Smart Window Film Laminate for Pressure-Uniform LC Bonding

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Solution Overview

Problem

Conventional transmittance variable optical laminates experience liquid crystal mura due to uneven pressure distribution during glass bonding, especially when a polarizing plate and conductive layer are in direct contact without a substrate, leading to fixed transmittance issues that cause glare or visibility problems depending on ambient light conditions.

Innovation Solution

A film laminate with a surface protective layer and gap layer having specific properties and structures, including a low-temperature curable PVB film, minimizes pressure on the liquid crystal layer through a two-step bonding process, eliminating uneven pressure distribution and preventing mura.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If glass bonding is performed on an optical laminate with direct contact between polarizing plate and conductive layer, then the laminate thickness is reduced, but liquid crystal mura occurs due to uneven pressure distribution

Engineering Contradiction:
Improvelaminate thicknessVSAvoidliquid crystal distribution uniformity
Core Design Contradiction:
Length of stationary objectVSManufacturing precision

Solution Approach 1:

A substrate is introduced as an intermediary element between the polarizing plate and conductive layer. This substrate acts as a pressure-distributing medium that prevents direct contact between the polarizing plate and conductive layer during glass bonding, thereby eliminating uneven pressure distribution and liquid crystal mura while maintaining the overall thin structure of the optical laminate.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If fixed transmittance is used in conventional windows, then manufacturing is simple, but visibility problems occur under different ambient light conditions

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidtransmittance adaptability
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The optical laminate incorporates a liquid crystal layer that can dynamically change its light transmittance properties in response to applied voltage. This dynamic characteristic allows the window to adapt to different ambient light conditions (day/night, bright/dim environments), solving the visibility and glare problems associated with fixed transmittance windows while maintaining relatively simple manufacturing processes.

Inventive Principle:
Principle #15Dynamics

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 solution effectively reduces liquid crystal mura occurrence, ensuring a smart window with improved appearance and reduced thickness by optimizing pressure application during glass bonding.

Implementation Method 1

a transmittance variable optical laminate capable of changing the transmittance of light when a voltage is applied has been developed. The transmittance variable optical laminate is driven to change transmittance by driving liquid crystals in response to application of a voltage.

Methodology Applied
Scientific EffectLiquid crystal effect: Liquid Crystals

Implementation Method 2

a surface protective layer having an optimally small thickness on at least one outer surface of an optical laminate... a gap layer having suitable optimal properties and structure at an end thereof... minimize the pressure applied to a liquid crystal layer in an optical laminate during glass bonding

Methodology Applied
Scientific EffectViscoelasticity: Viscoelasticity

Data Source

PatentEP4684962A1Film laminate, smart window including the same, and method for manufacturing the smart window
Publication Date: 2026.01.28 DONGWOO FINE CHEM CO LTD
  • EP4684962A1 patent drawingFigure 1~2
  • EP4684962A1 patent drawingFigure 3~4
  • EP4684962A1 patent drawingFigure 5

AI summary

Disclosed are a film laminate, a smart window including the same, and a method for manufacturing the same. The film laminate includes: an optical laminate; and a surface protective layer laminated on at least one of the upper and lower surfaces of the optical laminate, wherein the surface protective layer is a low-temperature curable polyvinyl butyral (PVB) film that is cured at a temperature of 90°C or lower, has a thickness of 0.01 mm to 0.35 mm, and has a total area larger than the area of the optical laminate that is in contact with the surface protective layer.