Method for producing a matte color recipe for a matte color standard and use of this method

Abstract

Method for producing a matte color recipe for a matte color standard, wherein the method comprises the steps of: A) Experimental determination of reflection spectra R(exp) of the matte color standard, comprising a first reflection spectrum and a second reflection spectrum, using an integrating sphere color measuring instrument, wherein the first reflection spectrum is obtained at (A1) d / 8° geometry or 8° / d geometry with included directional component, and the second reflection spectrum is obtained at (A2) d / 8° geometry or 8° / d geometry with excluded directional component; B) Comparing the experimentally determined reflectance spectrum R(exp) with included directional component (A1), which has been corrected for the directional component, with reflectance spectra assigned to color pigment color recipes from a color recipe database for specular color shades and identifying a stored reflectance spectrum from the color recipe database that is closest to the experimentally determined reflectance spectrum R(exp) of the matte color standard, as well as identifying the assigned color pigment color recipe based on the identified stored reflectance spectrum; C) Converting reflectance spectral data of the experimentally determined reflectance spectra R(exp) of the matte color standard to gloss values ​​by: C1) Determining a difference reflection spectrum ΔR between the experimentally determined reflection spectrum R(exp) with included directed component (A1) and the experimentally determined reflection spectrum R(exp) with excluded directed component (A2), and C2) Determining the gloss values ​​corresponding to the difference reflectance spectrum ΔR, with the aid of previously prepared initial calibration curves for an available dye system, where the first calibration curves represent the functional relationship between the difference reflection spectrum ΔR and the gloss values ​​measured at one or more gloss angles, D) Generating the matt color recipe for the matt color standard by determining an amount of at least one matting agent based on the gloss values ​​obtained for a given amount of matting agent, with the aid of previously prepared second calibration curves for an available dye system, wherein the second calibration curves represent the gloss values ​​measured at one or more gloss angles as a function of the amount of the at least one matting agent in matt color recipes; wherein the color pigment color recipe obtained in step B and the amount of matting agent determined in step D are output separately, or the amount of matting agent determined in step D is directly incorporated into the color pigment color recipe determined in step B.

Description

[0001] The invention relates to a method for producing a matte color recipe for a matte color standard and the use of this method. The method can be used in the coatings industry or other coatings-related fields.

[0002] Efficiently matching color shades of unknown pigments can be considered a significant challenge for all color applications within a coatings company. In the automotive coatings industry in particular, the range of pigments has undergone a constant expansion in recent years. Given this development, providing methods to reduce the effort involved in matching color shades is of great economic importance.

[0003] The efficient matching of color shades of unknown pigmentation in the color laboratory is now supported by computer-aided color recipe calculation methods. The color recipe calculation method is a tool for pigmentation analysis of color shades that utilizes visible reflectance spectroscopy to characterize the reflective properties of target colors and, using a suitable radiative transfer model, to describe the diffusion of light in particulate media and thus the macroscopically detectable reflectance spectra. The Schuster-Kubelka-Munk theory is frequently used for opaque and translucent pigmented solid surface coatings. The calculation of color recipes is generally accompanied by reference to pigment databases that provide details of the optical properties of all pigments contained in available colorant systems.Reference can also be made to color recipe databases if only a correction of an existing, but not perfectly matched formulation is required.

[0004] In addition to glossy color shades, matte color shades are also frequently used in color-imparting surface coatings. To date, only a few different methods for controlling the gloss level of surface coatings are known. It is possible to mat a pigmented surface coating or to cover a glossy pigmented surface coating with a matte clear coat. Adding a matting agent to a paint formulation is most commonly used to introduce the desired degree of surface texture into a polymeric material. These matting agents are homogeneously dispersed in the embedding medium; the matting effect is achieved through a certain micro-heterogeneity within the layer, which causes an increase in diffuse light scattering from the sample surface. Various inorganic compounds, such as silica gel, kaolin, bentonite, and others, serve as matting agents.

[0005] Since the determination of optical material parameters is a time-consuming and costly procedure, it seems advantageous to formulate color shades of different surface textures (glossy, semi-glossy, matte) using a common colorant database. Such an approach implicitly assumes that the characterization data determined for glossy colorants will not change significantly when a certain surface texture is introduced into the system, and that the resulting error in the recipe calculation can be compensated for by one or at most two additional correction steps. The time required for the additional correction steps appears to be acceptable compared to the effort required to determine optical material parameters for several colorant systems that differ only in the degree of surface texture.Working with only one dye database also offers the advantage of fewer inventory items.

[0006] Fig. 4 shows details of the workflow of color development processes of matte solid color shades (hereinafter also referred to as solid color shades).

[0007] Current color development or current batch tinting processes for matte color shades make use of two different instrumental approaches depending on whether an integrating sphere instrument or an instrument equipped with a collimated (directional) measurement geometry is used.

[0008] In the case of the integrating sphere instrument (d / 8° or 8° / d measurement geometry; Fig. 1A and Fig.1B) with a light source (1), a detector (2), a reflector (3), a white sphere attachment or a black trap (4), and a sample (5), the difference spectrum ΔR=R(SPIN)-R(SPEX) between the specular fraction included (SPIN) and the specular fraction excluded (SPEX) readings or measurements is a function of the surface gloss, determined by the amount of matting agent. Once this relationship has been established using a suitable set of calibration charts, the measured difference spectrum can be adjusted to derive the amount of matting agent (MAA) required in a formulation to match a matte color standard.

[0009] In the case of instruments equipped with a collimated measuring geometry (such as 45° / 0°; Fig.2), with a light source (1) and a detector (2) above a sample (5) with illumination angles measured from the normal direction (z-z') of the sample surface, optimal color recipe predictions can only be expected for color standards with a gloss level above ~30 gloss units, measured at the 60° geometry. In the case of low-gloss samples, the spectrophotometer will pick up an undefined amount of surface gloss, resulting in a suboptimal prediction for pigmentation. Below this limit, the quality of predicted formulations deteriorates considerably with decreasing surface gloss level. A gloss meter must be applied to set a calibration function for the MAA=f(gloss) relationship at the three different gloss geometries recommended in technical standards. These two methods of color recipe calculation are disclosed in EP 1 631 802 A1.The methods refer to color pigment and color recipe databases for gloss color shades, which allow the matching of matte color samples. For both methodological approaches, the same set of calibration charts can be used to define the MAA=f(gloss) relationship. This set of charts should encompass different color centers in color space. The color centers can be represented, for example, by binary mixtures of colored (blue, green, red, yellow, violet) and achromatic pigments (black, white). For each formulation, a set of charts with increasing amounts of matting agent must be prepared, covering the entire range from perfectly glossy to completely matte.

[0010] The above methods still have a gap concerning the unification of the two approaches: integrating sphere instruments and spectrophotometers equipped with a collimated 45° / 0° measurement geometry. Another disadvantage is that an additional gloss measurement device is required to obtain gloss values.

[0011] Consequently, there is still a need for a practical method to automate the paint development process and improve the recipe calculation results of matte surface coatings, which can be directly introduced and used in the paint development process.

[0012] It is therefore the object of the invention to provide a color recipe calculation method for matte color standards which, on the basis of a colorant system for producing gloss color shades, enables acceptably accurate results to be obtained without requiring additional tinting steps and to additionally obtain gloss values ​​for the corresponding matte color standard to be matched.

[0013] This problem is solved by the subject matter of claim 1. Further developments emerge from the dependent claims and the following description.

[0014] The present invention provides a method for color recipe calculation of matte color standards, particularly matte solid color standards, using common instrument profiles between an integrating sphere colorimeter and a glossmeter equipped with three gloss angle measurement geometries. These instrument profiles allow the conversion of reflectivity data to gloss information, so that once the profiles are created, the integrating sphere instrument would provide reflectivity data and gloss data, thus rendering the glossmeter obsolete. This latter fact is particularly interesting for applications involving decentralized systems, such as those operated in paint shops to instrumentally support the coating repair process for a car.The required equipment can be further reduced, making it more cost-effective. Processing time can also be reduced in general for any application requiring the determination of reflectivity and gloss data.

[0015] It goes without saying that all data, for example the dye system and the associated data, e.g. the optical material parameters, and the previously prepared calibration curves for the available dye systems (as used in steps C2) and D)), are preferably stored in a database. Fig. 1 explains the standard d / 8° or 8° / d measurement geometries, recommended by technical standards (such as DIN 5033), to be used for glossy and matt solid color standards (hereinafter also referred to as solid color standards). Fig.2 explains standard 45° / 0° or 0° / 45° measurement geometries, recommended by technical standards (such as DIN 5033) to be used for glossy and matt solid color standards. Fig. Figure 3 shows the recommended geometric conditions for measuring surface gloss. Fig. 4 shows the procedure for recipe calculation of matt spot colors (hereinafter also referred to as solid colors). Fig. Figure 5 shows the variation of surface gloss according to DIN 67530 for a typical solvent-based paint mixing system at three different angles and for different chromatic and achromatic samples with matting agent content together with the model functions fitted to the experimental data (MA = matting agent). Fig.Figure 6 shows the process flow diagram of the recipe calculation procedure for matte color shades for the two standard measurement geometries 45° / 0° (left part of the diagram; MAA = matting agent quantity) and d / 8° (middle part of the diagram). The right diagram shows the new process flow when spectral data is converted to gloss values, before converting these gloss values ​​to a matting agent quantity. Fig.Figures 7 to 9 show gloss profiles obtained for three typical integrating sphere colorimeters for the three angular geometries (20°, 60°, and 85°) recommended by technical standards to access surface gloss of matte finish coatings. The curves passing through the data points represent fits to appropriate model functions. The experimental data sets were obtained for two different paint systems (Paint Grade 1 and Paint Grade 2). Both paint systems represent solvent-based paint mixing systems, with Paint Grade 1 being a balanced grade and Paint Grade 2 being a concentrated grade (pastes). In the latter case, formulations must be supplemented by the addition of an appropriate amount of binder.

[0016] The gloss values ​​were measured using the micro TRI-Gloss instrument from Byk-Gardner. The reflectivity data were measured using the SP64 colorimeter from X-Rite ( Fig. 7), with the color measuring instrument SF600 from Datacolor International ( Fig. 8), and with the color measuring instrument Color-Eye 7000 from Gretag-Macbeth ( Fig. 9) measured.

[0017] Fig. Figure 10 shows the experimental reflectivity functions of two semi-gloss RAL colours 3000 and 7005 with the visible spectral range.

[0018] Reflectivity data were obtained using an integrating sphere instrument with a d / 8° geometry, operated in the directional included (SPIN) and excluded (SPEX) modes.

[0019] Fig.Figure 11 illustrates the correlation of gloss data obtained using two instruments from different manufacturers (micro TRI-Glanz from Byk-Gardner and REFO 3-D from Hach Lange GmbH) for all three evaluation geometries. The correlation index r for all evaluation geometries exceeds a value of 0.999, indicating that the instrument scales of both instruments are consistent.

[0020] "Color standard" shall mean any coated or painted surface for which gloss values ​​are to be determined. A color standard may be a cured or dried paint film, a wet paint film, an inherently colored substrate surface, or any other colored substrate of any character. When measuring the reflectivity spectrum of wet paint films, typical methods and apparatus for measuring wet paint films can be used. The color standard may be, for example, a surface of a substrate to be coated for repair or a portion thereof, in particular the coated surface of a motor vehicle body to be coated for repair or a portion thereof. The color standard encompasses color standards with various surface glosses. It includes gloss and matte color standards, solid color standards, effect color standards, and combinations thereof.

[0021] "Matte color standard" shall mean any color standard that does not have a perfectly glossy surface. The initial gloss of a color shade can be reduced to a desired gloss level, for example, by adding one or more matting agents to the paint composition to create the matte color standard. The matte color standard can be a matte solid color standard or a matte effect standard. The matte color standard also includes so-called semi-gloss color standards.

[0022] "Solid color standard" shall mean, herein and hereinafter, a color shade or color standard with the optical property of isotropically reflecting a beam of collimated or diffusely incident light. For example, if such a color shade is illuminated by a collimated beam of light at a constant angle, the degree of reflected light, and hence the color, will be independent of the viewing angle. Such color shades can be formulated using solid pigments or dyes, which can be embedded and dispersed in various media, such as paint, ceramic, glass, or plastic, etc.

[0023] "Solid pigment" shall mean, herein and in the following, an inorganic or organic substance consisting of small particles that are practically insoluble in the applied medium and used for their coloring, protective, or electromagnetic properties. Solid pigments can be characterized by their chemical composition and their optical and technical properties. Their optical properties are determined by their light-scattering and -absorbing properties, which can be selective (colored pigments) or non-selective (black and white pigments).

[0024] "Colorant system" shall mean, herein and hereinafter, any system of solid and / or effect pigments, including all pigments intended for use in the manufacture or formulation of paints. The number and selection of pigment components are not subject to any limitations herein. They can be adapted in any way to the relevant requirements, e.g., according to the needs of the paint manufacturers or their users.

[0025] The term “matte solid color standard” may be used here and in the following interchangeably with the terms “matte solid color sample,” “matte solid color shade,” and “matte color standard with a solid color.”

[0026] The term “matte color standard” may be used here and in the following interchangeably with the terms “matte color sample” and “matte color shade.”

[0027] The principle and the individual steps of the method according to the invention are explained in more detail below. The method of the present invention is preferably a method for calculating color recipes for matte solid color standards. Therefore, the term "matte solid color standard" is used here and below. However, it is self-evident that the method of the present invention also includes a method for calculating color recipes for matte effect color shades, and the individual steps and features are also explained in more detail below with reference to a method for calculating color recipes for matte effect color shades.

[0028] The starting point is a matt solid color standard that is to be matched or is being matched to, from which a suitable color recipe is to be developed.

[0029] First, according to step A) of the method according to the invention, the reflection spectra R(exp) of the matte solid color standard are determined experimentally over a defined wavelength range using a suitable color measurement instrument equipped with a d / 8° measurement geometry. The reflection spectra are preferably determined over a wavelength range of 400-700 nm. The reflection spectra are measured at d / 8° or 8° / d geometry with included specular component (A1) and at d / 8° or 8° / d geometry with excluded specular component (A2).

[0030] It is self-evident and well known to those skilled in the art that an integrating sphere colorimeter can be equipped with a d / 8° measurement geometry or, alternatively, with an 8° / d measurement geometry, since both measurement geometries are equivalent. Therefore, when only the term "d / 8° measurement geometry" is used below, the equivalent 8° / d measurement geometry is also meant and can also be used.

[0031] The d / 8° measurement geometry is based on diffuse illumination (using an integrating sphere) and directional observation at an angle of 8° with respect to the normal to the surface (d / 8°) of a sample (as in Fig. 1). In the present case of matte solid paint samples, two measurements can be performed by operating the instrument in the directional included and excluded modes.

[0032] D / 8° measuring geometries, e.g. according to the one in Fig.The measurement geometries listed in Chapter 1 are extensively described in specialized literature, are familiar to color measurement experts, and are implemented in common conventional measuring instruments. Furthermore, the measurement geometries are defined and recommended, for example, in the technical standard DIN 5033 (color measurement) or CIE Publication 15.3 (colorimetry).

[0033] If necessary, e.g., if required for further processing, the color positions (X, Y, Z, or L*, a*, b*) can be determined or measured in a conventional manner known to those skilled in the art of color measurement. The color positions can be determined based on the experimentally determined reflectance spectrum of the matte solid color standard for both the data series including and excluding the specular portion. The color positions can also be measured using a suitable measuring device. The color positions can then be used in subsequent process steps instead of or in addition to the reflectance data.

[0034] Depending on which initial database is accessed, the next step of the method according to the invention includes

[0035] B) Comparing the experimentally determined reflection spectrum R(exp) including the specular component (1) which has been corrected for the specular component with reflection spectra assigned to color pigment color recipes from a color recipe database for glossy color shades and identifying a stored reflection spectrum from the color recipe database which is closest to the experimentally determined reflection spectrum R(exp) of the matt color standard, and identifying the assigned color pigment color recipe based on the identified stored reflection spectrum.

[0036] Step B) of the process according to the invention proceeds according to the art using pigment databases, e.g., discrete solid pigment (coloring pigment) databases or color recipe databases containing the required optical material parameters of the pigments of the available colorant systems. It is advantageous that it is possible to access colorant systems or color recipes such as those used to produce gloss color shades.

[0037] According to step B), the spectrum from which the specular component has been removed is used as usual to identify the appropriate reflection spectrum and the color recipe associated with it from a color recipe database.

[0038] After performing step B), it is possible, if necessary, to correct the identified color recipe and adjust the resulting matte solid color standard, based on the color recipe calculated or identified in the first matching step, to the desired matte solid color standard. Correction steps can be repeated until the resulting matched matte solid color standard is within the desired tolerance.

[0039] In step C) of the method according to the invention, the reflection data of the experimentally determined reflection spectra R(exp) of the matt color standard are converted or converted into gloss values.

[0040] This requires first (step C1) recording the difference reflectance spectrum ΔR between the experimentally determined reflectance spectrum R(exp) with the specular component included (A1) and the reflectance spectrum R(exp) with the specular component excluded (A2). Then, in step C2), the gloss values ​​corresponding to the difference reflectance spectrum ΔR are determined using the previously prepared first calibration curves for an available dye system. The first calibration curves represent the functional relationship between the difference reflectance spectrum ΔR and the degree of surface gloss (the gloss values ​​measured at one or more gloss angles).

[0041] The determination of the functional relationship between the difference reflectance spectrum ΔR and surface gloss is explained in more detail below. Production of calibration panels

[0042] The color shades used to generate the gloss=f(ΔR) profiles must cover the entire range of gloss levels if well-functioning gloss=f(ΔR) model functions are to be created. It is not the number of samples that is important for model construction, but rather a uniform distribution of gloss levels within the sample set. To generate the gloss=f(ΔR) profiles (calibration curves), it is not necessary to create a new, special set of calibration charts if data (gloss data and R(exp) with specular component included and excluded) are already available. If such a sample set of data is not available, a special set of calibration charts must be created, which can later be expanded with additional, already existing data. The basis for creating the calibration charts is the available dye systems.

[0043] To keep the number of calibration charts as low as possible, yet sufficiently high to achieve the desired accuracy, and to be representative of the corresponding paint mixing system and related color system, charts only need to be produced for a subset of pigments. Such a subset can include black, white, red, green, blue, yellow, and violet pigments. The colored pigments are blended with the white-mixing paint of the paint system, while the neutral pigments are used as a pure shade. One-coat topcoat systems already produce glossy surfaces, whereas in the case of two-coat topcoat systems (primer + clearcoat), the pigmented primer must be covered with a glossy clearcoat. This set of charts defines the gloss end of the ranking list for a surface texture.All of these formulations must be mixed with a matting agent (in the case of single-coat topcoat systems) or covered with a matting clearcoat (in the case of two-coat topcoat systems) to achieve the desired level of surface gloss. For each coating system, there is generally a natural upper limit for the addition of matting agent to the primer or clearcoat, which will define the second extreme matte end of the surface texture ranking. The gloss variant will assume gloss values ​​in the order of 90-100 units, while gloss values ​​at the other extreme of a matte variant will be in the order of less than 5 units. These two extreme points of the surface texture ranking must be supplemented by N additional calibration charts with gloss values, almost equally spaced between the two extreme points.The production of, for example, N=4 to 6 panels per pigment of varying gloss level will be sufficient to define a well-balanced calibration level.

[0044] For a uniform paint system, the preparation of calibration charts for a single pigment would be sufficient to define a generalized instrument profile. This ideal situation is only encountered in practical applications of single-coat topcoat paint systems. The integration of pigments into the paint-air interface will influence surface gloss, adding colored contributions to the regularly reflected neutral gloss component. Consequently, even if the same amount of matting agent is used in different paint formulations, the resulting surface gloss level can vary considerably.

[0045] An alternative approach for defining generalized instrument profiles can be used when a sufficiently large number of data sets from the history of previously developed matte paint shades are available. Plotting surface gloss values ​​against the difference measure of the specular fraction of included and excluded reflectivity spectra at each gloss rating geometry will also provide calibration curves if the paint system is as expected and usable, and there is a good correlation between the two sets.

[0046] The calibration curves are generated for a specific pair of instruments: the color meter and the gloss meter. Gloss measurement

[0047] For instrumental gloss characterization, collimated measurement geometries have been recommended in technical standards. In the case of glossy samples, the light partially reflected at the air / paint interface follows the law of reflection (reflection angle = illumination angle) and can be quantitatively described by the Fresnel equations. The intensity of the reflected light depends on the angle of the incident light and the optical material properties (complex refractive index). The component that is refracted in the medium undergoes selective absorption and scattering when it interacts with the embedded pigment particles and is reflected almost diffusely from the coating. This diffusely reflected light also contributes to the specularly reflected component and therefore also has an effect on the gloss perception.In the case of textured surfaces, the light reflected from the surface can be divided into a specularly reflected and a diffusely reflected portion. As the degree of surface roughness increases, the energy of the specularly reflected portion will steadily decrease and progressively contribute to the diffusely reflected portion.

[0048] Surface gloss is determined experimentally using a suitable reflectometer according to technical standards DIN 67530 or ASTM D 523-89, which specify the experimental conditions for instrumental evaluation of surface gloss. The technical standard recommends three different measurement geometries to measure surface gloss at 20°, 60°, and 85° with respect to the perpendicular to the surface (see Fig.3) to characterize. The 20° angle is used to characterize glossy samples, the 60° angle is recommended for semi-glossy samples, and the 85° angle is suggested to provide reliable information for matte samples.

[0049] The measured reflectometer values ​​are referenced to the corresponding values ​​of a glossy black glass with a refractive index of n=1.567. The black glass has an assigned specular gloss value of 100 for each measurement geometry. Since none of the recommended measurement angles provides results of the highest accuracy for all gloss levels (see Fig.3), the first step in determining the gloss level of a specimen is to identify the appropriate measurement geometry. If the 60° gloss value is between 10 and 70 units, this is suggested as the correct measurement geometry. If the 60° gloss is less than 10 units, the 85° geometry should be used instead, while the 20° geometry result will be advantageous for comparison in the event that the 60° value exceeds the 70-unit limit. Consequently, there are two discontinuities in the gloss scale that can only be mitigated by some form of averaging of the gloss values ​​obtained from the three measurement geometries.

[0050] Gloss data obtained using different instruments from different manufacturers are generally comparable within the measurement tolerance if their setup follows the guidelines recommended in the above-mentioned technical standards. To demonstrate the validity of this claim, a set of matte panels with varying degrees of surface texture were measured on two different gloss measuring instruments from different manufacturers (micro TRI-Glanz from Byk-Gardner, REFO 3-D from Hach Lange GmbH) for a quantitative comparison. All experimental data obtained are presented in Fig. 11 collected.

[0051] As from Fig. 11, all gloss data experimentally determined for both types of gloss meters correlate strongly with a correlation index of r c>0.999 at all three evaluation angles. Within the measurement tolerance, at least these two instrument types can be interchanged without expected disruption of the corresponding gloss scales. Therefore, only gloss data from the micro TRI gloss instrument from Byk-Gardner were used for all numerical analyses. Generalized gloss profiles

[0052] Both gloss and color readings can be combined in three mathematical models involving gloss data obtained at the three recommended different gloss geometries (20°, 60°, and 85°) to determine the spectral difference ΔR=R(SPIN)-R(SPEX) using an integrating sphere instrument. Fig.Figure 7 shows experimental data obtained from carefully selected sets of calibration charts of two different paint mixing systems, along with model functions fitted to the experimental data. Apparently, all data sets are as expected and useful, following universal functions for all three measurement geometries. The functional behavior can be approximated by a single nonlinear model function with only three parameters, which must be tuned for each glancing angle geometry in the sense of the L2 norm using an efficient nonlinear fitting routine that minimizes the sum of the weighted squares of the residuals, or differences, between the model function and the experimental data. The parameter sets depend on the type of spectrophotometer used to collect spectral data.This dependence is a consequence of the fact that each instrument manufacturer selects its own integrating sphere with setup parameters for optimal performance of the respective instrument. The size of the sample port and the gloss trap, the efficiency of the gloss trap, and the apertures of the optical system will influence the measurement results. The derived gloss profiles can be used to calculate gloss values ​​for all three gloss angles for a given difference reflectance spectrum ΔR between the experimentally determined reflectance spectrum R(exp) with specular component included (A1) and the experimentally determined reflectance spectrum R(exp) with specular component excluded (A2).

[0053] The performance of the generalized instrument profile approach is illustrated below using the example of different types of spectrophotometers from three instrument manufacturers: SP64 from X-Rite, Color-Eye 7000 from Gretag-Macbeth, and SF600 from Datencolor International.

[0054] All of these instruments are equipped with integrating spheres that can be operated in specularly included and specularly excluded modes. However, the geometric size and design of the apertures are different for each of these integrating spheres, so different experimental results for the difference ΔR = R(SPIN) - R(SPEX) can be expected for color standards of different gloss levels.

[0055] To define the generalized instrument profiles, two sets of matte calibration panels of different gloss levels were prepared from two different paint systems and measured on all three instruments. Both paint systems represent solvent-based touch-up paint mixing systems, with Paint Grade 1 being a balanced grade and Paint Grade 2 being a concentrated grade (pastes). The surface gloss of the entire set of calibration panels was measured using a micro TRI-Gloss instrument from Byk-Gardner (see Fig. 7-9).

[0056] In other words, the standardization of the approaches based on the directional 45° / 0° and diffuse d / 8° measurement geometries was achieved by introducing common instrument profiles between an integrating sphere instrument and a gloss meter, which refers to the difference spectrum ΔR=R(SPIN) - R(SPEX) to the gloss information derived from the three recommended gloss geometries. Therefore, three instrument profiles were generated. Based on readings taken from an appropriately selected set of matte calibration panels with varying degrees of surface gloss and independent gloss measurements, calibration curves (profiles) can be generated related to the difference spectrum ΔR=R(SPIN) - R(SPEX) to the gloss values ​​obtained from the three standard measurement geometries.These calibration curves are independent of the selected paint quality (assuming the paint quality is as expected and acceptable, and it will not integrate pigment particles into the air / paint interface) and will depend only on the optical details and the configuration of the hardware used (spectrophotometer, gloss meter). Individual instrument profiles must be generated for each pair of instruments—color meter and gloss meter.

[0057] The gloss information obtained in step C2) can then be fed into the gloss profile converter regarding surface gloss and matting agent quantity to derive the matting agent quantity required to match a matte solid color standard.

[0058] Therefore, in step D) of the present invention, the amount of matting agent is determined according to the determined gloss values ​​in the matte solid color standard with the aid of previously prepared calibration curves for the available dye system. The calibration curves were prepared by previously measuring the gloss level at one or more gloss angles on calibration chart sets containing different amounts of matting agent and plotting the gloss level as a function of the matting agent concentration.

[0059] If different matting agents or mixtures of matting agents are used in the available dye systems, corresponding calibration curves must be prepared for each matting agent and each matting agent mixture. Further details of this step are disclosed in EP 1 631 802 A1.

[0060] The color recipe obtained in B) and the determined amount of matting agent can be issued separately, or the determined amount of matting agent can be incorporated directly into the previously determined color recipe as appropriate. In the latter case, the amount of matting agent obtained in step D) is combined with the color recipe identified in step B), resulting in a color recipe for matching the matte solid color standard. The recipe contains the nature of the coloring pigments and their concentrations, as well as the amount of matting agent.

[0061] Obviously, when performing steps A) to D) of the method according to the invention, the specified sequence is not mandatory, but can be modified according to the knowledge of a person skilled in the art. For example, after performing step A), it is therefore possible to first perform steps C) and D) (determining the degree of gloss and determining the matting agent concentration) and then perform step B) (identifying the color recipe). The recipe and the amount of matting agent can be determined independently of each other. Typically, the necessary calibration curves are prepared beforehand, based on the components of the available dye systems and available matting agents, and are stored and maintained in a database. Thus, when a new matte solid color standard actually needs to be adjusted, the calibration curves and the data and models used to define the instrument profile are already available.

[0062] Furthermore, any necessary correction of the color shade produced with the specific color recipe identified in step B) can also be made until the complete recipe, including the matting agent content, has been obtained. It is also clear that the resulting degree of gloss / mattness can also be corrected, if necessary, by adjusting the matting agent concentration.

[0063] The process flow for the known approaches to recipe prediction of matte color shades and the new approach of the present invention is described in Fig. 6, ie the known methods with measuring geometry 45° / 0° with gloss measurement; the known methods with measuring geometry d / 8° without gloss measurement and without obtaining the gloss values; and the method of the present invention with measuring geometry d / 8° and without gloss measurement, but with obtaining the gloss values.

[0064] Useful matting agents include conventional products known to those skilled in the art of color development and generally commercially available. The matting agents may be inorganic or organic in nature. Examples of inorganic matting agents are amorphous or fumed silica, silica gels, and sheet silicates, for example, magnesium silicate hydrate (talc). The inorganic matting agents may be in untreated form or in a form surface-treated with organic compounds, for example, with suitable grades of wax, or also with inorganic compounds. Examples of organic matting agents are Al, Zn, Ca, or Mg stearate, waxy compounds, such as micronized polypropylene waxes, along with urea / formaldehyde condensation products.

[0065] The matting agents can be used individually or in a combination of two or more matting agents.

[0066] The solid color pigments used in the process according to the invention comprise conventional inorganic and / or organic absorption pigments such as those used in coating production. Examples of inorganic or organic color pigments are titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone, or pyrrolopyrrole pigments. Examples of effect pigments include platelet-like pigments that impart additional optical properties to a substrate in addition to color, such as angle-dependent color and brightness shift and visual texture. The range of effect pigments is diverse and can be divided into interference and specular reflecting pigments.

[0067] The described procedure can be used to determine a color recipe.

[0068] The described method can be used to produce a coating based on the color recipe produced by the method of this invention. The coating can be an OEM automotive coating, a touch-up coating, any other industrial coating, or a combination thereof.

[0069] The method of the present invention can be advantageously used in all fields of application where matte color standards, particularly matte solid color standards, need to be developed or corresponding batches need to be shaded, such as in automotive and industrial coating applications. In automotive coatings, the method can be used for OEM coatings as well as touch-up coatings, such as in paint laboratories, in paint touch-up workshops, in the paint manufacturing process, and in the standardization of paints. The method is applicable to matte color standards, particularly matte solid color standards of unknown or known pigmentation.

[0070] The main advantage of the method of the present invention is that an integrating sphere colorimeter, e.g. a d / 8° spectrophotometer, can provide, in addition to the spectral information, gloss information for the three standard measurement geometries of typical glossmeters (20°, 60°, and 85°; see Fig. 3). Therefore, the functionality of the integrating sphere spectrophotometer is significantly expanded, as it can now replace the gloss meter in practical applications (for example, in paint tools used in workshops for touch-up paints), which is required in this type of application when spectrophotometers equipped with a collimated 45° / 0° measurement geometry are used. The resulting MAA=f(gloss) gloss profiles (for example, as shown in Fig.5) can now be used for both types of colorimetry instruments, colorimetry instruments with d / 8° geometry and colorimetry instruments with 45° / 0° geometry.

[0071] The following examples explain the invention in more detail: Examples

[0072] A first step in using the method of the present invention in color development is to calibrate the optical behavior of all colorants of a colorant system using a suitable mixing model, such as the Schuster-Kubelka-Munk theory or its variants, and to determine the universal gloss=f(c MA ) To determine functions between gloss and matting agent (MA) content for the recommended gloss angle geometries.

[0073] Fig.Figure 5 shows such universal functions derived for a selection of colorants (solid pigments) from a solvent-based paint mixing system for all three angles of light incidence (20°, 60°, 85°) recommended in DIN 67530. A commercially available gloss meter was used to perform the measurements. The most striking result of the application is the almost universal functional behavior of gloss versus matting agent content for the 20° and 60° angles. At the 85° angle, a somewhat broader distribution of the curves is evident. Fitting the gloss = f(c MA ) to a model function of this data set would certainly result in the least accurate function of the three. When comparing the variance of the curves, the 20° and 60° angle results appear to be almost comparable in deriving the matting agent content. The maximum error Δc MA,max the 20° gloss = f(c MA) function is approximately 4.3% and is for the remaining two angles Δc MA,max about 3.1% for the 60° angle and 10.6% for the 85° angle. However, considering the variability of the matting agent content in real color shades, which predominantly cover the concentration range 25-65% and the highest sensitivity of the gloss = f(c MA ) curves, the 60° function is superior to the 20° function in terms of accuracy. Under Δc MA,max = 30%, the 20° function demonstrates greater sensitivity than the 60° function. To achieve the most accurate results across the entire concentration range, a combination of both universal functions, the 20° and 60° angles, is recommended in this specific example.

[0074] For interpolation purposes, the experimentally determined calibration data were described by a suitable model function that represents the data with a sufficient degree of accuracy. From the sets of gloss functions, the maximum deviation along the abscissa can be estimated for any given gloss value. The expected maximum error Ac MA,max is calculated at 7% for the 20° angle, 6% for the 60° angle and 10% for the 85° angle. Given that the majority of the formulas fall within the range of 25% ≤ c MA ≤ 65%, the glancing angle of 60° seems to be the best geometry to measure, since the area of ​​highest dynamics falls in the same concentration interval.

[0075] Two semi-gloss color shades from the RAL system (RAL 3000, RAL 7005), which represent a well-accepted and typical collection of color standards in industrial applications, were selected to demonstrate the effectiveness of the method of the invention. The experimentally determined reflectivity functions of the two selected color standards in the visible spectral range are shown in Fig.10. The commercially available measuring instrument used for color development was equipped with a d / 8° measuring geometry and could be operated in the specularly included (SPIN) and excluded (SPEX) modes. It was the same instrument used to determine the calibration function. The gloss values ​​were measured at the three recommended angles of 20°, 60°, and 85° using the same commercially available gloss meter (see Table II) that was used to determine the calibration function. Both color standards were subsequently processed through the standard color development procedure using a set of optical material parameters (wavelength-dependent scattering and absorption coefficients) derived from a set of gloss calibration charts.After identifying the appropriate pigmentation of the optimized recipe, the formulation is sprayed, re-measured and corrected in further steps (if necessary) using an effective recipe correction algorithm.

[0076] The calibration curve of the pair of instruments used (gloss meter = micro TRI-Gloss Instrument from Byk-Gardner; color meter = SP64 from X-Rite) is shown in Fig. 11 shown.

[0077] The first example shows the matching prediction and correction results of the semi-gloss orange RAL 3000 standard, recorded from the RAL 840-HR register. The formulation used to match the standard includes the matting agent and five colorants (pigments): two red, orange, and magenta colorants to adjust the color, and a white desaturator to adjust the brightness. The color shade was formulated without the addition of a carbon black pigment. All component quantities are given in Table I. As can be seen from Table II, the residual color difference between the on-load position and the color standard is already within the target range, while regarding the surface texture, the sample is obviously too matte. An added correction step does not further improve the color position of the match, but the gloss level is appropriately adjusted to enable matching of the RAL 3000 standard.

[0078] In the second example, the formulation selected to match the semi-gloss green RAL 7005 standard, also taken from the RAL 840-HR register, is similarly complex. In addition to the matting agent, five colorants (pigments) had to be used to achieve an acceptable spectral match: two yellow pigments and one blue to adjust the color, and black and white desaturators to adjust the brightnesses. All component quantities are summarized in Table I for all predicted and corrected formulations. Regarding color position, only after the second correction step is the match sufficiently close to the RAL 7005 color standard (see Table II). Since the adjusted gloss level of the match is also close to the corresponding property of the standard, the match can be unlocked.

[0079] The test results compiled in Tables I and II can be summarized as follows: (i) color differences of the on-load positions vary between 0.3 to 2.3 ΔE94 units, (ii) initial correction steps lead to a significant improvement in the color position, (iii) the degree of surface gloss could be adjusted very precisely using the designated calibration function, and (iv) the convergence properties are comparable to those generally observed for glossy solid inks, thus demonstrating that in the case of matte solid inks, no additional tinting steps (on average) are needed in the color development process. Table I: Color development information for two test samples (RAL 3000 and RAL 7005). The on-load formulation represents the initial adjustment. The last column indicates the first corrected formulation (MA - matting agent). standard Components On-load formulation (%) 1. Correction step (%) 2. Correction step (%) RAL 3000 White 3,37 3,95 ------ Red1 15,97 15,67 ------ Red2 5,06 5,97 ------ Orange 28,53 33,7 ------ magenta 11,37 13,44 ------ MA 35,7 27,27 ------ RAL 7005 White 30,09 30,67 32,6 Black 10,93 12,89 12,45 Yellow1 5,01 5,11 5,32 Yellow2 2,79 2,09 2,02 Blue 0,1 0,27 0,3 MA 51,08 48,97 47,31 Table II: Experimental results (color and gloss information) of the two test color shades taken from the RAL system, prepared in a solvent-based touch-up paint line for passenger cars (STD - standard; R - recipe; CR - corrected recipe). In the three columns indicating surface gloss, the gloss numbers in bold (second row, respectively) are derived from the generalized instrument profile, while those indicated in the normal mode (first row, respectively) were determined experimentally using a gloss meter. L* ΔL* a* Δa* b* Δb* C* ΔC* h ab ΔH* ΔE* (76) ΔE* (94) Gloss (20°) Gloss (60°) Gloss (85°) RAL 3000 HOURS 35,0 52,30 41,70 66,90 38,60 ------ ------ 13,2 12,8 58,9 50,5 88,5 87,4 1R -0,07 0,51 0,73 0,85 0,25 0,89 0,26 25,1 3,1 34,6 25,7 78,9 66,8 1CR -0,14 0,22 0,68 0,60 0,39 0,73 0,29 36,8 15,5 77,1 53,9 95,3 89,3 RAL 7005 HOURS 44,9 -1,70 2,90 3,40 120,70 ------ 2,1 2,5 18,7 22,5 36,2 62,6 1R 1,72 0,45 1,45 1,16 -0,98 2,29 2,29 1,7 1,3 15,6 14,2 50,9 47,6 1CR -1,25 0,11 -0,16 -0,19 -0,01 1,27 1,26 1,9 1,5 17,4 15,8 55,0 51,0 2CR 0,47 0,04 -0,10 -0,10 0,01 0,48 0,48 3,2 3,2 24,9 26,1 58,6 67,4 Table III: instrument STDDEV 20° 60° 85° SP64 12,19 6,46 7,15 SF600 14,10 6,51 5,82 Color-Eye 7000 3,60 2,99 5,00

Claims

[1] A method for preparing a matte color recipe for a matte color standard, the method comprising the steps of: A) experimentally determining reflection spectra R(exp) of the matte color standard, comprising a first reflection spectrum and a second reflection spectrum, with an integrating sphere colorimeter, wherein the first reflection spectrum is obtained at (A1) d / 8° geometry or 8° / d geometry with included directional component, and the second reflection spectrum is obtained at (A2) d / 8° geometry or 8° / d geometry with the specular component excluded; B) comparing the experimentally determined reflection spectrum R(exp) with the specular component included (A1), which has been corrected for the specular component, with reflection spectra assigned to color pigment recipes from a color recipe database for glossy color shades and identifying a stored reflection spectrum from the color recipe database that is closest to the experimentally determined reflection spectrum R(exp) of the matte color standard, and identifying the assigned color pigment recipe based on the identified stored reflection spectrum; C) Converting reflectance spectra data of the experimentally determined reflectance spectra R(exp) of the matte color standard to gloss values ​​by: C1) Determining a difference reflection spectrum ΔR between the experimentally determined reflection spectrum R(exp) with included directional component (A1) and the experimentally determined reflection spectrum R(exp) with excluded directional component (A2), and C2) Determination of the gloss values ​​corresponding to the difference reflection spectrum ΔR, with the help of previously prepared initial calibration curves for an available dye system, where the first calibration curves represent the functional relationship between the difference reflection spectrum ΔR and the gloss values ​​measured at one or more gloss angles, D) Generating the matte color recipe for the matte color standard by determining an amount of at least one matting agent based on the gloss values ​​obtained for a matting agent amount with the aid of previously prepared second calibration curves for an available dye system, wherein the second calibration curves represent the gloss values ​​measured at one or more gloss angles as a function of the amount of the at least one matting agent in matte color recipes; wherein the color pigment color recipe obtained in step B and the amount of matting agent determined in step D are output separately or the amount of matting agent determined in step D is incorporated directly into the color pigment color recipe determined in step B. [2] The method of claim 1, wherein the matte color recipe is for the matte color standard with a solid color. [3] A method according to claim 1 or 2, wherein color positions X, Y, Z, or L*, a*, b*, measured or derived from the measured reflectance spectrum R(exp), are used in addition to the reflectance spectrum R(exp). [4] Method according to one of claims 1 to 3, wherein the reflection spectrum R(exp) is measured with a spectrophotometer with d / 8° measuring geometry or with 8° / d measuring geometry. [5] Method according to one of claims 1 to 4, wherein the reflection spectrum R(exp) of the matte color standard is recorded over a wavelength range of 400-700 nm. [6] Use of the process according to any one of claims 1 to 5 in paint development, standardization of paints and paint production. [7] Use of the method according to any one of claims 1 to 5 in OEM automotive coatings and touch-up coatings.

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