IMAGE FORMING APPARATUS

• US 20150132030A1
• Filed: 11/05/2014
• Published: 05/14/2015
• Est. Priority Date: 11/13/2013
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Orihara, Tatsuaki, Hagiwara, Kazunari, Haraguchi, Manami, Fukatsu, Makoto, Tokiwa, Shuhei, Nakamoto, Atsushi
• Granted Patent: US 9,298,128 B2
• Time in Patent Office: Days
• US Class Current: 399/285
• CPC Class Codes: G03G 15/065 Arrangements for controlling the potential of the developing electrode
• CPC Class Codes: G03G 15/0812 characterised by the developer regulating means, e.g. structure of doctor blade
• CPC Class Codes: G03G 15/0818 characterised by the structure of the donor member, e.g. surface properties
• CPC Class Codes: G03G 15/5037 the characteristics being an electrical parameter, e.g. voltage
• CPC Class Codes: G03G 2215/0861 Particular composition or materials

Abstract

In an image forming apparatus having a photosensitive drum that carries a toner image, a developing roller that is provided to be capable of rotating while carrying toner, and that supplies the toner to the photosensitive drum in order to develop a latent image, and voltage applying device for applying a voltage to the developing roller, the developing roller includes a conductive base layer and a surface layer covering the base layer, and a surface charge density of the developing roller is equal to or smaller than a surface charge density of the toner.

Claims

1. An image forming apparatus comprising:

an image bearing member capable of bearing a developer image that is formed by supplying a developer to a latent image formed on a surface thereof;

a developer carrying member that is provided to be capable of rotating while carrying the developer, and that supplies the developer to the image bearing member by contacting the image bearing member;

a regulating member that regulates a layer thickness of the developer carried on the developer carrying member; and

a voltage applying device for applying a voltage to the developer carrying member,

wherein the developer carrying member includes a conductive base layer and a surface layer covering the base layer, and

when a volume resistance of the surface layer is ρ

c, a film thickness thereof is dc, and a relative dielectric constant thereof is ∈

c,

a surface charge density of the developer on the developer carrying member, the film thickness of which has been regulated by the regulating member, is q/s, a relative dielectric constant thereof is ∈

t, and a layer thickness thereof is dt,

a potential of the surface of the image bearing member in a contact region with the developer carrying member is V, and

a time required for the developer to pass through the contact region after entering the contact region as the developer carrying member rotates is T,

2. The image forming apparatus according to claim 1, wherein the film thickness dc is smaller than 1 μ

m.

3. The image forming apparatus according to claim 1, further comprising:

a charging device for charging the surface of the image bearing member; and

an exposure device for forming the latent image by exposing the charged surface of the image bearing member,

wherein, when a capacitance of the image bearing member is Cp,

a capacitance of the developer on the developer carrying member, the film thickness of which has been regulated by the regulating member, is Ct, and

a potential difference between a surface potential of an unexposed region of the surface of the image bearing member charged by the charging device and a surface potential of the developer carrying member is Vback,

6. The image forming apparatus according to claim 1, wherein the image bearing member is provided to be capable of rotating such that a surface movement direction in the contact region is identical to a direction of the developer carrying member, and

the developer carrying member rotates at a higher rotation speed than the image bearing member.

7. The image forming apparatus according to claim 1, wherein the developer carrying member is provided to be capable of contacting and separating from the image bearing member.

8. The image forming apparatus according to claim 1, wherein the image bearing member includes a first mode for rotating at a first speed and a second mode for rotating at a second speed that is higher than the first speed.

9. The image forming apparatus according to claim 1, wherein the developer is a single component non-magnetic toner.

10. The image forming apparatus according to claim 1, wherein the surface layer is formed from alumina.

4. An image forming apparatus comprising:

an image bearing member capable of bearing a developer image that is formed by supplying a developer to a latent image formed on a surface thereof;

a charging device for charging the surface of the image bearing member;

an exposure device for forming the latent image by exposing the charged surface of the image bearing member;

a developer carrying member that is provided to be capable of rotating while carrying the developer, and that supplies the developer to the image bearing member by contacting the image bearing member;

a regulating member that regulates a layer thickness of the developer carried on the developer carrying member; and

a voltage applying device for applying a voltage to the developer carrying member,

wherein the developer carrying member includes a conductive base layer and a surface layer covering the base layer, and

when a volume resistance of the surface layer is ρ

c, a film thickness thereof is dc, and a relative dielectric constant thereof is ∈

c,

a surface charge density of the developer on the developer carrying member, the film thickness of which has been regulated by the regulating member, is q/s, a relative dielectric constant thereof is ∈

t, and a layer thickness thereof is dt,

a potential difference between a surface potential of an unexposed region of the surface of the image bearing member charged by the charging device and a surface potential of the developer carrying member is Vback, and

a time required for the developer to pass through the contact region after entering the contact region as the developer carrying member rotates is T,

5. The image forming apparatus according to claim 4, wherein the film thickness dc is smaller than 1 μ

m.