Circularly Polarizing Plate with Retardation Control for Oblique Black Visibility
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Solution Overview
Problem
Conventional circularly polarizing plates used in display devices do not adequately improve visibility of black color when viewed obliquely and are not thin enough, failing to meet modern requirements for display device performance.
Innovation Solution
A circularly polarizing plate configuration comprising a polarizer, a λ/2 plate laminate of a first A-plate and a first C-plate, and a λ/4 plate laminate of a second A-plate and a second C-plate, where one C-plate is a cellulose acylate film with specific retardation properties and the other is an optically anisotropic layer, achieving improved visibility of black color and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional circularly polarizing plate configuration is used, then the basic function of suppressing external light reflection is achieved, but the visibility of black color in oblique directions is not sufficiently improved
Solution Approach 1:
The patent applies parameter changes by precisely controlling the retardation values (Re and Rth) of each optical layer. The first C-plate has Rth of 30-50 nm, the optically anisotropic layer has Rth of -60 to -30 nm, and specific Re values are mandated for both λ/2 plate and λ/4 plate. These parameter specifications optimize the visibility of black color in oblique directions while maintaining structural feasibility.
Solution Approach 2:
The patent employs composite materials by combining a cellulose acylate film (first C-plate) with an optically anisotropic layer containing liquid crystal compounds. This composite structure integrates the advantages of both materials: the cellulose acylate provides positive birefringence and structural stability, while the liquid crystal layer provides negative birefringence and optical control, together achieving superior black visibility.
2Length of moving object
If the circularly polarizing plate is made thinner to meet thinning requirements, then the overall device thickness is reduced, but the optical performance and visibility improvement may be compromised
Solution Approach 1:
The patent achieves thinning while maintaining performance through parameter optimization. The first C-plate (cellulose acylate) has Rth of 30-50 nm which can be achieved with reduced thickness, and the optically anisotropic layer has Rth of -60 to -30 nm. The combined thickness is controlled to be 60 μm or less, demonstrating that proper parameter selection enables thinning without sacrificing optical performance.
Solution Approach 2:
The patent applies local quality by assigning specific functional characteristics to different layers. The cellulose acylate layer provides localized positive birefringence with controlled Rth, while the optically anisotropic layer provides localized negative birefringence. This distributed functional allocation allows each layer to be optimized for minimal thickness while contributing to overall performance.
3Illumination intensity
If multiple optical layers are combined to improve visibility, then the optical performance is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent manages manufacturing precision by establishing clear parameter ranges for each layer. The first C-plate Rth is specified as 30-50 nm, the optically anisotropic layer Rth as -60 to -30 nm, and the combined thickness is controlled to 60 μm or less. These ranges provide manufacturing flexibility while ensuring performance, balancing precision requirements with manufacturability.
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 proposed configuration enhances the visibility of black color in oblique directions while maintaining a thin profile, addressing the limitations of existing technologies by utilizing cellulose acylate films and optically anisotropic layers with precise retardation properties.
Implementation Method 1
one of the first C-plate and the second C-plate is a cellulose acylate film having a retardation Rth in a thickness direction at a wavelength of 550 nm of 30 to 50 nm, the other of the first C-plate and the second C-plate is an optically anisotropic layer including a liquid crystal compound having a retardation Rth in a thickness direction at a wavelength of 550 nm of −60 to −30 nm
Data Source
AI summary
The present invention provides a circularly polarizing plate that improves the visibility of black color in an oblique direction when being applied to a display device and having a small thickness, the display device including a circularly polarizing plate. The circularly polarizing plate is a circularly polarizing plate including, in this order, a polarizer, a λ/2 plate, and a λ/4 plate, in which the λ/2 plate is a laminate of a first A-plate and a first C-plate, the λ/4 plate is a laminate of a second A-plate and a second C-plate, one of the first C-plate and the second C-plate is a cellulose acylate film having a predetermined Rth, and the other of the first C-plate and the second C-plate is an optically anisotropic layer including a liquid crystal compound having a predetermined Rth or a cellulose acylate film having a predetermined Rth.