Touch Sensor Bezel Electrode Pad Stepped Structure
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Solution Overview
Problem
Touch sensors face issues with bubbles being visually recognized in the display area due to separation spaces between the touch sensor layer and the printed circuit board, and corrosion and cracking caused by iodine release from the polarizing layer, leading to bonding defects and electrode pad damage.
Innovation Solution
The touch sensor design features a polarizing layer with altered and straight line surfaces that have cross-sectional inclination angles of 30° or less, specifically 5° or less for the altered surface and 5° to 30° for the straight line surface, to minimize iodine release and prevent bonding defects and cracking, while also protecting the passivation layer from processing impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bonding pad portion is formed at the lower edge of the transparent base layer to connect to the printed circuit board, then electrical connection is achieved, but a separation space forms at the boundary due to step difference causing bubbles to be visually recognized in the display area
Solution Approach 1:
The invention transitions from a conventional planar bonding structure to a three-dimensional stepped structure. The bonding pad portion is formed to protrude from the lower edge of the transparent base layer, creating multiple height levels. This dimensional change allows the bonding connection to be made at a lower level while maintaining a flat upper surface, thereby preventing bubble formation in the display area.
Solution Approach 2:
The bonding structure is segmented into distinct height levels. The bonding pad portion protrudes from the base layer to create a stepped configuration, separating the bonding function from the display surface. This segmentation allows independent optimization of bonding reliability and visual appearance without mutual interference.
2Reliability
If the polarizing layer is coupled to the touch sensor layer, then optical polarization function is achieved, but iodine release from the polarizing layer causes corrosion and cracking of metal wiring and electrode pads
Solution Approach 1:
A barrier layer is introduced as an intermediary between the polarizing layer and the touch sensor layer. This barrier layer selectively blocks iodine release from the polarizing layer while maintaining optical transmission properties. The barrier layer acts as a protective mediator that prevents harmful chemical interactions while preserving the optical polarization function.
Solution Approach 2:
The invention converts the harmful iodine release property of the polarizing layer into a beneficial protective function. The barrier layer is specifically designed to block iodine while being transparent to light, transforming what would be a harmful chemical emission into a controlled and protected interface that maintains both optical and chemical stability.
3Adaptability or versatility
If the bonding pad portion is formed at the lower edge of the transparent base layer, then connection to printed circuit board is enabled, but cracks occur in the wiring and electrode pads due to stress concentration
Solution Approach 1:
The bonding structure is extended into the vertical dimension, creating a stepped configuration where the bonding pad protrudes from the base layer. This three-dimensional structure distributes mechanical stress across multiple levels and interfaces, preventing stress concentration at the bonding interface and reducing crack formation in the wiring and electrode pads.
Data Source
AI summary
A touch sensor comprises a touch sensor layer having an electrode pad portion formed in a bezel area, and a polarizing layer coupled to the touch sensor layer while opening an area of the electrode pad portion and having a side surface of an area of the electrode pad portion defining an altered surface and a side surface excluding the area of the electrode pad portion defining a straight line surface. The altered surface and the straight line surface have a cross-sectional inclination angle of 30° or less in a lateral direction with respect to a vertical direction.