Linear Polyester Toner for Low-Temperature Fixing and Offset Resistance

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Solution Overview

Problem

Current toners for electrophotographic image formation face challenges with low-temperature fixability, heat-resistant storage stability, and offset resistance due to high softening points of binder resins, leading to issues like offset, blocking, and poor image quality, particularly under high-temperature conditions and in high-speed printing.

Innovation Solution

A toner composition using a linear polyester resin obtained by reacting a polyester diol with a polyhydroxycarboxylic acid skeleton and a chain extending agent, combined with other resins like vinyl, polyurethane, or epoxy resins, and incorporating a wax with grafted vinyl polymer chains, to achieve uniform particle diameter and improved thermal properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a binder resin with low softening point is used to achieve low-temperature fixability, then fixability at low temperature is improved, but offset resistance deteriorates and heat-resistant storage stability worsens

Engineering Contradiction:

Improvefixing temperatureVSAvoidoffset resistance

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent uses a composite binder resin system comprising a polyester resin (providing low-temperature fixability) and a polyurethane resin or epoxy resin (providing offset resistance and heat-resistant storage stability). This composite material approach allows simultaneous achievement of low-temperature fixability and offset resistance by combining materials with complementary properties.

Inventive Principle:

Principle #40Composite materials

2Temperature

If the softening point of binder resin is lowered to improve low-temperature fixability, then transparency and image quality are improved, but blocking and smear occur under high-temperature conditions

Engineering Contradiction:

Improvesoftening pointVSAvoidblocking

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the molecular structure and composition of the binder resin to achieve appropriate softening point and glass transition temperature parameters. By controlling the polyester resin composition and adding polyurethane or epoxy resins, the patent optimizes thermal parameters to prevent blocking while maintaining low-temperature fixability.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If conventional polyester resin is used to improve low-temperature fixability, then fixability is improved, but thermal properties and storage stability are insufficient

Engineering Contradiction:

Improvefixing temperatureVSAvoidstorage stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent combines polyester resin with polyurethane resin or epoxy resin to create a composite binder system. The polyurethane or epoxy resin components provide enhanced thermal stability and storage stability, compensating for the insufficient thermal properties of conventional polyester resin while maintaining low-temperature fixability.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS8741520B2Image forming toner, image forming apparatus, image forming method, and process cartridge

Publication Date: 2014.06.03 RICOH CO LTD

AI summary

The present invention provides an image forming toner including at least a linear polyester resin (b1) as a binder resin, wherein the linear polyester resin (b1) is obtained by reacting a polyester diol (b11) having a polyhydroxycarboxylic acid skeleton, with a polyester diol (b12) other than the polyester diol (b11) in the presence of a chain extending agent.