JP2705232B2 - Charging device and image forming apparatus using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a charging device and an image forming apparatus using the same.

More specifically, a contact charging device (or a direct charging device) that charges a charged body surface to a predetermined potential (including static elimination processing, the same applies hereinafter) by bringing a charged member (direct charging member) to which a voltage is applied into contact with the charged body surface. Charging device) and an image forming apparatus using the same.

(Prior art) For example, electrophotographic devices (copiers, optical printers, etc.)
2. Description of the Related Art In an image forming apparatus such as an electrostatic recording apparatus, a corona discharge device has been widely used as a device for charging a surface of an image carrier as a member to be charged such as a photoreceptor or a dielectric.

The corona discharge device is effective as a means for uniformly charging a surface of a charged body such as an image carrier to a predetermined potential. However, there is a problem that a high-voltage power supply is required and undesired ozone is generated due to corona discharge.

In contrast to such a corona discharge device, a contact charging device that performs charging processing on the surface of the charged object by bringing the charging member to which the voltage is applied into contact with the surface of the charged object as described above can reduce the power supply pressure and generate ozone. Because of its advantages such as small amount, it is attracting attention, for example, as an image carrier such as a photoconductor and a dielectric, and other charging means for a surface of an object to be charged, in place of a corona discharge device in an image forming apparatus. It is being studied for practical use.

For example, the applicant has previously proposed (Japanese Patent Application No. 62-51492,
As described in JP-A-62-230334, an oscillating electric field (alternating electric field) having a peak-to-peak voltage that is twice or more the charging start voltage when a DC voltage is applied to a charging member in a contact charging device.
Is formed between the charging member and the member to be charged, and further, by using a charging member having a high resistance layer on the surface layer, the uniformity of charging of the member to be charged, the pin on the surface of the member to be charged such as a photoreceptor, etc. Leakage due to holes, scratches, etc. can be prevented.

5 (a) and 5 (b) are a cross-sectional view and a vertical cross-sectional view of a schematic configuration of an example of the contact charging device.

Reference numeral 1 denotes a member to be charged. In this embodiment, a rotating drum type electrophotographic photosensitive member is used. The photoreceptor 1 of this example has a configuration in which a conductive base layer 1b of aluminum or the like and a photoconductive layer 1a formed on the outer surface thereof are used as basic layers.

102 is a charging member. This example is a roller type (hereinafter, referred to as a charging roller). The charging roller is the center metal core
102c, a conductive layer 102b formed on the outer periphery thereof, and a resistance layer 102a further formed on the outer periphery thereof.

The charging roller 102 has both ends of a cored bar 102c rotatably supported by bearing members (not shown), and is disposed in parallel with the drum-type photoreceptor 1. The photosensitive member 1 is pressed and pressed by the pressing force, and is rotated by the rotation of the photosensitive member 1.

Reference numeral 3 denotes a power supply for applying a bias to the charging roller 102. The power supply 3 is electrically connected to the metal core 102c of the charging roller 102, and a predetermined bias is applied to the charging roller 102 by the power supply 3.

When the photoreceptor 1 to be charged is driven to rotate, the outer peripheral surface of the photoreceptor is brought into a predetermined polarity / potential by a charging roller 102 as a charging member pressed against the photoreceptor 1 and applied with a bias voltage. Is charged.

(Problems to be Solved by the Invention) Conventionally, for the charging member 102, a resistance layer 102a as an outer layer that is directly pressed against the surface of the belt 1 to be charged is formed by dispersing carbon or the like in rubber or resin in an organic solvent. It is formed by dissolving, coating the solution on the surface of the conductive layer 102b, drying and evaporating the solvent.

If the drying time is short during the formation of the coating resistance layer 102a, the surface layer of the resistance layer 102a that is in contact with air is mainly dried, and the solvent remains in the lower layer.

This residual solvent gradually moves to the surface layer side of the resistance layer 102a and exudes to the surface of the resistance layer to make the surface redissolved.

Therefore, if the charging member 102 is in contact with the surface of the charging member 1 for a long time, the charging member is fixed to the surface of the charging member, or the portion of the charging member surface that has been in contact with the charging member for a long time becomes a solvent. May be affected by the transition.

If the member to be charged 1 is, for example, the electrophotographic photosensitive member of the above-described example, local deterioration due to solvent migration occurs on the long-time contact surface with the charging member 102, and as a result, an image portion corresponding to the deteriorated portion on the output image surface Is a white line called roller marks
It becomes an abnormal image part such as a black stripe.

The photoreceptor 1 is roughly classified into an inorganic photoreceptor such as amorphous silicon and selenium, and an organic photoreceptor called OPC. Organic photoconductors include those having a photosensitive layer configuration in which inorganic material particles are dispersed in an organic material such as a resin, and those having a photosensitive layer configuration in which an inorganic material is coated with an organic material such as a resin.

Thus, as described above, the charging member 102 due to long-time contact
Is fixed to the member 1 to be charged, local deterioration of the member to be charged due to solvent transfer, and the adverse effect caused by the fixation is remarkable when the member to be charged is a photosensitive member, particularly when it is an organic photosensitive member. . This is because the organic photoreceptor has higher chemical reactivity than the inorganic photoreceptor.

Therefore, the drying of the coating resistance layer 102a is performed by elongating the drying time, for example, by drying under reduced pressure for one day to substantially eliminate the residual solvent component. In this case, the manufacturing time of the charging member is reduced. It will be long.

In view of the above, the present invention provides a charging member of this type which does not cause problems such as fixation of the charging member to the surface of the member to be charged due to surface bleeding of the residual solvent as described above, and deterioration of the member to be charged. It is an object of the present invention to provide a product having an advantage that it can be easily manufactured in a short time. It is another object of the present invention to provide an image forming apparatus using the charging device.

(Means for Solving the Problems) The present invention is a charging device or an image forming device having the following configuration.

(1) A charging device for charging a surface of a member to be charged by bringing a charging member to which a voltage is applied into contact with the surface of the member to be charged, wherein the charging member has a resistive layer in contact with the surface of the member to be charged. A charging device comprising a resin emulsion composition or a rubber latex composition.

(2) An image forming apparatus, wherein the charging device is used as charging means for an image carrier.

(3) The image forming apparatus according to (2), wherein the image carrier is an organic photosensitive member.

(Operation) The resistive layer of the charging member is formed by applying and drying a resin emulsion composition or a rubber latex composition (hereinafter, referred to as resin emulsion or latex rubber), and thus the drying time, and thus the charging member itself, is reduced. Manufacturing time can be reduced.

That is, in a resin emulsion or latex rubber, a resin or rubber which is a main dispersoid does not dissolve in a solution (dispersion medium) in which it is dispersed. Therefore, the time required for drying the resin emulsion or latex rubber coating layer as the resistance layer is short, and even if the dispersion medium remains under the formed resistance layer, the surface layer of the resistance layer is re-dissolved by the residual dispersion medium. Such a phenomenon does not occur, and the residual dispersion medium does not come out on the surface of the resistance layer. For this reason, even if the drying time is short, the charging member is fixed to the member to be charged,
It does not cause deterioration of the surface of the member to be charged, so that the member to be charged is the image carrier of the image forming apparatus, and there is no problem even if the image carrier is an organic photosensitive member that is easily affected by the solvent, and is inexpensive. It is possible to configure an image forming apparatus with good economy by using a simple organic photoreceptor and a contact charging device.

In the case of an aqueous emulsion or latex using water as a dispersion medium, the drying time is further reduced. Resins and rubbers that are dispersoids are water-insoluble, and the constituent materials of the image carrier such as an electrophotographic photosensitive member and an electrostatic recording conductor as a member to be charged are generally insoluble in water. . Therefore, even when moisture as a residual dispersion medium is present on the surface of the resistance layer of the charging member in contact with the surface of the charged member, this may cause a situation in which the charging member is fixed to the surface of the charged member or deteriorates on the surface of the charged member. No drying occurs and the drying time can be shorter.

Furthermore, in water-based resin emulsions and latexes, most of the resin and rubber, which are the main dispersoids, are hydrophobic, and the volume resistance of the resistive layer formed by the change is very small due to humidity. For example, when a resistance layer is formed by dispersing carbon in hydrophilic nylon, the volume resistance value, that is, the roller resistance, changes by two digits or more due to a change in humidity. Therefore, for example, in an image forming apparatus using a charging device including such a charging member as a charging unit of the image carrier, the charging potential on the image carrier changes due to a change in humidity,
Image density and line width change greatly. On the other hand, when the aqueous resin emulsion / latex is used, the change in the roller resistance value due to the humidity is within half an order, and a stable image density and line width are always obtained.

(Examples) (A) Various Embodiments of Charging Member The charging member 2 is a blade-type or block-type in addition to the roller type as the charging device for the image carrier 1 in the image forming apparatus of FIG. It can be configured in a type such as a type, a rod type, and a belt type.

The roller-type charging member 2 may be driven to rotate or non-rotatably driven by the surface of the member to be charged 1 that is driven to move in the surface direction, or may be in the forward or reverse direction in the surface movement direction of the member to be charged 1. May be positively driven to rotate at a predetermined peripheral speed.

FIG. 2 (a) shows a cross-sectional view of an example of the blade type. In this case, the direction of the blade-shaped charging member 2 abutting on the surface of the charged member 1 may be either the forward direction or the reverse direction of the surface movement direction of the charged band 1 surface. FIG. 2 (b) shows a cross-sectional view of an example of a block or rod. In each type of charging member 2, 2c indicates a conductive core member, 2b indicates a conductive layer, and 2a indicates a resistance layer.

In the case of a block type or rod type, in the case of a rotatable roller type, the core metal member 2c does not have the power supply sliding contact 3a required for applying the bias voltage to the core metal member 2c. On the other hand, a lead wire leading to the power supply 3 can be directly connected, and there is an advantage that electric noise which may be generated from the power supply sliding contact 3a is eliminated, space is saved, and furthermore, a cleaning blade for the surface of the charged object is used. Can also be used.

(B) Example of Image Forming Apparatus FIG. 1 shows a schematic configuration of an example of an image forming apparatus provided with a charging device according to the present invention.

Reference numeral 1 denotes an image bearing member as a member to be charged. In this embodiment, a drum-type electrophotographic photosensitive member having a conductive base layer 1b of aluminum or the like and a photoconductive layer 1a formed on the outer peripheral surface thereof as a basic constituent layer. Body. It is driven to rotate around the support shaft 1d clockwise in the drawing at a predetermined peripheral speed.

2 is in contact with the surface of the photoconductor 1 so that the surface of the photoconductor has a predetermined polarity.
This is a charging member that performs a primary charging process uniformly at a potential, and this example is a roller type. Hereinafter, it is referred to as a charging roller. The charging roller 2 has a central core 2c and a conductive layer formed on the outer periphery thereof.
2b, and a resistance layer 2a formed on the outer periphery thereof. Both ends of the cored bar 2c are rotatably supported by bearing members (not shown), and are arranged in parallel with the drum-type photoreceptor 1. The photosensitive member 1 is pressed against the surface of the photosensitive member 1 with a predetermined pressing force by the pressing means, and is rotated by the rotation of the photosensitive member 1.

A predetermined direct current (DC) bias is applied to the core metal 2c by the power source 3,
Alternatively, the peripheral surface of the rotary photoreceptor 1 is contact-charged to a predetermined polarity / potential by applying a DC + AC (DC + AC) bias.

The surface of the photoreceptor 1 which has been uniformly charged by the charging member 2 is then subjected to exposure of target image information (laser beam scanning exposure, slit exposure of a document image, etc.) by the exposure means 10 so that the peripheral surface thereof An electrostatic latent image corresponding to the image information is formed.

The latent image is then sequentially visualized as a toner image by the developing means 11.

The toner image is then transferred from a paper feeding unit (not shown) by a transfer unit 12 to a transfer unit between the photosensitive member 1 and the transfer unit 12 at an appropriate timing in synchronization with the rotation of the photoconductor 1. It is sequentially transferred to the surface of the transfer material 14. The transfer unit 12 of this embodiment is a transfer roller, and the toner image on the photoconductor 1 side is transferred to the front side of the transfer material 14 by performing charging of the opposite polarity to the toner from the back of the transfer material 14.

The transfer material 14 to which the toner image has been transferred is separated from the surface of the photoreceptor 1, conveyed to an image fixing means (not shown), subjected to image fixing, and output as an image formed product. Alternatively, in the case of forming an image on the back surface, the sheet is conveyed to a re-conveying unit to the transfer unit.

The surface of the photoreceptor 1 after the image transfer is cleaned by the cleaning means 13 to remove adhered contaminants such as untransferred toner, and is repeatedly used for image formation.

(C) Charging roller 2 The charging layer 2b of the charging roller 2 is made of carbon, metal,
Dispersion of metal oxide, etc. in rubber or resin, volume resistance value 10 ⁸ Ω
- those with less than cm, or volume resistivity 10 ⁸ Omega · cm or more rubber or the surface of less than 10 ⁸ · cm of the resin conductive substance coating, or good those laminates. Alternatively, the core metal 2c can also serve as the conductive layer 2b. Desirably hardness JIS
A material of less than 90 ° in A is preferred.

The volume resistance value of the resistance layer 2a needs to be larger than that of the conductive layer 2b as shown in Japanese Patent Application No. 62-230334, and is preferably 10 ⁶ to 10 ¹² Ω · cm.

By providing such a resistance layer 2a, the charging roller 2
When pin contacts pinhole 1c of photoconductor 1, pinhole 1c
When a large amount of current flows, the output voltage of the power supply 3 decreases, causing poor charging in the entire nip direction of the roller 2 around the pinhole, causing white streaks in the normal development and black streaks in the reverse development on the image. (Hereinafter referred to as charging failure at the time of pinhole contact) can be prevented.

If the thickness of the resistance layer 2a is too thin, the resistance layer 2a
When contact is made, destruction of electric current occurs, and poor contact occurs when contacting with a pinhole. On the other hand, if the thickness is too large, the current tends to flow in the direction parallel to the roller surface, and the roller surface potential decreases over a few mm in the roller nip direction with the pinhole as a center.
Poor charging occurs. The thickness of the resistance layer 2a is 20 μm or more, 1 mm
If it is less than the value, it is possible to limit the defective charging area when the roller contacts the pinhole 1c to only the pinhole 1c portion.

If the surface of the resistance layer 2a has a rough surface, the adhesion to the photoreceptor 1 is deteriorated, resulting in poor charging. Therefore, the ten-point average roughness Rz is set to less than 10 μm in order to enhance the adhesion to the photoconductor 1.

In the present invention, as described above, the resistance layer 2a of the charging roller 2 as a charging member (not limited to the roller type, but also the blade type, rod type, block type, belt type, etc.) A resin emulsion composition (resin emulsion) or a rubber latex composition (latex rubber) is formed by coating and drying, and carbon / metal / metal oxide is mixed and dispersed in the composition. The resistance layer 2a having a required volume resistance value is formed, for example, by using a resin or rubber itself having conductivity.

Specific examples of resin emulsions and latex rubbers include vinyl acetate emulsions, acrylic emulsions,
Natural rubber latex, isoprene rubber latex, butadiene rubber latex, styrene-butadiene rubber latex, carboxy-modified styrene-butadiene rubber latex, styrene-butadiene-vinylpyridine latex, carboxy-modified acrylonitrile-butadiene rubber latex, chloroprene latex, acrylate-butadiene rubber latex -Ethylene-vinyl acetate emulsion, vinyl chloride emulsion, vinylidene chloride emulsion, polyurethane and the like can be used.

The resistance layer 2a is made by applying a resin emulsion or rubber latex as described above. Coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating can be used.

A configuration in which a second resistance layer is further provided as necessary on the resistance layer 2a can be adopted. FIG. 3 shows a roller type charging member in which a second resistance layer 4a is further formed on the outer peripheral surface of the resistance layer 2a. That is, the resin emulsion or latex as a coating liquid for forming the resistance layer 2a contains an emulsifier or a dispersant, but these are deposited on the layer surface during film formation, and the deposited emulsifier / dispersed. When the agent or the like adheres to the photoreceptor as a member to be charged, image deterioration may be caused. Therefore, in order to prevent this, the above-described second resistance layer 4a is formed and provided as necessary.

As a material of the second resistance layer 4a, a resin having a volume resistance of 10 ⁶ to 10 ¹² Ω · cm by dispersing carbon, metal, metal oxide, or the like, or a resin having conductivity itself, for example, methoxymethylated Nylon, polypyrrole, polythiophene, polyacetylene, etc. are used. The film thickness is about 5 to 50 μm. It goes without saying that a resin emulsion or latex can be used.

(D) Example of execution Example 1 a) Organic photoreceptor An organic photoreceptor was prepared as a member to be charged in the following manner.

An aluminum cylinder having a thickness of 0.5 mm and a size of 60φ × 260 mm was prepared as the base 1b.

Copolymer nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) 4
Part and type 8 nylon (trade name: Lacamide 500
3, 4 parts by Dainippon Ink and 50 parts of methanol
-Dissolved in 50 parts of butanol and dip coated on the substrate
A polyamide undercoat layer having a thickness of 0.6 μm was formed.

Next, 10 parts of a disazo pigment having the following structural formula and 10 parts of polyvinyl butyral (Eslec BM2, manufactured by Sekisui Chemical) were dispersed together with 120 parts of cyclohexanone in a sand mill for 10 hours. 30 parts of methyl ethyl ketone was added to the dispersion and applied onto the undercoat layer to form a charge generation layer having a pressure of 0.15 μm.

Polycarbonate Z resin (Mitsubishi Gas Chemical Co., Ltd.)
10 parts of a weight average molecular weight of 120,000 were prepared, and monochlorobenzene 80 was added together with 10 parts of a hydrazone compound having the following structural formula.
Dissolves in the part.

This was applied on the charge generation layer to form a charge transport layer having a thickness of 18 μm, thereby preparing an organic photoreceptor.

b) Charging roller 2 The roller body used before forming the resistance layer 2a of the charging roller 2 to be used was prepared as a charging roller base layer in the following manner.

100 parts by weight of chloroprene rubber was melt-kneaded in 100 parts by weight of chloroprene rubber as a material of the conductive layer 2b, and the center was formed through a 10φ stainless steel shaft as a cored bar 2c to 20φ × 240mm to form a charging roller base layer. .

The resistance value of the charging roller base layer was measured as follows.

That is, as shown in FIG. 4, an aluminum foil 201 having a width of 10 mm is wound on a charging roller base layer 200 which is a roller to be measured, and a current of 1 KV is applied between a cored bar and the aluminum foil by a power source 202 to measure a current. Measure the resistance between the metal core and the aluminum foil. Hereinafter, this resistance value is called roller resistance.

When the roller resistance temperature 15 ° C. · humidity of 10% of the charging roller base layer (hereinafter L environment hereinafter) in 3 × 10 ⁴ Ω, when the temperature 32.5 ° C. · 85% humidity (hereinafter referred to as H environment) in 1 × 10 ⁴ Ω was.

Next, an aqueous acrylic emulsion (solid content 50 wt%) 10
0 parts by weight was dispersed together with 2 parts by weight of conductive carbon in a sand mill for 10 hours. This dispersion was dip-coated on the above-mentioned charging roller base layer, dried at 100 ° C. for 10 minutes, and formed a dried 200 μm-thick resistive layer 2 a to form a charging roller 2.

The roller resistance of the charging roller 2 was measured in an L environment and an H environment in the same manner as in the charging roller base layer. Table 1 shows the results.

c) Performance The organic photoconductor prepared in the above item a) was mounted as a photoconductor on a regular development type copying machine PC-20 (manufactured by Canon Inc.), and the charging roller 2 prepared in the above item b) was used as a primary charging means. The image forming is executed by mounting the contact charging device including the image forming apparatus.

The charging roller 2 has a DC voltage of -750 V and an AC peak-to-peak voltage.
By applying a superimposed voltage (bias) of 1800 V to perform primary charging of the photoreceptor, the charging potential on the photoreceptor is set to L environment and H
Measured in the environment. Table 1 shows the results.

In addition, the image density and the image when a 1 mm pinhole was formed on the photoreceptor were examined in both L and H environments. Further, the output image after the charging roller 2 was left in contact with the photosensitive member for 7 days was examined. Table 1 shows the results.

Example 2 A charging roller 2 having a resistance layer 2a formed as described below was prepared, and measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Water-based styrene-butadiene rubber latex (solid content 50
wt%) was dispersed in a sand mill for 10 hours together with 2 parts by weight of conductive carbon. This dispersion was dip-coated on the charging roller base layer, dried at 150 ° C. for 10 minutes, and provided with a dried 200 μm-thick resistive layer 2a.

Example 3 A charging roller 2 having a resistance layer 2a formed as described below was prepared, and measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

100 parts by weight of an aqueous acrylonitrile-butadiene rubber latex (solid content: 50 wt%) were dispersed together with 2 parts by weight of conductive carbon in a sand mill for 10 hours. This dispersion was dip-coated on the charging roller base layer, dried at 150 ° C. for 10 minutes, and provided with a dried 200 μm-thick resistive layer 2a.

Example 4 A charging roller 2 having a resistance layer 2a formed as described below was prepared, and measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Water-based ethylene-vinyl acetate emulsion (solid content 50wt
%) Was dispersed together with 2 parts by weight of conductive carbon in a sand mill for 10 hours. This dispersion was dip-coated on the above-mentioned charging roller base layer, dried at 100 ° C. for 10 minutes, and provided with a 200 μm-thick resistive layer 2a after drying.

Example 5 A charging roller 2 having a resistance layer 2a formed as described below was prepared, and the same measurements and evaluations as in Example 1 were performed. The results are shown in Table 1.

100 parts by weight of an aqueous natural rubber latex (solid content 50 wt%) was dispersed together with 2 parts by weight of conductive carbon in a sand mill for 10 hours. This dispersion was dip-coated on the charging roller base layer, dried at 150 ° C. for 10 minutes, and provided with a 200 μm-thick resistive layer 2a after drying.

Comparative Example 1 (without resistance layer) Measurement and evaluation were performed in the same manner as in Example 1 using the charging roller base layer as a charging roller without forming a resistance layer on its outer peripheral surface, and the results are shown in Table 2. .

Comparative Example 2 (Using Organic Solvent) A charging roller 2 having a resistance layer 2a formed as described below was prepared, and measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

0.2 parts by weight of conductive carbon and 90 parts by weight of n-butyl acetate were added to 10 parts by weight of acryl and dispersed by a ball mill. This dispersion is applied onto the charging roller base layer by dip coating, and
After drying for 0 minutes, the resistance layer 2a having a thickness of 200 μm after drying was provided.

Comparative Example 3 (Using Organic Solvent) A charging roller 2 having a resistive layer 2a formed as described below was prepared, and measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Conductive carbon is added to 10 parts by weight of styrene butadiene rubber.
2 parts by weight and 90 parts by weight of methyl ethyl ketone were added and dispersed by a ball mill. This dispersion was dip-coated on the charging roller base layer, dried at 150 ° C. for 10 minutes, and dried to a thickness of 200 μm.
A 2 μm resistive layer was provided.

Comparative Example 4 (Use of Organic Solvent / Drying under Reduced Pressure) A charging roller 2 having a resistance layer 2a formed as described below was formed and measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

8 parts by weight of alcohol-soluble nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) were dispersed in a ball mill together with 0.1 parts by weight of conductive carbon, 50 parts by weight of methanol, and 50 parts by weight of butanol. This dispersion was dip-coated on the charging roller base layer, and dried under reduced pressure at 100 ° C. for 1 day.
A μm resistance layer 2a was provided.

Comparative Example 5 (Using Organic Solvent) A charging roller 2 having a resistive layer 2a formed as described below was prepared and measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

0.2 parts by weight of conductive carbon and 90 parts by weight of methyl ethyl ketone were added to 10 parts by weight of chloroprene rubber and dispersed by a ball mill. This dispersion was applied onto the charging roller base layer by immersion coating and dried at 150 ° C. for 10 minutes. After drying, the resistive layer 2a having a thickness of 200 μm was provided.

Example 6 A charging roller 2 having a resistive layer 2a formed as described below was prepared and measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

100 parts by weight of an aqueous chloroprene latex (solid content: 50 wt%) was dispersed together with 2 parts by weight of conductive carbon in a sand mill for 10 minutes. This dispersion is dip-coated on the charging roller base layer, dried at 150 ° C. for 10 minutes, and dried to a thickness of 200 μm.
A μm resistance layer 2a was provided.

Comparative Example 6 (Second Resistive Layer) A coating layer (second resistive layer) was further provided outside the resistive layer of the charging roller prepared in Comparative Example 5 in the following manner, and the charging roller was measured in the same manner as in Example 1. Evaluation was performed, and the results are shown in Table 2.

8 parts by weight of alcohol-soluble nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) were dispersed in a ball mill together with 0.1 parts by weight of conductive carbon, 50 parts by weight of methanol, and 50 parts by weight of butanol. The dispersion was dip-coated on the charging roller prepared in Comparative Example 5, dried at 100 ° C. for 60 minutes, and provided with a coating layer having a thickness of 20 μm after drying.

Example 7 (Second Resistive Layer) A second resistive layer was further provided outside the resistive layer of the charging roller prepared in Example 6 in the following manner, and the charging roller was measured and evaluated in the same manner as in Example 1. Table 1 shows the results.
It was shown to.

8 parts by weight of alcohol-soluble nylon (trade name: CM8000, manufactured by Toray Industries, Inc.) were dispersed in a ball mill together with 0.1 parts by weight of conductive carbon, 50 parts by weight of methanol, and 50 parts by weight of butanol. This dispersion was applied onto the charging roller prepared in Example 6 by dip coating, dried at 100 ° C. for 60 minutes, and provided with a second resistance layer having a thickness of 20 μm after drying.

Example 8 (second resistance layer) A second resistance layer was further provided outside the resistance layer of the charging roller prepared in Example 6 in the following manner, and the charging roller was measured and evaluated in the same manner as in Example 1. Table 1 shows the results.
It was shown to.

100 parts by weight of water-based acrylic emulsion (solid content: 50 wt%) together with 2 parts by weight of conductive carbon in a sand mill
Dispersed for 10 minutes. This dispersion was applied onto the charging roller prepared in Example 6 by dip coating, dried at 100 ° C. for 10 minutes, and a dried second resistive layer having a thickness of 20 μm was provided.

Comparing Examples 1 to 8 with Comparative Example 1, it can be seen that the provision of the resistance layer prevents white streaks due to poor charging at the time of pinhole contact.

Comparing Comparative Examples 2 and 3 with Examples 1 and 2, the solvent-type acryl had a roller mark at a drying time of 100 ° C. for 10 minutes, but the acrylic emulsion did not have a roller mark, and the solvent-type styrene-butadiene rubber had a drying time. Although there was a roller mark at 150 ° C. for 10 minutes, styrene butadiene rubber latex did not have a roller mark. In addition, it can be seen that all of Examples 3, 4, and 5 have no roller mark within a drying time of 10 minutes or less.

In the case of nylon 4, the roller resistance greatly fluctuates in the L environment and the H environment, and the image density fluctuates. Further, the resistance value of the resistive layer decreases in the H environment, causing poor charging at the time of pinhole contact. On the other hand, in all of Examples 1 to 5, the fluctuation of the roller resistance is small depending on the environment, the image density is always appropriate, and there is no charging failure at the time of pinhole contact.

Comparing Comparative Example 5 with Example 6, both solvent type and latex of chloroprene have roller marks. However, in Comparative Example 6 and Example 7 in which nylon was applied on the roller, the solvent mark still left the roller mark, whereas the latex did not have the roller mark. The cause of the roller marks was the residual solvent in chloroprene in Comparative Examples 5 and 6, and the solvent passed through the nylon and reached the photoreceptor. In Example 6, the cause of the roller marks was the non-solvent in the latex. Ingredient
Because it cannot pass through nylon.

In Example 7, the solvent is used for nylon, but no roller marks are generated. This is because the nylon layer is thin and the drying time is short, and the residual solvent is eliminated.

Example 8 uses an acrylic emulsion instead of the solvent-type nylon of Example 7.

(E) Organic photoreceptor, etc. According to the charging device of the present invention, as described in the section of (action) above, the member to be charged is the image carrier of the image forming apparatus, and it is not affected by the solvent. Since there is no problem of solvent exudation from the charging member side even with an organic photosensitive member that is easily susceptible, use an inexpensive organic photosensitive member and a contact charging device to construct an economically advantageous image forming apparatus. Is possible.

 Hereinafter, a configuration example of the organic photoconductor will be described.

The photosensitive layer is provided on a substrate having a conductive layer. As the substrate having a conductive layer, a substrate having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum, or the like can be used. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, acrylic resin, polyfluoroethylene, etc.) having a layer formed by vacuum deposition of aluminum, aluminum alloy, indium oxide-tin oxide alloy, etc., and conductive particles (e.g., Substrates obtained by impregnating plastic or paper with carbon black, tin oxide particles and the like together with a suitable binder, plastics having a conductive binder, and the like can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer. The undercoat layer is casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed of an acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, etc.), polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is 5 μm or less, preferably 0.5 to
3 μm is appropriate. The barrier layer preferably has a resistivity of 10 ⁷ Ωcm or more in order to exhibit its function.

The photosensitive layer is formed, for example, by coating a photoconductor such as a phthalocyanine pigment or an azo pigment with a binder as necessary. When an organic photoconductor is used, a photosensitive layer composed of a combination of a charge generation layer that generates charge carriers upon exposure and a charge transport layer capable of transporting the generated charge carriers can also be used effectively.

The charge generation layer is composed of azo pigments such as Sudan Red, Diane Blue, and Dienes Green B; quinone pigments such as alcohol yellow, pinone quinone, and indanthrene brilliant violet RRP; quinocyanine pigments; One or two or more kinds of charge generation layers such as bisbenzimidazole pigments such as India First Orange Toner, phthalocyanine pigments such as copper phthalocyanine, quinacdrine pigments, etc .; ) Can be formed by dispersion and coating. The binder can be selected from a wide range of insulating resins or organic photoconductive polymers. Examples of the insulating resin include polyvinyl butyral, polyarylate (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, and cellulose resin. , Urethane resin, epoxy resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone and the like. In addition, examples of the organic photoconductive polymer include carbazole, polyvinyl anthracene, and polyvinylvinylene.

The thickness of the charge generation layer is 0.01 to 15 μm, preferably 0.05 to 5 μm.
μm, and the weight ratio between the charge generation layer and the binder is 10: 1 to 1:
20.

The solvent used for the charge generation layer paint is selected from the solubility and dispersion stability of the resin and the charge transport material used.Specifically, organic solvents such as methanol, ethanol, alcohols such as isopropanol, acetone, Methyl ethyl ketone, cyclohexanone, NN-dimethylformamide, sulfoxides such as NN-dimethylacetamide, tetrahydrofuran, dioxane, ethylene glycol, ethers such as monomethyl ether, methyl acetate, esters such as ethyl acetate, chloroform,
Aliphatic halogenated hydrocarbons such as methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene, or aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

Coating includes dip coating, spray coating, spinner coating, bead coating,
The coating can be performed by using a coating method such as a Meyer bar coating method, a blade coating method, a roller coating method, and a curtain coating method.

The charge transport layer is formed by dissolving a charge transport material in a film-forming resin.

Examples of the organic charge transporting material used in the present invention include pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, NN-diphenylhydrazine. Dino-3-methylidene-9-ethylcarbazole, NN-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, NN-diphenylhydrazino-3-methylidene-10-ethylphenoxazine,
P-diethylaminobenzaldehyde-NN-diphenylhydrazone, P-diethylaminobenzaldehyde-
N-α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-NN-diphenylhydrazone, 1.3.5-trimethylindolenine-ω-aldehyde-NN-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazoli Hydrazones such as non-2-hydrazone, 2.5 bis (P-diethylaminophenyl) -1.3.4-oxadiazole, 1-phenyl-3- (P-diethylaminostyryl) -5- (P-
Diethylaminoethylphenyl) pyrazolin, 1- [quinolyl (2)]-3- (P-diethylaminostyryl)
-5- (P-diethylaminophenyl) pyrazolin, 1
-[Pyridyl (2)]-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazolin, 1- [6-methoxy-pyridyl (2)]-3- (P
-Diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (3)]-3
-(P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (P-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (P-diethylaminostyryl)
-4-methyl-5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (α-methyl-P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1-phenyl -3- (P
-Diethylaminostyryl) -4-methyl-5- (P-
Diethylaminophenyl) pyrazoline, 1-phenyl-
3- (α-benzyl-P-diethylaminostyryl)-
Pyrazolines such as 5- (P-diethylaminophenyl) pyrazoline and spirpyrazoline, 2- (P-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (P-diethylaminophenyl) -4- (P
Oxazole compounds such as -diethylaminophenyl) -5 (2-chlorophenyl) oxazole;
Thiazole compounds such as (P-diethylaminostyryl) -6-diethylaminobenzothiazole;
Triarylmethane compounds such as -diethylamino-2-methylphenyl) -phenylmethane, polyarylalkanes such as 1.1-bis (4-NN-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N -Vinyl carbazole, polyvinyl pyrene, polyvinyl anthracene, polyvinyl acridine,
Examples thereof include poly-9-vinylphenylanthracene, a bilen-formaldehyde resin, and an ethyl carbazole formaldehyde resin. These charge transport materials can be used alone or in combination of two or more.

Examples of the binder used for the charge transport layer include phenoxy resin, polyacrylamide, polyvinyl butyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy Tree, polyester, alkyd resin, polycarbonate,
Polyurethane or a copolymer containing two or more of the repeating units of these resins, such as a styrene-butadiene copolymer, a styrene-acrylonitrile copolymer, and a styrene-maleic acid copolymer can be used. Further, it can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

The thickness of the charge transport layer is 5 to 50 μm, preferably 8 to 20 μm.
The weight ratio of the charge transport material to the binder is 5: 1 to 1: 5, preferably about 3: 1 to 1: 3.

Coating includes dip coating, spray coating, spinner coating, beat coating,
The coating can be performed using a coating method such as a Meyer bar coating method, a blade coating method, a roller coating method, and a carden coating method.

In addition, since dyes, pigments, organic charge transporting substances, and the like are generally vulnerable to stains by ultraviolet rays, ozone, oil, and the like, metals, and the like, a protective layer may be provided as necessary. In order to form an electrostatic latent image on the protective layer, the surface resistivity is desirably 10 ¹¹ Ω or more.

The protective layer used in the present invention is a resin such as polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer. A solution dissolved by an organic solvent can be formed on the photosensitive layer by coating and drying. At this time, the thickness of the protective layer is generally in the range of 0.05 to 20 μm. The protective layer may contain an ultraviolet absorber or the like.

In the present invention, the setting of the charging member to be brought into contact with the member to be charged such as the photoreceptor is not limited to a specific method. Either method can be used.
Further, it is also possible to make the charging member function as a cleaning device for the surface of the member to be charged such as a photoreceptor.

The voltage applied to the charging member in the direct charging of the present invention.
Regarding the application method, for example, in the case of an image forming apparatus, it depends on the use of the apparatus, but in addition to the method of applying a desired voltage instantaneously, a method of gradually increasing the applied voltage for the purpose of protecting the photoconductor. In the case of application in a form in which AC is superimposed on DC, a method of applying a voltage in the order of DC → AC or AC → DC can be adopted.

The photoreceptor is not limited to a specific one, and may be, for example, selenium, cadmium sulfide, zinc oxide, amorphous silicon, an organic photoconductor, or the like.

Also, the image forming process of the image forming apparatus can employ any known method, and is not limited to a specific type such as a type of developer, regular development, and reversal development. Not only copiers but also laser printers and CRT printers,
It can also be used in electrophotographic application fields such as electrophotographic plate making systems.

(Effects of the Invention) As described above, according to the present invention, for a contact-type (direct) charging device, the charging member itself is manufactured by coating and drying a resistive layer with a resin emulsion composition or a rubber latex composition. It is possible to easily carry out in a short time by providing, and, of course, fixation of the charging member to the surface of the member to be charged or deterioration of the member to be charged due to seepage of the residual solvent in the resistance layer. It is possible to avoid problems such as a reduction in output image quality due to the occurrence of so-called roller marks in the image forming apparatus.

In this case, by using an aqueous emulsion or latex, a resistance layer having a volume resistivity independent of humidity can be obtained, and a stable image density and line width can be obtained.

The member to be charged is the image carrier of the image forming apparatus, and even if the image carrier is an organic photosensitive member that is easily affected by the solvent,
Since the problem of solvent seepage from the charging member side does not occur,
An economical image forming apparatus using an inexpensive organic photoreceptor and a contact charging device can be configured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus using a contact-type charging device as a primary charging unit, and FIGS. 2 (a) and 2 (b).
Is a cross-sectional view of an example of a charging member other than the roller type, and FIG.
FIG. 4 is a cross-sectional view of a roller-type charging member provided with a second resistance layer. FIG. 4 is an explanatory view of a roller resistance measuring procedure. FIGS. 5A and 5B are cross-sectional views of a roller-type charging member. It is a figure and the longitudinal cross-section omitted on the way. 1 is a photosensitive member as a member to be charged, 2 · 102 is a charging member, 2c
102c is a metal core, 2b and 102b are conductive layers, and 2a and 102a are resistance layers.

Claims (3)

(57) [Claims] 1. A charging device for charging a surface of a member to be charged by bringing a charging member to which a voltage is applied into contact with the surface of the member to be charged, wherein the charging member has a resistive layer contacting the surface of the member to be charged. A charging device, wherein the resistance layer comprises a resin emulsion composition or a rubber latex composition. 2. An image forming apparatus, wherein the charging device according to claim 1 is used as charging means for an image carrier. 3. The image forming apparatus according to claim 2, wherein the image bearing member is an organic photosensitive member.