Electrostatic Toner with Crystalline Polyester Resin
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Solution Overview
Problem
Electrostatic image developing toners face challenges with low heat-resistant storage stability and image storage stability due to plasticization from the mutual dissolution of amorphous and crystalline polyester resins, and they are prone to crushing during the developing process due to insufficient affinity between the resin components.
Innovation Solution
The toner particles are formulated with a binder resin comprising an amorphous resin and a crystalline polyester resin, where specific ratios of heat absorption are maintained to ensure adequate low-temperature fixability and heat-resistant storage stability, and the crystalline polyester resin is adjusted to have a melting point between 65°C to 85°C, enhancing the toner's crush resistance and image stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a crystalline polyester resin is introduced to the toner as a binding resin to decrease the glass transition point or melt viscosity, then low-temperature fixability is improved, but heat-resistant storage stability deteriorates due to plasticization caused by mutual dissolution between the amorphous resin and the crystalline polyester resin
Solution Approach 1:
The invention changes the physical and chemical parameters of the crystalline polyester resin, specifically controlling its melting point (65-85°C) and limiting its content to 5-30 mass% of the total binder resin. Additionally, the invention controls the ratio of heat absorption (ΔH1/ΔH(theo.)) to be 0.2-0.5, which optimizes the balance between low-temperature fixability and heat-resistant storage stability by preventing excessive plasticization while maintaining adequate melting behavior.
Solution Approach 2:
The invention uses a composite binder resin system combining amorphous resin and crystalline polyester resin in specific proportions (5-30 mass% crystalline content). This composite structure allows the amorphous resin to provide heat-resistant storage stability while the crystalline polyester resin contributes to low-temperature fixability, achieving a synergistic effect that resolves the contradiction between the two opposing requirements.
2Temperature
If the amorphous resin and crystalline polyester resin are used together to improve low-temperature fixability, then image storage stability deteriorates due to plasticization from mutual dissolution
Solution Approach 1:
The invention controls the melting point of the crystalline polyester resin within 65-85°C and limits its content to 5-30 mass% of the total binder resin. By controlling these parameters, the invention reduces excessive plasticization between the amorphous resin and crystalline polyester resin, thereby maintaining image storage stability while still achieving adequate low-temperature fixability.
Solution Approach 2:
The invention creates local structural differentiation within the toner particles by forming a core-shell structure where the crystalline polyester resin and amorphous resin are distributed in specific patterns. This local quality control prevents uniform plasticization throughout the particle, maintaining structural integrity and image storage stability while enabling low-temperature fixing at the surface level.
3Reliability
If the amorphous resin and crystalline polyester resin do not exhibit sufficient affinity to each other, then low-temperature fixability is improved through reduced plasticization, but toner particles become more crushable during the developing process
Solution Approach 1:
The invention optimizes the content of crystalline polyester resin to 5-30 mass% of the total binder resin and controls the heat absorption ratio (ΔH1/ΔH(theo.)) to be 0.2-0.5. These parameter changes ensure sufficient affinity between the amorphous resin and crystalline polyester resin, maintaining toner particle strength and crush resistance during the developing process while preventing excessive plasticization that would compromise heat-resistant storage stability.
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 provides long-lasting crush resistance, adequate heat-resistant storage stability, and good image storage stability, enabling effective low-temperature fixability and maintaining image quality over time.
Implementation Method 1
ΔH1 (J/g) is the amount of heat absorption based on a melting peak of the crystalline polyester resin in a first heating step from room temperature to 150° C.
Implementation Method 2
ΔH2 (J/g) is the amount of heat absorption based on a melting peak of the crystalline polyester resin in a second heating step from 0° C. to 150° C.
Implementation Method 3
low heat-resistant storage stability of the toners and low image storage stability of a fixed image obtained by heat fixing, which are due to plasticization caused by mutual dissolution between the amorphous resin and the crystalline polyester resin
Data Source
AI summary
An electrostatic image developing toner includes toner particles that contain a binder resin and a coloring agent. The binder resin includes an amorphous resin and a crystalline polyester resin. The toner satisfies Relations (1) and (2). ΔH1 is the amount of heat absorption based on a melting peak of the crystalline polyester resin in a first heating step from room temperature to 150° C. ΔH2 is the amount of heat absorption based on a melting peak of the crystalline polyester resin in a second heating step from 0° C. to 150° C. ΔH(theo.) is a value of fusion enthalpy calculated from a mass ratio of a structural unit derived from a linear aliphatic monomer contained in the binder resin based on a group contribution method.0.2≦ΔH1/ΔH(theo.)≦0.5 Relation (1):0.1≦ΔH2/ΔH(theo.)≦0.3 Relation (2):