Integrated Touch Sensor Circuit on LCD Substrate
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Solution Overview
Problem
Conventional liquid crystal display devices with capacitive coupling touch sensors suffer from thickness issues due to the combination of separate substrates, leading to inferior display performance and complex manufacturing processes, especially in in-plane switching driving mode devices, where the electrical field affects liquid crystal alignment and touch sensor functionality.
Innovation Solution
A liquid crystal display device with a built-in capacitive coupling touch sensor function, where the touch sensor circuit is integrated on one substrate, using thin film transistors, transparent pixel electrodes, and a common electrode with an insulating film, allowing horizontal liquid crystal alignment and sensitive touch detection without disturbing the electrical field, and featuring a color filter on the substrate with thin film transistors for color display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitive coupling touch sensor device and a liquid crystal display device are pasted together, then touch sensor function is achieved, but the overall thickness increases
Solution Approach 1:
The patent merges the touch sensor circuit with the liquid crystal display substrate by forming the touch sensor circuit on the same substrate as the liquid crystal display device. This integration eliminates the need for a separate touch sensor substrate, thereby reducing the overall thickness while maintaining touch sensor functionality.
2Power
If conductors having constant potential are formed on both facing surfaces of substrates for pixel electrodes and common electrode, then electrical field is generated for liquid crystal driving, but liquid crystal alignment is disturbed causing display spots
Solution Approach 1:
The patent applies different electrical properties to different regions of the substrate. The pixel electrode and common electrode regions maintain conductive properties for liquid crystal driving, while the touch sensor electrode region uses a high-resistance conductor that does not generate interfering electrical fields, thus preventing display spots while maintaining display functionality.
Solution Approach 2:
The patent changes the electrical resistance parameter of the conductor used for touch sensor electrodes. By using a conductor with high resistance value, the touch sensor electrodes do not generate significant electrical fields that would disturb liquid crystal alignment, thereby preventing display spots while maintaining touch sensor functionality.
3Length of stationary object
If the circuit for touch sensor functions is formed on the substrate on the liquid crystal display device side, then the thickness is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent designs the substrate to serve multiple functions: it acts as both the liquid crystal display substrate and the touch sensor substrate. By integrating both functions into a single substrate, the manufacturing process is simplified compared to assembling separate substrates, as the same substrate fabrication processes can be used for both display and touch sensor circuits.
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 enables a thinner, more sensitive, and mass-producible liquid crystal display device with improved touch sensor functionality and display performance by isolating the touch sensor circuit from the electrical field, simplifying the manufacturing process while maintaining the basic performance of both touch sensor and liquid crystal display functions.
Implementation Method 1
detect the change in capacitance between the tip of the finger and a location detecting electrode
Implementation Method 2
an electrical field is generally not generated between the pixel electrodes and the common electrode, and thus, the movement of the liquid crystal molecules aligned due to the electrical field is affected
Data Source
AI summary
In a liquid crystal display device having a built-in capacitive coupling touch sensor, a pair of facing transparent substrates sandwich a liquid crystal layer 113 and a liquid crystal display circuit for driving liquid crystal using a lateral electrical field having a color filter layer 107 is formed on one of the transparent substrates 101 in order to make the touch sensor highly sensitive to change in the capacitance, and a capacitive coupling touch sensor circuit layer 117 is formed on the other substrate 116, on the side opposite to the liquid crystal.