Method for producing coating composition

Abstract

An object of the present invention is to provide a method for producing a coating composition, which can improve the productivity of the coating composition. [Solution] The method includes a correction value acquisition step of acquiring a correction value, which is the color difference between the color obtained by liquid colorimetry of a paint composition and the color obtained by colorimetry of a coating film, for a specific color, and a prediction step of predicting a blend composition of raw materials for color adjustment suitable for obtaining a target color using the pre-adjustment liquid colorimetry color obtained by performing liquid colorimetry of the paint composition before adjustment and the correction value, and the prediction step is repeated until the difference between the color obtained by adding the predicted blend composition and the target color falls below a predetermined reference value.

Description

[Technical field]

[0001] The present invention relates to a method for producing a coating composition. [Background technology]

[0002] Conventionally, when producing a paint composition, a paint composition before adjustment is first prepared, and then the adjustment is repeated to approach the desired paint properties. When preparing a paint composition before adjustment, a pigment, a resin, and a solvent are first dispersed in an SG mill or the like to prepare and prepare a large number of primary color paint compositions. Then, as a preparation step, a primary color paint composition, a resin, a solvent, and an additive are added to the prepared paint composition before adjustment, and the paint composition is prepared by dispersing and mixing them. Here, the amount of the primary color paint composition, the resin, the solvent, and the additives added can be recorded, for example, in past data such as a work management table, and by referring to the data, the paint properties can be approached to a certain extent.

[0003] For example, the process for adjusting the paint composition before adjusting the paint properties to the desired color and gloss is as follows (also called the color matching process). That is, the prepared paint composition before adjusting the paint properties is applied to a substrate such as art paper or a steel plate to form a coating film, and the color and gloss are measured using a color difference meter or gloss meter. Based on the color difference and gloss difference from each target painted plate and past data such as a work management sheet, a color matcher manually adds a primary color paint composition for adjustment, a solvent, and a gloss adjuster. By repeating this process until the color difference and gloss difference from the target painted plate are equal to or less than a certain value, a paint composition having a predetermined paint property can be obtained.

[0004] Computer color matching (also called CCM) devices are used to mechanize the repetitive work of such color matching processes. Computer color matching devices for general automotive repair paint compositions and architectural paint compositions obtain color expression patterns when mixing basic primary colors according to the theoretical formulas of Kubelka-Munk and Duncan. Next, the color measurement values ​​of the spectral reflectance spectrum of the paint composition when each actual single primary color is used and the color measurement values ​​when they are mixed in a predetermined ratio are used to correct the theoretical calculation based on actual measurements, and the color of an unknown mixture ratio is calculated from a small amount of actual measurement data (primary data) or the mixture ratio of a target color is calculated. From this calculation mechanism, the correction mixture amount to change (fill the mixture difference) from the current color (known mixture) to the target color (calculated mixture) is calculated.

[0005] Furthermore, in order to more accurately predict colors and to calculate corrected blend amounts based on the predictions, it has been proposed to improve the efficiency of paint composition production by using a prediction method based on an artificial intelligence model using machine learning instead of calculations based on theoretical formulas (e.g., Patent Documents 1 and 2).

[0006] However, although these methods can reduce the number of repetitive operations in the color-matching process, there is a limit to improving the productivity of the coating composition. That is, when measuring the color of a coating composition (also called colorimetry), the coating composition must be applied to a substrate such as art paper or a steel plate, cured and dried at 100 to 140°C for 20 to 30 minutes, a coating film must be formed, and then the color must be measured, and therefore, each time the adjustment is repeated, it takes time to cure and dry the coating film.

[0007] In response to this, for example, Patent Document 3 proposes a method for estimating the color of a coating film, in which a theoretical formula is used to convert the color of a coating composition (colored liquid) into the color of a dried coating film. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 4-235322 [Patent Document 2] Patent Publication No. 2021-107781 [Patent Document 3] Japanese Patent Application Publication No. 6-050816 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the method of Patent Document 3 is to calculate parameters that enable estimation of the color of a coating film for any color of coating composition. Therefore, for a specific color, the accuracy of converting the color of a coating composition into the color of a dried coating film measured is not sufficient, and when applied to color matching, the number of times that the paint properties need to be repeatedly adjusted increases, which does not lead to a sufficient improvement in productivity, and when the control range (tolerance range) for the target value is small, there are cases where color matching is not completed.

[0010] Therefore, an object of the present invention is to provide a method for producing a coating composition, which can improve the productivity of the coating composition. [Means for solving the problem]

[0011] The gist and configuration of the present invention are as follows. (1) A method for producing a coating composition, comprising adding a raw material for adjusting a color to a coating composition before preparation to produce a coating composition having a target color, A correction value acquisition step for acquiring a correction value, which is a color difference between a color measured by colorimetry of a liquid of a coating composition and a color measured by colorimetry of a coating film, for a specific color; A prediction step of predicting a blending composition of the raw materials for color adjustment suitable for obtaining the target color by using a color measured by performing color measurement of the coating composition before adjustment and the correction value, A method for producing a coating composition, characterized in that the prediction step is repeated until the difference between the color obtained by adding the predicted blend composition and the target color becomes equal to or less than a predetermined reference value.

[0012] (2) In the prediction step, the liquid color measurement of the coating composition before adjustment is carried out immediately after a predetermined time has elapsed by placing the coating composition in a transparent cell for color measurement and stirring the coating composition before adjustment in the transparent cell; The predetermined time is fixed the same when the prediction step is repeated, The method for producing a coating composition according to (1) above, wherein the predetermined time period is selected from the range of 0.1 to 600 seconds.

[0013] (3) The method for producing a coating composition according to (1) or (2) above, wherein the correction value is fixed the same when the prediction step is repeated.

[0014] (4) further comprising a gap target value setting step of setting a color gap target value; In the gap target value setting step, the absolute value of the difference between the value obtained by converting the acquired liquid colorimetric color of the coating composition before adjustment into the colorimetric colorimetric color of the coating film using the correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the acquired liquid colorimetric color of the coating composition before adjustment into the colorimetric colorimetric color of the coating film using the correction value and the target color, The method for producing a coating composition according to any one of (1) to (3), wherein the prediction step is a gap target value corresponding blend composition prediction step for predicting a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value.

[0015] (5) The method for producing a coating composition according to (4) above, wherein in the gap target value setting step, the gap target value is set so that the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the coating composition before adjustment into the color measurement of the coating film using the correction value, the closer the gap target value becomes to the target color, either continuously or stepwise.

[0016] (6) In the gap target value corresponding composition prediction step, the composition of the color adjusting raw materials is predicted by theoretical calculation by a computer under conditions in which each amount in the composition of the color adjusting raw materials is individually limited to a solution candidate generated from a finite numerical range, and the solution candidate includes a case in which the amount is 0.

[0017] (7) A method for producing a coating composition as described in (6) above, comprising, when a composition of the raw materials for color adjustment suitable for obtaining the color of the target gap value cannot be calculated by the theoretical calculation by the computer in the gap target value corresponding composition prediction step, releasing some or all of the conditions and re-predicting the composition of the raw materials for color adjustment by the theoretical calculation by the computer.

[0018] (8) The method further includes a main colorant specifying step of specifying a main colorant that is the most abundant in the colorant blend composition of the coating composition before the preparation, 7. The method for producing a coating composition according to claim 6, wherein in the gap target value corresponding blend composition prediction step, a prediction is made for at least the main colorant using conditions limited to solution candidates generated from the finite numerical range.

[0019] (9) The method for producing a coating composition according to any one of (4) to (8), wherein in the gap target value corresponding blend composition prediction step, a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value is calculated using any one of a brute force search method, a mathematical optimization method, and a random search method. Effect of the Invention

[0020] According to the present invention, it is possible to provide a method for producing a coating composition, which can improve the productivity of the coating composition. [Brief description of the drawings]

[0021] [Figure 1] 1 is a flowchart of a method for producing a coating composition according to a first embodiment of the present invention. [Diagram 2] 5 is a flowchart of a method for producing a coating composition according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0023] <First embodiment> The method for producing a coating composition according to a first embodiment of the present invention is a method for producing a coating composition having a target color by adding raw materials for adjusting color to an unadjusted coating composition.

[0024] The term "paint composition before adjustment" refers to a paint composition in which, among the materials constituting the target paint composition, raw materials having the same function as the raw materials for color adjustment are mixed in a predetermined amount of 0 to 100%, and raw materials other than the raw materials having the same function as the raw materials for color adjustment are mixed in a predetermined amount of 100%, and the color of the paint composition is approximately similar to the target color. It may or may not contain raw materials for color adjustment. In addition, the amount of each material may be unknown. Here, the coating composition is, for example, a colorant prepared by dispersing a resin, a solvent, and one type of color pigment in an SG mill or the like, for various color pigments, and in order to adjust to an arbitrary color, a resin, a solvent, and an additive are added to one or more colorants and mixed together. The coating composition is not particularly limited, and may be in the form of, for example, an aqueous coating composition, a solvent-based coating composition, a powder coating composition, a solventless coating composition, or the like. Examples of the blended composition include resin raw materials, pigments, design raw materials, solvents (including water), additives, etc. Examples of resin raw materials include acrylic resins, polyester resins, epoxy resins, alkyd resins, fluororesins, urethane resins, aminomelamine resins, isocyanate resins, blocked isocyanate resins, urethane-modified polyester resins, and other modified resins of these resins, examples of pigments include inorganic pigments, organic pigments, coloring pigments, and extender pigments, examples of design raw materials include glittering materials such as metallics and pearls, aggregates, silica, resin beads, wax, and examples of additives include viscosity adjusters, silicone additives, rust inhibitors, catalysts, and defoamers. Examples of uses include coil coating compositions, general industrial coating compositions, automotive coating compositions, automotive repair coating compositions, architectural coating compositions, heavy-duty anticorrosive coating compositions, and marine coating compositions. Coating methods include spray coating, roller coating, brush coating, roll coating (including natural and reverse rotation), curtain flow coating, die coating, electrodeposition coating, powder coating, and electrostatic coating. Drying methods include bake drying, forced drying, natural drying, and ultraviolet curing.

[0025] In addition, the term "color-adjusting raw material" refers to a general term for, for example, colorants, gloss regulators, viscosity regulators, and design raw materials used for adjusting colors. The color-adjusting raw material includes at least one of a plurality of types of colorants, one or more types of gloss regulators, and one or more types of viscosity regulators. It is preferable that the color-adjusting raw material includes at least a plurality of types of colorants. The colorant includes a color pigment, and examples of the color pigment include black pigments, white pigments, yellow pigments, green pigments, red pigments, blue pigments, titanium oxide, and red iron oxide. Examples of the gloss regulator include aggregates (sand, etc.), silica, reflective materials, and alumina as components. Examples of the viscosity regulator include synthetic resin-based viscosity regulators, natural product-based viscosity regulators, and inorganic viscosity regulators. Furthermore, examples of the synthetic resin-based viscosity regulator include polymer-type viscosity regulators and association-type viscosity regulators. Solvents such as water and organic solvents can also be used as viscosity regulators. The coloring agent, gloss modifier, viscosity modifier, and design raw material may be used as the raw material itself, or may be dispersed in a solvent such as water or an organic solvent using a dispersant or the like.

[0026] Also, "color" is, for example, L * a * b * L in color space * Value, a * Value, b * Value (JIS Z 8781-4 (2013)), XYZ color system, RGB color system, Yxy color system, Hunter Lab color system, L * C * h * The color can be measured using a known color measurement method, for example, a spectrophotometer CM-M6 (Konica Minolta) is used to measure the L value measured by irradiating a light source at angles of 25°, 45°, and 75° with a light receiving part perpendicular to the coating film formed on a test plate as 0°. * Value, a * Value, b *The value can be measured. Alternatively, it can be measured using a spectrophotometer X-Rite MA68II (manufactured by X-Rite). The measurement angle can be appropriately adjusted depending on the purpose or the equipment used. Any other index can be used. Furthermore, for example, any index can be used, such as reflection spectrum data, which is an index in which the reflection spectrum intensity at every 5 nm from 400 nm to 780 nm is used as the color. The color may be evaluated directly from the obtained coating composition. As an example, the coating composition can be measured in a state where it is placed in a quartz glass cell or a plastic cell using a spectrophotometer SE7700 (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0027] FIG. 1 is a flow chart of a method for producing a coating composition according to a first embodiment of the present invention. The example of FIG. 1 involves theoretical calculation by a computer. The adjustment is to be performed on color. As shown in FIG. 1, in the first embodiment, first, primary data is acquired (step S101). The primary data is actual measurement data of the spectral reflectance at wavelengths of 400 to 700 nm for each coating composition for calculation. By acquiring such data, the relationship between the composition of the coating composition for calculation in an arbitrary coating composition and the change in color can be obtained, and the composition of the raw material for color adjustment suitable for obtaining the target color can be predicted by theoretical calculation by a computer. In the present disclosure, the prediction is not limited to the case of performing theoretical calculation by a computer, and it is preferable to omit step S101 when a computer is not used.

[0028] Next, in the first embodiment, data necessary for converting the color measured by liquid colorimetry of a coating composition that will result in a coating film having a target color into the color measured by colorimetry of the coating film is prepared (steps S102, S103). That is, a coating composition capable of producing a coating film having a target color and a coating film obtained by applying the same are prepared, and the colors of each are measured (Step S102). The method of liquid color measurement of the coating composition is to put the coating composition before adjustment into a transparent cell for color measurement, stir the coating composition before adjustment in the transparent cell, and perform the measurement immediately after a predetermined time has elapsed. The predetermined time is fixed to the same when the color measurement is repeated, and the fixed predetermined time is preferably selected from 0.1 to 600 seconds. Although it should not be interpreted as being limited to a specific theory, by performing color measurement after stirring and a predetermined time has elapsed, the dispersion of the components of the coating composition in the transparent cell is made uniform, while the liquid color measurement can be easily performed without requiring a large-scale device or the like as in the case of performing liquid color measurement during stirring. In addition, by fixing the same time when repeating color measurement, it is possible to prevent variation between repetitions. In addition, by selecting from 0.01 seconds or more, the liquid color measurement can be easily performed as described above, while by selecting from 600 seconds or less, the liquid color measurement can be performed before the components in the transparent cell become non-uniform again. Incidentally, color measurement in the paint composition state is sometimes called "liquid color measurement." Also, liquid colorimetry may not be performed in all steps of measuring color, and some of them may be replaced with colorimetry of the coating film. For example, only when it is expected to be the last adjustment, colorimetry of the coating film may be performed without liquid colorimetry.

[0029] For example, the color of the coating film can be measured by applying the coating composition to a substrate, such as art paper or a metal plate, to prepare a sample plate, and measuring the color using a color difference meter or the like.

[0030] With respect to the target color, a correction value is obtained, which is the color difference between the color obtained in step S102 by liquid color measurement of the coating composition and the color obtained by color measurement of the coating film (step S103: correction value obtaining step). As an example, it may be expressed as "correction value = (color of the paint composition measured in liquid form) - (color of the paint film measured in liquid form)". In this case, the correction value is subtracted from the color of the paint composition measured in liquid form, so that the color of the paint composition measured in liquid form can be converted into the color of the paint film measured in liquid form. As another example, the formula may be "correction value = (color measured by colorimetry of the coating film) - (color measured by liquid colorimetry of the paint composition)". In this case, the correction value is added to the color measured by liquid colorimetry of the paint composition, so that the color measured by liquid colorimetry of the paint composition can be converted into the color measured by colorimetry of the coating film. In either case, the correction value can be positive, zero, or negative. As another example, the correction value may be defined as the absolute value of the color difference, and the color of the coating composition measured by liquid colorimetry can be converted to the color of the coating film measured by colorimetry by subtracting the absolute value from the larger color measurement value, or by performing an equivalent calculation. In addition, various modifications and variations equivalent to the above examples are possible.

[0031] Next, in the first embodiment, the coating composition before adjustment is charged (step S104). At this time, the main colorant, which is the colorant with the largest blending amount, may be multiplied by a rate of 100%, and other colorants may be mainly adjusted. In the first embodiment, the coating composition before adjustment is charged for a specific color, for example, an industrial coating composition, whose target color is predetermined.

[0032] Next, the color measurement of the (initial) coating composition before adjustment that was charged in step S104 is performed (step of acquiring color data of the coating composition: step S105). The color measurement of the (initial) coating composition before adjustment is performed immediately after the coating composition before adjustment is placed in a transparent cell for color measurement and the coating composition before adjustment in the transparent cell is stirred and a predetermined time has elapsed, and the predetermined time is preferably selected from 0.1 to 600 seconds. Although it should not be interpreted as being limited to a specific theory, by performing color measurement after a predetermined time has elapsed after stirring, the dispersion of the components of the coating composition in the transparent cell is made uniform, while the liquid color measurement can be easily performed without requiring a large-scale device or the like as in the case of performing liquid color measurement during stirring, and by selecting from 0.01 seconds or more, the liquid color measurement can be easily performed as described above, while by selecting from 600 seconds or less, the liquid color measurement can be performed before the components in the transparent cell become non-uniform again.

[0033] Next, the color data of the liquid color measurement before adjustment obtained by performing liquid color measurement of the coating composition before adjustment and the correction value are used to convert the color data of the liquid color measurement before adjustment into color data of the coating film (step S106).

[0034] Furthermore, instead of measuring and converting the correction values ​​each time the paint is adjusted, values ​​for each paint color may be registered in a computer in advance and used each time.

[0035] Next, using the color data obtained by converting the coating composition before adjustment into a coating film, a blending composition of raw materials for color adjustment suitable for obtaining a target color is predicted (step S107: prediction step).

[0036] Since the target color is the color of the coating, the prediction is made by converting the color measured using the liquid into the color of the coating. That is, by adding or subtracting the correction value obtained in the correction value acquisition process (step S106) to the color of the paint composition determined by liquid colorimetry, the color of the paint composition determined by liquid colorimetry can be converted into the color of the coating film determined by colorimetry. In this embodiment, the prediction is performed by theoretical calculation of a computer (having a calculation unit). As described above, the theoretical calculation can be performed by a known method such as the Kubelka-Munk formula or mathematical optimization using the primary data acquired in step S101. On the other hand, the prediction can be performed by a method using an artificial intelligence model, or can be performed without using a computer.

[0037] From the predicted blend compositions, one blend composition is selected in which the difference between the target color difference and the calculated color difference is equal to or less than a predetermined reference value. When multiple candidates are predicted, the one in which the difference between the target color difference and the calculated color difference is the smallest can be selected, although this is not particularly limited. In a calculation method in which only one blend composition can be selected, the one in which the difference between the target color difference and the calculated color difference is the smallest is calculated and used as the blend composition of the raw material for color adjustment. In the prediction process (step S107), when calculating the blend composition of raw materials for color adjustment suitable for obtaining the target color, it is preferable to use any one of the following methods: brute force search method, mathematical optimization method, and random search method. The brute force search method is a method of specifying a parameter range and a numerical interval or an arbitrary numerical value, and calculating the color variation value by theoretical calculation for all patterns of the extracted variation amount (for example, 100,000 to 1 billion), thereby finding various variation amounts when the difference from the target value is less than a certain value. Here, it is synonymous with grid search. The mathematical optimization method is a technique for finding x1, x2, x3, and x4 as an optimization problem of a function of the amount of variation x1 in the addition ratio of colorant 1, the amount of variation x2 in the addition ratio of colorant 2, the amount of variation x3 in the addition ratio of gloss modifier, and the amount of variation x4 in the addition ratio of viscosity modifier. As the mathematical optimization method, it is preferable to use the simplex method, the interior point method, the gradient descent method, the quadratic programming method, the continuous linear programming method, the sequential quadratic programming method, the Lagrange undetermined multiplier method, the barrier function method, or the like. Random search is a method of specifying the number of trials and calculating color variation values ​​using theoretical calculations for patterns of variation amounts randomly extracted from within the specified range of parameter values, thereby determining various variation amounts when the difference from the target value is within a certain level.

[0038] Next, the predicted composition is added to prepare the adjusted paint composition (step S108). Next, the liquid color measurement of the adjusted paint composition is performed (step S109). Next, the color of the paint composition before adjustment is corrected (step S110). Next, it is determined whether the difference between the color obtained by adding the predicted composition and the target color is equal to or less than a predetermined reference value (step S111). The color obtained by adding the predicted composition is predicted in the prediction step of step S107, and the color obtained by liquid color measurement of the paint composition adjusted by adding the selected composition as described above can be obtained by converting it into the color of the coating film using the correction value. The target color can be obtained by measuring the color of a standard plate (if it has already been measured, it is used). Then, it is determined whether the color difference between them is equal to or less than a predetermined reference value. If the color difference is greater than the predetermined reference value, the process returns to step S107 and repeats the prediction step. In this case, the "paint composition before adjustment" in the n-th (n≧2) prediction step is obtained by adding the blend composition predicted in the (n-1) prediction step, and is the paint composition before the n-th adjustment is performed. The correction value when repeating the step of acquiring color data of the paint composition (step S109) may be the correction value acquired in the step S103. On the other hand, if the color difference is equal to or less than the predetermined reference value, the color matching is completed (step S112). The effects of the method for producing a coating composition according to the first embodiment will be described below.

[0039] The method for producing a coating composition according to the first embodiment includes a correction value acquisition step (step S103) for acquiring a correction value, which is the color difference between the color of the coating composition measured by liquid colorimetry and the color of the coating film measured by liquid colorimetry, and a prediction step (step S107) for predicting a blending composition of raw materials for color adjustment suitable for obtaining the target color using the color of the coating composition measured by liquid colorimetry before adjustment and the correction value, and repeating the prediction step (step S107) until the difference between the color obtained by adding the predicted blending composition and the target color becomes equal to or less than a predetermined reference value. As a result, as described above, the color of the liquid colorimetry is converted into the color of the coating film measured by the correction value for a specific color, so that it is not necessary to create a coating film from the coating composition each time, and the curing and drying time when creating a coating film can be omitted, thereby reducing the number of steps. In addition, when obtaining the correction value, color measurement is performed for a specific color to obtain a correction value specific to that specific color, so that highly accurate prediction (as shown in the examples described later) is possible, and the number of repetitions of the prediction process is reduced, which also makes it possible to reduce the number of steps. The reduction in the number of steps mentioned above leads to an improvement in the productivity of the coating composition. As described above, according to the method for producing a coating composition according to the first embodiment, it is possible to provide a method for producing a coating composition that can improve the productivity of the coating composition.

[0040] <Second embodiment> Next, a method for producing a coating composition according to a second embodiment of the present invention will be described. FIG. 2 is a flow chart of the method for producing a coating composition according to the second embodiment of the present invention. The method for producing a coating composition according to the second embodiment of the present invention is also a method for producing a coating composition having a target color by adding a raw material for adjusting color to a coating composition before adjustment. Steps S201 (obtaining primary data) to S206 (performing correction) are similar to steps S101 (obtaining primary data) to S106 (performing correction) of the method for producing a coating composition according to the first embodiment shown in FIG. 1, so repeated explanation will be omitted.

[0041] As shown in FIG. 2, in the second embodiment, after the correction is performed (step S206), a color gap target value is set (step S207: gap target value setting step) prior to the prediction step (step S208).

[0042] Here, the absolute value of the difference between the value obtained by converting the liquid color measurement of the coating composition before adjustment to the color measurement of the coating film using the acquired correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the liquid color measurement of the coating composition before adjustment to the color measurement of the coating film using the correction value and the target color. For example, if the liquid color measurement of the coating composition before adjustment is 23, and a correction value of 2 is added to it to make the color of the coating film 25, and the target color is 30, the absolute value of the difference between the color (converted value) of the coating film and the target color is 5 (=30-(23+2)), and the value multiplied by a rate of 0.5 to 0.9 (hereinafter also referred to as the approach rate) is 3.5 (=5×0.7) if the approach rate is 0.7. In this case, the gap target value can be 28.5 (=23+2+3.5). In this case, the absolute value of the difference between the coating color (converted value) and the gap target value is 3.5 (=28.5-25), which is smaller than the absolute value of the difference between the coating color (converted value) and the target color, which is 5 (=30-25). When managing the same thing using color difference, if the difference (color difference) between the coating color (conversion value) and the target color is -5 and the approach rate is 0.7, the initial gap target value can be a color difference of -1.5. In this case, the absolute value of the color difference of the gap target value is "1.5", which is smaller than the absolute value of the color difference before multiplying by the approach rate, which is "5".

[0043] Next, the mixture composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value is predicted using the color of the liquid color measurement before adjustment and the correction value (step S208). That is, the prediction process in the second embodiment is a gap target value corresponding mixture composition prediction process that predicts the mixture composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value. As described above, the theoretical calculation can be calculated by a known method such as the Kubelka-Munk equation or mathematical optimization using the primary data acquired in step S201.

[0044] Next, from among the predicted blend compositions, one blend composition is selected in which the difference between the color difference of the gap target value and the calculated color difference is equal to or less than a predetermined reference value. When multiple candidates are predicted, the one in which the difference between the color difference of the gap target value and the calculated color difference is the smallest can be selected, although this is not particularly limited. In a calculation method in which only one blend composition can be selected, the one in which the difference between the color difference of the gap target value and the calculated color difference is the smallest is calculated and used as the blend composition of the raw material for color adjustment. In the gap target value corresponding blend composition prediction step (step S208), it is preferable to use any one of the methods of brute force search method, mathematical optimization method, and random search method when calculating the blend composition of raw materials for color adjustment suitable for obtaining the color of the gap target value.

[0045] Next, the predicted formulation is added to prepare an adjusted paint composition (step S209). Next, the liquid color measurement of the adjusted paint composition is performed (step S210). Next, the color of the paint composition before adjustment is corrected (step S211). Next, it is determined whether the difference between the color obtained by adding the predicted formulation and the target color is equal to or less than a predetermined reference value (step S212). Here, the liquid color measurement of the paint composition adjusted by adding the selected formulation is performed, and the correction value is used to convert it into the color of the coating, and it is determined whether the color difference is equal to or less than a predetermined reference value.

[0046] If the measured color difference exceeds the predetermined reference value, the process returns to step S207, and steps S207 to S212 are repeated. However, in the repetition, the gap target value set in step S207 is set based on the color obtained by adding the predicted blending composition. For example, in the first step S207, when the color (conversion value) of the coating film before adjustment is 25, the target color is 30, and the approach rate is 0.7, the first gap target value is 28.5 as described above. As a result, if the color (conversion value) of the coating film formed from the coating composition adjusted by adding the selected blending composition is 28.4, in the second step S207, the absolute value of the difference between the current color (conversion value) and the target color based on the current "28.4" is 1.6 (=30-28.4), and this can be multiplied by, for example, an approach rate of 0.9 to set the gap target value to 29.84 (=28.4+1.6×0.9). In the case of a method of managing using color difference, for example, when the difference (color difference) between the color of the coating film (converted value) and the target color is -5 and the approach rate is 0.7, the initial gap target value is a color difference of -1.5 as described above. As a result, if the similar color difference for the coating composition adjusted by adding the selected blending composition is -1.6, which is 0.1 lower than the gap target value (0.1 larger in absolute value) due to the influence of the lot difference of the raw materials, in the second step S206, this can be multiplied by, for example, an approach rate of 0.9 to set the gap target value to a color difference of -0.16 (=-1.6+1.6×0.9). On the other hand, if the difference between the color obtained by adding the predicted blend composition and the target color is equal to or less than the predetermined reference value, the color matching is completed (step S213). The effects of the method for producing a coating composition according to the second embodiment will be described below.

[0047] First, the method for producing a coating composition according to the second embodiment of the present invention can provide a method for producing a coating composition that can improve the productivity of the coating composition, similar to the method for producing a coating composition according to the first embodiment of the present invention. Furthermore, the method for producing a coating composition according to the second embodiment of the present invention further includes a gap target value setting step (step S207) for setting a gap target value for color. In the gap target value setting step (step S207), the absolute value of the difference between the value obtained by converting the acquired liquid color measurement color of the coating composition before adjustment to the color measurement color of the coating film before adjustment using a correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the acquired liquid color measurement color of the coating composition before adjustment to the color measurement color of the coating film before adjustment using a correction value and the target color. Then, in the gap target value corresponding blend composition prediction step (step S208), a blend composition of raw materials for color adjustment suitable for obtaining the color of the gap target value is predicted. In this way, in the second embodiment, a gap target value that is lower than the original target value (the difference from the current color is smaller) is set, and the composition of the raw materials for color adjustment that corresponds to that gap target value is predicted. From the predicted compositions, one composition is selected such that the difference between the color difference of the gap target value and the calculated color difference is equal to or less than a predetermined reference value (in this example, the color difference is 0.1 or less), and the color is adjusted. Therefore, when adjusting the color of the paint composition, it is possible to prevent the amount of adjustment from becoming excessive. Then, the liquid color of the paint composition adjusted by adding the selected blending composition is measured, and the correction value is used to convert it into the color of the coating film, and it is determined whether the color difference is below a predetermined reference value (step S212).By repeating steps S207 to S212 as necessary based on the results, a paint composition having the final target color can be produced. Here, the color is not linear in relation to the amount of color mixed and the amount of color change. * , a * , b * In contrast, in the second embodiment, the gap target value is set by multiplying the approach rate based on the color, so that it is possible to more accurately prevent the blend amount for adjustment from becoming excessive, compared to a method in which the approach rate is multiplied by the predicted blend amount, for example. For example, the amount of colorant added and the amount of color change are not in a linear relationship, and the more colorant added, the smaller the color change. In other words, if the predicted blend amount is multiplied by 90% of the approach rate, the color difference will be closer than if the color difference was multiplied by 90% of the approach rate. For example, if a white paint composition is used in combination with a black paint composition, the color difference will be closer than if the white paint composition is used with a black paint composition. * When the value is adjusted from -0.5 to -0.05 at 90% of the approach rate of the color difference, the color difference is too close at -0.5 to -0.02 at the approach rate of the amount of addition. If there is no difference in the lot of the colorant, the number of times of adjustment may be reduced because the color difference is closer, but if there is a difference in the lot of the colorant and its coloring power is 20% stronger, the color difference is only slightly over at 90% of the approach rate of the color difference, from -0.5 to 0.04 (=-0.5+0.5×0.9×1.2), and the adjustment is completed if the control width is ±0.05. However, if the approach rate of the amount of addition is 90%, the color difference will exceed the opposite side, from -0.5 to 0.076 (=-0.5+(0.5-0.02)×1.2), and more black paint composition must be added to bring the color back, which leads to the above-mentioned overproduction. It may be possible to anticipate this and lower the approach rate of the amount of addition, but this would require checking the fluctuation curve of the amount of addition and the color, which would be cumbersome and prone to errors. On the other hand, the color difference approach rate is efficient and easy to set because it is faithful to the intended approach to the target property.

[0048] Here, in the preparation of industrial paints manufactured in large quantities at paint factories, if too much of the preparation compound is added, it is necessary to add more of the preparation compound to restore the color of the coating film. For example, if the color is gray, a colorant of the opposite color (for example, if too much black colorant is added, a white colorant) is added to restore the color. In such cases, the amount of paint produced is significantly more than the planned amount, and waste such as material costs and disposal of the excess production is often generated. In particular, in the case of industrial paints manufactured in large quantities at paint factories, several hundred kg to several tons (tons) may be manufactured per batch, and the waste is more noticeable. In addition, there are also disadvantages such as an increase in labor hours, such as transferring the paint to a larger manufacturing container to prevent it from overflowing from the manufacturing container, so adjustments were made by relying on the skills of skilled workers, but adjustments made exclusively by skilled workers have problems such as quality variations and high costs due to increased labor hours due to differences in adjustment accuracy depending on the level of skill. In addition, in the adjustment process, a specific colorant with a maximum blend amount is often blended close to the target value when the paint before adjustment is prepared, and even a small amount of a colorant with a minimum blend amount can result in a large excess, resulting in a noticeable problem of overproduction, where an amount far exceeding the planned amount is produced in order to return to the original amount. For example, if the correct blend amount is 99 kg of white colorant and 1 kg of black colorant, even if each colorant is blended in the correct amount, if the coloring strength of the black colorant is 10% higher, 9.9 kg of white colorant must be added to return to the original amount, resulting in at least 9.9 kg of overproduction. The second embodiment, which uses a gap target value, has the advantage that such overproduction can be suppressed.

[0049] Here, in the second embodiment, in the gap target value setting process (step S207), it is preferable to set the gap target value so that the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the coating composition before adjustment into the color measurement of the coating film using a correction value, the closer the gap target value becomes to the target color, either continuously or stepwise. As described above, the second embodiment involves repeating steps S207 to S212. As the color of the paint composition gradually approaches the target color, less and less of the compounding composition needs to be added for adjustment. Therefore, the excess amount in case of adding too much of the compounding composition also becomes smaller, and the risk becomes smaller. Therefore, as steps S207 to S212 are repeated, the smaller the absolute value of the difference between the value obtained by converting the liquid color measurement of the paint composition before adjustment into the color measurement of the coating film using the correction value, and the gap target value, the closer the gap target value becomes to the target color either continuously or stepwise (for example, by adopting an approach rate closer to "1"), thereby reducing the number of repetitions until paint is produced as much as possible, and improving production efficiency without compromising the effect of suppressing overproduction.

[0050] In the second embodiment, in the gap target value setting step (step S207), L * , a * , b * It is preferable to set the gap target value independently for each of the L. If a common gap target value is used, overproduction will occur if any of the L exceeds the target value due to overfilling. Also, if the common gap target value is set too low compared to the target color, productivity will decrease. * , a * , b * Independently setting gap target values ​​for each of the above can further reduce overproduction while maintaining manufacturing efficiency.

[0051] For example, ΔL * If is greater than 1, the approach rate is 50% and ΔL * When ΔL is between 0.5 and 1.0, the approach rate is set to 70%. * If Δa is 0.5 or less, the approach rate can be set to 100%. * , Δb *can also be applied independently.

[0052] In the second embodiment, a prepared coating composition (hereinafter also referred to as a finished coating composition) and a coating film obtained by applying the same are prepared, and the color data of each is measured. The difference between the measured values ​​is then calculated as a correction value (Δdw), and the measured value of the coating film is estimated from the measured value of the coating composition. This method has the advantage that, when the target color changes each time, such as in the case of automotive repair paint, it is difficult to prepare Δdw in advance, but when the target color is predetermined, the color of the coating film can be predicted with high accuracy. Here, the coating color of industrial products is usually prepared in advance in a laboratory, and the color is confirmed and agreed upon using a standard plate. When the product is produced in the factory based on the color of the standard plate, slight color changes resulting from pigment lots and production variations are adjusted in an adjustment process. Therefore, the target color is determined in advance, and the Δdw of the finished coating composition can be prepared in advance. Here, Δdw varies depending on the color. For example, even a slight change in color will cause a change in Δdw. Therefore, when high-precision color adjustment is required, if the Δdw of the color during adjustment is not known, the color of the coating film cannot be accurately predicted. However, it is not realistic to measure Δdw in advance for all colors in the process of adjustment. In order to solve this problem, when adjusting colors, * , Δa * , Δb * Instead of setting a correction compounding composition that makes the value zero from the beginning, a gap target is set, and even if the Δdw after adjustment is used as the true Δdw for all colors in the process leading up to the adjustment, the true Δdw during the adjustment process gradually approaches the Δdw after adjustment, enabling precise adjustment. In this way, the method of converting the liquid color measurement into the color of the coating film using the correction value is of course useful on its own, but by using it in combination with the method using the cap target value, the particularly advantageous effects described above can be obtained. EXAMPLES

[0053] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0054] The coating compositions were each produced 20 times by the methods according to Examples 1 and 2 and Comparative Examples 1 and 2, and the color matching accuracy (ΔL * , Δa * , Δb * ) and production rate were calculated and the arithmetic mean values ​​were compared.

[0055] First, the methods for preparing the colorants used in Examples 1 and 2 and Comparative Examples 1 and 2 will be described.

[0056] <White paint composition> A white coating composition was prepared by mixing 65.3 parts by mass of an acrylic resin emulsion as the resin, 23.0 parts by mass of titanium oxide as the white pigment, and 12.0 parts by mass of tap water, and dispersing the mixture using a sand mill (dispersion medium: glass beads) until the maximum particle size of the coarse pigment particles was 20 μm or less. <Preparation examples of other color coating compositions> A black coating composition, a red coating composition, and a yellow coating composition were prepared in the same manner as in the preparation example of the white coating composition, except that the types and amounts of each material were changed as shown in Table 1. The formulations of each color coating composition are shown in Table 1. Each coating composition was used to adjust the color of the coating composition described below (color-adjusting coating composition (white), (black), (red), (yellow)).

[0057] [Table 1]

[0058] Next, the methods for preparing the pre-adjusted coating compositions used in Examples 1 and 2 and Comparative Examples 1 and 2 will be described. <Preparation Example of Pre-Adjusted Paint Composition 1> 98.2 parts by mass of the white paint composition, 0.4 parts by mass of the black paint composition, 0.2 parts by mass of the red paint composition and 1.2 parts by mass of the yellow paint composition were mixed and stirred for about 10 minutes using a disper to prepare pre-adjusted paint composition 1. <Preparation examples of other pre-adjusted coating compositions> Pre-prepared coating compositions 2 to 4 were obtained by the same preparation method as in the preparation example of pre-prepared coating composition 1, except that the types and amounts of each material were changed as shown in Table 2 below. The formulations of the pre-prepared coating compositions are shown in Table 2.

[0059] [Table 2]

[0060] Details of the materials used in preparing the coating compositions are as follows: Resin: Dianall BR112 (acrylic resin emulsion, manufactured by Mitsubishi Rayon Co., Ltd.), solid content: 40% by mass White pigment: TIPAQUE R-820 (titanium oxide, manufactured by Ishihara Sangyo Kaisha) Black pigment: Mitsubishi Carbon Black MA100 (carbon black, manufactured by Mitsubishi Chemical Corporation) Yellow pigment: TAROX synthetic iron oxide LL-XLO (yellow iron oxide, manufactured by Titan Kogyo Co., Ltd.) Red pigment: Bayferrox 180M (iron oxide, manufactured by LANXESS)

[0061] <How to prepare the dry coating> The coating composition was applied to the surface of a hiding power test paper (manufactured by Motofuji Co., Ltd.) using a 6 mil doctor blade and baked at 100° C. for 15 minutes to obtain a dry coating film (film thickness: 40 μm) of the coating composition.

[0062] The color data obtained in each of the Examples and Comparative Examples was measured by the following method. <Measuring method for color data of coating film> (Color measurement of dry coating film) The coating film obtained by the above coating composition and the method for preparing the dried coating film was measured for color (L) using a spectrophotometer CM-3600A (Konica Minolta, Inc.). * , a * , b * value, or the L with the target standard plate * , a * , b * The difference between the values ​​was measured.

[0063] <Method for measuring color data of coating composition> (liquid color measurement) First, the coating composition was placed in a transparent cell. Next, the transparent cell was fixed with a support jig so that the side of the transparent cell was in close contact with the window of the colorimeter. Furthermore, the coating composition in the transparent cell was stirred with a stirring rod, and the color (L * , a * , b * value, or the L with the target standard plate * , a * , b * The colorimeter used was a spectrophotometer CM-3600A (manufactured by Konica Minolta).

[0064] A method for predicting the color of a dried coating film obtained by color measurement from the color of a coating composition obtained by liquid color measurement will be described below.

[0065] A method for obtaining the correction value (color difference between the color of the coating composition measured in liquid form and the color of the dried coating film measured) will be described below.

[0066] <How to obtain correction values> First, the color data of the paint composition that can produce a coating film having the target color and the dried coating film obtained by applying the same are measured, and each measured value (L * , a * , b * The differences between the values ​​(Δdw(L), Δdw(a), Δdw(b)) were calculated and used as correction values.

[0067] <How to predict color data of dried coating> The correction value was added to the color data of the liquid color measurement to obtain a predicted value of the dried coating film. L(d) = L(w) + Δdw(L) a(d)=a(w)+Δdw(a) b(d)=b(w)+Δdw(b) (where L(d), a(d), and b(d) are the L values ​​of the colorimetry of the coating film. * , a * , b *where L(w), a(w), and b(w) are the L values ​​of the liquid colorimeter. * , a * , b * value.)

[0068] The correction values ​​for each paint composition before adjustment are shown in Table 3.

[0069] [Table 3]

[0070] <Paint preparation pass / fail criteria> For each adjustment, the target value and the actual value L * Value, a * Value, b * The difference between the values ​​is called ΔL * , Δa * , Δb * Then, ΔE[=√(ΔL *2 +Δa *2 +Δb *2 )] is 0.2 or less, and ΔL * , Δa * , Δb * When each of the above values ​​was 0.2 or less, the paint was deemed to have passed the test, and the paint preparation was completed. The target values ​​refer to the color data of the dried coating film obtained by applying a coating composition that gives a coating film having the target color, and the actual values ​​refer to the color data obtained by liquid color measurement. <Adjustment time pass criteria> A test piece was judged to have passed if the average adjustment time taken to pass was less than 130 minutes over 20 adjustments, and failed if it took more than 130 minutes. <Criteria for pass / fail number of adjustments> Of the 20 adjustments, a test piece was deemed to have passed if the average number of adjustments required to pass was less than 5, and failed if it was more than 5. <Production rate pass criteria> In the 20 adjustments, if the average production rate up to passing was less than 105%, it was considered to be a pass, and if it was 105% or more, it was considered to be a fail. <Final pass criteria> The paint composition that has been adjusted by liquid color measurement is applied and dried to obtain a dried coating film. The target value of ΔE is 0.2 or less and ΔL * , Δa * , Δb * The test was deemed to have passed when each of the above was 0.2 or less.

[0071] <Example of creating primary data> <Example 1 of obtaining absorption coefficient and scattering coefficient> The white paint composition, the black paint composition, and a paint composition in which the white paint composition and the black paint composition were mixed in a ratio of 80:20 were each painted and dried to obtain a dried coating film. The spectral reflectance of each was measured, and the absorption coefficient K of the white paint composition and the absorption coefficient K and scattering coefficient S of the black paint composition were calculated.

[0072] <Example 2 of obtaining absorption coefficient and scattering coefficient> Except for changing the black paint composition to a red paint composition or a yellow paint composition, the absorption coefficient K and scattering coefficient S of the dried coating film of each of the red paint composition and the yellow paint composition were calculated in the same manner as in Example 1 for obtaining the absorption coefficient and scattering coefficient.

[0073] <Example of obtaining the theoretical formula for color variation> The theoretical calculation formula for color variation was obtained using these absorption coefficients and scattering coefficients, the refractive index of pigments and dried coatings, and the Kubelka-Munk theory, Duncan theory, and Sanderson correction formula.

[0074] <Example 1> In Example 1, as shown in FIG. 2, there are a correction value acquisition process for acquiring a correction value, which is the color difference between the color of the coating composition obtained by liquid color measurement and the color of the coating film obtained by color measurement, a gap target value setting process for setting a color gap target value, and a gap target value corresponding composition prediction process for predicting a composition of the color adjusting raw materials suitable for obtaining the color of the gap target value using the correction value, and the prediction process is repeated until the difference between the color obtained by adding the predicted composition and the target color becomes equal to or less than a predetermined reference value.

[0075] <Getting correction values> First, the color data (color data 1) of the finished coating composition 1 and the coating film obtained by applying the finished coating composition 1 were measured. Correction values ​​were calculated from the measurement data. Each correction value is shown in Table 3. Next, the color data of the pre-adjusted coating composition 1 prepared above was measured. The correction value was added to the obtained color data to convert it into color data of the coating film obtained from Paint Composition 1 before adjustment. The difference between the converted color data and color data 1 is ΔL * Value = 3.44, Δa * Value=0.45, Δb * The value was 0.35.

[0076] <Setting color gap targets using approach rates> The target gap value was set to an approach rate of 0.7. That is, the color difference was ΔL * Value = 1.03, Δa * Value = 0.14, Δb * The value was set to 0.11.

[0077] <Theoretical calculation and prediction of corrected blend composition for each paint color> Gap target value ΔL * Value, Δa * Value, Δb * The combination of corrected formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) to obtain the value was calculated by mathematical optimization using a theoretical calculation formula. The corrected predicted blend values ​​for each color paint composition were 1.3 g for the black paint composition, 5.4 g for the red paint composition, and 18.8 g for the yellow paint composition, respectively.

[0078] <Acquisition of color data of the adjusted paint composition and acquisition of the difference from the target color> The predicted correction blend of each color paint composition was added to the unadjusted paint composition 1 to prepare the adjusted paint composition 1, and the color data of the paint composition was obtained. The color data of the dried coating film was predicted from the above-mentioned correction value. The difference between the finished paint composition 1 and the dried coating film was ΔL *Value=1.0, Δa * Value = 0.62, Δb * The value was 0.6.

[0079] <Re-adjustment of the paint composition after adjustment> The color of the paint composition 1 after preparation did not satisfy the pass / fail criteria for the target values ​​of the paint properties, and therefore was rejected. The paint composition before readjustment and its color data at the time of readjustment were the paint composition after adjustment that had failed the previous adjustment and its color data after adjustment. As in the previous example, the gap target value ΔL * Value, Δa * Value, Δb * The combination of corrected formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) to obtain the value was calculated by mathematical optimization using a theoretical calculation formula. The corrected predicted blend values ​​for each color paint composition were 0.1 g for the black paint composition, 0.2 g for the red paint composition, and 0.8 g for the yellow paint composition. In the same manner as for the unadjusted paint composition 1, the predicted correction blend of each color paint composition was added to the unadjusted paint, and the adjusted paint composition was adjusted to obtain color data. This readjustment operation was repeated, and it was confirmed that the dried coating film properties of the adjusted paint composition met the target pass criteria, and the paint adjustment was completed (number of adjustments: 3, color matching time: 93 minutes, production rate: 101%). The same procedure was carried out four times (a total of five times). The same operation was carried out for unadjusted paint compositions 2, 3, and 4, and for each of the four types of paint, including unadjusted paint composition 1, the operation was repeated five times for a total of 20 adjustments. The number of adjustments was 2.8, the adjustment time was 91 minutes, and the production rate was 101%, which was acceptable. The results are shown in Table 5.

[0080] <Example 2> Example 2 was carried out in the same manner as Example 1, except that the target gap value was not set using the approach rate in <Setting the target gap value for paint properties>.

[0081] Four types of paint (pre-adjusted paint compositions 1 to 4) were adjusted 5 times each, for a total of 20 adjustments. The number of adjustments was 3.5, the adjustment time was 121 minutes, and the production rate was 103%, which was acceptable. The results are shown in Table 5. In Example 2, the container of the pre-adjusted paint composition was replaced 2 times out of the 20 times, and it took 300 minutes each time to replace the container, for a total of 600 minutes, so this time was added to the total adjustment time.

[0082] <Comparative Example 1> It was assumed that within a given wavelength range, the reflectance of the coating composition at wavelength λi [Rw(λi)] and the reflectance of the dried coating film of the coating composition [Rd(λi)] approximately represent a linear function, and αi and βi corresponding to the following formula within that range were determined. First, a coating composition that can obtain a coating film having a target color and a coating film obtained by applying the same were prepared, and the colors of each were measured. The color measurement method for the dried coating film and the coating composition was performed using the same device as in Example 1, and the reflectance Rw(λi) and Rd(λi) of each coating composition and the dried coating film obtained therefrom were measured every 10 nm in the wavelength range of 400 to 700 nm. This was repeated for 19 coating colors with different colors. The values ​​of αi and βi were calculated for each wavelength using the least squares method from the values ​​of Rd(λi) and Rw(λi) corresponding to each wavelength obtained above. The values ​​of αi and βi calculated for each wavelength are shown in Table 4. Rd(λi) = αiRw(λi) + βi Rd(λi): Reflectance of dry coating film at wavelength λi (%) Rw(λi): Reflectance (%) of the coating composition at wavelength λi αi, βi: Coefficients when α and β depend on wavelength λi

[0083] [Table 4]

[0084] <Method for predicting dry coating film color data of unadjusted coating composition> First, the reflectance Rw(λi) of the coating composition 1 before preparation was measured. Next, the reflectance of the coating composition at a wavelength of 400 nm, Rw(400) = 26.2%, with αi = 0.93 and βi = 1.67, was converted to the reflectance of the dried coating film at a wavelength of 400 nm, Rd(400), using the above formula. Similarly, the reflectance Rw(λi) for every 10 nm from 410 to 700 nm was converted to the reflectance Rd(λi) of the dry coating film using the above formula. The reflectance Rd(λi) of the dry coating film for each wavelength obtained was converted to the XYZ color system hue value using the Sanderson correction formula, and then further * , a * , b * was calculated and used as a predicted value for the color data of the dried coating film. Similarly, for Pre-Adjusted Paint Compositions 2 to 4, prediction of color data of the dried coating film was carried out.

[0085] <Theoretical calculation and prediction of corrected blend composition for each paint color> Target value ΔL * Value, Δa * Value, Δb * The combination of corrected formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) to obtain the value was calculated by mathematical optimization using a theoretical calculation formula.

[0086] <Acquisition of color data of the adjusted paint composition and acquisition of the difference from the target color> The predicted corrective blend of each color paint composition was added to the unadjusted paint composition 1 to prepare the adjusted paint composition 1, and the color data of the paint composition was obtained. The color data of the dried coating film was calculated using the conversion formula.

[0087] <Re-adjustment of the paint composition after adjustment> The color of the paint composition 1 after preparation did not satisfy the pass / fail criteria for the target values ​​of the paint properties, and therefore was rejected. The paint composition before readjustment and its color data at the time of readjustment were the paint composition after adjustment that had failed the previous adjustment and its color data after adjustment. As in the previous example, the gap target value ΔL * Value, Δa * Value, Δb *The combination of corrected formulations (combination of white paint composition, black paint composition, red paint composition and yellow paint composition) to obtain the value was calculated by mathematical optimization using a theoretical calculation formula. In the same manner as for the unadjusted paint composition 1, the predicted correction formulation of each color paint composition was added to the unadjusted paint, and the adjusted paint composition was adjusted to obtain color data. Repeat the same procedure, and after completing the color adjustment, create a dry coating film and measure ΔL * , Δa * and Δb * When we checked, ΔE=6.0 and ΔL * = 5.6, Δa * =-0.1 and Δb * = 2.6, and the pass criteria for paint adjustment (ΔE and ΔL * , Δa * and Δb * The test was rejected because the test results did not reach the standard deviation (each of which was 0.2 or less). In addition, the same operation was carried out for unadjusted paint compositions 2, 3, and 4, and for the four types of paint, including unadjusted paint composition 1, it was repeated five times for each. In all cases, the pass criteria for paint adjustment (ΔE and ΔL * , Δa * and Δb * The test was rejected because the test results did not reach the standard deviation (each of which was 0.2 or less).

[0088] <Comparative Example 2> Comparative Example 2 was carried out in the same manner as Example 1, except that the color data of the coating composition (liquid color measurement) was not measured, the color data of the dried coating film was measured, and no target gap value was set. That is, a pre-adjustment color information acquisition process is carried out to acquire color data before adjustment, and a composition prediction process is carried out to predict a composition of raw materials for color adjustment suitable for obtaining a target color. The prediction process is repeated until the difference between the color obtained by adding the predicted composition and the target color falls below a predetermined reference value. In addition, the primary data was obtained by calculating the absorption coefficient K and scattering coefficient S of each of the dried coating films obtained by applying and drying each of the color paint compositions and mixed paint compositions used in the liquid color measurement described above, and a theoretical calculation formula for color variation was obtained. Four types of paint (paint compositions 1 to 4 before preparation) were prepared 5 times each, for a total of 20 preparations. The number of preparations was 3.5, the preparation time was 174 minutes, and the production rate was 104%, which was unacceptable.

[0089] In this disclosure, each term has the following meaning. "Number of adjustments" refers to the arithmetic average number of times that the color had to be adjusted before passing the test when a total of 20 paint compositions, five for each of the four paint colors, were prepared and adjusted. Here, a smaller number of adjustments means higher prediction accuracy. "Adjustment time" refers to the arithmetic mean value of the adjustment time required to pass a test when a total of 20 paint compositions, five for each of the four paint colors, were prepared and adjusted. A short adjustment time here means a short manufacturing process and good manufacturing efficiency. Specifically, in step S211 of FIG. 2, if the value did not reach the predetermined standard value or below, and there was a risk that the paint composition would overflow from the container if the next predicted blending composition was added (when the production rate exceeded approximately 105%), the container was replaced. The "production volume rate" refers to the proportion of the adjusted production volume when the planned production volume of the target paint composition is taken as 1. Here, the fact that the production volume rate does not greatly exceed 100% means that the accuracy of the color prediction and the accuracy of the calculation method of the corrected blend composition are high, and that it is an efficient method that does not produce more paint composition than necessary, while allowing for raw materials and errors. The evaluation results are shown in Table 5 below.

[0090] [Table 5]

Claims

1. A method for producing a coating composition, comprising adding a raw material for adjusting a color to a coating composition before preparation to produce a coating composition having a target color, A correction value acquisition step of acquiring a correction value, which is a color difference between a color obtained by performing color measurement of a liquid of a coating composition and a color obtained by performing color measurement of a coating film, for a specific color; A prediction step of predicting a blending composition of the raw materials for color adjustment suitable for obtaining the target color by using a color measured by performing color measurement of the coating composition before adjustment and the correction value, A method for producing a coating composition, characterized in that the prediction step is repeated until the difference between the color obtained by adding the predicted blend composition and the target color becomes equal to or less than a predetermined reference value.

2. In the prediction step, the liquid color measurement of the coating composition before adjustment is performed immediately after a predetermined time has elapsed by placing the coating composition in a transparent cell for color measurement and stirring the coating composition before adjustment in the transparent cell; The predetermined time is fixed the same when the prediction step is repeated, The method for producing a coating composition according to claim 1, wherein the predetermined time is selected from the range of 0.1 to 600 seconds.

3. The method for producing a coating composition according to claim 1 or 2, wherein the correction value is fixed to the same value when the prediction step is repeated.

4. The method further includes a gap target value setting step of setting a color gap target value, In the gap target value setting step, the absolute value of the difference between the value obtained by converting the acquired liquid colorimetric color of the coating composition before adjustment into the colorimetric colorimetric color of the coating film using the correction value and the gap target value is smaller than the absolute value of the difference between the value obtained by converting the acquired liquid colorimetric color of the coating composition before adjustment into the colorimetric colorimetric color of the coating film using the correction value and the target color, 3. The method for producing a coating composition according to claim 1, wherein the prediction step is a gap target value corresponding blend composition prediction step for predicting a blend composition of the raw materials for color adjustment suitable for obtaining a color of the gap target value.

5. 5. A method for producing a coating composition according to claim 4, wherein in the gap target value setting step, the gap target value is set so that the smaller the absolute value of the difference between the value obtained by converting the acquired liquid colorimetric color of the coating composition before adjustment into a color obtained by colorimetric measurement of the coating film using the correction value, the closer the gap target value becomes to the target color, either continuously or stepwise.

6. 5. The method for producing a coating composition according to claim 4, wherein in the gap target value corresponding composition prediction step, the composition of the color adjusting raw materials is predicted by theoretical calculation by a computer under conditions in which each amount in the composition of the color adjusting raw materials is individually limited to a solution candidate generated from a finite numerical range, and the solution candidate includes a case in which the amount is 0.

7. 7. The method for producing a coating composition according to claim 6, further comprising, when a composition of the raw materials for color adjustment suitable for obtaining a color of the target gap value is not calculated by the theoretical calculation by the computer in the gap target value corresponding composition prediction step, releasing a part or all of the conditions and re-predicting the composition of the raw materials for color adjustment by the theoretical calculation by the computer.

8. The method further includes a main colorant specifying step of specifying a colorant that is blended in the largest amount in the colorant blend composition of the coating composition before the preparation, 7. The method for producing a coating composition according to claim 6, wherein in the gap target value corresponding blend composition prediction step, a prediction is made for at least the main colorant using conditions limited to solution candidates generated from the finite numerical range.

9. 5. The method for producing a coating composition according to claim 4, wherein in the gap target value corresponding blend composition prediction step, when calculating a blend composition of the raw materials for color adjustment suitable for obtaining the color of the gap target value, any one of a brute force search method, a mathematical optimization method, and a random search method is used.

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