JP4656297B2 - Conductive belt and method for producing conductive belt - Google Patents

Description

  The present invention provides a conductive belt in which at least three layers of a base layer, an elastic layer, and a surface layer are sequentially laminated from an inner peripheral surface to an outer peripheral surface, a method for manufacturing the conductive belt, and the conductive belt attached thereto. The present invention relates to an image forming apparatus. The conductive belt of the present invention is suitably used as an intermediate transfer belt in an electrophotographic image forming apparatus. In the image forming apparatus, not only powder toner but also liquid toner can be used.

An electrostatic latent image corresponding to image information is formed by exposing the surface of an image carrier such as a positively or negatively charged photoconductor, and the latent image is formed as a toner image using toner charged by a developing device. An electrophotographic image forming apparatus that develops, electrostatically copies the visualized toner image onto a recording medium such as paper, and fixes the toner on the recording medium by heating and melting it to obtain a predetermined image Is being actively developed and applied to laser printers, copiers and facsimiles.
In recent years, a toner image formed on an image carrier such as a photoconductor with color toners is sequentially superimposed on an intermediate transfer member (hereinafter referred to as primary transfer) on a toner image of another color that has been separately formed. Many color image forming apparatuses are commercially available that can obtain a desired color image by batch transfer (hereinafter referred to as secondary transfer) of a color toner image formed on a transfer body to a recording medium.

In such a color image forming apparatus, a belt made of a relatively hard material such as polyimide or polycarbonate is used as an intermediate transfer member so that a toner image of each color does not shift.
In recent years, various intermediate transfer belts have been developed.
For example, in Japanese Patent No. 3248455 (Patent Document 1), a surface made of a resin material having a large Young's modulus, an elastic material layer, and a non-adhesive material and having a volume resistivity set to a specific range is disclosed. An intermediate transfer belt having a laminated structure with layers is described.
Japanese Patent Laid-Open No. 2001-312159 (Patent Document 2) describes an intermediate transfer belt having an elastic layer having a predetermined hardness.
Japanese Patent Application Laid-Open No. 2002-229345 (Patent Document 3) has a resin base layer having a predetermined volume resistivity by a predetermined tensile elastic modulus and electronic conductivity, and has a predetermined hardness, electric resistance value, and thickness. A conductive belt provided with an intermediate layer made of an ion conductive elastomer and a resin surface coating layer is described.

When a single layer belt made of polyimide or polycarbonate and the belts described in Patent Documents 1 to 3 are used, color misregistration that is a concern when toner images are superimposed in forming a color image is unlikely to occur.
However, it is generally recognized that an electrophotographic image forming apparatus has characteristics that allow a wide variety of paper to be used as a recording medium, as compared with an inkjet type image forming apparatus, and it is required to make use of this characteristic. However, the belt does not fully exhibit this characteristic. Specifically, there are large surface irregularities such as “Capital Bond” manufactured by Fox River (USA), “Classic Raid Lighting” manufactured by Nina (USA), and “Strathmore Lighting Raid” manufactured by Strathmore (USA). When paper is used as a recording medium, in the secondary transfer in which a color image formed on the intermediate transfer belt is transferred to the recording medium, the toner is not transferred to the concave portion of the paper, so-called whitening. Secondary transfer failure is observed.

Accordingly, the applicant of the present invention has provided a conductive belt having improved transferability of a toner image from an image holding member and transferability to a recording medium by providing appropriate flexibility in the thickness direction on the outer surface of the belt. (Japanese Patent Application No. 2003-373640 (Patent Document 4)).
However, even in such a conductive belt, secondary transfer to “Capital Bond” manufactured by Fox River (USA), which has relatively small unevenness among the above-mentioned paper types, is satisfactory, but Nina (US), which has even more unevenness, is used. The secondary transfer to “Classic Raid Writing” manufactured by Strathmore, Inc. and “Strathmore Lighting Raid” manufactured by Strathmore (USA) was insufficient, and there was room for further improving the secondary transferability of the conductive belt.

Japanese Patent No. 3248455 JP 2001-312159 A JP 2002-229345 A Japanese Patent Application No. 2003-373640

  In view of the above problems, the present invention is suitable for use as a conductive belt, particularly an intermediate transfer belt, which is excellent in secondary transfer to a recording medium having a large unevenness on the surface and capable of transferring an image cleanly even in a concave portion. It is an object to provide a conductive belt.

In order to solve the above problems, the present invention is a conductive belt in which at least three layers of a base layer, an elastic layer, and a surface layer are sequentially laminated from the inner peripheral surface toward the outer periphery,
The hardness measured from the surface side of the belt in a laminated state by the IRHD hardness test micro method is 40 or more and 60 or less,
Furthermore, the base layer has a thickness of 50 to 150 μm, a tensile elastic modulus of 2000 MPa to 8000 MPa and a surface electrical resistivity on the inner peripheral surface side of 10 ⁶ Ω / □ to 10 ¹¹ Ω / □,
The elastic layer has a thickness of 400 to 1500 μm, a JISA hardness of 25 to 60 and a volume resistivity of 10 ⁶ Ω · cm to 10 ⁸ Ω · cm,
The surface layer provides a conductive belt having a thickness of 3 to 30 μm and a complex elastic modulus of 30 MPa to 250 MPa.

The present inventor makes the thickness of the elastic layer relatively large at 400 to 1500 μm in the conductive belt in which at least three layers of the base layer, the elastic layer, and the surface layer are sequentially laminated from the inner peripheral surface to the outer peripheral surface. JIS for elastic layer
A paper having large irregularities is used as a recording medium by satisfying two conditions regarding hardness: A hardness is 60 or less, and hardness measured from the surface layer side of the belt in a laminated state by IRHD hardness test micro method is 60 or less. However, it has been found that the occurrence of white spots in the recesses can be suppressed.
As described above, the volume resistivity of the elastic layer is set to 10 ⁶ Ω · cm or more and 10 ⁸ Ω · cm or less so that the transfer voltage is not increased by the relatively large thickness of the elastic layer of 400 to 1500 μm. Furthermore, in order to improve transferability in primary transfer and secondary transfer, the surface electrical resistivity on the inner peripheral surface side of the base layer is set to 10 ⁶ Ω / □ or more and 10 ¹¹ Ω / □ or less.
Furthermore, the surface layer has a complex elastic modulus of 250 MPa or less in order to suppress wear or delamination of the surface layer and improve durability.

In the present invention, at least three layers of a base layer, an elastic layer, and a surface layer are sequentially laminated from the inner peripheral surface to the outer peripheral surface, and measured according to the IRHD hardness test micro method from the surface layer side of the laminated conductive belt. The hardness is 60 or less.
By setting the hardness to 60 or less, the nip width between the belt and the recording medium at the time of secondary transfer is widened, and the belt surface and the recording medium are in soft contact with each other. Will be better. Furthermore, as will be described in detail below, when the thickness of the elastic layer is relatively large, distortion generated on the belt surface when the belt is stretched on the drive shaft increases, but by reducing the hardness to 60 or less, The followability can be improved, and the above problems can be improved.
The hardness measurement by the IRHD hardness test micro method is performed in accordance with JIS K 6253 by cutting out a part from a conductive belt in a laminated state and using it as a test piece.

Moreover, in the electroconductive belt of this invention, the tensile elasticity modulus of a base layer is 2000 Mpa or more. As a result, the belt stretch can be suppressed, and the belt speed change can be reduced. As a result, it can sufficiently cope with the recent increase in the speed of the image forming apparatus, and in color printers and color copiers, image color misregistration can be achieved. Can be prevented.
The tensile elastic modulus of the base layer is more preferably 2300 MPa or more, and the upper limit is not particularly limited, but is usually 8000 MPa or less. The tensile elastic modulus is measured according to JIS K 7113.

In the conductive belt of the present invention, the surface resistivity of the base layer is 10 ⁶ Ω / □ or more and 10 ¹¹ Ω / □ or less, and the volume resistivity of the elastic layer laminated on the front side of the base layer is 10 ^6. Ω · cm or more and 10 ⁸ Ω · cm or less.
With this setting, even when the elastic layer thickness is relatively large as described in detail below, excellent transferability is exhibited in both primary transfer and secondary transfer when used as an intermediate transfer belt. Appropriate conductivity can be imparted.
The surface electrical resistivity and volume resistivity are measured using a “HIRESTA UP MCP-HT450 type” manufactured by Dia Instruments Co., Ltd. with a URS probe under an applied voltage of 250 V and a measurement time of 10 seconds. The measurement environment is a temperature of 23 ° C. and a relative humidity of 55%.

The surface resistivity of the base layer is set to 10 ⁶ Ω / □ or more. If it is less than 10 ⁶ Ω / □, the charging characteristics of the belt deteriorate, the charge of the charged toner becomes easy to move, and the toner to be transferred This is because the image is disturbed. The surface electrical resistivity of the base layer is set to 10 ¹¹ Ω / □ or less. If it exceeds 10 ¹¹ Ω / □, a large transfer voltage is required for primary transfer, transfer efficiency is deteriorated, and belt neutralization is difficult. This is because the cleaning performance of the excess toner remaining on the belt is deteriorated. More preferably, the surface electrical resistivity of the base layer is 10 ⁷ Ω / □ or more and 10 ¹⁰ Ω / □ or less.
The volume resistivity of the elastic layer is set to 10 ⁶ Ω · cm or more. If the elastic layer is less than 10 ⁶ Ω · cm, the charging characteristics of the belt deteriorate, the charge of the charged toner easily moves, and the transferred toner image. This is because disturbance occurs. The reason why the volume resistivity of the elastic layer is set to 10 ⁸ Ω · cm or less is that if it exceeds 10 ⁸ Ω · cm, a large transfer voltage is required for primary transfer and transfer efficiency deteriorates.

  In the conductive belt of the present invention, the thickness of the base layer is 50 to 150 μm. The reason why the thickness is 50 μm or more is to obtain a good image by holding the strength sufficient to regulate the elongation in the circumferential direction and suppressing fluctuations in the belt speed. On the other hand, the reason why the thickness is 150 μm or less is to prevent the occurrence of cracks in the base layer. More preferably, the thickness of the base layer is 70 to 110 μm.

  Although the material which comprises a base layer will not be specifically limited if the said physical property can be shown, It is preferable that it is resin. Resins that can constitute the base layer include polyimide resins, polyamideimide resins, polyetherimide resins, silicone imide resins, urethane imide resins, polyurethane resins, polyurea resins, epoxy resins, melanin resins, unsaturated polyester resins, or vinyl ester resins. Etc. Of these, polyimide resin, polyamideimide resin, polyurethane resin or polyurea resin are preferable, and polyimide resin or polyamideimide resin is particularly preferable.

  The constituent material of the base layer is blended with an electronic conductive agent in order to keep the surface electrical resistivity within the predetermined range. Electronic conductive agents such as carbon blacks such as ketjen black, furnace black or acetylene black, conductive metal oxides such as zinc oxide, potassium titanate, antimony doped titanium oxide, tin oxide or graphite, or electronic conductivity such as carbon fiber Agent is used. Among these, it is preferable to use carbon black as the electronic conductive agent. The amount of the electronic conductive agent depends on the type of the electronic conductive agent and the type of the resin constituting the base layer, so it cannot be generally stated, but generally about 1 to 50 parts by mass with respect to 100 parts by mass of the resin solid content. More preferably, it is about 3 to 40 parts by mass.

In the conductive belt of the present invention, the elastic layer has a JIS A hardness of 60 or less.
When the JIS A hardness exceeds 60, the nip width at the time of transfer cannot be sufficiently obtained, and when paper with large irregularities is used as a recording medium, white spots may occur in the concave portions of the paper. If the hardness is too low, the shape retention of the elastic layer is deteriorated, so the lower limit is preferably about 25. JIS
The A hardness is measured in accordance with JIS K 6253.

  The elastic layer has a thickness of 400 to 1500 μm. When the thickness of the elastic layer is less than 400 μm, the nip width at the time of transfer cannot be sufficiently obtained, and when paper with large irregularities is used as a recording medium, white spots may occur in the concave portions of the paper. On the other hand, if the thickness of the elastic layer exceeds 1500 μm, the weight of the belt becomes too large, and the mechanical load applied during driving becomes too large. The thickness of the elastic layer is more preferably 500 to 1200 μm.

The elastic layer is made of an elastomer, and the elastomer may be either an ionic conductive elastomer or an electronic conductive elastomer as long as it exhibits a volume resistivity in the above-mentioned predetermined range. However, since it is excellent in the uniformity of electrical resistance, it is preferably an elastomer having ionic conductivity.
As the ionic conductive elastomer, known ionic conductive rubber can be used, and an elastomer to which an ionic conductive agent is added may be used. Examples of the ion conductive rubber include rubber materials having a polar group in the composition, and specific examples include acrylonitrile butadiene rubber, epihalohydrin rubber (particularly epichlorohydrin rubber), chloroprene rubber, acrylic rubber, polyurethane elastomer, and the like. Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (for example, lauryltrimethylammonium), octadecyltrimethylammonium (for example, stearyltrimethylammonium), hexadecyltrimethylammonium, benzyltrimethylammonium, and modified aliphatic dimethyl. Perchlorate such as ethylammonium, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, alkyl sulfate, carboxylate, sulfonate, etc .; lithium, sodium, Perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, sulfates, alkyl sulfates, calcium sulfates of alkali metals or alkaline earth metals such as potassium, calcium, and magnesium Emissions salt, trifluoromethyl sulfate, sulfonate, and a bis-trifluoromethanesulfonyl imide salt. These may be used alone or in combination of two or more.

  Especially, it is preferable that the elastomer which comprises an elastic layer contains the polyurethane elastomer as a main component in the ratio of 50-100 mass parts. As the polyurethane elastomer, a main component is a terminal isocyanate prepolymer obtained from a polyol mainly composed of polypropylene glycol and / or a hydroxyl-terminated liquid rubber and an aromatic diisocyanate, and this is an aromatic diamine or / and a polyol as a curing agent. It is more preferable to use a polyurethane elastomer obtained by curing. This is because low hardness is easily achieved and flame retardancy is easily imparted, and it can be manufactured at a relatively low cost.

Examples of the hydroxyl-terminated liquid rubber include hydroxyl-terminated liquid polybutadiene, hydroxyl-terminated liquid polyisoprene, hydroxyl-terminated liquid styrene-butadiene rubber, hydroxyl-terminated liquid acrylonitrile-butadiene rubber, liquid poly (oxypropylene) glycol, and liquid poly (oxytetramethylene). ) Glycol, liquid polyolefin glycol, hydroxyl group-terminated liquid silicone rubber, etc. are used, and among them, hydroxyl group-terminated liquid polybutadiene is preferably used from the viewpoint of balance of physical properties.
The polyol is more preferably a hydroxyl-terminated liquid rubber such as a phosphorus-containing polyol or a hydroxyl-terminated liquid polybutadiene for reasons of physical properties, and can be used alone or in combination.

The terminal isocyanate prepolymer is obtained by mixing two reactants, a reaction product of polypropylene glycol and aromatic diisocyanate, and a reaction product of polyol and aromatic diisocyanate mainly composed of a hydroxyl group-terminated liquid rubber. It is preferable to do this. Thereby, the variation in electrical resistance can be further reduced.
In addition, the above-mentioned terminal isocyanate prepolymer is
(1) Only those comprising a reaction product of polypropylene glycol and aromatic diisocyanate,
(2) Only those composed of a reaction product of a polyol and an aromatic diisocyanate mainly composed of a hydroxyl group-terminated liquid rubber,
(3) A mixture of polypropylene glycol and a polyol mainly composed of a hydroxyl-terminated liquid rubber may be reacted with an aromatic diisocyanate.

  When a polyurethane elastomer is used for the elastic layer, in order to reduce the JIS A hardness of the elastic layer to 60 or less as specified in the present invention, a long-chain linear polyol is introduced into the terminal isocyanate prepolymer, or the prepolymer For example, a technique such as reducing the ratio of amine compounds at both ends that undergo a crosslinking curing reaction can be used.

  The elastomer having ionic conductivity may be supplemented with conductivity by an electronic conductive agent within a range in which variation in electric resistance does not occur. Thereby, the environmental dependence of electrical resistance can be reduced. The addition amount of the electronic conductive agent may be appropriately selected. The volume resistivity of the elastic layer supplementarily applied with the electronic conductive agent under the conditions of an applied voltage of 250 V, a temperature of 23 ° C., and a relative humidity of 55% is defined as R. When the volume resistivity of the elastic layer containing no electronic conductive agent under the conditions is R1, and Log (R) −Log (R1) = Log (R2), 0.1 ≦ Log (R2) ≦ 5 About, preferably 0.2 ≦ Log (R2) ≦ 3, more preferably about 0.3 ≦ Log (R2) ≦ 2, it is preferable to supplement the electronic conductive agent.

  When an electronic conductive agent is blended in the elastomer constituting the elastic layer, as with the base layer, carbon black such as ketjen black, furnace black or acetylene black, zinc oxide, potassium titanate, antimony doped titanium oxide In addition, a conductive metal oxide such as tin oxide or graphite or an electronic conductive agent such as carbon fiber is used.

In addition, various polyols, additives for adjusting the molecular weight, antifoaming agents, leveling agents, and curing agents that improve processability when processed into a belt shape can be blended in the material constituting the elastic layer. Among these, it is preferable to add a flame retardant compound. Examples of the flame retardant compound include flame retardants such as phosphorus compounds, halogen compounds, phosphate ester compounds, red phosphorus compounds, magnesium hydroxide compounds, aluminum hydroxide compounds, and flame retardant polymer graft polyols. . It is particularly preferable to use a flame retardant compound having reactivity such as a phosphorus compound or a halogen compound. By blending such a flame retardant compound having reactivity, flame retardancy can be imparted, and problems such as photoreceptor contamination and toner adhesion due to bleeding can be reduced.
On the other hand, when the conductive belt of the present invention is incorporated and used in an image forming apparatus, it exudes like a plasticizer in order to avoid problems such as contamination to other members such as a photoreceptor due to long-term use. It is preferable not to add the easy substance to the material constituting the elastic layer.

In the present invention, the complex elastic modulus of the surface layer is 250 MPa or less, preferably 200 MPa or less, more preferably 150 MPa or less.
The complex elastic modulus is measured under measurement conditions of dynamic strain 10 Hz, amplitude 0.2%, initial strain 10%, and temperature 23 ° C. based on JIS K 7198. The reason why the surface layer has a complex elastic modulus of 250 MPa or less is that it is possible to suppress surface cracking, abrasion, or peeling due to surface cleaning with a cleaning blade or pressure at the time of transfer, and to increase the durability of the conductive belt. Because it can. Note that the complex elastic modulus of the surface layer is preferably 30 MPa or more, and this is due to poor cleaning properties when it is less than 30 MPa.

  The surface layer has a thickness of 3 to 30 μm. The reason why the thickness is set to 3 μm or more is to prevent the surface layer from being worn out during use and reducing the detachability of the toner particles. The reason why the thickness is 30 μm or less is to save time and labor required for forming the surface layer and to reduce the manufacturing cost. Preferably, the thickness of the surface layer is 5 to 20 μm.

Although the material which comprises the said surface layer will not be specifically limited if the complex elastic modulus of the said fixed range can be exhibited, It is preferable to use a fluororubber. Even in the case of an image forming apparatus of a wet development type using a liquid toner as a toner, the fluororubber is stable with respect to a paraffinic solvent used as a solvent for the liquid toner and does not swell, so that sufficient durability can be maintained.
The kind of fluororubber is not particularly limited, and a copolymer of VdF and hexafluoropropylene (HFP) mainly composed of vinylidene fluoride (VdF), VdF-chlorotrifluoroethylene copolymer, VdF-pentafluoropropene. Examples thereof include fluorine-based elastomers such as copolymers, ternary copolymers of VdF, HFP, and tetrafluoroethylene (TFE), and alternating copolymers of TFE and propylene. These may be used singly or in combination, and for example, may be used by mixing with silicone rubber or fluorosilicone rubber.

The surface layer is preferably ion-conductive and non-electron-conductive, so that local variations in surface electrical resistance can be eliminated. The surface layer is preferably adjusted to have a volume resistivity of about 10 ¹⁰ Ω · cm or more and about 10 ¹⁵ Ω · cm or less when 250 V is applied in order to improve toner delivery. The surface layer may be insulative.

The present invention provides a method for producing a conductive belt having the above-described configuration,
While rotating the cylindrical mold, the material constituting the base layer is continuously supplied from the nozzle to the outer surface of the mold, and at the same time, the nozzle is moved in the direction of the rotation axis of the mold to uniformly apply the material. After that, the base layer is formed by curing,
Next, an elastic layer is formed on the base layer by the same method,
Then, the manufacturing method which coats a surface layer on an elastic layer is provided.

Below, the said manufacturing method is explained in full detail.
In order to improve mold releasability, a mold release agent made of silicone oil or the like may be applied to the mold surface, or the mold may be coated with ceramics. Examples of the ceramic include silica, alumina, zirconia, silicon nitride coated by a sol-gel method; alumina, zirconia coated by a thermal spray method; or aluminum nitride coated by a sputtering method.

When forming the base layer, the nozzle for supplying the material constituting the base layer has its liquid discharge port in contact with the mold, and the nozzle moving speed V (mm / second) and the rotational speed R (rotation) of the cylindrical mold. / Sec) is expressed by the following equation (1).
(V / R) <1.5 (mm / rotation) (1)
By performing application under the conditions in the above range, it is possible to prevent the occurrence of stripes and irregularities due to the liquid stirring effect in the vicinity of the liquid discharge port of the nozzle.

  In consideration of cost reduction, it is preferable that the coating time is short. The coating time can be shortened by increasing the number of rotations of the mold, but there is an upper limit to the number of rotations of the mold because it is necessary to prevent the liquid from splashing due to centrifugal force. Therefore, the liquid discharge port of the nozzle is tubular and the wall thickness is set to about 0.3 to 3.0 mm, more preferably about 0.5 to 2.0 mm, so that the application time is shortened and striped patterns and unevenness are not generated. I have to.

  The elastic layer can be formed on the base layer in exactly the same manner as the base layer forming method. After forming the elastic layer on the base layer, a primer may be applied to the surface of the elastic layer in order to improve the adhesion between the elastic layer and the surface layer.

  Examples of methods for coating the material constituting the surface layer on the elastic layer include roll coater or bar coating, spray coating, electrostatic coating, dip coating, etc., but they must be applied relatively thinly and uniformly. To electrostatic coating is preferred. In painting, it is preferable to use a water-based fluororubber paint obtained by coating a fluororubber emulsion or a solvent-based fluororubber paint obtained by dissolving fluororubber in an organic solvent.

  According to the said manufacturing method, there exists an advantage that the precision of the thickness of each layer is favorable and material loss is small. Furthermore, there is an advantage that a belt whose thickness varies in the axial direction can be obtained by adjusting the amount of material supplied from the nozzle, the moving speed of the nozzle in the rotational axis direction, and the like. Furthermore, when the material constituting the base layer or the material constituting the elastic layer is a two-liquid mixing type material, an apparatus capable of mixing the two liquids at a desired ratio and supplying them to the nozzle can be used. As a result, the efficiency of the production process can be improved.

In addition, the manufacturing method of the electroconductive belt of this invention is not limited to the said method, You may manufacture with a conventionally well-known method. For example,
(1) A method of centrifugal molding in the order of a surface layer, an elastic layer, and a base layer,
(2) A method of applying a surface layer after centrifugal molding in the order of an elastic layer and a base layer, removing the mold,
(3) A method in which only the base layer is centrifugally molded, removed from the mold, and then applied in the order of the elastic layer and surface layer.

  The conductive belt composed of the base layer, the elastic layer, and the surface layer has been described above. However, the conductive belt of the present invention has at least three layers of the base layer, the elastic layer, and the surface layer. You may have a laminated structure. For example, another layer may be sandwiched between the base layer and the elastic layer or / and the elastic layer and the surface layer.

  The conductive belt of the present invention can be suitably used as an intermediate transfer belt in an electrophotographic image forming apparatus such as a laser beam printer, an ink jet printer, a copying machine, a facsimile machine or an ATM. Among these, it is more preferable to use as an intermediate transfer member of an electrophotographic color printer or a color copier. The image forming apparatus may be either a dry development type image forming apparatus using powder toner or a wet development type image forming apparatus using liquid toner. Note that the electrophotographic image forming apparatus develops an electrostatic latent image formed on an image carrier with toner, primarily transfers the toner image to an intermediate transfer belt, and a plurality of color toners as necessary. The apparatus can obtain a desired image by superimposing the image on an intermediate transfer belt and then secondarily transferring the image onto a recording medium such as paper.

In the present invention, the thickness of the elastic layer is relatively large, and the hardness of the elastic layer and the hardness of the entire belt are kept somewhat low, thereby widening the nip width between the belt and the recording medium during secondary transfer. Even when paper with large irregularities is used as the recording medium, the occurrence of white spots in the concave portions of the paper can be suppressed and a good image can be obtained.
Furthermore, as described above, the volume resistivity of the elastic layer and the surface resistivity on the inner peripheral surface side of the base layer are controlled within a certain range so that the transfer voltage is not increased by the relatively large thickness of the elastic layer. Therefore, the transferability is very good not only in the secondary transfer from the intermediate transfer belt to the recording medium but also in the primary transfer from the image carrier such as a photoconductor to the intermediate transfer belt.
In addition, since the complex elastic modulus of the surface layer is 250 MPa or less, abrasion or peeling of the surface layer is suppressed, and the durability is excellent. In the case of a wet development type electrophotographic apparatus, the solvent of the liquid toner may enter the conductive belt, the base layer and the elastic layer may swell, and the durability of the belt may be remarkably deteriorated. However, if the abrasion or peeling of the surface layer is suppressed, the penetration of the solvent of the liquid toner can be suppressed, and the durability of the belt can also be improved in this respect. If fluororubber is used as the material constituting the surface layer, the penetration of the solvent of the liquid toner can be more effectively prevented, and the durability of the belt is further improved.

Embodiments of the present invention will be described below.
FIG. 1 shows a conductive belt 1 made of a seamless belt according to an embodiment of the present invention. The overall shape of the conductive belt 1 is a substantially cylindrical seamless belt. Since the conductive belt 1 is rich in flexibility and can be freely deformed by its own weight or the like, it can have various shapes.
As shown in FIG. 2, the conductive belt has a three-layer structure in which a base layer 3, an elastic layer 5, and a surface layer 7 are sequentially laminated. When the conductive belt 1 is used as an intermediate transfer belt of an image forming apparatus, the outer peripheral surface 9 is a surface to which toner or the like adheres, and the inner peripheral surface 11 is a surface that directly contacts a drive shaft or the like during rotation.

The base layer 3 is composed of a resin-made rigid layer having electronic conductivity, and is blended with carbon black, which is mainly composed of polyamideimide resin and is an electronic conductive agent.
The elastic layer 5 is an elastic layer made of an elastomer having ion conductivity, and is a two-component curable urethane having a terminal isocyanate prepolymer obtained from polypropylene glycol and aromatic diisocyanate as a main component and polypropylene glycol and aromatic diamine as a curing agent. Made of rubber.
The surface layer 7 is formed by applying a water-based fluororubber paint.

The base layer 3 has a tensile elastic modulus of 2300 to 3500 Mpa and a surface electrical resistivity of 10 ⁹ Ω / □ (1.0 × 10 ⁹ Ω / □ or more and 9.9 × 10 ⁹ Ω / □ or less) on the inner peripheral surface side. The thickness is about 70 to 90 μm.
Elastic layer 5 is JIS
The A hardness is 25 to 50, the volume resistivity is 10 ⁷ Ω · cm (1.0 × 10 ⁷ Ω · cm or more and 9.9 × 10 ⁷ Ω · cm or less), and the thickness is 600 to 1200 μm.
The surface layer 7 has a complex elastic modulus of 70 to 150 MPa and a thickness of 5 to 15 μm.
The hardness measured from the surface layer side of the conductive belt 1 in the laminated state according to the IRHD hardness test micro method is 40-60.

The conductive belt 1 can be used as an intermediate transfer belt 20 of a tandem type full-color image forming apparatus as shown in FIG.
The intermediate transfer belt 20 is installed between the drive rollers 24a and 24b, and is driven at a constant speed in the direction of the arrow by a drive mechanism (not shown). Four developing units 21a, 21b, 21c, and 21d of black (B), magenta (M), cyan (C), and yellow (Y), each having a charging device, a photosensitive member, an exposure device, and a developing device, Primary transfer rolls 23a, 23b, which are arranged in a line along the intermediate transfer belt 20 and are opposed to the photoreceptors 22a, 22b, 22c, 22d of the developing units 21a-d with the intermediate transfer belt 20 interposed therebetween. 23c and 23d are arranged.
The full-color toner image formed on the intermediate transfer belt 20 is transferred onto a recording medium 26 typified by paper at the transfer position by the operation of the secondary transfer roll 25, and is subjected to fixing processing by a fixing unit 27. A full-color image is formed.

The conductive belt 1 is manufactured by a manufacturing apparatus shown in FIGS.
As shown in FIG. 4, while the cylindrical mold 33 is rotated in the circumferential direction, the material 32 constituting the base layer is continuously supplied from the nozzle 31 and at the same time, the nozzle 31 is moved in the direction of the rotation axis of the mold. ing. Thereby, the material 32 which comprises the supplied base layer is wound helically. By adjusting the moving speed of the nozzle 31 and the rotating speed of the mold 33, the liquid material 32 wound in a spiral shape is bonded at adjacent portions to form a uniform coating layer. After this coating step, the liquid material applied by a conventional method is cured to form a base layer.

  As shown in FIG. 5, the nozzle 31 for applying the material 32 constituting the base layer to the mold 33 has a liquid discharge port formed in a tubular shape, its tip is inclined, and its wall thickness is 0.3-3. It is about 0 mm, more preferably about 0.5 to 2.0 mm. The inner diameter of the nozzle (liquid discharge port) is 0.5 to 5 mm, preferably about 1 to 3 mm. The central part of the liquid discharge port of the nozzle 31 is set so as to move in the direction of the rotation axis of the mold while being in contact with the outer surface of the mold 33, and the liquid discharge port of the nozzle 31 and the material applied to the mold 33 are in contact with each other. Has been. The nozzle moving speed V (mm / second) and the rotational speed R (rotation / second) of the mold are set so as to satisfy the relationship of 0.85 <(V / R) <1.5. Occurrence of striped patterns and irregularities due to the liquid stirring effect in the vicinity is prevented.

Subsequently, the material which comprises an elastic layer is apply | coated to the surface of the said base layer by the same method, and an elastic layer is formed.
Thereafter, water-based fluororubber is applied to the surface of the elastic layer by electrostatic coating to form a surface layer.

(Example)
Conductive belts of Examples 1 to 3 and Comparative Examples 1 to 4 shown in Table 1 below were prepared. Note that the conductive belt of Comparative Example 1 is a single-layered conductive belt made only of an elastic layer and a base layer having no surface layer.

Base layer material Polyamideimide varnish 100 parts by weight Carbon black (use furnace black) 7.0 parts by weight Dispersant 0.1 parts by weight

Elastic layer material (the numbers in the table indicate parts by mass)

・ Main agent: NCO obtained from polypropylene glycol and tolylene diisocyanate
6.9% terminal prepolymer (manufactured by Sumika Bayer Urethane Co., Ltd.)
・ Acclaim series: Polypropylene glycol (manufactured by Sumika Bayer Urethane Co., Ltd.)
・ Etacure 300; Dimethylthiotoluenediamine (manufactured by Albemarle)
・ Antistatic agent: “Sanconol PEO-20R” (lithium-bis (tri
(Fluoromethanesulfonyl) imide solution in polyol)
・ Defoaming agent: “Floren AC326F” manufactured by Kyoeisha Chemical Co., Ltd.

Surface layer material Water-based fluororubber paint (GLS-213F, manufactured by Daikin Industries, Ltd.)

The conductive belts of Examples 1 to 3 and Comparative Examples 1 to 4 were produced as follows.
100 parts by mass of polyamideimide varnish synthesized by a known method from trimellitic acid and diphenylmethane diisocyanate, 7.0 parts by mass of carbon black (using furnace black) and 0.1 part by mass of a dispersing agent are uniformly mixed in a bead mill. A base layer material was prepared.
An aluminum cylinder having an outer diameter of 20 mmφ coated with ceramics was used as the mold, and the nozzle was brought into contact with the outer surface of the mold while rotating the cylindrical mold. In this state, the base layer material was quantitatively supplied from the nozzle, and the nozzle was moved at a constant speed in the direction of the rotation axis of the mold to apply the material. At this time, the rotor rotation speed is 6 rpm, (V / R) = 1.17 (mm / rotation) (where V is the moving speed (mm / second), and R is the mold rotation speed (rotation / second). )). As the nozzle, a PTFE tube having an inner diameter of 2 mm and an outer diameter of 4 mm was used. As shown in FIG. 5, the tip of the nozzle 31 was cut off at 45 degrees, and the nozzle position was set so that the center of the cut-off surface moved in the axial direction of the mold while contacting the outer surface of the mold 33.
Next, the material was cured by gradually heating to 400 ° C. while rotating the mold and cooling to form a base layer having a thickness of 80 μm.

For the conductive belts of Examples 1 to 3 and Comparative Examples 2 to 4, the following steps were further performed.
The components contained in the curing agent shown in Table 2 were first mixed at the ratio shown in Table 2, and the obtained curing agent and the main agent were mixed at the ratio shown in Table 2 to prepare elastic layer materials 1 to 4. This material was coated on the base layer using the same apparatus as that used for the base layer preparation to form an elastic layer. Next, the belt coated with the elastic layer material on the base layer was heated at 150 ° C. for 1 hour to cure the elastic layer. The thickness of the elastic layer is as shown in Table 1.
A surface layer material was applied on the elastic layer by electrostatic coating to form a surface layer having a thickness of 10 μm.

The physical properties of the conductive belts produced in the examples and comparative examples were measured as follows.
(1) Tensile modulus: measured according to JIS K 7113.
(2) Surface resistivity: Measured with a URS probe using a "HIRESTA UP MCP-HT450 type" manufactured by Dia Instruments Co., Ltd. under the conditions of an applied voltage of 250 V and a measurement time of 10 seconds. The measurement environment was a temperature of 23 ° C. and a relative humidity of 55%.
(3) Volume resistivity: Measured with a URS probe using a “HIRESTA UP MCP-HT450 type” manufactured by Dia Instruments Co., Ltd. under the conditions of an applied voltage of 250 V and a measurement time of 10 seconds. The measurement environment was a temperature of 23 ° C. and a relative humidity of 55%.
(4) Hardness: Measured according to JIS K 6253 (1993), and type A was used.
(5) Complex elastic modulus: Measured under measurement conditions of dynamic strain 10 Hz, amplitude 2%, initial strain 10%, temperature 23 ° C. based on JIS K 7198. As a measuring device, DVE-V4 manufactured by Rheology was used.
(6) Belt hardness: A part of the belt was cut out and measured from the surface side according to the micro method of the IRHD hardness test method.

(Evaluation of transferability of toner to rough paper)
Each of the conductive belts produced in Examples and Comparative Examples was mounted as an intermediate transfer belt on a color laser beam printer (“WORKKIO KX-CL500” manufactured by Panasonic Communications Co., Ltd.).
Using the printer, a solid black image was printed on two types of paper. The paper used was paper with relatively small irregularities (“Capital Bond” manufactured by Fox River (USA)) (hereinafter referred to as paper type A), and paper with relatively large irregularities (“Strathmore (USA) manufactured by“ Strathmore writing raid ") (hereinafter referred to as paper type B).
The toner transferability of the conductive belt was evaluated based on whether or not white spots occurred in the solid black image printed on the paper. That is, “◯” indicates that the black solid image has been completely transferred to the concave portion of the paper, “△” indicates that the white void has slightly occurred, and “×” indicates that the white void has occurred. "

[Table 3]

Paper type Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4
A ○ ○ ○ × △ ○ △
B ○ ○ ○ × × × ×

  When the conductive belts produced in Comparative Examples 1 to 4 were used, the toner was not transferred to the concave portions of the paper, particularly in the paper type B, and white spots were generated, whereas those produced in Examples 1 to 3 were used. When the conductive belt of the present invention was used, it was found that the black solid image was completely transferred to the concave portion of the paper in both the paper type A and the paper type B, and the toner transferability was excellent.

1 is a perspective view illustrating a conductive belt according to an embodiment of the present invention. It is sectional drawing of the said electroconductive belt. 1 is a schematic front view showing a full-color image forming apparatus equipped with a conductive belt as an intermediate transfer belt. It is a figure for demonstrating the process of forming a base layer in the manufacturing method of the electroconductive belt of this invention. It is explanatory drawing of the shape of the nozzle tip in FIG. 4, and the contact position of a nozzle and a metal mold | die.

Explanation of symbols

1 Conductive belt (intermediate transfer belt)
Reference Signs List 3 Base layer 5 Elastic layer 7 Surface layer 9 Outer peripheral surface 11 Inner peripheral surface 20 Intermediate transfer belt 21a-d Developing unit 22a-d Photoconductor in developing unit 23a-d Primary transfer roll 24a, b Drive shaft 25 Secondary transfer roll 26 Recording medium (paper)
27 Fixing unit 31 Nozzle 32 Base layer material 33 Mold

Claims (4)

A conductive belt in which at least three layers of a base layer, an elastic layer, and a surface layer are sequentially laminated from the inner peripheral surface toward the outer periphery,
The hardness measured from the surface side of the belt in a laminated state by the IRHD hardness test micro method is 40 or more and 60 or less,
Furthermore, the base layer has a thickness of 50 to 150 μm, a tensile elastic modulus of 2000 MPa to 8000 MPa and a surface electrical resistivity on the inner peripheral surface side of 10 ⁶ Ω / □ to 10 ¹¹ Ω / □,
The elastic layer has a thickness of 400 to 1500 μm, a JISA hardness of 25 to 60 and a volume resistivity of 10 ⁶ Ω · cm to 10 ⁸ Ω · cm,
The surface layer has a thickness of 3 to 30 μm and a complex elastic modulus of 30 MPa to 250 MPa. The base layer is made of a resin containing polyimide or polyamideimide mixed with an electronic conductive agent,
The elastic layer is made of a polyurethane elastomer having ionic conductivity,
The conductive belt according to claim 1, wherein the surface layer is made of fluororubber.   The conductive belt according to claim 1, which is used as an intermediate transfer belt of an electrophotographic image forming apparatus. It is a manufacturing method of the conductive belt according to any one of claims 1 to 3,
While continuously rotating the cylindrical mold from the nozzle to the outer surface of the mold constituting the base layer, simultaneously moving the nozzle in the rotation direction of the mold and uniformly applying the material, Harden to form a base layer,
Next, an elastic layer is formed on the surface of the base layer by the same method,
Thereafter, a surface layer is formed by coating a surface layer material on the surface of the elastic layer to form a conductive belt.

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