Toner with Embedded Resin Protrusions for Image Quality

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Solution Overview

Problem

Existing electrostatic image developing toners face challenges with low chargeability, adhesion resistance, transferability, cleanability, and heat resistance storage stability, particularly in high-temperature, high-humidity environments, due to limitations in particle size, shape, and surface modification methods.

Innovation Solution

A dry electrostatic image developing toner is formulated with toner core particles containing a first resin and protrusions of a second resin, where the fine resin particles are embedded in the toner core particles with an average embedment rate of 40% to 80% and an average sphericity of 0.90 or more, using a process that includes emulsification or dispersion in an aqueous medium to attach and fuse the fine resin particles onto the toner core particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If polymerization toners are used to conglobate and minimize particle size, then image definition is improved, but adhesion force increases causing filming and transfer efficiency degrades

Engineering Contradiction:
Improveimage definitionVSAvoidtransfer efficiency
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The invention uses composite materials by combining polymerized toner particles (for small size and high definition) with unpolymerized toner particles (for low adhesion). This composite structure allows the toner to achieve both high image definition through small particle size and good transfer efficiency through reduced adhesion force from the unpolymerized component.

Inventive Principle:
Principle #40Composite materials

2Manufacturing precision

If polymerization toners are used to conglobate and minimize particle size, then image definition is improved, but cleanability deteriorates due to spherical shape

Engineering Contradiction:
Improveimage definitionVSAvoidcleanability
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention combines spherical polymerized particles (providing small size for high definition) with non-spherical unpolymerized particles (providing better cleanability). The mixture of particle shapes allows the toner to maintain high image definition while improving cleanability through the presence of less spherical particles that are easier to remove from surfaces.

Inventive Principle:
Principle #40Composite materials

3Use of energy by moving object

If low melt temperature binder resin is used to achieve low-temperature fixing property, then energy saving is improved, but blocking occurs at high-temperature causing degradation in heat resistance storage stability

Engineering Contradiction:
Improvefixing temperatureVSAvoidheat resistance storage stability
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the binder resin by using a copolymer with specific monomer ratios (styrene 80-100%, acid monomer 0-20%). This parameter adjustment allows the resin to have low melt temperature for energy-saving fixing while maintaining sufficient heat resistance for storage stability through the specific copolymer structure.

Inventive Principle:
Principle #35Parameter changes

4Manufacturing precision

If fine particles are added to toner surfaces by dry methods, then surface modification is attempted, but particles are ununiform and exfoliate causing filming and adhesion

Engineering Contradiction:
Improvesurface uniformityVSAvoidadhesion resistance
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The invention replaces mechanical impact methods (dry methods) with a wet method using a dispersing agent. The dispersing agent facilitates uniform attachment of fine particles to toner surfaces through chemical interaction rather than mechanical force, resulting in uniform particle distribution that does not exfoliate and causes no filming or adhesion.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

5Ease of manufacture

If wet methods are used to cover toner core particles with resin particles, then cleanability is improved, but background smear occurs and transferability degrades due to sparse and ununiform coverage

Engineering Contradiction:
ImprovecleanabilityVSAvoidsurface coverage uniformity
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention introduces a dispersing agent as an intermediary substance that facilitates uniform distribution and attachment of resin particles to toner core particles. The dispersing agent acts as a mediator between the resin particles and toner surface, ensuring dense and uniform coverage that improves cleanability without causing background smear or transferability degradation.

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 toner exhibits improved chargeability, developing durability, adhesion resistance, transferability, and heat resistance storage stability, while maintaining low-temperature fixing property, enabling the formation of high-quality images.

Implementation Method 1

a process that includes emulsification or dispersion in an aqueous medium to attach and fuse the fine resin particles onto the toner core particles

Methodology Applied
Scientific EffectEmulsification: Emulsion

Implementation Method 2

a process that includes emulsification or dispersion in an aqueous medium to attach and fuse the fine resin particles onto the toner core particles

Methodology Applied
Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 3

attach and fuse the fine resin particles onto the toner core particles

Methodology Applied
Scientific EffectFusion: Melting

Data Source

PatentEP2390724B1Toner, image forming apparatus, image forming method and process cartridge
Publication Date: 2015.08.26 RICOH CO LTD
  • EP2390724B1 patent drawingFigure 1A~1B
  • EP2390724B1 patent drawingFigure 2
  • EP2390724B1 patent drawingFigure 3

AI summary

An electrostatic image developing toner including toner core particles each containing at least a first resin and a colorant, and fine resin particles formed of a second resin, wherein part of each of the fine resin particles is embedded in each of the toner core particles, and the remaining part of the fine resin particle is exposed on a surface of the toner core particle to form a protrusion, and wherein when a rate of the part of the fine resin particle to the fine resin particle is indicated by an embedment rate, an average of the embedment rates in the fine resin particles is 40% to 80%.