Electrostatic Image Developing White Toner with Controlled Particle Size
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Solution Overview
Problem
Existing electrostatic image developing white toners face challenges in maintaining whiteness and transferability, especially in repeated formation of low-area-coverage images, due to degradation from external additives and charge polarity reversal.
Innovation Solution
The development of an electrostatic image developing white toner with specific particle size, specific surface area, and external additive composition, including poly(meth)acrylate particles and silica particles, to enhance physical spacing and charge injection blocking, thereby maintaining whiteness and transferability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volume-average particle size D50W is less than 6.0 μm or more than 10 μm, then the transferability is improved, but the whiteness lowering occurs in repeated low-area-coverage image formation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the volume-average particle size D50W within 6.0-10 μm and the specific surface area Sw within 0.7-1.3 cm²/g. These parameter optimizations ensure that the white toner particles maintain appropriate charge injection blocking capability while preventing excessive adhesion that would cause whiteness degradation in repeated low-area-coverage image formation.
Solution Approach 2:
The patent uses composite materials by combining white pigment particles with binder resin to form white toner particles with specific physical properties. The composite structure allows the particles to exhibit both sufficient charge injection blocking (maintaining whiteness) and appropriate transferability, resolving the contradiction between whiteness maintenance and image formation capability.
2Reliability
If external additives are added to improve transferability, then the transferability is enhanced, but the whiteness degradation accelerates in repeated low-area-coverage image formation
Solution Approach 1:
The patent applies the extraction principle by removing harmful external additives from the white toner composition. By eliminating substances like silica particles and titanium oxide that accelerate whiteness degradation, the patent achieves both good transferability and sustained whiteness in repeated low-area-coverage image formation without the need for traditional external additives.
Solution Approach 2:
The patent optimizes the physical parameters of white toner particles, specifically controlling the specific surface area Sw within 0.7-1.3 cm²/g and particle size distribution. This parameter optimization provides inherent transferability through controlled surface properties without requiring external additives that would compromise whiteness stability.
3Reliability
If the specific surface area Sw is less than 0.7 cm²/g or more than 1.3 cm²/g, then the charge injection blocking is improved, but the transferability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the specific surface area Sw within the optimal range of 0.7-1.3 cm²/g. This parameter optimization balances charge injection blocking capability (for maintaining whiteness) with transferability, as the surface area is sufficient to provide charge control but not excessive to cause adhesion problems.
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 proposed white toner effectively suppresses the lowering of whiteness even in repeated low-area-coverage image formation, maintaining high transferability and image quality by utilizing the external additives as physical spacers and charge injection blockers.
Implementation Method 1
utilizing the external additives as physical spacers
Implementation Method 2
charge injection blocking, thereby maintaining whiteness and transferability
Data Source
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AI summary
An electrostatic image developing white toner includes white toner particles including a binder resin and a white coloring agent; and an external additive including poly(meth)acrylate particles, wherein the white toner particles have a volume-average particle size D50W of 6.0 µm or more and 10 µm or less, a ratio of the white toner particles having a particle size of 3.2 µm or less relative to all the white toner particles is 0.5 vol% or more and 3 vol% or less, the white toner particles have a specific surface area Sw of 0.7 cm2/g or more and 1.2 cm2/g or less, and an external addition amount of the poly(meth)acrylate particles relative to the white toner particles is 0.1 mass% or more and 2.0 mass% or less.