Alignment Film Segmentation for Moisture Resistance in LCDs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal display devices experience non-uniformity in luminance when used in high humidity environments due to moisture absorption by the alignment film on the second substrate, which affects the voltage holding ratio of the liquid crystal layer.
Innovation Solution
The alignment film is provided only on the first substrate, with its end portion extending between the sealing part and the terminal, and is designed to be thinner in the second area to reduce moisture absorption, while maintaining adequate adhesive strength and being removable through an ashing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the alignment film is provided on the entire second area of the first substrate, then the adhesive strength is improved, but moisture absorption increases causing non-uniformity in luminance
Solution Approach 1:
The alignment film is segmented into two regions: a first area extending to the sealing part with adequate thickness for adhesion, and a second area extending to the edge with reduced thickness to minimize moisture absorption. This segmentation allows different portions of the alignment film to serve different functions - the first area provides bonding strength while the second area reduces harmful moisture uptake.
Solution Approach 2:
The alignment film exhibits local quality variation through different thicknesses in different areas. The first area has a first thickness optimized for adhesive strength near the sealing part, while the second area has a second thickness (smaller than the first) to reduce moisture absorption near the edge. This local differentiation resolves the contradiction between adhesion and moisture resistance.
2Object-affected harmful factors
If the alignment film thickness is reduced in the second area, then moisture absorption is decreased, but adhesive strength may be compromised
Solution Approach 1:
The alignment film is divided into functional segments with different thicknesses. The first area maintains sufficient thickness for strong adhesion to the substrate, while the second area uses reduced thickness to minimize moisture absorption. The segmentation ensures that adhesive strength is not compromised in critical regions while reducing overall moisture uptake.
Solution Approach 2:
Different local regions of the alignment film have different thickness properties optimized for their specific functions. The first area near the sealing part has greater thickness for bonding strength, while the second area at the edge has smaller thickness for moisture resistance. This local quality differentiation resolves the trade-off between adhesion and moisture absorption.
3Area of stationary object
If the alignment film extends to the edge of the substrate, then coverage is improved, but moisture reach to liquid crystal layer increases
Solution Approach 1:
The alignment film's thickness varies locally across different areas. In the first area near the sealing part, the film has sufficient thickness for adhesion. In the second area extending to the edge, the film has reduced thickness that limits moisture penetration pathways while still providing coverage. This local thickness variation allows extended coverage without proportionally increased moisture risk.
Solution Approach 2:
The alignment film structure can be viewed as a composite configuration with different thickness zones serving different protective functions. The multi-zone thickness design creates a gradient structure that balances coverage area with moisture barrier effectiveness, allowing the film to extend to the edge while maintaining protection of the liquid crystal layer.
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 configuration effectively suppresses non-uniformity in luminance and maintains high adhesive strength, preventing moisture from reaching the liquid crystal layer, thus ensuring stable display performance even in humid conditions.
Implementation Method 1
the alignment film provided on the entire second area except the terminal to which an external circuit or the like is connected, absorbs moisture in the atmosphere
Implementation Method 2
designed to be thinner in the second area to reduce moisture absorption, while maintaining adequate adhesive strength and being removable through an ashing process
Data Source
AI summary
According to one embodiment, a liquid crystal display device includes a first substrate including a first area and a second area, a second substrate opposing the first substrate but not opposing the second area, a sealing part which adheres the first substrate and the second substrate to each other, a liquid crystal layer located between the first substrate and the second substrate and surrounded by the sealing part, an alignment film disposed on the first substrate so as to be in contact with the liquid crystal layer and a terminal located in the second area and connected to an external circuit. In plan view, the alignment film includes an end located between the sealing part and the terminal.