Photo-Decomposition Alignment Film Thickness Control on LCD Spacer Pedestals
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Solution Overview
Problem
Liquid crystal display devices face display defects due to peeling or abrasion of alignment films on spacer pedestals, which are not adequately addressed by existing methods that focus solely on reducing film thickness or viscosity adjustments.
Innovation Solution
A photo-decomposition-type alignment film is used, with a volatile organic solvent containing a photo-decomposition-type polyimide acid, where the film is baked and then exposed to polarized ultraviolet light, allowing for controlled film thickness reduction on both pillar-shaped spacers and spacer pedestals, ensuring the alignment film remains thin and adherent on the pedestals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the alignment film thickness is reduced on spacer pedestals to prevent peeling, then the reliability is improved, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent applies different alignment film thicknesses to different locations: a first thickness on pixel electrodes and a second (thinner) thickness on spacer pedestals. This local differentiation resolves the contradiction by ensuring adequate adhesion on pedestals while maintaining proper alignment function on electrodes.
Solution Approach 2:
The patent changes the film thickness parameter spatially across the substrate, creating a gradient or stepped thickness profile. This allows optimization of adhesion on pedestals without compromising the alignment performance on pixel electrodes.
2Object-generated harmful factors
If the alignment film is made thinner on spacer pedestals, then the peeling defect is reduced, but the film may become too thin to maintain proper alignment function
Solution Approach 1:
Different regions of the alignment film serve different functions: the portion on pixel electrodes maintains sufficient thickness for alignment control, while the portion on spacer pedestals is thinner to prevent peeling during assembly.
Solution Approach 2:
The alignment film is effectively segmented into functional zones with different thickness characteristics, allowing each zone to be optimized for its specific role without compromising the other.
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 method effectively reduces the alignment film thickness on spacer pedestals to prevent peeling, maintaining adhesiveness and preventing display defects like bright spots, while ensuring sufficient film thickness on pixel electrodes for proper alignment.
Implementation Method 1
A liquid crystal display device having alignment films includes a first alignment film formed on one of opposedly-facing surfaces of a pair of substrates
Implementation Method 2
a coated film is leveled for 60 seconds, and the leveled coated film is dried at a temperature of 100° C., and is baked at a temperature of 180° C. for 1 hour
Implementation Method 3
the leveled coated film is dried at a temperature of 100° C., and is baked at a temperature of 180° C. for 1 hour thus forming an alignment film having a thickness of 1000 angstrom
Data Source
AI summary
A liquid crystal display device includes a first substrate, a first alignment film formed over the first substrate, a second substrate, a second alignment film formed over the second substrate, a liquid crystal layer sandwiched between the first alignment film and the second alignment film, and a projecting portion formed over the second substrate. The first film is a photo alignment film, and a thickness “d2” of the second alignment film over the projecting portion and a film thickness “d1” of a portion of the first alignment film facing the projecting portion satisfy formula (2),d2<d1 (2).