In-Cell Touch Sensor Contact Hole Structure for Aperture Ratio
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Solution Overview
Problem
In ultra-high density in-cell type touch panel displays, the parasitic capacitance between the touch electrode and the routing line interferes with accurate touch sensing, and the storage capacitance between the pixel and common electrodes is insufficient, complicating the line structure and reducing the aperture ratio.
Innovation Solution
The display design includes a touch sensor with a touch contact hole and passivation contact hole structure that minimizes the contact area between the touch electrode and the routing line, ensuring high insulating properties and sufficient storage capacitance, while maintaining a high aperture ratio through an asymmetric and vertically overlapping contact hole configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the touch electrode and routing line are placed close together in ultra-high density display, then the aperture ratio is improved, but the parasitic capacitance between touch electrode and routing line increases interfering with touch sensing accuracy
Solution Approach 1:
A passivation layer is introduced as an intermediary between the routing line and touch electrode. This passivation layer acts as a mediator that provides electrical insulation while allowing the structures to be positioned close together, thereby reducing parasitic capacitance without compromising aperture ratio
Solution Approach 2:
The contact area between routing line and touch electrode is segmented into multiple small contact holes rather than a large continuous contact area. This segmentation reduces the total overlapping area and thus minimizes parasitic capacitance while maintaining electrical connectivity
2Measurement precision
If the insulating layer between common electrode and pixel electrode is thickened to reduce parasitic capacitance, then the parasitic capacitance is reduced, but the storage capacitance becomes insufficient
Solution Approach 1:
The insulating structure is segmented into multiple layers with different functions: a thicker passivation layer for parasitic capacitance reduction and a thinner insulation layer for storage capacitance maintenance. This layered segmentation allows optimization of both parameters simultaneously
Solution Approach 2:
Different insulating layers are applied with different thicknesses at different locations: the passivation layer between routing line and touch electrode is thick for parasitic capacitance reduction, while the insulation layer between common electrode and pixel electrode is thin for storage capacitance preservation
3Area of stationary object
If asymmetric and vertically overlapping contact hole configuration is used, then the aperture ratio is maintained high, but the manufacturing precision requirements increase
Solution Approach 1:
The asymmetric contact hole configuration is designed and predetermined in the manufacturing process. By establishing the asymmetric pattern early in the fabrication sequence, the alignment requirements are built into the process flow, making the precision requirements manageable through standardized manufacturing steps
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
This design enhances the accuracy of touch sensing performance by reducing parasitic capacitance and maintaining a high aperture ratio, even in ultra-high density displays, while simplifying manufacturing processes and reducing costs.
Implementation Method 1
a first passivation layer covering the routing line
Implementation Method 2
the parasitic capacitance between the touch electrode and the routing line is reduced
Implementation Method 3
a touch terminal disposed on the second passivation layer and connecting the touch electrode exposed through the passivation contact hole to the routing line exposed through the touch contact hole
Data Source
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AI summary
A display having a touch sensor comprises: a plurality of pixel areas disposed in a matrix manner on a substrate; a routing line (TW) running along a first direction on the substrate; a first passivation layer (PAS1) covering the routing line (TW); a touch electrode (Tx) covering the routing line (TW) and corresponding to grouped pixel areas on the first passivation layer (PAS1); a touch contact hole (TH) exposing some portions of the routing line (TW) by penetrating the touch electrode (Tx) and the first passivation layer (PAS1); a second passivation layer (PAS2) covering the touch electrode (Tx); a passivation contact hole (PAH) exposing the touch contact hole (TH) and some portions of the touch electrode (Tx) around the touch contact hole (TH) by penetrating the second passivation layer (PAS2); and a touch terminal (TT) connecting the touch electrode (Tx) and the routing line (TW) on the second passivation layer (PAS2).