Precision in the reproduction of colored coatings

The objective of this study was to apply Hotelling's T²‐statistics to color measurement data of colored coatings. It is described, how outliers can be detected by comparing T² with an appropriate statistical distribution function. As an example, the precision in the reproduction of colored coatings produced in laboratory and prepared by a robot for high‐throughput experimentation was investigated on a turquoise coating. After elimination of outliers the precision of reproduction of the coatings color was determined by the sample color differences to the average color coordinates in CIELAB and DIN99 color spaces as well as with CIEDE2000 color differences. As expected, laboratory experimentation (reproducibility conditions) showed a lower precision of color reproduction as samples prepared with the high‐throughput experimentation device (repeatability conditions).     

Towards a practical metric of surface gloss for metallic coatings from automotive industry

The specular gloss of metallic coatings from the automotive industry can be well measured by current glossmeters when the geometry is appropriately chosen from 20°, 60°, and 85° based on the gloss levels observed. However, the measurements are discontinuous and even nonmonotonic at the breakpoints dividing samples into different gloss levels in the whole range, which causes confusion and inconvenience for industry applications. In this study, attempts were made to link the measurements at the three geometries to be continuous monotonically and in the meanwhile to improve the accuracy of estimating visual gloss. A psychophysical experiment based on a magnitude method was carried out to assess the gloss of metallic coatings with different colors and textures. The visually scaled gloss data were compared with spectrophotometric measurements and instrumental specular gloss values under different geometries. With different weighing coefficients for measurements at individual geometries depending on the gloss levels, a model was proposed to describe the visual surface gloss of metallic coatings comprehensively via a practical metric based on the geometry-dependent measurements. In this way, each sample would have a unique overall gloss value highly correlated with its perceptual evaluation over the entire gloss range.     

Measuring flake orientation for metallic coatings

Metallic and pearlescent coatings, very popular in automotive applications, contain flake shaped pigments. The orientation distribution of these flakes inside the effect coatings determines to a large extend the color and visual appearance of the coating. Unfortunately the measurement of flake orientation distributions is far from straightforward. The two main current techniques use analysis with light microscopy on cross cuts, and confocal microscopy.We used both techniques on a large set of samples. A set of 117 metallic coatings were analyzed, where we varied the concentration of metallic pigment, the concentration of so-called disorienting agent and the type and size of metallic pigment. Trends that for a long time have been assumed to be true were now unambiguously proven true, and can now be stated in a quantitative manner. For example, large flakes generally show better orientation than small flakes. For waterborne cornflake pigments, we measured an orientation width of 19.4° for flakes with a median diameter of 16 μm, and only 7.2° for flakes with a median diameter of 35 μm. Surprisingly we found only a small effect on flake orientation when disorienting agent was added to a color formula.     

Reproducibility comparison among multiangle spectrophotometers

New color‐measuring instruments known as multiangle spectrophotometers have been recently created to measure and characterize the goniochromism of special‐effect pigments in many materials with a particular visual appearance (metallic, interference, pearlescent, sparkle, or glitter). These devices measure the gonioapparent color from the spectral relative reflectance factor and the L*a*b* values of the sample with different illumination and observation angles. These angles usually coincide with requirements marked in American Society for Testing and Materials (ASTM) and Deutsches Institut Für Normung standards relating to the gonioapparent color, but the results of comparisons between these instruments are still inconclusive. Therefore, the main purpose of this study is to compare several multiangle spectrophotometers at a reproducibility level according to ASTM E2214‐08 guidelines. In particular, we compared two X‐Rite multi‐gonio spectrophotometers (MA98 and MA68II), a Datacolor multi‐gonio spectrophotometer (FX10), and a BYK multi‐gonio spectrophotometer (BYK‐mac). These instruments share only five common measurement geometries: 45° × ?30° (as 15°), 45° × ?20° (as 25°), 45° × 0° (as 45°), 45° × 30° (as 75°), 45° × 65° (as 110°). Specific statistical studies were used for the reproducibility comparison, including a Hotelling test and a statistical intercomparison test to determine the confidence interval of the partial color differences ΔL*, Δa*, Δb*, and the total color difference ΔE*_ab. This was conducted using a database collection of 88 metallic and pearlescent samples that were measured 20 times without the replacement of all the instruments. The final findings show that in most measurement geometries, the reproducibility differences between pairs of instruments are statistically significant, although in general, there is a better reproducibility level at certain common geometries for newer instruments (MA98 and BYK‐mac). This means that these differences are due to systematic or bias errors (angle tolerances for each geometry, photometric scales, white standards, etc.), but not exclusively to random errors. However, neither of the statistical tests used is valid to discriminate and quantify the detected bias errors in this comparison between instruments. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 160–167, 2013.     

Color measurements for pearlescent coatings

This article describes recent developments at the National Institution of Standards and Technology in the colorimetric characterization of pearlescent coatings. The goal of this research is to develop a measurement protocol for the accurate color characterization of these coatings using an understanding of their scattering mechanism as a guide. A large ensemble of bi‐directional reflectance measurements on a series of pearl interference pigmented coatings show general trends in the color variations with illumination and viewing angles. These measurements were used to define a set of geometries (illumination angles of 15°, 45°, and 65° and aspecular angles of 15°, 35°, 45°, 70°, and 85°) to characterize the angle dependent color travel observed in these coatings. © 2003 Wiley Periodicals, Inc. Col Res Appl, 29, 38–42, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10210     

Setting tolerances on color and texture for automotive coatings

In the automotive industry, color quality control is increasingly done by reflection measurements. We discuss how color tolerances are set in specifications to suppliers of add‐on parts and to paint suppliers. We mention several factors that often lead to unrealistically tight settings, and therefore to incorrect rejections and unnecessary high productions costs. We show that this is likely to occur when the dE_ab color difference equation is used, or when a strict criterion separating pass from fail is used instead of specifying a “grey area” where instrumental monitoring needs to be followed by visual assessments. Unrealistically, tight tolerances also result from halving tolerances in the supply‐customer chain in an attempt to compensate color variations due to uncontrolled application conditions. Tolerances should be widened further when a gap separates an add‐on part from the car body, making visual discrimination of color differences less critical. Other common situations where tolerances should be widened are the presence of visual texture in effect coatings, the lightness of metallic coatings becoming very high (L*> 100) and measurement geometries close to the gloss angle. Finally, we address the issue that instrumental color tolerances should not be tighter than what is allowed by instrumental reproducibility, repeatability, and inter‐instrument agreement. Accounting for these factors, we provide a set of reasonable values for tolerances on color and on visual texture parameters, based on our own practical experience. But realistic tolerance values depend very much on actual conditions, and should be agreed in tripartite discussions among automotive industry, suppliers of add‐on parts, and paint supplier. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 88–98, 2014     

Visual and instrumental assessments of color differences in automotive coatings

The interest in gonioapparent pigments (metallic, pearlescent, interference, or diffractive) has increased in the last few years, especially for applications in the automotive industry. To assure a proper characterization of colors with gonioapparent pigments, commercial devices have appeared to characterize the color in different geometries, which are called multiangle spectrophotometers. As the gonioapparent pigments and multiangle instruments are relatively new, no studies exist regarding the instrumental‐based procedure followed in the industry, and if the results provided are in agreement with the observer perception. Consequently, the main objective of this study was to examine the correlation of the instrumental color differences with visual assessments. The instrumental color difference was calculated with the color difference formula AUDI2000 (specific for this sector) between the pairs of similar samples of three types of coated panels (solid, metallic, and pearlescent). The values measured by a telespectroradiometer in a directional lighting booth and the colorimetric values obtained by means of a multiangle spectrophotometer BYK‐mac were considered for this purpose. Additionally, a visual experiment was conducted to quantify the color difference by using the gray‐scale method. The results revealed that an acceptable instrumental correlation existed despite the visual and the instrumental correlation being worse. In particular, it was checked that observers accepted a larger number of color pairs, that is, the visual color difference was smaller than the tolerance demanded by the industry (derived from AUDI2000). © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 384–391, 2016     

全新的测量技术描述对效应涂料全面颜色的印象

简介效应涂料颜色测量的机理,并叙述了效应涂料箔状(片状)特性以及使用毕克-加特纳仪器对颜色的测量。通过模拟晴天和阴天的照射条件测量闪烁和砂粒状,以表征箔片特性。从多角度和光照条件较全面评估、描述效应涂料的表面状态。     

Effect of surface texture on color appearance of metallic coatings

In this study, the effect of aluminum flake size on the color appearance of metallic coatings has been investigated. To this end, metallic solvent-borne basecoat-clear coat systems with seven different surface textures using different sizes of aluminum flakes were prepared corresponding to nine color centers including blue, yellow, red, green, purple, cyan, orange, greenish yellow and gray. The color changes via texture differences were assessed by visual experiments carried out by 25 observers including 14 women and 11 men using gray scale method and under semi-diffuse illumination conditions. The assessed pairs had the same color center and different visual texture caused by different aluminum flake sizes. Texture analysis was performed using autocorrelation function and fractal dimension on gray scale images of the samples, captured by a scanner, and texture difference for each assessed pair was computed.     

Total appearance differences for metallic and pearlescent materials: Contributions from color and texture

We have investigated how texture and color combine when assessing the appearance of special effect coatings. In a previous study, the most important aspects of the texture of special effect coatings were identified as diffuse coarseness and glint impression. In the present study, objective measurements of these parameters are carried out using a recently developed instrument, and these data are combined with spectrophotometer data under six geometries. The instrumental data and visual data are analyzed using statistical techniques. From these visual data we were able to create a total appearance score which strongly correlates with the measurements of color and texture differences using this instrument. In this way a calculation procedure has been developed yielding predictions on acceptability that correlate well with visual judgments. Also, the added value of reflection data close to the gloss angle is demonstrated. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

浅谈金属闪光漆的配色方法

重点介绍了金属闪光漆的配色方法,并运用涂料知识和色彩学原理分析每个步骤,总结配色规律和技巧,旨在将配色过程归纳成简单的流程,让汽车涂料配色有径可寻,满足工业化生产快速规范的要求。     

闪光涂料色差的控制与应用探讨

从闪光涂料的成膜特性上,对色差理论进行了简单描述,并分析了其应用技术。联系涂装生产现场,介绍了涂膜色差的控制对策与应用。     

Radiative transfer theory solid color-matching calculations

Radiative transfer theory concepts for color-matching calculations of solid color coatings are reviewed. Two flux approximations to the exact radiative transfer theory for isotropic scatters are developed. The Kubelka-Munk theory is discussed in the framework of two flux theories. A comparison is made between reflectances calculated from the Kubelka-Munk, two flux approximate radiative transfer, and the exact radiative transfer theory for 45/0 and diffuse/near-normal measuring geometries. A color-matching method is presented for radiative transfer color-matching calculations. This method, which can be implemented on a personal computer, is shown to give good color matches for the exact radiative transfer theory. The proposed color-matching algorithm, which can be applied to all three models, gives results equivalent to established Kubelka-Munk calculations. A comparison of the Kubelka-Munk, two flux approximate radiative transfer, and exact radiative transfer color calculations shows them to give equivalent results for diffuse/near-normal reflectance data. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 72–87, 1997     

水性聚偏氟乙烯型反射隔热涂层的耐久性研究

研究了在酸、碱、盐和UV辐照等环境作用下水性聚偏氟乙烯型(PVDF)反射隔热涂层性能的时变规律。使用扫描电镜(SEM)和能谱分析表征了涂层微观形貌及断面中的氟元素分布,对涂层在经各类环境作用前后的明度、光泽、色差、力学性能和反射隔热性能进行了测试,并使用ATR-FTIR对表面涂层的官能团变化进行了分析。结果表明:氟元素在涂层树脂基体中的垂向分布较均匀;56 d UV处理会提升涂层光泽;经酸、盐和UV处理后,涂层明度未见明显变化且色差较小,涂层断裂伸长率降低且抗拉强度提升,最高达8.4 MPa,反射隔热性能指标未见明显变化;碱处理后的涂层出现明显的色差和明度下降,涂层变脆且抗拉强度下降,同时太阳光反射比由0.70降至0.65。ATRFTIR分析结果表明:涂层的耐酸、盐和UV能力较强,但在碱性条件下存在含氟组分的降解破坏情况。     

反应喷墨打印技术及其在功能材料领域的研究进展

反应喷墨打印技术作为喷墨打印电子技术的重要分支,因其可以在沉积材料的同时可得到器件而受到人们的广泛关注.本文详细阐述了反应喷墨打印技术在功能材料制备领域,特别是在金属材料、高分子材料、无机材料等方面的研究进展,说明了反应喷墨打印用墨水是未来喷墨印刷电子研究的关键技术之一,简要介绍了反应喷墨打印技术与三维打印的联系,指出其在金属电路、有机发光二极管等印刷电子产业领域有广阔的应用前景.     

Effects of Pores on Mechanical Properties of Plasma-Sprayed Ceramic Coatings

The effects of pore sizes, shapes, and orientations on the mechanical properties of thermally sprayed ceramic coatings are investigated. The analysis is conducted using detailed finite-element models with geometries similar to those of actual ceramic coatings containing many embedded pores. These microstructural models include many randomly placed pores of different sizes and shapes and are loaded in tension to determine their effective elastic moduli along the spray and transverse directions. We modeled coatings with statistical distributions of pore sizes and shapes that followed those of actual Al₂O₃–TiO₂ coatings. Because the pores in such a model are of different sizes and shapes, the model must be large enough to contain sufficient pores before the average modulus obtained from uniaxial loading can be identified as an effective property. Using differently sized models, we determined the variability of the average moduli. Such information is valuable when homogenized or continuum material models are used in the stress analyses of coatings. Our computed results show that a model must be large enough to contain 50–100 pores before the averaging of properties is accurate. Using the Al₂O₃–TiO₂ models, we also simulated microindentation tests. Unlike the results determined from uniaxial loading, the elastic moduli estimated from indentation possessed large variations. Apparently, the morphology of the pores immediately beneath the indentation or within the zone of influence has a significant effect on the response of the indenter and the measured modulus. The implications of these results and the computational capability to predict the mechanical properties of porous, plasma-sprayed ceramic coatings are discussed here.     

Formation of single-walled carbon nanotube thin films enriched with semiconducting nanotubes and their application in photoelectrochemical devices

Single-walled carbon nanotube (SWCNT) thin films, containing a high-density of semiconducting nanotubes, were obtained by a gel-centrifugation method. The agarose gel concentration and centrifugation force were optimized to achieve high semiconducting and metallic nanotube separation efficiency at 0.1 wt% agarose gel and 18,000g. The thickness of SWCNT films can be precisely controlled from 65 to 260 nm with adjustable transparency. These SWCNT films were applied in photoelectrochemical devices. Photocurrents generated by semiconducting SWCNT enriched films are 15-35% higher than those by unsorted SWCNT films. This is because of reducing exciton recombination channels as a result of the removal of metallic nanotubes. Thinner films generate higher photocurrents because charge carriers have less chances going in metallic nanotubes for recombination, before they can reach electrodes. Developing more scalable and selective methods for high purity semiconducting SWCNTs is important to further improve the photocurrent generation efficiency by using SWCNT-based photoelectrochemical devices.     

影响PVDF氟碳金属面漆耐酸性的因素探讨

考察了氟碳金属面漆应用铝粉类型、氟碳清漆膜厚以及PMT（最高金属板温）对PVDF氟碳金属面漆耐酸性试验结果的影响。试验表明氟碳清漆膜厚、铝粉类型及PMT对耐酸试验后色差变化均有影响,其中氟碳清漆膜厚和铝粉类型影响色差较为明显,色差变化值随清漆膜厚增加而减小,随氟碳金属面漆使用的铝粉颗粒的平均粒径的增加而减小。同为小粒径铝粉时,表面进行处理的包裹型铝粉制作的氟碳金属面漆耐酸试验后的色差变化小于使用普通工业级铝粉制作的氟碳面漆。     

高装饰性金属色汽车面漆涂装工艺

金属闪光色已成为汽车面漆的流行色，并有逐年增多之势，基于高装饰性的金属色面漆的涂装工艺较本色面漆复杂、难掌握，作从金属色面漆组成及特性等方面向读介绍汽车车身及零部件的金属色面漆的涂装工艺及操作要点。     

Colorimetric characteristics of colored single-coat enamels

Compositions for single-coat glass enamels that allow obtaining a wide color range of coatings with sufficiently good surface quality for steel articles were developed. Different dyes were tested. Properties of the coatings such as the chemical stability, adhesive strength, gloss, and thermal stability were investigated and the firing temperature range, 670–740°C on average, was determined. The colorimetric characteristics of single-coat enamels were calculated. The enamel coatings obtained can be used in mass production.