In-Cell Touch Sensor for TN LCDs Using Inverted Common Electrode

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Solution Overview

Problem

The existing in-cell touch technology faces limitations when applied to twisted nematic (TN) mode LCDs, as the common electrode on the upper substrate blocks touch signals and complicates the configuration of touch electrodes, making it difficult to implement a functional touch function while maintaining the TN structure.

Innovation Solution

The implementation of a self-capacitance type in-cell touch sensor is achieved by forming a common electrode on the entire surface of the lower substrate, with gate and data lines on the upper substrate intersecting to define pixel areas, allowing for a sensing signal output by detecting changes in self-capacitance between a touch object and these lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a common electrode is provided on the upper substrate of a TN panel, then the TN mode LCD structure is maintained, but touch signals are blocked by the common electrode making it difficult to implement touch function

Engineering Contradiction:

Improvetouch function implementationVSAvoidtouch electrode configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional placement of the common electrode from the upper substrate to the lower substrate. This inversion allows the touch sensor to be formed on the upper substrate without being blocked by a common electrode, enabling touch functionality while maintaining the TN mode LCD structure.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The lower substrate's common electrode is designed to serve dual functions: as the common electrode for the TN mode LCD and as part of the touch sensor structure. This multi-functionality reduces the need for separate components and simplifies the overall device configuration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If in-cell touch scheme is applied to TN mode LCD, then touch functionality is added, but the existing TN structure becomes complicated and difficult to maintain

Engineering Contradiction:

Improvetouch functionalityVSAvoidTN structure maintenance

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent segments the touch sensor functionality from the main LCD structure by placing the touch sensor on the upper substrate while maintaining the TN mode structure on the lower substrate. This segmentation allows independent optimization and manufacturing of each component while maintaining overall compatibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

By inverting the common electrode placement to the lower substrate, the patent eliminates the conflict between touch sensor formation and TN structure maintenance, allowing both functions to coexist without complicating the manufacturing process.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If conventional in-cell touch technology is used, then touch sensing is achieved, but the common electrode blocks touch signals and requires additional masks

Engineering Contradiction:

Improvetouch sensing capabilityVSAvoidnumber of masks

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent inverts the common electrode placement from upper substrate to lower substrate, which eliminates the blocking effect on touch signals and reduces the number of masks required during manufacturing.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts the common electrode function from the upper substrate and relocates it to the lower substrate, freeing the upper substrate for touch sensor formation without requiring additional masking steps.

Inventive Principle:

Principle #2Taking out (Extraction)

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 approach enables the successful implementation of a self-capacitance type in-cell touch sensor in TN mode LCDs, enhancing the touch functionality without altering the existing TN structure and reducing the number of masks required, thereby increasing the value of the LCD device.

Implementation Method 1

a sensing signal is output by detecting a change in self-capacitance between a touch object contacting the upper substrate and the gate line and the data line

Methodology Applied

Scientific EffectSelf-capacitance: Capacitance

Data Source

PatentUS9715137B2Liquid crystal display device using in-cell touch mode and method for manufacturing the same

Publication Date: 2017.07.25 LG DISPLAY CO LTD

AI summary

A liquid crystal display (LCD) device includes a lower substrate and an upper substrate disposed to face each other and having a liquid crystal layer interposed therebetween, black matrices provided on the lower substrate, a color filter provided between the black matrices, and a common electrode provided on the entire surface of the lower substrate, a gate line and a data line provided on the upper substrate and intersect with each other to define a pixel area, a thin film transistor (TFT) present in the pixel area of the upper substrate, and a pixel electrode electrically in contact with the TFT, wherein a sensing signal is output by detecting a change in self-capacitance between a touch object contacting the upper substrate and the gate line and the data line.