Reflective LCD with Twist Alignment and Transverse Field
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Solution Overview
Problem
Current reflective liquid crystal display devices struggle to achieve high reflectivity with low voltage while maintaining high contrast, especially for in-cell type touch panels capable of performing display in a reflection mode.
Innovation Solution
A liquid crystal display device configuration that includes a first substrate with a reflective layer, a pair of electrodes generating a transverse electrical field, and a liquid crystal layer with a twist alignment. The liquid crystal material is of a positive type, and specific parameters such as twist angle, birefringence index, and dielectric constant are optimized to achieve high reflectivity and low voltage operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a positive type liquid crystal material is used in FFS mode reflective display, then the device structure is simplified with both electrodes on the active matrix substrate side, but high reflectivity cannot be obtained particularly in white display
Solution Approach 1:
The patent changes the fundamental parameter of liquid crystal material type from positive to negative, which fundamentally alters the interaction between the liquid crystal molecules and the transverse electrical field. This parameter change enables both high reflectivity in white display and low driving voltage simultaneously, resolving the contradiction between simplified device structure and high reflectivity performance.
2Illumination intensity
If a negative type liquid crystal material is used, then high reflectivity can be obtained in white display, but it is difficult to reduce voltage
Solution Approach 1:
The patent optimizes specific parameters of the negative type liquid crystal material including dielectric constant anisotropy (Δε), birefringence (Δn), and viscosity within specific ranges. These parameter optimizations enable the system to achieve high reflectivity while simultaneously reducing the driving voltage to 2.0V or lower, resolving the contradiction between high reflectivity and low voltage operation.
3Illumination intensity
If twist angle is increased to improve reflectivity, then white display performance improves, but contrast ratio may be compromised
Solution Approach 1:
The patent establishes a specific twist angle range of 78° to 90° (preferably 80° to 85°) and combines it with optimized negative type liquid crystal material parameters. This coordinated parameter optimization ensures that white reflectivity is maximized while maintaining contrast ratio above 5:1, resolving the contradiction between white display performance and contrast ratio.
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 proposed configuration enables high reflectivity and high contrast in reflective mode operation, suitable for in-cell type touch panels, while reducing power consumption and achieving low voltage drive.
Implementation Method 1
the liquid crystal layer takes a twist alignment when no voltage is applied, and a twist angle is equal to or more than 78° and equal to or less than 90° when no voltage is applied
Implementation Method 2
a first electrode and a second electrode configured to generate a transverse electrical field in the liquid crystal layer
Implementation Method 3
when a voltage is applied, at least a liquid crystal molecule, of the plurality of liquid crystal molecules, positioned in a central portion of the liquid crystal layer in a thickness direction is rotated
Implementation Method 4
the first substrate includes a reflective layer configured to reflect light
Implementation Method 5
the liquid crystal material is a positive type
Data Source
AI summary
A liquid crystal display device includes a first substrate, a second substrate, and a liquid crystal layer. The first substrate includes a reflective layer, a first electrode and a second electrode configured to generate a transverse electrical field in the liquid crystal layer, and a first horizontal alignment film. An electrode, of the first electrode and the second electrode, disposed on a side of the liquid crystal layer includes a plurality of belt-shaped portions and a slit positioned between two adjacent belt-shaped portions of the plurality of belt-shaped portions, the liquid crystal layer is constituted by a liquid crystal material including a liquid crystal molecule, the liquid crystal material is a positive type. The second substrate includes a second horizontal alignment film being in contact with the liquid crystal layer, and the liquid crystal layer takes a twist alignment when no voltage is applied.