Abstract
A set of aluminum-flake pigmented coatings having different flake orientations was prepared using various spraying conditions. The flake surface topography and the orientations of individual flakes were determined from images obtained by laser scanning confocal microscopy. Reflectance measurements were carried out to quantify the optical properties of the coatings. Both a Gaussian distribution (used to represent the measured flake orientation distribution) and a topographic map (including local surface roughness and orientation) of the flakes were then used as input to a ray scattering model to calculate the optical reflectance of each coatings Flake orientation distributions and examples of measured optical reflectance as a function of scattering angle are shown, and the latter are compared to calculated reflectance values.
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References
Wicks, Z.W., Jones, F.N. Jr., and Pappas, S.P.,Organic Coatings: Science and Technology, John Wiley & Sons, Inc., 1992.
McCamy, C.S., “Observation and Measurement of the Appearance of Metallic Materials, Part I. Macro Appearance & Part II. Micro Appearance,”Color Research and Application, 21, 292–304 (1996), 23, 362–372 (1998).
Rodrigues, A.B.J., “Color and Appearance Measurement of Metallic and Pearlescent Finishes,”ASTM Standardization News, 68–72, October (1995).
Tachi, K., Okuda, C., and Suzuki, S., “Mechanism of Aluminum Flake Orientation in Metallic Topcoats,”Journal of Coatings Technology,62, No. 782, 43 (1990).
Tachi, K. and Okuda, C., “Color Variation of Automotive Metallic Finishes,”Journal of Coatings Technology,64, No. 811, 71–77 (1992).
Wojtkowiak, J.J., “Effect of Film Viscosity on Aluminum Flake Orientation in Thermoplastic Acrylic Coatings,”Journal of Coatings Technology,51, No. 658, 111 (1979).
Kettler, W.H. and Richter, G., “Investigation on Topology of Platelet-Like Effect-Pigments in Automotive Surface-Coatings,”Prog. Org. Coat., 31, 297–306 (1997).
Sung, L.-P., Nadal, M.E., McKnight, M.E., Marx, E., Dutruc, R., and Laurenti, B., “Effect of Aluminum Flake Orientation on Coating Appearance,”Proc. 79th Annual Meeting Technical Program of the FSCT, Nov. 5–7, 2001, Atlanta, GA, 453–466 (2001).
Corle, T.R., and Kino, G.S.,Confocal Scanning Optical Microscopy and Related Imaging Systems, Academic Press (1996).
Barnes, P.Y., Early, E.A., and Parr, A.C.,Spectral Reflectance, NIST Special Publication, 250–48, 1998.
McKnight, M.E., Marx, E., Nadal, M.E., Vorburger, T.V., Barnes, P.Y., and Galler, M., “Measurements and Predictions of Light Scattering by Clear Epoxy Coatings,”Applied Optics, 40, 2159–2168 (2001).
Germer, T.A. and Asmail, C.C., “Polarization of Light Scattered by Microrough Surfaces and Subsurface Defects,”J. Opt. Soc. Am. A, 16, 1326–1332 (1999).
Barrick, D.E., “Rough Surface Scattering Based on the Specular Point Theory,”IEEE Trans. Antennas Propagat., 16, 449–454 (1968).
Born, M. and Wolf, E.,Principles of Optics, 6th Edition, p. 42, Pergamon, 1980.
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Gaithersburg, MD 20899.
Louisville, KY 40211.
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Sung, LP., Nadal, M.E., McKnight, M.E. et al. Optical reflectance of metallic coatings: Effect of aluminum flake orientation. Journal of Coatings Technology 74, 55–63 (2002). https://doi.org/10.1007/BF02697975
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DOI: https://doi.org/10.1007/BF02697975