Amorphous Polyester Resin for Toner Low-Temperature Fixing
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Solution Overview
Problem
Conventional binder resins for toners face challenges in achieving both high-speed printing and energy savings while maintaining image quality, as they struggle to balance low-temperature fixing properties with hot offset resistance and storability, due to contradictory molecular weight requirements.
Innovation Solution
An amorphous polyester resin is developed with specific molecular weight and chemical composition, including a polyhydric alcohol component and a second poly-carboxylic acid component, to achieve excellent low-temperature fixing, hot offset resistance, and storability, with a weight-average molecular weight of 8,000 to 50,000 and a hydroxyl value of 10 to 60 mgKOH/g, allowing for improved dispersibility and image gloss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the average molecular weight of polyester resin is decreased to improve low-temperature fixing property, then low-temperature fixing property is improved, but hot offset resistance deteriorates
Solution Approach 1:
The invention changes the molecular weight parameters of the polyester resin to a specific range (Mn: 5,000-20,000, Mw: 20,000-80,000, Mw/Mn: 2.5-4.0) to simultaneously achieve low-temperature fixing and hot offset resistance. This parameter optimization resolves the contradiction by finding the optimal balance point where the resin is soft enough for low-temperature fixing but maintains sufficient structural integrity for hot offset resistance.
Solution Approach 2:
The invention uses a composite binder resin system combining amorphous polyester resin and crystalline polyester resin in specific proportions (amorphous: 70-95 mass%, crystalline: 5-30 mass%). This composite approach allows the amorphous component to provide low-temperature fixing while the crystalline component contributes to hot offset resistance, resolving the contradiction through synergistic material combination.
2Reliability
If the average molecular weight of polyester resin is increased to improve hot offset resistance, then hot offset resistance is improved, but low-temperature fixing property deteriorates
Solution Approach 1:
The invention optimizes the molecular weight parameters (Mn: 5,000-20,000, Mw: 20,000-80,000, Mw/Mn: 2.5-4.0) to achieve the optimal balance. The controlled molecular weight distribution ensures the resin has sufficient chain length for hot offset resistance while maintaining adequate chain mobility for low-temperature fixing, resolving the contradiction through precise parameter control.
Solution Approach 2:
The composite binder system with amorphous polyester (70-95 mass%) and crystalline polyester (5-30 mass%) allows the amorphous phase to dominate the low-temperature fixing behavior while the crystalline phase provides thermal stability for hot offset resistance, effectively resolving the contradiction through material composition design.
3Manufacturing precision
If the particle diameter of toner is decreased to improve image quality, then image quality is improved, but blocking resistance deteriorates
Solution Approach 1:
The invention optimizes the binder resin molecular weight and composition parameters to enable the use of smaller toner particles (3-9 μm) without compromising blocking resistance. The specific molecular weight range and Mw/Mn ratio ensure that even fine particles maintain sufficient inter-particle forces to prevent blocking during storage and handling, resolving the contradiction between image quality and blocking resistance.
Solution Approach 2:
The composite binder resin system provides enhanced adhesion and cohesion properties that allow smaller toner particles to be used. The combination of amorphous and crystalline polyester resins creates a matrix that maintains particle separation and prevents blocking even when toner particle diameter is reduced for high-quality imaging, resolving the contradiction through improved material properties.
Data Source
AI summary
An amorphous polyester resin of the invention is obtained by reaction between a polyester resin (A), obtained by reaction between a polyhydric alcohol component and a first poly-carboxylic acid component, either or both including a 3 or higher valent component, and having a weight-average molecular weight of 6,000 to 40,000 and a hydroxyl value of 15 to 70 mgKOH/g, and a second poly-carboxylic acid component (a), under conditions satisfying the following equations (1), (2) and (3), and the amorphous polyester resin satisfying the following equation (4). AVB-AVA/AVa=0.5-0.7 MwB/MwA=1.1-2.0 OHVB/AVB=1.0-6.0 MwB/MnB=3.0-15.0 [In the equations, AVB, OHVB, MwB and MnB respectively represent an acid value, a hydroxyl value, a weight-average molecular weight and a number-average molecular weight, and AVA and MwA of the amorphous polyester resin respectively represent an acid value and a weight-average molecular weight of the polyester resin (A), where AVa represents a theoretical acid value of the second poly-carboxylic acid component (a).]