Integrated Pressure Sensing Units in LCD Panels
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Solution Overview
Problem
The integration of touch sensing capabilities into liquid crystal displays (LCDs) often increases costs, reduces yield, and deteriorates luminance and viewing angles due to the need for separate touch screen panels, and existing methods for embedding sensors, such as capacitance variation sensing, face challenges with terminal distance and uniform semiconductor characteristics in thin film transistors.
Innovation Solution
Integrating pressure-sensitive sensing units between subpixel units of an LCD panel, utilizing a variable capacitor with a voltage change sensing electrode and insulating layers, and selectively activating these units via gate lines to provide accurate pressure detection signals, while maintaining a uniform distance between sensing and common electrodes to prevent shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate touch screen panel is mounted on the liquid crystal display, then touch sensing capability is provided, but cost increases, yield is reduced, and luminance and viewing angle are deteriorated
Solution Approach 1:
The patent merges the touch sensing function with the liquid crystal display by integrating pressure-sensitive sensing units directly into the LCD panel structure. The sensing units are formed between subpixel units using the same manufacturing process, eliminating the need for a separate touch screen panel and avoiding the associated problems of increased cost, reduced yield, and deteriorated optical properties.
2Adaptability or versatility
If capacitance variation sensing is used with a variable capacitor, then touch detection is enabled, but a relatively large distance between terminals must be maintained which increases cell gap
Solution Approach 1:
The patent applies local quality by creating distinct regions with different functions within the same structure. The pressure-sensitive sensing units are localized between specific subpixel units, with sensing electrodes and insulating layers positioned only where needed for touch detection. This allows the sensing function to be integrated without requiring a uniformly large cell gap across the entire display.
3Ease of manufacture
If thin film transistors are manufactured with semiconductive active layers, then the liquid crystal display can be manufactured, but uniform semiconductor characteristics are difficult to obtain causing detection errors
Solution Approach 1:
The patent addresses the uniformity issue by carefully controlling the thickness and material composition of the insulating layer in the pressure-sensitive sensing units. By maintaining a uniform insulating layer thickness of 50-200 nm, the capacitance characteristics become consistent across different positions, compensating for variations in TFT characteristics and enabling accurate touch detection throughout the display.
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 approach allows for accurate detection of pressure application on LCD panels without increasing the cell gap, improving the reliability of touch position and force determination while maintaining the display's luminance and viewing angles.
Implementation Method 1
contact information is obtained through determination of a capacitance variation between two terminals due to corresponding variation of a distance between the two terminals
Data Source
AI summary
Capacitively actuated touch sensor units are integrated between subpixel light emitters of a liquid crystal display panel. In one embodiment, a sensor unit is monolithically integrated on a same substrate as are a plurality of associated subpixel units and the sensor unit includes a variable capacitor and a reference capacitor connected to define a voltage splitting circuit having a split voltage generating node. The sensor unit also includes a sensing transistor operatively coupled to the split voltage generating node and a voltage resetting transistor operatively coupled to the split voltage generating node. In one embodiment, one plate of the variable capacitor is defined by a touchwise flexed portion of a common electrode of the display and an opposed plate is defined by a spaced apart facing electrode provided on a TFT array substrate of the liquid crystal display.