Optically Anisotropic Layered Body for Reflective Displays
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Solution Overview
Problem
Image display devices, particularly organic EL devices with reflective electrodes, suffer from reduced image quality due to outside light reflection, and existing circularly polarizing plates using positive C plates face issues with heat resistance, material scarcity, and high production costs, leading to color tone changes and coloring when viewed from an inclined direction.
Innovation Solution
An optically anisotropic layered body comprising a first and second optically anisotropic layer with specific refractive index relationships and retardations, combined with a linear polarizer, to suppress reflection and coloring without the need for positive C plates, using materials like polyphenylene ether and polystyrene-based polymers with syndiotactic structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circularly polarizing plate using a positive C plate is provided on the display surface, then reflection of outside light is suppressed, but coloring of the display surface is observed when viewed from an inclined direction
Solution Approach 1:
The patent divides the circularly polarizing plate into two separate functional layers: a first optically anisotropic layer (positive A plate with nx>ny≥nz) and a second optically anisotropic layer (negative A plate with ny≥nx>nz). This segmentation allows each layer to be optimized independently, with the first layer providing reflection suppression and the second layer correcting coloring when viewed from inclined directions, thereby resolving the contradiction between suppressing reflection and preventing coloring.
Solution Approach 2:
The patent uses a composite structure combining two different optically anisotropic materials with opposite birefringence signs. The first layer uses a material with positive birefringence (nx>ny≥nz) and the second layer uses a material with negative birefringence (ny≥nx>nz). This composite approach enables the system to achieve both reflection suppression and coloring correction simultaneously, as each material contributes its specific optical properties to the overall performance.
2Ease of manufacture
If a positive C plate is used to reduce coloring when viewed from an inclined direction, then coloring is suppressed, but heat resistance decreases and production cost increases
Solution Approach 1:
The patent replaces the expensive and heat-sensitive positive C plate with a combination of two relatively simple positive A plates and negative A plates that can be manufactured using conventional techniques. The second optically anisotropic layer (negative A plate) provides the necessary optical compensation for inclined viewing without requiring the specialized positive C plate material, thereby reducing production cost and improving heat resistance while maintaining coloring suppression.
Solution Approach 2:
The patent changes the optical parameters of the system by using a negative A plate (with ny≥nx>nz) instead of a positive C plate. This parameter change allows the second layer to provide optical compensation for inclined viewing angles through its negative birefringence properties, achieving the same coloring suppression effect as a positive C plate but with better heat resistance and lower manufacturing complexity.
3Ease of manufacture
If a positive C plate is used to suppress coloring, then coloring is reduced, but the number of material choices is small and production cost is high
Solution Approach 1:
The patent makes the second optically anisotropic layer (negative A plate) a universal component that can be manufactured from various materials including conventional polymers and resins. This negative A plate serves multiple functions: it compensates for coloring when viewed from inclined directions, maintains optical performance across different wavelengths, and can be produced using standard manufacturing processes. The universality of this layer provides design flexibility and expands material choices beyond the limited options available for positive C plates.
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 coloring and color tone changes when viewing the display surface from an inclined direction, offering improved heat resistance and lower production costs while maintaining image quality by using a layered body with specific optical characteristics.
Implementation Method 1
an optically anisotropic layered body including a first optically anisotropic layer and a second optically anisotropic layer
Implementation Method 2
the first optically anisotropic layer satisfies nx1≥ny1>nz1, the second optically anisotropic layer satisfies ny22≤nz2
Implementation Method 3
the optically anisotropic layered body satisfies Re(450)Re(550)Re(650) and 0
Implementation Method 4
Outside light is converted to circularly polarized light in a certain rotation direction by the circularly polarizing plate
Data Source
AI summary
An optically anisotropic layered body including a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer satisfies the following formula (1), the second optically anisotropic layer satisfies the following formula (2), and the optically anisotropic layered body satisfies the following formulae (3) and (4):nx1≥ny1>nz1 Formula (1),ny2<nx2≤nz2 Formula (2),Re(450)<Re(550)<Re(650) Formula (3), and0<NZ<1.0 Formula (4),wherein nx1, ny1, nz1, nx2, ny2, nz2, Re(450), Re(550), Re(650) and NZ are as defined in the Specification.