EL Display Device Wiring Substrate for Voltage Drop Reduction
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Solution Overview
Problem
Large active-matrix EL display devices experience increased voltage drops and heat issues due to high sheet resistance in cathode electrodes, leading to brightness-shading and cross-talk, and thick wiring solutions compromise display area size and reliability.
Innovation Solution
Incorporating a wiring substrate with a reinforcement wiring pattern electrically parallel to the display panel's wiring, connected to the source and gate signal lines, to reduce sheet resistance and distribute current more evenly, preventing overheating and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick wiring portion made of low resistance metal material is formed to reduce voltage drop and prevent overheating, then reliability and heat dissipation improve, but the display area becomes smaller and the frame becomes larger
Solution Approach 1:
The patent moves the reinforcement wiring from the display area to the peripheral area, utilizing the peripheral space for current distribution. The wiring substrate is positioned in the peripheral portion of the EL display panel, allowing current to be distributed before reaching the display area, thus reducing the need for thick wirings within the display area itself.
Solution Approach 2:
The wiring substrate acts as an intermediary component between the power supply and the EL elements. It includes a reinforcement wiring pattern that distributes current evenly to multiple cathode electrodes before they reach the display area, preventing current concentration and overheating at connection points while maintaining a thin profile in the display area.
2Loss of energy
If a thick wiring portion is formed to reduce sheet resistance, then voltage drop and heat generation are reduced, but the connecting points still melt due to current concentration
Solution Approach 1:
The reinforcement wiring pattern is divided into multiple wirings that connect to different cathode electrodes. Each wiring in the reinforcement pattern connects to a corresponding cathode electrode, distributing the current load across multiple connection points rather than concentrating it at a single point, thus preventing melting at connection points.
Solution Approach 2:
The wiring substrate provides localized current distribution at the connection points between the power supply and cathode electrodes. The reinforcement wiring pattern is specifically designed to distribute current at these critical connection points, ensuring even current distribution and preventing overheating at these locations.
3Illumination intensity
If the cathode electrode is made very thin to achieve light transmittance, then optical performance improves, but sheet resistance increases causing voltage drop and brightness-shading
Solution Approach 1:
The wiring substrate with reinforcement wiring pattern serves as an intermediary that compensates for the high sheet resistance of the thin cathode electrode. By distributing current before it reaches the cathode electrode, the reinforcement wiring ensures adequate current supply despite the electrode's thinness, maintaining both optical performance and electrical reliability.
Data Source
AI summary
A EL display device has EL display panel including the a display area where a pixel is arranged in matrix, and a wiring pattern formed in a circumferential portion of the display area and supplying voltage to a pixel. The EL display panel includes a flexible substrate having an electrode connected to a source signal line or a gate signal line arranged thereon. The flexible substrate includes an anode reinforcement wiring and a cathode reinforcement wiring which are electrically parallel to the wiring pattern.