Bending Protection Layer Design for Display Signal Line Stress
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Solution Overview
Problem
Display devices face issues with signal line deterioration due to increased resistance and heat generation in the non-display area, leading to potential crack defects when bent, as the reduction in bezel width concentrates electric current and increases voltage line resistance.
Innovation Solution
A display device design featuring multiple signal lines under a bending protection layer with specific thickness and surface configurations to distribute bending stress and prevent crack defects, including a first portion with an inclined surface, a second portion with an approximately flat surface, and a third portion with an inclined surface, ensuring the signal lines are protected from external impact and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the non-display area (bezel area) is reduced to widen the display area, then the display area increases, but the resistance of voltage lines increases and heat is generated due to concentrated electric current
Solution Approach 1:
The bending protection layer is divided into multiple portions (first portion with inclined surface, second portion with flat surface, third portion with inclined surface) with different thicknesses. The second portion has greater thickness than the first and third portions, creating a segmented structure that distributes bending stress differently across various regions of the bending area, thereby protecting signal lines while maintaining the reduced bezel design
Solution Approach 2:
Different portions of the bending protection layer are designed with different thicknesses to provide localized protection. The second portion, which overlaps with signal lines, has greater thickness to provide enhanced protection where it is most needed, while the first and third portions have smaller thicknesses. This local quality approach ensures reliable signal line protection without unnecessarily increasing the overall structure's complexity
2Area of stationary object
If the width of voltage lines is reduced in the non-display area, then the non-display area is minimized, but the resistance increases and heat is generated due to concentrated electric current
Solution Approach 1:
The bending protection layer acts as an intermediary structure between the signal lines and the external bending forces. By positioning the signal lines under the bending protection layer in the bending area, the protection layer mediates the mechanical stress, distributing it across its structure (particularly through the thicker second portion) and preventing direct concentration of stress on the signal lines, thereby reducing heat generation and protecting against crack defects
3Adaptability or versatility
If the display device is bent, then flexibility is achieved, but crack defects occur in the signal lines due to bending stress
Solution Approach 1:
The bending protection layer is designed with a specific thickness profile (greater thickness in the second portion that overlaps signal lines) to provide beforehand cushioning against bending stresses. This pre-engineered protective structure absorbs and distributes the mechanical stress before it can reach the signal lines, preventing crack defects while maintaining the device's bending flexibility
Solution Approach 2:
The bending protection layer functions as a flexible protective shell that can accommodate device bending while protecting the underlying signal lines. The layer's design with varying thicknesses (flat second portion with greater thickness, inclined first and third portions with smaller thicknesses) allows it to flex with the device while distributing stress away from the signal lines, preventing crack defects during bending operations
Data Source
AI summary
A display device including a first substrate including a first area, a second area and a bending area between the first area and the second area; a display element layer disposed on the first area of the first substrate; multiple signal lines disposed on the bending area of the first substrate, the signal lines being spaced apart from one another in a first direction and electrically connected to the display element layer; and a bending protection layer disposed on the bending area of the first substrate and covering the signal lines, wherein the bending protection layer includes a first portion and a second portion, the first portion has an inclined surface, the second portion having an approximately flat surface, the second portion overlapping the signal lines including outermost signal lines, the first portion not overlapping the signal lines.