Low Water Absorption Adhesive for Liquid Crystal Light Control

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Solution Overview

Problem

Light control sheets in humid environments face a decline in light transmittance alteration functionality due to liquid crystal layer wetting, necessitating enhanced waterproofness to maintain performance.

Innovation Solution

A light control device comprising a first and second transparent coating substrate sandwiching a light control sheet with a liquid crystal layer, where the sheet edge face is covered by a transparent adhesive layer with a water absorption rate of 2% or less, ensuring waterproofness and preventing layer separation, and utilizing spacers with compressive fracture strength for maintaining electrode layer distance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the light control sheet is used in humid environments, then the liquid crystal layer becomes wet, but the light transmittance alteration functionality declines

Engineering Contradiction:

Improvelight transmittance alteration functionalityVSAvoidliquid crystal layer wetting

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A transparent adhesive layer with water absorption rate of 2% or less is introduced as an intermediary between the light control sheet and the external humid environment. This adhesive layer acts as a barrier that prevents water from penetrating into the liquid crystal layer, thereby maintaining the light transmittance alteration functionality even in humid environments.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The transparent adhesive layer functions as a thin film barrier that covers the sheet edge face of the light control sheet. This thin film structure provides waterproof protection while maintaining the flexibility and optical properties of the overall device, preventing water ingress without compromising the light control functionality.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If the transparent adhesive layer is applied to cover the sheet edge face, then waterproofness is enhanced, but the device structure becomes more complex

Engineering Contradiction:

ImprovewaterproofnessVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The transparent adhesive layer serves multiple functions simultaneously: it provides waterproof protection by covering the sheet edge face, maintains optical transparency to allow light transmission, and bonds the light control sheet to the transparent coating substrate. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The adhesive layer is made transparent to match the optical properties of the surrounding components (transparent coating substrate and light control sheet). This homogeneity in optical properties allows the adhesive layer to blend seamlessly with the existing structure, minimizing the visual and functional impact of the additional layer and reducing perceived structural complexity.

Inventive Principle:

Principle #33Homogeneity

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 enhances waterproofness, maintains light transmittance alteration functionality in humid conditions, prevents layer separation, and allows for designable thickness adjustment of the transparent adhesive layer, ensuring the light control device's operational integrity.

Implementation Method 1

The transparent adhesive layer covers the sheet edge face and has a water absorption rate of 2% or less

Methodology Applied

Scientific EffectWater absorption resistance: Absorption (physical)

Implementation Method 2

Changing a voltage applied across the electrode layers alters a light transmittance of the liquid crystal layer

Methodology Applied

Scientific EffectElectro-optic effect: Electro-Optic Effects

Implementation Method 3

The liquid crystal layer includes a polymer network and a liquid crystal composition that fills voids of the polymer network

Methodology Applied

Scientific EffectMechanical strength: Mechanical Force

Data Source

PatentUS11448924B2Light control device comprising a transparent adhesive layer covering a sheet edge face of a light control sheet and method for producing the same

Publication Date: 2022.09.20 TOPPAN HOLDINGS INC

AI summary

A light control device includes a first transparent coating substrate having a first bonding surface, a second transparent coating substrate having a second bonding surface, a light control sheet located between the first and second bonding surfaces, and a transparent adhesive layer that joins the first and second bonding surfaces together around the light control sheet. The light control sheet includes a first transparent electrode film, a second transparent electrode film, and a liquid crystal layer including a liquid crystal composition that fills space between the first transparent electrode film and the second transparent electrode film. The light control sheet has a sheet edge face, and the transparent adhesive layer covers the sheet edge face and has a water absorption rate of 2% or less in accordance with a method of JIS K 7209:2000 A.