In-Cell Touch LCD ITO Segmentation for Charge Leakage
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Solution Overview
Problem
In-cell type touch panel LCD devices face challenges with touch sensing performance due to charge leakage through low-resistance ITO films and suffer from electromagnetic interference (EMI) noise when using high-resistance Y3 films for touch sensing.
Innovation Solution
Divide the bottom ITO film into blocks and apply a Load Free Driving (LFD) signal to the gate lines, data lines, and common electrodes during the touch sensing period, with the LFD signal sequentially applied to each block of the ITO film, while grounding the ITO film during the display period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low-resistance ITO film is used for touch sensing, then the touch panel can be manufactured with standard materials, but charges generated during touch leak externally through the ITO film, deteriorating touch sensing performance
Solution Approach 1:
The ITO film is divided into multiple blocks (first block, second block, third block, etc.) arranged in rows and columns. Each block is independently controlled with separate driving signals and grounding connections. This segmentation allows the patent to apply LFD signals to specific blocks during touch sensing while grounding other blocks, preventing charge leakage and improving touch sensing performance while maintaining manufacturability with standard ITO materials
Solution Approach 2:
The patent employs periodic switching between display mode and touch sensing mode. During touch sensing period, LFD signals are applied to specific ITO blocks in a periodic sequence while other blocks are grounded. This periodic action allows the low-resistance ITO film to function effectively for touch sensing without charge leakage, as the grounding periods prevent external charge discharge while signal periods enable touch detection
2Measurement precision
If a high-resistance Y3 film is used for touch sensing, then touch sensing performance is improved, but electromagnetic interference (EMI) noise is generated
Solution Approach 1:
The patent changes the resistance parameter of the touch sensing film by using low-resistance ITO material instead of high-resistance Y3 film. This parameter change eliminates EMI noise generation while maintaining touch sensing performance through the combination of ITO's low resistance properties with the segmented block structure and periodic LFD signal application that prevents charge leakage
3Reliability
If the ITO film is grounded during display period, then charge leakage is prevented, but the touch panel cannot sense touch during this period
Solution Approach 1:
The patent implements periodic switching between display period and touch sensing period. During display period, ITO blocks are grounded to prevent charge leakage and maintain image stability. During touch sensing period, specific ITO blocks are switched to receive LFD signals for touch detection. This periodic action ensures both charge stability during display and touch sensing availability during sensing periods, achieving reliable operation in both modes
Solution Approach 2:
The patent dynamically switches the electrical state of ITO blocks between grounded state and LFD signal state based on operational requirements. The driving circuit dynamically controls which blocks are grounded and which receive signals, allowing flexible transition between display and touch sensing functions. This dynamic control enables the system to optimize performance for the current operational mode
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
Enhances touch sensing performance and reduces EMI noise by minimizing the influence of initial capacitance and optimizing signal application to the touch electrodes, allowing for a thinner and more compact touch panel design.
Implementation Method 1
The ITO film 5 having a low resistance is formed on the substrate to sense touch through self-capacitance
Implementation Method 2
applying a Load Free Driving (LFD) signal to the gate lines, data lines, and common electrodes during the touch sensing period
Data Source
AI summary
A touch panel liquid crystal display device and a method of driving the same are discussed. The touch panel liquid crystal display device in one embodiment includes a thin film transistor array substrate including a plurality of gate lines, a plurality of data lines, and a plurality of common electrodes, a color filter array substrate including a black matrix layer and a color filter layer, and an indium tin oxide (ITO) film of a plurality of blocks on the color filter array substrate for touch sensing, wherein a scan signal, a data signal, and a common voltage are applied to the plurality of gate lines, the plurality of data lines, and the plurality of common electrodes, respectively, and the ITO film of the plurality of blocks is grounded, during a display period, and a load free driving (LFD) signal is applied to the plurality of gate lines, the plurality of data lines, and the plurality of common electrodes.