Polysilicon TFT Substrate with Curved Insulating Layers
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Solution Overview
Problem
Current thin film transistor (TFT) substrates face challenges in increasing storage capacities of pixels and contact areas of insulating layers, which affect the display quality of LCD and OLED devices, particularly in achieving improved adhesion and preventing peeling between layers.
Innovation Solution
The TFT substrate design includes a substrate with polysilicon active layers, insulating layers with varying roughness and protrusions, and metal layers with protrusions, creating increased contact areas and enhanced adhesion, thereby increasing storage capacities and preventing peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional flat insulating layers are used in TFT substrates, then the manufacturing process is simple, but the contact area between layers is insufficient and adhesion is poor
Solution Approach 1:
The insulating layer is designed with a convex curved surface instead of a flat surface. The curvature increases the contact area between the insulating layer and adjacent layers, thereby improving adhesion and preventing peeling without significantly complicating the manufacturing process
Solution Approach 2:
The insulating layer has different surface properties in different regions: the top surface has a convex curvature to increase contact area, while the side surfaces have specific curvature characteristics to match adjacent layers. This local differentiation optimizes adhesion at each interface
2Area of stationary object
If the insulating layer has high roughness throughout, then contact area increases, but adhesion outside the active layer region deteriorates
Solution Approach 1:
The insulating layer has different roughness values in different regions: the first region (corresponding to the active layer) has higher roughness to increase contact area and adhesion, while the second region (outside the active layer) has lower roughness to maintain good adhesion properties. This spatial differentiation resolves the contradiction between maximizing contact area and maintaining adhesion quality
3Quantity of substance
If pixel storage capacity is increased by enlarging capacitor structures, then storage capacity improves, but the area available for other pixel components decreases
Solution Approach 1:
The capacitor electrodes and insulating layers are designed with convex curved surfaces that increase their effective contact area and volume. This allows the capacitor structures to achieve higher storage capacity within the same planar footprint, leaving more area available for other pixel components like TFTs and light-emitting elements
Data Source
AI summary
An OLED display device is disclosed, which comprises: a TFT substrate, comprising a substrate and plural TFT units disposed on the substrate; and an OLED unit electrically connected to one of the plural TFT units. The TFT units respectively comprise: an active layer disposed on the substrate and made of polysilicon; a first insulating layer disposed on the active layer; source and drain electrodes disposed on the first insulating layer; a metal layer disposed on the first insulating layer; and a second insulating layer disposed on the metal layer, wherein the metal layer has plural first protrusions at a top surface thereof, the second insulating layer comprises a first region corresponding to the active layer and a second region corresponding to a region outside the active layer, and a roughness of a top surface of the first region is greater than that of the second region.