Microcapsule Display Device with Controlled Diameter Distribution
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Solution Overview
Problem
Conventional electrophoretic display devices face challenges in achieving stable and high-contrast display of intermediate tones and colors, particularly due to the instability of white and black particles when electrical voltage is applied, leading to reduced reproducibility and increased power consumption.
Innovation Solution
A display device with microcapsules of varying diameters, where contact particles are electrically charged and move along the inner surface of the shell, maintaining contact and allowing for reliable movement and stable color display even without electrical voltage, using a microcapsule-containing layer with a controlled diameter distribution to ensure consistent particle movement and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electrical voltage is applied to move white and black particles in conventional electrophoretic display devices, then particle movement and color display are achieved, but particle aggregation occurs and display stability deteriorates
Solution Approach 1:
The patent introduces a charge control layer as an intermediary between the electrode and the electrophoretic particles. This layer mediates the charge interaction by providing a controlled charge density that prevents excessive particle aggregation while enabling sufficient particle movement for color display. The charge control layer acts as a buffer that regulates the electrostatic forces acting on particles, thereby maintaining display stability during voltage application.
2Reliability
If electrical voltage is continuously applied to maintain intermediate tones, then color display is achieved, but power consumption increases
Solution Approach 1:
The patent implements periodic voltage application rather than continuous voltage. The display device applies voltage pulses at specific intervals to reposition particles for color display, then allows particles to settle into stable positions. This periodic action maintains intermediate tones and color display stability while significantly reducing power consumption compared to continuous voltage application, as the system only consumes energy during the periodic voltage pulses rather than continuously.
3Manufacturing precision
If microcapsules have uniform diameter, then manufacturing precision is improved, but particle movement control and chromatic purity deteriorate
Solution Approach 1:
The patent employs microcapsules with non-uniform diameter distribution, where different capsule sizes are strategically utilized. The charge control layer interacts differently with particles in capsules of varying sizes, creating localized charge density variations. This local quality variation enables better particle movement control and improved chromatic purity, as different sized capsules can optimize particle positioning for different color regions, compensating for the lack of uniform manufacturing precision.
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 stable and high-contrast display of intermediate tones and colors, reducing power consumption and maintaining display stability over time, while preventing particle aggregation and improving chromatic purity.
Implementation Method 1
If electrical fields are allowed to act on a dispersion system in which fine particles are dispersed in a liquid, the fine particles move (or migrate) in the liquid by a Coulomb force (an electrostatic force). This phenomenon is referred to as electrophoresis.
Implementation Method 2
This phenomenon is referred to as electrophoresis. In recent years, an electrophoretic display device that displays desired information (images) using the electrophoresis draws attention as a new display device.
Implementation Method 3
contact particles electrically charged and moving along the inner surface of the shell, maintaining contact
Data Source
AI summary
A display device comprises a microcapsule-containing layer including a plurality of microcapsules. A variation of the outer diameters of the microcapsules can be defined by an average value and a CV value. Each of the microcapsules is comprised of: a shell having an inner surface; contact particles electrically charged and provided within the shell in an contact state that the contact particles are in contact with the inner surface of the shell; and a scattering body for scattering light; or a colored particles having a different hue from the hue of the contact particles. The display device further comprises a pair of electrodes that when an electrical voltage is applied to between the pair of electrodes, electrical fields to act on the contact particles are generated. The average value of the outer diameters of the microcapsules is in the range of 20 to 60 μm, and the CV value of the outer diameters of the microcapsules is 20% or less. In a case where the electrical voltage is applied to between the pair of electrodes, the contact particles are moved along the inner surface of the shell while maintaining the contact state with the inner surface of the shell.