Reflective LCD Using Dye-Doped LC Without Polarizers
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Solution Overview
Problem
Conventional reflective liquid crystal display devices face challenges with high manufacturing costs, poor viewing angle characteristics, and low contrast due to the requirement for polarizers, brightness enhancement films, and phase retarders, as well as issues with high driving voltage and slow response speed.
Innovation Solution
A reflective liquid crystal display device utilizing a dye-doped liquid crystal composition with specific compounds and a chiral dopant, which includes a specular or diffuse reflective layer and optimized liquid crystal composition to enhance contrast, viewing angle, and operating temperature range, eliminating the need for polarizers and improving solubility of dichroic dyes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarizers, brightness enhancement films, and phase retarders are used in reflective liquid crystal display devices, then the display function is achieved, but manufacturing costs increase and viewing angle characteristics deteriorate
Solution Approach 1:
The patent extracts and eliminates the polarizers from the reflective liquid crystal display device structure. By using a dye-doped liquid crystal composition with inherent optical activity, the device achieves reflection and display functions without requiring external polarizing films, thereby reducing component count and manufacturing costs while improving viewing angle characteristics
Solution Approach 2:
The dye-doped liquid crystal composition serves multiple functions simultaneously: it provides the liquid crystal display function, generates optical activity for reflection, and eliminates the need for separate polarizer and brightness enhancement film components. This multi-functionality reduces device complexity while maintaining display performance
2Device complexity
If cholesteric liquid crystal is used to achieve reflection, then polarizers are not needed, but driving voltage increases and response speed decreases
Solution Approach 1:
The patent changes the key parameter of optical activity source from the helical structure of cholesteric liquid crystal to dichroic dye molecules aligned with liquid crystal molecules. This parameter change maintains the reflection function without requiring the helical structure, thereby reducing viscosity and improving response speed while keeping the device structure simple
Solution Approach 2:
The patent creates a composite liquid crystal composition by doping dichroic dyes into the liquid crystal matrix. This composite material combines the alignment properties of liquid crystal molecules with the optical absorption properties of dichroic dyes, achieving reflection without the slow response characteristics of pure cholesteric liquid crystal
3Ease of manufacture
If conventional liquid crystal composition is used, then manufacturing is simple, but contrast and viewing angle characteristics are poor
Solution Approach 1:
The patent develops a composite liquid crystal composition containing specific liquid crystal compounds (cyclic carbonates, cyclohexyl compounds) and dichroic dyes. This composite formulation achieves high contrast and wide viewing angle characteristics while maintaining manufacturability through established liquid crystal processing techniques
Solution Approach 2:
The patent optimizes the local molecular environment by selecting specific liquid crystal compounds with particular molecular structures (cyclic carbonate groups, cyclohexyl rings) that enhance the alignment and optical properties of the dichroic dye molecules, thereby improving contrast and viewing angle characteristics at the molecular level
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 achieves high contrast, wide viewing angles, and a wider operating temperature range while reducing manufacturing costs and eliminating disclination in intermediate states, with improved solubility and stability of the dye-doped liquid crystal composition.
Implementation Method 1
The liquid crystal molecular axis is in a direction perpendicular to that of the electric field when no electric field is applied, the light may transmit through the liquid crystal cell to the reflective layer, and re-transmit through the liquid crystal cell after being reflected
Implementation Method 2
the light can reach the reflective layer and be reflected via the retardation effect of the liquid crystal layer
Implementation Method 3
the light may transmit through the liquid crystal cell to the reflective layer, and re-transmit through the liquid crystal cell after being reflected
Implementation Method 4
a dye-doped liquid crystal composition... dichroic dyes have anisotropic absorption of visible light in the direction of long and short axes of molecules. The light is absorbed when the vibration direction of an incident light is consistent with the long axis of the dyes
Implementation Method 5
Due to the helical structure of the cholesteric liquid crystal molecules, there will be a Bragg reflection wherein the reflection wavelength is associated with the pitch and average refractivity of the cholesteric liquid crystal molecules
Data Source
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Figure 3(a)~3(b)
AI summary
A reflective liquid crystal display device comprising a dye-doped liquid crystal composition is disclosed in the present invention. The reflective liquid crystal display device comprises from top to bottom: an upper substrate, an upper conductive layer, an upper alignment layer, a dye-doped liquid crystal composition layer, a lower alignment layer, a lower conductive layer, a lower substrate and a reflective layer, the reflective liquid crystal display device does not comprise a polarizer, the dye-doped liquid crystal composition layer comprises a liquid crystal composition, a chiral dopant and a dichroic dye, the liquid crystal composition has a clearing point of no less than100°C and a K33/K22 of greater than 2. The reflective liquid crystal display device comprising the dye-doped liquid crystal composition provided by the present invention has advantages such as high contrast, high reliability, wide operating temperature range, wide viewing angle, good low-temperature stability, wide application range and no disclination in the intermediate state when applying a voltage, and overcomes the shortcomings of traditional reflective display devices, such as an increased costs caused by the requirements for polarizers, brightness enhancement films and phase retarders, and poor viewing angle characteristics.