JPH11295968A - Electrifying member and electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member excellent in durability and capable of achieving performance stable over a long term without the deterioration of performance caused by the adhesion of toner. SOLUTION: This member is provided with an elastic layer 3 and an outer layer 4 consisting of one or plural layers formed outside of the layer 3 directly or through other layer. When it is assumed that universal hardness in depth equivalent to the thickness of the layer 4 is H<1> and the universal hardness in depth ten times as large as in the case of H1 is H<2> , (H<1> /H<2> )<50 is satisfied. Thus, the universal hardness of the surface of the electrifying member is optimized and the deterioration of the electrification performance is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used for charging an object to be charged such as a photoreceptor used in an electrostatic latent image process in a copying machine, a printer, and the like, and a charging device using the same. About.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic process such as a copying machine or a printer, first, the surface of a photoreceptor is charged uniformly.
An image is projected from the optical system onto the photoreceptor to form a latent image by erasing the charged portion of the light, and then a toner image is formed by toner adhesion, and a toner is formed on a recording medium such as paper. Printing is performed by transferring an image.

In this case, a corona discharge method has been generally adopted as an operation for initially charging the photosensitive member. However, since this corona discharge method requires application of a high voltage of 6 to 10 kV, it is not preferable from the viewpoint of safe maintenance of the machine. In addition, there is an environmental problem because harmful substances such as ozone are generated during corona discharge.

[0004] For this reason, efforts have been made for a charging system that can perform charging with an applied voltage lower than that of corona discharge and can suppress generation of harmful substances such as ozone. As an attempt of such a charging method, there has been proposed a contact method in which a charging member to which a voltage is applied is brought into contact with a member to be charged such as a photosensitive member at a predetermined pressure to charge the member to be charged.

As a charging member used in the contact charging system, for example, a resin solution of nylon, acrylic, urethane or the like is applied to the surface of an elastic layer such as rubber or urethane foam by dipping or spraying. A coating film layer is known.

[0006]

However, in this contact charging method, since the charging member and the member to be charged are always in contact, a corona system in which the member to be charged is charged in a non-contact manner by a discharge from a conventional wire or the like. Compared to
The durability of the charging member tends to be a problem.

[0007] Residual toner greatly affects the durability of the charging member in this contact charging system. That is, a small amount of toner remaining on the surface of the photosensitive drum gradually adheres to the charging member due to poor transfer and poor cleaning. In severe cases, the toner is embedded and fixed on the surface of the charging member, which causes poor charging. Originally, to solve such a problem, the fundamental measure is to improve the transfer efficiency and the cleaning efficiency so that the residual toner does not reach the charging section by the charging member. It is difficult to eliminate 100%. In order to prevent the residual toner from adhering to the surface of the charging member, it has been proposed to coat the surface of the charging member with a fluorine-based material having excellent antifouling properties. At present, durability has not been obtained.

In this case, the residual toner does not seem to adversely affect the image to the extent that the residual toner slightly adheres to the surface of the charging member. It seems that the residual toner is embedded in the charging member surface from a state of simply adhering to the charging member surface, and once embedded in the charging member, the residual toner starts accumulating at an accelerated rate, and at this point, the image is Bad things begin to appear.

The present invention has been made in view of such circumstances, and even when used in an electrostatic latent image process of a copying machine, a printer, or the like, the performance is maintained for a long time without causing deterioration in performance due to toner adhesion. It is an object of the present invention to provide a charging member having excellent durability and capable of exhibiting stable performance, and a charging device using the charging member.

[0010]

Means for Solving the Problems and Embodiments of the Invention As a result of diligent studies to achieve the above object, the present inventor has found that an elastic layer is provided directly or through another layer outside the elastic layer. The charging member having a single layer or a plurality of outer layers formed as described above, has a universal hardness H ¹ at a depth corresponding to the thickness of the outermost layer forming the member surface, and 10
By adjusting the hardness of the member surface so that (H ¹ / H ² ) <50 when the universal hardness at twice the depth is H ² ,
The inventors have found that a stable charging operation can be performed for a long period of time without lowering the performance of the charging member due to toner adhesion, and the present invention has been completed.

Accordingly, the present invention provides a charging member for charging a member to be charged by applying a voltage between the member and the member to be charged, by contacting the member with the member. It has an outer layer composed of one or more layers formed directly or via another layer on the outside, and has a universal hardness H ¹ at a depth corresponding to the thickness of the outermost layer, and a universal hardness at a depth 10 times that of H ¹ . Is H ² ,
(H ¹ / H ² ) <50, and a charging member that contacts the member to be charged and charges the member to be charged; A charging device comprising a voltage applying means for applying a voltage therebetween, wherein the charging device according to the present invention is used as the charging member.

Hereinafter, the present invention will be described in more detail.
As described above, the charging member of the present invention optimizes the universal hardness of the surface of the member, thereby preventing deterioration of the charging performance due to adhesion and fixation of toner as much as possible, and improves durability. Things.

The above universal hardness is a physical property value obtained by pushing an indenter into a measurement object while applying a load, and is obtained as (test load) / (indenter surface area under test load). Is expressed in N / mm ² .

The universal hardness can be measured using a commercially available hardness measuring device, for example, using an ultra-micro hardness meter H-100V (manufactured by Fischer). In this measuring device, a quadrangular pyramid or triangular pyramid-shaped indenter is pushed into the object to be measured while applying a test load, and when a predetermined indentation depth is reached, the surface area with which the indenter is in contact is determined from the indentation depth. The universal hardness is determined as (Test load) / (Indenter surface area under test load).

In this case, in the charging member of the present invention, the hardness of the surface of the member is defined as H ¹ , the universal hardness at the indentation depth corresponding to the depth of the outermost layer forming the surface of the member, and the indentation depth ten times as large. The universal hardness in H
² , the relationship between the two universal hardnesses is (H ¹ /
H ² ) <50, preferably 1 <(H ¹ / H ² ) <40, more preferably 1 <(H ¹ / H ² ) <30. Specifically, for example, if the thickness of the outermost layer forming the surface of the charging member of the present invention is 5 μm, the universal hardness at the time when the indenter of the measuring device is pushed 5 μm from the surface of the charging member is H ¹ , and the indenter is charged. the universal hardness at the time pushed 50μm from the surface of the member and ^{H 2, (H 1 / H} 2) is used to adjust so that the above-mentioned range.

The conditions for measuring the universal hardness are not particularly limited, and any conditions may be used as long as the universal hardnesses H ¹ and H ² can be obtained based on the indentation depth.
For example, when measuring the universal hardness using the ultra-micro hardness tester H-100V (manufactured by Fischer),
The following conditions can be exemplified, and the indenter is gradually pushed into the charging member surface up to a predetermined indentation depth under the following conditions, and the contact area between the load and the indenter when the indentation reaches the predetermined depth. Thus, the universal hardnesses H ¹ and H ² can be obtained. Measurement condition example Indenter: Square pyramidal diamond indenter with facing angle of 136 degrees Initial load: 0.02 mN Maximum load: 100 to 400 mN

[0017] The charging member of the present invention may be formed by molding an elastic layer and one or more outer layers formed outside the elastic layer and satisfying the above universal hardness condition. Any form may be used as long as it can be stably contacted with the member to be charged and can uniformly apply a charge to the member to be charged by applying a voltage, such as a roll, a plate, and a block. Although various forms can be used, such as a roll form, it is usually preferable. For example, as shown in FIG. 1, a charging member 1 in which an elastic layer 3 is formed on the outer periphery of the shaft 2 and an outer layer 4 is formed outside the elastic layer 3 can be exemplified. In this case, the shaft 2 is made of metal. Alternatively, a plastic shaft can be used, and depending on the form of the charging member and the mechanism of the charging device in which the charging member is used, this shaft 2 can be used.
Can also be omitted.

The elastic layer 3 may be any material that can finally form a charging member that satisfies the above-mentioned universal hardness condition. For example, a rubber or resin conventionally used as an elastic layer of the charging member may be used. Alternatively, it can be formed of a foam. Specifically, a rubber having a base rubber of polyurethane, silicone rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene-butadiene rubber, ethylene-propylene rubber, polynorbornene rubber, styrene-butadiene-styrene rubber, epichlorohydrin rubber, or the like The composition is exemplified, but polyurethane is particularly preferable, and the expansion ratio is more preferably 1.5 to 50.
Double polyurethane foam is used. The foaming density in this case is suitably about 0.05 to 0.9 g / cm ³ .

A conductive agent is added to the elastic layer 3.
Thereby, a predetermined conductivity can be imparted. Its guidance
The electric agent is not particularly limited, and may be lauryl trimethyl alcohol.
Ammonium, stearyltrimethylammonium, octane
Tadodecyl trimethyl ammonium, dodecyl trimethyl
Luammonium, hexadecyltrimethylammonium
Dimethyl ethyl ammonium perchlorate
Acid salt, chlorate, borofluoride, ethosulfate
Halogenation of salt, benzyl bromide, benzyl chloride, etc.
Cationic field of quaternary ammonium salts such as benzyl salts
Surfactants, aliphatic sulfonates, higher alcohol sulfates
Steal salt, higher alcohol ethylene oxide added sulfuric acid
Ester salt, higher alcohol phosphate ester salt, higher alcohol
Acetonitrile such as phosphoric acid oxide addition phosphate salt
Zwitterionic surfactants such as on-surfactants and various betaines
Agent, higher alcohol ethylene oxide, polyethylene
Glycol fatty acid esters, polyhydric alcohol fatty acid esters
Antistatic agents such as nonionic antistatic agents such as tellurium, LiC
F_ThreeSO_Three, NaClO_Four, LiAsF₆, LiBF_Four, N
aSCN, KSCN, Li such as NaCl⁺, Na⁺, K⁺
Metal salt of Group 1 of the Periodic Table, or NH_Four ⁺Such as salt
Electrolyte and Ca (ClO_Four)_TwoCa such as²⁺ , Ba²⁺ etc
Metal salts of the second group of the periodic table, and their antistatic agents
Has at least one or more hydroxyl groups, carboxyl groups,
Activity that reacts with isocyanates such as secondary or secondary amine groups
And those having a group having an acidic hydrogen. Furthermore,
1,4-butanediol, ethylene glycol
, Polyethylene glycol, propylene glycol,
Polyhydric alcohols such as polyethylene glycol and their derivatives
Or ethylene glycol monomethyl ate
Mono such as ter, ethylene glycol monoethyl ether
Ion conductive agent such as complex with all, or Ketjembler
EC, conductive carbon such as acetylene black, S
AF, ISAF, HAF, FEF, GPF, SRF, F
Rubber carbon such as T, MT, etc., oxidized color
(Ink) carbon, pyrolytic carbon, natural grapher
Site, artificial graphite, antimony-doped tin oxide,
Titanium oxide, zinc oxide, nickel, copper, silver, germanium
Metals and metal oxides, polyaniline, polypillow
And conductive polymers such as polyacetylene.
You. In this case, the amount of these conductive agents depends on the type of the composition.
And the volume resistivity of the elastic layer 3 is usually 1
0⁰-10⁸Ω · cm, preferably 10^Two-10⁶Ω · cm
It is adjusted so that

The outer layer 4 is not particularly limited as long as it can form a charging member that satisfies the above-mentioned universal hardness condition when formed on the surface of the charging member. In this case, a fluororesin is preferably used from the viewpoint of the surface smoothness of the member and low adhesion to the member to be charged. In this case, as the fluororesin, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, Polychlorotrifluoroethylene, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, and the like, and a dispersion-type aqueous fluororesin obtained by dispersing these fine particles in water is particularly preferably used. More preferably, a dispersion type aqueous fluororesin in which fine particles of polytetrafluoroethylene are dispersed in water is used. The particle size of the fluororesin fine particles used is not particularly limited, but is preferably 5 μm or less, particularly preferably 0.05 to 1 μm.

The outer layer 4 can be formed by mixing other resins with these fluororesins as long as the effect of the fluororesins is not impaired. In this case, as the other resin mixed with the fluororesin, polyvinyl acetal resin, urethane resin, polyester resin, acrylic resin, nylon resin, epoxy resin, vinylidene chloride copolymer, etc. The outer layer 4 can be formed by mixing two or more kinds with the fluororesin. Among these resins, polyvinyl acetal resin, urethane resin, polyester resin, and vinylidene chloride-based copolymer are preferable from the viewpoint of film formation and uniformity of the fluororesin, and polyvinyl acetal resin is particularly preferably used.

The outer layer 4 can be provided with or adjusted for conductivity by adding a conductive agent. In this case, the conductive agent is not particularly limited, but carbon is preferably used, and particularly, When forming the outermost layer that forms the surface of the member, it is preferable to use carbon as the conductive agent. In this case, the carbon used for the outer layer 4 is not particularly limited, but has an oxygen content of 5%.
%, Particularly preferably 7% or more, more preferably 9% or more, and the pH is preferably 5 or more, particularly 6 or more, and more preferably 7 or more. That is, the oxygen content of ordinary carbon is about 0.1 to 3%, and there is carbon partially oxidized, but the carbon oxidized slightly increases the oxygen content. PH tends to shift toward the acidic side as the carbon becomes acidic, and when carbon is added to an aqueous resin (specifically, an aqueous fluororesin), the stability may decrease. On the other hand, the carbon suitably used in the present invention maintains neutrality or alkalinity despite having a high oxygen content, and can be stably added to the aqueous fluororesin. . Although the detailed structure of carbon having such an oxygen content and pH is not clear, a functional group such as a carboxyl group, a hydroxyl group, or a ketone group is attached to the carbon surface, and a part of the hydrogen contained in these functional groups is removed. Those substituted with an alkali metal such as sodium are preferably used.

The amount of the conductive agent to be added depends on the desired resistance.
It can be adjusted appropriately to obtain. in this case,
The resistance of the outer layer 4 has a volume resistivity of 10^Three-10¹² Ω · cm,
Especially 10^Five-10^TenΩ · cm is preferable.
The amount of conductive agent added to achieve volume resistivity
Can be adjusted and can be adjusted using carbon as the conductive agent.
The amount of addition is usually 0.01 to 40% by weight of the outer layer 4,
In particular, it is about 5 to 20% by weight.

It is to be noted that an appropriate additive such as a thickener, a thixotropy-imparting agent, or a structural viscosity-imparting agent can be added to the outer layer 4 if necessary. May be either inorganic or organic.

The thickness of the outer layer 4 is not particularly limited, but is preferably 30 μm or less, particularly preferably 1 to 15 μm. If the thickness of the outer layer 4 exceeds 30 μm, the outer layer 4 becomes harder. The flexibility may be impaired, the durability may be reduced, and cracks may occur during use.

Although not particularly shown in FIG. 1, one or more resin layers are further provided between the outer layer 4 and the elastic layer 3 so that the outer layer has a multilayer structure of two or more layers. Thereby, the universal hardness of the member surface can be favorably adjusted.

The resin layer is not particularly limited as long as it can adjust the hardness of the surface of the member to the above-mentioned universal hardness, and is not particularly limited. It is preferably used. In particular,
Polyester resin, acrylic resin, urethane resin, acrylic urethane resin, nylon resin, epoxy resin, polyvinyl acetal resin, vinylidene chloride resin, fluororesin, silicone resin, etc. can be used. In particular, when this resin layer is formed directly on the elastic layer 3, an aqueous resin is preferably used in order to ensure smoothness, and the elastic body that forms the elastic layer 3 by using the aqueous resin is preferably used. The elastic body does not swell even when dipped in this water-based resin paint, so that good surface smoothness can be easily obtained, and a charging member excellent in toner adhesion prevention and durability can be obtained. . As the water-based resin, if the solvent is water, any of a water-soluble type, an emulsion type, a suspension type and the like may be used. In particular, a resin having an active hydrogen such as a carboxyl group, a hydroxyl group or an amino group is preferably used. Specific examples of such an aqueous resin include warm water-soluble resins such as polyester, acrylic, urethane, and polydioxolane, and acrylic resins are particularly preferably used.

Further, appropriate additives such as a crosslinking agent, a thickener, a thixotropy-imparting agent, and a structural viscosity-imparting agent can be added to this resin layer as needed. In this case, any crosslinking agent may be used as long as a desired crosslinking effect can be obtained. For example, epoxy-based, oxazoline-based, melamine-based, isocyanate-based, and phenol-based cross-linking agents can be exemplified.Epoxy-based, oxazoline-based cross-linking agents are preferably used in view of the cross-linking effect, low hardness, and the like. The amount of the crosslinking agent is not particularly limited, but is usually in the range of 0.1 to 50 parts by weight based on 100 parts by weight of the resin. The thickener, the thixotropy-imparting agent, the structural viscosity-imparting agent and the like may be any of inorganic and organic.

A conductive agent is added to this resin layer to make it conductive.
Can be given or adjusted, and the volume resistivity is usually 1
0^Three-10¹² Ωcm, especially 10^Five-10^TenΩcm
It is preferable to adjust as follows. In this case, as a conductive agent
Is the same conductive agent as that exemplified in the elastic layer 3 above.
However, carbon is particularly preferably used.
You. The amount of conductive agent added depends on the type of conductive agent, etc.
Appropriately selected so as to obtain volume resistivity, particularly limited
Although it is not a thing, when using carbon as a conductive agent
Is usually 0.01 to 60% by weight, especially 10 to 40% by weight
Degree.

Although the thickness of the resin layer is not particularly limited, it is preferably a thin layer so as not to impair the flexibility of the elastic layer 3, specifically 1 mm or less, particularly 8 mm.
It is preferably not more than 00 μm, more preferably 20 to 600 μm.

The method of forming the outer layer 4 is not particularly limited, but a method of preparing a paint containing each component and applying the paint by dipping or spraying to form a coating film is preferably used. Can be In this case, when a plurality of outer layers are used, dipping and spraying may be repeated using a paint for forming each layer. In addition, as a method for forming the outer layer, the above-described dipping method and spray method are preferably adopted, but the method is not limited thereto.
As long as the condition of the universal hardness described above is satisfied, it may be formed by extrusion molding or the like.

As described above, the charging member of the present invention has an improved durability by optimizing the universal hardness of the member surface and preventing adhesion and sticking of toner, but is not particularly limited. However, it is preferable that the Asker C hardness of the member surface is 65 degrees or less, particularly preferably 60 degrees or less, and by controlling the Asker C hardness in this way,
Adhesion of toner can be more effectively prevented.

If the surface of the charging member has irregularities, toner is clogged in the irregularities and causes an image defect. Therefore, it is preferable that the surface of the member is as smooth as possible.
Although not particularly limited, JIS 10
It is preferable that the point average roughness Rz is 4 μm or less, particularly 3 μm or less, and further preferably 2 μm or less.

The charging member of the present invention is disposed in contact with a member to be charged such as a photosensitive drum, and is charged by applying a voltage between the member to be charged and the charging member of the present invention. Although the body is charged, in this case, the voltage applied between the charging member and the member to be charged may be a DC voltage or an AC voltage, but is not particularly limited, It is preferable to perform charging by applying a voltage in which an AC voltage is superimposed on a DC voltage, so that the member to be charged can be charged more uniformly. Although not particularly limited, the contact pressure between the charging member of the present invention and the member to be charged is 50 to 2000 g, particularly 100 to 100 g.
It is preferably 0 g, whereby good charging can be reliably obtained.

As shown in FIG. 2, for example, a charging device using the charging member of the present invention is formed by applying a charging member 1 of the present invention formed in a roller shape to a member to be charged 5 such as a photosensitive drum at a predetermined pressure. A charging device configured to contact and apply a voltage between the voltage applying means 6 and the charged object 5 can be exemplified, but is not limited thereto. The form of the member 1, the voltage application method by the voltage application means 6, and the like may be appropriately changed.

[0036]

According to the charging member of the present invention, it is possible to effectively prevent sticking of the residual toner, obtain good durability, and exhibit stable performance for a long period of time. Therefore, according to the charging device using the charging member of the present invention, a favorable charging operation can be stably performed over a long period of time.

[0037]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following.

Example 1 A metal shaft having a thickness of 30
An elastic layer A having a thickness of 2,000 μm is formed thereon.
Is formed, and a coating layer B (outermost layer) having a thickness of 5 μm is further formed thereon. The coating layer A and the coating layer B (outermost layer) are formed outside the elastic layer A. A charging roller (charging member) having a two-layer outer layer made of The elastic layer A, the coating layer A and the coating layer B (outermost layer) are as follows.
The universal hardness H ^{1 at a} depth of 5 μm from the surface of the obtained charging roller is 6.1 N / mm ² and the depth from the surface is 50 N / mm ² .
The universal hardness H ^{2 at} μm was 0.8 N / mm ² , and (H ¹ / H ² ) = 7.6. The Asker C hardness of the roller surface is 58.8 degrees and the surface roughness is JIS1
The zero point average roughness Rz was 0.62 μm.

Elastic Layer A A urethane foam having a density of 0.55 g / cm ³ produced by adding carbon to a polyester polyol or isocyanate. Coating layer A is formed by applying a paint obtained by adding carbon to an aqueous acrylic resin, and has a volume resistivity of 7.6 × 10 ⁷ Ωcm.
It is a coating layer adjusted to. Coating layer B (outermost layer) formed by applying a paint obtained by adding carbon to a resin obtained by blending a water-dispersible fluororesin, a vinylidene chloride copolymer latex, and a polyvinyl acetal resin,
It is a coating layer whose volume resistivity is adjusted to 4.2 × 10 ⁷ Ωcm. The carbon used had an oxygen content of 10% and a pH of 7.33.

When the obtained charging roller was mounted on a printer to produce an image, a good image was obtained. Furthermore,
Even when 9000 sheets of images were continuously output, no image abnormality occurred.

Example 2 Example 1 on a metal shaft
An elastic layer A having a thickness of 3000 μm is formed in the same manner as described above, a coating layer C having a thickness of 160 μm is formed thereon, and a coating layer D (outermost layer) having a thickness of 10 μm is further formed thereon. Elastic layer A
A charging roller (charging member) having a two-layered outer layer composed of a coating layer C and a coating layer D (outermost layer) was prepared on the outside. The coating layer C and the coating layer D (outermost layer) are as follows. 10 μm deep from the surface of the obtained charging roller
Universal hardness H ¹ is in 7.1 N / mm ^2, the universal hardness H ² at a depth 100μm from the surface is 0.7 N / mm ^2, it was ^{(H 1 / H 2) =} 10.1. The Asker C hardness of the roller surface is 58.0.
Degree and surface roughness are 0.71μ in JIS 10 point average roughness Rz
m.

Coating layer C is formed by applying a paint obtained by adding carbon to an aqueous urethane resin, and has a volume resistivity of 5.5 × 10 ⁷ Ωcm.
It is a coating layer adjusted to. Coating layer D (outermost layer) Formed by applying a paint obtained by adding carbon to a resin obtained by blending a water-dispersed fluororesin, an aqueous polyester resin, and a polyvinyl acetal resin, and having a volume resistivity of 5.6 × 10 ⁷ Ωcm. It is a coating layer adjusted to. In addition,
Carbon having an oxygen content of 10% and a pH of 7.33 was used.

When the obtained charging roller was mounted on a printer and an image was formed, a good image was obtained. Further, even when 9000 continuous images were output, no image abnormality occurred.

Comparative Example 1 The coating layer A was replaced with the coating layer E.
Example 1 was repeated except that the coating layer B was replaced with the coating layer F.
A charging roller was prepared in the same manner as described above. The coating layer E and the coating layer F (outermost layer) are as follows. Universal hardness H ¹ in the obtained depth 5μm from the surface of the charging roller is 46.9N / mm ^2, the universal hardness H ² at a depth 50μm from the surface is 0.7 N / mm ^2,
(H ¹ / H ² ) = 67. Further, Asker C hardness of the roller surface was 61.1 degrees, and surface roughness was 0.75 μm in JIS 10 point average roughness Rz.

Coating layer E is formed by applying a paint obtained by adding conductive titanium oxide to an aqueous acrylic resin, and has a volume resistivity of 8.9 × 10
It is a coating layer adjusted to ⁷ Ωcm. Coating layer F (outermost layer) formed by applying a coating material obtained by adding conductive titanium oxide to an aqueous silicone resin, and having a volume resistivity of 5.4 × 1
It is a coating layer adjusted to 0 ⁷ Ωcm.

When the obtained charging roller was mounted on a printer and an image was formed, a good image was obtained in the initial stage. However, when a continuous image was formed, a dot-like defect was found in the image from around 4,700 sheets. When the roller is observed,
The toner was digging into the surface.

Comparative Example 2 The coating layer A was replaced with the coating layer G.
Example 1 except that the coating layer B was replaced with the coating layer H
A charging roller was prepared in the same manner as described above. The coating layer G and the coating layer H (outermost layer) are as follows. The universal hardness H ^{1 at a} depth of 5 μm from the surface of the obtained charging roller is 55.6 N / mm ² , the universal hardness H ^{2 at a} depth of 50 μm from the surface is 0.9 N / mm ² ,
Was ^{(H 1 / H 2) =} 61.7. The Asker C hardness of the roller surface was 62.1 degrees, and the surface roughness was 4.9 μm in JIS 10 point average roughness Rz.

The coating layer G is formed by applying a coating material obtained by adding conductive tin oxide to an organic polyester resin, and has a volume resistivity of 3.4 × 1.
It is a coating layer adjusted to 0 ⁷ Ωcm. Coating layer H is formed by applying a paint obtained by adding conductive tin oxide to an organic acrylic resin, and has a volume resistivity of 2.3 × 10 ^7.
It is a coating layer adjusted to Ωcm.

When the obtained charging roller was mounted on a printer and an image was formed, a good image was obtained in the initial stage. However, when a continuous image was formed, a dot-like defect was found in the image from around 400 sheets. When the roller was observed, it was found that the toner had penetrated the surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the charging member of the present invention.

FIG. 2 is a schematic view showing an example of the charging device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging member 2 Shaft 3 Elastic layer 4 Outer layer 5 Charged body 6 Voltage applying means

Claims (7)

[Claims] 1. A charging member for charging a member to be charged by applying a voltage between the member and a member to be charged by contacting the member with the member. It has an outer layer composed of one layer or a plurality of layers formed with another layer interposed therebetween. The universal hardness at a depth corresponding to the thickness of the outermost layer is H ¹ , and the universal hardness at a depth ten times that of the outer layer is H ² . (H ¹ / H ² ) <50. 2. The charging member according to claim 1, wherein Asker C hardness of the member surface is 65 degrees or less. 3. The JIS 10-point average roughness Rz of the member surface
3. The charging member according to claim 1, wherein the thickness is 4 μm or less. 4. 4. The elastic layer has a density of 0.05 to 0.9 g.
/ Cm ³ of the charging member according to any one of claims 1 to 3 is a urethane foam. 5. The charging member according to claim 1, wherein the outermost layer of the outer layer is a coating film containing a fluororesin. 6. The charging member according to claim 5, wherein the outermost layer of the outer layer is a coating film containing an aqueous fluororesin containing carbon having an oxygen content of 5% or more and a pH of 5 or more. 7. A charging apparatus comprising: a charging member that contacts a member to be charged and charges the member; and voltage applying means that applies a voltage between the member and the charging member. A charging device, wherein the charging member according to claim 1 is used as the charging member.