OLED Top Metal Non-Overlap with Color Filter

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Solution Overview

Problem

In organic light emitting display devices, the low electrical resistance of color filters, particularly those containing copper, causes short-circuiting between the driving TFT and the storage capacitor, leading to unintended light emission during non-emission periods due to leakage currents.

Innovation Solution

The top metals of the driving TFT and storage capacitor are designed not to overlap with the color filter, ensuring a non-overlapping configuration to prevent short-circuiting and maintaining the gate-source voltage, thereby reducing leakage currents and preventing excessive light emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the top metal of the driving TFT and storage capacitor are formed to overlap the color filter, then the device complexity is reduced and manufacturing is simplified, but short-circuiting occurs between the driving TFT and storage capacitor due to the conductive color filter

Engineering Contradiction:

Improvestructure complexityVSAvoidelectrical isolation

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The harmful overlapping configuration is extracted and removed from the design. The color filter is positioned to exclude the top metal regions of the driving TFT and storage capacitor, effectively taking out the short-circuit path caused by the conductive color filter material containing copper compounds.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The color filter is designed with spatially varying properties - it is formed to overlap certain regions while deliberately excluding the top metal areas. This local differentiation in overlap regions prevents short-circuiting in critical areas while maintaining color filtering functionality in emission regions.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If the color filter contains copper compounds to achieve green color, then the color quality is improved, but the electrical resistance decreases and permittivity increases causing leakage current

Engineering Contradiction:

Improvecolor qualityVSAvoidelectrical resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The harmful electrical conductivity of the copper-containing green color filter is converted into a beneficial design constraint. By recognizing the conductive nature of Cu-Phthalocyanine, the design positions the color filter to overlap the top metal regions, transforming the harmful electrical property into a guiding principle for spatial arrangement that prevents short-circuits.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Productivity

If leakage current flows through the color filter, then the device operates during non-emission periods, but unintended light emission occurs from the OLED

Engineering Contradiction:

Improveoperation continuityVSAvoidlight emission control

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The leakage current path is extracted and removed from the system by preventing the formation of a continuous conductive path. The color filter is positioned to exclude top metal regions, taking out the harmful current flow that causes unintended light emission during non-emission periods.

Inventive Principle:

Principle #2Taking out (Extraction)

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 prevents short-circuiting and maintains the gate-source voltage, eliminating unintended light emission during non-emission periods and reducing parasitic capacitance.

Implementation Method 1

The white OLED emits white light from an organic material layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

a red color filter, a green color filter, and a blue color filter 30 are formed in each sub-pixel

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS9559155B2Organic light emitting display device with short-circuit prevention

Publication Date: 2017.01.31 LG DISPLAY CO LTD

AI summary

Disclosed is an organic light emitting display device. The organic light emitting display device includes a white organic light emitting diode (OLED) formed in an emission area of each of a plurality of sub-pixels, a driving thin film transistor (TFT) configured to supply a driving current to the white OLED, a storage capacitor configured to include a first terminal coupled to the driving TFT and a second terminal coupled to an anode electrode of the white OLED, and a color filter formed in the emission area. At least one of a top metal of the storage capacitor and a top metal of the driving TFT is formed to not overlap the color filter.