Optical Compensation Films for TN LCD Viewing Angle and Brightness
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Solution Overview
Problem
TN mode liquid crystal display devices suffer from deterioration in front white brightness and impaired viewing angle performance, particularly experiencing gradation inversion when observed obliquely, which affects display quality.
Innovation Solution
A liquid crystal display device configuration with orthogonal polarizing layers, twisted alignment mode liquid crystal cells, and specific optical compensation films with carefully aligned and retardation-controlled layers to maintain front white brightness and enhance viewing angle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an optically anisotropic layer is arranged at an angle of 45 degrees to the absorption axis of polarizing plate, then viewing angle display performance is improved, but front white brightness is deteriorated due to front retardation
Solution Approach 1:
The optical compensation system is divided into multiple independent layers: a first optical compensation film with a first optically anisotropic layer, a second optical compensation film with a second optically anisotropic layer, and transparent supports. Each layer has specific retardation values and orientation arrangements that work together to resolve the contradiction between viewing angle performance and front brightness.
Solution Approach 2:
Different regions of the optical compensation system have different optical properties. The first and second optically anisotropic layers have specific retardation values (Re1, Re2) and orientation angles (θ1, θ2) that are locally optimized to compensate for viewing angle dependence while maintaining front brightness. The transparent supports also have specific retardation characteristics that contribute to the overall optical compensation.
2Reliability
If absorption axis of polarizing plate is arranged neither in parallel nor orthogonal to director direction of liquid crystals, then gradation inversion is reduced, but front white brightness is deteriorated
Solution Approach 1:
The orientation angles of the optically anisotropic layers relative to the absorption axis of the polarizing plate are precisely controlled to specific values (θ1 and θ2). This parameter optimization allows the system to reduce gradation inversion while minimizing the impact on front white brightness by achieving the right balance between compensation effectiveness and light transmission.
3Adaptability or versatility
If multiple optical compensation films with different retardation values are used, then viewing angle characteristic in all directions is improved, but device complexity increases
Solution Approach 1:
Multiple optical compensation functions are merged into an integrated system consisting of two optical compensation films with transparent supports. The first and second optically anisotropic layers are arranged in a specific sequence with defined orientation relationships, creating a unified optical compensation mechanism that achieves wide viewing angle characteristics without requiring separate complex compensation systems.
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 improves viewing angle performance with reduced asymmetry and gradation inversion, maintaining high front white brightness and providing excellent display quality across various observation angles.
Implementation Method 1
an optically anisotropic layer made from a liquid crystal composition on a transparent support composed of a polymer film
Implementation Method 2
the first transparent support has retardation and its in-plane slow axis is arranged in parallel or orthogonal to the director direction of liquid crystals
Implementation Method 3
a twisted alignment mode liquid crystal cell arranged between the first and the second substrates
Implementation Method 4
an absorption axis of a first polarizing plate is arranged at an angle of 45° to a director direction of liquid crystals on a surface of substrate in the liquid crystal cell
Data Source
AI summary
A liquid crystal display device has at least: a first and a second polarizing layers arranged so that respective absorption axes thereof are orthogonal to each other; a first and a second substrates arranged opposite to each other between the first and second polarizing layers, at least either one of which has a transparent electrode; a twisted alignment mode liquid crystal cell arranged between the first and the second substrates; a first optical compensation film arranged between the first polarizing layer and the liquid crystal cell, including a first transparent support and a layer formed by curing a composition containing a first liquid crystal compound; and a second optical compensation film arranged between the second polarizing layer and the liquid crystal cell, including a second transparent support and a layer formed by curing a composition containing a second liquid crystal compound, as defined herein.