Flexible Display Wiring Adhesion via Localized Surface Roughness
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Solution Overview
Problem
Flexible display devices face adhesion issues between the resin substrate and metal wiring, particularly at bent portions, leading to peeling due to stress problems, which affects the reliability and durability of the device.
Innovation Solution
A display device design featuring a substrate with an insulating layer and exposed surface roughness greater than the surrounding areas, where the wiring is in contact with the insulating layer and substrate, enhancing the anchoring effect and improving adhesion between the substrate and wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible resin substrate is used to provide flexibility and curved shape capability, then the display device can be deformed and bent, but adhesion between the resin substrate and metal wiring deteriorates at bent portions causing peeling
Solution Approach 1:
The patent applies local quality by creating an uneven surface structure specifically at the wiring formation region of the substrate, while keeping other regions relatively smooth. This localized surface modification enhances adhesion only where needed (at the wiring-substrate interface) without affecting the overall flexibility of the display device. The unevenness is formed by controlling the resin composition and curing process in specific areas to create anchor points for the metal wiring.
Solution Approach 2:
The patent implements preliminary action by pre-forming an uneven surface structure on the substrate before depositing the metal wiring. This preliminary surface preparation creates a roughened topology that provides mechanical interlocking sites for the subsequent wiring layer, ensuring strong adhesion from the outset. The unevenness is created during the substrate formation process itself, before the wiring is added, allowing the wiring to conform to and bond with the pre-prepared surface.
2Ease of manufacture
If a smooth substrate surface is used for easy manufacturing, then the manufacturing process is simplified, but adhesion between the substrate and metal wiring is insufficient leading to peeling at bent portions
Solution Approach 1:
The patent applies local quality by creating an uneven surface structure specifically at the wiring formation region of the substrate, while keeping other regions relatively smooth. This localized surface modification enhances adhesion only where needed (at the wiring-substrate interface) without affecting the overall flexibility of the display device. The unevenness is formed by controlling the resin composition and curing process in specific areas to create anchor points for the metal wiring.
Solution Approach 2:
The patent implements parameter changes by modifying the surface roughness parameter of the substrate in the wiring region. By controlling the resin composition (using a resin with specific functional groups), curing temperature, and curing time, the surface creates controlled unevenness with specific roughness parameters. This parameter modification enhances the surface area and mechanical interlocking capability without fundamentally changing the manufacturing process flow.
3Reliability
If stress-relief structures are added to improve adhesion at bent portions, then wiring peeling is reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by creating an uneven surface structure specifically at the wiring formation region of the substrate, while keeping other regions relatively smooth. This localized surface modification enhances adhesion only where needed (at the wiring-substrate interface) without affecting the overall flexibility of the display device. The unevenness is formed by controlling the resin composition and curing process in specific areas to create anchor points for the metal wiring.
Solution Approach 2:
The patent implements a simplified stress-relief approach by using the substrate's own uneven surface structure to provide adhesion enhancement, rather than adding separate complex stress-relief layers or structures. The surface unevenness itself acts as the adhesion-promoting feature, eliminating the need for additional intermediary layers or complex multi-layer structures that would increase device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The enhanced adhesion reduces the likelihood of wiring peeling or disconnection when the device is bent, maintaining high reliability and durability even when deformed.
Implementation Method 1
The substrate is a sheet-like member including fibers which are impregnated with a resin
Implementation Method 2
A surface roughness of the exposed surface of the substrate is larger than a surface roughness of a region in which the substrate is in contact with the insulating layer
Data Source
AI summary
A display device includes a substrate; an insulating layer in contact with a first surface of the substrate; a display region with a plurality of pixels each including a transistor and a display element on the insulating layer; a terminal region in a region outside the display region over the insulating layer; a wiring between the display region and the terminal region; and a resin film on the substrate. The insulating layer includes an opening in a region between the display region and the terminal region. The resin film is in contact with the first surface in the opening. The wiring is in contact with an upper surface of the resin film through the opening. A surface roughness of the resin film in the opening is larger than a surface roughness of the substrate at a region where the substrate is in contact with the insulating layer.