Array Substrate Surface Flatness via Sacrificial Layer Embedding
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Solution Overview
Problem
The existing methods for manufacturing array substrates in TFT-LCD technology result in significant segment differences between layers, leading to issues such as picture ghosting, light leaks, and decreased production yield due to the formation of rubbing weak regions during the alignment film coating process.
Innovation Solution
The proposed solution involves forming an array substrate with a functional film layer pattern on a base substrate, where the insulating layer covers the pattern, and sacrificial layers are used to embed the metal and active layers, ensuring that their surfaces are flush with the sacrificial layers, thereby reducing the segment difference and smoothing the surface, which prevents the breaking of the alignment film and formation of rubbing weak regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If functional patterns (gate electrode, active layer, source-drain electrode) are arranged on the array substrate, then the TFT functionality is achieved, but large segment difference is created on the surface
Solution Approach 1:
The patent divides the array substrate into two distinct regions: a first area containing the TFT functional patterns (gate electrode, active layer, source-drain electrode) and a second area without these patterns. This segmentation allows each region to serve its specific purpose while managing the segment difference issue by creating a dedicated flat surface region for alignment film formation.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary element that covers the functional patterns and provides a flat upper surface. This insulating layer acts as a mediator between the uneven functional patterns below and the alignment film above, enabling the alignment film to be formed on a flat surface even when TFT patterns are present underneath.
2Ease of manufacture
If alignment film coating is performed on the array substrate with large segment difference, then the alignment film may break during rubbing process, but this leads to formation of rubbing weak regions causing picture ghosting and light leaks
Solution Approach 1:
The patent applies different surface quality requirements to different regions: the second area (without TFT patterns) is designed to have a flat upper surface of the insulating layer suitable for alignment film coating and rubbing, while the first area (with TFT patterns) can have the necessary functional structures. This local differentiation allows the alignment film to be properly formed and rubbed without breaking in the critical second area.
Data Source
AI summary
An array substrate, a method for forming an array substrate, a display panel and a display device are provided, which relate to the field of display technology. The array substrate includes a functional film layer pattern on a base substrate and an insulating layer covering the functional film layer pattern, and a segment difference of a surface of the insulating layer is smaller than a segment difference threshold.