JPS60864A - Painting method - Google Patents

Abstract

PURPOSE:To obtain easily a bright painting color having high designability at a low cost by using a primer paint color having the average surface reflectivity higher by a specified level or above than that of a finish painting color. CONSTITUTION:The average surface reflectivity in the specific wavelength region of a spectral reflectivity curve in the visible ray wavelength region of a paint-coated film formed in the case when a base surface is thoroughly covered by a finishing paint is calculated. A primer paint film having the average surface reflectivity higher by >=10% than the calculated surface reflectivity in the specific wavelength region is formed on a base material of a metal or plastic, etc. A paint having >=60mu thickness of the covering film is thereafter used in the case of one-coat one-bake type finishing and a pant having >=20mu said thickness is used in the case of a two-coat one-bake type. The paint color having excellent designability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a coating method for obtaining a coating color tone that is more vivid than the conventional method.

(Prior Art) In recent years, users' hobbies have become more diverse and their preference for luxury goods has increased, and these trends have also affected the color tone of automobile bodies.

In order to cope with this, development is progressing such as more vivid paint colors (hereinafter referred to as paint colors), more transparent paint colors, or whiter metallic paint colors.

However, with the coating film forming method using conventional coating techniques, it is difficult to obtain a brighter coating color without increasing costs, and the design of the vehicle body coating color can only be done within a limited range.

(Objective of the Invention) The present invention is intended to solve the above-mentioned problems in the prior art, and its purpose is to provide a coating method that can easily obtain a coating color with a more vivid design than before at a low cost. It's about doing.

(Structure of the Invention) In other words, the coating method of the present invention is based on the average surface reflection in a specific wavelength region of the spectral reflectance curve in the visible light wavelength region of the coating film formed when the base is completely hidden with the paint used for the top coating. After forming a base coat having an average surface reflectance that is 10% or more higher than the average surface reflectance in the specific wavelength range on a base material such as metal or synthetic resin, a one-layer coating is applied onto the base coat. When performing a one-coat one-bake type topcoat, use a paint with a hiding film thickness of 60μ or more, and when performing a two-coat, one-bake type topcoat on the base coat, use a paint with a hiding film thickness of 20μ or more. The present invention is characterized in that a coating film having a thickness equal to or less than the concealing film thickness of the top coat film is formed using a paint having a concealing film thickness of a predetermined value or more in accordance with the coating form. Furthermore, in the case of yellow, red, and orange paint colors, the specific wavelength region of the spectral reflectance curve is 600n! Use a topcoat paint that has a peak wavelength range of # to 700 raa and whose light transmittance at a wavelength of 400mμ to 500μ when forming the topcoat film is less than ION. Regarding the coating color, as mentioned above, the peak of the specific wavelength region of the spectral reflectance curve is in the wavelength region of 550 mp or less, and the average surface reflectance in the peak wavelength region including 50 - around the peak wavelength is 30% or less. A top coat that forms a coating film, and a coat that has an average surface reflectance of 40% or more in the peak wavelength region and 10 to 40% higher than the average surface reflectance of the top coat when completely concealed. It is characterized by using a base paint that forms a film.

The top coating color used in the present invention is a coating color with a high hiding film thickness, that is, a coating color with high transparency, as will be described in detail later. This topcoat is applied in a known manner, for example, in several coats, to completely hide the base layer, and a spectral reflectance curve is determined for the visible wavelength region of 400 ma to 700 mIt. In this case, the shape of the curve naturally differs depending on the paint color, but the point where the surface reflectance is highest is called the peak wavelength, and the area around +/-50 wavelengths is called the peak wavelength region. 7 like the red and orange paint colors
If the peak wavelength is at 00 hard, 600~
The peak wavelength is 700 cm. Then, calculate the average reflectance for this peak wavelength region, and use this as the average surface reflectance of the top coat color. In addition, for paint colors that are flat and have no peak over the entire wavelength range, such as silver metallic paint color, the average surface reflectance over the entire wavelength range is taken as the average surface reflectance.

Figure 1 shows the spectral reflectance curves of typical paint colors, their peak wavelength regions, and average surface reflectances.

(measured using Hitachi COLORANALYZER).

In the normal 3-coat painting method (base coat, intermediate coat, top coat) for four automobiles, the base coat refers to the intermediate coat. The color of the base coat must have an average surface reflectance that is 10% or more higher in the same peak wavelength region than the average surface reflectance of the top coat color at the time of concealment. Examples of such paint colors include whitish paint colors that are similar to the top coat color, bright gray, and white.

Among those skilled in the art, the coating method in which one top coat is applied once on the base coat and then baked is generally known as the one-coat, one-bake type (hereinafter referred to as IC).
It is abbreviated as type IB. ), and is a coating method commonly used for solid color painting of automobile bodies. And, the ICIB type top coating for automobile bodies is usually 30~
It is painted with a film thickness of about 50μ. This is because if it is less than 30μ, it is difficult to obtain a smooth surface and it is difficult to ensure sufficient paint film quality for rust prevention, etc., and if it is more than 50μ, paint defects such as sagging and pinholes will occur during painting. This is because it is easy to use, and the cost of paint increases. Therefore, the I of the car body
CIB type topcoat paints are usually designed to have a concealing property of about 30μ so that there is no influence from the base layer during painting.

However, the present invention is characterized by using a topcoat having a hiding film thickness of 60 μm or more, preferably 80 μm or more, which has poor hiding properties but is highly transparent.

Along with the ICIB type, there is also a painting method for automobile bodies that involves applying two top coats on the base coat and then baking it, i.e. the two-coat, one-bake type (hereinafter abbreviated as the 2CIB type) as it is called in the industry. . This is generally used for metallic coatings, and is made by applying two coats, a base coat for coloring and a clear coat for increasing gloss, without drying out. At the same time, baking is a drying method.

Generally, the base coat is coated with a film thickness of 10 to 20 μm, and the clear coat is coated with a film thickness of about 20 to 40 μm. Therefore, the base coat is usually designed to have a film thickness of about 10 μ so that it is not affected by the underlying layer. However, as the base coat of the present invention, one having a hiding film thickness of 20μ or more, preferably 25μ or more is used;
The mold type is characterized by a top coat of 60μ or less, and the 2CIB type is coated with a base coat only, excluding the clear coat, and 20 to 25μ or less.

Pigments used in the top coating of automobile bodies come in a variety of colors, including primary colors using yellow, red, and orange quinacridone pigments, threne pigments, azo pigments, and flavanthrone pigments. has a peak wavelength of 700 mμ in the visible region. Therefore, in the case of these colors, the peak wavelength region is set to 600 to 700-. FIG. 2 shows the spectral reflectance curves of these primary colors for reference.

As shown above, in the present invention, the thickness of the concealing film is set to be 60μ or more for the ICIB type, and the base coat thickness is set to be 20μ or more for the 2CIB type. At the time of formation, that is, normal IC
When forming a coating film of 30 to 50μ for type IB and 10 to 20μ for 2CIB type, 400 to 50
The light transmittance of the top coat film at a wavelength of 0 mμ is IOX
The following is desirable. This is because if there is a light transmission of 10% or more in those wavelength ranges, and if the base coating color is white or light gray, the overall color will become whitish and lack vividness. be.

Furthermore, when the light transmittance is IOX, Rambθr t −Bθ
According to the law of θr, among the light in the wavelength range of 400 m/J to 500 ma, the light that reaches the substrate and is reflected again is 1(X)% reflected by the substrate, and the IX of the incident light ray is ! : Therefore, there is no practical problem.

Among the pigments used in the top coating of five motorbikes, phthalocyanine pigments and thren pigments are typical for green, blue, and purple pigments. The peak of the surface reflectance of these primary colors is in the wavelength region of 550 m# or less.

FIG. 3 shows the spectral reflectance curves for complete concealment and for a coating color in which each pigment was mixed with titanium white at a weight ratio of 4:6.

As can be seen from FIGS. 2 and 3, green-blue paint colors and yellow, red, and orange paint colors clearly have different properties.

Comparing the spectral reflection curves when the primary colors are completely hidden, the peak reflectance for the primary colors in Figure 2 is almost 50.
% or more, whereas for blue and green primary colors, the peak reflectance is 10% or less. This means that when only the primary colors are used, the paint film tone is almost black, and to obtain so-called blue or green paint colors, white pigments must be added to the primary colors as shown in Figure 3. It means that. However, what the inventors of the present invention intended is a bright and transparent paint color, and since mixing a large amount of white into the top coat color will cause the transparency and brightness to be lost, the present invention For blue and green coating colors, it is desirable that the average surface reflectance in the peak wavelength region is 30% or less.

The feature of this invention is that the average surface reflectance is 10% higher than that of the top coat color.
Kokichi uses a base paint color that is higher than %. However, when using a paint color close to a primary color such as blue or green as the topcoat color, it is possible to use a basecoat color with an average surface reflectance of about 20%; The extent of the coating is not necessarily sufficient to obtain the bright coating color intended by the present invention. Therefore, the average surface reflectance of the base coating color is particularly preferably 3ON or more.

On the other hand, for example, if a blue or green primary color with an average surface reflectance of 10% or less is applied to the top coat, and a white color with an average surface reflectance of 90% is applied as the base paint color, the thickness of the top coat will decrease slightly. The paint color fluctuates due to variations in color. That is, the color varies depending on each part of the automobile body, making it difficult to ensure desired quality. Therefore, the base color should be 10% or more, 40% more than the topcoat color.
A material having a high average surface reflectance in the following range is desirable in terms of overall properties, and a material having a high average surface reflectance in the range of 30 to 4Q5 is most preferred.

(effect) The effects of the present invention will be explained in detail below.

Curve A in FIG. 4 is a surface reflectance curve of the primary color of quinacridone red, which is a typical red pigment used in automobile paint. If you want to obtain a more vivid red than this, for example, as shown at the top of Figure 4, it is necessary to increase the reflectance of the light rays only for the red wavelength range -600.- or above. .

However, no pigment is known that has such a surface reflectance and can provide stable quality.

That is, the curved line in FIG. 4 represents a hypothetical desired curve that cannot be obtained by conventional methods. However, as a result of many years of research, the inventors of the present invention have discovered this method that allows a paint color having a reflectance curve close to the curve opening in FIG. 4 to be obtained.

What we perceive as the color of a paint film is the combination of the paint color reflected on the surface of the paint film and the paint color reflected in some form inside the paint film.

Among these, the present inventors focused on the color reflected from the inside of the coating film, conducted various experiments, and obtained the findings shown in Table 1. In Table 1, X is the hiding film thickness (μ) of the topcoat film, Y is the average reflectance Q of the topcoat color in the peak wavelength region, M is the film thickness of the topcoat film (μ), and D is the topcoat color. It represents the average reflectance (to) of the base coating color in the peak wavelength region of the film.

Table 1: Color tone compared to complete concealment under various conditions However, caution is required when the topcoat film thickness is extremely thin, or when the pigment concentration is extremely low and the concealment film thickness exceeds several 100 microns. It is. In such cases, even in a wavelength range far away from the peak wavelength region that determines color tone, light rays are not absorbed by the top coat, but are reflected by the base coat, pass through the top coat again, and are mixed with the light reflected from the surface. I decided to come,
Rather than being bright like curve C in Figure 4, it becomes whitish. According to the research conducted by the present inventors, this is noticeable in red, yellow, and orange paint colors. Therefore, as mentioned earlier, in the present invention, in the case of red and orange paint colors, the proportion of light reaching the base coating film in the wavelength range of 400 to 500 mJJ, that is, the light transmittance, is 10% or less. It is desirable that there be.

(Example) The present invention will be explained in further detail in the following example. Note that the present invention is not limited to the following examples.

Example 1: The body of a popular vehicle was subjected to a full-dip degreasing and chemical conversion treatment process used in a typical automobile painting line, and then subjected to a cationic/electrodeposition coating process and then undercoated. Next, each body was coated with an average of 35 μm of polyester or melamine intermediate paint having the surface reflectance curve shown in Figure 5.
After coating with a film thickness of , normal water polishing was performed. Next, the masking film thickness 12 having the surface reflectance curve E in FIG.
Each body was coated with a 40μ thick red polyester/melamine top coat of 0μ. The results are shown in Table 2.

Table 2: Red-based topcoat ζKoyoru' painting results 1) The judgment symbols in the table represent the following meanings.

◎...Very good O...Good △...Average ×・
...Inferior 2) Quality equivalent to that obtained when the top coat used was applied two to three times.

As is clear from the results in Table 2, good results were obtained when a white or nearly white intermediate coating was used in the case of a red top coating.

Example 2: Example 1 (!: Four automobile bodies were manufactured up to the water polishing process using the same method, and the top coat had a concealing film thickness of 120 to 150 μm.
The surface reflectance at the time of concealment was painted in a blue color with an average film thickness of 40μ as shown in Figure 6.

The results are shown in Table 3.

Table 3=Results of coating with blue topcoat paint 1) The judgment symbols in the table have the same meanings as in Table 2.

In the case of a blue topcoat, the color tone and its variations must be taken into consideration, but overall, the best results were obtained when a gray intermediatecoat was used.

Example 3: Four car bodies were treated up to the water polishing process in the same manner as in Example 1, and the car bodies were further coated with a concealing film thickness of 30 μm, and the surface reflectance at the time of concealment was as shown in Figure 7. The silver metallic pacecoat shown in the curved line has an average weight of 15
Paint with a film thickness of μ, followed by clear coat with an average thickness of 25μ
It was coated with a film thickness of The results are shown in Table 4.

Table 4 = Coating results using silver metallic top coat paint 1) The judgment symbols in the table represent the same meanings as in Table 2.

In the case of a silver metallic top coat, the best results were obtained when a white intermediate coat was used.

Also, for 2CIB type solid colors, it is possible to obtain coatings with extremely bright colors by the same method.

FIG. 8 shows a partially enlarged sectional view of the surface of the one-coat, one-bake type coated article obtained in Examples 1 and 2, and the surface of the two-coat, one-bake type coated article obtained in Example 3. A partially enlarged cross-sectional view is shown in FIG. In the figure, 1 is a base material such as a steel plate, 2 is an undercoat film, 3 is an intermediate coat film, 4 is a top coat film,
5 represents a clear coating film.

(Effects of the Invention) As described above, according to the coating method of the present invention, it is possible to easily obtain extremely vivid color tones at a low cost that cannot be achieved with paints using existing pigments, and it is possible to easily obtain various color tones. And different painting methods such as solid colors, metallic colors, etc.? Since ζ can be widely applied, it is possible to obtain highly decorative paint colors, and we can provide cars with extremely high commercial value by quickly responding to the increasingly sophisticated and diversified demands of users. It became possible.

Further, although the present invention has been mainly described with respect to car painting, it is of course applicable to other types of painting.

[Brief explanation of drawings]

Figure 1 is the spectral reflectance curve of various paint colors, Figure 2 is the spectral reflectance curve of yellow to red, Figure 3 is the spectral reflectance curve of green to r color, and Figure 4 is the spectral reflectance of quinacridone red. Fig. 5 is a spectral reflectance curve of a red paint color obtained by the method of the present invention, Fig. 6 is a partially enlarged cross-sectional view of the surface of a paste-type coated object with a blue color paint obtained by the method of the present invention, and Fig. 9 is a spectral reflectance curve of a red paint color obtained by the method of the present invention. FIG. 1 is a partially enlarged cross-sectional view of the surface of a two-coat, one-piece type coated article according to the method of the present invention. In the figure, 1...Base material 2...Undercoat film 3...Intermediate coat film 4...Top coat film 5...Clear paint film

Claims (3)

[Claims] (1) Calculate the average surface reflectance in a specific wavelength region of the spectral reflectance curve in the visible light wavelength region of the paint film that is formed when the base is completely hidden with the paint used for top coating, and calculate the average surface reflectance in a specific wavelength region. After forming a lower coating film having an average surface reflectance higher than IOX in the above specific wavelength range on a base material such as metal or synthetic resin, when performing a one-coat one-bake type top coating on the base coating film. Use a paint with a hiding film thickness of 60 μm or more, and when performing a two-coat, one-bake top coat on the base coat, use a paint with a hidden film thickness of 20 μm or more, depending on the coating form. 1. A coating method comprising forming a coating film having a thickness equal to or less than the concealed film thickness using a paint having a concealed film thickness equal to or greater than a predetermined value. (2) The specific wavelength range of the above odor 'c1 spectral reflectance curve is a peak wavelength range of 600 mμ to 700 mμ, and when forming the top coat, the coating film has a peak wavelength range of 400 mμ to 50 mμ.
The coating method according to claim 1, characterized in that a top coating material having a light transmittance of 10% or less at a wavelength of 00 mμ is used. (3) In the above, the peak of the specific wavelength region of the spectral reflectance curve is in a wavelength region of 550 mμ or less, and a coating film with an average surface reflectance power of 430% or less in the peak wavelength region including 50 mμ before and after the peak wavelength is formed. and a top coat with an average surface reflectance of 4 in the peak wavelength region.
Claims characterized by using a base paint that forms a coating film having an average surface reflectance of 0% or more and 10 to 40% higher than the average surface reflectance of the top coating when completely concealed. The coating method described in paragraph 1.