WO2015092097A1 - Method and matrix for measuring the colour gamut of a gonio-apparent coating - Google Patents

Method and matrix for measuring the colour gamut of a gonio-apparent coating Download PDF

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Publication number
WO2015092097A1
WO2015092097A1 PCT/ES2014/070897 ES2014070897W WO2015092097A1 WO 2015092097 A1 WO2015092097 A1 WO 2015092097A1 ES 2014070897 W ES2014070897 W ES 2014070897W WO 2015092097 A1 WO2015092097 A1 WO 2015092097A1
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Prior art keywords
angle
values
observation
matrix
irradiation
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PCT/ES2014/070897
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Spanish (es)
French (fr)
Inventor
Francisco Miguel MARTÍNEZ VERDÚ
Esther PERALES ROMERO
Elisabet CHORRO CALDERÓN
Alejandro FERRERO TURRIÓN
Joaquín CAMPOS ACOSTA
Alicia PONS AGLIO
Ana María RABAL ALMAZOR
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Universidad De Alicante
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Publication of WO2015092097A1 publication Critical patent/WO2015092097A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/504—Goniometric colour measurements, for example measurements of metallic or flake based paints
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/462—Computing operations in or between colour spaces; Colour management systems

Definitions

  • the present invention belongs to the field of optics, and more specifically to the field of gonioaparentes coatings whose visual appearance changes depending on the angle of irradiation and the angle of observation.
  • a first object of the present invention is a new method that allows to measure in a direct and simple way the whole range of colors that has a gonioaparente coating depending on the type of light source, its angle of irradiation, and the angle of observation.
  • Another object of the invention is a color representation matrix of a gonioaparente coating obtained by the above method.
  • Gonioaparentes coatings are pigments that undergo color changes when changes occur in the angle of incidence of light (irradiation angle, 0 ⁇ ) or the viewing angle of the observer (observation angle, 0 S ). These coatings create illusion of optical depth and have a striking effect of color variation as irradiation and observation angles change. See, for example, the document: FJ Maile, G. Pfaff and P. Reynders, "Effect pigments: past, present and future", Progress in Organic Coat ⁇ ngs 54, 150-163 (2005).
  • the gonioaparentes coatings consist of a translucent substrate that contains traditional pigments of color (or absorption) and pigments of special effect (micro-mirrors or interference) that produce the selective reflections, both by additive and subtractive mixture, which give rise to the change of color of these coatings by changing the angle of irradiation / observation.
  • the color change which is one of the most attractive characteristics of these coatings, can become very extreme, and the most favorable conditions to achieve this effect take place when the lighting is dim, it is that is, when most of the light that illuminates the object comes from a very specific direction. This is the case of a single and distant light source such as direct sunlight.
  • catalogs may contain real samples of coatings, in which case the observer must have the ability to change the irradiation conditions.
  • Another option is a catalog capable of displaying all the color change by conventional color printing, after evaluating the color reproduction capabilities of the system and printing technology, so that several different colors representative of different conditions of different colors will be necessary. irradiation and observation of the gonioaparente coating in question.
  • An alternative or intermediate option could be the use of a lighting and observation booth-type device that would allow to really perceive the variety of colors of a gonioaparente sample with the maximum number of combinations of irradiation and observation that are considered interesting for various industrial sectors or that follow metrological recommendations
  • a lighting and observation booth-type device that would allow to really perceive the variety of colors of a gonioaparente sample with the maximum number of combinations of irradiation and observation that are considered interesting for various industrial sectors or that follow metrological recommendations
  • gonio-vision-box can be found at the link http://www.goniovision.com/
  • white LED flashlight as a light source and which can be placed at various angles of irradiation on the sample.
  • the inventors of the present application solve the above problem by means of a procedure that allows measuring and representing the entire range of colors that a gonioaparente coating can adopt.
  • the result of this procedure is a matrix that allows to appreciate in a direct and intuitive way the whole range of colors that can be adopted by a transparent gonioa coating as changes occur in the angles of irradiation and observation, or in the variation of the spectral content of The source of light.
  • a first aspect of the invention is thus directed to a method of measuring the color gamut of a gonioaparente coating comprising the following steps: a) Obtain the spectral reflectance factor R (X) for various combinations of regularly spaced values of irradiation angle and observation angle.
  • sBRDF bidirectional spectral reflectance function
  • this step is carried out through empirical measures using specific instruments, such as the gonio-spectrophotometer described in the article by Rabal et al, Metrology 49, 213-223 (2012).
  • the sBRDF it is multiplied by the value ⁇ to obtain the reflectance factor corresponding to each specific angle of irradiation and observation.
  • the result of this first step is a set of reflectance factors corresponding to the selected irradiation and observation angles, and corresponding to an intrinsic optical property of the colored material.
  • b) Calculate the XYZ tristimulus values corresponding to a standardized illuminant and observer from the reflectance factor obtained in the previous step.
  • both the standardized illuminant and the observer must be chosen in such a way that they constitute a reasonable approximation to the lighting conditions of the place where the gonioaparente coating in question is to be observed and to the perception abilities of the observer to whom the representation is directed .
  • the standard illuminant may be the CIE-D65.
  • the CIE-D65 is a standard illuminant defined by the International Lighting Commission (CIE, Commision Internationale de l'Eclairage) that corresponds approximately to a Sunny noon in Western Europe.
  • CIE International Lighting Commission
  • the standardized observer can be ICD-1964, which includes the spectral matching functions of a standard (or average) observer defined for a 10 ° stimulus (equivalent to a diameter of 90 mm and a visual distance of 0.5 m).
  • RGB values corresponding to the XYZ tristimulus are carried out by transforming the XYZ tristimulus values into the sRGB color space according to international IEC 61966-2-1: 1999. First, a linear transformation is carried out using a matrix:
  • spectral reflectances R (X) of a series of printed colors, both monochrome and polychrome, with varying concentrations of ink (or digital level of the primary color, "Cyan, Magenta, Yellow or blacK”) , and its subsequent color coding to tristimulus values CI E-XYZ, or later to CI E-L * a * b *, to establish non-linear mathematical transformations or initial data conversion dictionaries XYZ or L * a * b * a CMYK, or vice versa.
  • d) Represent the RGB or CMYK values of each combination of irradiation angle and observation angle in the cells of a matrix.
  • each row of the matrix corresponds to an irradiation angle and each column of the matrix corresponds to an observation angle, although it would also be possible to do it the other way around.
  • the matrix is represented on the screen, the RGB values are used, while if the matrix is to be represented on paper, the CMYK values are used, after spectral and colorimetric characterization of the chosen printing device, either with offset technology, inkjet , laser or xerographic, etc., in accordance with established and consolidated procedures (such as in WO2013066720A1).
  • a second aspect of the invention is directed to the matrix obtained according to the above procedure where each row of the matrix corresponds to an incident angle and each column of the matrix corresponds to an observation angle, and where the irradiation and Observation are regularly spaced.
  • Fig. 1 shows a graphic diagram of the basic variables that affect the behavior of a gonioaparente coating.
  • Fig. 2 shows a representation matrix of a gonioaparente coating obtained with the method of the invention.
  • Fig. 3 shows the result of applying the process of the invention to a commercial gonioaparente coating called Lapis Sunlight, from Merck.
  • Fig. 4 shows the result of applying the process of the invention to a commercial gonioaparente coating called Artic Fire, from Merck. PREFERRED EMBODIMENT OF THE INVENTION
  • Fig. 1 graphically shows the basic variables that will be used to carry out the process of the invention. It has been considered that both the direction of irradiation (DI) and that of observation (DO) are contained within the plane of incidence (Pl) determined by the direction of irradiation (DI) and the normal vector (VN) to the surface of the coating (SR). The reason is that it has been proven that observation directions outside the plane of incidence (Pl) do not provide much more additional colorimetric information.
  • the irradiation angle 0 ⁇ characterizes the direction of irradiation (DI), and is defined as the angle between the normal vector (VN) to the surface of the coating (SR) and the direction of irradiation (DI).
  • the irradiation angle 0 ⁇ always has a positive value.
  • the observation angle Q s characterizes the observation direction (OD), and is defined as the angle between the normal vector (VN) to the surface of the coating (SR) and the observation direction (OD).
  • the observation angle Q s can have a positive or negative sign to differentiate between observation directions (OD) contained in the incidence half-plane of the irradiation direction (positive Q s ) and observation directions (OD) contained in the opposite half-plane ( Q s negative).
  • Fig. 1 two examples of observation directions (OD) respectively positive (OD +) and negative (OD-) have been represented.
  • the measurements are carried out using the gonio-spectrophotometer described by A. Rabal et al., Metrology 49, 213-223 (2012).
  • the procedure consists essentially of illuminating the sample from the different directions with a beam of highly collimated and uniform light on the sample, and measuring the spectral radiance to the different directions of observation.
  • the spectral BRDF is calculated from the quotient between the measured spectral radiance and the irradiance on the sample at the different lighting directions. Once the measurements are made, the values obtained are multiplied by ⁇ to obtain the reflectance value and, at Then, the XYZ tristimulus values corresponding to the CIE-D65 illuminant and the CIE-1964 observer are calculated. Finally, the corresponding RGB values are determined for an on-screen representation or those based on another system such as CMYK for paper printing.
  • the result is a set of RGB or CMYK values corresponding to the colors adopted by the coating surface (SR) for each combination of irradiation angle (0 ⁇ ) and observation angle (0 S ).
  • This information is shown, either on screen or on paper, through a matrix like the one shown in Fig. 2 where each row corresponds to an irradiation angle (0 ⁇ ) and each column corresponds to an observation angle (0 S ).
  • This form of concrete representation has advantages related to the way in which various important characteristics of the gonioaparente coating in question are visualized.
  • the rows of the matrix correspond to the color change that occurs in the gonioaparente coating for the entire range of observation angles (0 S ) keeping the irradiation angle (0 ⁇ ) constant.
  • These horizontal lines are known as "aspecular lines,” and it is currently believed that they can give information about diffuse reflection of absorption pigments.
  • the columns of the matrix correspond to the color change that occurs in the gonioaparente coating for the entire range of irradiation angles (0 ⁇ ) keeping the observation angle (0 S ) constant.
  • the diagonal lines from top-right to bottom-left are called “interference lines”, and are defined as the geometric place of the color coordinates in which the aspecular angle remains constant, where the aspecular angle is defined as:
  • the interference lines show the total change in tone that can be observed in the coating.
  • the cis region is determined by matrix cells that have a value positive of the aspecular angle, while the trans region is determined by the matrix cells that have a negative value of the aspecular angle.
  • FIGs. 3 and 4 show two matrices that are obtained as a result of carrying out the process of the invention for the mentioned coatings T20-04 WNT Lapis Sunlight and T20-02 WNT Artic Fire.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

The invention relates to a method for measuring and representing the colours acquired by a gonio-apparent coating depending on the observation and irradiation angles, for any type of spectral content of a standard or non-standard light source. The method comprises the following steps: measuring the reflectance factor for different combinations of regularly spaced irradiation angle (θi) and observation angle (θs) values; calculating the XYZ tristimulus values corresponding to a standard illuminant and observer, on the basis of the reflectance factor obtained in the previous step; calculating the RGB or CMYK values based on the XYZ tristimulus values obtained in the previous step; and representing the RGB or CMYK values of each incident angle (θi) and observation angle (θs) combination in the cells of a matrix. The invention also relates to the matrix produced using this method.

Description

PROCEDIMIENTO Y MATRIZ DE MEDICIÓN DE LA GAMA CROMÁTICA DE UN RECUBRIMIENTO GONIOAPARENTE OBJETO DE LA INVENCIÓN  PROCEDURE AND MATRIX OF MEASUREMENT OF THE CHROMATIC RANGE OF A GONIOAPARENT COATING OBJECT OF THE INVENTION
La presente invención pertenece al campo de la óptica, y más concretamente al campo de los recubrimientos gonioaparentes cuya apariencia visual cambia en función del ángulo de irradiación y del ángulo de observación. The present invention belongs to the field of optics, and more specifically to the field of gonioaparentes coatings whose visual appearance changes depending on the angle of irradiation and the angle of observation.
Un primer objeto de la presente invención es un nuevo procedimiento que permite medir de una manera directa y sencilla toda la gama de colores que posee un recubrimiento gonioaparente en función del tipo de fuente de luz, su ángulo de irradiación, y del ángulo de observación. A first object of the present invention is a new method that allows to measure in a direct and simple way the whole range of colors that has a gonioaparente coating depending on the type of light source, its angle of irradiation, and the angle of observation.
Otro objeto de la invención es una matriz de representación del color de un recubrimiento gonioaparente obtenida mediante el método anterior. Another object of the invention is a color representation matrix of a gonioaparente coating obtained by the above method.
ANTECEDENTES DE LA INVENCIÓN BACKGROUND OF THE INVENTION
Los recubrimientos gonioaparentes (también conocidos como recubrimientos con pigmentos de efecto especial o goniocromáticos) son pigmentos que sufren cambios de color cuando se producen cambios en el ángulo de incidencia de la luz (ángulo de irradiación, 0¡) o el ángulo de visión del observador (ángulo de observación, 0S). Estos recubrimientos crean ilusión de profundidad óptica y presentan un efecto llamativo de variación de color a medida que cambian los ángulos de irradiación y observación. Véase, por ejemplo, el documento: F. J. Maile, G. Pfaff and P. Reynders, "Effect pigments: past, present and future", Progress in Organic Coatí ngs 54, 150-163 (2005). Los recubrimientos gonioaparentes constan de un substrato translúcido que contiene unos pigmentos tradicionales de color (o de absorción) y pigmentos de efecto especial (microespejos o de interferencia) que producen las reflexiones selectivas, tanto por mezcla aditiva y sustractiva, que dan lugar al cambio de color de estos recubrimientos al cambiar el ángulo de irradiación/observación. El cambio de color, que es una de las características más atractivas de estos recubrimientos, puede llegar a ser muy extremo, y las condiciones más favorables para conseguir este efecto tienen lugar cuando la iluminación es poco difusa, es decir, cuando la mayor parte de la luz que ilumina el objeto viene de una dirección muy concreta. Este es el caso de una fuente de luz única y distante como es la luz directa del Sol. Los cambios de color, que se aprecian tanto en claridad como en croma y, a diferencia de los recubrimientos metalizados (con pigmentos de tipo microespejos), también en tono, hacen que estos recubrimientos sean especialmente atractivos en la industria de la automoción (véase, por ejemplo, el documento H. J. Streitberger and K. F. Dóssel, Automotive Paints and Coatings (Wiley-VCH.Weinheim, 2008)), siendo además muy utilizados en otros mercados (por ejemplo, el de la cosmética), o en aplicaciones de seguridad (anti-falsificación de dinero), plásticos para electrónica de consumo, etc. Gonioaparentes coatings (also known as coatings with pigments of special effect or goniochromatic) are pigments that undergo color changes when changes occur in the angle of incidence of light (irradiation angle, 0¡) or the viewing angle of the observer (observation angle, 0 S ). These coatings create illusion of optical depth and have a striking effect of color variation as irradiation and observation angles change. See, for example, the document: FJ Maile, G. Pfaff and P. Reynders, "Effect pigments: past, present and future", Progress in Organic Coatí ngs 54, 150-163 (2005). The gonioaparentes coatings consist of a translucent substrate that contains traditional pigments of color (or absorption) and pigments of special effect (micro-mirrors or interference) that produce the selective reflections, both by additive and subtractive mixture, which give rise to the change of color of these coatings by changing the angle of irradiation / observation. The color change, which is one of the most attractive characteristics of these coatings, can become very extreme, and the most favorable conditions to achieve this effect take place when the lighting is dim, it is that is, when most of the light that illuminates the object comes from a very specific direction. This is the case of a single and distant light source such as direct sunlight. The color changes, which can be seen in both clarity and chroma and, unlike metallic coatings (with micro-mirror type pigments), also in tone, they make these coatings especially attractive in the automotive industry (see, for example, the document HJ Streitberger and KF Dóssel, Automotive Paints and Coatings (Wiley-VCH.Weinheim, 2008)), being also widely used in other markets (for example, cosmetics), or in security applications (anti-counterfeit money), plastics for consumer electronics, etc.
Los fabricantes de pigmentos especiales y de formulaciones para recubrimientos gonioaparentes deben transmitir a los potenciales clientes de la manera más eficiente posible sus características especiales, prestando particular atención a los cambios de color cuando se varían las condiciones de irradiación y observación. Sin embargo, debido precisamente a la complejidad de tales cambios de color, resulta difícil caracterizarlos y mostrar sus propiedades de reflectancia en un formato sencillo e intuitivo, y los sistemas de medida y especificaciones actuales no dan una idea completa de la gama de color que puede percibirse de estas muestras. The manufacturers of special pigments and formulations for gonioaparentes coatings should transmit their special characteristics to potential customers as efficiently as possible, paying particular attention to color changes when irradiation and observation conditions are varied. However, due precisely to the complexity of such color changes, it is difficult to characterize them and show their reflectance properties in a simple and intuitive format, and current measurement systems and specifications do not give a complete idea of the color range that can Perceive of these samples.
Este problema ha tratado de solucionarse por medio de nuevas técnicas e instrumentos para caracterizar la reflectancia espectral y el color de un recubrimiento gonioaparente para cualquier geometría de irradiación/observación y para cualquier fuente de luz, como describen los siguientes artículos: This problem has been solved by means of new techniques and instruments to characterize the spectral reflectance and the color of a gonioaparente coating for any irradiation / observation geometry and for any light source, as described in the following articles:
- M. E. Nadal, T. A. Germer, "Colorimetric characterization of pearlescent coatings", Proceedings of AIC Color (Rochester, 2001), pp. 757-760. - M. E. Nadal, T. A. Germer, "Colorimetric characterization of pearlescent coatings", Proceedings of AIC Color (Rochester, 2001), pp. 757-760.
- B. Parker, "Color shift of light interference pigments", Surf. Coat. Aust. 39, 10-13 (2002).  - B. Parker, "Color shift of light interference pigments", Surf. Coat Aust 39, 10-13 (2002).
- F. Leloup, P. Hanselaer, M. Pointer and J. Versluys, "Characterization of gonio- apparent colours", Proceedings of AIC Color (Granada, 2005), 515-518.  - F. Leloup, P. Hanselaer, M. Pointer and J. Versluys, "Characterization of gonio- apparent colors", Proceedings of AIC Color (Granada, 2005), 515-518.
- C. A. Nicholls, "Visual and Instrumental Characterisation of Special-Effect Colours", PhD Thesis (University of Leeds, Leeds, 2000).  - C. A. Nicholls, "Visual and Instrumental Characterization of Special-Effect Colors", PhD Thesis (University of Leeds, Leeds, 2000).
- R. Besold, "Metallic effect-Characterization, parameter and methods for instrumentally determination", Die Farbe 37, 79-85 (1990). - DIN standard 6175-2, "Colour tolerances for automobile lacquer finishes, Part 2: Effect lacquer finishes", 2001. - R. Besold, "Metallic effect-Characterization, parameter and methods for instrumentally determination", Die Farbe 37, 79-85 (1990). - DIN standard 6175-2, "Color tolerances for automobile lacquer finishes, Part 2: Effect lacquer finishes", 2001.
- DIN 6175-2, "Tolerances for automotive paints, Part 2: Goniochromatic paints (Farbtoleranzen für Automobillackierungen-teil 2: Effektlackierungen)", 2001.  - DIN 6175-2, "Tolerances for automotive paints, Part 2: Goniochromatic paints (Farbtoleranzen für Automobillackierungen-teil 2: Effektlackierungen)", 2001.
- E. Chorro, E. Perales, F. M. Martínez-Verdú, J. Campos and A. Pons, "Colorimetric and spectral evaluation of the optical anisotropy of metallic and pearlescent samples", Journal of Modern Optics 56, 1457-1465 (2009).  - E. Chorro, E. Perales, FM Martínez-Verdú, J. Campos and A. Pons, "Colorimetric and spectral evaluation of the optical anisotropy of metallic and pearlescent samples", Journal of Modern Optics 56, 1457-1465 (2009) .
- E. Kirchner, G. J. Van den Kiebomm, L. Njo, R. Supér and R. Gottenbos, "Observation of Visual Texture of Metallic and Pearlescent Materials", Color Res. Appl. 32, 256-266 (2007).  - E. Kirchner, G. J. Van den Kiebomm, L. Njo, R. Supér and R. Gottenbos, "Observation of Visual Texture of Metallic and Pearlescent Materials", Color Res. Appl. 32, 256-266 (2007).
- W. R. Cramer, "Reflections on the right angle", European Coating Journal 4, 32-37 (2012).  - W. R. Cramer, "Reflections on the right angle", European Coating Journal 4, 32-37 (2012).
- E. Perales, E. Chorro, W. R. Cramer, and F. M. Martínez-Verdú, "Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources", Applied Optics 50, 5271-5278 (2011).  - E. Perales, E. Chorro, W. R. Cramer, and F. M. Martínez-Verdú, "Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources", Applied Optics 50, 5271-5278 (2011).
Actualmente existen fundamentalmente varios modos de representar los colores gonioaparentes por parte de los fabricantes. Un primer modo consiste en utilizar un programa informático que permite reproducir en la pantalla del ordenador la apariencia que tendría un objeto específico con un determinado recubrimiento. Un ejemplo de este sistema se describe en las solicitudes de patente US 2007/00971 19 A1 o US 2013/8374831 B2. Estas sofisticadas técnicas están mejorando en términos de reproducibilidad de color, y tienen la ventaja de que muestran aproximadamente el resultado global de aplicar el recubrimiento, aunque siempre teniendo en cuenta las limitaciones de reproducción de colores de una pantalla. Sin embargo, presenta como principales inconvenientes su elevada complejidad y también el hecho basarse en simulaciones por ordenador en lugar de partir directamente de datos metrológicos verdaderos. There are currently several ways to represent gonioaparentes colors by manufacturers. A first way is to use a computer program that allows you to reproduce on the computer screen the appearance that a specific object would have with a certain coating. An example of this system is described in patent applications US 2007/00971 19 A1 or US 2013/8374831 B2. These sophisticated techniques are improving in terms of color reproducibility, and have the advantage that they show approximately the overall result of applying the coating, although always taking into account the limitations of color reproduction of a screen. However, it presents as its main drawbacks its high complexity and also the fact that it is based on computer simulations instead of directly from true metrological data.
Otra alternativa es producir catálogos. Estos catálogos pueden contener muestras reales de recubrimientos, en cuyo caso el observador deberá de disponer de la capacidad de cambiar las condiciones de irradiación. Otra opción es un catálogo capaz de mostrar todo el cambio de color mediante impresiones en color de tipo convencional, previa evaluación de las capacidades de reproducción del color del sistema y tecnología de impresión, de modo que serán necesarios varios colores diferentes representativos de diferentes condiciones de irradiación y observación del recubrimiento gonioaparente en cuestión. Una opción alternativa o intermedia podría ser el usar un dispositivo tipo cabina de iluminación y observación que permitiera percibir realmente la variedad de colores de una muestra gonioaparente con el máximo número de combinaciones de irradiación y observación que se consideren interesantes para diversos sectores industriales o que sigan recomendaciones metrológicas. Es por ejemplo el caso del dispositivo disponible actualmente en el mercado y denominado gonio-vision-box (puede consultarse en el enlace http://www.goniovision.com/), y que usa una linterna de LEDs blancos como fuente de luz y que puede colocarse a varios ángulos de irradiación sobre la muestra. Pero, como principal desventaja con el caso anterior, impide visualizar de forma integral, como en un catálogo, toda la variedad de colores que podrían percibirse en un recubrimiento gonioaparente (metalizado, perlado o de interferencia, etc.). Another alternative is to produce catalogs. These catalogs may contain real samples of coatings, in which case the observer must have the ability to change the irradiation conditions. Another option is a catalog capable of displaying all the color change by conventional color printing, after evaluating the color reproduction capabilities of the system and printing technology, so that several different colors representative of different conditions of different colors will be necessary. irradiation and observation of the gonioaparente coating in question. An alternative or intermediate option could be the use of a lighting and observation booth-type device that would allow to really perceive the variety of colors of a gonioaparente sample with the maximum number of combinations of irradiation and observation that are considered interesting for various industrial sectors or that follow metrological recommendations For example, the case of the device currently available on the market and called gonio-vision-box (can be found at the link http://www.goniovision.com/), and which uses a white LED flashlight as a light source and which can be placed at various angles of irradiation on the sample. But, as a main disadvantage with the previous case, it prevents to visualize in an integral way, as in a catalog, all the variety of colors that could be perceived in a gonioaparente coating (metallic, pearlized or of interference, etc.).
DESCRIPCIÓN DE LA INVENCIÓN Los inventores de la presente solicitud resuelven el problema anterior mediante un procedimiento que permite medir y representar toda la gama de colores que puede adoptar un recubrimiento gonioaparente. El resultado de este procedimiento es una matriz que permite apreciar de un modo directo e intuitivo toda la gama de colores que puede adoptar un recubrimiento gonioaparente a medida que se producen cambios en los ángulos de irradiación y observación, o en la variación del contenido espectral de la fuente de luz. DESCRIPTION OF THE INVENTION The inventors of the present application solve the above problem by means of a procedure that allows measuring and representing the entire range of colors that a gonioaparente coating can adopt. The result of this procedure is a matrix that allows to appreciate in a direct and intuitive way the whole range of colors that can be adopted by a transparent gonioa coating as changes occur in the angles of irradiation and observation, or in the variation of the spectral content of The source of light.
Un primer aspecto de la invención está dirigido, pues, a un procedimiento de medición de la gama cromática de un recubrimiento gonioaparente que comprende los siguientes pasos: a) Obtener el factor de reflectancia espectral R(X) para varias combinaciones de valores regularmente espaciados de ángulo de irradiación y ángulo de observación. A first aspect of the invention is thus directed to a method of measuring the color gamut of a gonioaparente coating comprising the following steps: a) Obtain the spectral reflectance factor R (X) for various combinations of regularly spaced values of irradiation angle and observation angle.
Se trata de un factor independiente del contenido espectral de la fuente de luz elegida, puesto que es una propiedad óptica intrínseca del material coloreado y su formulación de pigmentos. It is an independent factor of the spectral content of the chosen light source, since it is an intrinsic optical property of the colored material and its pigment formulation.
Para llevar a cabo este paso, en primer lugar se realiza su medida directamente o bien se calcula indirectamente a partir de la función bidireccional de reflectancia espectral (spectral Bidirectional Reflectance Distribution Function, sBRDF) para las combinaciones de ángulo de irradiación y ángulo de observación elegidas.In order to carry out this step, firstly its measurement is carried out directly or it is indirectly calculated from the bidirectional spectral reflectance function (sBRDF) for the combinations of irradiation angle and observation angle chosen .
Actualmente, este paso se lleva a cabo a través de medidas empíricas utilizando instrumentos específicos, como por ejemplo el gonio-espectrofotómetro descrito en el artículo de Rabal et al, Metrología 49, 213-223 (2012). En el caso de medirse la sBRDF, ésta se multiplica por el valor π para obtener el factor de reflectancia correspondiente a cada ángulo concreto de irradiación y observación. Currently, this step is carried out through empirical measures using specific instruments, such as the gonio-spectrophotometer described in the article by Rabal et al, Metrology 49, 213-223 (2012). In the case of measuring the sBRDF, it is multiplied by the value π to obtain the reflectance factor corresponding to each specific angle of irradiation and observation.
En este paso, es importante seleccionar adecuadamente los valores del ángulo de irradiación y del ángulo de observación para que la representación obtenida permita apreciar de una manera sencilla las características del recubrimiento gonioaparente que se está estudiando. Para ello, se deben elegir valores de ángulo de irradiación y ángulo de observación que estén regularmente espaciados, es decir, valores tales que la diferencia entre cada par de ángulos contiguos sea constante e igual tanto para el ángulo de irradiación como para el ángulo de observación. Por ejemplo, se pueden elegir valores de ángulo de irradiación y de ángulo de observación que estén separados de 10° en 10°. Además, no es necesario representar todos los valores posibles de ambos ángulos, ya que para ángulos de irradiación y de observación por encima de 70° ya apenas se producen cambios en la apariencia del recubrimiento gonioaparente. Por tanto, preferiblemente el ángulo de irradiación adopta valores entre 0o y 70° y el ángulo de observación adopta valores entre -70° y 70°. En definitiva, el resultado de este primer paso es un conjunto de factores de reflectancia correspondientes a los ángulos de irradiación y observación seleccionados, y que corresponde a una propiedad óptica intrínseca del material coloreado. b) Calcular los valores triestímulo XYZ correspondientes a un iluminante y un observador normalizados a partir del factor de reflectancia obtenido en el paso anterior. In this step, it is important to properly select the values of the irradiation angle and the observation angle so that the representation obtained allows to appreciate in a simple way the characteristics of the gonioaparente coating that is being studied. For this, values of irradiation angle and observation angle that are regularly spaced must be chosen, that is, values such that the difference between each pair of contiguous angles is constant and equal for both the irradiation angle and the observation angle . For example, irradiation angle and observation angle values that are separated from 10 ° to 10 ° can be chosen. In addition, it is not necessary to represent all the possible values of both angles, since for irradiation and observation angles above 70 ° there are hardly any changes in the appearance of the gonioaparente coating. Thus, preferably the irradiation angle values between 0 and 70 ° or the angle of observation values between -70 ° and 70 °. In short, the result of this first step is a set of reflectance factors corresponding to the selected irradiation and observation angles, and corresponding to an intrinsic optical property of the colored material. b) Calculate the XYZ tristimulus values corresponding to a standardized illuminant and observer from the reflectance factor obtained in the previous step.
En principio, tanto el iluminante como el observador normalizados se deben elegir de manera que constituyan una aproximación razonable a las condiciones de iluminación del lugar donde se va a observar el recubrimiento gonioaparente en cuestión y a las capacidades de percepción del observador al que está dirigida la representación. In principle, both the standardized illuminant and the observer must be chosen in such a way that they constitute a reasonable approximation to the lighting conditions of the place where the gonioaparente coating in question is to be observed and to the perception abilities of the observer to whom the representation is directed .
Por ejemplo, el iluminante normalizado puede ser el CIE-D65. El CIE-D65 es un iluminante estándar definido por la Comisión Internacional de Iluminación (CIE, Commision Internationale de l'Eclairage) que corresponde aproximadamente a un mediodía soleado en Europa Occidental. For example, the standard illuminant may be the CIE-D65. The CIE-D65 is a standard illuminant defined by the International Lighting Commission (CIE, Commision Internationale de l'Eclairage) that corresponds approximately to a Sunny noon in Western Europe.
El observador normalizado puede ser CIE-1964, el cual recoge las funciones de igualación espectral de un observador patrón (o medio) definido para un estímulo de 10° (equivalente a un diámetro de 90 mm y una distancia visual de 0.5 m). The standardized observer can be ICD-1964, which includes the spectral matching functions of a standard (or average) observer defined for a 10 ° stimulus (equivalent to a diameter of 90 mm and a visual distance of 0.5 m).
Los valores triestímulo XYZ pueden obtenerse multiplicando el factor de reflectancia R(X) obtenido en el paso anterior por las funciones de igualación espectral del observador estándar, io y10 zio , y la distribución espectral del iluminante correspondiente 8(λ) para cada longitud de onda, e integrando cada producto para todo el intervalo de longitud de onda (λ) del espectro visible: io = ∑Κ(λ) · Χιο (λ)· 8(λ)· Δλ
Figure imgf000008_0001
z ∑F?(A)- Z10(A)- S(A)- AA The triestimulus XYZ values can be obtained by multiplying the reflectance factor R (X) obtained in the previous step by the spectral equalization functions of the standard observer, io and 10 zio, and the corresponding illuminant spectral distribution 8 (λ) for each length of wave, and integrating each product for the entire wavelength range (λ) of the visible spectrum: io = ∑Κ (λ) · Χιο (λ) · 8 (λ) · Δλ
Figure imgf000008_0001
z ∑F? (A) - Z 10 (A) - S (A) - AA
c) Calcular los valores RGB o CMYK a partir de los valores triestímulo XYZ obtenidos en el paso anterior. c) Calculate the RGB or CMYK values from the XYZ tristimulus values obtained in the previous step.
En caso de que se vayan a mostrar los colores a través de una pantalla, es necesario calcular los valores RGB correspondientes a los triestímulo XYZ. El cálculo de los valores RGB se lleva a cabo mediante la transformación de los valores triestímulo XYZ al espacio de color sRGB según normativa internacional IEC 61966-2-1 : 1999. En primer lugar, se realiza una transformación lineal mediante una matriz: If the colors are to be shown through a screen, it is necessary to calculate the RGB values corresponding to the XYZ tristimulus. The calculation of the RGB values is carried out by transforming the XYZ tristimulus values into the sRGB color space according to international IEC 61966-2-1: 1999. First, a linear transformation is carried out using a matrix:
3.2410 1 .5374 - 0.4986 3.2410 1 .5374 - 0.4986
0.9692 1 .8760 0.0416  0.9692 1 .8760 0.0416
0.0556 0.2040 1 .0570 0.0556 0.2040 1 .0570
Figure imgf000008_0002
Figure imgf000008_0003
Figure imgf000008_0002
Figure imgf000008_0003
Los valores RGB intermedios (R lineal, Glineal, Büneai) están definidos en el intervalo [0, 1], por tanto, previamente los valores triestímulo XYZ deben normalizarse a la misma escala. A continuación, se calculan los valores sRGB aplicando la corrección gamma como sigue: The intermediate RGB values (linear R, Glineal, Büneai) are defined in the interval [0, 1], therefore, previously the XYZ tristimulus values must be normalized to the same scale. Next, sRGB values are calculated by applying gamma correction as follows:
12.92 - R„,ea/ Rlineal≤ 0.00304 12.92 - R „, ea / R linear ≤ 0.00304
(1 .055) - R^ - 0.055 Rlineal > 0.00304 (1 .055) - R ^ - 0.055 Linear R> 0.00304
12.92 - G„,ea/ G„,ea/ < 0.00304 12.92 - G „, ea / G„, ea / <0.00304
(1 .055) · G¡^ - 0.055 Glineal > 0.00304 (1 .055) G¡ ^ - 0.055 G linear > 0.00304
12.92 - S/(,ea/ S„,ea/ < 0.00304 12.92 - S / ( , ea / S „, ea / <0.00304
(1 .055) - S^ - 0.055 S„,ea/ > 0.00304 (1 .055) - S ^ - 0.055 S „, ea / > 0.00304
Por otro lado, si los colores se van a imprimir en un medio físico como un papel, será necesario transformar los valores triestímulo XYZ en los valores CMYK (acrónimo inglés de "Cyan, Magenta, Yellow and Key") correspondientes. Para ello, sería necesario caracterizar espectral y colorimétricamente el sistema de impresión elegido, así como el tipo de papel y el conjunto de tintas, mediante procedimientos bien establecidos aunque extensos y complejos en Artes Gráficas, los cuales pueden consultarse en varios libros como por ejemplo: On the other hand, if the colors are to be printed on a physical medium such as paper, it will be necessary to transform the XYZ tristimulus values into the corresponding CMYK (English acronym for "Cyan, Magenta, Yellow and Key"). For this, it would be necessary to spectrally and colorimetrically characterize the printing system chosen, as well as the type of paper and the set of inks, by well established but extensive and complex procedures in Graphic Arts, which can be consulted in several books such as:
F.M. Martínez-Verdú: "Reproducción del color en impresoras" ', en Tecnología del color, J.M. Artigas, P. Capilla, J. Pujol (eds.), Valencia: Universidad de Valencia (2002), Cap. 6, pág. 181 -251 . FM Martínez-Verdú: "Color reproduction Printers"'Color Technology, JM Artigas, P. Chapel, J. Pujol (eds.), Valencia University of Valencia (2002), Cap. 6, p. 181-251.
R. Balasubramanian: "Device characterization". En Color Imaging Handbook, G. Sharma (ed.), Boca Ratón: CRC Press (2003), Cap. 5, pág. 281 -395. R. Balasubramanian: "Device characterization". In Color Imaging Handbook, G. Sharma (ed.), Boca Raton: CRC Press (2003), Cap. 5, p. 281-395.
Es decir, que implica la medición de las reflectancias espectrales R(X) de una serie de colores impresos, tanto monocromos como policromos, con concentraciones variables de tinta (o nivel digital del color primario, "Cian, Magenta, Yellow or blacK"), y su posterior codificación cromática a valores triestímulo CI E-XYZ, o posteriormente a CI E- L*a*b*, para establecer los transformaciones matemáticas no lineales o diccionarios de conversión de datos iniciales XYZ o L*a*b* a CMYK, o viceversa. d) Representar los valores RGB o CMYK de cada combinación de ángulo de irradiación y ángulo de observación en las celdas de una matriz. That is, it involves the measurement of the spectral reflectances R (X) of a series of printed colors, both monochrome and polychrome, with varying concentrations of ink (or digital level of the primary color, "Cyan, Magenta, Yellow or blacK") , and its subsequent color coding to tristimulus values CI E-XYZ, or later to CI E-L * a * b *, to establish non-linear mathematical transformations or initial data conversion dictionaries XYZ or L * a * b * a CMYK, or vice versa. d) Represent the RGB or CMYK values of each combination of irradiation angle and observation angle in the cells of a matrix.
Una vez obtenidos los valores RGB o CMYK correspondientes al color de cada combinación de ángulo de irradiación y ángulo de observación seleccionados, es necesario decidir de qué manera se presentan para que den una idea intuitiva de la variación de color del recubrimiento gonioaparente en cuestión. Los inventores de la presente solicitud han descubierto que disponer los valores obtenidos como celdas de una matriz donde ángulo de irradiación y ángulo de observación constituyen filas y columnas proporciona dicha información de una manera visual inmediata.Once the RGB or CMYK values corresponding to the color of each combination of irradiation angle and observation angle selected are obtained, it is It is necessary to decide how they are presented to give an intuitive idea of the color variation of the gonioaparente coating in question. The inventors of the present application have discovered that arranging the values obtained as cells of a matrix where irradiation angle and observation angle constitute rows and columns provides such information in an immediate visual manner.
Preferentemente, cada fila de la matriz corresponde a un ángulo de irradiación y cada columna de la matriz corresponde a un ángulo de observación, aunque también sería posible hacerlo al revés. En caso de representar la matriz por pantalla, se utilizan los valores RGB, mientras que si la matriz se va a representar sobre papel se utilizan los valores CMYK, previa caracterización espectral y colorimétrica del dispositivo de impresión elegido, ya sea con tecnología offset, inkjet, láser o xerográfica, etc., de acuerdo con procedimientos ya establecidos y consolidados (como por ejemplo en WO2013066720A1). Preferably, each row of the matrix corresponds to an irradiation angle and each column of the matrix corresponds to an observation angle, although it would also be possible to do it the other way around. If the matrix is represented on the screen, the RGB values are used, while if the matrix is to be represented on paper, the CMYK values are used, after spectral and colorimetric characterization of the chosen printing device, either with offset technology, inkjet , laser or xerographic, etc., in accordance with established and consolidated procedures (such as in WO2013066720A1).
Un segundo aspecto de la invención está dirigido a la matriz obtenida de acuerdo con el procedimiento anterior donde cada fila de la matriz corresponde a un ángulo incidente y cada columna de la matriz corresponde a un ángulo de observación, y donde los ángulos de irradiación y de observación están regularmente espaciados. A second aspect of the invention is directed to the matrix obtained according to the above procedure where each row of the matrix corresponds to an incident angle and each column of the matrix corresponds to an observation angle, and where the irradiation and Observation are regularly spaced.
Las ventajas de la invención serán más aparentes a partir de la siguiente descripción, donde las figuras permiten apreciar el modo en que importantes características ópticas de un recubrimiento gonioaparente pueden apreciarse de un modo directo e intuitivo gracias a la matriz obtenida por medio del procedimiento de la invención. The advantages of the invention will be more apparent from the following description, where the figures allow us to appreciate the way in which important optical characteristics of a gonioaparente coating can be appreciated in a direct and intuitive way thanks to the matrix obtained by means of the process of the invention.
BREVE DESCRIPCIÓN DE LAS FIGURAS BRIEF DESCRIPTION OF THE FIGURES
La Fig. 1 muestra un esquema gráfico de las variables básicas que afectan al comportamiento de un recubrimiento gonioaparente. Fig. 1 shows a graphic diagram of the basic variables that affect the behavior of a gonioaparente coating.
La Fig. 2 muestra una matriz de representación de un recubrimiento gonioaparente obtenida con el método de la invención. Fig. 2 shows a representation matrix of a gonioaparente coating obtained with the method of the invention.
La Fig. 3 muestra el resultado de aplicar el procedimiento de la invención a un recubrimiento gonioaparente comercial denominado Lapis Sunlight, de Merck. Fig. 3 shows the result of applying the process of the invention to a commercial gonioaparente coating called Lapis Sunlight, from Merck.
La Fig. 4 muestra el resultado de aplicar el procedimiento de la invención a un recubrimiento gonioaparente comercial denominado Artic Fire, de Merck. REALIZACIÓN PREFERENTE DE LA INVENCIÓN Fig. 4 shows the result of applying the process of the invention to a commercial gonioaparente coating called Artic Fire, from Merck. PREFERRED EMBODIMENT OF THE INVENTION
La Fig. 1 muestra gráficamente las variables básicas que se utilizarán para llevar a cabo el procedimiento de la invención. Se ha considerado que tanto la dirección de irradiación (DI) como la de observación (DO) se encuentran contenidas dentro del plano de incidencia (Pl) determinado por la dirección de irradiación (DI) y el vector normal (VN) a la superficie del recubrimiento (SR). El motivo es que se ha comprobado que direcciones de observación fuera del plano de incidencia (Pl) no aportan mucha más información colorimétrica adicional. Fig. 1 graphically shows the basic variables that will be used to carry out the process of the invention. It has been considered that both the direction of irradiation (DI) and that of observation (DO) are contained within the plane of incidence (Pl) determined by the direction of irradiation (DI) and the normal vector (VN) to the surface of the coating (SR). The reason is that it has been proven that observation directions outside the plane of incidence (Pl) do not provide much more additional colorimetric information.
El ángulo de irradiación 0¡ caracteriza la dirección de irradiación (DI), y se define como el ángulo entre el vector normal (VN) a la superficie del recubrimiento (SR) y la dirección de irradiación (DI). El ángulo de irradiación 0¡ siempre tiene valor positivo. Igualmente, el ángulo de observación Qs caracteriza la dirección de observación (DO), y se define como el ángulo entre el vector normal (VN) a la superficie del recubrimiento (SR) y la dirección de observación (DO). El ángulo de observación Qs puede tener signo positivo o negativo para diferenciar entre direcciones de observación (DO) contenidas en el semiplano de incidencia de la dirección de irradiación (Qs positivo) y direcciones de observación (DO) contenidas en el semiplano opuesto (Qs negativo). En la Fig. 1 se han representado dos ejemplos de direcciones de observación (DO) respectivamente positiva (DO+) y negativa (DO-). The irradiation angle 0¡ characterizes the direction of irradiation (DI), and is defined as the angle between the normal vector (VN) to the surface of the coating (SR) and the direction of irradiation (DI). The irradiation angle 0¡ always has a positive value. Similarly, the observation angle Q s characterizes the observation direction (OD), and is defined as the angle between the normal vector (VN) to the surface of the coating (SR) and the observation direction (OD). The observation angle Q s can have a positive or negative sign to differentiate between observation directions (OD) contained in the incidence half-plane of the irradiation direction (positive Q s ) and observation directions (OD) contained in the opposite half-plane ( Q s negative). In Fig. 1 two examples of observation directions (OD) respectively positive (OD +) and negative (OD-) have been represented.
En este ejemplo, se seleccionan los siguientes valores de los ángulos de irradiación y de observación: Qs = -70°, -60°, -50°, -40°, -30°, -20°, -10°, 0o, 10°, 20°, 30°, 40°, 50°, 60°, 70° 9¡ = 0o, 10°, 20°, 30°, 40°, 50°, 60°, 70° In this example, the following values of the irradiation and observation angles are selected: Q s = -70 °, -60 °, -50 °, -40 °, -30 °, -20 °, -10 °, 0 o , 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 ° 9¡ = 0 or , 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °
A continuación, como se ha descrito anteriormente, se mide la función bidireccional de reflectancia espectral de cada combinación de ángulo de irradiación (0S) y de ángulo de observación (0¡) correspondiente a dos recubrimientos comerciales denominados T20-04 WNT Lapis Sunlight y T20-02 WNT Artic Fire. Ambos son producidos por Merck y utilizan el pigmento de interferencia Colorstream®. Las medidas se llevan a cabo utilizando el gonio- espectrofotómetro descrito por A. Rabal et al., Metrología 49, 213-223 (2012). El procedimiento consiste fundamentalmente en iluminar la muestra desde las distintas direcciones con un haz de luz altamente colimado y uniforme sobre la muestra, y medir la radiancia espectral a las distintas direcciones de observación. La BRDF espectral se calcula a partir del cociente entre la radiancia espectrales medidas y la irradiancia sobre la muestra a las distintas direcciones de iluminación.. Una vez realizadas las medidas, los valores obtenidos se multiplican por π para obtener el valor de reflectancia y, a continuación, se calculan los valores triestímulo XYZ correspondientes al iluminante CIE-D65 y al observador CIE-1964. Por último, se determinan los correspondientes valores RGB para una representación en pantalla o los basados en otro sistema como CMYK para la impresión en papel. Next, as described above, the bidirectional spectral reflectance function of each combination of irradiation angle (0 S ) and observation angle (0¡) corresponding to two commercial coatings called T20-04 WNT Lapis Sunlight and T20-02 WNT Artic Fire. Both are produced by Merck and use the Colorstream® interference pigment. The measurements are carried out using the gonio-spectrophotometer described by A. Rabal et al., Metrology 49, 213-223 (2012). The procedure consists essentially of illuminating the sample from the different directions with a beam of highly collimated and uniform light on the sample, and measuring the spectral radiance to the different directions of observation. The spectral BRDF is calculated from the quotient between the measured spectral radiance and the irradiance on the sample at the different lighting directions. Once the measurements are made, the values obtained are multiplied by π to obtain the reflectance value and, at Then, the XYZ tristimulus values corresponding to the CIE-D65 illuminant and the CIE-1964 observer are calculated. Finally, the corresponding RGB values are determined for an on-screen representation or those based on another system such as CMYK for paper printing.
El resultado es un conjunto de valores RGB o CMYK correspondientes a los colores que adopta la superficie del recubrimiento (SR) para cada combinación de ángulo de irradiación (0¡) y ángulo de observación (0S). Esta información se muestra, bien por pantalla o sobre papel, a través de una matriz como la mostrada en la Fig. 2 donde cada fila corresponde a un ángulo de irradiación (0¡) y cada columna corresponde a un ángulo de observación (0S). Esta forma de representación concreta presenta ventajas relacionadas con el modo en que se visualizan diversas características importantes del recubrimiento gonioaparente en cuestión. Las filas de la matriz corresponden al cambio de color que se produce en el recubrimiento gonioaparente para toda la gama de ángulos de observación (0S) manteniendo constante el ángulo de irradiación (0¡). Estas líneas horizontales son conocidas como "líneas aspeculares", y actualmente se cree que pueden dar información acerca de la reflexión difusa de los pigmentos de absorción. The result is a set of RGB or CMYK values corresponding to the colors adopted by the coating surface (SR) for each combination of irradiation angle (0¡) and observation angle (0 S ). This information is shown, either on screen or on paper, through a matrix like the one shown in Fig. 2 where each row corresponds to an irradiation angle (0¡) and each column corresponds to an observation angle (0 S ). This form of concrete representation has advantages related to the way in which various important characteristics of the gonioaparente coating in question are visualized. The rows of the matrix correspond to the color change that occurs in the gonioaparente coating for the entire range of observation angles (0 S ) keeping the irradiation angle (0¡) constant. These horizontal lines are known as "aspecular lines," and it is currently believed that they can give information about diffuse reflection of absorption pigments.
Las columnas de la matriz corresponden al cambio de color que se produce en el recubrimiento gonioaparente para toda la gama de ángulos de irradiación (0¡) manteniendo constante el ángulo de observación (0S). Las líneas diagonales de arriba-derecha hacia abajo-izquierda se denominan "líneas de interferencia", y se definen como el lugar geométrico de las coordenadas de color en el que el ángulo aspecular se mantiene constante, donde el ángulo aspecular se define como:
Figure imgf000012_0001
The columns of the matrix correspond to the color change that occurs in the gonioaparente coating for the entire range of irradiation angles (0¡) keeping the observation angle (0 S ) constant. The diagonal lines from top-right to bottom-left are called "interference lines", and are defined as the geometric place of the color coordinates in which the aspecular angle remains constant, where the aspecular angle is defined as:
Figure imgf000012_0001
Las líneas de interferencia muestran el cambio total de tono que se puede observar en el recubrimiento. La región cis está determinada por las celdas de la matriz que tienen un valor positivo del ángulo aspecular, mientras que la región trans está determinada por las celdas de la matriz que tienen un valor negativo del ángulo aspecular. The interference lines show the total change in tone that can be observed in the coating. The cis region is determined by matrix cells that have a value positive of the aspecular angle, while the trans region is determined by the matrix cells that have a negative value of the aspecular angle.
La variación de color a lo largo de las direcciones especulares se produce en la diagonal que representa el lugar geométrico donde 9¡ = -Qs. The variation of color along the mirror directions occurs in the diagonal that represents the geometric place where 9¡ = -Q s .
La variación de color a lo largo de las direcciones de retrorreflexión se produce en la diagonal que representa el lugar geométrico donde 9¡ = Qs. The color variation along the retroreflection directions occurs in the diagonal that represents the geometric place where 9¡ = Q s .
Por último, las Figs. 3 y 4 muestran sendas matrices que se obtienen como resultado de llevar a cabo el procedimiento de la invención para los mencionados recubrimientos T20-04 WNT Lapis Sunlight y T20-02 WNT Artic Fire. Finally, Figs. 3 and 4 show two matrices that are obtained as a result of carrying out the process of the invention for the mentioned coatings T20-04 WNT Lapis Sunlight and T20-02 WNT Artic Fire.

Claims

REIVINDICACIONES
1. Procedimiento de medición de la gama cromática de un recubrimiento gonioaparente, caracterizado por que comprende los siguientes pasos: 1. Procedure for measuring the chromatic range of a gonioaparente coating, characterized in that it comprises the following steps:
a) obtener el factor de reflectancia espectral R(X) para varias combinaciones de valores regularmente espaciados de ángulo de irradiación (0¡) y ángulo de observación (0S); b) calcular los valores triestímulo XYZ correspondientes a un iluminante y un observador normalizados a partir del factor de reflectancia obtenido en el paso anterior; c) calcular los valores RGB o CMYK a partir de los valores triestímulo XYZ obtenidos en el paso anterior; y a) obtain the spectral reflectance factor R (X) for various combinations of regularly spaced values of irradiation angle (0¡) and observation angle (0 S ); b) calculate the XYZ tristimulus values corresponding to a standardized illuminant and observer from the reflectance factor obtained in the previous step; c) calculate the RGB or CMYK values from the XYZ tristimulus values obtained in the previous step; Y
d) representar los valores RGB o CMYK de cada combinación de ángulo incidente (0¡) y ángulo de observación (Qs) en las celdas de una matriz. d) represent the RGB or CMYK values of each combination of incident angle (0¡) and observation angle (Q s ) in the cells of a matrix.
2. Procedimiento de acuerdo con la reivindicación 1 , donde cada fila de la matriz corresponde a un ángulo incidente (0¡) y cada columna de la matriz corresponde a un ángulo de observación (0S). 2. A method according to claim 1, wherein each row of the matrix corresponds to an incident angle (0¡) and each column of the matrix corresponds to an observation angle (0 S ).
3. Procedimiento de acuerdo con cualquiera de las reivindicaciones anteriores, donde el ángulo incidente (0¡) adopta valores entre 0o y 70° y el ángulo de observación (Qs) adopta valores entre -70° y 70°. 3. Process according to any of the preceding claims, wherein the incident angle (0¡) values between 0 and 70 ° and the observation angle (Q s) -70 values between 70 °.
4. Procedimiento de acuerdo con cualquiera de las reivindicaciones anteriores, donde el espaciado entre valores contiguos de ángulo incidente (0¡) y valores contiguos de ángulo de observación (0S) es de 10°. 4. Method according to any of the preceding claims, wherein the spacing between contiguous incident angle values (0¡) and contiguous observation angle values (0 S ) is 10 °.
5. Procedimiento de acuerdo con cualquiera de las reivindicaciones anteriores, donde el iluminante normalizado es CIE-D65. 5. Method according to any of the preceding claims, wherein the standard illuminant is CIE-D65.
6. Procedimiento de acuerdo con cualquiera de las reivindicaciones anteriores, donde el observador normalizado es CIE-1964. 6. Method according to any of the preceding claims, wherein the standardized observer is ICD-1964.
7. Matriz de representación del color de un recubrimiento gonioaparente obtenida de acuerdo con el procedimiento de cualquiera de las reivindicaciones anteriores, caracterizada por que cada fila de la matriz corresponde a un ángulo de irradiación (0¡) y cada columna de la matriz corresponde a un ángulo de observación (0S), estando los ángulos de irradiación (0¡) y de observación (0S) regularmente espaciados. 7. Color representation matrix of a gonioaparente coating obtained according to the method of any of the preceding claims, characterized in that each row of the matrix corresponds to an irradiation angle (0¡) and each column of the matrix corresponds to an observation angle (0 S ), the irradiation (0¡) and observation (0 S ) angles being regularly spaced.
PCT/ES2014/070897 2013-12-16 2014-12-04 Method and matrix for measuring the colour gamut of a gonio-apparent coating WO2015092097A1 (en)

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