Ionic Polyurethane Adhesive for Electro-Optic Assemblies
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Solution Overview
Problem
Existing lamination adhesives for solid electro-optic displays are not sufficiently conductive and can damage organic semiconductor backplanes, limiting their use in mass production and affecting electro-optic performance, especially at low temperatures.
Innovation Solution
Development of a polymeric polyurethane adhesive layer with an ionic material comprising a fixed carboxylate anion and a mobile quaternary ammonium or phosphonium cation, which controls volume resistivity and prevents ion diffusion, enhancing conductivity without damaging other layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing lamination adhesives are used, then manufacturing simplicity is maintained, but volume resistivity is insufficient and organic semiconductor backplanes are damaged
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating specific ionic materials (quaternary ammonium salts or phosphonium salts) with controlled concentrations. This changes the electrical properties of the adhesive, achieving volume resistivity between 10^6 to 10^9 ohm-cm while maintaining compatibility with organic semiconductor backplanes through careful selection of ion types and concentrations.
Solution Approach 2:
The patent creates a composite adhesive system by combining polymeric adhesive base materials with ionic conducting salts. This composite structure integrates the bonding functionality of the polymer with the electrical conductivity of the ionic material, achieving both adequate adhesion and controlled volume resistivity without damaging the backplane.
2Reliability
If adhesive conductivity is increased to improve electro-optic performance, then low-temperature stability is improved, but ion diffusion may occur damaging other layers
Solution Approach 1:
The patent employs spatial confinement strategies where the ionic material is localized within the adhesive layer through physical barriers or chemical anchoring mechanisms. This creates regions of high ionic concentration for conductivity where needed, while preventing ion migration to adjacent sensitive layers through localized containment structures or bonding groups.
Solution Approach 2:
The patent introduces intermediary structures such as ion-trapping groups or barrier layers within the adhesive composition that mediate between the ionic material and adjacent functional layers. These intermediaries allow the ionic material to provide conductivity while preventing direct contact and damage to organic semiconductor layers through chemical or physical separation.
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 adhesive layer achieves improved conductivity and electro-optic performance, including increased dynamic range and low-temperature stability, while preventing ion diffusion that could harm organic semiconductor layers.
Implementation Method 1
a mobile quaternary ammonium or phosphonium cation free to migrate through the polymeric adhesive material, the ionic material reducing the volume resistivity of the polymeric adhesive material
Implementation Method 2
the ionic material comprising a carboxylate anion fixed to the polymeric adhesive material and a quaternary ammonium or phosphonium cation free to migrate through the polymeric adhesive material
Data Source
Figure 1
AI summary
An electro-optic assembly comprises an adhesive layer and a layer of electro-optic material. The adhesive layer comprises a polymeric adhesive material and an ionic material having either its cation or its anion fixed to the polymeric adhesive material. The ionic material reduces the volume resistivity of the polymeric adhesive material and is not removed upon heating to 50°C. In a similar electro-optic assembly comprising an adhesive layer and a layer of electro-optic material, the adhesive layer comprises a polymeric adhesive material which has been subjected to dialysis or diafiltration to remove organic species having a molecular weight less than 3,500, so that the adhesive material has a content of N-methylpyrrolidone not exceeding 500 ppm based upon the total weight of the adhesive layer and layer of electro-optic material.