Liquid Crystal Display Panel Retardation Layer Configuration
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Solution Overview
Problem
Liquid crystal display panels face challenges in maintaining a high contrast ratio due to manufacturing variations in retardation, particularly in bright environments, which affect display luminance and power consumption.
Innovation Solution
A liquid crystal display panel configuration with specific arrangements of linear polarizers and retardation layers, where the absorption axes of polarizers and slow axes of retardation layers are set to optimize the retardation difference and angles, ensuring that at least one of the formulas (A) or (B) is satisfied, thereby minimizing the impact of manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the luminance of the backlight is increased to improve display luminance and contrast ratio, then the display luminance and contrast ratio are improved, but the power consumption increases
Solution Approach 1:
The patent changes the optical parameters of the display panel by introducing a retardation plate with specific retardation value (λ/4 plate) and controlling the thickness and refractive index of the hard coat layer. This modifies the phase difference of reflected light to achieve contrast ratio improvement without increasing backlight luminance, thereby resolving the contradiction between display luminance and power consumption
2Reliability
If the luminance of the backlight is increased to improve contrast ratio in bright environment, then the contrast ratio is improved, but the power consumption increases
Solution Approach 1:
The patent modifies the optical parameters by adding a retardation plate and controlling the hard coat layer thickness to be 50-200 nm, which changes the phase difference of reflected light. This parameter change enables contrast ratio improvement in bright environments without requiring increased power consumption from the backlight
3Reliability
If a retardation plate is added to suppress reflection and improve contrast ratio, then the contrast ratio is improved, but the device complexity increases
Solution Approach 1:
The patent combines the retardation plate with the protective hard coat layer, making the hard coat layer itself function as the retardation plate. This merging of functions reduces the number of separate components and simplifies the overall structure while maintaining the contrast ratio improvement effect
Solution Approach 2:
The hard coat layer is given multiple functions: it serves as both the protective coating and the retardation plate. By making the hard coat layer have dual functionality, the patent reduces device complexity while achieving the desired optical performance for improved contrast ratio
4Device complexity
If the retardation plate is made as a coating film to simplify structure, then the device complexity is reduced, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent specifies precise parameter ranges for the hard coat layer: thickness of 50-200 nm and refractive index of 1.5-2.0. By defining these parameter ranges, the patent balances the simplification of structure with the need for controllable manufacturing precision, ensuring consistent retardation performance
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
This configuration effectively suppresses contrast ratio reduction caused by manufacturing variations, enhancing display performance in bright environments while maintaining efficient power usage.
Implementation Method 1
a liquid crystal display panel in which a retardation plate (also referred to as a 'front-side retardation plate') is provided between a linearly polarizing plate (also referred to as a 'front-side linearly polarizing plate') arranged on an observer side
Implementation Method 2
The front-side retardation plate is a so-called λ/4 plate that is set so that linearly polarized light transmitted through the front-side linearly polarizing plate becomes circularly polarized light
Implementation Method 3
When the circularly polarized light is reflected (by an interface where a refractive index changes from a low level to a high level), phases of both a P wave and an S wave are shifted by n radian, resulting that a rotation direction is reversed
Data Source
AI summary
A liquid crystal display panel includes: a liquid crystal cell that has a liquid crystal layer; first and second linear polarizers arranged on an observer side and a back surface side of the liquid crystal cell; a first retardation layer arranged between the first linear polarizer and the liquid crystal layer; and a second retardation layer arranged between the first retardation layer and the second linear polarizer. The first and second linear polarizers and the first and second retardation layers are arranged so that at least one of following formulas (A) and (B) is satisfied:⅓≤(cos 2θ1)2/sin Δ≤ 3/2 (A)⅓≤(cos 2θ2)2/sin Δ≤ 3/2 (B)where a difference of retardation between the first retardation layer and the second retardation layer for light with a wavelength of 550 nm is Δ [rad], an angle formed by an absorption axis of the first linear polarizer and a slow axis of the first retardation layer is θ1, and an angle formed by an absorption axis of the second linear polarizer and a slow axis of the second retardation layer is θ2.