Electrophoretic Display Sheet With Particle Constrained Layer
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Solution Overview
Problem
Existing electrophoretic displays face issues such as reduced effective display area, decreased display characteristics, leakage current, and particle precipitation due to partition types, microcapsule gaps, and gravity-induced particle movement in liquid crystal types.
Innovation Solution
A display sheet configuration with a first and second substrate, a display layer filled with charged particles in a dispersion medium, and a particle constrained layer with varying void ratios and fiber structures to prevent particle movement in the in-plane direction while allowing movement in the thickness direction, enhancing display reliability and characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a partition type display layer is used, then the display layer can be structured with electrodes and particles, but the effective display area is reduced by the partitions
Solution Approach 1:
The invention removes the partition structure entirely from the display layer, extracting the harmful element that reduced effective display area. The partition walls that previously divided the display layer into cells are completely eliminated, allowing the entire display area to be utilized without obstruction.
Solution Approach 2:
The display layer is designed to serve multiple functions without partitions: it provides both the structural framework for electrodes and the medium for particle dispersion simultaneously. The binder resin performs both structural support and particle constraint functions, eliminating the need for separate partition structures.
2Reliability
If a microcapsule type display layer is used, then the dispersion liquid is sealed in microcapsules, but gaps occur between microcapsules reducing effective display area and leakage current is generated by the binder
Solution Approach 1:
The invention merges multiple microcapsules into a continuous display layer medium. Instead of discrete microcapsules with gaps, the binder resin creates a continuous matrix that eliminates voids and gaps, allowing the entire area to function as effective display area without leakage current paths.
Solution Approach 2:
The binder resin creates a controlled porous structure that allows particle movement while preventing leakage. The porous network of the binder provides pathways for particle electrophoresis while maintaining structural integrity and preventing short-circuit current paths that would occur with gaps between discrete microcapsules.
3Area of stationary object
If a liquid crystal type display layer is used, then almost the whole area can be used as effective display area, but white particles and black particles move down by gravity causing image degradation
Solution Approach 1:
The binder resin acts as an intermediary medium between the particles and the electrodes. It provides a structured environment that allows particle movement in response to electric fields while preventing gravity-driven sedimentation. The binder's viscoelastic properties mediate between the conflicting requirements of particle mobility and position stability.
Solution Approach 2:
The binder resin is pre-configured with a structured network that anticipates and prevents particle sedimentation before it occurs. The pre-formed gel or semi-solid matrix creates a scaffold that supports particles against gravity, eliminating the need for corrective measures after particle movement degrades the image.
4Reliability
If a particle constrained layer with low void ratio is used, then particle movement is constrained, but particle dispersion uniformity and electrophoresis efficiency are reduced
Solution Approach 1:
The binder resin provides different local properties within the display layer: in regions near electrodes, it allows particle accumulation and movement for efficient electrophoresis, while in bulk regions, it provides structural support to prevent gravity-driven sedimentation. The void ratio and constraint strength vary locally to optimize both stability and efficiency.
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 display sheet with high reliability and excellent display characteristics by preventing particle precipitation and maintaining image clarity, while allowing for uniform particle dispersion and effective electrophoresis, thus improving the overall performance of electrophoretic displays.
Implementation Method 1
voltage is applied between the pair of electrodes to electrophorese the white particles and the black particles in a desired direction
Implementation Method 2
the white particles and the black particles move (precipitate) down in the vertical direction by gravity
Data Source
AI summary
A display device includes a substrate that is provided on a display face side, an opposed substrate that is provided opposing the substrate, a display layer that is provided between the substrate and the opposed substrate and is filled with a dispersion liquid in which white particles and black particles are dispersed in a dispersion medium, and a particle constrained layer that is provided in the display layer to allow the particles to move in a thickness direction of the display layer and to prevent the particles from moving in an in-plane direction of the display layer. A void ratio of the particle constrained layer of the substrate side is higher than that of the opposed substrate side.