CIE x050-PO149 PDF

Chromic materials, frequently called as color-changeable materials, became more important in many applications. For example, photochromic colorants are used as in adaptive sunglasses, rewritable CD and its alternatives, indicators, etc. Photochromic dye reversible changes their color with the incoming light intensity or spectral distribution of the light. They are nearly invisible when they are not exposed to UV light; exposure to UV light causes fast transition and increasing of color depth. Because photochromic materials are based on generally unstable organic molecules, one of important characteristics relating to optical properties of such kind of materials is relating to kinetic of color change itself. Obvious in literature mentioned description of experimental method used during test of optical properties of photochromic materials is reduced on used conventional UV-VIS spectrophotometer, wavelength and power of exposure light source that is necessary to ad as accessory. Necessary information about irradiance of tested sample is obviously missing, which cause problems with comparison of data measured on different laboratories. Problem with the measurement of the kinetic behavior of opaque photochromic substrates with a commercial spectrophotometer is the relatively long period of time between individual measurements (cca 5 s) and the difficulty in measuring all the color change during exposure without interruption from illumination of the sample during measurement. That means commercial spectrophotometers enable off-line measurement of kinetic behavior during exposure period and quasi on-line measurement during the reversion period. The difference in the time delay between exposure and real measurement of photochromic change affects the validity of the measured data. Based on that it was decided to check influence of used temperature, irradiance, and setup of testing cycle on obtained results in case of color depth measured as K/S value, color change half-life and possible fading effect.