Touch Sensor Common Electrode Noise Correction

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Solution Overview

Problem

Capacitance-type touch sensors in liquid crystal display devices face challenges with increased thickness due to the need for a protective layer, limited design flexibility, and noise interference from image signal writing operations, which affects detection accuracy and power consumption.

Innovation Solution

A new configuration that includes a common electrode and a touch detection electrode forming a capacitor, using the display drive voltage as a touch-sensor drive signal, and correcting detection signals based on the gray scale of the image signal to reduce noise influence without a shielding layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a protective layer is added to the touch sensor for scratch protection, then the durability and protection of the touch sensor is improved, but the thickness of the liquid crystal module increases

Engineering Contradiction:

Improveprotection from scratchesVSAvoidthickness of liquid crystal module

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent combines the protective layer function with the touch sensor structure by integrating the conductive film for touch sensor use directly onto the polarizing plate substrate. This merging eliminates the need for separate protective layers while maintaining scratch resistance, thereby preventing thickness increase.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The polarizing plate serves multiple functions: it provides polarization for display, serves as a substrate for the touch sensor conductive film, and acts as a protective surface. This multi-functionality reduces the need for additional separate components that would increase thickness.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If the conductive film for touch sensor use is positioned deep inside the liquid crystal display element, then the design flexibility is improved, but the touch detection accuracy deteriorates due to increased distance from user's finger

Engineering Contradiction:

Improvedesign flexibilityVSAvoidtouch detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent positions the touch sensor conductive film on the outer surface dimension (on the polarizing plate) rather than deep inside the structure. This dimensional placement optimizes the distance to the user's finger for accurate capacitive coupling while maintaining design flexibility through the integrated structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If separate circuit portions are provided for touch sensor drive and coordinate detection, then the touch sensor functionality is improved, but the circuit integration difficulty increases

Engineering Contradiction:

Improvetouch sensor functionalityVSAvoidcircuit integration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the touch sensor drive circuit and coordinate detection circuit into a single integrated circuit unit. This integration maintains full touch sensor functionality while simplifying the overall device structure and reducing integration complexity compared to separate circuit portions.

Inventive Principle:

Principle #5Merging (Combining)

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 configuration enhances object detection accuracy and design flexibility while reducing the thickness of the liquid crystal display module and minimizing noise interference, making it suitable for mobile units.

Implementation Method 1

a capacitance-type touch sensor, which is formed with a common electrode (43) and a sensor-use detection electrode (44)

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a liquid crystal layer (6) inserted between the pixel substrate (2) and the opposing substrate (4)

Methodology Applied

Scientific EffectLiquid crystal effect: Liquid Crystals

Data Source

PatentUS8976123B2Display device and electronic unit

Publication Date: 2015.03.10 MAGNOLIA WHITE CORP

AI summary

The display device with high detection accuracy includes: display pixel electrodes; a common electrode; a display function layer; a display control circuit performing image display control by applying a pixel voltage to each of the display pixel electrodes and applying a common drive voltage to the common electrode, the common drive voltage inverting in synchronization with a drive cycle of the image display control; a touch detection electrode cooperating with the common electrode to form a capacitor; and a touch detection circuit detecting an external proximity object, based on a detection signal obtained from the touch detection electrode in response to the common drive voltage applied to the common electrode. The touch detection circuit corrects the detection signal based on a gray scale of the image signal at the time of acquisition of the detection signal, and performs the detection operation.