Effects of crease features on crease visibility and goodness of smartphone foldable display

Recently, foldable smartphones have become popular due to their flexibility and portability. However, the line-shaped mark (crease) produced by folding and unfolding can negatively affect user experience. Since eliminating the mark is difficult with current technology, it is important to understand the relationship between crease features and human perception, and develop a grading system to establish crease design guidelines to improve user experience. In this study, 25 participants were recruited, and 17 prototypes with different crease features were compared in terms of crease visibility. The findings showed that deeper crease depth and larger folding radius increased crease visibility, with depth being the more influential factor. The grading system established that foldable display prototypes with a crease depth below 60 µm were considered "good" or better. Also, the study found that a single-line crease was less visible/noticeable than a multi-line crease. These findings may provide practical guidelines for designing creases for foldable displays.