Electrochromic Viologen Composition for Neutral Ophthalmic Lenses
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Solution Overview
Problem
Developing an electrochromic composition for high-quality ophthalmic lenses that balances high absorption in the colored state, low absorption in the bleached state, fast coloration and bleaching rates, long-term stability, and compatibility of electrochromic compounds with similar oxydo-reduction potentials for achieving neutral colors like brown, grey, and grey-green.
Innovation Solution
An electrochromic composition comprising at least one reducing compound and two oxidizing compounds with similar oxydo-reduction potentials, specifically selected from viologen derivatives, which can change color simultaneously when a potential is applied, allowing for a wide range of colors including neutral shades without the need for a specifically colored reducing compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrochromic compound is used, then the device structure is simple, but it is difficult to achieve both high absorption in colored state and neutral color (brown, grey, grey-green)
Solution Approach 1:
The patent combines multiple electrochromic compounds (viologen derivatives and phenothiazine derivatives) in a single composition to achieve neutral colors (brown, grey, grey-green) and high absorption. The compounds work synergistically where the viologen provides the colored state and phenothiazine acts as a reducing compound, creating the desired neutral color palette that cannot be achieved with a single compound.
2Adaptability or versatility
If multiple electrochromic compounds are mixed to achieve desired color, then the color range and neutral colors are improved, but the compatibility and simultaneous color change of compounds become problematic
Solution Approach 1:
The patent carefully selects compounds with matched electrochemical parameters, specifically choosing viologen derivatives and phenothiazine derivatives whose oxidation-reduction potentials are close enough to ensure simultaneous color change. The patent specifies that the compounds should have oxydo-reducing potentials close enough so that they can change color simultaneously when a potential is applied, ensuring reliable and coordinated electrochromic response.
3Illumination intensity
If electrochromic compounds with high absorption coefficient are used, then the absorption in colored state is improved, but the absorption in bleached state increases and stability in presence of oxygen decreases
Solution Approach 1:
The patent uses phenothiazine derivatives as intermediary reducing compounds that work with the viologen oxidizing compounds. The phenothiazine derivatives have appropriate reduction potentials and provide the necessary reducing power while maintaining system stability. This intermediary approach allows the viologen to achieve high absorption in colored state while the phenothiazine maintains the system's stability and ensures low absorption in the bleached state through proper redox balance.
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 composition achieves the desired color in the colored state with high absorption and low absorption in the bleached state, maintaining stability and fast switching performance, ensuring high transmittance and long-term stability, particularly in the presence of oxygen.
Implementation Method 1
Electrochromism is a well-known physical phenomenon which is observed with certain classes of chemical compounds that change reversibly colour when a voltage is applied to them. The material undergoes reversible changes in optical properties by oxidation and reduction.
Implementation Method 2
The material undergoes reversible changes in optical properties by oxidation and reduction
Data Source
Figure 1
AI summary
The present invention relates to an electrochromic composition comprising at least one reducing compound and at least two oxidizing compounds, said at least two oxidizing compounds having similar oxydo-reduction potentials. More specifically, said at least two oxidizing compounds are selected from viologen derivatives. Said composition can be used as a variable transmittance medium for the manufacture of an optical article, such as an ophthalmic lens.