Touch Sensor Device Using Common Electrode for Display
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Solution Overview
Problem
Existing liquid crystal display devices with integrated touch sensors face challenges in thinness, design flexibility, and circuit integration, particularly in mobile device applications, where the need for a protective layer and conductive films limits their thickness and design options.
Innovation Solution
A display device with a touch sensor that utilizes a common electrode for both display and touch functionality, forming capacitance with a touch detection electrode, allowing for touch detection using the existing display drive voltage and enabling flexible design and integration of circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conductive film for the touch panel is provided between the substrate and polarizing plate, then touch detection function is achieved, but the thickness of the liquid crystal module increases
Solution Approach 1:
The patent merges the touch detection electrode with the common electrode used in the liquid crystal display driving structure. By making the common electrode serve dual purposes (both for liquid crystal control and touch detection), the need for a separate conductive film is eliminated, thus achieving touch detection without increasing module thickness
Solution Approach 2:
The common electrode is designed to perform multiple functions: it serves as both the common electrode for liquid crystal display operation and as the detection electrode for the capacitive touch panel. This multi-functionality reduces the number of additional components needed and maintains thin profile
2Measurement precision
If the conductive film for the touch panel is placed close to the user's finger, then touch detection sensitivity is improved, but the arrangement region is limited and design flexibility is reduced
Solution Approach 1:
The patent moves the detection function from requiring a surface-level conductive film to utilizing the common electrode that can be positioned at different depths within the liquid crystal module. This dimensional flexibility allows the touch detection to work effectively regardless of the exact position, as the electric field extends through the liquid crystal layer
3Adaptability or versatility
If a separate touch panel drive section and coordinate detection section are provided, then touch detection function is achieved, but circuit integration becomes difficult
Solution Approach 1:
The patent combines the touch detection circuit with the existing liquid crystal drive circuit. The same drive circuit that controls the liquid crystal display is used to drive the touch detection electrode, and the same signal lines are used for both display and touch detection functions, thereby achieving circuit integration
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
Enables touch detection in mobile devices with indefinite user electric potential, reduces the need for additional drive signals, and allows for high design flexibility and easy circuit integration, making it suitable for mobile device applications.
Implementation Method 1
a common electrode 43, which is also used as a drive electrode for a sensor, and a detection electrode 44 for the sensor, the capacitive element being configured with the common electrode 43, the detection electrode 44, and a dielectric 6 interposed between the common electrode 43 and the detection electrode 44
Data Source
AI summary
A common electrode for a display, which is originally provided in a liquid crystal display element, is also used as one (drive electrode) of a pair of electrodes for a touch sensor, and the other (detection-electrode-for-the-sensor) of the pair of electrodes is newly formed. An existing common drive signal as a drive signal for display is used in common for a drive signal for the touch sensor. A capacitance is formed between the common electrode and the detection-electrode-for-the-sensor, and touch detection is performed by utilizing a change of this capacitance caused by a finger touch of a user. Thus, a display device with a touch sensor is also applicable to a mobile device in which electric potential of the user is inconstant in many cases. The newly-provided electrode is only the detection-electrode-for-the-sensor, and it is unnecessary to newly prepare a drive signal for the touch sensor.