Color Filter Substrate with Segmented Column Spacers for Cell Gap Stability
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Solution Overview
Problem
In liquid crystal display devices, the uniformity of cell gap maintenance is compromised when exposed to high temperatures, as the liquid crystal layer expands, leading to reliability issues due to the equal heights of column spacers used.
Innovation Solution
Implementing double column spacers with different heights, where a main column spacer and a sub-column spacer are formed using a single mask, with the sub-column spacer being shorter and spaced apart to reduce external pressure, and an auxiliary pattern within the color filter helps in maintaining the cell gap without additional masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If column spacers of equal height are used, then manufacturing process is simple, but cell gap maintenance reliability deteriorates under high temperature due to liquid crystal expansion
Solution Approach 1:
The column spacer structure is segmented into two distinct types: main column spacers with greater height and sub-column spacers with lesser height. This segmentation allows differential response to thermal expansion, where main spacers maintain cell gap while sub-spacers accommodate liquid crystal expansion, thereby resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
Different regions of the display device are assigned different spacer heights based on local requirements. Main column spacers are positioned in regions requiring strict cell gap maintenance, while sub-column spacers are positioned to accommodate expansion. This local differentiation optimizes reliability without uniformly increasing complexity throughout the entire device.
2Reliability
If double column spacers with different heights are implemented, then cell gap maintenance reliability improves, but manufacturing process complexity increases
Solution Approach 1:
The formation of main column spacers and sub-column spacers is merged into a single photolithography process step. By designing the mask pattern to simultaneously define both spacer types, the manufacturing process achieves the complex dual-height structure without requiring separate fabrication steps, thereby maintaining ease of manufacture while improving reliability.
Solution Approach 2:
The mask pattern serves multiple functions: it defines the positions of main column spacers, defines the positions of sub-column spacers, and establishes the height differential between them. This multi-functionality reduces the number of separate manufacturing steps needed, counteracting the increased structural complexity with process efficiency.
3Manufacturing precision
If additional masks are used to form double column spacers, then manufacturing precision improves, but device complexity and cost increase
Solution Approach 1:
The mask pattern employs asymmetric design elements that inherently differentiate between main column spacer regions and sub-column spacer regions. This asymmetry is encoded in the single mask's geometry, allowing the photolithography process to self-differentiate spacer types without requiring multiple masks, thereby maintaining positioning precision while avoiding additional mask complexity.
Data Source
AI summary
In a color filter substrate and a liquid crystal display device including the same, the color filter substrate includes: a first black matrix not having an opening; a second black matrix having an opening; the first black matrix and the second black matrix being formed on a substrate; an auxiliary pattern disposed in the opening; a color filter covering the first and second black matrixes and formed in each of a plurality of pixels; an overcoat layer formed on the color filter; a first column spacer formed on the overcoat layer so as to correspond to the first black matrix; and a second column spacer formed above the auxiliary pattern so as to correspond to the second black matrix.