Dual-Sided Conductive Film for Resistance Balance and Curl Control
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Solution Overview
Problem
Electroconductive films with metallic nanowires face issues such as significant differences in electrical resistance between layers, thermal shrinkage leading to wiring failures, and curling during heating processes, especially when used with flexible base materials and protective films.
Innovation Solution
An electroconductive film design featuring a first and second electroconductive part with electroconductive fibers, where the surface resistance values are within ±30% of each other, and a resin layer and light-transmitting base material are used to minimize resistance differences and prevent curling during heating, with a protective film to manage thermal shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If electroconductive parts containing metallic nanowires are formed on both faces of an electroconductive film, then the thickness of the touch panel is reduced, but the electrical resistance value of one electroconductive part becomes extremely larger than the other
Solution Approach 1:
The patent applies different formation conditions to the first and second electroconductive parts. Specifically, the second electroconductive part is formed with different nanowire suspension concentration, drying conditions, or heating treatment compared to the first electroconductive part, resulting in different nanowire network structures that compensate for the resistance difference caused by the dual-face configuration.
Solution Approach 2:
The patent changes physical or chemical parameters during the formation process of the electroconductive parts. By adjusting parameters such as nanowire suspension concentration, drying temperature, drying time, or heating treatment conditions, the patent achieves uniform electrical resistance values between the two electroconductive parts despite their different positions on the film.
2Reliability
If a protective film is adhered to the surface of an electroconductive part, then the surface is protected from scratches and winding is facilitated, but the electroconductive film curls when heated
Solution Approach 1:
The patent performs preliminary heating treatment on the electroconductive film before applying the protective film. This pre-heating causes the light-transmitting base material to undergo thermal shrinkage in advance, so that subsequent heating during silver paste firing does not cause additional curling that would affect the protective film adhesion or cause film deformation.
Solution Approach 2:
The patent applies a release film to the electroconductive film before heating, and this release film has specific thermal shrinkage characteristics that counteract the shrinkage of the light-transmitting base material. This preliminary anti-action prevents the electroconductive film from curling during the heating process while still allowing surface protection.
3Ease of manufacture
If the electroconductive film is heated to fire silver paste, then electrical lead-out lines can be formed, but the light-transmitting base material undergoes thermal shrinkage causing wiring failure
Solution Approach 1:
The patent performs preliminary heating treatment at a higher temperature (150°C or higher) before applying and firing the silver paste. This pre-heating causes the light-transmitting base material to complete its thermal shrinkage in advance, ensuring that the subsequent silver paste firing at lower temperature (130°C) does not cause additional shrinkage that would misalign the wiring patterns.
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 uniform electrical resistance across layers, enhances flexibility, and reduces curling and thermal shrinkage, ensuring reliable performance and durability in touch panels and image display devices.
Implementation Method 1
the first electroconductive part and the second electroconductive part each contain electroconductive fibers
Implementation Method 2
heating the electroconductive film at such a temperature causes the light-transmitting base material to undergo thermal shrinkage
Data Source
AI summary
An aspect of the present invention provides an electroconductive film 10 including a first electroconductive part 11 and a second electroconductive part 14, wherein the surface 14A of the second electroconductive part 14 forms at least a part of the surface 10A of the electroconductive film 10, the surface 11A of the first electroconductive part 11 forms at least a part of the back face 10B of the electroconductive film 10, the first electroconductive part 11 and the second electroconductive part 14 each contain electroconductive fibers 15 and 17, and the surface resistance value of the second electroconductive part 14 is within ±30% of the surface resistance value of the first electroconductive part 11.