Segmented Bonding in Stretchable Elastic Films

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Solution Overview

Problem

Elastic films in stretchable structures used in disposable wearing articles, such as diapers, are prone to tearing between stretchable regions due to thermal damage during bonding, leading to increased stretching stress and poor fitting.

Innovation Solution

A stretchable member with an elastic sheet interposed between two sheet layers, where the layers are bonded at numerous fused dot-like portions arranged at intervals, with distinct arrangement patterns and shapes in different stretchable regions, maintaining a separation distance of 10 mm or less between bonded portions to prevent tearing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the elastic film is bonded between sheet layers at multiple points, then the structural stability is improved, but the stretching stress increases and the elastic film may tear

Engineering Contradiction:

Improvestructural stabilityVSAvoidtear resistance

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The bonding structure is segmented into multiple discrete dot-like bonded portions arranged at intervals rather than continuous bonding. This segmentation allows the elastic film to maintain structural stability through multiple attachment points while preserving sufficient material between bonds to prevent tearing under stretching stress.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the elastic film have different bonding characteristics - dot-like bonded portions are localized at specific intervals rather than uniform continuous bonding. This local quality approach provides stability where needed while maintaining tear resistance in the unbonded regions.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If the bonded portions are arranged closely together, then the structural stability is improved, but the air permeability decreases

Engineering Contradiction:

Improvestructural stabilityVSAvoidair permeability

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The bonded portions are segmented and arranged at optimized intervals rather than continuously or too closely together. This segmentation maintains structural stability through sufficient bonding points while preserving adequate spacing to allow air permeability through the elastic film.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If the elastic film is elongated to increase stretchability, then the fitting performance is improved, but the risk of tearing between bonded portions increases

Engineering Contradiction:

ImprovestretchabilityVSAvoidtear resistance

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The elastic film is pre-elongated during the bonding process to create a stretched state before final assembly. This preliminary action reduces the risk of tearing during subsequent use by distributing stress more evenly across the pre-stretched film and minimizing additional elongation demands on the bonded structure.

Inventive Principle:

Principle #10Preliminary action

4Strength

If thermal bonding is applied to bond the sheet layers, then the bonding strength is improved, but thermal damage occurs to the elastic film

Engineering Contradiction:

Improvebonding strengthVSAvoidthermal damage

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The bonding parameters are changed from conventional thermal bonding to ultrasonic bonding. This parameter change achieves sufficient bonding strength through mechanical vibration and friction heating localized at the bonding interface, while avoiding the excessive thermal exposure that causes damage to the elastic film material.

Inventive Principle:

Principle #35Parameter changes

5Reliability

If the bonding area is increased to improve bonding strength, then the bonding reliability is improved, but the flexibility and air permeability decrease

Engineering Contradiction:

Improvebonding reliabilityVSAvoidflexibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The bonding area is segmented into multiple small dot-like portions rather than a large continuous bonded region. This segmentation provides sufficient bonding reliability through multiple attachment points while maintaining flexibility and air permeability in the unbonded portions of the elastic film.

Inventive Principle:

Principle #1Segmentation

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 reduces tearing of the elastic film and lowers stretching stress, enhancing the wearing experience by maintaining flexibility and air permeability while providing a comfortable fit.

Implementation Method 1

A stretchable region having the elastic sheet stretchable structure can be expanded and contracted in a stretchable direction due to a contraction force of the elastic sheet

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the first sheet layer and the second sheet layer are bonded at a large number of fused dot-like bonded portions arranged at intervals

Methodology Applied

Scientific EffectThermal bonding: Heating

Data Source

PatentUS12187023B2Stretchable member and disposable wear article using stretchable member

Publication Date: 2025.01.07 DAIO PAPER CORP

AI summary

To prevent or suppress the occurrence of tearing of an elastic film between stretchable regions in an elastic sheet stretchable structure. An elastic sheet stretchable structure is provided, in which an elastic film is laminated between a first sheet layer having air permeability and a second sheet layer having air permeability, and the first sheet layer and the second sheet layer are bonded at a large number of sheet bonded portions arranged at intervals. At the boundary between a first stretchable region and a second stretchable region, a separation distance Px in an elastic limit elongation state between a bonded portion located on a side of the boundary of the first stretchable region in a stretchable direction and a bonded portion located on a side of the boundary of the second stretchable region in a stretchable direction is 10 mm or less.