Smart Window Optical Stack Without Spacers for Uniform Transmittance
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Solution Overview
Problem
Conventional variable transmittance optical stacks face challenges such as increased manufacturing complexity and costs due to the use of spacers, difficulty in maintaining a consistent cell gap and uniform optical color, and the complexity of the roll-to-roll manufacturing process.
Innovation Solution
A variable transmittance optical stack is developed that includes a liquid crystal layer with a polymer network and uniform initial alignment of liquid crystal compounds, eliminating the need for spacers and simplifying the manufacturing process by using a roll-to-roll continuous process. The conductive polymer layer serves as both an electrode and an alignment film, reducing the thickness and complexity of the stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spacer is used to maintain cell gap in liquid crystal layer, then the cell gap can be maintained, but the manufacturing process becomes more complex and manufacturing costs increase
Solution Approach 1:
The invention removes the spacer component from the liquid crystal display structure. Instead of using physical spacers to maintain cell gap, the patent employs a polymer network formed within the liquid crystal layer itself to maintain the cell gap, thereby eliminating the need for separate spacer components and simplifying the manufacturing process.
Solution Approach 2:
The invention combines the cell gap maintenance function with the liquid crystal layer by forming a polymer network within it. This merging of functions eliminates the need for separate spacer components, as the polymer network simultaneously provides structural support and maintains the required cell gap.
2Manufacturing precision
If a column spacer is used to maintain cell gap, then the cell gap can be maintained, but the alignment film is damaged in the process of emitting UV rays to photoresist and forming spacer
Solution Approach 1:
The invention removes the column spacer component and the associated UV irradiation process that damages the alignment film. By using a polymer network formed within the liquid crystal layer to maintain cell gap, the damaging UV exposure step is eliminated, preserving alignment film integrity.
Solution Approach 2:
The polymer network acts as an intermediary that performs the cell gap maintenance function without requiring the harmful UV irradiation process. Instead of using UV rays to cure photoresist for spacer formation, the polymer network is formed through a gentler process that does not damage the alignment film.
3Manufacturing precision
If a ball spacer is used to maintain cell gap, then the cell gap can be maintained, but it is impossible to solidly maintain cell gap and it is difficult to maintain uniform optical color in plane
Solution Approach 1:
The invention creates a homogeneous polymer network distributed throughout the liquid crystal layer, replacing the discrete ball spacers. This homogeneous distribution ensures uniform cell gap maintenance across the entire display area, resulting in consistent optical color and eliminating the non-uniformity caused by scattered ball spacers.
Solution Approach 2:
The invention uses a composite structure where a polymer network is integrated within the liquid crystal layer. This composite material approach provides solid and uniform cell gap maintenance, unlike loose ball spacers, ensuring consistent optical properties across the display surface.
4Reliability
If two polarizing plates are stacked with absorption axes orthogonal to each other for variable transmittance, then the desired transmittance can be achieved, but the manufacturing process becomes complex and roll-to-roll process cannot be applied
Solution Approach 1:
The invention integrates multiple functions into a single polarizing plate structure. Instead of requiring two separate polarizing plates with orthogonal absorption axes, the patent incorporates the transmittance control function directly into one polarizing plate through the liquid crystal layer configuration, enabling both polarization and variable transmittance control in a single component.
Solution Approach 2:
The invention merges the functions of two separate polarizing plates into a single integrated structure. By incorporating the liquid crystal layer with polymer network directly on one polarizing plate, the system achieves variable transmittance control without requiring the complex stacking and alignment of two orthogonal polarizing plates.
5Reliability
If each stack is manufactured in separate sheet with liquid crystal layer formed after cutting, then the absorption axis can be arranged orthogonal, but the manufacturing process becomes complex and cost reduction is difficult
Solution Approach 1:
The invention enables continuous manufacturing through roll-to-roll processing. Instead of manufacturing separate sheets and assembling them, the patent allows for continuous production of the liquid crystal display structure, maintaining absorption axis alignment while significantly improving manufacturing efficiency and reducing costs.
Solution Approach 2:
The invention segments the manufacturing process into continuous stages suitable for roll-to-roll processing. By designing the structure to be manufacturable in continuous strips rather than discrete sheets, the patent enables efficient segmentation and assembly that maintains alignment while reducing overall manufacturing complexity and cost.
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 solution prevents damage to the alignment film, maintains consistent in-plane optical color, and simplifies the manufacturing process, resulting in a more stable and cost-effective variable transmittance optical stack with improved transmittance control.
Implementation Method 1
the variable transmittance optical stack is driven by varying the transmittance by driving liquid crystal according to application of voltage
Implementation Method 2
a transmittance variable optical stack capable of changing the transmittance of light when a voltage is applied has been developed
Implementation Method 3
including a liquid crystal layer containing a polymer network
Data Source
AI summary
The optical stack, a manufacturing method for the same, a smart window including the same, and vehicles or building windows using the same are proposed. The optical stack includes a first polarizing plate, a transparent substrate laminated on one surface of the first polarizing plate, a first transparent conductive layer formed on the transparent substrate, a second polarizing plate opposite to the first polarizing plate, a second transparent conductive layer formed on one surface of the second polarizing plate, and opposite to the first transparent conductive layer, and a liquid crystal layer provided between the first transparent conductive layer and the second transparent conductive layer. The second transparent conductive layer includes a conductive polymer, the liquid crystal layer includes a polymer network and a liquid crystal compound, and the liquid crystal compound is aligned with a uniform initial alignment.