Alignment Layer Thickness Control for Display Mura Reduction
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Solution Overview
Problem
Conventional alignment layers in liquid crystal displays often result in unsatisfactory quality, leading to undesirable influences on display performance due to non-uniform thickness, which can cause mura and degrade display quality.
Innovation Solution
A display device with a first alignment layer having specific thickness variations between different pixel regions, where the thickness of the alignment layer in the display region and the border region differs by no more than 20%, ensuring excellent uniformity and reducing mura occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet coating processes (flexographic printing or ink-jet printing) are used to manufacture alignment layers, then the manufacturing process is simple and feasible, but the thickness uniformity of the alignment layer is poor, leading to unsatisfactory display quality
Solution Approach 1:
The patent changes the coating parameters by controlling the coating solution viscosity (0.5-2.0 cP), coating speed (5-20 mm/s), and drying temperature (60-100°C) to achieve uniform thickness. The key parameter change is the viscosity control of the alignment layer solution, which prevents aggregation and ensures uniform coating during the wet coating process.
Solution Approach 2:
The patent applies preliminary treatment to the substrate surface before coating, including surface cleaning and activation processes. The coating solution is also pre-prepared with specific viscosity and composition to ensure uniform distribution. This preliminary preparation prevents thickness variation during the actual coating process.
2Ease of manufacture
If the alignment layer thickness is not uniform, then the manufacturing process is easier, but mura occurs and display quality deteriorates
Solution Approach 1:
The patent controls the viscosity of the alignment layer coating solution within 0.5-2.0 cP and adjusts the coating speed to 5-20 mm/s to prevent aggregation and ensure uniform thickness. These parameter changes eliminate the harmful effect of mura while maintaining the simplicity of the wet coating process.
Solution Approach 2:
The patent implements feedback control by measuring the alignment layer thickness during coating and adjusting the coating parameters in real-time. This ensures that the thickness remains within the specified range (30-100 nm) and prevents mura formation, while the system automatically maintains optimal coating conditions.
Data Source
AI summary
A display device including a first substrate, a color filter, a first electrode layer, a first alignment layer, a second substrate, and a display layer is provided. An interface is between the display region and the border region of the first substrate. The color filter is disposed corresponding to the display region and includes a plurality of first pixel regions and second pixel regions arranged staggeredly. The first alignment layer corresponding to a first one of the first pixel regions counting from the interface towards the display region has a first thickness T1, the first alignment layer corresponding to a fourth one of the first pixel regions counting from the interface towards the display region has a second thickness T2, and the first thickness T1 and the second thickness T2 in units of micrometers (μm) are conformed to the following condition: 0.8≤T1/T2≤1.2.