Toner Core-Shell Structure for Low-Temperature Fogging
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Solution Overview
Problem
Electrophotographic image forming apparatuses experience 'fogging' issues at low temperatures due to insufficient toner charge quantity, leading to poor image quality and reduced durability.
Innovation Solution
A developing unit comprising toner particles with a core-shell structure, an inorganic fine powder, and a developing roller with a surface layer containing a specific urethane resin structure, which maintains flexibility and reduces stress on the toner, ensuring adequate toner charge and preventing fogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the developing roller and toner are improved for suppressing reduction in developability due to toner deformation stress, then the toner durability is improved, but fogging occurs in low-temperature environments due to insufficient toner charge quantity
Solution Approach 1:
The invention changes the physical and chemical parameters of the toner particles by forming a core-shell structure with specific glass transition temperatures. The core resin has Tg of 50-90°C and the shell resin has Tg of -50-50°C, creating a gradient structure that optimizes both durability and charge retention at low temperatures
Solution Approach 2:
The invention uses composite materials by combining different resin types in a core-shell structure. The core uses resin A (Tg: 50-90°C) for durability while the shell uses resin B (Tg: -50-50°C) for low-temperature flexibility and charge retention, creating a material that exhibits both properties simultaneously
2Strength
If a polyurethane surface layer is formed on the developing roller to reduce stress on toner, then toner deformation is suppressed, but the toner charge quantity becomes insufficient at low temperatures
Solution Approach 1:
The invention changes the temperature parameter by specifying different glass transition temperatures for core and shell resins. The shell resin's lower Tg (-50-50°C) ensures the toner surface remains flexible and maintains charge at low temperatures, while the core resin's higher Tg (50-90°C) provides structural strength
3Reliability
If the toner particles are made with hard surface and soft inside for toughness, then the toner durability against external factors is improved, but the toner charge quantity is reduced in cold environments
Solution Approach 1:
The invention applies local quality by creating a core-shell structure where different regions of the toner particle have different properties. The core (resin A, Tg: 50-90°C) provides toughness and durability, while the shell (resin B, Tg: -50-50°C) provides low-temperature flexibility and charge retention, allowing each region to optimize its local function
Data Source
Figure 1
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AI summary
Provided are a development device in which it is possible to reduce the occurrence of fogging in a low temperature environment, and an electrophotographic image formation device with which it is possible to stably form an image over a long period of time. The development device has a toner (1), a development roller (2), and a toner restriction member. The toner (1) satisfies the following conditions: 40≤Z(25)≤80 and 10≤Z(10)≤55 (wherein Z(Y) represents the percentile of (X3(Y)-X4(Y)) relative to X3(Y) at Y°C, X3(Y) represents the displacement amount obtained after displacement amount (X2(Y)) is left to stand for 0.1 seconds, X2(Y) represents the displacement amount when a 2.94×10-4N load is applied at 9.8×10-5N/sec, and X4(Y) represents the displacement amount at 0N when the load is reduced by 9.8×10-5N/sec); 0.49×10-3≤R(25)≤1.70×10-3 (wherein R(25) represents the tilt from the starting point to the maximum load in the load displacement curve of the toner at 25°C); and 15°C≤(P1-TgA)≤70°C (wherein TgA represents a glass transition temperature between 40 and 60°C, and P1 represents the maximum heat absorption peak temperature between 70 and 110°C). The development roller (2) has a surface layer containing a urethane resin, wherein the urethane resin has at least one of the structures selected from among (a), and (b) and (c). -CH2-CH2-CH2-CH2-O- Structural formula (a)