ECB Liquid Crystal Display Black Level Optimization
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Solution Overview
Problem
Existing liquid crystal display (LCD) devices face black level degradation issues, particularly in achieving high-quality normally black displays with low light transmissivity, which current technologies have not adequately addressed.
Innovation Solution
An electrically controlled birefringence LCD device is designed with a liquid crystal layer and a half-wavelength plate, where the phase difference of the liquid crystal layer is less than half of the half-wavelength plate's phase difference, and both exhibit positively dispersive wavelengths, along with a specific orientation of the slow axis of the half-wavelength plate intersecting with the liquid crystal molecules' orientation axis, enabling improved black and white levels and high contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional LCD structure is used, then the device can display images, but the black level degrades and cannot achieve high-quality normally black display
Solution Approach 1:
The LCD device segments the optical path into distinct functional layers: a first polarizing plate, a liquid crystal layer with specific phase difference characteristics, a half-wavelength plate with controlled phase difference, and a reflective portion. This segmentation allows each layer to be optimized independently for its specific function, achieving superior black level quality through precise control of light polarization and phase at each interface.
Solution Approach 2:
The invention changes critical optical parameters: the liquid crystal layer is designed with a phase difference of less than 90 degrees and positive wavelength dispersion, while the half-wavelength plate has a phase difference between 180-360 degrees with positive wavelength dispersion. These parameter changes enable the system to achieve normally black display with high contrast by controlling the polarization state of reflected light.
2Use of energy by stationary object
If low-voltage driving is implemented for power savings, then power consumption reduces, but display quality may deteriorate
Solution Approach 1:
The invention changes the electrical operating parameters by designing the liquid crystal layer with specific birefringence and phase difference characteristics that enable effective switching at low voltages. The positive wavelength dispersion and controlled phase difference allow the liquid crystal molecules to reorient efficiently under low electric fields, maintaining high display quality while reducing power consumption compared to conventional high-voltage LCD designs.
3Illumination intensity
If the phase difference of the liquid crystal layer is increased to improve display contrast, then contrast ratio improves, but the black level quality deteriorates
Solution Approach 1:
The invention changes the phase difference parameter to be less than 90 degrees (specifically 45-90 degrees), which is counterintuitive but effective. Combined with the half-wavelength plate having phase difference between 180-360 degrees, this creates a synergistic effect where the reflected light undergoes precise polarization transformation. The positive wavelength dispersion in both layers ensures that the contrast improvement is maintained across the visible spectrum without compromising black level quality.
Solution Approach 2:
The half-wavelength plate acts as an intermediary optical element between the liquid crystal layer and the exit polarizer. It mediates the polarization state transformation by introducing a controlled phase shift, allowing the system to achieve high contrast and good black level quality simultaneously. The intermediary converts the sub-90 degree phase difference from the liquid crystal layer into the appropriate polarization state for high-quality 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 configuration enhances the black level quality and display contrast, improving viewability and reducing power consumption for mobile applications by allowing low-voltage driving, while maintaining high display quality in both reflective and transmissive modes.
Implementation Method 1
an electrically controlled birefringence liquid crystal display device
Implementation Method 2
the slow axis of the half-wavelength plate intersects with an orientation axis of liquid crystal molecules in the liquid crystal layer under no electric field being applied
Implementation Method 3
a half-wavelength plate between the liquid crystal display panel and the first polarizing plate. A phase difference of the liquid crystal layer is less than a half of a phase difference of the half-wavelength plate
Implementation Method 4
a reflective portion to reflect light that is incident through a display surface of the liquid crystal display panel and that passes through the liquid crystal layer
Implementation Method 5
a first polarizing plate on the display surface of the liquid crystal display panel
Data Source
AI summary
An electrically controlled birefringence liquid crystal display device performs a normally black display. The display device includes a liquid crystal display panel including a liquid crystal layer and a reflective portion to reflect light that is incident through a display surface of the liquid crystal display panel and that passes through the liquid crystal layer, a first polarizing plate on the display surface, and a half-wavelength plate between the liquid crystal display panel and the first polarizing plate. A phase difference Δnd−1 of the liquid crystal layer is less than a half of a phase difference Δnd−2 of the half-wavelength plate. The phase difference Δnd−2 of the half-wavelength plate indicates a positively dispersive wavelength, and a low axis of the half-wavelength plate intersects with an orientation axis of liquid crystal molecules in the liquid crystal layer under no electric field being applied. The liquid crystal layer has a birefringence index Δn indicating a positively dispersive wavelength.