Polyester Resin Emulsion for Uniform Toner Shell Adhesion
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Solution Overview
Problem
Existing toners with core-shell structures face issues of non-uniform shell distribution, leading to mechanical durability and charging stability problems due to shell peeling under stress, especially in high-speed image forming apparatuses.
Innovation Solution
A polyester resin emulsion with a specific OHV/AV ratio of 0.3 to 1.0, using tri- or tetra-valent alcohols with 4 to 6 carbon atoms, is dispersed in an aqueous medium to form a core-shell structure, enhancing shell aggregation and adhesion to core particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional polyester resin emulsion is used to form core-shell toner structure, then low-temperature fixability is improved, but shell distribution uniformity deteriorates leading to mechanical durability problems
Solution Approach 1:
The patent applies parameter changes by precisely controlling the acid value (AV) and hydroxyl value (OHV) of the polyester resin to achieve a specific OHV/AV ratio range (0.3 to 1.0). This parameter optimization ensures both low-temperature fixability and uniform shell distribution, resolving the contradiction between these two properties through chemical composition control
2Strength
If shell particles are applied to core particles to enhance heat resistance, then mechanical durability is improved, but shell adhesion deteriorates under agitation stress causing peeling
Solution Approach 1:
The patent resolves the adhesion problem by optimizing the OHV/AV ratio parameter within 0.3 to 1.0, which enhances the chemical bonding between shell and core particles. This parameter control ensures strong adhesion under agitation stress while maintaining mechanical durability
Solution Approach 2:
The patent uses composite materials by combining polyester resin with specific functional groups (controlled by OHV/AV ratio) to create a shell layer that integrates seamlessly with the core particle. This composite structure provides both mechanical strength and reliable adhesion, preventing shell peeling under stress
3Productivity
If high-speed performance is achieved in image forming apparatus, then productivity is improved, but charging stability deteriorates due to stress from high-speed operation
Solution Approach 1:
The patent addresses charging stability by optimizing the polyester resin composition through controlled OHV/AV ratio, which affects the electrical properties of the toner. This parameter control ensures stable charging characteristics even under high-speed operation conditions, maintaining reliability while achieving high productivity
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 solution results in toners with improved mechanical durability and charging stability by ensuring uniform shell distribution, reducing peeling and maintaining stable charge levels under agitation stress.
Implementation Method 1
adding the polyester resin emulsion mentioned above to the liquid dispersion of the core particles to form a shell on a surface of the core particles
Data Source
AI summary
A polyester resin emulsion for toner contains an aqueous medium and resin particles S dispersed in the aqueous medium, the resin particles S containing a polyester resin A of a polycondensate of an alcohol component and a carboxylic acid component,wherein the alcohol component comprises tri- or tetra-valent alcohol having a straight chained or branched aliphatic saturated hydrocarbon backbone with 4 to 6 carbon atoms,the following relationship is satisfied,0.3≤OHV/AV≤1.,where AV (mgKOH/g) represents an acid value of the polyester resin A and OHV (mgKOH/g) represents a hydroxyl value of the polyester resin A,AV is between 10 mgKOH/g and 25 mgKOH/g, andthe polyester resin A has a repeated unit derived from polyethylene terephthalate of a condensate of terephthalic acid and ethylene glycol in an amount between 40 percent by mass and 70 percent by mass.