JPH11202648A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a high-quality transferred image without requiring a discharge mechanism by preventing toner from being splashed at transfer time. SOLUTION: This image forming device is provided with an image carrier 1 on which an electrostatic latent image corresponding to image information is formed, a developing device 4 visualizing the electrostatic latent image formed on the carrier 1 as a toner image by the toner, an intermediate transfer body B on which the unfixed toner image carried on the carrier 1 is primarily transferred and a secondary transfer unit T2 secondarily transferring the unfixed toner image transferred on the transfer body B on a recording medium. Then, the transfer body B is constituted of plural layers whose layer structure is provided with at least a base material and the surface layer. The base material is constituted of a resin material obtained by dispersing electrical conductive agent. The surface layer is constituted of a resin material obtained by dispersing the electrical conductive agent and a hydrophobic inorganic material whose average grain size is <=1 μm. Besides, the volume resistivity of the surface layer is set within the range of 10<9.5> Ωcm to 10 Ωcm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
Laser printer, facsimile, composite OA of these
And an image forming apparatus using an electrophotographic method. More specifically, the present invention is used in an image forming apparatus in which a toner image formed on an image carrier is once primarily transferred to an intermediate transfer body, and then transferred to a recording medium such as paper to obtain a reproduced image. .

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic system modulates an image signal by forming a uniform charge on an image bearing member composed of a photoreceptor made of an inorganic or organic photoconductive material. After forming an electrostatic latent image with a laser beam or the like, the electrostatic latent image is developed with a charged toner to obtain a visualized toner image. Then, the required reproduced image is obtained by transferring the toner image directly or via an intermediate transfer member onto a recording medium such as paper. An image forming apparatus adopting a system in which a toner image formed on an image carrier is primarily transferred to an intermediate transfer body and a toner image on the intermediate transfer body is secondarily transferred to a recording medium is disclosed in, for example, -206567.

Belt materials used in an image forming apparatus employing an intermediate transfer member system include, for example, polyvinylidene fluoride (PVDF) (JP-A-5-200904 and JP-A-6-228335) and polycarbonate (PC). ) (JP-A-6-95521), polyalkylene phthalate (PAT) (JP-A-6-149081)
No., JP-A 6-1), PC and PAT blend materials
No. 49083), thermoplastic materials such as a blend material of ethylene tetrafluoroethylene copolymer (ETFE) and PC, a blend material of ETFE and PAT, and a blend material of ETFE, PC and PAT (JP-A-6-149079). A conductive endless belt in which a conductive agent such as carbon black is dispersed in a resin has been proposed. The above, PVD
Conductive materials made of thermoplastic resins such as F and PC have poor mechanical properties with a Young's modulus of 24000 kg / cm ² or less. However, there is a problem in that high quality transfer image quality cannot be stably obtained, and cracks are generated from the belt end portion during driving, so that the durability of the belt is poor.

[0004] Materials having excellent mechanical properties include polyimide resin materials. For example, JP
JP-A-3-11263 proposes a seamless belt made of carbon black-dispersed polyimide resin. This seamless belt is made by dispersing carbon black as a conductive agent in a solution of polyamic acid which is a polyimide precursor, casting the dispersion on a metal drum, drying it, and stretching the film peeled from the drum at a high temperature. To form an endless belt. A general method of forming the film is to inject a polymer solution in which carbon black is dispersed into a cylindrical mold, for example, by adding 10%.
The film is formed into a film by centrifugal molding while rotating the cylindrical mold while heating to 0 ° C to 200 ° C. The obtained film is released in a semi-cured state, covered with an iron core, and
The main curing is carried out by advancing the polyimideation reaction (ring-closing reaction of the polyimide acid) at 00 ° C to 450 ° C.

[0005] However, in the rotary molding method such as the centrifugal molding described above, when the evaporation of the solvent becomes uneven in the molding and main curing steps, minute irregularities are formed on the film surface. Therefore, when transfer is performed using an intermediate transfer belt manufactured from such a film, minute transfer defects (white spots) may occur in an image transferred to a recording medium due to minute unevenness. There's a problem. On the other hand, if a smooth film is to be obtained, a long time is required for the forming and curing steps for evaporating and drying the solvent and curing the polyimide acid, and the belt manufacturing cost will increase.

When the surface resistivity of the intermediate transfer belt is higher than 10 ¹³ Ω / □, a peeling discharge occurs at a post nip portion where the image carrier and the transfer belt are separated from each other, and a discharge-generating portion becomes white. The discharge will be lost. FIG. 7 shows the relationship between the surface resistivity and the volume resistivity of the carbon black-dispersed polyimide film formed by the above molding method. As shown in FIG. 7, when the surface resistivity of the polyimide resin film is 10 ¹³ Ω / □, the volume resistivity is 10 ^9.5 cm. Therefore, when trying to avoid white spots using the intermediate transfer belt having a single layer of the resin film, the usable range of the volume resistivity is 10 ^9.5 c.
m. In this case, due to the conductivity of the intermediate transfer belt itself, the electrostatic force for holding the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer member does not work, so that the electrostatic repulsive force between toners And the fringe electric field near the edge of the image causes the toner to scatter around the image (blurring), resulting in a problem that an image with large noise is formed.

FIG. 8 shows the relationship between the surface resistivity and the volume resistivity of a conductive metal oxide-dispersed polyimide resin film. As shown in FIG. 8, the surface resistivity of the resin film is 10 ¹³ Ω / □.
In this case, the volume resistivity is 10 ^7.3 Ωcm. Therefore, when a metal oxide is used as the conductive agent, there is no volume resistivity region of the polyimide resin film that can simultaneously avoid the occurrence of white spots and blur. Since the polyimide resin has excellent mechanical properties, when the intermediate transfer belt is pressed against the image carrier by the primary transfer roll, the deformation of the belt due to the pressing force is small. In such a state,
When an electric field is applied to electrostatically transfer the toner image to the intermediate transfer member, the load of the pressing force by the bias roller concentrates in the primary transfer area Q3. As a result, the toner image is aggregated and the charge density is increased, so that a discharge may occur inside the toner layer and the polarity of the toner may be changed.

Due to such factors, there is a problem that an image quality defect occurs in a hollow character in which a line image is missing. This point has a similar problem in the secondary transfer area Q4 where the secondary transfer roll is pressed against the intermediate transfer belt via the sheet. As a countermeasure for preventing the image quality defect, for example, a belt material having a surface made of an elastic material can be mentioned. However, when a rubber material such as silicone rubber is used as the surface material, the rubber material has an adhesive property. There is a problem that the toner image is not transferred to the recording medium at the time of the next transfer.

[0009] As measures against image quality defects such as hollow characters, we consist of an intermediate layer composed of a base material having excellent mechanical properties and an elastic material such as fluorine rubber, and a material having a small surface energy such as fluororesin. An intermediate transfer belt composed of a belt material having a three-layer structure of a surface layer and having a conductive agent dispersed only in the base material has already been filed (Japanese Patent Application No. 8-23601).
No. 1). However, the volume resistivity of the elastic material is 10 ¹⁴ Ωcm
If the height becomes higher, the surface of the intermediate belt is charged by the transfer electric field in the primary transfer, so that there is a disadvantage that a charge elimination mechanism is newly required.

Also, a conductive filler is blended in a predetermined ratio with a fluororesin, so that the volume resistivity is 10 ⁷ to 10 ¹⁰ Ωcm.
Japanese Patent Application Laid-Open No. 7-92825 proposes a conductive plastic belt having a surface layer made of a conductive material adjusted as described above. However, the belt disclosed in this publication is substantially made of a single-layer resin material, and the resin material of the surface layer has no elasticity, which causes a problem that an image defect of a hollow character in which a line image is missing occurs. . In addition, when a belt having a volume resistivity as shown in the embodiment is used, the electric charge given by the primary transfer device such as a bias roller or a corona discharger at the time of the primary transfer from the image carrier to the intermediate transfer belt is used. However, the charged charges are removed due to the conductivity of the intermediate transfer body itself. As a result, there is a problem that blur occurs as described above and an image with large noise is formed. In particular, this phenomenon appears remarkably around an image having many toner images per unit area, such as a multiple transfer image,
This is a fatal defect for the color image forming apparatus.

When the generation of the hollow character is divided into the primary transfer area Q3 and the secondary transfer area Q4, the surface is made of the above-mentioned fluororesin-based material having a small surface energy (water contact angle of 100 ° or more). The transfer of the belt material to the transfer member in the secondary transfer area Q4 is facilitated by coating, so that the occurrence of hollow characters in the secondary transfer area Q4 can be greatly improved. The hollow character in the primary transfer area Q3 can also be improved by providing an elastic layer on the surface layer. However, if the contact angle of water on the belt surface is larger than that of the image carrier, the The primary transfer area Q is smaller than the case where the contact angle of water is smaller than the contact angle of water of the image carrier.
Since the transfer from the image carrier to the belt material in 3 is not easy, the effect of improving the hollow character is small.

[0012]

SUMMARY OF THE INVENTION In the prior art,
A conductive belt material made of a thermoplastic resin having inferior mechanical properties causes a large deformation of the belt due to a stress at the time of driving, so that a high quality transfer image cannot be stably obtained. In addition, the belt material having a single layer structure made of conductive polyimide resin or fluorine resin has a problem that the usable area of the volume resistivity is too low to cause a blur, and the elastic material in which the conductive agent is not dispersed is used. The intermediate transfer belt provided with the layer has a drawback that a charge eliminating mechanism is required because the volume resistivity is too high.

On the other hand, a belt material made of a polyimide resin having excellent mechanical properties causes a small deformation of the belt due to a pressing force of a transfer roll at a transfer portion, so that a toner image is aggregated and an image quality defect of a hollow character occurs. There is a problem of causing. Furthermore, in the case of a belt material whose surface layer is coated with a rubber material such as silicone rubber, there is a problem that the toner image is not transferred to the recording medium during the secondary transfer because the rubber material is sticky.

The present invention has been made in view of the above problems, and has the following (O0
1) and (O02) are to be described. (O01) To provide an image forming apparatus capable of obtaining a high quality image with no toner scattering at the time of transfer, requiring no static elimination mechanism, and stably obtaining a high quality transferred image. (O02) Provided is an image forming apparatus which has good secondary transferability and is capable of preventing occurrence of image defects such as hollow characters due to small deformation of a belt material due to stress during driving. thing.

[0015]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies and studies to solve the above-mentioned problems, and found that a base material made of a resin material having excellent mechanical properties and a non-adhesive material were used. It has been found that the former main object can be achieved by using a belt material composed of a surface layer having a low surface energy and a volume resistivity set in a specific range as an intermediate transfer belt material. Further, by forming the surface layer of a flexible material, and by setting the thickness of the base material and the surface layer to a predetermined value or more as necessary, the belt material deforms following the pressing force of the transfer roll. The inventors have found that the latter object is achieved, and have accomplished the present invention.

That is, the image forming apparatus according to the present invention comprises: an image carrier for forming an electrostatic latent image corresponding to image information; and a developing device for visualizing the electrostatic latent image formed on the image carrier with a toner as a toner image. An intermediate transfer member on which an unfixed toner image carried on an image carrier is primarily transferred, and a secondary transfer device for secondary-transferring the unfixed toner image on the intermediate transfer member to a recording medium The intermediate transfer body has a layer structure having a plurality of layers having at least a base material and a surface layer, the base material is formed of a resin material in which a conductive agent is dispersed, and the surface layer is an average of the conductive agent. It is composed of a resin material in which a hydrophobic inorganic material having a particle diameter of 1 μm or less is dispersed, and has a volume resistivity of 10
It is in the range of ^9.5 Ωcm to 10 ¹³ Ωcm. In the present invention, the surface layer is formed of a flexible conductive resin material having a contact angle with a water droplet when expressed by wettability of water, which is smaller than that of the image carrier and is 85 ° or more. Is preferred. In addition, the intermediate transfer body substrate,
It is preferable that the Young's modulus is 30,000 kg / cm ² or more.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention is not particularly limited as long as the image forming apparatus uses an intermediate transfer member. For example, a normal monocolor image forming apparatus containing only a single color toner in a developing device, or an intermediate transfer member such as an intermediate transfer drum or an intermediate transfer belt for transferring a toner image carried on an image carrier such as a photosensitive drum. And a tandem-type color image forming apparatus in which a plurality of image carriers having developing units for each color are arranged in series on an intermediate transfer belt. FIG. 1 shows an example of the image forming apparatus of the present invention.
This will be described below. FIG. 1 is a schematic view of an intermediate transfer belt type image forming apparatus provided with main components. In FIG. 1, a charger 2, a latent image writing device 3, a rotary developing device 4, a primary transfer device 5, A cleaning device 6 and the like are arranged. The latent image writing device 3 writes an electrostatic latent image by exposing the surface of the image carrier 1 at the latent image writing position Q1. The rotary type developing device 4 includes K (black), Y (yellow), and M rotating with the rotation shaft 4a.
(Magenta), C (cyan) four color developing units 4k, 4y,
4c and 4m, and develops the electrostatic latent image on the image carrier 1 into a toner image in the development area Q2.

An intermediate transfer belt B which travels between the image carrier 1 and the primary transfer device 5 in the direction of the arrow while contacting the surface of the image carrier 1 comprises a driving roll 7, a tension roll 8, an idler roll. 9 and 10 and the inner secondary transfer roll 11. An outer secondary transfer roll 12 is disposed at a position facing the inner secondary transfer roll 11 with the intermediate transfer belt B interposed therebetween, and a voltage application roll 13 contacts the inner secondary transfer roll 11. I have. The rolls 11 to 13 constitute a secondary transfer roll unit T2. The area where the primary transfer roll 5 is in pressure contact with the intermediate transfer belt B is the primary transfer area Q3, and the area where the outer secondary transfer roll 12 is in pressure contact with the intermediate transfer belt B is the secondary transfer area Q4. . A belt cleaner 14 is disposed at a position facing the drive roll 7 with an intermediate transfer belt B interposed therebetween.

In the color image forming apparatus shown in FIG.
After the surface of the image carrier 1 rotating in the direction of the arrow is uniformly charged by the charger 2, the latent image writing device 3 such as an image-processed laser beam is used to write the first color at the latent image writing position Q 1. Is formed, and a toner image is formed in the development area Q2. When the toner image passes through the primary transfer area Q <b> 3, the primary transfer is electrostatically primary-transferred onto the intermediate transfer belt B by the primary transfer device 5. Thereafter, similarly, the second color toner image is placed on the intermediate transfer belt B carrying the first color toner image.
The primary transfer is performed so that the third color and the fourth color toner images are sequentially superimposed, and a full-color multiplex toner image is finally obtained.

The multi-toner image is collectively electrostatically transferred onto a recording medium (hereinafter, represented by a recording sheet S) supplied at a predetermined timing from the paper supply tray 15 except for passing through the secondary transfer area Q4. Is done. The recording sheet S to which the toner image has been transferred is conveyed to the fixing device 16 and subjected to a fixing process.
Emitted outside the machine. After the primary transfer, the residual toner and the electric charge are removed from the image carrier 1 by the cleaning device 6 and the like. The residual toner is removed from the intermediate transfer belt B after the secondary transfer by the belt cleaner 14, so that the intermediate transfer belt B is prepared for the next image forming process. . When a single-color monocolor image is formed in the image forming apparatus, only one developing unit is used. Further, the image carrier 1 can be replaced with a known belt photoconductor instead of the photoconductor drum.

As the primary transfer device 5, a corona transfer device such as a corotron, a transfer roll, a transfer blade or the like is used. A voltage of about 1 to 4 KV having a polarity opposite to the charge polarity of the toner is applied to the primary transfer unit 5, and the primary transfer unit 5 carries the image on the image carrier 1 by the action of an electric field generated between the image carrier 1 and the primary transfer unit 5. The transferred toner image is primarily transferred to the intermediate transfer belt B. The voltage applying roll 13 is not particularly limited as long as it is a member having good electrical conductivity. For example, a metal roll made of aluminum, stainless steel, or copper, a conductive rubber roll, a conductive brush, a metal plate, a conductive resin A plate or the like is used. From the voltage application roll 13, a secondary transfer voltage of −1 to −5 KV is applied to the inner secondary transfer roll 11. The secondary transfer voltage can be applied to the outer secondary transfer roll 12. In the above secondary transfer area Q4, the voltage applying roll 13 is not necessarily a necessary member, and the transfer voltage may be applied to the conductive shaft of the inner secondary transfer roll 11 or the outer secondary transfer roll 12, for example.

FIG. 2 is an explanatory view showing a sectional structure of the intermediate transfer belt according to the present invention. In the present invention, the intermediate transfer belt B is composed of a base material having a Young's modulus within a predetermined range and a plurality of belt materials having at least a surface layer having a volume resistivity within a predetermined range. As an example of the plurality of layers, as shown in FIG.
In addition to the layer structure, an intermediate layer B between the substrate Ba and the surface layer Bb
c, for example, made of a conductive dispersed or non-dispersed elastic material. Examples of the resin material constituting the base material Ba include resins having excellent mechanical properties such as polyimide, polyetherphone, and polyetherketone (including polyetheretherketone). Among them, a polyimide resin is preferably used from the viewpoint of availability. These resins are characterized in that belt deformation during driving is smaller than that of thermoplastic resins that have been conventionally used.

Polyimide is generally a polymer synthesized by polycondensation using tetracarboxylic dianhydride and diamine or diisocyanate as monomer components. The tetracarboxylic acid component of the dianhydride includes pyromellitic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid,
3,5,6-biphenyltetracarboxylic acid, 2,2 ', 3,
3′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-diphenylethertetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetra Carboxylic acid, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid, 3,3 ′, 4,4′-azobenzenetetracarboxylic acid, bis (2,3-dicaroxyphenyl) methane, bis (3, 4-dicaroxyphenyl) methane, β, β-bis (3,4-dicaroxyphenyl) propane, β, β-bis (3,4-dicaroxyphenyl) hexafluoropropane and the like.

As the diamine component, m-phenyldiamine, p-phenyldiamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, m-xylylenediamine, p-xylylenediamine 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4′-diaminonaphthalebiphenyl, benzidine, 3,3-dimethylbenzidine, 3,3′-dimethoxybenzidine, ,
4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether (oxy-p, p'-dianiline; O
DA) 4,4'-diaminodiphenyl sulfide, 3,
3'-diaminobenzophenone, 4,4'-diaminophenylsulfone, 4,4'-diaminoazobenzene, 4,4 '
-Diaminodiphenylmethane, β, β-bis (4-aminephenyl) propane and the like. A compound in which an amino group in the above-described diamine component as the isocyanate component is substituted with an isocyanate group is exemplified. Commercially available products of these polyimides include, for example, pyromellitic acid-based polyimides containing ODA as a diamine component (Kapton H
A: manufactured by DuPont) or 3,3 ′, 4,4′-biphenyltetracarboxylic acid-based polyimide (Upilex S: manufactured by Ube Industries, Ltd.) 3,3′-diaminobenzophenone having a diamine component 3 ', 4,4'-benzophenonetetracarboxylic acid-based thermoplastic polyimide (LARC-TP
I: Mitsui Toatsu Chemical Industry Co., Ltd.).

Examples of the conductive agent dispersed in the base material Ba include conductive carbon-based materials such as carbon black and graphite;
Metals or alloys such as aluminum and copper alloys, and further, tin oxide, zinc oxide, antimony oxide, indium oxide, potassium titanate, and antimony tin oxide composite oxide (A
TO), conductive metal oxides such as indium tin oxide composite oxide (ITO), and electrolytes such as lithium perchlorate, quaternary ammonium perchlorate, quaternary ammonium chloride, and sodium trifluoromethanesulfonate. 1
One or more fine powders are used. The metal oxide may be coated with insulating fine particles such as barium sulfate, calcium carbonate, magnesium silicate and the like.

Among these conductive agents, carbon black is preferred in view of cost and environmental safety. Further, from the viewpoint of dispersibility, the average particle size of Mitsui Kinzoku Co., Ltd. is 0.1.
μm tin oxide complex compound (product name: UF), 0.3μ
m, zinc-based oxide (Pastran Type-II), barium sulfate having an average particle diameter of 0.4 μm coated with a tin-based compound, (Pastran Type-IV), 0.2 μm
ATO, 0.2 μm ITO etc. have an average particle size of 1 μm
The following metal oxides are also preferably used. The conductive metal oxide is preferably surface-treated with one or more of various silane coupling agents. The surface-treated metal oxide has improved compatibility with the resin constituting the base material, so that the dispersion is uniform and the variation in the resistance value of the base material is suppressed.

By the way, it is known that the elongation and contraction (displacement) of the belt due to the load at the time of driving the belt are inversely proportional to the Young's modulus of the belt material. That is, the relationship between the Young's modulus of the belt material and the amount of displacement due to the load when the belt is driven can be expressed by the following equation (1). ΔL = α · P · L / (t · w · E) (1) where: ΔL: belt displacement (μm) α: coefficient P: load ( N) L: Length of belt between two tension rolls (mm) t: Belt thickness (mm) w: Belt width (mm) E: Young's modulus of belt material (N / mm ² ) PC, PVD, etc. Conventionally used thermoplastic resin materials have a Young's modulus of 24 when carbon black is dispersed.
000 kg / cm ² or less. On the other hand, in the present invention, the Young's modulus of the base material is 30,000 kg / cm ²
As described above, when the disturbance (load fluctuation) at the time of driving the belt is the same, the elongation / shrinkage of the belt is reduced by 25% or more as compared with the related art. Therefore, for example, by forming the surface layer above the base material, and in some cases, the intermediate layer from a material having flexibility or elasticity, high quality transfer image quality can be stably obtained. In order to reduce the amount of displacement of the belt due to disturbance during belt drive and obtain good transfer image quality,
The thickness of the substrate is preferably 50 μm or more. Also, if the base material is too thick, the deformation of the belt surface at the portion of the belt support roll increases, and when forming a color image, the position of the multiple toner image is shifted and color misregistration occurs, The thickness of the substrate is preferably in the range of 50 to 150 μm, particularly 70 to 100 μm.

In the present invention, the surface layer is formed of a resin material in which a silica powder having an average particle size of 1 μm or less is dispersed in addition to the conductive agent. As the resin material, an aliphatic polyester resin in which polymer segments such as Byron 30SS, Byron 200, and Byron 300 manufactured by Toyobo Co., Ltd. are linearly bonded, and a polyurethane resin having a soft segment in a molecule are preferable. . Since these resins have flexibility in themselves, flexibility can be imparted to the surface layer. As the conductive agent dispersed in the surface layer, those described above are used. For the same reason, carbon black is preferable. Examples of the carbon black include furnace black, acetylene black, ketchen black, and channel black. As the hydrophobic silica powder, R202 manufactured by Nippon Aerosil Co., Ltd., which has been subjected to a surface treatment with silicone oil as a hydrophobic treatment, and Nippon Aerosil Co., Ltd. having an average primary particle system of 0.16 μm coated and treated with a methyl group. R
972, R974 of Nippon Aerosil Co., Ltd. having an average primary particle size of 0.12 μm.

The above silica powder has an average particle size of 1 μm.
The following fine powder is used: When the average particle diameter is larger than 1 μm, the surface of the intermediate transfer belt becomes rough, so that the transferability deteriorates. Also, by dispersing 5 parts by weight or more of silica powder with respect to 100 parts by weight of the resin material, the contact angle between the surface layer and the water droplet can be made 85 ° or more. However, the dispersion is preferably 20 parts by weight or less so that the smoothness of the surface of the intermediate transfer belt is not impaired, and the preferable blending amount with respect to 100 parts by weight of the resin material is 8 to 15 parts by weight. As described above, by setting the blending amount of the silica powder to 5 parts by weight or more, the surface energy of the surface layer is small, and the contact angle with a water droplet when expressed by wettability of water becomes 85 ° or more.

(Water wettability) The water wettability is expressed by using the material constituting the surface layer as a test piece and measuring the contact angle between the plane of the test piece and a water droplet. Here, when a water drop is placed on the surface of the test piece, the surface tension γs of the test piece, the interfacial tension γi between the liquid and the test piece, and the surface tension γl of the liquid are balanced. Form the shape of At this time, if the droplet is small and the influence of gravity can be ignored, the following Young's equation (2) holds. (Γs−γi) / γl = cosθ (2) Further, from the viewpoint of “wetting” regarding surface energy, wetting is a macroscopic viewpoint. From the viewpoint, it is a phenomenon that the contact surface between the solid and the gas spontaneously replaces the contact surface between the solid and the liquid, accompanied by a decrease in free energy of the system. Also, from a microscopic point of view, this phenomenon is observed when the intermolecular attraction (adhesion) of the liquid is large.

The change in free energy starts from a system in which a solid and a liquid are already in contact with each other, and reverses the sign (±) of the work required to separate the solid and the liquid. It is known. The work W is represented by the following equation (3). W = γsg + γlg−γsl (3) Here, γsg, γlg, and γsl are a solid / gas, respectively.
It is the free energy at the interface between liquid / gas and between solid / liquid, and has the same meaning as γs, γl, γi in equation (2). As is clear from the above equation (3), the change in free energy includes the surface free energy of the solid and the free energy between the solid and the liquid. However, since both cannot be directly measured, the contact angle between the solid and the liquid is used. Is done. That is, the aforementioned γ
The above-mentioned Young's equation holds between sg, γlg, γsl and the contact angle θ. cosθ = (γsg−γsl) / γlg (2 ′) Therefore, in the present invention, the surface energy of the material constituting the surface layer is determined by the contact angle of the surface layer with the water droplet. It was determined to be indicated by θ.

The volume resistivity of the surface layer is from 10 ^9.5 Ωcm to
10 ¹³ Ωcm range, preferably 10 ^10.5 Ωcm to 10
It is in the range of ¹² Ωcm. This volume resistivity can be easily adjusted to the above range by selecting the conductive agent and adjusting the amount of the conductive agent, as in the case of the base material. For example, when carbon black is dispersed in a polyester resin, it may be blended in a range of 7 to 12 parts by weight with respect to 100 parts by weight of the resin material (see FIG. 5). Volume resistivity is 10 ^9.5 Ω
If it is lower than cm, the charge provided by the primary transfer device during the primary transfer of the toner image from the image carrier to the intermediate transfer belt is removed by the conductivity of the intermediate transfer belt itself. As a result, the electrostatic force that holds the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer belt does not work, so that the electrostatic repulsive force between the toners and the fringe electric field near the image edge are reduced. Due to the force, the toner scatters around the image (blurring occurs), and an image with large noise is formed. On the other hand, when the volume resistivity is higher than 10 ¹³ Ωcm, especially 10 ¹⁴ Ωcm or more, the surface of the intermediate transfer belt is charged by the transfer electric field at the time of the primary transfer.

In order to prevent the occurrence of hollow characters, the thickness of the surface layer is preferably at least three times the average particle diameter of the toner. Here, the toner average particle diameter means its volume average particle diameter, and toner particles in the range of usually 3 to 13 μm are used. As an example, a volume average particle diameter of 7
When using μm, the thickness of the surface layer is preferably 21 μm or more. Also, if the surface layer becomes too thick,
Since the difference in the amount of deformation between the front surface of the belt and the back surface of the belt at the tension rolls (8a to 8c: 9) increases, the thickness of the surface layer is generally set to 80 μm or less. A more preferable range of the thickness is 30 to 65 μm. When the thickness is more than 80 μm, liquid dripping occurs at the time of forming a coating film by a coating method generally adopted as a thin film coating forming method, and it is difficult to stably form a smooth and uniform coating film. .

The surface layer in which the hydrophobic silica powder is dispersed is
Since the surface energy is low, and the adhesive is non-adhesive and flexible, there is a characteristic that the toner hardly adheres to the belt surface, and not only the secondary transfer from the belt material to the paper becomes easy, but also the toner adhesion and The generation of a hollow character due to the load of the nip can be prevented. Therefore, a high-quality image can be obtained. Incidentally, the surface layer in the present invention has flexibility, and its elongation is 50 to 100.
%, And the hardness of the surface layer is such that the dynamic microhardness (DHK) is 10 ° or less.

The surface layer is desirably formed by the above-mentioned coating method using a conductive paint containing the above-mentioned resin material amount, conductive agent, hydrophobic silica powder and, if necessary, a curing agent. Since the hydrophobic silica powder of the conductive paint may aggregate to a secondary particle size of 2 to 5 μm, the (primary) average particle size needs to be 1 μm or less as described above. Further, as the curing agent, for example, when the resin component is a polyester resin, a melamine resin or the like is preferable, and when the resin component is a polyurethane resin, a polyisocyanate compound is suitably used. As the diluent for the conductive paint, hexane, benzene, toluene, hydrocarbons such as xylene,
Examples include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and esters such as ethyl acetate, butyl acetate and ethyl butyrate. These diluents may be used alone or in combination of two or more. As the coating method, a brush coating, a dipping method, a spray method, a roll coater method or the like can be adopted. Further, the resin component is cured by heating the coating film formed on the base material at 140 to 180 ° C. for 10 to 60 minutes.

Further, when the intermediate transfer belt is a belt material having a three-layer structure, as described above, the intermediate layer is made of, for example, the conductive material-dispersed or non-dispersed elastic material. The elastic material is not particularly limited,
Any rubber material can be used. Specific examples thereof include isoprene rubber, chloroprene rubber, butyl rubber, norbornene rubber, fluorine rubber, silicone rubber,
One or more of urethane rubber, acrylic rubber, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), and EPDM (ethylene propylene diene rubber) are used. As the conductive agent,
Although the above-mentioned materials are used, for example, when a highly polar rubber material such as urethane rubber or NBR is used, it is not always necessary to disperse the conductive agent. That is, the volume resistivity of the intermediate layer is 10 ⁹ Ωcm to 10 ¹³ Ωc.
m is preferably in the range. If the volume resistivity is out of this range, the same problem as in the case of the surface layer having the two-layer structure causes a problem that the above-described blur occurs and a static elimination mechanism is required. The thickness of the intermediate layer is 50-100.
It is preferably in the range of μm, in which case the thickness of the surface layer is preferably in the range of 20 to 40 μm.

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the following examples. (Image Forming Apparatus) FIG. 4 is an overall explanatory view of Embodiment 1 of a digital color copying machine provided with an intermediate transfer belt as an image forming apparatus of the present invention. In FIG. 4, the image forming apparatus F
Has a UI (user interface) and a transparent platen glass 22 on which a document (not shown) is placed. The original placed on the platen glass 22 is illuminated by the light source 24 of the original illumination unit 23. The original reflected light is transmitted to the first mirror 25 of the original illumination unit 23 and the second mirror 27 and the third mirror 28 of the mirror unit 26.
, Passes through the imaging lens 29, and is CCD
The signals are read as G and B analog signals. The read image signal of the CCD is controlled by the IPS controlled by the controller C.
Is input to IPS image reading data output means 31
A / D-converts the input read image signal, and the image data output means 37 has an image memory 33 and converts the AD-converted data into Y, M, C, and K image data to perform density correction. Data processing such as enlargement / reduction correction is performed and output as write image data (laser drive data).

The laser drive signal output device 34 is provided with the IP
A laser drive signal of an image corresponding to the image data output from S is output to the latent image writing device 3 at a predetermined timing. The latent image writing device 3 outputs a laser beam L modulated by the laser drive signal. After the rotating image carrier 1 is charged by the charger 2, an electrostatic latent image is written by the laser beam L at the latent image writing position Q1, and the electrostatic latent image is rotated by the rotating shaft 4a in the developing area Q2. The toner image is developed by a rotary developing unit 4 having developing units 4k to 4c for K (black), Y (yellow), M (magenta), and C (cyan), which rotate together. The developed toner image is primarily transferred to the intermediate transfer belt B by a primary transfer roll (primary transfer device) 5 in a primary transfer area Q3. In the case of full-color recording, the process from the formation of the latent image on the surface of the image carrier to the primary transfer of the toner image is performed for the required colors Y (yellow), M (magenta), C (cyan), and K (black). The multicolor toner is repeatedly transferred onto the intermediate transfer belt B in a superimposed manner. The residual toner is removed from the surface of the image carrier 1 that has passed the primary transfer area Q3 by the image carrier cleaner 6, and the charge is removed by the charge remover 36. The intermediate transfer belt B is rotatably supported by belt support rolls 7 to 11 including a drive roll 7, a tension roll 8, idler rolls 9 and 10, and an inner secondary transfer roll 11.

The outer secondary transfer arranged so as to be able to be separated (separated and approached) between the inner secondary transfer roll 11 and a separated position separated from the inner secondary transfer roll 11 and a close position pressed. The secondary transfer unit T2 is constituted by the roll 12 and the voltage applying roll 13 which is in contact with the inner secondary transfer roll 11. The secondary transfer unit T2 applies a recording sheet S passing through a secondary transfer area Q4 formed by a nip (pressing area) of the outer secondary transfer roll 12 and the intermediate transfer belt B onto the intermediate transfer belt B. Is secondarily transferred. The voltage applied to the primary transfer device roll (primary transfer device) 5 and the secondary transfer device T2 is supplied from a transfer power supply circuit 37. When the outer secondary transfer roll 12 moves to the separated position, the secondary transfer roll cleaner 3
8 cleaning blade 3 made of polyurethane
By 8a, foreign substances such as toner and paper dust adhered to the surface are removed. A peeling claw 39 and a belt cleaner 14 are arranged along the surface of the intermediate transfer belt B and downstream of the secondary transfer area Q4.

Recording sheet S stored in paper feed tray 15
Are taken out by a pickup roll 42, separated one by one by a separation roll 43, temporarily stopped by a registration roll 44, and conveyed from the guide conveyance path 45 to the secondary transfer area Q4 at a predetermined timing. The recording sheet S, on which the toner image has been secondarily transferred when passing through the secondary transfer area Q4, is fixed to the fixing device 16 by a sheet guide 46 and a sheet conveying belt 47.
Transported to The recording sheet S on which the toner image is fixed when passing through the fixing device 16 is discharged to a discharge tray 49 by a discharge roller 48.

While the transfer of a full-color image has been described above, in the case of forming a mono-color image, for example, a K-color toner image primarily transferred onto the intermediate transfer belt B moves to the secondary transfer area Q4. Then, the toner image is immediately transferred to the recording sheet S. When forming a two-color or three-color image, a desired hue may be selected and the toner image may be transferred to the recording sheet S when the multiple toner image moves to the transfer section.

(Intermediate Transfer Belt of Example 1) In the following composition, "parts" indicating the ratio means "parts by weight". A polyimide varnish (UPILEX S: manufactured by Ube Industries, Ltd.) using N-methyl-2-pyrrolidone as a solvent,
18 parts of carbon black was added to 100 parts of the resin component and mixed with a mixer. The obtained membrane-forming stock solution was poured into a stainless steel cylindrical mold having a diameter of 168 mm and a height of 500 mm, and was subjected to centrifugal molding while drying with hot air at 120 ° C. for 120 minutes. Next, the cylindrical film removed from the semi-cured state is covered with an iron core, heated from 120 ° C. to 350 ° C. over 30 minutes to evaporate the solvent, and then heated at 450 ° C. for 20 minutes. Then, main curing for dehydrating and condensing the polyamic acid was performed. The obtained carbon black-dispersed polyimide film having a thickness of 80 μm was cut into a width of 370 mm to complete a seamless belt substrate (Ba).

Next, as a component for forming a surface layer, a linear polyester resin (byron SS, manufactured by Toyobo Co., Ltd.) 8
0 parts, melamine resin (trade name: Super Beckamine G8)
21-60, 20 parts by Dainippon Ink & Chemicals, Inc .; 5 parts of carbon black (trade name: FW200, Tegusa); and hydrophobic silica powder having an average primary particle size of 0.14 μm (trade name: R202, Japan) 10 parts of Aerosil Co., Ltd.) were mixed by a sand mill. 100 parts of this surface layer forming component was diluted with 100 parts of xylene to adjust the viscosity to prepare a conductive paint. This conductive paint was coated on the surface of the above-mentioned belt substrate (Ba) by a bell type electrostatic coating machine (manufactured by Lands Hague Industry Co., Ltd.),
For 30 minutes to form a surface layer (Bb) having a thickness of 50 μm (about 7 times the toner volume average particle diameter). This surface layer (B
In b), the volume resistivity was 10 ^12.5 Ωcm, and the contact angle θ with a water droplet was 89 °. The surface resistivity of the manufactured intermediate transfer belt B was 10 ^11.6 Ω / □, and the volume resistivity was 10 ^12.4 Ωcm. The volume resistivity and the surface resistivity were all measured using a resistance meter (HR probe of Hiresta IP: manufactured by Mitsubishi Yuka Co., Ltd.), and the current value 30 seconds after applying a voltage of 100 V was measured. I read and asked.

(Intermediate Transfer Belt of Second Embodiment) The intermediate transfer belt B used in the second embodiment of the image forming apparatus of the present invention.
Is manufactured as follows. As a conductive metal oxide, an average particle size of 0.4 μm coated with a tin oxide-based conductive agent
m barium sulfate (Pastran Type-IV) treated with γ-aminopropyltriethoxysilane was used. 37 parts of this conductive metal oxide was added to 100 parts of the resin component of the polyimide varnish used in Example 1, and the mixture was sufficiently mixed with a mixer. The obtained film-forming stock solution was uniformly cast on a stainless steel sheet to a thickness of 300 μm and dried in an atmosphere of 120 ° C. for 120 minutes, and then further at 150 ° C. for 30 minutes, and at 200 ° C. for 30 minutes.
The temperature was raised stepwise at 250 ° C. for 60 minutes and at 420 ° C. for 30 minutes to obtain a 75 μm thick polyimide sheet. After cutting the obtained polyimide sheet to a length of 540 mm and a width of 370 mm, a one-part one-part elastic adhesive (Super X8008: manufactured by Semedai Inn Co., Ltd.) is applied to one end of the sheet, and both ends are joined to form a seamless belt A substrate (Ba) was formed. Thereafter, in the same manner as in Example 1, the surface layer (B
b) formed. The surface resistivity of the manufactured intermediate transfer belt (7) is 10 ^11.8 Ω / □, and the volume resistivity is 10 ^12.2.
Ωcm.

(Comparative Example 1 of Intermediate Transfer Belt) A single-layer carbon material having a surface resistivity of 10 ^11.8 Ω / □ and a volume resistivity of 10 ^8.9 Ωcm was produced by the same production method as that of the substrate Ba of Example 1. A polyimide seamless belt of black dispersion was manufactured. (Comparative Example 2 of Intermediate Transfer Belt) The surface resistivity was 10 ^12.5 Ω by the same manufacturing method as that of the base material Ba of Example 2.
A single layer of a metal oxide-dispersed polyimide seamless belt having a volume resistivity of 10 ^7.3 Ωcm was prepared at / □. (Comparative Example 3 of Intermediate Transfer Belt)
A 0 μm-thick carbon black-dispersed thermoplastic PC (polycarbonate) resin seamless belt was produced. The surface resistivity of this PC resin belt is 10 ^11.9 Ω / □, and the volume resistivity is 10 ^12.5 Ωcm. (Comparative Example 4 of Intermediate Transfer Belt)
A 0 μm-thick carbon black-dispersed thermoplastic ETFE resin seamless belt was manufactured. The surface resistivity of this ETFE resin belt is 10 ^11.5 Ω / □, and the volume resistivity is 10 ^9.0 Ωcm.

(Comparative Example 5 of Intermediate Transfer Belt) A linear polyester resin (trade name: Byron 30SS, manufactured by Toyobo Co., Ltd.) as a component for forming a surface layer in the carbon black-dispersed polyimide obtained in the same manner as in Example 1. ) 80 parts, melamine resin (trade name: Super Beckamine G821-6)
0, 20 parts of Dainippon Ink and Chemicals, Inc., and 5 parts of carbon black (trade name: FW200, Tegusa) were mixed by a sand mill. 100 parts of this surface layer forming component was diluted with 100 parts of xylene to adjust the viscosity to prepare a conductive paint. This conductive paint is coated on the surface of the above-mentioned belt base material (Ba) by a bell-type electrostatic coating machine (manufactured by Ransberg Industry Co., Ltd.), and then is heated at 160 ° C. for 30 minutes.
Heated for 50 minutes to a thickness of 50 μm (about 7
Times) surface layer (Bb). This surface layer (Bb)
^Had a volume resistivity of 10 ^11.0 Ωcm and a contact angle θ with a water droplet of 83 °. The surface resistivity of the manufactured intermediate transfer belt B is 10 ^11.8 Ω / □, and the volume resistivity is 1
0 ^10.8 Ωcm.

(Mechanical Properties Test of Intermediate Transfer Belt) Tensile strength and Young's modulus of the base materials of the belt materials manufactured in Examples 1 and 2, and the belt materials manufactured in Comparative Examples 1 to 4. (Tensile modulus)
127. That is, the tensile strength is 5
Test speed 200m using strip test piece of × 40mm
It was measured at m / min. The Young's modulus is 25 × 25
Test speed 20 mm / m using a 0 mm strip test piece
Measured in.

(Evaluation Results of Image Quality) The intermediate transfer belts of the embodiment and the comparative example were mounted on the above-described image forming apparatus shown in FIG. 4, and the image quality obtained by performing a copy test was evaluated according to the following criteria. More evaluated. Hollow character evaluation ◎: No hollow character is generated ○: Hollow character is slightly generated ×: Hollow character is generated Blur evaluation ○: No blur is generated ×: Blur is generated

Measurement results of surface resistivity and volume resistivity of each intermediate transfer belt material, tensile strength and Young's modulus of base material (example) or belt sample (comparative example), volume resistivity of surface layer and contact angle θ Table 1 summarizes the evaluation results of the image quality.

[0050]

[Table 1]

As shown in Table 1, in the intermediate transfer belts of Examples 1 and 2, the contact angle θ was 85 ° or more and the surface energy of the surface layer was small despite the large Young's modulus of the base material. Moreover, since the surface layer has flexibility, no hollow character was generated. Further, since the surface resistivity of the belt material and the volume resistivity of the surface layer were within appropriate ranges, no blurring occurred. On the other hand, in Comparative Examples 1 and 2 having a single-layer structure using a base material as a belt material in the present invention, since the Young's modulus is as large as 62,000 kg / cm ² , the deformation of the belt due to the stress during driving is small, but a hollow character is generated. did. At the same time, because the surface energy is large,
In addition to the difficulty in transferring the toner to the paper, blurring occurred because the volume resistivity was lower than an appropriate range.

Also, in Comparative Example 3 in which a PC resin having a large contact angle θ of 75 ° and having a large surface energy was used as the belt, not only the transfer of the toner to the paper was difficult, but also a hollow character occurred. In Comparative Example 4 in which the ETFE resin having a small contact angle θ of 100 ° and a low surface energy was used as the belt material, a hollow character was slightly generated.
Blurring occurred because the volume resistivity was lower than the proper range. Further, in Comparative Example 3 or 4, the Young's modulus was 240
Since it was as small as 00 kg / cm ² or 11000 kg / cm ² , the belt was greatly deformed by the stress during driving, and color shift was observed in the obtained image. As shown in Table 1, the intermediate transfer belt of Comparative Example 5 had flexibility in the surface layer despite the large Young's modulus of the base material. Since the surface energy of was slightly large, a hollow character was slightly generated. Since the surface resistivity of the belt material and the volume resistivity of the surface layer were within appropriate ranges, no blurring occurred.

(Volume Resistivity of Carbon Black Dispersed Polyester Resin) FIG. 5 shows the amount of carbon black blended in 100 parts of resin component and 10 parts of hydrophobic silica powder in the polyester conductive paint used in Examples 1 and 2. Shows the relationship between the same blending amount and the volume resistivity of the surface layer forming material when the surface roughness is changed. As shown in FIG. 5, in order to adjust the volume resistivity of the surface layer within the range of 10 ^9.5 to 10 ¹³ Ωcm, carbon black is blended in the range of about 7 to 12 parts with respect to 100 parts of the resin component. It turns out to be good.

(Contact Angle of Water with Hydrophobic Silica Powder-Dispersed Polyester Resin and Water) FIG. 6 shows the resin component 100 in the polyester conductive paint used in Examples 1 and 2.
4 shows the relationship between the amount of the hydrophobic silica powder and the contact angle θ of the surface layer forming material when the amount of the hydrophobic silica powder was changed with respect to 5 parts of carbon black and 5 parts of carbon black. As shown in FIG. 6, it can be seen that in order to set the contact angle θ of the surface layer to 90 ° or more, 5 parts or more of hydrophobic silica powder may be blended.

(Relationship between Conductive Dispersed Polyimide Resin Material, Surface Resistivity, and Volume Resistivity) FIG. 7 shows the surface resistance of the polyimide resin film when the amount of carbon black dispersed in the polyimide resin was changed. FIG. 4 is a diagram showing a relationship between the ratio and the volume resistivity. In addition, the said polyimide resin film was manufactured by the method similar to Example 1. FIG. FIG. 8 shows the relationship between the surface resistivity and the volume resistivity of the polyimide resin film when the amount of the conductive metal oxide surface-treated with the silane coupling agent dispersed in the polyimide resin was changed. FIG. The resin sheet was manufactured in the same manner as in Example 2.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) The present invention is applicable to an image forming apparatus using an intermediate transfer drum instead of an intermediate transfer belt.

[0057]

The above-described image forming apparatus of the present invention has the following effects. (E01) Average particle diameter of 1 μm dispersed in the intermediate transfer member surface layer
By setting the blending amount of the hydrophobic inorganic material of m or less to a predetermined ratio or more, the surface layer of the intermediate transfer member is non-adhesive and the surface energy is reduced. There is no fear of transfer failure that the next transfer will not be performed, and generation of a hollow character can be suppressed. Therefore, a high-quality image can be obtained. (E02) The Young's modulus of the intermediate transfer member base material is 3000 kg / c
When it is increased to m ² or more, the deformation of the belt due to the stress during driving is small, and high quality transfer image quality can be obtained stably. (E03) The volume resistivity of the surface layer of the intermediate transfer member is 10 ^9.5-
When it is in the range of 10 ¹³ Ωcm, there is no blurring at the time of transfer, and the charge eliminating mechanism can be omitted. (E04) When the intermediate transfer member surface layer is formed of a flexible material, the intermediate transfer member is deformed following the pressing force of the transfer roll, so that the occurrence of image defects due to the generation of hollow characters is reduced.

[0058]

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus of an intermediate transfer member type provided with main constituent members.

FIG. 2 is an explanatory diagram illustrating a cross-sectional structure of an intermediate transfer member according to the present invention.

FIG. 3 is a cross-sectional view of a test piece plane and a water droplet showing a contact angle as a measure of surface energy.

FIG. 4 is an overall view of an image forming apparatus shown as one embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the blending amount of carbon black and the volume resistivity of the surface layer forming material.

FIG. 6 is a graph showing the relationship between the amount of silica powder and the contact angle of the surface layer forming material with water.

FIG. 7 is a diagram showing the relationship between the surface resistivity and the volume resistivity of a carbon black-dispersed polyimide resin material.

FIG. 8 is a diagram showing the relationship between the surface resistivity and the volume resistivity of a conductive metal oxide-dispersed polyimide resin material.

[Explanation of symbols]

B: intermediate transfer belt (intermediate transfer member), 1: image carrier, 2
... Charging device, 3 ... Latent image writing device, 4 ... Developing device, 5 ... Primary transfer device, 6 ... Cleaning device, 7 ... Drive roll, 8 ...
Tension roll, 9,10 idler roll, 11 inner secondary transfer roll, 12 outer secondary transfer roll, 13 ...
Voltage applying roll, 14: belt cleaner, 15: paper feed tray, 16: fixing device.

Claims (7)

[Claims] An image bearing member for forming an electrostatic latent image corresponding to image information; a developing device for visualizing the electrostatic latent image formed on the image bearing member as a toner image with toner; An intermediate transfer member on which the unfixed toner image thus formed is primarily transferred, and an unfixed toner image on the intermediate transfer member,
A secondary transfer device for performing a secondary transfer, wherein the intermediate transfer member has a layer structure composed of a plurality of layers having at least a substrate and a surface layer, and the substrate is composed of a resin material in which a conductive agent is dispersed. The surface layer is made of a resin material in which a conductive agent and a hydrophobic inorganic material having an average particle diameter of 1 μm or less are dispersed, and
An image forming apparatus having a volume resistivity in a range of 10 ^9.5 Ωcm to 10 ¹³ Ωcm. 2. The base material has a Young's modulus of 30,000 k
The image forming apparatus according to claim 1, wherein g / cm ² or more. 3. The surface layer has a contact angle with a water droplet when expressed by wettability of water smaller than that of the image carrier, and
The image forming apparatus according to claim 1, wherein the number is not less than ゜. 4. The method according to claim 1, wherein the surface layer is formed of a polyester-based conductive paint, and comprises the conductive agent containing carbon black and the hydrophobic inorganic material containing hydrophobic silica powder. 4. The image forming apparatus according to any one of claims 1 to 3. 5. The intermediate transfer member according to claim 1, wherein the intermediate transfer member is made of a belt material having a two-layer structure, the base material has a thickness of 50 μm or more, and the thickness of the surface layer is three times or more the toner particle size. An image forming apparatus according to any one of claims 1 to 4. 6. The image forming apparatus according to claim 1, wherein the substrate is made of a carbon black-dispersed polyimide resin material. 7. The image forming apparatus according to claim 1, wherein said base material is made of a metal oxide-dispersed polyimide resin material.