Twisted Vertical Alignment LCD with Multi-Domain Reflective Electrode
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Solution Overview
Problem
Reflective and transflective liquid crystal display devices using the twisted vertical alignment mode suffer from poor viewing angle characteristics and low contrast ratios, particularly in specific azimuths, limiting their design flexibility and outdoor application effectiveness.
Innovation Solution
A liquid crystal display device with a twisted vertical alignment mode, featuring a reflective region and a transmissive region, utilizes a silver or silver alloy reflective electrode, photo-alignment films, and a chiral agent in the liquid crystal layer, along with a two-domain or four-domain structure in each region, to improve viewing angle characteristics through controlled alignment azimuths and retardation dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a twisted vertical alignment mode is used in reflective and transflective LCDs, then the display can perform in both reflection mode and transmission mode, but the viewing angle characteristics become poor and contrast ratio becomes low in specific azimuth
Solution Approach 1:
The pixel is divided into multiple liquid crystal domains (typically four domains) with different alignment azimuths. Each domain has liquid crystal molecules aligned at different angles (e.g., 0°, 45°, 90°, 135°), so that when viewed from different directions, at least one domain maintains good contrast ratio and viewing angle characteristics. This segmentation resolves the contradiction by making the display adaptable to multiple viewing angles simultaneously.
Solution Approach 2:
The invention introduces asymmetric alignment configurations by setting different pretilt azimuths for different regions of the vertical alignment film. The alignment film is divided into multiple regions with different alignment directions, creating an asymmetric multi-domain structure that improves viewing angle characteristics across different azimuths while maintaining dual-mode operation capability.
2Illumination intensity
If a twisted vertical alignment mode is used in reflective LCDs, then display in reflection mode is achieved, but contrast ratio becomes low in specific azimuth
Solution Approach 1:
The reflective pixel is segmented into multiple liquid crystal domains with different alignment azimuths. Each domain maintains different molecular orientations that compensate for each other when viewed from different angles, ensuring that the contrast ratio remains high across all viewing directions while maintaining reflection mode display functionality.
3Reliability
If multi-domain structure is introduced to improve viewing angle characteristics, then viewing angle characteristics improve, but device complexity increases
Solution Approach 1:
The invention implements local quality by applying different alignment properties to different regions of the vertical alignment film within each pixel. The alignment film is divided into multiple regions with different pretilt azimuths, creating local variations in liquid crystal molecule orientation. This approach achieves multi-domain structure and improved viewing angle characteristics without requiring complex additional components, as the complexity is distributed locally within the film structure 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
The solution significantly enhances viewing angle characteristics and contrast ratios, enabling better performance in both reflective and transmissive modes, particularly in outdoor applications by optimizing liquid crystal domain alignment and retardation dispersion.
Implementation Method 1
at least one of the first vertical alignment film and the second vertical alignment film is a photo-alignment film including an alignment film material having a reaction wavelength with respect to light of at least 313 nm
Implementation Method 2
the liquid crystal layer includes a liquid crystal material having negative dielectric anisotropy
Implementation Method 3
the liquid crystal layer includes a liquid crystal material having negative dielectric anisotropy and a chiral agent
Implementation Method 4
the reflective electrode includes silver or a silver alloy
Data Source
AI summary
A liquid crystal display device includes a first substrate, a second substrate located closer to an observer than the first substrate, and a liquid crystal layer provided between the first substrate and the second substrate, and performs display in a twisted vertical alignment mode. Each pixel includes a reflective region where display is performed in a reflection mode. The first substrate includes a reflective electrode including a portion located in the reflective region, and a first vertical alignment film. The second substrate includes a second vertical alignment film. The liquid crystal layer includes a liquid crystal material having negative dielectric anisotropy, and a chiral agent. The reflective electrode includes silver or a silver alloy. The reflective region includes a plurality of liquid crystal domains in which reference alignment azimuths of liquid crystal molecules are different from each other.