Capacitive Touch Panel with Diagonal Voltage Detection
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Solution Overview
Problem
Existing liquid crystal display devices with electrostatic capacitance coupling type touch panels face issues of reduced transmittance due to thick transparent conductive films and complex circuitry required for position detection, which increases costs and noise susceptibility.
Innovation Solution
A display device with a touch panel featuring a planar transparent conductive film and a position detection pulsating voltage production circuit that applies voltages to diagonal corners at different timings, using an integration circuit and analog-to-digital conversion to calculate touched positions without decreasing transmittance and simplifying circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the transparent conductive film is made thick to preserve current and decrease resistance, then the current detection accuracy is improved, but the light transmittance of the touch panel deteriorates
Solution Approach 1:
The patent changes the detection parameter from direct current measurement through thick film to voltage measurement through thin film. By applying pulsating voltage and measuring the voltage output through diagonally opposite corners, the system achieves accurate position detection while maintaining thin transparent conductive film for high light transmittance.
2Measurement precision
If four sets of current detection circuits are disposed at each corner to detect current accurately, then the position detection precision is improved, but the circuit complexity increases
Solution Approach 1:
The patent merges the detection function into a single integrated circuit that processes signals from all four corners. Instead of four separate detection circuits, one circuit receives voltage outputs from all corners and computes the touched position, significantly reducing circuit complexity while maintaining detection precision.
Solution Approach 2:
The integrated circuit performs multiple functions: it receives voltage signals from all four corners, determines which corner was touched based on voltage thresholds, and computes the position coordinates. This multi-functional approach eliminates the need for separate detection circuits at each corner.
3Reliability
If four sets of current detection circuits with noise filters and sample and hold are implemented, then the detection reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent combines noise filtering, signal sampling, and position computation functions into a single integrated circuit. The circuit processes signals from all four corners through unified noise filtering and sampling mechanisms, reducing the total number of components while maintaining detection 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
The solution reduces costs and maintains high transmittance while minimizing noise susceptibility, enabling accurate position detection and reducing the thickness of the transparent conductive film for improved transmittance.
Implementation Method 1
a current flowing into a finger with which the touch panel is touched is detected
Implementation Method 2
electrostatic capacitance coupling type touch panel includes a touch panel substrate having a conductive coating (transparent conductive film) formed on the surface of a glass substrate
Data Source
AI summary
Provided is a display device with a touch panel having the cost thereof reduced without a decrease in the transmittance ratio of light. A substrate has a planar transparent conductive film formed on an observer side thereof. The transparent conductive film is used as a transparent electrode of an electrostatic capacitance coupling type touch panel. A position detection pulsating voltage production circuit that inputs a pulsating voltage for position detection, and a coordinate position arithmetic circuit that computes a touched position on the transparent conductive film touched with an observer's finger are included. The transparent conductive film is shaped to have four corners. The position detection pulsating voltage generation circuit applies the position detection pulsating voltage to each of the four corners of the transparent conductive film at different timings. When the position detection pulsating voltage is applied to one of the four corners of the transparent conductive film, the coordinate position arithmetic circuit computes the touched position on the transparent conductive film, which is touched with the observer's finger, on the basis of a voltage outputted through the corner diagonally opposite to the corner to which the pulsating voltage is applied.