JP4654727B2 - Semiconductive belt and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a semiconductive belt used in an image forming apparatus such as a copying machine, a printer, and a facsimile, in particular, a semiconductive belt containing an elastic material, and an image forming apparatus using the same.

In an image forming apparatus such as a copying machine, a printer, or a facsimile, an image is formed on an image carrier such as a photosensitive drum, and this image is indirectly applied to a recording material via a semiconductive belt (intermediate transfer belt). There are already provided ones that transfer or directly transfer to a recording material on a semiconductive belt (paper conveying belt).
On the other hand, in order to obtain high-quality transfer image quality in recent years, there is a tendency to use a small-diameter spherical toner as the toner. Since the toner is reduced in diameter and spherical, the toner is easily moved by a transfer electric field. This causes a problem of toner scattering.

  In this type of intermediate transfer belt (paper conveyance belt), from the viewpoint of maintaining good transfer performance of the image from the image carrier, the nip area between the intermediate transfer belt (paper conveyance belt) and the image carrier, It is necessary to increase the pressure in the nip region between the intermediate transfer belt (paper conveyance belt) and the transfer member sufficiently and to increase the adhesion.

On the other hand, an intermediate transfer belt (paper transport belt) having a belt base material itself formed of an elastic material such as a flexible rubber material has already been provided.
In general, when a rubber material is used as the belt base material, various chemicals are added to the rubber material in order to satisfy the properties such as ozone resistance, flame retardancy, and deterioration prevention. There is a concern that a so-called bleed phenomenon that precipitates on the surface of the conveyor belt may occur. Therefore, when a flexible rubber material is used, a surface layer is provided to prevent bleeding.

Further, when an elastic body such as chloropyrene rubber in which carbon black or the like is dispersed is used as a transfer / conveying belt, a semiconductive resistance region at a level of 10 ⁹ Ωcm is a region where resistance control is difficult, and therefore a normal rubber It is almost impossible to stably obtain a desired resistance value by adding ordinary conductive carbon black to the material. It is difficult to stably produce variations in the resistance of the elastic belt within one digit (log Ωcm value), and when the in-plane variation in resistance is more than one digit, the transfer voltage cannot be applied uniformly, so the transfer image quality is low. There is a problem that it is not stable.
Furthermore, the belt holds the transfer material, and a transfer voltage of 1 kV to 5 KV is applied to transfer the toner image to the transfer material. However, the applied voltage changes the resistance value of the belt material, and the transfer material There was a problem that the resistance value changed between a certain part and a part without a transfer material.

  In response to such technical problems, if a mixed base material of chloroprene rubber and EPDM is used as the belt base material of the paper conveyance belt, excellent ozone resistance and flame retardancy can be exhibited, and the bleed phenomenon A technology that can effectively avoid the above has already been provided (for example, see Patent Document 1). Further, in Patent Document 1, if acetylene black, furnace black and acetylene black, or acetylene black and ketjen black are dispersed in the belt base material, fluctuations in electrical resistance over time can be suppressed. It is also disclosed that this can be done.

  Further, the conveyor belt has the same problem as the conventional semiconductive belt. That is, when a filler such as carbon or a metal compound is dispersed in a polymer resin, the resistance variation in the intermediate transfer body due to the dispersed state of the filler is as large as about one digit or more, and a slight high between the filler and the filler. For example, the resistance of the intermediate transfer member is lowered with time due to dielectric breakdown of the molecular resin portion or rearrangement of the filler due to energization. As described above, when the printout is performed, there is a problem that the volume resistivity of the intermediate transfer member is partly or entirely deviated from the range of the good volume resistivity with time and the image quality is deteriorated.

Furthermore, by using a water-based urethane resin containing fluororesin particles as the surface layer of the transport belt having a two-layer structure, the surface roughness of the surface layer and the elastic layer is regulated, thereby suppressing the belt surface wear. It has been proposed that generation of cracks can be prevented (see, for example, Patent Document 2).
However, this proposal uses a carbon-dispersed rubber material as a belt for the elastic layer, and it is difficult to stably produce the above-described elastic belt resistance variation within one digit (log Ωcm value). Is larger than 1 digit, the transfer voltage cannot be applied uniformly, and there is a problem that the transfer image quality is not stable. Further, the belt holds the transfer material, and a transfer voltage of 1 kV to 5 KV is applied to transfer the toner image to the transfer material. This applied voltage changes the resistance value of the belt material, and the transfer material There was a problem that the resistance value changed between a certain part and a part without a transfer material.

On the other hand, as a belt material having a multi-layer structure, for example, a multi-layered endless belt made of plastic, or a belt in which a polyolefin urethane layer is applied to the surface of a rubber belt has been proposed (see, for example, Patent Documents 3 and 4). . However, a multi-layered endless belt made of plastic has a problem of poor toner transfer due to its high hardness. Also, the belt with a polyolefin urethane layer, which is a thermoplastic elastomer, applied to the rubber belt surface is spray-coated with polyolefin urethane on the rubber belt, resulting in variations in the coating thickness in the surface direction. There is a drawback that the dimensional accuracy is poor. In addition, polyolefin-based urethane has a large amount of sag (deformation with time), and has a disadvantage that it adversely affects a copied image.
JP-A-9-179414 JP-A-11-352802 Japanese Patent Laid-Open No. 11-24428 Japanese Patent Laid-Open No. 11-45015

  The present invention has been made in order to solve the above technical problem. By uniforming the electric resistance, the present invention has a simple structure, is stable over a long period of time, and has good uniform transferability and image quality. Furthermore, by using a specific surface layer, the bleeding phenomenon can be surely prevented even when the surface is always in contact with the image carrier, and transfer caused by contamination on the surface of the semiconductive belt member can be prevented. An object of the present invention is to provide a semiconductive belt which prevents a decrease in performance. Another object of the present invention is to provide an image forming apparatus that includes the semiconductive belt and can stably obtain a high-quality transfer image quality.

The object has been achieved by the present invention described below.
That is, the present invention
<1> A semiconductive belt used in an image forming apparatus for electrophotography, which has at least a base material and a surface layer, and the base material uses a rubber material as a matrix, and at least a part of the belt is conductive. an elastic material containing rubber particles at least part of which is crosslinked and has a further, JIS a hardness of the elastic material state, and are 70 degrees or less than 50 degrees,
Absolute value of the difference between the solubility parameter [delta] (SP1) of the rubber material is a matrix of the base material, the solubility parameter of the rubber material which is a main component of the rubber particles [delta] (SP2) is that having a following relationship This is a semiconductive belt.
| SP1-SP2 | <1.0 [J ^1/2 cm ^2/3 ]

< 2 > A semiconductive belt used in an electrophotographic image forming apparatus, having at least a base material and a surface layer, wherein the base material has a rubber material as a matrix, and at least a part of the belt is conductive. And elastic material containing rubber particles that are at least partially crosslinked, and the elastic material has a JIS A hardness of 50 degrees or more and 70 degrees or less,
The material constituting the surface layer is a two-component curable water-based urethane resin coating composition containing at least fluororesin particles and carbon black, and the content of the fluororesin in the surface layer is The semiconductive belt is 30 to 70 parts by mass with respect to 100 parts by mass of the urethane resin, and further contains 5 to 20 parts by mass of carbon black in the surface layer.

< 3 > The semiconductive belt according to <1> or <2> is stretched between a plurality of stretch rolls and is arranged in contact with the drum-shaped image carrier. An image forming apparatus.

< 4 > The image forming apparatus according to < 3 >, wherein a spherical toner having a shape factor SF defined by the following formula (1) of 100 to 140 is used.
Formula (1)
SF = [(maximum length of toner particles) ² / (projected area of toner particles)] × π / 4 × 100

  The present invention makes it possible to obtain a uniform transfer property and image quality that are stable over a long period of time and have good image quality by making the electric resistance uniform, and further, by using a specific surface layer, image bearing is achieved. Even if it is always in contact with the body, the bleed phenomenon can be reliably prevented, and a semiconductive belt can be provided that prevents the transfer performance from deteriorating due to contamination on the surface of the semiconductive belt member. In addition, the present invention can provide an image forming apparatus that includes the semiconductive belt and can stably obtain high-quality transfer image quality.

<Semiconductive belt>
The semiconductive belt of the present invention is a semiconductive belt used in an image forming apparatus for electrophotography, and has at least a base material and a surface layer, and the base material uses a rubber material as a matrix, It is made of an elastic material containing rubber particles (hereinafter sometimes referred to as “rubber particles in the present invention”) having at least a part of conductivity and at least a part of which is cross-linked. The hardness is 50 degrees or more and 70 degrees or less. The semiconductive belt of the present invention having the above-described configuration can obtain stable and good uniform transferability and image quality over a long period of time with a simple configuration by making the electric resistance uniform.

The semiconductive belt according to the first aspect of the present invention includes a solubility parameter δ (SP1) of a rubber material that is a matrix of a base material and a solubility parameter δ (SP2) of a rubber material that is a main component of the rubber particles. The absolute value of the difference has the following relationship.
| SP1-SP2 | <1.0 [ J 1/2 cm 2/3]
Furthermore, in the semiconductive belt of the second aspect of the present invention, the material constituting the surface layer is a two-component curable water-based urethane resin coating composition comprising at least fluororesin particles and carbon black, And content of the fluororesin in the said surface layer is 30-70 mass parts with respect to 100 mass parts of urethane-type resin, Furthermore, content of carbon black in the said surface layer is 5-20 mass parts. . By having the surface layer, the bleeding phenomenon can be surely prevented even when it is always in contact with the image bearing member, and the transfer performance can be prevented from being deteriorated due to contamination on the surface of the semiconductive belt member. Can do.

(Base material)
First, the base material (elastic layer) in the semiconductive belt of the present invention will be described.
The base material in the semiconductive belt of the present invention is made of an elastic material containing rubber particles having a rubber material as a matrix, at least a part of which is conductive, and at least a part of which is cross-linked. The JIS A hardness is 50 degrees or more and 70 degrees or less.
Here, the above “at least a part is electrically conductive and at least a part is crosslinked” means that the rubber particles in the present invention are mixed with a rubber material and a conductivity imparting agent and crosslinked as described later. Therefore, it means that there are variations in conductivity and cross-linking in the rubber particles.

  Some of the rubber particles have conductivity. The rubber particles, which are partially conductive, can be solidified in a state where the rubber particles are dispersed in a small amount by crosslinking while kneading together with the rubber material that is the matrix of the base material. Accordingly, the rubber particle diameter is reduced, and variations in resistance value can be suppressed.

The conductivity is obtained by adding a conductive agent and crosslinking while kneading. Carbon black is preferable as the conductive agent. It is preferable that a rubber component having a small resistance variation in the middle resistance region is uniformly dispersed in a rubber material which is a matrix of the base material by using a conductive agent such as carbon black. Therefore, the volume resistivity of the rubber component is preferably 10 ⁰ to 10 ⁴ Ωcm (more preferably 10 ² to 10 ⁴ ), and the amount added is 2 to 2 in the rubber material which is the matrix of the base material. It is preferably 50 parts by mass (more preferably 10 to 30 parts by mass).
As the conductive agent, in addition to carbon black, a known conductive material such as a conductive metal oxide such as tin oxide can be used.

The degree of crosslinking of the rubber particles can be determined from the ratio of the amount of rubber components in the residue to the initial composition after the rubber particles are dissolved in an appropriate solvent (for example, trifluoroacetic acid) and filtered. The value is preferably 80% or more (gelation rate 80% or more).
As the crosslinking agent, isocyanates, melamines, methylated, ethylated, epoxy resins, bisphenol type epoxy resins, epoxy-based polymers, and the like, and blends thereof can be used. Moreover, other additives other than these can also be used as needed. The addition amount of the crosslinking agent is preferably 0.1 to 10 parts by mass (more preferably 0.5 to 5 parts by mass) with respect to 100 parts by mass of the rubber particles in the present invention.

Various rubbers can be used as the rubber material which is the main component of the rubber particles in the present invention. For example, diene rubber and hydrogenated products thereof (for example, NR, IR, hydrogenated NBR, hydrogenated SBR), olefin rubber (for example, ethylene propylene (EPDM, EPM), maleic acid modified ethylene / propylene rubber (M- EPM), IIR, isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM) ionomer, halogen-containing rubber (for example, bromide of Br-IIR, Cl-IIR, isobutylene paramethylstyrene copolymer ( BIMS), CR, hydrin rubber (CHR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid modified chlorinated polyethylene (M-CM), silicone rubber (eg methyl vinyl silicone rubber, methyl phenyl vinyl) Silicone rubber), ion-containing rubber (example) If, Porisufidogomu), fluororubber (for example, vinylidene fluoride rubbers, fluorine-containing vinyl ether rubbers, fluorine-containing phosphazene rubbers) can be mentioned, NR Among these, EPDM is preferable.
In the present invention, “main component” means that the content in the rubber particles in the present invention is 50% by mass or more.

  In the present invention, the blending amount of the rubber particles with respect to 100 parts by mass of the elastic material is added so as to obtain a desired volume resistivity, preferably 2 to 50 parts by mass, and more preferably 10 to 40 parts by mass. When the blending amount of the rubber particles in the elastic material is less than 2 parts by mass, the resistance becomes high and a desired resistance may not be obtained. On the other hand, if it exceeds 50 parts by mass, the resistance is too low and image quality defects such as white spots may occur.

On the other hand, specific examples of the rubber material that is the matrix of the base material include rubber materials similar to the rubber material that is the main component of the rubber particles in the present invention, and preferred examples are also the same.
In addition to the rubber particles in the present invention, the elastic material is appropriately blended with a crosslinking agent, a filler and the like as necessary.
The crosslinking agent in this case is not particularly limited, and conventionally known ones such as thiourea, triazine, sulfur and the like can be mentioned. Examples of the filler include insulating fillers such as silica, talc, clay and titanium oxide, and these may be used alone or in combination.

  In the semiconductive belt of the present invention, it is preferable that the rubber material which is the matrix of the base material and the rubber material which is the main component of the rubber particles in the present invention are substantially the same. When the rubber material that is the matrix of the base material and the rubber material that is the main component of the rubber particles are substantially the same, the rubber particles in the present invention are uniformly dispersed in the rubber material that is the matrix of the base material. This is preferable because the conductive agent can be dispersed well and a specific volume resistivity can be stably obtained. In the present invention, “substantially the same” means that 70 mol% or more of the constituent components are the same.

In the semiconductive belt of the present invention, the rubber material that is the matrix of the base material and the rubber material that is the main component of the rubber particles in the present invention are preferably compatible.
Specifically, the absolute value of the difference between the solubility parameter δ (SP1) of the rubber material that is the matrix of the base material and the solubility parameter δ (SP2) of the rubber material that is the main component of the rubber particles in the present invention is: It is preferable to have the following relationship.
| SP1-SP2 | <1.0 [J ^1/2 cm ^2/3 ]

  The | SP1-SP2 | is preferably less than 1.0, and more preferably less than 0.5. When | SP1-SP2 | is 1.0 or more, the rubber particles in the present invention may not be uniformly dispersed in the rubber material that is the matrix of the base material.

The solubility parameter δ (SP value) is represented by the following formula (2). In the following formula (2), δ2d, δ2p ′, and δ2h are SP values due to dispersion force, polarity effect, and hydrogen bonding, respectively. In general, the solubility parameter δ (SP value) is a value represented by δ = (E / Vm) 1/2 where E (cal = 4.1868J) and the molecular volume are Vm, where δ is large. It shows that polarity is so large.
Expression (2) δ = δ2d + δ2p ′ + δ2h

  As the SP value of the rubber material, polyurethane (SP value = 10), chlorinated polyisoprene (SP value = 9.35), NBR (SP value = 9.3), chloropyrene rubber (SP value = 8.71) EPDM (SP value = 8.0), hydrogenated polybutadiene (SP value = 8.08), butyl rubber (SP value = 7.85), silicone rubber (SP value = 7.45). Examples of the resin material having a large SP value include polyacrylonitrile (SP value = 13.55), polyvinyl alcohol (SP value = 12.60), epoxy resin (SP value = 10.9), and polyvinyl chloride (SP value = 9). .74), polyvinyl acetate (SP value = 9.57), and polystyrene (SP value = 9.03). Examples of the resin material having a small SP value include polyethylene (SP value = 7.88), polyisobutylene ((SP value = 7.7), polytetrafluoroethylene (SP value = 6.2).

  As described above, the JIS A hardness of the elastic material is required to be 50 degrees or more and 70 degrees or less, preferably 52 degrees or more and 68 degrees or less, and 55 degrees or more and 65 degrees or less. More preferred. If the JIS A hardness of the elastic material is less than 50 degrees, the dimensional change over time due to the belt tension becomes large, the dimensional change of the belt becomes large for long-term use, and the belt driving becomes difficult. Problems such as deterioration in toner superimposition accuracy and color misregistration occur. On the other hand, when the JIS A hardness of the elastic material exceeds 70 degrees, the belt becomes hard, and the followability to the surface can be improved when used in close contact with the surface of the image carrier or when using paper with irregularities on the surface. As a result, problems such as poor toner transferability occur.

  The elastic material in the present invention can be produced by mixing the above components with a mixer such as a tumbler, V-type blender, Nauta mixer, Banbury mixer, kneading roller, extruder or the like. In the production of the substrate in the present invention, the mixing method of each component and the order of mixing are not particularly limited. As a general method, all components are mixed in advance with a tumbler, V blender, etc., and uniformly melt-mixed by an extruder. Depending on the shape of the components, two or more types of molten mixtures in these components are used. Alternatively, a method of melt-mixing the remaining components can be used.

(Surface layer)
The surface layer in the present invention is a two-component curable water-based urethane resin coating composition comprising at least fluororesin particles and carbon black, and the fluororesin in the surface layer. It is preferable that the content is 30 to 70 parts by mass with respect to 100 parts by mass of the urethane-based resin, and further the content of carbon black in the surface layer is 5 to 20 parts by mass.
Since the surface layer having the above-described structure includes fluororesin particles having a small surface energy, the surface energy of the semiconductive belt surface can be reduced, and therefore, the dirt adheres to the surface of the semiconductive belt. Hateful. Furthermore, since carbon black is contained, the dynamic friction coefficient between the semiconductive belt and the semiconductive belt surface (image carrier) can be reduced, and the surface energy of the semiconductive belt surface is reduced. Due to this synergistic effect, contamination of the surface of the semiconductive belt can be effectively prevented.

  The material constituting the surface layer is a material using water as a solvent, and usually does not require characteristics such as solvent resistance to the material of the base material compared to the solvent-based material. Since there is no evaporation, there are advantages such as environmental friendliness. Furthermore, by using a urethane resin as a binder resin material, the urethane resin is composed of a soft segment mainly composed of a long-chain polyol and a hard segment containing an isocyanate compound, so that it is easy to deform the substrate. Can follow. Further, by using a blocked isocyanate compound used as a curing agent, bleeding (bleeding) of the low molecular component of the base material to the surface layer can be suppressed.

  Although content of the fluororesin contained in the said surface layer is not specifically limited, It is preferable to exist in the range of 30-70 mass parts with respect to 100 mass parts of urethane resins, and exists in the range of 40-60 mass parts. It is more preferable. The surface layer may also contain other resin components other than the fluororesin. When the content of the fluororesin contained in the surface layer is less than 30 parts by mass, the surface energy of the surface of the semiconductive belt member becomes large, so that dirt such as toner adhesion may easily adhere. is there. Moreover, when larger than 70 mass parts, other required components other than a fluororesin may not be contained in a required amount in a surface layer.

  Examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polyvinylidene fluoride (PVDF). , Tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), fluoroolefin-vinyl ether copolymer, Examples thereof include resins such as vinylidene fluoride-tetrafluoroethylene copolymer and vinylidene fluoride-hexafluoropropylene copolymer. You may use these individually or in combination of 2 or more types.

(Surface roughness)
The ten-point average surface roughness Rz of the surface layer in the semiconductive belt of the present invention is preferably in the range of 1.5 to 9.0 μm, and more preferably in the range of 3.0 to 6.0 μm. If the 10-point average surface roughness Rz is less than 1.5 μm, it may be in close contact with the contact member, and if the 10-point average surface roughness Rz is greater than 9.0 μm, the toner and paper dust may be formed on the uneven portions. And the like, and the slight unevenness of discharge due to the unevenness may cause uniform transferability and image quality to deteriorate over time.

In the present invention, the ten-point average surface roughness Rz is the surface roughness defined in JIS B0601.
The ten-point average surface roughness Rz can be measured using a surface roughness measuring instrument or the like. In the present invention, however, a contact-type surface roughness measuring device (in a 23 ° C./55 RH% environment) Surfcom 570A, manufactured by Tokyo Seimitsu Co., Ltd.) was used. When measuring the surface of the semiconductive belt member, the measurement distance was 2.5 mm, the tip of the contact needle was diamond (5 μmR, 90 ° cone), and the measurement was repeated three times at different locations. The average value was determined as the ten-point average surface roughness Rz of the semiconductive belt member.

  The thickness of the surface layer is preferably in the range of 5 μm to 100 μm, and more preferably in the range of 15 to 50 μm. When the thickness of the surface layer is less than 5 μm, the effect of preventing the contamination of the surface of the semiconductive belt member may not be obtained. On the other hand, when the thickness is larger than 100 μm, the surface hardness of the semiconductive belt member becomes unnecessarily large, so that sufficient adhesion to the surface of the image carrier may not be obtained.

  In the semiconductive belt of the present invention, the contact angle of the surface layer with respect to water (hereinafter sometimes abbreviated as “contact angle”) is preferably 90 degrees or more, more preferably 100 degrees or more, Preferably it is 115 degrees or more. When the contact angle of the surface layer with respect to water is 90 degrees or more, the surface is hardly contaminated, and contamination of the surface of the semiconductive belt member can be effectively prevented. On the other hand, when the contact angle is less than 90 degrees, the toner gradually adheres and accumulates on the surface of the semiconductive belt member. Image quality may be degraded. The method for measuring the contact angle is as follows.

-Contact angle measurement method-
The contact angle can be measured using a goniometer or the like. In the present invention, water is dropped on the surface of the semiconductive belt in an environment of 23 ° C. and 55% RH, and the contact is left for 10 seconds. The angle was measured using a contact angle measuring device CA-X roll type (manufactured by Kyowa Interface Science Co., Ltd.). In addition, the average value at the time of repeating the measurement three times at different locations was determined as the contact angle of the semiconductive belt member.

(Volume resistivity)
The volume resistivity of the semiconductive belt of the present invention is preferably 1 × 10 ⁸ to 1 × 10 ¹³ Ωcm, more preferably 1 × 10 ⁹ to 1 × 10 ¹² Ωcm. If the volume resistivity is 1 × 10 ⁸ to 1 × 10 ¹³ Ωcm, the toner is scattered around the image due to electrostatic repulsion between the toners and the fringe electric field near the image edge (blur). Problems are less likely to occur. In addition, within the above range, the volume resistivity of the semiconductive belt (especially when applied to an intermediate transfer member) is in a range where the charged charge is appropriately attenuated. Image formation can be performed continuously.

Here, the volume resistivity can be measured according to JIS K6911 using a circular electrode (for example, HR probe of Hiresta IP manufactured by Dia Instruments). A method for measuring the volume resistivity will be described with reference to FIG. FIG. 3 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode. The circular electrode shown in FIG. 3 includes a first voltage application electrode A ′ and a second voltage application electrode B ′. The first voltage application electrode A ′ has a cylindrical electrode part C ′ and a cylindrical shape having an inner diameter larger than the outer diameter of the cylindrical electrode part C ′ and surrounding the cylindrical electrode part C ′ at a constant interval. Ring-shaped electrode portion D ′. The semiconductive belt 101 is sandwiched between the cylindrical electrode portion C ′ and the ring-shaped electrode portion D ′ and the second voltage application electrode B ′ in the first voltage application electrode A ′, and the first voltage application electrode A ′. The current I (A) that flows when the voltage V (V) is applied between the cylindrical electrode portion C ′ and the second voltage application electrode B ′ is measured, and the volume resistance of the semiconductive belt 1 is calculated by the following equation. The rate ρv (Ωcm) can be calculated. Here, in the following formula, t represents the thickness of the semiconductive belt 1.
Formula: ρv = 19.6 × (V / I) × t

<Image forming apparatus>
The image forming apparatus of the present invention is an intermediate transfer member type image forming apparatus, and the above-described semiconductive belt of the present invention is stretched around a plurality of stretching rolls to form a drum-shaped image carrier. There is no particular limitation as long as they are arranged in contact with each other. For example, a normal monocolor image forming apparatus that contains only a single color toner in a developing device, or a color image in which a toner image carried on an image carrier such as a photosensitive drum is subjected to primary transfer sequentially to an intermediate transfer member Any of a forming apparatus, a tandem color image forming apparatus in which a plurality of image carriers having developing units for respective colors are arranged in series on an intermediate transfer member may be used.
In the image forming apparatus of the present invention, even when the semiconductive belt of the present invention is used in a state of being stretched on a plurality of stretch rolls, the resistance stability is good and preferable.

In the image forming apparatus of the present invention, the above-described semiconductive belt of the present invention is preferably used as a transfer conveyance belt and an intermediate transfer belt.
In this case, for example, as shown in FIG. 1, the image forming apparatus of the present invention has an image carrier 6 and a semiconductive belt 1 facing the image carrier 6, and a toner image formed on the image carrier 6 is semi-finished. In the image forming apparatus for transferring to the recording material 7 on the conductive belt (intermediate transfer belt) 1 or the semiconductive belt (transfer conveyance belt) 1, the above-described semiconductive belt is used as the semiconductive belt 1. It is characterized by.

Here, in the embodiment in which the semiconductive belt 1 is used as an intermediate transfer belt, as shown in FIG. 1, the toner image on the image carrier 6 is transferred to the semiconductive belt (intermediate transfer belt) by the primary transfer device 8a. After the primary transfer to the belt 1, the toner image on the semiconductive belt (intermediate transfer belt) 1 is secondarily transferred to the recording material 7 by the secondary transfer device 8 b.
On the other hand, in a mode in which the semiconductive belt 1 is used as a transfer conveyance belt (recording material holding belt), the recording material 7 is held on the semiconductive belt (transfer conveyance belt) 1 as shown in FIG. After that, the toner image on the image carrier 6 is transferred to the recording material 7 on the semiconductive belt (transfer conveyor belt) 1 by the transfer device 8.

In the image forming apparatus shown in FIG. 1, it is preferable that the semiconductive belt 1 is stretched around a plurality of stretching rolls 9 and is arranged in contact with the drum-shaped image carrier 6.
According to this aspect, by causing the semiconductive belt 1 to follow the shape of the image carrier 6 as much as possible, discharge due to useless gaps before and after the nip area at the time of transfer is eliminated, and scattering of the toner image is prevented. be able to.
Further, in the image forming apparatus shown in FIG. 1, it is preferable that one of the image carrier 6 and the semiconductive belt 1 is used as a drive source and the other is driven to rotate.
According to this aspect, by adopting such a drive configuration, one drive mechanism can be omitted, the drive cost can be reduced correspondingly, and the drive between the semiconductive belt 1 and the image carrier 6 can be suppressed. Variation factors such as thickness variation of the semiconductive belt 1 due to interference and feed variation in the process direction can be excluded.

Hereinafter, an embodiment of the image forming apparatus of the present invention will be described in detail with reference to FIG.
In FIG. 2, the image forming apparatus follows the shape of the photosensitive drum 10 in a certain area to the photosensitive drum 10 and the photosensitive drum 10 in order to transfer the toner image from the photosensitive drum (image carrier) 10. The intermediate transfer belt 20 in contact therewith. The photosensitive drum 10 is provided with a photosensitive layer whose resistance value is reduced by light irradiation. Around the photosensitive drum 10, a charging device 11 for charging the photosensitive drum 10 and a charged photosensitive member are provided. An exposure device 12 for writing an electrostatic latent image of each color component (in this example, yellow, magenta, cyan, black) on the drum 10 and each color component latent image formed on the photosensitive drum 10 with each color component toner A rotary type developing device 13 that visualizes the image, the intermediate transfer belt 20, and a cleaning device 17 that cleans residual toner on the photosensitive drum 10 are disposed.

Here, as the charging device 11, for example, a charging roll is used, but a charging device such as a corotron may be used.
The exposure device 12 may be any device that can write an image on the photosensitive drum 10 with light. In this example, for example, a print head using LEDs is used, but the present invention is not limited to this. The print head used may be selected as appropriate, such as a scanner that scans a laser beam with a polygon mirror.

Further, the rotary type developing device 13 is rotatably mounted with developing units 13a to 13d containing respective color component toners. For example, the respective color component toners are attached to a portion of the photosensitive drum 10 where the potential is lowered by exposure. The toner to be used is not particularly limited in shape and particle size, and any toner may be used as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 10. In this example, the rotary developing device 13 is used, but four developing devices may be used.
Furthermore, the cleaning device 17 may be appropriately selected as long as it cleans the residual toner on the photosensitive drum 10 and employs a blade cleaning method. However, there may be a mode in which the cleaning device 17 is not used when toner having a high transfer rate is used.

Further, the intermediate transfer belt 20 is stretched around four stretching rolls 21 to 24 and is predetermined along the surface of the photosensitive drum 10 positioned between the rotary developing device 13 and the cleaning device 17. Only the contact region is closely arranged.
Here, the intermediate transfer belt 20 and the photosensitive drum 10 may be driven by separate drive systems, but in the present embodiment, the intermediate transfer belt 20 is an elastic belt as described later, The intermediate transfer belt 20 is driven and rotated by using, for example, the photosensitive drum 10 as a driving source because it is disposed in contact with the circumferential surface of the photosensitive drum 10.

A primary transfer roll 25 as a primary transfer device is disposed in contact with a part of the contact area where the intermediate transfer belt 20 is in close contact with the photosensitive drum 10 from the back side of the intermediate transfer belt 20, and a predetermined primary transfer bias is applied. Applied.
Further, a secondary transfer roll 30 as a secondary transfer device is disposed as a backup roll of the stretching roll 22 at a portion facing the stretching roll 22 of the intermediate transfer belt 20, for example, the secondary transfer roll 30. A predetermined secondary transfer bias is applied to the tension roller 22 and the tension roll 22 that also serves as a backup roll is grounded.

Furthermore, a cleaning roll 26 serving as a belt cleaning device is disposed at a portion of the intermediate transfer belt 20 that faces the stretching roll 23. A predetermined cleaning bias is applied to the cleaning roll 26, and the stretching roll 23 is stretched. The roll 23 is grounded.
A recording material 40 such as paper is accommodated in a supply tray 41, supplied by a pickup roll 42, guided to a secondary transfer portion through a registration roll 43, and then to a fixing device 45 through a conveyance belt 44. It is conveyed and discharged to a discharge tray 48 through a transfer roll 46 and a discharge roll 47.

In the present embodiment, the intermediate transfer belt 20 which is a semiconductive belt of the present invention is
The substrate has at least a base material and a surface layer, and the base material is made of an elastic material containing rubber particles having a rubber material as a matrix, at least partly conductive and at least partly crosslinked rubber particles, Further, the elastic material has a JIS A hardness of 50 degrees or more and 70 degrees or less, preferably a solubility parameter δ (SP1) of a rubber material which is a matrix of the base material, and a rubber material which is a main component of the rubber particles. The absolute value of the difference from the solubility parameter δ (SP2) of the above has the following relationship, and the material constituting the surface layer is a two-component curable aqueous system comprising at least fluororesin particles and carbon black And the content of the fluororesin in the surface layer is 30 to 70 parts by mass with respect to 100 parts by mass of the urethane resin. , The carbon black content of the surface layer is 5 to 20 parts by weight.

When the image forming apparatus shown in FIG. 2 starts an image forming operation, each color component toner image on the photoconductive drum 10 is sequentially formed and sequentially transferred onto the intermediate transfer belt 20 by the transfer electric field of the primary transfer roll 25.
Thereafter, the toner image primarily transferred to the intermediate transfer belt 20 is secondarily transferred to the recording material 40 by the transfer electric field of the secondary transfer roll 30, and is carried to the fixing step.

  Even if the photosensitive drum 10 and the intermediate transfer belt 20 are always arranged in contact with each other, the bleed phenomenon can be prevented, so that a retract mechanism for separating the photosensitive drum 10 and the intermediate transfer belt 20 is not required. In accordance with the fact that an inexpensive elastic material can be used as the base material 51, it is possible to reduce the cost by eliminating the need for a retract mechanism.

Further, in the present embodiment model, the intermediate transfer belt 20 is driven to rotate by driving the photosensitive drum 10, so that the drive control cost of the intermediate transfer belt 20 can be greatly reduced.
Furthermore, since the contact width of the intermediate transfer belt 20 to the photosensitive drum 10 in the primary transfer is set to be very wide, for example, 50 mm or more, stable follow-up to the intermediate transfer belt 20 can be realized, and the transfer nip can be realized. Since there is no useless gap before and after the area, primary transfer is performed in a state where there is no scattering of toner due to discharge.
In particular, in the present embodiment, since a wide transfer nip area between the photosensitive drum 10 and the intermediate transfer belt 20 is ensured, it is possible to reduce the pressure in the transfer nip area. The situation where the body drum 10 and the intermediate transfer belt 20 are completely in close contact with each other is more reliably avoided.

  In the present embodiment, the photosensitive drum 10 and the intermediate transfer belt 20 are placed in contact with each other in an overlapping state, and the intermediate transfer belt 20 is driven based on the driving force from the photosensitive drum 10. However, the present invention is not limited to this. The photosensitive drum 10 and the intermediate transfer belt 20 have separate drive systems, and the intermediate transfer belt 20 is linearly connected to the photosensitive drum 10. Of course, the present invention can also be applied to an embodiment in which contact is made.

  Furthermore, when the semiconductive belt of the present invention is incorporated and used as an intermediate transfer belt or transfer / conveying belt in an image forming apparatus, it is preferable to use a spherical toner. By using spherical toner as the toner, the material constituting the transfer surface has a low surface hardness and a high volume resistance, thereby obtaining a high-quality transfer image quality free from image quality defects (holocharacter, blur, color registration). be able to.

However, the spherical toner means that the shape factor SF is 100 to 140. The shape factor is preferably 100 to 130, more preferably 100 to 120. If the average shape factor SF is greater than 140, the transfer efficiency may be reduced, and a reduction in the image quality of the print sample may be visually confirmed.
Here, the shape factor SF is a factor defined by the following equation.
SF = [(maximum length of toner particles) ² / (projected area of toner particles)] × (π / 4) × 100

  The maximum length of toner particles and the projected area of the toner particles are measured by using a Luzex image analysis device (manufactured by Nireco Co., Ltd., FT) with an optical microscope image of the toner dispersed on a slide glass through a video camera. This was carried out by importing into an image analyzer and processing the image.

  The spherical toner contains at least a binder resin and a colorant. The spherical toner may preferably use 2 to 12 μm particles, more preferably 3 to 9 μm particles.

  Examples of the binder resin contained in the toner include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, and vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. , Α-methylene aliphatic monocarboxylic such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Homopolymers and copolymers of acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, Examples include styrene-maleic anhydride copolymer, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax, and the like can be given.

  The colorant contained in the toner includes magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, and malachite green. Oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

  In addition to the binder resin and the colorant, the spherical toner may be internally added or externally added with known additives such as a charge control agent, a release agent, and other inorganic fine particles. Typical examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

  As the charge control agent, known ones can be used, but azo metal complex compounds, metal complex compounds of salicylic acid, and resin type charge control agents containing polar groups can be used. When the toner is manufactured by a wet manufacturing method, it is preferable to use a material that is difficult to dissolve in water in terms of controlling ionic strength and reducing wastewater contamination.

As the other inorganic fine particles, small-sized inorganic fine particles having an average primary particle size of 40 nm or less are used for the purpose of powder flowability, charge control, etc. Inorganic or organic fine particles having a diameter may be used in combination. As these other inorganic fine particles, known ones can be used. Examples thereof include silica, alumina, titania, metatitanic acid, zinc oxide, zirconia, magnesia, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, and strontium titanate.
In addition, the surface treatment of the small-diameter inorganic fine particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  The spherical toner is not particularly limited by the production method, and can be obtained by a known method. Specifically, for example, the particles obtained by the kneading and pulverization method in which the binder resin and the colorant are mixed, pulverized, and classified, if necessary, the release agent and the charge control agent are mechanically impacted. Method of changing shape by force or heat energy, emulsion polymerization of binder resin polymerizable monomer, dispersion of formed dispersion, colorant, release agent and charge control agent as required The emulsion polymerization aggregation method to obtain a spherical toner by mixing and agglomerating and heat-fusing the solution, a polymerizable monomer for obtaining a binder resin, a colorant, and a release agent, if necessary, a charge control agent A suspension polymerization method in which a solution such as a suspension is polymerized by suspending in an aqueous solvent, a binder resin and a colorant, and if necessary, a release agent and a charge control agent are suspended in an aqueous solvent and granulated. Examples thereof include a dissolution suspension method. In addition, a manufacturing method may be performed in which the spherical toner obtained by the above method is used as a core, and aggregated particles are further adhered and heat-fused to give a core-shell structure. When the external additive is added, it can be produced by mixing the spherical toner and the external additive with a Henschel mixer or a V blender. In addition, when the spherical toner is manufactured by a wet method, it can be externally added by a wet method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Example 1>
(Formation of elastic material)
-Production of rubber particles 1-
A composition having the following composition was put into a Banbury mixer, kneaded at an initial temperature of 50 ° C. for 2 minutes, then a vulcanizing agent was added, and after further kneading for 1 minute, it was discharged to prepare rubber composition 1. The produced rubber compound 1 was pulverized at 100 ° C. with a rubber pelletizer to form rubber particles 1. The resulting rubber particles 1 had a volume resistance of 10 ³ Ω and a crosslinking rate of 80%.
EPDM: Mitsui EPT4021 (Mitsui Chemicals): 100 parts by mass Liquid rubber: (NBR): Nipol 1312 (Neon Nippon): 50 parts by mass Carbon black: Ketchien EC (Lion Akzo): 55 parts by mass Carbon black: Seast V (Tokai Carbon): 20 parts by mass, vulcanizing agent: powder ion (Karuizawa Refinery): 0.5 part by mass, vulcanization accelerator: Noxeller TT (Ouchi Shinsei Chemical): 3 parts by mass, anti-aging agent: Irganox 1010 (Nippon Chibagagi): 1.5 parts by mass Lubricant: Beads stearic acid (Japanese fats and oils): 1 part by mass Filler: Aenka 3 (same chemical): 2 parts by mass

Formation of base material (elastic layer) 1 EPDM: Esprene 505A (Sumitomo Rubber): 100 parts by mass Vulcanizing agent: Powder ion (Karuizawa Refinery): 1 part by mass Vulcanization accelerator: Noxeller DT (Emerging Ouchi) Chemistry): 1 part by mass, vulcanization accelerator: Noxeller TS (Ouchi Emerging Chemical): 1 part by mass, filler: Aenka 3 (Same Chemical): 2 parts by mass, filler: Magsarat 150ST (Kyowa Chemical) : 2 parts by mass / Filler: Nipsil VM-3 (Nippon Silica): A rubber composition in which 2 parts by mass of the rubber particles 1 were blended at a blending ratio of 20 parts by mass was kneaded by two rolls. The obtained kneaded material was formed into a tube shape by a tube cross head extruder. Subsequently, the molded blended rubber material was heated and vulcanized in a vulcanizing can with pressurized steam at a temperature of 126 ° C. and a pressure of 1.5 kg / cm ² G to form a base material. The obtained base material is put on the outside of a metal tube, the surface is polished, and a rubber belt (base material) made of a base material having a thickness of 0.5 mm, an inner diameter of 140 mm, a width of 320 mm, and a volume resistivity of 3 × 10 ⁹ Ωcm 1) was formed.
The rubber material used for the substrate 1 is a rubber having a JIS A hardness of 50 in a sample having a thickness of 12 mm.

(Volume resistivity)
As described above, the volume resistivity of the obtained rubber belt is measured using a circular electrode (High Probe IP HR probe manufactured by Dia Instruments Co., Ltd.) shown in FIG. 3 in a 22 ° C./55% RH environment. Then, a voltage of 100 (V) was applied between the cylindrical electrode portion C ′ and the second voltage application electrode B ′ in the first voltage application electrode A ′, and the current value after 10 seconds was obtained.

-Formation of surface layer-
Fluororesin (volume average particle size 0.3 μm Teflon (registered trademark), manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) as a two-component curable water-based urethane resin coating containing fluororesin particles and carbon black Water-based urethane-based resin paint (Emulalon 345: manufactured by Nihon Atison Co., Ltd.) containing 30 parts by mass of particles and 10 parts by mass of carbon black, and block isocyanate (WH-2: manufactured by Nihon Atison Co., Ltd.) as a curing agent are 100. : The mixture obtained by mixing at a compounding ratio of 10 was spray-coated on the surface of the obtained base material, and then heated and dried at 120 ° C. for 15 minutes to obtain fluorine resin particles and carbon black. A surface layer made of urethane resin and having a thickness of 20 μm was formed.

The volume resistivity of the semiconductive belt of Example 1 manufactured as described above is 8 × 10 ⁹ Ωcm, the contact angle of the belt surface is 92 degrees, and the ten-point average surface roughness Rz. Was 3 μm.

<Example 2>
-Production of rubber particles 2-
A composition having the following composition was put into a Banbury mixer, kneaded for 2 minutes at an initial temperature of 50 ° C., then a vulcanizing agent was added, and after further kneading for 1 minute, it was discharged to prepare rubber composition 2. The produced rubber compound 2 was pulverized at 100 ° C. with a rubber pelletizer to form a rubber particle 2.
NBR: Nipol 1072 (Nippon Zeon): 100 parts by mass Liquid rubber (NBR): Nipol 1312 (Nippon Zeon): 50 parts by mass Carbon black: Ketchien EC (Lion Akzo): 55 parts by mass Carbon black: Seast V ( Tokai Carbon): 20 parts by mass Crosslinking agent: Powder ion (Karuizawa Smelter): 0.5 parts by mass Crosslinking agent: Noxeller TT (Ouchi Shinsei Chemical): 3 parts by mass Anti-aging agent: Irganox 1010 (Japan) Cibagagi-): 1.5 parts by mass, stearic acid: bead stearic acid (Japanese fats and oils): 1 part by mass, zinc white: Aenka 3 (same chemical): 2 parts by mass The volume resistance of the rubber particles obtained is 10 ² Ω and the crosslinking rate was 85%.

Formation of base material (elastic layer) 2 CR: Neoprene WRT (Showa Denko-DuPont: 60 parts by mass EPDM: Esprene 505A (Sumitomo Rubber): 40 parts by mass Vulcanizing agent: Powder ion (Karuizawa Smelter): 1 part by weight, vulcanization accelerator: Noxeller DT (Ouchi Shinsei Chemical): 1 part by weight, vulcanization accelerator: Noxeller TS (Ouchi Shinsei Chemical): 1 part by weight, filler: Aenka 3 ): 5 parts by mass-Filler: Magsarat 150ST (Kyowa Chemical); 4 parts by mass-Filler: Nipsil VM-3 (Nippon Silica): Rubber in which 5 parts by mass of rubber particles 2 are blended in a mixing ratio The composition was kneaded with two rolls, and the resulting kneaded product was molded into a tube shape by a tube cross head extruder, and then the blended rubber material was molded in a vulcanizing can at a temperature of 126 ° C. and a pressure of 1 .5kg / by vulcanizing by heating with pressurized steam of m ² G, to form a conductive belt material. Cover the obtained belt material on the outside of the metal tube, and polished surface, thickness 0.5mm A rubber belt made of a base material having an inner diameter of 140 mm, a width of 320 mm, and a volume resistivity of 3 × 10 ⁹ Ωcm was prepared.
The rubber material used for the substrate is a rubber having a JIS A hardness of 60 in a sample having a thickness of 12 mm.

-Formation of surface layer-
Fluororesin (volume average particle size 0.3 μm Teflon (registered trademark), manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) as a two-component curable water-based urethane resin coating containing fluororesin particles and carbon black Water based urethane resin paint (Emulalon 345: manufactured by Nippon Atchison Co., Ltd.) containing 40 parts by mass of particles and 15 parts by mass of carbon black, and blocked isocyanate (WH-2: manufactured by Nippon Atson Co., Ltd.) as a curing agent are 100. : After mixing at a compounding ratio of 10 and spray-coating the resulting dispersion on the surface of the elastic belt on which the resistance layer is formed, it is heated and dried at 120 ° C. for 15 minutes to obtain fluororesin particles. A surface layer having a thickness of 20 μm made of carbon black and urethane resin was formed to produce a semiconductive belt.

The volume resistivity of the semiconductive belt of Example 2 manufactured as described above is 4 × 10 ⁹ Ωcm, the contact angle of the belt surface is 105 degrees, and the ten-point average surface roughness Rz. Was 6 μm.

<Example 3>
-Formation of base material (elastic layer) 3-
-CR: Neoprene WRT (Showa Denko-DuPont): 100 parts by mass-EPDM: Esprene 505A (Sumitomo Rubber): 18 parts by mass-Vulcanizing agent: Powder ion (Karuizawa Refinery): 1 part by mass-Vulcanization accelerator : Noxeller DT (Ouchi Emerging Chemical): 1 part by mass, Vulcanization Accelerator: Noxeller TS (Ouchi Emerging Chemical): 1 part by mass, Filler: Aenka 3 (same chemical): 5 parts by mass, filler : Magsarat 150ST (Kyowa Chemical): 4 parts by mass Filler: Nipsil VM-3 (Nippon Silica): A rubber composition containing 30 parts by mass of the rubber particles 2 used in Example 2 in 10 parts by mass. It knead | mixed with two rolls. The obtained kneaded material was formed into a tube shape by a tube cross head extruder. Next, the molded blended rubber material was heated and vulcanized in a vulcanizing can with pressurized steam at a temperature of 126 ° C. and a pressure of 1.5 kg / cm ² G to form a conductive belt material. The obtained belt material was placed on the outside of a metal tube, and the surface was polished to produce a rubber belt made of a base material having a thickness of 0.5 mm, an inner diameter of 140 mm, a width of 320 mm, and a volume resistivity of 3 × 10 ⁹ Ωcm. .
The rubber material used for the base material is a rubber having a JIS A hardness of 70 in a sample having a thickness of 12 mm.

-Formation of surface layer-
Fluororesin (volume average particle size 0.3 μm Teflon (registered trademark), manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) as a two-component curable water-based urethane resin coating containing fluororesin particles and carbon black Water based urethane resin paint (Emulalon 345: manufactured by Nihon Atchison Co., Ltd.) containing 50 parts by mass of particles and 15 parts by mass of carbon black, and blocked isocyanate (WH-2: manufactured by Nihon Athison Co., Ltd.) as a curing agent are 100. : The mixture obtained by mixing at a blending ratio of 5 was spray-coated on the surface of the elastic belt on which the resistance layer was formed, and then heated and dried at 120 ° C. for 15 minutes to obtain fluororesin particles. A surface layer having a thickness of 20 μm made of carbon black and urethane resin was formed to produce a semiconductive belt.

The volume resistivity of the semiconductive belt of Example 1 manufactured as described above is 9 × 10 ⁹ Ωcm, the contact angle of the belt surface is 110 degrees, and the ten-point average surface roughness Rz. Was 8 μm.

<Example 4>
In Example 2, the semiconductive belt was formed in the same manner as in Example 2 except that the amount of the fluororesin particles was changed to 70 parts by mass and the amount of carbon black was changed to 20 parts by mass when forming the surface layer. Produced. The volume resistivity of the semiconductive belt member of Example 4 obtained in this way is volume resistivity 1.0 × 10 ¹⁰ Ωcm, surface contact angle is 120 degrees, and 10-point average surface roughness The thickness Rz was 9 μm.

<Comparative Example 1>
-Formation of base material (elastic layer) 4-
-CR: Neoprene WRT (Showa Denko-DuPont: 60 parts by mass-EPDM: Esprene 505A (Sumitomo Rubber): 40 parts by mass-Carbon black: Acetylene black (Electrochemical Industry): 30 parts by mass-Vulcanizing agent: Powder ion (Karuizawa Refinery): 1 part by mass, vulcanization accelerator: Noxeller DT (Ouchi Emerging Chemical): 1 part by mass, vulcanization accelerator: Noxeller TS (Ouchi Emerging Chemical): 1 part by mass, filler: Aenka 3 parts (same chemical): 5 parts by mass. Filler: Magsarat 150ST (Kyowa Chemical); 4 parts by mass. Filler: Nipsil VM-3 (Nippon Silica): 2 rolls of rubber composition. The obtained kneaded material was molded into a tube shape by a tube cross head extruder, and the molded blended rubber material was then placed in a vulcanizing can at a temperature of 126 ° C. and a pressure of 1. by vulcanizing by heating with pressurized steam of kg / cm ² G, to form a conductive belt material. Cover the obtained belt material on the outside of the metal tube, and polished surface, thickness 0 A rubber belt made of a base material having a diameter of 0.5 mm, an inner diameter of 140 mm, a width of 320 mm, and a volume resistivity of 5 × 10 ⁸ Ωcm was produced.
The rubber material used for the substrate is a rubber having a JIS A hardness of 60 in a sample having a thickness of 12 mm.

In Example 1, a semiconductive belt was produced in the same manner as in Example 1 except that the above base material was used as the base material, and the surface layer was changed to 100 parts by mass of the fluorine resin. The volume resistivity of the semiconductive belt of Comparative Example 1 thus obtained was 5 × 10 ⁹ Ωcm, the contact angle of the surface was 120 degrees, and the ten-point average surface roughness Rz was 11 μm. It was.

<Comparative Example 2>
70 parts by mass of chloroprene rubber is kneaded for 2 minutes using a 6 inch diameter open roll, and 30 parts by mass of ethylene / propylene / non-conjugated diene terpolymer (EPDM) is added thereto and kneaded for 13 minutes. Went. Next, 5 parts by mass of zinc oxide, 4 parts by mass of magnesium oxide, 1 part by mass of stearic acid, and 0.35 parts by mass of Sunseller 22C (ethylene / thiourea manufactured by Sanshin Chemical Co., Ltd.) were added to the polymer kneaded product of chloroprene rubber and EPDM. Are successively added, and 1.5 parts by mass of Noxarer BZ (Zinc di-n-butyl dithiocarbamate manufactured by Ouchi Shinko Co., Ltd.), 1 part by mass of Noxeller DM (dibenzothiazyl disulfide manufactured by Ouchi Shinko Co., Ltd.), After adding 0.7 parts by mass of Noxeller TRA (dipentamethylene thiuram tetrasulfide manufactured by Ouchi Shinko Co., Ltd.) and 1.5 parts by mass of sulfur, thinning was performed 10 times using an open roll. After the rubber kneaded material is removed from the open roll, it is divided into three equal parts. Each of the rubber kneaded materials has 23 parts by mass of furnace black (manufactured by Asahi Carbon Co., Ltd.) and 6 parts by mass of Denka black (granular acetylene black produced by Electrochemical Co., Ltd.). Were added in respective amounts and kneaded with an open roll. The rubber material used for the base material is a rubber having a JIS A hardness of 70 in a sample having a thickness of 12 mm.

The kneaded material to which carbon black was added in this way was formed into a belt shape using an extruder, and then vulcanized using a steam kettle. Then, the thickness of the belt was processed to 0.5 mm by grinding. The belt surface was spray-coated with a mixture of 100 parts by mass of C-230U main agent (polyester urethane manufactured by Hirono Chemical Co., Ltd.) and 30 parts by mass of C-230U curing agent (isocyanate manufactured by Hirono Chemical Co., Ltd.) at 160 ° C. for 30 parts. Firing was performed for a minute to form a surface layer, and a belt having an inner diameter of 140 mm and a width of 300 mm was produced.
The volume resistivity of the semiconductive belt of the thus obtained Comparative Example 2 is 6 × ¹⁰ 10 Ωcm, the contact angle of the surface is 85 degrees, ten-point average surface roughness Rz of 12μm met It was.

<Comparative Example 3>
Using the same rubber particles 2 as in Example 2 and using the elastic layer of Example 1 as an elastic layer (base material), the rubber particles 2 are blended in an amount of 18 parts by mass with respect to 100 parts by mass of the elastic layer (base material). The rubber composition blended at a ratio was kneaded with two rolls. The obtained kneaded material was formed into a tube shape by a tube cross head extruder. Subsequently, the molded blended rubber material was heated and vulcanized in a vulcanizing can with pressurized steam at a temperature of 126 ° C. and a pressure of 1.5 kg / cm ² G to form a base material. The obtained base material is put on the outside of a metal tube, the surface is polished, and a rubber belt made of a base material having a thickness of 0.5 mm, an inner diameter of 140 mm, a width of 320 mm, and a volume resistivity of 1 × 10 ⁹ Ωcm (base material) 1) was formed.
The rubber material used for the substrate 1 is a rubber having a JIS A hardness of 45 in a sample having a thickness of 12 mm.

A semiconductive belt was produced in the same manner as in Example 1, using the same surface layer as in Example 1 as the surface layer. The volume resistivity of the semiconductive belt member of Comparative Example 3 thus obtained is 7 × 10 ⁹ Ωcm, the contact angle of the surface is 92 degrees, and the ten-point average surface roughness Rz. Was 3 μm.

<Evaluation>
About the semiconductive belts obtained in Examples 1 to 4 and Comparative Examples 1 to 3, volume resistivity, variation in volume resistivity, water contact angle, surface roughness, presence or absence of bleeding, transfer image quality (blur Table 1 shows the results of evaluating the image quality after 3000 consecutive copies of postcards.

(1) Volume resistivity, variation in volume resistivity Measure the volume resistivity at the time of applying 100 volts at 3 points in the length direction of the belt and 8 points in the circumferential direction (24 points in total). The difference between the maximum value and the minimum value of the logarithmic value was the variation in the volume resistivity, and the average value of the 24-point measurement was the volume resistivity of the belt.

(2) Contact angle of water The contact angle can be measured using a goniometer or the like. In the present invention, water is dropped on the surface of the semiconductive belt in an environment of 23 ° C. and 55% RH. The contact angle after standing for 10 seconds was measured using a contact angle measuring device CA-X roll type (manufactured by Kyowa Interface Science Co., Ltd.). The average value when the measurement was repeated three times at different locations was obtained as the contact angle of the belt.

(3) Measuring method of 10-point average surface roughness Rz The 10-point average surface roughness Rz is a contact type surface roughness measuring device (Surfcom 570A, in an environment of 23 ° C. and 55 RH% in accordance with JIS B601-1994. Tokyo Seimitsu Co., Ltd.) was used. When measuring the surface of the semiconductive belt, the measurement distance was 2.5 mm, and the tip of the contact needle was diamond (5 μmR, 90 ° cone). The value was determined as the ten-point average surface roughness Rz of the belt member.

(4) Bleed property The obtained semiconductive belt was brought into contact with the OPC photoreceptor for 2 weeks in a high-temperature and high-humidity environment (48 ° C., 90% RH). Evaluated by criteria.
Judgment: ○: No problem in transfer image quality ×: There is a problem in the transfer image quality at the part where the semiconductive belt is in contact (whiteout occurs)

<Evaluation of transfer image quality>
The obtained semiconductive belt was mounted on an image forming apparatus having the configuration of FIG. 2 modified from Fuji Xerox Co., Ltd. Docu Color 1255CP, and the transfer image quality of the following items was evaluated. An OPC photoconductor was used as the photoconductor.

(Blur evaluation)
The occurrence of blur was evaluated according to the following criteria.
○: No blurring or slight blurring, no problem in image quality ×: Bluring, problem in image quality

(Holo character evaluation)
The occurrence of holo-characters was evaluated according to the following criteria.
○: Occurrence is small and there are few image quality problems ×: Image quality problems

<Continuous running test>
Image quality defect (whiteout occurrence situation) when copying 30 postcards of magenta 30% halftone after copying 3000 postcards continuously in the environment of 22 ° C 55% RH The color misregistration in the color image was evaluated according to the following criteria.
○: Image quality defects (white spots, color shifts in color images) do not occur. ×: White spots, color shifts occur in color images, and there is a problem in image quality.

  From the results in Table 1, the semiconductive belts of Examples 1 to 4 of the present invention were free from image quality defects and could stably obtain excellent image quality over a long period of time. On the other hand, in Comparative Examples 1 and 2, there was no occurrence of image quality defects of blur and holographic characters, but in the continuous paper running test, white-out image quality defects occurred due to contamination of the belt surface. In Comparative Example 2, a so-called bleed phenomenon occurred in which a low molecular oil component dispersed in the base material was deposited on the surface of the conveyor belt. In Comparative Example 3, since the rubber hardness was as small as 45 degrees, color shift occurred in the color image in the continuous running test.

1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention. 1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to an embodiment. It is a figure which shows the measuring method of volume resistivity.

Explanation of symbols

1 Semiconductive belt 6 Image carrier (photosensitive member)
Reference Signs List 7 Recording material 8 Transfer device 8a Primary transfer device 8b Secondary transfer device 9 Stretch roll 10 Photosensitive drum 11 Charging device 12 Exposure device 13 Rotary developing device 17 Cleaning device 20 Intermediate transfer belt 21 Stretch roll 22 Stretch roll 23 Tension roll 24 Tension roll 25 Primary transfer roll 26 Cleaning roll 30 Secondary transfer roll 40 Recording material 41 Supply tray 42 Pickup roll 43 Registration roll 44 Conveyor belt 45 Fixing device 46 Conveyance roll 47 Discharge roll 48 Discharge tray

Claims (4)

A semiconductive belt used in an electrophotographic image forming apparatus,
The substrate has at least a base material and a surface layer, and the base material is made of an elastic material containing rubber particles having a rubber material as a matrix, at least partly conductive and at least partly crosslinked rubber particles, further, JIS a hardness of the elastic material state, and are 70 degrees or less than 50 degrees,
Absolute value of the difference between the solubility parameter [delta] (SP1) of the rubber material is a matrix of the base material, the solubility parameter of the rubber material which is a main component of the rubber particles [delta] (SP2) is that having a following relationship A semiconductive belt characterized in that.
| SP1-SP2 | <1.0 [J ^1/2 cm ^2/3 ] A semiconductive belt used in an electrophotographic image forming apparatus,
The substrate has at least a base material and a surface layer, and the base material is made of an elastic material containing rubber particles having a rubber material as a matrix, at least partly conductive and at least partly crosslinked rubber particles, further, JIS a hardness of the elastic material state, and are 70 degrees or less than 50 degrees,
The material constituting the surface layer is a two-component curable water-based urethane resin coating composition containing at least fluororesin particles and carbon black, and the content of the fluororesin in the surface layer is urethane 30 to 70 parts by mass relative to the resin 100 parts by weight, further, semiconductive belt content of carbon black of the surface layer is characterized by 5 to 20 parts by der Rukoto. 3. An image forming apparatus, wherein the semiconductive belt according to claim 1 is stretched between a plurality of stretching rolls and is arranged in contact along the shape of a drum-shaped image carrier. The image forming apparatus according to claim 3 , wherein a spherical toner having a shape factor SF defined by the following formula (1) of 100 to 140 is used.
Formula (1)
SF = [(maximum length of toner particles) ² / (projected area of toner particles)] × π / 4 × 100

Images