Current Blocking Transistor for Flexible Display Bright Spot Prevention
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Solution Overview
Problem
Flexible display devices face issues with cracks in transistors due to stress from folding and external shocks, leading to unintended light emission from pixels, which results in bright spot defects and reduced display quality.
Innovation Solution
Incorporating a second pixel circuit part with a current blocking transistor that prevents the output current from the driving transistor from reaching the light emitting diode when cracks occur, ensuring the light emitting diode does not emit light even if the second or third transistor is non-functional.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible substrate is used to enable bending and folding, then flexibility and portability are improved, but cracks occur in transistors due to stress from folding and external shocks
Solution Approach 1:
The current blocking transistor is pre-configured in the pixel circuit to block current flow to the light emitting diode when cracks occur in other transistors. This preliminary protective mechanism ensures that even if folding or external shocks cause transistor cracks, the light emitting diode will not emit unintended light, thus maintaining display quality while preserving the flexibility benefits of the flexible substrate
2Reliability
If the current blocking transistor blocks the light emitting current, then bright spot defects are prevented, but the pixel circuit complexity increases
Solution Approach 1:
The current blocking transistor is integrated into the existing pixel circuit architecture and shares control signals with other circuit elements. It utilizes the same initialization voltage line and coordinates with the driving transistor's gate electrode, allowing it to perform protective function without requiring completely separate control mechanisms, thus minimizing the increase in circuit complexity while ensuring display quality
Data Source
AI summary
A display device including a light emitting diode, a driving transistor, a second transistor, a third transistor, a fourth transistor, and a current blocking transistor. The current blocking transistor is a transistor of a different type from the driving transistor, and in case that a voltage of a gate electrode of the driving transistor is maintained at an initialization voltage, the current blocking transistor is turned off during a light emitting period to not transmit the light emitting current outputted by the driving transistor to an anode of the light emitting diode.