Display Driver Circuit Stray Capacitance Isolation
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Solution Overview
Problem
Conventional liquid crystal display devices face issues with operational margin, reliability, frame size, and cost due to stray capacitance effects when the potential of the counter electrode varies temporally, leading to malfunction, decreased operational margin, and increased cost.
Innovation Solution
A driving circuit integrated-type active matrix display device is designed with a conductive seal to isolate circuit elements affected by stray capacitance, positioning these elements apart from the seal to prevent influence from voltage fluctuations, thereby ensuring high operational margin and reliability while minimizing frame size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If circuit elements are positioned close to the conductive seal for compact layout, then device area is reduced, but stray capacitance increases causing operational margin degradation and reliability decrease
Solution Approach 1:
The patent introduces a non-conductive seal as an intermediary barrier between the conductive seal and circuit elements. This non-conductive seal (formed by insulating films) acts as a mediator that blocks the harmful electromagnetic coupling and stray capacitance from the conductive seal, allowing circuit elements to be positioned close to the seal without suffering from capacitance effects. The non-conductive seal is formed by insulating films 10a and 10b that extend over the conductive seal structure.
2Reliability
If circuit elements are positioned away from the conductive seal to avoid stray capacitance, then operational reliability is improved, but device area increases leading to larger frame size
Solution Approach 1:
The non-conductive seal formed by insulating films serves as a protective intermediary that allows circuit elements to be positioned adjacent to the conductive seal without experiencing harmful stray capacitance. This enables maximum space utilization while maintaining operational reliability, as the non-conductive barrier eliminates the need for additional spacing that would otherwise be required.
3Manufacturing precision
If conventional separate IC chip configuration is used for driver circuits, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the driver circuit with the display device substrate by forming the driver circuit directly on the substrate using the same polysilicon TFT technology. This integration eliminates the need for separate IC chips and their associated mounting structures, reducing device complexity while maintaining manufacturing precision through unified process control. The driver circuit shares the same substrate and manufacturing process as the display pixels.
4Ease of manufacture
If polysilicon TFT technology is used for driver circuit integration, then manufacturing cost is reduced, but stray capacitance effects increase causing malfunction
Solution Approach 1:
The non-conductive seal formed by insulating films acts as a protective intermediary that blocks stray capacitance effects from reaching the polysilicon TFT driver circuit. This allows the use of cost-effective polysilicon TFT technology for driver circuit integration without suffering from the harmful capacitance coupling that would otherwise cause malfunction.
Data Source
AI summary
A display device includes: a pair of substrates disposed opposite each other; a conductive seal for sealing the gap of the outer peripheral part between the pair of substrates; an electric optical element disposed in an area defined by the substrates and the seal; a display area, formed on one substrate, having a plurality of pixels for controlling the electric optical element; and a driver circuit for controlling the pixels. The driver circuit is so configured that a circuit element affected by stray capacitance formed between the conductive seal and the driver circuit is disposed apart from the conductive seal.