Liquid Crystal Mirror with Dichroic Dye for Rapid Glare Reduction
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Solution Overview
Problem
Existing rearview mirrors with electrochromic technology face limitations in response time, power consumption, and practicality for large sizes, especially in after-market applications, due to slow dimming processes and high electrical current requirements.
Innovation Solution
A Liquid Crystal (LC) mirror system using a LC cell with dichroic dye mixture between glass or plastic substrates, controlled by a custom-designed light sensing electronic system, allowing for rapid and low-power switching between bright and dark modes, and compatible with internal batteries or solar power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If electrochromic technology is used for automatic darkening mirrors, then the mirror can automatically vary reflectance from bright-mode to dark-mode, but the response time is slow (6-10 seconds) and the mirror size is limited
Solution Approach 1:
The patent changes the fundamental operating parameter from electrochemical (EC) to liquid crystal (LC) technology. The LC mirror uses voltage-controlled molecular orientation of dichroic dye molecules in the LC fluid, which rapidly changes the mirror's reflectance state from bright-mode to dark-mode in seconds or less, resolving the slow response time issue while maintaining automatic operation
Solution Approach 2:
The patent replaces the electrochemical platting mechanism with a liquid crystal optical modulation mechanism. Instead of using DC current to drive electrochemical reactions that slowly alter the mirror surface, the invention applies voltage to reorient LC molecules, which instantly changes the optical properties of the dichroic dye mixture, achieving rapid automatic darkening without the size limitations of EC technology
2Extent of automation
If electrochromic technology is used for automatic darkening mirrors, then the mirror can automatically vary reflectance, but the electrical current consumption is high (80-120 milliamperes) requiring direct battery wiring
Solution Approach 1:
The patent changes the energy consumption parameter by switching from EC to LC technology. The LC mirror requires only micro-amperes of current to switch between bright-mode and dark-mode states, compared to the 80-120 milliamperes required by EC mirrors. This dramatic reduction in power consumption enables the mirror to operate from small internal batteries or solar cells, making it suitable for after-market applications without direct battery wiring
Solution Approach 2:
The patent enables self-sustained operation through ultra-low power consumption. The LC mirror's minimal current requirement allows it to be powered by integrated solar cells or small rechargeable batteries, making the system self-sufficient and eliminating the need for direct connection to the vehicle's main power source, thus enabling independent after-market installation
3Area of stationary object
If electrochromic technology is used for large mirrors, then the mirror area can be increased for commercial truck applications, but the response time increases and becomes impractical
Solution Approach 1:
The patent changes the technology parameter from electrochemical to liquid crystal, which fundamentally alters the scaling behavior. The LC mirror's response time does not critically depend on mirror size because the voltage-controlled molecular reorientation mechanism operates uniformly across the entire LC fluid layer regardless of area. This allows construction of large mirrors for commercial truck applications while maintaining rapid response times
Solution Approach 2:
The patent avoids the scaling limitations of EC technology by using LC technology that can be uniformly applied across large areas. The liquid crystal fluid with dichroic dye can be distributed evenly across large mirror surfaces, and the voltage field penetrates uniformly through the LC layer, ensuring consistent rapid response across the entire mirror area without the progressive slowing seen in EC mirrors
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 LC mirror system achieves instantaneous switching, extremely low power consumption, and is not limited by mirror size, addressing the shortcomings of electrochromic mirrors with faster response times and reduced power needs, enabling self-sustained operation and integration with various automotive features.
Implementation Method 1
A LC fluid with a dichroic dye mixture is enclosed in the mirror cell between the front and back panels for affecting the light reflectance of the mirror. If the molecules in the LC fluid are oriented parallel to the mirror surface, then the fluid is less transparent and the mirror is darkened. Conversely, if the molecules are oriented perpendicular to the mirror surface, then the fluid is more transparent and the mirror is lightened.
Implementation Method 2
A LC fluid with a dichroic dye mixture is enclosed in the mirror cell between the front and back panels for affecting the light reflectance of the mirror
Implementation Method 3
An Ultraviolet (UV) protective coating of inorganic or organic material, or an UV protective polymer film on the exposed surface of the front panel prevents the LC-dye mixture from degrading due to extended exposure of the mirror to sunlight
Implementation Method 4
An antireflective (AR) optical thin film coating is deposited atop the UV coating or the UV polymer film on the front panel to reduce unwanted reflection from the exposed surface of the mirror
Data Source
AI summary
An automatic darkening and glare reducing liquid crystal mirror for vehicles is disclosed. The mirror has a front substrate (101) of transparent glass or plastic and a back substrate (109) of glass or plastic with a highly reflective or transflective mirrored coating (108). The front and back substrates are spaced apart a small distance to define a liquid crystal cell between the substrates and a liquid crystal fluid (106) incorporating dichroic dyes is contained within the liquid crystal cell. A conductive thin film (102) is applied onto the interior surface of the front substrate and the reflective or transflective coating (108) of the back substrate also is conductive. An alignment compound is deposited on the conductive thin film (102) and on the reflective or transflective coating (108) and the alignment compound bounds the liquid crystal cell. An electronic control circuit is adapted to apply selectively a voltage signal to the conductive thin film and the reflective or transflective coating (108) to affect the transmittance of the liquid crystal fluid, and thereby the darkness of the mirror.