VA LCD Domain Division for Gray Scale Viewing Angle
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The circularly polarizing VA mode liquid crystal display device faces challenges in achieving a high contrast ratio and sufficient viewing angle characteristics, particularly at oblique angles, due to light leakage and inconsistent gray scale viewing angles, which affect display quality.
Innovation Solution
The implementation of a liquid crystal display device with a specific configuration including first and second λ/4 plates, a second-type birefringent layer, and a third-type birefringent layer, where the λ/4 plates have in-plane phase differences adjusted to λ/4, and the birefringent layers are arranged to optimize the Nz-coefficients and phase differences, ensuring that the liquid crystal molecules are tilted in specific azimuth ranges to improve transmissivity and reduce light leakage across various viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If liquid crystal molecules are tilted in one direction at voltage application time, then transmissivity in white display state is maximized, but asymmetry (skewness) is generated in viewing angle characteristic
Solution Approach 1:
The pixel is divided into multiple domains, with each domain having liquid crystal molecules tilted in different azimuth directions. This segmentation allows the device to achieve good viewing angle characteristics in multiple directions simultaneously, resolving the asymmetry problem while maintaining high transmissivity in each domain.
Solution Approach 2:
The invention intentionally introduces asymmetric elements (protrusions) in the pixel structure to control and create the desired asymmetric tilt patterns. By strategically placing these asymmetric features, the patent achieves symmetric viewing angle characteristics across multiple domains, effectively resolving the original asymmetry problem.
2Stability of the object's composition
If domain division is implemented to improve viewing angle characteristics, then asymmetry is reduced, but device complexity increases due to additional alignment control parts
Solution Approach 1:
The alignment control parts (protrusions) are placed only in specific local regions where needed to induce domain division, rather than uniformly across the entire pixel. This localized approach achieves the desired multi-domain effect while minimizing the overall complexity of the pixel structure.
Solution Approach 2:
The protrusions serve as intermediary elements that mediate between the liquid crystal molecules and the substrate, providing a simple structural means to control molecular orientation and achieve domain division without complex electrode patterns or additional control mechanisms.
3Illumination intensity
If circularly polarizing plate is used to improve transmissivity independence from polarizer angle, then transmissivity is enhanced, but contrast ratio deteriorates at oblique viewing angles due to light leakage
Solution Approach 1:
The invention optimizes the Nz-coefficient (biaxiality parameter) of the λ/4 plates to specific ranges (1.05-1.30 for first λ/4 plate, 1.00-1.25 for second λ/4 plate) to compensate for viewing angle dependency. This parameter optimization reduces light leakage at oblique angles while maintaining high transmissivity, thereby improving contrast ratio without sacrificing the benefits of circularly polarized light.
Solution Approach 2:
The patent uses composite optical structures combining circularly polarizing plates with specifically designed λ/4 plates having optimized Nz-coefficients. This composite approach leverages the high transmissivity advantage of circularly polarized light while compensating for its viewing angle limitations, achieving both high transmissivity and good contrast ratio.
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 gray scale viewing angle from intermediate to high gray scales at a 45° azimuth angle, improving display quality and contrast ratio in a wider viewing range while maintaining excellent black display performance.
Implementation Method 1
first and second λ/4 plates with in-plane phase differences adjusted to λ/4
Implementation Method 2
second-type birefringent layer and a third-type birefringent layer, where the λ/4 plates have in-plane phase differences adjusted to λ/4, and the birefringent layers are arranged to optimize the Nz-coefficients and phase differences
Implementation Method 3
liquid crystals having negative dielectric anisotropy are vertically aligned between the mutually opposing substrates
Implementation Method 4
the liquid crystal molecules are tilted so as to be approximately parallel to the substrate, thus exhibiting a great birefringence and realizing a white display
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 4~5
AI summary
The present invention provides a circularly polarizing VA mode liquid crystal display device having an excellent gray scale viewing angle from an intermediate gray scale to a high gray scale at an azimuth angle of 45°. The liquid crystal display device according to the present invention includes: a first polarizer; a first λ/4 plate; liquid crystal cell; a second λ/4 plate; and a second polarizer in this order, wherein when an azimuth of an absorption axis of the second polarizer is defined as 0°, an in-plane slow axis of the second λ/4 plate forms an angle of approximately 45°; an in-plane slow axis of the first λ/4 plate forms an angle of approximately 135°; the absorption axis of the first polarizer forms an angle of approximately 90°, and wherein a display brightness is varied by changing an alignment state of liquid crystal molecules in a liquid crystal layer from a state that the liquid crystal molecules are approximately vertically aligned to a substrate surface, to a state that the liquid crystal molecules are tilted to the substrate surface; and the liquid crystal layer has a domain in which the liquid crystal molecules are tilted in an azimuth angle range of 12.5° to 32.5°, a domain in which the liquid crystal molecules are tilted in an azimuth angle range of 102. 5° to 122.5°, and a domain in which the liquid crystal molecules are tilted in an azimuth angle range of 192.5° to 212.5°, and a domain in which the liquid crystal molecules are tilted in an azimuth angle range of 282.5° to 302.5°.