Toner Composition with Composite Polyester Resin for Fixing
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Solution Overview
Problem
Existing toners for electrophotographic systems face challenges in achieving a balance between low-temperature fixability and hot offset resistance, often resulting in increased adhesive force between the fixing member and recording paper, reduced toner chargeability, and increased image density variations and fogging, especially at high print coverage rates in high temperature/high humidity environments.
Innovation Solution
A toner comprising binder resin particles with a combination of polyester resin A and polyester resin B, where resin A is obtained by condensation polymerization of a polyvalent carboxylic acid and an aromatic diol, and resin B by condensation polymerization of a polyvalent carboxylic acid and an aliphatic diol, along with inorganic fine particles and wax, optimized through surface treatment with a hot air current to enhance chargeability and resist charge relaxation, while controlling the wax distribution to prevent wraparound and maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a polyester resin with sharp-melt property is used to improve low-temperature fixability, then fixation temperature is reduced, but adhesive force between fixing member and recording paper increases causing wraparound
Solution Approach 1:
The patent uses a composite binder resin system combining polyester resin A (sharp-melt type) and polyester resin B (high softening point type) in specific ratios. This composite approach allows the toner to achieve both low-temperature fixability (from resin A's sharp-melt property) and sufficient hot offset resistance (from resin B's high softening point), preventing the wraparound issue that occurs with single-resin systems
Solution Approach 2:
The patent optimizes the weight ratio parameters of polyester resin A and polyester resin B within specific ranges (resin A: 20-70 parts, resin B: 30-80 parts based on total binder resin). By adjusting these compositional parameters, the toner achieves the desired balance between low-temperature fixability and resistance to wraparound, controlling the adhesive force characteristics
2Temperature
If polyester resin composition is optimized for low-temperature fixing, then fixability improves, but toner chargeability decreases and charge relaxation increases
Solution Approach 1:
The patent controls the chemical composition parameters of the polyester resins, specifically maintaining acid values within 5-50 mg KOH/g and hydroxyl values within 5-20 mg KOH/g for polyester resin A, and acid values within 5-30 mg KOH/g for polyester resin B. These parameter controls ensure adequate toner chargeability while maintaining low-temperature fixability
Solution Approach 2:
The composite binder resin system balances the complementary properties of polyester resin A (sharp-melt, low temperature) and polyester resin B (high softening point, charge stability). This composite approach maintains sufficient toner chargeability and charge retention while achieving improved low-temperature fixability
3Productivity
If high print coverage rate is used in high temperature/high humidity environment, then productivity increases, but image density variations and fogging increase
Solution Approach 1:
The composite binder resin system provides stable toner properties that resist charge relaxation even under high temperature and high humidity conditions. This stability maintains consistent toner charge and image density uniformity across high print coverage rates, preventing fogging in white background regions
Solution Approach 2:
The patent optimizes the compositional parameters of the binder resin and controls the particle size distribution (D10: 2.0-5.0 μm, D50: 4.0-7.0 μm, D90: 8.0-15.0 μm) to ensure uniform toner behavior at high coverage rates, reducing image density variations and preventing fogging
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 achieves a balance between low-temperature fixability and hot offset resistance, reducing image density variations and fogging, and improving resistance to wraparound during fixing, even at high print coverage rates in challenging environmental conditions.
Implementation Method 1
The toner particles have been subjected to a surface treatment using a hot air current
Implementation Method 2
In the FT-IR spectrum obtained by attenuated total reflectance (ATR) method by using Ge as the ATR crystal and under the condition of an infrared light-incidence angle of 45°
Data Source
Figure 1
AI summary
An object of the present invention is to improve resistance to wraparound during fixing while achieving both low-temperature fixability and resistance to hot offset. A further object is to suppress image density variations and fogging in white background regions during use at high print coverage rate at high temperature and high humidity. A toner containing inorganic fine particles and toner particles containing a binder resin and a wax being provided, the toner being characterized in that the binder resin contains a polyester resin A obtained by condensation polymerization of a polyvalent carboxylic acid and an alcohol component mainly containing an aromatic diol and a polyester resin B obtained by condensation polymerization of a polyvalent carboxylic acid and an alcohol component mainly containing an aliphatic diol, and in that the degree of segregation of the wax in the toner depth direction from the toner surface toward the toner center is controlled.