Inspection Apparatus for Display Substrates Using Twisted Nematic Liquid Crystal
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Solution Overview
Problem
Current inspection apparatuses for display substrates in liquid crystal display panels face challenges in effectively detecting defects due to insufficient light transmission and slow response times of liquid crystal molecules, leading to noise in data signals.
Innovation Solution
An inspection apparatus is designed with a reflection plate, a liquid crystal layer operated in twisted nematic mode, an electrode layer, a ¼ wavelength retardation plate, and a polarization plate, which increases light transmission and allows for precise control of light timing, enhancing defect detection and reducing noise in data signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional inspection apparatus structure is used, then device complexity is reduced, but light transmission is insufficient and response speed is slow
Solution Approach 1:
The inspection module is divided into distinct functional layers: liquid crystal layer, first polarization plate, second polarization plate, quarter-wave plate, and reflection plate. Each layer performs a specific optical function, allowing optimized light control while maintaining manageable system complexity through modular design.
Solution Approach 2:
The liquid crystal layer acts as an intermediary between the light source and the display substrate, dynamically controlling light transmission and timing. The quarter-wave plate serves as an intermediary to convert linearly polarized light to circularly polarized light, enhancing the optical path efficiency and response characteristics.
2Reliability
If conventional liquid crystal response time is used, then manufacturing simplicity is maintained, but noise in data signals increases
Solution Approach 1:
The liquid crystal molecules are operated in twisted nematic mode with specific retardation values (140-200 nm), optimizing the response time constant. The voltage waveform is specifically designed with rapid rise time (10-100 μs) to achieve fast liquid crystal response, reducing the time loss while improving signal quality by enabling precise timing control.
3Measurement precision
If light transmission is increased, then defect detection accuracy is improved, but device structure becomes more complex
Solution Approach 1:
The inspection process uses periodic voltage application to the liquid crystal layer, switching between high-transmission and low-transmission states. This periodic control allows the same optical path to serve multiple measurement purposes, improving defect detection accuracy without proportionally increasing structural complexity.
Solution Approach 2:
The optical system utilizes polarization state changes (effectively optical 'color' changes) rather than intensity changes alone. The quarter-wave plate and polarization plates create distinct polarization states that enhance contrast for defect detection, improving measurement precision while using existing optical components efficiently.
4Loss of time
If response speed is doubled, then timing control precision is improved, but energy consumption increases
Solution Approach 1:
The voltage waveform is designed with a rapid initial rise (10-100 μs) that pre-charges the liquid crystal layer quickly, achieving the desired response speed. The subsequent voltage maintenance phase uses lower energy, as the liquid crystal molecules remain in the desired state without requiring continuous high energy input, thus balancing timing precision with energy efficiency.
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 apparatus improves light transmission by 17% and response speed, resulting in more accurate defect detection and reduced noise in data signals, with a 10% improvement in contrast ratio and a response time twice as fast as comparison examples.
Implementation Method 1
liquid crystal molecules which have a retardation value of about 140 nanometers (nm) to about 200 nm and which are operated in a twisted nematic mode
Implementation Method 2
liquid crystal molecules which have a retardation value of about 140 nanometers (nm) to about 200 nm
Implementation Method 3
a 1/4 wavelength retardation plate is disposed on the electrode layer
Implementation Method 4
a polarization plate is disposed on the 1/4 wavelength retardation plate
Implementation Method 5
The electrode layer is disposed on the liquid crystal layer and generates an electric field in cooperation with an electrode of the display substrate
Data Source
AI summary
An inspection apparatus for a display substrate includes a reflection plate, a liquid crystal layer, an electrode layer, a ¼ wavelength retardation plate and a polarization plate. The liquid crystal layer is disposed on the reflection plate and includes liquid crystal molecules which have a retardation value of about 140 nanometers to about 200 nanometers and are operated in a twisted nematic mode. The electrode layer is disposed on the liquid crystal layer and generates an electric field in cooperation with an electrode of the display substrate. The ¼ wavelength retardation plate is disposed on the electrode layer and the polarization plate is disposed on the ¼ wavelength retardation plate.