Liquid Crystal Display Reactive Mesogen Alignment UV Curing
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Solution Overview
Problem
The manufacturing of liquid crystal displays faces issues with vertical stripe patterns and water spots due to the use of reactive mesogen alignment layers, which are not fully hardened and reacted during the photo-alignment process, leading to defects and reduced production yield.
Innovation Solution
A method involving the use of ultraviolet rays with specific wavelengths to pre-tilt and align liquid crystals, followed by secondary irradiation to fully react and remove remaining reactive mesogen, improving the voltage holding rate and eliminating vertical stripe patterns and water spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If photo-alignment process is used to eliminate rubbing process, then scratches and static electricity problems are solved, but vertical stripe patterns and water spots occur due to incomplete reaction of reactive mesogen
Solution Approach 1:
The patent divides the photo-alignment process into two separate stages: first irradiation (310-380 nm UV) to pre-react the reactive mesogen and form initial alignment, and second irradiation (300-360 nm UV) to complete the reaction and remove remaining reactive mesogen. This segmentation resolves the contradiction by addressing both the initial alignment need and the complete reaction requirement separately, eliminating vertical stripe patterns and water spots while maintaining the benefits of photo-alignment over rubbing process.
2Device complexity
If single wavelength UV irradiation is used for photo-alignment, then process is simple, but reactive mesogen does not fully react leading to alignment defects
Solution Approach 1:
The patent segments the UV irradiation into two distinct steps with different wavelength ranges: first irradiation using 310-380 nm UV light to initiate alignment, and second irradiation using 300-360 nm UV light to complete the reaction. This segmentation ensures full reaction of reactive mesogen without excessive complexity, achieving high alignment quality while maintaining reasonable process simplicity.
Solution Approach 2:
The patent changes the irradiation parameters by using different wavelength ranges for the two irradiation steps. The first step uses longer wavelength (310-380 nm) UV to pre-react, and the second step uses shorter wavelength (300-360 nm) UV to complete the reaction. This parameter change optimizes the reaction progression and ensures complete conversion of reactive mesogen, eliminating alignment defects.
3Manufacturing precision
If reactive mesogen alignment layer is used to achieve precise alignment, then alignment precision is improved, but unreacted reactive mesogen causes vertical stripe patterns
Solution Approach 1:
The patent segments the photo-reaction process into two stages: first irradiation to achieve initial alignment precision, and second irradiation to complete the reaction of remaining reactive mesogen. This segmentation maintains the high alignment precision benefits of reactive mesogen while eliminating the harmful effects of unreacted mesogen that cause vertical stripe patterns and water spots.
Solution Approach 2:
The first UV irradiation step performs a preliminary reaction to pre-align the liquid crystals and partially react the reactive mesogen. This preliminary action establishes the alignment structure before the second irradiation completes the reaction, ensuring both precise alignment and complete reaction without vertical stripe patterns.
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 method achieves a voltage holding rate of 96.7% or more, effectively removing non-reacted reactive mesogen and preventing vertical stripe patterns and water spots, thereby enhancing the display quality and production efficiency.
Implementation Method 1
a step of pre-tilting the liquid crystal by applying a voltage to the display panel assembly and primarily irradiating ultraviolet rays having a wavelength of 310 nm to 380 nm
Implementation Method 2
a step of removing remaining reactive mesogen by secondarily irradiating ultraviolet rays having a wavelength of 300 nm to 360 nm to the display panel assembly
Implementation Method 3
a step of pre-tilting the liquid crystal by applying a voltage to the display panel assembly
Data Source
AI summary
A manufacturing method of a liquid crystal display according to an exemplary embodiment of the present invention includes: a step of preparing a lower panel in which a pixel electrode is formed and which is coated with a lower alignment layer including reactive mesogen; a step of preparing an upper panel in which a common electrode is formed and which is coated with an upper alignment layer including reactive mesogen; a step of forming a display panel assembly by injecting a liquid crystal between the lower panel and the upper panel and bonding the lower panel and the upper panel; a step of pre-tilting the liquid crystal by applying a voltage to the display panel assembly and primarily irradiating ultraviolet rays having a wavelength of 310 nm to 380 nm; and a step of removing remaining reactive mesogen by secondarily irradiating ultraviolet rays having a wavelength of 300 nm to 360 nm to the display panel assembly.