Decolorizable Toner Capsule Structure and Homogenizer Treatment
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Solution Overview
Problem
Conventional decolorizable electrophotographic toners with colorants in capsule form are prone to breakage and generate fine powder when used in image forming apparatuses, leading to image quality issues like fogging and toner scattering due to insufficient encapsulation and stress exposure.
Innovation Solution
A method involving a polyster-based binder resin with a weight average molecular weight between 5000 and 30000, a colorant with a capsule structure and volume average particle diameter of 0.5 to 3.5 µm, and a homogenizer treatment to achieve a specific particle distribution and circularity, reducing the ratio of fine powder generation and improving charging properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If colorant is incorporated in capsule form with size of several micrometers, then color development function is achieved, but toner is easily broken at the interface between binder resin and colorant, generating fine powder
Solution Approach 1:
The patent applies parameter changes by carefully controlling the volume average particle diameter of the colorant capsule within the range of 0.5 to 3.5 μm, and the weight average molecular weight of the binder resin within 5000 to 30000. These parameter optimizations ensure sufficient encapsulation of the colorant while maintaining toner particle strength, preventing breakage and fine powder generation during use in image forming apparatuses.
2Volume of moving object
If colorant capsule size is reduced to several micrometers to 20 μm, then toner particle size is minimized for better image quality, but colorant encapsulation becomes insufficient, increasing surface exposure and breakage risk
Solution Approach 1:
The patent optimizes the colorant capsule size parameter to maintain a volume average particle diameter of 0.5 to 3.5 μm, which provides sufficient encapsulation protection. Simultaneously, the binder resin molecular weight is controlled at 5000 to 30000 to ensure adequate adhesion and structural integrity, resolving the contradiction between small particle size and sufficient encapsulation.
3Ease of manufacture
If conventional ultrasonic wave measurement is used to measure fine powder, then measurement process is simplified, but amount of fine powder increases due to ultrasonic stress, failing to reproduce actual usage conditions
Solution Approach 1:
The patent replaces the conventional ultrasonic wave measurement method with a flow particle image analyzer that uses fluid flow to transport and measure particles. This substitution eliminates the harmful ultrasonic stress that generates additional fine powder, allowing accurate measurement of fine powder content under conditions that closely reproduce actual usage environments in image forming apparatuses.
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 method effectively suppresses fine powder generation and improves image quality by ensuring the toner's structural integrity and charging properties, reducing fogging and toner scattering when used in image forming devices.
Implementation Method 1
subjected to a stirring treatment in which stirring is performed at 5000 rpm for 30 minutes using a homogenizer
Implementation Method 2
aggregating and fusing the dispersed particles containing a binder resin and the dispersed colorant
Implementation Method 3
a color developable compound and a color developing agent and is decolorized by heating so that an image formed using the toner can be erased
Data Source
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AI summary
Disclosed is a decolorizable electrophotographic toner, including: a binder resin; and a colorant which contains at least a color developable compound and a color developing agent and is covered with an outer shell so as to have a capsule structure, wherein the number ratio of particles having an equivalent circle diameter of 0.6 µm or more and 2.5 µm or less of the toner when measured using a flow particle image analyzer after the toner is dispersed in an aqueous medium at a ratio of 0.08% by weight and the resulting dispersion is subjected to a stirring treatment in which stirring is performed at 5000 rpm for 30 minutes using a homogenizer (T-25 digital ULTRA-TURRAX (manufactured by IKA Japan K.K., provided with a shaft generator S25N-10G)) is 30% by number or less.