Retardation Layer Inclined Azimuth Alignment for Transflective LCD Contrast
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Solution Overview
Problem
Transflective liquid crystal display devices face issues with reduced contrast ratio due to unneeded retardation in transmissive light caused by λ/4 retarders, leading to light leakage in black display states, particularly in regions with inclined portions of the retardation layer.
Innovation Solution
A λ/4 retardation layer is formed on one substrate with an inclined portion parallel to its slow axis azimuth, ensuring that the LC molecules compensate for the retardation in the inclination region, thereby suppressing light leakage and improving contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a λ/4 retarder is arranged in the reflective display region, then effective reflective display is achieved, but unneeded retardation is given to transmissive light causing reduction in contrast ratio and luminance
Solution Approach 1:
The patent applies local quality by making the retardation layer thickness non-uniform: thicker in the reflective display region to provide necessary λ/4 retardation for reflective mode, and thinner in the transmissive display region to minimize unwanted retardation effects. This spatial variation in thickness allows each region to optimize its optical properties for its specific display function.
Solution Approach 2:
The patent segments the retardation layer into distinct regions with different thickness characteristics - a first region (thicker) corresponding to the reflective display region and a second region (thinner) corresponding to the transmissive display region. This segmentation allows independent optimization of optical properties for each display mode without requiring separate retardation layers.
2Reliability
If a circularly polarizing plate including λ/4 retarder is attached over the entire viewing-side surface, then reflective display region benefits from retardation, but transmissive display region suffers from unneeded retardation
Solution Approach 1:
Instead of uniform coverage, the patent implements local quality by varying the thickness of the retardation layer across different regions. The thicker portion is positioned over the reflective display region where λ/4 retardation is essential, while the thinner portion covers the transmissive display region where minimal retardation is desired, thus optimizing both display modes simultaneously.
Solution Approach 2:
The patent introduces a new dimension of control by varying the thickness parameter of the retardation layer in the vertical direction (depth dimension). This thickness variation creates different optical path lengths and retardation values in different regions, enabling simultaneous optimization for both reflective and transmissive display modes without adding separate layers.
3Manufacturing precision
If λ/4 retarders are arranged on both front and back sides to eliminate unneeded retardation, then transmissive light is not retarded, but production accuracy must be improved and costs increase
Solution Approach 1:
The patent makes the single retardation layer multi-functional by designing it with spatially varying thickness. The same layer simultaneously provides λ/4 retardation for reflective display in the thicker region and minimal retardation for transmissive display in the thinner region. This eliminates the need for separate retardation layers on front and back sides, reducing device complexity while maintaining display quality.
Solution Approach 2:
The patent merges the functions of multiple retardation layers into a single retardation layer with non-uniform thickness. Instead of placing separate λ/4 retarders on both front and back sides (which would require precise matching), the invention combines all retardation functionality into one layer whose thickness varies to provide different retardation values in different regions, simplifying the overall structure.
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 effectively reduces light leakage in black display states, enhancing the contrast ratio and display quality by aligning the azimuth of the inclined portion with the slow axis of the λ/4 retardation layer, ensuring proper retardation compensation.
Implementation Method 1
The λ/4 retarder gives a retardation of λ/4 between two polarization components that oscillate in mutually-perpendicular two directions of transmissive light having a wavelength of A, whereby the transmissive light is converted into circularly polarized light.
Implementation Method 2
an azimuth of the inclined portion is substantially parallel to a slow axis azimuth of the λ/4 retardation layer
Data Source
AI summary
The present invention provides a liquid crystal display device which allows an improvement in contrast ratio by compensating retardation given in a liquid crystal layer, even if a retardation layer has an inclined portion, and a desired retardation is varied at the inclined portion. The present invention is a vertical alignment liquid crystal display device, including:a pair of substrates facing each other;a liquid crystal layer disposed between the pair of substrates;a transmissive display region; anda reflective display region,wherein one of the pair of substrates includes a λ/4 retardation layer in the reflective display region, the λ/4 retardation layer protruding towards the liquid crystal layer,the λ/4 retardation layer includes an inclined portion inclined to a flat face of the substrate, andan azimuth of the inclined portion is substantially parallel to a slow axis azimuth of the λ/4 retardation layer.