JP2013200501A - Charging device, image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging device capable of preventing contamination of a surface of a charging roll.SOLUTION: A charging device 12 comprises: a charging roll 121 which comprises a base material 121A, and an outermost surface layer 121C including a resin having a solubility parameter of 20 [MPa] or more on an outer peripheral surface of the base material 121A, and which is in contact with or close to a body to be charged to charge the body to be charged; and a cleaning roll 122 which comprises a core body 122A, and an elastic layer 122B provided on an outer peripheral surface of the core body 122A and constituted of a foamed body having a continuous bubble structure including a block copolymer having polyurethane having a polypropylene glycol ether structure as a constitutional unit and an ether part and a silicone part having a polypropylene glycol ether structure as a constitutional unit, and which is brought into contact with the charging roll 121 to clean the surface of the charging roll 121.

Description

  The present invention relates to a charging device, an image forming apparatus, and a process cartridge.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, a contact charging type is used in which a charging member is brought into contact with an image carrier to charge the image carrier. In such a contact charging type charging member, since the charging member is always in contact with the image carrier, the surface of the charging member is contaminated with toner components, paper powder, and the like. On the other hand, a cleaning member has been proposed in which a plate-like brush or sponge is brought into contact with the surface of the charging member to scrape off the surface contamination of the charging member.

  For example, Patent Document 1 describes a charging roll cleaning member using a block copolymer of dimethylpolysiloxane and polyether as a foam stabilizer.

Japanese Patent Laying-Open No. 2005-085689

  The subject of this invention is providing the charging device by which the contamination of the surface of a charging roll is suppressed.

The above problem is solved by the following means. That is,
The invention according to claim 1
A charging device comprising: a substrate; and an outermost surface layer containing a resin having a solubility parameter of 20 [MPa ^1/2 ] or more on the outer peripheral surface of the substrate, and charging the object to be charged by contacting or approaching the object to be charged Rolls, and
Continuously containing a core, a polyurethane having a polypropylene glycol ether structure as a structural unit, and a block copolymer having an ether part and a silicone part having a polypropylene glycol ether structure as a structural unit on the outer peripheral surface of the core An elastic layer composed of a foam having a cellular structure, and a cleaning roll for cleaning the surface of the charging roll in contact with the charging roll,
Is a charging device.

The invention according to claim 2
2. The charging device according to claim 1, wherein the surface roughness Rz of the outermost surface layer of the charging roll is 7 μm or more and 12 μm or less.

The invention according to claim 3
3. The charging device according to claim 1, wherein the outermost surface layer includes at least one selected from a nylon resin and a urethane resin as the resin having the solubility parameter of 20 [MPa ^1/2 ] or more. .

The invention according to claim 4
The constituent molar ratio of the silicone part to the ether part of the block copolymer having an ether part and a silicone part having the polypropylene glycol ether structure as a constituent unit is 100 constituent mol% or more and 300 constituent mol% or less. The charging device according to any one of claims 1 to 3.

The invention according to claim 5
The charge according to any one of claims 1 to 4, wherein the block copolymer having an ether part and a silicone part having the polypropylene glycol ether structure as a structural unit has a weight average molecular weight of 1000 or more and 5000 or less. Device.

The invention according to claim 6
An image carrier,
The charging device according to claim 1, wherein the image carrier is charged.
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring a toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus.

The invention according to claim 7 provides:
A process cartridge comprising the charging device according to claim 1 for charging an image holding member and detachable from an image forming apparatus.

According to the first aspect of the present invention, a charging roll having an outermost surface layer containing a resin having a solubility parameter of 20 [MPa ^1/2 ] or more, and a polyurethane and a polypropylene glycol ether structure having a polypropylene glycol ether structure as a structural unit are configured. As compared with the case where the cleaning roll having an elastic layer composed of a foam containing a block copolymer having an ether part and a silicone part as a unit is not satisfied, the surface of the charging roll is contaminated. A suppressed charging device is provided.

  According to the second aspect of the present invention, there is provided a charging device in which contamination of the surface of the charging roll is suppressed as compared with a case where the surface roughness Rz of the outermost surface layer of the charging roll is not 7 μm or more and 12 μm or less.

According to the invention of claim 3, the outermost surface layer is charged as compared with the case where the resin having the solubility parameter of 20 [MPa ^1/2 ] or more does not contain at least one selected from nylon resins and urethane resins. A charging device in which contamination of the roll surface is suppressed is provided.

  According to the invention of claim 4, the constituent molar ratio of the silicone part to the ether part of the block copolymer having an ether part and a silicone part having a polypropylene glycol ether structure as a constituent unit is 100 constituent mol% or more and 300 A charging device is provided in which contamination of the surface of the charging roll is suppressed as compared with a case where it is not in the range of the constituent mol% or less.

  According to the invention which concerns on Claim 5, the weight average molecular weights of the said silicone part with respect to the said ether part of the block copolymer which has an ether part which has a polypropylene glycol ether structure as a structural unit, and a silicone part are 1000 or more and 5000 or less. A charging device is provided in which contamination of the surface of the charging roll is suppressed as compared with the case where it is not in the range.

According to the inventions according to claims 6 and 7, a charging roll having an outermost surface layer containing a resin having a solubility parameter of 20 [MPa ^1/2 ] or more, a polyurethane having a polypropylene glycol ether structure as a structural unit, and a polypropylene glycol ether structure Compared to the case without a charging device having a cleaning roll having an elastic layer composed of a foam containing a block copolymer having an ether part and a silicone part, the white line image defect A process cartridge and an image forming apparatus are provided.

It is a schematic perspective view which shows the charging member which concerns on this embodiment. It is a schematic sectional drawing of the charging member which concerns on this embodiment. 1 is a schematic perspective view of a charging device according to an embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the process cartridge which concerns on this embodiment. FIG.

  Hereinafter, embodiments of the present invention will be described in detail.

<Charging device>
The charging device according to the present embodiment includes a base and an outermost surface layer containing a resin having a solubility parameter of 20 [MPa ^1/2 ] or more on the outer peripheral surface of the base, and contacts or approaches the object to be charged. A charging roll for charging the object to be charged, a core, a polyurethane having a polypropylene glycol ether structure as a structural unit on an outer peripheral surface of the core, and an ether portion having a polypropylene glycol ether structure as a structural unit; And an elastic layer composed of a foam having an open-cell structure containing a block copolymer having a silicone part, and a cleaning roll for cleaning the surface of the charging roll in contact with the charging roll.

  The surface of the charging roll used as a charging member for charging the image carrier (photosensitive body) of the image forming apparatus is cleaned by bringing a cleaning roll having an ether urethane foam as the outermost surface layer into contact therewith. The method is commonly used. From the viewpoint of foaming the ether-based urethane foam, it is widely practiced to include a foam stabilizer of ether-modified silicone oil in the foam. However, the ether-modified silicone oil contained in the foam may ooze out to the surface over time, and this tendency becomes more prominent as the temperature is higher and the humidity is higher. Since the ether-modified silicone oil that has oozed out on the surface of the cleaning roll moves to the charging roll that is in contact with the cleaning roll, charging failure occurs in the portion of the charging roll surface where the ether-modified silicone oil has migrated. A streak image defect may occur.

  On the other hand, the charging device according to the present embodiment has the above-described configuration, so that the surface of the charging roll using a block copolymer (foam stabilizer) having an ether portion and a silicone portion having a polypropylene glycol ether structure as a structural unit. Contamination is suppressed. As a result, when the charging device is applied to an image forming apparatus, the occurrence of white stripe image defects in the obtained image is suppressed.

This mechanism is not necessarily clear, but is considered as follows.
As a foam stabilizer composed of a block copolymer having an ether part and a silicone part, a block copolymer, a side chain-modified copolymer, and a terminal group-modified copolymer are known. Among these, the block copolymer has a long main chain and is likely to be entangled with urethane molecules, so that exudation to the surface of the foam is suppressed and the transfer to the charging roll is difficult.

  Furthermore, since both the polyurethane and the block copolymer (foam stabilizer) have a polypropylene glycol ether structure as a structural unit, the familiarity between the block copolymer (foam stabilizer) and the polyurethane is improved. It is considered that exudation to the surface is suppressed and the transfer to the charging roll is suppressed.

Further, since the resin of the outermost surface layer of the charging roll has a solubility parameter of 20 [MPa ^1/2 ] or more, the affinity with the silicone part of the block copolymer is low, that is, the outermost surface layer constitutes a polypropylene glycol ether structure. Familiarity with a block copolymer (foam stabilizer) having an ether part and a silicone part as units, and even if the block copolymer (foam stabilizer) adheres, it is easily removed by a cleaning roll. It is considered a thing.
From the above, it is presumed that contamination of the surface of the charging roll by the block copolymer (foam stabilizer) is suppressed.

  Hereinafter, each structural member of this embodiment is demonstrated using drawing.

(Cleaning roll)
FIG. 1 is a schematic perspective view showing a cleaning roll in the present embodiment.
FIG. 2 is a schematic cross-sectional view showing the cleaning roll in the present embodiment, and corresponds to the AA cross-sectional view of FIG.

As shown in FIGS. 1 and 2, the cleaning roll in the present embodiment is a roll-shaped member for cleaning (cleaning) the surface of the charging roll, for example.
Specifically, the cleaning roll 122 in the present embodiment includes, for example, a core body 122A (shaft) and an elastic layer 122B disposed on the outer peripheral surface of the core body 122A.
The elastic layer 122B is a foam having an open-cell structure containing a polyurethane having a polypropylene glycol ether structure as a structural unit, and a block copolymer having an ether part and a silicone part having a polypropylene glycol ether structure as a structural unit. Consists of.

  The cleaning roll 122 according to the present embodiment is not limited to the above-described configuration. For example, the cleaning roll 122 has a configuration in which other intermediate layers such as an adhesive layer (primer layer) disposed between the core body 122A and the elastic layer 122B are provided. May be.

  Hereinafter, each member of the cleaning roll 122 in this embodiment is demonstrated.

-Core-
The core body 122A is a conductive rod-like member, and examples of the material thereof include metals such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel, and the like. Examples of the core body 122A include a member (for example, a resin or a ceramic member) whose outer peripheral surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like. The core body 122A may be a hollow member (cylindrical member) or a non-hollow member.

-Elastic layer-
The elastic layer 122B is a surface layer for cleaning in contact with the surface of the charging roll 121, and is made of a urethane foam having an open cell structure. More specifically, it contains a polyurethane having a polypropylene glycol ether structure as a structural unit, and a block copolymer having an ether part and a silicone part having a polypropylene glycol ether structure as a structural unit.

For the open cell structure of the elastic layer 122B (foam), a method A breathability test apparatus conforming to JISK6400-7: 2004 (soft foaming agent-how to obtain physical properties-part 7: breathability) was used. In the test method, the air flow rate exceeds 0 dm ³ / s, and the air bubbles in the foam are connected to each other.
Note that the closed cell with respect to the open cell indicates that the air flow rate by the test method is 0 dm ³ / s, and the bubbles exist independently.

  Hereinafter, polyurethane (urethane foam) constituting the elastic layer 122B having the above characteristics will be described in detail.

-Polyurethane Urethane foam includes at least a foam of a reaction product of polyol and isocyanate. Since the foam in this embodiment contains polyurethane having a polypropylene glycol ether structure as a structural unit, at least polypropylene glycol (PPG) And a reaction product derived from isocyanate.

  A polyol other than polypropylene glycol (PPG) may be used in combination. Examples of polyols that can be used in combination include polyether polyols and polyester polyols.

Examples of polyether polyols that can be used in combination include polyethylene glycol (PEG), polytetramethylene ether glycol (PTMEG), polyethylene adipate glycol (PEAG), polybutylene adipate glycol (PBAG), and polybutylene azelate glycol (PBAZG). And polycaprolactone glycol (PCLG).
In addition, the polyether polyol which can be used together may use together 1 type, and may use multiple types together.

Examples of the polyester polyol that can be used in combination include main adipate-based polyols and condensation-based polyester polyols obtained by dehydration condensation of dibasic acids and hydroxyl compounds.
Examples of the adipate-based polyol include ethylene glycol adipate, diethylene glycol adipate, butylene glycol adipate, trimethylolpropane / diethylene glycol adipate, and the like.
Examples of the condensed polyester polyol include dicarboxylic acids such as adipic acid, glutaric acid, succinic acid, sebacic acid, pimelic acid, suberic acid, ethylene glycol; diethylene glycol; 1,4-butanediol; 1,6-hexanediol. Propylene glycol; those obtained by condensation with diols such as neopentyl glycol and triols such as trimethylolethane and trimethylolpropane.
Examples of the condensed polyester polyol include polycarbonate polyols such as polycarbonate diol having a structure in which an alkylene group (for example, hexylene group) or a xylylene group is arranged in the main chain through a carbonate bond.
In addition, the polyester polyol which can be used together may use together 1 type, and may use multiple types together.

As isocyanates, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, triisocyanate, tetramethylxylene diisocyanate, lysine ester Tosic isocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate and the like are used.
In addition, isocyanate may be used individually by 1 type and may be used together with multiple types.

  Here, the urethane foam may be, for example, a reaction product obtained by reacting at least polypropylene glycol (PPG) and isocyanate with a chain extender (for example, 1,4-butanediol, trimethylolpropane, etc.).

In the urethane foam, the use amount of the polyol containing polypropylene glycol (PPG) is, for example, 68% by mass or more and 80% by mass or less based on the total mass of the solid content of the urethane foam constituting the elastic layer 122B. It is preferably 70% by mass or more and 78% by mass or less. Further, the proportion of polypropylene glycol (PPG) in the total polyol is preferably 30% by mass or more, desirably 50% by mass or more, and more desirably closer to 100% by mass.
On the other hand, the amount of isocyanate used is, for example, preferably from 16% by weight to 28% by weight, and preferably from 18% by weight to 26% by weight, based on the total solid content of the urethane foam constituting the elastic layer 122B. % Or less.

  In general, foaming of polyurethane is performed using a foaming agent such as water or an azo compound (for example, azodicarbonamide, azobisisobutyronitrile). Further, an auxiliary agent such as a foaming auxiliary agent may be added to the urethane foam.

- foam stabilizer urethane foam in this embodiment, at least a polypropylene glycol ether structure as a foam stabilizer _{(- [O-CH (CH} 2) -CH 2 -O] n -) ether unit and a silicone having a constitutional unit A block copolymer (silicone oil) having a part (— [Si (R) (R ′) — O] _n —).
Examples of the block copolymer include reactants derived from at least polypropylene glycol (PPG) and polysilicone.

  An example of the polysilicon is polydimethylsiloxane.

The block copolymer may be polymerized with a monomer or prepolymer other than polypropylene glycol (PPG) and polysilicone.
Examples of the monomer and prepolymer used in combination include polyethylene glycol and polyester polyol.

Next, the manufacturing method of the block copolymer which has the ether part which has the said polypropylene glycol ether structure as a structural unit, and a silicone part is demonstrated. There is no restriction | limiting in particular about the manufacturing method of the said block copolymer, Although what is necessary is just according to a conventional method, if the example is shown, it will be as follows.
In the presence of at least one polysiloxane having Si-H groups at both ends at least partially, a polyoxyalkylene polyether having terminal carbon-carbon double bond groups at both ends at least partially, and a platinum-based catalyst. Addition reaction.

  As described above, the block copolymer has an ether part and a silicone part, and the constituent molar ratio of the silicone part to the ether part is preferably 100 constituent mol% or more and 300 constituent mol% or less. Is more preferably 120 constituent mol% or more and 200 constituent mol% or less.

The block copolymer preferably has a weight average molecular weight of 1000 or more and 5000 or less, and more preferably 1500 or more and 3000 or less.
The weight average molecular weight is a polyethylene glycol equivalent molecular weight measured by GPC method.

  Moreover, you may use together foam stabilizers other than the said block copolymer as a foam stabilizer. Examples of the foam stabilizer that can be used in combination include an anionic surfactant, a cationic surfactant, dimethyl silicone oil, and polyether-modified silicone oil.

  The amount of the foam stabilizer used is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.3% by mass or more and 3% by mass or less, and still more preferably, based on the total amount of polyol and isocyanate. Is 0.5 mass% or more and 2 mass% or less. In addition, the ratio of the block copolymer to the total foam stabilizer is preferably 50% by mass or more, and more preferably closer to 100% by mass.

-Other formulations Next, other formulations will be described. Examples of other blends include a catalyst and a conductive agent.
Examples of the catalyst include triethylamine, tetramethylethylenediamine, triethylenediamine (TEDA), bis (N, N-dimethylamino-2-ethyl) ether, N, N, N ′, N′-tetramethylhexamethylenediamine, bis Examples include amine compounds such as (2-dimethylaminoethyl) ether (TOYOCAT-ET, manufactured by Tosoh Corporation), carboxylic acid metal salts such as potassium acetate and potassium octylate, and organometallic compounds such as dibutyltin dilaurate. Among these, the use of an amine catalyst is preferable because it is suitable for the production of water-foamed polyurethane foam. These reaction catalysts may be used alone or in combination of two or more.

  The amount of the catalyst used is desirably 0.01% by mass or more and 5% by mass or less, more desirably 0.05% by mass or more and 3% by mass or less, and further desirably 0% by mass with respect to the total amount of polyol and isocyanate. It is 1 mass% or more and 1 mass% or less.

  Examples of the conductive agent include carbon conductive agents such as ketjen black, acetylene black, oil furnace black, and thermal black, and ionic conductive agents such as ammonium compounds such as tetraethylammonium and stearyltrimethylammonium chloride.

  Examples of other blends include additives such as flame retardants, deterioration inhibitors, and plasticizers. In addition, these other compounds may be used alone or in combination. These additives may be used alone or in combination.

-Manufacturing method of urethane foam Next, the manufacturing method of a urethane foam is demonstrated. There is no restriction | limiting in particular about the manufacturing method of a urethane foam, Although what is necessary is just according to a conventional method, if the example is shown, it will be as follows. First, after mixing a polyurethane polyol, a foam stabilizer, a catalyst, and a conductive agent as necessary as raw materials, a urethane foam is obtained by heating and reaction curing.

  The temperature and time for mixing the raw materials are not particularly limited, but the mixing temperature is usually from 10 ° C. to 90 ° C., preferably from 20 ° C. to 60 ° C. The mixing time is usually from 10 seconds to 20 minutes, preferably from 30 seconds to 5 minutes. Moreover, when making it heat-react and cure, a polyurethane foam is obtained by making it foam by a conventionally well-known method.

  Here, the foaming method is not particularly limited, and any method such as a method using a foaming agent or a method of mixing bubbles by mechanical stirring may be used.

  The thickness of the elastic layer 122B is preferably 1 mm or more and 10 mm or less in terms of average film thickness, and more preferably 2 mm or more and 5 mm or less.

Hereinafter, the manufacturing method of the cleaning roll 122 in this embodiment is demonstrated.
The cleaning roll 122 in this embodiment is, for example,
1) A through-hole is formed in a polyurethane foam foamed by a slab molding method, a core body 122A is inserted into the through-hole and bonded, and then the polyurethane foam is subjected to a cutting process to form an elastic layer 122B. How to form.
2) A method of forming the elastic layer 122B by injecting a raw material into a mold in which the core body 122A is disposed, and performing a curing reaction and foaming.

(Charging roll)
Next, the charging roll will be described with reference to the drawing of the charging device.
FIG. 3 is a schematic perspective view of the charging device according to the present embodiment. The charging device according to the present embodiment is a form in which the cleaning roll in the present embodiment is applied as a cleaning roll.

  As shown in FIG. 3, the charging device 12 according to the present embodiment is arranged such that, for example, a charging roll 121 and a cleaning roll 122 are in contact with each other with a specific biting amount. Then, both ends in the axial direction of the base body 121A of the charging roll 121 and the core body 122A of the cleaning roll 122 are held by bearings 123 (bearings) so that the respective members can rotate.

Here, the charging roll 121 will be described.
The charging roll 121 is, for example, a roll having a base 121A (shaft), an elastic layer 121B disposed on the outer peripheral surface of the base 121A, and a surface layer 121C disposed on the outer peripheral surface of the elastic layer 121B. It is configured.

  The charging roll 121 is not limited to the above configuration, and includes, for example, an adhesive layer (primer layer) disposed between the elastic layer 121B and the base 121A, and a resistor disposed between the elastic layer 121B and the surface layer 121C. The structure which provided the adjustment layer or the transfer prevention layer may be sufficient.

Base body The base body 121A is a conductive rod-like member, and examples of the material thereof include metals such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, and nickel. Examples of the base 121A include a member (for example, a resin or a ceramic member) whose outer peripheral surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like. The base 121A may be a hollow member (cylindrical member) or a non-hollow member.

Elastic layer The elastic layer 121B includes, for example, an elastic material, a conductive agent, and other additives as necessary.
The elastic layer 121B may be a resin layer to which a resin material (for example, a resin used in the surface layer 121C) is applied instead of the elastic material.

  Elastic materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, polyurethane, silicone rubber, fluorine rubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide- Examples include allyl glycidyl ether copolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, and blend rubbers thereof. Among these, polyurethane, silicone rubber, EPDM, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, NBR and blended rubbers thereof are desirably used. These elastic materials may be foamed or non-foamed.

  Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. Examples of electronic conductive agents include carbon blacks such as ketjen black and acetylene black; pyrolytic carbon, graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; tin oxide, indium oxide, titanium oxide And various conductive metal oxides such as tin oxide-antimony oxide solid solution and tin oxide-indium oxide solid solution; Examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; alkali metals such as lithium and magnesium; perchlorates and chlorates of alkaline earth metals ; These conductive agents may be used alone or in combination of two or more.

  The addition amount of the conductive agent is not particularly limited, but in the case of the electronic conductive agent, it is preferably in the range of 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the elastic material. It is more desirable that the amount be in the range of parts by mass or less. On the other hand, in the case of the ionic conductive agent, it is desirable that the amount be in the range of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the elastic material, and 0.5 to 3.0 parts by weight. The following range is more desirable.

  As other additives blended in the elastic layer 121B, for example, a softener, a plasticizer, a curing agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, a coupling agent, a filler (silica, Examples thereof include materials that can be added to a normal elastic layer such as calcium carbonate).

The thickness of the elastic layer 121B is preferably 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 5 mm or less.
The volume resistivity of the elastic layer 121B is preferably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less.

-Surface layer The surface layer 121C contains at least a resin having a solubility parameter of 20 [MPa ^1/2 ] or more, and may further contain other resins, conductive agents, other additives, and the like.

The solubility parameter is a value calculated by the following Fedors formula from the evaporation energy (Δei) and the molar volume (Δvi) of atoms or atomic groups having a chemical structure.
(ΣΔei / ΣΔvi) ^1/2

  The solubility parameter is adjusted by selecting the type of resin.

Here, examples of the resin having a solubility parameter of 20 [MPa ^1/2 ] or more include nylon resins, urethane resins, polyvinylidene chloride, polyvinyl alcohol, and epoxy resins.

  Examples of the nylon resin include those containing one or more of 6 nylon, 66 nylon, 610 nylon, 11 nylon, 12 nylon, and methoxymethylated nylon as a polymerization unit. Among these, methoxymethylated nylon and 6 nylon / 66 nylon / 610 nylon / 12 nylon copolymers are preferable.

A preferable example of the urethane resin is a reaction product of a polyol and an isocyanate.
Polyols include polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene ether glycol (PTMEG), polyethylene adipate glycol (PEAG), polybutylene adipate glycol (PBAG), polybutylene azelate glycol (PBAZG), Polyethers such as polycaprolactone glycol (PCLG), main adipate polyols obtained by dehydration condensation of dibasic acids and hydroxyl compounds, polyesters such as condensation polyester polyols, copolymers of propylene glycol and ethylene glycol, Or, a mixture of polypropylene glycol and polyethylene glycol can be mentioned. Among these, polypropylene glycol, propylene glycol A copolymer of ethylene glycol, or a mixture of polypropylene glycol and polyethylene glycol.

  Isocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, triisocyanate, tetramethylxylene diisocyanate, lysine ester tosiisocyanate. Lysine diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate and the like. Among these, tolylene diisocyanate and diphenylmethane diisocyanate are preferable.

In addition, other resins may be used in combination, such as acrylic resin, cellulose resin, polyamide resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyarylate resin, styrene butadiene resin, melamine resin. Epoxy resin, silicone resin, fluororesin (for example, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, etc.), urea resin, and the like.
However, the ratio of the resin having a solubility parameter of 20 [MPa ^1/2 ] or more in the total resin is preferably 70% by mass or more, and is preferably closer to 100% by mass.

Examples of the conductive agent blended in the surface layer 121C include a conductive agent blended in the elastic layer 121B.
Other additives include, for example, materials that can be added to the normal surface layer such as softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, antioxidants, surfactants, and coupling agents. Can be mentioned.

The surface roughness Rz of the outer peripheral surface of the surface layer is preferably 5 μm or more and 15 μm or less, and more preferably 7 μm or more and 12 μm or less.
When an image is formed by applying the charging device according to the present embodiment to an image forming apparatus, even if white streak occurs at the initial stage because the surface roughness Rz of the surface layer of the charging roll is in the above range. The occurrence of white streaks is improved by repeating the image formation. Although this is not clear, it is considered as follows.
That is, even when the foam stabilizer exudes from the cleaning roll and shifts to the charging roll, it is estimated that the surface of the charging roll is controlled within the above-mentioned appropriate range, so that it is spread on the charging roll. As a result, it is considered that the occurrence of white streak is improved by repeating the image formation.

  The surface roughness Rz refers to a ten-point average roughness value measured according to JIS B0601-1994 using a surface roughness meter surfcom 1400A (manufactured by Tokyo Seimitsu Co., Ltd.). The measurement is performed in an environment of 22 ° C. and 55% RH.

The thickness (overall thickness) of the surface layer 121C is desirably 7 μm or more and 25 μm or less.
The volume resistivity of the surface layer 121C is preferably 10 ³ Ωcm or more and 10 ¹⁴ Ωcm or less.

-Bearing The bearing 123 is a member that holds the charging roll 121 and the cleaning roll 122 integrally and rotatably, and also holds the inter-axis distance between the members. The conductive bearing 123 may be of any material and form as long as it is made of a conductive material. For example, a bearing or a sliding bearing is applied.

  Here, the bearing 123 may have conductivity when the elastic layer 122B of the cleaning roll 122 has conductivity. In the case of this embodiment, a voltage is applied to the conductive bearing 123. The charging roll 121 and the cleaning roll 122 are charged with the same polarity. As a result, foreign matter (for example, toner and external additives) on the surface of the image carrier is prevented from accumulating on the surfaces of the cleaning roll 122 and the charging roll 121, transferred to the image carrier, and the foreign matter is removed by the image carrier cleaning device. Is recovered.

(Image forming device, process cartridge)
The image forming apparatus according to the present embodiment includes an image carrier, a charging device that charges the image carrier, a latent image forming device that forms a latent image on the surface of the charged image carrier, and the image carrier. A developing device that forms a toner image by developing the latent image formed on the surface of the toner image with toner, and a transfer device that transfers the toner image formed on the surface of the image carrier to a recording medium. The charging device according to the present embodiment is applied as the charging device (charging device).

  On the other hand, the process cartridge according to the present embodiment includes a charging device that is attached to and detached from the image forming apparatus having the above-described configuration and charges the image carrier. The charging device according to the present embodiment is applied as the charging device. The process cartridge according to the present embodiment is formed on the surface of the image holding body, the image holding body, a developing device that develops the latent image formed on the surface of the image holding body with toner, and forms a toner image, as necessary. And at least one selected from the group consisting of a transfer device that transfers the toner image to a recording medium and a cleaning device that removes residual toner on the surface of the image carrier after transfer.

  Next, an image forming apparatus and a process cartridge according to the present embodiment will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment. FIG. 5 is a schematic configuration diagram showing a process cartridge according to the present embodiment.

  As shown in FIG. 4, the image forming apparatus 101 according to the present embodiment includes an image carrier 10, and a charging device 12 that charges the image carrier 10 and an image carrier charged by the charging device 12 around the image carrier 10. An exposure device 14 for exposing the body 10 to form a latent image, a developing device 16 for developing the latent image formed by the exposure device 14 with toner to form a toner image, and a toner image formed by the developing device 16 are recorded. A transfer device 18 for transferring to the medium A and a cleaning device 20 for removing residual toner on the surface of the image carrier 10 after transfer are provided. Further, a fixing device 22 for fixing the toner image transferred to the recording medium A by the transfer device 18 is provided.

The image forming apparatus 101 according to the present embodiment includes, as the charging device 12, for example, a charging roll 121, a cleaning roll 122 disposed in contact with the charging roll 121, and axial ends of the charging roll 121 and the cleaning roll 122. According to the present embodiment, a conductive bearing 123 (conductive bearing) that holds each member so as to be rotatable and a power source (not shown) connected to one of the conductive bearings 123 are disposed. A charging device is applied.
Here, in the present embodiment, for example, the image carrier 10 side is driven to rotate, the charging roll 121 is rotated by the rotation, and the cleaning roll is rotated by the rotation of the charging roll 121. 121 or the cleaning roll 122 may be connected to a driving device (not shown) for rotation.

  On the other hand, in the image forming apparatus 101 according to the present exemplary embodiment, a known configuration is conventionally applied as each configuration of the electrophotographic image forming apparatus except for the charging device 12 (charging roll 121). Hereinafter, an example of each configuration will be described.

  The image carrier 10 is not particularly limited, and a known photoreceptor can be used. An organic photoreceptor having a so-called function separation type structure in which a charge generation layer and a charge transport layer are separated is preferably used. In addition, the image carrier 10 is preferably applied to a photoconductor whose surface layer is made of a siloxane resin or a phenol resin having a charge transporting property and a crosslinked structure.

  As the exposure apparatus 14, for example, a laser optical system, an LED array, or the like is applied.

  For example, the developing device 16 brings a toner image onto the latent image on the surface of the image carrier 10 by bringing a developer carrier having a developer layer formed on the surface thereof into contact with or close to the image carrier 10. A developing device to be formed. As a developing method of the developing device 16, a developing method using a two-component developer is suitably applied as a known method. Examples of the developing method using the two-component developer include a cascade method and a magnetic brush method.

  Examples of the transfer device 18 include a non-contact transfer method such as corotron and scorotron, and a contact transfer method in which a conductive transfer roll is brought into contact with the image carrier 10 via the recording medium A to transfer a toner image to the recording medium A. Either may be applied.

  The cleaning device 20 is, for example, a member that removes toner, paper dust, dust, and the like attached to the surface by bringing a cleaning blade into direct contact with the surface of the image carrier 10. As the cleaning device 20, a cleaning brush, a cleaning roll, or the like may be applied in addition to the cleaning blade.

  As the fixing device 22, a heat fixing device using a heat roll is suitably applied. The heat fixing device includes, for example, a fixing roller in which a so-called release layer is formed of a heat-resistant resin coating layer or a heat-resistant rubber coating layer on the outer peripheral surface thereof with a heater lamp for heating inside a cylindrical metal core, A pressure roller or a pressure belt that is disposed in contact with the fixing roller at a specific contact pressure and has a heat-resistant elastic body layer formed on the outer peripheral surface of the cylindrical core metal or the surface of the belt-like base material. . The fixing process of the unfixed toner image is performed, for example, by inserting the recording medium A onto which the unfixed toner image is transferred between a fixing roller and a pressure roller or a pressure belt, and binding resin in the toner, Fixing by heat melting of additives and the like.

  The image forming apparatus 101 according to the present embodiment is not limited to the above configuration. For example, an intermediate transfer type image forming apparatus using an intermediate transfer member and an image forming unit that forms toner images of each color are arranged in parallel. A so-called tandem image forming apparatus may be used.

  On the other hand, as shown in FIG. 5, the process cartridge according to the present embodiment includes an opening 24A for exposure, an opening 24B for static elimination exposure, and a mounting rail 24C in the image forming apparatus shown in FIG. By the housing 24, the image carrier 10, the charging device 12 for charging the image carrier, the developing device 16 for developing the latent image formed by the exposure device 14 with toner and forming a toner image, and after the transfer And a cleaning device 20 that removes residual toner on the surface of the image holding body 10 and is integrally assembled and held. The process cartridge 102 is detachably attached to the image forming apparatus 101 shown in FIG.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited by the following Example. Unless otherwise specified, “part” means “part by mass”.

-Preparation of foam stabilizer (1)-
A foam stabilizer (1) comprising a block copolymer having an ether part having a polypropylene glycol ether unit and a silicone part was prepared by the following method.
100 parts of a molecular hydrogen-terminated methylhydrogen polysiloxane compound having a weight average molecular weight of 200, average structural formula: CH ₂ ═CHCH ₂ O (C ₂ H ₄ O) ₁₀ (C ₃ H ₆ O) ₁₀ CH ₂ CH═CH _A platinum catalyst was added to 100 parts of polyoxyalkylene allyl butyl ether represented by ₂ and 50 parts of isopropyl alcohol, and an addition reaction was carried out at 80 ° C. for 5 hours to obtain a foam stabilizer (1) which is a polyether-modified silicone compound.
In the obtained foam stabilizer, the constituent molar ratio of the silicone part to the ether part was 100 constituent mol%, and the weight average molecular weight was 1500.

-Preparation of foam stabilizer (2)-
A foam stabilizer (2) comprising a block copolymer having an ether part having a polypropylene glycol ether unit and a silicone part was prepared by the following method.
200 parts of a methyl hydrogen polydimethylsiloxane compound having a weight average molecular weight of 200 at both ends of the molecular chain, average structural formula: CH ₂ ═CHCH ₂ O (C ₂ H ₄ O) ₁₀ (C ₃ H ₆ O) ₁₀ CH ₂ CH = A platinum catalyst was added to 100 parts of polyoxyalkylene allyl butyl ether represented by CH ₂ and 50 parts of isopropyl alcohol, and an addition reaction was carried out at 80 ° C. for 5 hours to obtain a foam stabilizer (2) which is a polyether-modified silicone compound. .
In the obtained foam stabilizer, the constituent molar ratio of the silicone part to the ether part was 200 constituent mol%, and the weight average molecular weight was 3000.

-Preparation of foam stabilizer (3)-
A foam stabilizer (3) composed of a comb copolymer (side chain modified copolymer) having an ether part having a polypropylene glycol ether unit in the side chain and a silicone part was prepared by the following method.
200 parts of a trimethylsilyl group-blocked methylhydrogen polysiloxane compound having a weight average molecular weight of 1500 and an average structural formula: CH ₂ ═CHCH ₂ O (C ₂ H ₄ O) ₁₀ (C ₃ H ₆ O) ₁₀ CH ₂ A platinum catalyst is added to 100 parts of polyoxyalkylene allyl butyl ether represented by CH = CH ₂ and 50 parts of isopropyl alcohol, and an addition reaction is carried out at 80 ° C. for 5 hours to obtain a foam stabilizer (3) which is a polyether-modified silicone compound. Obtained.
In the obtained foam stabilizer, the constituent molar ratio of the silicone part to the ether part was 300 constituent mol%, and the weight average molecular weight was 2000.

-Preparation of foam stabilizer (4)-
A foam stabilizer (4) comprising a block copolymer having an ether part having a polyethylene glycol ether unit and no polypropylene glycol ether unit and a silicone part was prepared by the following method.
Polyoxyalkylene represented by 100 parts of a molecular chain both-end methylhydrogen polysiloxane compound having a weight average molecular weight of 200, represented by the average structural formula: CH ₂ ═CHCH ₂ O (C ₂ H ₄ O) ₂₀ CH ₂ CH═CH ₂ A platinum catalyst was added to 100 parts of allyl butyl ether and 50 parts of isopropyl alcohol, and an addition reaction was carried out at 80 ° C. for 5 hours to obtain a foam stabilizer (4) which is a polyether-modified silicone compound.
In the obtained foam stabilizer, the constituent molar ratio of the silicone part to the ether part was 200 constituent mol%, and the weight average molecular weight was 2000.

-Production of cleaning roll (1)-
(1) Bifunctional polypropylene glycol: 20 parts (average molecular weight 2000, trade name: Actol P23, made by Mitsui Chemicals Polyurethane)
(2) Trifunctional polypropylene glycol ······················································· 80 parts
(3) Foam stabilizer comprising a block copolymer having an ether part having a polypropylene glycol ether unit and a silicone part (1) ........ 1 part
(4) Catalyst ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 0.5 parts (Product name: Kaulizer No31, Kao Corporation Made)
(5) Foaming agent (water) ... 5 parts
(6) Isocyanate: 66.2 parts (Product name: Cosmonate T-80, made by Mitsui Chemicals Polyurethane)
The above compositions (1) to (5) were mixed, and (6) was further mixed and foamed. Furthermore, this foam was heated at 80 ° C. for 1 hour, allowed to stand at room temperature (25 ° C.), and then cooled to produce a urethane foam.
This urethane foam is cut into a size of 15 mm x 15 mm x 350 mm, a through hole is made in the center, and an adhesive is applied to the core metal (outer diameter: 6 mm, shaft length: 337 mm, the length of both ends of the shaft 6 mm, only 4 mm outer diameter) was inserted and bonded, and then the outer diameter of the urethane foam was polished to obtain a cleaning roll (1) having an elastic layer with an axial length of 320 mm and an outer diameter of φ10 mm.

-Production of cleaning roll (2)-
A cleaning roll, except that (3) the foam stabilizer (1) is replaced by a foam stabilizer (2) comprising a block copolymer having an ether part having a polypropylene glycol ether unit and a silicone part. A cleaning roll was produced by the method described in the production of (1).

-Production of cleaning roll (3)-
(3) Instead of the foam stabilizer (1), a foam stabilizer (3) composed of a comb copolymer having an ether part and a silicone part having the above-mentioned polypropylene glycol ether unit in the side chain was blended. A cleaning roll was prepared by the method described in Preparation of Cleaning Roll (1).

-Production of cleaning roll (4)-
(3) Instead of the foam stabilizer (1), a foam stabilizer comprising a block copolymer having an ether part having a polyethylene glycol ether unit and not having a polypropylene glycol ether unit and a silicone part ( A cleaning roll was produced by the method described in the production of the cleaning roll (1) except that 4) was blended.

-Production of charging roll (1)-
[Formation of elastic layer]
The following mixture was kneaded with an open roll, coated on the surface of a conductive substrate made of SUS416 with a diameter of 6 mm in a cylindrical shape so as to have a thickness of 3 mm, put into a cylindrical mold with an inner diameter of 18.0 mm, and 170 ° C. Was vulcanized for 30 minutes, removed from the mold, and then polished to obtain a cylindrical conductive elastic layer.
・ Rubber material ... 100 parts (Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber,
(Gechron 3106: 75 parts made by Nippon Zeon, and nitrile butadiene rubber, N250S: 25 parts made by JSR)
・ Conducting agent (benzyltriethylammonium chloride: manufactured by Kanto Chemical Co., Ltd.) ... 0.9 parts ・ Conducting agent (Ketjen Black EC: manufactured by Lion) ... 15 parts・ Vulcanizing agent (sulfur, 200 mesh: manufactured by Tsurumi Chemical Co., Ltd.) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 1 part ・ Vulcanizing accelerator (Noxeller DM: manufactured by Ouchi Shinsei Chemical Co., Ltd.)・ ・ ・ ・ 2.0 parts ・ Vulcanization accelerator (Noxeller TT: Ouchi Shinsei Chemical Co., Ltd.) ・ ・ ・ ・ 0.5 parts

[Formation of surface layer]
A dispersion obtained by dispersing the following mixture with a bead mill is diluted with methanol, dip-coated on the surface of the conductive elastic layer, and then heated and dried at 140 ° C. for 15 minutes to form a surface layer having a thickness of 10 μm. Thus, a charging roll was obtained. The surface roughness Rz of the surface layer was 10 μm. The solubility parameter of nylon is 27.
・ Polymer material ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 100 parts (N-methoxymethylated nylon, F30K: manufactured by Nagase Chemtech) ,
Solubility parameter 27MPa ^1/2 )
・ Conductive agent ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 20 parts (Carbon Black, Ketjen Black EC: Lion Corporation)
・ Porous filler ... 30 parts (polyamide resin particles, 2001UDNAT1: manufactured by Akerma)
・ Catalyst ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 7 parts (Phosphate dissociation, isopropanol / isobutanol catalyst,
NACURE 4167: King Industries, Inc.)
・ Solvent (methanol) ・ ・ ・ ・ ・ 900 parts

-Production of charging roll (2)-
A charging roll was prepared by the method described in the preparation of the charging roll (1) except that the amount of the porous filler (polyamide resin particles, 2001UDNAT1: manufactured by Akerma) was changed from 30 parts to 15 parts. The surface roughness Rz was 7 μm.

-Production of charging roll (3)-
A charging roll was prepared by the method described in the preparation of the charging roll (1), except that the amount of the porous filler (polyamide resin particles, 2001UDNAT1: manufactured by Akerma) was changed from 30 parts to 10 parts. The surface roughness Rz was 5 μm.

-Production of charging roll (4)-
A charging roll was prepared by the method described in the preparation of the charging roll (1) except that the amount of the porous filler (polyamide resin particles, 2001UDNAT1: manufactured by Akerma) was changed from 30 parts to 40 parts. The surface roughness Rz was 13 μm.

-Production of charging roll (5)-
Except for changing the polymeric material (N-methoxymethylated nylon) to a polyurethane resin solution (Nipporan 3113, manufactured by Nippon Polyurethane Co., Ltd.), changing the solvent methanol to MEK, and adding no catalyst, A charging roll was prepared by the method described in 1). The solubility parameter of polyurethane is 21 MPa ^1/2 .

-Production of charging roll (6)-
For the production of the charging roll (1) except that the polymer material (N-methoxymethylated nylon) was changed to PMMA (molecular weight: 200,000), the solvent methanol was changed to tetrahydrofuran, and no catalyst was added. A charging roll was produced by the method described. The solubility parameter of PMMA is 19 MPa ^1/2 .

(Examples 1-6, Comparative Examples 1-3)
Image quality evaluation after running The cleaning roll and charging roll shown in Table 1 below were mounted on an image forming apparatus DocuCenter-IV C5570 manufactured by Fuji Xerox Co., Ltd., and stored for 7 days under conditions of a temperature of 22 ° C. and a humidity of 55%. Thereafter, a 20,000 print test was performed under low temperature and low humidity conditions (10 ° C., 15% condition), the image after the 20000 print test was observed, and the following evaluation criteria for the occurrence of image quality defects (white streaks) It was evaluated with.

-Image quality evaluation after storage under high temperature and high humidity conditions A process cartridge equipped with the cleaning roll and charging roll listed in Table 1 below was subjected to a storage test at 40 ° C and 90% for 3 days. It was mounted on an image forming apparatus DocuCentre-IV C5570 made by the company. A print test was performed to observe the image, and the occurrence of image quality defects (white streaks) was evaluated according to the following evaluation criteria.
(Evaluation criteria)
◎: Defect in image quality was not observed ○: Defect in image quality was insignificant △: Defect in image quality was inferior to ○ but acceptable range ×: Tolerable range Table 1 below shows the results of the above two image quality evaluations.

DESCRIPTION OF SYMBOLS 10 Image carrier, 12 Charging device, 14 Exposure device, 16 Developing device, 18 Transfer device, 20 Cleaning device, 22 Fixing device, 24 Housing, 24A Opening, 24B Opening, 24C Mounting rail, 101 Image forming device, 102 process cartridge, 121 charging roll, 121A substrate, 121B elastic layer, 121C surface layer, 122 cleaning roll, 122A core, 122B elastic layer, 123 bearing

Claims (7)

A charging device comprising: a substrate; and an outermost surface layer containing a resin having a solubility parameter of 20 [MPa ^1/2 ] or more on the outer peripheral surface of the substrate, and charging the object to be charged by contacting or approaching the object to be charged Rolls, and
Continuously containing a core, a polyurethane having a polypropylene glycol ether structure as a structural unit, and a block copolymer having an ether part and a silicone part having a polypropylene glycol ether structure as a structural unit on the outer peripheral surface of the core An elastic layer composed of a foam having a cellular structure, and a cleaning roll for cleaning the surface of the charging roll in contact with the charging roll,
A charging device.   The charging device according to claim 1, wherein the surface roughness Rz of the outermost surface layer of the charging roll is 7 μm or more and 12 μm or less. The charging device according to claim 1, wherein the outermost surface layer includes at least one selected from a nylon-based resin and a urethane-based resin as the resin having the solubility parameter of 20 [MPa ^1/2 ] or more.   The constituent molar ratio of the silicone part to the ether part of the block copolymer having an ether part and a silicone part having the polypropylene glycol ether structure as a constituent unit is 100 constituent mol% or more and 300 constituent mol% or less. The charging device according to any one of claims 1 to 3.   The charge according to any one of claims 1 to 4, wherein the block copolymer having an ether part and a silicone part having the polypropylene glycol ether structure as a structural unit has a weight average molecular weight of 1000 or more and 5000 or less. apparatus. An image carrier,
The charging device according to claim 1, wherein the image carrier is charged.
A latent image forming apparatus for forming a latent image on the surface of the charged image carrier;
A developing device for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
A transfer device for transferring a toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus comprising:   A process cartridge comprising the charging device according to claim 1 for charging an image holding member and detachable from an image forming apparatus.