In-Cell Touch LCD Surface Charge Detection
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Solution Overview
Problem
In-cell touch panel type liquid crystal displays face challenges in accurately determining whether the panel is touched, leading to reduced sensing accuracy, especially in varying illuminance environments, as they rely on relative differences in light currents which can be ambiguous between actual touches and proximity in strong illuminance conditions.
Innovation Solution
The implementation of a liquid crystal display with a transparent conductive layer connected to a ground voltage source, a polarizing plate, and a signal transmitting unit that generates driving voltages based on changes in surface charge when touched, forming an equivalent capacitor between the user's finger and the conductive layer to differentiate touch and non-touch operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an in-cell touch panel type liquid crystal display uses relative difference in light currents to detect touch position, then the device can perform touch sensing without additional panels, but sensing accuracy deteriorates in strong illuminance environments due to ambiguity between actual touches and proximity
Solution Approach 1:
The patent introduces a transparent conductive layer as an intermediary element between the user's finger and the liquid crystal display panel. This layer forms an equivalent capacitor with the polarizing plate, enabling the system to detect touch positions through changes in surface charge rather than relying solely on light current relative differences, thereby improving sensing accuracy without increasing structural complexity
Solution Approach 2:
The patent changes the detection parameter from light current relative difference to surface charge change. By monitoring the surface charge of the transparent conductive layer, which changes when a user touches the panel, the system achieves more accurate touch detection that is not affected by ambient illuminance conditions
2Measurement precision
If the transparent conductive layer is connected to ground voltage source, then sensing accuracy is enhanced through surface charge detection, but device complexity increases due to additional voltage supply circuit
Solution Approach 1:
The transparent conductive layer serves multiple functions: it acts as a touch sensor electrode, forms an equivalent capacitor with the polarizing plate for surface charge detection, and is connected to ground voltage source for reference. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving enhanced sensing accuracy
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 solution significantly enhances sensing accuracy by reliably detecting touch positions through changes in surface charge, reducing maloperations and improving the overall performance of the liquid crystal display across different lighting conditions.
Implementation Method 1
forming an equivalent capacitor between the user's finger and the conductive layer
Implementation Method 2
detecting touch positions through changes in surface charge
Data Source
AI summary
A liquid crystal display is disclosed. The liquid crystal display includes a liquid crystal display panel including a pixel array and touch sensors, a transparent conductive layer on one substrate of the liquid crystal display panel transmitting display light, a polarizing plate on the transparent conductive layer, a driving voltage supply circuit, and a signal transmitting unit electrically connecting the transparent conductive layer to the driving voltage supply circuit. A portion of the transparent conductive layer is connected to a ground level voltage source. The driving voltage supply circuit generates a driving voltage required to perform light sensing operations of the touch sensors during a touch period based on changes in an amount of surface charge of the transparent conductive layer depending on whether or not the polarizing plate is touched.