Display Spacer Alignment via Planarization Layer
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Solution Overview
Problem
In liquid crystal displays, the alignment of spacers between substrates is challenging due to topography variations, leading to inconsistent cell gaps and deteriorated optical properties, such as contrast ratio, if spacers fall into through holes, affecting light penetration and chroma.
Innovation Solution
A planarization layer is introduced on the pixel electrode layer, extending into concave portions and filled with a material like acrylic or silicon-based photo-sensitive material, ensuring a flat surface area and maintaining consistent cell gaps between substrates, even with reduced spacer size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spacers are disposed directly on the pixel electrode layer without planarization, then the manufacturing process is simpler, but the spacers may fall into through holes causing inconsistent cell gaps and deteriorated optical properties
Solution Approach 1:
A planarization layer is formed before disposing the spacers to pre-establish a flat surface. This preliminary action prevents spacers from falling into through holes during subsequent processing, ensuring consistent cell gaps without complicating the overall manufacturing flow.
Solution Approach 2:
The planarization layer acts as an intermediary between the pixel electrode layer (with through holes) and the spacers. It mediates the interaction by providing a flat supporting surface that prevents direct contact between spacers and through holes, thereby maintaining alignment precision.
2Reliability
If a planarization layer is added to ensure flat surface and consistent cell gaps, then the optical properties are improved, but the device structure becomes more complex
Solution Approach 1:
The planarization layer serves multiple functions simultaneously: it provides a flat surface for spacer alignment, fills concave portions to maintain uniform cell gaps, and acts as a structural support. This multi-functionality justifies the added structural element by delivering multiple benefits from a single component.
3Area of stationary object
If spacers are made smaller to increase aperture ratio, then the light penetration is improved, but the alignment becomes more difficult due to topography variations
Solution Approach 1:
The planarization layer is formed in advance to create a flat surface before placing smaller spacers. This preliminary flattening action compensates for topography variations, enabling precise alignment of even smaller spacers while maintaining the desired aperture ratio.
Data Source
AI summary
A display including a first substrate, a second substrate and spacers is provided. The first substrate includes a first base body, a device structure, an insulating layer, a pixel electrode layer and a planarization layer. The device structure is formed on the first base body. The insulating layer is formed on the device structure, and has at least one through hole. The pixel electrode layer is formed on the insulating layer. A portion of the pixel electrode layer extends into the through hole and electrically connects to the device structure. The pixel electrode layer forms a concave portion corresponding to the through hole. The planarization layer is formed on the pixel electrode layer and filled into the concave portion. The second substrate is disposed opposite to the first substrate. The spacers are disposed between the first substrate and the second substrate, and are correspondingly disposed on the planarization layer.