Liquid Crystal Display Pad Structure for Resistance Variance Reduction
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Solution Overview
Problem
In liquid crystal display devices, particularly those using fringe field switching (FFS) or in-plane switching (IPS) modes, the formation of resistive layers between electrodes due to impurities or oxide films on lower-layer electrodes can lead to increased resistance variance, potentially causing system driver malfunctions and display defects during mounting.
Innovation Solution
A liquid crystal display device structure where the first pad portion is not exposed from the contact hole, and the second pad portion, formed of electrically conductive oxide, is stacked on top, preventing impurity adhesion and oxide film formation, thereby reducing resistance variance between pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower-layer electrode is exposed during contact hole formation to enable electrical connection, then the upper-layer electrode can be formed, but impurities and oxide films adhere to the exposed surface, increasing resistance variance
Solution Approach 1:
The patent applies preliminary action by forming a protective film on the lower-layer electrode surface before the electrode is exposed during contact hole formation. This protective film prevents impurity adhesion and oxide film formation in advance, ensuring that when the electrode is later exposed for electrical connection, the surface remains clean and resistant to contamination, thus maintaining both connection reliability and resistance uniformity
Solution Approach 2:
The patent introduces an intermediary substance (protective film) between the lower-layer electrode and the external environment during the manufacturing process. This protective film acts as a mediator that prevents direct contact between the electrode surface and impurities or oxygen, thereby eliminating the formation of resistive layers while still allowing electrical connection to be established when needed
2Reliability
If a resistive layer forms between electrodes due to impurity adhesion, then electrical connection is established, but resistance variance increases causing system driver malfunction
Solution Approach 1:
The protective film is formed preliminarily on the lower-layer electrode before any exposure occurs, preventing impurity adhesion and oxide film formation at the source. This advance protection ensures that when the electrode is exposed for contact hole formation, no resistive layer develops, maintaining both system driver reliability and wiring resistance uniformity
Solution Approach 2:
The patent converts the potentially harmful exposure of the electrode surface during manufacturing into a beneficial opportunity by having the protective film already in place. The exposure process, which would normally cause impurity adhesion and resistance increase, becomes harmless because the protective film prevents contamination while still allowing the necessary electrical connection to be established
Data Source
AI summary
According to one embodiment, a liquid crystal display device includes a first substrate including an insulative substrate, a first electrically conductive layer, a second electrically conductive layer, a third electrically conductive layer, a fourth electrically conductive layer. The first electrically conductive layer includes a gate line located on the insulative substrate, a common potential line and a first pad portion. The second electrically conductive layer includes a common electrode which is located on the insulative substrate and is put in contact with the common potential line, and a second pad portion stacked on the first pad portion. The fourth electrically conductive layer includes a pixel electrode in which a slit facing the common electrode is formed, and a third pad portion which is put in contact with the second pad portion.