Touch Display Pad Electrode Structure for Smooth Lift-Off Separation
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Solution Overview
Problem
Existing touch display devices, particularly flexible or foldable OLED devices, face manufacturing defects due to complex encapsulation methods and issues with the pad region for transmitting and receiving touch-related data, which are exacerbated by bending stress and structural bonding challenges.
Innovation Solution
A touch display device design featuring a plurality of emitting elements, an adhesive layer, first and second touch electrodes insulated by an insulating layer, a pad electrode with multiple layers extending from these electrodes, and a protection layer with contact holes, along with a manufacturing method involving a sacrificial layer and laser lift-off process to minimize defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the touch sensor is disposed on the encapsulation layer in an on-cell type configuration, then the device achieves flexibility and foldability, but the pad region cannot be smoothly separated from the temporary manufacturing substrate causing defects
Solution Approach 1:
A release layer is introduced as an intermediary between the pad electrode and the temporary manufacturing substrate. This release layer enables smooth separation during the manufacturing process while maintaining the structural integrity of the pad region, thereby resolving the separation defect issue in on-cell type flexible touch displays
Solution Approach 2:
The release layer is formed on the temporary manufacturing substrate before the pad electrode is deposited. This preliminary action ensures that the separation interface is already prepared in advance, preventing defects during the subsequent separation process from the temporary substrate
2Ease of manufacture
If a bonding method is used to attach the touch sensor to the display panel, then the device can be manufactured, but defects occur due to the pad region not separating smoothly from the temporary manufacturing substrate
Solution Approach 1:
The release layer serves as a mediator between the pad electrode and the temporary manufacturing substrate, enabling the bonding method to proceed while preventing separation defects. This intermediary layer allows smooth delamination after bonding, thereby maintaining manufacturing ease while improving reliability
3Ease of operation
If the pad region is disposed on the outside where the touch sensor and display substrate are bonded, then data transmission is enabled, but defects are generated due to separation issues
Solution Approach 1:
The release layer is specifically positioned in the pad region to enable data transmission functionality while preventing separation-related defects. This intermediary structure allows the pad region to be disposed on the outside for data transmission without compromising manufacturing precision
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 solution effectively reduces defects in the pad region, enhancing the manufacturing yield and reliability of touch display devices by improving adhesion strength and heat dissipation during the laser lift-off process, thus supporting flexible and foldable display capabilities.
Implementation Method 1
a step of removing the temporary substrate and the sacrificial layer
Implementation Method 2
laser lift-off process to minimize defects
Data Source
AI summary
A display device may include a substrate having a multi-layered structure and including an active area and a touch pad area, a light emitting element over the substrate, an encapsulation layer covering the light emitting element, a passivation layer over the encapsulation layer, a first touch electrode on the passivation layer and in the active area, a first pad electrode on the passivation layer and in the touch pad area, an insulating layer disposed on the first touch electrode and including a first hole, a second touch electrode on the insulating layer and in the active area, a second pad electrode on the first pad electrode, a barrier layer on at least a portion of the second pad electrode and including a second hole, a third pad electrode on the second pad electrode, and a protection layer on the third pad electrode and the barrier layer and including an opening.