Rollable Display Glass Thinning and Compressive Stress
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Solution Overview
Problem
Electronic devices with displays face challenges in portability, as the limited real estate often restricts the size of displays, and the bending mechanism during rolling can cause scratches and cracking of the glass layer due to uneven stress distribution.
Innovation Solution
A rollable display design where the outwardly facing surface experiences compressive stress and the inwardly facing surface experiences tensile stress during rolling, with a locally thinned glass layer in the rollable portion to facilitate bending and prevent cracking, while maintaining structural integrity and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the display is made larger to improve viewing experience, then the display area increases, but the device becomes less portable and harder to store
Solution Approach 1:
The display transitions from a static fixed size to a dynamic variable size through rolling and unrolling mechanisms, allowing the display area to change based on user needs while maintaining compact portability when rolled
Solution Approach 2:
The display is rolled into a compact form that can be stored within or alongside the device body, similar to nesting concepts where a larger structure is condensed into a smaller contained space for portability
2Adaptability or versatility
If the glass layer is made thinner to facilitate bending during rolling, then the flexibility improves, but the structural strength and resistance to cracking decrease
Solution Approach 1:
The glass layer is selectively thinned only in the rollable portion while maintaining full thickness in non-rollable areas, providing localized flexibility where needed while preserving overall structural strength and protection
Solution Approach 2:
The thickness parameter of the glass layer is varied spatially across different regions of the display, creating a gradient structure that optimizes both flexibility for rolling and structural strength for protection
3Ease of operation
If the outwardly facing surface is exposed to external objects during use, then the display remains functional, but scratches and surface irregularities increase leading to cracking during bending
Solution Approach 1:
Compressive stress is pre-applied to the outwardly facing glass surface during manufacturing or initial setup, creating a residual stress state that counteracts tensile stresses during rolling and prevents crack propagation from surface scratches
Solution Approach 2:
The compressive stress acts as a pre-established protective mechanism that cushions against the harmful effects of scratches and surface irregularities before they can lead to cracking during bending operations
Data Source
AI summary
An electronic device may have a rollable display. The display may be moved between an unrolled state in which the display is planar and a rolled state in which a rollable portion of the display is rolled up for storage. The display may have a display panel with a pixel array that produces images and a transparent protective layer that overlaps the pixel array. The transparent protective layer may contain a layer of glass. The glass layer may be locally thinned in the rollable portion to facilitate rolling of the display. The display may be configured to apply compressive stress to the outwardly facing surface of the glass layer when the display is rolled up. Compressive stress in the outwardly facing glass surface may help prevent damage to the display when the display is bent during rolling operations.