Liquid Crystal Smart Window Voltage Control Method
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Solution Overview
Problem
Commercially available liquid crystal-based smart windows require constant power consumption to maintain the clear state, leading to high energy usage, whereas electrochromic windows only consume power during switching, indicating a need for an improved method to efficiently control the states of a switchable optical element using an electric field.
Innovation Solution
A method involving a multilayer structure with a liquid-crystalline medium between transparent electrodes, where the state is controlled by applying specific voltage levels, allowing the liquid-crystal molecules to transition between clear, scattering, and planar cholesteric states with reduced power consumption by using a weaker electric field to maintain the clear state and alternating voltages to stabilize the scattering state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a strong electric field is continuously applied to maintain the clear state, then the optical element remains in the clear state, but power consumption increases
Solution Approach 1:
The patent applies periodic voltage pulses instead of continuous voltage to maintain the clear state. The control unit sends voltage pulses at specific intervals (e.g., every 1-10 seconds) to refresh the liquid crystal alignment, allowing the system to maintain the clear state with intermittent rather than continuous power application, thereby reducing overall power consumption while ensuring state stability
Solution Approach 2:
The patent applies a stronger voltage pulse for a brief period to transition the liquid crystal to the clear state, then maintains it with weaker or no voltage. The preliminary strong electric field reorients the liquid crystal molecules into the desired state, after which the system can maintain this state with minimal additional energy input, effectively performing the heavy work upfront and sustaining with lesser effort
2Adaptability or versatility
If liquid crystal-based smart windows are used to control light transmittance, then optical control is achieved, but constant power consumption is required to maintain the clear state
Solution Approach 1:
The control unit implements periodic voltage application to maintain the clear state, sending refresh pulses at intervals rather than continuous voltage. This allows the smart window to maintain its optical control capability and clear state without requiring constant power supply, significantly reducing energy consumption compared to conventional liquid crystal windows that need continuous power
Solution Approach 2:
The liquid crystal material inherently maintains its molecular alignment and optical state without requiring continuous external energy input. Once the liquid crystal molecules are oriented by an applied voltage, they maintain this configuration through their material properties, allowing the system to 'serve itself' by maintaining the clear state without constant power consumption from external sources
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 reduces power consumption by applying the strong electric field only long enough to achieve the clear state and using a weaker field to maintain it, while alternating voltages to minimize energy usage in the scattering state, resulting in a more energy-efficient switchable optical element.
Implementation Method 1
the switching layer comprises a liquid-crystalline medium having at least three states, the state of the liquid-crystalline medium being controlled by an applied electric field
Implementation Method 2
the state of the liquid-crystalline medium being controlled by an applied electric field
Data Source
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AI summary
A method for electrically driving a switchable optical element is provided wherein the state of a liquid-crystalline medium is controlled by an applied electric field. The provided method comprises at least one of a) switching from a scattering state to a clear state by raising the driving voltage to a first clear voltage Vc1 and maintaining the driving voltage at the first clear voltage Vc1 for a first period of time t and then lowering the driving voltage to a second clear voltage Vc2 until the state is switched again, b) switching from the clear state to the scattering state by lowering the driving voltage from the second clear voltage Vc2 to a low voltage VL for a second period of time t2 and then raising the driving voltage to a privacy voltage Vp, c) holding the scattering state by alternating the driving voltage between a privacy voltage Vp and a low voltage VL until the state is switched again, wherein the privacy voltage Vp is maintained for a fourth period of time t4 and the low voltage VL is maintained for a fifth period of time t5.