Reflective LCD Contrast at 60° Viewing Angle
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Solution Overview
Problem
Reflective-type liquid crystal display devices often exhibit a contrast ratio of less than 1.0 at a 60° viewing angle, which is inadequate for maintaining display quality in outdoor applications.
Innovation Solution
A reflective-type liquid crystal display device is designed with a specific configuration including a light-reflective first electrode, a light-transmissive second electrode, a liquid crystal layer that takes a generally vertical alignment during black display, a polarizing layer, and three retardation layers arranged to satisfy specific angular relationships, along with a nematic liquid crystal material and chiral agent, to achieve a contrast ratio of 1.0 or more at a 60° viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reflective-type liquid crystal display device uses a liquid crystal layer with vertical alignment and twist alignment, then light efficiency is improved and contrast ratio reaches 20:1 or more, but contrast ratio at diagonal viewing angle (60°) becomes less than 1.0
Solution Approach 1:
The patent introduces a third dimension to the optical path by adding a quarter-wave plate (third retardation layer) with specific optical axis orientation. This transforms the linearly polarized light from the polarizing layer into circularly polarized light before it enters the liquid crystal layer, enabling the reflected light to maintain proper polarization state after passing through the liquid crystal layer twice, thereby improving contrast ratio at diagonal viewing angles while maintaining the vertical alignment configuration
Solution Approach 2:
The patent creates a composite optical system combining multiple functional layers with different optical properties: a polarizing layer for polarization, a quarter-wave plate for circular polarization conversion, and a liquid crystal layer with vertical alignment for voltage-controlled optical modulation. This composite structure achieves both high contrast ratio and improved diagonal viewing angle characteristics that cannot be achieved with single-layer configurations
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 configuration enhances the contrast ratio to 1.0 or more at a 60° viewing angle, improving display quality and maintaining high contrast even at diagonal viewing positions, thereby addressing the limitations of existing devices.
Implementation Method 1
the liquid crystal layer includes a nematic liquid crystal material whose dielectric anisotropy is negative and a chiral agent, and takes a generally vertical alignment in an absence of voltage application
Implementation Method 2
a first retardation layer, a second retardation layer and a third retardation layer that are arranged in this order from a side of the polarizing layer
Data Source
AI summary
A reflective-type liquid crystal display device includes: a first substrate including a light-reflective first electrode; a second substrate including a light-transmissive second electrode; a liquid crystal layer that is provided between the first electrode and the second electrode and takes a generally vertical alignment during black display; a polarizing layer provided on a viewer side of the second substrate; and a first retardation layer, a second retardation layer and a third retardation layer that are arranged in this order from a side of the polarizing layer, wherein 40°≤|θ3−2×θ2+2×θ1|≤50°, 130°≤|θ3−2×θ2+2×θ1|≤140°, 220°≤|θ3−2×θ2+2×θ1|≤230° or 310°≤|θ3−2×θ2+2×θ1|≤320° is satisfied, where θ1 denotes an angle formed between an absorption axis or a transmission axis of the polarizing layer and a slow axis of the first retardation layer, θ2 an angle formed between the absorption axis or the transmission axis of the polarizing layer and the slow axis of second retardation layer, and θ3 an angle formed between the absorption axis or the transmission axis of the polarizing layer and the slow axis of the third retardation layer.