Viewing Angle Film Stack for Moire-Free Oblique Light Shielding
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Solution Overview
Problem
Existing viewing angle control systems for image display devices, such as louver films, suffer from moire interference with high-definition pixels and are difficult to apply to curved surfaces, while other systems fail to adequately shield light emitted obliquely, leading to insufficient light shielding performance.
Innovation Solution
A viewing angle control system comprising a first polarizer with an absorption axis at 45° or greater, a retardation layer with 80 nm < Re < 250 nm, and a second polarizer with specific optical configurations, including B-plates and combinations of A- and C-plates, to compensate for vertical deviations and enhance light shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a louver film with alternating light transmission and absorption regions is used for viewing angle control, then light shielding performance in oblique directions is improved, but moire interference occurs with high-definition pixels
Solution Approach 1:
The patent extracts the periodic structure from the viewing angle control system by using a polarizer without periodic patterns combined with a retardation layer. This removes the source of moire interference while maintaining the light shielding function through optical polarization effects rather than physical blockage patterns.
Solution Approach 2:
The patent introduces a retardation layer as an intermediary between the polarizer and the display panel. This intermediary component modifies the polarization state of light to achieve viewing angle control without requiring periodic absorption patterns that cause moire effects.
2Object-affected harmful factors
If a thick louver film with base material layer is used for viewing angle control, then light shielding performance is improved, but the film becomes difficult to bend and apply to curved surfaces
Solution Approach 1:
The patent employs thin film structures (polarizer and retardation layer) that are inherently flexible and can conform to curved surfaces. This eliminates the need for thick rigid base material layers while maintaining viewing angle control functionality through optical effects.
Solution Approach 2:
The patent replaces the mechanical light blocking mechanism of thick louver films with an optical mechanism using polarizers and retardation layers. This substitution enables the system to achieve light shielding through polarization control rather than physical thickness, providing flexibility for curved applications.
3Device complexity
If a polarizer with absorption axis in in-plane direction is used for viewing angle control, then device complexity is reduced, but light shielding performance in oblique directions is insufficient
Solution Approach 1:
The patent combines a polarizer with a retardation layer to create a composite optical system. This composite structure achieves superior light shielding performance in oblique directions by leveraging the complementary optical properties of both components, while maintaining relative structural simplicity.
Solution Approach 2:
The patent addresses the limitation of in-plane polarizers by introducing the retardation layer that operates in the thickness dimension. This additional dimensional control mechanism enhances light shielding in oblique directions without significantly increasing in-plane structural complexity.
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 system effectively shields light emitted obliquely without causing moire, easily conforms to curved surfaces, and provides enhanced light shielding performance for high-definition image display devices.
Implementation Method 1
a first polarizer; a retardation layer; and a second polarizer in this order, in which an absorption axis of the first polarizer forms an angle of 45° or greater with respect to a surface
Implementation Method 2
the retardation layer satisfies Expression (1) and Expression (2), and the second polarizer has an absorption axis in an in-plane direction, an in-plane retardation Re of the retardation layer satisfies an expression of 80 nm
Data Source
AI summary
A viewing angle control system is used in combination with a high-definition image display device and sufficiently shields light emitted in a direction oblique to a normal direction of a film. The viewing angle control system includes at least a first polarizer, a retardation layer, and a second polarizer in this order, where an absorption axis of the first polarizer forms an angle of 45° or greater with respect to a surface, the retardation layer satisfies Expression (1): an in-plane retardation Re of the retardation layer satisfies an expression of 80 nm<Re<250 nm, and Expression (2): in a case of Nz=Rth/Re+0.5, an expression of 1.5<Nz<6 or −5<Nz<−0.5 is satisfied, where Rth represents a retardation of the retardation layer in a thickness direction, and the second polarizer has an absorption axis in an in-plane direction.