LCD Pixel Circuit Proximity Sensing Burn-In Prevention
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Solution Overview
Problem
Conventional liquid crystal displays (LCDs) lack the ability to integrate touch-sensitive functionality while maintaining transparency and preventing burn-in effects, limiting their application in devices that require both display and input capabilities.
Innovation Solution
An LCD circuit and method that applies a transparency voltage and a sensor voltage to the electrodes, allowing the pixel to switch between transparent and non-transparent states while using the existing ITO layers for capacitive measurements to detect object proximity, thereby enabling touch-sensitive functionality without compromising the liquid crystal molecule orientation or causing burn-in.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant voltage is applied to switch the pixel into a non-transparent state, then the display function is achieved, but burn-in effects occur due to prolonged voltage application
Solution Approach 1:
The patent applies alternating voltage pulses to switch the liquid crystal molecules between transparent and non-transparent states. Instead of maintaining a constant voltage that causes burn-in, the system uses periodic voltage applications with defined pulse widths, allowing the display to function while preventing degradation from prolonged static voltage exposure.
2Adaptability or versatility
If additional sensor layers are added to enable touch-sensitive functionality, then touch detection capability is improved, but device complexity and structural layers increase
Solution Approach 1:
The patent makes the existing ITO electrode layers serve dual purposes: they function as electrodes for liquid crystal switching and simultaneously as capacitive sensor elements for touch detection. By measuring capacitance changes of these existing layers, the system achieves touch-sensitive functionality without adding separate sensor layers, thereby maintaining structural simplicity while enabling versatile input capabilities.
3Adaptability or versatility
If the ITO electrode layers are used for capacitive measurements, then touch detection is enabled, but the transparency and display quality may be compromised
Solution Approach 1:
The patent introduces a transparent conductive oxide layer (ITO) as an intermediary that enables both optical transparency and electrical capacitance measurement. This layer acts as a mediator between the liquid crystal molecules and the touch detection function, allowing light to pass through while providing the necessary electrical properties for capacitive sensing without compromising display quality.
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 enhances the functionality of LCDs by allowing them to function as both a display and a touch-sensitive input device, providing additional application areas while maintaining transparency and preventing burn-in, with the added capability of detecting object proximity through capacitive measurements.
Implementation Method 1
the molecules of the liquid crystals will be oriented such that light may pass through the entire assembly. If the voltage applied to the electrodes exceeds the threshold value, the molecules will re-orientate themselves so that the light incident in the crystal layer is turned and light will be prevented from passing.
Implementation Method 2
using the existing ITO layers for capacitive measurements to detect object proximity
Data Source
AI summary
The invention relates to an LCD circuit and a method for triggering at least one pixel (3) of a liquid crystal display (LCD) in order to optionally apply a voltage (V) between a first and a second electrode (1, 2), between which a layer (4) of liquid crystals is arranged. The pixel (3) switches into a non-transparent state when a voltage (V) is applied whose value is greater than or equal to the value of a threshold voltage (VD, VD−) between the electrodes (1, 2), a sensor voltage (VS) which changes across a sensor period (T) being applied to at least one of the electrodes (1; 1, 2) as said voltage (V) or part of said voltage (V) in order to generate a sensor signal for detecting an object (5) approaching the pixel (3). Also disclosed are an advantageous liquid crystal display encompassing such a circuit as well as an advantageous communication device (7) comprising a first housing part (8) that is provided with a display device (9), a second housing part (10), and an adjusting mechanism (11) for moving the housing parts into a position in which the display device is located at a distance from the second housing part and moving the housing parts into a position in which the display device adjoins a bottom area (12) of the second housing part, said bottom area (12) being embodied by means of such a liquid crystal display.