Photoalignment Film for LCD Reliability
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Solution Overview
Problem
Liquid crystal display (LCD) elements face issues with poor reliability and residual images due to dust and static electricity generated during the rubbing treatment process, which affects the uniformity and quality of liquid crystal alignment.
Innovation Solution
A liquid crystal alignment agent comprising a polymer obtained from a tetracarboxylic dianhydride component and a diamine component, combined with a photosensitive polysiloxane containing cinnamic acid and aromatic heterocyclic derivatives, and a solvent, which allows for precise control of liquid crystal alignment without generating static electricity or dust, thereby improving reliability and reducing residual images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubbing treatment is used to perform liquid crystal alignment, then liquid crystal alignment can be achieved, but dust and static electricity are generated causing poor display and reduced yield
Solution Approach 1:
The patent replaces the mechanical rubbing treatment with a photoalignment method using polarized or non-polarized radiation. The photosensitive alignment film undergoes photoinduced in-plane rotation of its transition moment, achieving liquid crystal alignment without mechanical contact. This substitution eliminates dust generation and static electricity problems inherent in rubbing treatment.
Solution Approach 2:
The patent changes the alignment mechanism from mechanical force (rubbing) to optical field interaction (photoinduced rotation). By using polarized radiation with specific polarization directions and the photosensitive material's optical properties, the liquid crystal molecules are aligned through photoinduced in-plane rotation of the transition moment, fundamentally changing the physical parameter from mechanical to optical.
2Manufacturing precision
If a rubbing treatment is used to perform liquid crystal alignment, then alignment can be achieved, but the treatment time and cost increase for large substrates
Solution Approach 1:
The patent replaces the time-consuming mechanical rubbing process with rapid photoalignment using polarized radiation. The photoinduced in-plane rotation of the transition moment in the photosensitive alignment film occurs quickly under irradiation, significantly reducing treatment time while maintaining uniform alignment across large substrate areas.
Solution Approach 2:
The photoalignment method using polarized radiation can uniformly treat entire large substrate surfaces simultaneously, unlike rubbing treatment which requires sequential mechanical contact. The photosensitive alignment film provides universal applicability across different substrate sizes and shapes, achieving consistent alignment uniformity regardless of substrate dimensions.
3Manufacturing precision
If a rubbing treatment is used to perform liquid crystal alignment, then alignment can be achieved, but the surface unevenness of dense pixels makes uniform rubbing difficult
Solution Approach 1:
The patent replaces mechanical rubbing with optical field-based photoalignment. The polarized radiation penetrates and interacts with the photosensitive alignment film regardless of surface micro-unevenness caused by dense pixel structures. The photoinduced in-plane rotation of the transition moment occurs uniformly across the entire surface, overcoming the limitation of mechanical contact methods on uneven surfaces.
Solution Approach 2:
The patent transitions from two-dimensional mechanical surface contact (rubbing) to three-dimensional optical field penetration. The polarized radiation acts throughout the volume of the photosensitive alignment film, inducing uniform photoinduced in-plane rotation of the transition moment regardless of surface topography variations from dense pixel structures.
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 enables the formation of LCD elements with improved reliability and reduced residual images, enhancing display quality by providing a uniform and stable liquid crystal alignment film.
Implementation Method 1
provides liquid crystal alignment capability by irradiating polarized or non-polarized radiation on a photosensitive film
Implementation Method 2
a photoalignment method, such as that described in JP 2005-037654 A, provides liquid crystal alignment capability by irradiating polarized or non-polarized radiation on a photosensitive film
Data Source
AI summary
A liquid crystal alignment agent allowing formation of an LCD element having good reliability and less residual image, a liquid crystal alignment film, and an LCD element having the liquid crystal alignment film are shown. The liquid crystal alignment agent includes a polymer (A), a photosensitive polysiloxane (B), and a solvent (C). The polymer (A) is obtained by reacting a mixture that includes a tetracarboxylic dianhydride component (a-1) and a diamine component (a-2). The photosensitive polysiloxane (B) is obtained by reacting a polysiloxane (b-1) having an epoxy group with a cinnamic acid derivative (b-2) and an aromatic heterocyclic derivative (b-3) containing nitride, oxide or sulfide.