EVOH Back Coating for Heat-Sensitive Recording Materials

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Solution Overview

Problem

Heat-sensitive recording materials face processing difficulties due to rheological peculiarities of self-crosslinking back coatings, leading to surface quality deficits like 'orange peel' and printing irregularities, such as 'mottling' and 'missing dots', especially when exposed to organic solvents and plasticizers.

Innovation Solution

A heat-sensitive recording material with a back coating primarily composed of ethylene-vinyl-alcohol copolymer (EVOH) and calcium carbonate, which provides an improved barrier effect against organic solvents and plasticizers, facilitating easy printing without defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional self-crosslinking back coatings are used, then barrier effect against plasticizers is achieved, but surface quality deficits occur leading to printing irregularities

Engineering Contradiction:

Improvebarrier effect against plasticizersVSAvoidsurface quality

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent changes the chemical composition parameters of the back coating by incorporating specific polymers (polyvinyl alcohol, carboxymethyl cellulose, styrene-maleic anhydride copolymer) and controlling pH (5-9) and temperature (20-80°C) to prevent self-crosslinking while maintaining barrier properties. This resolves the contradiction by adjusting parameters to eliminate surface defects while preserving plasticizer resistance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite coating materials combining multiple polymers (polyvinyl alcohol, carboxymethyl cellulose, styrene-maleic anhydride copolymer) with specific functional properties. This composite approach provides both barrier effect against plasticizers and good surface quality for printing, resolving the contradiction between protection and surface integrity.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If barrier coatings are applied to prevent chemical penetration, then protection against discoloration is achieved, but printing defects such as mottling and missing dots occur

Engineering Contradiction:

Improveprotection against discolorationVSAvoidprinting quality

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent adjusts coating parameters including pH (5-9), temperature (20-80°C), and polymer composition to create a barrier coating that prevents chemical penetration without causing surface defects. This resolves the contradiction by optimizing parameters to maintain both protection and printability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a back coating with specific local properties - sufficient barrier function to prevent chemical penetration and discoloration, while maintaining surface characteristics suitable for printing. The differentiated polymer composition provides localized quality control to satisfy both requirements.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If conventional back coatings are used, then barrier effect is provided, but processing difficulties arise due to rheological peculiarities

Engineering Contradiction:

Improvebarrier effectVSAvoidprocessing ease

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent modifies rheological parameters by controlling pH (5-9), temperature (20-80°C), and polymer composition to eliminate self-crosslinking issues. This resolves the contradiction by adjusting parameters to improve processability while maintaining barrier effectiveness.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces specific polymers (carboxymethyl cellulose, styrene-maleic anhydride copolymer) as intermediaries that prevent unwanted self-crosslinking reactions. These intermediary substances improve processing ease while preserving the barrier function of the coating.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 EVOH-based back coating significantly enhances the barrier effect against organic solvents and plasticizers, preventing thermal reactions and coating defects, ensuring high-quality printing without 'mottling' or 'missing dots'.

Implementation Method 1

a back coating that has a barrier effect against plasticizers in self-adhesive coatings for labels and in particular a very excellent barrier effect against organic solvents

Methodology Applied

Scientific EffectBarrier effect:

Implementation Method 2

at least one heat-sensitive recording layer, which in turn has at least one dye precursor and at least one color acceptor, which react with one another to form color under the influence of heat

Methodology Applied

Scientific EffectThermal reaction:

Data Source

PatentEP2329958B1Heat sensitive recording material with reverse coating

Publication Date: 2012.10.03 MITSUBISHI HITEC PAPER EURO

AI summary

A heat-sensitive recording material is proposed comprising a substrate, a front-applied heat-sensitive recording layer, and a back-side coating containing ethylene vinyl alcohol copolymer (EVOH).