Phase Difference Plate Structure for Low Viewing-Angle Tint Shift
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Solution Overview
Problem
Conventional phase difference plates with multiple liquid crystal layers require multiple applications of liquid crystal compounds, leading to industrial inefficiencies and unfavorable handleability, and result in significant differences in tint between the front and oblique directions when used in image display elements.
Innovation Solution
A phase difference plate comprising a first optically anisotropic polymer film layer with specific in-plane and thickness direction retardations, combined with a second optically anisotropic layer of twist-aligned liquid crystal compounds, and optionally a third layer, to achieve a small tint difference in image display apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase difference plate includes multiple liquid crystal layers, then the optical performance can be improved, but the manufacturing process becomes complex and handleability deteriorates
Solution Approach 1:
The patent combines multiple liquid crystal layers into a single integrated phase difference plate structure, where the liquid crystal layers are formed within one plate rather than as separate components. This merging approach maintains the optical performance benefits of multiple layers while simplifying the manufacturing process and improving handleability by reducing the number of separate components that need to be assembled and handled.
Solution Approach 2:
The patent uses a composite structure comprising multiple liquid crystal layers with different refractive indices and orientations within a single phase difference plate. This composite material approach allows optimization of optical performance through material selection while maintaining a unified structure that is easier to manufacture and handle compared to multiple separate layers.
2Object-affected harmful factors
If a phase difference plate is combined with a polarizer to form a circularly polarizing plate, then external light reflection can be suppressed, but tint difference between front and oblique directions increases
Solution Approach 1:
The patent applies local quality by creating liquid crystal layers with different optical properties at different locations or orientations within the phase difference plate. Specifically, the liquid crystal layers are configured with different refractive indices and alignment directions to compensate for viewing angle-dependent tint variations, while maintaining effective suppression of external light reflection through the overall circularly polarizing 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 provides a phase difference plate that minimizes tint variation between front and oblique directions, enhancing the performance of circularly polarizing plates in image display devices.
Implementation Method 1
an in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is 60 to 300 nm, a thickness direction retardation of the first optically anisotropic layer at a wavelength of 550 nm is −150 to −30 nm
Implementation Method 2
the second optically anisotropic layer is a layer formed by fixing a liquid crystal compound twist-aligned with a thickness direction as a helical axis
Implementation Method 3
a layer formed by fixing a liquid crystal compound twist-aligned with a thickness direction as a helical axis
Data Source
AI summary
Provided is a phase difference plate including a polymer film, which achieves a small difference in tint between a front direction and an oblique direction of an obtained image display apparatus in a case where the phase difference plate is combined with a polarizer and then applied to an image display element as a circularly polarizing plate. The phase difference plate includes a first and a second optically anisotropic layer, in which the first layer is a polymer film, an in-plane retardation of the first layer at a wavelength of 550 nm is 60 to 300 nm, a thickness direction retardation of the first layer at a wavelength of 550 nm is −150 to −30 nm, the second layer is a layer formed by fixing a liquid crystal compound twist-aligned with a thickness direction as a helical axis, and the second layer satisfies a predetermined relationship with respect to Δnd.