Organic TFT Pixel Electrode Sealing for Moisture Protection
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Solution Overview
Problem
Existing display apparatus using organic thin film transistors face challenges in protecting the organic material from gas and moisture without increasing the number of constituent members, leading to reduced lifespan and thickness issues.
Innovation Solution
A display apparatus configuration where the thin film transistor unit and display element unit are laminated on a substrate, with the pixel electrode functioning as a drain electrode and a conductive film formed to suppress gas and moisture permeation, ensuring the entire top surface of the channel region is protected, and the substrate is designed to be flexible and impermeable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional sealing methods (metal cap, desiccant, polymer film with barrier layer) are used to protect organic material from gas and moisture, then the lifespan of the organic TFT is extended, but the number of constituent members increases and the device thickness increases
Solution Approach 1:
The invention combines the sealing function with the existing pixel electrode structure. The pixel electrode is configured to extend over the organic TFT unit and function as both the electrode for the display element and the sealing structure, merging two functions into a single component without increasing the number of constituent members.
Solution Approach 2:
The pixel electrode is designed to perform multiple functions: it serves as the electrical electrode for the display element and simultaneously acts as the sealing structure that prevents gas and moisture entry. This multi-functional design eliminates the need for separate sealing components.
2Duration of action of stationary object
If conventional sealing methods (metal cap, desiccant, polymer film with barrier layer) are used to protect organic material from gas and moisture, then the lifespan of the organic TFT is extended, but the device thickness increases
Solution Approach 1:
The sealing function is merged with the pixel electrode structure, eliminating the need for additional sealing layers that would increase device thickness. The pixel electrode itself is configured to provide the sealing barrier.
Solution Approach 2:
The pixel electrode structure is designed as a thin film configuration that provides effective sealing against gas and moisture permeation without adding significant thickness to the device. The conductive film forms a thin protective barrier.
3Device complexity
If the pixel electrode functions as drain electrode and the structure is laminated, then the number of components is reduced, but protection against gas and moisture permeation must be ensured
Solution Approach 1:
The pixel electrode and drain electrode functions are merged into a single structure. The pixel electrode extends to function as the drain electrode of the organic TFT, reducing component count while the same structure provides the sealing barrier against gas and moisture.
Solution Approach 2:
A conductive film is used as an intermediary material that provides both the electrical conductivity needed for the drain electrode function and the barrier properties needed to prevent gas and moisture permeation. This single material layer mediates both requirements.
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 extends the life of the organic TFT unit by preventing gas and moisture entry, achieving a long-life, flexible, and lightweight display apparatus without increasing the number of components, with a gas transmission rate less than 10 ml/m2/day/MPa and suitable for large-screen and sheet-like displays.
Implementation Method 1
a method is disclosed in which a transparent conductive film formed of a metal oxide deficient in oxygen as compared with a stoichiometric composition is formed on a surface of an organic EL element, so that moisture and oxygen are absorbed
Implementation Method 2
a current flowing between a source electrode and a drain electrode provided in contact with a semiconductor layer is controlled by a voltage (i.e., an electric field generated by the applied voltage) applied to a gate electrode
Data Source
AI summary
In a display apparatus according to the present invention, a pixel is driven by using a thin film transistor (10) including an organic material in at least an active layer. The thin film transistor unit (10) and a display element unit (20) are laminated on a substrate (11) in this order, and a pixel electrode (15) formed on a substrate (10) side of the display element unit (20) also functions as a drain electrode of the thin film transistor (10). Therefore, when an organic material is used for a transistor for driving a display apparatus, there is provided a display apparatus that can provide effective protection without increasing the number of constituent members.