SPD Film Dark Off-State Transmittance via Emulsion Optimization
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Solution Overview
Problem
Conventional SPD films face limitations in achieving significant ranges of light transmission between their OFF and ON states, with prior art struggling to produce films with very dark OFF states and very light ON states simultaneously, leading to issues such as reduced cohesion, incomplete curing, and increased power consumption.
Innovation Solution
The development of new SPD emulsion formulations with specific ranges of particle loading in the capsule phase and adjustments to the ratio of the continuous matrix phase to the discontinuous capsule phase, allowing for the production of films with very dark OFF states (70% T) and very light ON states (>70% T) while maintaining a high ΔT (>57%) by optimizing the weight of polyiodide particles and matrix polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the SPD film is increased to achieve darker OFF state transmittance, then the OFF state transmittance is improved, but the on-state transmittance decreases and power consumption increases
Solution Approach 1:
The patent changes the concentration parameters of particles and polymers in the emulsion formulation. Specifically, it uses particle concentrations of 0.5-5.0 wt% and polymer concentrations of 5-20 wt%, optimizing these parameters to achieve dark OFF state without requiring increased film thickness, thereby avoiding the associated power consumption penalties.
Solution Approach 2:
The patent employs composite emulsion formulations combining multiple components: polyiodide particles, non-aqueous liquid suspending medium, and polymer materials. This composite approach allows optimization of optical properties through material composition rather than geometric changes, achieving dark OFF state with maintained on-state transmittance and lower power consumption.
2Illumination intensity
If the thickness of the SPD film is increased to achieve darker OFF state transmittance, then the OFF state transmittance is improved, but the film cohesion and integrity deteriorate
Solution Approach 1:
The patent optimizes the polymer concentration parameter within 5-20 wt% range and particle concentration within 0.5-5.0 wt% range. This parameter optimization achieves the desired dark OFF state transmittance while maintaining adequate polymer matrix to ensure film cohesion and structural integrity, eliminating the need for increased thickness.
Solution Approach 2:
The patent uses a standardized emulsion formulation approach that can be replicated across different applications. The optimized concentration ranges provide a reliable recipe that ensures both optical performance and mechanical integrity without requiring thickness variations, enabling consistent film quality through formulation control.
3Illumination intensity
If the particle loading is increased to achieve darker OFF state, then the OFF state transmittance is improved, but the on-state transmittance and ΔT range are reduced
Solution Approach 1:
The patent optimizes the particle concentration parameter to 0.5-5.0 wt% and polymer concentration to 5-20 wt%. This balanced parameter selection ensures sufficient particles for dark OFF state while maintaining adequate polymer matrix for high on-state transmittance, achieving ΔT greater than 50 percentage points.
Solution Approach 2:
The patent creates a composite emulsion system where polyiodide particles (0.5-5.0 wt%) are dispersed in non-aqueous liquid with polymer (5-20 wt%). This composite structure allows particles to provide dark OFF state while the polymer matrix ensures high on-state transmittance when particles align, maintaining wide ΔT range.
4Illumination intensity
If the ratio of matrix polymer to capsule phase is adjusted to improve OFF state darkness, then the OFF state transmittance is improved, but the film integrity and curing completeness deteriorate
Solution Approach 1:
The patent optimizes the polymer concentration parameter to 5-20 wt% and particle concentration to 0.5-5.0 wt%, establishing an optimal ratio between matrix and dispersed phase. This parameter optimization ensures adequate polymer matrix for complete curing and film integrity while providing sufficient particles for dark OFF state transmittance.
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
This approach enables the production of SPD films with a high ΔT, ensuring both dark OFF states and light ON states, improving film integrity and reducing power consumption, while avoiding the technical difficulties associated with thickness adjustments in prior methods.
Implementation Method 1
SPD light valves have been known for more than seventy years for use in the modulation of light... When an electric field is applied through the liquid light valve suspension in the light valve, the particles become aligned and for many suspensions most of the light can pass through the cell.
Implementation Method 2
In the absence of an applied electrical field, the particles in the liquid suspension assume random positions due to Brownian movement.
Data Source
AI summary
A light valve film forming a light-modulating element of a light valve, the film comprised of a cross-linked polymer matrix with a plurality of droplets of a liquid light valve suspension distributed therein. The film has a phase ratio: % particle number value calculated by the formula (I). In one embodiment the light valve film has a relatively low visible transmittance in the unpowered Off state such that the film has a %T of < 0.05 and a ΔΤ of > 42%. In another embodiment the light valve film has a relatively high visible transmittance in the On state such that the film has a %T of > 70% and a ΔΤ of > 57%.