Liquid Crystal Display Column Spacer Design for Light Leakage
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Solution Overview
Problem
Conventional liquid crystal display devices face issues with inconsistent intervals between TFT and opposed substrates due to bead dispersion, leading to reduced image contrast and manufacturing inefficiencies, and column formation on substrates can cause light leakage and transmittance reduction.
Innovation Solution
A column is formed on the TFT substrate at the crossing point between a drain electrode and a scanning line, with adjusted widths of these lines to minimize light leakage and parasitic capacitance, and the column is only formed at specific pixel positions to prevent color inconsistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If beads are dispersed to set the interval between TFT substrate and opposed substrate, then the interval can be established, but the beads may not be dispersed consistently leading to inconsistent interval and may cause light leakage
Solution Approach 1:
The patent removes the problematic dispersed beads from the system and replaces them with column-type spacers that are integrally formed on the substrate. This extraction eliminates the light leakage issue caused by beads while maintaining the interval-setting function through the column structure.
Solution Approach 2:
The patent replaces the reusable dispersed beads with column-type spacers that are designed to be removed after serving their purpose of defining the interval during manufacturing. The columns are intentionally placed in non-display areas and can be removed without affecting the final product quality.
2Ease of manufacture
If liquid crystal is injected using atmospheric pressure, then liquid crystal can be filled into the sealed space, but the process takes time when the interval is small and surface is large, reducing manufacturing throughput
Solution Approach 1:
The patent performs preliminary action by pre-defining the interval using column-type spacers before liquid crystal injection. This ensures proper spacing is established in advance, allowing for more efficient liquid crystal filling processes and improving overall manufacturing throughput.
3Manufacturing precision
If a column is formed on the opposed substrate to define the interval, then the interval can be set, but if substrates are displaced during combination, the column may abut outside the predetermined position causing light leakage or improper interval definition
Solution Approach 1:
The column-type spacers are formed preliminarily on the TFT substrate with built-in positioning features (protrusions fitting into recesses) that ensure accurate alignment. This preliminary positioning action prevents displacement issues during substrate combination and ensures the column always abuts at the correct position on the pixel electrode.
Solution Approach 2:
The patent introduces an intermediary positioning mechanism (protrusions and recesses) that mediates between the column formation and substrate combination processes. This intermediary structure ensures accurate positioning and prevents displacement, maintaining both interval definition precision and position accuracy.
4Reliability
If the width of drain line or scanning line is increased at column position, then light leakage due to orientation disturbance is reduced, but parasitic capacitance increases
Solution Approach 1:
The patent applies local quality by making the drain line or scanning line width variable - wider at the column position to prevent light leakage and narrower elsewhere to minimize parasitic capacitance. This localized width adjustment optimizes both light leakage reduction and capacitance minimization at different positions.
Data Source
AI summary
A column for defining the interval between a TFT substrate and an opposed substrate is formed at a crossing point between a drain line and a scanning line. At the crossing point where the column is formed, the drain line is formed to have a wider width to prevent light leakage. Further, at the crossing point where the column is formed, the scanning line is formed to have a narrower width to prevent increase of capacitance between the drain line and the scanning line. The column is formed at a crossing point corresponding to a specific color, e.g., a blue pixel B, so that a difference in transmittance and in characteristic of thin film transistors due to formation of the column is initially compensated.