Thin PSA Sheet with Black Colorant for Light Blocking

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Solution Overview

Problem

Conventional light-blocking pressure-sensitive adhesive (PSA) sheets used in portable electronic devices face challenges in achieving effective light-blocking properties in both in-plane and thickness directions, especially when made thinner and narrower, which compromises adhesive properties and light-blocking efficiency.

Innovation Solution

A PSA sheet with a support substrate thickness of less than 75 μm and a PSA layer on at least one face, featuring XY-directional and Z-directional light transmittances of 0.04% or lower, utilizing a black colorant in both the support substrate and PSA layer to enhance light-blocking properties while maintaining adhesive strength and precision processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the PSA sheet is made thinner and narrower to reduce device thickness and weight, then the mobility and design freedom are improved, but the light-blocking properties degrade due to decreased light-transmitting distance

Engineering Contradiction:

Improveweight of portable electronic deviceVSAvoidlight leakage

Core Design Contradiction:

Weight of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent merges the light-blocking function with the adhesive sheet itself by incorporating a light-blocking layer containing black colorant into the PSA sheet structure. This integration allows the adhesive sheet to perform both adhesion and light-blocking functions simultaneously, preventing light leakage even when the sheet is made thinner and narrower for portable electronic devices.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses composite materials by combining the pressure-sensitive adhesive layer with a light-blocking layer containing black colorant (such as carbon black). This composite structure enables the adhesive sheet to maintain both its adhesive properties and enhanced light-blocking performance, resolving the contradiction between sheet thickness reduction and light-blocking effectiveness.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a black colorant is added to the PSA layer to achieve light-blocking properties in in-plane directions, then the light-blocking performance is improved, but the adhesive properties are compromised

Engineering Contradiction:

Improvelight leakage preventionVSAvoidadhesive strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent segments the adhesive sheet into distinct functional layers: a pressure-sensitive adhesive layer and a separate light-blocking layer containing black colorant. This segmentation allows each layer to optimize its specific function without interfering with the other, maintaining adhesive strength while achieving effective light-blocking performance in in-plane directions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by concentrating the black colorant specifically in the light-blocking layer rather than dispersing it throughout the entire adhesive layer. This localized application ensures that the adhesive layer maintains its bonding properties while the light-blocking layer provides the necessary optical shielding in critical areas.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If a support substrate is used to enable precise processing of narrow PSA sheets, then the manufacturing precision is improved, but the device thickness increases due to the additional substrate layer

Engineering Contradiction:

Improveprocessing precisionVSAvoidsheet thickness

Core Design Contradiction:

Manufacturing precisionVSLength of stationary object

Solution Approach 1:

The patent changes the parameter of support substrate thickness to less than 75 μm, which is sufficiently thin to maintain overall device thickness constraints while still providing adequate mechanical support for precise processing. This parameter optimization resolves the contradiction between needing support for precision manufacturing and maintaining thin overall dimensions.

Inventive Principle:

Principle #35Parameter changes

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 provides excellent light-blocking properties in both in-plane and thickness directions, preventing light leakage and ensuring visibility in portable electronic devices, while allowing for precise processing and thinner designs.

Implementation Method 1

utilizing a black colorant in both the support substrate and PSA layer to enhance light-blocking properties

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS10983377B2Liquid crystal display and pressure-sensitive adhesive sheet

Publication Date: 2021.04.20 NITTO DENKO CORP

AI summary

Provided is a PSA sheet that can be processed with excellent precision while providing excellent light-blocking properties in an in-plane direction and in the thickness direction in an embodiment where the support substrate has a limited thickness. The PSA sheet has a support substrate having a thickness less than 75 μm and a PSA layer placed at least on one face of the support substrate. The PSA sheet has light transmittances of 0.04% or lower in XY and Z directions thereof.