Liquid Crystal Display Lead Line Resistance Equalization
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Solution Overview
Problem
In liquid crystal display devices, the small terminal pitch of IC drivers leads to uneven brightness due to differences in lead line resistance, as existing methods to equalize resistance, such as widening lead lines or using low-resistance metals, are difficult to implement when pitch is small.
Innovation Solution
A configuration where lead lines connecting the IC driver to image or scan lines are bridged with ITO, with longer bridging ITO lengths near the center of the IC driver, equalizing resistance without additional process steps and maintaining uniform screen brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the terminal pitch of IC driver is reduced to reduce costs, then productivity is improved, but lead line resistance becomes uneven causing brightness non-uniformity
Solution Approach 1:
The patent applies local quality by making the lead line width variable rather than uniform. Specifically, the lead line width is increased in regions where the lead line length is longer (such as near the center of the IC driver) and reduced where the lead line length is shorter (near the edges). This local adjustment compensates for the uneven resistance distribution caused by small pitch, ensuring uniform current density and brightness across the display without requiring larger overall terminal pitch.
2Illumination intensity
If lead line width is increased to equalize resistance, then brightness uniformity is improved, but device area increases
Solution Approach 1:
The patent implements local quality by selectively varying the lead line width at different spatial locations. The lead line width is adjusted locally based on the specific lead line length at each position, rather than uniformly increasing the width across all lead lines. This approach equalizes resistance and ensures brightness uniformity while minimizing the overall area occupation, as only specific regions require wider lead lines.
3Reliability
If low-resistance metal is laminated on lead line, then resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameter (width) of the existing lead line rather than changing the material parameter (resistivity) through lamination. This approach adjusts the resistance by varying the cross-sectional area of the lead line in different regions, which can be achieved through standard photolithography patterning processes without requiring additional material deposition steps, thus avoiding increased manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively equalizes lead line resistance, reducing uneven brightness in liquid crystal display devices without increasing production costs or complexity, even at small pitch sizes.
Implementation Method 1
the resistance value of lead lines can be equalized even if the pitch of the lead lines becomes small
Data Source
AI summary
A drain layer lead line connecting an image signal line and a terminal of an IC driver is interrupted in the middle, and the gap is bridged by bridging ITO that is formed at the same time as pixel ITO. Thus, the difference in the length of the lead lines is adjusted such that the length of the bridging ITO in the lead line connected to the terminal in the center of the IC driver is longer than the length of the bridging ITO in the lead line connected to the terminal in the end of the IC driver to reduce the difference in the wiring resistance of the lead lines due to the difference in the length of the lead lines depending on the location.