Core-Shell Toner Composition Balancing Fixability and Transfer Voids

Solution Overview

Problem

Existing toners suffer from transfer voids in vertical thin-line images, compromising low-temperature fixability and gloss, despite efforts to improve adhesion and chargeability.

Innovation Solution

A core-shell toner particle design is employed, where the core contains polyester derived from isophthalic acid and the shell includes a resin with salicylate or sulfonate functional groups, enhancing charge control and flexibility to prevent adhesion force increases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a toner containing amorphous composite resin with isophthalic acid is used to improve low-temperature fixability and gloss, then fixability and gloss are improved, but transfer voids occur in vertical thin-line images

Engineering Contradiction:

Improvelow-temperature fixabilityVSAvoidimage quality (transfer voids)

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The toner particle is divided into a core portion and a shell portion. The core contains polyester A with isophthalic acid units for low-temperature fixability and gloss, while the shell contains resin B with salicylate or sulfonate groups to control charge and prevent adhesion. This segmentation allows each region to perform its specific function without interfering with the other, resolving the contradiction between fixability and image quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the toner particle are given different chemical compositions and properties. The core has high polyester A content for fixability, while the shell has specific functional groups for charge control and adhesion prevention. This local differentiation enables the toner to simultaneously achieve good fixability and prevent transfer voids in vertical thin-line images.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If the binder resin contains high proportion of isophthalic acid to suppress offset, then offset is suppressed, but transfer voids still occur in vertical thin-line images

Engineering Contradiction:

ImproveoffsetVSAvoidimage quality (transfer voids)

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The toner particle is divided into a core portion and a shell portion. The core contains polyester A with isophthalic acid units for low-temperature fixability and gloss, while the shell contains resin B with salicylate or sulfonate groups to control charge and prevent adhesion. This segmentation allows each region to perform its specific function without interfering with the other, resolving the contradiction between fixability and image quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The toner uses a composite binder resin system combining polyester A (with isophthalic acid for offset suppression) and resin B (with salicylate or sulfonate groups for charge control and adhesion prevention). This composite approach allows the toner to suppress offset while preventing transfer voids in vertical thin-line images by leveraging the complementary properties of both resin components.

Inventive Principle:

Principle #40Composite materials

3Reliability

If the shell portion contains resin B with salicylate or sulfonate groups to control charge, then chargeability is improved, but adhesion force increases causing transfer voids

Engineering Contradiction:

ImprovechargeabilityVSAvoidadhesion force

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The shell portion contains resin B with specific functional groups (salicylate or sulfonate) that change the charge characteristics of the toner particle. These functional groups provide necessary chargeability for image formation while the controlled structure of resin B prevents excessive adhesion force that would cause transfer voids. The parameter change in functional group type achieves the desired balance.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250208531A1toner

Publication Date: 2025.06.26 CANON KK

AI summary

A toner includes a toner particle containing a binder resin. The binder resin contains 50 mass % or more of polyester A, and the polyester A contains a unit Uiso derived from isophthalic acid in an amount of 60 mol % or more based on total units derived from acid components. The toner particle is a core-shell particle composed of a core portion and a shell portion, and the shell portion contains resin B including a monomer unit having a functional group selected from the group consisting of a salicylate functional group and a sulfonate group.