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

Songil Lee,Gyouhyung Kyung

doi:10.1109/access.2021.3095502

Abstract

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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -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.

Highlights

Mobile devices with a fixed-size non-flexible display cannot effectively accommodate diverse user needs and tasks, as evidenced by the possession and alternative use of multiple smart devices as well as the introduction of foldable display applications
The objective of this study was to examine the effects of rollable-screen height, task type, and hand length on the preferred screen width, preferred screen aspect ratio, user satisfaction, gripping comfort, device portability, design attractiveness, and gripping methods, to determine rollable screen size requirements
Post hoc testing showed that the Height × Task treatments were statistically split into four groups (A-D; Fig. 4)

Summary

Introduction

Mobile devices with a fixed-size non-flexible display cannot effectively accommodate diverse user needs and tasks, as evidenced by the possession and alternative use of multiple smart devices (e.g., small- and large-screen devices for texting and video viewing, respectively; [1], [2]) as well as the introduction of foldable display applications (e.g., foldable smartphones; [3]). The associate editor coordinating the review of this manuscript and approving it for publication was Kang Li. to non-flexible displays, flexible displays (e.g., foldable, rollable) enable a single device to accommodate two important, yet mutually conflicting user needs of a compact device size for portability and a large screen for visual effects [4]. To non-flexible displays, flexible displays (e.g., foldable, rollable) enable a single device to accommodate two important, yet mutually conflicting user needs of a compact device size for portability and a large screen for visual effects [4] In this regard, rollable displays are apparently more effective to varying user needs than foldable displays. Wide screens reduce wrist extension during mobile device gripping, and large on-screen buttons can reduce

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Discussion

Conclusion