EA07 EA19 EA43 EB22 EB35 EB38 EC02

Claims (6)

[Claims] 1. A method for forming a multi-layer metallic coating by sequentially applying an undercoating metallic paint (A), a transparent metallic paint (B) and a clear paint (C) on an object to be coated, The content of the metallic pigment in the transparent metallic paint (B) is as follows:
A method for forming a multilayer coating film, wherein the amount is 0.5 to 10 parts by weight. 2. A three coat 1 in which a metallic paint (A), a metallic paint (B) and a clear paint (C) are sequentially applied and then heated to cross-link and cure the three-layer coating together.
2. The method according to claim 1, wherein the method is a baking method. 3. A metallic paint (A) is applied, cured by heating, and then coated with a metallic paint (B) and a clear paint (C).
2. The method for forming a multilayer coating film according to claim 1, wherein the coating method is a three-coat two-bake method in which the two coating films are sequentially coated and heated to crosslink and cure the two-layer coating film together. 4. An uncured coated surface obtained by applying a metallic paint (A) and heating to remove a part or most of volatile components,
Apply metallic paint (B) and clear paint (C),
2. The method for forming a multi-layer coating film according to claim 1, wherein the method is a three-coat one-bake system in which the three-layer coating film is heated and cross-linked and cured together. 5. The method according to claim 1, wherein the metallic paint (A) contains microtitanium and / or titanium oxide. 6. The method according to claim 1, wherein the metallic pigment of the metallic paint (B) is at least one selected from aluminum flakes and / or alumina flakes.