Display Substrate Planarization for Rubbing Mura Reduction
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Solution Overview
Problem
The occurrence of Rubbing Mura, or irregularities in the alignment film grooves, during the rubbing process for liquid crystal display (LCD) panels due to inconsistent rubbing cloth orientation over uneven non-display regions, affects display quality and causes wear on the rubbing cloth.
Innovation Solution
A display substrate with a non-display region featuring an uneven layer and a first film layer that forms a flat surface, ensuring consistent rubbing cloth orientation and reducing the occurrence of Rubbing Mura, while also extending the life of the rubbing cloth and lowering production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the non-display region has an uneven surface with signal testing lines and pads, then electrical testing functions are enabled, but the rubbing cloth orientation becomes inconsistent causing Rubbing Mura
Solution Approach 1:
The patent introduces a third dimension (vertical layering) by forming a flat surface layer over the uneven non-display region. This flat surface layer, created through additional film deposition or planarization processes, provides a uniform rubbing surface while the underlying uneven structure with signal testing lines and pads remains intact for electrical testing functions.
Solution Approach 2:
The patent introduces an intermediary flat surface layer between the rubbing cloth and the uneven non-display region. This intermediate layer acts as a mediator that provides consistent rubbing characteristics while allowing the underlying electrical testing structures to function normally, thus resolving the conflict between testing functionality and rubbing consistency.
2Device complexity
If the rubbing cloth contacts the uneven non-display region directly, then the structure remains simple, but the rubbing cloth suffers wear and damage
Solution Approach 1:
The patent applies beforehand cushioning by forming a protective flat surface layer over the non-display region before the rubbing process. This pre-established protective layer cushions the rubbing cloth from direct contact with the uneven underlying structures, reducing wear and extending the rubbing cloth's service life.
Solution Approach 2:
The flat surface layer serves as an intermediary between the rubbing cloth and the uneven non-display region, protecting the rubbing cloth from damage caused by direct contact with signal testing lines, pads, and other underlying structures while maintaining structural simplicity.
3Manufacturing precision
If a flat surface layer is added to the non-display region, then Rubbing Mura is reduced and display quality improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the flat surface formation with existing manufacturing processes by integrating it into the film deposition sequence. The flat surface layer is formed as part of the overall film stack using standard deposition techniques, combining the planarization function with the existing fabrication workflow to minimize additional process complexity.
Solution Approach 2:
The flat surface layer serves multiple functions: it provides a uniform rubbing surface to prevent Rubbing Mura, protects underlying structures during rubbing, and maintains electrical isolation. This multi-functionality justifies the added manufacturing step by delivering multiple benefits from a single structural addition.
Data Source
AI summary
A display substrate (100) is provided for a display device. The display substrate (100) includes a display region with an alignment film formed on one side of the display region. A non-display region at a peripheral area of the substrate and adjacent to the display region. An uneven layer (1) formed on the non-display region at a same side as the alignment film. A first film layer (2) formed on the uneven layer (1) and covering the uneven layer (1) to form a substantially flat surface of the non-display region with respect to the display region.