Circularly-Polarizing Plate with Low Nz λ/4 Plates
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Solution Overview
Problem
The existing manufacturing methods for circularly-polarizing plates, particularly those using roll-to-roll lamination technology, face challenges with high Nz coefficient λ/4 plates, leading to decreased productivity and increased costs, and the viewing angle properties of circularly-polarized VA mode liquid crystal display devices remain suboptimal.
Innovation Solution
The solution involves using biaxial λ/4 plates with adjusted Nz coefficients and incorporating specific birefringent layers to optimize the retardation conditions between polarizers, allowing for flexible design changes and compensation of the liquid crystal layer, thereby improving the viewing angle properties and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If roll-to-roll lamination technology is used to manufacture circularly-polarizing plates with high Nz coefficient λ/4 plates, then manufacturing speed and productivity are improved, but manufacturing precision and product quality deteriorate
Solution Approach 1:
The patent changes the key parameter from high Nz coefficient to low Nz coefficient (specifically Nz<1.5), which fundamentally alters the optical properties of the λ/4 plate. This parameter change enables the use of roll-to-roll lamination technology while maintaining manufacturing precision, as lower Nz coefficients are more tolerant to the variations introduced by high-speed lamination processes.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: polarizer layer, λ/4 plate layer (with low Nz coefficient), and protective film layers. This composite material approach allows optimization of each layer's properties independently, enabling the λ/4 plate to have low Nz coefficient while the overall circularly-polarizing plate maintains its optical performance through proper design of the composite structure.
2Adaptability or versatility
If high Nz coefficient λ/4 plates are used in circularly-polarizing plates, then viewing angle properties are improved, but manufacturing costs and complexity increase
Solution Approach 1:
The patent inverts the traditional approach by using low Nz coefficient λ/4 plates instead of high Nz coefficient plates. This parameter change is compensated by optimizing other parameters such as the retardation values of the λ/4 plate and the thickness of the liquid crystal layer, thereby achieving wide viewing angle properties without the manufacturing complexity and costs associated with high Nz coefficient plates.
Solution Approach 2:
The patent optimizes the optical properties locally by carefully selecting the retardation value of the λ/4 plate layer and its positioning within the circularly-polarizing plate structure. This local optimization approach allows the system to achieve wide viewing angle performance through the coordinated design of multiple layers rather than relying on the expensive and complex high Nz coefficient material throughout.
3Manufacturing precision
If traditional VA mode with linear polarizers is used, then contrast ratio is improved, but viewing angle properties deteriorate
Solution Approach 1:
The patent introduces dynamic optical compensation by using circularly-polarizing plates with low Nz coefficient λ/4 plates. This dynamic approach allows the optical properties of the display to be compensated across different viewing angles through the specific optical path differences introduced by the low Nz coefficient material, maintaining contrast ratio performance while expanding viewing angle adaptability.
Solution Approach 2:
The patent creates a composite optical system combining the liquid crystal layer with low Nz coefficient λ/4 plates and polarizer layers. This composite structure works together to maintain the high contrast ratio characteristics of VA mode while adding wide viewing angle properties, as the low Nz coefficient λ/4 plates provide optical compensation that benefits both contrast and viewing angle performance simultaneously.
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 approach enables the production of circularly-polarizing plates with higher productivity and lower costs, while achieving a high contrast ratio over a wide viewing angle range, enhancing the performance of circularly-polarized VA mode liquid crystal display devices.
Implementation Method 1
a first-type birefringent layer of which the in-plane retardation has been adjusted to λ/4 (first λ/4 plate), a second first-type birefringent layer of which the in-plane retardation has been adjusted to λ/4 (second λ/4 plate), and a second-type birefringent layer
Data Source
AI summary
The present invention provides a liquid crystal display device which enables costs to be reduced, excels in productivity, and enables a high contrast ratio over a wide viewing angle range to be realized. The present invention is a liquid crystal display device including a first polarizer, a second-type (nx<ny≦nz) birefringent layer, a first λ/4 plate (nx>ny≧nz), a liquid crystal cell, a second λ/4 plate having an Nz coefficient different from the first λ/4, and a second polarizer in this order, wherein an in-plane slow axis of the first λ/4 plate forms generally 45 degrees as to an absorption axis of the first polarizer, an in-plane slow axis of the second λ/4 plate is generally orthogonal to the in-plane slow axis of the first λ/4 plate, an absorption axis of the second polarizer is orthogonal to the absorption axis of the first polarizer, an in-plane fast axis of the second-type birefringent layer is generally orthogonal to the absorption axis of the first polarizer, and black display is performed by aligning liquid crystal molecules within a liquid crystal layer in a manner generally perpendicular to substrate faces.