Display Test Line Layout Across Cut-Outs for Defect Diagnosis
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Solution Overview
Problem
Stretchable display devices face challenges in identifying disconnections in conductive layers and uniformity of transistor characteristic values, leading to display defects, which are difficult to trace due to stress concentration and varied causes.
Innovation Solution
A display device with a substrate featuring a cut-out portion and a conductive layer including a signal line and a test line that crosses the cut-out portion, with expanded pad regions for easy resistance measurement, and a test transistor with a layered structure similar to pixel circuit transistors for accurate characteristic value analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a cut-out portion is created in the substrate to reduce stress, then substrate stress is reduced, but stress concentration occurs in the conductive layer at the cut-out portion leading to disconnection
Solution Approach 1:
The conductive layer is divided into multiple segments with different patterns (mesh pattern, dot pattern, etc.) at different regions relative to the cut-out portion. This segmentation allows each segment to independently manage stress, preventing disconnection while maintaining conductivity.
Solution Approach 2:
Different conductive layer patterns are applied to different regions: the first conductive layer portion at the cut-out portion uses a stress-relief pattern (mesh, dot, or hollow), while the second conductive layer portion away from the cut-out uses a standard continuous pattern. This local differentiation optimizes both stress management and conductivity in each region.
2Measurement precision
If display defects are observed, then display performance issues are detected, but the exact causes and specific transistor positions cannot be accurately identified
Solution Approach 1:
A test transistor is introduced as an intermediary element that replicates the structure and characteristics of pixel circuit transistors. This test transistor serves as a reference for comparing and identifying abnormalities in actual pixel transistors, enabling precise localization and diagnosis of defects.
Solution Approach 2:
The test transistor is designed as a copy of the pixel circuit transistor with the same layered structure and material composition. By creating this identical copy, the system can compare expected performance (from the test transistor) against actual performance (from pixel transistors) to identify deviations and their causes.
Data Source
AI summary
A display device includes a substrate in which a cut-out portion is defined, and a first conductive layer disposed on the substrate and including a first signal line and a first test line, where the first test line crosses the cut-out portion, and one end portion of the first test line includes a first pad region that is expanded.