In-Cell Touch LCD Noise Reduction via Orthogonal Wiring
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Solution Overview
Problem
Existing liquid crystal display devices with in-cell touch sensing structures face noise issues due to source wiring and lack sensitivity and rapid response time, particularly in resuming a black display state after touch sensing operations.
Innovation Solution
A liquid crystal display device with a specific wiring structure including first and second touch sensing wirings orthogonally intersecting, a common electrode, and a controller that applies synchronized image signals and touch sensing signals to drive the liquid crystal layer, using a reset voltage to rapidly return to a black display state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If in-cell touch sensing structure is used, then touch sensing function is integrated into display device, but noise is induced from source wiring
Solution Approach 1:
The touch sensing wirings are segmented into first and second orthogonal sets, with specific portions positioned to minimize overlap with source wiring. This spatial segmentation reduces electromagnetic coupling and noise interference while maintaining touch sensing functionality across the display surface.
Solution Approach 2:
Insulation layers are introduced as intermediary structures between the touch sensing wirings and source wiring. These insulation layers act as electromagnetic shields, reducing noise coupling from source wiring to touch sensing signals while allowing the integrated in-cell structure to function.
2Measurement precision
If conventional touch sensing operation is performed, then touch detection is achieved, but response time is slow and sensitivity is insufficient
Solution Approach 1:
A reset voltage is applied to the liquid crystal layer before touch sensing operations to preliminarily establish a black display state with uniform liquid crystal alignment. This preliminary action reduces the time required for liquid crystal response during touch sensing, improving both sensitivity and response time by starting from a known stable state.
Solution Approach 2:
The display device alternates between image display periods and touch sensing periods in a periodic manner. During touch sensing periods, the reset voltage is reapplied to maintain optimal liquid crystal alignment, enabling rapid and sensitive touch detection while allowing normal image display during other periods.
3Duration of action of stationary object
If image display is performed continuously, then display function is maintained, but liquid crystal sticking occurs
Solution Approach 1:
Polarity inversion driving is implemented where the voltage polarity applied to liquid crystal pixels is periodically inverted between positive and negative. This periodic polarity inversion prevents charge accumulation and liquid crystal molecule sticking to electrodes, enabling continuous display operation without degradation or sticking issues.
Solution Approach 2:
Instead of maintaining constant voltage polarity for continuous display, the system inverts the voltage polarity periodically. This inversion approach counteracts the sticking effect by repeatedly reversing the electric field direction, preventing liquid crystal molecules from adhering to electrode surfaces during prolonged operation.
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
The solution effectively reduces noise and improves sensitivity and response time by allowing the liquid crystal display device to rapidly resume a black display state and perform stable touch sensing operations.
Implementation Method 1
an electric field is applied to the liquid crystal molecules in a vertical direction along a thickness direction of the liquid crystal layer, thereby driving the liquid crystals
Implementation Method 2
Liquid crystal display devices having wide viewing angle. The liquid crystal displays device using the FFS mode have great advantages in that the liquid crystal display can be driven faster
Implementation Method 3
a change in electrostatic capacitance produced when a pointer such as a finger or a pen contacts or approaches a display screen is detected by, for example, touch sensing wirings (touch electrodes)
Data Source
AI summary
A liquid crystal display device includes a display device substrate including a first touch sensing wiring, an array substrate including a second touch sensing wiring orthogonally intersecting the first touch sensing wiring, a liquid crystal layer disposed between the display device substrate and the array substrate, a controller that supplies a positive first image signal to the first source wiring, supplies a negative second image to the second source wiring, applies a liquid crystal display voltage between the pixel electrode and the common electrode being synchronized to supply of the first image signal and the second image signal, thereby driving the liquid crystal layer, performing an image display, and applying a voltage to the second touch sensing wiring after performing the image display.