抄録
A method of gloss measurement was studied experimentally, which can obtain physical quantities closely related to psychological gloss levels, unaffected by the detrimental effect of orange peel.
In the experiments, a series of six standard samples were prepared which possesed appropriate gloss intervals scaled by the sensory evaluation using a modified paired comparison method and have various levels of orange peel. Physical gloss evaluation was made for the samples, using an apparatus that sensed a distinctness of a' reflected knife edge pattern image or a square wave pattern image. Correlations were investigated between the gloss intervals and the following physical quantities: the maximum tangent slope of a dark-to-bright transition curve for the knife edge pattern, and the contrast for the square wave pattern. The effects of spatial resolution Am and floating range Δb (distance between a sample and an image plane) were also investigated.
A good linearity was obtained between the gloss intervals and the physical quantities, for Am=0.5mm and Δb=50mm. The linearity was considered to be caused by the elimination of the orange peel effect on gloss, as shown in the following equation for the elimination, derived from consideration of geometrical optics: Am<λw/2 and Δb<<rw/2 where λw and rw are wavelength and radius of curvature of waviness, respectively. Since λw≥2.8mm and rw≥580mm, substitution of the experimental values of Am and Δb are shown to satisfy the above conditions. It was found that a better correlation with gloss intervals isobtained for maximum tangent slope than for contrast. The reason is considered below. The main factor for the psychological gloss is roughness and subfactors are refractive index and others. On the contrary, the contrast is a quantity related to only the roughness, while the slope is a quantity related to roughness and the refractive index.
