Viscid Binder for Electrophoretic Sheet Uniformity
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Solution Overview
Problem
Existing electrophoretic devices face display unevenness due to the hardening of emulsion adhesives at normal temperatures, leading to regions with overlapping and no microcapsules, which affects the display performance.
Innovation Solution
An electrophoretic sheet with a binder having viscid properties at normal temperatures, specifically (metha)acrylic acid ester with a melting point of 25 degrees centigrade or less, is used to maintain fluidity and ensure proper adhesion, combined with a microcapsule dispersion medium like liquid paraffin to prevent sedimentation and improve display performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an emulsion adhesive is used as the binder to hold microcapsules, then the microcapsules are fixed on the substrate, but the adhesive hardens at normal temperature making it difficult to re-arrange the microcapsules, resulting in display unevenness
Solution Approach 1:
The patent changes the temperature parameter of the binder to resolve the contradiction. The binder is designed to be in a liquid state at normal temperature (20-25°C) allowing microcapsule arrangement, and transitions to a solid state at elevated temperature (40-60°C) providing strong adhesion. This temperature-dependent phase change enables both easy operation during assembly and strong bonding during use.
2Strength
If the binder hardens at normal temperature to provide strong bonding, then adhesion is improved, but microcapsule uniformity is compromised leading to regions with overlapping or no microcapsules
Solution Approach 1:
The patent applies preliminary action by arranging microcapsules uniformly while the binder is in liquid state at normal temperature, before the bonding process. This allows precise positioning and uniform distribution of microcapsules on the substrate. Subsequently, the binder is heated to solidify and lock the microcapsules in their arranged positions, ensuring both uniformity and strong bonding.
3Strength
If a thermoplastic resin with high melting point is used as binder, then strong adhesion is achieved, but the binder lacks fluidity at normal temperature making it difficult to handle and arrange microcapsules
Solution Approach 1:
The patent selects a thermoplastic resin with a specific melting point range (40-60°C) that enables operational fluidity at normal temperature while providing strong adhesion when heated. This parameter selection allows the binder to be easily handled and arranged with microcapsules during assembly, then transitions to a strong bonding state during the heating and pressing process.
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 enables reliable bonding of the electrophoretic sheet and counter substrate, preventing display unevenness and enhancing the electrophoretic device's reliability and performance by maintaining microcapsule uniformity and fluidity, thus improving response speed and holding characteristics.
Implementation Method 1
a binder having viscid property at normal temperature and holding the microcapsule
Implementation Method 2
fine particles move (migrate) in a liquid by a coulomb power if an electric field is applied to a dispersal system in which fine particles are dispersed into a liquid. This phenomenon is called an electrophoresis
Implementation Method 3
a melting point of the binder is preferably 25 degrees centigrade or less. Such binder shows sufficient fluidity at normal temperature
Data Source
AI summary
An electrophoretic sheet, comprises: a substrate having a first side; a microcapsule contained layer having a second side and a third side facing the second side, the second side being disposed on the first side of the substrate, the layer including: a microcapsule; and a binder having viscid property at normal temperature and holding the microcapsule, the microcapsule including: a shell; an electrophoretic dispersion liquid included in the shell; and at least one electrophoretic particle included in the electrophoretic dispersion liquid.