Inkjet Printed Transparent Conductive Polymer Electrode with Gradient Droplet Density
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Solution Overview
Problem
Transparent electrodes made of indium tin oxide (ITO) are prone to fracture in flexible devices under stress and are expensive, necessitating the development of alternative materials with high electrical conductivity that are also difficult to visually perceive.
Innovation Solution
A transparent conductive polymer electrode is formed using inkjet printing with varying conductive polymer droplet hit densities along the electrode line, where the first region has a specific ratio of b/a (0.2 to 0.8) and the second region has a lower droplet hit density, allowing for adjustable thickness and reduced visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conductive polymer droplets are uniformly ejected onto the entire region of a pattern, then the pattern can be rapidly formed without waste and optical mask, but the pattern becomes easily visible due to light transmittance difference, lowering visual quality
Solution Approach 1:
The patent applies local quality by varying the droplet hit density across different regions of the electrode line. The first region (central part) has a higher droplet hit density with a ratio of b/a within 0.2 to 0.8, while the second region (edge part) has a lower droplet hit density. This creates a gradient structure where the thickness and light transmittance vary locally, making the electrode line visually imperceptible while maintaining electrical conductivity.
2Illumination intensity
If the thickness of conductive polymer pattern is reduced to lower light transmittance difference, then visual quality improves, but electrical conductivity is lowered in proportion to thickness
Solution Approach 1:
The patent resolves this contradiction by creating non-uniform local quality in the conductive polymer pattern. The first region maintains sufficient thickness to ensure electrical conductivity, while the second region has reduced thickness to minimize visual perception. This gradient structure allows different parts of the same electrode line to serve different functions: electrical conduction and visual transparency.
Solution Approach 2:
The patent introduces a spatial dimension variation by creating a gradient in droplet hit density across the electrode line width. Instead of uniform thickness in one dimension, the pattern varies in thickness across the width dimension, with the first region having higher density and the second region having lower density. This dimensional variation allows simultaneous optimization of conductivity and transparency.
3Reliability
If ITO is used for transparent electrodes, then good electrical conductivity and transparency are achieved, but the electrodes are expensive and prone to fracture under stress in flexible devices
Solution Approach 1:
The patent replaces expensive ITO with conductive polymers that are more cost-effective and suitable for flexible applications. The conductive polymer pattern can be formed using inkjet printing, which is a low-cost additive manufacturing process that eliminates the need for expensive vacuum deposition equipment required for ITO.
Solution Approach 2:
The patent changes the material parameter from inorganic ITO to organic conductive polymer, which fundamentally alters the mechanical properties to enable flexibility while maintaining electrical conductivity. The inkjet printing process parameters are optimized to create the gradient droplet distribution pattern that achieves both conductivity and visual transparency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a cost-effective, electrically conductive, and visually imperceptible transparent conductive polymer electrode with adjustable thickness, suitable for flexible devices like touch sensors and displays, maintaining high light transmittance and conductivity.
Implementation Method 1
a transparent conductive polymer electrode formed by inkjet printing
Data Source
AI summary
The present invention relates to a transparent conductive polymer electrode including a plurality of electrode lines formed of droplets of conductive polymer, each of the electrode lines including first and second regions having different conductive polymer droplet hit densities. The first region has a ratio of b/a within a range of 0.2 to 0.8, where “a” is a distance from a center to an edge of the electrode line in at least one direction of width and length directions thereof, and “b” is a distance from the center to an edge of the first region in the at least one direction. The second region is the remaining region of the electrode line, and the conductive polymer droplet hit density of the second region is lower than that of the first region.