Transparent Conductive Sheet for Touch Panels
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Solution Overview
Problem
Touch panels require high conductivity, transparency, water resistance, adhesion, and durability, but existing transparent conductive sheets fail to meet these requirements, particularly in maintaining low surface resistivity and transparency under high temperature and humidity conditions.
Innovation Solution
A transparent conductive sheet with a π-conjugated conductive polymer, polyanion, and ester compound, optionally including a conductivity improver or polymerizable compound, is formed by applying a conductive polymer coating material to a transparent substrate, enhancing adhesion and conductivity while maintaining low haze and high light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ITO conductive layer is formed on a PET film, then electrical conductivity is achieved, but light transmittance decreases and the layer turns yellow due to high refractive index and surface reflection
Solution Approach 1:
The patent changes the material parameters by replacing ITO (indium tin oxide) with organic conductive polymers such as polythiophene derivatives. This material substitution fundamentally alters the optical and electrical parameters, achieving conductivity through molecular structure rather than metal oxide, thereby reducing light reflection and maintaining high transmittance.
Solution Approach 2:
The patent employs composite material structures by combining conductive polymers with transparent substrates and interface layers. The composite approach allows optimization of both electrical conductivity and optical transparency through the synergistic combination of materials with complementary properties, avoiding the trade-off inherent in single-material ITO layers.
2Reliability
If an ITO conductive layer is used, then conductivity is provided, but the layer cracks when bent due to poor flexibility
Solution Approach 1:
The patent changes the mechanical parameters by transitioning from rigid ITO layers to flexible organic conductive polymer layers. The molecular structure of conductive polymers inherently provides flexibility and bendability, allowing the conductive layer to maintain electrical conductivity even when bent or deformed, thus resolving the brittleness issue of ITO.
3Reliability
If an ITO conductive layer is formed, then conductivity is achieved, but formation on PET film is difficult
Solution Approach 1:
The patent replaces the complex physical vapor deposition or sputtering processes required for ITO formation with solution-based coating methods for conductive polymers. This substitution of manufacturing methodology simplifies the production process, allowing direct coating on flexible substrates without requiring vacuum equipment or high-temperature processing.
4Reliability
If conventional transparent conductive sheets are used, then basic conductivity is provided, but surface resistivity increases and durability decreases under high temperature and humidity conditions
Solution Approach 1:
The patent changes the chemical composition parameters by using environmentally stable conductive polymer structures that resist degradation from moisture and heat. The molecular design of the conductive polymers includes features that prevent electrochemical reactions and oxidation, maintaining consistent electrical properties under varying environmental conditions.
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 achieves a surface resistivity of ≤1000 Ω, total light transmittance of ≥80%, and haze of ≤5%, ensuring excellent operational reliability and durability under varying environmental conditions.
Implementation Method 1
The transparent conductive layer contains a π-conjugated conductive polymer
Implementation Method 2
the ester compound is obtained by a dehydration reaction between a carboxylic acid compound containing two or more carboxyl groups and a polyhydric alcohol compound containing two or more hydroxyl groups
Implementation Method 3
the light transmittance decreases, and because the layers tend to be tinged yellow, the color tone of the image also changes
Implementation Method 4
the haze is not more than 5%
Data Source
Figure 1~2
AI summary
A transparent conductive sheet for a touch panel, comprising a transparent substrate and a transparent conductive layer formed on top of said transparent substrate, wherein said transparent conductive layer comprises a π-conjugated conductive polymer, a polyanion, and a polymerizable compound, wherein said polymerizable compound is (a) and (b), or only (b), and (a): a compound containing a glycidyl group, (b): a compound containing a hydroxyl group, and one group selected from the group consisting of an allyl group, vinyl ether group, methacryl group, acryl group, methacrylamide group and acrylamide group.