Charging member with electro-conductive elastic layer having exposed bowl-shaped resin particles, process cartridge and electrophotographic apparatus
Provided is a charging member capable of suppressing the occurrence of an image defect due to the non-uniform abrasion of a photosensitive member and a stain, in a long-term use. The charging member includes an electro-conductive elastic layer as a surface layer. The electro-conductive elastic layer contains a binder and a bowl-shaped resin particle having an opening. The surface of the charging member has a concavity and a protrusion derived from the bowl-shaped resin particle. The relations represented by the following formulae are satisfied, 0.2 ≤ S = S 5 - S 1 S 1 ≤ 0.5 0.15 ≤ d = d 5 - d 1 d 1 ≤ 0.5 wherein, when the charging member is pressed onto a glass plate with 100 (g) load, S1 is the average value of contact areas, d1 is the average value of heights of spaces formed in a contact region; and when the load is changed to 500 (g), S5 is the average value of contact areas, d5 is the average value of heights of spaces.
1. A charging member comprising:
an electro-conductive substrate; and
an electro-conductive elastic layer as a surface layer on the substrate,
wherein
the electro-conductive elastic layer
comprises a binder, and
retains a bowl-shaped resin particle having an opening, so that the opening of the bowl-shaped resin particle is exposed at a surface of the charging member;
the surface of the charging member comprises:
a concavity derived from the opening of the bowl-shaped resin particle exposed at the surface, and
a protrusion derived from an edge of the opening of the bowl-shaped resin particle exposed at the surface;
a part of the surface of the charging member is constituted by the electro-conductive elastic layer; and
relations represented by the following formulae (1) and (2) are satisfied,
0.2
≤
S
=
S
5
-
S
1
S
1
≤
0.5
Formula
(
1
)
0.15
≤
d
=
d
5
-
d
1
d
1
≤
0.5
Formula
(
2
)
wherein
when the charging member is pressed onto a glass plate so that a load on the glass plate is 100 (g),
in a contact region R1 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S1 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d1 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R1; and
when the charging member is pressed onto a glass plate so that a load on the glass plate is 500 (g),
in a contact region R5 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S5 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d5 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R5.
2. The charging member according to claim 1 , wherein,
when
Martens hardness of the binder on the surface of the charging member is defined as M1, and
Martens hardness of the binder immediately beneath a bottom of the concavity derived from the opening of the bowl-shaped resin particle on the surface of the charging member is defined as M2,
a value of M2/M1 is less than 1.
3. A process cartridge comprising a charging member and an electrophotographic photosensitive member and being configured to be attachable to and detachable from a main body of an electrophotographic apparatus,
wherein
the charging member comprises:
an electro-conductive substrate; and
an electro-conductive elastic layer as a surface layer on the substrate,
wherein
the electro-conductive elastic layer
comprises a binder, and
retains a bowl-shaped resin particle having an opening, so that the opening of the bowl-shaped resin particle is exposed at a surface of the charging member;
the surface of the charging member comprises:
a concavity derived from the opening of the bowl-shaped resin particle exposed at the surface, and
a protrusion derived from an edge of the opening of the bowl-shaped resin particle exposed at the surface;
a part of the surface of the charging member is constituted by the electro-conductive elastic layer; and
relations represented by the following formulae (1) and (2) are satisfied,
0.2
≤
S
=
S
5
-
S
1
S
1
≤
0.5
Formula
(
1
)
0.15
≤
d
=
d
5
-
d
1
d
1
≤
0.5
Formula
(
2
)
wherein
when the charging member is pressed onto a glass plate so that a load on the glass plate is 100 (g),
in a contact region R1 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S1 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d1 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R1, and
when the charging member is pressed onto a glass plate so that a load on the glass plate is 500 (g),
in a contact region R5 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S5 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d5 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R5.
4. The process cartridge according to claim 3 , wherein,
when
Martens hardness of the binder on the surface of the charging member is defined as M1, and
Martens hardness of the binder immediately beneath a bottom of the concavity derived from the opening of the bowl-shaped resin particle on the surface of the charging member is defined as M2,
a value of M2/M1 is less than 1.
5. An electrophotographic apparatus comprising a charging member and an electrophotographic photosensitive member,
wherein
the charging member comprises:
an electro-conductive substrate; and
an electro-conductive elastic layer as a surface layer on the substrate,
wherein
the electro-conductive elastic layer
comprises a binder, and
retains a bowl-shaped resin particle having an opening, so that the opening of the bowl-shaped resin particle is exposed at a surface of the charging member;
the surface of the charging member comprises:
a concavity derived from the opening of the bowl-shaped resin particle exposed at the surface, and
a protrusion derived from an edge of the opening of the bowl-shaped resin particle exposed at the surface;
a part of the surface of the charging member is constituted by the electro-conductive elastic layer; and
relations represented by the following formulae (1) and (2) are satisfied,
0.2
≤
S
=
S
5
-
S
1
S
1
≤
0.5
Formula
(
1
)
0.15
≤
d
=
d
5
-
d
1
d
1
≤
0.5
Formula
(
2
)
wherein
when the charging member is pressed onto a glass plate so that a load on the glass plate is 100 (g),
in a contact region R1 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S1 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d1 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R1, and
when the charging member is pressed onto a glass plate so that a load on the glass plate is 500 (g),
in a contact region R5 comprising at least one contact portion between the charging member and the glass plate in a nip between the charging member and the glass plate, S5 is defined as an average value of contact areas between the charging member and the glass plate in the respective contact portions and
d5 is defined as an average value of heights of respective spaces formed between the charging member and the glass plate in the contact region R5.
6. The electrophotographic apparatus according to claim 5 , wherein,
when
Martens hardness of the binder on the surface of the charging member is defined as M1, and
Martens hardness of the binder immediately beneath a bottom of the concavity derived from the opening of the bowl-shaped resin particle on the surface of the charging member is defined as M2,
a value of M2/M1 is less than 1.