Abstract
When evaluating the efficacy of cosmetic products, it is important to analyze the state of cosmetic products on the skin. Especially in case of make-up products, the state of them on the skin has a profound influence on the efficacy of make-up. Therefore, the detailed analysis of the make-up layer is important for the development of highly functional products. In general, the make-up layer on the skin has been analyzed visually, or using a digital microscope. However by those methods, only macroscopic or two-dimensional information can be obtained. It is impossible to evaluate the microscopic state of powder particles or the three-dimensional conformation of the make-up layer, though they are very important for product development. In this study, we established a novel method to analyze the state of the make-up layer on the skin by sampling the make-up layers from the skin and observing them using scanning electron microscopy (SEM). First, we investigated the method for sampling the make-up layer on the skin and selected the appropriate resin. Next, the sampled make-up layers were observed using SEM and the conditions for the observation were configured. Finally this method was applied to the evaluation of the function of make-up products. The difference of the state of the make-up layer attributed to the make-up technique, the collapse of the make-up layer during make-up deterioration, and the relationship between the dispersibility of the powder particles and the SPF value of the products were evaluated. As a result, the difference of the make-up layer recognized visually can be evaluated microscopically and objectively. The changing state of the make-up layer during deterioration can also be analyzed microscopically and the mechanism of the deterioration was clarified. As regards the relationship between the dispersibility and the SPF value, it was revealed that the distribution of the powder particles was directly linked to the function of the products. The established method enables us to analyze the state of the powder particles in the make-up layer on the skin and contributes to the evaluation of the efficacy of make-up products.
