COLORIMETRY OF DURABLE FLUORESCENT RETROREFLECTIVE MATERIALS

The development of durable daylight fluorescent retroreflective sheeti ngs has led us to investigate same of the factors that influence color measurement of these materials. The colorimetry of retroreflective ma terials is particularly sensitive to measurement geometry. The added a spect of fluorescence increases the spectral uncertainties, making app earance measurements even more difficult. The visual properties used t o describe fluorescent retroreflective materials should include chroma ticity, lightness, peak spectral radiance factor, nighttime color, and color stability on exposure. A number of test methods exist for these measurements. however, practical experience in applying these methods to fluorescent materials shows significant variation in the resulting measured values. Colorimetric measurements on commercial instruments using 45/0 (0/45) geometry, a stimulated D65 illuminant, and the CIE 2 degrees standard observer yield results that are inadequate for preci se quality control of durable fluorescent retroreflective materials. T he uncertainty can be reduced by the use of transfer standards, provid ed that the standard is similar to the sample in both hue and fluoresc ent emission. Ultimately, the wide availability of commercial 2-monoch romator spectrocolorimeters will be required. (C) 1995 John Wiley & So ns, Inc.