LCD Alignment Layer Fabrication via UV and Thermal Processing
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Solution Overview
Problem
The existing methods for fabricating alignment layers in LCD devices, particularly the non-contact type orientation process using polyimide resins with cyclobutane dianhydride (CBDA), suffer from side reactions during photodecomposition, which degrade the molecular weight and heat-resistant properties of the alignment layer, leading to issues like afterimages and increased production costs.
Innovation Solution
A method involving the simultaneous irradiation of UV rays and heating of the alignment material layer, under nitrogen to minimize oxidation, with controlled UV energy density and subsequent post-baking to enhance the formation of a network structure and prevent side reactions, thereby improving the alignment layer's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV rays are irradiated onto the alignment material layer to induce photodecomposition, then the alignment layer forms orientation properties, but side reactions occur during photodecomposition which degrade the molecular weight and heat-resistant properties of the alignment layer
Solution Approach 1:
The patent changes the physical parameters of UV irradiation by controlling energy density within a specific range (0.05-3.0 J/cm²) and combining it with thermal parameters (simultaneous heating at 25-230°C). This parameter optimization prevents excessive photodecomposition and side reactions while maintaining alignment properties, thereby preserving molecular weight and heat resistance.
Solution Approach 2:
The patent uses a polyimide resin containing specific chemical structures (cyclobutane dianhydride or oxi-dianiline groups) that are designed to undergo controlled photodecomposition. The composite molecular structure enables the material to achieve orientation properties through UV irradiation while maintaining stability against molecular weight degradation and heat resistance loss.
2Reliability
If contact type orientation process is used with rubbing cloth, then alignment layer obtains orientation properties, but additional processes are required which increase production costs
Solution Approach 1:
The patent replaces the mechanical rubbing process with a photochemical process. UV rays irradiate the alignment material layer to induce photodecomposition and form orientation properties without physical contact. This substitution eliminates the need for rubbing cloths and additional mechanical processing steps, thereby reducing production costs while maintaining alignment quality.
3Ease of manufacture
If non-contact type orientation process is used with UV irradiation, then production cost is reduced, but side reactions during photodecomposition still occur degrading alignment layer properties
Solution Approach 1:
The patent optimizes UV irradiation parameters by controlling energy density within 0.05-3.0 J/cm² and implementing simultaneous heating at 25-230°C. These parameter changes prevent excessive photodecomposition and side reactions, maintaining molecular weight and heat resistance while achieving the cost benefits of the non-contact process.
Solution Approach 2:
The patent applies preliminary heating to the alignment material layer before or during UV irradiation. This preliminary thermal action prepares the material structure to undergo controlled photodecomposition, reducing the likelihood of side reactions and preserving alignment layer properties while maintaining the efficiency of the non-contact process.
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 approach results in an alignment layer with improved anisotropic properties, reduced afterimages, and lower production costs, as evidenced by increased retardation values and glass transition temperatures, along with enhanced contrast ratio and reduced brightness issues.
Implementation Method 1
irradiating UV rays onto the alignment material layer, thereby pre-baking the alignment material layer
Implementation Method 2
A method involving the simultaneous irradiation of UV rays and heating of the alignment material layer
Implementation Method 3
post-baking the alignment material layer
Data Source
AI summary
A method of fabricating an alignment layer for a liquid crystal display device includes forming an alignment material layer on a substrate by coating an alignment material, irradiating UV rays onto the alignment material layer and pre-baking the alignment material layer; and post-baking the alignment material layer.