LCD Alignment Marks in Active Region for Precision
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Solution Overview
Problem
Existing liquid crystal display (LCD) technologies face challenges in accurately aligning highly integrated and minute lines due to the limitations of alignment marks being formed only on non-active regions, which fail to provide precise alignment information between lines or elements in the active region, leading to potential misalignment and degraded color reproducibility.
Innovation Solution
The introduction of first and second alignment marks disposed on both sides of gate lines and data lines within the active region of the LCD, which are designed to overlap with black matrixes on the upper substrate, allowing for precise alignment checks by observing the visibility of these marks relative to the black matrixes, thereby ensuring accurate alignment of substrates and wiring patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alignment marks are formed only on non-active regions, then the manufacturing process is simple and the substrate structure is maintained, but the alignment precision between lines or elements in the active region cannot be accurately checked
Solution Approach 1:
The alignment mark is divided into two separate parts: a first alignment mark formed on the lower substrate in the non-active region, and a second alignment mark formed on the upper substrate in the active region. This segmentation allows each mark to serve its specific function - the first for overall substrate alignment and the second for precise line/element alignment in the active region.
Solution Approach 2:
Different alignment marks are placed in different locations with different functions. The first alignment mark is located in the non-active region for general alignment, while the second alignment mark is located in the active region near the lines or elements that need precise alignment. This local differentiation enables precise alignment checking where it is most needed.
2Measurement precision
If alignment marks are formed on corner portions only, then the substrate structure is simple, but the precise degree of alignment between lines or elements in the active region cannot be recognized
Solution Approach 1:
The alignment measurement capability is extended from the corner region (2D plane) to the active region (also 2D plane but functionally different). By placing the second alignment mark in the active region, the measurement capability is distributed across different spatial dimensions, enabling detection of alignment precision both at the corner level and at the line/element level within the active region.
3Productivity
If the element density is increased to implement full colors, then the integration is improved and the element size is reduced, but the alignment sensitivity increases and any deviation degrades color reproducibility
Solution Approach 1:
The second alignment mark is formed in advance on the upper substrate in the active region before the final assembly. This preliminary placement of the alignment mark in the active region allows for early detection and correction of alignment deviations, ensuring that the high-density elements are positioned correctly before the substrate is fully assembled and sealed.
Data Source
AI summary
A liquid crystal display device (LCD) includes an alignment mark in a pixel region. The LCD includes upper and lower substrates; a plurality of gate lines; a plurality of data lines arranged to perpendicularly cross the gate lines on the lower substrate and defining unit pixels together with the gate lines; a switching element at each crossing of the gate lines and the data lines; first and second alignment marks disposed on respective sides of at least one of the gate lines and the data lines; a pixel electrode at each unit pixel; a black matrix on a region of the upper substrate corresponding to a boundary region of the unit pixels; and a liquid crystal layer between the upper and lower substrates. One side of the first alignment mark and one side of the black matrix lie on one straight line, and one side of the second alignment mark and the other side of the black matrix lie on one straight line.