Magnetic toner

• US 20070072102A1
• Filed: 10/28/2004
• Published: 03/29/2007
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Dojo, Tadashi, Sano, Tomohisa, Dojo, Nene
• Granted Patent: US 8,518,620 B2
• Time in Patent Office: Days
• US Class Current: 430/106.100
• CPC Class Codes: G03G 9/0819 characterised by the dimensions of the particles
• CPC Class Codes: G03G 9/0821 characterised by physical parameters magnetic parameters G03G9/083
• CPC Class Codes: G03G 9/0825 characterised by their structure; characterised by non-homogenuous distribution of components microcapsular toners G03G9/093
• CPC Class Codes: G03G 9/0827 characterised by their shape, e.g. degree of sphericity
• CPC Class Codes: G03G 9/0833 Oxides
• CPC Class Codes: G03G 9/0834 Non-magnetic inorganic compounds chemically incorporated in magnetic components
• CPC Class Codes: G03G 9/0835 Magnetic parameters of the magnetic components
• CPC Class Codes: G03G 9/0836 Other physical parameters of the magnetic components
• CPC Class Codes: G03G 9/0837 Structural characteristics of the magnetic components, e.g. shape, crystallographic structure
• CPC Class Codes: G03G 9/0838 Size of magnetic components
• CPC Class Codes: G03G 9/08755 Polyesters
• CPC Class Codes: G03G 9/08795 characterised by their chemical properties, e.g. acidity, molecular weight, sensitivity to reactants
• CPC Class Codes: G03G 9/08797 characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature

Abstract

To provide a magnetic toner which: enables a stable image density to be obtained irrespective of a use environment; and exhibits excellent low-temperature fixability, little image deterioration upon fixation, high coloring power, and a reduced toner consumption. The present invention relates to a magnetic toner containing at least: a binder resin; and a magnetic body. The binder resin contains a polyester unit. The toner has a weight average particle size of 5.0 to 9.0 μm, a true specific gravity of 1.3 to 1.7 g/cm³, and a saturated magnetization of 20 to 35 Am²/kg in a magnetic field of 796 kA/m. The dielectric loss tangent (tan δ) of the toner satisfies (tan δ_H−tan δ_L)/tan δ_L≦0.20 at 100 kHz.

Claims

1. A magnetic toner comprising magnetic toner base particles each containing at least a binder resin and a magnetic body, wherein:

(i) the binder resin contains a polyester unit;

(ii) the toner has a weight average particle size (D4) of 5.0 to 9.0 μ

m;

(iii) the toner has a true specific gravity of 1.3 to 1.7 g/cm³;

(iv) the toner has a saturated magnetization of 20 to 35 Am²/kg in a magnetic field of 796 kA/m;

(v) the toner contains 60 number % or more of toner having a circularity of 0.93 or more; and

(vi) a dielectric loss tangent (tan δ

) of the toner at 100 kHz satisfies the following formula (1).

[Formula]

(tan δ

_H−

tan δ

_L)/tan δ

_L≦

0.20 

 

(1)

[In the formula, tan δ

_H represents a dielectric loss tangent of the toner at a glass transition temperature (°

C.)+10°

C. and tan δ

_L represents a dielectric loss tangent of the toner at the glass transition temperature (°

C.)−

10°

C.]

2. A magnetic toner according to claim 1, wherein the toner contains 75 number % or more of toner having a circularity of 0.93 or more.

3. A magnetic toner according to claim 1 or 2, wherein a dielectric loss tangent (tan δ

) of the toner at 100 kHz and 40°

C. is 2×

10<sup>−

3</sup> to 1×

10<sup>−

2</sup>.

4. A magnetic toner according to any one of claims 1 to 3, wherein a dielectric constant of the toner at 100 kHz and 40°

C. is 15 to 40 (pF/m).

5. A magnetic toner according to any one of claims 1 to 4, wherein the magnetic body has a number average particle size of 0.08 to 0.30 μ

m.

6. A magnetic toner according to any one of claims 1 to 5, further comprising 30 mass % or more of a component having a molecular weight of 10,000 or less in a molecular weight distribution of the toner.

7. A magnetic toner according to any one of claims 1 to 6, wherein the binder resin contains two or more kinds of resins different from each other in softening point.

8. (canceled)

9. (canceled)