LCD Light Sensor Dummy Electrode Prevents Light Leakage
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Solution Overview
Problem
Liquid crystal display devices waste power due to constant backlight brightness, and light sensors malfunction in sensing external light intensity due to voltage generation and light leakage through openings in the black matrix, leading to incorrect power control.
Innovation Solution
A liquid crystal display device with a light sensor on a first substrate and a dummy electrode on a passivation layer, which applies a constant voltage to prevent light leakage and ensure consistent light sensing, allowing the backlight brightness to be adjusted based on external light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light sensor is formed at an edge of the TFT array substrate with an opening in the black matrix, then the light sensor can sense external light, but light leaks through the opening causing display defects
Solution Approach 1:
A dummy electrode is introduced as an intermediary element positioned between the light sensor and the liquid crystal layer. This dummy electrode creates an electric field that acts as a mediator to control the liquid crystal molecules directly above the light sensor opening, forcing them into a black state to block light leakage while allowing the light sensor to function beneath it.
2Ease of operation
If the liquid crystal layer is driven to control display, then the display function operates, but the light sensor malfunctions due to voltage-generated electric fields altering light characteristics
Solution Approach 1:
The electrode structure is segmented into two independent parts: the pixel electrode for display control and the dummy electrode for light sensor protection. This segmentation allows the pixel electrode to drive the liquid crystal for display purposes while the dummy electrode independently maintains a controlled electric field above the light sensor, preventing interference with light sensing operations.
3Illumination intensity
If the backlight provides constant brightness, then the display has sufficient illumination, but power is wasted in dark environments
Solution Approach 1:
A feedback control system is implemented where the light sensor continuously monitors external light intensity and sends signals to a control circuit. Based on this feedback information, the control circuit dynamically adjusts the backlight brightness - reducing it when external light is sufficient and increasing it when external light is dim, thereby optimizing power consumption while maintaining display visibility.
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 power consumption by accurately controlling backlight brightness and prevents light leakage, ensuring precise light sensing and efficient operation of the light sensor.
Implementation Method 1
a light sensor on the first substrate in the non-display area that senses the intensity of external light
Implementation Method 2
a voltage may be generated by the light sensor and a common electrode formed on the color filter array substrate to create an electric field that drives the liquid crystal of the liquid crystal layer
Data Source
AI summary
Provided is a liquid crystal display device. The liquid crystal display device includes: a first substrate and a second substrate each having a display area and a non-display area defined; a liquid crystal layer between the first and second substrates; a light sensor on the first substrate in the non-display area that senses the intensity of external light; a passivation layer on an entire upper surface of the first substrate including the light sensor; and a dummy electrode on the passivation layer at a location corresponding to the light sensor.