Core-shell polymer nanoparticles for toner charge stability

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Solution Overview

Problem

Current toner particles containing crystalline or semi-crystalline polyester resins face challenges with low charge maintainability and relative humidity sensitivity, particularly in high-humidity environments, due to the low resistivity of crystalline resin, which affects their performance in image development systems.

Innovation Solution

The development of core-shell nano-sized particles with a crystalline core and an amorphous shell, where the amorphous shell encapsulates the crystalline core, preventing migration and diffusion of the crystalline resin, allowing for higher crystalline resin content without compromising charge maintainability or RH sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the amount of crystalline resin in toner particles is increased to lower the minimum fixing temperature, then the melt fusing temperature decreases, but the charge maintainability and relative humidity sensitivity deteriorate due to low resistivity of crystalline resin

Engineering Contradiction:

Improveminimum fixing temperatureVSAvoidcharge maintainability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The toner particle is segmented into a core region containing crystalline resin and a shell region containing amorphous resin. This segmentation allows the crystalline resin to be isolated in the core, preventing its migration to the surface and maintaining low minimum fixing temperature while preserving charge maintainability through the amorphous shell.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the toner particle are assigned different material compositions: the core region contains crystalline resin for low melting point, while the shell region contains amorphous resin for high resistivity and charge maintainability. This local quality differentiation resolves the contradiction between lowering melting temperature and maintaining charge properties.

Inventive Principle:

Principle #3Local quality

2Temperature

If crystalline resin is included in toner particles to achieve ultra-low melt fusing, then the gloss and fusing performance improve, but the resistivity decreases causing poor charge maintainability in high humidity environments

Engineering Contradiction:

Improvemelt fusing temperatureVSAvoidrelative humidity sensitivity

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The toner particle is divided into core and shell regions, with crystalline resin confined to the core and amorphous resin forming the shell. This segmentation prevents crystalline resin from reaching the surface, maintaining ultra-low melt fusing through the core while preserving high resistivity and humidity resistance through the amorphous shell.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The amorphous resin shell acts as an intermediary barrier between the crystalline resin core and the external environment. This shell prevents direct contact between the low-resistivity crystalline resin and the humid environment, eliminating RH sensitivity while preserving the low melting point properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If amorphous resin shell is grown around crystalline resin core, then the charge maintainability should improve, but the crystalline resin migrates into the shell or to the surface during coalescence, causing poor charge maintainability

Engineering Contradiction:

Improvecharge maintainabilityVSAvoidcrystalline resin distribution

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The core-shell structure is formed preliminarily before the coalescence step, with the amorphous resin shell already encapsulating the crystalline resin core. This preliminary encapsulation prevents crystalline resin migration during subsequent coalescence, maintaining both charge maintainability and compositional stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The amorphous resin shell is formed beforehand to cushion and contain the crystalline resin core, preventing its migration during subsequent processing steps such as coalescence. This prior protective structure ensures both charge maintainability and compositional stability are maintained throughout the toner manufacturing process.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This approach enables the creation of toner particles with ultra-low melt properties and improved charge maintainability, even in high-humidity conditions, by ensuring the crystalline resin remains within the core, thus enhancing the performance and reliability of toner particles in various environmental conditions.

Implementation Method 1

the amorphous shell encapsulates the crystalline core, preventing migration and diffusion of the crystalline resin

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS8088544B2Core-shell polymer nanoparticles and method of making emulsion aggregation particles using same

Publication Date: 2012.01.03 XEROX CORP

AI summary

Nano-sized particles for use in making emulsion aggregation toner particles have a core portion and a shell portion, wherein the core portion of the nano-sized particles includes crystalline resin and the shell portion includes amorphous resin and is substantially to completely free of the crystalline resin.