Cholesteric Liquid Crystal Display Without Polarizers
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Solution Overview
Problem
Conventional liquid crystal display devices face challenges in achieving high transmittance and efficient light usage while minimizing manufacturing costs and processing steps, particularly in utilizing cholesteric liquid crystals for reflective and bistable state performances.
Innovation Solution
A liquid crystal display device configuration incorporating a backlight source, a first handedness cholesteric liquid crystal film layer, an array substrate, a color filter substrate, and a second handedness cholesteric liquid crystal layer, with an optional reflective sheet, which eliminates the need for polarizers and allows for improved light reuse and reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional liquid crystal display devices use traditional configurations with polarizers, then the structure is simple to manufacture, but the transmittance is low and light source efficiency is poor
Solution Approach 1:
The patent removes the polarizer layer from the conventional LCD structure. By extracting this component, the device achieves higher transmittance and light source efficiency while maintaining manufacturability through the use of cholesteric liquid crystal's inherent optical properties
Solution Approach 2:
The patent changes the optical parameters by using cholesteric liquid crystal with specific pitch values (380-420nm for first layer, 620-680nm for second layer) that selectively reflect different wavelengths. This parameter change enables wavelength-specific reflection without requiring polarizers, improving both transmittance and manufacturing simplicity
2Loss of energy
If cholesteric liquid crystal is used for reflective performance, then light source efficiency can be improved, but the device complexity increases due to multiple cholesteric layers
Solution Approach 1:
The patent divides the cholesteric liquid crystal system into two distinct layers with different handedness and pitch values. The first layer (380-420nm pitch) handles blue-green reflection while the second layer (620-680nm pitch) handles red reflection. This segmentation enables broad-spectrum reflective performance while maintaining a relatively simple overall structure
Solution Approach 2:
The cholesteric liquid crystal layers serve multiple functions simultaneously: they act as wavelength-selective mirrors, polarization-free reflectors, and bistable state elements. This multi-functionality reduces the need for additional components, balancing improved light source efficiency with controlled device complexity
3Illumination intensity
If a reflective sheet is added below the backlight source, then brightness is improved, but the device complexity increases
Solution Approach 1:
The patent combines the reflective sheet function with the cholesteric liquid crystal layers. The reflective sheet below the backlight source and the cholesteric layers above work together as an integrated light management system, merging reflection and wavelength selection functions to improve brightness without proportionally increasing complexity
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 configuration enhances transmittance, light source efficiency, and brightness, while reducing energy consumption and manufacturing costs by leveraging the reflective and bistable properties of cholesteric liquid crystals, and simplifying the manufacturing process.
Implementation Method 1
When the arrangement of the molecules of an upper layer is rotated by 360 degrees with respect to a lower layer, the distance between the upper layer and the lower layer is a pitch p. According to the direction of the spiral structure, the cholesteric liquid crystal is divided into left-handed cholesteric liquid crystal and right-handed cholesteric liquid crystal, which can respectively reflect left circularly polarized light and right circularly polarized light.
Implementation Method 2
The reflection of the cholesteric liquid crystal follows the Bragg law: λ=n*p (wherein n is average refractivity of the cholesteric liquid crystal, and p is a pitch of the cholesteric liquid crystal).
Implementation Method 3
Cholesteric liquid crystal comprises a plurality of layers. Molecules are arranged along a same direction in each of the layers, but the arrangement directions of molecules are rotated by an angle of about 15 minutes between any two adjacent layers, so that a spiral structure can be obtained in the stacked layers.
Data Source
AI summary
A liquid crystal display device, which comprises: a backlight source (1); a first handedness cholesteric liquid crystal film layer (2), located at an upper side of the backlight source (1) as a light emitting surface; an array substrate (3), located at an upper side of the first handedness cholesteric liquid crystal film layer (2); a color filter substrate (5), located at an upper side of the array substrate (3); and a second handedness cholesteric liquid crystal layer (4), sandwiched between the array substrate (3) and the color filter substrate (5), the first handedness being opposite to the second handedness. The liquid crystal display device greatly improves light efficiency and transmittance of the display and saves the processing steps and manufacturing costs.