Charging member, manufacturing method of charging member, electrophotographic apparatus, and process cartridge

• US 10,558,136 B2
• Filed: 04/02/2019
• Issued: 02/11/2020
• Est. Priority Date: 04/18/2018
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Furukawa, Takumi, Watanabe, Hiroaki, Terada, Kenya, Tomomizu, Yuya, Nakazawa, Toshimitsu
• Primary Examiner(s): Royer, William J
• Application Number:
  US16/372,834
• Publication Number:
  US 20190324379A1
• Time in Patent Office: 315 Days
• Field of Search: 399176
• CPC Class Codes: G03G 15/0216 by bringing a charging member into contact with the member to be charged, e.g. roller, brush chargers
• CPC Class Codes: G03G 15/0233 Structure, details of the charging member, e.g. chemical composition, surface properties
• CPC Class Codes: G03G 2215/021 by contact, friction or induction

Abstract

A charging member including an electro-conductive support; and an elastic layer, the elastic layer is a surface layer thereof and is constituted by a mono layer, the elastic layer includes domains and a matrix, an outer surface of the charging member is constituted by a surface of the matrix and surfaces of the domains, and the charging member has concave portions on the outer surface, the domains exist at bottom portions of the respective concave portions and are exposed to the outer surface of the charging member only at the bottom portions of the respective concave portions, the elastic layer has a volume resistivity of 1×10⁵ Ωcm or more and 1×10⁸ Ωcm or less, and A2 is 20 times or more of A1, wherein A1 and A2 are current values obtained by a prescribed method.

Claims

1. A charging member comprising:

an electro-conductive support; and

an elastic layer,

wherein the elastic layer is a surface layer of the charging member, and is constituted by a mono layer,

the elastic layer includes domains and a matrix, the domains each containing carbon black and rubber, the matrix containing rubber and having an electrical resistance higher than that of the domains,

an outer surface of the charging member is constituted by a surface of the matrix and surfaces of the domains, and the charging member has concave portions on the outer surface,

the domains exist at bottom portions of the respective concave portions and are exposed to the outer surface of the charging member only at the bottom portions of the respective concave portions,

the elastic layer has a volume resistivity of 1×

10⁵ Ω

cm or more and 1×

10⁸ Ω

cm or less, and

when A1 is defined as a current value at the time of applying a direct current (DC) voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with a surface of the matrix constituting the outer surface of the charging member and A2 is defined as a current value at the time of applying a DC voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with surfaces of the respective domains constituting the outer surface of the charging member, A2 is 20 times or more of A1.

2. The charging member according to claim 1, wherein a volume fraction of the domains is 5 vol % or more and 25 vol % or less based on a volume of the elastic layer.

3. The charging member according to claim 1, wherein the number of domains existing in a piece of cube of 10 μ

m in the elastic layer is 1 or more and 500 or less.

4. An electrophotographic apparatus comprising:

an electrophotographic photosensitive member; and

a charging member disposed to be capable of charging the electrophotographic photosensitive member,

wherein the charging member includes;

an electro-conductive support; and

an elastic layer, and

the elastic layer is a surface layer of the charging member, and is constituted by a mono layer, the elastic layer includes domains and a matrix, the domains each containing carbon black and rubber, the matrix containing rubber and having an electrical resistance higher than that of the domains,

an outer surface of the charging member is constituted by a surface of the matrix and surfaces of the domains, and the charging member has concave portions on the outer surface,

the domains exist at bottom portions of the respective concave portions and are exposed to the outer surface of the charging member only at the bottom portions of the respective concave portions,

the elastic layer has a volume resistivity of 1×

10⁵ Ω

cm or more and 1×

10⁸ Ω

cm or less, and

when A1 is defined as a current value at the time of applying a direct current (DC) voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with a surface of the matrix constituting the outer surface of the charging member and A2 is defined as a current value at the time of applying a DC voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with surfaces of the respective domains constituting the outer surface of the charging member, A2 is 20 times or more of A1.

5. A process cartridge attachable to and detachable from a body of an electrophotographic apparatus, the process cartridge comprising:

an electrophotographic photosensitive member; and

a charging member disposed to be capable of charging the electrophotographic photosensitive member,

wherein the charging member includes;

an electro-conductive support; and

an elastic layer, and

the elastic layer is a surface layer of the charging member, and is constituted by a mono layer, the elastic layer includes domains and a matrix, the domains each containing carbon black and rubber, the matrix containing rubber and having an electrical resistance higher than that of the domains,

an outer surface of the charging member is constituted by a surface of the matrix and surfaces of the domains, and the charging member has concave portions on the outer surface,

the domains exist at bottom portions of the respective concave portions and are exposed to the outer surface of the charging member only at the bottom portions of the respective concave portions,

the elastic layer has a volume resistivity of 1×

10⁵ Ω

cm or more and 1×

10⁸ Ω

cm or less, and

when A1 is defined as a current value at the time of applying a direct current (DC) voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with a surface of the matrix constituting the outer surface of the charging member and A2 is defined as a current value at the time of applying a DC voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with surfaces of the respective domains constituting the outer surface of the charging member, A2 is 20 times or more of A1.

6. A manufacturing method of a charging member, the charging member including an electro-conductive support and an elastic layer, the elastic layer being a surface layer of the charging member, being constituted by a mono layer, and including domains and a matrix, the domains each containing carbon black and rubber, the matrix containing rubber and having an electrical resistance higher than that of the domains, an outer surface of the charging member being constituted by surfaces of the matrix and a surface of the domains and having concave portions, and the domains existing at bottom portions of the respective concave portions and being exposed to the outer surface of the charging member only at the bottom portions of the respective concave portions, the manufacturing method of a charging member comprising:

(A) preparing a carbon master batch (CMB) for forming the domains, each containing carbon black and rubber;

(B) kneading the carbon master batch and a rubber composition that becomes the matrix to prepare a rubber composition having a domain-matrix structure; and

(C) extruding the rubber composition having the domain-matrix structure together with a mandrel from a crosshead to cover the surrounding of the mandrel with the rubber composition having the domain-matrix structure,

wherein when DS(d) is defined as a die swell value of the carbon master batch and DS(m) is defined as a die swell value of the rubber composition that becomes the matrix, a ratio between the die swell values DS(m)/DS(d) is greater than 1.0.

7. The manufacturing method of a charging member according to claim 6, wherein DS(m)/DS(d) is 1.1 or more.

8. The manufacturing method of a charging member according to claim 6, wherein the elastic layer has a volume resistivity of 1×

10⁵ Ω

cm or more and 1×

10⁸ Ω

cm or less, and

when A1 is defined as a current value at the time of applying a DC voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with a surface of the matrix constituting the outer surface of the charging member and A2 is defined as a current value at the time of applying a DC voltage of 80 V between the electro-conductive support and a cantilever of an atomic force microscope in contact with surfaces of the respective domains constituting the outer surface of the charging member, A2 is 20 times or more of A1.