LCD Alignment Layer Composition for Uniform Pretilt Angle
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Solution Overview
Problem
In liquid crystal display (LCD) devices, the use of reactive mesogens (RMs) can lead to non-uniform pretilt angles of liquid crystal molecules due to incomplete curing, resulting in afterimages and reliability issues, and high-intensity UV light can cause organic material decomposition.
Innovation Solution
An LCD device with a composition including a lower and upper alignment layer formed from a polyimide mixture containing a base dianhydride, diamine, crosslinker, and RM diamine, where the RM diamine content is between 10 wt% to 80 wt%, and an additional RM is used in the liquid crystal layer in minimal amounts, allowing for improved alignment and curing with low-intensity UV light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-intensity UV light is used to completely remove reactive mesogen from liquid crystal molecules, then alignment uniformity is improved, but organic material decomposition occurs and reliability deteriorates
Solution Approach 1:
The patent changes the chemical structure parameters of the reactive mesogen by introducing specific functional groups (carboxyl, hydroxyl, or amino groups) that enable complete curing at lower UV intensities, thereby preventing organic material decomposition while achieving uniform alignment
Solution Approach 2:
The patent uses specific functional groups as intermediaries that facilitate the curing reaction between the reactive mesogen and the alignment layer, enabling complete removal of the reactive mesogen at lower UV intensities without causing material decomposition
2Ease of operation
If reactive mesogen is used to align liquid crystal molecules, then alignment direction is induced, but non-uniform pretilt angles occur due to incomplete curing resulting in afterimages
Solution Approach 1:
The patent modifies the chemical parameters of the reactive mesogen by incorporating specific functional groups that enhance reactivity and ensure complete curing, thereby achieving uniform pretilt angles and eliminating afterimages while maintaining alignment direction induction
Solution Approach 2:
The patent performs preliminary chemical modification of the reactive mesogen structure before the alignment process, ensuring that the curing reaction will proceed completely under the applied UV conditions, which prevents non-uniform pretilt angles and afterimages
3Reliability
If patterned vertical alignment mode is used to achieve high contrast ratio and wide viewing angle, then slit portions are formed through electric field generating electrode, but aperture ratio decreases
Solution Approach 1:
The patent applies local quality by forming slit portions only in specific regions (microslit mode) or using selective alignment layer treatment in specific areas, allowing the alignment function to be localized where needed while preserving aperture ratio in other regions
Solution Approach 2:
The patent segments the alignment function by dividing the electrode structure into regions with and without slit portions, or by segmenting the alignment layer treatment, thereby achieving the necessary alignment control while minimizing the impact on aperture 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
This configuration enhances display quality by improving viewing angle and response time, reducing afterimages, and preventing organic material decomposition while minimizing UV power consumption.
Implementation Method 1
a photocrosslinkable copolymer including a mesogenic group, called a reactive mesogen (RM), having liquid crystal properties, is irradiated by polarized ultraviolet (UV) light to induce anisotropy
Implementation Method 2
heat processing is performed on the photocrosslinkable copolymer to enhance the anisotropy of the alignment layer
Implementation Method 3
a voltage is applied to an electric field generating electrode to provide the liquid crystal layer with an electric field. The arrangement of liquid crystal molecules of the liquid crystal layer is controlled in response to the electric field
Data Source
AI summary
A liquid crystal display device that includes an array substrate, an opposite substrate and a liquid crystal display layer is described. The array substrate includes a pixel electrode and a lower alignment layer. The pixel electrode has a plurality of slit portions extending in different directions. The lower alignment layer includes a reactive mesogen (RM) diamine is formed on the pixel electrode to induce an alignment direction of the liquid crystal molecules. An upper alignment layer is formed on a common electrode of the opposite substrate. The RM is cured at surfaces of the lower and upper alignment layers in response to ultraviolet (UV) light, so that liquid crystal molecules have a pretilt angle. Therefore, the aperture ratio and the response time may be improved, and afterimages may be decreased, so that display quality may be improved.