Anisotropic Light Control Member for TN LCD Viewing Angle
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Solution Overview
Problem
Liquid crystal display devices with twisted nematic mode suffer from increased luminance change when viewed from the vertical direction due to varying retardation of liquid crystal molecules, leading to poor viewing angle characteristics and gray scale inversion, which existing solutions like biaxial retardation plates and isotropic scattering films fail to adequately address.
Innovation Solution
A liquid crystal display device configuration featuring a liquid crystal panel with polarizers on both sides, an illumination device, and a light control member that anisotropically diffuses light in the azimuthal direction, aligning the luminance viewing angle's narrow direction with the light control member's high diffusivity direction to enhance viewing angle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a biaxial retardation plate is used to compensate liquid crystal layer retardation, then the retardation compensation is effective and cost is reduced, but the luminance change in the vertical direction is increased
Solution Approach 1:
An isotropic scattering film is introduced as an intermediary component between the liquid crystal panel and the viewer. This scattering film diffuses light in the vertical direction to reduce luminance change, while maintaining the effectiveness of the biaxial retardation plate for retardation compensation. The scattering film acts as a mediator that addresses the luminance uniformity issue without interfering with the optical compensation function.
2Illumination intensity
If an isotropic scattering film is disposed on the viewing side to improve luminance uniformity, then light diffusion is enhanced, but the luminance viewing angle is not sufficiently widened
Solution Approach 1:
The patent combines an isotropic scattering film with a biaxial retardation plate to create a composite optical compensation system. The scattering film provides luminance uniformity through light diffusion, while the biaxial retardation plate maintains proper retardation compensation across different viewing angles. This composite structure achieves both luminance uniformity and wide viewing angle characteristics that neither component can achieve alone.
3Ease of manufacture
If the liquid crystal cell uses twisted nematic mode for simple structure, then manufacturing is easier, but gray scale inversion occurs when viewed from oblique directions
Solution Approach 1:
Optical compensation elements (biaxial retardation plate and isotropic scattering film) are introduced as intermediary components between the twisted nematic liquid crystal cell and the viewer. These elements compensate for the viewing angle limitations and gray scale inversion inherent in TN mode without requiring a change in the liquid crystal cell structure itself, thus maintaining manufacturing simplicity while improving viewing angle characteristics.
Solution Approach 2:
The patent creates a composite display system combining twisted nematic liquid crystal material with biaxial retardation plate and isotropic scattering film. This composite structure allows the simple TN mode cell to achieve wide viewing angle characteristics and prevent gray scale inversion through the combined optical effects of the multiple layers.
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 improves luminance viewing angle characteristics and suppresses gray scale inversion when the screen is viewed from an oblique direction, providing a wider viewing angle with enhanced display quality.
Implementation Method 1
a light control member that is arranged on the light emission side of the liquid crystal panel, and anisotropically diffuses light emitted from the liquid crystal panel in an azimuthal direction as viewed from a direction normal to the liquid crystal panel
Implementation Method 2
liquid crystal molecules are aligned while being twisted in the liquid crystal cell of a TN mode, and thus the retardation of the liquid crystal differs depending on the angle for observing the screen and the gray scale
Implementation Method 3
a biaxial film as a retardation compensation element provided between at least one of the pair of polarizers and the liquid crystal cell
Data Source
AI summary
A liquid crystal display device includes a liquid crystal panel that includes a liquid crystal cell including a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates, and a pair of polarizers arranged on a light incident side and a light emission side of the liquid crystal layer; an illumination device that is arranged on the light incident side of the liquid crystal cell, and emits light toward the liquid crystal cell; and a light control member that is arranged on the light emission side of the liquid crystal panel, and controls an emission direction of light emitted from the liquid crystal panel by anisotropically diffusing the light in an azimuthal direction as viewed from a direction normal to the liquid crystal panel. The light control member is arranged such that an azimuthal direction in which a luminance viewing angle of the liquid crystal panel is relatively narrow and an azimuthal direction in which diffusivity of the light control member is relatively high approximately coincide with each other.