Active Matrix Substrate Storage Capacitor Misalignment Compensation

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Solution Overview

Problem

In the production of TFT substrates for liquid crystal display devices, misalignment during the formation of storage capacitor components can lead to fluctuations in storage capacitance, resulting in deteriorated display quality, including flickering and unevenness in block or strip shapes, due to variations in feed-through voltage across pixels.

Innovation Solution

An active matrix substrate design that includes a storage capacitor counter electrode with specific structural features such as a compensation portion overlapping the storage capacitor bus line, which helps stabilize storage capacitance by compensating for misalignment, ensuring consistent display quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the storage capacitor counter electrode is formed as an extension of the drain electrode overlapping the storage capacitor bus line, then storage capacitance is created to retain pixel electrode potential, but misalignment during production causes fluctuations in storage capacitance and feed-through voltage

Engineering Contradiction:

Improvestorage capacitance stabilityVSAvoidalignment accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The storage capacitor counter electrode is designed with a compensation portion that protrudes from the storage capacitor bus line in advance, before misalignment occurs during production. This pre-configured compensation structure ensures that even when misalignment happens, the storage capacitance remains stable by automatically compensating for the deviation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the geometric parameters of the storage capacitor counter electrode by adding a compensation portion with specific dimensions (width and length) that extend beyond the storage capacitor bus line. This parameter modification creates a buffer zone that compensates for misalignment-induced capacitance variations, maintaining stable storage capacitance despite production tolerances.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the extension of the drain electrode is provided inside the edge of the storage capacitor electrode, then storage capacitance is formed, but the aperture ratio of the pixel is reduced

Engineering Contradiction:

Improvestorage capacitance formationVSAvoidaperture ratio

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The storage capacitor counter electrode is extended in a direction perpendicular to the storage capacitor bus line by adding a compensation portion that protrudes from the bus line edge. This dimensional extension allows the electrode to achieve proper overlap and capacitance formation without encroaching on the pixel aperture area, thereby maintaining both storage capacitance and aperture ratio.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If the storage capacitor counter electrode extends beyond the storage capacitor bus line to compensate for misalignment, then storage capacitance stability is improved, but the risk of current leakage or electrical conduction at intersecting portions increases

Engineering Contradiction:

Improvestorage capacitance stabilityVSAvoidcurrent leakage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The compensation portion is designed with specific local dimensions (width and length) that are optimized to provide sufficient overlap for capacitance compensation while avoiding excessive extension that could cause leakage. The local geometry is carefully controlled to balance compensation effectiveness with leakage prevention.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

An insulating film is introduced as an intermediary layer between the storage capacitor counter electrode and the storage capacitor bus line, particularly at the compensation portion that protrudes from the bus line. This insulating layer prevents direct electrical contact and current leakage at the intersecting portions while allowing the electrode to extend for compensation purposes.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The proposed substrate design effectively maintains appropriate storage capacitance even with misalignment, enhancing display quality by reducing fluctuations in feed-through voltage and parasitic capacitance, thereby preventing flickering and display unevenness.

Implementation Method 1

a storage capacitor counter electrode electrically connected to the drain electrode to create a storage capacitance with the storage capacitor bus line

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8947607B2Active matrix substrate and display device

Publication Date: 2015.02.03 SHARP KK

AI summary

A storage capacitor counter electrode (22) provided on an active matrix substrate (100) includes a first portion (22b) creating a storage capacitance with a storage capacitor bus line (12), a second portion (22a) interposed between the first portion (22b) and a drain electrode (24), and a third portion (22c) being provided opposite from the second portion (22a) with the first portion (22b) sandwiched therebetween and protruding from the first portion (22b). The third portion (22c) is disposed so as not to overlie any pixel electrode other than a pixel electrode (30) that is electrically connected to the drain electrode (24).