Array Substrate Passivation Layer Segmentation for Touch Display
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Solution Overview
Problem
In in-cell touch display devices, the residual photoresist from the photolithographic process reduces the adhesive strength between the touch common line and the touch common electrode, leading to detachment issues and decreased yield, while thinning the passivation layers to improve touch sensing also deteriorates image displaying properties.
Innovation Solution
A method of forming a relatively thick first passivation layer between the touch common line and electrode and a thin second passivation layer between the touch common electrode and pixel electrode, preventing residual photoresist and enhancing adhesive strength, thereby reducing parasitic capacitance and improving both touch sensing and image displaying properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the passivation layers are thinned to improve touch sensing, then touch sensing property is improved, but image displaying property deteriorates
Solution Approach 1:
The passivation layer is divided into two separate layers: a first passivation layer between the touch common line and touch common electrode, and a second passivation layer between the touch common electrode and pixel electrode. This segmentation allows each layer to be optimized independently for its specific function, resolving the contradiction between touch sensing and image displaying properties.
Solution Approach 2:
Different thickness requirements are applied to different regions of the passivation structure. The first passivation layer is made thicker to reduce parasitic capacitance and improve touch sensing, while the second passivation layer is made thinner to maintain image displaying quality. This local differentiation of quality parameters resolves the contradiction.
2Manufacturing precision
If photolithographic process is used to form touch common contact hole, then contact hole is formed, but residual photoresist reduces adhesive strength causing detachment
Solution Approach 1:
The first passivation layer serves as an intermediary structure that is specifically designed to be etched away to form the touch common contact hole. By making this layer thicker and compositionally distinct, it provides a robust etching target that completely removes photoresist residues, preventing adhesive strength reduction and detachment issues.
Solution Approach 2:
The first passivation layer is formed in advance with specific material composition and thickness before the photolithographic process. This preliminary preparation ensures that when the photoresist is applied and subsequently removed, no residues remain that could compromise adhesive strength, thus preventing detachment.
Data Source
AI summary
An array substrate for a touch display device includes: a substrate having a pixel region; a thin film transistor on the substrate in the pixel region; a planarizing layer on the thin film transistor; a touch common line on the planarizing layer; a first passivation layer on the touch common line, the first passivation layer having a touch common contact hole exposing the touch common line; a touch common electrode on the first passivation layer in the pixel region, the touch common electrode contacting the touch common line through the touch common contact hole; a second passivation layer on the touch common electrode; and a pixel electrode on the second passivation layer, the pixel electrode connected to the thin film transistor.