Quantification of Conspicuity Using Optical Properties and Evaluation of Impression of Pseudo-Fingerprints on Touch Panels

Abstract

In recent years, the spread of electronic devices, such as smartphones, has increased the demand for touch panels, and the development of touch panels with excellent conspicuity has been promoted. In particular, it is important to ensure the conspicuity of touch panels in car navigation systems involved in driving, and conspicuity evaluations are conducted during development. However, currently, conspicuity evaluation is often performed using sensory evaluation, and conspicuity has not been quantified. In this study, to quantify the conspicuity of touch panels used in automobiles, we evaluated the relationship between the optical characteristics and impression evaluation by conducting evaluations of the impression and luminance of pseudo-fingerprints on a touch panel using a simulated in-vehicle environment and pseudo-sunlight. The experiment was conducted with 10 adult males, who evaluated their impressions of the panels with pseudo-fingerprints. The SD method was used to evaluate the impressions, and the Visual Analog Scale (VAS) was used as the evaluation scale. Eleven adjective pairs related to the conspicuity of pseudo-fingerprints were selected from previous studies. Eight samples were prepared for the panels-to-be-evaluated, including four for each of the lipophilic and oleophobic panels. A spin coater and pseudo-fingerprint solution were used to transfer the pseudo-fingerprints to the panels at 50 N force from the thin film by spinning the spin coater. For the position of the source of pseudo-sunlight, three conditions were selected by considering the lighting conditions that could be assumed where sunlight shines on the vehicle. These included a sunlight source directly above the sample panel, behind the left side from the viewpoint of the observer, and in an arrangement where the relationship between the pseudo-sunlight, reflective objects, and sample panel was positive reflection. In the impression evaluation experiment, the subject was asked to sit on a chair, and the position of the chinrest was adjusted after explaining the experiment. The subject was presented with the panel for 30 s while on the chinrest. Then, the tablet was handed to the subject, who evaluated the panel with the pseudo-fingerprints as observed from the chinrest position. The results of the impression evaluation were analyzed using factor analysis. Based on this analysis, the first factor, including factors such as likes/dislikes, hygiene, and prominence, was named as the conspicuity factor. The second factor related to artistry was named as the artistry factor, and the factor related to the material of the panel was named as the materiality factor. This study focused on the conspicuity factor. From the relationship between the evaluation of luminance and impression, a positive correlation of r=0.46 was achieved between the conspicuity factor score and the rate of change of luminance, and a positive correlation of r=0.56 was observed between the artistic factor score and the rate of change of luminance. In the future, we will evaluate the relationship between the factor scores and luminance change across lighting conditions and quantify the conspicuity through follow-up experiments on sensory evaluation based on luminance change.