IPS LCD Viewing Angle Compensation via Retardation Films
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Solution Overview
Problem
IPS-mode LCD devices suffer from reduced viewing angle characteristics when viewed diagonally due to light leakage, as the polarization axes of the polarizers are not perpendicular in this direction, leading to incomplete light absorption and a compromised black state.
Innovation Solution
Incorporating a positive C-film and a positive biaxial film between the polarizers and the liquid crystal display panel to alter the polarization state of light, ensuring the optical axis of the second polarizer matches its absorption axis, thereby improving viewing angles in the diagonal direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IPS-mode LCD device is used to improve viewing angle in vertical and horizontal directions, then viewing angle in those directions is improved, but viewing angle in diagonal direction deteriorates due to light leakage
Solution Approach 1:
A compensation film with specific retardation characteristics is introduced as an intermediary optical element between the liquid crystal layer and the polarizer. This film mediates the optical interaction by compensating for the phase difference between light components, thereby eliminating diagonal light leakage while preserving the IPS-mode's vertical and horizontal viewing angle advantages.
Solution Approach 2:
The patent changes the optical parameters of the system by selecting a compensation film with specific retardation values (Re=0 nm, Rth=-50 to -200 nm) and combining it with a biaxial film having controlled retardation ratios. This parameter optimization adjusts the polarization state transformation to achieve complete light absorption in diagonal directions while maintaining display performance in other directions.
2Object-affected harmful factors
If polarization axes of polarizers are arranged perpendicular to each other for complete light absorption, then black state is improved, but viewing angle in diagonal direction deteriorates
Solution Approach 1:
The compensation film acts as an intermediary that transforms the polarization state of light between the perpendicular polarizer axes. It introduces a controlled phase shift that rotates the polarization ellipse, enabling complete light absorption by the second polarizer even when viewing from diagonal directions, thus resolving the conflict between polarization geometry and viewing angle.
Solution Approach 2:
The patent employs a composite optical system combining the liquid crystal layer, compensation film with specific retardation characteristics, and biaxial film. This composite structure creates a multi-stage polarization transformation that simultaneously achieves complete light absorption and wide viewing angle coverage in all directions.
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 light leakage in the diagonal direction, maintaining a completely black state and enhancing the viewing angle characteristics by ensuring complete absorption of light by the second polarizer.
Implementation Method 1
the positive C-film having a retardation value of Re=0 nm in a horizontal direction and a retardation value of Rth=−50 ̃−200 nm in a thickness direction, and a positive biaxial film disposed between the liquid crystal display panel and the second polarizer to change a polarized state of light, the positive biaxial film having a retardation value of Re=80 ̃160 nm in a horizontal direction and a retardation value of Rth=−24 ̃−160 nm in a thickness direction
Data Source
AI summary
Disclosed is a liquid crystal display device having a wide viewing angle, in which compensation films are disposed between a liquid crystal display panel and polarizers to change a polarized state of light, which is incident on the liquid crystal display panel and output therefrom through the polarizers, thereby preventing light from being leaked in a diagonal direction of the liquid crystal display device in a normally black mode.