Optical Laminate Hardness Tuning for Bubble-Free Smart Windows

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Solution Overview

Problem

Conventional optical laminates for smart windows suffer from issues such as bubbles and black spots due to the direct compression of polarizing plates and transparent conductive layers during manufacturing, leading to poor mechanical properties and fixed transmittance, which can cause glare or reduced visibility depending on ambient light conditions.

Innovation Solution

The optical laminate is designed with first and second laminates of polarizing plates and transparent conductive layers having specific Martens hardness (100 N/mm² to 430 N/mm²) and elastic recovery rates (40% to 87%), allowing direct contact without a separate substrate, thus minimizing defects and enabling smooth transmittance variation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a polarizing plate and transparent conductive layer are brought into direct contact to simplify manufacturing and reduce thickness, then device complexity and thickness are reduced, but mechanical properties deteriorate causing bubbles and black spots

Engineering Contradiction:

Improvemanufacturing process complexityVSAvoidmechanical properties

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The patent applies parameter changes by optimizing the thickness of the polarizing plate (30-200 μm) and transparent conductive layer (50-200 nm) to achieve the right balance between mechanical strength and overall thinness. It also changes the elastic recovery rate parameter to 40-87% to prevent permanent deformation during lamination, resolving the contradiction between simplified structure and mechanical properties

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by combining the polarizing plate with a transparent conductive layer formed directly on it, creating a laminated structure that integrates multiple functions. This composite approach eliminates the need for separate substrates while maintaining mechanical integrity through proper material selection and thickness control

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If the polarizing plate and transparent conductive layer are compressed during manufacturing, then the liquid crystal layer is properly positioned, but the layers do not recover causing bubbles and black spots

Engineering Contradiction:

Improveliquid crystal layer positioningVSAvoidappearance quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by designing the polarizing plate and transparent conductive layer with sufficient elastic recovery rate (40-87%) to act as a cushioning structure during compression. This elastic property allows the layers to temporarily deform during manufacturing compression and then recover, preventing permanent damage like bubbles and black spots while still achieving proper liquid crystal positioning

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Object-affected harmful factors

If the transmittance is preset low to prevent glare during day, then glare is reduced, but visibility at night deteriorates

Engineering Contradiction:

Improveglare reductionVSAvoidvisibility

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The patent applies dynamics by making the transmittance variable rather than fixed. The optical laminate can dynamically adjust its light transmittance based on ambient conditions - maintaining low transmittance during daytime to prevent glare, and switching to high transmittance at night to improve visibility. This dynamic adaptation resolves the contradiction between glare reduction and visibility

Inventive Principle:

Principle #15Dynamics

4Illumination intensity

If the transmittance is preset high to improve night visibility, then visibility is improved, but glare to driver during day increases

Engineering Contradiction:

ImprovevisibilityVSAvoidglare

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent uses dynamic control to adjust transmittance based on ambient light conditions. During nighttime, the laminate maintains high transmittance to improve visibility for the driver. During daytime, it switches to low transmittance to prevent glare. This dynamic adaptation allows the system to optimize both visibility and glare reduction at different times, resolving the contradiction

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250389984A1Optical laminate and smart window including the same

Publication Date: 2025.12.25 DONGWOO FINE CHEM CO LTD

AI summary

Disclosed is an optical laminate including: a first laminate comprising a first polarizing plate and a first transparent conductive layer; a second laminate opposite to the first laminate and comprising a second polarizing plate and a second transparent conductive layer; and a liquid crystal layer disposed between the first laminate and the second laminate, wherein the first laminate and the second laminate each has a Martens hardness (HM) of 100 N/mm2 to 430 N/mm2 and an elastic recovery rate (nIT) of 40% to 87%, as measured when a pressing load of 1 mN is applied thereto for 15 seconds using a nanoindenter. Also disclosed is a smart window including the optical laminate. A polarizing plate-transparent conductive layer laminate positioned above and below the liquid crystal layer is not deformed due to its excellent hardness and may be recovered after being compressed, due to its excellent elastic recovery rate.