JPH09146346A - Electrifying member and electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrifying member being excellent in the uniformity of resistance, the uniformization of a contact stage, electrifiability and durability by forming an outer layer including resin to which specific carbon is added, on the surface of an inner layer consisting of an elastic body. SOLUTION: As the inner layer, an elastic body is used and urethane foam is preferable. Carbon and metallic oxide are added to impart conductivity to the foam. The outer layer is made of the resin to which the carbon is added. As the carbon, one having an oxygen content of >=6%, preferably >=7% and further, a carbon pH of >=5, preferably >=6 is desirable. Thus, the uniformity of the resistance of the electrifying member can be made compatible with a sufficient contact state with an electrified member by the fact that the hardness of the electrifying member is made low and moreover, the uniform contact state with the electrified member by the fact that the surface smoothness of the electrifying member is secured. Therefore, the uniformity of electrifying work is improved, sandy soil, a defect in an image, etc., are eliminated and further, the durability is improved.

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 photosensitive member used in an electrostatic latent image process in a copying machine, a printer and the like, and a charging device using the same. Things.

[0002]

2. Description of the Related Art Conventionally, in electrophotographic processes such as copying machines and printers, first, the surface of a photoconductor is uniformly charged,
A latent image is formed by projecting an image from the optical system onto the photoconductor to erase the electrification of a portion exposed to light, and then a toner image is formed by adhesion of toner, and toner is attached to a recording medium such as paper. Printing is performed by transferring an image. In this case, a corona discharge method has generally been used for the first operation of charging the photoconductor. However, since this corona discharge method requires application of a high voltage of 6-10 kV, it is not preferable from the viewpoint of safe maintenance of the machine. Further, there are environmental problems because harmful substances such as ozone are generated during corona discharge.

[0003] For this reason, efforts have been made for a charging method that can perform charging at a lower applied voltage than corona discharge and that can suppress generation of harmful substances such as ozone. As a trial of such a charging method, a method by a contact method has been proposed in which a charging member to which a voltage is applied is brought into contact with an object to be charged such as a photoconductor to charge the object.

As a charging member used in this contact charging system, for example, one in which the surface of an elastic layer is coated with a resin layer is known, and in order to secure a sufficient nip width with the member to be charged, the charging member is A foam body is used for the elastic layer and a resin such as urethane or nylon is used for the resin layer.

However, since all of these resins are organic solvent-soluble resins, a resin layer is formed by dipping or spraying these organic solvent-soluble resins on the surface of the elastic layer made of foam. However, there is a problem in that the surface smoothness cannot be obtained. This is because the organic solvent swells the foam body to form surface irregularities, or the organic solvent that has entered the foam body breaks through the coating film during drying and forms crater holes on the coating surface. . Of course, in order to prevent this, a slight improvement can be seen if the elastic layer is not formed of a foam body, but in this case, the hardness of the charging member increases and a sufficient nip width with the charged member is obtained. The desired physical contact state cannot be maintained.

Further, in order to improve the performance of charging property and durability, it is necessary to uniformly supply the charge from the charging member to the member to be charged. It is thought that a measure for achieving this favorably is to make the electrical state of the charging member, that is, the resistance, more uniform, and further make the physical contact state between the charging member and the member to be charged even more uniform.

Further, in order to make the resistance uniform, it is sufficient to disperse the conductive material well, but in reality it is quite difficult. This is because the resistance region generally used for the charging member is not a good conductive region in which a solid conductive path is formed by a conductive material, but a semiconductive region that is halfway. Of course, if a dispersant is used, it seems that the dispersed state of the conductive material can be improved and the uniformity of resistance can be improved, but addition of a dispersant, etc. due to the problem of migration to the charged body and contamination. It is not preferable to use a product.

As described above, it is difficult to improve the performance such as charging property and durability while achieving both the electrical uniformity of the charging member and the uniformity of the physical contact state with the member to be charged.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in the formation of a latent image in a copying machine, a printer, etc., the uniformity of the resistance of the charging member and the physical contact with the member to be charged are An object of the present invention is to provide a charging member that achieves both uniformity of contact state and improved performance such as charging property and durability, and a charging device using the charging member.

[0010]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention firstly contacted the charged body with a charged body as described in claim 1, and applied a voltage to the charged body. In a charging member for charging the charged body by applying
The charging member is characterized in that an outer layer containing a resin added with carbon having an oxygen content of 6% or more is formed on the surface of the inner layer made of an elastic body, and the carbon member according to claim 2 further comprises: Is characterized by having a pH of 5 or more. Further, according to claim 3, the charging member is characterized in that an aqueous resin is used as the resin to which the carbon is added, and further, as described in claim 4, the elastic body is a foam. A charging member characterized by being present. Then, as described in claim 5, the surface of the charging member is 4 μm on the JIS 10-point average roughness Rz scale.
A charging member characterized by the following:
7. A charging device, comprising: a charging member for contacting a member to be charged to charge the member to be charged; and voltage applying means for applying a voltage between the member to be charged and the charging member. The charging device is characterized by using the above charging member as the charging member.

If necessary, a layer containing carbon having an oxygen content of 6% or more, preferably a pH of 5 or more added to an aqueous resin is used as the outer layer or a part of the outer layer, and if the elastic layer is formed, the foam body is used. It was found that the above object can be achieved by using a charging member having the elastic layer as an inner layer, and thus the present invention has been completed. That is, in the present invention, the resistance of the charging member is uniform, and the hardness of the charging member is low, so that the charging member has a sufficient contact state with the charged member, and the surface smoothness of the charging member is ensured. It is possible to achieve both the contact state, the uniformity of the charging action is improved, and sandy ground, image defects, etc. are eliminated,
Furthermore, the durability is also improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Since the charging member of the present invention is of the contact charging type, it is not particularly limited to the shape as long as it contacts the member to be charged. For example, various shapes such as roll shape, plate shape and block shape The thing of what is applicable is a roll shape normally. In the case of a roll, a shaft made of metal or plastic may be provided inside these.

The structure of the charging member provided by the present invention is not particularly limited as long as it has the above-mentioned inner layer and outer layer, but at least one outermost layer is also formed on the surface of the outer layer according to the purpose. can do.

An elastic material is used as the inner layer, and a foam is preferable, and a urethane foam is particularly preferable. Carbon and metal oxides are added to the foam in order to impart conductivity. Also, the foam density is
0.05 to 0.9 g / cm ³ is suitable.

The outer layer is made of a resin containing carbon. The carbon used here has an oxygen content of 6% or more, preferably 7% or more, more preferably 9% or more. Further, the pH of carbon is 5 or more, preferably 6 or more, and more preferably 7 or more. Normal carbon has an oxygen content of 0.1 to
It is about 3%. Some of the carbons have been oxidized. However, the oxidizing treatment slightly increases the oxygen content and shifts the pH of the carbon toward the acidic side. It seems that the higher the oxygen content is, the better the dispersibility is. However, when the pH is acidic, there arises a problem that the stability is lowered particularly when it is added to the water-based resin. The carbon used in the present invention can maintain neutrality or alkalinity despite having a large oxygen content. Although the detailed structure of the carbon is not clear, it is preferable that a carboxyl group, a hydroxyl group, a ketone group, or the like be provided on the carbon surface, and that hydrogen of those groups be partially substituted with an alkali metal such as sodium.

The resin used for the outer layer is not particularly limited as long as the above-mentioned carbon can be added, and examples thereof include fluororesin, urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, nylon resin, epoxy resin, Examples thereof include styrene resin, butyral resin, polyvinyl acetal resin, etc., but for the purpose of ensuring surface smoothness, it is preferable to use an aqueous resin, particularly an aqueous resin such as an acrylic resin, a polyester resin, a fluororesin, or a urethane resin. Is more preferable.

Further, a thickener, a thixotropy-imparting agent, a structural viscosity-imparting agent and the like can be added to these carbon and water-based resin at any time, and either inorganic or organic type may be used. Aqueous resins are often low in viscosity, so it is difficult to increase the thickness of the coating film, but by adding these thickeners, thixotropic agents, structural viscosity imparting agents, etc.,
It becomes possible to easily form a coating film having a desired thickness.

In the case of a charging member having a structure in which the outer layer is formed only on the surface of the inner layer, the layer with good carbon dispersion is located on the outermost surface of the charging member, so that the resistance of the charging member is uniform. It has the advantage of being easy to obtain. Further, in the case of a charging member having a structure in which the outermost layer is formed on the surface of the outer layer, swelling of the elastic inner layer, which often occurs when an organic solvent-soluble resin or the like is coated by the dip method, or drying. At this time, there is no generation of crater-like holes on the coating film due to solvent evaporation that has penetrated into the elastic body layer, and there is an advantage that a charging member having good surface smoothness can be obtained.

The outermost layer is not particularly limited,
Urethane resin, acrylic resin, polyester resin, urethane modified acrylic resin, nylon resin, epoxy resin,
Examples thereof include styrene resin and butyral resin. Among them, acrylic resin, polyester resin, urethane-modified acrylic resin and nylon resin are preferably used. Also,
The conductive substance added to these resins is not particularly limited, and examples thereof include carbon, metal oxides, and conductive polymers. The thickness of these layers is not particularly limited, but is usually adjusted to about 1 to 600 μm. In the case of the outermost layer or the innermost layer, it is preferably thin, for example, about 1 to 70 μm.

The amount of carbon added is adjusted so that the desired resistance can be obtained. A suitable resistance for the charging member is a volume resistance of 10 ² to 10 ¹⁰ Ωcm, and the addition amount is determined so as to obtain this resistance value, but it is usually 5 to 80 parts by weight with respect to 100 parts by weight of the resin. .

The method for forming the outer layer or the outermost layer may be a dipping method or a spray method in which the inner layer material is dipped to form a coating film in a coating state containing the above.
The surface roughness of the charging member surface created as described above is 4 μm on the JIS 10-point average roughness Rz scale.
Or less, preferably 3 μm or less, more preferably 2 μm
The following adjustments are appropriate.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following.

Example 1 An outer layer having a thickness of 100 μm was formed on a conductive urethane foam roller (inner layer).
The outer layer was applied by a dipping method using a paint in which SMP-4 was used as carbon and mixed with a water-dispersible polyester resin. The volume resistivity of the outer layer was adjusted to about 10 ⁸ Ωcm. SMP-4 is carbon having an oxygen content of 10% and a pH of 7.33. The paint used to form the outer layer is
It was stable with no change even after 1 week from the preparation. JIS 10-point average roughness of roller surface 1.2 μm on Rz scale
And the micro hardness was 55 degrees. The micro hardness referred to here is 0.16 mm in diameter and 0.1 mm in length.
A 5 mm push needle is pressed against a sample to deform the sample, and the hardness value is obtained from the push needle biting amount (displacement) at that time, which is difficult to measure with a conventional hardness meter. The hardness of the sample can be measured. The micro hardness of the present invention is a commercially available micro hardness meter,
It was obtained by measuring with a micro hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. When this roller was attached to a printer and an image was printed at a temperature of 15 ° C. and a humidity of 10% RH, a good image was obtained. Furthermore, continuous 6000
Even if one image was printed, there was almost no deterioration of the image.

Example 2 An outer layer A having a thickness of 20 μm was formed on a conductive urethane foam roller (inner layer), and an outermost layer B having a thickness of 100 μm was further formed thereon. Outer layer A
Is a coating material A1 in which SMP-4 is mixed with a water-dispersible polyester resin as carbon, and the outermost layer B is a coating material B1 in which carbon is mixed with a urethane-modified acrylic resin. The outer layer A has a volume resistivity of about 10 ⁶ Ωcm, and the outermost layer B has a volume resistivity of 10
^It was adjusted to about ⁸ Ωcm. SMP-4 is carbon having an oxygen content of 10% and a pH of 7.33. Outer layer A
The coating material A1 used for the formation was stable with no change even after 1 week from the preparation. The JIS 10-point average roughness Rz of the roller surface was 1.7 μm, and the micro hardness was 62 degrees. Attach this roller to the printer and set the temperature to 15 ° C /
When an image was displayed at a humidity of 10% RH, a good image was obtained. Furthermore, even when images were continuously printed on 6000 sheets, almost no image deterioration was observed.

Example 3 An outer layer C having a thickness of 80 μm was formed on a conductive urethane foam roller (inner layer), and an outermost layer D having a thickness of 10 μm was further formed thereon. The outer layer C is
A coating material C1 in which SMP-4 was mixed with a water-dispersible polyester resin as carbon was used, and a coating material D1 in which SMP-4 was mixed with a water-dispersible polyester resin as carbon was used and applied by a dipping method. Outer layer C
Was adjusted to about 2 × 10 ⁷ Ωcm, and the outermost layer D was adjusted to about 3 × 10 ⁸ Ωcm. As described above, SMP-4 is carbon having an oxygen content of 10% and a pH of 7.33. Both the coating materials C1 and D1 used for forming the outer layer and the outermost layer were stable with no change even after 1 week from the preparation. The JIS 10-point average roughness Rz of the roller surface was 1.6 μm, and the micro hardness was 68 degrees. Attach this roller to the printer and set the temperature to 15 ° C /
When an image was displayed at a humidity of 10% RH, a good image was obtained. Furthermore, even if the continuous 6000 images are output,
In particular, there was almost no deterioration of the image.

Example 4 An outer layer E having a thickness of 20 μm and an outermost layer F having a thickness of 90 μm were formed on a conductive urethane foam roller (inner layer). The outer layer E is
Paint E in which carbon is mixed with water-dispersible polyester resin
1 was used as the outermost layer F, and a coating material F1 in which carbon was mixed with a urethane-modified acrylic resin was used, and each was applied by a dipping method. The volume resistivity of the outer layer E was adjusted to about 3 × 10 ⁶ Ωcm, and the volume resistivity of the outermost layer F was adjusted to about 2 × 10 ⁸ Ωcm. The carbon used in the coating material E1 has an oxygen content of 6.1% and a pH of 2.3. The coating material E1 used for forming the outer layer could be used immediately after preparation without any problem in coating film formation, but was gelled slightly 1 week after preparation. However, as described below, there was no problem in the performance of the produced roller. JIS 10 point average roughness R of roller surface
z was 2.6 μm and the micro hardness was 66 degrees. When this roller was attached to a printer and an image was printed at a temperature of 15 ° C. and a humidity of 10% RH, a good image was obtained. Furthermore, even when images were continuously printed on 6000 sheets, almost no image deterioration was observed.

Comparative Example 1 An outer layer G having a thickness of 95 μm was formed on a conductive urethane foam roller (inner layer).
As the outer layer G, a coating material G1 in which carbon (channel black) was mixed with a water-dispersible polyester resin was used and applied by a dipping method. The volume resistivity of the outer layer G is 2 × 10 ⁸ Ω
It was adjusted to about cm. Channel black is carbon having an oxygen content of 2.9% and a pH of 4.1. The coating material G1 used for forming the outer layer was poorly dispersed immediately after preparation and was partly lumpy. The roller surface has a JIS 10-point average roughness Rz of 3.6 μm and a micro hardness of 6
4 degrees. When this roller was attached to a printer and an image was displayed at a temperature of 15 ° C. and a humidity of 10% RH, a sandy image that was considered to be due to nonuniform resistance was formed. Further, when 6000 images were continuously printed, the image quality was further deteriorated, and black spots were generated on a part of the image.

Comparative Example 2 An outer layer H having a thickness of 105 μm was formed on a conductive urethane foam roller (inner layer). The outer layer H was applied by a dipping method using a coating material H1 in which carbon (channel black) was mixed with urethane-modified acrylic resin. The volume resistivity of the outer layer H is 4 × 10
^It was adjusted to about ⁸ Ωcm. Channel black is carbon having an oxygen content of 2.9% and a pH of 4.1. The coating material H1 used for forming the outer layer was apparently beautiful. However, numerous crater-like holes were formed on the surface of the coating film, which are thought to be due to the evaporation of the solvent that has penetrated into the urethane foam during drying after dipping. JI on the roller surface
The S10-point average roughness Rz was severely varied from 5.4 to 11 μm, and the micro hardness was 67 degrees. Attach this roller to the printer and set the temperature to 15 ° C and the humidity to 10% R.
When an image was displayed with H, it became a black dot image which is probably due to the unevenness of the surface. Furthermore, continuous 6000
When a single image was printed, the image became even worse and part of the image became almost black.

[0029]

As described above in detail with respect to the present invention, first, as described in claim 1, by contacting the charged body and applying a voltage between the charged body and the charged body. In the charging member for charging the body to be charged, an outer layer containing a resin to which carbon having an oxygen content of 6% or more is added is formed on the surface of the inner layer made of an elastic body. As described in claim 2, the carbon has a pH of 5 or more. Further, according to claim 3, the charging member is characterized in that an aqueous resin is used as the resin to which the carbon is added, and further, as described in claim 4, the elastic body is a foam. A charging member characterized by being present. Further, as described in claim 5, the surface of the charging member is 4 μm in JIS 10-point average roughness Rz scale.
A charging member characterized by the following:
7. A charging device, comprising: a charging member for contacting a member to be charged to charge the member to be charged; and voltage applying means for applying a voltage between the member to be charged and the charging member. The charging device is characterized by using the charging member of the present invention as described above as the charging member, so that the charging property is excellent in the uniformity of the resistance and the uniformity of the contact state, and the charging is excellent in durability. A member and a charging device were obtained.

Claims (6)

[Claims] 1. A charging member for charging a charged body by bringing it into contact with the charged body and applying a voltage between the charged body and the surface of the inner layer made of an elastic material,
A charging member, wherein an outer layer containing a resin added with carbon having an oxygen content of 6% or more is formed. 2. The charging member according to claim 1, wherein the carbon has a pH of 5 or more. 3. The charging member according to claim 1, wherein an aqueous resin is used as the resin. 4. The charging member according to claim 1, wherein the elastic body is foam. 5. The charging member according to claim 1, wherein the surface of the charging member has a JIS 10-point average roughness Rz scale of 4 μm or less. 6. A charging device comprising: a charging member that is in contact with a charged body to charge the charged body; and a voltage applying unit that applies a voltage between the charged body and the charging member. A charging device comprising the charging member according to claim 1 as a member.