Reflective Polarizing Plate for Liquid Crystal Display Light Efficiency
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Solution Overview
Problem
Liquid crystal display devices using backlights suffer from reduced light efficiency due to absorption by polarizing plates, leading to decreased display brightness and a reddish phenomenon caused by increased transmittance in the longer wavelength range.
Innovation Solution
Incorporating a reflective polarizing plate with layers of different refractive indices and compensation layers with reverse wavelength distribution features in the upper polarizing plate to optimize light reflection and transmission, minimizing the reddish phenomenon while enhancing light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflective polarizing plate with layers of different refractive indices is used, then light efficiency is improved, but a reddish phenomenon occurs due to increased transmittance in the longer wavelength range
Solution Approach 1:
The patent applies parameter changes by carefully controlling the refractive indices and thicknesses of the first and second layers in the reflective polarizing plate. By adjusting these parameters, the invention optimizes light reflection efficiency while compensating for the reddish phenomenon through precise refractive index matching and layer thickness optimization.
Solution Approach 2:
The patent uses composite materials by combining the first layer (with refractive index n1) and the second layer (with refractive index n2) in a multi-layer structure. This composite approach allows the reflective polarizing plate to achieve both high light efficiency and color balance by leveraging the complementary optical properties of different materials.
2Illumination intensity
If a polarizing plate absorbs 50% of incident light, then polarization function is achieved, but display brightness deteriorates
Solution Approach 1:
The patent inverts the conventional approach by using a reflective polarizing plate instead of an absorptive polarizing plate. Rather than absorbing 50% of incident light, the reflective type reflects unwanted polarized light while transmitting desired light, thereby improving display brightness without sacrificing polarization function.
Solution Approach 2:
The patent converts the harmful effect of light absorption into a beneficial reflective mechanism. By using the reflective polarizing plate, light that would have been absorbed is instead reflected, turning energy loss into a useful function that maintains brightness while achieving polarization.
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 light efficiency by reflecting light in the x-axis direction and allowing light in the y-axis direction to pass through, reducing the reddish phenomenon and maintaining display brightness across various viewing angles.
Implementation Method 1
A reflective polarizing plate including first and second layers having different refractive indexes which are repeatedly stacked to allow some light to pass through and allow remaining light to be reflected
Implementation Method 2
Since the first and second layers have different refractive indexes in a reflective polarizing plate, a refractive index in one axis direction among three axes directions may be different
Implementation Method 3
The liquid crystal display device generates an electric field in the liquid crystal layer by applying a voltage to the electric field generating electrode, determines an alignment of liquid crystal molecules of the liquid crystal layer through the generated electric field, and controls polarization of incident light
Data Source
AI summary
Disclosed is a liquid crystal display device, including: first and second substrates, which are spaced apart from each other by a predetermined interval while facing each other; a reflective polarizing plate disposed under the first substrate, and including a first refractive index layer and a second refractive index layer, which have different refractive indexes and are repeatedly stacked; first and second compensation layers sequentially stacked on the second substrate, and an upper polarizing plate including a polarizing layer formed on the second compensation layer; and a liquid crystal layer formed between the first and second substrates.