Touch Sensor Planarization Layout for Uniform Display Sensitivity
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Solution Overview
Problem
Display devices with capacitive touch sensors experience reduced touch sensitivity due to increased parasitic capacitance, particularly in areas where the distance between electrodes and conductive layers is close, leading to variations in capacitance across the screen.
Innovation Solution
A display device design that includes a planarization layer with varying thicknesses in non-display areas, an encapsulation layer structure with inorganic and organic layers, and a sensing electrode configuration to maintain consistent distances between electrodes and common electrodes, reducing parasitic capacitance and enhancing touch sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the electrode of the touch sensor and the conductive layer is reduced in certain areas, then the touch sensor can be more compact, but parasitic capacitance increases and touch sensitivity deteriorates
Solution Approach 1:
The patent applies local quality by creating a non-uniform planarization layer thickness distribution. The planarization layer has different thicknesses in different regions: thicker in non-display areas to increase distance and reduce parasitic capacitance, and thinner in display areas to maintain compactness. This spatially varying structure optimizes both compactness and touch sensitivity in different locations.
Solution Approach 2:
The patent changes the geometric parameter of the planarization layer (thickness) to control the distance between the electrode and conductive layer. By adjusting the thickness parameter in different regions, the patent achieves optimal balance between compactness and touch sensitivity, directly addressing the technical contradiction.
2Reliability
If the planarization layer thickness is increased to reduce parasitic capacitance, then touch sensitivity improves, but the overall device thickness increases
Solution Approach 1:
The patent uses local quality by making the planarization layer thickness position-dependent. Only non-display areas have increased thickness for parasitic capacitance reduction, while display areas maintain thinner thickness. This localized approach improves touch sensitivity without uniformly increasing overall device thickness.
Solution Approach 2:
The patent segments the planarization layer into different thickness zones: a first thickness in display areas and a second (greater) thickness in non-display areas. This segmentation allows independent optimization of different regions, achieving touch sensitivity improvement while controlling overall device thickness.
3Ease of manufacture
If uniform thickness planarization layer is used, then manufacturing is simpler, but parasitic capacitance varies across positions leading to inconsistent touch sensitivity
Solution Approach 1:
The patent implements local quality by specifying different thickness values for different regions (display vs. non-display areas). This creates a non-uniform planarization layer that compensates for position-dependent parasitic capacitance variations, ensuring consistent touch sensitivity across the device while maintaining manufacturability through defined thickness zones.
Data Source
AI summary
A display device includes a display area and a non-display area; a light emitting element disposed on a display area of a substrate; a dam disposed on a non-display area of the substrate; an encapsulation layer disposed on the light emitting element and the dam; a planarization layer disposed on the encapsulation layer; and a sensing electrode disposed on the planarization layer, wherein a thickness of a portion of the planarization layer disposed in the non-display area gradually increases as the portion of the planarization layer is away from the display area.