Optical Properties and Visual Appearance of Printed Special Effect Colors.
Technische Universität, Darmstadt
[Ph.D. Thesis], (2013)
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|Item Type:||Ph.D. Thesis|
|Title:||Optical Properties and Visual Appearance of Printed Special Effect Colors|
Think of perfume wrappings and chocolate boxes. For such high quality printing products, printing inks with special effect pigments are used more frequently due to the unique optical properties and visual appearance. The shifting color, the pearlescent gloss and the visible texture of printed special effect colors fascinate the observer. A lack of knowledge about the printing of special effect colors and about the description of the optical properties and visual appearance causes problems. First, special effect printing calls for knowledge about the influence of different printing parameters. Therefore, multiple samples varying in the special effect pigment, paper quality, varnishing state and background color were printed. In screen printing, 22 inks with pigments of BASF SE were applied on a white glossy and black uncoated paper. The combination of 22 pigments with two paper grades or background colors results in 44 application cases. In total, 224 application cases were realized in flexo printing with 28 pigments of MERCK KGaA, two paper qualities, two background colors and two varnishing states. A white glossy and matt coated paper was partially primed with a black light-absorbing ink and partly varnished with a clear gloss varnish. Furthermore, some knowledge about the bidirectional reflectance and texture distribution is required to specify the optical properties. A database was thus generated basing on spectral and imaging measurements in multiple geometric configurations. The determined reflectance spectra, color coordinates and texture parameters are filed in a hierarchical structure. Using the freely available bidirectional reflectance and texture data (www.idd.tu-darmstadt.de, email@example.com), the influence of the varied printing parameters on perception-related parameters was investigated. A medium and very high hue difference sum is caused by interference effect and multi-color pigments, respectively. For the comparably large sparkle pigments, the sparkle parameters are particularly high. Perceptually, the lightness difference sum and the relative luminance difference do not satisfactorily represent the lightness shift and the contrast gloss or distinctness-of-image gloss. All considered parameters are significantly lower for the white paper than the black printed background. Finally, the essential visual appearance attributes should be known for the description of the visual appearance. Their number and nature was determined by means of visual experiments and statistical evaluations. In a color matching light both and a multi-angle test bench, 14 rolled screen and 20 planar flexo printing samples were presented, respectively. Visual differences and twelve attributes were rated in relative and absolute category scaling experiments, respectively. They were evaluated in classical multidimensional scaling, in two correlation analyses, a principal component analysis and in an exploratory factor analysis. According to the STRESS values, cumulated variances and the eigenvalues, at most six attributes are essential. Significantly positive correlation coefficients between the two and three tested gloss and texture attributes, respectively, suggest their joint consideration. The composition and factor loadings indicate that the six essential attributes are the four color attributes hue, chroma, lightness and hue shift as well as the two combined attributes for gloss and texture.
|Place of Publication:||Darmstadt|
|Uncontrolled Keywords:||gedruckte Spezialeffektfarbe, optische Eigenschaft, visuelle Wahrnehmung, Druckparameter, bidirektionale Reflexions- und Texturverteilung, visuelles Wahrnehmungsattribut|
|Classification DDC:||600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften|
|Divisions:||16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Institute of Printing Science and Technology (IDD)
|Date Deposited:||05 Jul 2013 11:31|
|Last Modified:||05 Jul 2013 11:31|
|Refereed:||30 April 2013|
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