Developing Toner Void Structure for Fixability and Gloss Stability

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Solution Overview

Problem

Existing electrostatic image developing toners face challenges in achieving both low temperature fixability and stability of image gloss during high temperature storage, as the glossiness of fixed images increases when stored stacked at high temperatures.

Innovation Solution

The toner includes a binder resin and crosslinked resin particles with specific void fractions and ratios, reducing heat conduction and exposure of resin particles at the surface, thereby maintaining image gloss stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If resin particles with low glass transition temperature are added to enhance fixability, then low temperature fixability is improved, but image gloss stability during high temperature storage deteriorates

Engineering Contradiction:
ImprovefixabilityVSAvoidimage gloss stability
Core Design Contradiction:
Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent controls the glass transition temperature of the binder resin within a specific range (0°C to 80°C) and regulates the proportion of voids (1% to 10%) to balance fixability and gloss stability. By adjusting these parameters, the toner achieves adequate low-temperature fixability while preventing excessive gloss increase during high-temperature storage.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The toner uses a composite binder resin system combining polyester resin and styrene-acrylic resin in specific proportions. This composite structure provides both the low-temperature flexibility needed for fixability and the thermal stability required for gloss maintenance during storage.

Inventive Principle:
Principle #40Composite materials

2Ease of operation

If the proportion of voids in the toner is increased to improve fixability, then low temperature fixability is improved, but image gloss stability during high temperature storage deteriorates

Engineering Contradiction:
ImprovefixabilityVSAvoidimage gloss stability
Core Design Contradiction:
Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent optimizes the void proportion to fall within 1% to 10%, balancing the competing requirements. This controlled porosity allows sufficient space for resin flow during fixation while preventing excessive void-related gloss changes during high-temperature storage.

Inventive Principle:
Principle #35Parameter changes

3Stability of the object's composition

If the proportion of voids in the toner is decreased to improve image gloss stability, then image gloss stability is improved, but low temperature fixability deteriorates

Engineering Contradiction:
Improveimage gloss stabilityVSAvoidfixability
Core Design Contradiction:
Stability of the object's compositionVSEase of operation

Solution Approach 1:

The patent sets the void proportion lower bound at 1% to ensure sufficient space for binder resin flow during the fixation process, maintaining adequate fixability even when void content is minimized for gloss stability.

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 described toner structure achieves both low temperature fixability and stability of image gloss during high temperature storage by limiting heat conduction and exposure of resin particles, ensuring consistent image quality.

Implementation Method 1

the glass transition temperature of the polymer constituting the domain phase is -85 to +35°C

Methodology Applied
Scientific EffectGlass transition:

Implementation Method 2

the binder resin having a domain-matrix structure

Methodology Applied
Scientific EffectPhase separation:

Data Source

PatentEP4435521B1Electrostatic image developing toner
Publication Date: 2026.04.29 FUJIFILM BUSINESS INNOVATION CORP
  • EP4435521B1 patent drawingFigure 1
  • EP4435521B1 patent drawingFigure 2
  • EP4435521B1 patent drawing

AI summary

An electrostatic image developing toner includes a binder resin and crosslinked resin particles. In a cross section of the electrostatic image developing toner, the area fraction Sc of the crosslinked resin particles is 5% or more and 40% or less, the proportion Se of voids in the cross section is 1% or more and 10% or less, and the ratio Se/Sc of the proportion Se of voids to the area fraction Sc is 0.05 or more and 1.5 or less.