Switchable Window with Dichroic Dye for Color-Neutral Transmission
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Solution Overview
Problem
Existing smart windows cannot simultaneously and independently control their reflective and transmissive properties, which limits their ability to achieve a desired color appearance and color-neutral light transmission.
Innovation Solution
A switchable optical device with a layer structure comprising a liquid-crystalline material and dichroic dyes, where the absorption spectrum of the dye is adjusted to be complementary to the reflection band of the optical layer, allowing for independent control of light transmission and reflection across the visible spectrum, using electric fields to switch between bright and dark states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a reflective optical layer is added to control the outside appearance color, then the reflection control is improved, but the transmission spectrum becomes colored and loses color neutrality
Solution Approach 1:
The patent applies different optical properties to different parts of the spectrum: the optical layer reflects specific wavelengths (e.g., green light at 500-600nm) to control appearance color, while the switchable layer with dichroic dyes selectively absorbs light in the transmission path to maintain color neutrality. This local differentiation of optical functions resolves the contradiction between appearance control and transmission quality.
Solution Approach 2:
The patent combines multiple materials with complementary optical properties: a reflective optical layer (metal oxide coatings, dielectric stacks) for appearance control and a switchable layer containing liquid crystals and dichroic dyes for transmission control. The composite structure allows simultaneous optimization of reflection and transmission properties that single materials cannot achieve.
2Device complexity
If the switchable layer uses standard dyes, then the switching mechanism is simple, but the transmission spectrum is colored and color neutrality is lost
Solution Approach 1:
The patent modifies the absorption spectrum parameters of the dye to be complementary to the reflection band of the optical layer. By adjusting the dye's absorption characteristics (wavelength range, absorption coefficient) to match the reflection profile, the transmitted light achieves color neutrality while maintaining simple switching operation through standard electrochromic or liquid crystal mechanisms.
3Ease of manufacture
If the optical layer reflects a broad spectrum, then the appearance color control is improved, but the light transmission is reduced and energy loss increases
Solution Approach 1:
The patent confines the reflection function to specific wavelength bands rather than the entire spectrum. The optical layer is designed to reflect only the wavelengths needed for appearance color control (e.g., 500-600nm for green appearance), while allowing other wavelengths to transmit. This localized reflection approach minimizes energy loss while achieving the desired appearance effect.
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 device achieves color-neutral light transmission and high contrast between states, minimizing reflection losses and optimizing the appearance of the window by adjusting the dye's absorption spectrum to match the reflection band, resulting in improved color neutrality and reduced coloration in both bright and dark states.
Implementation Method 1
Liquid crystal based devices employ a change in the orientation of liquid crystal molecules between two conductive electrodes by applying an electric field which results in a change of their transmittance
Implementation Method 2
by applying an electric field
Implementation Method 3
The luminescent material exhibits dichroism such that the luminescent material has a strong absorption along a first axis and in any other axis the absorption is lower
Implementation Method 4
strong absorption along a first axis
Implementation Method 5
The at least one optical layer has at least one reflection band which includes at least a first part of the visible spectrum and has at least one transmission band which includes at least a second part of the visible spectrum
Data Source
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AI summary
The invention relates to a switchable optical device (10) having a layer structure comprising at least one switchable layer (15) and at least one optical layer (20, 22). The at least one switchable layer (15) comprises a liquid-crystalline material and at least one dye. The at least one optical layer (20, 22) has at least one reflection band (32) which includes at least a first part of the visible spectrum and has at least one transmission band (30, 34) which includes at least a second part of the visible spectrum.The absorption spectrum of the at least one switchable layer (15) is adjusted by means of the at least one dye such that the light transmission through the switchable optical device (10) for incident light in the visible light spectrum for at least one of the states of the switchable layer (15) is set to a predetermined transmission spectrum.