How Wide Is Enough? Effects of Screen Height, Task Type, and Hand Length on Rollable Display Requirements

Although rollable displays must be unrolled for on-screen interaction, it is unknown whether screen height, task type, and hand length affect rollable display requirements. This study examined the effects of screen height, task type, and hand length on the rollable display requirements. A total of 30 young individuals (22.9 ± 2.3 years; 10 in each hand-length group) performed three tasks (web searching, video viewing, and e-mail composition) using three prototypes with different screen heights (H) of 50, 120, and 190 mm. Dependent variables were preferred screen width, preferred screen width-to-height aspect ratio, user satisfaction, gripping comfort, device portability, design attractiveness, and gripping method. As screen height increased, the preferred screen width increased, but the preferred screen aspect ratio decreased. The 95
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-percentile screen width (aspect ratio) of 100 mm (2:1) was required for 50H versus 204 mm (1.7:1) for 120H and 304 mm (1.6:1) for 190H. The highest 95
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-percentile screen aspect ratio of 1.9:1 was required for video viewing. The long-hand-length group preferred significantly wider screens for 190H only. Bilateral grasping was predominantly used for 50H and 120H, whereas non-grasping was for 190H due to limited thumb reach and insufficient screen reaction force. Considering user satisfaction, device portability, and design attractiveness, 120H was recommended, and a screen aspect ratio of 2:1 appeared sufficient for the performance of three mobile tasks on a 120H rollable screen.