Capacitive Touch Panel Using Liquid Crystal Module as Ground for Pen Writing
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Solution Overview
Problem
Conventional capacitive touch panels face challenges in providing effective pen writing capabilities due to the requirement for large conductive pen tips, increased cost, complex mechanical designs, and signal interference, which hinder sophisticated writing experiences, especially for characters like Chinese script.
Innovation Solution
A capacitive touch panel design featuring a flexible dielectric layer with individually controlled one-dimensional sensor cells, where press sensing control is achieved through capacitance changes between the sensor array and a liquid crystal module serving as the ground, allowing for non-conductive pens with smaller tips and improved resolution, and touch or gesture-based sensing without involving the base.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional capacitive touch panels use large conductive pen tips to achieve writing function, then writing capability is provided, but writing resolution deteriorates and sophisticated writing experience is hindered
Solution Approach 1:
The patent replaces the conventional capacitive sensing mechanism (which requires large conductive tips) with a press sensing mechanism that detects capacitance changes caused by mechanical pressure. This allows the use of smaller, non-conductive pen tips while maintaining writing capability and significantly improving writing resolution, as the sensing is based on pressure-induced capacitance variation rather than conductive tip contact area
2Ease of operation
If additional digitizer or active writing pen is added to conventional capacitive touch display, then pen writing function is provided, but device cost increases dramatically
Solution Approach 1:
The patent makes the liquid crystal module serve multiple functions: it acts as both the display component and the ground reference for press sensing. This eliminates the need for separate ground planes or additional sensing layers, allowing the same hardware infrastructure to support both display and pen writing functions, thereby significantly reducing device cost
Solution Approach 2:
The liquid crystal module serves itself by providing both display functionality and acting as the ground reference for press sensing. The existing liquid crystal module structure is utilized for dual purposes, eliminating the need for additional dedicated components for pen writing functionality
3Measurement precision
If conventional capacitive touch panel uses two-dimensional sensor array for multi-touch applications, then touch accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent divides the sensing function into two independent dimensions: one-dimensional sensor arrays for touch/gesture detection and press sensing for writing detection. This segmentation allows each subsystem to use optimized, cost-effective sensor arrangements while maintaining high accuracy for their respective functions, avoiding the need for expensive two-dimensional sensor arrays for all sensing purposes
4Reliability
If complex mechanical design is implemented to avoid signal interference in conventional capacitive touch display, then signal interference is reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical shielding and isolation designs with an electrical solution based on press sensing. By detecting capacitance changes caused by pressure rather than relying on conductive tip sensing, the system inherently avoids signal interference issues without requiring complex mechanical designs, thereby reducing device complexity while maintaining reliability
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 design reduces manufacturing costs, eliminates the need for additional ground planes, and enhances touch accuracy and pen writing resolution by using a liquid crystal module as the ground for press sensing control, enabling effective multi-touch and pen writing functions with non-conductive pens.
Implementation Method 1
press sensing control is conducted according to a capacitance change resulting from a distance change between the sensor array and the base
Implementation Method 2
Capacitive sensing is a technology based on capacitive coupling which takes human body capacitance as an input
Data Source
AI summary
A touch panel includes a base, which is a liquid crystal module serving as a ground; a flexible dielectric layer over the base; and a one-dimensional pattern layer with sensor cells positioned as the same layer over the flexible dielectric layer. The sensor cells form a sensor array, and each of the sensor cells is individually controlled and sensed via an independent sensing line, wherein press sensing control is conducted according to a capacitance change resulting from a distance change between the sensor array and the base in response to an external force, and touch or gesture-based sensing control is conducted according to a capacitance change in the sensor array without involving the base.