Touch Sensor Planarization Layout for Stable Display Capacitance
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Solution Overview
Problem
Existing display devices experience variations in parasitic capacitance and reduced touch sensitivity due to differing distances between electrodes and underlying conductive layers, leading to inconsistent performance across the panel.
Innovation Solution
The display device incorporates a structured design with a planarization layer and encapsulation layers that vary in thickness to stabilize capacitance and improve sensitivity, featuring a gradual increase in planarization layer thickness in non-display areas and a decreasing organic encapsulation layer thickness, along with specific insulating and light-blocking layers to enhance touch sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the distance between the electrode of the touch sensor and the conductive layer is reduced in certain areas, then the parasitic capacitance increases, but the touch sensitivity deteriorates
Solution Approach 1:
The planarization layer is designed with spatially varying thickness: thicker in non-display areas to increase distance and reduce parasitic capacitance, and thinner in display areas to maintain touch sensitivity. This local differentiation allows each region to be optimized for its specific function.
Solution Approach 2:
The thickness parameter of the planarization layer is changed across different regions of the substrate. By controlling the thickness distribution, the patent adjusts the distance between the touch sensor electrode and underlying conductive layers, thereby controlling parasitic capacitance while maintaining touch sensitivity in display areas.
2Ease of manufacture
If a uniform thickness planarization layer is used, then the manufacturing process is simplified, but the parasitic capacitance varies across different positions
Solution Approach 1:
Instead of uniform thickness, the planarization layer implements local quality variation with different thicknesses in different regions. The non-display areas have greater thickness to reduce parasitic capacitance, while display areas have smaller thickness to maintain touch sensitivity.
Solution Approach 2:
The planarization layer transitions from a static uniform structure to a dynamic gradient structure where thickness varies continuously or in steps across the substrate, allowing optimization of electrical characteristics in different regions.
3Reliability
If the planarization layer thickness is increased in non-display areas, then the parasitic capacitance is reduced, but the overall device thickness increases
Solution Approach 1:
The thickness increase is localized only to non-display areas where it is needed for parasitic capacitance reduction. Display areas maintain thinner construction to preserve overall device profile and touch sensitivity, so the thickness increase does not uniformly affect the entire device.
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.