Display TFT Test Layout Using Dummy Pixel Circuits
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Solution Overview
Problem
Conventional display devices have test element groups (TEG) located near the perimeter, which are away from the thin film transistors (TFTs) in the display region, leading to characteristic values that do not accurately reflect the TFTs within the display region, thus not accurately representing the display characteristics.
Innovation Solution
A display device design that includes a TEG pattern adjacent to a dummy pixel circuit and a trench in the frame region, with the TEG pattern surrounded by the dummy pixel circuit or pixel circuit, allowing for accurate characterization of TFTs within the display region by mimicking their operating environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the TEG is disposed near the perimeter of the frame region, then the TEG is easily accessible for measurement, but the TEG characteristics change differently from the TFT characteristics within the display region
Solution Approach 1:
The patent introduces a dummy pixel circuit as an intermediary element between the perimeter TEG and the actual pixel circuits in the display region. This dummy circuit serves as a mediator that replicates the operating environment of real pixel circuits, allowing the TEG to be positioned at the perimeter for easy access while still providing accurate measurements through the intermediary's characteristic behavior
Solution Approach 2:
The dummy pixel circuit is designed to copy the configuration and electrical characteristics of the actual pixel circuits used in the display region. By creating this replica, the system enables accurate TFT characteristic measurement through the TEG without requiring the TEG to be physically located within the display region, thus resolving the contradiction between accessibility and measurement accuracy
2Device complexity
If the TEG is placed away from the pixel circuit, then the frame region structure is simplified, but the measured characteristic values do not exactly reflect the TFT characteristics within the display region
Solution Approach 1:
The dummy pixel circuit acts as an intermediary that bridges the gap between the simplified frame region structure and the need for accurate TFT characteristic measurement. It allows the TEG to remain in the frame region while the dummy circuit replicates the display region's electrical environment, maintaining both structural simplicity and measurement accuracy
Solution Approach 2:
The patent changes the electrical parameters and configuration of the dummy pixel circuit to match those of the actual pixel circuits in the display region. By adjusting these parameters, the system ensures that the TEG measurements taken in the frame region accurately reflect the TFT characteristics that would be measured in the display region, without increasing physical structural complexity
Data Source
AI summary
A TEG near the perimeter of a frame region is away from a TFT, which is disposed in a display region and is actually used for screen display. Hence, the characteristics of the TEG can change in a manner different from that in the characteristics of the TFT within the display region. Accordingly, provided is a display device that includes a TEG pattern disposed between the display region and a trench, and includes a dummy pixel circuit disposed between the display region and a barrier wall. The TEG pattern is outside the display region and is adjacent to at least the dummy pixel circuit.