JP2018146796A - Conductive roller, transfer roller, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roller that has low resistance and is excellent in resistance stability and resistance uniformity.SOLUTION: A conductive roller has a foam rubber layer containing carbon black and a rubber coating layer containing carbon black in this order on a conductive core material. The surface resistivity μ(Ω/sq.) of the rubber coating layer and the nip resistance value μ(Ω) of the conductive roller satisfy the formula (1), and the μis 10Ω or less. (1) μ<μ.SELECTED DRAWING: None

Description

  The present invention relates to a conductive roll, a transfer roll, a process cartridge, and an image forming apparatus.

  In many electrophotographic image forming apparatuses (also referred to as electrophotographic apparatuses and electrophotographic image forming apparatuses) such as copying machines and printers, conductive rubber rolls such as a charging roll, a transfer roll, and a developing roll are used. These rubber rolls are required to maintain a uniform nip width by contact with the photoreceptor in order to respond to higher speed and better image quality of the apparatus. When the rubber layer is a foam, It is desired that the foam cell is dense and uniform.

  For example, Patent Document 1 discloses a charging roll having a foamed elastic layer support member composed of at least a conductive substrate and a conductive sponge rubber substrate, and a conductive coating member, wherein the conductive sponge rubber substrate is a styrene butadiene rubber. (SBR) or ethylene propylene diene rubber (EPDM), and the conductive covering member includes a thermoplastic elastomer, the conductive covering member is composed of two layers, and the inner layer is formed by dynamic viscoelasticity. The value of tan δ represented by the ratio between the storage elastic modulus and the loss elastic modulus is 10 Hz, 0.2 or more in the range of 10 ° C. or more and 50 ° C. or less, and the tan δ value in the entire cross section direction of the charging roll is 10 Hz, A charging roll characterized by being 0.2 or less in the range of 10 to 50 ° C. is disclosed.

  Patent Document 2 discloses a process for producing a conductive rubber roller in which a foam rubber layer made of a rubber composition is formed on a conductive core material, wherein the main rubber in the rubber composition is epichlorohydrin rubber, acrylonitrile. Butadiene rubber or a mixture thereof, and the rubber composition contains 0.1 to 10 parts by mass of liquid polybutadiene having a molecular weight of 1000 to 2000 with respect to 100 parts by mass of the main rubber, A chemical foaming agent is included, and after the rubber composition is extruded into a cylindrical shape, the foam rubber layer is irradiated with microwaves having an irradiation interval length of 2 m or less and an irradiation intensity of 0.5 kW to 2.5 kW. A method for manufacturing a conductive rubber roller is disclosed.

  Furthermore, in Patent Document 3, an inner layer obtained by kneading a thermoplastic resin, a conductivity-imparting agent and a foaming agent and an outer layer obtained by kneading a thermoplastic resin and a conductivity-imparting agent were obtained by simultaneous hot-melt extrusion. A conductive resin tube is disclosed.

  Further, Patent Document 4 discloses that an outer tube having an outer diameter matched to the outer diameter of a tube roll to be obtained, a shaft arranged with a central axis aligned with the outer tube, and a space between the outer tube and the shaft. The polyurethane foam raw material injected into the formed annular space is foamed and cured to form a polyurethane foam filling the annular space, and each of the outer tube and the shaft is joined to the expanded and cured polyurethane foam. The tube roll characterized by having been disclosed is disclosed.

JP 2010-191443 A JP 2008-176027 A Japanese Patent Laid-Open No. 2004-9588 JP 2004-190774 A

  The problem to be solved by the present invention is that the conductive core material has a low resistance and has excellent resistance stability and resistance uniformity compared to the case where a foamed rubber layer and a non-rubber resin layer are provided in this order. Is to provide a role.

Specific means for solving the above-described problems include the following modes.
The invention according to claim 1
On the conductive core material, a foamed rubber layer containing carbon black and a rubber coating layer containing carbon black are provided in this order, and the surface resistivity μ _R (Ω / □) of the rubber coating layer, The conductive roll has a nip resistance value μ _N (Ω) satisfying the following formula (1), and the μ _N is 10 ⁶ Ω or less.
μ _R <μ _N (1)

The invention according to claim 2
2. The conductive roll according to claim 1, wherein the foamed rubber layer contains rubber obtained by foaming and vulcanizing ethylene-propylene-diene rubber.

The invention according to claim 3
3. The conductive roll according to claim 1, wherein the rubber coating layer contains rubber obtained by vulcanizing ethylene-propylene-diene rubber.

The invention according to claim 4
The conductive rubber roll according to any one of claims 1 to 3, wherein the foamed rubber layer contains two or more types of carbon blacks having different oil absorption properties as the carbon black.

The invention according to claim 5
5. The conductive material according to claim 4, wherein, in the foamed rubber layer, the content of carbon black having the lowest oil absorbency among the two or more types of carbon black having different oil absorbability is higher than the content of other carbon blacks. Sex roll.

The invention according to claim 6
6. The conductive roll according to claim 1, wherein the rubber coating layer includes two or more carbon blacks having different oil absorption properties as the carbon black.

The invention according to claim 7 provides:
7. The conductive material according to claim 6, wherein, in the rubber coating layer, the content of the carbon black having the lowest oil absorption among the two or more types of carbon blacks having different oil absorption is higher than the content of the other carbon blacks. Sex roll.

The invention according to claim 8 provides:
The conductive roll according to any one of claims 1 to 7, wherein a thickness of the rubber coating layer is smaller than a thickness of the foamed rubber layer.

The invention according to claim 9 is:
It is a transfer roll which has the electroconductive roll of any one of Claim 1 thru | or 8.

The invention according to claim 10 is:
A process cartridge having the transfer roll according to claim 9, comprising transfer means for transferring the toner image formed on the surface of the image holding member to a recording medium, and detachable from the image forming apparatus.

The invention according to claim 11 is:
An image carrier, a charging unit for charging the image carrier, a latent image forming unit for forming a latent image on the surface of the charged image carrier, and a latent image formed on the surface of the image carrier. An image comprising: a developing unit that forms a toner image by developing the toner image; and a transfer unit that includes the transfer roll according to claim 9 and that transfers the toner image formed on the surface of the image carrier to a recording medium. Forming device.

According to the first aspect of the present invention, compared to the case where the foamed rubber layer and the non-rubber resin layer are provided in this order on the conductive core material, the resistance is low, and the conductivity is excellent in resistance stability and resistance uniformity. A role is provided.
According to the invention which concerns on Claim 2 or 3, compared with the case where only a styrene butadiene rubber is used, the conductive roll which is lower resistance and is excellent by resistance stability is provided.
According to the invention which concerns on Claim 4 or 6, compared with the case where only 1 type of carbon black is carbon black, the electroconductive roll excellent in resistance stability is provided.
According to the invention according to claim 5 or 7, when the content of the carbon black having the lowest oil absorbency among the two or more types of carbon blacks having different oil absorbability is less than the content of the other carbon black Compared to the above, a conductive roll having superior resistance stability is provided.
According to the invention which concerns on Claim 8, compared with the case where the thickness of the said rubber coating layer is more than the thickness of the said foaming rubber layer, the electroconductive foam member excellent in resistance stability is provided.
According to the invention which concerns on Claim 9, it is low resistance compared with the case where the conductive roll which has a foaming rubber layer and the resin layer which is not rubber | gum in this order on a conductive core material, resistance stability and resistance uniformity A transfer roll having excellent properties is provided.
According to the invention which concerns on Claim 10, it is low resistance compared with the case where the conductive roll which has a foaming rubber layer and the resin layer which is not rubber | gum in this order on a conductive core material, resistance stability and resistance uniformity A process cartridge having a transfer roll having excellent properties is provided.
According to the eleventh aspect of the present invention, compared to the case where a conductive roll having a foamed rubber layer and a non-rubber resin layer in this order is used on the conductive core material, the resistance is low, the resistance is stable, and the resistance is uniform. An image forming apparatus having a transfer roll having excellent properties is provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described in detail.

<Conductive roll>
The conductive roll according to the present embodiment has a foamed rubber layer containing carbon black and a rubber coating layer containing carbon black in this order on a conductive core material, and the surface resistance of the rubber coating layer. The rate μ _R (Ω / □) and the nip resistance value μ _N (Ω) of the conductive roll satisfy the following formula (1), and the μ _N is 10 ⁶ Ω or less.
μ _R <μ _N (1)
Further, the conductive roll according to the present embodiment is suitably used for a conductive roll for an electrophotographic apparatus such as a charging roll, a transfer roll, a developing roll, and a power feeding roll.
Among these, it is particularly suitably used for a transfer roll.

Conventionally, nitrile rubber (NBR) / epichlorohydrin-based materials and urethane-based foam materials have been used for conductive rolls. However, in these materials, sufficient resistance stability due to ozone deterioration resistance, hygroscopicity, and hydrolyzability is not sufficient, and a lower resistance is required.
On the other hand, the conductive foam member according to the present embodiment has a low resistance and excellent resistance stability due to the above configuration. The reason is not clear, but is presumed as shown below.

By having a foamed rubber layer containing carbon black and a rubber coating layer containing carbon black in this order on the conductive core material, sufficient conductivity is ensured. It is estimated that a conductive roll with low resistance and excellent resistance stability and resistance uniformity can be obtained because it suppresses ozone degradation, moisture absorption and hydrolysis, etc., and also suppresses distortion of the roll shape over time. The
Further, the surface resistivity μ _R (Ω / □) of the rubber coating layer and the nip resistance value μ _N (Ω) of the conductive roll satisfy the formula (1), and the μ _N is 10 ⁶ Ω. By using the following conductive roll, it is presumed that an electrical roll over time is suppressed, a low resistance, and excellent resistance stability and resistance uniformity can be obtained.

  Hereinafter, the detail of the electroconductive roll which concerns on this embodiment is demonstrated.

(Nip resistance value)
The conductive roll according to this embodiment has a nip resistance value μ _N (Ω) of 10 ⁶ Ω or less, and from the viewpoint of low resistance and resistance stability, 10 ^3.5 Ω or more and 10 ⁶ Ω or less. Is more preferably 10 ^4.0 Ω or more and 10 ^5.7 Ω or less, and particularly preferably 10 ^4.5 Ω or more and 10 ^5.5 Ω or less.

  The nip resistance in the present embodiment is obtained by applying a load of 500 g and applying a voltage of 1 kV (10-second charge) at 23 ° C. and 55% using a cylinder electrode HR probe of Hiresta IP manufactured by Mitsubishi Oil Corporation. This is a value measured at RH, and is measured at the nip portion of the aluminum drum contacted.

(Surface resistivity of rubber coating layer)
The surface resistivity μ _R (Ω / □) of the rubber coating layer in the conductive roll according to the present embodiment and the nip resistance value μ _N (Ω) of the conductive roll satisfy the formula (1).
The surface resistivity of the rubber-coated layer μ _R (Ω / □), from the viewpoint of low resistance and resistance stability, is preferably 10 ³ Ω / □ or more 10 ⁶ Ω / □ less ^{than, 10 3.5} Omega More preferably, it is 10 or more and 10 ^5.5 Ω / □ or less, and particularly preferably 10 ^4.0 Ω / □ or more and 10 ^5.3 Ω / □ or less.

The surface resistivity of the rubber coating layer in this embodiment is 12 mm in diameter and 330 mm in length at a distance of 10 mm in the circumferential direction from the surface of a conductive roll that has been energized for 100 hours after application of a voltage of 3 kV at 23 ° C. and 55% RH. These two SUS metal rolls were brought into contact with each other with a biting amount of 0.2 mm, a DC voltage (V) of 1 kV was applied between the metal rolls, and the current value (I) after 10 seconds from the voltage application The surface resistivity μ _R (Ω / □) is obtained by reading and the following formula.
μ _R (Ω / □) = LV / GI
Here, L represents the length (cm) of the charging roll, and G represents the distance (cm) between the two metal rolls.

(Conductive core)
The conductive roll according to the present embodiment has a conductive core material.
Examples of the conductive core material include metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel, and the like.
Examples of the conductive core material include a member (for example, a resin or a ceramic member) whose outer surface is plated, a member in which a conductive agent is dispersed (for example, a resin or a ceramic member), and the like.
Further, the conductive core material may be a hollow member (cylindrical member) or a non-hollow member.
Moreover, the magnitude | size and shape of an electroconductive core material do not have a restriction | limiting in particular, What is necessary is just to set suitably according to a desired use.

(Foam rubber layer)
The conductive roll according to the present embodiment has a foamed rubber layer containing carbon black on a conductive core material.

-Rubber material-
Examples of the rubber material (elastic material) used for producing the foamed rubber layer include so-called elastic materials having a double bond in at least a chemical structure.
Specifically, for example, isoprene rubber, chloroprene rubber, epichlorohydrin rubber (ECO), 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-allyl glycidyl ether copolymer rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber and the like, and rubbers obtained by mixing these.
Among these, ethylene-propylene-diene rubber is preferable.
The foamed rubber layer preferably contains a rubber obtained by foaming and vulcanizing ethylene-propylene-diene rubber from the viewpoint of low resistance and resistance stability.
Further, from the viewpoint of compatibility and reactivity between rubber materials, a combination of EPDM and at least one rubber material selected from the group consisting of styrene-butadiene rubber, butyl rubber, NBR, and chloroprene rubber is preferable.

Examples of the ethylene-propylene-diene rubber include copolymers of ethylene, propylene, and dienes (such as ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene, and isophorone structures).
The content of the monomer unit obtained by polymerizing ethylene in the ethylene-propylene-diene rubber (ethylene content) is preferably 40% by mass or more and 80% by mass or less, and preferably 40% by mass or more and 70% by mass from the viewpoint of ozone resistance. It is more preferable that the amount is not more than mass%.
Further, the content of the monomer unit obtained by polymerizing propylene in the ethylene-propylene-diene rubber (propylene content) is preferably 20% by mass or more and 60% by mass or less from the viewpoint of ozone resistance, and 30% by mass. More preferably, it is 50 mass% or less.
The diene component in the ethylene-propylene-diene rubber is preferably ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene and the like from the viewpoint of ozone resistance.

An ethylene-propylene-diene rubber may be used individually by 1 type, or may use 2 or more types together.
The content of rubber obtained by foaming and vulcanizing ethylene-propylene-diene rubber in the foamed rubber layer is 50% by mass with respect to all rubber components forming the foamed rubber layer from the viewpoint of low resistance and resistance stability. Preferably, it is 80% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

The rubber material used for producing the foamed rubber layer may be used alone or in combination of two or more.
The rubber content in the foamed rubber layer is preferably 30% by mass or more and 90% by mass or less, and 40% by mass or more and 80% by mass or less with respect to the total mass of the foamed rubber layer from the viewpoint of resistance stability. It is more preferable that it is 50 mass% or more and 70 mass% or less.

-Carbon black-
The foamed rubber layer contains carbon black.
Examples of the carbon black include carbon black produced by a contact method (for example, channel black, roll black, disk black, etc.), carbon black produced by a furnace method (for example, gas furnace black, oil furnace black, etc.) And carbon black produced by a thermal method (for example, thermal black, acetylene black, etc.).
Among these, from the viewpoints of conductivity and resistance stability, at least one carbon black selected from the group consisting of ketjen black, oil furnace black, channel black, acetylene black, and thermal black is preferable, and includes acetylene black and thermal black. More preferred is at least one carbon black selected from the group.
Carbon black may be used independently and may be used in combination of 2 or more type.

As the carbon black, it is preferable to use two or more types of carbon blacks having different oil absorbability from the viewpoint of reducing variation in resistance. Specifically, it is preferable to use at least one of ketjen black and acetylene black, which have high oil absorption and excellent conductivity, and thermal black, which has low oil absorption and excellent rubber reinforcement. The combined use of these carbon blacks reduces belt resistance variations. Carbon blacks having different oil absorbency indicate carbon blacks having different DBP (dibutyl phthalate) oil absorption. The DBP oil absorption is a value defined in ASTM D2414-6TT.
Here, the use ratio of the carbon black is, for example, preferably at least one of ketjen black and acetylene black: thermal black = 1: 1 to 1: 8, and more preferably 1: 2 to 1: 5 by mass ratio. .

  In addition, from the viewpoint of resistance stability, in the rubber coating layer, among the two or more types of carbon blacks having different oil absorbability, the content of carbon black having the lowest oil absorbency is higher than the content of other carbon blacks. It is also preferable that there are many.

  The content of carbon black is preferably 10% by mass or more and 60% by mass or less, and preferably 20% by mass or more and 50% by mass or less with respect to the total mass of the foamed rubber layer, from the viewpoint of low resistance and resistance stability. More preferably, it is more preferably 25 mass% or more and 45 mass parts or less.

-Acid acceptor-
The foamed rubber layer preferably contains an acid acceptor from the viewpoint of resistance stability, and more preferably contains the foamed resin containing epichlorohydrin rubber and the acid acceptor.
Preferred examples of the acid acceptor include at least one compound selected from the group consisting of metal oxides and hydrotalcite.
Examples of the metal oxide include zinc oxide, magnesium oxide, lead oxide, calcium oxide, iron oxide, copper oxide, tin oxide, nickel oxide, titanium oxide, chromium oxide, cobalt oxide, and aluminum oxide.
Examples of the hydrotalcite include Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ hydrate.
Among these, as the acid acceptor, at least one compound selected from the group consisting of zinc oxide and magnesium oxide is particularly preferable from the viewpoint of resistance stability.

The acid acceptor may be used alone or in combination of two or more.
The content of the acid acceptor is preferably 0.1 parts by mass or more and 30 parts by mass or less, and 0.5% by mass or more and 20% by mass or less with respect to the total mass of the foam rubber layer from the viewpoint of resistance stability. It is more preferable that it is 1 mass% or more and 10 mass% or less.

-Vulcanizing agent-
The foamed rubber layer preferably contains rubber formed by foaming and vulcanization.
Examples of the vulcanizing agent for vulcanizing rubber include organic peroxides in addition to sulfur and organic sulfur-containing compounds. Examples of the organic sulfur-containing compound include tetramethylthiuram disulfide, N, N′-dithiobismorpholine, and the like. Examples of the organic peroxide include dicumyl peroxide and benzoyl peroxide.
A vulcanizing agent may be used individually by 1 type, or may use 2 or more types together.
The addition amount of the vulcanizing agent can be appropriately adjusted depending on the characteristics of the resin used and the use of the conductive roll, but 0.3 parts by mass with respect to 100 parts by mass of all rubber components used for forming the foam rubber layer. It is preferably 10 parts by mass or less, more preferably 1 part by mass or more and 8 parts by mass or less.

The foam rubber layer may contain rubber formed by foaming and peroxide vulcanization.
In the present embodiment, the crosslinking by the peroxide does not use a sulfur atom, but is also referred to as peroxide vulcanization.
The peroxide vulcanization in the production of the foamed resin is preferably performed using a peroxide.
The peroxide may be an inorganic peroxide or an organic peroxide, but an organic peroxide is preferred.
Examples of the organic peroxide include diisopropylbenzene hydroperoxide, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, t-butyl perbenzoate, cumyl hydroperoxide, t-butyl hydroperoxide, 1,1. -Di (t-butylperoxy) -3,3,5-trimethylhexane, n-butyl-4,4-di (t-butylperoxy) valerate, α, α'-bis (t-butylperoxyisopropyl) ) Benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, t-butylperoxycumene and the like.

A peroxide may be used individually by 1 type, or may use 2 or more types together.
The amount of peroxide used can be adjusted as appropriate depending on the characteristics of the resin used and the application of the conductive roll, but it is 0.1 parts by mass with respect to 100 parts by mass of the total rubber component used for forming the foam rubber layer. It is preferably -20 parts by mass, and more preferably 0.5-10 parts by mass.

-Vulcanization accelerator-
A vulcanization accelerator may be used for forming the foamed rubber layer in the conductive roll according to this embodiment.
As the vulcanization accelerator, various conventionally used ones are used, and it is particularly preferable to use a sulfenamide vulcanization accelerator. The addition amount of the vulcanization accelerator is preferably 0.3 parts by mass or more and 4 parts by mass or less, and 0.5 parts by mass or more and 3 parts by mass with respect to 100 parts by mass of all rubber components used for forming the foamed rubber layer. The following is more preferable.

-Foaming agent-
The foamed rubber layer is preferably formed using a foaming agent.
A known foaming agent can be used as the foaming agent, and it may be a chemical foaming agent or a physical foaming agent, but a chemical foaming agent is preferred from the viewpoint of handleability and storage stability.
The chemical foaming agent may be an inorganic compound or an organic compound, or two or more kinds may be used in combination.
Examples of organic chemical foaming agents include nitrosamine compounds such as dinitrosopentamethylenetetramine (DPT), azo compounds such as azodicarbonamide (ADCA), 4,4′-oxybisbenzenesulfonyl hydrazide (OBSH), and hydrazodicarbon. And hydrazine compounds such as amide (HDCA).
Examples of the inorganic chemical foaming agent include bicarbonates such as sodium bicarbonate, carbonates, combinations of bicarbonates and organic acid salts, and the like.
Among them, organic chemical foaming agents are preferable, nitrosamine compounds, azo compounds and hydrazine compounds are more preferable, azodicarbonamide (ADCA), 4,4′-oxybis (benzenesulfonylhydrazide) (OBSH), and dinitrosopentamethylenetetramine. Particularly preferred is at least one compound selected from the group consisting of (DTP).

  Examples of the physical foaming agent include inert gases such as nitrogen and carbon dioxide, and volatile organic compounds. Among them, it is preferable to use an inert gas, and it is preferable to use supercritical carbon dioxide, nitrogen, or a mixture thereof.

When using a chemical foaming agent, it is preferable to mix with the composition containing resin A, resin B, and ethylene-propylene-diene rubber, and to foam by heat.
When a physical foaming agent is used, it may be mixed with a composition containing Resin A, Resin B and ethylene-propylene-diene rubber under normal pressure or under pressure, and the composition may be foamed. May be impregnated and foamed.
There are no particular restrictions on the foaming method, but specific examples include a batch foaming method, a press foaming method, an atmospheric pressure foaming method, an atmospheric pressure secondary foaming method, and steam pressure heating foaming in a vulcanizer. Can be mentioned.
As the foaming agent and foaming method, the foaming agent and foaming method described in JP-A No. 11-106543, “Basic edition of new edition rubber technology”, edited by Japan Rubber Association can be referred to.

A foaming agent may be used individually by 1 type, may use 2 or more types together, and may use a chemical foaming agent and a physical foaming agent together.
Although the usage-amount of a foaming agent can be suitably adjusted with the characteristic of the resin to be used, and the use of a foam, it is 0.1-30 mass parts with respect to 100 mass parts of all the rubber components used for formation of a foamed rubber layer. It is preferably part by mass, more preferably 0.5 part by mass to 20 parts by mass, still more preferably 1 part by mass to 15 parts by mass, and particularly preferably 2 parts by mass to 10 parts by mass. preferable. It is excellent in resistance stability as it is the said range.

-Other additives-
The foamed rubber layer may contain other additives.
Examples of other additives include various known rubber additives. Specifically, for example, processing aids (such as stearic acid), foaming aids, softeners, plasticizers, curing agents, antioxidants, surfactants, coupling agents, fillers (silica, calcium carbonate, etc.) Etc.

There is no restriction | limiting in particular in the thickness of the said foamed rubber layer, What is necessary is just to select suitably according to a use. For example, when the conductive roll according to this embodiment is used as a transfer roll, the thickness of the foamed rubber layer is preferably 2 mm or more and 20 mm or less, and more preferably 2 mm or more and 15 mm or less.
Further, from the viewpoint of resistance stability, the thickness of the rubber coating layer is preferably smaller than the thickness of the foamed rubber layer.

The method of forming the foamed rubber layer is not particularly limited, but a method of forming a foamed rubber layer by vulcanizing and foaming a composition containing a rubber component, carbon black, a vulcanizing agent, and a foaming agent is preferable. Can be mentioned.
Vulcanization and foaming in the step of obtaining the foamed resin may be performed simultaneously or sequentially. When performing sequentially, it is preferable to foam after vulcanization.
The temperature and time during vulcanization and foaming are not particularly limited, and may be set as appropriate according to the vulcanization and foaming agent used.
Vulcanization and foaming are preferably performed by heating, and the heating temperature is preferably 50 ° C. or higher and 100 ° C. or lower.
The vulcanization may be performed by microwave vulcanization.
As a method for performing microwave vulcanization, for example, a method described in JP 2008-176027 A can be mentioned.

(Rubber coating layer)
The conductive roll according to the present embodiment has a rubber coating layer containing carbon black on the foamed rubber layer.
The preferred component and its preferred content in the rubber coating layer are the same as the preferred component and its preferred content in the foamed rubber layer, except that it is not foamed.
Moreover, it is preferable that the said rubber | gum coating layer contains the rubber | gum formed by vulcanizing ethylene-propylene-diene rubber from a viewpoint of low resistance and resistance stability.
Furthermore, from the viewpoint of resistance stability, the composition of the rubber component in the rubber coating layer and the composition of the rubber component in the foamed rubber layer are preferably 90% by mass or more, and preferably 95% by mass or more. It is more preferable.

  There is no restriction | limiting in particular in the thickness of the said rubber coating layer, What is necessary is just to select suitably according to a use. For example, when the conductive roll according to this embodiment is used as a transfer roll, the thickness of the rubber coating layer is preferably 0.1 mm or more and 5 mm or less, more preferably 0.2 mm or more and 2 mm or less, More preferably, it is 0.5 mm or more and 1.5 mm or less.

  The conductive roll according to the present embodiment is, for example, a charging roll for charging a surface on an image carrier in an electrophotographic copying machine, an electrostatic printer, or the like, and a toner image formed on the image carrier is used as a transfer medium. Transfer roller for transferring, toner conveying roll for conveying toner onto the image carrier, conductive roller for feeding or driving in combination with a conductive belt for electrostatically conveying paper, removing toner on the image carrier Used for cleaning rolls and the like. Further, in an inkjet image forming apparatus, the ink is used as a power supply roll for charging an intermediate transfer body before ink is ejected from an inkjet head.

<Transfer roll>
The transfer roll according to this embodiment is a transfer roll having the conductive roll according to this embodiment, and the conductive roll according to this embodiment itself is preferably a transfer roll.

<Image forming apparatus and process cartridge>
The image forming apparatus according to the present embodiment is an image forming apparatus having a conductive roll according to the present embodiment, and is preferably an image forming apparatus having a transfer roll according to the present embodiment. A charging unit that charges the image carrier, a latent image forming unit that forms a latent image on the surface of the charged image carrier, and a latent image formed on the surface of the image carrier is developed with toner to form a toner image. It is more preferable that the image forming apparatus includes: a developing unit that forms a toner image; and a transfer unit that includes the transfer roll according to the present embodiment and transfers the toner image formed on the surface of the image carrier to a recording medium. preferable.

In the transfer means, for example, a structure of a direct transfer system to a recording medium provided with a transfer roll alone, or an intermediate transfer member to which a toner image formed on the surface of the image carrier is transferred and the surface of the image carrier are used. The intermediate transfer system includes a primary transfer roll that transfers the formed toner image onto the surface of the intermediate transfer member and a secondary transfer roll that transfers the toner image transferred onto the surface of the intermediate transfer member onto a recording medium. It is done.
In the configuration of the direct transfer system, it is preferable that the transfer roll according to the present embodiment is provided as a transfer roll disposed to face the image carrier.
In the configuration of the intermediate transfer system, it is preferable that the transfer roll according to the present embodiment is provided as at least one of the primary transfer roll and the secondary transfer roll.
Furthermore, the conductive roll according to the present embodiment may be used as a power feeding or driving roll within the paper transport belt.

  As the image forming apparatus according to the present embodiment, for example, a normal monocolor image forming apparatus in which only a single color toner is accommodated in a developing device, a toner image held on an image holding member is directly transferred to a recording medium. An image forming apparatus, a color image forming apparatus that sequentially repeats primary transfer of a toner image held on an image holding member to an intermediate transfer member, and a plurality of image holding members each having a developing device for each color are connected in series on the intermediate transfer member. Any of the tandem type color image forming apparatuses arranged in the above may be used.

The process cartridge according to the present embodiment is a process cartridge having the conductive roll according to the present embodiment, and is preferably a process cartridge having the transfer roll according to the present embodiment, and has the transfer roll according to the present embodiment. It is more preferable that the process cartridge be provided with a transfer unit that transfers the toner image formed on the surface of the image carrier to a recording medium, and is detachable from the image forming apparatus.
Further, the process cartridge according to the present embodiment includes an image carrier, a charging unit that charges the image carrier, a latent image forming unit that forms a latent image on the surface of the charged image carrier, and an image carrier, as necessary. You may provide at least 1 type of means chosen from the image development means which develops the latent image formed on the surface of the body with toner, and forms a toner image.

  Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the present embodiment. The image forming apparatus forms an image in which the conductive roll according to the present embodiment is adapted to a primary transfer roll and a secondary transfer roll. Device.

  The image forming apparatus shown in FIG. 1 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed at a specific distance in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 as an intermediate transfer member is disposed through each unit. The intermediate transfer belt 20 is wound with tension applied to a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other in the left to right direction in FIG. The transfer unit for the image forming apparatus is configured to run in the direction toward the fourth unit 10K.
The support roll 24 is biased in a direction away from the drive roll 22 by a spring or the like (not shown), and a specific tension is applied to the intermediate transfer belt 20 wound around the support roll 24. An intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the drive roll 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K includes yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four color toners can be supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first unit 10Y that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. This will be explained as a representative. It should be noted that the second to fourth units are denoted by adding reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y) to the same parts as the first unit 10Y. Description of 10M, 10C, 10K is omitted.

The first unit 10Y has a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, a charging roll 2Y for charging the surface of the photoreceptor 1Y to a specific potential, and the charged surface is exposed by a laser beam 3Y based on the color-separated image signal to form an electrostatic image. An exposure device 3; a developing device (developing means) 4Y for developing the electrostatic image by supplying toner charged to the electrostatic image; a primary transfer roll 5Y (primary) for transferring the developed toner image onto the intermediate transfer belt 20; A transfer unit) and a photoconductor cleaning device (cleaning unit) 6Y for removing toner remaining on the surface of the photoconductor 1Y after the primary transfer with a cleaning blade are sequentially arranged.
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging roll 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive (volume resistivity at 20 ° C .: 1 × 10 ⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, it is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic image formed on the photoreceptor 1Y in this way is rotated to a specific development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

  For example, yellow toner is accommodated in the developing device 4Y. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoconductor 1Y on which the yellow toner image is formed continues to run at a specific speed, and the toner image developed on the photoconductor 1Y is conveyed to a specific primary transfer position.

When the yellow toner image on the photoconductor 1Y is conveyed to the primary transfer portion, a specific primary transfer bias is applied to the primary transfer roll 5Y, and the electrostatic force from the photoconductor 1Y toward the primary transfer roll 5Y generates toner. By acting on the image, the toner image on the photoreceptor 1 </ b> Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner.

  The intermediate transfer belt 20 onto which the four color toner images have been transferred through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20, the support roll 24 that contacts the inner surface of the intermediate transfer belt 20. To the secondary transfer portion constituted by the secondary transfer roll (secondary transfer means) 26. Note that a cleaning blade 27 made of an elastic material is in contact with the outer peripheral surface of the secondary transfer roll 26, and is not transferred from the intermediate transfer belt 20 to the recording medium P without being transferred to the outer peripheral surface of the secondary transfer roll 26. Adhering toner is removed.

  On the other hand, the recording medium P is fed at a specific timing to a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact via the supply mechanism, and a specific secondary transfer bias is applied to the support roll 24. . The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording medium P is applied to the toner image, so The toner image is transferred onto the recording medium P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording medium P is sent to a fixing device (fixing means) 28, the toner image is heated, and the color-superposed toner image is melted and fixed on the recording medium P. The recording medium P on which the color image has been fixed is unloaded to the discharge unit, and a series of color image forming operations is completed.

  The image forming apparatus exemplified above is configured to transfer the toner image to the recording medium P via the intermediate transfer belt 20, but the image forming apparatus according to the present embodiment is limited to the above configuration. Instead, a structure in which the toner image is directly transferred from the photosensitive member to the recording medium P may be employed.

  Examples will be described below, but the present invention is not limited to these examples. In the following description, “part” and “%” are all based on mass unless otherwise specified.

Example 1
As a rubber component, 60 parts of EPDM (ethylene-propylene-diene rubber, Esprene 505 manufactured by Sumitomo Chemical Co., Ltd.) was kneaded with a pressure kneader, and 7 parts of 4,4′-oxybisbenzenesulfonylhydrazide (OBSH) as a chemical foaming agent, As fillers, 12 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., DBP oil absorption = 212 ml / 100 g), 23 parts of thermal black (Asahi Carbon, DBP oil absorption = 103 ml / 100 g), zinc oxide (Nippon Chemical Industry ( 5 parts), vulcanization accelerator (Noxeller TS, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.5 parts, and vulcanization accelerator (Noxeller DT, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) 1.5 parts was added and further kneaded with two heating rolls. This mixture was inserted into a SUS cored bar (6 mmφ) and foamed into a roll to obtain a foamed roll.

60 parts of EPDM (ethylene-propylene-diene rubber, Esprene 505 manufactured by Sumitomo Chemical Co., Ltd.) as a rubber component was kneaded with a pressure kneader, and acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., dibutyl phthalate (DBP) oil absorption) Amount = 212 ml / 100 g) 12 parts, thermal black (Asahi Carbon Co., Ltd., DBP oil absorption = 103 ml / 100 g) 23 parts, zinc oxide (Nihon Chemical Industry Co., Ltd.) 5 parts, stearic acid 1 part, Sulfur accelerator (Noxeller TS, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.5 parts, and vulcanization accelerator (Noxeller DT, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) 1.5 parts are added 2 Further kneading was carried out with this heating roll. The obtained composition was extruded into a tube shape, and the outer tube was coated on the obtained foam roll to obtain a coated roll.
The resulting coated roll was cut to a size that was taken through a vulcanization furnace and dropped to 28 mmφ by cylindrical polishing, and a two-layer foam roll (conductive roll, rubber hardness 45 degrees, nip resistance 5.3 squared) Product, DC100V volume resistance value).

(Example 2)
In the same manner as in Example 1, except that each part of EPDM used in Example 1 was 40 parts, and 20 parts each of chloroprene rubber (CR, chloroprene WRT manufactured by Showa Denko KK) was used instead. A roll (nip resistance 4.7th power, rubber hardness 52 degrees product) was produced.

(Comparative Example 1)
Instead of 60 parts of EPDM, 30 parts of EPDM (ethylene-propylene-diene rubber, Esprene 505 manufactured by Sumitomo Chemical Co., Ltd.), 30 parts of NBR (Nipol DN401LL manufactured by Nippon Zeon Co., Ltd.), and GECO (epichlorohydrin-ethylene oxide) -Allyl glycidyl ether copolymer, 40 parts of Epichromer CG-107 (GECO, EO = 41%) manufactured by Osaka Soda Co., Ltd. was used in the same manner as in Example 1 except that 12 parts of acetylene black was not added. A two-layer foam roll was obtained (conductive roll, rubber hardness 43 degrees, nip resistance 6.7 product) The resistance of the conductive roll of Comparative Example 1 was not reduced sufficiently, and the environmental fluctuation was 1.2 digits. Yes, image quality was poor in a low temperature and low humidity environment.

(Comparative Example 2)
A conductive roll without a rubber coating layer was obtained in the same manner as in Example 1 except that the amount of acetylene black was changed from 12 parts to 23 parts and no outer tube was used (hardness 38 degrees, nip Resistance 4.35 product). In the conductive roll of Comparative Example 2, resistance unevenness was large, and meandering in the belt portion proceeded due to uneven wear of the foamed layer due to running, resulting in poor image quality such as density unevenness. In addition, secondary troubles (belt, paper stains, poor cleaning) due to transfer roll abrasion powder also occur, shortening the service life.

(Comparative Example 3)
When the amount of acetylene black of Example 2 was changed from 12 parts to 23 parts and no thermal black was used, the resistance decreased even though the resistance decreased (rubber hardness 63 degrees, nip resistance 4.3 product). In addition, resistance unevenness was 1.3 digits, and uneven density occurred.

<Evaluation>
The following evaluation was performed with respect to the obtained electroconductive roll, respectively.

(Measurement method of surface resistivity (Ω / □))
The surface resistivity of the rubber coating layer was measured at 23 ° C. and 55% RH on the surface of a conductive roll that had been energized for 100 hours after application of a voltage of 3 kV, with a diameter of 12 mm and a length of 330 mm separated by 10 mm in the circumferential direction. A SUS metal roll was brought into contact with a bite amount of 0.2 mm, a DC voltage (V) of 1 kV was applied between the metal rolls, and a current value (I) after 10 seconds from the voltage application was read. The surface resistivity μ _R (Ω / □) was obtained from the equation.
μ _R (Ω / □) = LV / GI
Here, L represents the length (cm) of the charging roll, and G represents the distance (cm) between the two metal rolls.

(Measurement method of nip resistance (Ω))
The nip resistance value (Ω) is a resistance when the load of 500 g is applied and a voltage of 1 kV (charge for 10 seconds) is applied, using a cylindrical electrode HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd. Measured at RH. In addition, the said measurement was made to contact the aluminum drum and measured at the nip part.

(Resistance stability)
A current was applied to a 78 mmφ aluminum drum with a direct current (DC) application current of 100 μA at a load of 500 g at both ends at 100 rpm for 100 hours, and resistance change and voltage dependency (difference between 10 V and 100 V values) were observed.

(Resistance unevenness (resistance uniformity))
The surface resistance on the surface of the conductive roll was measured at five locations, and the difference between the maximum value and the minimum value was defined as resistance unevenness.

(Image density unevenness)
When the conductive roll is mounted on a DC1100 (Fuji Xerox Co., Ltd.) belt tension cartridge as a power supply roll and a 50% halftone image is printed in a 23 ° C. and 55% RH environment, the image density unevenness (light / dark) And the occurrence of bleeding (smear)) was visually determined.

  Tables 1 and 2 list the composition of the foam rubber layer and the rubber coating layer and the evaluation results in the conductive rolls of each example.

1Y, 1M, 1C, 1K photoconductor (an example of an image carrier)
2Y, 2M, 2C, 2K charging roll (an example of charging means)
3. Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K Laser beams 4Y, 4M, 4C, 4K Developing device (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt (an example of an intermediate transfer member)
22 Drive roll 24 Support roll 26 Secondary transfer roll (an example of secondary transfer means)
30 Intermediate transfer member cleaning device P Recording paper (an example of a recording medium)

Claims (11)

On the conductive core material, it has a foam rubber layer containing carbon black, and a rubber coating layer containing carbon black in this order,
The surface resistivity μ _R (Ω / □) of the rubber coating layer and the nip resistance value μ _N (Ω) of the conductive roll satisfy the following formula (1),
The mu _N is conductive roll is less than 10 ⁶ Omega.
μ _R <μ _N (1)   The conductive roll according to claim 1, wherein the foamed rubber layer contains rubber obtained by foaming and vulcanizing ethylene-propylene-diene rubber.   The conductive roll according to claim 1 or 2, wherein the rubber coating layer includes a rubber obtained by vulcanizing ethylene-propylene-diene rubber.   The conductive roll according to any one of claims 1 to 3, wherein the foamed rubber layer contains two or more carbon blacks having different oil absorption properties as the carbon black.   5. The conductive material according to claim 4, wherein, in the foamed rubber layer, the content of carbon black having the lowest oil absorbency among the two or more types of carbon black having different oil absorbability is higher than the content of other carbon blacks. Sex roll.   The conductive roll according to any one of claims 1 to 5, wherein the rubber coating layer includes two or more carbon blacks having different oil absorption properties as the carbon black.   7. The conductive material according to claim 6, wherein, in the rubber coating layer, the content of the carbon black having the lowest oil absorption among the two or more types of carbon blacks having different oil absorption is higher than the content of the other carbon blacks. Sex roll.   The conductive roll according to any one of claims 1 to 7, wherein a thickness of the rubber coating layer is smaller than a thickness of the foamed rubber layer.   A transfer roll comprising the conductive roll according to claim 1.   A process cartridge having the transfer roll according to claim 9, comprising transfer means for transferring a toner image formed on the surface of the image holding member to a recording medium, and detachable from the image forming apparatus. An image carrier,
Charging means for charging the image carrier;
Latent image forming means for forming a latent image on the surface of the charged image carrier;
Developing means for developing a latent image formed on the surface of the image carrier with toner to form a toner image;
Transfer means comprising the transfer roll according to claim 9 and transferring a toner image formed on the surface of the image carrier to a recording medium;
An image forming apparatus comprising: