Magnetic toner

Patent metadata

Field	Value
Publication number	US-9304422-B2
Application number	US-201414571167-A
Country	US
Kind code	B2
Filing date	Dec 15, 2014
Priority date	Dec 26, 2013
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

It is intended to provide magnetic toner that produces a stable image density in long-term use and can prevent ghosting under conditions of low-temperature and low-humidity. The present invention provides magnetic toner including magnetic toner particles each containing a binder resin, a magnetic material and a releasing agent, and silica fine particles, wherein the silica fine particles include silica fine particles A and B, the silica fine particles A have a number-average particle size of 5-20 nm as primary particles, the silica fine particles B are produced by a sol-gel method, and have a number-average particle size of 40-200 nm as primary particles, an abundance ratio of secondary particles of the silica fine particles B is 5-40% by number, and a coverage ratio X1 of the surface of the magnetic toner particles with the silica fine particles determined by ESCA is 40.0-75.0% by area.

First claim

What is claimed is:

1. Magnetic toner comprising
magnetic toner particles each containing a binder resin, a magnetic material and a releasing agent, and
silica fine particles present on the surfaces of the magnetic toner particles, wherein
the silica fine particles comprise silica fine particles A and silica fine particles B,
the silica fine particles A have a number-average particle size (D1) of 5 nm or larger and 20 nm or smaller as primary particles,
the silica fine particles B are produced by a sol-gel method, and have a number-average particle size (D1) of 40 nm or larger and 200 nm or smaller as primary particles,
an abundance ratio of secondary particles of the silica fine particles B is 5% by number or more and 40% by number or less, and
a coverage ratio X1 of the surface of the magnetic toner particles with the silica fine particles determined by electron spectroscopy for chemical analysis (ESCA) is 40.0% by area or more and 75.0% by area or less.

2. The magnetic toner according to claim 1 , wherein when a theoretical coverage ratio of the surface of the magnetic toner with the silica fine particles is defined as X2, a diffusion index represented by the following Expression 1 satisfies the following Expression 2:
Diffusion index= X 1/ X 2  (Expression 1)

Diffusion index≧−0.0042× X 1+0.62.  (Expression 2)

3. The magnetic toner according to claim 1 , wherein with respect to 100 parts by mass of the magnetic toner particles,
a total amount of the silica fine particles is 0.6 parts by mass or larger and 2.0 parts by mass or smaller,
an amount of the silica fine particles A is 0.5 parts by mass or larger and 1.5 parts by mass or smaller, and
an amount of the silica fine particles B is 0.1 parts by mass or larger and 0.5 parts by mass or smaller.

4. The magnetic toner according to claim 1 , wherein the magnetic toner has a total energy of 280 mJ/(g/mL) or higher and 355 mJ/(g/mL) or lower.

Assignees

• Canon Kk

Inventors

• Matsui Takashi
• Magome Michihisa
• Uratani Kozue
• Ohmori Atsuhiko

Classifications

• G03G9/09725

  Silicon-oxides; Silicates · CPC title

• G03G9/0819

  characterised by the dimensions of the particles · CPC title

• G03G9/083 Primary

  Magnetic toner particles · CPC title

• G03G9/0806

  whereby chemical synthesis of at least one of the toner components takes place · CPC title

• G03G9/0821

  characterised by physical parameters (magnetic parameters G03G9/083) · CPC title