Richard Kennedy (Paint Research Association)

摘要

For a measurement that is taken very much at face value, gloss is actually quite a complex phenomenon. There are actually several different types of gloss: the type most often considered in coatings technology is specular gloss or the fraction of light that is reflected from the surface where the angle of reflection is equal to the angle of incidence. Consequently high gloss coatings reflect a higher proportion of incident light at the specular angle and lower gloss coatings actually reflect a larger fraction of light at non-specular angles. Gloss, however, is not directly related to the fraction of light reflected from the surface, because the fraction of light reflected increases as the angle of illumination increases and as the refractive index increases. Clearly if a surface is rough on a micro-scale, the angle of incidence of a beam of light is not necessarily the same as the geometric angle of the whole surface to the beam of light. Thus surface roughness is a critical means of affecting the specular gloss of a coating.