JP2018025621A - Electrophotographic belt and electrophotographic apparatus - Google Patents

Abstract

An electrophotographic belt provided with a conductive layer having high conductivity is provided. An electrophotographic belt 100 having an endless belt shape includes a base layer 101 having an endless belt shape and a conductive layer 102 provided on the base layer 101, and all or one of the conductive layers 102 is provided. Part is exposed on at least one of the outer peripheral surface and the inner peripheral surface of the electrophotographic belt 100, and the conductive layer 102 contains a resin as a binder, carbon black, a specific cation, and a specific anion. To do. [Selection] Figure 1

Description

  The present invention relates to an electrophotographic belt and an electrophotographic apparatus used in an electrophotographic image forming apparatus (hereinafter referred to as “electrophotographic apparatus”) such as a copying machine or a printer.

  In an electrophotographic apparatus, an electrostatic charge image carrier such as a photosensitive drum is charged, and the charged electrostatic charge image carrier is exposed to form an electrostatic latent image. Thereafter, the electrostatic latent image is developed with the frictionally charged toner, and the toner image is transferred and fixed to a recording medium such as paper, thereby forming a desired image on the recording medium.

  As a transfer method of an electrophotographic apparatus, an unfixed toner image on an electrostatic charge image carrier such as a photosensitive drum is primarily transferred to an intermediate transfer member, and then the unfixed toner image is transferred from the intermediate transfer member to a recording medium. An intermediate transfer method is used in which secondary transfer is performed. Such an intermediate transfer method is particularly employed in color electrophotographic apparatuses. In a color electrophotographic apparatus, toners of four colors (yellow, magenta, cyan, and black) are sequentially transferred from an image forming portion of each color onto an intermediate transfer member, and the resultant composite image is collectively transferred to a recording medium. Therefore, there are advantages such as high-speed printing and high-quality images. Each color image forming unit has primary transfer members (rollers or the like) facing each other through an intermediate transfer member, and a voltage power source dedicated to primary transfer is connected to each. Further, in the secondary transfer unit that transfers the composite image to the recording medium, there is similarly a secondary transfer member (a roller or the like) that faces the intermediate transfer member via the recording medium, and a voltage power source dedicated to secondary transfer. Is connected. Each of the power supplies individually sets an optimal primary transfer voltage and secondary transfer voltage.

  As described above, the conventional intermediate transfer method requires a plurality of power supplies in order to set appropriate primary transfer voltage and secondary transfer voltage. As a result, the image forming apparatus is increased in size and the cost is increased due to an increase in power supply. In order to deal with this problem, Patent Document 1 proposes an image forming apparatus that uses an intermediate transfer belt having conductivity in the circumferential direction and has a common primary transfer power source and secondary transfer power source. It is described that according to such an image forming apparatus, the number of power supplies can be reduced, and the cost and size of the image forming apparatus can be reduced.

JP 2012-137733 A

Patent Document 1 describes that, as an intermediate transfer belt for an image forming apparatus according to Patent Document 1, a belt having a multi-layer configuration and a surface layer having a higher resistance than other layers is used. Yes. Specifically, a base layer in which electric resistance is adjusted by dispersing carbon black in a polyphenylene sulfide resin having a thickness of 100 μm is formed, and a surface layer of a high-resistance acrylic resin having a thickness of 0.5 to 3 μm is formed on the outer surface of the base layer. The provided intermediate transfer belt is described.
The inventors of the present invention have studied to increase the amount of carbon black in the base layer in order to further improve the conductivity of the base layer in the intermediate transfer belt disclosed in Patent Document 1. However, as described in [0037] of Patent Document 1, the base layer containing a large amount of carbon black has insufficient strength and may be easily cracked. Therefore, in order to obtain an intermediate transfer belt having a highly conductive layer that can be suitably used in an image forming apparatus such as Patent Document 1, the conductivity is improved by a method other than increasing the amount of carbon black in the conductive layer. The present inventors have recognized that it is necessary to develop a technology capable of performing the above.

  Therefore, one embodiment of the present invention is directed to providing an electrophotographic belt including a conductive layer having high conductivity. The present invention is also directed to providing an electrophotographic apparatus that can be further reduced in cost and size.

According to one aspect of the invention,
An electrophotographic belt having an endless belt shape,
A base layer having an endless belt shape, and
Having a conductive layer provided on the base layer;
All or part of the conductive layer is exposed on at least one of the outer peripheral surface and the inner peripheral surface of the electrophotographic belt,
The conductive layer is
An electrophotographic belt containing a resin as a binder, carbon black, a cation represented by the following formula (1), and an anion represented by the following formula (2) is provided:

[R ₁ and R _{2 in} Formula (1) each independently represent a hydrocarbon group having 1 to 3 carbon atoms. ]

[R ₃ in Formula (2) represents a perfluoroalkyl group having 1 to 3 carbon atoms. ].

  According to another aspect of the present invention, there is provided an electrophotographic apparatus comprising the electrophotographic belt as an intermediate transfer belt.

  According to one embodiment of the present invention, a conductive layer having higher conductivity exceeding the conductivity exhibited by a conductive layer containing carbon black as the only conductive agent is provided, and the electrophotographic image can be stably formed over a long period of time. An electrophotographic conductive member that can be used for formation can be obtained. According to another aspect of the present invention, an electrophotographic apparatus that can achieve further cost reduction and size reduction can be obtained.

1 is a schematic view of an electrophotographic belt according to an embodiment of the present invention. It is the schematic of the belt for electrophotography which concerns on other embodiment of this invention. 1 is a schematic diagram of an electrophotographic apparatus according to an embodiment of the present invention. FIG. 4 is an enlarged schematic diagram of an image forming unit 205a in FIG. 3.

The present inventors have intensively studied a method for improving the conductivity of the conductive layer of the electrophotographic member without relying on an increase in the amount of carbon black.
By the way, the conductive agent includes an electronic conductive agent such as carbon black and an ionic conductive agent such as an ionic liquid.
Here, when a large amount of ionic liquid is contained in the conductive layer, leaching of the ionic liquid from the conductive layer over time (hereinafter also referred to as “bleed”) may occur. In consideration of such an upper limit, the conductivity that can be imparted to the conductive layer by the ionic liquid was considered to be lower than the conductivity that can be imparted by the electronic conductive agent.

  However, as a result of the study by the present inventors, a specific ionic liquid has a limited conductivity imparting ability when used alone as a conductive agent, but when used in combination with carbon black, It has been found that conductivity higher than that which can be imparted by black can be imparted. The specific ionic liquid is composed of a cation represented by the following formula (1) and an anion represented by the following formula (2).

In formula (1), R ₁ and R ₂ each independently represents a hydrocarbon group having 1 to 3 carbon atoms.

In Formula (2), R ₃ represents a perfluoroalkyl group having 1 to 3 carbon atoms.

  And the improvement effect of electroconductivity which is show | played by the combination of the ionic liquid which consists of the cation which concerns on Formula (1), and the anion which concerns on Formula (2), and carbon black is the combination of another ionic liquid and carbon black This combination is considered unique because it was not obtained.

The present invention has been made based on the above-described new findings by the present inventors.
Hereinafter, an electrophotographic member having an endless belt shape (hereinafter, also referred to as “electrophotographic belt”) according to one embodiment of the present invention will be described in detail.

<Electrophotographic belt>
The electrophotographic belt includes a base layer having an endless belt shape, and a conductive layer provided on the base layer. All or part of the conductive layer is exposed on at least one of the outer peripheral surface and the inner peripheral surface of the electrophotographic belt. The conductive layer contains a resin as a binder, carbon black, a cation represented by the following formula (1), and an anion represented by the following formula (2).

[R ₁ and R _{2 in} Formula (1) each independently represent a hydrocarbon group having 1 to 3 carbon atoms. ]

[R ₃ in Formula (2) represents a perfluoroalkyl group having 1 to 3 carbon atoms. ]

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following forms. First, the configuration of the electrophotographic belt according to the present invention will be described.

  FIG. 1A is a perspective view of a cylindrical electrophotographic belt according to an embodiment of the present invention. FIG.1 (b) is an enlarged view of the axial cross section of Fig.1 (a). In the electrophotographic belt 100 shown in FIG. 1, the conductive layer 102 exists on the inner peripheral surface of the base layer 101, and the entire conductive layer 102 is exposed on the inner peripheral surface of the electrophotographic belt. FIG. 2A is a perspective view of a cylindrical electrophotographic belt according to another embodiment of the present invention. FIG.2 (b) is an enlarged view of the axial cross section of Fig.2 (a). In the electrophotographic belt 100 shown in FIG. 2, the conductive layer 102 exists on the outer peripheral surface of the base layer 101. On the conductive layer 102, an outermost layer 103 that is in contact with a photosensitive drum or another member may be provided. In this case, the outermost layer 103 is preferably provided only in the image forming area, not on the entire surface in the axial direction of the electrophotographic belt. That is, it is preferable that a part of the conductive layer 102 is exposed on the surface (outer peripheral surface) of the electrophotographic belt in the non-image forming region and has the exposed portion 104 of the conductive layer. Although not shown, a conductive layer may be provided on both the inner and outer peripheral surfaces of the electrophotographic belt.

  The potential of the conductive layer can be made constant by connecting a constant voltage element such as a Zener diode to the exposed portion of the conductive layer in FIGS. 1 and 2 via a member that contacts the exposed portion. It becomes. As a result, a desired current can be supplied to all the photosensitive drums through the conductive layer, and not only secondary transfer but also primary transfer is possible. Details will be described later.

  Since the electrophotographic belt according to the present invention is used while being stretched by a plurality of rollers, it has an endless belt shape. The endless belt shape refers to, for example, a shape obtained by joining a sheet or film-like molded product in a cylindrical shape, and refers to a shape that can be stretched and rotated by a plurality of rollers. Among endless belt shapes, a seamless shape having no seam is preferable from the viewpoint of uneven thickness of the belt.

  Next, the constituent materials and forming method of each layer of the electrophotographic belt will be described in detail. In addition, the manufacturing method of the electrophotographic belt of the present invention is not particularly limited, and any manufacturing method other than the method described below may be used as long as the effects of the present invention are obtained.

[Base layer]
The base layer has an endless belt shape. Specific examples of the base layer include a semiconductive film in which a conductive agent is contained in a resin or a cylindrical seamless belt.

(resin)
As the resin, any of a thermoplastic resin and a thermosetting resin can be used. Examples of the thermoplastic resin include the following. Polycarbonate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polylactic acid (PLLA), polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, Polyphenylene sulfide, polyether sulfone, polyether nitrile, thermoplastic polyimide, polyether ether ketone, thermotropic liquid crystal polymer, polyamic acid and the like. Moreover, as a thermosetting resin, the following are mentioned, for example. Thermosetting polyimide, phenol resin, polyester resin, amino resin, epoxy resin, melamine resin, thermosetting polyurethane resin, thermosetting acrylic resin, fluorine-modified resin, etc. One of these may be used alone, or two or more may be used as a blended and alloyed mixture.

(Conductive agent)
In the base layer, an electron conductive material, an ion conductive material, or the like can be used as a conductive agent. As the electron conductive substance, conductive polymers such as carbon black, antimony-doped tin oxide, titanium oxide, polyaniline, polypyrrole, and polythiophene can be used. As the ion conductive substance, sodium perchlorate, lithium, cationic or anionic ionic surfactant, nonionic surfactant, ionic liquid, oligomer or polymer compound having an oxyalkylene repeating unit can be used. It is. In the base layer, additives such as an antioxidant, an ultraviolet absorber, a pH adjuster, a crosslinking agent, a pigment, and an elastomer can be added as necessary.

(Formation method of base layer)
For example, when a thermosetting resin such as polyimide is used as the resin, the base layer disperses carbon black as a conductive agent as a varnish together with a polyimide precursor or a soluble polyimide and a solvent. Then, it coats using apparatuses, such as centrifugal molding, and can shape | mold as a seamless belt through a baking process. The thickness of the base layer is preferably 10 μm or more and 500 μm or less, and more preferably 30 μm or more and 150 μm or less.
When a thermoplastic resin is used as the resin, carbon black, which is a conductive agent, resin, and additives as necessary are mixed, melted and kneaded using a biaxial kneader, etc. Conductive pellets are produced. Next, a semiconductive film can be obtained by extruding the pellets into a sheet shape, a film shape or a seamless belt shape by melt extrusion. Moreover, it can also shape | mold by hot press and injection molding, and a semiconductive film can also be obtained by extending-blowing the preform formed.

The electric resistance of the base layer thus obtained is preferably such that the volume resistivity when 250 V is applied is 1.0 × 10 ⁸ Ω · cm or more and 1.0 × 10 ¹² Ω · cm or less. The rate is preferably 1.0 × 10 ⁸ Ω / □ or more and 1.0 × 10 ¹² Ω / □ or less. By controlling the electrical resistance within the semiconductive region, it is possible to suppress transfer image defects due to a transfer voltage shortage associated with charge-up in a low humidity environment or during continuous driving.

[Conductive layer]
The conductive layer contains carbon black as a conductive agent, a resin as a binder, a cation represented by the formula (1), and an anion represented by the formula (2). The surface resistivity of the conductive layer when 10 V is applied is 1.0 × 10 ⁷ Ω / □ from the viewpoint of supplying a primary transfer voltage equivalent to a conventional primary transfer configuration having a plurality of transfer power sources to each photosensitive drum. Or less, more preferably 5.0 × 10 ⁶ Ω / □ or less.

(Carbon black)
As carbon black, it is preferable to use ketjen black having high conductivity. The content of carbon black in the conductive layer is preferably 14 parts by mass or more with respect to 100 parts by mass of the resin used for the conductive layer. Further, from the viewpoint of physical deterioration such as wear and wear due to rubbing with other sliding members (for example, a transfer roller and a cleaning blade), the carbon black content is 18 masses relative to 100 mass parts of the resin. Part or less. That is, the content of carbon black is more preferably 14 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the resin.

(resin)
The resin used for the conductive layer is not particularly limited, and any of a thermoplastic resin, a thermosetting resin, and a photocurable resin can be used. Considering the thickness of the conductive layer, the resin or the raw material of the resin is preferably one that can be dissolved in a solvent to form a thin layer containing the resin or a thin layer containing the resin raw material. For example, soluble polyimide, curable urethane resin, and curable acrylic resin can be used. In particular, a curable acrylic resin is preferable as a raw material of the resin from the viewpoint of improving the rubbing resistance and increasing the hardness of the conductive layer. Examples of the curable acrylic resin include a monomer having a (meth) acryloyl group, an oligomer having a (meth) acryloyl group, and a polymer having a (meth) acryloyl group. And it is more preferable that a conductive layer contains 1 or more types of hardened | cured material selected from the group which consists of the said monomer, the said oligomer, and the said polymer. The “(meth) acryloyl group” means an acryloyl group or a methacryloyl group.

  Examples of monomers and oligomers having a (meth) acryloyl group include polyfunctional (meth) acrylic monomers and oligomers. Specific examples include tri (meth) acrylate of ethoxylated isocyanuric acid, 2-hydroxy-3- (meth) acryloyloxypropyl methacrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, tricyclodecane dimethanol Di (meth) acrylate, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, trimethylolpropane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate , Isocyanuric acid ethylene oxide modified tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (Meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and dipentaerythritol poly (meth) acrylate. Note that “(meth) acryl” means acryl or methacryl, and “(meth) acrylate” means acrylate or metallate.

  As the polymer having a (meth) acryloyl group, a solvent-soluble acrylic polymer or the like can be used. The solvent-soluble acrylic polymer can form a resin film only by volatilizing the solvent from the coating film of the solution. Therefore, cost merit can be obtained in manufacturing the conductive layer. These curable resins may be used alone or in combination of two or more for curing shrinkage and hardness adjustment.

  In addition to the hardened | cured material of above-described curable resin, the conductive layer may contain other resin in the range which does not impair the effect of this invention. Other resin may be used individually by 1 type, and may use 2 or more types together.

(Cation and anion)
The cation used in the present invention has an imidazolium structure represented by the formula (1). R ₁ and R ₂ in the formula (1) each independently represent a hydrocarbon group having 1 to 3 carbon atoms. The hydrocarbon group is preferably an alkyl group having 1 to 3 carbon atoms. Specific examples of the imidazolium structure represented by the formula (1) include 1,3-dimethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1,3-diethylimidazolium cation, 1-propyl- Examples thereof include 3-ethylimidazolium cation and 1,3-dipropylimidazolium cation.

The anion has a sulfonate structure represented by the formula (2). R ₃ in the formula (2) represents a perfluoroalkyl group having 1 to 3 carbon atoms. Specific examples of the sulfonate structure represented by the formula (2) include a trifluoromethanesulfonate anion, a pentafluoroethanesulfonate anion, and a heptafluoropropanesulfonate anion.

  As said cation and anion, the thing derived from an ionic liquid with high compatibility to resin can be used, for example. The cation and anion are preferably derived from an ionic liquid comprising the cation and anion. When using an ionic liquid, it is preferable to contain 0.1 mass part or more and 5 mass parts or less of ionic liquid with respect to 100 mass parts of resin used for the said conductive layer. When the content of the ionic liquid is 0.1 parts by mass or more, the conductivity necessary for this configuration can be sufficiently obtained. In addition, when the content of the ionic liquid is 5 parts by mass or less, it is possible to suppress the occurrence of contamination of the photosensitive drum and other contact members due to bleedout of the ionic liquid.

  The cation and the anion may be contained in the electroconductive belt of the electrophotographic belt which is the final form. Therefore, for example, a cation and an anion are previously contained in the base layer adjacent to the conductive layer, and when the conductive layer is wet-coated on the base layer, a cation and an anion are used using a solvent that erodes the base layer. It is also possible to use a method such as elution (migration) of ions into the conductive layer and inclusion in the conductive layer.

  The chemical structure of the ionic liquid can be identified using pyrolysis GC / MS, IR, NMR, or elemental analysis after the ionic liquid is isolated from the conductive layer by an appropriate means. Further, the content of the ionic liquid in the conductive layer can be determined by a quantitative ratio relationship when extracting from the conductive layer shaved from the transfer belt. As a solvent used for extraction, a solvent capable of dissolving the ionic liquid is selected. Specifically, solvents such as tetrahydrofuran (THF), ethyl acetate, and methyl ethyl ketone (MEK) are preferable. And the content of an ionic liquid can be quantified by removing the solvent in the solution after extraction using a rotary evaporator, and isolating by various chromatography.

(Method for forming conductive layer)
Although the formation method of a conductive layer is not specifically limited, For example, the raw material which comprises the said conductive layer, and a solvent are mixed, and additives, such as a polymerization initiator and a leveling agent, are added as needed, and a liquid mixture is obtained. As the solvent, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or the like can be used. As the polymerization initiator and the leveling agent, known ones can be appropriately selected and used. The obtained mixed solution is applied onto the endless belt-like base layer by application means such as dip coating, spray coating, ring coating, roll coating and the like. Thereafter, the solvent is dried and removed, and then the coating film is cured by heat curing or an active energy irradiation device such as an ultraviolet ray or an electron beam to form a conductive layer. The thickness of the conductive layer is preferably 0.05 μm or more and 20 μm or less, and more preferably 0.1 or more and 5 μm or less from the viewpoint of cracking or bending resistance.

  The conductive layer preferably has an average hardness of 0.10 GPa or more in a region of 10% to 20% in the thickness (film thickness) direction from the outermost surface in a nanoindenter measurement method using a Barkovic indenter. The region below 10% of the film thickness of the conductive layer near the outermost surface is easily affected by the measurement environment such as indenter vibration, and the region outside 20% of the film thickness of the conductive layer is affected by the base layer. Easy to receive. Therefore, excluding these regions, the average hardness in the region of 10% to 20% of the film thickness of the conductive layer is calculated. By setting the average hardness in the region of the conductive layer to 0.10 GPa or more, physical properties such as wear and wear due to friction with other sliding members (for example, a transfer roller and a cleaning blade) mounted on the electrophotographic apparatus. Generation of mechanical deterioration can be suppressed. The upper limit of the average hardness in the region of the conductive layer is not particularly limited, but by setting it to 0.50 GPa or less, physical damage to a sliding member mounted in a general electrophotographic apparatus can be suppressed. This is preferable because it is possible. That is, the average hardness in the region of the conductive layer is more preferably 0.10 GPa or more and 0.50 GPa or less.

[Outermost layer]
The electrophotographic belt according to the present invention is suitably applied to the outer peripheral surface of the base layer or the conductive layer on the base layer for the purpose of close contact with other contact members such as a photosensitive drum or a cleaning blade and prevention of blocking. An outer layer can be provided. The resin used for the outermost layer is not particularly limited, but considering the thickness of the outermost layer, a resin that is soluble in a solvent and capable of forming a thin layer is preferable. As the resin, for example, a soluble polyimide curable urethane resin or acrylic resin can be used. Of these, acrylic resins are preferred from the viewpoint of rubbing resistance and hardness. Specifically, acrylic monomers, oligomers, polymers, and other resins exemplified as the raw material of the resin in the conductive layer can be used as the outermost layer resin.

  In addition to the resin, it is preferable to add filler particles or a lubricant as an additive to the outermost layer, and specific examples include the following. Alumina, titania, silica, zirconia, zinc oxide, zinc antimonate, tin oxide, ITO (tin doped indium oxide), ATO (antimony doped tin oxide), molybdenum disulfide, boron nitride, silicon nitride, layered clay mineral, silicone particles, PTFE (polytetrafluoroethylene) particles, fluororesin particles, carbon black, graphite, carbon nanotubes, carbon microcoils, graphene, silicone oil, fluorine oil, perfluoropolyether. Among these, PTFE particles are preferable from the viewpoint of reducing frictional resistance.

  When using PTFE particles, it is preferable to contain PTFE particles in a range of 10% by mass to 70% by mass, and in a range of 30% by mass to 50% by mass with respect to 100% by mass of the resin used for the outermost layer. More preferably. By containing the PTFE particles in the above range, adhesion with other contact members and blocking can be prevented. Moreover, a conductive agent, a curing agent, an antioxidant, an ultraviolet absorber, a pH adjuster, a crosslinking agent, and a pigment can be added to the outermost layer as necessary.

  Furthermore, the surface of the outermost layer may be provided with an uneven shape. By providing an uneven shape, in addition to the effects of the filler particles and additives such as lubricants, the contact area with other contact members is reduced, and a further reduction in frictional resistance is possible. The method for imparting the uneven shape is not particularly limited.For example, the transfer belt having the outermost layer supported by the core or the like is rotated in the circumferential direction while contacting the wrapping film containing abrasive grains. The method of grind | polishing the surface of an outer layer and providing uneven | corrugated shape is mentioned. Also, a method such as imprinting for contacting a mold that has been processed into a desired shape in advance can be used. The thickness of the outermost layer is preferably 0.05 μm or more and 20 μm or less, and more preferably 0.1 or more and 5 μm or less from the viewpoint of cracking and bending resistance.

<Electrophotographic device>
Next, an example in which the electrophotographic belt of the present invention is used as an intermediate transfer belt in an electrophotographic apparatus will be described with reference to FIG.
FIG. 3 is a schematic diagram of a full-color electrophotographic apparatus using the intermediate transfer belt 200 of the present invention. The intermediate transfer belt 200 is supported by three rollers including a driving roller / secondary transfer counter roller 201 and stretching rollers 202 and 203. In order to drive the intermediate transfer belt 200, the driving roller / secondary transfer counter roller 201 is provided with a rubber layer having a high frictional resistance on the surface layer. The rubber layer has a conductivity with a volume resistivity of 1.0 × 10 ⁵ Ω · cm or less. The driving roller / secondary transfer counter roller 201 forms a secondary transfer roller 204 and a secondary transfer portion via the intermediate transfer belt 200. The tension roller 202 is provided with a rubber layer, and the rubber layer has a conductivity with a volume resistivity of 1.0 × 10 ⁵ Ω · cm or less. Further, the tension roller 203 can be a metal roller. The secondary transfer roller 204 is pressed against the driving roller / secondary transfer counter roller 201 via the intermediate transfer belt 200. As the secondary transfer roller 204, an elastic roller having a volume resistivity of 1.0 × 10 ⁷ Ω · cm to 1.0 × 10 ⁹ Ω · cm can be used. The tension rollers 202 and 203 and the secondary transfer roller 204 rotate following the intermediate transfer belt 200.

  The electrophotographic apparatus according to the present invention includes a photosensitive drum for forming a toner image, an intermediate transfer belt on which the toner image is primarily transferred in contact with the photosensitive drum, and the intermediate transfer belt facing the intermediate transfer belt. A secondary transfer member for secondary transfer of the toner image, and the secondary transfer member has a power supply capable of applying a voltage for secondary transfer. As the intermediate transfer belt, the electrophotographic belt according to the present invention can be used. The power supply applies a voltage to the secondary transfer member, and causes a current to flow from the secondary transfer member to the photosensitive drum via the intermediate transfer belt, thereby causing the intermediate transfer belt to transfer the current from the photosensitive drum to the intermediate transfer belt. The toner image is primarily transferred. Thus, in the present invention, the primary transfer power source and the secondary transfer power source are shared.

  The electrophotographic apparatus according to the present invention will be described more specifically. The electrophotographic apparatus according to the present invention includes an image forming unit 205a that forms a yellow image, an image forming unit 205b that forms a magenta image, an image forming unit 205c that forms a cyan image, and a black color. The image forming unit 205d is provided with four image forming units. The image forming unit 205a will be described in detail below as an example. FIG. 4 is an enlarged schematic diagram of the image forming unit 205a. The image forming unit 205a includes a photosensitive drum 206a that is an image carrier, and is driven to rotate at a predetermined process speed. Around the photosensitive drum 206a, a charging roller 207a as a charging member, a developing member 209a in which toner 208a is stored, and a drum cleaning member 210a are installed. Further, an exposure member 211a is installed on the photosensitive drum 206a between the charging roller 207a and the developing member 209a. The photosensitive drum 206a is charged by the charging roller 207a, and the charged electrostatic charge image carrier is exposed by the exposure member 211a to form an electrostatic latent image (toner image). Thereafter, the electrostatic latent image is developed by the toner 208a frictionally charged in the developing member 209a, and transferred to the intermediate transfer belt 200 installed at a position facing each image forming portion by the primary transfer voltage (hereinafter, “ Referred to as “primary transfer”). Similarly, in the image forming units 205b, 205c, and 205d, primary transfer is performed in synchronization with the rotation of the intermediate transfer belt 200, and a four-color toner composite image is formed. At this time, it is preferable that one or more metal rollers 212 serving as a primary transfer facing member are provided between the image forming units 205b and 205c via the intermediate transfer belt 200 at a position facing the image forming unit. By forming the primary transfer portion with the metal roller 212 that presses the intermediate transfer belt 200 against the opposing image forming portion, the primary transfer portion width (nip) can be stabilized widely.

  A recording medium 213 such as paper is supplied to a position on the intermediate transfer belt 200 that is downstream of the position of the fourth image forming unit 205d. At the same position, a secondary transfer roller 204 (secondary transfer member) is disposed. The gap formed by the intermediate transfer belt 200 and the secondary transfer roller 204 and the vicinity thereof where the toner image is transferred onto the recording medium on the intermediate transfer belt 200 is referred to as a secondary transfer portion. As shown in FIG. 3, the secondary transfer unit preferably includes a nip between the driving roller / secondary transfer counter roller 201 and the secondary transfer roller 204. When the non-image portion immediately before the toner composite image formed on the intermediate transfer belt 200 reaches the secondary transfer portion, a voltage having a polarity opposite to that of the toner is applied from the voltage power source 214 that supplies current to the secondary transfer roller 204. Is done. Then, when the recording medium 213 passes through the secondary transfer portion in the direction of the arrow Vf in FIG. 3, the four color toner composite images on the intermediate transfer belt 200 are collectively transferred onto the recording medium 213. . This transfer is referred to as “secondary transfer”. The recording medium 213 on which the secondary transfer has been performed is subjected to a fixing process by a fixing unit (not shown) to become a color image. On the other hand, the toner remaining on the intermediate transfer belt 200 without being subjected to the secondary transfer is scraped off by a cleaning blade 215 that comes into contact with the belt surface on which the stretching roller 202 is disposed at an arbitrary timing, and is stored in the waste toner box 216. To be recovered. In this way, the surface of the intermediate transfer belt 200 returns to the initial state.

  The electrophotographic apparatus according to the present invention obtains the transfer voltage necessary for the primary transfer from the voltage power source 214 in addition to the transfer voltage necessary for the secondary transfer. The intermediate transfer belt 200 in the present invention has, for example, a conductive layer on the inner peripheral surface of the belt. Also, as shown in FIG. 3, the four rollers 201, 202, 203, and 212 that are in contact with the inner peripheral surface of the intermediate transfer belt are connected to a Zener diode 217 that is a constant voltage element and are grounded. For this reason, the potential of the conductive layer of the intermediate transfer belt becomes constant in the circumferential direction by the voltage applied from the voltage power source 214. As a result, the potential difference between the photosensitive drum and the intermediate transfer belt in each of the image forming units 205a, 205b, 205c, and 205d is substantially equal, and the currents flowing through the photosensitive drums are also substantially equal, enabling primary transfer. Since the resistance value of the recording medium itself changes due to environmental changes such as temperature and humidity during image formation, the secondary transfer voltage is preferably changed within a certain range. In the electrophotographic apparatus according to the present invention, the Zener diode 217 is connected even when the secondary transfer voltage fluctuates, for example, when the secondary transfer voltage further increases. Flows. Thereby, the potential of the conductive layer can be kept constant, and the primary transferability can be stabilized. Specifically, the applied voltage of the voltage power source 214 is preferably 1000 to 3500 V, and the Zener potential is preferably 220 to 300 V. According to the present invention, by having the above-described transfer configuration, primary transfer and secondary transfer can be stably performed by one transfer power source.

  In addition, the electrophotographic apparatus having the above-described transfer configuration in which the electrophotographic belt of the present invention is mounted as an intermediate transfer belt can supply a sufficient transfer voltage to the image forming unit even when the amount of carbon black added is reduced. It is possible to suppress the occurrence of image defects over a long period of time.

  Hereinafter, the present invention will be described using examples and comparative examples. Prior to the examples, a method for measuring each of the conductive layers of the intermediate transfer belt (hereinafter also referred to as “transfer belt”) and image quality evaluation will be described.

<Evaluation 1. Measurement of hardness of conductive layer>
The hardness of the conductive layer was measured using a Barcovic indenter using a microindentation hardness tester (trade name: Nanoindenter G200, manufactured by Agilent Technologies, Inc.). The measurement region was a region of 10% to 20% in the thickness direction from the outermost surface of the conductive layer, and the average hardness in this region was calculated.

<Evaluation 2. Measurement of surface resistivity of conductive layer>
The surface resistivity of the conductive layer was measured using a resistivity meter (trade name: Hiresta UP MCP-HT450 type, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) in accordance with Japanese Industrial Standard (JIS) K6911. Under an environment of a temperature of 23 ° C. and a relative humidity of 50%, the URS probe was brought into contact with the exposed portion of the conductive layer, and the value after 10 seconds was taken as a measured value. Four points were measured in the circumferential direction of the belt for each 90 ° phase, and an average value of the measured values was calculated.

<Evaluation 3. Image quality evaluation>
The primary transfer counter member and the like provided in the electrophotographic apparatus (trade name: LaserJet Enterprise Color M552dn, manufactured by Japan HP Co., Ltd.) were removed and changed to the apparatus configuration shown in FIG. At that time, the Zener potential was set to 220V. Further, the transfer belt provided in the electrophotographic apparatus was removed, and a transfer belt according to each of the following examples and comparative examples was attached instead.
For image evaluation, a solid image of a secondary color was output on A4 size plain paper (trade name: CS814, manufactured by Canon Inc.) using cyan and magenta developers, and the resulting solid image was output. It was observed visually. And the presence or absence of the local image quality defect resulting from the transfer nonuniformity accompanying the transfer voltage shortage and the lack of carbon black was evaluated according to the following criteria.
Rank A: Good with no transfer unevenness or image quality defect.
Rank B: There is transfer unevenness.
Rank C: There is an image defect.
Rank N: Cannot be evaluated due to film scraping of the conductive layer.

  In Table 1, the first solid image for a new transfer belt is designated as “initial” for image evaluation, and the first image output after endurance of paper passing is “after 75,000 images” (in Table 1). (Abbreviated as “75k sheets”). The paper passing durability conditions are shown below. On an A4 size plain paper, 75,000 images (hereinafter referred to as “E character images”) in which the letter “E” of size 4 points was formed to have a printing density of 1% were output. For the image formation, a black developer mounted on the print cartridge of the electrophotographic apparatus was used. The image was output in an environment of normal humidity and normal temperature (23 ° C., relative humidity 50%).

  Hereinafter, specific examples and comparative examples will be described. In the following examples and comparative examples, some of the mixed liquid materials are diluted / dispersed with a solvent, but the amount of each material used (parts by mass) is the amount related to the nonvolatile content unless otherwise specified. It means the amount from which the solvent (volatile matter) has been removed. In Table 1, the material composition of the conductive layers of the transfer belts 1 to 16 and the evaluation results of the transfer belt according to Examples 1 to 5 and Comparative Examples 1 to 11 are shown. Moreover, in Table 2, it shows about the ionic compounds 1-4 in Table 1.

[Example 1]
(Preparation of base layer)
As a base layer, a transfer belt (endless belt shape, thickness 70 μm, electric resistance; volume resistivity: 2.2 × 10 ¹⁰ ) provided in an electrophotographic apparatus (trade name: LaserJet Enterprise Color M552dn, manufactured by Japan HP). Ω · cm, surface resistivity: 1.0 × 10 ¹⁰ Ω / □) was used.

(Formation of conductive layer)
As resin of the conductive layer, dipentaerythritol hexaacrylate (hereinafter referred to as “DPHA”) (trade name: Light Acrylate DPE-6A, manufactured by Kyoeisha Chemical Co., Ltd.) 100 parts by mass, carbon black (Ketjen Black), MHI 15 parts by mass of black # 273 (trade name, manufactured by Mikuni Color Co., Ltd.), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (ionic compound 1, manufactured by Wako Pure Chemical Industries, Ltd.) 3 as an ionic liquid Part by mass and 5 parts by mass of a photopolymerization initiator (trade name: Irgacure (registered trademark) 184, manufactured by BASF Japan Ltd.) were mixed. And it diluted with methyl ethyl ketone so that resin solid content concentration might be 6 mass%, and it stirred with the stirrer, and obtained the liquid mixture for uniform conductive layer formation. This mixed solution is uniformly applied to the inner peripheral surface of the base layer by a spray method, dried at 60 ° C. for 1 minute to remove the solvent, and then cured by irradiating with ultraviolet rays to form a thickness on the inner peripheral surface of the base layer. A transfer belt 1 having a 2 μm conductive layer was obtained. In addition, using an ultraviolet irradiation device (trade name: UE06 / 81-3, manufactured by Eye Graphics Co., Ltd.) as an ultraviolet ray source, the ultraviolet ray is irradiated until the integrated light quantity reaches 1000 mJ / cm ² , and the conductive layer UV is irradiated. Curing was performed. The obtained transfer belt 1 was subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

[Examples 2 and 3]
Transfer belts 2 and 3 were produced in the same manner as in Example 1 except that each component was blended in the content shown in Table 1 when the mixed liquid for forming the conductive layer was obtained. The obtained transfer belts 2 and 3 were subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

[Example 4]
When obtaining a mixed liquid for forming a conductive layer, the resin is changed from DPHA to pentaerythritol triacrylate (abbreviated as “PETA” in the table) (trade name: Aronix (registered trademark) M-305, manufactured by Toagosei Co., Ltd.). A transfer belt 4 was produced in the same manner as in Example 1 except that the change was made. The obtained transfer belt 4 was subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

[Example 5]
Except that the resin was changed from DPHA to UV curable acrylic polymer (trade name: Acryt 8KX-012C, manufactured by Taisei Fine Chemical Co., Ltd.) when obtaining the mixed liquid for forming the conductive layer, the same as in Example 1. A transfer belt 5 was produced. The obtained transfer belt 5 was subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

[Comparative Examples 1-3]
Transfer belts 6 to 8 were produced in the same manner as in Example 1 except that each component was blended in the contents shown in Table 1 when the mixed liquid for forming the conductive layer was obtained. The obtained transfer belts 6 to 8 were subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

[Comparative Examples 4 to 6]
Transfer belts 9 to 11 were produced in the same manner as in Example 1 except that the ionic compounds 2 to 4 shown in Table 1 were used when obtaining the mixed liquid for forming the conductive layer. The obtained transfer belts 9 to 11 were subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1. Table 2 shows the properties of the products used as the ionic compounds 2 to 4 and the structures of cations and anions contained in the ionic compounds.

[Comparative Examples 7 to 11]
When obtaining the liquid mixture for forming the conductive layer, as shown in Table 1, Example 1 was used except that carbon black was not used and ionic compounds 1 to 4 were blended in the blending amounts shown in Table 1, respectively. In the same manner, transfer belts 12 to 16 were produced. The obtained transfer belts 12 to 16 were subjected to the above evaluations 1 to 3. The evaluation results are shown in Table 1.

  The evaluation results shown in Table 1 are described below. As for the surface resistivity of the conductive layer, it was found from the results of the transfer belts 1 and 3 that the transfer belt according to the present invention exhibited sufficiently high conductivity even when the amount of carbon black was reduced.

  Further, regarding the transfer belts 12 to 13 including the conductive layer containing the ionic compound 1 as the only conductive agent and the transfer belts 6 to 7 including the conductive layer including carbon black as the only conductive agent, When the surface resistivity is compared, the transfer belts 12 to 13 are larger. However, the surface resistivity of the conductive layers of the transfer belts 1 and 2 according to Examples 1 and 2 in which carbon black and the ionic compound 1 are used together as the conductive agent is that of the transfer belts 6 to 7 and 12 to 13. It is smaller than them. That is, when the ionic compound 1 and carbon black are used in combination as the conductive agent, it can be seen that the conductivity of the conductive layer is improved as compared with the case where each conductive agent is used alone.

  On the other hand, the transfer belts 14 to 16 provided with a conductive layer containing the ionic compounds 2 to 4 as the only conductive agent and the transfer belts 6 to 7 provided with the conductive layer containing carbon black as the only conductive agent were electrically conductive. When comparing the surface resistivity of the layers, the transfer belts 14 to 16 using an ionic conductive agent are still larger. The surface resistivity of the conductive layer of the transfer belts 9 to 11 that uses carbon black and any one of the ionic compounds 2 to 4 as the conductive agent includes the same amount of carbon black as the only conductive agent. It is about the same as the surface resistivity of the conductive layer of the transfer belt 7.

  From these results, it can be seen that the combination of ionic compound 1 and carbon black has an effect of improving conductivity, which cannot be obtained by any combination of ionic compounds 2 to 4 and carbon black.

  Regarding the image quality evaluation, in the transfer belts 1 to 5 containing the ionic compound 1, from the initial stage until after the end of 75,000 sheets, a local image resulting from transfer unevenness or carbon black loss due to insufficient transfer voltage is obtained. Defects did not occur and good images were obtained. On the other hand, in the transfer belts 6 and 7 containing only carbon black as a conductive agent, local image defects due to the lack of carbon black occurred after the paper passing durability. Although the addition of the ionic compound 1 to the conductive layer may have contributed to the binding property between the carbon black and the resin, details are not clear.

DESCRIPTION OF SYMBOLS 100 Electrophotographic belt 101 Base layer 102 Conductive layer 103 Outermost layer 104 Exposed portion 200 of conductive layer Intermediate transfer belt

Claims (12)

An electrophotographic belt having an endless belt shape,
A base layer having an endless belt shape, and
Having a conductive layer provided on the base layer;
All or part of the conductive layer is exposed on at least one of the outer peripheral surface and the inner peripheral surface of the electrophotographic belt,
The conductive layer is
An electrophotographic belt comprising a resin as a binder, carbon black, a cation represented by the following formula (1), and an anion represented by the following formula (2):

[R ₁ and R _{2 in} Formula (1) each independently represent a hydrocarbon group having 1 to 3 carbon atoms. ]

[R ₃ in Formula (2) represents a perfluoroalkyl group having 1 to 3 carbon atoms. ].   The electrophotographic belt according to claim 1, wherein the resin contains an acrylic resin.   The acrylic resin includes one or more cured products selected from the group consisting of a monomer having a (meth) acryloyl group, an oligomer having a (meth) acryloyl group, and a polymer having a (meth) acryloyl group. 2. An electrophotographic belt according to 2.   The electrophotographic belt according to any one of claims 1 to 3, wherein the cation is a 1-ethyl-3-methylimidazolium cation, and the anion is a trifluoromethanesulfonate anion.   The belt for electrophotography according to any one of claims 1 to 4, wherein the cation and the anion are derived from an ionic liquid composed of the cation and the anion.   6. The electrophotographic belt according to claim 5, wherein the conductive layer contains the ionic liquid in an amount of 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the resin.   The belt for electrophotography according to any one of claims 1 to 6, wherein the conductive layer contains the carbon black in an amount of 14 parts by mass to 18 parts by mass with respect to 100 parts by mass of the resin.   The conductive layer according to any one of claims 1 to 7, wherein an average hardness in a region of 10% to 20% in the thickness direction from the outermost surface is 0.10 GPa or more in a nanoindenter measurement method using a Barkovic indenter. The electrophotographic belt according to one item.   The electrophotographic belt according to claim 1, wherein all or part of the conductive layer is exposed on an outer peripheral surface or an inner peripheral surface of the electrophotographic belt.   An electrophotographic apparatus comprising the electrophotographic belt according to claim 1 as an intermediate transfer belt. A photosensitive drum for forming a toner image;
An intermediate transfer belt on which the toner image is primarily transferred in contact with the photosensitive drum;
A secondary transfer member facing the intermediate transfer belt and secondarily transferring the toner image to a recording medium;
A power source capable of applying a secondary transfer voltage to the secondary transfer member;
With
The intermediate transfer belt is the electrophotographic belt according to any one of claims 1 to 9,
The power source applies a voltage to the secondary transfer member to cause a current to flow from the secondary transfer member to the photosensitive drum via the intermediate transfer belt, so that the toner is transferred from the photosensitive drum to the intermediate transfer belt. An electrophotographic apparatus characterized by primary transfer of an image.   The electrophotographic apparatus according to claim 11, wherein the intermediate transfer belt is connected to a constant voltage element and grounded.

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