Photoalignment Layer for LCDs Using CBDA Copolymers
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Solution Overview
Problem
Conventional liquid crystal display manufacturing methods using the rubbing process can generate minute particles and electrostatic discharge, leading to alignment issues and reduced display quality due to the lack of effective photoalignment techniques.
Innovation Solution
A photoalignment agent comprising a copolymer formed from cyclobutanedianhydride and its derivative, combined with a cross-linking agent and a diamine, is used to create a photoalignment layer that optimizes afterimage and film strength through controlled anisotropy induction by light irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rubbing method using fiber material and polymer layer is used to align liquid crystals, then liquid crystal alignment is achieved, but minute particles and electrostatic discharge are generated causing manufacturing problems
Solution Approach 1:
The patent replaces the mechanical rubbing method with a photoalignment method using light irradiation. The polymer layer is treated with polarized light to create anisotropic alignment without physical contact, thereby eliminating particle generation and electrostatic discharge while maintaining liquid crystal alignment uniformity.
Solution Approach 2:
The patent changes the alignment mechanism from mechanical force to optical field interaction. By using polarized light with specific wavelength and intensity parameters, the polymer molecules are oriented through photoinduced anisotropy, achieving alignment without the harmful side effects of mechanical rubbing.
2Object-generated harmful factors
If a photoalignment method is used to avoid particles and ESD, then manufacturing cleanliness is improved, but afterimage and film strength need optimization
Solution Approach 1:
The patent uses a composite polymer system comprising multiple polymer components with different functions. One polymer provides photoalignment capability while another enhances film strength and reduces afterimage. This composite approach allows simultaneous optimization of cleanliness, reliability, and display quality.
Solution Approach 2:
The patent applies different polymer components in specific ratios to achieve local optimization of properties. The polymer composition is designed to have specific regions or aspects optimized for photoalignment while other aspects are optimized for film strength and afterimage reduction, achieving overall performance balance.
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 enhances the alignment of liquid crystals, improving display quality by minimizing afterimage issues and maintaining film strength, thereby addressing the limitations of traditional rubbing methods.
Implementation Method 1
a photoalignment agent including: (a) a copolymer formed from at least one compound of cyclobutanedianhydride (CBDA) and a cyclobutanedianhydride derivative, and a first diamine including alkylene group (—CkH2k−, k being a natural number); and (b) a cross-linking agent including an alkylene group (—CnH2n−, n being a natural number)
Implementation Method 2
a photoalignment method where anisotropy is induced to the polymer layer by light irradiation to align the liquid crystals
Data Source
AI summary
A liquid crystal display device is provided. An exemplary embodiment of the present invention provides a liquid crystal display device including: a first substrate; a thin film transistor disposed on the first substrate; a first electrode connected to the thin film transistor; and a first alignment layer disposed on the first electrode. The first alignment layer includes: a copolymer formed from at least one compound of cyclobutane dianhydride (CBDA) and a cyclobutane dianhydride derivative, and a first diaminean including alkylene group (—CkH2k−, k being a natural number); and a cross-linking agent including an alkylene group (—CnH2n−, n being a natural number), wherein the copolymer includes polyimide.