Positive Toner Additive Composition for Stable Charging and Flow
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Solution Overview
Problem
Conventional positively charged toners face challenges in achieving simultaneous stability of charging, charging rise property, and fluidity, particularly under mechanical stress, due to the use of resin fine particles as external additives which impair toner fluidity and cause clogging.
Innovation Solution
A positively charged toner formulation incorporating silica particles with positively charged surfaces, strontium titanate particles with uncharged surfaces, and resin fine particles formed of acrylic resin, with specified particle diameters and coverage ratios to enhance charging stability and fluidity while minimizing mechanical stress effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin fine particles are used as external additive to enhance charging stability, then charging stability is improved, but toner fluidity deteriorates and clogging occurs
Solution Approach 1:
The patent changes the particle size parameter of the external additive from conventional large particles to ultra-fine particles (1-10 nm). This parameter change allows the external additive to provide sufficient charging stability while the reduced size prevents impairment of toner fluidity and eliminates clogging issues during discharge
Solution Approach 2:
The patent uses a composite external additive system comprising ultra-fine inorganic particles (silica, strontium titanate) combined with organic compounds. This composite approach achieves both charging stability through the inorganic particles and maintains fluidity through the ultra-fine size and organic components, resolving the contradiction between reliability and ease of operation
2Reliability
If silica particles are used as external additive for positively charged toner, then charging is enhanced, but charging failure occurs due to positive chargeability of silica
Solution Approach 1:
The patent introduces an intermediary substance (organic compound or surface treatment layer) between the silica particles and the toner base. This intermediary controls the charge transfer, allowing silica to contribute to charging stability without causing excessive positive charge that leads to charging failure and fogging
Solution Approach 2:
The patent changes the surface properties parameter of the silica particles by applying surface treatments or selecting specific crystal structures. This modifies the chargeability of silica particles to provide stable charging without excessive positive charge accumulation that causes charging failure
3Reliability
If coverage ratio of external additive is increased to suppress embedment, then charging stability is improved, but mechanical stress effects worsen
Solution Approach 1:
The patent changes the particle size parameter to ultra-fine (1-10 nm), which allows achieving sufficient coverage for charging stability without creating large aggregates that would be vulnerable to mechanical stress. The ultra-fine particles distribute uniformly and resist embedment better
Solution Approach 2:
The patent combines multiple external additives (silica, strontium titanate, and organic compounds) in a synergistic formulation. This combination provides comprehensive protection against mechanical stress while maintaining charging stability, as different materials contribute different protective mechanisms
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 formulation achieves stable charging performance, maintains fluidity, and prevents clogging, ensuring high-quality image formation over time by controlling charging variations under mechanical stress.
Implementation Method 1
a silica particle the surface of which has been positively charged
Implementation Method 2
the surface of an electrostatic latent image carrying member is charged by corona discharge or the like
Data Source
Figure 1
AI summary
A positively charged toner (101) includes a toner base particle (102) and an external additive (103) that is adhered to the surface of the toner base particle (102). The external additive (103) includes a silica particle (104) the surface of which has been positively charged, a strontium titanate particle (105) the surface of which is not positively charged and a resin fine particle (106) that is formed of an acrylic resin. The number average primary particle diameter of the silica particle (104) is equal to or greater than 10 nm but equal to or less than 40 nm. The number average primary particle diameter of the strontium titanate particle (105) is equal to or greater than 10 nm but equal to or less than 40 nm. The coverage ratio of the silica particle (104) to the surface region of the toner base particle (102) is equal to or greater than 30% but equal to or less than 40% and the coverage ratio of the strontium titanate particle (105) to the surface region of the toner base particle (102) is equal to or greater than 5% but equal to or less than 10%.