Liquid Crystal Display Polymer Barrier Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal display devices with photoalignment films suffer from image sticking and stains due to radical decomposition from photoreactive functional groups, leading to decreased voltage holding ratio and contrast ratio, especially in high-temperature environments.
Innovation Solution
A polymer layer is formed between the photoalignment film and the liquid crystal layer using thermally polymerizable monomers with epoxy groups and a curing agent containing amino, hydrazide, or imidazole groups, reducing direct contact between photoreactive functional groups and liquid crystal molecules and preventing radical transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photoalignment film containing photoreactive functional groups is used, then liquid crystal alignment is improved, but image sticking and stains occur due to radical decomposition
Solution Approach 1:
A polymer layer is introduced as an intermediary between the photoalignment film and the liquid crystal layer. This polymer layer acts as a barrier that prevents radicals generated from the photoreactive functional groups in the photoalignment film from transferring to the liquid crystal molecules, thereby eliminating image sticking and stains while maintaining the alignment function of the photoalignment film.
2Manufacturing precision
If light irradiation is applied to the photoalignment film, then liquid crystal alignment is achieved, but radicals are generated causing voltage holding ratio degradation
Solution Approach 1:
The polymer layer serves as a protective intermediary that blocks the transfer of radicals from the photoalignment film to the liquid crystal layer during light irradiation. This prevents the degradation of voltage holding ratio caused by radical-induced damage to liquid crystal molecules, while still allowing the photoalignment process to proceed effectively.
3Temperature
If high-temperature environment is used, then display performance is enhanced, but radical dissolution into liquid crystal layer increases causing image sticking
Solution Approach 1:
The polymer layer acts as a thermal and radical barrier between the photoalignment film and the liquid crystal layer. In high-temperature environments, this intermediary layer prevents radicals from dissolving into the liquid crystal layer, thereby maintaining display performance while preventing image sticking and other reliability issues.
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 maintains a favorable voltage holding ratio and prevents image sticking and contrast ratio degradation in both room-temperature and high-temperature environments by reducing radical transfer, thus enhancing the stability and performance of liquid crystal display devices.
Implementation Method 1
Irradiating a photoalignment film with light (e.g., light from a backlight including visible light and ultraviolet light) causes decomposition of photoreactive functional groups, resulting in radicals.
Implementation Method 2
thermally polymerizable monomers with epoxy groups and a curing agent containing amino, hydrazide, or imidazole groups... thermally polymerizing these components so as to form a polymer layer
Data Source
AI summary
With the use of a photoalignment film, the present invention provides a liquid crystal display device capable of maintaining a favorable voltage holding ratio and reducing or preventing image sticking, stains, and a decrease in contrast ratio for a long time not only in a room-temperature environment but also in a high-temperature environment; and a method for producing such a liquid crystal display device. The liquid crystal display device of the present invention includes paired substrates; a liquid crystal layer disposed between the substrates; a photoalignment film disposed between at least one of the substrates and the liquid crystal layer; and a polymer layer disposed between the photoalignment film and the liquid crystal layer, wherein the polymer layer has a structure derived from a specific epoxy-based monomer and a structure derived from a specific curing agent.