Columnar Spacer Covering Concave to Prevent Alignment Film Scraping
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Solution Overview
Problem
Liquid crystal display devices using columnar spacers face issues with bright spots due to scraping of the alignment film, which affects view angle characteristics and reliability, especially when subjected to external pressure or temperature cycles.
Innovation Solution
A liquid crystal display device configuration where the columnar spacer is designed to cover a concave portion on the TFT substrate, reducing the contact area with the alignment film, thereby minimizing scraping and preventing bright spots without altering the manufacturing process or increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If columnar spacers are used to accurately control the gap between substrates, then manufacturing precision is improved, but the alignment film is scraped causing bright spots and reliability deteriorates
Solution Approach 1:
The invention forms a pedestal structure with different heights: a first region with height h1 and a second region with height h2 (where h1 > h2). The columnar spacer contacts the TFT substrate at the lower second region while the alignment film remains on the higher first region. This local height differentiation allows the spacer to define the gap accurately without scraping the alignment film, resolving the contradiction between manufacturing precision and reliability.
2Manufacturing precision
If columnar spacers are used to control the gap, then manufacturing precision is improved, but device complexity increases due to additional structures
Solution Approach 1:
The invention combines the pedestal structure formation with the existing columnar spacer formation process. The pedestal is formed by depositing and patterning material in the same manufacturing sequence as the columnar spacer, integrating two functions (gap definition and alignment film protection) into a single structural element rather than adding separate components.
Solution Approach 2:
The pedestal structure serves multiple functions: it defines the liquid crystal layer gap height, protects the alignment film from scraping, and provides a stable contact surface for the columnar spacer. This multi-functionality reduces the need for additional separate structures, thereby limiting the increase in device complexity while maintaining improved manufacturing precision.
Data Source
AI summary
A pixel electrode is formed on a TFT substrate, and a gate insulating film, an inorganic passivation film, a common electrode, and an alignment film are formed in this order thereover. A columnar spacer is formed to the counter substrate and is adapted to define a gap between the TFT substrate and the counter substrate. A through hole is formed in the gate insulating film of the TFT substrate, and the columnar spacer is disposed so as to cover a concave portion formed by the through hole. Since the area of contact between the columnar spacer and the TFT substrate is decreased, it is possible to suppress scraping of the alignment film and thus to prevent occurrence of bright spots.