Liquid Crystal Device Touch Detection Aperture Ratio
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Solution Overview
Problem
Liquid crystal devices with touch panel functions face challenges in accurately locating the position of a pointing object, such as a finger, due to saturation of photoelectric currents from high light levels and difficulty in distinguishing between image portions and shadows, especially when images include both white and black portions, leading to reduced aperture ratios and detection accuracy.
Innovation Solution
The liquid crystal device incorporates a configuration with selection lines, signal lines, pixel portions, photosensor portions, and power lines, where photosensor selection lines are used to control switching elements, reducing wiring and allowing for improved aperture ratios by adjusting light amounts entering photosensors, and utilizing a control portion to read out reference and measurement light signals to differentiate incident light levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photosensors are arranged in each pixel portion to enable touch panel function, then position detection capability is improved, but aperture ratio deteriorates due to increased wiring and sensor area
Solution Approach 1:
The patent combines the photosensor portion with the pixel portion structure, sharing common electrodes and wiring. The photosensor uses the same transparent electrode and pixel electrode as the display pixel, merging detection and display functions into a unified structure that reduces total wiring and maintains aperture ratio.
Solution Approach 2:
The pixel portion structure serves dual functions: display function through liquid crystal modulation and touch detection function through photosensor. The same physical components (electrodes, wiring) are used for both display and detection, eliminating the need for separate dedicated detection structures.
2Measurement precision
If photosensor area is increased to improve light detection capability, then detection accuracy is improved, but aperture ratio deteriorates
Solution Approach 1:
The patent applies different functional properties to different regions of the pixel structure. The photosensor portion has optimized light reception properties with appropriate electrode transparency and spacing, while maintaining the overall pixel aperture ratio. Local optimization of sensor region allows sufficient light detection without compromising total display area.
3Measurement precision
If wiring for photosensors is added to each pixel, then detection capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the photosensor wiring with the display pixel wiring structure. Common source lines, gate lines, and control signals are shared between display pixels and photosensor portions, significantly reducing the number of additional wiring required for touch detection functionality.
4Measurement precision
If light amount adjustment is implemented to maintain detectable range, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The liquid crystal layer itself serves as the light amount adjustment mechanism. By controlling the liquid crystal state (transparent or opaque), the system automatically regulates the light reaching the photosensor without requiring external shutters or additional control components, achieving adaptive light control through the display function itself.
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 accurate detection of pointing objects by adjusting light amounts within detectable ranges, improving detection accuracy and maintaining high aperture ratios, thus enhancing the ability to distinguish between image portions and shadows without reducing display performance.
Implementation Method 1
Each of the plurality of photosensor portions includes a photoelectric conversion element, which generates an electric current corresponding to the amount of light received
Data Source
AI summary
A liquid crystal device includes a plurality of selection lines, a plurality of signal lines, a plurality of pixel portions, a plurality of photosensor portions, a plurality of first power lines, and a plurality of sense lines. The plurality of selection lines are provided in a line direction. The plurality of signal lines are provided in a column direction. The plurality of pixel portions are provided at positions corresponding to intersections of the selection lines and the signal lines. The plurality of photosensor portions are provided in correspondence with a portion of the plurality of pixel portions. The plurality of first power lines are provided in the line direction. The plurality of sense lines are provided in the column direction. Each of the plurality of pixel portions includes a first switching element and a liquid crystal.