JP2002214118A - Color changing/fading evaluation method of paint color - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict quickly color changing/fading property of a paint color including multiple kinds of color pigments at optional ratios without executing an actual outdoor exposure test. SOLUTION: Color specification values (L, a, b) before and after a color changing/fading test of a paint film containing the color pigments and bright material in two or more kinds of ratios are measured to thereby operate a recurrence formula, and the operation is executed relative to all color pigments included in the paint color, and the concentrations of each color pigment in the paint color to be evaluated are applied to the recurrence formula, to thereby estimate the color specification values (Ln, an, bn), (Ln', an', bn') before and after the color changing/fading test. Then tristimulus values (Xn, Yn, Zn), (Xn', Yn', Zn') before and after the color changing/fading test are determined therefrom, and the tristimulus values are divided respectively by tristimulus values (X0, Y0, Z0) of the bright material, to thereby calculate respectively spectral transmittance substitute values (Xn/X0, Yn/Y0, Zn/Z0), (Xn'/X0, Yn'/Y0, Zn'/Z0) before and after the color changing/fading test. The substitute values are multiplied respectively by the tristimulus values (X0, Y0, Z0) of the bright material, to thereby calculate tristimulus values (Xm, Ym, Zm), (Xm', Ym', Zm') before and after the color changing/ fading test of the paint color. Then, the color specification values (Lm, am, bm), (Lm', am', bm') before and after the color changing/fading test are calculated therefrom and evaluated. Hereby, evaluation agreeing well with the evaluation by the outdoor exposure can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating discoloration of a colored coating film without performing an actual discoloration test and having a high correlation with the actual discoloration test.

[0002]

2. Description of the Related Art In recent years, the market needs for products such as automobiles have been diversified, and the trend has been changing quickly, and it has become important to provide products that meet the needs in a timely manner. Paint colors for cars are no exception, and shortening the development period of new colors is an issue.

[0003] In the case of a coating film for an outer panel of an automobile, physical properties, workability and weather resistance are extremely important characteristics, and the actual vehicle is painted only when these characteristics pass the standards. Regarding the discoloration and fading of the coating color among the weather resistance, since the color tone of the coating film determines the evaluation of the appearance quality, the accelerated weather resistance tester whose reliability is not sufficient is used as an auxiliary, and the actual outdoor exposure test is performed. It is usually evaluated. However, in the outdoor exposure test, an extremely long-term test is required because the deterioration of the resin component of the coating film and the deterioration of the pigment gradually progress.

New products have been developed one after another for coloring pigments.
For the coating colors containing each pigment alone, data from an outdoor exposure test has been accumulated in advance. However,
In an actual coating color, a plurality of coloring pigments are mixed, and a glittering material such as aluminum foil or mica is often included. The inclusion of the brilliant material lowers the concentration of the coloring pigment in the coating film, so that the discoloration is often more conspicuous than the accumulated data.

Therefore, in the case of developing a new color, the coating color must be actually formed as a coating film and subjected to a long-term outdoor exposure test for evaluation. It is a bottleneck for shortening the period.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances. The purpose of the present invention is to quickly predict the discoloration and discoloration of the color.

[0007]

[MEANS FOR SOLVING THE PROBLEMS]
The feature of the evaluation method for discoloration and fading of light paint colors is that
Method for evaluating the discoloration and fading of metallic paint colors containing brilliant materials
And at least a kind of coloring pigment and a glittering material are different
Also form coating films from paints mixed in two ratios
Film formation step to be performed and color values before the color change and fading test of the film
(L, a, b) and the color values (L ', a', b ') after the discoloration test
Colorimetric steps for each colorimetric measurement
Regression to calculate regression formula of colorimetric values before and after the experiment
Steps for coating film formation, colorimetry
Colored faces used for the paint color for the regression step
Prepare multiple regression equations for each of the fees
Composition of each color pigment contained in 1 to n types in the target coating color
Apply the ratio to the above regression equation and change color for each color pigment
Color value before test (L_n, a_n, b_n) And color values after discoloration test
(L_n', a_n', b_n') To estimate each and each estimated color
Color value before pigment discoloration test (L_n, a_n, b_n) And discoloration test
Color specification value after (L_n', a_n', b_n') Tristimulus values before discoloration test
(X_n, Y_n, Z_n) And tristimulus values (X_n', Y_n',
Z_n') And convert it to the tristimulus value (X₀,
Y ₀, Z₀) And the spectral transmittance before the discoloration test
Substitute value (X_n/ X₀, Y_n/ Y₀, Z_n/ Z₀) And spectral transmission after discoloration test
Percentage substitution value (X_n'/ X₀, Y_n'/ Y₀, Z_n'/ Z₀)
And the spectral transmittance of each color pigment obtained before the discoloration test.
Percentage surrogate value (X_n/ X₀, Y_n/ Y₀, Z_n/ Z₀) And minutes after discoloration test
Light transmittance substitute value (X_n'/ X₀, Y_n'/ Y₀, Z_n'/ Z₀) And glitter material
Tristimulus value (X₀, Y₀, Z₀) For each of X, Y, and Z
The tristimulus value (X_m, Y_m, Z_m) And regression
Tristimulus value after color test (X_m', Y_m', Z_m') Calculate the paint color
Tristimulus value before discoloration test (X_m, Y_m, Z_m) And after the discoloration test
Tristimulus value (X_m', Y_m', Z_mTable before color change / fading test of paint color
Color value (L_m, a_m, b_m) And the color value after the discoloration test (L_m', a_m', b
_m') And calculate the color specification value (L_m, a_m, b_m) And strange
Color value after color fading test (L_m', a_m', b_m') From discoloration of paint color
Is to evaluate gender.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for evaluating the discoloration and discoloration of a coating color according to the present invention, first, in a coating film forming step, a coating material in which a kind of a coloring pigment and a brilliant material are mixed in at least two different ratios is used. To form Examples of the glittering material include aluminum foil, mica powder, pearl mica powder, silver-plated mica powder, and transparent iron oxide powder. It is desirable that the coloring pigment and the glittering material are formed into a paint by using a paint resin component actually used, and then coated and dried in the same manner as in practice to form a coating film.

In the case of a coating color having a low concealing property, the color tone of the base may appear, so it is desirable to form an intermediate coating film or the like which is actually used on the base.

The mixing ratio of the coloring pigment and the glittering material is not particularly limited, but it is desirable to increase the accuracy of the regression equation described later. In this sense, mixing is performed in at least three or more ratios within a practical range. It is desirable.

In the colorimetry step, the color values (L, a, b) of the coating film before the discoloration test and the color values (L ', a', b ') after the discoloration test are measured.
Are measured respectively. It is desirable that the discoloration test be a normal outdoor exposure test, but an accelerated weathering test may be performed in some cases. The color measurement of the color specification value can be performed using a normal color difference meter or a spectral altimeter.

In the regression step, the color values (L, a, b) of the coating film before the discoloration test and the color values (L ',
From the values of a ′, b ′), regression formulas of color values before and after the discoloration test are calculated. This regression equation is represented by the color value L
Component or component a or component b, and the pigment concentration in the coating color are variables, and three types of regression formulas are used for one kind of color pigment before and after the discoloration test and three types after the discoloration test, respectively. It will be calculated. This calculation can be performed using the least squares method or the like.

In the present invention, a coating film forming step, a color measuring step, and a regression step are performed for all of a plurality of coloring pigments used for a target coating color, and a regression equation is obtained. This regression equation is generally a linear equation or a quadratic equation. Since the steps up to this point are performed for each color pigment, it can be performed even when the pigment composition of the coating color is unknown, and may be stored in advance as data.

Next, in the present invention, since the pigment concentrations of a plurality of coloring pigments contained in the coating color to be evaluated are known, the pigment concentration of each coloring pigment is applied to the above regression equation to change each coloring pigment. color values before fading test _{(L n, a n, b} n) and the color value after discoloration test _{(L n ', a n'} , b n ') estimates, respectively.

The color mixture obtained by mixing a plurality of color pigments is a subtractive color mixture, and corresponds to, for example, a case where filters of various colors are superimposed. In the case of overlapping filters, the spectral transmittance of each filter is set to τ ₁ , τ ₂ ,.
Assuming that τ _n , the spectral transmittance τ _u of the mixed color can be expressed by the following equation multiplied by all.

Τ _u = τ ₁ × τ ₂ ×... × τ _n However, in the case of a colored pigment, it is difficult to measure the spectral transmittance, and the color specification value (L, a, b) is It does not directly represent spectral characteristics. Therefore, in the present invention, tristimulus values (X, Y, Z) that can be calculated from the color specification values and represent the light intensities having three types of spectral distributions are used. Then there tristimulus values when the coloring pigment was included predetermined concentration _{p (X p, Y p,} Z p) tristimulus values for luminous material alone _{(X 0, Y 0, Z} 0) with a spectral transmittance obtained by dividing each at a rate substitute value _{(X p / X 0, Y} p / Y 0, Z p / Z 0), it was decided to substitute the spectral transmittance of the colored pigment.

Accordingly, the tristimulus values (X _u , Yu _u , Z _u ) of the paint color containing the n kinds of coloring pigments and the brilliant material are the tristimulus values (X ₀ , Y ₀ , Z) of the brilliant material alone. _0), it is calculated by the following equation spectral transmittance substitute values _{(X p / X 0, Y} p / Y 0, Z p / Z 0) multiplied by each of the colored pigment.

(X_u, Y_u, Z_u) = (X₀* X₁* X_Two..X_n/ X₀ ⁿ, Y₀*
Y₁* Y_Two・ ・ Y_n/ Y₀ ⁿ, Z₀* Z₁* Z_Two..Z_n/ Z ₀ ⁿTherefore, from this equation, the discoloration of the paint color to be evaluated
Tristimulus value before test (X_m, Y_m, Z_m) And three stabs after discoloration test
Extreme value (X_m', Y_m', Z_m') Is required, and the paint color will change
Color specification value before color test (L_m, a_m, b_m) And color values after discoloration test
(L_m', a_m', b_m') Can be calculated. And this
Can be used to evaluate the discoloration and discoloration of the paint color.
Compute the square root of the sum of the squares of the differences a and b
It is also preferable that the color difference ΔE is calculated and evaluated.

The tristimulus values (X ₀ , Y ₀ , Z ₀ ) of the glitter material alone
May be determined by measuring the colorimetric value of the glittering material alone, but the colorimetric value of a coating film containing the glittering material alone in the same amount as that in the paint color to be actually evaluated is measured. It is preferable to obtain it. By doing so, the error can be further reduced, and the correlation with the actual exposure test is further improved.

[0020]

The present invention will be described below in detail with reference to examples.

The coating colors to be evaluated contain known amounts of three kinds of coloring pigments, A, B and C, and an aluminum foil pigment as a glitter.

First, the color pigment A and the aluminum foil pigment are mixed at three mixing ratios shown in Table 1 to form paints.
Here, an acrylic-melamine resin paint was used, and the total concentration of the pigment was 15 PWC (Pigment Weight Content = 100 × the weight of the pigment / (the weight of the pigment + the weight of the solid content of the resin)).

[0023]

[Table 1]

An undercoat film is formed in advance for each paint.
The coated test piece was applied and baked to form a coating film. So
Discoloration test for 24 months outdoor exposure
Colorimetric value (L_A, a_A, b_A) And discoloration
Color value after test (L_A', a_A', b _A') Were each measured.
The results are shown in FIG. From the obtained values, by the least square method
Find the regression equation between the concentration of color pigment A (PWC) and the color value
Was.

[0025] The pigment concentration and x, Table color value before discoloration test, L = -2.6092x + 65.982, a = 0.1929x 2 -3.9913x-6.
0472, expressed as ^{b = -0.1097x 2 + 2.2242x + 0.1906} . The correlation coefficient R ² of each regression equation is 0.9689 or 1,
Extremely high correlation. Also after the discoloration test
Regression equations were obtained for L, a, and b.

The same color measurement is performed for the pigments B and C, and a regression equation is obtained in the same manner.

On the other hand, only the aluminum foil pigment was made into a paint so as to have 15 PWC, and similarly, the color value (L ₀ , a) before the color change test was performed.
_0, b ₀₎ and colorimetry, then advance to calculate the tristimulus values _{(X 0, Y 0, Z} 0). In the case of an aluminum foil pigment, since the color specification value hardly changes before and after the discoloration test, only the value before the discoloration test is sufficient. It is desirable that the concentration of the aluminum foil pigment be the concentration in the coating color to be evaluated.

Next, the concentration of the color pigment A in the coating color to be evaluated was applied to the above regression equation, and the color values (L _A , a _A , b _A ) before the discoloration test and the color values after the discoloration test were determined. Color values (L _A ', a _A ', b
_A ') and tristimulus values (X _A , Y
_A, Z _A) and tristimulus values after the discoloration test _{(X A ', Y A'} , calculates Z _A '), respectively. Similarly, for the color pigment B and the color pigment C, the tristimulus values (X _B , Y _B , Z _B ) before the fading test were performed.
_{(X C, Y C, Z} C) and tristimulus value after discoloration test _{(X B ', Y B'} ,
_{Z B ') (X C'} , Y C ', Z C' calculates a).

Then, each tristimulus value is divided by the tristimulus value (X ₀ , Y ₀ , Z ₀ ) of the previously obtained aluminum foil pigment, and
As shown in Table 2, the spectral transmittance substitute values are calculated.

[0030]

[Table 2]

The tristimulus values (X _m , Y _m , Z _m ) of the paint color to be evaluated before the discoloration test and the tristimulus values after the discoloration test (X _m , Y _m , Z _m )
X _m ′, Y _m ′, Z _m ′) are obtained by multiplying the spectral transmittance substitute values by the tristimulus values (X ₀ , Y ₀ , Z ₀ ) of the aluminum foil pigment. You can ask.

[0032]

[Table 3]

The tristimulus values (X _m , Y _m , Z _m ) before and after the discoloration test of the paint color to be evaluated and the tristimulus values (X _m ′, Y _m ′, Z _m ′) after the discoloration test ) Are the color values (L _m , a _m , b _m ) before the discoloration test and the color values (L _m ′, a _m ′,
b _m ′) and calculate the color difference ΔE from the following equation.

ΔE = ((L _m −L _m ′) ² + (a _m −a _m ′) ² + (b _m −b _m ′) ² ) ^1/2 According to the method of the above embodiment, a plurality of coatings are performed. The color difference ΔE was calculated for the color. An outdoor exposure test was performed for each coating color for 18 months, and then the color difference ΔE was measured using a color difference meter. The results are shown in FIG.

From FIG. 2, it is apparent that the difference between the color difference ΔE calculated by the evaluation method of the present invention and the color difference ΔE measured by the actual exposure test is ± 1 or less, and that they are highly consistent with each other. It is.

[0036]

According to the method for evaluating discoloration and discoloration of a coating color of the present invention, data of pigments to be used are stored in advance so that the discoloration and discoloration of the coating color to be evaluated can be performed without actually performing a discoloration test. Can be predicted with high accuracy.
Therefore, it is possible to eliminate the necessity of the color change test of the paint color to be evaluated, which greatly reduces the man-hour and cost, and greatly shortens the development period of the new color. Lee.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a pigment concentration of a color pigment A measured in one embodiment of the present invention and a color specification value (L, a, b).

FIG. 2 is a graph showing a relationship between a color difference ΔE calculated in one embodiment of the present invention and a color difference ΔE actually measured after outdoor exposure.

Claims (1)

[Claims] 1. A metallurgy comprising a plurality of coloring pigments and a glitter.
A method for evaluating the discoloration and fading of paint coating colors, wherein at least two kinds of pigments differing from one kind of pigment and a brilliant material.
Coating form to form a coating from paint mixed at different ratios
And a coloration value (L, a,
b) and the color values (L ', a', b ') after the discoloration test were measured.
Colorimetric steps to color and their values before and after the color change test
The regression step to calculate the regression equation
The coating film forming step, the color measurement step, and the regression step.
Color pigments used for the target coating color
To prepare a plurality of regression formulas, the composition of each color pigment contained in 1 to n kinds in the target coating color
Apply the ratio to the above regression equation and change color for each color pigment
Color value before test (L_n, a_n, b_n) And color values after discoloration test
(L_n', a_n', b_n'), And the color specification value (L_n, a_n,
b_n) And the color value after the discoloration test (L_n', a_n', b_n') Discolored
Tristimulus value before test (X_n, Y_n, Z_n) And tristimulus after discoloration test
Value (X_n', Y_n', Z_n') And convert it to brilliant
Tristimulus value (X₀, Y ₀, Z₀) Before the color change test
The spectral transmittance substitute value of (X_n/ X₀, Y_n/ Y₀, Z_n/ Z₀) And discoloration test
The spectral transmittance substitute value (X_n'/ X₀, Y_n'/ Y₀, Z_n'/ Z₀)
Spectral transmittance before discoloration and fading test obtained for each color pigment
Substitute value (X_n/ X₀, Y_n/ Y₀, Z_n/ Z₀) And spectral transmission after discoloration test
Percentage substitution value (X_n'/ X₀, Y_n'/ Y₀, Z_n'/ Z₀) And glitter
Extreme value (X₀, Y₀, Z₀) Is multiplied for each of X, Y, and Z,
Tristimulus value before color discoloration test (X_m, Y_m, Z_m) And discoloration test
Later tristimulus values (X_m', Y_m', Z_m') And calculate the tristimulus value (X_m, Y_m, Z_m) And discoloration test
Tristimulus value after test (X_m', Y_m', Z_m') Color change test of paint color
Previous color specification value (L_m, a_m, b_m) And the color value after the discoloration test (
L_m', a_m', b_m') And calculate the color specification value (L_m,
a_m, b_m) And the color value after the discoloration test (L_m', a_m', b_mFrom ')
Discoloration of paint characterized by evaluating discoloration of paint
Color evaluation method.