JPS63240971A - Formation of coated film - Google Patents

Abstract

PURPOSE:To form the title coated film with stronger deepness of color, saturation of color, and pitch blackness than before by coating a dark-colored base coat with a clear coat layer having a refractive index lower than a specified value. CONSTITUTION:The dark-colored base coat is coated with the clear coat layer having <=1.51 refractive index. The deep-colored base coat can be coated with the use of a paint capable of being produced by adding an inorg. pigment and other additives to a common paint so that the brightness and chroma are in the region A, or more preferably in the region B, in the figure M presenting the relation between brightness and chroma in the Munsell value. The total thickness of the clear coat layers is controlled to >=10mu, and the total thickness of the clear coat layers having <=1.485 refractive index among the layers is adjusted to >=5mu. As a result, a coated film with greater deepness of color, saturation of color, and pitch blackness than before can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for forming a coating film that can be applied to general agricultural color coatings, such as automotive top coatings.

[Conventional technology]

Conventionally, in 2-coat 1-1 hake solid coating, a one-sided cloudy clear method has been used, and in 1-coat solid, the depth and brightness of dark colors have been brought out by appropriately selecting pigments. In addition, in the case of black paint films, jet blackness has been enhanced by appropriately selecting pigments or using dispersion technology in two-coat, one-baked solid coatings or one-coat soliso coatings.

By the way, it is known to use clear coating 1'4 as a Tombu coat to protect metallic coatings and solid coatings, as described in Japanese Patent Publication No. 58-44430. It is also known to use a clear coat as an intermediate layer in a coating system, as described in Japanese Patent Laid-Open No. 53-108134. However, the Clear2-1 paint and coating system was seen to only serve the function of protecting the base coat.

[Problem that the invention seeks to solve]

As mentioned in the 11th revision, in the conventional technology, there is a turbidity clearing method using two coats of dark colored baked solid paint,
When selecting pigments for one-coat solid painting, it is not possible to obtain sufficient color depth and color uniformity, and for black painting, even if a pigment with a high jet blackness is selected, the jet blackness of the pigment is not reflected in the paint film. There was a problem that it was not done.

Therefore, the present invention eliminates the problems of the prior art;
The objective is to provide a method for forming a paint film that can bring out the depth and brightness of the color of a J-color paint film.

[Means for solving the above problems]

According to the invention, this object is achieved by covering the four-color base coat with a clear coat layer having a refractive index of 1.51 or less.

[Specific explanation of the means and their effects] Painting systems for automobiles, etc. are generally composed of an electrodeposition paint, an intermediate paint, and one or two layers of top coat.

Electrodeposition paints are anionic and cationic paints that are commonly used for automobiles, and intermediate paints are generally made of a polyester resin made of polyhydric alcohol and polybasic acid, and a mixture of oil, etc. It is a paint made by using an alkyd resin modified with or an acrylic resin made of acrylic acid as a vehicle and a crosslinking agent such as a melamine resin or bronc isocyanate, and appropriately blending this with rust-preventive pigments, chimping-resistant pigments, and other materials. .

The dark colored base coat used in the present invention preferably falls within region A, more preferably within region B in the drawing showing the relationship between lightness (V) and chroma (C) of the Munsell value shown in FIG. It can be painted using ordinary paints that can be produced by adding inorganic pigments and other additives such as vehicle coloring pigments, carbon black, titanium oxide, metal flake pigments, coating mica, white mica, etc. can. If the brightness and chroma are outside the above J·n range, the object of the present invention tends not to be fully achieved even if a low refractive index clear coat is applied. As described above, the method of the present invention is particularly effective for dark colors such as blank, blue, and red, and is not so effective for light colors.

In the present invention, the resin used as the vehicle for the deep color base coat paint and the medium refractive index clear coat paint with a refractive index of more than 1.51 and less than 1.535 is an acrylic resin that has been commonly used. , polyester resin, alkyd resin, etc.

The acrylic resin that can be used in the present invention can be produced, for example, by polymerizing the following monomers by a conventional method.

(1) Ethylene 1 raw monomers having hydroxyl groups such as hydroxylmethyl (meth)acrylate, hydroxyl ethyl (meth)acrylate, hydroxylpropyl (meth)acrylate, hydroxylbutyl (meth)acrylate, N-methylolacrylamine, etc. , (2) (meth)acrylic acid, crotonic acid, itaconic acid,
Ethylenic monomers having a carboxyl group such as fumaric acid and maleic acid, (3) methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl acrylate, n-propy acrylate , the monomer (1) such as (meth)al-1-acrylic acid esters such as n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and n-dodecyl acrylate; Ethylenic monomers copolymerizable with (2), as well as (meth)acrylonitrile, styrene, and the like are used.

Next, as is well known, polyester resin can be produced from polyhydric alcohol and polybasic acid. Polyhydric alcohols that can be used in the present invention include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 4-millipropylene glycol, neopentyl glycol, ■, 2-1l, 8-12,3- 11.4-
Butandani 4-ol, 1,5-bentanediol, 1,
6-he-1-sanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexane dimetatool, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropyl Pionate (RASIIPN), 2,2.4-trimethy/I/1.3FW Product name - Bentanediol, N, N-
Bis-(2-hydroxyethyl)dimethylhydantoin, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, annitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol, tris One or more polyhydric alcohols such as -(hydroxyethyl)isocyanate can be used in appropriate combination.

On the other hand, examples of polybasic acids used in the present invention include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid,
Methyltetrahydro! ]! (hydrophthalic acid, hymic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid) A combination of one or more polybasic acids such as sebacic acid, succinic acid, succinic anhydride, lactic acid, dodecenyl succinic anhydride, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, endo acid anhydride, etc. Can be done.

If necessary, up to about 30% of oil or fat or fatty acid can be added to these polyester resins to impart flexibility to the resin.

The acrylic, polyester and alkyne l-'H(
Cross-linking of fats can be achieved using, for example, alkoxymethylmelamine resins in which the alkoxy groups include methoxy, ethoxy, n-butoxy, or i-butoxy groups, such as n-butylated melamine resins and isobutylated melamine resins, and benzoguanamine resins. This is done using a crosslinking agent. These resins are usually obtained by subjecting an amino compound such as melamine or benzoguanamine to an addition reaction or addition condensation reaction with an aldehyde such as formaldehyde or paraformaldehyde, and then etherifying it with a monohydric alcohol having 1 to 4 carbon atoms. be able to.

When these melamine resins are used as crosslinking agents for polyester resins, it is preferable to mix 60 to 80% of polyester resins and 40 to 20% of amino resins.

As the crosslinking agent component of the acrylic resin, amino resins, particularly melamine resins, blocked isocyanates, etc. can be used. The ratio (weight ratio) of the thermosetting resin acrylic resin or polyester resin/melamine resin or block isocyanate is preferably 9/1 to 6/4, more preferably 8/2 to 7/3.

The most important thing in the method of the present invention is, of course, to protect the dark colored base coat by forming a film with a refractive index of 1.51 or less and preferably a thickness of 5 μm or more on the dark colored base coat. Furthermore, it adds clarity and depth to the color of the base coat. Resins that provide a clear coat with a refractive index of 1.51 or less, particularly a clear coat with a refractive index of 1.480 or less, include polyester resins, alkyd resins, acrylic resins, and soft-containing resins, as well as the vehicle for the medium refractive index clear coat. There is a base resin. As for the components constituting these resins, those with a high content of aliphatic groups and feces have a low refractive index. From the viewpoints described above, a vehicle having a low refractive index can be manufactured by adjusting the raw materials.

As the fluorine-containing resin, for example, JP-A-57-341
No. 07 (Japanese Patent Publication No. 60-21686) Publication G discloses a fluorine-containing copolymer that can be cured at room temperature, and according to this publication, fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether, and hydroxyalkyl vinyl ether are essential. By using a copolymer containing a specific amount as a constituent component, the curing properties of the resin are greatly improved, and not only can it be cured in a short time using a general-purpose curing agent such as melamine, but also the isocyanate It is stated that when used, a weather-resistant coating film that can be cured at room temperature, is rich in gloss, and has excellent solvent resistance is obtained.

Further, JP-A-59-197471 describes a thermosetting resin composition for coatings containing a fluorine-containing copolymer, and this publication describes a fluorine-containing copolymer containing a hydroxyl group,
A thermosetting resin till composition for coatings is used, which is composed of a copolymer mixture of an alkyl ester of acrylic acid or methacrylic acid and a copolymer of other acrylic monomers, and a curing agent containing a functional group that reacts with a hydroxyl group. It is disclosed that solid color paints, metallic paints, clear paints, etc., having excellent water resistance, solvent resistance, weather resistance, etc. can be obtained by this method.

Further, JP-A-61-46283 discloses a coating composition containing a fluorine-containing copolymer, and according to this publication, fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether, hydroxyalkyl vinyl ether and other copolymers are used. Examples include fluorine-containing copolymers formed by polymerizing a combination at a specific ratio.

By the way, according to the research of the present inventors, the refractive index is 1.5.
A clear paint that forms a high refractive index layer of 35 or more! It was found that * does not meet the purpose of the present invention.

Examples of resins that form such a high refractive index clear coat include polyester resins, alkyd resins, and the like as well as the medium refractive index clear coat vehicle described above.
There are acrylic resins and fluorine-containing resins. In general, the components that make up these resins have a high refractive index when they have a high concentration of aromatic groups and highly polar groups.From this point of view, it is possible to manufacture a vehicle with a low refractive index by adjusting the raw materials. can.

The clear coat used in the present invention is, for example, a clear coat for automobile topcoating, and is a two-coat, one-bake,
Includes 2-coat, 2-bake, 3-coat, 2-hake, and multilayer clear coat.

When clear films with different refractive indexes constitute a multilayer system, interference fringes tend to occur if one layer is thin, but if I is 5 μm or more, interference fringes no longer occur. As mentioned above, the refractive index of the clear coat is classified as a coating in the present invention.

High refractive index (H) 1.535 Medium refractive index (M) 1.505 Low refractive index (L) 1.480 Also, preferred when using two or more layers of clear coats of each refractive index to improve the performance of the base. The combinations are as follows.

○ ○ △ ○ OO○ [Function] In the coating film forming method according to the present invention, as the refractive index of the clear increases, the reflectance on the surface increases, and the color becomes whitish due to surface reflected light. The depth of color, evenness, and jet blackness disappear. Also, by clear coating with a low refractive index clear, the reflectance on the surface is reduced and the amount of light reflected from the surface is reduced, resulting in deeper colors and even jet blackness than ever before.

The present invention will be explained in more detail according to examples below.
It goes without saying that the technical scope of the present invention is not limited to these Examples. In the following description, "parts" and "%" are based on weight unless otherwise specified.

3゜'1 of LIk color base coat (1) Preparation of polyester resin 21.05 parts of phthalic anhydride, 23.61 parts of isophthalic acid, 16.80 parts of trimethylol propuff, 6.21 parts of neopentyl glycol, 3 parts of ethylene glycol 83 parts of coconut oil, 18.44 parts of coconut oil, and 59 parts of Cardura-Elo were added to the resin obtained by adding pheasant roll to a solid content of 60 parts.
% polyester resin was obtained.

(2) Preparation of paint Disperse the following pigments using this resin using a santo grind mill.
0) were mixed to produce the following paint.

8' Blue: Shanin Blue NK Made by Dainippon Ink σ (1) 92 Red: Shinkasha Red Y RT-759DC Made by Dupont ■ 3 Black: Mitsubishi Carbon MA -100C Made by Mitsubishi Kasei ■ Yuban 2O-SF-60: Mitsui Higashi Pressure (I gradient (3)
) Preparation of coating film A dull steel plate that had been chemically treated with 0.8 x 90 x 300 nun of zinc phosphate was coated with cationic electrodeposition (Power Coat U-500 manufactured by Nippon Paint (I(1)) and intermediate coating film (Japan A paint whose viscosity was adjusted as specified below was applied to a test piece coated with Olga 0P-2 Gray (manufactured by Paint ■) to a specified film thickness.
After setting at nl, test pieces were prepared by baking at 140°C for 30 minutes.

(・1) Base coat and clear coating method Example 1
: A base coat was applied and baked as is.

Examples 2 to 5: Both 2-coat 1-bake, where the base is painted, clear is applied and baked, and 2-coat, 1-2 hake, where the base is painted, baked, clear is painted and baked, but both are the same. Got the results. Note that the film j7 of each clear film was 20 μm.

Examples 6 to 11: A base is painted, a clear coat (1) is coated as it is, a clear coat (2) is coated thereon, and the coated coat is baked. I performed both 3 coats, 1 bake, and 3 coats, 2 bakes, in which the base was painted and baked, then Clear (1) was painted, and Clear (2) was painted on top of that and baked, and the same results were obtained in both cases. Note that the film thickness of each clear was 20 μm.

(Note) In the table below, A/C first forms C,
This indicates that A will be formed later.

Examples 12 to 15: Coating films were obtained by adding 1 coat of clear to Examples 6 to 11 and applying 4 coats and 3 bakes.

Example 16: D=3μm A-20μm C-20μm Example 17: D=6μm A-20μm C=20μm The results of Examples 1 to 5 are shown in Table 1.

*5: Polyester resin 21.05 parts of phthalic anhydride, 23.61 parts of isophthalic acid, 16.80 parts of trimethylolpropane, 6.21 parts of neopentyl glycol, 3.83 parts of ethylene glycol, 18.44 parts of coconut oil , Kijirol was added to a resin obtained by reducing 10.59 parts of Cardura-E to obtain a polyester resin having a solid content of 60%.

*6: Acrylic resin, then 30 parts of styrene, 4 parts of ethylhexyl methacrylate
5.2 parts, ethylhexyl acrylate 5.5 parts, 2-
Polymerization of 16.2 parts of hydroxyl methacrylate, 3.1 parts of methacrylic acid, and 4.5 parts of abbisisobutyronitrile in 80 parts of xylene and 20 parts of n-butanol, with a number average molecular weight of 13,400 and a non-volatile content of 50%. of acrylic resin was obtained.

*7: Acrylic resin 1.8 parts of methacrylic acid, 39.4 parts of methyl methacrylate, 43.6 parts of ethyl acrylate, 3.2 parts of isobutyl acrylate, 12 parts of 2-hydroxyethyl acrylate
．． 0 parts, azobisisobutyronitrile 1.8 parts in 90 parts of xylene and 10 parts of methyl isobutyl ketone, number average molecular weight 18,000, non-volatile content 50% acrylic resin A-C Fes and Mitsui Mix methamine resin kneepan 20-SE-60 manufactured by Toatsu ■ so that the solid content ratio is 70/30, and make N014 photo cups with diluted thinner (methyl isobutyl ketone/xylene/Solhesso 100 = 2/4/4). Dilute to 15 seconds/20°C with
A sample was obtained.

*8: Fluorine-containing copolymer of fluorine resin (Lumiflon LF-20 manufactured by Asahi Glass Company)
A 50% Quijirol solution of 0) was prepared. The hydroxyl value of this fluorine-containing copolymer was 52 (mgKOH7g).

78 parts of this resin and Sumidur N-7 manufactured by Sumitomo Bayer
5 (urethane curing agent, solid content 75%) and xylene/Tsurupez 100=515 were mixed to prepare a paint.

Dilute paints from A to D with thinner (methyl isobutyl ketone/Tsurupets 100/Tsurupets 150; 2/4/
4) was diluted with a N004 food cup for 15 seconds/20°C.

Next, Table 2 shows the results of Examples 6 to 17 in which the film thickness of the clear film was changed as follows.

Margin below (5) Evaluation method (based on JIS-54006, 1) (
i) Visual judgment of coating film ◎...Excellent depth of color, even color, and jet blackness.

○...Good depth of color, even color, and jet blackness.

Δ...The depth of the color is whitish, and even the color is not very jet black.

×...The white is very blurred and even the colors lack jet blackness at all.

*...Interference fringes occur in the coating film, making it impossible to determine the color. (ii) The refractive index free film can be peeled off and measured using an Atsube refractometer using a prescribed method.

[Effects] As explained above, according to the present invention, by using a low refractive index clear in the clear coat of an automotive top-coat paint, it is possible to obtain deeper colors, sharper colors, and lacquer IW properties than ever before. A coating film can be obtained.

In other words, by lowering the refractive index of the currently used deep-colored automotive topcoat paints and the paints used as clear coats to the paint film to 1.510 or less, it is possible to achieve a refractive index that could not be obtained with conventional clear A-coats; The depth of color, evenness, and jet blackness of agricultural and black colors are improved, giving you a better appearance than ever before.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing preferred dark colored regions in which the depth and brightness of colors can be brought out according to the method of the present invention in relation to the lightness and saturation of the colors. Preferred and particularly preferred areas are indicated.

Claims (1)

[Scope of Claims] 1. A method for forming a coating film, which comprises covering a deep colored base coat with a clear coat layer having a refractive index of 1.51 or less. 2. The method of forming a coating film according to claim 1, wherein the dark color has a brightness and chroma of the Munsell value shown in FIG. 1 in region A. 3. Claims characterized in that the total thickness of the clear coat layers is 10 μm or more, and among the clear coat layers, the total thickness of the clear coat layers having a refractive index of 1.485 or less is 5 μm or more. The method for forming a coating film according to item 1.